/// <loc filename="Metadata\ui_loc_oam.xml" format="messagebundle" />
/*!
  © Microsoft. All rights reserved.

  This library is supported for use in Windows Store apps only.

  Build: 1.0.9200.20602.win8_ldr.130108-1504
  
  Version: Microsoft.WinJS.1.0
*/
/// <reference path="ms-appx://Microsoft.WinJS.1.0/js/base.js" />
/// <reference path="ms-appx://Microsoft.WinJS.1.0/js/ui.js" />



(function animationsInit(WinJS) {
    "use strict";

var thisWinUI = WinJS.UI;
var mstransform = "transform";

// Default to 11 pixel from the left (or right if RTL)
var defaultOffset = [{ top: "0px", left: "11px", rtlflip: true }];

var OffsetArray = WinJS.Class.define (function OffsetArray_ctor(offset, keyframe, defOffset) {
    // Constructor
    defOffset = defOffset || defaultOffset;
    if (Array.isArray(offset) && offset.length > 0) {
        this.offsetArray = offset;
        if (offset.length === 1) {
            this.keyframe = checkKeyframe(offset[0], defOffset[0], keyframe);
        }
    } else if (offset && offset.hasOwnProperty("top") && offset.hasOwnProperty("left")) {
        this.offsetArray = [offset];
        this.keyframe = checkKeyframe(offset, defOffset[0], keyframe);
    } else {
        this.offsetArray = defOffset;
        this.keyframe = chooseKeyframe(defOffset[0], keyframe);
    }
}, { // Public Members
    getOffset: function (i) {
        if (i >= this.offsetArray.length) {
            i = this.offsetArray.length - 1;
        }
        return this.offsetArray[i];
    }
}, { // Static Members
    supportedForProcessing: false,
});

function checkKeyframe(offset, defOffset, keyframe) {
    if (!keyframe ||
        offset.left !== defOffset.left ||
        offset.top !== defOffset.top ||
        (offset.rtlflip && !defOffset.rtlflip)) {
        return null;
    }

    if (!offset.rtlflip) {
        return keyframe;
    }

    return keyframeCallback(keyframe);
}

function chooseKeyframe(defOffset, keyframe) {
    if (!keyframe || !defOffset.rtlflip) {
        return keyframe;
    }

    return keyframeCallback(keyframe);
}

function keyframeCallback(keyframe) {
    var keyframeRtl = keyframe + "-rtl";
    return function (i, elem) {
        return window.getComputedStyle(elem).direction === "ltr" ? keyframe : keyframeRtl;
    }
}

function makeArray(elements)
{
    if (Array.isArray(elements) || elements instanceof NodeList || elements instanceof HTMLCollection) {
        return elements;
    } else if (elements) {
        return [elements];
    } else {
        return [];
    }
}

var isSnapped = function() {
    if (WinJS.Utilities.hasWinRT) {
        var appView = Windows.UI.ViewManagement.ApplicationView;
        var snapped = Windows.UI.ViewManagement.ApplicationViewState.snapped;
        isSnapped = function() {
            return appView.value === snapped;
        };
    } else {
        isSnapped = function() { return false; }
    }
    return isSnapped();
};

function collectOffsetArray(elemArray) {
    var offsetArray = [];
    for (var i = 0; i < elemArray.length; i++) {
        var offset = {
            top: elemArray[i].offsetTop,
            left: elemArray[i].offsetLeft
        };
        var matrix = window.getComputedStyle(elemArray[i], null).transform.split(",");
        if (matrix.length === 6) {
            offset.left += parseFloat(matrix[4]);
            offset.top += parseFloat(matrix[5]);
        }
        offsetArray.push(offset);
    }
    return offsetArray;
}

function staggerDelay(initialDelay, extraDelay, delayFactor, delayCap) {
    return function (i) {
        var ret = initialDelay;
        for (var j = 0; j < i; j++) {
            extraDelay *= delayFactor;
            ret += extraDelay;
        }
        if (delayCap) {
            ret = Math.min(ret, delayCap);
        }
        return ret;
    };
}

function makeOffsetsRelative(elemArray, offsetArray) {
    for (var i = 0; i < offsetArray.length; i++) {
        offsetArray[i].top -= elemArray[i].offsetTop;
        offsetArray[i].left -= elemArray[i].offsetLeft;
    }
}

function animTranslate2DTransform(elemArray, offsetArray, transition) {
    makeOffsetsRelative(elemArray, offsetArray);
    for (var i = 0; i < elemArray.length; i++) {
        if (offsetArray[i].top !== 0 || offsetArray[i].left !== 0) {
            elemArray[i].style.transform = "translate(" + offsetArray[i].left + "px, " + offsetArray[i].top + "px)";
        }
    }
    return thisWinUI.executeTransition(elemArray, transition);
}

function translateCallback(offsetArray, prefix) {
    prefix = prefix || "";
    return function (i, elem) {
        var offset = offsetArray.getOffset(i);
        var left = offset.left;
        if (offset.rtlflip && window.getComputedStyle(elem).direction === "rtl") {
            left = left.toString();
            if (left.charAt(0) === "-") {
                left = left.substring(1);
            } else {
                left = "-" + left;
            }
        }
        return prefix + "translate(" + left + ", " + offset.top + ")";
    };
}

function translateCallbackAnimate(offsetArray, suffix)
{
    suffix = suffix || "";
    return function (i, elem) {
        var offset = offsetArray[i];
        return "translate(" + offset.left + "px, " + offset.top + "px) " + suffix;
    };
}

function keyframeCallbackAnimate(offsetArray, keyframe)
{
    return function (i, elem) {
        var offset = offsetArray[i];
        return (offset.left === 0 && offset.top === 0) ? keyframe : null;
    };
}

function layoutTransition(LayoutTransition, target, affected, extra)
{
    var targetArray = makeArray(target);
    var affectedArray = makeArray(affected);
    var offsetArray = collectOffsetArray(affectedArray);
    return new LayoutTransition(targetArray, affectedArray, offsetArray, extra);
}

var ExpandAnimation = WinJS.Class.define(function ExpandAnimation_ctor(revealedArray, affectedArray, offsetArray) {
    // Constructor
    this.revealedArray = revealedArray;
    this.affectedArray = affectedArray;
    this.offsetArray = offsetArray;
},{ // Public Members
    execute: function () {
        var promise1 = thisWinUI.executeAnimation(
            this.revealedArray,
            {
                keyframe: "WinJS-opacity-in",
                property: "opacity",
                delay: this.affectedArray.length > 0 ? 200 : 0,
                duration: 167,
                timing: "cubic-bezier(0.1, 0.9, 0.2, 1)",
                from: 0,
                to: 1
            });
        var promise2 = animTranslate2DTransform(
            this.affectedArray,
            this.offsetArray,
            {
                property: mstransform,
                delay: 0,
                duration: 367,
                timing: "cubic-bezier(0.1, 0.9, 0.2, 1)",
                to: ""
            });
        return WinJS.Promise.join([promise1, promise2]);
    }
}, { // Static Members
    supportedForProcessing: false,
});

var CollapseAnimation = WinJS.Class.define(function CollapseAnimation_ctor(hiddenArray, affectedArray, offsetArray) {
    // Constructor
    this.hiddenArray = hiddenArray;
    this.affectedArray = affectedArray;
    this.offsetArray = offsetArray;
},{ // Public Members
    execute: function () {
        var promise1 = thisWinUI.executeAnimation(
            this.hiddenArray,
            {
                keyframe: "WinJS-opacity-out",
                property: "opacity",
                delay: 0,
                duration: 167,
                timing: "cubic-bezier(0.1, 0.9, 0.2, 1)",
                from: 1,
                to: 0
            });
        var promise2 = animTranslate2DTransform(
            this.affectedArray,
            this.offsetArray,
            {
                property: mstransform,
                delay: this.hiddenArray.length > 0 ? 167 : 0,
                duration: 367,
                timing: "cubic-bezier(0.1, 0.9, 0.2, 1)",
                to: ""
            });
        return WinJS.Promise.join([promise1, promise2]);
    }
}, { // Static Members
    supportedForProcessing: false,
});

var RepositionAnimation = WinJS.Class.define(function RepositionAnimation_ctor(target, elementArray, offsetArray) {
    // Constructor
    this.elementArray = elementArray;
    this.offsetArray = offsetArray;
},{ // Public Members
    execute: function () {
        return animTranslate2DTransform(
            this.elementArray,
            this.offsetArray,
            {
                property: mstransform,
                delay : staggerDelay(0, 33, 1, 250),
                duration : 367,
                timing: "cubic-bezier(0.1, 0.9, 0.2, 1)",
                to: ""
            });
    }
}, { // Static Members
    supportedForProcessing: false,
});

var AddToListAnimation = WinJS.Class.define(function AddToListAnimation_ctor(addedArray, affectedArray, offsetArray) {
    // Constructor
    this.addedArray = addedArray;
    this.affectedArray = affectedArray;
    this.offsetArray = offsetArray;
},{ // Public Members
    execute: function () {
        var delay = this.affectedArray.length > 0 ? 240 : 0;
        var promise1 = thisWinUI.executeAnimation(
            this.addedArray,
            [{
                keyframe: "WinJS-scale-up",
                property: mstransform,
                delay: delay,
                duration: 120,
                timing: "cubic-bezier(0.1, 0.9, 0.2, 1)",
                from: "scale(0.85)",
                to: "none"
            },
            {
                keyframe: "WinJS-opacity-in",
                property: "opacity",
                delay: delay,
                duration: 120,
                timing: "linear",
                from: 0,
                to: 1
            }]
        );
        var promise2 = animTranslate2DTransform(
            this.affectedArray,
            this.offsetArray,
            {
                property: mstransform,
                delay: 0,
                duration: 400,
                timing: "cubic-bezier(0.1, 0.9, 0.2, 1)",
                to: ""
            });
        return WinJS.Promise.join([promise1, promise2]);
    }
}, { // Static Members
    supportedForProcessing: false,
});

var DeleteFromListAnimation = WinJS.Class.define(function DeleteFromListAnimation_ctor(deletedArray, remainingArray, offsetArray) {
    // Constructor
    this.deletedArray = deletedArray;
    this.remainingArray = remainingArray;
    this.offsetArray = offsetArray;
},{ // Public Members
    execute: function () {
        var promise1 = thisWinUI.executeAnimation(
            this.deletedArray,
            [{
                keyframe: "WinJS-scale-down",
                property: mstransform,
                delay: 0,
                duration: 120,
                timing: "cubic-bezier(0.11, 0.5, 0.24, .96)",
                from: "none",
                to: "scale(0.85)"
            },
            {
                keyframe: "WinJS-opacity-out",
                property: "opacity",
                delay: 0,
                duration: 120,
                timing: "linear",
                from: 1,
                to: 0
            }]);
        var promise2 = animTranslate2DTransform(
            this.remainingArray,
            this.offsetArray,
            {
                property: mstransform,
                delay: this.deletedArray.length > 0 ? 60 : 0,
                duration: 400,
                timing: "cubic-bezier(0.1, 0.9, 0.2, 1)",
                to: ""
            });
        return WinJS.Promise.join([promise1, promise2]);
    }
}, { // Static Members
    supportedForProcessing: false,
});

var _UpdateListAnimation = WinJS.Class.define(function _UpdateListAnimation_ctor(addedArray, affectedArray, offsetArray, deleted) {
    // Constructor
    this.addedArray = addedArray;
    this.affectedArray = affectedArray;
    this.offsetArray = offsetArray;
    var deletedArray = makeArray(deleted);
    this.deletedArray = deletedArray;
    this.deletedOffsetArray = collectOffsetArray(deletedArray);
},{ // Public Members
    execute: function () {
        makeOffsetsRelative(this.deletedArray, this.deletedOffsetArray);

        var delay = 0;
        var promise1 = thisWinUI.executeAnimation(
            this.deletedArray,
            [{
                keyframe: keyframeCallbackAnimate(this.deletedOffsetArray, "WinJS-scale-down"),
                property: mstransform,
                delay: 0,
                duration: 120,
                timing: "cubic-bezier(0.11, 0.5, 0.24, .96)",
                from: translateCallbackAnimate(this.deletedOffsetArray),
                to: translateCallbackAnimate(this.deletedOffsetArray, "scale(0.85)")
            },
            {
                keyframe: "WinJS-opacity-out",
                property: "opacity",
                delay: 0,
                duration: 120,
                timing: "linear",
                from: 1,
                to: 0
            }]);

        if (this.deletedArray.length > 0) {
            delay += 60;
        }

        var promise2 = animTranslate2DTransform(
            this.affectedArray,
            this.offsetArray,
            {
                property: mstransform,
                delay: delay,
                duration: 400,
                timing: "cubic-bezier(0.1, 0.9, 0.2, 1)",
                to: ""
            });

        if (this.affectedArray.length > 0) {
            delay += 240;
        } else if (delay) {
            delay += 60;
        }

        var promise3 = thisWinUI.executeAnimation(
            this.addedArray,
            [{
                keyframe: "WinJS-scale-up",
                property: mstransform,
                delay: delay,
                duration: 120,
                timing: "cubic-bezier(0.1, 0.9, 0.2, 1)",
                from: "scale(0.85)",
                to: "none"
            },
            {
                keyframe: "WinJS-opacity-in",
                property: "opacity",
                delay: delay,
                duration: 120,
                timing: "linear",
                from: 0,
                to: 1
            }]
        );
        return WinJS.Promise.join([promise1, promise2, promise3]);
    }
}, { // Static Members
    supportedForProcessing: false,
});


var AddToSearchListAnimation = WinJS.Class.define(function AddToSearchListAnimation_ctor(addedArray, affectedArray, offsetArray) {
    // Constructor
    this.addedArray = addedArray;
    this.affectedArray = affectedArray;
    this.offsetArray = offsetArray;
},{ // Public Members
    execute: function () {
        var promise1 = thisWinUI.executeAnimation(
            this.addedArray,
            {
                keyframe: "WinJS-opacity-in",
                property: "opacity",
                delay: this.affectedArray.length > 0 ? 240 : 0,
                duration: 117,
                timing: "linear",
                from: 0,
                to: 1
            });
        var promise2 = animTranslate2DTransform(
            this.affectedArray,
            this.offsetArray,
            {
                property: mstransform,
                delay: 0,
                duration: 400,
                timing: "cubic-bezier(0.1, 0.9, 0.2, 1)",
                to: ""
            });
        return WinJS.Promise.join([promise1, promise2]);
    }
}, { // Static Members
    supportedForProcessing: false,
});

var DeleteFromSearchListAnimation = WinJS.Class.define(function DeleteFromSearchListAnimation_ctor(deletedArray, remainingArray, offsetArray) {
    // Constructor
    this.deletedArray = deletedArray;
    this.remainingArray = remainingArray;
    this.offsetArray = offsetArray;
},{ // Public Members
    execute: function () {
        var promise1 = thisWinUI.executeAnimation(
            this.deletedArray,
            {
                keyframe: "WinJS-opacity-out",
                property: "opacity",
                delay: 0,
                duration: 93,
                timing: "linear",
                from: 1,
                to: 0
            });
        var promise2 = animTranslate2DTransform(
            this.remainingArray,
            this.offsetArray,
            {
                property: mstransform,
                delay: this.deletedArray.length > 0 ? 60 : 0,
                duration: 400,
                timing: "cubic-bezier(0.1, 0.9, 0.2, 1)",
                to: ""
            });
        return WinJS.Promise.join([promise1, promise2]);
    }
}, { // Static Members
    supportedForProcessing: false,
});

var PeekAnimation = WinJS.Class.define(function PeekAnimation_ctor(target, elementArray, offsetArray) {
    // Constructor
    this.elementArray = elementArray;
    this.offsetArray = offsetArray;
},{ // Public Members
    execute: function () {
        return animTranslate2DTransform(
            this.elementArray,
            this.offsetArray,
            {
                property: mstransform,
                delay : 0,
                duration : 2000,
                timing : "cubic-bezier(0.1, 0.9, 0.2, 1)",
                to: ""
            });
    }
}, { // Static Members
    supportedForProcessing: false,
});

WinJS.Namespace.define("WinJS.UI.Animation", {

    createExpandAnimation: function (revealed, affected) {
        /// <signature helpKeyword="WinJS.UI.Animation.createExpandAnimation">
        /// <summary locid="WinJS.UI.Animation.createExpandAnimation">
        /// Creates an expand animation.
        /// After creating the ExpandAnimation object,
        /// modify the document to move the elements to their new positions,
        /// then call the execute method on the ExpandAnimation object.
        /// </summary>
        /// <param name="revealed" locid="WinJS.UI.Animation.createExpandAnimation_p:revealed">
        /// Single element or collection of elements which were revealed.
        /// </param>
        /// <param name="affected" locid="WinJS.UI.Animation.createExpandAnimation_p:affected">
        /// Single element or collection of elements whose positions were
        /// affected by the expand.
        /// </param>
        /// <returns type="{ execute: Function }" locid="WinJS.UI.Animation.createExpandAnimation_returnValue">
        /// ExpandAnimation object whose execute method returns
        /// a Promise that completes when the animation is complete.
        /// </returns>
        /// </signature>
        return layoutTransition(ExpandAnimation, revealed, affected);
        },

    createCollapseAnimation: function (hidden, affected) {
        /// <signature helpKeyword="WinJS.UI.Animation.createCollapseAnimation">
        /// <summary locid="WinJS.UI.Animation.createCollapseAnimation">
        /// Creates a collapse animation.
        /// After creating the CollapseAnimation object,
        /// modify the document to move the elements to their new positions,
        /// then call the execute method on the CollapseAnimation object.
        /// </summary>
        /// <param name="hidden" locid="WinJS.UI.Animation.createCollapseAnimation_p:hidden">
        /// Single element or collection of elements being removed from view.
        /// When the animation completes, the application should hide the elements
        /// or remove them from the document.
        /// </param>
        /// <param name="affected" locid="WinJS.UI.Animation.createCollapseAnimation_p:affected">
        /// Single element or collection of elements whose positions were
        /// affected by the collapse.
        /// </param>
        /// <returns type="{ execute: Function }" locid="WinJS.UI.Animation.createCollapseAnimation_returnValue">
        /// CollapseAnimation object whose execute method returns
        /// a Promise that completes when the animation is complete.
        /// </returns>
        /// </signature>
        return layoutTransition(CollapseAnimation, hidden, affected);
    },

    createRepositionAnimation: function (element) {
        /// <signature helpKeyword="WinJS.UI.Animation.createRepositionAnimation">
        /// <summary locid="WinJS.UI.Animation.createRepositionAnimation">
        /// Creates a reposition animation.
        /// After creating the RepositionAnimation object,
        /// modify the document to move the elements to their new positions,
        /// then call the execute method on the RepositionAnimation object.
        /// </summary>
        /// <param name="element" locid="WinJS.UI.Animation.createRepositionAnimation_p:element">
        /// Single element or collection of elements which were repositioned.
        /// </param>
        /// <returns type="{ execute: Function }" locid="WinJS.UI.Animation.createRepositionAnimation_returnValue">
        /// RepositionAnimation object whose execute method returns
        /// a Promise that completes when the animation is complete.
        /// </returns>
        /// </signature>
        return layoutTransition(RepositionAnimation, null, element);
    },

    fadeIn: function (shown) {
        /// <signature helpKeyword="WinJS.UI.Animation.fadeIn">
        /// <summary locid="WinJS.UI.Animation.fadeIn">
        /// Execute a fade-in animation.
        /// </summary>
        /// <param name="shown" locid="WinJS.UI.Animation.fadeIn_p:element">
        /// Single element or collection of elements to fade in.
        /// At the end of the animation, the opacity of the elements is 1.
        /// </param>
        /// <returns type="WinJS.Promise" locid="WinJS.UI.Animation.fadeIn_returnValue">
        /// Promise object that completes when the animation is complete.
        /// </returns>
        /// </signature>
        return thisWinUI.executeTransition(
            shown,
            {
                property: "opacity",
                delay: 0,
                duration: 250,
                timing: "linear",
                from: 0,
                to: 1
            });
    },

    fadeOut: function (hidden) {
        /// <signature helpKeyword="WinJS.UI.Animation.fadeOut">
        /// <summary locid="WinJS.UI.Animation.fadeOut">
        /// Execute a fade-out animation.
        /// </summary>
        /// <param name="hidden" locid="WinJS.UI.Animation.fadeOut_p:element">
        /// Single element or collection of elements to fade out.
        /// At the end of the animation, the opacity of the elements is 0.
        /// </param>
        /// <returns type="WinJS.Promise" locid="WinJS.UI.Animation.fadeOut_returnValue">
        /// Promise object that completes when the animation is complete.
        /// </returns>
        /// </signature>
        return thisWinUI.executeTransition(
            hidden,
            {
                property: "opacity",
                delay: 0,
                duration: 167,
                timing: "linear",
                to: 0
            });
    },

    createAddToListAnimation: function (added, affected) {
        /// <signature helpKeyword="WinJS.UI.Animation.createAddToListAnimation">
        /// <summary locid="WinJS.UI.Animation.createAddToListAnimation">
        /// Creates an animation for adding to a list.
        /// After creating the AddToListAnimation object,
        /// modify the document to move the elements to their new positions,
        /// then call the execute method on the AddToListAnimation object.
        /// </summary>
        /// <param name="added" locid="WinJS.UI.Animation.createAddToListAnimation_p:added">
        /// Single element or collection of elements which were added.
        /// </param>
        /// <param name="affected" locid="WinJS.UI.Animation.createAddToListAnimation_p:affected">
        /// Single element or collection of elements whose positions were
        /// affected by the add.
        /// </param>
        /// <returns type="{ execute: Function }" locid="WinJS.UI.Animation.createAddToListAnimation_returnValue">
        /// AddToListAnimation object whose execute method returns
        /// a Promise that completes when the animation is complete.
        /// </returns>
        /// </signature>
        return layoutTransition(AddToListAnimation, added, affected);
        },

    createDeleteFromListAnimation: function (deleted, remaining) {
        /// <signature helpKeyword="WinJS.UI.Animation.createDeleteFromListAnimation">
        /// <summary locid="WinJS.UI.Animation.createDeleteFromListAnimation">
        /// Crestes an animation for deleting from a list.
        /// After creating the DeleteFromListAnimation object,
        /// modify the document to reflect the deletion,
        /// then call the execute method on the DeleteFromListAnimation object.
        /// </summary>
        /// <param name="deleted" locid="WinJS.UI.Animation.createDeleteFromListAnimation_p:deleted">
        /// Single element or collection of elements which will be deleted.
        /// When the animation completes, the application should hide the elements
        /// or remove them from the document.
        /// </param>
        /// <param name="remaining" locid="WinJS.UI.Animation.createDeleteFromListAnimation_p:remaining">
        /// Single element or collection of elements whose positions were
        /// affected by the deletion.
        /// </param>
        /// <returns type="{ execute: Function }" locid="WinJS.UI.Animation.createDeleteFromListAnimation_returnValue">
        /// DeleteFromListAnimation object whose execute method returns
        /// a Promise that completes when the animation is complete.
        /// </returns>
        /// </signature>
        return layoutTransition(DeleteFromListAnimation, deleted, remaining);
        },

    _createUpdateListAnimation: function (added, deleted, affected) {
        return layoutTransition(_UpdateListAnimation, added, affected, deleted);
        },

    createAddToSearchListAnimation: function (added, affected) {
        /// <signature helpKeyword="WinJS.UI.Animation.createAddToSearchListAnimation">
        /// <summary locid="WinJS.UI.Animation.createAddToSearchListAnimation">
        /// Creates an animation for adding to a list of search results.
        /// This is similar to an AddToListAnimation, but faster.
        /// After creating the AddToSearchListAnimation object,
        /// modify the document to move the elements to their new positions,
        /// then call the execute method on the AddToSearchListAnimation object.
        /// </summary>
        /// <param name="added" locid="WinJS.UI.Animation.createAddToSearchListAnimation_p:added">
        /// Single element or collection of elements which were added.
        /// </param>
        /// <param name="affected" locid="WinJS.UI.Animation.createAddToSearchListAnimation_p:affected">
        /// Single element or collection of elements whose positions were
        /// affected by the add.
        /// </param>
        /// <returns type="{ execute: Function }" locid="WinJS.UI.Animation.createAddToSearchListAnimation_returnValue">
        /// AddToSearchListAnimation object whose execute method returns
        /// a Promise that completes when the animation is complete.
        /// </returns>
        /// </signature>
        return layoutTransition(AddToSearchListAnimation, added, affected);
        },

    createDeleteFromSearchListAnimation: function (deleted, remaining) {
        /// <signature helpKeyword="WinJS.UI.Animation.createDeleteFromSearchListAnimation">
        /// <summary locid="WinJS.UI.Animation.createDeleteFromSearchListAnimation">
        /// Creates an animation for deleting from a list of search results.
        /// This is similar to an DeleteFromListAnimation, but faster.
        /// After creating the DeleteFromSearchListAnimation object,
        /// modify the document to move the elements to their new positions,
        /// then call the execute method on the DeleteFromSearchListAnimation object.
        /// </summary>
        /// <param name="deleted" locid="WinJS.UI.Animation.createDeleteFromSearchListAnimation_p:deleted">
        /// Single element or collection of elements which will be deleted.
        /// When the animation completes, the application should hide the elements
        /// or remove them from the document.
        /// </param>
        /// <param name="remaining" locid="WinJS.UI.Animation.createDeleteFromSearchListAnimation_p:remaining">
        /// Single element or collection of elements whose positions were
        /// affected by the deletion.
        /// </param>
        /// <returns type="{ execute: Function }" locid="WinJS.UI.Animation.createDeleteFromSearchListAnimation_returnValue">
        /// DeleteFromSearchListAnimation object whose execute method returns
        /// a Promise that completes when the animation is complete.
        /// </returns>
        /// </signature>
        return layoutTransition(DeleteFromSearchListAnimation, deleted, remaining);
        },


    showEdgeUI: function (element, offset) {
        /// <signature helpKeyword="WinJS.UI.Animation.showEdgeUI">
        /// <summary locid="WinJS.UI.Animation.showEdgeUI">
        /// Slides an element or elements into position at the edge of the screen.
        /// This animation is designed for a small object like an appbar.
        /// </summary>
        /// <param name="element" locid="WinJS.UI.Animation.showEdgeUI_p:element">
        /// Single element or collection of elements to be slid into position.
        /// The elements should be at their final positions
        /// at the time the function is called.
        /// </param>
        /// <param name="offset" locid="WinJS.UI.Animation.showEdgeUI_p:offset">
        /// Optional offset object or collection of offset objects
        /// array describing the starting point of the animation.
        /// If the number of offset objects is less than the length of the
        /// element parameter, then the last value is repeated for all
        /// remaining elements.
        /// If this parameter is omitted, then a default value is used.
        /// </param>
        /// <returns type="WinJS.Promise" locid="WinJS.UI.Animation.showEdgeUI_p:returnValue">
        /// Promise object that completes when the animation is complete.
        /// </returns>
        /// </signature>
        var offsetArray = new OffsetArray(offset, "WinJS-showEdgeUI", [{ top: "-70px", left: "0px" }]);
        return thisWinUI.executeAnimation(
            element,
            {
                keyframe: offsetArray.keyframe,
                property: mstransform,
                delay: 0,
                duration: 367,
                timing: "cubic-bezier(0.1, 0.9, 0.2, 1)",
                from: offsetArray.keyframe || translateCallback(offsetArray),
                to: "none"
            });
    },

    showPanel: function (element, offset) {
        /// <signature helpKeyword="WinJS.UI.Animation.showPanel">
        /// <summary locid="WinJS.UI.Animation.showPanel">
        /// Slides an element or elements into position at the edge of the screen.
        /// This animation is designed for a large object like a keyboard.
        /// </summary>
        /// <param name="element" locid="WinJS.UI.Animation.showPanel_p:element">
        /// Single element or collection of elements to be slid into position.
        /// The elements should be at their final positions
        /// at the time the function is called.
        /// </param>
        /// <param name="offset" locid="WinJS.UI.Animation.showPanel_p:offset">
        /// Optional offset object or collection of offset objects
        /// array describing the starting point of the animation.
        /// If the number of offset objects is less than the length of the
        /// element parameter, then the last value is repeated for all
        /// remaining elements.
        /// If this parameter is omitted, then a default value is used.
        /// </param>
        /// <returns type="WinJS.Promise" locid="WinJS.UI.Animation.showPanel_returnValue">
        /// promise object
        /// </returns>
        /// </signature>
        var offsetArray = new OffsetArray(offset, "WinJS-showPanel", [{ top: "0px", left: "364px", rtlflip: true }]);
        return thisWinUI.executeAnimation(
            element,
            {
                keyframe: offsetArray.keyframe,
                property: mstransform,
                delay: 0,
                duration: 550,
                timing: "cubic-bezier(0.1, 0.9, 0.2, 1)",
                from: offsetArray.keyframe || translateCallback(offsetArray),
                to: "none"
            });
    },


    hideEdgeUI: function (element, offset) {
        /// <signature helpKeyword="WinJS.UI.Animation.hideEdgeUI">
        /// <summary locid="WinJS.UI.Animation.hideEdgeUI">
        /// Slides an element or elements at the edge of the screen out of view.
        /// This animation is designed for a small object like an appbar.
        /// </summary>
        /// <param name="element" locid="WinJS.UI.Animation.hideEdgeUI_p:element">
        /// Single element or collection of elements to be slid out.
        /// The elements should be at their onscreen positions
        /// at the time the function is called.
        /// </param>
        /// <param name="offset" locid="WinJS.UI.Animation.hideEdgeUI_p:offset">
        /// Optional offset object or collection of offset objects
        /// array describing the ending point of the animation.
        /// If the number of offset objects is less than the length of the
        /// element parameter, then the last value is repeated for all
        /// remaining elements.
        /// If this parameter is omitted, then a default value is used.
        /// </param>
        /// <returns type="WinJS.Promise" locid="WinJS.UI.Animation.hideEdgeUI_returnValue">
        /// Promise object that completes when the animation is complete.
        /// </returns>
        /// </signature>
        var offsetArray = new OffsetArray(offset, "WinJS-hideEdgeUI", [{ top: "-70px", left: "0px" }]);
        return thisWinUI.executeAnimation(
            element,
            {
                keyframe: offsetArray.keyframe,
                property: mstransform,
                delay: 0,
                duration: 367,
                timing: "cubic-bezier(0.1, 0.9, 0.2, 1)",
                from: "none",
                to: offsetArray.keyframe || translateCallback(offsetArray)
            });
    },

    hidePanel: function (element, offset) {
        /// <signature helpKeyword="WinJS.UI.Animation.hidePanel">
        /// <summary locid="WinJS.UI.Animation.hidePanel">
        /// Slides an element or elements at the edge of the screen out of view.
        /// This animation is designed for a large object like a keyboard.
        /// </summary>
        /// <param name="element" locid="WinJS.UI.Animation.hidePanel_p:element">
        /// Single element or collection of elements to be slid out.
        /// The elements should be at their onscreen positions
        /// at the time the function is called.
        /// </param>
        /// <param name="offset" locid="WinJS.UI.Animation.hidePanel_p:offset">
        /// Optional offset object or collection of offset objects
        /// array describing the ending point of the animation.
        /// If the number of offset objects is less than the length of the
        /// element parameter, then the last value is repeated for all
        /// remaining elements.
        /// If this parameter is omitted, then a default value is used.
        /// </param>
        /// <returns type="WinJS.Promise" locid="WinJS.UI.Animation.hidePanel_returnValue">
        /// Promise object that completes when the animation is complete.
        /// </returns>
        /// </signature>
        var offsetArray = new OffsetArray(offset, "WinJS-hidePanel", [{ top: "0px", left: "364px", rtlflip: true }]);
        return thisWinUI.executeAnimation(
            element,
            {
                keyframe: offsetArray.keyframe,
                property: mstransform,
                delay: 0,
                duration: 550,
                timing: "cubic-bezier(0.1, 0.9, 0.2, 1)",
                from: "none",
                to: offsetArray.keyframe || translateCallback(offsetArray)
            });
    },

    showPopup: function (element, offset) {
        /// <signature helpKeyword="WinJS.UI.Animation.showPopup">
        /// <summary locid="WinJS.UI.Animation.showPopup">
        /// Displays an element or elements in the style of a popup.
        /// </summary>
        /// <param name="element" locid="WinJS.UI.Animation.showPopup_p:element">
        /// Single element or collection of elements to be shown like a popup.
        /// </param>
        /// <param name="offset" locid="WinJS.UI.Animation.showPopup_p:offset">
        /// Optional offset object or collection of offset objects
        /// array describing the starting point of the animation.
        /// If the number of offset objects is less than the length of the
        /// element parameter, then the last value is repeated for all
        /// remaining elements.
        /// If this parameter is omitted, then a default value is used.
        /// </param>
        /// <returns type="WinJS.Promise" locid="WinJS.UI.Animation.showPopup_returnValue">
        /// Promise object that completes when the animation is complete.
        /// </returns>
        /// </signature>
        var offsetArray = new OffsetArray(offset, "WinJS-showPopup", [{ top: "50px", left: "0px" }]);
        return thisWinUI.executeAnimation(
            element,
            [{
                keyframe: "WinJS-opacity-in",
                property: "opacity",
                delay: 83,
                duration: 83,
                timing: "linear",
                from: 0,
                to: 1
            },
            {
                keyframe: offsetArray.keyframe,
                property: mstransform,
                delay: 0,
                duration: 367,
                timing: "cubic-bezier(0.1, 0.9, 0.2, 1)",
                from: offsetArray.keyframe || translateCallback(offsetArray),
                to: "none"
            }]);
        },

    hidePopup: function (element) {
        /// <signature helpKeyword="WinJS.UI.Animation.hidePopup">
        /// <summary locid="WinJS.UI.Animation.hidePopup">
        /// Removes a popup from the screen.
        /// </summary>
        /// <param name="element" locid="WinJS.UI.Animation.hidePopup_p:element">
        /// Single element or collection of elements to be hidden like a popup.
        /// When the animation completes, the application should hide the elements
        /// or remove them from the document.
        /// </param>
        /// <returns type="WinJS.Promise" locid="WinJS.UI.Animation.hidePopup_returnValue">
        /// Promise object that completes when the animation is complete.
        /// </returns>
        /// </signature>
        return thisWinUI.executeAnimation(
            element,
            {
                keyframe: "WinJS-opacity-out",
                property: "opacity",
                delay: 0,
                duration: 83,
                timing: "linear",
                from: 1,
                to: 0
            });
    },

    pointerDown: function (element) {
        /// <signature helpKeyword="WinJS.UI.Animation.pointerDown">
        /// <summary locid="WinJS.UI.Animation.pointerDown">
        /// Execute a pointer-down animation.
        /// Use the pointerUp animation to reverse the effect of this animation.
        /// </summary>
        /// <param name="element" locid="WinJS.UI.Animation.pointerDown_p:element">
        /// Single element or collection of elements responding to the
        /// pointer-down event.
        /// At the end of the animation, the elements' properties have been
        /// modified to reflect the pointer-down state.
        /// </param>
        /// <returns type="WinJS.Promise" locid="WinJS.UI.Animation.pointerDown_returnValue">
        /// Promise object that completes when the animation is complete.
        /// </returns>
        /// </signature>
       return thisWinUI.executeTransition(
            element,
            {
                property: mstransform,
                delay: 0,
                duration: 167,
                timing: "cubic-bezier(0.1, 0.9, 0.2, 1)",
                to: "scale(0.975, 0.975)"
            });
    },

    pointerUp: function (element) {
        /// <signature helpKeyword="WinJS.UI.Animation.pointerUp">
        /// <summary locid="WinJS.UI.Animation.pointerUp">
        /// Execute a pointer-up animation.
        /// This reverses the effect of a pointerDown animation.
        /// </summary>
        /// <param name="element" locid="WinJS.UI.Animation.pointerUp_p:element">
        /// Single element or collection of elements responding to
        /// the pointer-up event.
        /// At the end of the animation, the elements' properties have been
        /// returned to normal.
        /// </param>
        /// <returns type="WinJS.Promise" locid="WinJS.UI.Animation.pointerUp_returnValue">
        /// Promise object that completes when the animation is complete.
        /// </returns>
        /// </signature>
       return thisWinUI.executeTransition(
            element,
            {
                property: mstransform,
                delay: 0,
                duration: 167,
                timing: "cubic-bezier(0.1, 0.9, 0.2, 1)",
                to: ""
            });
    },

    dragSourceStart: function (dragSource, affected) {
        /// <signature helpKeyword="WinJS.UI.Animation.dragSourceStart">
        /// <summary locid="WinJS.UI.Animation.dragSourceStart">
        /// Execute a drag-start animation.
        /// Use the dragSourceEnd animation to reverse the effects of this animation.
        /// </summary>
        /// <param name="dragSource" locid="WinJS.UI.Animation.dragSourceStart_p:dragSource">
        /// Single element or collection of elements being dragged.
        /// At the end of the animation, the elements' properties have been
        /// modified to reflect the drag state.
        /// </param>
        /// <param name="affected" locid="WinJS.UI.Animation.dragSourceStart_p:affected">
        /// Single element or collection of elements to highlight as not
        /// being dragged.
        /// At the end of the animation, the elements' properties have been
        /// modified to reflect the drag state.
        /// </param>
        /// <returns type="WinJS.Promise" locid="WinJS.UI.Animation.dragSourceStart_returnValue">
        /// Promise object that completes when the animation is complete.
        /// </returns>
        /// </signature>
        var promise1 = thisWinUI.executeTransition(
            dragSource,
            [{
                property: mstransform,
                delay: 0,
                duration: 240,
                timing : "cubic-bezier(0.1, 0.9, 0.2, 1)",
                to: "scale(1.05)"
            },
            {
                property: "opacity",
                delay: 0,
                duration: 240,
                timing: "cubic-bezier(0.1, 0.9, 0.2, 1)",
                to: 0.65
            }]);
        var promise2 = thisWinUI.executeTransition(
            affected,
            {
                property: mstransform,
                delay: 0,
                duration: 240,
                timing: "cubic-bezier(0.1, 0.9, 0.2, 1)",
                to: "scale(0.95)"
            });
        return WinJS.Promise.join([promise1, promise2]);
    },

    dragSourceEnd: function (dragSource, offset, affected) {
        /// <signature helpKeyword="WinJS.UI.Animation.dragSourceEnd">
        /// <summary locid="WinJS.UI.Animation.dragSourceEnd">
        /// Execute a drag-end animation.
        /// This reverses the effect of the dragSourceStart animation.
        /// </summary>
        /// <param name="dragSource" locid="WinJS.UI.Animation.dragSourceEnd_p:dragSource">
        /// Single element or collection of elements no longer being dragged.
        /// At the end of the animation, the elements' properties have been
        /// returned to normal.
        /// </param>
        /// <param name="offset" locid="WinJS.UI.Animation.dragSourceEnd_p:offset">
        /// Optional offset object or collection of offset objects
        /// array describing the starting point of the animation.
        /// If the number of offset objects is less than the length of the
        /// dragSource parameter, then the last value is repeated for all
        /// remaining elements.
        /// If this parameter is omitted, then a default value is used.
        /// </param>
        /// <param name="affected" locid="WinJS.UI.Animation.dragSourceEnd_p:affected">
        /// Single element or collection of elements which were highlighted as not
        /// being dragged.
        /// At the end of the animation, the elements' properties have been
        /// returned to normal.
        /// </param>
        /// <returns type="WinJS.Promise" locid="WinJS.UI.Animation.dragSourceEnd_returnValue">
        /// Promise object that completes when the animation is complete.
        /// </returns>
        /// </signature>
        var offsetArray = new OffsetArray(offset, "WinJS-dragSourceEnd");
        var promise1 = thisWinUI.executeTransition(
            dragSource,
            [{
                property: mstransform,
                delay: 0,
                duration : 500,
                timing : "cubic-bezier(0.1, 0.9, 0.2, 1)",
                to: "" // this removes the scale
            },
            {
                property: "opacity",
                delay: 0,
                duration: 500,
                timing: "cubic-bezier(0.1, 0.9, 0.2, 1)",
                to: 1
            }]);

        var promise2 = thisWinUI.executeAnimation(
            dragSource,
            {
                keyframe: offsetArray.keyframe,
                property: mstransform,
                delay: 0,
                duration: 500,
                timing: "cubic-bezier(0.1, 0.9, 0.2, 1)",
                from: offsetArray.keyframe || translateCallback(offsetArray, "scale(1.05) "),
                to: "none"
            });

       var promise3 = thisWinUI.executeTransition(
            affected,
            {
                property: mstransform,
                delay : 0,
                duration : 500,
                timing : "cubic-bezier(0.1, 0.9, 0.2, 1)",
                to: ""
            });
        return WinJS.Promise.join([promise1, promise2, promise3]);
    },


    enterContent: function (incoming, offset) {
        /// <signature helpKeyword="WinJS.UI.Animation.enterContent">
        /// <summary locid="WinJS.UI.Animation.enterContent">
        /// Execute an enter-content animation.
        /// </summary>
        /// <param name="incoming" locid="WinJS.UI.Animation.enterContent_p:incoming">
        /// Single element or collection of elements which represent
        /// the incoming content.
        /// At the end of the animation, the opacity of the elements is 1.
        /// </param>
        /// <param name="offset" locid="WinJS.UI.Animation.enterContent_p:offset">
        /// Optional offset object or collection of offset objects
        /// array describing the starting point of the animation.
        /// If the number of offset objects is less than the length of the
        /// incoming parameter, then the last value is repeated for all
        /// remaining elements.
        /// If this parameter is omitted, then a default value is used.
        /// </param>
        /// <returns type="WinJS.Promise" locid="WinJS.UI.Animation.enterContent_returnValue">
        /// Promise object that completes when the animation is complete.
        /// </returns>
        /// </signature>
        var offsetArray;
        if (isSnapped()) {
            offsetArray = new OffsetArray(offset, "WinJS-enterContent-snapped", [{ top: "0px", left: "20px", rtlflip: true }]);
        } else {
            offsetArray = new OffsetArray(offset, "WinJS-enterContent", [{ top: "0px", left: "40px", rtlflip: true }]);
        }
        var promise1 = thisWinUI.executeAnimation(
            incoming, 
            {
                keyframe: offsetArray.keyframe,
                property: mstransform,
                delay: 0,
                duration: 550,
                timing: "cubic-bezier(0.1, 0.9, 0.2, 1)",
                from: offsetArray.keyframe || translateCallback(offsetArray),
                to: "none"
        });
        var promise2 = thisWinUI.executeTransition(
            incoming, 
            {
                property: "opacity",
                delay: 0,
                duration: 170,
                timing: "cubic-bezier(0.1, 0.9, 0.2, 1)",
                from: 0,
                to: 1
            });
        return WinJS.Promise.join([promise1, promise2]);
    },

    exitContent: function (outgoing, offset) {
        /// <signature helpKeyword="WinJS.UI.Animation.exitContent">
        /// <summary locid="WinJS.UI.Animation.exitContent">
        /// Execute an exit-content animation.
        /// </summary>
        /// <param name="outgoing" locid="WinJS.UI.Animation.exitContent_p:outgoing">
        /// Single element or collection of elements which represent
        /// the outgoing content.
        /// At the end of the animation, the opacity of the elements is 0.
        /// </param>
        /// <param name="offset" locid="WinJS.UI.Animation.exitContent_p:offset">
        /// Optional offset object or collection of offset objects
        /// array describing the ending point of the animation.
        /// If the number of offset objects is less than the length of the
        /// outgoing parameter, then the last value is repeated for all
        /// remaining elements.
        /// If this parameter is omitted, then a default value is used.
        /// </param>
        /// <returns type="WinJS.Promise" locid="WinJS.UI.Animation.exitContent_returnValue">
        /// Promise object that completes when the animation is complete.
        /// </returns>
        /// </signature>
        var offsetArray = new OffsetArray(offset, "WinJS-exit", [{ top: "0px", left: "0px" }]);
        var promise1 = thisWinUI.executeAnimation(
            outgoing, 
            offset && {
                keyframe: offsetArray.keyframe,
                property: mstransform,
                delay: 0,
                duration: 117,
                timing: "linear",
                from: "none",
                to: offsetArray.keyframe || translateCallback(offsetArray)
            });

        var promise2 = thisWinUI.executeTransition(
            outgoing,
            {
                property: "opacity",
                delay: 0,
                duration: 117,
                timing: "linear",
                to: 0
            }); 
        return WinJS.Promise.join([promise1, promise2]);
    },

    dragBetweenEnter: function (target, offset) {
        /// <signature helpKeyword="WinJS.UI.Animation.dragBetweenEnter">
        /// <summary locid="WinJS.UI.Animation.dragBetweenEnter">
        /// Execute an animation which indicates that a dragged object
        /// can be dropped between other elements.
        /// Use the dragBetweenLeave animation to reverse the effects of this animation.
        /// </summary>
        /// <param name="target" locid="WinJS.UI.Animation.dragBetweenEnter_p:target">
        /// Single element or collection of elements (usually two)
        /// that the dragged object can be dropped between.
        /// At the end of the animation, the elements' properties have been
        /// modified to reflect the drag-between state.
        /// </param>
        /// <param name="offset" locid="WinJS.UI.Animation.dragBetweenEnter_p:offset">
        /// Optional offset object or collection of offset objects
        /// array describing the ending point of the animation.
        /// If the number of offset objects is less than the length of the
        /// element parameter, then the last value is repeated for all
        /// remaining elements.
        /// If this parameter is omitted, then a default value is used.
        /// </param>
        /// <returns type="WinJS.Promise" locid="WinJS.UI.Animation.dragBetweenEnter_returnValue">
        /// Promise object that completes when the animation is complete.
        /// </returns>
        /// </signature>
        var offsetArray = new OffsetArray(offset, null, [{ top: "-40px", left: "0px" }, { top: "40px", left: "0px" }]);
        return thisWinUI.executeTransition(
            target,
            {
                property: mstransform,
                delay: 0,
                duration: 200,
                timing: "cubic-bezier(0.1, 0.9, 0.2, 1)",
                to: translateCallback(offsetArray, "scale(0.95) ")
            });
    },

    dragBetweenLeave: function (target) {
        /// <signature helpKeyword="WinJS.UI.Animation.dragBetweenLeave">
        /// <summary locid="WinJS.UI.Animation.dragBetweenLeave">
        /// Execute an animation which indicates that a dragged object
        /// will no longer be dropped between other elements.
        /// This reverses the effect of the dragBetweenEnter animation.
        /// </summary>
        /// <param name="target" locid="WinJS.UI.Animation.dragBetweenLeave_p:target">
        /// Single element or collection of elements (usually two)
        /// that the dragged object no longer will be dropped between.
        /// At the end of the animation, the elements' properties have been
        /// set to the dragSourceStart state.
        /// </param>
        /// <returns type="WinJS.Promise" locid="WinJS.UI.Animation.dragBetweenLeave_returnValue">
        /// Promise object that completes when the animation is complete.
        /// </returns>
        /// </signature>
        return thisWinUI.executeTransition(
            target,
            {
                property: mstransform,
                delay: 0,
                duration: 200,
                timing: "cubic-bezier(0.1, 0.9, 0.2, 1)",
                to: "scale(0.95)"
            });
    },

    swipeSelect: function (selected, selection) {
        /// <signature helpKeyword="WinJS.UI.Animation.swipeSelect">
        /// <summary locid="WinJS.UI.Animation.swipeSelect">
        /// Slide a swipe-selected object back into position when the
        /// pointer is released, and show the selection mark.
        /// </summary>
        /// <param name="selected" locid="WinJS.UI.Animation.swipeSelect_p:selected">
        /// Single element or collection of elements being selected.
        /// At the end of the animation, the elements' properties have been
        /// returned to normal.
        /// </param>
        /// <param name="selection" locid="WinJS.UI.Animation.swipeSelect_p:selection">
        /// Single element or collection of elements that is the selection mark.
        /// </param>
        /// <returns type="WinJS.Promise" locid="WinJS.UI.Animation.swipeSelect_returnValue">
        /// Promise object that completes when the animation is complete.
        /// </returns>
        /// </signature>
        var promise1 = thisWinUI.executeTransition(
            selected,
            {
                property: mstransform,
                delay: 0,
                duration: 300,
                timing: "cubic-bezier(0.1, 0.9, 0.2, 1)",
                to: ""
            });

        var promise2 = thisWinUI.executeAnimation(
            selection,
            {
                keyframe: "WinJS-opacity-in",
                property: "opacity",
                delay: 0,
                duration: 300,
                timing: "cubic-bezier(0.1, 0.9, 0.2, 1)",
                from: 0,
                to: 1
            });
        return WinJS.Promise.join([promise1, promise2]);
    },

    swipeDeselect: function (deselected, selection) {
        /// <signature helpKeyword="WinJS.UI.Animation.swipeDeselect">
        /// <summary locid="WinJS.UI.Animation.swipeDeselect">
        /// Slide a swipe-deselected object back into position when the
        /// pointer is released, and hide the selection mark.
        /// </summary>
        /// <param name="deselected" locid="WinJS.UI.Animation.swipeDeselect_p:deselected">
        /// Single element or collection of elements being deselected.
        /// At the end of the animation, the elements' properties have been
        /// returned to normal.
        /// </param>
        /// <param name="selection" locid="WinJS.UI.Animation.swipeDeselect_p:selection">
        /// Single element or collection of elements that is the selection mark.
        /// </param>
        /// <returns type="WinJS.Promise" locid="WinJS.UI.Animation.swipeDeselect_returnValue">
        /// Promise object that completes when the animation is complete.
        /// </returns>
        /// </signature>
        var promise1 = thisWinUI.executeTransition(
            deselected,
            {
                property: mstransform,
                delay: 0,
                duration: 300,
                timing: "cubic-bezier(0.1, 0.9, 0.2, 1)",
                to: ""
            });

        var promise2 = thisWinUI.executeAnimation(
            selection,
            {
                keyframe: "WinJS-opacity-out",
                property: "opacity",
                delay: 0,
                duration: 300,
                timing: "cubic-bezier(0.1, 0.9, 0.2, 1)",
                from: 1,
                to: 0
            });
        return WinJS.Promise.join([promise1, promise2]);
    },

    swipeReveal: function (target, offset) {
        /// <signature helpKeyword="WinJS.UI.Animation.swipeReveal">
        /// <summary locid="WinJS.UI.Animation.swipeReveal">
        /// Reveal an object as the result of a swipe, or slide the
        /// swipe-selected object back into position after the reveal.
        /// </summary>
        /// <param name="target" locid="WinJS.UI.Animation.swipeReveal_p:target">
        /// Single element or collection of elements being selected.
        /// At the end of the animation, the elements' properties have been
        /// modified to reflect the specified offset.
        /// </param>
        /// <param name="offset" locid="WinJS.UI.Animation.swipeReveal_p:offset">
        /// Optional offset object or collection of offset objects
        /// array describing the ending point of the animation.
        /// When moving the object back into position, the offset should be
        /// { top: "0px", left: "0px" }.
        /// If the number of offset objects is less than the length of the
        /// element parameter, then the last value is repeated for all
        /// remaining elements.
        /// If this parameter is omitted, then a default value is used.
        /// The default value describes the motion for a reveal.
        /// </param>
        /// <returns type="WinJS.Promise" locid="WinJS.UI.Animation.swipeReveal_returnValue">
        /// Promise object that completes when the animation is complete.
        /// </returns>
        /// </signature>
        var offsetArray = new OffsetArray(offset, null, [{ top: "25px", left: "0px" }]);
        return thisWinUI.executeTransition(
            target,
            {
                property: mstransform,
                delay: 0,
                duration: 300,
                timing: "cubic-bezier(0.1, 0.9, 0.2, 1)",
                to: translateCallback(offsetArray)
            });
    },

    enterPage: function (element, offset) {
        /// <signature helpKeyword="WinJS.UI.Animation.enterPage">
        /// <summary locid="WinJS.UI.Animation.enterPage">
        /// Execute an enterPage animation.
        /// </summary>
        /// <param name="element" locid="WinJS.UI.Animation.enterPage_p:element">
        /// Single element or collection of elements representing the
        /// incoming page.
        /// At the end of the animation, the opacity of the elements is 1.
        /// </param>
        /// <param name="offset" locid="WinJS.UI.Animation.enterPage_p:offset">
        /// Optional offset object or collection of offset objects
        /// array describing the starting point of the animation.
        /// If the number of offset objects is less than the length of the
        /// element parameter, then the last value is repeated for all
        /// remaining elements.
        /// If this parameter is omitted, then a default value is used.
        /// </param>
        /// <returns type="WinJS.Promise" locid="WinJS.UI.Animation.enterPage_returnValue">
        /// Promise object that completes when the animation is complete.
        /// </returns>
        /// </signature>
        var offsetArray;
        if (isSnapped()) {
            offsetArray = new OffsetArray(offset, "WinJS-enterPage-snapped", [{ top: "0px", left: "40px", rtlflip: true }]);
        } else {
            offsetArray = new OffsetArray(offset, "WinJS-enterPage", [{ top: "0px", left: "100px", rtlflip: true }]);
        }
        var promise1 = thisWinUI.executeAnimation(
            element,
            {
                keyframe: offsetArray.keyframe,
                property: mstransform,
                delay: staggerDelay(0, 83, 1, 333),
                duration: 1000,
                timing: "cubic-bezier(0.1, 0.9, 0.2, 1)",
                from: offsetArray.keyframe || translateCallback(offsetArray),
                to: "none"
            });
        var promise2 = thisWinUI.executeTransition(
            element,
            {
                property: "opacity",
                delay: staggerDelay(0, 83, 1, 333),
                duration: 170,
                timing: "cubic-bezier(0.1, 0.9, 0.2, 1)",
                from: 0,
                to: 1
            });
        return WinJS.Promise.join([promise1, promise2]);
    },

    exitPage: function (outgoing, offset) {
        /// <signature helpKeyword="WinJS.UI.Animation.exitPage">
        /// <summary locid="WinJS.UI.Animation.exitPage">
        /// Execute an exitPage animation.
        /// </summary>
        /// <param name="outgoing" locid="WinJS.UI.Animation.exitPage_p:outgoing">
        /// Single element or collection of elements representing
        /// the outgoing page.
        /// At the end of the animation, the opacity of the elements is 0.
        /// </param>
        /// <param name="offset" locid="WinJS.UI.Animation.exitPage_p:offset">
        /// Optional offset object or collection of offset objects
        /// array describing the ending point of the animation.
        /// If the number of offset objects is less than the length of the
        /// outgoing parameter, then the last value is repeated for all
        /// remaining elements.
        /// If this parameter is omitted, then a default value is used.
        /// </param>
        /// <returns type="WinJS.Promise" locid="WinJS.UI.Animation.exitPage_returnValue">
        /// Promise object that completes when the animation is complete.
        /// </returns>
        /// </signature>
        var offsetArray = new OffsetArray(offset, "WinJS-exit", [{ top: "0px", left: "0px" }]);
        var promise1 = thisWinUI.executeAnimation(
            outgoing, 
            offset && {
                keyframe: offsetArray.keyframe,
                property: mstransform,
                delay: 0,
                duration: 117,
                timing: "linear",
                from: "none",
                to: offsetArray.keyframe || translateCallback(offsetArray)
            });

        var promise2 = thisWinUI.executeTransition(
            outgoing,
            {
                property: "opacity",
                delay: 0,
                duration: 117,
                timing: "linear",
                to: 0
            }); 
        return WinJS.Promise.join([promise1, promise2]);
    },

    crossFade: function (incoming, outgoing) {
        /// <signature helpKeyword="WinJS.UI.Animation.crossFade">
        /// <summary locid="WinJS.UI.Animation.crossFade">
        /// Execute a crossFade animation.
        /// </summary>
        /// <param name="incoming" locid="WinJS.UI.Animation.crossFade_p:incoming">
        /// Single incoming element or collection of incoming elements.
        /// At the end of the animation, the opacity of the elements is 1.
        /// </param>
        /// <param name="outgoing" locid="WinJS.UI.Animation.crossFade_p:outgoing">
        /// Single outgoing element or collection of outgoing elements.
        /// At the end of the animation, the opacity of the elements is 0.
        /// </param>
        /// <returns type="WinJS.Promise" locid="WinJS.UI.Animation.crossFade_returnValue">
        /// Promise object that completes when the animation is complete.
        /// </returns>
        /// </signature>
        var promise1 = thisWinUI.executeTransition(
            incoming,
            {
                property: "opacity",
                delay: 0,
                duration: 167,
                timing: "linear",
                to: 1
            });

        var promise2 = thisWinUI.executeTransition(
            outgoing,
            {
                property: "opacity",
                delay: 0,
                duration: 167,
                timing: "linear",
                to: 0
            });
    return WinJS.Promise.join([promise1, promise2]);
    },

    createPeekAnimation: function (element) {
        /// <signature helpKeyword="WinJS.UI.Animation.createPeekAnimation">
        /// <summary locid="WinJS.UI.Animation.createPeekAnimation">
        /// Creates a peek animation.
        /// After creating the PeekAnimation object,
        /// modify the document to move the elements to their new positions,
        /// then call the execute method on the PeekAnimation object.
        /// </summary>
        /// <param name="element" locid="WinJS.UI.Animation.createPeekAnimation_p:element">
        /// Single element or collection of elements to be repositioned for peek.
        /// </param>
        /// <returns type="{ execute: Function }" locid="WinJS.UI.Animation.createPeekAnimation_returnValue">
        /// PeekAnimation object whose execute method returns
        /// a Promise that completes when the animation is complete.
        /// </returns>
        /// </signature>
        return layoutTransition(PeekAnimation, null, element);
    },

    updateBadge: function (incoming, offset) {
        /// <signature helpKeyword="WinJS.UI.Animation.updateBadge">
        /// <summary locid="WinJS.UI.Animation.updateBadge">
        /// Execute an updateBadge animation.
        /// </summary>
        /// <param name="incoming" locid="WinJS.UI.Animation.updateBadge_p:incoming">
        /// Single element or collection of elements representing the
        /// incoming badge.
        /// </param>
        /// <param name="offset" locid="WinJS.UI.Animation.updateBadge_p:offset">
        /// Optional offset object or collection of offset objects
        /// array describing the starting point of the animation.
        /// If the number of offset objects is less than the length of the
        /// incoming parameter, then the last value is repeated for all
        /// remaining elements.
        /// If this parameter is omitted, then a default value is used.
        /// </param>
        /// <returns type="WinJS.Promise" locid="WinJS.UI.Animation.updateBadge_returnValue">
        /// Promise object that completes when the animation is complete.
        /// </returns>
        /// </signature>
        var offsetArray = new OffsetArray(offset, "WinJS-updateBadge", [{ top: "24px", left: "0px" }]);
        return thisWinUI.executeAnimation(
            incoming,
            [{
                keyframe: "WinJS-opacity-in",
                property: "opacity",
                delay: 0,
                duration: 367,
                timing: "cubic-bezier(0.1, 0.9, 0.2, 1)",
                from: 0,
                to: 1
            },
            {
                keyframe: offsetArray.keyframe,
                property: mstransform,
                delay: 0,
                duration: 1333,
                timing: "cubic-bezier(0.1, 0.9, 0.2, 1)",
                from: offsetArray.keyframe || translateCallback(offsetArray),
                to: "none"
            }]);
    }
});

})(WinJS);

/*#DBG
var _ASSERT = function (condition) { 
    if (!condition) { 
        throw "ASSERT FAILED"; 
    } 
};
var _TRACE = function (text) { 
    if (window.console && console.log) {
        console.log(text);
    }
};
#DBG*/


// WinJS.Binding.ListDataSource
//
(function bindingListDataSourceInit(global, undefined) {
    "use strict";


    var errors = {
        get noLongerMeaningful() { return WinJS.Promise.wrapError(new WinJS.ErrorFromName(WinJS.UI.EditError.noLongerMeaningful)); }
    };

    function findNextKey(list, index) {
        var len = list.length;
        while (index < len - 1) {
            var item = list.getItem(++index);
            if (item) {
                return item.key;
            }
        }
        return null;
    }

    function findPreviousKey(list, index) {
        while (index > 0) {
            var item = list.getItem(--index);
            if (item) {
                return item.key;
            }
        }
        return null;
    }

    function subscribe(target, handlers) {
        Object.keys(handlers).forEach(function (handler) {
            target.addEventListener(handler, handlers[handler]);
        });
    }

    function unsubscribe(target, handlers) {
        Object.keys(handlers).forEach(function (handler) {
            target.removeEventListener(handler, handlers[handler]);
        });
    }

    var CompletePromise = WinJS.Promise.wrap().constructor;

    var NullWrappedItem = WinJS.Class.derive(CompletePromise,
        function () {
            this._value = null;
        }, {
            release: function () { },
            retain: function () { return this; }
        }, {
            /* empty */
        }, {
            supportedForProcessing: false,
        }
    );

    var WrappedItem = WinJS.Class.derive(CompletePromise,
        function (listBinding, item) {
            this._value = item;
            this._listBinding = listBinding;
        }, {
            handle: {
                get: function () { return this._value.key; }
            },
            index: {
                get: function () { return this._value.index; }
            },
            release: function () { 
                this._listBinding._release(this._value, this._listBinding._list.indexOfKey(this._value.key));
            },
            retain: function () { 
                this._listBinding._addRef(this._value, this._listBinding._list.indexOfKey(this._value.key));
                return this;
            }
        }, {
            /* empty */
        }, {
            supportedForProcessing: false,
        }
    );

    var AsyncWrappedItem = WinJS.Class.derive(WinJS.Promise, 
        function (listBinding, item) {
            var that = this;
            this._item = item;
            this._listBinding = listBinding;
            WinJS.Promise.call(this, function (c) {
                setImmediate(function () { 
                    if (listBinding._released) {
                        that.cancel();
                        return;
                    }
                    c(item); 
                });
            });
        }, {
            handle: {
                get: function () { return this._item.key; }
            },
            index: {
                get: function () { return this._item.index; }
            },
            release: function () { 
                this._listBinding._release(this._item, this._listBinding._list.indexOfKey(this._item.key));
            },
            retain: function () { 
                this._listBinding._addRef(this._item, this._listBinding._list.indexOfKey(this._item.key));
                return this;
            }
        }, {
            /* empty */
        }, {
            supportedForProcessing: false,
        }
    );

    function wrap(listBinding, item) {
        return item ? new WrappedItem(listBinding, item) : new NullWrappedItem();
    }

    function wrapAsync(listBinding, item) {
        return item ? new AsyncWrappedItem(listBinding, item) : new NullWrappedItem();
    }

    function cloneWithIndex(list, item, index) {
        return item && list._annotateWithIndex(item, index);
    }

    var ListBinding = WinJS.Class.define(
        function ListBinding_ctor(dataSource, list, notificationHandler) {
            this._dataSource = dataSource;
            this._list = list;
            this._editsCount = 0;
            this._notificationHandler = notificationHandler;
            this._pos = -1;
            this._retained = [];
            this._retained.length = list.length;
            this._retainedKeys = {};
            if (this._notificationHandler) {
                var that = this;
                this._handlers = {
                    itemchanged: function (event) {
                        var key = event.detail.key;
                        var index = event.detail.index;
                        var newItem = event.detail.newItem;
                        var oldItem = that._retained[index];
                        if (oldItem) {
                            if (oldItem.index !== index) {
                                var oldIndex = oldItem.index;
                                oldItem.index = index;
                                if (that._notificationHandler.indexChanged) {
                                    that._notificationHandler.indexChanged(newItem.key, index, oldIndex);
                                }
                            }
                            newItem = cloneWithIndex(list, newItem, index);
                            newItem._retainedCount = oldItem._retainedCount;
                            that._retained[index] = newItem;
                            that._retainedKeys[key] = newItem;

                            that._beginEdits(list.length);
                            if (notificationHandler && notificationHandler.changed) {
                                notificationHandler.changed(
                                    newItem,
                                    oldItem
                                );
                            }
                            that._endEdits();
                        }
                    },
                    iteminserted: function (event) {
                        var key = event.detail.key;
                        var index = event.detail.index;
                        that._beginEdits(list.length - 1);
                        if (index <= that._pos) {
                            that._pos = Math.min(that._pos + 1, list.length);
                        }
                        var retained = that._retained;
                        // create a hole for this thing and then immediately make it undefined
                        retained.splice(index, 0, 0);
                        delete retained[index];
                        if (that._shouldNotify(index) || list.length === 1) {
                            if (notificationHandler && notificationHandler.inserted) {
                                notificationHandler.inserted(
                                    wrap(that, cloneWithIndex(list, list.getItem(index), index)),
                                    findPreviousKey(list, index),
                                    findNextKey(list, index)
                                );
                            }
                        }
                        that._endEdits();
                    },
                    itemmoved: function (event) {
                        var key = event.detail.key;
                        var oldIndex = event.detail.oldIndex;
                        var newIndex = event.detail.newIndex;
                        that._beginEdits(list.length);
                        if (oldIndex < that._pos || newIndex <= that._pos) {
                            if (newIndex > that._pos) {
                                that._pos = Math.max(-1, that._pos - 1);
                            } else if (oldIndex > that._pos) {
                                that._pos = Math.min(that._pos + 1, list.length);
                            }
                        }
                        var retained = that._retained;
                        var item = retained.splice(oldIndex, 1)[0];
                        retained.splice(newIndex, 0, item);
                        if (!item) {
                            delete retained[newIndex];
                            item = cloneWithIndex(list, list.getItem(newIndex), newIndex);
                        }
                        item._moved = true;
                        that._addRef(item, newIndex);
                        that._endEdits();
                    },
                    itemremoved: function (event) {
                        var key = event.detail.key;
                        var index = event.detail.index;
                        that._beginEdits(list.length + 1);
                        if (index < that._pos) {
                            that._pos = Math.max(-1, that._pos - 1);
                        }
                        var retained = that._retained;
                        var retainedKeys = that._retainedKeys;
                        var wasRetained = index in retained;
                        retained.splice(index, 1);
                        delete retainedKeys[key];
                        if (wasRetained && notificationHandler && notificationHandler.removed) {
                            notificationHandler.removed(key, false);
                        }
                        that._endEdits();
                    },
                    reload: function () {
                        that._retained = [];
                        that._retainedKeys = {};
                        if (notificationHandler && notificationHandler.reload) {
                            notificationHandler.reload();
                        }
                    }
                };
                subscribe(this._list, this._handlers);
            }
        }, {
            _addRef: function (item, index) {
                if (index in this._retained) {
                    this._retained[index]._retainedCount++;
                } else {
                    this._retained[index] = item;
                    this._retainedKeys[item.key] = item;
                    item._retainedCount = 1;
                }
            },
            _release: function (item, index) {
                var retained = this._retained[index];
                if (retained) {
                    //#DBG _ASSERT(retained.key === item.key);
                    if (retained._retainedCount === 1) {
                        delete this._retained[index];
                        delete this._retainedKeys[retained.key];
                    } else {
                        retained._retainedCount--;
                    }
                }
                /*#DBG
                // If an item isn't found in the retained map, it was either removed from retainedCount reaching zero, or removed from the map by a removed notification.
                // We'll decrement the count here for debugging purposes. If retainedCount is less than zero, there's a refcounting error somewhere.
                if (!retained) {
                    item._retainedCount--;
                    _ASSERT(item._retainedCount >= 0);
                }
               #DBG*/
            },
            _shouldNotify: function (index) {
                var retained = this._retained;
                return index in retained || index + 1 in retained || index - 1 in retained;
            },

            _notifyCountChanged: function () {
                var oldCount = this._countAtBeginEdits;
                var newCount = this._list.length;
                if (oldCount !== newCount) {
                    if (this._notificationHandler && this._notificationHandler.countChanged) {
                        this._notificationHandler.countChanged(newCount, oldCount);
                    }
                }
            },
            _notifyIndicesChanged: function () {
                var retained = this._retained;
                for (var i = 0, len = retained.length; i < len; i++) {
                    var item = retained[i];
                    if (item && item.index !== i) {
                        var newIndex = i;
                        var oldIndex = item.index;
                        item.index = newIndex;
                        if (this._notificationHandler && this._notificationHandler.indexChanged) {
                            this._notificationHandler.indexChanged(item.key, newIndex, oldIndex);
                        }
                    }
                }
            },
            _notifyMoved: function () {
                var retained = this._retained;
                for (var i = 0, len = retained.length; i < len; i++) {
                    var item = retained[i];
                    if (item && item._moved) {
                        item._moved = false;
                        this._release(item, i);
                        if (this._shouldNotify(i)) {
                            if (this._notificationHandler && this._notificationHandler.moved) {
                                this._notificationHandler.moved(
                                    wrap(this, item),
                                    findPreviousKey(this._list, i),
                                    findNextKey(this._list, i)
                                );
                            }
                        }
                    }
                }
            },

            _beginEdits: function (length, explicit) {
                this._editsCount++;
                if (this._editsCount === 1 && this._notificationHandler) {
                    if (!explicit) {
                        // Batch all edits between now and the setImmediate firing. This has the effect
                        // of batching synchronous edits.
                        //
                        this._editsCount++;
                        var that = this;
                        setImmediate(function () {
                            that._endEdits();                            
                        });
                    }
                    if (this._notificationHandler && this._notificationHandler.beginNotifications) {
                        this._notificationHandler.beginNotifications();
                    }
                    this._countAtBeginEdits = length;
                }
            },
            _endEdits: function () {
                this._editsCount--;
                if (this._editsCount === 0 && this._notificationHandler) {
                    this._notifyIndicesChanged();
                    this._notifyMoved();
                    this._notifyCountChanged();
                    if (this._notificationHandler && this._notificationHandler.endNotifications) {
                        this._notificationHandler.endNotifications();
                    }
                }
            },

            jumpToItem: function (item) {
                var index = this._list.indexOfKey(item.handle);
                if (index === -1) {
                    return WinJS.Promise.wrap(null);
                }
                this._pos = index;
                return this.current();
            },
            current: function () {
                return this.fromIndex(this._pos);
            },
            previous: function () {
                this._pos = Math.max(-1, this._pos - 1);
                return this._fromIndex(this._pos, true);
            },
            next: function () {
                this._pos = Math.min(this._pos + 1, this._list.length);
                return this._fromIndex(this._pos, true);
            },
            releaseItem: function (item) { 
                if (item.release) {
                    item.release();
                } else {
                    this._release(item, this._list.indexOfKey(item.key));
                }
            },
            release: function () {
                if (this._notificationHandler) {
                    unsubscribe(this._list, this._handlers);
                }
                this._notificationHandler = null;
                this._dataSource._releaseBinding(this);
                this._released = true;
            },
            first: function () {
                return this.fromIndex(0);
            },
            last: function () {
                return this.fromIndex(this._list.length - 1);
            },
            fromKey: function (key) {
                var retainedKeys = this._retainedKeys;
                var item;
                if (key in retainedKeys) {
                    item = retainedKeys[key];
                } else {
                    item = cloneWithIndex(this._list, this._list.getItemFromKey(key), this._list.indexOfKey(key));
                }
                return wrap(this, item);
            },
            fromIndex: function (index) {
                return this._fromIndex(index, false);
            },
            _fromIndex: function (index, async) {
                var retained = this._retained;
                var item;
                if (index in retained) {
                    item = retained[index];
                } else {
                    item = cloneWithIndex(this._list, this._list.getItem(index), index);
                }
                return async ? wrapAsync(this, item) : wrap(this, item);
            },
        }, {
            supportedForProcessing: false,
        }
    );

    function insertAtStart(unused, data) {
        // List ignores the key because its key management is internal
        this._list.unshift(data);
        return this.itemFromIndex(0);
    }
    function insertBefore(unused, data, nextKey) {
        // List ignores the key because its key management is internal
        var index = this._list.indexOfKey(nextKey);
        if (index === -1) {
            return errors.noLongerMeaningful;
        }
        this._list.splice(index, 0, data);
        return this.itemFromIndex(index);
    }
    function insertAfter(unused, data, previousKey) {
        // List ignores the key because its key management is internal
        var index = this._list.indexOfKey(previousKey);
        if (index === -1) {
            return errors.noLongerMeaningful;
        }
        index += 1;
        this._list.splice(index, 0, data);
        return this.itemFromIndex(index);
    }
    function insertAtEnd(unused, data) {
        // List ignores the key because its key management is internal
        this._list.push(data);
        return this.itemFromIndex(this._list.length - 1);
    }
    function change(key, newData) {
        var index = this._list.indexOfKey(key);
        if (index === -1) {
            return errors.noLongerMeaningful;
        }
        this._list.setAt(index, newData);
        return this.itemFromIndex(index);
    }
    function moveToStart(key) {
        var sourceIndex = this._list.indexOfKey(key);
        if (sourceIndex === -1) {
            return errors.noLongerMeaningful;
        }
        var targetIndex = 0;
        this._list.move(sourceIndex, targetIndex);
        return this.itemFromIndex(targetIndex);
    }
    function moveBefore(key, nextKey) {
        var sourceIndex = this._list.indexOfKey(key);
        var targetIndex = this._list.indexOfKey(nextKey);
        if (sourceIndex === -1 || targetIndex === -1) {
            return errors.noLongerMeaningful;
        }
        targetIndex = sourceIndex < targetIndex ? targetIndex - 1 : targetIndex;
        this._list.move(sourceIndex, targetIndex);
        return this.itemFromIndex(targetIndex);
    }
    function moveAfter(key, previousKey) {
        var sourceIndex = this._list.indexOfKey(key);
        var targetIndex = this._list.indexOfKey(previousKey);
        if (sourceIndex === -1 || targetIndex === -1) {
            return errors.noLongerMeaningful;
        }
        targetIndex = sourceIndex <= targetIndex ? targetIndex : targetIndex + 1;
        this._list.move(sourceIndex, targetIndex);
        return this.itemFromIndex(targetIndex);
    }
    function moveToEnd(key) {
        var sourceIndex = this._list.indexOfKey(key);
        if (sourceIndex === -1) {
            return errors.noLongerMeaningful;
        }
        var targetIndex = this._list.length - 1;
        this._list.move(sourceIndex, targetIndex);
        return this.itemFromIndex(targetIndex);
    }
    function remove(key) {
        var index = this._list.indexOfKey(key);
        if (index === -1) {
            return errors.noLongerMeaningful;
        }
        this._list.splice(index, 1);
        return WinJS.Promise.wrap();
    }

    var bindingId = 0;
    var DataSource = WinJS.Class.define(
        function DataSource_ctor(list) {
            this._bindings = [];
            this._list = list;

            if (list.unshift) {
                this.insertAtStart = insertAtStart;
            }
            if (list.push) {
                this.insertAtEnd = insertAtEnd;
            }
            if (list.setAt) {
                this.change = change;
            }
            if (list.splice) {
                this.insertAfter = insertAfter;
                this.insertBefore = insertBefore;
                this.remove = remove;
            }
            if (list.move) {
                this.moveAfter = moveAfter;
                this.moveBefore = moveBefore;
                this.moveToEnd = moveToEnd;
                this.moveToStart = moveToStart;
            }
        }, {
            _releaseBinding: function (binding) {
                delete this._bindings[binding._id];
            },

            addEventListener: function () {
                // nop, we don't send statusChanged
            },
            removeEventListener: function () {
                // nop, we don't send statusChanged
            },

            createListBinding: function (notificationHandler) {
                var binding = new ListBinding(this, this._list, notificationHandler);
                binding._id = (++bindingId);
                this._bindings[binding._id] = binding;
                return binding;
            },

            getCount: function () {
                return WinJS.Promise.wrap(this._list.length);
            },

            itemFromKey: function (key) {
                // Clone with a dummy index
                var list = this._list,
                    item = cloneWithIndex(list, list.getItemFromKey(key), -1);

                // Override the index property with a getter
                Object.defineProperty(item, "index", {
                    get: function () {
                        return list.indexOfKey(key);
                    },
                    enumerable: false,
                    configurable: true
                });

                return WinJS.Promise.wrap(item);
            },
            itemFromIndex: function (index) {
                return WinJS.Promise.wrap(cloneWithIndex(this._list, this._list.getItem(index), index));
            },

            list: {
                get: function () { return this._list; }
            },

            beginEdits: function () {
                var length = this._list.length;
                this._bindings.forEach(function (binding) {
                    binding._beginEdits(length, true);
                });
            },
            endEdits: function () {
                this._bindings.forEach(function (binding) {
                    binding._endEdits();
                });
            },

            invalidateAll: function() {
                return WinJS.Promise.wrap();
            },

            //
            // insert* and change are not implemented as I don't understand how they are 
            //  used by the controls since it is hard to fathom how they would be able
            //  to make up unique keys. Manual editing of the List is meant to go through
            //  the list itself.
            //
            // move* are implemented only if the underlying list supports move(). The 
            //  GroupsListProjection for instance does not.
            //
            moveAfter: undefined,
            moveBefore: undefined,
            moveToEnd: undefined,
            moveToStart: undefined

        }, {
            supportedForProcessing: false,
        }
    );

    if (WinJS.Binding && WinJS.Binding.List) {
        Object.defineProperty(Object.getPrototypeOf(Object.getPrototypeOf(WinJS.Binding.List.prototype)), "dataSource", {
            get: function () { return (this._dataSource = this._dataSource || new DataSource(this)); }
        });
    }

}(this));

// Virtualized Data Source

(function listDataSourceInit(undefined) {
    "use strict";


var Promise = WinJS.Promise,
    Signal = WinJS._Signal,
    UI = WinJS.UI;

// Private statics

var strings = {
    get listDataAdapterIsInvalid() { return WinJS.Resources._getWinJSString("ui/listDataAdapterIsInvalid").value; },
    get indexIsInvalid() { return WinJS.Resources._getWinJSString("ui/indexIsInvalid").value; },
    get keyIsInvalid() { return WinJS.Resources._getWinJSString("ui/keyIsInvalid").value; },
    get invalidItemReturned() { return WinJS.Resources._getWinJSString("ui/undefinedItemReturned").value; },
    get invalidKeyReturned() { return WinJS.Resources._getWinJSString("ui/invalidKeyReturned").value; },
    get invalidIndexReturned() { return WinJS.Resources._getWinJSString("ui/invalidIndexReturned").value; },
    get invalidCountReturned() { return WinJS.Resources._getWinJSString("ui/invalidCountReturned").value; },
    get invalidRequestedCountReturned() { return WinJS.Resources._getWinJSString("ui/invalidRequestedCountReturned").value; },
};

var statusChangedEvent = "statuschanged";

function _baseDataSourceConstructor(listDataAdapter, options) {
    /// <signature helpKeyword="WinJS.UI.VirtualizedDataSource._baseDataSourceConstructor">
    /// <summary locid="WinJS.UI.VirtualizedDataSource._baseDataSourceConstructor">
    /// Initializes the VirtualizedDataSource base class of a custom data source.
    /// </summary>
    /// <param name="listDataAdapter" type="IListDataAdapter" locid="WinJS.UI.VirtualizedDataSource._baseDataSourceConstructor_p:itemIndex">
    /// An object that implements IListDataAdapter and supplies data to the VirtualizedDataSource.
    /// </param>
    /// <param name="options" optional="true" type="Object" locid="WinJS.UI.VirtualizedDataSource._baseDataSourceConstructor_p:options">
    /// An object that contains properties that specify additonal options for the VirtualizedDataSource:
    /// 
    /// cacheSize
    /// A Number that specifies minimum number of unrequested items to cache in case they are requested.
    /// 
    /// The options parameter is optional.
    /// </param>
    /// </signature>

    // Private members

    var listDataNotificationHandler,
        cacheSize,
        status,
        statusPending,
        statusChangePosted,
        bindingMap,
        nextListBindingID,
        nextHandle,
        nextListenerID,
        getCountPromise,
        resultsProcessed,
        beginEditsCalled,
        editsInProgress,
        firstEditInProgress,
        editQueue,
        editsQueued,
        synchronousEdit,
        waitForRefresh,
        dataNotificationsInProgress,
        countDelta,
        indexUpdateDeferred,
        nextTempKey,
        currentRefreshID,
        fetchesPosted,
        nextFetchID,
        fetchesInProgress,
        fetchCompleteCallbacks,
        startMarker,
        endMarker,
        knownCount,
        slotsStart,
        slotListEnd,
        slotsEnd,
        handleMap,
        keyMap,
        indexMap,
        releasedSlots,
        lastSlotReleased,
        reduceReleasedSlotCountPosted,
        refreshRequested,
        refreshInProgress,
        refreshSignal,
        refreshFetchesInProgress,
        refreshItemsFetched,
        refreshCount,
        refreshStart,
        refreshEnd,
        keyFetchIDs,
        refreshKeyMap,
        refreshIndexMap,
        deletedKeys,
        synchronousProgress,
        reentrantContinue,
        synchronousRefresh,
        reentrantRefresh;

    /*#DBG

    var totalSlots = 0;

    function VERIFYLIST() {
        _ASSERT(slotListEnd.lastInSequence);
        _ASSERT(slotsEnd.firstInSequence);
        checkListIntegrity(slotsStart, slotsEnd, keyMap, indexMap);
    }

    function VERIFYREFRESHLIST() {
        checkListIntegrity(refreshStart, refreshEnd, refreshKeyMap, refreshIndexMap);
    }

    function checkListIntegrity(listStart, listEnd, keyMapForSlot, indexMapForSlot) {
        if (UI.VirtualizedDataSource._internalValidation) {
            var listEndReached,
                slotWithoutIndexReached;
            for (var slotCheck = listStart; slotCheck !== listEnd; slotCheck = slotCheck.next) {
                _ASSERT(slotCheck.next);
                _ASSERT(slotCheck.next.prev === slotCheck);
                if (slotCheck.lastInSequence) {
                    _ASSERT(slotCheck.next.firstInSequence);
                }

                if (slotCheck !== listStart) {
                    _ASSERT(slotCheck.prev);
                    _ASSERT(slotCheck.prev.next === slotCheck);
                    if (slotCheck.firstInSequence) {
                        _ASSERT(slotCheck.prev.lastInSequence);
                    }
                }

                if (slotCheck.item || slotCheck.itemNew) {
                    _ASSERT(editsQueued || slotCheck.key);
                }

                if (slotCheck.key) {
                    _ASSERT(keyMapForSlot[slotCheck.key] === slotCheck);

                    if (slotCheck.item) {
                        _ASSERT(slotCheck.item.key === slotCheck.key);
                    }
                }

                if (typeof slotCheck.index === "number") {
                    _ASSERT(!listEndReached);

                    if (!indexUpdateDeferred) {
                        _ASSERT(indexMapForSlot[slotCheck.index] === slotCheck);
                        _ASSERT(slotCheck === listStart || slotCheck.prev.index < slotCheck.index);
                        _ASSERT(!slotCheck.firstInSequence || !slotCheck.prev || slotCheck.prev.index !== slotCheck.index - 1);
                        _ASSERT(!slotCheck.lastInSequence || !slotCheck.next || slotCheck.next.index !== slotCheck.index + 1);

                        if (slotCheck.item) {
                            _ASSERT(listStart === refreshStart || slotCheck.item.index === slotCheck.index);
                        }
                    }
                } else {
                    slotWithoutIndexReached = true;
                }

                if (slotCheck === slotListEnd) {
                    listEndReached = true;
                }

                if (slotCheck.lastInSequence && !listEndReached && !indexUpdateDeferred) {
                    _ASSERT(!slotWithoutIndexReached);
                }
            }
        }
    }

    function OUTPUTLIST() {
        outputList("Main List", slotsStart);
    }

    function OUTPUTREFRESHLIST() {
        outputList("Refresh List", refreshStart);
    }

    function outputList(header, slotFirst) {
        _TRACE("-- " + header + " --");

        for (var slot = slotFirst; slot; slot = slot.next) {
            var line = (slot.firstInSequence ? "[" : " ");

            if (slot.index !== undefined && slot !== slotsStart && slot !== refreshStart) {
                line += slot.index + ": ";
            }

            if (slot === slotsStart || slot === refreshStart) {
                line += "{";
            } else if (slot === slotListEnd || slot === refreshEnd) {
                line += "}";
            } else if (slot === slotsEnd) {
                line += "-";
            } else {
                line += (slot.key ? '"' + slot.key + '"' : "?");
            }

            if (slot.bindingMap) {
                line += " (";
                var first = true;
                for (var listBindingID in slot.bindingMap) {
                    if (first) {
                        first = false;
                    } else {
                        line += ", ";
                    }

                    line += listBindingID;
                }
                line += ")";
            }

            if (slot.itemNew) {
                line += " itemNew";
            }

            if (slot.item) {
                line += " item";
            }

            if (slot.fetchListeners) {
                line += " fetching";
            }

            if (slot.directFetchListeners) {
                line += " directFetching";
            }

            if (slot.indexRequested) {
                line += " index";
            }

            if (slot.keyRequested) {
                line += " key";
            }

            if (slot.description) {
                line += " description=" + JSON.stringify(slot.description);
            }

            if (slotFetchInProgress(slot)) {
                line += " now";
            }

            if (typeof slot.handle === "string") {
                line += " <" + slot.handle + ">";
            }

            if (slot.lastInSequence) {
                line += "]";
            }

            _TRACE(line);
        }
    }

    #DBG*/

    function isNonNegativeNumber(n) {
        return (typeof n === "number") && n >= 0;
    }

    function isNonNegativeInteger(n) {
        return isNonNegativeNumber(n) && n === Math.floor(n);
    }

    function validateIndexReturned(index) {
        // Ensure that index is always undefined or a non-negative integer
        if (index === null) {
            index = undefined;
        } else if (index !== undefined && !isNonNegativeInteger(index)) {
            throw new WinJS.ErrorFromName("WinJS.UI.ListDataSource.InvalidIndexReturned", strings.invalidIndexReturned);
        }

        return index;
    }

    function validateCountReturned(count) {
        // Ensure that count is always undefined or a non-negative integer
        if (count === null) {
            count = undefined;
        } else if (count !== undefined && !isNonNegativeInteger(count) && count !== CountResult.unknown) {
            throw new WinJS.ErrorFromName("WinJS.UI.ListDataSource.InvalidCountReturned", strings.invalidCountReturned);
        }

        return count;
    }

    // Slot List

    function createSlot() {
        var handle = (nextHandle++).toString(), 
            slotNew = {
                handle: handle,
                item: null,
                itemNew: null,
                fetchListeners: null,
                cursorCount: 0,
                bindingMap: null
            };

        // Deliberately not initialized:
        //   - directFetchListeners

        handleMap[handle] = slotNew;

        return slotNew;
    }

    function createPrimarySlot() {
        /*#DBG
        totalSlots++;
        #DBG*/

        return createSlot();
    }

    function insertSlot(slot, slotNext) {
        //#DBG _ASSERT(slotNext);
        //#DBG _ASSERT(slotNext.prev);

        slot.prev = slotNext.prev;
        slot.next = slotNext;

        slot.prev.next = slot;
        slotNext.prev = slot;
    }

    function removeSlot(slot) {
        //#DBG _ASSERT(slot.prev.next === slot);
        //#DBG _ASSERT(slot.next.prev === slot);
        //#DBG _ASSERT(slot !== slotsStart && slot !== slotListEnd && slot !== slotsEnd);

        if (slot.lastInSequence) {
            delete slot.lastInSequence;
            slot.prev.lastInSequence = true;
        }
        if (slot.firstInSequence) {
            delete slot.firstInSequence;
            slot.next.firstInSequence = true;
        }
        slot.prev.next = slot.next;
        slot.next.prev = slot.prev;
    }

    function sequenceStart(slot) {
        while (!slot.firstInSequence) {
            slot = slot.prev;
        }

        return slot;
    }

    function sequenceEnd(slot) {
        while (!slot.lastInSequence) {
            slot = slot.next;
        }

        return slot;
    }

    // Does a little careful surgery to the slot sequence from slotFirst to slotLast before slotNext
    function moveSequenceBefore(slotNext, slotFirst, slotLast) {
        //#DBG _ASSERT(slotFirst !== slotsStart && slotLast !== slotListEnd && slotLast !== slotsEnd);
        //#DBG _ASSERT(slotFirst.firstInSequence && slotLast.lastInSequence);
        //#DBG _ASSERT(slotNext.firstInSequence && slotNext.prev.lastInSequence);

        slotFirst.prev.next = slotLast.next;
        slotLast.next.prev = slotFirst.prev;

        slotFirst.prev = slotNext.prev;
        slotLast.next = slotNext;

        slotFirst.prev.next = slotFirst;
        slotNext.prev = slotLast;

        return true;
    }

    // Does a little careful surgery to the slot sequence from slotFirst to slotLast after slotPrev
    function moveSequenceAfter(slotPrev, slotFirst, slotLast) {
        //#DBG _ASSERT(slotFirst !== slotsStart && slotLast !== slotsEnd);
        //#DBG _ASSERT(slotFirst.firstInSequence && slotLast.lastInSequence);
        //#DBG _ASSERT(slotPrev.lastInSequence && slotPrev.next.firstInSequence);

        slotFirst.prev.next = slotLast.next;
        slotLast.next.prev = slotFirst.prev;

        slotFirst.prev = slotPrev;
        slotLast.next = slotPrev.next;

        slotPrev.next = slotFirst;
        slotLast.next.prev = slotLast;

        return true;
    }

    function mergeSequences(slotPrev) {
        delete slotPrev.lastInSequence;
        delete slotPrev.next.firstInSequence;
    }

    function splitSequence(slotPrev) {
        var slotNext = slotPrev.next;

        slotPrev.lastInSequence = true;
        slotNext.firstInSequence = true;

        if (slotNext === slotListEnd) {
            // Clear slotListEnd's index, as that's now unknown
            changeSlotIndex(slotListEnd, undefined);
        }
    }

    // Inserts a slot in the middle of a sequence or between sequences.  If the latter, mergeWithPrev and mergeWithNext
    // parameters specify whether to merge the slot with the previous sequence, or next, or neither.
    function insertAndMergeSlot(slot, slotNext, mergeWithPrev, mergeWithNext) {
        insertSlot(slot, slotNext);

        var slotPrev = slot.prev;

        if (slotPrev.lastInSequence) {
            //#DBG _ASSERT(slotNext.firstInSequence);

            if (mergeWithPrev) {
                delete slotPrev.lastInSequence;
            } else {
                slot.firstInSequence = true;
            }

            if (mergeWithNext) {
                delete slotNext.firstInSequence;
            } else {
                slot.lastInSequence = true;
            }
        }
    }

    // Keys and Indices

    function setSlotKey(slot, key) {
        //#DBG _ASSERT(!slot.key);
        //#DBG _ASSERT(!keyMap[key]);

        slot.key = key;

        // Add the slot to the keyMap, so it is possible to quickly find the slot given its key
        keyMap[slot.key] = slot;
    }

    function setSlotIndex(slot, index, indexMapForSlot) {
        // Tolerate NaN, so clients can pass (undefined - 1) or (undefined + 1)
        if (+index === index) {
            //#DBG _ASSERT(indexUpdateDeferred || !indexMapForSlot[index]);

            slot.index = index;

            // Add the slot to the indexMap, so it is possible to quickly find the slot given its index
            indexMapForSlot[index] = slot;

            if (!indexUpdateDeferred) {
                // See if any sequences should be merged
                if (slot.firstInSequence && slot.prev && slot.prev.index === index - 1) {
                    mergeSequences(slot.prev);
                }
                if (slot.lastInSequence && slot.next && slot.next.index === index + 1) {
                    mergeSequences(slot);
                }
            }
        }
    }

    // Creates a new slot and adds it to the slot list before slotNext
    function createAndAddSlot(slotNext, indexMapForSlot) {
        var slotNew = (indexMapForSlot === indexMap ? createPrimarySlot() : createSlot());

        insertSlot(slotNew, slotNext);

        return slotNew;
    }

    function createSlotSequence(slotNext, index, indexMapForSlot) {
        //#DBG _ASSERT(slotNext.prev.lastInSequence);
        //#DBG _ASSERT(slotNext.firstInSequence);

        var slotNew = createAndAddSlot(slotNext, indexMapForSlot);

        slotNew.firstInSequence = true;
        slotNew.lastInSequence = true;

        setSlotIndex(slotNew, index, indexMapForSlot);

        return slotNew;
    }

    function createPrimarySlotSequence(slotNext, index) {
        return createSlotSequence(slotNext, index, indexMap);
    }

    function addSlotBefore(slotNext, indexMapForSlot) {
        //#DBG _ASSERT(slotNext.firstInSequence);
        //#DBG _ASSERT(slotNext.prev.lastInSequence);
        var slotNew = createAndAddSlot(slotNext, indexMapForSlot);
        delete slotNext.firstInSequence;

        // See if we've bumped into the previous sequence
        if (slotNew.prev.index === slotNew.index - 1) {
            delete slotNew.prev.lastInSequence;
        } else {
            slotNew.firstInSequence = true;
        }

        setSlotIndex(slotNew, slotNext.index - 1, indexMapForSlot);

        return slotNew;
    }

    function addSlotAfter(slotPrev, indexMapForSlot) {
        //#DBG _ASSERT(slotPrev !== slotListEnd);
        //#DBG _ASSERT(slotPrev.lastInSequence);
        //#DBG _ASSERT(slotPrev.next.firstInSequence);
        var slotNew = createAndAddSlot(slotPrev.next, indexMapForSlot);
        delete slotPrev.lastInSequence;

        // See if we've bumped into the next sequence
        if (slotNew.next.index === slotNew.index + 1) {
            delete slotNew.next.firstInSequence;
        } else {
            slotNew.lastInSequence = true;
        }

        setSlotIndex(slotNew, slotPrev.index + 1, indexMapForSlot);

        return slotNew;
    }

    function reinsertSlot(slot, slotNext, mergeWithPrev, mergeWithNext) {
        insertAndMergeSlot(slot, slotNext, mergeWithPrev, mergeWithNext);
        //#DBG _ASSERT(!keyMap[slot.key]);
        keyMap[slot.key] = slot;
        var index = slot.index;
        if (slot.index !== undefined) {
            indexMap[slot.index] = slot;
        }
    }

    function removeSlotPermanently(slot) {
        /*#DBG
        _ASSERT(totalSlots > 0);
        totalSlots--;
        #DBG*/

        removeSlot(slot);

        if (slot.key) {
            delete keyMap[slot.key];
        }
        if (slot.index !== undefined && indexMap[slot.index] === slot) {
            delete indexMap[slot.index];
        }

        var bindingMap = slot.bindingMap;
        for (var listBindingID in bindingMap) {
            var handle = bindingMap[listBindingID].handle;
            if (handle && handleMap[handle] === slot) {
                delete handleMap[handle];
            }
        }

        // Invalidating the slot's handle marks it as deleted
        if (handleMap[slot.handle] === slot) {
            delete handleMap[slot.handle];
        }
    }

    function slotPermanentlyRemoved(slot) {
        return !handleMap[slot.handle];
    }

    function successorFromIndex(index, indexMapForSlot, listStart, listEnd, skipPreviousIndex) {
        //#DBG _ASSERT(index !== undefined);

        // Try the previous index
        var slotNext = (skipPreviousIndex ? null : indexMapForSlot[index - 1]);
        if (slotNext && (slotNext.next !== listEnd || listEnd.firstInSequence)) {
            // We want the successor
            slotNext = slotNext.next;
        } else {
            // Try the next index
            slotNext = indexMapForSlot[index + 1];
            if (!slotNext) {
                // Resort to a linear search
                slotNext = listStart.next;
                var lastSequenceStart;
                while (true) {
                    //#DBG _ASSERT(slotNext);
                    //#DBG _ASSERT(slotNext.index !== index);

                    if (slotNext.firstInSequence) {
                        lastSequenceStart = slotNext;
                    }

                    if (!(index >= slotNext.index) || slotNext === listEnd) {
                        break;
                    }

                    slotNext = slotNext.next;
                }

                if (slotNext === listEnd && !listEnd.firstInSequence) {
                    // Return the last insertion point between sequences, or undefined if none
                    slotNext = (lastSequenceStart && lastSequenceStart.index === undefined ? lastSequenceStart : undefined);
                }
            }
        }

        return slotNext;
    }

    // Slot Items

    function isPlaceholder(slot) {
        //#DBG _ASSERT(slot !== slotsStart && slot !== slotsEnd);
        return !slot.item && !slot.itemNew && slot !== slotListEnd;
    }

    function defineHandleProperty(item, handle) {
        Object.defineProperty(item, "handle", {
            value: handle,
            writable: false,
            enumerable: false,
            configurable: true
        });
    }

    function defineCommonItemProperties(item, slot, handle) {
        defineHandleProperty(item, handle);

        Object.defineProperty(item, "index", {
            get: function () {
                while (slot.slotMergedWith) {
                    slot = slot.slotMergedWith;
                }

                return slot.index;
            },
            enumerable: false,
            configurable: true
        });
    }

    function validateData(data) {
        if (data === undefined) {
            return data;
        } else {
            // Convert the data object to JSON to enforce the constraints we want.  For example, we don't want
            // functions, arrays with extra properties, DOM objects, cyclic or acyclic graphs, or undefined values.
            var dataValidated = JSON.stringify(data);

            if (dataValidated === undefined) {
                throw new WinJS.ErrorFromName("WinJS.UI.ListDataSource.ObjectIsNotValidJson", strings.objectIsNotValidJson);
            }

            return dataValidated;
        }
    }

    function itemSignature(item) {
        return (
            listDataAdapter.itemSignature ?
                listDataAdapter.itemSignature(item.data) :
                validateData(item.data)
        );
    }

    function prepareSlotItem(slot) {
        var item = slot.itemNew;
        slot.itemNew = null;

        if (item) {
            defineCommonItemProperties(item, slot, slot.handle);
        
            if (!listDataAdapter.compareByIdentity) {
                // Store the item signature or a stringified copy of the data for comparison later
                slot.signature = itemSignature(item);
            }
        }

        slot.item = item;

        delete slot.indexRequested;
        delete slot.keyRequested;
    }

    // Slot Caching

    function slotRetained(slot) {
        return slot.bindingMap || slot.cursorCount > 0;
    }

    function slotRequested(slot) {
        return slotRetained(slot) || slot.fetchListeners || slot.directFetchListeners;
    }

    function slotLive(slot) {
        return slotRequested(slot) || (!slot.firstInSequence && slotRetained(slot.prev)) || (!slot.lastInSequence && slotRetained(slot.next)) ||
            (!listDataAdapter.itemsFromIndex && (
                (!slot.firstInSequence && slot.prev !== slotsStart && !(slot.prev.item || slot.prev.itemNew)) |
                (!slot.lastInSequence && slot.next !== slotListEnd && !(slot.next.item || slot.next.itemNew))
            ));
    }

    function deleteUnnecessarySlot(slot) {
        splitSequence(slot);
        removeSlotPermanently(slot);
    }

    function reduceReleasedSlotCount() {
        // Must not release slots while edits are queued, as undo queue might refer to them
        if (!editsQueued) {
            // If lastSlotReleased is no longer valid, use the end of the list instead
            if (!lastSlotReleased || slotPermanentlyRemoved(lastSlotReleased)) {
                lastSlotReleased = slotListEnd.prev;
            }

            // Now use the simple heuristic of walking outwards in both directions from lastSlotReleased until the
            // desired cache size is reached, then removing everything else.
            var slotPrev = lastSlotReleased.prev,
                slotNext = lastSlotReleased.next,
                releasedSlotsFound = 0;

            var considerDeletingSlot = function (slotToDelete) {
                if (slotToDelete !== slotListEnd && !slotLive(slotToDelete)) {
                    if (releasedSlotsFound <= cacheSize) {
                        releasedSlotsFound++;
                    } else {
                        deleteUnnecessarySlot(slotToDelete);
                    }
                }
            }

            while (slotPrev || slotNext) {
                if (slotPrev) {
                    var slotPrevToDelete = slotPrev;
                    slotPrev = slotPrevToDelete.prev;
                    if (slotPrevToDelete !== slotsStart) {
                        considerDeletingSlot(slotPrevToDelete);
                    }
                }
                if (slotNext) {
                    var slotNextToDelete = slotNext;
                    slotNext = slotNextToDelete.next;
                    if (slotNextToDelete !== slotsEnd) {
                        considerDeletingSlot(slotNextToDelete);
                    }
                }
            }

            // Reset the count to zero, so this method is only called periodically
            releasedSlots = 0;
        }
    }

    function releaseSlotIfUnrequested(slot) {
        if (!slotRequested(slot)) {
            if (UI._PerfMeasurement_leakSlots) {
                return;
            }

            releasedSlots++;

            // Must not release slots while edits are queued, as undo queue might refer to them.  If a refresh is in
            // progress, retain all slots, just in case the user re-requests some of them before the refresh completes.
            if (!editsQueued && !refreshInProgress) {
                // Track which slot was released most recently
                lastSlotReleased = slot;

                // See if the number of released slots has exceeded the cache size.  In practice there will be more
                // live slots than retained slots, so this is just a heuristic to periodically shrink the cache.
                if (releasedSlots > cacheSize && !reduceReleasedSlotCountPosted) {
                    reduceReleasedSlotCountPosted = true;
                    setImmediate(function () {
                        reduceReleasedSlotCountPosted = false;
                        reduceReleasedSlotCount();
                    });
                }
            }
        }
    }
    
    // Notifications
    
    function forEachBindingRecord(callback) {
        for (var listBindingID in bindingMap) {
            callback(bindingMap[listBindingID]);
        }
    }

    function forEachBindingRecordOfSlot(slot, callback) {
        for (var listBindingID in slot.bindingMap) {
            callback(slot.bindingMap[listBindingID].bindingRecord, listBindingID);
        }
    }

    function handlerToNotify(bindingRecord) {
        //#DBG _ASSERT(bindingRecord.notificationHandler);

        if (!bindingRecord.notificationsSent) {
            bindingRecord.notificationsSent = true;

            if (bindingRecord.notificationHandler.beginNotifications) {
                bindingRecord.notificationHandler.beginNotifications();
            }
        }
        return bindingRecord.notificationHandler;
    }

    function finishNotifications() {
        if (!editsInProgress && !dataNotificationsInProgress) {
            forEachBindingRecord(function (bindingRecord) {
                if (bindingRecord.notificationsSent) {
                    //#DBG _ASSERT(bindingRecord.notificationHandler);

                    bindingRecord.notificationsSent = false;

                    if (bindingRecord.notificationHandler.endNotifications) {
                        bindingRecord.notificationHandler.endNotifications();
                    }
                }
            });
        }
    }

    function handleForBinding(slot, listBindingID) {
        var bindingMap = slot.bindingMap;
        if (bindingMap) {
            var slotBinding = bindingMap[listBindingID];
            if (slotBinding) {
                var handle = slotBinding.handle;
                if (handle) {
                    return handle;
                }
            }
        }
        return slot.handle;
    }

    function itemForBinding(item, handle) {
        if (item && item.handle !== handle) {
            item = Object.create(item);
            defineHandleProperty(item, handle);
        }
        return item;
    }

    function changeCount(count) {
        var oldCount = knownCount;
        knownCount = count;

        forEachBindingRecord(function (bindingRecord) {
            if (bindingRecord.notificationHandler && bindingRecord.notificationHandler.countChanged) {
                handlerToNotify(bindingRecord).countChanged(knownCount, oldCount);
            }
        });
    }

    function sendIndexChangedNotifications(slot, indexOld) {
        forEachBindingRecordOfSlot(slot, function (bindingRecord, listBindingID) {
            //#DBG _ASSERT(bindingRecord.notificationHandler);
            if (bindingRecord.notificationHandler.indexChanged) {
                handlerToNotify(bindingRecord).indexChanged(handleForBinding(slot, listBindingID), slot.index, indexOld);
            }
        });
    }

    function changeSlotIndex(slot, index) {
        //#DBG _ASSERT(indexUpdateDeferred || ((typeof slot.index !== "number" || indexMap[slot.index] === slot) && !indexMap[index]));

        var indexOld = slot.index;

        if (indexOld !== undefined && indexMap[indexOld] === slot) {
            // Remove the slot's old index from the indexMap
            delete indexMap[indexOld];
        }

        // Tolerate NaN, so clients can pass (undefined - 1) or (undefined + 1)
        if (+index === index) {
            setSlotIndex(slot, index, indexMap);
        } else if (+indexOld === indexOld) {
            //#DBG _ASSERT(!slot.indexRequested);
            delete slot.index;
        } else {
            // If neither the new index or the old index is defined then there was no index changed.
            return;
        }

        sendIndexChangedNotifications(slot, indexOld);
    }

    function insertionNotificationRecipients(slot, slotPrev, slotNext, mergeWithPrev, mergeWithNext) {
        var bindingMapRecipients = {};

        // Start with the intersection of the bindings for the two adjacent slots
        if ((mergeWithPrev || !slotPrev.lastInSequence) && (mergeWithNext || !slotNext.firstInSequence)) {
            if (slotPrev === slotsStart) {
                if (slotNext === slotListEnd) {
                    // Special case: if the list was empty, broadcast the insertion to all ListBindings with
                    // notification handlers.
                    for (var listBindingID in bindingMap) {
                        bindingMapRecipients[listBindingID] = bindingMap[listBindingID];
                    }
                } else {
                    // Include every binding on the next slot
                    for (var listBindingID in slotNext.bindingMap) {
                        bindingMapRecipients[listBindingID] = bindingMap[listBindingID];
                    }
                }
            } else if (slotNext === slotListEnd || slotNext.bindingMap) {
                for (var listBindingID in slotPrev.bindingMap) {
                    if (slotNext === slotListEnd || slotNext.bindingMap[listBindingID]) {
                        bindingMapRecipients[listBindingID] = bindingMap[listBindingID];
                    }
                }
            }
        }

        // Use the union of that result with the bindings for the slot being inserted
        for (var listBindingID in slot.bindingMap) {
            bindingMapRecipients[listBindingID] = bindingMap[listBindingID];
        }

        return bindingMapRecipients;
    }

    function sendInsertedNotification(slot) {
        var slotPrev = slot.prev,
            slotNext = slot.next,
            bindingMapRecipients = insertionNotificationRecipients(slot, slotPrev, slotNext),
            listBindingID;

        for (listBindingID in bindingMapRecipients) {
            var bindingRecord = bindingMapRecipients[listBindingID];
            if (bindingRecord.notificationHandler) {
                handlerToNotify(bindingRecord).inserted(bindingRecord.itemPromiseFromKnownSlot(slot),
                    slotPrev.lastInSequence || slotPrev === slotsStart ? null : handleForBinding(slotPrev, listBindingID),
                    slotNext.firstInSequence || slotNext === slotListEnd ? null : handleForBinding(slotNext, listBindingID)
                );
            }
        }
    }

    function changeSlot(slot) {
        var itemOld = slot.item;
        prepareSlotItem(slot);

        forEachBindingRecordOfSlot(slot, function (bindingRecord, listBindingID) {
            //#DBG _ASSERT(bindingRecord.notificationHandler);
            var handle = handleForBinding(slot, listBindingID);
            handlerToNotify(bindingRecord).changed(itemForBinding(slot.item, handle), itemForBinding(itemOld, handle));
        });
    }

    function moveSlot(slot, slotMoveBefore, mergeWithPrev, mergeWithNext, skipNotifications) {
        var slotMoveAfter = slotMoveBefore.prev,
            listBindingID;

        // If the slot is being moved before or after itself, adjust slotMoveAfter or slotMoveBefore accordingly. If
        // nothing is going to change in the slot list, don't send a notification.
        if (slotMoveBefore === slot) {
            if (!slot.firstInSequence || !mergeWithPrev) {
                return;
            }
            slotMoveBefore = slot.next;
        } else if (slotMoveAfter === slot) {
            if (!slot.lastInSequence || !mergeWithNext) {
                return;
            }
            slotMoveAfter = slot.prev;
        }

        if (!skipNotifications) {
            // Determine which bindings to notify

            var bindingMapRecipients = insertionNotificationRecipients(slot, slotMoveAfter, slotMoveBefore, mergeWithPrev, mergeWithNext);

            // Send the notification before the move
            for (listBindingID in bindingMapRecipients) {
                var bindingRecord = bindingMapRecipients[listBindingID];
                //#DBG _ASSERT(bindingRecord.notificationHandler);
                handlerToNotify(bindingRecord).moved(bindingRecord.itemPromiseFromKnownSlot(slot),
                    ((slotMoveAfter.lastInSequence || slotMoveAfter === slot.prev) && !mergeWithPrev) || slotMoveAfter === slotsStart ? null : handleForBinding(slotMoveAfter, listBindingID),
                    ((slotMoveBefore.firstInSequence || slotMoveBefore === slot.next) && !mergeWithNext) || slotMoveBefore === slotListEnd ? null : handleForBinding(slotMoveBefore, listBindingID)
                );
            }

            // If a ListBinding cursor is at the slot that's moving, adjust the cursor
            forEachBindingRecord(function (bindingRecord) {
                bindingRecord.adjustCurrentSlot(slot);
            });
        }

        removeSlot(slot);
        insertAndMergeSlot(slot, slotMoveBefore, mergeWithPrev, mergeWithNext);
    }

    function deleteSlot(slot, mirage) {
        //#DBG _ASSERT((!slot.fetchListeners && !slot.directFetchListeners) || !slot.item);
        completeFetchPromises(slot, true);

        forEachBindingRecordOfSlot(slot, function (bindingRecord, listBindingID) {
            //#DBG _ASSERT(bindingRecord.notificationHandler);
            handlerToNotify(bindingRecord).removed(handleForBinding(slot, listBindingID), mirage);
        });

        // If a ListBinding cursor is at the slot that's being removed, adjust the cursor
        forEachBindingRecord(function (bindingRecord) {
            bindingRecord.adjustCurrentSlot(slot);
        });

        removeSlotPermanently(slot);
    }

    function deleteMirageSequence(slot) {
        // Remove the slots in order

        while (!slot.firstInSequence) {
            slot = slot.prev;
        }

        //#DBG _ASSERT(slot !== slotsStart);

        var last;
        do {
            last = slot.lastInSequence;

            var slotNext = slot.next;
            deleteSlot(slot, true);
            slot = slotNext;
        } while (!last);
    }

    // Deferred Index Updates

    // Returns the index of the slot taking into account any outstanding index updates
    function adjustedIndex(slot) {
        var undefinedIndex;

        if (!slot) {
            return undefinedIndex;
        }

        var delta = 0;
        while (!slot.firstInSequence) {
            //#DBG _ASSERT(typeof slot.indexNew !== "number");
            
            delta++;
            slot = slot.prev;
        }

        return (
            typeof slot.indexNew === "number" ?
                slot.indexNew + delta :
            typeof slot.index === "number" ?
                slot.index + delta :
                undefinedIndex
        );
    }

    // Updates the new index of the first slot in each sequence after the given slot
    function updateNewIndicesAfterSlot(slot, indexDelta) {
        // Adjust all the indexNews after this slot
        for (slot = slot.next; slot; slot = slot.next) {
            if (slot.firstInSequence) {
                var indexNew = (slot.indexNew !== undefined ? slot.indexNew : slot.index);
                if (indexNew !== undefined) {
                    slot.indexNew = indexNew + indexDelta;
                }
            }
        }

        // Adjust the overall count
        countDelta += indexDelta;

        indexUpdateDeferred = true;

        // Increment currentRefreshID so any outstanding fetches don't cause trouble.  If a refresh is in progress,
        // restart it (which will also increment currentRefreshID).
        if (refreshInProgress) {
            beginRefresh();
        } else {
            currentRefreshID++;
        }
    }

    // Updates the new index of the given slot if necessary, and all subsequent new indices
    function updateNewIndices(slot, indexDelta) {
        //#DBG _ASSERT(indexDelta !== 0);

        // If this slot is at the start of a sequence, transfer the indexNew
        if (slot.firstInSequence) {
            var indexNew;

            if (indexDelta < 0) {
                // The given slot is about to be removed
                indexNew = slot.indexNew;
                if (indexNew !== undefined) {
                    delete slot.indexNew;
                } else {
                    indexNew = slot.index;
                }

                if (!slot.lastInSequence) {
                    // Update the next slot now
                    slot = slot.next;
                    if (indexNew !== undefined) {
                        slot.indexNew = indexNew;
                    }
                }
            } else {
                // The given slot was just inserted
                if (!slot.lastInSequence) {
                    var slotNext = slot.next;

                    indexNew = slotNext.indexNew;
                    if (indexNew !== undefined) {
                        delete slotNext.indexNew;
                    } else {
                        indexNew = slotNext.index;
                    }

                    if (indexNew !== undefined) {
                        slot.indexNew = indexNew;
                    }
                }
            }
        }

        updateNewIndicesAfterSlot(slot, indexDelta);
    }

    // Updates the new index of the first slot in each sequence after the given new index
    function updateNewIndicesFromIndex(index, indexDelta) {
        //#DBG _ASSERT(indexDelta !== 0);

        for (var slot = slotsStart; slot !== slotListEnd; slot = slot.next) {
            var indexNew = slot.indexNew;

            if (indexNew !== undefined && index <= indexNew) {
                updateNewIndicesAfterSlot(slot, indexDelta);
                break;
            }
        }        
    }

    // Adjust the indices of all slots to be consistent with any indexNew properties, and strip off the indexNews
    function updateIndices() {
        var slot,
            slotFirstInSequence,
            indexNew;

        for (slot = slotsStart; ; slot = slot.next) {
            if (slot.firstInSequence) {
                slotFirstInSequence = slot;
                if (slot.indexNew !== undefined) {
                    indexNew = slot.indexNew;
                    delete slot.indexNew;
                    if (isNaN(indexNew)) {
                        break;
                    }
                } else {
                    indexNew = slot.index;
                }

                // See if this sequence should be merged with the previous one
                if (slot !== slotsStart && slot.prev.index === indexNew - 1) {
                    mergeSequences(slot.prev);
                }
            }

            if (slot.lastInSequence) {
                var index = indexNew;
                for (var slotUpdate = slotFirstInSequence; slotUpdate !== slot.next; slotUpdate = slotUpdate.next) {
                    //#DBG _ASSERT(index !== slotUpdate.index || +index !== index || indexMap[index] === slotUpdate);
                    if (index !== slotUpdate.index) {
                        changeSlotIndex(slotUpdate, index);
                    }
                    if (+index === index) {
                        index++;
                    }
                }
            }
            
            if (slot === slotListEnd) {
                break;
            }
        }

        // Clear any indices on slots that were moved adjacent to slots without indices
        for ( ; slot !== slotsEnd; slot = slot.next) {
            if (slot.index !== undefined && slot !== slotListEnd) {
                changeSlotIndex(slot, undefined);
            }
        }

        indexUpdateDeferred = false;

        if (countDelta && +knownCount === knownCount) {
            if (getCountPromise) {
                getCountPromise.reset();
            } else {
                changeCount(knownCount + countDelta);
            }

            countDelta = 0;
        }
    }
    
    // Fetch Promises
    
    function createFetchPromise(slot, listenersProperty, listenerID, listBindingID, onComplete) {
        if (slot.item) {
            return new Promise(function (complete) {
                if (onComplete) {
                    onComplete(complete, slot.item);
                } else {
                    complete(slot.item);
                }
            });
        } else {
            var listener = {
                listBindingID: listBindingID,
                retained: false
            };

            if (!slot[listenersProperty]) {
                slot[listenersProperty] = {};
            }
            slot[listenersProperty][listenerID] = listener;

            listener.promise = new Promise(function (complete, error) {
                listener.complete = (onComplete ? function (item) {
                    onComplete(complete, item);
                } : complete);
                listener.error = error;
            }, function () {
                // By now the slot might have been merged with another

                while (slot.slotMergedWith) {
                    slot = slot.slotMergedWith;
                }
                
                var fetchListeners = slot[listenersProperty];
                if (fetchListeners) {
                    delete fetchListeners[listenerID];

                    // See if there are any other listeners
                    for (var listenerID2 in fetchListeners) {
                        return;
                    }
                    delete slot[listenersProperty];
                }
                releaseSlotIfUnrequested(slot);
            });

            return listener.promise;
        }
    }

    function completePromises(item, listeners) {
        for (var listenerID in listeners) {
            listeners[listenerID].complete(item);
        }
    }

    function completeFetchPromises(slot, completeSynchronously) {
        var fetchListeners = slot.fetchListeners,
            directFetchListeners = slot.directFetchListeners;

        if (fetchListeners || directFetchListeners) {
            prepareSlotItem(slot);

            // By default, complete asynchronously to minimize reentrancy

            var item = slot.item;

            var completeOrQueuePromises = function (listeners) {
                if (completeSynchronously) {
                    completePromises(item, listeners);
                } else {
                    fetchCompleteCallbacks.push(function () {
                        completePromises(item, listeners);
                    });
                }
            }

            if (directFetchListeners) {
                slot.directFetchListeners = null;
                completeOrQueuePromises(directFetchListeners);
            }

            if (fetchListeners) {
                slot.fetchListeners = null;
                completeOrQueuePromises(fetchListeners);
            }

            releaseSlotIfUnrequested(slot);
        }
    }

    function callFetchCompleteCallbacks() {
        var callbacks = fetchCompleteCallbacks;

        // Clear fetchCompleteCallbacks first to avoid reentrancy problems
        fetchCompleteCallbacks = [];

        for (var i = 0, len = callbacks.length; i < len; i++) {
            callbacks[i]();
        }
    }

    function returnDirectFetchError(slot, error) {
        var directFetchListeners = slot.directFetchListeners;
        if (directFetchListeners) {
            slot.directFetchListeners = null;

            for (var listenerID in directFetchListeners) {
                directFetchListeners[listenerID].error(error);
            }

            releaseSlotIfUnrequested(slot);
        }
    }

    // Item Requests

    function requestSlot(slot) {
        // Ensure that there's a slot on either side of each requested item
        if (slot.firstInSequence) {
            //#DBG _ASSERT(slot.index - 1 !== slot.prev.index);
            addSlotBefore(slot, indexMap);
        }
        if (slot.lastInSequence) {
            //#DBG _ASSERT(slot.index + 1 !== slot.next.index);
            addSlotAfter(slot, indexMap);
        }

        // If the item has already been fetched, prepare it now to be returned to the client
        if (slot.itemNew) {
            prepareSlotItem(slot);
        }

        // Start a new fetch if necessary
        postFetch();

        return slot;
    }

    function requestSlotBefore(slotNext) {
        // First, see if the previous slot already exists
        if (!slotNext.firstInSequence) {
            var slotPrev = slotNext.prev;

            // Next, see if the item is known to not exist
            return (slotPrev === slotsStart ? null : requestSlot(slotPrev));
        }

        return requestSlot(addSlotBefore(slotNext, indexMap));
    }

    function requestSlotAfter(slotPrev) {
        // First, see if the next slot already exists
        if (!slotPrev.lastInSequence) {
            var slotNext = slotPrev.next;

            // Next, see if the item is known to not exist
            return (slotNext === slotListEnd ? null : requestSlot(slotNext));
        }

        return requestSlot(addSlotAfter(slotPrev, indexMap));
    }

    function itemDirectlyFromSlot(slot) {
        // Return a complete promise for a non-existent slot
        return (
            slot ?
                createFetchPromise(slot, "directFetchListeners", (nextListenerID++).toString()) :
                Promise.wrap(null)
        );
    }    

    function validateKey(key) {
        if (typeof key !== "string" || !key) {
            throw new WinJS.ErrorFromName("WinJS.UI.ListDataSource.KeyIsInvalid", strings.keyIsInvalid);
        }
    }

    function createSlotForKey(key) {
        var slot = createPrimarySlotSequence(slotsEnd);

        setSlotKey(slot, key);
        slot.keyRequested = true;

        return slot;
    }

    function slotFromKey(key, hints) {
        validateKey(key);

        var slot = keyMap[key];

        if (!slot) {
            slot = createSlotForKey(key);
            slot.hints = hints;
        }

        //#DBG _ASSERT(slot.key === key);

        return requestSlot(slot);
    }

    function slotFromIndex(index) {
        if (typeof index !== "number" || index < 0) {
            throw new WinJS.ErrorFromName("WinJS.UI.ListDataSource.IndexIsInvalid", strings.indexIsInvalid);
        }

        if (slotListEnd.index <= index) {
            return null;
        }

        var slot = indexMap[index];
        //#DBG _ASSERT(slot !== slotListEnd);

        if (!slot) {
            var slotNext = successorFromIndex(index, indexMap, slotsStart, slotListEnd);

            if (!slotNext) {
                // The complete list has been observed, and this index isn't a part of it; a refresh may be necessary
                return null;
            }

            if (slotNext === slotListEnd && index >= slotListEnd) {
                // Clear slotListEnd's index, as that's now unknown
                changeSlotIndex(slotListEnd, undefined);
            }

            // Create a new slot and start a request for it
            if (slotNext.prev.index === index - 1) {
                slot = addSlotAfter(slotNext.prev, indexMap);
            } else if (slotNext.index === index + 1) {
                slot = addSlotBefore(slotNext, indexMap);
            } else {
                slot = createPrimarySlotSequence(slotNext, index);
            }
        }

        //#DBG _ASSERT(slot.index === index);

        if (!slot.item) {
            slot.indexRequested = true;
        }

        return requestSlot(slot);
    }

    function slotFromDescription(description) {
        // Create a new slot and start a request for it
        var slot = createPrimarySlotSequence(slotsEnd);

        slot.description = description;

        return requestSlot(slot);
    }

    // Status

    var that = this;
    function setStatus(statusNew) {
        statusPending = statusNew;
        if (status !== statusPending) {
            var dispatch = function () {
                statusChangePosted = false;

                if (status !== statusPending) {
                    status = statusPending;
                    that.dispatchEvent(statusChangedEvent, status);
                }
            };
            if (statusPending === WinJS.UI.DataSourceStatus.failure) {
                dispatch();
            } else if (!statusChangePosted) {
                statusChangePosted = true;

                // Delay the event to filter out rapid changes
                setTimeout(dispatch, 40);
            }
        }
    }

    // Slot Fetching

    function slotFetchInProgress(slot) {
        var fetchID = slot.fetchID;
        return fetchID && fetchesInProgress[fetchID];
    }

    function setFetchID(slot, fetchID) {
        slot.fetchID = fetchID;
    }

    function newFetchID() {
        var fetchID = nextFetchID;
        nextFetchID++;

        fetchesInProgress[fetchID] = true;

        return fetchID;
    }

    function setFetchIDs(slot, countBefore, countAfter) {
        var fetchID = newFetchID();
        setFetchID(slot, fetchID);

        var slotBefore = slot;
        while (!slotBefore.firstInSequence && countBefore > 0) {
            slotBefore = slotBefore.prev;
            countBefore--;
            setFetchID(slotBefore, fetchID);
        }

        var slotAfter = slot;
        while (!slotAfter.lastInSequence && countAfter > 0) {
            slotAfter = slotAfter.next;
            countAfter--;
            setFetchID(slotAfter, fetchID);
        }

        return fetchID;
    }

    // Adds markers on behalf of the data adapter if their presence can be deduced
    function addMarkers(fetchResult) {
        var items = fetchResult.items,
            offset = fetchResult.offset,
            totalCount = fetchResult.totalCount,
            absoluteIndex = fetchResult.absoluteIndex,
            atStart = fetchResult.atStart,
            atEnd = fetchResult.atEnd;

        if (isNonNegativeNumber(absoluteIndex)) {
            if (isNonNegativeNumber(totalCount)) {
                var itemsLength = items.length;
                if (absoluteIndex - offset + itemsLength === totalCount) {
                    atEnd = true;
                }
            }

            if (offset === absoluteIndex) {
                atStart = true;
            }
        }

        if (atStart) {
            items.unshift(startMarker);
            fetchResult.offset++;
        }

        if (atEnd) {
            items.push(endMarker);
        }
    }

    function resultsValid(slot, refreshID, fetchID) {
        // This fetch has completed, whatever it has returned
        //#DBG _ASSERT(!fetchID || fetchesInProgress[fetchID]);
        delete fetchesInProgress[fetchID];

        if (refreshID !== currentRefreshID || slotPermanentlyRemoved(slot)) {
            // This information is out of date, or the slot has since been discarded

            postFetch();
            return false;
        }

        return true;
    }

    function fetchItems(slot, fetchID, promiseItems, index) {
        var refreshID = currentRefreshID;
        promiseItems.then(function (fetchResult) {
            if (fetchResult.items && fetchResult.items.length) {
                if (resultsValid(slot, refreshID, fetchID)) {
                    if (+index === index) {
                        fetchResult.absoluteIndex = index;
                    }
                    addMarkers(fetchResult);
                    processResults(slot, fetchResult.items, fetchResult.offset, fetchResult.totalCount, fetchResult.absoluteIndex);
                }
            } else {
                return Promise.wrapError(new WinJS.ErrorFromName(FetchError.doesNotExist));
            }
        }).then(null, function (error) {
            if (resultsValid(slot, refreshID, fetchID)) {
                processErrorResult(slot, error);
            }
        });
    }

    function fetchItemsForIndex(indexRequested, slot, promiseItems) {
        var refreshID = currentRefreshID;
        promiseItems.then(function (fetchResult) {
            if (fetchResult.items && fetchResult.items.length) {
                if (resultsValid(slot, refreshID, null)) {
                    //#DBG _ASSERT(+indexRequested === indexRequested);
                    fetchResult.absoluteIndex = indexRequested;
                    addMarkers(fetchResult);
                    processResultsForIndex(indexRequested, slot, fetchResult.items, fetchResult.offset, fetchResult.totalCount, fetchResult.absoluteIndex);
                }
            } else {
                return Promise.wrapError(new WinJS.ErrorFromName(FetchError.doesNotExist));
            }
        }).then(null, function (error) {
            if (resultsValid(slot, refreshID, null)) {
                processErrorResultForIndex(indexRequested, slot, refreshID, name);
            }
        });
    }

    function fetchItemsFromStart(slot, count) {
        //#DBG _ASSERT(!refreshInProgress);

        var fetchID = setFetchIDs(slot, 0, count - 1);

        if (listDataAdapter.itemsFromStart) {
            fetchItems(slot, fetchID, listDataAdapter.itemsFromStart(count), 0);
        } else {
            fetchItems(slot, fetchID, listDataAdapter.itemsFromIndex(0, 0, count - 1), 0);
        }
    }

    function fetchItemsFromEnd(slot, count) {
        //#DBG _ASSERT(!refreshInProgress);

        fetchItems(slot, setFetchIDs(slot, count - 1, 0), listDataAdapter.itemsFromEnd(count));
    }

    function fetchItemsFromKey(slot, countBefore, countAfter) {
        //#DBG _ASSERT(!refreshInProgress);
        //#DBG _ASSERT(listDataAdapter.itemsFromKey);
        //#DBG _ASSERT(slot.key);

        fetchItems(slot, setFetchIDs(slot, countBefore, countAfter), listDataAdapter.itemsFromKey(slot.key, countBefore, countAfter, slot.hints));
    }

    function fetchItemsFromIndex(slot, countBefore, countAfter) {
        //#DBG _ASSERT(!refreshInProgress);
        //#DBG _ASSERT(slot !== slotsStart);

        var index = slot.index;

        // Don't ask for items with negative indices
        if (countBefore > index) {
            countBefore = index;
        }

        if (listDataAdapter.itemsFromIndex) {
            var fetchID = setFetchIDs(slot, countBefore, countAfter);

            fetchItems(slot, fetchID, listDataAdapter.itemsFromIndex(index, countBefore, countAfter), index);
        } else {
            // If the slot key is known, we just need to request the surrounding items
            if (slot.key) {
                fetchItemsFromKey(slot, countBefore, countAfter);
            } else {
                // Search for the slot with the closest index that has a known key (using the start of the list as a
                // last resort).
                var slotClosest = slotsStart,
                    closestDelta = index + 1,
                    slotSearch,
                    delta;

                // First search backwards
                for (slotSearch = slot.prev; slotSearch !== slotsStart; slotSearch = slotSearch.prev) {
                    if (slotSearch.index !== undefined && slotSearch.key) {
                        //#DBG _ASSERT(index > slotSearch.index);
                        delta = index - slotSearch.index;
                        if (closestDelta > delta) {
                            closestDelta = delta;
                            slotClosest = slotSearch;
                        }
                        break;
                    }
                }

                // Then search forwards
                for (slotSearch = slot.next; slotSearch !== slotListEnd; slotSearch = slotSearch.next) {
                    if (slotSearch.index !== undefined && slotSearch.key) {
                        //#DBG _ASSERT(slotSearch.index > index);
                        delta = slotSearch.index - index;
                        if (closestDelta > delta) {
                            closestDelta = delta;
                            slotClosest = slotSearch;
                        }
                        break;
                    }
                }

                if (slotClosest === slotsStart) {
                    fetchItemsForIndex(0, slot, listDataAdapter.itemsFromStart(index + 1));
                } else {
                    fetchItemsForIndex(slotClosest.index, slot, listDataAdapter.itemsFromKey(
                        slotClosest.key,
                        Math.max(slotClosest.index - index, 0),
                        Math.max(index - slotClosest.index, 0),
                        slot.hints
                    ));
                }
            }
        }
    }

    function fetchItemsFromDescription(slot, countBefore, countAfter) {
        //#DBG _ASSERT(!refreshInProgress);

        fetchItems(slot, setFetchIDs(slot, countBefore, countAfter), listDataAdapter.itemsFromDescription(slot.description, countBefore, countAfter));
    }

    function fetchItemsForAllSlots() {
        if (!refreshInProgress) {
            var slotFirstPlaceholder,
                placeholderCount,
                fetchInProgress = false,
                fetchesInProgress = false,
                slotRequestedByKey,
                requestedKeyOffset,
                slotRequestedByDescription,
                requestedDescriptionOffset,
                slotRequestedByIndex,
                requestedIndexOffset;

            for (var slot = slotsStart.next; slot !== slotsEnd; ) {
                var slotNext = slot.next;

                if (slot !== slotListEnd && isPlaceholder(slot)) {
                    fetchesInProgress = true;

                    if (!slotFirstPlaceholder) {
                        slotFirstPlaceholder = slot;
                        placeholderCount = 1;
                    } else {
                        placeholderCount++;
                    }

                    if (slotFetchInProgress(slot)) {
                        fetchInProgress = true;
                    }

                    if (slot.keyRequested && !slotRequestedByKey) {
                        //#DBG _ASSERT(slot.key);
                        slotRequestedByKey = slot;
                        requestedKeyOffset = placeholderCount - 1;
                    }

                    if (slot.description !== undefined && !slotRequestedByDescription) {
                        slotRequestedByDescription = slot;
                        requestedDescriptionOffset = placeholderCount - 1;
                    }

                    if (slot.indexRequested && !slotRequestedByIndex) {
                        //#DBG _ASSERT(typeof slot.index === "number");
                        slotRequestedByIndex = slot;
                        requestedIndexOffset = placeholderCount - 1;
                    }

                    if (slot.lastInSequence || slotNext === slotsEnd || !isPlaceholder(slotNext)) {
                        if (fetchInProgress) {
                            fetchInProgress = false;
                        } else {
                            resultsProcessed = false;

                            // Start a new fetch for this placeholder sequence

                            // Prefer fetches in terms of a known item
                            if (!slotFirstPlaceholder.firstInSequence && slotFirstPlaceholder.prev.key && listDataAdapter.itemsFromKey) {
                                fetchItemsFromKey(slotFirstPlaceholder.prev, 0, placeholderCount);
                            } else if (!slot.lastInSequence && slotNext.key && listDataAdapter.itemsFromKey) {
                                fetchItemsFromKey(slotNext, placeholderCount, 0);
                            } else if (slotFirstPlaceholder.prev === slotsStart && !slotFirstPlaceholder.firstInSequence && (listDataAdapter.itemsFromStart || listDataAdapter.itemsFromIndex)) {
                                fetchItemsFromStart(slotFirstPlaceholder, placeholderCount);
                            } else if (slotNext === slotListEnd && !slot.lastInSequence && listDataAdapter.itemsFromEnd) {
                                fetchItemsFromEnd(slot, placeholderCount);
                            } else if (slotRequestedByKey) {
                                fetchItemsFromKey(slotRequestedByKey, requestedKeyOffset, placeholderCount - 1 - requestedKeyOffset);
                            } else if (slotRequestedByDescription) {
                                fetchItemsFromDescription(slotRequestedByDescription, requestedDescriptionOffset, placeholderCount - 1 - requestedDescriptionOffset);
                            } else if (slotRequestedByIndex) {
                                fetchItemsFromIndex(slotRequestedByIndex, requestedIndexOffset, placeholderCount - 1 - requestedIndexOffset);
                            } else if (typeof slotFirstPlaceholder.index === "number") {
                                fetchItemsFromIndex(slotFirstPlaceholder, placeholderCount - 1, 0);
                            } else {
                                // There is no way to fetch anything in this sequence
                                //#DBG _ASSERT(slot.lastInSequence);
                                deleteMirageSequence(slotFirstPlaceholder);
                            }

                            if (resultsProcessed) {
                                // A re-entrant fetch might have altered the slots list - start again
                                postFetch();
                                return;
                            }

                            if (refreshInProgress) {
                                // A re-entrant fetch might also have caused a refresh
                                return;
                            }
                         }

                        slotFirstPlaceholder = slotRequestedByIndex = slotRequestedByKey = null;
                    }
                }

                slot = slotNext;
            }

            setStatus(fetchesInProgress ? DataSourceStatus.waiting : DataSourceStatus.ready);
        }
    }

    function postFetch() {
        if (!fetchesPosted) {
            fetchesPosted = true;
            setImmediate(function () {
                fetchesPosted = false;
                fetchItemsForAllSlots();
                
                // A mirage sequence might have been removed
                finishNotifications();
            });
        }
    }

    // Fetch Result Processing
    
    function itemChanged(slot) {
        var itemNew = slot.itemNew;

        if (!itemNew) {
            return false;
        }

        var item = slot.item;

        for (var property in item) {
            switch (property) {
                case "data":
                    // This is handled below
                    break;

                default:
                    //#DBG _ASSERT(property !== "handle");
                    //#DBG _ASSERT(property !== "index");
                    if (item[property] !== itemNew[property]) {
                        return true;
                    }
                    break;
            }
        }

        return (
            listDataAdapter.compareByIdentity ?
                item.data !== itemNew.data :
                slot.signature !== itemSignature(itemNew)
        );
    }
    
    function changeSlotIfNecessary(slot) {
        if (!slotRequested(slot)) {
            // There's no need for any notifications, just delete the old item
            slot.item = null;
        } else if (itemChanged(slot)) {
            changeSlot(slot);
        } else {
            slot.itemNew = null;
        }
    }

    function updateSlotItem(slot) {
        //#DBG _ASSERT(slot.itemNew);

        if (slot.item) {
            changeSlotIfNecessary(slot);
        } else {
            //#DBG _ASSERT(slot.key);
            completeFetchPromises(slot);
        }
    }

    function updateSlot(slot, item) {
        //#DBG _ASSERT(item !== startMarker && item !== endMarker);

        if (!slot.key) {
            setSlotKey(slot, item.key);
        }
        slot.itemNew = item;

        //#DBG _ASSERT(slot.key === item.key);

        updateSlotItem(slot);
    }

    function sendMirageNotifications(slot, slotToDiscard, listBindingIDsToDelete) {
        var bindingMap = slotToDiscard.bindingMap;
        if (bindingMap) {
            for (var listBindingID in listBindingIDsToDelete) {
                if (bindingMap[listBindingID]) {
                    var fetchListeners = slotToDiscard.fetchListeners;
                    for (var listenerID in fetchListeners) {
                        var listener = fetchListeners[listenerID];

                        if (listener.listBindingID === listBindingID && listener.retained) {
                            delete fetchListeners[listenerID];
                            listener.complete(null);
                        }
                    }

                    var bindingRecord = bindingMap[listBindingID].bindingRecord;
                    //#DBG _ASSERT(bindingRecord.notificationHandler);

                    handlerToNotify(bindingRecord).removed(handleForBinding(slotToDiscard, listBindingID), true, handleForBinding(slot, listBindingID));

                    // A re-entrant call to release from the removed handler might have cleared slotToDiscard.bindingMap
                    if (slotToDiscard.bindingMap) {
                        delete slotToDiscard.bindingMap[listBindingID];
                    }
                }
            }
        }
    }

    function mergeSlots(slot, slotToDiscard) {
        // This shouldn't be called on a slot that has a pending change notification
        //#DBG _ASSERT(!slot.item || !slot.itemNew);

        // Only one of the two slots should have a key
        //#DBG _ASSERT(!slot.key || !slotToDiscard.key);

        // If slotToDiscard is about to acquire an index, send the notifications now; in rare cases, multiple
        // indexChanged notifications will be sent for a given item during a refresh, but that's fine.
        if (slot.index !== slotToDiscard.index) {
            // If slotToDiscard has a defined index, that should have been transferred already
            //#DBG _ASSERT(refreshInProgress || slot.index !== undefined);

            var indexOld = slotToDiscard.index;
            slotToDiscard.index = slot.index;
            sendIndexChangedNotifications(slotToDiscard, indexOld);
        }

        slotToDiscard.slotMergedWith = slot;

        // Transfer the slotBindings from slotToDiscard to slot
        var bindingMap = slotToDiscard.bindingMap;
        for (var listBindingID in bindingMap) {
            if (!slot.bindingMap) {
                slot.bindingMap = {};
            }

            //#DBG _ASSERT(!slot.bindingMap[listBindingID]);

            var slotBinding = bindingMap[listBindingID];

            if (!slotBinding.handle) {
                slotBinding.handle = slotToDiscard.handle;
            }
            //#DBG _ASSERT(handleMap[slotBinding.handle] === slotToDiscard);
            handleMap[slotBinding.handle] = slot;

            slot.bindingMap[listBindingID] = slotBinding;
        }

        // Update any ListBinding cursors pointing to slotToDiscard
        forEachBindingRecord(function (bindingRecord) {
            bindingRecord.adjustCurrentSlot(slotToDiscard, slot);
        });

        // See if the item needs to be transferred from slotToDiscard to slot
        var item = slotToDiscard.itemNew || slotToDiscard.item;
        //#DBG _ASSERT(!item || !slot.key);

        if (item) {
            defineCommonItemProperties(item, slot, slot.handle);
            updateSlot(slot, item);
        }

        // Transfer the fetch listeners from slotToDiscard to slot, or complete them if item is known
        if (slot.item) {
            if (slotToDiscard.directFetchListeners) {
                fetchCompleteCallbacks.push(function () {
                    completePromises(slot.item, slotToDiscard.directFetchListeners);
                });
            }
            if (slotToDiscard.fetchListeners) {
                fetchCompleteCallbacks.push(function () {
                    completePromises(slot.item, slotToDiscard.fetchListeners);
                });
            }
        } else {
            var listenerID;

            for (listenerID in slotToDiscard.directFetchListeners) {
                if (!slot.directFetchListeners) {
                    slot.directFetchListeners = {};
                }
                slot.directFetchListeners[listenerID] = slotToDiscard.directFetchListeners[listenerID];
            }

            for (listenerID in slotToDiscard.fetchListeners) {
                if (!slot.fetchListeners) {
                    slot.fetchListeners = {};
                }
                slot.fetchListeners[listenerID] = slotToDiscard.fetchListeners[listenerID];
            }
        }

        // This might be the first time this slot's item can be prepared
        if (slot.itemNew) {
            completeFetchPromises(slot);
        }

        // Give slotToDiscard an unused handle so it appears to be permanently removed
        slotToDiscard.handle = (nextHandle++).toString();

        splitSequence(slotToDiscard);
        removeSlotPermanently(slotToDiscard);
    }

    function mergeSlotsAndItem(slot, slotToDiscard, item) {
        if (slotToDiscard && slotToDiscard.key) {
            //#DBG _ASSERT(!item || slotToDiscard.key === item.key);
            //#DBG _ASSERT(!slotToDiscard.bindingMap);

            if (!item) {
                item = slotToDiscard.itemNew || slotToDiscard.item;
            }

            // Free up the key for the promoted slot
            delete slotToDiscard.key;
            delete keyMap[item.key];

            slotToDiscard.itemNew = null;
            slotToDiscard.item = null;
        }

        if (item) {
            updateSlot(slot, item);
        }

        if (slotToDiscard) {
            mergeSlots(slot, slotToDiscard);
        }
    }

    function slotFromResult(result) {
        if (typeof result !== "object") {
            throw new WinJS.ErrorFromName("WinJS.UI.ListDataSource.InvalidItemReturned", strings.invalidItemReturned);
        } else if (result === startMarker) {
            return slotsStart;
        } else if (result === endMarker) {
            return slotListEnd;
        } else if (!result.key) {
            throw new WinJS.ErrorFromName("WinJS.UI.ListDataSource.InvalidKeyReturned", strings.invalidKeyReturned);
        } else {
            if (WinJS.validation) {
                validateKey(result.key);
            }
            return keyMap[result.key];
        }
    }

    function matchSlot(slot, result) {
        //#DBG _ASSERT(result !== startMarker && result !== endMarker);

        // First see if there is an existing slot that needs to be merged
        var slotExisting = slotFromResult(result);
        if (slotExisting === slot) {
            slotExisting = null;
        }

        if (slotExisting) {
            sendMirageNotifications(slot, slotExisting, slot.bindingMap);
        }

        mergeSlotsAndItem(slot, slotExisting, result);
    }

    function promoteSlot(slot, item, index, insertionPoint) {
        //#DBG _ASSERT(typeof slot.index !== "number");
        //#DBG _ASSERT(+index === index || !indexMap[index]);

        if (item && slot.key && slot.key !== item.key) {
            // A contradiction has been found
            beginRefresh();
            return false;
        }

        // The slot with the key "wins"; slots without bindings can be merged without any change in observable behavior
        
        var slotWithIndex = indexMap[index];
        if (slotWithIndex) {
            if (slotWithIndex === slot) {
                slotWithIndex = null;
            } else if (slotWithIndex.key && (slot.key || (item && slotWithIndex.key !== item.key))) {
                // A contradiction has been found
                beginRefresh();
                return false;
            } else if (!slot.key && slotWithIndex.bindingMap) {
                return false;
            }
        }

        var slotWithKey;
        if (item) {
            slotWithKey = keyMap[item.key];

            if (slotWithKey === slot) {
                slotWithKey = null;
            } else if (slotWithKey && slotWithKey.bindingMap) {
                return false;
            }
        }

        if (slotWithIndex) {
            sendMirageNotifications(slot, slotWithIndex, slot.bindingMap);

            // Transfer the index to the promoted slot
            delete indexMap[index];
            changeSlotIndex(slot, index);

            // See if this sequence should be merged with its neighbors
            if (slot.prev.index === index - 1) {
                mergeSequences(slot.prev);
            }
            if (slot.next.index === index + 1) {
                mergeSequences(slot);
            }

            insertionPoint.slotNext = slotWithIndex.slotNext;

            if (!item) {
                item = slotWithIndex.itemNew || slotWithIndex.item;
                if (item) {
                    slotWithKey = keyMap[item.key];
                }
            }
        } else {
            changeSlotIndex(slot, index);
        }

        if (slotWithKey && slotWithIndex !== slotWithKey) {
            sendMirageNotifications(slot, slotWithKey, slot.bindingMap);
        }

        mergeSlotsAndItem(slot, slotWithKey, item);

        // Do this after mergeSlotsAndItem, since its call to updateSlot might send changed notifications, and those
        // wouldn't make sense to clients that never saw the old item.
        if (slotWithIndex && slotWithIndex !== slotWithKey) {
            mergeSlots(slot, slotWithIndex);
        }

        //#DBG _ASSERT(!slotWithIndex || slotWithIndex.prev.next !== slotWithIndex);

        return true;
    }

    function mergeAdjacentSlot(slotExisting, slot, listBindingIDsToDelete) {
        if (slot.key && slotExisting.key && slot.key !== slotExisting.key) {
            // A contradiction has been found
            beginRefresh();
            return false;
        }

        for (var listBindingID in slotExisting.bindingMap) {
            listBindingIDsToDelete[listBindingID] = true;
        }

        sendMirageNotifications(slotExisting, slot, listBindingIDsToDelete);
        mergeSlotsAndItem(slotExisting, slot);

        return true;
    }

    function mergeSlotsBefore(slot, slotExisting) {
        var listBindingIDsToDelete = {};

        while (slot) {
            var slotPrev = (slot.firstInSequence ? null : slot.prev);

            if (!slotExisting.firstInSequence && slotExisting.prev === slotsStart) {
                deleteSlot(slot, true);
            } else {
                if (slotExisting.firstInSequence) {
                    slotExisting = addSlotBefore(slotExisting, indexMap);
                } else {
                    slotExisting = slotExisting.prev;
                }

                if (!mergeAdjacentSlot(slotExisting, slot, listBindingIDsToDelete)) {
                    return;
                }
            }

            slot = slotPrev;
        }
    }

    function mergeSlotsAfter(slot, slotExisting) {
        var listBindingIDsToDelete = {};

        while (slot) {
            var slotNext = (slot.lastInSequence ? null : slot.next);

            if (!slotExisting.lastInSequence && slotExisting.next === slotListEnd) {
                deleteSlot(slot, true);
            } else {
                if (slotExisting.lastInSequence) {
                    slotExisting = addSlotAfter(slotExisting, indexMap);
                } else {
                    slotExisting = slotExisting.next;
                }

                if (!mergeAdjacentSlot(slotExisting, slot, listBindingIDsToDelete)) {
                    return;
                }
            }

            slot = slotNext;
        }
    }

    function mergeSequencePairs(sequencePairsToMerge) {
        for (var i = 0; i < sequencePairsToMerge.length; i++) {
            var sequencePairToMerge = sequencePairsToMerge[i];
            mergeSlotsBefore(sequencePairToMerge.slotBeforeSequence, sequencePairToMerge.slotFirstInSequence);
            mergeSlotsAfter(sequencePairToMerge.slotAfterSequence, sequencePairToMerge.slotLastInSequence);
        }
    }
    
    // Removes any placeholders with indices that exceed the given upper bound on the count
    function removeMirageIndices(countMax, indexFirstKnown) {
        //#DBG _ASSERT(isNonNegativeInteger(countMax));

        var placeholdersAtEnd = 0;

        function removePlaceholdersAfterSlot(slotRemoveAfter) {
            for (var slot2 = slotListEnd.prev; !(slot2.index < countMax) && slot2 !== slotRemoveAfter; ) {
                var slotPrev2 = slot2.prev;
                if (slot2.index !== undefined) {
                    deleteSlot(slot2, true);
                }
                slot2 = slotPrev2;
            }

            placeholdersAtEnd = 0;
        }

        for (var slot = slotListEnd.prev; !(slot.index < countMax) || placeholdersAtEnd > 0; ) {
            //#DBG _ASSERT(!refreshInProgress);

            var slotPrev = slot.prev;

            if (slot === slotsStart) {
                removePlaceholdersAfterSlot(slotsStart);
                break;
            } else if (slot.key) {
                if (slot.index >= countMax) {
                    beginRefresh();
                    return false;
                } else if (slot.index >= indexFirstKnown) {
                    removePlaceholdersAfterSlot(slot);
                    //#DBG _ASSERT(slot.index < countMax);
                } else {
                    if (listDataAdapter.itemsFromKey) {
                        fetchItemsFromKey(slot, 0, placeholdersAtEnd);
                    } else {
                        fetchItemsFromIndex(slot, 0, placeholdersAtEnd);
                    }

                    // Wait until the fetch has completed before doing anything
                    return false;
                }
            } else if (slot.indexRequested || slot.firstInSequence) {
                removePlaceholdersAfterSlot(slotPrev);
            } else {
                placeholdersAtEnd++;
            }

            slot = slotPrev;
        }

        return true;
    }

    // Merges the results of a fetch into the slot list data structure, and determines if any notifications need to be
    // synthesized.
    function processResults(slot, results, offset, count, index) {
        index = validateIndexReturned(index);
        count = validateCountReturned(count);

        // If there are edits queued, we need to wait until the slots get back in sync with the data
        if (editsQueued) {
            return;
        }

        if (indexUpdateDeferred) {
            updateIndices();
        }

        // If the count has changed, and the end of the list has been reached, that's a contradiction
        if ((isNonNegativeNumber(count) || count === CountResult.unknown) && count !== knownCount && !slotListEnd.firstInSequence) {
            beginRefresh();
            return;
        }

        resultsProcessed = true;

        /*#DBG
        VERIFYLIST();
        #DBG*/

        (function () {
            var i,
                j,
                resultsCount = results.length,
                slotExisting,
                slotBefore;

            // If an index wasn't passed in, see if the indices of these items can be determined
            if (typeof index !== "number") {
                for (i = 0; i < resultsCount; i++) {
                    slotExisting = slotFromResult(results[i]);
                    if (slotExisting && slotExisting.index !== undefined) {
                        index = slotExisting.index + offset - i;
                        break;
                    }
                }
            }

            // See if these results include the end of the list
            if (typeof index === "number" && results[resultsCount - 1] === endMarker) {
                // If the count wasn't known, it is now
                count = index - offset + resultsCount - 1;
            } else if (isNonNegativeNumber(count) && index == undefined) {
                // If the index wasn't known, it is now
                index = count - (resultsCount - 1) + offset;
            }
            
            // If the count is known, remove any mirage placeholders at the end
            if (isNonNegativeNumber(count) && !removeMirageIndices(count, index - offset)) {
                // "Forget" the count - a subsequent fetch or refresh will update the count and list end
                count = undefined;
            }

            // Find any existing slots that correspond to the results, and check for contradictions
            var offsetMap = new Array(resultsCount);
            for (i = 0; i < resultsCount; i++) {
                var slotBestMatch = null;

                slotExisting = slotFromResult(results[i]);

                if (slotExisting) {
                    // See if this item is currently adjacent to a different item, or has a different index
                    if ((i > 0 && !slotExisting.firstInSequence && slotExisting.prev.key && slotExisting.prev.key !== results[i - 1].key) ||
                            (typeof index === "number" && slotExisting.index !== undefined && slotExisting.index !== index - offset + i)) {
                        // A contradiction has been found, so we can't proceed further
                        beginRefresh();
                        return;
                    }

                    if (slotExisting === slotsStart || slotExisting === slotListEnd || slotExisting.bindingMap) {
                        // First choice is a slot with the given key and at least one binding (or an end of the list)
                        slotBestMatch = slotExisting;
                    }
                }

                if (typeof index === "number") {
                    slotExisting = indexMap[index - offset + i];

                    if (slotExisting) {
                        if (slotExisting.key && slotExisting.key !== results[i].key) {
                            // A contradiction has been found, so we can't proceed further
                            beginRefresh();
                            return;
                        }

                        if (!slotBestMatch && slotExisting.bindingMap) {
                            // Second choice is a slot with the given index and at least one binding
                            slotBestMatch = slotExisting;
                        }
                    }
                }

                if (i === offset) {
                    if ((slot.key && slot.key !== results[i].key) || (typeof slot.index === "number" && typeof index === "number" && slot.index !== index)) {
                        // A contradiction has been found, so we can't proceed further
                        beginRefresh();
                        return;
                    }

                    if (!slotBestMatch) {
                        // Third choice is the slot that was passed in
                        slotBestMatch = slot;
                    }
                }

                offsetMap[i] = slotBestMatch;
            }

            // Update items with known indices (and at least one binding) first, as they will not be merged with
            // anything.
            for (i = 0; i < resultsCount; i++) {
                slotExisting = offsetMap[i];
                if (slotExisting && slotExisting.index !== undefined && slotExisting !== slotsStart && slotExisting !== slotListEnd) {
                    matchSlot(slotExisting, results[i]);
                }
            }

            var sequencePairsToMerge = [];

            // Now process the sequences without indices
            var firstSequence = true;
            for (i = 0; i < resultsCount; i++) {
                slotExisting = offsetMap[i];
                if (slotExisting && slotExisting !== slotListEnd) {
                    var iLast = i;

                    if (slotExisting.index === undefined) {
                        var insertionPoint = {};

                        promoteSlot(slotExisting, results[i], index - offset + i, insertionPoint);

                        // Find the extents of the sequence of slots that we can use
                        var slotFirstInSequence = slotExisting,
                            slotLastInSequence = slotExisting,
                            result;

                        for (j = i - 1; !slotFirstInSequence.firstInSequence; j--) {
                            // Keep going until we hit the start marker or a slot that we can't use or promote (it's ok
                            // if j leaves the results range).

                            result = results[j];
                            if (result === startMarker) {
                                break;
                            }

                            // Avoid assigning negative indices to slots
                            var index2 = index - offset + j;
                            if (index2 < 0) {
                                break;
                            }

                            if (promoteSlot(slotFirstInSequence.prev, result, index2, insertionPoint)) {
                                slotFirstInSequence = slotFirstInSequence.prev;
                                if (j >= 0) {
                                    offsetMap[j] = slotFirstInSequence;
                                }
                            } else {
                                break;
                            }
                        }

                        for (j = i + 1; !slotLastInSequence.lastInSequence; j++) {
                            // Keep going until we hit the end marker or a slot that we can't use or promote (it's ok
                            // if j leaves the results range).

                            // If slotListEnd is in this sequence, it should not be separated from any predecessor
                            // slots, but they may need to be promoted.
                            result = results[j];
                            if ((result === endMarker || j === count) && slotLastInSequence.next !== slotListEnd) {
                                break;
                            }

                            if (slotLastInSequence.next === slotListEnd || promoteSlot(slotLastInSequence.next, result, index - offset + j, insertionPoint)) {
                                slotLastInSequence = slotLastInSequence.next;
                                if (j < resultsCount) {
                                    offsetMap[j] = slotLastInSequence;
                                }

                                iLast = j;

                                if (slotLastInSequence === slotListEnd) {
                                    break;
                                }
                            } else {
                                break;
                            }
                        }

                        var slotBeforeSequence = (slotFirstInSequence.firstInSequence ? null : slotFirstInSequence.prev),
                            slotAfterSequence = (slotLastInSequence.lastInSequence ? null : slotLastInSequence.next);

                        if (slotBeforeSequence) {
                            splitSequence(slotBeforeSequence);
                        }
                        if (slotAfterSequence) {
                            splitSequence(slotLastInSequence);
                        }

                        // Move the sequence if necessary
                        if (typeof index === "number") {
                            if (slotLastInSequence === slotListEnd) {
                                // Instead of moving the list end, move the sequence before out of the way
                                if (slotBeforeSequence) {
                                    moveSequenceAfter(slotListEnd, sequenceStart(slotBeforeSequence), slotBeforeSequence);
                                }
                                //#DBG _ASSERT(!slotAfterSequence);
                            } else {
                                var slotInsertBefore = insertionPoint.slotNext;
                                if (!slotInsertBefore) {
                                    slotInsertBefore = successorFromIndex(slotLastInSequence.index, indexMap, slotsStart, slotListEnd, true);
                                }
                                moveSequenceBefore(slotInsertBefore, slotFirstInSequence, slotLastInSequence);
                            }
                            if (slotFirstInSequence.prev.index === slotFirstInSequence.index - 1) {
                                mergeSequences(slotFirstInSequence.prev);
                            }
                            if (slotLastInSequence.next.index === slotLastInSequence.index + 1) {
                                mergeSequences(slotLastInSequence);
                            }
                        } else if (!firstSequence) {
                            //#DBG _ASSERT(slotFirstInSequence === slotExisting);
                            slotBefore = offsetMap[i - 1];

                            if (slotBefore) {
                                if (slotFirstInSequence.prev !== slotBefore) {
                                    if (slotLastInSequence === slotListEnd) {
                                        // Instead of moving the list end, move the sequence before out of the way and
                                        // the predecessor sequence into place.
                                        if (slotBeforeSequence) {
                                            moveSequenceAfter(slotListEnd, sequenceStart(slotBeforeSequence), slotBeforeSequence);
                                        }
                                        moveSequenceBefore(slotFirstInSequence, sequenceStart(slotBefore), slotBefore);
                                    } else {
                                        moveSequenceAfter(slotBefore, slotFirstInSequence, slotLastInSequence);
                                    }
                                }
                                mergeSequences(slotBefore);
                            }
                        }
                        firstSequence = false;

                        if (refreshRequested) {
                            return;
                        }

                        sequencePairsToMerge.push({
                            slotBeforeSequence: slotBeforeSequence,
                            slotFirstInSequence: slotFirstInSequence,
                            slotLastInSequence: slotLastInSequence,
                            slotAfterSequence: slotAfterSequence
                        });
                    }

                    // See if the fetched slot needs to be merged
                    if (i === offset && slotExisting !== slot && !slotPermanentlyRemoved(slot)) {
                        //#DBG _ASSERT(!slot.key);

                        slotBeforeSequence = (slot.firstInSequence ? null : slot.prev);
                        slotAfterSequence = (slot.lastInSequence ? null : slot.next);

                        //#DBG _ASSERT(!slotBeforeSequence || !slotBeforeSequence.key);
                        //#DBG _ASSERT(!slotAfterSequence || !slotAfterSequence.key);
                        
                        sendMirageNotifications(slotExisting, slot, slotExisting.bindingMap);
                        mergeSlots(slotExisting, slot);

                        sequencePairsToMerge.push({
                            slotBeforeSequence: slotBeforeSequence,
                            slotFirstInSequence: slotExisting,
                            slotLastInSequence: slotExisting,
                            slotAfterSequence: slotAfterSequence
                        });
                    }

                    // Skip past all the other items in the sequence we just processed
                    i = iLast;
                }
            }

            // If the count is known, set the index of the list end (wait until now because promoteSlot can sometimes
            // delete it; do this before mergeSequencePairs so the list end can have slots inserted immediately before
            // it).
            if (isNonNegativeNumber(count) && slotListEnd.index !== count) {
                changeSlotIndex(slotListEnd, count);
            }

            // Now that all the sequences have been moved, merge any colliding slots
            mergeSequencePairs(sequencePairsToMerge);
            
            // Match or cache any leftover items
            for (i = 0; i < resultsCount; i++) {
                // Find the first matched item
                slotExisting = offsetMap[i];
                if (slotExisting) {
                    for (j = i - 1; j >= 0; j--) {
                        var slotAfter = offsetMap[j + 1];
                        matchSlot(offsetMap[j] = (slotAfter.firstInSequence ? addSlotBefore(offsetMap[j + 1], indexMap) : slotAfter.prev), results[j]);
                    }
                    for (j = i + 1; j < resultsCount; j++) {
                        slotBefore = offsetMap[j - 1];
                        slotExisting = offsetMap[j];
                        if (!slotExisting) {
                            matchSlot(offsetMap[j] = (slotBefore.lastInSequence ? addSlotAfter(slotBefore, indexMap) : slotBefore.next), results[j]);
                        } else if (slotExisting.firstInSequence) {
                            // Adding the cached items may result in some sequences merging
                            if (slotExisting.prev !== slotBefore) {
                                //#DBG _ASSERT(slotExisting.index === undefined);
                                moveSequenceAfter(slotBefore, slotExisting, sequenceEnd(slotExisting));
                            }
                            mergeSequences(slotBefore);
                        }
                    }
                    break;                    
                }
            }

            // The description is no longer required
            delete slot.description;
        })();

        if (!refreshRequested) {
            // If the count changed, but that's the only thing, just send the notification
            if (count !== undefined && count !== knownCount) {
                changeCount(count);
            }

            // See if there are more requests we can now fulfill
            postFetch();
        }

        finishNotifications();

        /*#DBG
        VERIFYLIST();
        #DBG*/

        // Finally complete any promises for newly obtained items
        callFetchCompleteCallbacks();
    }

    function processErrorResult(slot, error) {
        switch (error.name) {
            case FetchError.noResponse:
                setStatus(DataSourceStatus.failure);
                returnDirectFetchError(slot, error);
                break;

            case FetchError.doesNotExist:
                // Don't return an error, just complete with null (when the slot is deleted)

                if (slot.indexRequested) {
                    //#DBG _ASSERT(isPlaceholder(slot));
                    //#DBG _ASSERT(slot.index !== undefined);
                    
                    // We now have an upper bound on the count
                    removeMirageIndices(slot.index);
                } else if (slot.keyRequested || slot.description) {
                    // This item, and any items in the same sequence, count as mirages, since they might never have
                    // existed.
                    deleteMirageSequence(slot);
                }

                finishNotifications();

                // It's likely that the client requested this item because something has changed since the client's
                // latest observations of the data.  Begin a refresh just in case.
                beginRefresh();
                break;
        }
    }

    function processResultsForIndex(indexRequested, slot, results, offset, count, index) {
        index = validateIndexReturned(index);
        count = validateCountReturned(count);

        var indexFirst = indexRequested - offset;

        var resultsCount = results.length;
        if (slot.index >= indexFirst && slot.index < indexFirst + resultsCount) {
            // The item is in this batch of results - process them all
            processResults(slot, results, slot.index - indexFirst, count, slot.index);
        } else if ((offset === resultsCount - 1 && indexRequested < slot.index) || (isNonNegativeNumber(count) && count <= slot.index)) {
            // The requested index does not exist
            processErrorResult(slot, new WinJS.ErrorFromName(UI.FetchError.doesNotExist));
        } else {
            // We didn't get all the results we requested - pick up where they left off
            if (slot.index < indexFirst) {
                fetchItemsForIndex(indexFirst, slot, listDataAdapter.itemsFromKey(
                    results[0].key,
                    indexFirst - slot.index,
                    0
                ));
            } else {
                var indexLast = indexFirst + resultsCount - 1;
                //#DBG _ASSERT(slot.index > indexLast);

                fetchItemsForIndex(indexLast, slot, listDataAdapter.itemsFromKey(
                    results[resultsCount - 1].key,
                    0,
                    slot.index - indexLast
                ));
            }
        }
    }

    function processErrorResultForIndex(indexRequested, slot, error) {
        // If the request was for an index other than the initial one, and the result was doesNotExist, this doesn't
        switch (error.name) {
            case FetchError.doesNotExist:
                if (indexRequested === slotsStart.index) {
                    // The request was for the start of the list, so the item must not exist, and we now have an upper
                    // bound of zero for the count.
                    removeMirageIndices(0);
                    
                    processErrorResult(slot, error);

                    // No need to check return value of removeMirageIndices, since processErrorResult is going to start
                    // a refresh anyway.
                    //#DBG _ASSERT(refreshRequested);
                } else {
                    // Something has changed, but this index might still exist, so request a refresh
                    beginRefresh();
                }
                break;

            default:
                processErrorResult(slot, error);
                break;
        }
    }

    // Refresh

    function resetRefreshState() {
        // Give the start sentinel an index so we can always use predecessor + 1
        refreshStart = {
            firstInSequence: true,
            lastInSequence: true,
            index: -1
        };
        refreshEnd = {
            firstInSequence: true,
            lastInSequence: true
        };
        refreshStart.next = refreshEnd;
        refreshEnd.prev = refreshStart;

        /*#DBG
        refreshStart.debugInfo = "*** refreshStart ***";
        refreshEnd.debugInfo = "*** refreshEnd ***";
        #DBG*/

        refreshItemsFetched = false;
        refreshCount = undefined;
        keyFetchIDs = {};
        refreshKeyMap = {};
        refreshIndexMap = {};
        refreshIndexMap[-1] = refreshStart;
        deletedKeys = {};
    }

    function beginRefresh() {
        if (refreshRequested) {
            // There's already a refresh that has yet to start
            return;
        }

        refreshRequested = true;

        setStatus(DataSourceStatus.waiting);

        if (waitForRefresh) {
            waitForRefresh = false;

            // The edit queue has been paused until the next refresh - resume it now
            //#DBG _ASSERT(editsQueued);
            applyNextEdit();
            return;
        } 
        
        if (editsQueued) {
            // The refresh will be started once the edit queue empties out
            return;
        }

        var refreshID = ++currentRefreshID;
        refreshInProgress = true;
        refreshFetchesInProgress = 0;

        // Do the rest of the work asynchronously
        setImmediate(function () {
            if (currentRefreshID !== refreshID) {
                return;
            }

            //#DBG _ASSERT(refreshRequested);
            refreshRequested = false;

            resetRefreshState();

            // Remove all slots that aren't live, so we don't waste time fetching them
            for (var slot = slotsStart.next; slot !== slotsEnd; ) {
                var slotNext = slot.next;

                if (!slotLive(slot) && slot !== slotListEnd) {
                    deleteUnnecessarySlot(slot);
                }

                slot = slotNext;
            }

            startRefreshFetches();
        });
    }

    function requestRefresh() {
        refreshSignal = refreshSignal || new Signal();

        beginRefresh();

        return refreshSignal.promise;
    }

    function resultsValidForRefresh(refreshID, fetchID) {
        // This fetch has completed, whatever it has returned
        //#DBG _ASSERT(fetchesInProgress[fetchID]);
        delete fetchesInProgress[fetchID];

        if (refreshID !== currentRefreshID) {
            // This information is out of date.  Ignore it.
            return false;
        }

        //#DBG _ASSERT(refreshFetchesInProgress > 0);
        refreshFetchesInProgress--;

        return true;
    }

    function fetchItemsForRefresh(key, fromStart, fetchID, promiseItems, index) {
        var refreshID = currentRefreshID;

        refreshFetchesInProgress++;

        promiseItems.then(function (fetchResult) {
            if (fetchResult.items && fetchResult.items.length) {
                if (resultsValidForRefresh(refreshID, fetchID)) {
                    addMarkers(fetchResult);
                    processRefreshResults(key, fetchResult.items, fetchResult.offset, fetchResult.totalCount, (typeof index === "number" ? index : fetchResult.absoluteIndex));
                }
            } else {
                return Promise.wrapError(new WinJS.ErrorFromName(FetchError.doesNotExist));
            }
        }).then(null, function (error) {
            if (resultsValidForRefresh(refreshID, fetchID)) {
                processRefreshErrorResult(key, fromStart, error);
            }
        });
    }

    function refreshRange(slot, fetchID, countBefore, countAfter) {
        if (listDataAdapter.itemsFromKey) {
            // Keys are the preferred identifiers when the item might have moved
            fetchItemsForRefresh(slot.key, false, fetchID, listDataAdapter.itemsFromKey(slot.key, countBefore, countAfter, slot.hints));
        } else {
            // Request additional items to try to locate items that have moved
            var searchDelta = 10,
                index = slot.index;

            //#DBG _ASSERT(+index === index);

            if (refreshIndexMap[index] && refreshIndexMap[index].firstInSequence) {
                // Ensure at least one element is observed before this one
                fetchItemsForRefresh(slot.key, false, fetchID, listDataAdapter.itemsFromIndex(index - 1, Math.min(countBefore + searchDelta, index) - 1, countAfter + 1 + searchDelta), index - 1);
            } else if (refreshIndexMap[index] && refreshIndexMap[index].lastInSequence) {
                // Ask for the next index we need directly
                fetchItemsForRefresh(slot.key, false, fetchID, listDataAdapter.itemsFromIndex(index + 1, Math.min(countBefore + searchDelta, index) + 1, countAfter - 1 + searchDelta), index + 1);
            } else {
                fetchItemsForRefresh(slot.key, false, fetchID, listDataAdapter.itemsFromIndex(index, Math.min(countBefore + searchDelta, index), countAfter + searchDelta), index);
            }
        }
    }

    function refreshFirstItem(fetchID) {
        if (listDataAdapter.itemsFromStart) {
            fetchItemsForRefresh(null, true, fetchID, listDataAdapter.itemsFromStart(1), 0);
        } else if (listDataAdapter.itemsFromIndex) {
            fetchItemsForRefresh(null, true, fetchID, listDataAdapter.itemsFromIndex(0, 0, 0), 0);
        }
    }

    function keyFetchInProgress(key) {
        return fetchesInProgress[keyFetchIDs[key]];
    }

    function refreshRanges(slotFirst, allRanges) {
        // Fetch a few extra items each time, to catch insertions without requiring an extra fetch
        var refreshFetchExtra = 3;

        var refreshID = currentRefreshID;

        var slotFetchFirst,
            slotRefreshFirst,
            fetchCount = 0,
            fetchID;

        // Walk through the slot list looking for keys we haven't fetched or attempted to fetch yet.  Rely on the
        // heuristic that items that were close together before the refresh are likely to remain so after, so batched
        // fetches will locate most of the previously fetched items.
        for (var slot = slotFirst; slot !== slotsEnd; slot = slot.next) {
            if (!slotFetchFirst && slot.key && !deletedKeys[slot.key] && !keyFetchInProgress(slot.key)) {
                var slotRefresh = refreshKeyMap[slot.key];

                // Keep attempting to fetch an item until at least one item on either side of it has been observed, so
                // we can determine its position relative to others.
                if (!slotRefresh || slotRefresh.firstInSequence || slotRefresh.lastInSequence) {
                    slotFetchFirst = slot;
                    slotRefreshFirst = slotRefresh;
                    fetchID = newFetchID();
                }
            }

            if (!slotFetchFirst) {
                // Also attempt to fetch placeholders for requests for specific keys, just in case those items no
                // longer exist.
                if (slot.key && isPlaceholder(slot) && !deletedKeys[slot.key]) {
                    // Fulfill each "itemFromKey" request
                    //#DBG _ASSERT(listDataAdapter.itemsFromKey);
                    if (!refreshKeyMap[slot.key]) {
                        // Fetch at least one item before and after, just to verify item's position in list
                        fetchItemsForRefresh(slot.key, false, newFetchID(), listDataAdapter.itemsFromKey(slot.key, 1, 1, slot.hints));
                    }
                }
            } else {
                var keyAlreadyFetched = keyFetchInProgress(slot.key);

                if (!deletedKeys[slot.key] && !refreshKeyMap[slot.key] && !keyAlreadyFetched) {
                    if (slot.key) {
                        keyFetchIDs[slot.key] = fetchID;
                    }
                    fetchCount++;
                }

                if (slot.lastInSequence || slot.next === slotListEnd || keyAlreadyFetched) {
                    refreshRange(slotFetchFirst, fetchID, (!slotRefreshFirst || slotRefreshFirst.firstInSequence ? refreshFetchExtra : 0), fetchCount - 1 + refreshFetchExtra);

                    /*#DBG
                    fetchID = undefined;
                    #DBG*/

                    if (!allRanges) {
                        break;
                    }

                    slotFetchFirst = null;
                    fetchCount = 0;
                }
            }
        }

        if (refreshFetchesInProgress === 0 && !refreshItemsFetched && currentRefreshID === refreshID) {
            // If nothing was successfully fetched, try fetching the first item, to detect an empty list
            refreshFirstItem(newFetchID());
        }

        //#DBG _ASSERT(fetchID === undefined);
    }

    function startRefreshFetches() {
        var refreshID = currentRefreshID;

        do {
            synchronousProgress = false;
            reentrantContinue = true;
            refreshRanges(slotsStart.next, true);
            reentrantContinue = false;
        } while (refreshFetchesInProgress === 0 && synchronousProgress && currentRefreshID === refreshID && refreshInProgress);

        if (refreshFetchesInProgress === 0 && currentRefreshID === refreshID) {
            concludeRefresh();
        }
    }

    function continueRefresh(key) {
        var refreshID = currentRefreshID;

        // If the key is absent, then the attempt to fetch the first item just completed, and there is nothing else to
        // fetch.
        if (key) {
            var slotContinue = keyMap[key];
            if (!slotContinue) {
                // In a rare case, the slot might have been deleted; just start scanning from the beginning again
                slotContinue = slotsStart.next;
            }

            do {
                synchronousRefresh = false;
                reentrantRefresh = true;
                refreshRanges(slotContinue, false);
                reentrantRefresh = false;
            } while (synchronousRefresh && currentRefreshID === refreshID && refreshInProgress);
        }

        if (reentrantContinue) {
            synchronousProgress = true;
        } else {
            if (refreshFetchesInProgress === 0 && currentRefreshID === refreshID) {
                // Walk through the entire list one more time, in case any edits were made during the refresh
                startRefreshFetches();
            }
        }
    }

    function slotRefreshFromResult(result) {
        if (typeof result !== "object" || !result) {
            throw new WinJS.ErrorFromName("WinJS.UI.ListDataSource.InvalidItemReturned", strings.invalidItemReturned);
        } else if (result === startMarker) {
            return refreshStart;
        } else if (result === endMarker) {
            return refreshEnd;
        } else if (!result.key) {
            throw new WinJS.ErrorFromName("WinJS.UI.ListDataSource.InvalidKeyReturned", strings.invalidKeyReturned);
        } else {
            return refreshKeyMap[result.key];
        }
    }

    function processRefreshSlotIndex(slot, expectedIndex) {
        while (slot.index === undefined) {
            setSlotIndex(slot, expectedIndex, refreshIndexMap);

            if (slot.firstInSequence) {
                return true;
            }

            slot = slot.prev;
            expectedIndex--;
        }

        if (slot.index !== expectedIndex) {
            // Something has changed since the refresh began; start again
            beginRefresh();
            return false;
        }

        return true;
    }

    function setRefreshSlotResult(slotRefresh, result) {
        //#DBG _ASSERT(result.key);
        slotRefresh.key = result.key;
        //#DBG _ASSERT(!refreshKeyMap[slotRefresh.key]);
        refreshKeyMap[slotRefresh.key] = slotRefresh;

        slotRefresh.item = result;
    }

    // Returns the slot after the last insertion point between sequences
    function lastRefreshInsertionPoint() {
        var slotNext = refreshEnd;
        while (!slotNext.firstInSequence) {
            slotNext = slotNext.prev;

            if (slotNext === refreshStart) {
                return null;
            }
        }

        return slotNext;
    }

    function processRefreshResults(key, results, offset, count, index) {
        index = validateIndexReturned(index);
        count = validateCountReturned(count);

        /*#DBG
        VERIFYREFRESHLIST();
        #DBG*/

        var keyPresent = false;

        refreshItemsFetched = true;

        var indexFirst = index - offset,
            result = results[0];

        if (result.key === key) {
            keyPresent = true;
        }

        var slot = slotRefreshFromResult(result);
        if (!slot) {
            if (refreshIndexMap[indexFirst]) {
                // Something has changed since the refresh began; start again
                beginRefresh();
                return;
            }

            // See if these results should be appended to an existing sequence
            var slotPrev;
            if (index !== undefined && (slotPrev = refreshIndexMap[indexFirst - 1])) {
                if (!slotPrev.lastInSequence) {
                    // Something has changed since the refresh began; start again
                    beginRefresh();
                    return;
                }
                slot = addSlotAfter(slotPrev, refreshIndexMap);
            } else {
                // Create a new sequence
                var slotSuccessor = (
                    +indexFirst === indexFirst ?
                        successorFromIndex(indexFirst, refreshIndexMap, refreshStart, refreshEnd) :
                        lastRefreshInsertionPoint(refreshStart, refreshEnd)
                );

                if (!slotSuccessor) {
                    // Something has changed since the refresh began; start again
                    beginRefresh();
                    return;
                }

                slot = createSlotSequence(slotSuccessor, indexFirst, refreshIndexMap);
            }

            setRefreshSlotResult(slot, results[0]);
        } else {
            if (+indexFirst === indexFirst) {
                if (!processRefreshSlotIndex(slot, indexFirst)) {
                    return;
                }
            }
        }

        var resultsCount = results.length;
        for (var i = 1; i < resultsCount; i++) {
            result = results[i];

            if (result.key === key) {
                keyPresent = true;
            }

            var slotNext = slotRefreshFromResult(result);

            if (!slotNext) {
                if (!slot.lastInSequence) {
                    // Something has changed since the refresh began; start again
                    beginRefresh();
                    return;
                }
                slotNext = addSlotAfter(slot, refreshIndexMap);
                setRefreshSlotResult(slotNext, result);
            } else {
                if (slot.index !== undefined && !processRefreshSlotIndex(slotNext, slot.index + 1)) {
                    return;
                }

                // If the slots aren't adjacent, see if it's possible to reorder sequences to make them so
                if (slotNext !== slot.next) {
                    if (!slot.lastInSequence || !slotNext.firstInSequence) {
                        // Something has changed since the refresh began; start again
                        beginRefresh();
                        return;
                    }

                    var slotLast = sequenceEnd(slotNext);
                    if (slotLast !== refreshEnd) {
                        moveSequenceAfter(slot, slotNext, slotLast);
                    } else {
                        var slotFirst = sequenceStart(slot);
                        if (slotFirst !== refreshStart) {
                            moveSequenceBefore(slotNext, slotFirst, slot);
                        } else {
                            // Something has changed since the refresh began; start again
                            beginRefresh();
                            return;
                        }
                    }

                    mergeSequences(slot);
                } else if (slot.lastInSequence) {
                    //#DBG _ASSERT(slotNext.firstInSequence);

                    mergeSequences(slot);
                }
            }

            slot = slotNext;
        }

        if (!keyPresent) {
            deletedKeys[key] = true;
        }

        // If the count wasn't provided, see if it can be determined from the end of the list.
        if (!isNonNegativeNumber(count) && !refreshEnd.firstInSequence) {
            var indexLast = refreshEnd.prev.index;
            if (indexLast !== undefined) {
                count = indexLast + 1;
            }
        }

        if (isNonNegativeNumber(count) || count === CountResult.unknown) {
            if (isNonNegativeNumber(refreshCount)) {
                if (count !== refreshCount) {
                    // Something has changed since the refresh began; start again
                    beginRefresh();
                    return;
                }
            } else {
                refreshCount = count;
            }

            if (isNonNegativeNumber(refreshCount) && !refreshIndexMap[refreshCount]) {
                setSlotIndex(refreshEnd, refreshCount, refreshIndexMap);
            }
        }

        /*#DBG
        VERIFYREFRESHLIST();
        #DBG*/

        if (reentrantRefresh) {
            synchronousRefresh = true;
        } else {
            continueRefresh(key);
        }
    }

    function processRefreshErrorResult(key, fromStart, error) {
        switch (error.name) {
            case FetchError.noResponse:
                setStatus(DataSourceStatus.failure);
                break;

            case FetchError.doesNotExist:
                if (fromStart) {
                    // The attempt to fetch the first item failed, so the list must be empty
                    //#DBG _ASSERT(refreshStart.next === refreshEnd);
                    //#DBG _ASSERT(refreshStart.lastInSequence && refreshEnd.firstInSequence);

                    setSlotIndex(refreshEnd, 0, refreshIndexMap);
                    refreshCount = 0;

                    concludeRefresh();
                } else {
                    deletedKeys[key] = true;

                    if (reentrantRefresh) {
                        synchronousRefresh = true;
                    } else {
                        continueRefresh(key);
                    }
                }
                break;
        }
    }

    function slotFromSlotRefresh(slotRefresh) {
        if (slotRefresh === refreshStart) {
            return slotsStart;
        } else if (slotRefresh === refreshEnd) {
            return slotListEnd;
        } else {
            return keyMap[slotRefresh.key];
        }
    }

    function slotRefreshFromSlot(slot) {
        if (slot === slotsStart) {
            return refreshStart;
        } else if (slot === slotListEnd) {
            return refreshEnd;
        } else {
            return refreshKeyMap[slot.key];
        }
    }

    function mergeSequencesForRefresh(slotPrev) {
        mergeSequences(slotPrev);

        // Mark the merge point, so we can distinguish insertions from unrequested items
        slotPrev.next.mergedForRefresh = true;
    }

    function copyRefreshSlotData(slotRefresh, slot) {
        setSlotKey(slot, slotRefresh.key);
        slot.itemNew = slotRefresh.item;
    }

    function addNewSlotFromRefresh(slotRefresh, slotNext, insertAfter) {
        var slotNew = createPrimarySlot();

        copyRefreshSlotData(slotRefresh, slotNew);
        insertAndMergeSlot(slotNew, slotNext, insertAfter, !insertAfter);

        var index = slotRefresh.index;
        if (+index !== index) {
            index = (insertAfter ? slotNew.prev.index + 1 : slotNext.next.index - 1);
        }

        setSlotIndex(slotNew, index, indexMap);

        return slotNew;
    }

    function matchSlotForRefresh(slotExisting, slot, slotRefresh) {
        if (slotExisting) {
            sendMirageNotifications(slotExisting, slot, slotExisting.bindingMap);
            mergeSlotsAndItem(slotExisting, slot, slotRefresh.item);
        } else {
            copyRefreshSlotData(slotRefresh, slot);

            // If the index was requested, complete the promises now, as the index might be about to change
            if (slot.indexRequested) {
                updateSlotItem(slot);
            }
        }
    }

    function updateSlotForRefresh(slotExisting, slot, slotRefresh) {
        if (!slot.key) {
            if (slotExisting) {
                // Record the relationship between the slot to discard and its neighbors
                slotRefresh.mergeWithPrev = !slot.firstInSequence;
                slotRefresh.mergeWithNext = !slot.lastInSequence;
            } else {
                slotRefresh.stationary = true;
            }
            matchSlotForRefresh(slotExisting, slot, slotRefresh);
            return true;
        } else {
            //#DBG _ASSERT(!slotExisting);
            return false;
        }
    }

    function indexForRefresh(slot) {
        var indexNew;

        if (slot.indexRequested) {
            //#DBG _ASSERT(!slot.key);
            indexNew = slot.index;
        } else {
            var slotRefresh = slotRefreshFromSlot(slot);
            if (slotRefresh) {
                indexNew = slotRefresh.index;
            }
        }

        return indexNew;
    }

    function concludeRefresh() {
        //#DBG _ASSERT(refreshInProgress);
        //#DBG _ASSERT(!indexUpdateDeferred);

        indexUpdateDeferred = true;

        keyFetchIDs = {};

        var i,
            j,
            slot,
            slotPrev,
            slotNext,
            slotBefore,
            slotAfter,
            slotRefresh,
            slotExisting,
            slotsAvailable = [],
            slotFirstInSequence,
            sequenceCountOld,
            sequencesOld = [],
            sequenceOld,
            sequenceOldPrev,
            sequenceOldBestMatch,
            sequenceCountNew,
            sequencesNew = [],
            sequenceNew,
            index,
            offset;

        /*#DBG
        VERIFYLIST();
        VERIFYREFRESHLIST();
        #DBG*/

        // Assign a sequence number to each refresh slot
        sequenceCountNew = 0;
        for (slotRefresh = refreshStart; slotRefresh; slotRefresh = slotRefresh.next) {
            slotRefresh.sequenceNumber = sequenceCountNew;

            if (slotRefresh.firstInSequence) {
                slotFirstInSequence = slotRefresh;
            }

            if (slotRefresh.lastInSequence) {
                sequencesNew[sequenceCountNew] = {
                    first: slotFirstInSequence,
                    last: slotRefresh,
                    matchingItems: 0
                };
                sequenceCountNew++;
            }
        }

        // Remove unnecessary information from main slot list, and update the items
        lastSlotReleased = null;
        releasedSlots = 0;
        for (slot = slotsStart.next; slot !== slotsEnd; ) {
            slotRefresh = refreshKeyMap[slot.key];
            slotNext = slot.next;

            if (slot !== slotListEnd) {
                if (!slotLive(slot)) {
                    // Some more items might have been released since the refresh started.  Strip them away from the
                    // main slot list, as they'll just get in the way from now on.  Since we're discarding these, but
                    // don't know if they're actually going away, split the sequence as our starting assumption must be
                    // that the items on either side are in separate sequences.
                    deleteUnnecessarySlot(slot);
                } else if (slot.key && !slotRefresh) {
                    // Remove items that have been deleted (or moved far away) and send removed notifications
                    deleteSlot(slot, false);
                } else if (refreshCount === 0 || (slot.indexRequested && slot.index >= refreshCount)) {
                    // Remove items that can't exist in the list and send mirage removed notifications
                    deleteSlot(slot, true);
                } else if (slot.item || slot.keyRequested) {
                    //#DBG _ASSERT(slotRefresh);

                    // Store the new item; this value will be compared with that stored in slot.item later
                    slot.itemNew = slotRefresh.item;
                } else {
                    //#DBG _ASSERT(!slot.item);

                    // Clear keys and items that have never been observed by client
                    if (slot.key) {
                        if (!slot.keyRequested) {
                            delete keyMap[slot.key];
                            delete slot.key;
                        }
                        slot.itemNew = null;
                    }
                }
            }

            slot = slotNext;
        }

        /*#DBG
        VERIFYLIST();
        #DBG*/

        // Placeholders generated by itemsAtIndex should not move.  Match these to items now if possible, or merge them
        // with existing items if necessary.
        for (slot = slotsStart.next; slot !== slotListEnd; ) {
            slotNext = slot.next;

            //#DBG _ASSERT(!slot.key || refreshKeyMap[slot.key]);

            if (slot.indexRequested) {
                //#DBG _ASSERT(!slot.item);
                //#DBG _ASSERT(slot.index !== undefined);

                slotRefresh = refreshIndexMap[slot.index];
                if (slotRefresh) {
                    matchSlotForRefresh(slotFromSlotRefresh(slotRefresh), slot, slotRefresh);
                }
            }

            slot = slotNext;
        }

        /*#DBG
        VERIFYLIST();
        #DBG*/

        // Match old sequences to new sequences
        var bestMatch,
            bestMatchCount,
            previousBestMatch = 0,
            newSequenceCounts = [],
            slotIndexRequested,
            sequenceIndexEnd,
            sequenceOldEnd;

        sequenceCountOld = 0;
        for (slot = slotsStart; slot !== slotsEnd; slot = slot.next) {
            if (slot.firstInSequence) {
                slotFirstInSequence = slot;
                slotIndexRequested = null;
                for (i = 0; i < sequenceCountNew; i++) {
                    newSequenceCounts[i] = 0;
                }
            }

            if (slot.indexRequested) {
                slotIndexRequested = slot;
            }

            slotRefresh = slotRefreshFromSlot(slot);
            if (slotRefresh) {
                //#DBG _ASSERT(slotRefresh.sequenceNumber !== undefined);
                newSequenceCounts[slotRefresh.sequenceNumber]++;
            }

            if (slot.lastInSequence) {
                // Determine which new sequence is the best match for this old one.  Use a simple greedy algorithm to
                // ensure the relative ordering of matched sequences is the same; out-of-order sequences will require
                // move notifications.
                bestMatchCount = 0;
                for (i = previousBestMatch; i < sequenceCountNew; i++) {
                    if (bestMatchCount < newSequenceCounts[i]) {
                        bestMatchCount = newSequenceCounts[i];
                        bestMatch = i;
                    }
                }

                sequenceOld = {
                    first: slotFirstInSequence,
                    last: slot,
                    sequenceNew: (bestMatchCount > 0 ? sequencesNew[bestMatch] : undefined),
                    matchingItems: bestMatchCount
                };

                if (slotIndexRequested) {
                    sequenceOld.indexRequested = true;
                    sequenceOld.stationarySlot = slotIndexRequested;
                }

                sequencesOld[sequenceCountOld] = sequenceOld;

                if (slot === slotListEnd) {
                    sequenceIndexEnd = sequenceCountOld;
                    sequenceOldEnd = sequenceOld;
                }

                sequenceCountOld++;

                if (sequencesNew[bestMatch].first.index !== undefined) {
                    previousBestMatch = bestMatch;
                }
            }
        }

        //#DBG _ASSERT(sequenceOldEnd);

        // Special case: split the old start into a separate sequence if the new start isn't its best match
        if (sequencesOld[0].sequenceNew !== sequencesNew[0]) {
            //#DBG _ASSERT(sequencesOld[0].first === slotsStart);
            //#DBG _ASSERT(!slotsStart.lastInSequence);
            splitSequence(slotsStart);
            sequencesOld[0].first = slotsStart.next;
            sequencesOld.unshift({
                first: slotsStart,
                last: slotsStart,
                sequenceNew: sequencesNew[0],
                matchingItems: 1
            });
            sequenceIndexEnd++;
            sequenceCountOld++;
        }

        var listEndObserved = !slotListEnd.firstInSequence;

        // Special case: split the old end into a separate sequence if the new end isn't its best match
        if (sequenceOldEnd.sequenceNew !== sequencesNew[sequenceCountNew - 1]) {
            //#DBG _ASSERT(sequenceOldEnd.last === slotListEnd);
            //#DBG _ASSERT(!slotListEnd.firstInSequence);
            splitSequence(slotListEnd.prev);
            sequenceOldEnd.last = slotListEnd.prev;
            sequenceIndexEnd++;
            sequencesOld.splice(sequenceIndexEnd, 0, {
                first: slotListEnd,
                last: slotListEnd,
                sequenceNew: sequencesNew[sequenceCountNew - 1],
                matchingItems: 1
            });
            sequenceCountOld++;
            sequenceOldEnd = sequencesOld[sequenceIndexEnd];
        }

        // Map new sequences to old sequences
        for (i = 0; i < sequenceCountOld; i++) {
            sequenceNew = sequencesOld[i].sequenceNew;
            if (sequenceNew && sequenceNew.matchingItems < sequencesOld[i].matchingItems) {
                sequenceNew.matchingItems = sequencesOld[i].matchingItems;
                sequenceNew.sequenceOld = sequencesOld[i];
            }
        }

        // The old end must always be the best match for the new end (if the new end is also the new start, they will
        // be merged below).
        sequencesNew[sequenceCountNew - 1].sequenceOld = sequenceOldEnd;
        sequenceOldEnd.stationarySlot = slotListEnd;

        // The old start must always be the best match for the new start
        sequencesNew[0].sequenceOld = sequencesOld[0];
        sequencesOld[0].stationarySlot = slotsStart;

        /*#DBG
        VERIFYLIST();
        #DBG*/

        // Merge additional indexed old sequences when possible

        // First do a forward pass
        for (i = 0; i <= sequenceIndexEnd; i++) {
            sequenceOld = sequencesOld[i];

            //#DBG _ASSERT(sequenceOld);
            if (sequenceOld.sequenceNew && (sequenceOldBestMatch = sequenceOld.sequenceNew.sequenceOld) === sequenceOldPrev && sequenceOldPrev.last !== slotListEnd) {
                //#DBG _ASSERT(sequenceOldBestMatch.last.next === sequenceOld.first);
                mergeSequencesForRefresh(sequenceOldBestMatch.last);
                sequenceOldBestMatch.last = sequenceOld.last;
                delete sequencesOld[i];
            } else {
                sequenceOldPrev = sequenceOld;
            }
        }

        // Now do a reverse pass
        sequenceOldPrev = null;
        for (i = sequenceIndexEnd; i >= 0; i--) {
            sequenceOld = sequencesOld[i];
            // From this point onwards, some members of sequencesOld may be undefined
            if (sequenceOld) {
                if (sequenceOld.sequenceNew && (sequenceOldBestMatch = sequenceOld.sequenceNew.sequenceOld) === sequenceOldPrev && sequenceOld.last !== slotListEnd) {
                    //#DBG _ASSERT(sequenceOld.last.next === sequenceOldBestMatch.first);
                    mergeSequencesForRefresh(sequenceOld.last);
                    sequenceOldBestMatch.first = sequenceOld.first;
                    delete sequencesOld[i];
                } else {
                    sequenceOldPrev = sequenceOld;
                }
            }
        }

        // Since we may have forced the list end into a separate sequence, the mergedForRefresh flag may be incorrect
        if (listEndObserved) {
            delete slotListEnd.mergedForRefresh;
        }

        var sequencePairsToMerge = [];

        // Find unchanged sequences without indices that can be merged with existing sequences without move
        // notifications.
        for (i = sequenceIndexEnd + 1; i < sequenceCountOld; i++) {
            sequenceOld = sequencesOld[i];
            if (sequenceOld && (!sequenceOld.sequenceNew || sequenceOld.sequenceNew.sequenceOld !== sequenceOld)) {
                //#DBG _ASSERT(!sequenceOld.indexRequested);

                // If the order of the known items in the sequence is unchanged, then the sequence probably has not
                // moved, but we now know where it belongs relative to at least one other sequence.
                var orderPreserved = true,
                    slotRefreshFirst = null,
                    slotRefreshLast = null,
                    sequenceLength = 0;                
                slotRefresh = slotRefreshFromSlot(sequenceOld.first);
                if (slotRefresh) {
                    slotRefreshFirst = slotRefreshLast = slotRefresh;
                    sequenceLength = 1;
                }
                for (slot = sequenceOld.first; slot != sequenceOld.last; slot = slot.next) {
                    var slotRefreshNext = slotRefreshFromSlot(slot.next);

                    if (slotRefresh && slotRefreshNext && (slotRefresh.lastInSequence || slotRefresh.next !== slotRefreshNext)) {
                        orderPreserved = false;
                        break;
                    }

                    if (slotRefresh && !slotRefreshFirst) {
                        slotRefreshFirst = slotRefreshLast = slotRefresh;
                    }

                    if (slotRefreshNext && slotRefreshFirst) {
                        slotRefreshLast = slotRefreshNext;
                        sequenceLength++;
                    }

                    slotRefresh = slotRefreshNext;
                }

                // If the stationary sequence has indices, verify that there is enough space for this sequence - if
                // not, then something somewhere has moved after all.
                if (orderPreserved && slotRefreshFirst && slotRefreshFirst.index !== undefined) {
                    var indexBefore;
                    if (!slotRefreshFirst.firstInSequence) {
                        slotBefore = slotFromSlotRefresh(slotRefreshFirst.prev);
                        if (slotBefore) {
                            indexBefore = slotBefore.index;
                        }
                    }

                    var indexAfter;
                    if (!slotRefreshLast.lastInSequence) {
                        slotAfter = slotFromSlotRefresh(slotRefreshLast.next);
                        if (slotAfter) {
                            indexAfter = slotAfter.index;
                        }
                    }

                    if ((!slotAfter || slotAfter.lastInSequence || slotAfter.mergedForRefresh) &&
                            (indexBefore === undefined || indexAfter === undefined || indexAfter - indexBefore - 1 >= sequenceLength)) {
                        sequenceOld.locationJustDetermined = true;

                        // Mark the individual refresh slots as not requiring move notifications
                        for (slotRefresh = slotRefreshFirst; ; slotRefresh = slotRefresh.next) {
                            slotRefresh.locationJustDetermined = true;

                            if (slotRefresh === slotRefreshLast) {
                                break;
                            }
                        }

                        // Store any adjacent placeholders so they can be merged once the moves and insertions have
                        // been processed.
                        var slotFirstInSequence = slotFromSlotRefresh(slotRefreshFirst),
                            slotLastInSequence = slotFromSlotRefresh(slotRefreshLast);
                        sequencePairsToMerge.push({
                            slotBeforeSequence: (slotFirstInSequence.firstInSequence ? null : slotFirstInSequence.prev),
                            slotFirstInSequence: slotFirstInSequence,
                            slotLastInSequence: slotLastInSequence,
                            slotAfterSequence: (slotLastInSequence.lastInSequence ? null : slotLastInSequence.next)
                        });
                    }
                }
            }
        }

        // Remove placeholders in old sequences that don't map to new sequences (and don't contain requests for a
        // specific index or key), as they no longer have meaning.
        for (i = 0; i < sequenceCountOld; i++) {
            sequenceOld = sequencesOld[i];
            if (sequenceOld && !sequenceOld.indexRequested && !sequenceOld.locationJustDetermined && (!sequenceOld.sequenceNew || sequenceOld.sequenceNew.sequenceOld !== sequenceOld)) {
                sequenceOld.sequenceNew = null;

                slot = sequenceOld.first;

                var sequenceEndReached;
                do {
                    sequenceEndReached = (slot === sequenceOld.last);

                    slotNext = slot.next;

                    if (slot !== slotsStart && slot !== slotListEnd && slot !== slotsEnd && !slot.item && !slot.keyRequested) {
                        //#DBG _ASSERT(!slot.indexRequested);
                        deleteSlot(slot, true);
                        if (sequenceOld.first === slot) {
                            if (sequenceOld.last === slot) {
                                delete sequencesOld[i];
                                break;
                            } else {
                                sequenceOld.first = slot.next;
                            }
                        } else if (sequenceOld.last === slot) {
                            sequenceOld.last = slot.prev;
                        }
                    }

                    slot = slotNext;
                } while (!sequenceEndReached);
            }
        }

        /*#DBG
        VERIFYLIST();
        #DBG*/

        // Locate boundaries of new items in new sequences
        for (i = 0; i < sequenceCountNew; i++) {
            sequenceNew = sequencesNew[i];
            for (slotRefresh = sequenceNew.first; !slotFromSlotRefresh(slotRefresh) && !slotRefresh.lastInSequence; slotRefresh = slotRefresh.next) {
                /*@empty*/
            }
            if (slotRefresh.lastInSequence && !slotFromSlotRefresh(slotRefresh)) {
                sequenceNew.firstInner = sequenceNew.lastInner = null;
            } else {
                sequenceNew.firstInner = slotRefresh;
                for (slotRefresh = sequenceNew.last; !slotFromSlotRefresh(slotRefresh); slotRefresh = slotRefresh.prev) {
                    /*@empty*/
                }
                sequenceNew.lastInner = slotRefresh;
            }
        }

        // Determine which items to move
        for (i = 0; i < sequenceCountNew; i++) {
            sequenceNew = sequencesNew[i];
            if (sequenceNew && sequenceNew.firstInner) {
                sequenceOld = sequenceNew.sequenceOld;
                if (sequenceOld) {
                    // Number the slots in each new sequence with their offset in the corresponding old sequence (or
                    // undefined if in a different old sequence).
                    var ordinal = 0;
                    for (slot = sequenceOld.first; true; slot = slot.next, ordinal++) {
                        slotRefresh = slotRefreshFromSlot(slot);
                        if (slotRefresh && slotRefresh.sequenceNumber === sequenceNew.firstInner.sequenceNumber) {
                            slotRefresh.ordinal = ordinal;
                        }

                        if (slot.lastInSequence) {
                            //#DBG _ASSERT(slot === sequenceOld.last);
                            break;
                        }
                    }

                    // Determine longest subsequence of items that are in the same order before and after
                    var piles = [];
                    for (slotRefresh = sequenceNew.firstInner; true; slotRefresh = slotRefresh.next) {
                        ordinal = slotRefresh.ordinal;
                        if (ordinal !== undefined) {
                            var searchFirst = 0,
                                searchLast = piles.length - 1;
                            while (searchFirst <= searchLast) {
                                var searchMidpoint = Math.floor(0.5 * (searchFirst + searchLast));
                                if (piles[searchMidpoint].ordinal < ordinal) {
                                    searchFirst = searchMidpoint + 1;
                                } else {
                                    searchLast = searchMidpoint - 1;
                                }
                            }
                            piles[searchFirst] = slotRefresh;
                            if (searchFirst > 0) {
                                slotRefresh.predecessor = piles[searchFirst - 1];
                            }
                        }

                        if (slotRefresh === sequenceNew.lastInner) {
                            break;
                        }
                    }

                    // The items in the longest ordered subsequence don't move; everything else does
                    var stationaryItems = [],
                        stationaryItemCount = piles.length;
                    //#DBG _ASSERT(stationaryItemCount > 0);
                    slotRefresh = piles[stationaryItemCount - 1];
                    for (j = stationaryItemCount; j--; ) {
                        slotRefresh.stationary = true;
                        stationaryItems[j] = slotRefresh;
                        slotRefresh = slotRefresh.predecessor;
                    }
                    //#DBG _ASSERT(!slotRefresh);
                    sequenceOld.stationarySlot = slotFromSlotRefresh(stationaryItems[0]);

                    // Try to match new items before the first stationary item to placeholders
                    slotRefresh = stationaryItems[0];
                    slot = slotFromSlotRefresh(slotRefresh);
                    slotPrev = slot.prev;
                    var sequenceBoundaryReached = slot.firstInSequence;
                    while (!slotRefresh.firstInSequence) {
                        slotRefresh = slotRefresh.prev;
                        slotExisting = slotFromSlotRefresh(slotRefresh);
                        if (!slotExisting || slotRefresh.locationJustDetermined) {
                            // Find the next placeholder walking backwards
                            while (!sequenceBoundaryReached && slotPrev !== slotsStart) {
                                slot = slotPrev;
                                slotPrev = slot.prev;
                                sequenceBoundaryReached = slot.firstInSequence;

                                if (updateSlotForRefresh(slotExisting, slot, slotRefresh)) {
                                    break;
                                }
                            }
                        }
                    }

                    // Try to match new items between stationary items to placeholders
                    for (j = 0; j < stationaryItemCount - 1; j++) {
                        slotRefresh = stationaryItems[j];
                        slot = slotFromSlotRefresh(slotRefresh);
                        //#DBG _ASSERT(slot);
                        var slotRefreshStop = stationaryItems[j + 1],
                            slotRefreshMergePoint = null,
                            slotStop = slotFromSlotRefresh(slotRefreshStop),
                            slotExisting;
                        //#DBG _ASSERT(slotStop);

                        // Find all the new items
                        slotNext = slot.next;
                        for (slotRefresh = slotRefresh.next; slotRefresh !== slotRefreshStop && !slotRefreshMergePoint && slot !== slotStop; slotRefresh = slotRefresh.next) {
                            slotExisting = slotFromSlotRefresh(slotRefresh);
                            if (!slotExisting || slotRefresh.locationJustDetermined) {
                                // Find the next placeholder
                                while (slotNext !== slotStop) {
                                    // If a merge point is reached, match the remainder of the placeholders by walking backwards
                                    if (slotNext.mergedForRefresh) {
                                        slotRefreshMergePoint = slotRefresh.prev;
                                        break;
                                    }

                                    slot = slotNext;
                                    slotNext = slot.next;

                                    if (updateSlotForRefresh(slotExisting, slot, slotRefresh)) {
                                        break;
                                    }
                                }
                            }
                        }

                        // Walk backwards to the first merge point if necessary
                        if (slotRefreshMergePoint) {
                            slotPrev = slotStop.prev;
                            for (slotRefresh = slotRefreshStop.prev; slotRefresh !== slotRefreshMergePoint && slotStop !== slot; slotRefresh = slotRefresh.prev) {
                                slotExisting = slotFromSlotRefresh(slotRefresh);
                                if (!slotExisting || slotRefresh.locationJustDetermined) {
                                    // Find the next placeholder walking backwards
                                    while (slotPrev !== slot) {
                                        slotStop = slotPrev;
                                        slotPrev = slotStop.prev;

                                        if (updateSlotForRefresh(slotExisting, slotStop, slotRefresh)) {
                                            break;
                                        }
                                    }
                                }
                            }
                        }

                        // Delete remaining placeholders, sending notifications
                        while (slotNext !== slotStop) {
                            slot = slotNext;
                            slotNext = slot.next;

                            if (slot !== slotsStart && isPlaceholder(slot) && !slot.keyRequested) {
                                // This might occur due to two sequences - requested by different clients - being
                                // merged.  However, since only sequences with indices are merged, if this placehholder
                                // is no longer necessary, it means an item actually was removed, so this doesn't count
                                // as a mirage.
                                deleteSlot(slot);
                            }
                        }
                    }

                    // Try to match new items after the last stationary item to placeholders
                    slotRefresh = stationaryItems[stationaryItemCount - 1];
                    slot = slotFromSlotRefresh(slotRefresh);
                    slotNext = slot.next;
                    sequenceBoundaryReached = slot.lastInSequence;
                    while (!slotRefresh.lastInSequence) {
                        slotRefresh = slotRefresh.next;
                        slotExisting = slotFromSlotRefresh(slotRefresh);
                        if (!slotExisting || slotRefresh.locationJustDetermined) {
                            // Find the next placeholder
                            while (!sequenceBoundaryReached && slotNext !== slotListEnd) {
                                slot = slotNext;
                                slotNext = slot.next;
                                sequenceBoundaryReached = slot.lastInSequence;

                                if (updateSlotForRefresh(slotExisting, slot, slotRefresh)) {
                                    break;
                                }
                            }
                        }
                    }
                }
            }
        }

        /*#DBG
        VERIFYLIST();
        #DBG*/

        // Move items and send notifications
        for (i = 0; i < sequenceCountNew; i++) {
            sequenceNew = sequencesNew[i];

            if (sequenceNew.firstInner) {
                slotPrev = null;
                for (slotRefresh = sequenceNew.firstInner; true; slotRefresh = slotRefresh.next) {
                    slot = slotFromSlotRefresh(slotRefresh);
                    if (slot) {
                        if (!slotRefresh.stationary) {
                            //#DBG _ASSERT(slot !== slotsStart);
                            //#DBG _ASSERT(slot !== slotsEnd);

                            var slotMoveBefore,
                                mergeWithPrev = false,
                                mergeWithNext = false;
                            if (slotPrev) {
                                slotMoveBefore = slotPrev.next;
                                mergeWithPrev = true;
                            } else {
                                // The first item will be inserted before the first stationary item, so find that now
                                var slotRefreshStationary;
                                for (slotRefreshStationary = sequenceNew.firstInner; !slotRefreshStationary.stationary && slotRefreshStationary !== sequenceNew.lastInner; slotRefreshStationary = slotRefreshStationary.next) {
                                    /*@empty*/
                                }

                                if (!slotRefreshStationary.stationary) {
                                    // There are no stationary items, as all the items are moving from another old
                                    // sequence.

                                    index = slotRefresh.index;

                                    // Find the best place to insert the new sequence
                                    if (index === 0) {
                                        // Index 0 is a special case
                                        slotMoveBefore = slotsStart.next;
                                        mergeWithPrev = true;
                                    } else if (index === undefined) {
                                        slotMoveBefore = slotsEnd;
                                    } else {
                                        // Use a linear search; unlike successorFromIndex, prefer the last insertion
                                        // point between sequences over the precise index
                                        slotMoveBefore = slotsStart.next;
                                        var lastSequenceStart = null;
                                        while (true) {
                                            if (slotMoveBefore.firstInSequence) {
                                                lastSequenceStart = slotMoveBefore;
                                            }

                                            if ((index < slotMoveBefore.index && lastSequenceStart) || slotMoveBefore === slotListEnd) {
                                                break;
                                            }

                                            slotMoveBefore = slotMoveBefore.next;
                                        }

                                        if (!slotMoveBefore.firstInSequence && lastSequenceStart) {
                                            slotMoveBefore = lastSequenceStart;
                                        }
                                    }
                                } else {
                                    slotMoveBefore = slotFromSlotRefresh(slotRefreshStationary);
                                    mergeWithNext = true;
                                }
                            }

                            // Preserve merge boundaries
                            if (slot.mergedForRefresh) {
                                delete slot.mergedForRefresh;
                                if (!slot.lastInSequence) {
                                    slot.next.mergedForRefresh = true;
                                }
                            }

                            mergeWithPrev = mergeWithPrev || slotRefresh.mergeWithPrev;
                            mergeWithNext = mergeWithNext || slotRefresh.mergeWithNext;

                            var skipNotifications = slotRefresh.locationJustDetermined;
                            
                            moveSlot(slot, slotMoveBefore, mergeWithPrev, mergeWithNext, skipNotifications);

                            if (skipNotifications && mergeWithNext) {
                                // Since this item was moved without a notification, this is an implicit merge of
                                // sequences.  Mark the item's successor as mergedForRefresh.
                                slotMoveBefore.mergedForRefresh = true;
                            }
                        }

                        slotPrev = slot;
                    }

                    if (slotRefresh === sequenceNew.lastInner) {
                        break;
                    }
                }
            }
        }

        /*#DBG
        VERIFYLIST();
        #DBG*/

        // Insert new items (with new indices) and send notifications
        for (i = 0; i < sequenceCountNew; i++) {
            sequenceNew = sequencesNew[i];

            if (sequenceNew.firstInner) {
                slotPrev = null;
                for (slotRefresh = sequenceNew.firstInner; true; slotRefresh = slotRefresh.next) {
                    slot = slotFromSlotRefresh(slotRefresh);
                    if (!slot) {
                        var slotInsertBefore;
                        if (slotPrev) {
                            slotInsertBefore = slotPrev.next;
                        } else {
                            // The first item will be inserted *before* the first old item, so find that now
                            var slotRefreshOld;
                            for (slotRefreshOld = sequenceNew.firstInner; !slotFromSlotRefresh(slotRefreshOld); slotRefreshOld = slotRefreshOld.next) {
                                /*@empty*/
                                //#DBG _ASSERT(slotRefreshOld !== sequenceNew.lastInner);
                            }
                            slotInsertBefore = slotFromSlotRefresh(slotRefreshOld);
                        }

                        // Create a new slot for the item
                        slot = addNewSlotFromRefresh(slotRefresh, slotInsertBefore, !!slotPrev);

                        var slotRefreshNext = slotRefreshFromSlot(slotInsertBefore);
                        
                        if (!slotInsertBefore.mergedForRefresh && (!slotRefreshNext || !slotRefreshNext.locationJustDetermined)) {
                            prepareSlotItem(slot);

                            // Send the notification after the insertion
                            sendInsertedNotification(slot);
                        }
                    }
                    slotPrev = slot;

                    if (slotRefresh === sequenceNew.lastInner) {
                        break;
                    }
                }
            }
        }

        /*#DBG
        VERIFYLIST();
        #DBG*/

        // Rebuild the indexMap from scratch, so it is possible to detect colliding indices
        indexMap = [];

        // Send indexChanged and changed notifications
        var indexFirst = -1;
        for (slot = slotsStart, offset = 0; slot !== slotsEnd; offset++) {
            var slotNext = slot.next;

            if (slot.firstInSequence) {
                slotFirstInSequence = slot;
                offset = 0;
            }

            if (indexFirst === undefined) {
                var indexNew = indexForRefresh(slot);
                if (indexNew !== undefined) {
                    indexFirst = indexNew - offset;
                }
            }

            // See if the next slot would cause a contradiction, in which case split the sequences
            if (indexFirst !== undefined && !slot.lastInSequence) {
                var indexNewNext = indexForRefresh(slot.next);
                if (indexNewNext !== undefined && indexNewNext !== indexFirst + offset + 1) {
                    splitSequence(slot);

                    // 'Move' the items in-place individually, so move notifications are sent.  In rare cases, this
                    // will result in multiple move notifications being sent for a given item, but that's fine.
                    var first = true;
                    for (var slotMove = slot.next, lastInSequence = false; !lastInSequence && slotMove !== slotListEnd; ) {
                        var slotMoveNext = slotMove.next;
                        
                        lastInSequence = slotMove.lastInSequence;

                        moveSlot(slotMove, slotMoveNext, !first, false);

                        first = false;
                        slotMove = slotMoveNext;
                    }
                }
            }

            if (slot.lastInSequence) {
                index = indexFirst;
                for (var slotUpdate = slotFirstInSequence; slotUpdate !== slotNext; ) {
                    var slotUpdateNext = slotUpdate.next;

                    if (index >= refreshCount && slotUpdate !== slotListEnd) {
                        deleteSlot(slotUpdate, true);
                    } else {
                        var slotWithIndex = indexMap[index];

                        if (index !== slotUpdate.index) {
                            delete indexMap[index];
                            changeSlotIndex(slotUpdate, index);
                        } else if (+index === index && indexMap[index] !== slotUpdate) {
                            indexMap[index] = slotUpdate;
                        }

                        if (slotUpdate.itemNew) {
                            updateSlotItem(slotUpdate);
                        }

                        if (slotWithIndex) {
                            // Two slots' indices have collided - merge them
                            if (slotUpdate.key) {
                                sendMirageNotifications(slotUpdate, slotWithIndex, slotUpdate.bindingMap);
                                mergeSlots(slotUpdate, slotWithIndex);                            
                                if (+index === index) {
                                    indexMap[index] = slotUpdate;
                                }
                            } else {
                                sendMirageNotifications(slotWithIndex, slotUpdate, slotWithIndex.bindingMap);
                                mergeSlots(slotWithIndex, slotUpdate);
                                if (+index === index) {
                                    indexMap[index] = slotWithIndex;
                                }
                            }
                        }

                        if (+index === index) {
                            index++;
                        }
                    }

                    slotUpdate = slotUpdateNext;
                }

                indexFirst = undefined;
            }

            slot = slotNext;
        }

        // See if any sequences need to be moved and/or merged
        var indexMax = -2,
            listEndReached;

        for (slot = slotsStart, offset = 0; slot !== slotsEnd; offset++) {
            var slotNext = slot.next;

            if (slot.firstInSequence) {
                slotFirstInSequence = slot;
                offset = 0;
            }

            // Clean up during this pass
            delete slot.mergedForRefresh;

            if (slot.lastInSequence) {
                // Move sequence if necessary
                if (slotFirstInSequence.index === undefined) {
                    slotBefore = slotFirstInSequence.prev;
                    var slotRefreshBefore;
                    if (slotBefore && (slotRefreshBefore = slotRefreshFromSlot(slotBefore)) && !slotRefreshBefore.lastInSequence &&
                            (slotRefresh = slotRefreshFromSlot(slot)) && slotRefresh.prev === slotRefreshBefore) {
                        moveSequenceAfter(slotBefore, slotFirstInSequence, slot);
                        mergeSequences(slotBefore);
                    } else if (slot !== slotListEnd && !listEndReached) {
                        moveSequenceBefore(slotsEnd, slotFirstInSequence, slot);
                    }
                } else {
                    //#DBG _ASSERT(slot.index !== undefined);
                    if (indexMax < slot.index && !listEndReached) {
                        indexMax = slot.index;
                    } else {
                        // Find the correct insertion point
                        for (slotAfter = slotsStart.next; slotAfter.index < slot.index; slotAfter = slotAfter.next) {
                            /*@empty*/
                        }

                        // Move the items individually, so move notifications are sent
                        for (var slotMove = slotFirstInSequence; slotMove !== slotNext; ) {
                            var slotMoveNext = slotMove.next;
                            slotRefresh = slotRefreshFromSlot(slotMove);
                            moveSlot(slotMove, slotAfter, slotAfter.prev.index === slotMove.index - 1, slotAfter.index === slotMove.index + 1, slotRefresh && slotRefresh.locationJustDetermined);
                            slotMove = slotMoveNext;
                        }
                    }

                    // Store slotBefore here since the sequence might have just been moved
                    slotBefore = slotFirstInSequence.prev;

                    // See if this sequence should be merged with the previous one
                    if (slotBefore && slotBefore.index === slotFirstInSequence.index - 1) {
                        mergeSequences(slotBefore);
                    }
                }
            }

            if (slot === slotListEnd) {
                listEndReached = true;
            }

            slot = slotNext;
        }

        indexUpdateDeferred = false;

        /*#DBG
        VERIFYLIST();
        #DBG*/

        // Now that all the sequences have been moved, merge any colliding slots
        mergeSequencePairs(sequencePairsToMerge);

        /*#DBG
        VERIFYLIST();
        #DBG*/

        // Send countChanged notification
        if (refreshCount !== undefined && refreshCount !== knownCount) {
            changeCount(refreshCount);
        }

        /*#DBG
        VERIFYLIST();
        #DBG*/

        finishNotifications();

        // Before discarding the refresh slot list, see if any fetch requests can be completed by pretending each range
        // of refresh slots is an incoming array of results.
        var fetchResults = [];
        for (i = 0; i < sequenceCountNew; i++) {
            sequenceNew = sequencesNew[i];

            var results = [];

            slot = null; 
            offset = 0;

            var slotOffset;

            for (slotRefresh = sequenceNew.first; true; slotRefresh = slotRefresh.next, offset++) {
                if (slotRefresh === refreshStart) {
                    results.push(startMarker);
                } else if (slotRefresh === refreshEnd) {
                    results.push(endMarker);
                } else {
                    results.push(slotRefresh.item);

                    if (!slot) {
                        slot = slotFromSlotRefresh(slotRefresh);
                        slotOffset = offset;
                    }
                }

                if (slotRefresh.lastInSequence) {
                    //#DBG _ASSERT(slotRefresh === sequenceNew.last);
                    break;
                }
            }

            if (slot) {
                fetchResults.push({
                    slot: slot,
                    results: results,
                    offset: slotOffset
                });
            }
        }

        resetRefreshState();
        refreshInProgress = false;

        /*#DBG
        VERIFYLIST();
        #DBG*/

        // Complete any promises for newly obtained items
        callFetchCompleteCallbacks();

        // Now process the 'extra' results from the refresh list
        for (i = 0; i < fetchResults.length; i++) {
            var fetchResult = fetchResults[i];
            processResults(fetchResult.slot, fetchResult.results, fetchResult.offset, knownCount, fetchResult.slot.index);
        }

        if (refreshSignal) {
            var signal = refreshSignal;

            refreshSignal = null;

            signal.complete();
        }

        // Finally, kick-start fetches for any remaining placeholders
        postFetch();
    }

    // Edit Queue

    // Queues an edit and immediately "optimistically" apply it to the slots list, sending re-entrant notifications
    function queueEdit(applyEdit, editType, complete, error, keyUpdate, updateSlots, undo) {
        var editQueueTail = editQueue.prev,
            edit = {
                prev: editQueueTail,
                next: editQueue,
                applyEdit: applyEdit,
                editType: editType,
                complete: complete,
                error: error,
                keyUpdate: keyUpdate
            };
        editQueueTail.next = edit;
        editQueue.prev = edit;
        editsQueued = true;

        // If there's a refresh in progress, abandon it, but request that a new one be started once the edits complete
        if (refreshRequested || refreshInProgress) {
            currentRefreshID++;
            refreshInProgress = false;
            refreshRequested = true;
        }

        if (editQueue.next === edit) {
            // Attempt the edit immediately, in case it completes synchronously
            applyNextEdit();
        }

        // If the edit succeeded or is still pending, apply it to the slots (in the latter case, "optimistically")
        if (!edit.failed) {
            updateSlots();

            // Supply the undo function now
            edit.undo = undo;
        }

        if (!editsInProgress) {
            completeEdits();
        }
    }

    function dequeueEdit() {
        firstEditInProgress = false;

        //#DBG _ASSERT(editQueue.next !== editQueue);
        var editNext = editQueue.next.next;

        editQueue.next = editNext;
        editNext.prev = editQueue;
    }

    // Undo all queued edits, starting with the most recent
    function discardEditQueue() {
        while (editQueue.prev !== editQueue) {
            var editLast = editQueue.prev;

            if (editLast.error) {
                editLast.error(new WinJS.ErrorFromName(UI.EditError.canceled));
            }            

            // Edits that haven't been applied to the slots yet don't need to be undone
            if (editLast.undo && !refreshRequested) {
                editLast.undo();
            }

            editQueue.prev = editLast.prev;
        }
        editQueue.next = editQueue;

        editsInProgress = false;

        completeEdits();
    }

    var EditType = {
        insert: "insert",
        change: "change",
        move: "move",
        remove: "remove"
    };

    function attemptEdit(edit) {
        if (firstEditInProgress) {
            return;
        }

        var reentrant = true;

        function continueEdits() {
            if (!waitForRefresh) {
                if (reentrant) {
                    synchronousEdit = true;
                } else {
                    applyNextEdit();
                }
            }
        }

        var keyUpdate = edit.keyUpdate;

        function onEditComplete(item) {
            if (item) {
                if (keyUpdate && keyUpdate.key !== item.key) {
                    //#DBG _ASSERT(edit.editType === EditType.insert);
                
                    var keyNew = item.key;
                    if (!edit.undo) {
                        // If the edit is in the process of being queued, we can use the correct key when we update the
                        // slots, so there's no need for a later update.
                        keyUpdate.key = keyNew;
                    } else {
                        var slot = keyUpdate.slot;
                        if (slot) {
                            var keyOld = slot.key;
                            if (keyOld) {
                                //#DBG _ASSERT(slot.key === keyOld);
                                //#DBG _ASSERT(keyMap[keyOld] === slot);
                                delete keyMap[keyOld];
                            }
                            /*#DBG
                            // setSlotKey asserts that the slot key is absent
                            delete slot.key;
                            #DBG*/

                            setSlotKey(slot, keyNew);
                            slot.itemNew = item;
                            if (slot.item) {
                                changeSlot(slot);
                                finishNotifications();
                            } else {
                                completeFetchPromises(slot);
                            }
                        }
                    }
                } else if (edit.editType === EditType.change) {
                    //#DBG _ASSERT(slot.item);
                    slot.itemNew = item;

                    if (!reentrant) {
                        changeSlotIfNecessary(slot);
                    }
                }
            }

            dequeueEdit();

            if (edit.complete) {
                edit.complete(item);
            }

            continueEdits();
        }

        function onEditError(error) {
            switch (error.Name) {
                case EditError.noResponse:
                    // Report the failure to the client, but do not dequeue the edit
                    setStatus(DataSourceStatus.failure);
                    waitForRefresh = true;

                    firstEditInProgress = false;

                    // Don't report the error, as the edit will be attempted again on the next refresh
                    return;

                case EditError.notPermitted:
                    break;

                case EditError.noLongerMeaningful:
                    // Something has changed, so request a refresh
                    beginRefresh();
                    break;

                default:
                    break;
            }

            // Discard all remaining edits, rather than try to determine which subsequent ones depend on this one
            edit.failed = true;
            dequeueEdit();

            discardEditQueue();

            if (edit.error) {
                edit.error(error);
            }            

            continueEdits();
        }

        if (listDataAdapter.beginEdits && !beginEditsCalled) {
            beginEditsCalled = true;
            listDataAdapter.beginEdits();
        }

        // Call the applyEdit function for the given edit, passing in our own wrapper of the error handler that the
        // client passed in.
        firstEditInProgress = true;
        edit.applyEdit().then(onEditComplete, onEditError);
        reentrant = false;
    }

    function applyNextEdit() {
        // See if there are any outstanding edits, and try to process as many as possible synchronously
        while (editQueue.next !== editQueue) {
            synchronousEdit = false;
            attemptEdit(editQueue.next);
            if (!synchronousEdit) {
                return;
            }
        }

        // The queue emptied out synchronously (or was empty to begin with)
        concludeEdits();
    }

    function completeEdits() {
        //#DBG _ASSERT(!editsInProgress);

        updateIndices();

        finishNotifications();

        callFetchCompleteCallbacks();

        if (editQueue.next === editQueue) {
            concludeEdits();
        }
    }

    // Once the edit queue has emptied, update state appropriately and resume normal operation
    function concludeEdits() {
        editsQueued = false;

        if (listDataAdapter.endEdits && beginEditsCalled && !editsInProgress) {
            beginEditsCalled = false;
            listDataAdapter.endEdits();
        }

        // See if there's a refresh that needs to begin
        if (refreshRequested) {
            refreshRequested = false;
            beginRefresh();
        } else {
            // Otherwise, see if anything needs to be fetched
            postFetch();
        }
    }

    // Editing Operations

    function getSlotForEdit(key) {
        validateKey(key);

        return keyMap[key] || createSlotForKey(key);
    }

    function insertNewSlot(key, itemNew, slotInsertBefore, mergeWithPrev, mergeWithNext) {
        // Create a new slot, but don't worry about its index, as indices will be updated during endEdits
        var slot = createPrimarySlot();

        insertAndMergeSlot(slot, slotInsertBefore, mergeWithPrev, mergeWithNext);
        if (key) {
            setSlotKey(slot, key);
        }
        slot.itemNew = itemNew;

        updateNewIndices(slot, 1);

        // If this isn't part of a batch of changes, set the slot index now so renderers can see it
        if (!editsInProgress && !dataNotificationsInProgress) {
            if (!slot.firstInSequence && typeof slot.prev.index === "number") {
                setSlotIndex(slot, slot.prev.index + 1, indexMap);
            } else if (!slot.lastInSequence && typeof slot.next.index === "number") {
                setSlotIndex(slot, slot.next.index - 1, indexMap);
            }
        }

        prepareSlotItem(slot);

        // Send the notification after the insertion
        sendInsertedNotification(slot);

        return slot;
    }

    function insertItem(key, data, slotInsertBefore, append, applyEdit) {
        var keyUpdate = { key: key };

        return new Promise(function (complete, error) {
            queueEdit(
                applyEdit, EditType.insert, complete, error, keyUpdate,
            
                // updateSlots
                function () {
                    if (slotInsertBefore) {
                        var itemNew = {
                            key: keyUpdate.key,
                            data: data
                        };

                        keyUpdate.slot = insertNewSlot(keyUpdate.key, itemNew, slotInsertBefore, append, !append);
                    }
                },

                // undo
                function () {
                    var slot = keyUpdate.slot;

                    if (slot) {
                        updateNewIndices(slot, -1);
                        deleteSlot(slot, false);
                    }
                }
            );
        });
    }

    function moveItem(slot, slotMoveBefore, append, applyEdit) {
        return new Promise(function (complete, error) {
            var mergeAdjacent,
                slotNext,
                firstInSequence,
                lastInSequence;

            queueEdit(
                applyEdit, EditType.move, complete, error,

                // keyUpdate
                null,

                // updateSlots
                function () {
                    slotNext = slot.next;
                    firstInSequence = slot.firstInSequence;
                    lastInSequence = slot.lastInSequence;

                    var slotPrev = slot.prev;

                    mergeAdjacent = (typeof slot.index !== "number" && (firstInSequence || !slotPrev.item) && (lastInSequence || !slotNext.item));

                    updateNewIndices(slot, -1);
                    moveSlot(slot, slotMoveBefore, append, !append);
                    updateNewIndices(slot, 1);

                    if (mergeAdjacent) {
                        splitSequence(slotPrev);

                        if (!firstInSequence) {
                            mergeSlotsBefore(slotPrev, slot);
                        }
                        if (!lastInSequence) {
                            mergeSlotsAfter(slotNext, slot);
                        }
                    }
                },

                // undo
                function () {
                    if (!mergeAdjacent) {
                        updateNewIndices(slot, -1);
                        moveSlot(slot, slotNext, !firstInSequence, !lastInSequence);
                        updateNewIndices(slot, 1);
                    } else {
                        beginRefresh();
                    }
                }
            );
        });
    }

    function ListDataNotificationHandler() {
        /// <signature helpKeyword="WinJS.UI.VirtualizedDataSource.ListDataNotificationHandler">
        /// <summary locid="WinJS.UI.VirtualizedDataSource.ListDataNotificationHandler">
        /// An implementation of IListDataNotificationHandler that is passed to the
        /// IListDataAdapter.setNotificationHandler method.
        /// </summary>
        /// </signature>

        this.invalidateAll = function () {
            /// <signature helpKeyword="WinJS.UI.VirtualizedDataSource.ListDataNotificationHandler.invalidateAll">
            /// <summary locid="WinJS.UI.VirtualizedDataSource.ListDataNotificationHandler.invalidateAll">
            /// Notifies the VirtualizedDataSource that some data has changed, without specifying which data. It might
            /// be impractical for some data sources to call this method for any or all changes, so this call is optional.
            /// But if a given data adapter never calls it, the application should periodically call
            /// invalidateAll on the VirtualizedDataSource to refresh the data.
            /// </summary>
            /// <returns type="Promise" locid="WinJS.UI.VirtualizedDataSource.ListDataNotificationHandler.invalidateAll_returnValue">
            /// A Promise that completes when the data has been completely refreshed and all change notifications have
            /// been sent.
            /// </returns>
            /// </signature>

            if (knownCount === 0) {
                this.reload();
                return Promise.wrap();
            }

            return requestRefresh();
        };

        this.reload = function () {
            /// <signature helpKeyword="WinJS.UI.VirtualizedDataSource.ListDataNotificationHandler.reload">
            /// <summary locid="WinJS.UI.VirtualizedDataSource.ListDataNotificationHandler.reload">
            /// Notifies the list data source that the list data has changed so much that it is better
            /// to reload the data from scratch.
            /// </summary>
            /// </signature>

            // Cancel all promises

            if (getCountPromise) {
                getCountPromise.cancel();
            }

            if (refreshSignal) {
                refreshSignal.cancel();
            }

            for (var slot = slotsStart.next; slot !== slotsEnd; slot = slot.next) {
                var fetchListeners = slot.fetchListeners;
                for (var listenerID in fetchListeners) {
                    fetchListeners[listenerID].promise.cancel();
                }
                var directFetchListeners = slot.directFetchListeners;
                for (var listenerID in directFetchListeners) {
                    directFetchListeners[listenerID].promise.cancel();
                }
            }

            resetState();

            forEachBindingRecord(function (bindingRecord) {
                if (bindingRecord.notificationHandler) {
                    bindingRecord.notificationHandler.reload();
                }
            });
        };

        this.beginNotifications = function () {
            /// <signature helpKeyword="WinJS.UI.VirtualizedDataSource.ListDataNotificationHandler.beginNotifications">
            /// <summary locid="WinJS.UI.VirtualizedDataSource.ListDataNotificationHandler.beginNotifications">
            /// Indicates the start of a notification batch.
            /// Call it before a sequence of other notification calls to minimize the number of countChanged and
            /// indexChanged notifications sent to the client of the VirtualizedDataSource. You must pair it with a call
            /// to endNotifications, and pairs can't be nested.
            /// </summary>
            /// </signature>

            dataNotificationsInProgress = true;
        };

        function completeNotification() {
            if (!dataNotificationsInProgress) {
                updateIndices();
                finishNotifications();

                callFetchCompleteCallbacks();
            }
        }

        this.inserted = function (newItem, previousKey, nextKey, index) {
            /// <signature helpKeyword="WinJS.UI.VirtualizedDataSource.ListDataNotificationHandler.inserted">
            /// <summary locid="WinJS.UI.VirtualizedDataSource.ListDataNotificationHandler.inserted">
            /// Raises a notification that an item was inserted.
            /// </summary>
            /// <param name="newItem" type="Object" locid="WinJS.UI.VirtualizedDataSource.ListDataNotificationHandler.inserted_p:newItem">
            /// The inserted item. It must have a key and a data property (it must implement the IItem interface).
            /// </param>
            /// <param name="previousKey" mayBeNull="true" type="String" locid="WinJS.UI.VirtualizedDataSource.ListDataNotificationHandler.inserted_p:previousKey">
            /// The key of the item before the insertion point, or null if the item was inserted at the start of the
            /// list.  It can be null if you specified nextKey.
            /// </param>
            /// <param name="nextKey" mayBeNull="true" type="String" locid="WinJS.UI.VirtualizedDataSource.ListDataNotificationHandler.inserted_p:nextKey">
            /// The key of the item after the insertion point, or null if the item was inserted at the end of the list.
            /// It can be null if you specified previousKey.
            /// </param>
            /// <param name="index" optional="true" type="Number" integer="true" locid="WinJS.UI.VirtualizedDataSource.ListDataNotificationHandler.inserted_p:index">
            /// The index of the inserted item.
            /// </param>
            /// </signature>

            if (editsQueued) {
                // We can't change the slots out from under any queued edits
                beginRefresh();
            } else {
                var key = newItem.key,
                    slotPrev = keyMap[previousKey],
                    slotNext = keyMap[nextKey];

                var havePreviousKey = typeof previousKey === "string",
                    haveNextKey = typeof nextKey === "string";

                // Only one of previousKey, nextKey needs to be passed in
                //
                if (havePreviousKey) {
                    if (slotNext && !slotNext.firstInSequence) {
                        slotPrev = slotNext.prev;
                    }
                } else if (haveNextKey) {
                    if (slotPrev && !slotPrev.lastInSequence) {
                        slotNext = slotPrev.next;
                    }
                }

                // If the VDS believes the list is empty but the data adapter believes the item has
                // a adjacent item start a refresh.
                //
                if ((havePreviousKey || haveNextKey) && !(slotPrev || slotNext) && (slotsStart.next === slotListEnd)) {
                    beginRefresh();
                    return;
                }

                // If this key is known, something has changed, start a refresh.
                //
                if (keyMap[key]) {
                    beginRefresh();
                    return;
                }

                // If the slots aren't adjacent or are thought to be distinct sequences by the
                //  VDS something has changed so start a refresh.
                //
                if (slotPrev && slotNext) {
                    if (slotPrev.next !== slotNext || slotPrev.lastInSequence || slotNext.firstInSequence) {
                        beginRefresh();
                        return;
                    }
                }

                // If one of the adjacent keys or indicies has only just been requested - rare, 
                //  and easier to deal with in a refresh.
                //
                if ((slotPrev && (slotPrev.keyRequested || slotPrev.indexRequested)) ||
                    (slotNext && (slotNext.keyRequested || slotNext.indexRequested))) {
                    beginRefresh();
                    return;
                }

                if (slotPrev || slotNext) {
                    insertNewSlot(key, newItem, (slotNext ? slotNext : slotPrev.next), !!slotPrev, !!slotNext);
                } else if (slotsStart.next === slotListEnd) {
                    insertNewSlot(key, newItem, slotsStart.next, true, true);
                } else if (index !== undefined) {
                    updateNewIndicesFromIndex(index, 1);
                }

                completeNotification();
            }
        };

        this.changed = function (item) {
            /// <signature helpKeyword="WinJS.UI.VirtualizedDataSource.ListDataNotificationHandler.changed">
            /// <summary locid="WinJS.UI.VirtualizedDataSource.ListDataNotificationHandler.changed">
            /// Raises a notification that an item changed.
            /// </summary>
            /// <param name="item" type="Object" locid="WinJS.UI.VirtualizedDataSource.ListDataNotificationHandler.changed_p:item">
            /// An IItem that represents the item that changed.
            /// </param>
            /// </signature>

            if (editsQueued) {
                // We can't change the slots out from under any queued edits
                beginRefresh();
            } else {
                var key = item.key,
                    slot = keyMap[key];

                if (slot) {
                    if (slot.keyRequested) {
                        // The key has only just been requested - rare, and easier to deal with in a refresh
                        beginRefresh();
                    } else {
                        slot.itemNew = item;

                        if (slot.item) {
                            changeSlot(slot);

                            completeNotification();
                        }
                    }
                }
            }
        };

        this.moved = function (item, previousKey, nextKey, oldIndex, newIndex) {
            /// <signature helpKeyword="WinJS.UI.VirtualizedDataSource.ListDataNotificationHandler.moved">
            /// <summary locid="WinJS.UI.VirtualizedDataSource.ListDataNotificationHandler.moved">
            /// Raises a notfication that an item was moved.
            /// </summary>
            /// <param name="item" type="Object" locid="WinJS.UI.VirtualizedDataSource.ListDataNotificationHandler.moved_p:item">
            /// The item that was moved.
            /// </param>
            /// <param name="previousKey" mayBeNull="true" type="String" locid="WinJS.UI.VirtualizedDataSource.ListDataNotificationHandler.moved_p:previousKey">
            /// The key of the item before the insertion point, or null if the item was moved to the beginning of the list.
            /// It can be null if you specified nextKey.
            /// </param>
            /// <param name="nextKey" mayBeNull="true" type="String" locid="WinJS.UI.VirtualizedDataSource.ListDataNotificationHandler.moved_p:nextKey">
            /// The key of the item after the insertion point, or null if the item was moved to the end of the list.
            /// It can be null if you specified previousKey.
            /// </param>
            /// <param name="oldIndex" optional="true" type="Number" integer="true" locid="WinJS.UI.VirtualizedDataSource.ListDataNotificationHandler.moved_p:oldIndex">
            /// The index of the item before it was moved.
            /// </param>
            /// <param name="newIndex" optional="true" type="Number" integer="true" locid="WinJS.UI.VirtualizedDataSource.ListDataNotificationHandler.moved_p:newIndex">
            /// The index of the item after it was moved.
            /// </param>
            /// </signature>

            if (editsQueued) {
                // We can't change the slots out from under any queued edits
                beginRefresh();
            } else {
                var key = item.key,
                    slot = keyMap[key],
                    slotPrev = keyMap[previousKey],
                    slotNext = keyMap[nextKey];

                if ((slot && slot.keyRequested) || (slotPrev && slotPrev.keyRequested) || (slotNext && slotNext.keyRequested)) {
                    // One of the keys has only just been requested - rare, and easier to deal with in a refresh
                    beginRefresh();
                } else if (slot) {
                    if (slotPrev && slotNext && (slotPrev.next !== slotNext || slotPrev.lastInSequence || slotNext.firstInSequence)) {
                        // Something has changed, start a refresh
                        beginRefresh();
                    } else if (!slotPrev && !slotNext) {
                        // If we can't tell where the item moved to, treat this like a removal
                        updateNewIndices(slot, -1);
                        deleteSlot(slot, false);

                        if (oldIndex !== undefined) {
                            if (oldIndex < newIndex) {
                                newIndex--;
                            }

                            updateNewIndicesFromIndex(newIndex, 1);
                        }

                        completeNotification();
                    } else {
                        updateNewIndices(slot, -1);
                        moveSlot(slot, (slotNext ? slotNext : slotPrev.next), !!slotPrev, !!slotNext);
                        updateNewIndices(slot, 1);

                        completeNotification();
                    }
                } else if (slotPrev || slotNext) {
                    // If previousKey or nextKey is known, but key isn't, treat this like an insertion.

                    if (oldIndex !== undefined) {
                        updateNewIndicesFromIndex(oldIndex, -1);

                        if (oldIndex < newIndex) {
                            newIndex--;
                        }
                    }

                    this.inserted(item, previousKey, nextKey, newIndex);
                } else if (oldIndex !== undefined) {
                    updateNewIndicesFromIndex(oldIndex, -1);

                    if (oldIndex < newIndex) {
                        newIndex--;
                    }

                    updateNewIndicesFromIndex(newIndex, 1);

                    completeNotification();
                }
            }
        };

        this.removed = function (key, index) {
            /// <signature helpKeyword="WinJS.UI.VirtualizedDataSource.ListDataNotificationHandler.removed">
            /// <summary locid="WinJS.UI.VirtualizedDataSource.ListDataNotificationHandler.removed">
            /// Raises a notification that an item was removed.
            /// </summary>
            /// <param name="key" mayBeNull="true" type="String" locid="WinJS.UI.VirtualizedDataSource.ListDataNotificationHandler.removed_p:key">
            /// The key of the item that was removed.
            /// </param>
            /// <param name="index" optional="true" type="Number" integer="true" locid="WinJS.UI.VirtualizedDataSource.ListDataNotificationHandler.removed_p:index">
            /// The index of the item that was removed.
            /// </param>
            /// </signature>

            if (editsQueued) {
                // We can't change the slots out from under any queued edits
                beginRefresh();
            } else {
                var slot;
                
                if (typeof key === "string") {
                    slot = keyMap[key];
                } else {
                    slot = indexMap[index];
                }

                if (slot) {
                    if (slot.keyRequested) {
                        // The key has only just been requested - rare, and easier to deal with in a refresh
                        beginRefresh();
                    } else {
                        updateNewIndices(slot, -1);
                        deleteSlot(slot, false);

                        completeNotification();
                    }
                } else if (index !== undefined) {
                    updateNewIndicesFromIndex(index, -1);
                    completeNotification();
                }
            }
        };

        this.endNotifications = function () {
            /// <signature helpKeyword="WinJS.UI.VirtualizedDataSource.ListDataNotificationHandler.endNotifications">
            /// <summary locid="WinJS.UI.VirtualizedDataSource.ListDataNotificationHandler.endNotifications">
            /// Concludes a sequence of notifications that began with a call to beginNotifications.
            /// </summary>
            /// </signature>

            dataNotificationsInProgress = false;
            completeNotification();
        };

    } // ListDataNotificationHandler

    function resetState() {
        setStatus(DataSourceStatus.ready);

        // Track count promises
        getCountPromise = null;

        // Track whether listDataAdapter.endEdits needs to be called
        beginEditsCalled = false;

        // Track whether finishNotifications should be called after each edit
        editsInProgress = false;

        // Track whether the first queued edit should be attempted
        firstEditInProgress = false;

        // Queue of edis that have yet to be completed
        editQueue = {};
        editQueue.next = editQueue;
        editQueue.prev = editQueue;
        /*#DBG
        editQueue.debugInfo = "*** editQueueHead/Tail ***";
        #DBG*/

        // Track whether there are currently edits queued
        editsQueued = false;

        // If an edit has returned noResponse, the edit queue will be reapplied when the next refresh is requested
        waitForRefresh = false;

        // Change to count while multiple edits are taking place
        countDelta = 0;

        // True while the indices are temporarily in a bad state due to multiple edits
        indexUpdateDeferred = false;

        // Next temporary key to use
        nextTempKey = 0;

        // Set of fetches for which results have not yet arrived
        fetchesInProgress = {};

        // Queue of complete callbacks for fetches
        fetchCompleteCallbacks = [];

        // Tracks the count returned explicitly or implicitly by the data adapter
        knownCount = CountResult.unknown;

        // Sentinel objects for list of slots
        // Give the start sentinel an index so we can always use predecessor + 1.
        slotsStart = {
            firstInSequence: true,
            lastInSequence: true,
            index: -1
        };
        slotListEnd = {
            firstInSequence: true,
            lastInSequence: true
        };
        slotsEnd = {
            firstInSequence: true,
            lastInSequence: true
        };
        slotsStart.next = slotListEnd;
        slotListEnd.prev = slotsStart;
        slotListEnd.next = slotsEnd;
        slotsEnd.prev = slotListEnd;

        /*#DBG
        slotsStart.debugInfo = "*** slotsStart ***";
        slotListEnd.debugInfo = "*** slotListEnd ***";
        slotsEnd.debugInfo = "*** slotsEnd ***";
        #DBG*/

        // Map of request IDs to slots
        handleMap = {};

        // Map of keys to slots
        keyMap = {};

        // Map of indices to slots
        indexMap = {};
        indexMap[-1] = slotsStart;

        // Count of slots that have been released but not deleted
        releasedSlots = 0;

        lastSlotReleased = null;

        // At most one call to reduce the number of refresh slots should be posted at any given time
        reduceReleasedSlotCountPosted = false;

        // Multiple refresh requests are coalesced
        refreshRequested = false;

        // Requests do not cause fetches while a refresh is in progress
        refreshInProgress = false;

        // Refresh requests yield the same promise until a refresh completes
        refreshSignal = null;
    }

    // Construction

    // Process creation parameters
    if (!listDataAdapter) {
        throw new WinJS.ErrorFromName("WinJS.UI.ListDataSource.ListDataAdapterIsInvalid", strings.listDataAdapterIsInvalid);
    }

    // Minimum number of released slots to retain
    cacheSize = (listDataAdapter.compareByIdentity ? 0 : 200);

    if (options) {
        if (typeof options.cacheSize === "number") {
            cacheSize = options.cacheSize;
        }
    }

    // Cached listDataNotificationHandler initially undefined
    if (listDataAdapter.setNotificationHandler) {
        listDataNotificationHandler = new ListDataNotificationHandler();

        listDataAdapter.setNotificationHandler(listDataNotificationHandler);
    }

    // Current status
    status = DataSourceStatus.ready;

    // Track whether a change to the status has been posted already
    statusChangePosted = false;

    // Map of bindingIDs to binding records
    bindingMap = {};

    // ID to assign to the next ListBinding, incremented each time one is created
    nextListBindingID = 0;

    // ID assigned to a slot, incremented each time one is created - start with 1 so "if (handle)" tests are valid
    nextHandle = 1;

    // ID assigned to a fetch listener, incremented each time one is created
    nextListenerID = 0;

    // ID of the refresh in progress, incremented each time a new refresh is started
    currentRefreshID = 0;

    // Track whether fetchItemsForAllSlots has been posted already
    fetchesPosted = false;

    // ID of a fetch, incremented each time a new fetch is initiated - start with 1 so "if (fetchID)" tests are valid
    nextFetchID = 1;

    // Sentinel objects for results arrays
    startMarker = {};
    endMarker = {};

    resetState();

    /*#DBG
    this._debugBuild = true;

    Object.defineProperty(this, "_totalSlots", {
        get: function () {
            return totalSlots;
        }
    });

    Object.defineProperty(this, "_releasedSlots", {
        get: function () {
            return releasedSlots;
        }
    });
    #DBG*/

    // Public methods

    this.createListBinding = function (notificationHandler) {
        /// <signature helpKeyword="WinJS.UI.IListDataSource.createListBinding">
        /// <summary locid="WinJS.UI.IListDataSource.createListBinding">
        /// Creates an IListBinding object that allows a client to read from the list and receive notifications for
        /// changes that affect those portions of the list that the client already read.
        /// </summary>
        /// <param name="notificationHandler" optional="true" locid="WinJS.UI.IListDataSource.createListBinding_p:notificationHandler">
        /// An object that implements the IListNotificationHandler interface.  If you omit this parameter,
        /// change notifications won't be available.
        /// </param>
        /// <returns type="IListBinding" locid="WinJS.UI.IListDataSource.createListBinding_returnValue">
        /// An object that implements the IListBinding interface.
        /// </returns>
        /// </signature>

        var listBindingID = (nextListBindingID++).toString(),
            slotCurrent = null,
            released = false;

        function retainSlotForCursor(slot) {
            if (slot) {
                slot.cursorCount++;
            }
        }

        function releaseSlotForCursor(slot) {
            if (slot) {
                //#DBG _ASSERT(slot.cursorCount > 0);
                if (--slot.cursorCount === 0) {
                    releaseSlotIfUnrequested(slot);
                }
            }
        }

        function moveCursor(slot) {
            // Retain the new slot first just in case it's the same slot
            retainSlotForCursor(slot);
            releaseSlotForCursor(slotCurrent);
            slotCurrent = slot;
        }

        function adjustCurrentSlot(slot, slotNew) {
            if (slot === slotCurrent) {
                if (!slotNew) {
                    slotNew = (
                        !slotCurrent || slotCurrent.lastInSequence || slotCurrent.next === slotListEnd ?
                            null :
                            slotCurrent.next
                    );
                }
                moveCursor(slotNew);
            }
        }

        function releaseSlotFromListBinding(slot) {
            var bindingMap = slot.bindingMap,
                bindingHandle = bindingMap[listBindingID].handle;

            delete slot.bindingMap[listBindingID];
                    
            // See if there are any listBindings left in the map
            var releaseBindingMap = true,
                releaseHandle = true;
            for (var listBindingID2 in bindingMap) {
                releaseBindingMap = false;
                if (bindingHandle && bindingMap[listBindingID2].handle === bindingHandle) {
                    releaseHandle = false;
                    break;
                }
            }

            if (bindingHandle && releaseHandle) {
                delete handleMap[bindingHandle];
            }
            if (releaseBindingMap) {
                slot.bindingMap = null;
                releaseSlotIfUnrequested(slot);
            }
        }

        function retainItem(slot, listenerID) {
            if (!slot.bindingMap) {
                slot.bindingMap = {};
            }

            var slotBinding = slot.bindingMap[listBindingID];
            if (slotBinding) {
                slotBinding.count++;
            } else {
                slot.bindingMap[listBindingID] = {
                    bindingRecord: bindingMap[listBindingID],
                    count: 1
                };
            }

            if (slot.fetchListeners) {
                var listener = slot.fetchListeners[listenerID];
                if (listener) {
                    listener.retained = true;
                }
            }
        }

        function releaseItem(handle) {
            var slot = handleMap[handle];

            //#DBG _ASSERT(slot);
            if (slot) {
                var slotBinding = slot.bindingMap[listBindingID];
                if (--slotBinding.count === 0) {
                    var fetchListeners = slot.fetchListeners;
                    for (var listenerID in fetchListeners) {
                        var listener = fetchListeners[listenerID];
                        if (listener.listBindingID === listBindingID) {
                            listener.retained = false;
                        }
                    }

                    releaseSlotFromListBinding(slot);
                }
            }
        }

        function itemPromiseFromKnownSlot(slot) {
            var handle = handleForBinding(slot, listBindingID),
                listenerID = (nextListenerID++).toString();

            var itemPromise = createFetchPromise(slot, "fetchListeners", listenerID, listBindingID,
                function (complete, item) {
                    complete(itemForBinding(item, handle));
                }
            );

            defineCommonItemProperties(itemPromise, slot, handle);

            // Only implement retain and release methods if a notification handler has been supplied
            if (notificationHandler) {
                itemPromise.retain = function () {
                    listBinding._retainItem(slot, listenerID);
                    return itemPromise;
                };

                itemPromise.release = function () {
                    listBinding._releaseItem(handle);
                };
            }

            return itemPromise;
        }

        bindingMap[listBindingID] = {
            notificationHandler: notificationHandler,
            notificationsSent: false,
            adjustCurrentSlot: adjustCurrentSlot,
            itemPromiseFromKnownSlot: itemPromiseFromKnownSlot,
        };

        function itemPromiseFromSlot(slot) {
            var itemPromise;

            if (!released && slot) {
                itemPromise = itemPromiseFromKnownSlot(slot);
            } else {
                // Return a complete promise for a non-existent slot
                if (released) {
                    itemPromise = new Promise(function () { });
                    itemPromise.cancel();
                } else {
                    itemPromise = Promise.wrap(null);
                }
                defineHandleProperty(itemPromise, null);
                // Only implement retain and release methods if a notification handler has been supplied
                if (notificationHandler) {
                    itemPromise.retain = function () { return itemPromise; };
                    itemPromise.release = function () { };
                }
            }

            moveCursor(slot);

            return itemPromise;
        }

        /// <signature helpKeyword="WinJS.UI.IListBinding">
        /// <summary locid="WinJS.UI.IListBinding">
        /// An interface that enables a client to read from the list and receive notifications for changes that affect
        /// those portions of the list that the client already read.  IListBinding can also enumerate through lists
        /// that can change at any time.
        /// </summary>
        /// </signature>
        var listBinding = {
            _retainItem: function (slot, listenerID) {
                retainItem(slot, listenerID);
            },

            _releaseItem: function (handle) {
                releaseItem(handle);
            },

            jumpToItem: function (item) {
                /// <signature helpKeyword="WinJS.UI.IListBinding.jumpToItem">
                /// <summary locid="WinJS.UI.IListBinding.jumpToItem">
                /// Makes the specified item the current item.
                /// </summary>
                /// <param name="item" type="Object" locid="WinJS.UI.IListBinding.jumpToItem_p:item">
                /// The IItem or IItemPromise to make the current item.
                /// </param>
                /// <returns type="IItemPromise" locid="WinJS.UI.IListBinding.jumpToItem_returnValue">
                /// An object that implements the IItemPromise interface and serves as a promise for the specified item.  If
                /// the specified item is not in the list, the promise completes with a value of null.
                /// </returns>
                /// </signature>

                return itemPromiseFromSlot(item ? handleMap[item.handle] : null);
            },

            current: function () {
                /// <signature helpKeyword="WinJS.UI.IListBinding.current">
                /// <summary locid="WinJS.UI.IListBinding.current">
                /// Retrieves the current item.
                /// </summary>
                /// <returns type="IItemPromise" locid="WinJS.UI.IListBinding.current_returnValue">
                /// An object that implements the IItemPromise interface and serves as a promise for the current item.
                /// If the cursor has moved past the start or end of the list, the promise completes with a value
                /// of null.  If the current item has been deleted or moved, the promise returns an error.
                /// </returns>
                /// </signature>

                return itemPromiseFromSlot(slotCurrent);
            },

            previous: function () {
                /// <signature helpKeyword="WinJS.UI.IListBinding.previous">
                /// <summary locid="WinJS.UI.IListBinding.previous">
                /// Retrieves the item before the current item and makes it the current item.
                /// </summary>
                /// <returns type="IItemPromise" locid="WinJS.UI.IListBinding.previous_returnValue">
                /// An object that implements the IItemPromise interface and serves as a promise for the previous item.
                /// If the cursor moves past the start of the list, the promise completes with a value of null.
                /// </returns>
                /// </signature>

                return itemPromiseFromSlot(slotCurrent ? requestSlotBefore(slotCurrent) : null);
            },

            next: function () {
                /// <signature helpKeyword="WinJS.UI.IListBinding.next">
                /// <summary locid="WinJS.UI.IListBinding.next">
                /// Retrieves the item after the current item and makes it the current item.
                /// </summary>
                /// <returns type="IItemPromise" locid="WinJS.UI.IListBinding.next_returnValue">
                /// An object that implements the IItemPromise interface and serves as a promise for the next item.  If
                /// the cursor moves past the end of the list, the promise completes with a value of null.
                /// </returns>
                /// </signature>

                return itemPromiseFromSlot(slotCurrent ? requestSlotAfter(slotCurrent) : null);
            },

            releaseItem: function (item) {
                /// <signature helpKeyword="WinJS.UI.IListBinding.releaseItem">
                /// <summary locid="WinJS.UI.IListBinding.releaseItem">
                /// Creates a request to stop change notfications for the specified item. The item is released only when the
                /// number of release calls matches the number of IItemPromise.retain calls. The number of release calls cannot
                /// exceed the number of retain calls. This method is present only if you passed an IListNotificationHandler
                /// to IListDataSource.createListBinding when it created this IListBinding.
                /// </summary>
                /// <param name="item" type="Object" locid="WinJS.UI.IListBinding.releaseItem_p:item">
                /// The IItem or IItemPromise to release.
                /// </param>
                /// </signature>

                this._releaseItem(item.handle);
            },

            release: function () {
                /// <signature helpKeyword="WinJS.UI.IListBinding.release">
                /// <summary locid="WinJS.UI.IListBinding.release">
                /// Releases resources, stops notifications, and cancels outstanding promises
                /// for all tracked items that this IListBinding returned.
                /// </summary>
                /// </signature>

                released = true;

                releaseSlotForCursor(slotCurrent);
                slotCurrent = null;

                for (var slot = slotsStart.next; slot !== slotsEnd; ) {
                    var slotNext = slot.next;

                    var fetchListeners = slot.fetchListeners;
                    for (var listenerID in fetchListeners) {
                        var listener = fetchListeners[listenerID];
                        if (listener.listBindingID === listBindingID) {
                            listener.promise.cancel();
                            delete fetchListeners[listenerID];
                        }
                    }

                    if (slot.bindingMap && slot.bindingMap[listBindingID]) {
                        releaseSlotFromListBinding(slot);
                    }

                    slot = slotNext;
                }

                delete bindingMap[listBindingID];
            }
        };

        // Only implement each navigation method if the data adapter implements certain methods

        if (listDataAdapter.itemsFromStart || listDataAdapter.itemsFromIndex) {
            listBinding.first = function () {
                /// <signature helpKeyword="WinJS.UI.IListBinding.first">
                /// <summary locid="WinJS.UI.IListBinding.first">
                /// Retrieves the first item in the list and makes it the current item.
                /// </summary>
                /// <returns type="IItemPromise" locid="WinJS.UI.IListBinding.first_returnValue">
                /// An IItemPromise that serves as a promise for the requested item.
                /// If the list is empty, the Promise completes with a value of null.
                /// </returns>
                /// </signature>

                return itemPromiseFromSlot(requestSlotAfter(slotsStart));
            };
        }

        if (listDataAdapter.itemsFromEnd) {
            listBinding.last = function () {
                /// <signature helpKeyword="WinJS.UI.IListBinding.last">
                /// <summary locid="WinJS.UI.IListBinding.last">
                /// Retrieves the last item in the list and makes it the current item.
                /// </summary>
                /// <returns type="IItemPromise" locid="WinJS.UI.IListBinding.last_returnValue">
                /// An IItemPromise that serves as a promise for the requested item.
                /// If the list is empty, the Promise completes with a value of null.
                /// </returns>
                /// </signature>

                return itemPromiseFromSlot(requestSlotBefore(slotListEnd));
            };
        }

        if (listDataAdapter.itemsFromKey) {
            listBinding.fromKey = function (key, hints) {
                /// <signature helpKeyword="WinJS.UI.IListBinding.fromKey">
                /// <summary locid="WinJS.UI.IListBinding.fromKey">
                /// Retrieves the item with the specified key and makes it the current item.
                /// </summary>
                /// <param name="key" type="String" locid="WinJS.UI.IListBinding.fromKey_p:key">
                /// The key of the requested item. It must be a non-empty string.
                /// </param>
                /// <param name="hints" locid="WinJS.UI.IListBinding.fromKey_p:hints">
                /// Domain-specific hints to the IListDataAdapter
                /// about the location of the item to improve retrieval time.
                /// </param>
                /// <returns type="IItemPromise" locid="WinJS.UI.IListBinding.fromKey_returnValue">
                /// An IItemPromise that serves as a promise for the requested item.
                /// If the list doesn't contain an item with the specified key, the Promise completes with a value of null.
                /// </returns>
                /// </signature>

                return itemPromiseFromSlot(slotFromKey(key, hints));
            };
        }

        if (listDataAdapter.itemsFromIndex || (listDataAdapter.itemsFromStart && listDataAdapter.itemsFromKey)) {
            listBinding.fromIndex = function (index) {
                /// <signature helpKeyword="WinJS.UI.IListBinding.fromIndex">
                /// <summary locid="WinJS.UI.IListBinding.fromIndex">
                /// Retrieves the item with the specified index and makes it the current item.
                /// </summary>
                /// <param name="index" type="Nunmber" integer="true" locid="WinJS.UI.IListBinding.fromIndex_p:index">
                /// A value greater than or equal to 0 that is the index of the item to retrieve.
                /// </param>
                /// <returns type="IItemPromise" locid="WinJS.UI.IListBinding.fromIndex_returnValue">
                /// An IItemPromise that serves as a promise for the requested item.
                /// If the list doesn't contain an item with the specified index, the IItemPromise completes with a value of null.
                /// </returns>
                /// </signature>

                return itemPromiseFromSlot(slotFromIndex(index));
            };
        }

        if (listDataAdapter.itemsFromDescription) {
            listBinding.fromDescription = function (description) {
                /// <signature helpKeyword="WinJS.UI.IListBinding.fromDescription">
                /// <summary locid="WinJS.UI.IListBinding.fromDescription">
                /// Retrieves the item with the specified description and makes it the current item.
                /// </summary>
                /// <param name="description" locid="WinJS.UI.IListDataSource.fromDescription_p:description">
                /// The domain-specific description of the requested item, to be interpreted by the list data adapter.
                /// </param>
                /// <returns type="Promise" locid="WinJS.UI.IListDataSource.fromDescription_returnValue">
                /// A Promise for the requested item. If the list doesn't contain an item with the specified description,
                /// the IItemPromise completes with a value of null.
                /// </returns>
                /// </signature>

                return itemPromiseFromSlot(slotFromDescription(description));
            };
        }

        return listBinding;
    };

    this.invalidateAll = function () {
        /// <signature helpKeyword="WinJS.UI.IListDataSource.invalidateAll">
        /// <summary locid="WinJS.UI.IListDataSource.invalidateAll">
        /// Makes the data source refresh its cached items by re-requesting them from the data adapter.
        /// The data source generates notifications if the data has changed.
        /// </summary>
        /// <returns type="Promise" locid="WinJS.UI.IListDataSource.invalidateAll_returnValue">
        /// A Promise that completes when the data has been completely refreshed and all change notifications have been
        /// sent.
        /// </returns>
        /// </signature>

        return requestRefresh();
    };

    // Create a helper which issues new promises for the result of the input promise
    //  but have their cancelations ref-counted so that any given consumer canceling
    //  their promise doesn't result in the incoming promise being canceled unless
    //  all consumers are no longer interested in the result.
    //
    var countedCancelation = function (promise, dataSource) {
        var signal = new WinJS._Signal();
        promise.then(
            function (v) { signal.complete(v); },
            function (e) { signal.error(e); }
        );
        var count = 0;
        return {
            get: function () {
                count++;
                return new Promise(
                    function (c, error) {
                        signal.promise.then(c, function (e) {
                            if (e.name === "WinJS.UI.VirtualizedDataSource.resetCount") {
                                getCountPromise = null;
                                return dataSource.getCount();
                            }
                            error(e);
                        });
                    },
                    function () {
                        if (--count === 0) {
                            // when the count reaches zero cancel the incoming promise
                            promise.cancel();
                        }
                    }
                );
            },
            reset: function () {
                signal.error(new WinJS.ErrorFromName("WinJS.UI.VirtualizedDataSource.resetCount"));
            },
            cancel: function () {
                // if explicitly asked to cancel the incoming promise
                promise.cancel();
            }
        };
    }

    this.getCount = function () {
        /// <signature helpKeyword="WinJS.UI.IListDataSource.getCount">
        /// <summary locid="WinJS.UI.IListDataSource.getCount">
        /// Retrieves the number of items in the data source.
        /// </summary>
        /// </signature>

        if (listDataAdapter.getCount) {
            // Always do a fetch, even if there is a cached result
            //
            var that = this;
            return Promise.timeout().then(function () {
                if (editsInProgress || editsQueued) {
                    return knownCount;
                }

                var requestPromise;

                if (!getCountPromise) {

                    // Make a request for the count
                    //
                    requestPromise = listDataAdapter.getCount();
                    var synchronous;
                    requestPromise.then(
                        function () {
                            getCountPromise = null;
                            synchronous = true;
                        },
                        function () {
                            getCountPromise = null;
                            synchronous = true;
                        }
                    );

                    // Every time we make a new request for the count we can consider the 
                    //  countDelta to be invalidated
                    //
                    countDelta = 0;

                    // Wrap the result in a cancelation counter which will block cancelation
                    //  of the outstanding promise unless all consumers cancel.
                    //
                    if (!synchronous) {
                        getCountPromise = countedCancelation(requestPromise, that);
                    }
                }

                return getCountPromise ? getCountPromise.get() : requestPromise;

            }).then(function (count) {
                if (!isNonNegativeInteger(count) && count !== undefined) {
                    throw new WinJS.ErrorFromName("WinJS.UI.ListDataSource.InvalidRequestedCountReturned", strings.invalidRequestedCountReturned);
                }

                if (count !== knownCount) {
                    changeCount(count);
                    finishNotifications();
                }

                if (count === 0) {
                    if (slotsStart.next !== slotListEnd || slotListEnd.next !== slotsEnd) {
                        // A contradiction has been found
                        beginRefresh();
                    } else if (slotsStart.lastInSequence) {
                            // Now we know the list is empty
                        mergeSequences(slotsStart);
                        slotListEnd.index = 0;
                    }
                }

                return count;
            }).then(null, function (error) {
                if (error.name === UI.CountError.noResponse) {
                    // Report the failure, but still report last known count
                    setStatus(DataSourceStatus.failure);
                    return knownCount;
                }
                return WinJS.Promise.wrapError(error);
            });
        } else {
            // If the data adapter doesn't support the count method, return the VirtualizedDataSource's 
            //  reckoning of the count.
            return Promise.wrap(knownCount);
        }
    };

    if (listDataAdapter.itemsFromKey) {
        this.itemFromKey = function (key, hints) {
            /// <signature helpKeyword="WinJS.UI.IListDataSource.itemFromKey">
            /// <summary locid="WinJS.UI.IListDataSource.itemFromKey">
            /// Retrieves the item with the specified key.
            /// </summary>
            /// <param name="key" type="String" locid="WinJS.UI.IListDataSource.itemFromKey_p:key">
            /// The key of the requested item. It must be a non-empty string.
            /// </param>
            /// <param name="hints" locid="WinJS.UI.IListDataSource.itemFromKey_p:hints">
            /// Domain-specific hints to IListDataAdapter about the location of the item
            /// to improve the retrieval time.
            /// </param>
            /// <returns type="Promise" locid="WinJS.UI.IListDataSource.itemFromKey_returnValue">
            /// A Promise for the requested item. If the list doesn't contain an item with the specified key,
            /// the Promise completes with a value of null.
            /// </returns>
            /// </signature>

            return itemDirectlyFromSlot(slotFromKey(key, hints));
        };
    }

    if (listDataAdapter.itemsFromIndex || (listDataAdapter.itemsFromStart && listDataAdapter.itemsFromKey)) {
        this.itemFromIndex = function (index) {
            /// <signature helpKeyword="WinJS.UI.IListDataSource.itemFromIndex">
            /// <summary locid="WinJS.UI.IListDataSource.itemFromIndex">
            /// Retrieves the item at the specified index.
            /// </summary>
            /// <param name="index" type="Number" integer="true" locid="WinJS.UI.IListDataSource.itemFromIndex_p:index">
            /// A value greater than or equal to zero that is the index of the requested item.
            /// </param>
            /// <returns type="Promise" locid="WinJS.UI.IListDataSource.itemFromIndex_returnValue">
            /// A Promise for the requested item. If the list doesn't contain an item with the specified index,
            /// the Promise completes with a value of null.
            /// </returns>
            /// </signature>

            return itemDirectlyFromSlot(slotFromIndex(index));
        };
    }

    if (listDataAdapter.itemsFromDescription) {
        this.itemFromDescription = function (description) {
            /// <signature helpKeyword="WinJS.UI.IListDataSource.itemFromDescription">
            /// <summary locid="WinJS.UI.IListDataSource.itemFromDescription">
            /// Retrieves the item with the specified description.
            /// </summary>
            /// <param name="description" locid="WinJS.UI.IListDataSource.itemFromDescription_p:description">
            /// Domain-specific info that describes the item to retrieve, to be interpreted by the IListDataAdapter,
            /// </param>
            /// <returns type="Promise" locid="WinJS.UI.IListDataSource.itemFromDescription_returnValue">
            /// A Promise for the requested item. If the list doesn't contain an item with the specified description,
            /// the Promise completes with a value of null.
            /// </returns>
            /// </signature>

            return itemDirectlyFromSlot(slotFromDescription(description));
        };
    }

    this.beginEdits = function () {
        /// <signature helpKeyword="WinJS.UI.IListDataSource.beginEdits">
        /// <summary locid="WinJS.UI.IListDataSource.beginEdits">
        /// Notifies the data source that a sequence of edits is about to begin.  The data source calls
        /// IListNotificationHandler.beginNotifications and endNotifications each one time for a sequence of edits.
        /// </summary>
        /// </signature>

        editsInProgress = true;
    };

    // Only implement each editing method if the data adapter implements the corresponding ListDataAdapter method

    if (listDataAdapter.insertAtStart) {
        this.insertAtStart = function (key, data) {
            /// <signature helpKeyword="WinJS.UI.IListDataSource.insertAtStart">
            /// <summary locid="WinJS.UI.IListDataSource.insertAtStart">
            /// Adds an item to the beginning of the data source.
            /// </summary>
            /// <param name="key" mayBeNull="true" type="String" locid="WinJS.UI.IListDataSource.insertAtStart_p:key">
            /// The key of the item to insert, if known; otherwise, null.
            /// </param>
            /// <param name="data" locid="WinJS.UI.IListDataSource.insertAtStart_p:data">
            /// The data for the item to add.
            /// </param>
            /// <returns type="Promise" locid="WinJS.UI.IListDataSource.insertAtStart_returnValue">
            /// A Promise that contains the IItem that was added or an EditError if an error occurred.
            /// </returns>
            /// </signature>

            // Add item to start of list, only notify if the first item was requested
            return insertItem(
                key, data,
                    
                // slotInsertBefore, append
                (slotsStart.lastInSequence ? null : slotsStart.next), true,

                // applyEdit
                function () {
                    return listDataAdapter.insertAtStart(key, data);
                }
            );
        };
    }

    if (listDataAdapter.insertBefore) {
        this.insertBefore = function (key, data, nextKey) {
            /// <signature helpKeyword="WinJS.UI.IListDataSource.insertBefore">
            /// <summary locid="WinJS.UI.IListDataSource.insertBefore">
            /// Inserts an item before another item.
            /// </summary>
            /// <param name="key" mayBeNull="true" type="String" locid="WinJS.UI.IListDataSource.insertBefore_p:key">
            /// The key of the item to insert, if known; otherwise, null.
            /// </param>
            /// <param name="data" locid="WinJS.UI.IListDataSource.insertBefore_p:data">
            /// The data for the item to insert.
            /// </param>
            /// <param name="nextKey" type="String" locid="WinJS.UI.IListDataSource.insertBefore_p:nextKey">
            /// The key of an item in the data source. The new data is inserted before this item.
            /// </param>
            /// <returns type="Promise" locid="WinJS.UI.IListDataSource.insertBefore_returnValue">
            /// A Promise that contains the IItem that was added or an EditError if an error occurred.
            /// </returns>
            /// </signature>

            var slotNext = getSlotForEdit(nextKey);

            // Add item before given item and send notification
            return insertItem(
                key, data,

                // slotInsertBefore, append
                slotNext, false,
                        
                // applyEdit
                function () {
                    return listDataAdapter.insertBefore(key, data, nextKey, adjustedIndex(slotNext));
                }
            );
        };
    }

    if (listDataAdapter.insertAfter) {
        this.insertAfter = function (key, data, previousKey) {
            /// <signature helpKeyword="WinJS.UI.IListDataSource.insertAfter">
            /// <summary locid="WinJS.UI.IListDataSource.insertAfter">
            /// Inserts an item after another item.
            /// </summary>
            /// <param name="key" mayBeNull="true" type="String" locid="WinJS.UI.IListDataSource.insertAfter_p:key">
            /// The key of the item to insert, if known; otherwise, null.
            /// </param>
            /// <param name="data" locid="WinJS.UI.IListDataSource.insertAfter_p:data">
            /// The data for the item to insert.
            /// </param>
            /// <param name="previousKey" type="String" locid="WinJS.UI.IListDataSource.insertAfter_p:previousKey">
            /// The key for an item in the data source. The new item is added after this item.
            /// </param>
            /// <returns type="Promise" locid="WinJS.UI.IListDataSource.insertAfter_returnValue">
            /// A Promise that contains the IItem that was added or an EditError if an error occurred.
            /// </returns>
            /// </signature>

            var slotPrev = getSlotForEdit(previousKey);

            // Add item after given item and send notification
            return insertItem(
                key, data,
                    
                // slotInsertBefore, append
                (slotPrev ? slotPrev.next : null), true,

                // applyEdit
                function () {
                    return listDataAdapter.insertAfter(key, data, previousKey, adjustedIndex(slotPrev));
                }
            );
        };
    }

    if (listDataAdapter.insertAtEnd) {
        this.insertAtEnd = function (key, data) {
            /// <signature helpKeyword="WinJS.UI.IListDataSource.insertAtEnd">
            /// <summary locid="WinJS.UI.IListDataSource.insertAtEnd">
            /// Adds an item to the end of the data source.
            /// </summary>
            /// <param name="key" mayBeNull="true" type="String" locid="WinJS.UI.IListDataSource.insertAtEnd_p:key">
            /// The key of the item to insert, if known; otherwise, null.
            /// </param>
            /// <param name="data" locid="WinJS.UI.IListDataSource.insertAtEnd_data">
            /// The data for the item to insert.
            /// </param>
            /// <returns type="Promise" locid="WinJS.UI.IListDataSource.insertAtEnd_returnValue">
            /// A Promise that contains the IItem that was added or an EditError if an error occurred.
            /// </returns>
            /// </signature>

            // Add item to end of list, only notify if the last item was requested
            return insertItem(
                key, data,
                
                // slotInsertBefore, append
                (slotListEnd.firstInSequence ? null : slotListEnd), false,

                // applyEdit
                function () {
                    return listDataAdapter.insertAtEnd(key, data);
                }
            );
        };
    }

    if (listDataAdapter.change) {
        this.change = function (key, newData) {
            /// <signature helpKeyword="WinJS.UI.IListDataSource.change">
            /// <summary locid="WinJS.UI.IListDataSource.change">
            /// Overwrites the data of the specified item.
            /// </summary>
            /// <param name="key" type="String" locid="WinJS.UI.IListDataSource.change_p:key">
            /// The key for the item to replace.
            /// </param>
            /// <param name="newData" type="Object" locid="WinJS.UI.IListDataSource.change_p:newData">
            /// The new data for the item.
            /// </param>
            /// <returns type="Promise" locid="WinJS.UI.IListDataSource.change_returnValue">
            /// A Promise that contains the IItem that was updated or an EditError if an error occurred.
            /// </returns>
            /// </signature>

            var slot = getSlotForEdit(key);

            return new Promise(function (complete, error) {
                var itemOld;

                queueEdit(
                    // applyEdit
                    function () {
                        return listDataAdapter.change(key, newData, adjustedIndex(slot));
                    },

                    EditType.change, complete, error,

                    // keyUpdate
                    null,

                    // updateSlots
                    function () {
                        itemOld = slot.item;

                        slot.itemNew = {
                            key: key,
                            data: newData
                        };

                        if (itemOld) {
                            changeSlot(slot);
                        } else {
                            completeFetchPromises(slot);
                        }
                    },

                    // undo
                    function () {
                        if (itemOld) {
                            slot.itemNew = itemOld;
                            changeSlot(slot);
                        } else {
                            beginRefresh();
                        }
                    }
                );
            });
        };
    }

    if (listDataAdapter.moveToStart) {
        this.moveToStart = function (key) {
            /// <signature helpKeyword="WinJS.UI.IListDataSource.moveToStart">
            /// <summary locid="WinJS.UI.IListDataSource.moveToStart">
            /// Moves the specified item to the beginning of the data source.
            /// </summary>
            /// <param name="key" type="String" locid="WinJS.UI.IListDataSource.moveToStart_p:key">
            /// The key of the item to move.
            /// </param>
            /// <returns type="Promise" locid="WinJS.UI.IListDataSource.moveToStart_returnValue">
            /// A Promise that contains the IItem that was moved or an EditError if an error occurred.
            /// </returns>
            /// </signature>

            var slot = getSlotForEdit(key);

            return moveItem(
                slot,
                
                // slotMoveBefore, append
                slotsStart.next, true,

                // applyEdit
                function () {
                    return listDataAdapter.moveToStart(key, adjustedIndex(slot));
                }
            );
        };
    }

    if (listDataAdapter.moveBefore) {
        this.moveBefore = function (key, nextKey) {
            /// <signature helpKeyword="WinJS.UI.IListDataSource.moveBefore">
            /// <summary locid="WinJS.UI.IListDataSource.moveBefore">
            /// Moves the specified item before another item.
            /// </summary>
            /// <param name="key" type="String" locid="WinJS.UI.IListDataSource.moveBefore_p:key">
            /// The key of the item to move.
            /// </param>
            /// <param name="nextKey" type="String" locid="WinJS.UI.IListDataSource.moveBefore_p:nextKey">
            /// The key of another item in the data source. The item specified by the key parameter
            /// is moved to a position immediately before this item.
            /// </param>
            /// <returns type="Promise" locid="WinJS.UI.IListDataSource.moveBefore_returnValue">
            /// A Promise that contains the IItem that was moved or an EditError if an error occurred.
            /// </returns>
            /// </signature>

            var slot = getSlotForEdit(key),
                slotNext = getSlotForEdit(nextKey);

            return moveItem(
                slot,
                
                // slotMoveBefore, append
                slotNext, false,

                // applyEdit
                function () {
                    return listDataAdapter.moveBefore(key, nextKey, adjustedIndex(slot), adjustedIndex(slotNext));
                }
            );
        };
    }

    if (listDataAdapter.moveAfter) {
        this.moveAfter = function (key, previousKey) {
            /// <signature helpKeyword="WinJS.UI.IListDataSource.moveAfter">
            /// <summary locid="WinJS.UI.IListDataSource.moveAfter">
            /// Moves an item after another item.
            /// </summary>
            /// <param name="key" type="String" locid="WinJS.UI.IListDataSource.moveAfter_p:key">
            /// The key of the item to move.
            /// </param>
            /// <param name="previousKey" type="String" locid="WinJS.UI.IListDataSource.moveAfter_p:previousKey">
            /// The key of another item in the data source. The item specified by the key parameter will
            /// is moved to a position immediately after this item.
            /// </param>
            /// <returns type="Promise" locid="WinJS.UI.IListDataSource.moveAfter_returnValue">
            /// A Promise that contains the IItem that was moved or an EditError if an error occurred.
            /// </returns>
            /// </signature>

            var slot = getSlotForEdit(key),
                slotPrev = getSlotForEdit(previousKey);

            return moveItem(
                slot,
                
                // slotMoveBefore, append
                slotPrev.next, true,

                // applyEdit
                function () {
                    return listDataAdapter.moveAfter(key, previousKey, adjustedIndex(slot), adjustedIndex(slotPrev));
                }
            );
        };
    }

    if (listDataAdapter.moveToEnd) {
        this.moveToEnd = function (key) {
            /// <signature helpKeyword="WinJS.UI.IListDataSource.moveToEnd">
            /// <summary locid="WinJS.UI.IListDataSource.moveToEnd">
            /// Moves an item to the end of the data source.
            /// </summary>
            /// <param name="key" type="String" locid="WinJS.UI.IListDataSource.moveToEnd_p:key">
            /// The key of the item to move.
            /// </param>
            /// <returns type="Promise" locid="WinJS.UI.IListDataSource.moveToEnd_returnValue">
            /// A Promise that contains the IItem that was moved or an EditError if an error occurred.
            /// </returns>
            /// </signature>

            var slot = getSlotForEdit(key);

            return moveItem(
                slot,
                
                // slotMoveBefore, append
                slotListEnd, false,

                // applyEdit
                function () {
                    return listDataAdapter.moveToEnd(key, adjustedIndex(slot));
                }
            );
        };
    }

    if (listDataAdapter.remove) {
        this.remove = function (key) {
            /// <signature helpKeyword="WinJS.UI.IListDataSource.remove">
            /// <summary locid="WinJS.UI.IListDataSource.remove">
            /// Removes an item from the data source.
            /// </summary>
            /// <param name="key" type="String" locid="WinJS.UI.IListDataSource.remove_p:key">
            /// The key of the item to remove.
            /// </param>
            /// <returns type="Promise" locid="WinJS.UI.IListDataSource.remove_returnValue">
            /// A Promise that contains nothing if the operation was successful or an EditError if an error occurred.
            /// </returns>
            /// </signature>

            validateKey(key);

            var slot = keyMap[key];

            return new Promise(function (complete, error) {
                var slotNext,
                    firstInSequence,
                    lastInSequence;

                queueEdit(
                    // applyEdit
                    function () {
                        return listDataAdapter.remove(key, adjustedIndex(slot));
                    },

                    EditType.remove, complete, error,

                    // keyUpdate
                    null,

                    // updateSlots
                    function () {
                        if (slot) {
                            slotNext = slot.next;
                            firstInSequence = slot.firstInSequence;
                            lastInSequence = slot.lastInSequence;

                            updateNewIndices(slot, -1);
                            deleteSlot(slot, false);
                        }
                    },

                    // undo
                    function () {
                        if (slot) {
                            reinsertSlot(slot, slotNext, !firstInSequence, !lastInSequence);
                            updateNewIndices(slot, 1);
                            sendInsertedNotification(slot);
                        }
                    }
                );
            });
        };
    }

    this.endEdits = function () {
        /// <signature helpKeyword="WinJS.UI.IListDataSource.endEdits">
        /// <summary locid="WinJS.UI.IListDataSource.endEdits">
        /// Notifies the data source that a sequence of edits has ended.  The data source will call
        /// IListNotificationHandler.beginNotifications and endNotifications once each for a sequence of edits.
        /// </summary>
        /// </signature>

        editsInProgress = false;
        completeEdits();
    };
} // _baseDataSourceConstructor

// Public definitions

WinJS.Namespace.define("WinJS.UI", {

    DataSourceStatus: {
        ready: "ready",
        waiting: "waiting",
        failure: "failure"
    },

    CountResult: {
        unknown: "unknown"
    },

    CountError: {
        noResponse: "noResponse"
    },

    FetchError: {
        noResponse: "noResponse",
        doesNotExist: "doesNotExist"
    },

    EditError: {
        noResponse: "noResponse",
        canceled: "canceled",
        notPermitted: "notPermitted",
        noLongerMeaningful: "noLongerMeaningful"
    },
    
    VirtualizedDataSource: WinJS.Class.mix(
        WinJS.Class.define(function () {
            /// <signature helpKeyword="WinJS.UI.VirtualizedDataSource">
            /// <summary locid="WinJS.UI.VirtualizedDataSource">
            /// Use as a base class when defining a custom data source. Do not instantiate directly.
            /// </summary>
            /// <event name="statuschanged" locid="WinJS.UI.VirtualizedDataSource_e:statuschanged">
            /// Raised when the status of the VirtualizedDataSource changes between ready, waiting, and failure states.
            /// </event>
            /// </signature>
        }, {
            _baseDataSourceConstructor: _baseDataSourceConstructor
        }, { // Static Members
            supportedForProcessing: false,
        }),
        WinJS.Utilities.eventMixin
    )

});

var DataSourceStatus = UI.DataSourceStatus,
    CountResult = UI.CountResult,
    FetchError = UI.FetchError,
    EditError = UI.EditError;

})();


// Group Data Source

(function groupDataSourceInit() {
    "use strict";


var UI = WinJS.UI;
var Promise = WinJS.Promise;

// Private statics

function errorDoesNotExist() {
    return new WinJS.ErrorFromName(UI.FetchError.doesNotExist);
}

var batchSizeDefault = 101;

function groupReady(group) {
    return group && group.firstReached && group.lastReached;
}

var ListNotificationHandler = WinJS.Class.define(function ListNotificationHandler_ctor(groupDataAdapter) {
    // Constructor

    this._groupDataAdapter = groupDataAdapter;
}, {
    // Public methods

    beginNotifications: function () {
    },

    // itemAvailable: not implemented

    inserted: function (itemPromise, previousHandle, nextHandle) {
        this._groupDataAdapter._inserted(itemPromise, previousHandle, nextHandle);
    },

    changed: function (newItem, oldItem) {
        this._groupDataAdapter._changed(newItem, oldItem);
    },

    moved: function (itemPromise, previousHandle, nextHandle) {
        this._groupDataAdapter._moved(itemPromise, previousHandle, nextHandle);
    },

    removed: function (handle, mirage) {
        this._groupDataAdapter._removed(handle, mirage);
    },

    countChanged: function (newCount, oldCount) {
        if (newCount === 0 && oldCount !== 0) {
            this._groupDataAdapter.invalidateGroups();
        }
    },

    indexChanged: function (handle, newIndex, oldIndex) {
        this._groupDataAdapter._indexChanged(handle, newIndex, oldIndex);
    },

    endNotifications: function () {
        this._groupDataAdapter._endNotifications();
    },

    reload: function () {
        this._groupDataAdapter._reload();
    }
}, {
    supportedForProcessing: false,
});

var GroupDataAdapter = WinJS.Class.define(function GroupDataAdapater_ctor(listDataSource, groupKey, groupData, options) {
    // Constructor

    this._listBinding = listDataSource.createListBinding(new ListNotificationHandler(this));
    
    this._groupKey = groupKey;
    this._groupData = groupData;

    // _initializeState clears the count, so call this before processing the groupCountEstimate option
    this._initializeState();

    this._batchSize = batchSizeDefault;
    this._count = null;
    
    if (options) {
        if (typeof options.groupCountEstimate === "number") {
            this._count = (options.groupCountEstimate < 0 ? null : Math.max(options.groupCountEstimate , 1));
        }
        if (typeof options.batchSize === "number") {
            this._batchSize = options.batchSize + 1;
        }
    }

    if (this._listBinding.last) {
        this.itemsFromEnd = function (count) {
            var that = this;
            return this._fetchItems(
                // getGroup
                function () {
                    return that._lastGroup;
                },

                // mayExist
                function (failed) {
                    if (failed) {
                        return false;
                    }
                    var count = that._count;
                    if (+count !== count) {
                        return true;
                    }
                    if (count > 0) {
                        return true;
                    }
                },

                // fetchInitialBatch
                function () {
                    that._fetchBatch(that._listBinding.last(), that._batchSize - 1, 0);
                },

                count - 1, 0
            );
        };
    }
}, {
    // Public members

    setNotificationHandler: function (notificationHandler) {
        this._listDataNotificationHandler = notificationHandler;
    },
    
    // The ListDataSource should always compare these items by identity; in rare cases, it will do some unnecessary
    // rerendering, but at least fetching will not stringify items we already know to be valid and that we know
    // have not changed.
    compareByIdentity: true,

    // itemsFromStart: not implemented

    // itemsFromEnd: implemented in constructor

    itemsFromKey: function (key, countBefore, countAfter, hints) {
        var that = this;
        return this._fetchItems(
            // getGroup
            function () {
                return that._keyMap[key];
            },

            // mayExist
            function (failed) {
                var lastGroup = that._lastGroup;
                if (!lastGroup) {
                    return true;
                }
                if (+lastGroup.index !== lastGroup.index) {
                    return true;
                }
            },

            // fetchInitialBatch
            function () {
                hints = hints || {};
                var itemPromise = (
                    typeof hints.groupMemberKey === "string" && that._listBinding.fromKey ?
                        that._listBinding.fromKey(hints.groupMemberKey) :
                    typeof hints.groupMemberIndex === "number" && that._listBinding.fromIndex ?
                        that._listBinding.fromIndex(hints.groupMemberIndex) :
                    hints.groupMemberDescription !== undefined && that._listBinding.fromDescription ?
                        that._listBinding.fromDescription(hints.groupMemberDescription) :
                        that._listBinding.first()
                );

                var fetchBefore = Math.floor(0.5 * (that._batchSize - 1));
                that._fetchBatch(itemPromise, fetchBefore, that._batchSize - 1 - fetchBefore);
            },

            countBefore, countAfter
        );
    },
    
    itemsFromIndex: function (index, countBefore, countAfter) {
        var that = this;
        return this._fetchItems(
            // getGroup
            function () {
                return that._indexMap[index];
            },

            // mayExist
            function (failed) {
                var lastGroup = that._lastGroup;
                if (!lastGroup) {
                    return true;
                }
                if (+lastGroup.index !== lastGroup.index) {
                    return true;
                }
                if (index <= lastGroup.index) {
                    return true;
                }
            },

            // fetchInitialBatch
            function () {
                that._fetchNextIndex();
            },

            countBefore, countAfter
        );
    },

    // itemsFromDescription: not implemented

    getCount: function () {
        if (this._lastGroup && typeof this._lastGroup.index === "number") {
            //#DBG _ASSERT(this._count === this._lastGroup.index);

            return Promise.wrap(this._count);
        } else {
            // Even if there's a current estimate for _count, consider this call to be a request to determine the true
            // count.

            var that = this;
            var countPromise = new Promise(function (complete) {
                var fetch = {
                    initialBatch: function () {
                        that._fetchNextIndex();
                    },
                    getGroup: function () { return null; },
                    countBefore: 0,
                    countAfter: 0,
                    complete: function (failed) {
                        if (failed) {
                            that._count = 0;
                        }

                        var count = that._count;
                        if (typeof count === "number") {
                            complete(count);
                            return true;
                        } else {
                            return false;
                        }
                    }
                };

                that._fetchQueue.push(fetch);

                if (!that._itemBatch) {
                    //#DBG _ASSERT(that._fetchQueue[0] === fetch);
                    that._continueFetch(fetch);
                }
            });

            return (typeof this._count === "number" ? Promise.wrap(this._count) : countPromise);
        }
    },

    invalidateGroups: function () {
        this._beginRefresh();
        this._initializeState();
    },

    // Editing methods not implemented

    // Private members

    _initializeState: function () {
        this._count = null;
        this._indexMax = null;

        this._keyMap = {};
        this._indexMap = {};
        this._lastGroup = null;
        this._handleMap = {};

        this._fetchQueue = [];

        this._itemBatch = null;
        this._itemsToFetch = 0;

        this._indicesChanged = false;
    },

    _releaseItem: function (item) {
        delete this._handleMap[item.handle];
        this._listBinding.releaseItem(item);
    },

    _processBatch: function () {
        var previousItem = null,
            previousGroup = null,
            firstItemInGroup = null,
            itemsSinceStart = 0,
            failed = true;
        for (var i = 0; i < this._batchSize; i++) {
            var item = this._itemBatch[i],
                groupKey = (item ? this._groupKey(item) : null);

            if (item) {
                failed = false;
            }

            if (previousGroup && groupKey !== null && groupKey === previousGroup.key) {
                // This item is in the same group as the last item.  The only thing to do is advance the group's
                // lastItem if this is definitely the last item that has been processed for the group.
                itemsSinceStart++;
                if (previousGroup.lastItem === previousItem) {
                    if (previousGroup.lastItem.handle !== previousGroup.firstItem.handle) {
                        this._releaseItem(previousGroup.lastItem);
                    }
                    previousGroup.lastItem = item;
                    this._handleMap[item.handle] = previousGroup;

                    previousGroup.size++;
                } else if (previousGroup.firstItem === item) {
                    if (previousGroup.firstItem.handle !== previousGroup.lastItem.handle) {
                        this._releaseItem(previousGroup.firstItem);
                    }
                    previousGroup.firstItem = firstItemInGroup;
                    this._handleMap[firstItemInGroup.handle] = previousGroup;
                    
                    previousGroup.size += itemsSinceStart;
                }
            } else {
                var index = null;

                if (previousGroup) {
                    previousGroup.lastReached = true;

                    if (typeof previousGroup.index === "number") {
                        index = previousGroup.index + 1;
                    }
                }

                if (item) {
                    // See if the current group has already been processed
                    var group = this._keyMap[groupKey];

                    if (!group) {
                        group = {
                            key: groupKey,
                            data: this._groupData(item),
                            firstItem: item,
                            lastItem: item,
                            size: 1
                        };
                        this._keyMap[group.key] = group;
                        this._handleMap[item.handle] = group;
                    }

                    if (i > 0) {
                        group.firstReached = true;

                        if (!previousGroup) {
                            index = 0;
                        }
                    }

                    if (typeof group.index !== "number" && typeof index === "number") {
                        // Set the indices of as many groups as possible
                        for (var group2 = group; group2; group2 = this._nextGroup(group2)) {
                            //#DBG _ASSERT(typeof this._indexMap[index] !== "number");
                            group2.index = index;
                            this._indexMap[index] = group2;

                            index++;
                        }

                        this._indexMax = index;
                        if (typeof this._count === "number" && !this._lastGroup && this._count <= this._indexMax) {
                            this._count = this._indexMax + 1;
                        }
                    }

                    firstItemInGroup = item;
                    itemsSinceStart = 0;

                    previousGroup = group;
                } else {
                    if (previousGroup) {
                        this._lastGroup = previousGroup;

                        if (typeof previousGroup.index === "number") {
                            this._count = (previousGroup.index + 1);
                        }

                        // Force a client refresh (which should be fast) to ensure that a countChanged notification is
                        // sent.
                        this._listDataNotificationHandler.invalidateAll();

                        previousGroup = null;
                    }
                }
            }

            previousItem = item;
        }

        // See how many fetches have now completed
        var fetch;
        for (fetch = this._fetchQueue[0]; fetch && fetch.complete(failed); fetch = this._fetchQueue[0]) {
            this._fetchQueue.splice(0, 1);
        }

        // Continue work on the next fetch, if any
        if (fetch) {
            var that = this;
            Promise.timeout().then(function () {
                that._continueFetch(fetch);
            });
        } else {
            this._itemBatch = null;
        }
    },

    _processPromise: function (itemPromise, batchIndex) {
        itemPromise.retain();

        this._itemBatch[batchIndex] = itemPromise;

        var that = this;
        itemPromise.then(function (item) {
            that._itemBatch[batchIndex] = item;
            if (--that._itemsToFetch === 0) {
                that._processBatch();
            }
        });
    },

    _fetchBatch: function (itemPromise, countBefore, countAfter) {
        //#DBG _ASSERT(countBefore + 1 + countAfter === this._batchSize);
        this._itemBatch = new Array(this._batchSize);
        this._itemsToFetch = this._batchSize;

        this._processPromise(itemPromise, countBefore);

        var batchIndex;

        this._listBinding.jumpToItem(itemPromise);
        for (batchIndex = countBefore - 1; batchIndex >= 0; batchIndex--) {
            this._processPromise(this._listBinding.previous(), batchIndex);
        }

        this._listBinding.jumpToItem(itemPromise);
        for (batchIndex = countBefore + 1; batchIndex < this._batchSize; batchIndex++) {
            this._processPromise(this._listBinding.next(), batchIndex);
        }
    },

    _fetchAdjacent: function (item, after) {
        // Batches overlap by one so group boundaries always fall within at least one batch
        this._fetchBatch(
            (this._listBinding.fromKey ? this._listBinding.fromKey(item.key) : this._listBinding.fromIndex(item.index)),
            (after ? 0 : this._batchSize - 1),
            (after ? this._batchSize - 1 : 0)
        );
    },

    _fetchNextIndex: function () {
        var groupHighestIndex = this._indexMap[this._indexMax - 1];
        if (groupHighestIndex) {
            // We've already fetched some of the first items, so continue where we left off
            //#DBG _ASSERT(groupHighestIndex.firstReached);
            this._fetchAdjacent(groupHighestIndex.lastItem, true);
        } else {
            // Fetch one non-existent item before the list so _processBatch knows the start was reached
            this._fetchBatch(this._listBinding.first(), 1, this._batchSize - 2);
        }
    },

    _continueFetch: function (fetch) {
        if (fetch.initialBatch) {
            fetch.initialBatch();
            fetch.initialBatch = null;
        } else {
            var group = fetch.getGroup();
            if (group) {
                var groupPrev,
                    groupNext;

                if (!group.firstReached) {
                    this._fetchAdjacent(group.firstItem, false);
                } else if (!group.lastReached) {
                    this._fetchAdjacent(group.lastItem, true);
                } else if (fetch.countBefore > 0 && group.index !== 0 && !groupReady(groupPrev = this._previousGroup(group))) {
                    this._fetchAdjacent((groupPrev && groupPrev.lastReached ? groupPrev.firstItem : group.firstItem), false);
                } else {
                    groupNext = this._nextGroup(group);
                    //#DBG _ASSERT(fetch.countAfter > 0 && !groupReady(groupNext));
                    this._fetchAdjacent((groupNext && groupNext.firstReached ? groupNext.lastItem : group.lastItem), true);
                }
            } else {
                // Assume we're searching for a key, index or the count by brute force
                this._fetchNextIndex();
            }
        }
    },

    _fetchComplete: function (group, countBefore, countAfter, firstRequest, complete, error) {
        if (groupReady(group)) {
            // Check if the minimal requirements for the request are met
            var groupPrev = this._previousGroup(group);
            if (firstRequest || groupReady(groupPrev) || group.index === 0 || countBefore === 0) {
                var groupNext = this._nextGroup(group);
                if (firstRequest || groupReady(groupNext) || this._lastGroup === group || countAfter === 0) {
                    // Time to return the fetch results
                    
                    // Find the first available group to return (don't return more than asked for)
                    var countAvailableBefore = 0,
                        groupFirst = group;
                    while (countAvailableBefore < countBefore) {
                        groupPrev = this._previousGroup(groupFirst);

                        if (!groupReady(groupPrev)) {
                            break;
                        }

                        groupFirst = groupPrev;
                        countAvailableBefore++;
                    }

                    // Find the last available group to return
                    var countAvailableAfter = 0,
                        groupLast = group;
                    while (countAvailableAfter < countAfter) {
                        groupNext = this._nextGroup(groupLast);

                        if (!groupReady(groupNext)) {
                            break;
                        }

                        groupLast = groupNext;
                        countAvailableAfter++;
                    }

                    // Now create the items to return
                    var len = countAvailableBefore + 1 + countAvailableAfter,
                        items = new Array(len);

                    for (var i = 0; i < len; i++) {
                        var item = {
                            key: groupFirst.key,
                            data: groupFirst.data,
                            firstItemKey: groupFirst.firstItem.key,
                            groupSize: groupFirst.size
                        };

                        var firstItemIndex = groupFirst.firstItem.index; 
                        if (typeof firstItemIndex === "number") {
                            item.firstItemIndexHint = firstItemIndex;
                        }

                        items[i] = item;

                        groupFirst = this._nextGroup(groupFirst);
                    }

                    var result = {
                        items: items,
                        offset: countAvailableBefore
                    };

                    result.totalCount = (
                        typeof this._count === "number" ?
                            this._count :
                            UI.CountResult.unknown
                    );

                    if (typeof group.index === "number") {
                        result.absoluteIndex = group.index;
                    }

                    if (groupLast === this._lastGroup) {
                        result.atEnd = true;
                    }

                    complete(result);
                    return true;
                }
            }
        }

        return false;
    },

    _fetchItems: function (getGroup, mayExist, fetchInitialBatch, countBefore, countAfter) {
        var that = this;
        return new Promise(function (complete, error) {
            var group = getGroup(),
                firstRequest = !group,
                failureCount = 0;

            function fetchComplete(failed) {
                var group2 = getGroup();

                if (group2) {
                    return that._fetchComplete(group2, countBefore, countAfter, firstRequest, complete, error);
                } else if (firstRequest && !mayExist(failed)) {
                    error(errorDoesNotExist());
                    return true;
                } else if (failureCount > 2) {
                    error(errorDoesNotExist());
                    return true;
                } else {
                    // only consider consecutive failures
                    if (failed) {
                        failureCount++;
                    } else {
                        failureCount = 0;
                    }
                    // _continueFetch will switch to a brute force search
                    return false;
                }
            }

            if (!fetchComplete()) {
                var fetch = {
                    initialBatch: firstRequest ? fetchInitialBatch : null,
                    getGroup: getGroup,
                    countBefore: countBefore,
                    countAfter: countAfter,
                    complete: fetchComplete
                };

                that._fetchQueue.push(fetch);

                if (!that._itemBatch) {
                    //#DBG _ASSERT(that._fetchQueue[0] === fetch);
                    that._continueFetch(fetch);
                }
            }
        });
    },

    _previousGroup: function (group) {
        if (group && group.firstReached) {
            this._listBinding.jumpToItem(group.firstItem);

            return this._handleMap[this._listBinding.previous().handle];
        } else {
            return null;
        }
    },

    _nextGroup: function (group) {
        if (group && group.lastReached) {
            this._listBinding.jumpToItem(group.lastItem);

            return this._handleMap[this._listBinding.next().handle];
        } else {
            return null;
        }
    },

    _invalidateIndices: function (group) {
        this._count = null;

        if (typeof group.index === "number") {
            this._indexMax = (group.index > 0 ? group.index : null);
        }

        // Delete the indices of this and all subsequent groups
        for (var group2 = group; group2 && typeof group2.index === "number"; group2 = this._nextGroup(group2)) {
            delete this._indexMap[group2.index];
            group2.index = null;
        }
    },

    _releaseGroup: function (group) {
        this._invalidateIndices(group);

        delete this._keyMap[group.key];

        if (this._lastGroup === group) {
            this._lastGroup = null;
        }

        if (group.firstItem !== group.lastItem) {
            this._releaseItem(group.firstItem);
        }
        this._releaseItem(group.lastItem);
    },

    _beginRefresh: function () {
        // Abandon all current fetches
        
        this._fetchQueue = [];

        if (this._itemBatch) {
            for (var i = 0; i < this._batchSize; i++) {
                var item = this._itemBatch[i];
                if (item) {
                    if (item.cancel) {
                        item.cancel();
                    }
                    this._listBinding.releaseItem(item);
                }
            }

            this._itemBatch = null;
        }

        this._itemsToFetch = 0;

        this._listDataNotificationHandler.invalidateAll();
    },

    _processInsertion: function (item, previousHandle, nextHandle) {
        var groupPrev = this._handleMap[previousHandle],
            groupNext = this._handleMap[nextHandle],
            groupKey = null;
        
        if (groupPrev) {
            // If an item in a different group from groupPrev is being inserted after it, no need to discard groupPrev
            if (!groupPrev.lastReached || previousHandle !== groupPrev.lastItem.handle || (groupKey = this._groupKey(item)) === groupPrev.key) {
                this._releaseGroup(groupPrev);
            } else if (this._lastGroup === groupPrev) {
                this._lastGroup = null;
                this._count = null;
            }
            this._beginRefresh();
        }

        if (groupNext && groupNext !== groupPrev) {
            this._invalidateIndices(groupNext);

            // If an item in a different group from groupNext is being inserted before it, no need to discard groupNext
            if (!groupNext.firstReached || nextHandle !== groupNext.firstItem.handle || (groupKey !== null ? groupKey : this._groupKey(item)) === groupNext.key) {
                this._releaseGroup(groupNext);
            }
            this._beginRefresh();
        }
    },

    _processRemoval: function (handle) {
        var group = this._handleMap[handle];

        if (group && (handle === group.firstItem.handle || handle === group.lastItem.handle)) {
            this._releaseGroup(group);
            this._beginRefresh();
        } else if (this._itemBatch) {
            for (var i = 0; i < this._batchSize; i++) {
                var item = this._itemBatch[i];
                if (item && item.handle === handle) {
                    this._beginRefresh();
                    break;
                }
            }
        }
    },

    _inserted: function (itemPromise, previousHandle, nextHandle) {
        var that = this;
        itemPromise.then(function (item) {
            that._processInsertion(item, previousHandle, nextHandle);
        });
    },

    _changed: function (newItem, oldItem) {
        // A change to the first item could affect the group item
        var group = this._handleMap[newItem.handle];
        if (group && newItem.handle === group.firstItem.handle) {
            this._releaseGroup(group);
            this._beginRefresh();
        }

        // If the item is now in a different group, treat this as a move
        if (this._groupKey(newItem) !== this._groupKey(oldItem)) {
            this._listBinding.jumpToItem(newItem);
            var previousHandle = this._listBinding.previous().handle;
            this._listBinding.jumpToItem(newItem);
            var nextHandle = this._listBinding.next().handle;

            this._processRemoval(newItem.handle);
            this._processInsertion(newItem, previousHandle, nextHandle);
        }
    },

    _moved: function (itemPromise, previousHandle, nextHandle) {
        this._processRemoval(itemPromise.handle);

        var that = this;
        itemPromise.then(function (item) {
            that._processInsertion(item, previousHandle, nextHandle);
        });
    },

    _removed: function (handle, mirage) {
        // Mirage removals will just result in null items, which can be ignored
        if (!mirage) {
            this._processRemoval(handle);
        }
    },

    _indexChanged: function (handle, newIndex, oldIndex) {
        if (typeof oldIndex === "number") {
            this._indicesChanged = true;
        }
    },

    _endNotifications: function () {
        if (this._indicesChanged) {
            this._indicesChanged = false;

            // Update the group sizes
            for (var key in this._keyMap) {
                var group = this._keyMap[key];

                if (group.firstReached && group.lastReached) {
                    var newSize = group.lastItem.index + 1 - group.firstItem.index;
                    if (!isNaN(newSize)) {
                        group.size = newSize;
                    }
                }
            }

            // Invalidate the client, since some firstItemIndexHint properties have probably changed
            this._beginRefresh();
        }
    },

    _reload: function () {
        this._initializeState();
        this._listDataNotificationHandler.reload();
    }
}, {
    supportedForProcessing: false,
});

// Class definition

WinJS.Namespace.define("WinJS.UI", {

    _GroupDataSource: WinJS.Class.derive(UI.VirtualizedDataSource, function (listDataSource, groupKey, groupData, options) {
        var groupDataAdapter = new GroupDataAdapter(listDataSource, groupKey, groupData, options);

        this._baseDataSourceConstructor(groupDataAdapter);

        this.extensions = {
            invalidateGroups: function () {
                groupDataAdapter.invalidateGroups();
            }
        };
    }, {
        /* empty */
    }, {
        supportedForProcessing: false,
    })

});

})();


// Grouped Item Data Source

(function groupedItemDataSourceInit() {
    "use strict";


WinJS.Namespace.define("WinJS.UI", {

    computeDataSourceGroups: function (listDataSource, groupKey, groupData, options) {
        /// <signature helpKeyword="WinJS.UI.computeDataSourceGroups">
        /// <summary locid="WinJS.UI.computeDataSourceGroups">
        /// Returns a data source that adds group information to the items of another data source.  The "groups" property
        /// of this data source evaluates to yet another data source that enumerates the groups themselves.
        /// </summary>
        /// <param name="listDataSource" type="VirtualizedDataSource" locid="WinJS.UI.computeDataSourceGroups_p:listDataSource">
        /// The data source for the individual items to group.
        /// </param>
        /// <param name="groupKey" type="Function" locid="WinJS.UI.computeDataSourceGroups_p:groupKey">
        /// A callback function that takes an item in the list as an argument. The function is called
        /// for each item in the list and returns the group key for the item as a string.
        /// </param>
        /// <param name="groupData" type="Function" locid="WinJS.UI.computeDataSourceGroups_p:groupData">
        /// A callback function that takes an item in the IListDataSource as an argument.
        /// The function is called on one item in each group and returns
        /// an object that represents the header of that group.
        /// </param>
        /// <param name="options" type="Object" locid="WinJS.UI.computeDataSourceGroups_p:options">
        /// An object that can contain properties that specify additional options:
        /// 
        /// groupCountEstimate:
        /// A Number value that is the initial estimate for the number of groups. If you specify -1,
        /// this function returns no result is until the actual number of groups
        /// has been determined.
        /// 
        /// batchSize:
        /// A Number greater than 0 that specifies the number of items to fetch during each processing pass when
        /// searching for groups. (In addition to the number specified, one item from the previous batch
        /// is always included.)
        /// </param>
        /// <returns type="IListDataSource" locid="WinJS.UI.computeDataSourceGroups_returnValue">
        /// An IListDataSource that contains the items in the original data source and provides additional
        /// group info in a "groups" property. The "groups" property returns another
        /// IListDataSource that enumerates the different groups in the list.
        /// </returns>
        /// </signature>

        var groupedItemDataSource = Object.create(listDataSource);

        function createGroupedItem(item) {
            if (item) {
                var groupedItem = Object.create(item);

                groupedItem.groupKey = groupKey(item);

                if (groupData) {
                    groupedItem.groupData = groupData(item);
                }

                return groupedItem;
            } else {
                return null;
            }
        }

        function createGroupedItemPromise(itemPromise) {
            var groupedItemPromise = Object.create(itemPromise);

            groupedItemPromise.then = function (onComplete, onError, onCancel) {
                return itemPromise.then(function (item) {
                    return onComplete(createGroupedItem(item));
                }, onError, onCancel);
            };

            return groupedItemPromise;
        }

        groupedItemDataSource.createListBinding = function (notificationHandler) {
            var groupedNotificationHandler;
            
            if (notificationHandler) {
                groupedNotificationHandler = Object.create(notificationHandler);

                groupedNotificationHandler.inserted = function (itemPromise, previousHandle, nextHandle) {
                    return notificationHandler.inserted(createGroupedItemPromise(itemPromise), previousHandle, nextHandle);
                };

                groupedNotificationHandler.changed = function (newItem, oldItem) {
                    return notificationHandler.changed(createGroupedItem(newItem), createGroupedItem(oldItem));
                };

                groupedNotificationHandler.moved = function (itemPromise, previousHandle, nextHandle) {
                    return notificationHandler.moved(createGroupedItemPromise(itemPromise), previousHandle, nextHandle);
                };
            } else {
                groupedNotificationHandler = null;
            }

            var listBinding = listDataSource.createListBinding(groupedNotificationHandler),
                groupedItemListBinding = Object.create(listBinding);

            var listBindingMethods = [
                "first",
                "last",
                "fromDescription",
                "jumpToItem",
                "current"
            ];

            for (var i = 0, len = listBindingMethods.length; i < len; i++) {
                (function (listBindingMethod) {
                    if (listBinding[listBindingMethod]) {
                        groupedItemListBinding[listBindingMethod] = function () {
                            return createGroupedItemPromise(listBinding[listBindingMethod].apply(listBinding, arguments));
                        }
                    }
                })(listBindingMethods[i]);
            }

            // The following methods should be fast

            if (listBinding.fromKey) {
                groupedItemListBinding.fromKey = function (key) {
                    return createGroupedItemPromise(listBinding.fromKey(key));
                };
            }

            if (listBinding.fromIndex) {
                groupedItemListBinding.fromIndex = function (index) {
                    return createGroupedItemPromise(listBinding.fromIndex(index));
                };
            }

            groupedItemListBinding.prev = function () {
                return createGroupedItemPromise(listBinding.prev());
            };

            groupedItemListBinding.next = function () {
                return createGroupedItemPromise(listBinding.next());
            };

            return groupedItemListBinding;
        };

        var listDataSourceMethods = [
            "itemFromKey",
            "itemFromIndex",
            "itemFromDescription",
            "insertAtStart",
            "insertBefore",
            "insertAfter",
            "insertAtEnd",
            "change",
            "moveToStart",
            "moveBefore",
            "moveAfter",
            "moveToEnd"
            // remove does not return an itemPromise
        ];

        for (var i = 0, len = listDataSourceMethods.length; i < len; i++) {
            (function (listDataSourceMethod) {
                if (listDataSource[listDataSourceMethod]) {
                    groupedItemDataSource[listDataSourceMethod] = function () {
                        return createGroupedItemPromise(listDataSource[listDataSourceMethod].apply(listDataSource, arguments));
                    }
                }
            })(listDataSourceMethods[i]);
        }

        ["addEventListener", "removeEventListener", "dispatchEvent"].forEach(function (methodName) {
            if (listDataSource[methodName]) {
                groupedItemDataSource[methodName] = function () {
                    return listDataSource[methodName].apply(listDataSource, arguments);
                }
            }
        });

        var groupDataSource = null;
    
        Object.defineProperty(groupedItemDataSource, "groups", {
            get: function () {
                if (!groupDataSource) {
                    groupDataSource = new WinJS.UI._GroupDataSource(listDataSource, groupKey, groupData, options);
                }
                return groupDataSource;
            },
            enumerable: true,
            configurable: true
        });

        return groupedItemDataSource;
    }

});

})();


// Storage Item Data Source

(function storageDataSourceInit(global) {
    "use strict";


    var StorageDataAdapter = WinJS.Class.define(function StorageDataAdapter_ctor(query, options) {
        // Constructor
        msWriteProfilerMark("WinJS.UI.StorageDataSource:constructor,StartTM");

        var mode = Windows.Storage.FileProperties.ThumbnailMode.singleItem,
            size = 256,
            flags = Windows.Storage.FileProperties.ThumbnailOptions.useCurrentScale,
            delayLoad = true,
            library;

        if (query === "Pictures") {
            mode = Windows.Storage.FileProperties.ThumbnailMode.picturesView;
            library = Windows.Storage.KnownFolders.picturesLibrary;
            size = 190;
        } else if (query === "Music") {
            mode = Windows.Storage.FileProperties.ThumbnailMode.musicView;
            library = Windows.Storage.KnownFolders.musicLibrary;
            size = 256;
        } else if (query === "Documents") {
            mode = Windows.Storage.FileProperties.ThumbnailMode.documentsView;
            library = Windows.Storage.KnownFolders.documentsLibrary;
            size = 40;
        } else if (query === "Videos") {
            mode = Windows.Storage.FileProperties.ThumbnailMode.videosView;
            library = Windows.Storage.KnownFolders.videosLibrary;
            size = 190;
        }

        if (!library) {
            this._query = query;
        } else {
            var queryOptions = new Windows.Storage.Search.QueryOptions;
            queryOptions.folderDepth = Windows.Storage.Search.FolderDepth.deep;
            queryOptions.indexerOption = Windows.Storage.Search.IndexerOption.useIndexerWhenAvailable;
            this._query = library.createFileQueryWithOptions(queryOptions);
        }

        if (options) {
            if (typeof options.mode === "number") {
                mode = options.mode;
            }
            if (typeof options.requestedThumbnailSize === "number") {
                size = Math.max(1, Math.min(options.requestedThumbnailSize, 1024));
            } else {
                switch (mode) {
                    case Windows.Storage.FileProperties.ThumbnailMode.picturesView:
                    case Windows.Storage.FileProperties.ThumbnailMode.videosView:
                        size = 190;
                        break;
                    case Windows.Storage.FileProperties.ThumbnailMode.documentsView:
                    case Windows.Storage.FileProperties.ThumbnailMode.listView:
                        size = 40;
                        break;
                    case Windows.Storage.FileProperties.ThumbnailMode.musicView:
                    case Windows.Storage.FileProperties.ThumbnailMode.singleItem:
                        size = 256;
                        break;
                }
            }
            if (typeof options.thumbnailOptions === "number") {
                flags = options.thumbnailOptions;
            }
            if (typeof options.waitForFileLoad === "boolean") {
                delayLoad = !options.waitForFileLoad;
            }
        }

        this._loader = new Windows.Storage.BulkAccess.FileInformationFactory(this._query, mode, size, flags, delayLoad);
        this.compareByIdentity = false;
        this.firstDataRequest = true;
        msWriteProfilerMark("WinJS.UI.StorageDataSource:constructor,StopTM");
    }, {
        // Public members

        setNotificationHandler: function (notificationHandler) {
            this._notificationHandler = notificationHandler;
            this._query.addEventListener("contentschanged", function () {
                notificationHandler.invalidateAll();
            });
            this._query.addEventListener("optionschanged", function () {
                notificationHandler.invalidateAll();
            });
        },

        itemsFromEnd: function (count) {
            var that = this;
            msWriteProfilerMark("WinJS.UI.StorageDataSource:itemsFromEnd,info");
            return this.getCount().then(function (totalCount) {
                if (totalCount === 0) {
                    return WinJS.Promise.wrapError(new WinJS.ErrorFromName(WinJS.UI.FetchError.doesNotExist));
                }
                // Intentionally passing countAfter = 1 to go one over the end so that itemsFromIndex will
                // report the vector size since its known.
                return that.itemsFromIndex(totalCount - 1, Math.min(totalCount - 1, count - 1), 1);
            });
        },

        itemsFromIndex: function (index, countBefore, countAfter) {
            // don't allow more than 64 items to be retrieved at once
            if (countBefore + countAfter > 64) {
                countBefore = Math.min(countBefore, 32);
                countAfter = 64 - (countBefore + 1);
            }
            
            var first = (index - countBefore),
                count = (countBefore + 1 + countAfter);
            var that = this;
            // Fetch a minimum of 32 items on the first request for smoothness. Otherwise 
            // listview displays 2 items first and then the rest of the page.
            if (that.firstDataRequest) {
                that.firstDataRequest = false;
                count = Math.max(count, 32);
            }
            function listener(ev) {
                that._notificationHandler.changed(that._item(ev.target));
            };

            var perfId = "WinJS.UI.StorageDataSource:itemsFromIndex(" + first + "-" + (first + count - 1) + ")";
            msWriteProfilerMark(perfId + ",StartTM");
            return this._loader.getItemsAsync(first, count).then(function (itemsVector) {
                var vectorSize = itemsVector.size;
                if (vectorSize <= countBefore) {
                    return WinJS.Promise.wrapError(new WinJS.ErrorFromName(WinJS.UI.FetchError.doesNotExist));
                }
                var items = new Array(vectorSize);
                var localItemsVector = new Array(vectorSize);
                itemsVector.getMany(0, localItemsVector);
                for (var i = 0; i < vectorSize; i++) {
                    items[i] = that._item(localItemsVector[i]);
                    localItemsVector[i].addEventListener("propertiesupdated", listener);
                }
                var result = {
                    items: items,
                    offset: countBefore,
                    absoluteIndex: index
                };
                // set the totalCount only when we know it (when we retrieived fewer items than were asked for)
                if (vectorSize < count) {
                    result.totalCount = first + vectorSize;
                }
                msWriteProfilerMark(perfId + ",StopTM");
                return result;
            });
        },

        itemsFromDescription: function (description, countBefore, countAfter) {
            var that = this;
            msWriteProfilerMark("WinJS.UI.StorageDataSource:itemsFromDescription,info");
            return this._query.findStartIndexAsync(description).then(function (index) {
                return that.itemsFromIndex(index, countBefore, countAfter);
            });
        },

        getCount: function () {
            msWriteProfilerMark("WinJS.UI.StorageDataSource:getCount,info");
            return this._query.getItemCountAsync();
        },

        itemSignature: function (item) {
            return item.folderRelativeId;
        },

        // compareByIdentity: set in constructor
        // itemsFromStart: not implemented
        // itemsFromKey: not implemented
        // insertAtStart: not implemented
        // insertBefore: not implemented
        // insertAfter: not implemented
        // insertAtEnd: not implemented
        // change: not implemented
        // moveToStart: not implemented
        // moveBefore: not implemented
        // moveAfter: not implemented
        // moveToEnd: not implemented
        // remove: not implemented

        // Private members

        _item: function (item) {
            return {
                key: item.path || item.folderRelativeId,
                data: item
            };
        }
    }, {
        supportedForProcessing: false,
    });

    // Public definitions

    WinJS.Namespace.define("WinJS.UI", {
        StorageDataSource: WinJS.Class.derive(WinJS.UI.VirtualizedDataSource, function (query, options) {
            /// <signature helpKeyword="WinJS.UI.StorageDataSource">
            /// <summary locid="WinJS.UI.StorageDataSource">
            /// Creates a data source that enumerates an IStorageQueryResultBase.
            /// </summary>
            /// <param name="query" type="Windows.Storage.Search.IStorageQueryResultBase" locid="WinJS.UI.StorageDataSource_p:query">
            /// The object to enumerate. It must support IStorageQueryResultBase.
            /// </param>
            /// <param name="options" mayBeNull="true" optional="true" type="Object" locid="WinJS.UI.StorageDataSource_p:options">
            /// An object that specifies options for the data source. This parameter is optional. It can contain these properties:
            /// 
            /// mode:
            /// A Windows.Storage.FileProperties.ThumbnailMode - a value that specifies whether to request
            /// thumbnails and the type of thumbnails to request.
            /// 
            /// requestedThumbnailSize:
            /// A Number that specifies the size of the thumbnails.
            /// 
            /// thumbnailOptions:
            /// A Windows.Storage.FileProperties.ThumbnailOptions value that specifies additional options for the thumbnails.
            /// 
            /// waitForFileLoad:
            /// If you set this to true, the data source returns items only after it loads their properties and thumbnails.
            /// 
            /// </param>
            /// </signature>
            this._baseDataSourceConstructor(new StorageDataAdapter(query, options));
        }, {
            /* empty */
        }, {
            supportedForProcessing: false,
        })
    });

    WinJS.Namespace.define("WinJS.UI.StorageDataSource", {

        loadThumbnail: function (item, image) {
            /// <signature>
            /// <summary locid="WinJS.UI.StorageDataSource.loadThumbnail">
            /// Returns a promise for an image element that completes when the full quality thumbnail of the provided item is drawn to the
            /// image element.
            /// </summary>
            /// <param name="item" type="ITemplateItem" locid="WinJS.UI.StorageDataSource.loadThumbnail_p:item">
            /// The item to retrieve a thumbnail for.
            /// </param>
            /// <param name="image" type="Object" domElement="true" optional="true" locid="WinJS.UI.StorageDataSource.loadThumbnail_p:image">
            /// The image element to use. If not provided, a new image element is created.
            /// </param>
            /// </signature>
            var thumbnailUpdateHandler,
                thumbnailPromise,
                shouldRespondToThumbnailUpdate = false;
            
            return new WinJS.Promise(function (complete, error, progress) {
                // Load a thumbnail if it exists. The promise completes when a full quality thumbnail is visible.
                var tagSupplied = (image ? true : false);
                var processThumbnail = function (thumbnail) {
                    if (thumbnail) {
                        var url = URL.createObjectURL(thumbnail, {oneTimeOnly: true});

                        // If this is the first version of the thumbnail we're loading, fade it in.
                        if (!thumbnailPromise) {
                            thumbnailPromise = item.loadImage(url, image).then(function (image) {
                                // Wrapping the fadeIn call in a promise for the image returned by loadImage allows us to
                                // pipe the result of loadImage to further chained promises.  This is necessary because the
                                // image element provided to loadThumbnail is optional, and loadImage will create an image
                                // element if none is provided.
                                return item.isOnScreen().then(function (visible) {
                                    var imagePromise;
                                    if (visible && tagSupplied) {
                                        imagePromise = WinJS.UI.Animation.fadeIn(image).then(function () {
                                            return image;
                                        });
                                    } else {
                                        image.style.opacity = 1;
                                        imagePromise = WinJS.Promise.wrap(image);
                                    }
                                    return imagePromise;
                                });
                            });
                        }
                        // Otherwise, replace the existing version without animation.
                        else {
                            thumbnailPromise = thumbnailPromise.then(function (image) {
                                return item.loadImage(url, image);
                            });
                        }

                        // If we have the full resolution thumbnail, we can cancel further updates and complete the promise
                        // when current work is complete.
                        if ((thumbnail.type != Windows.Storage.FileProperties.ThumbnailType.icon) && !thumbnail.returnedSmallerCachedSize) {
                            msWriteProfilerMark("WinJS.UI.StorageDataSource:loadThumbnail complete,info");
                            item.data.removeEventListener("thumbnailupdated", thumbnailUpdateHandler);
                            shouldRespondToThumbnailUpdate = false;
                            thumbnailPromise = thumbnailPromise.then(function (image) {
                                thumbnailUpdateHandler = null;
                                thumbnailPromise = null;
                                complete(image);
                            });
                        }
                    }
                };

                thumbnailUpdateHandler = function (e) {
                    // Ensure that a zombie update handler does not get invoked.
                    if (shouldRespondToThumbnailUpdate) {
                        processThumbnail(e.target.thumbnail);
                    }
                };
                item.data.addEventListener("thumbnailupdated", thumbnailUpdateHandler);
                shouldRespondToThumbnailUpdate = true;
                
                // If we already have a thumbnail we should render it now.
                processThumbnail(item.data.thumbnail);
            }, function () {
                item.data.removeEventListener("thumbnailupdated", thumbnailUpdateHandler);
                shouldRespondToThumbnailUpdate = false;
                thumbnailUpdateHandler = null;
                if (thumbnailPromise) {
                    thumbnailPromise.cancel();
                    thumbnailPromise = null;
                }
            });
        }
    });
})();
// Items Manager

(function itemsManagerInit(global) {
    "use strict";

/*#DBG
    function dbg_stackTraceDefault() { return "add global function dbg_stackTrace to see stack traces"; }

    global.dbg_stackTrace = global.dbg_stackTrace || dbg_stackTraceDefault;
#DBG*/

    var markSupportedForProcessing = WinJS.Utilities.markSupportedForProcessing;

WinJS.Namespace.define("WinJS.UI", {
    _normalizeRendererReturn: function (v) {
        if (v) {
            if (typeof v === "object" && v.element) {
                var elementPromise = WinJS.Promise.as(v.element);
                return elementPromise.then(function (e) { return { element: e, renderComplete: WinJS.Promise.as(v.renderComplete) } });
            }
            else {
                var elementPromise = WinJS.Promise.as(v);
                return elementPromise.then(function (e) { return { element: e, renderComplete: WinJS.Promise.as() } });
            }
        }
        else {
            return { element: null, renderComplete: WinJS.Promise.as() };
        }
    },
    simpleItemRenderer: function (f) {
        return markSupportedForProcessing(function (itemPromise, element) {
            return itemPromise.then(function (item) {
                return (item ? f(item, element) : null);
            });
        });
    }
});
var Promise = WinJS.Promise;
var UI = WinJS.UI;

// Private statics

var strings = {
    get listDataSourceIsInvalid() { return WinJS.Resources._getWinJSString("ui/listDataSourceIsInvalid").value; },
    get itemRendererIsInvalid() { return WinJS.Resources._getWinJSString("ui/itemRendererIsInvalid").value; },
    get itemIsInvalid() { return WinJS.Resources._getWinJSString("ui/itemIsInvalid").value; },
    get invalidItemsManagerCallback() { return WinJS.Resources._getWinJSString("ui/invalidItemsManagerCallback").value; }
};

var Signal = WinJS._Signal;

var imageLoader;
var lastSort = new Date();
var minDurationBetweenImageSort = 64;

// This optimization is good for a couple of reasons:
// - It is a global optimizer, which means that all on screen images take precedence over all off screen images.
// - It avoids resorting too frequently by only resorting when a new image loads and it has been at least 64 ms since
//   the last sort.
// Also, it is worth noting that "sort" on an empty queue does no work (besides the function call).
function compareImageLoadPriority(a, b) {
    var aon = false;
    var bon = false;

    // Currently isOnScreen is synchronous and fast for list view
    a.isOnScreen().then(function (v) { aon = v; });
    b.isOnScreen().then(function (v) { bon = v; });

    return (aon ? 0 : 1) - (bon ? 0 : 1);
}

var seenUrls = {};
var seenUrlsMRU = [];
var SEEN_URLS_MAXSIZE = 250;
var SEEN_URLS_MRU_MAXSIZE = 1000;

function seenUrl(srcUrl) {
    if ((/^blob:/i).test(srcUrl)) {
        return;
    }

    seenUrls[srcUrl] = true;
    seenUrlsMRU.push(srcUrl);

    if (seenUrlsMRU.length > SEEN_URLS_MRU_MAXSIZE) {
        var mru = seenUrlsMRU;
        seenUrls = {};
        seenUrlsMRU = [];

        for (var count = 0, i = mru.length - 1; i >= 0 && count < SEEN_URLS_MAXSIZE; i--) {
            var url = mru[i];
            if (!seenUrls[url]) {
                seenUrls[url] = true;
                count++;
            }
        }
    }
}

// Exposing the seenUrl related members to use them in unit tests
WinJS.Namespace.define("WinJS.UI", {
    _seenUrl: seenUrl,
    _getSeenUrls: function () {
        return seenUrls;
    },
    _getSeenUrlsMRU: function () {
        return seenUrlsMRU;
    },
    _seenUrlsMaxSize: SEEN_URLS_MAXSIZE,
    _seenUrlsMRUMaxSize: SEEN_URLS_MRU_MAXSIZE
});

function loadImage(srcUrl, image, data) {
    imageLoader = imageLoader || new WinJS.UI._ParallelWorkQueue(6);
    return imageLoader.queue(function () {
        return new WinJS.Promise(function (c, e, p) {
            if (!image) {
                image = document.createElement("img");
            }

            var seen = seenUrls[srcUrl];

            if (!seen) {
                var tempImage = document.createElement("img");

                var cleanup = function () {
                    tempImage.removeEventListener("load", complete, false);
                    tempImage.removeEventListener("error", error, false);

                    // One time use blob images are cleaned up as soon as they are not referenced by images any longer.
                    // We set the image src before clearing the tempImage src to make sure the blob image is always
                    // referenced.
                    image.src = srcUrl;

                    var currentDate = new Date();
                    if (currentDate - lastSort > minDurationBetweenImageSort) {
                        lastSort = currentDate;
                        imageLoader.sort(compareImageLoadPriority);
                    }
                }

                var complete = function () {
                    seenUrl(srcUrl);
                    cleanup();
                    c(image);
                }

                var error = function () {
                    cleanup();
                    e(image);
                }

                tempImage.addEventListener("load", complete, false);
                tempImage.addEventListener("error", error, false);
                tempImage.src = srcUrl;
            } else {
                seenUrl(srcUrl);
                image.src = srcUrl;
                c(image);
            }
        });
    }, data);
}

function isImageCached(srcUrl) {
    return seenUrls[srcUrl];
}

function defaultRenderer(item) {
    return document.createElement("div");
}

// Type-checks a callback parameter, since a failure will be hard to diagnose when it occurs
function checkCallback(callback, name) {
    if (typeof callback !== "function") {
        throw new WinJS.ErrorFromName("WinJS.UI.ItemsManager.CallbackIsInvalid", WinJS.Resources._formatString(strings.invalidItemsManagerCallback, name));
    }
}

var ListNotificationHandler = WinJS.Class.define(function ListNotificationHandler_ctor(itemsManager) {
    // Constructor

    this._itemsManager = itemsManager;
    /*#DBG
    this._notificationsCount = 0;
    #DBG*/
}, {
    // Public methods

    beginNotifications: function () {
        /*#DBG
        if (this._notificationsCount !== 0) {
            throw new "ACK! Unbalanced beginNotifications call";
        }
        this._notificationsCount++;
        #DBG*/
        this._itemsManager._versionManager.beginNotifications();
        this._itemsManager._beginNotifications();
    },

    // itemAvailable: not implemented

    inserted: function (itemPromise, previousHandle, nextHandle) {
        this._itemsManager._versionManager.receivedNotification();
        this._itemsManager._inserted(itemPromise, previousHandle, nextHandle);
    },

    changed: function (newItem, oldItem) {
        this._itemsManager._versionManager.receivedNotification();
        this._itemsManager._changed(newItem, oldItem);
    },

    moved: function (itemPromise, previousHandle, nextHandle) {
        this._itemsManager._versionManager.receivedNotification();
        this._itemsManager._moved(itemPromise, previousHandle, nextHandle);
    },

    removed: function (handle, mirage) {
        this._itemsManager._versionManager.receivedNotification();
        this._itemsManager._removed(handle, mirage);
    },

    countChanged: function (newCount, oldCount) {
        this._itemsManager._versionManager.receivedNotification();
        this._itemsManager._countChanged(newCount, oldCount);
    },

    indexChanged: function (handle, newIndex, oldIndex) {
        this._itemsManager._versionManager.receivedNotification();
        this._itemsManager._indexChanged(handle, newIndex, oldIndex);
    },

    endNotifications: function () {
        /*#DBG
        if (this._notificationsCount !== 1) {
            throw new "ACK! Unbalanced endNotifications call";
        }
        this._notificationsCount--;
        #DBG*/
        this._itemsManager._versionManager.endNotifications();
        this._itemsManager._endNotifications();
    },

    reload: function () {
        this._itemsManager._versionManager.receivedNotification();
        this._itemsManager._reload();
    }
}, { // Static Members
    supportedForProcessing: false,
});

var ItemsManager = WinJS.Class.define(function ItemsManager_ctor(listDataSource, itemRenderer, elementNotificationHandler, options) {
    // Constructor

    if (!listDataSource) {
        throw new WinJS.ErrorFromName("WinJS.UI.ItemsManager.ListDataSourceIsInvalid", strings.listDataSourceIsInvalid);
    }
    if (!itemRenderer) {
        throw new WinJS.ErrorFromName("WinJS.UI.ItemsManager.ItemRendererIsInvalid", strings.itemRendererIsInvalid);
    }

    this.$pipeline_callbacksMap = {};

    this._listDataSource = listDataSource;

    this.dataSource = this._listDataSource;

    this._elementNotificationHandler = elementNotificationHandler;

    this._listBinding = this._listDataSource.createListBinding(new ListNotificationHandler(this));

    if (options) {
        if (options.ownerElement) {
            this._ownerElement = options.ownerElement;
        }
        this._versionManager = options.versionManager || new WinJS.UI._VersionManager();
    }

    this._resetItem = options && options.resetItem || function () { return null; };
    this._indexInView = options && options.indexInView;
    this._itemRenderer = itemRenderer;

    // Map of (the uniqueIDs of) elements to records for items
    this._elementMap = {};

    // Map of handles to records for items
    this._handleMap = {};

    // Worker queue to process ready events for async data sources
    this._workQueue = new WinJS.UI._TimeBasedQueue();
    this._workQueue.start();

    // Boolean to track whether endNotifications needs to be called on the ElementNotificationHandler
    this._notificationsSent = false;

    // Only enable the lastItem method if the data source implements the itemsFromEnd method
    if (this._listBinding.last) {
        this.lastItem = function () {
            return this._elementForItem(this._listBinding.last());
        };
    }
}, {
    _itemFromItemPromise: function (itemPromise) {
        return this._waitForElement(this._elementForItem(itemPromise))
    },
    _itemAtIndex: function (index) {
        /*#DBG
        var that = this;
        var startVersion = that._versionManager.version;
        #DBG*/
        var itemPromise = this._itemPromiseAtIndex(index)
        var result = this._itemFromItemPromise(itemPromise)/*#DBG .
            then(function (v) {
                var rec = that._recordFromElement(v);
                var endVersion = that._versionManager.version;
                if (rec.item.index !== index) {
                    throw "ACK! inconsistent index";
                }
                if (startVersion !== endVersion) {
                    throw "ACK! inconsistent version";
                }
                if (WinJS.Utilities.data(v).itemData &&
                        WinJS.Utilities.data(v).itemData.itemsManagerRecord.item.index !== index) {
                            throw "ACK! inconsistent itemData.index";
                        }
                return v;
            }) #DBG*/;
        return result.then(null, function (e) {
            itemPromise.cancel();
            return WinJS.Promise.wrapError(e);
        });
    },
    _itemPromiseAtIndex: function (index) {
        /*#DBG
        var that = this;
        var startVersion = that._versionManager.version;
        if (that._versionManager.locked) {
            throw "ACK! Attempt to get an item while editing";
        }
        #DBG*/
        var itemPromise = this._listBinding.fromIndex(index);
        /*#DBG
        itemPromise.then(function (item) {
            var endVersion = that._versionManager.version;
            if (item.index !== index) {
                throw "ACK! inconsistent index";
            }
            if (startVersion !== endVersion) {
                throw "ACK! inconsistent version";
            }
            return item;
        });
        #DBG*/
        return itemPromise;
    },
    _waitForElement: function (possiblePlaceholder) {
        var that = this;
        return new WinJS.Promise(function (c, e, p) {
            if (possiblePlaceholder) {
                if (!that.isPlaceholder(possiblePlaceholder)) {
                    c(possiblePlaceholder);
                }
                else {
                    var placeholderID = possiblePlaceholder.uniqueID;
                    var callbacks = that.$pipeline_callbacksMap[placeholderID];
                    if (!callbacks) {
                        that.$pipeline_callbacksMap[placeholderID] = [c];
                    } else {
                        callbacks.push(c);
                    }
                }
            }
            else {
                c(possiblePlaceholder);
            }
        });
    },
    _updateElement: function (newElement, oldElement) {
        var placeholderID = oldElement.uniqueID;
        var callbacks = this.$pipeline_callbacksMap[placeholderID];
        if (callbacks) {
            delete this.$pipeline_callbacksMap[placeholderID];
            callbacks.forEach(function (c) { c(newElement); });
        }
    },
    _firstItem: function () {
        return this._waitForElement(this._elementForItem(this._listBinding.first()));
    },
    _lastItem: function () {
        return this._waitForElement(this._elementForItem(this._listBinding.last()));
    },
    _previousItem: function (element) {
        this._listBinding.jumpToItem(this._itemFromElement(element));
        return this._waitForElement(this._elementForItem(this._listBinding.previous()));
    },
    _nextItem: function (element) {
        this._listBinding.jumpToItem(this._itemFromElement(element));
        return this._waitForElement(this._elementForItem(this._listBinding.next()));
    },
    _itemFromPromise: function (itemPromise) {
        return this._waitForElement(this._elementForItem(itemPromise));
    },
    isPlaceholder: function (item) {
        return !!this._recordFromElement(item).elementIsPlaceholder;
    },

    itemObject: function (element) {
        return this._itemFromElement(element);
    },

    release: function () {
        this._listBinding.release();
        this._elementNotificationHandler = null;
        this._listBinding = null;
        this._workQueue.cancel();
        this._released = true;
    },

    releaseItem: function (element) {
        var record = this._elementMap[element.uniqueID];
        if (!record) { return; }

        /*#DBG
        record = this._recordFromElement(element);
        if (record.released) {
            throw "ACK! Double release on item";
        }
        #DBG*/

        if (record.renderPromise) {
            record.renderPromise.cancel();
        }
        if (record.itemPromise) {
            record.itemPromise.cancel();
        }
        if (record.imagePromises) {
            record.imagePromises.cancel();
        }
        if (record.itemReadyPromise) {
            record.itemReadyPromise.cancel();
        }
        if (record.renderComplete) {
            record.renderComplete.cancel();
        }

        this._removeEntryFromElementMap(element);
        this._removeEntryFromHandleMap(record.item ? record.item.handle : record.itemPromise.handle, record);

        if (record.item) {
            this._listBinding.releaseItem(record.item);
        }

        /*#DBG
        record.released = true;
        if (record.updater) {
            throw "ACK! attempt to release item current held by updater";
        }
        #DBG*/
    },

    refresh: function () {
        return this._listDataSource.invalidateAll();
    },

    // Private members

    _handlerToNotify: function () {
        if (!this._notificationsSent) {
            this._notificationsSent = true;

            if (this._elementNotificationHandler && this._elementNotificationHandler.beginNotifications) {
                this._elementNotificationHandler.beginNotifications();
            }
        }
        return this._elementNotificationHandler;
    },

    _defineIndexProperty: function (itemForRenderer, item, record) {
        record.indexObserved = false;
        Object.defineProperty(itemForRenderer, "index", {
            get: function () {
                record.indexObserved = true;
                return item.index;
            }
        });
    },

    _renderPlaceholder: function (record) {
        var itemForRenderer = {};
        var elementPlaceholder = defaultRenderer(itemForRenderer);
        record.elementIsPlaceholder = true;
        return elementPlaceholder;
    },

    _renderItem: function (itemPromise, record) {
        var that = this;
        var indexInView = that._indexInView || function () { return true; };
        var readySignal = new Signal();
        var itemForRendererPromise = itemPromise.then(function(item) { 
            if (item) {
                var itemForRenderer = Object.create(item);
                // Derive a new item and override its index property, to track whether it is read
                that._defineIndexProperty(itemForRenderer, item, record);
                itemForRenderer.ready = readySignal.promise;
                itemForRenderer.isOnScreen = function() { 
                    return Promise.wrap(indexInView(item.index)); 
                };
                itemForRenderer.loadImage = function (srcUrl, image) {
                    var loadImagePromise = loadImage(srcUrl, image, itemForRenderer);
                    if (record.imagePromises) {
                        record.imagePromises = WinJS.Promise.join([record.imagePromises, loadImagePromise]);
                    } else {
                        record.imagePromises = loadImagePromise;
                    }
                    return loadImagePromise;
                };
                itemForRenderer.isImageCached = isImageCached;
                return itemForRenderer;
            } else {
                return WinJS.Promise.cancel;
            }
        });
        itemForRendererPromise.handle = itemPromise.handle;
        record.itemPromise = itemForRendererPromise;
        record.itemReadyPromise = readySignal.promise;
        record.readyComplete = false;
    
        return WinJS.Promise.as(that._itemRenderer(itemForRendererPromise, record.element)).
            then(WinJS.UI._normalizeRendererReturn).
            then(function (v) {
                if (that._released) {
                    return WinJS.Promise.cancel;
                }

                itemForRendererPromise.then(function (item) {
                    // Store pending ready callback off record so ScrollView can call it during realizePage. Otherwise
                    // call it ourselves.
                    record.pendingReady = function () {
                        if (record.pendingReady) {
                            readySignal.complete(item);
                            record.pendingReady = null;
                            record.readyComplete = true;
                        }
                    }
                    that._workQueue.push(record.pendingReady);
                });
                return v;
            });
    },

    _replaceElement: function (record, elementNew) {
        /*#DBG
        if (!this._handleInHandleMap(record.item.handle)) {
            throw "ACK! replacing element not present in handle map";
        }
        #DBG*/
        this._removeEntryFromElementMap(record.element);
        record.element = elementNew;
        this._addEntryToElementMap(elementNew, record);
    },

    _changeElement: function (record, elementNew, elementNewIsPlaceholder) {
        //#DBG _ASSERT(elementNew);
        record.renderPromise = null;
        var elementOld = record.element,
            itemOld = record.item;

        if (record.newItem) {
            record.item = record.newItem;
            record.newItem = null;
        }

        this._replaceElement(record, elementNew);

        if (record.item && record.elementIsPlaceholder && !elementNewIsPlaceholder) {
            record.elementDelayed = null;
            record.elementIsPlaceholder = false;
            this._updateElement(record.element, elementOld);
            this._handlerToNotify().itemAvailable(record.element, elementOld);
        } else {
            this._handlerToNotify().changed(elementNew, elementOld, itemOld);
        }
    },

    _elementForItem: function (itemPromise) {
        var handle = itemPromise.handle,
            record = this._recordFromHandle(handle, true),
            element;

        if (!handle) {
            return null;
        }

        if (record) {
            element = record.element;
        } else {
            // Create a new record for this item
            record = {
                item: itemPromise,
                itemPromise: itemPromise
            };
            this._addEntryToHandleMap(handle, record);

            var that = this;
            var mirage = false;
            var synchronous = false;

            var renderPromise =
                that._renderItem(itemPromise, record).
                then(function (v) {
                    var elementNew = v.element;
                    record.renderComplete = v.renderComplete;

                    itemPromise.then(function (item) {
                        record.item = item;
                        if (!item) {
                            mirage = true;
                            element = null;
                        }
                    });

                    synchronous = true;
                    record.renderPromise = null;

                    if (elementNew) {
                        if (element) {
                            that._presentElements(record, elementNew);
                        } else {
                            element = elementNew;
                        }
                    }
                });

            if (!mirage) {
                if (!synchronous) {
                    record.renderPromise = renderPromise;
                }

                if (!element) {
                    element = this._renderPlaceholder(record);
                }

                record.element = element;
                this._addEntryToElementMap(element, record);

                itemPromise.retain();
            }
        }
        
        return element;
    },

    _addEntryToElementMap: function (element, record) {
        /*#DBG 
        if (WinJS.Utilities.data(element).itemsManagerRecord) {
            throw "ACK! Extra call to _addEntryToElementMap, ref counting error";
        }
        WinJS.Utilities.data(element).itemsManagerRecord = record;
        #DBG*/
        this._elementMap[element.uniqueID] = record;
    },

    _removeEntryFromElementMap: function (element) {
        /*#DBG
        if (!WinJS.Utilities.data(element).itemsManagerRecord) {
            throw "ACK! Extra call to _removeEntryFromElementMap, ref counting error";
        }
        WinJS.Utilities.data(element).removeElementMapRecord = WinJS.Utilities.data(element).itemsManagerRecord;
        WinJS.Utilities.data(element).removeEntryMapStack = dbg_stackTrace();
        delete WinJS.Utilities.data(element).itemsManagerRecord;
        #DBG*/
        delete this._elementMap[element.uniqueID];
    },

    _recordFromElement: function (element, ignoreFailure) {
        var record = this._elementMap[element.uniqueID];
        if (!record) {
            /*#DBG
            var removeElementMapRecord = WinJS.Utilities.data(element).removeElementMapRecord;
            var itemsManagerRecord = WinJS.Utilities.data(element).itemsManagerRecord;
            #DBG*/
            throw new WinJS.ErrorFromName("WinJS.UI.ItemsManager.ItemIsInvalid", strings.itemIsInvalid);
        }

        return record;
    },

    _addEntryToHandleMap: function (handle, record) {
        /*#DBG
        if (this._handleMap[handle]) {
            throw "ACK! Extra call to _addEntryToHandleMap, ref counting error";
        }
        this._handleMapLeak = this._handleMapLeak || {};
        this._handleMapLeak[handle] = { record: record, addHandleMapStack: dbg_stackTrace() };
        #DBG*/
        this._handleMap[handle] = record;
    },

    _removeEntryFromHandleMap: function (handle, record) {
        /*#DBG
        if (!this._handleMap[handle]) {
            throw "ACK! Extra call to _removeEntryFromHandleMap, ref counting error";
        }
        this._handleMapLeak[handle].removeHandleMapStack = dbg_stackTrace();
        #DBG*/
        delete this._handleMap[handle];
    },

    _handleInHandleMap: function (handle) {
        return !!this._handleMap[handle];
    },

    _recordFromHandle: function (handle, ignoreFailure) {
        var record = this._handleMap[handle];
        if (!record && !ignoreFailure) {
            /*#DBG
            var leak = this._handleMapLeak[handle];
            #DBG*/
            throw new WinJS.ErrorFromName("WinJS.UI.ItemsManager.ItemIsInvalid", strings.itemIsInvalid);
        }
        return record;
    },

    _foreachRecord: function (callback) {
        var records = this._handleMap;
        for (var property in records) {
            var record = records[property];
            callback(record);
        }
    },

    _itemFromElement: function (element) {
        return this._recordFromElement(element).item;
    },

    _elementFromHandle: function (handle) {
        if (handle) {
            var record = this._recordFromHandle(handle, true);

            if (record && record.element) {
                return record.element;
            }
        }

        return null;
    },
    
    _inserted: function (itemPromise, previousHandle, nextHandle) {
        this._handlerToNotify().inserted(itemPromise, previousHandle, nextHandle);
    },

    _changed: function (newItem, oldItem) {
        if (!this._handleInHandleMap(oldItem.handle)) { return; }

        var record = this._recordFromHandle(oldItem.handle);

        //#DBG _ASSERT(record);
        if (record.renderPromise) {
            record.renderPromise.cancel();
        }
        if (record.itemPromise) {
            record.itemPromise.cancel();
        }
        if (record.imagePromises) {
            record.imagePromises.cancel();
        }
        if (record.itemReadyPromise) {
            record.itemReadyPromise.cancel();
        }
        if (record.renderComplete) {
            record.renderComplete.cancel();
        }
        
        record.newItem = newItem;

        var that = this;
        if (record.item && record.item.key) {
            this._resetItem(record.item, record.element);
        }
        record.renderPromise = this._renderItem(WinJS.Promise.as(newItem), record).
            then(function (v) {
                record.renderComplete = v.renderComplete;
                that._changeElement(record, v.element, false);
                that._presentElements(record);
            });
    },

    _moved: function (itemPromise, previousHandle, nextHandle) {
        // no check for haveHandle, as we get move notification for items we 
        // are "next" to, so we handle the "null element" cases below
        //
        var element = this._elementFromHandle(itemPromise.handle);
        var previous = this._elementFromHandle(previousHandle);
        var next = this._elementFromHandle(nextHandle);

        this._handlerToNotify().moved(element, previous, next, itemPromise);
        this._presentAllElements();
    },

    _removed: function (handle, mirage) {
        if (this._handleInHandleMap(handle)) {
            var element = this._elementFromHandle(handle),
                item = this.itemObject(element);

            //#DBG _ASSERT(element);
            if (item && item.key) {
                this._resetItem(item, element);
            }
            this._handlerToNotify().removed(element, mirage, handle);
            this.releaseItem(element);
            this._presentAllElements();
        } else {
            this._handlerToNotify().removed(null, mirage, handle);
        }
    },

    _countChanged: function (newCount, oldCount) {
        if (this._elementNotificationHandler && this._elementNotificationHandler.countChanged) {
            this._handlerToNotify().countChanged(newCount, oldCount);
        }
    },

    _indexChanged: function (handle, newIndex, oldIndex) {
        var element;
        if (this._handleInHandleMap(handle)) {
            var record = this._recordFromHandle(handle);
            if (record.indexObserved) {
                if (!record.elementIsPlaceholder) {
                    if (record.item.index !== newIndex) {
                        if (record.renderPromise) {
                            record.renderPromise.cancel();
                        }
                        if (record.renderComplete) {
                            record.renderComplete.cancel();
                        }

                        var itemToRender = record.newItem || record.item;
                        itemToRender.index = newIndex;

                        var that = this;
                        record.renderPromise = this._renderItem(itemToRender, record).
                            then(function (v) {
                                record.renderComplete = v.renderComplete;
                                that._changeElement(record, v.element, false);
                                that._presentElements(record);
                            });
                    }
                } else {
                    this._changeElement(record, this._renderPlaceholder(record), true);
                }
            }
            element = record.element;
        }
        if (this._elementNotificationHandler && this._elementNotificationHandler.indexChanged) {
            this._handlerToNotify().indexChanged(element, newIndex, oldIndex);
        }
    },
    _beginNotifications: function () {
        // accessing _handlerToNotify will force the call to beginNotifications on the client
        //
        this._externalBegin = true;
        var x = this._handlerToNotify();
    },
    _endNotifications: function () {
        if (this._notificationsSent) {
            this._notificationsSent = false;
            this._externalBegin = false;

            if (this._elementNotificationHandler && this._elementNotificationHandler.endNotifications) {
                this._elementNotificationHandler.endNotifications();
            }
        }
    },

    _reload: function () {
        if (this._elementNotificationHandler && this._elementNotificationHandler.reload) {
            this._elementNotificationHandler.reload();
        }
    },

    // Some functions may be called synchronously or asynchronously, so it's best to post _endNotifications to avoid
    // calling it prematurely.
    _postEndNotifications: function () {
        if (this._notificationsSent && !this._externalBegin && !this._endNotificationsPosted) {
            this._endNotificationsPosted = true;
            var that = this;
            setImmediate(function () {
                that._endNotificationsPosted = false;
                that._endNotifications();
            });
        }
    },

    _presentElement: function (record) {
        var elementOld = record.element;
        //#DBG _ASSERT(elementOld);

        // Finish modifying the slot before calling back into user code, in case there is a reentrant call
        this._replaceElement(record, record.elementDelayed);
        record.elementDelayed = null;

        record.elementIsPlaceholder = false;
        this._updateElement(record.element, elementOld);
        this._handlerToNotify().itemAvailable(record.element, elementOld);
    },

    _presentElements: function (record, elementDelayed) {
        if (elementDelayed) {
            record.elementDelayed = elementDelayed;
        }

        this._listBinding.jumpToItem(record.item);
        if (record.elementDelayed) {
            this._presentElement(record);
        }

        this._postEndNotifications();
    },

    // Presents all delayed elements
    _presentAllElements: function () {
        var that = this;
        this._foreachRecord(function (record) {
            if (record.elementDelayed) {
                that._presentElement(record);
            }
        });
    }
}, { // Static Members
    supportedForProcessing: false,
});

// Public definitions

WinJS.Namespace.define("WinJS.UI", {
    _createItemsManager: function (dataSource, itemRenderer, elementNotificationHandler, options) {
        return new ItemsManager(dataSource, itemRenderer, elementNotificationHandler, options);
    }
});

})(this);


(function parallelWorkQueueInit(global) {
    "use strict";


var ParallelWorkQueue = WinJS.Class.define(
    function ParallelWorkQueue_ctor(maxRunning) {
        var workIndex = 0;
        var workItems = {};
        var workQueue = [];
            
        maxRunning = maxRunning || 3;
        var running = 0;
        var processing = 0;
        function runNext() {
            running--; 
            // if we have fallen out of this loop, then we know we are already
            // async, so "post" is OK. If we are still in the loop, then the 
            // loop will continue to run, so we don't need to "post" or 
            // recurse. This avoids stack overflow in the sync case.
            // 
            if (!processing) {
                setImmediate(run);
            }
        }
        function run() {
            processing++;
            for (; running < maxRunning; running++) {
                var next;
                var nextWork;
                do {
                    next = workQueue.shift();
                    nextWork = next && workItems[next];
                } while (next && !nextWork);
                    
                if (nextWork) {
                    delete workItems[next]
                    try {
                        nextWork().then(runNext, runNext);
                    }
                    catch (err) {
                        // this will only get hit if there is a queued item that
                        // fails to return something that conforms to the Promise
                        // contract
                        // 
                        runNext();
                    }
                }
                else {
                    break;
                }
            }
            processing--;
        }
        function queue(f, data, first) {
            var id = "w" + (workIndex++);
            var workPromise;
            return new WinJS.Promise(
                function(c,e,p) {
                    var w = function() { 
                        workPromise = f().then(c,e,p); 
                        return workPromise;
                    };
                    w.data = data;
                    workItems[id] = w;
                    if (first) {
                        workQueue.unshift(id);
                    }
                    else {
                        workQueue.push(id);
                    }
                    run();
                }, 
                function() { 
                    delete workItems[id]; 
                    if (workPromise) { 
                        workPromise.cancel(); 
                    } 
                }
            );
        }
            
        this.sort = function (f) {
            workQueue.sort(function (a,b) {
                a = workItems[a];
                b = workItems[b];
                return a === undefined && b === undefined ? 0 : a === undefined ? 1 : b === undefined ? -1 : f(a.data, b.data);
            });
        };
        this.queue = queue;
    }, {
        /* empty */
    }, {
        supportedForProcessing: false,
    }
);

WinJS.Namespace.define("WinJS.UI", {
    _ParallelWorkQueue : ParallelWorkQueue
});

})(this);


(function versionManagerInit(global) {
    "use strict";


    WinJS.Namespace.define("WinJS.UI", {
        _VersionManager: WinJS.Class.define(
            function _VersionManager_ctor() {
                this._unlocked = new WinJS._Signal();
                this._unlocked.complete();
            },
            {
                _cancelCount: 0,
                _notificationCount: 0,
                _updateCount: 0,
                _version: 0,

                // This should be used generally for all logic that should be suspended while data changes are happening
                //
                locked: { get: function () { return this._notificationCount !== 0 || this._updateCount !== 0; } },

                // this should only be accessed by the update logic in ListViewImpl.js
                //
                noOutstandingNotifications: { get: function () { return this._notificationCount === 0; } },
                version: { get: function () { return this._version; } },

                unlocked: { get: function () { return this._unlocked.promise; } },

                _dispose: function () {
                    if (this._unlocked) {
                        this._unlocked.cancel();
                        this._unlocked = null;
                    }
                },

                beginUpdating: function () {
                    this._checkLocked();
                    /*#DBG
                    if (this._updateCount !== 0) {
                        throw "ACK! incorrect begin/endUpdating pair on version manager";
                    }
                    #DBG*/
                    this._updateCount++;
                },
                endUpdating: function() {
                    this._updateCount--;
                    /*#DBG
                    if (this._updateCount < 0) {
                        throw "ACK! incorrect begin/endUpdating pair on version manager";
                    }
                    #DBG*/
                    this._checkUnlocked();
                },
                beginNotifications: function () {
                    this._checkLocked();
                    this._notificationCount++;
                },
                endNotifications: function () {
                    this._notificationCount--;
                    /*#DBG
                    if (this._notificationCount < 0) {
                        throw "ACK! incorrect begin/endNotifications pair on version manager";
                    }
                    #DBG*/
                    this._checkUnlocked();
                },
                _checkLocked: function () {
                    if (!this.locked) {
                        this._dispose();
                        this._unlocked = new WinJS._Signal();
                    }
                },
                _checkUnlocked: function () {
                    if (!this.locked) {
                        this._unlocked.complete();
                    }
                },
                receivedNotification: function () {
                    this._version++;
                    if (this._cancel) {
                        var cancel = this._cancel;
                        this._cancel = null;
                        cancel.forEach(function (p) { p && p.cancel(); });
                    }
                },
                cancelOnNotification: function (promise) {
                    if (!this._cancel) {
                        this._cancel = [];
                        this._cancelCount = 0;
                    }
                    this._cancel[this._cancelCount++] = promise;
                    return this._cancelCount - 1;
                },
                clearCancelOnNotification: function (token) {
                    if (this._cancel) {
                        delete this._cancel[token];
                    }
                }
            }, {
                supportedForProcessing: false,
            }
        )
    });
})();


(function flipperInit(WinJS) {
    "use strict";

    var thisWinUI = WinJS.UI;
    var utilities = WinJS.Utilities;
    var animation = WinJS.UI.Animation;

    // Class names
    var navButtonClass = "win-navbutton",
        flipViewClass = "win-flipview",
        navButtonLeftClass = "win-navleft",
        navButtonRightClass = "win-navright",
        navButtonTopClass = "win-navtop",
        navButtonBottomClass = "win-navbottom";

    // Aria labels
    var previousButtonLabel = "Previous",
        nextButtonLabel = "Next";

    var buttonFadeDelay = 3000,
        leftArrowGlyph = "&#57570;",
        rightArrowGlyph = "&#57571;",
        topArrowGlyph = "&#57572;",
        bottomArrowGlyph = "&#57573;",
        animationMoveDelta = 40;

    function flipViewPropertyChanged(e) {
        var that = e.srcElement.winControl;
        if (that && that instanceof WinJS.UI.FlipView) {
            if (e.propertyName === "dir" || e.propertyName === "style.direction") {
                that._rtl = window.getComputedStyle(that._flipviewDiv, null).direction === "rtl";
                that._setupOrientation();
            }
        }
    }

    function flipviewResized(e) {
        var that = e.srcElement && e.srcElement.winControl;
        if (that && that instanceof WinJS.UI.FlipView) {
            msWriteProfilerMark("WinJS.UI.FlipView:resize,StartTM");
            that._resize();
        }
    }

    WinJS.Namespace.define("WinJS.UI", {
        /// <summary locid="WinJS.UI.FlipView">
        /// Displays a collection, such as a set of photos, one item at a time.
        /// </summary>
        /// <icon src="ui_winjs.ui.flipview.12x12.png" width="12" height="12" />
        /// <icon src="ui_winjs.ui.flipview.16x16.png" width="16" height="16" />
        /// <htmlSnippet><![CDATA[<div data-win-control="WinJS.UI.FlipView"></div>]]></htmlSnippet>
        /// <event name="datasourcecountchanged" bubbles="true" locid="WinJS.UI.FlipView_e:datasourcecountchanged">Raised when the number of items in the itemDataSource changes.</event>
        /// <event name="pagevisibilitychanged" bubbles="true" locid="WinJS.UI.FlipView_e:pagevisibilitychanged">Raised when a FlipView page becomes visible or invisible.</event>
        /// <event name="pageselected" bubbles="true" locid="WinJS.UI.FlipView_e:pageselected">Raised when the FlipView flips to a page.</event>
        /// <event name="pagecompleted" bubbles="true" locid="WinJS.UI.FlipView_e:pagecompleted">Raised when the FlipView flips to a page and its renderer function completes.</event>
        /// <part name="flipView" class="win-flipview" locid="WinJS.UI.FlipView_part:flipView">The entire FlipView control.</part>
        /// <part name="navigationButton" class="win-navbutton" locid="WinJS.UI.FlipView_part:navigationButton">The general class for all FlipView navigation buttons.</part>
        /// <part name="leftNavigationButton" class="win-navleft" locid="WinJS.UI.FlipView_part:leftNavigationButton">The left navigation button.</part>
        /// <part name="rightNavigationButton" class="win-navright" locid="WinJS.UI.FlipView_part:rightNavigationButton">The right navigation button.</part>
        /// <part name="topNavigationButton" class="win-navtop" locid="WinJS.UI.FlipView_part:topNavigationButton">The top navigation button.</part>
        /// <part name="bottomNavigationButton" class="win-navbottom" locid="WinJS.UI.FlipView_part:bottomNavigationButton">The bottom navigation button.</part>
        /// <resource type="javascript" src="//Microsoft.WinJS.1.0/js/base.js" shared="true" />
        /// <resource type="javascript" src="//Microsoft.WinJS.1.0/js/ui.js" shared="true" />
        /// <resource type="css" src="//Microsoft.WinJS.1.0/css/ui-dark.css" shared="true" />
        FlipView: WinJS.Class.define(function FlipView_ctor(element, options) {
            /// <signature helpKeyword="WinJS.UI.FlipView.FlipView">
            /// <summary locid="WinJS.UI.FlipView.constructor">
            /// Creates a new FlipView.
            /// </summary>
            /// <param name="element" domElement="true" locid="WinJS.UI.FlipView.constructor_p:element">
            /// The DOM element that hosts the control.
            /// </param>
            /// <param name="options" type="Object" locid="WinJS.UI.FlipView.constructor_p:options">
            /// An object that contains one or more property/value pairs to apply to the new control.
            /// Each property of the options object corresponds to one of the control's properties or events.
            /// Event names must begin with "on". For example, to provide a handler for the pageselected event,
            /// add a property named "onpageselected" to the options object and set its value to the event handler.
            /// This parameter is optional.
            /// </param>
            /// <returns type="WinJS.UI.FlipView" locid="WinJS.UI.FlipView.constructor_returnValue">
            /// The new FlipView control.
            /// </returns>
            /// </signature>
            msWriteProfilerMark("WinJS.UI.FlipView:constructor,StartTM");

            element = element || document.createElement("div");

            var horizontal = true,
                dataSource = null,
                itemRenderer = WinJS.UI._trivialHtmlRenderer,
                initialIndex = 0,
                itemSpacing = 0;

            if (options) {
                // flipAxis parameter checking. Must be a string, either "horizontal" or "vertical"
                if (options.orientation) {
                    if (typeof options.orientation === "string") {
                        switch (options.orientation.toLowerCase()) {
                            case "horizontal":
                                horizontal = true;
                                break;

                            case "vertical":
                                horizontal = false;
                                break;
                        }
                    }
                } 

                if (options.currentPage) {
                    initialIndex = options.currentPage >> 0;
                    initialIndex = initialIndex < 0 ? 0 : initialIndex;
                }

                if (options.itemDataSource) {
                    dataSource = options.itemDataSource;
                }

                if (options.itemTemplate) {
                    itemRenderer = this._getItemRenderer(options.itemTemplate);
                }

                if (options.itemSpacing) {
                    itemSpacing = options.itemSpacing >> 0;
                    itemSpacing = itemSpacing < 0 ? 0 : itemSpacing;
                }
            }

            if (!dataSource) {
                var list = new WinJS.Binding.List();
                dataSource = list.dataSource;
            }
            utilities.empty(element);

            this._initializeFlipView(element, horizontal, dataSource, itemRenderer, initialIndex, itemSpacing);

            element.winControl = this;
            
            // Call _setOption with eventsOnly flag on
            WinJS.UI._setOptions(this, options, true);

            msWriteProfilerMark("WinJS.UI.FlipView:constructor,StopTM");
        }, {

            // Public methods

            next: function () {
                /// <signature helpKeyword="WinJS.UI.FlipView.next">
                /// <summary locid="WinJS.UI.FlipView.next">
                /// Navigates to the next item.
                /// </summary>
                /// <returns type="Boolean" locid="WinJS.UI.FlipView.next_returnValue">
                /// true if the FlipView begins navigating to the next page;
                /// false if the FlipView is at the last page or is in the middle of another navigation animation.
                /// </returns>
                /// </signature>
                msWriteProfilerMark("WinJS.UI.FlipView:next,info");
                var cancelAnimationCallback = this._nextAnimation ? null : this._cancelDefaultAnimation;
                return this._navigate(true, cancelAnimationCallback);
            },

            previous: function () {
                /// <signature helpKeyword="WinJS.UI.FlipView.previous">
                /// <summary locid="WinJS.UI.FlipView.previous">
                /// Navigates to the previous item.
                /// </summary>
                /// <returns type="Boolean" locid="WinJS.UI.FlipView.previous_returnValue">
                /// true if FlipView begins navigating to the previous page;
                /// false if the FlipView is already at the first page or is in the middle of another navigation animation.
                /// </returns>
                /// </signature>
                msWriteProfilerMark("WinJS.UI.FlipView:prev,info");
                var cancelAnimationCallback = this._prevAnimation ? null : this._cancelDefaultAnimation;
                return this._navigate(false, cancelAnimationCallback);
            },

            /// <field type="HTMLElement" domElement="true" hidden="true" locid="WinJS.UI.FlipView.element" helpKeyword="WinJS.UI.FlipView.element">
            /// The DOM element that hosts the FlipView control.
            /// </field>
            element: {
                get: function () {
                    return this._flipviewDiv;
                }
            },

            /// <field type="Number" integer="true" locid="WinJS.UI.FlipView.currentPage" helpKeyword="WinJS.UI.FlipView.currentPage" minimum="0">
            /// Gets or sets the index of the currently displayed page. The minimum value is 0 and the maximum value is one less than the total number of items returned by the data source.
            /// </field>
            currentPage: {
                get: function () {
                    if (this._animating) {
                        this._cancelAnimation();
                    }
                    return this._getCurrentIndex();
                },
                set: function (index) {
                    msWriteProfilerMark("WinJS.UI.FlipView:set_currentPage,info");

                    if (this._pageManager._notificationsEndedSignal) {
                        var that = this;
                        this._pageManager._notificationsEndedSignal.promise.done(function () {
                            that._pageManager._notificationsEndedSignal = null;
                            that.currentPage = index;
                        });
                        return;
                    }

                    if (this._animating && !this._cancelAnimation()) {
                        return;
                    }

                    index = index >> 0;
                    index = index < 0 ? 0 : index;

                    if (this._refreshTimer) {
                        this._indexAfterRefresh = index;
                    } else {
                        if (this._pageManager._cachedSize > 0) {
                            index = Math.min(this._pageManager._cachedSize - 1, index);
                        } else if (this._pageManager._cachedSize === 0) {
                            index = 0;
                        }

                        var that = this;
                        var jumpAnimation = (this._jumpAnimation ? this._jumpAnimation : this._defaultAnimation.bind(this)),
                            cancelAnimationCallback = (this._jumpAnimation ? null : this._cancelDefaultAnimation),
                            completionCallback = function () { that._completeJump(); };
                        this._pageManager.startAnimatedJump(index, cancelAnimationCallback, completionCallback).
                        then(function (elements) {
                            if (elements) {
                                that._animationsStarted();
                                var currElement = elements.oldPage.pageRoot;
                                var newCurrElement = elements.newPage.pageRoot;      
                                that._contentDiv.appendChild(currElement);
                                that._contentDiv.appendChild(newCurrElement);

                                that._completeJumpPending = true;
                                jumpAnimation(currElement, newCurrElement).
                                    then(function () {
                                        if (that._completeJumpPending) {
                                            completionCallback();
                                            msWriteProfilerMark("WinJS.UI.FlipView:set_currentPage.animationComplete,info");
                                        }
                                    }).done();
                            }
                        });
                    }
                }
            },

            /// <field type="String" oamOptionsDatatype="WinJS.UI.FlipView.orientation" locid="WinJS.UI.FlipView.orientation" helpKeyword="WinJS.UI.FlipView.orientation">
            /// Gets or sets the layout orientation of the FlipView, horizontal or vertical.
            /// </field>
            orientation: {
                get: function () {
                    return this._axisAsString();
                },
                set: function (orientation) {
                    msWriteProfilerMark("WinJS.UI.FlipView:set_orientation,info");
                    var horizontal = orientation === "horizontal";
                    if (horizontal !== this._horizontal) {
                        this._horizontal = horizontal;
                        this._setupOrientation();
                        this._pageManager.setOrientation(this._horizontal);
                    }
                }
            },

            /// <field type="object" locid="WinJS.UI.FlipView.itemDataSource" helpKeyword="WinJS.UI.FlipView.itemDataSource">
            /// Gets or sets the data source that provides the FlipView with items to display.
            /// The FlipView displays one item at a time, each on its own page.
            /// </field>
            itemDataSource: {
                get: function () {
                    return this._dataSource;
                },

                set: function (dataSource) {
                    msWriteProfilerMark("WinJS.UI.FlipView:set_itemDataSource,info");
                    this._dataSourceAfterRefresh = dataSource || new WinJS.Binding.List().dataSource;
                    this._refresh();
                }
            },

            /// <field type="Function" locid="WinJS.UI.FlipView.itemTemplate" helpKeyword="WinJS.UI.FlipView.itemTemplate" potentialValueSelector="[data-win-control='WinJS.Binding.Template']">
            /// Gets or sets a WinJS.Binding.Template or a function that defines the HTML for each item's page.
            /// </field>
            itemTemplate: {
                get: function () {
                    return this._itemRenderer;
                },

                set: function (itemTemplate) {
                    msWriteProfilerMark("WinJS.UI.FlipView:set_itemTemplate,info");
                    this._itemRendererAfterRefresh = this._getItemRenderer(itemTemplate);
                    this._refresh();
                }
            },

            /// <field type="Number" integer="true" locid="WinJS.UI.FlipView.itemSpacing" helpKeyword="WinJS.UI.FlipView.itemSpacing">
            /// Gets or sets the spacing between items, in pixels.
            /// </field>
            itemSpacing: {
                get: function () {
                    return this._pageManager.getItemSpacing();
                },

                set: function (spacing) {
                    msWriteProfilerMark("WinJS.UI.FlipView:set_itemSpacing,info");
                    spacing = spacing >> 0;
                    spacing = spacing < 0 ? 0 : spacing;
                    this._pageManager.setItemSpacing(spacing);
                }
            },

            count: function () {
                /// <signature helpKeyword="WinJS.UI.FlipView.count">
                /// <summary locid="WinJS.UI.FlipView.count">
                /// Returns the number of items in the FlipView object's itemDataSource.
                /// </summary>
                /// <returns type="WinJS.Promise" locid="WinJS.UI.FlipView.count_returnValue">
                /// A Promise that contains the number of items in the list
                /// or WinJS.UI.CountResult.unknown if the count is unavailable.
                /// </returns>
                /// </signature>

                msWriteProfilerMark("WinJS.UI.FlipView:count,info");
                var that = this;
                return new WinJS.Promise(function (complete, error) {
                    if (that._itemsManager) {
                        if (that._pageManager._cachedSize === WinJS.UI.CountResult.unknown || that._pageManager._cachedSize >= 0) {
                            complete(that._pageManager._cachedSize);
                        } else {
                            that._dataSource.getCount().then(function (count) {
                                that._pageManager._cachedSize = count;
                                complete(count);
                            });
                        }
                    } else {
                        error(thisWinUI.FlipView.noitemsManagerForCount);
                    }
                });
            },

            setCustomAnimations: function (animations) {
                /// <signature helpKeyword="WinJS.UI.FlipView.setCustomAnimations">
                /// <summary locid="WinJS.UI.FlipView.setCustomAnimations">
                /// Sets custom animations for the FlipView to use when navigating between pages.
                /// </summary>
                /// <param name="animations" type="Object" locid="WinJS.UI.FlipView.setCustomAnimations_p:animations">
                /// An object containing up to three fields, one for each navigation action: next, previous, and jump
                /// Each of those fields must be a function with this signature: function (outgoingPage, incomingPage).
                /// This function returns a WinJS.Promise object that completes once the animations are finished.
                /// If a field is null or undefined, the FlipView reverts to its default animation for that action.
                /// </param>
                /// </signature>
                msWriteProfilerMark("WinJS.UI.FlipView:setCustomAnimations,info");

                if (animations.next !== undefined) {
                    this._nextAnimation = animations.next;
                }
                if (animations.previous !== undefined) {
                    this._prevAnimation = animations.previous;
                }
                if (animations.jump !== undefined) {
                    this._jumpAnimation = animations.jump;
                }
            },

            forceLayout: function () {
                /// <signature helpKeyword="WinJS.UI.FlipView.forceLayout">
                /// <summary locid="WinJS.UI.FlipView.forceLayout">
                /// Forces the FlipView to update its layout.
                /// Use this function when making the FlipView visible again after its style.display property had been set to "none".
                /// </summary>
                /// </signature>
                msWriteProfilerMark("WinJS.UI.FlipView:forceLayout,info");

                this._pageManager.resized();
            },

            // Private members

            _initializeFlipView: function (element, horizontal, dataSource, itemRenderer, initialIndex, itemSpacing) {
                this._flipviewDiv = element;
                utilities.addClass(this._flipviewDiv, flipViewClass);
                this._contentDiv = document.createElement("div");
                this._panningDivContainer = document.createElement("div");
                this._panningDivContainer.className = "win-surface";
                this._panningDiv = document.createElement("div");
                this._prevButton = document.createElement("button");
                this._nextButton = document.createElement("button");
                this._horizontal = horizontal;
                this._dataSource = dataSource;
                this._itemRenderer = itemRenderer;
                this._itemsManager = null;
                this._pageManager = null;

                var accName = this._flipviewDiv.getAttribute("aria-label");
                if (!accName) {
                    this._flipviewDiv.setAttribute("aria-label", "");
                }

                this._flipviewDiv.setAttribute("role", "listbox");
                if (!this._flipviewDiv.style.overflow) {
                    this._flipviewDiv.style.overflow = "hidden";
                }
                this._contentDiv.style.position = "relative";
                this._contentDiv.style.zIndex = 0;
                this._contentDiv.style.width = "100%";
                this._contentDiv.style.height = "100%";
                this._panningDiv.style.position = "relative";
                this._panningDivContainer.style.position = "relative";
                this._panningDivContainer.style.width = "100%";
                this._panningDivContainer.style.height = "100%";
                this._panningDivContainer.setAttribute("role", "group");
                this._panningDivContainer.setAttribute("aria-label", strings.panningContainerAriaLabel);

                this._contentDiv.appendChild(this._panningDivContainer);
                this._flipviewDiv.appendChild(this._contentDiv);

                this._panningDiv.style.width = "100%";
                this._panningDiv.style.height = "100%";
                this._setupOrientation();
                function setUpButton(button) {
                    button.setAttribute("aria-hidden", true);
                    button.style.visibility = "hidden";
                    button.style.opacity = 0.0;
                    button.tabIndex = -1;
                    button.style.zIndex = 1000;
                }
                setUpButton(this._prevButton);
                setUpButton(this._nextButton);
                this._prevButton.setAttribute("aria-label", previousButtonLabel);
                this._nextButton.setAttribute("aria-label", nextButtonLabel);
                this._prevButton.setAttribute("type", "button");
                this._nextButton.setAttribute("type", "button");
                this._panningDivContainer.appendChild(this._panningDiv);
                this._contentDiv.appendChild(this._prevButton);
                this._contentDiv.appendChild(this._nextButton);

                var that = this;

                this._itemsManagerCallback = {
                    // Callbacks for itemsManager
                    inserted: function (itemPromise, previousHandle, nextHandle) {
                        that._itemsManager._itemFromPromise(itemPromise).then(function (element) {
                            var previous = that._itemsManager._elementFromHandle(previousHandle);
                            var next = that._itemsManager._elementFromHandle(nextHandle);
                            that._pageManager.inserted(element, previous, next, true);
                        });
                    },

                    countChanged: function (newCount, oldCount) {
                        that._pageManager._cachedSize = newCount;

                        // Don't fire the datasourcecountchanged event when there is a state transition
                        if (oldCount !== WinJS.UI.CountResult.unknown) {
                            that._fireDatasourceCountChangedEvent();
                        }
                    },

                    changed: function (newElement, oldElement) {
                        that._pageManager.changed(newElement, oldElement);
                    },

                    moved: function (element, prev, next, itemPromise) {
                        var elementReady = function (element) {
                            //#DBG _ASSERT(element);
                            that._pageManager.moved(element, prev, next);
                        };

                        // If we haven't instantiated this item yet, do so now
                        if (!element) {
                            that._itemsManager._itemFromPromise(itemPromise).then(elementReady);
                        }
                        else {
                            elementReady(element);
                        }

                    },

                    removed: function (element, mirage) {
                        if (element) {
                            that._pageManager.removed(element, mirage, true);
                        }
                    },

                    knownUpdatesComplete: function () {
                    },

                    beginNotifications: function () {
                        that._pageManager.notificationsStarted();
                    },

                    endNotifications: function () {
                        that._pageManager.notificationsEnded();
                    },

                    itemAvailable: function (real, placeholder) {
                        that._pageManager.itemRetrieved(real, placeholder);
                    },

                    reload: function () {
                        that._pageManager.reload();
                    }
                };

                if (this._dataSource) {
                    this._itemsManager = thisWinUI._createItemsManager(this._dataSource, this._itemRenderer, this._itemsManagerCallback, {
                        ownerElement: this._flipviewDiv
                    });
                }

                this._pageManager = new thisWinUI._FlipPageManager(this._flipviewDiv, this._panningDiv, this._panningDivContainer, this._itemsManager, itemSpacing,
                {
                    hidePreviousButton: function () {
                        that._hasPrevContent = false;
                        that._fadeOutButton("prev");
                        that._prevButton.setAttribute("aria-hidden", true);
                    },

                    showPreviousButton: function () {
                        that._hasPrevContent = true;
                        that._fadeInButton("prev");
                        that._prevButton.setAttribute("aria-hidden", false);
                    },

                    hideNextButton: function () {
                        that._hasNextContent = false;
                        that._fadeOutButton("next");
                        that._nextButton.setAttribute("aria-hidden", true);
                    },

                    showNextButton: function () {
                        that._hasNextContent = true;
                        that._fadeInButton("next");
                        that._nextButton.setAttribute("aria-hidden", false);
                    }
                });

                this._pageManager.initialize(initialIndex, this._horizontal);

                this._dataSource.getCount().then(function (count) {
                    that._pageManager._cachedSize = count;
                });

                this._prevButton.addEventListener("click", function () {
                    that.previous();
                }, false);

                this._nextButton.addEventListener("click", function () {
                    that.next();
                }, false);

                this._flipviewDiv.attachEvent("onpropertychange", flipViewPropertyChanged, false);

                this._flipviewDiv.attachEvent("onresize", flipviewResized);

                this._contentDiv.addEventListener("mouseleave", function () {
                    that._mouseInViewport = false;
                }, false);

                var PT_TOUCH = 2;
                function handleShowButtons(e) {
                    if (e.pointerType !== PT_TOUCH) {
                        that._touchInteraction = false;
                        if (e.screenX === that._lastMouseX && e.screenY === that._lastMouseY) {
                            return;
                        }
                        that._lastMouseX = e.screenX;
                        that._lastMouseY = e.screenY;
                        that._mouseInViewport = true;
                        that._fadeInButton("prev");
                        that._fadeInButton("next");
                        that._fadeOutButtons();
                    }
                }
                this._contentDiv.addEventListener("MSPointerHover", handleShowButtons, false);
                this._contentDiv.addEventListener("MSPointerMove", handleShowButtons, false);

                this._contentDiv.addEventListener("MSPointerDown", function (e) {
                    if (e.pointerType === PT_TOUCH) {
                        that._mouseInViewport = false;
                        that._touchInteraction = true;
                        that._fadeOutButtons(true);
                    } else {
                        that._touchInteraction = false;
                        if (!that._isInteractive(e.srcElement)) {
                            // Disable the default behavior of the mouse wheel button to avoid auto-scroll
                            if ((e.buttons & 4) !== 0) {
                                e.stopPropagation();
                                e.preventDefault();
                            }
                        }
                    }
                }, false);

                this._contentDiv.addEventListener("MSPointerUp", function (e) {
                    if (e.pointerType !== PT_TOUCH) {
                        that._touchInteraction = false;
                    }
                }, false);

                this._panningDivContainer.addEventListener("wheel", function (e) {
                    if (!that._isInteractive(e.srcElement)) {
                        e.stopPropagation();
                        e.preventDefault();
                    }
                }, false);

                this._panningDivContainer.addEventListener("scroll", function () {
                    that._scrollPosChanged();
                }, false);

                this._panningDiv.addEventListener("deactivate", function (event) {
                    if (!that._touchInteraction) {
                        that._fadeOutButtons();
                    }
                }, true);

                // When an element is removed and inserted, its scroll position gets reset to 0 (and no onscroll event is generated). This is a major problem
                // for the flipview thanks to the fact that we 1) Do a lot of inserts/removes of child elements, and 2) Depend on our scroll location being right to
                // display the right stuff. The page manager preserves scroll location. When a flipview element is reinserted, it'll fire DOMNodeInserted and we can reset
                // its scroll location there.
                // This event handler won't be hit in IE8.
                this._flipviewDiv.addEventListener("DOMNodeInserted", function (event) {
                    if (event.target === that._flipviewDiv) {
                        that._pageManager.resized();
                    }
                }, false);

                this._flipviewDiv.addEventListener("keydown", function (event) {
                    function isInteractive(element) {
                        if (element.parentNode) {
                            var matches = element.parentNode.querySelectorAll(".win-interactive, .win-interactive *");
                            for (var i = 0, len = matches.length; i < len; i++) {
                                if (matches[i] === element) {
                                    return true;
                                }
                            }
                        }
                        return false;
                    }
                    var cancelBubbleIfHandled = true;
                    if (!that._isInteractive(event.srcElement)) {
                        var Key = utilities.Key,
                            handled = false;
                        if (that._horizontal) {
                            switch (event.keyCode) {
                                case Key.leftArrow:
                                    (that._rtl ? that.next() : that.previous());
                                    handled = true;
                                    break;

                                case Key.pageUp:
                                    that.previous();
                                    handled = true;
                                    break;

                                case Key.rightArrow:
                                    (that._rtl ? that.previous() : that.next());
                                    handled = true;
                                    break;

                                case Key.pageDown:
                                    that.next();
                                    handled = true;
                                    break;

                                // Prevent scrolling pixel by pixel, but let the event bubble up
                                case Key.upArrow:
                                case Key.downArrow:
                                    handled = true;
                                    cancelBubbleIfHandled = false;
                                    break;
                            }
                        } else {
                            switch (event.keyCode) {
                                case Key.upArrow:
                                case Key.pageUp:
                                    that.previous();
                                    handled = true;
                                    break;

                                case Key.downArrow:
                                case Key.pageDown:
                                    that.next();
                                    handled = true;
                                    break;

                                case Key.space:
                                    handled = true;
                                    break;
                            }
                        }

                        switch (event.keyCode) {
                            case Key.home:
                                that.currentPage = 0;
                                handled = true;
                                break;

                            case Key.end:
                                if (that._pageManager._cachedSize > 0) {
                                    that.currentPage = that._pageManager._cachedSize - 1;
                                }
                                handled = true;
                                break;
                        }

                        if (handled) {
                            event.preventDefault();
                            event.cancelBubble = cancelBubbleIfHandled;
                            return true;
                        }
                    }
                }, false);
            },

            _isInteractive: function (element) {
                if (element.parentNode) {
                    var matches = element.parentNode.querySelectorAll(".win-interactive, .win-interactive *");
                    for (var i = 0, len = matches.length; i < len; i++) {
                        if (matches[i] === element) {
                            return true;
                        }
                    }
                }
                return false;
            },

            _refreshHandler: function () {
                var dataSource = this._dataSourceAfterRefresh || this._dataSource,
                    renderer = this._itemRendererAfterRefresh || this._itemRenderer,
                    initialIndex = this._indexAfterRefresh || 0;
                this._setDatasource(dataSource, renderer, initialIndex);
                this._dataSourceAfterRefresh = null;
                this._itemRendererAfterRefresh = null;
                this._indexAfterRefresh = 0;
                this._refreshTimer = false;
            },

            _refresh: function () {
                if (!this._refreshTimer) {
                    var that = this;
                    this._refreshTimer = true;
                    setImmediate(function () {
                        if (that._refreshTimer) {
                            that._refreshHandler();
                        }
                    });
                }
            },

            _getItemRenderer: function (itemTemplate) {
                var itemRenderer = null;
                if (typeof itemTemplate === "function") {
                    var itemPromise = new WinJS.Promise(function (c, e, p) {});
                    var itemTemplateResult = itemTemplate(itemPromise);
                    if (itemTemplateResult.element) {
                        if (typeof itemTemplateResult.element === "object" && typeof itemTemplateResult.element.then === "function") {
                            // This renderer returns a promise to an element
                            itemRenderer = function (itemPromise) {
                                var elementRoot = document.createElement("div");
                                elementRoot.className = "win-template";
                                return {
                                    element: elementRoot,
                                    renderComplete: itemTemplate(itemPromise).element.then(function (element) {
                                        elementRoot.appendChild(element);
                                    })
                                };
                            };
                        } else {
                            // This renderer already returns a placeholder
                            itemRenderer = itemTemplate;
                        }
                    } else {
                        // Return a renderer that has return a placeholder
                        itemRenderer = function(itemPromise) {
                            var elementRoot = document.createElement("div");
                            elementRoot.className = "win-template";
                            // The pagecompleted event relies on this elementRoot
                            // to ensure that we are still looking at the same
                            // item after the render completes.
                            return {
                                element: elementRoot,
                                renderComplete: itemPromise.then(function (item) {
                                    return itemTemplate(itemPromise).then(function (element) {
                                        elementRoot.appendChild(element);
                                    });
                                })
                            };
                        }
                    };
                } else if (typeof itemTemplate === "object") {
                    itemRenderer = itemTemplate.renderItem;
                }
                return itemRenderer;
            },

            _navigate: function (goForward, cancelAnimationCallback) {
                if (WinJS.validation && this._refreshTimer) {
                    throw new WinJS.ErrorFromName("WinJS.UI.FlipView.NavigationDuringStateChange", strings.navigationDuringStateChange);
                }

                if (!this._animating) {
                    this._animatingForward = goForward;
                }
                this._goForward = goForward;

                if (this._animating && !this._cancelAnimation()) {
                    return false;
                }
                var that = this;
                var customAnimation = (goForward ? this._nextAnimation : this._prevAnimation),
                    animation = (customAnimation ? customAnimation : this._defaultAnimation.bind(this)),
                    completionCallback = function (goForward) { that._completeNavigation(goForward); },
                    elements = this._pageManager.startAnimatedNavigation(goForward, cancelAnimationCallback, completionCallback);
                if (elements) {
                    this._animationsStarted();
                    var outgoingElement = elements.outgoing.pageRoot,
                        incomingElement = elements.incoming.pageRoot;
                    this._contentDiv.appendChild(outgoingElement);
                    this._contentDiv.appendChild(incomingElement);

                    this._completeNavigationPending = true;
                    animation(outgoingElement, incomingElement).then(function () {
                        if (that._completeNavigationPending) {
                            completionCallback(that._goForward);
                        }
                    }).done();
                    return true;
                } else {
                    return false;
                }
            },

            _cancelDefaultAnimation: function (outgoingElement, incomingElement) {
                // Cancel the fadeOut animation
                outgoingElement.style.opacity = 0;

                // Cancel the enterContent animation
                incomingElement.style.animationName = "";
                incomingElement.style.opacity = 1;
            },

            _cancelAnimation: function () {
                if (this._pageManager._navigationAnimationRecord &&
                    this._pageManager._navigationAnimationRecord.completionCallback) {

                        var cancelCallback = this._pageManager._navigationAnimationRecord.cancelAnimationCallback;
                        if (cancelCallback) {
                            cancelCallback = cancelCallback.bind(this);
                        }

                        if (this._pageManager._navigationAnimationRecord && this._pageManager._navigationAnimationRecord.elementContainers) {
                            var outgoingPage = this._pageManager._navigationAnimationRecord.elementContainers[0],
                            incomingPage = this._pageManager._navigationAnimationRecord.elementContainers[1],
                            outgoingElement = outgoingPage.pageRoot,
                            incomingElement = incomingPage.pageRoot;

                            // Invoke the function that will cancel the animation
                            if (cancelCallback) {
                                cancelCallback(outgoingElement, incomingElement);
                            }

                            // Invoke the completion function after cancelling the animation
                            this._pageManager._navigationAnimationRecord.completionCallback(this._animatingForward);

                            return true;
                        }
                    }
                return false;
            },

            _completeNavigation: function (goForward) {
                this._pageManager._resizing = false;
                if (this._pageManager._navigationAnimationRecord &&
                    this._pageManager._navigationAnimationRecord.elementContainers) {

                    var outgoingPage = this._pageManager._navigationAnimationRecord.elementContainers[0],
                        incomingPage = this._pageManager._navigationAnimationRecord.elementContainers[1],
                        outgoingElement = outgoingPage.pageRoot,
                        incomingElement = incomingPage.pageRoot;

                    if (outgoingElement.parentNode) {
                        outgoingElement.parentNode.removeChild(outgoingElement);
                    }
                    if (incomingElement.parentNode) {
                        incomingElement.parentNode.removeChild(incomingElement);
                    }
                    this._pageManager.endAnimatedNavigation(goForward, outgoingPage, incomingPage);
                    this._fadeOutButtons();
                    this._scrollPosChanged();
                    this._pageManager._ensureCentered(true);
                    this._animationsFinished();
                }
                this._completeNavigationPending = false;
            },

            _completeJump: function () {
                this._pageManager._resizing = false;
                if (this._pageManager._navigationAnimationRecord &&
                    this._pageManager._navigationAnimationRecord.elementContainers) {

                    var outgoingPage = this._pageManager._navigationAnimationRecord.elementContainers[0],
                        incomingPage = this._pageManager._navigationAnimationRecord.elementContainers[1],
                        outgoingElement = outgoingPage.pageRoot,
                        incomingElement = incomingPage.pageRoot;

                    if (outgoingElement.parentNode) {
                        outgoingElement.parentNode.removeChild(outgoingElement);
                    }
                    if (incomingElement.parentNode) {
                        incomingElement.parentNode.removeChild(incomingElement);
                    }

                    this._pageManager.endAnimatedJump(outgoingPage, incomingPage);
                    this._animationsFinished();
                }
                this._completeJumpPending = false;
            },

            _resize: function () {
                this._pageManager.resized();
            },

            _setCurrentIndex: function (index) {
                return this._pageManager.jumpToIndex(index);
            },

            _getCurrentIndex: function () {
                return this._pageManager.currentIndex();
            },

            _setDatasource: function (source, template, index) {
                if (this._animating) {
                    this._cancelAnimation();
                }

                var initialIndex = 0;
                if (index !== undefined) {
                    initialIndex = index;
                }
                this._dataSource = source;
                this._itemRenderer = template;
                var oldItemsManager = this._itemsManager;
                this._itemsManager = thisWinUI._createItemsManager(this._dataSource, this._itemRenderer, this._itemsManagerCallback, {
                    ownerElement: this._flipviewDiv
                });
                this._dataSource = this._itemsManager.dataSource;

                var that = this;
                this._dataSource.getCount().then(function (count) {
                    that._pageManager._cachedSize = count;
                });
                this._pageManager.setNewItemsManager(this._itemsManager, initialIndex);
                oldItemsManager && oldItemsManager.release();
            },

            _fireDatasourceCountChangedEvent: function () {
                var that = this;
                setImmediate(function () {
                    var event = document.createEvent("Event");
                    event.initEvent(thisWinUI.FlipView.datasourceCountChangedEvent, true, true);
                    msWriteProfilerMark("WinJS.UI.FlipView:datasourceCountChangedEvent,info");
                    that._flipviewDiv.dispatchEvent(event);
                });
            },

            _scrollPosChanged: function () {
                this._pageManager.scrollPosChanged();
            },

            _axisAsString: function () {
                return (this._horizontal ? "horizontal" : "vertical");
            },

            _setupOrientation: function () {
                if (this._horizontal) {
                    this._panningDivContainer.style["overflow-x"] = "scroll";
                    this._panningDivContainer.style["overflow-y"] = "hidden";
                    var rtl = window.getComputedStyle(this._flipviewDiv, null).direction === "rtl";
                    this._rtl = rtl;
                    if (rtl) {
                        this._prevButton.className = navButtonClass + " " + navButtonRightClass;
                        this._nextButton.className = navButtonClass + " " + navButtonLeftClass;
                    } else {
                        this._prevButton.className = navButtonClass + " " + navButtonLeftClass;
                        this._nextButton.className = navButtonClass + " " + navButtonRightClass;
                    }
                    this._prevButton.innerHTML = (rtl ? rightArrowGlyph : leftArrowGlyph);
                    this._nextButton.innerHTML = (rtl ? leftArrowGlyph : rightArrowGlyph);
                } else {
                    this._panningDivContainer.style["overflow-y"] = "scroll";
                    this._panningDivContainer.style["overflow-x"] = "hidden";
                    this._prevButton.className = navButtonClass + " " + navButtonTopClass;
                    this._nextButton.className = navButtonClass + " " + navButtonBottomClass;
                    this._prevButton.innerHTML = topArrowGlyph;
                    this._nextButton.innerHTML = bottomArrowGlyph;
                }
                this._panningDivContainer.style["-ms-overflow-style"] = "none";
            },

            _fadeInButton: function (button, forceShow) {
                if (this._mouseInViewport || forceShow) {
                    if (button === "next" && this._hasNextContent) {
                        if (this._nextButtonAnimation) {
                            this._nextButtonAnimation.cancel();
                            this._nextButtonAnimation = null;
                        }

                        this._nextButton.style.visibility = "visible";
                        this._nextButtonAnimation = this._fadeInFromCurrentValue(this._nextButton);
                    } else if (button === "prev" && this._hasPrevContent) {
                        if (this._prevButtonAnimation) {
                            this._prevButtonAnimation.cancel();
                            this._prevButtonAnimation = null;
                        }

                        this._prevButton.style.visibility = "visible";
                        this._prevButtonAnimation = this._fadeInFromCurrentValue(this._prevButton);
                    }
                }
            },

            _fadeOutButton: function (button) {
                var that = this;
                if (button === "next") {
                    if (this._nextButtonAnimation) {
                        this._nextButtonAnimation.cancel();
                        this._nextButtonAnimation = null;
                    }

                    this._nextButtonAnimation = animation.fadeOut(this._nextButton).
                        then(function () {
                            that._nextButton.style.visibility = "hidden";
                        });
                    return this._nextButtonAnimation;
                } else {
                    if (this._prevButtonAnimation) {
                        this._prevButtonAnimation.cancel();
                        this._prevButtonAnimation = null;
                    }

                    this._prevButtonAnimation = animation.fadeOut(this._prevButton).
                        then(function () {
                            that._prevButton.style.visibility = "hidden";
                        });
                    return this._prevButtonAnimation;
                }
            },

            _fadeOutButtons: function (immediately) {
                if (this._buttonFadePromise) {
                    this._buttonFadePromise.cancel();
                    this._buttonFadePromise = null;
                }

                var that = this;
                this._buttonFadePromise = WinJS.Promise.timeout(immediately ? 0 : buttonFadeDelay).then(function () {
                    that._fadeOutButton("prev");
                    that._fadeOutButton("next");
                    that._buttonFadePromise = null;
                });
            },

            _animationsStarted: function () {
                this._animating = true;
            },

            _animationsFinished: function () {
                this._animating = false;
            },

            _defaultAnimation: function (curr, next) {
                var incomingPageMove = {};
                next.style.left = "0px";
                next.style.top = "0px";
                next.style.opacity = 0.0;
                var pageDirection = ((curr.itemIndex > next.itemIndex) ? -animationMoveDelta : animationMoveDelta);
                incomingPageMove.left = (this._horizontal ? (this._rtl ? -pageDirection : pageDirection) : 0) + "px";
                incomingPageMove.top = (this._horizontal ? 0 : pageDirection) + "px";
                var fadeOutPromise = animation.fadeOut(curr),
                    enterContentPromise = animation.enterContent(next, [incomingPageMove]);
                return WinJS.Promise.join([fadeOutPromise, enterContentPromise]);
            },

            _fadeInFromCurrentValue: function (shown) {
                // Intentionally not using the PVL fadeIn animation because we don't want
                // to start always from 0 in some cases
                return thisWinUI.executeTransition(
                    shown,
                    {
                        property: "opacity",
                        delay: 0,
                        duration: 167,
                        timing: "linear",
                        to: 1
                    });
            }
        })
    });

    // Statics

    // Events
    thisWinUI.FlipView.datasourceCountChangedEvent = "datasourcecountchanged";
    thisWinUI.FlipView.pageVisibilityChangedEvent = "pagevisibilitychanged";
    thisWinUI.FlipView.pageSelectedEvent = "pageselected";
    thisWinUI.FlipView.pageCompletedEvent = "pagecompleted";

    WinJS.Class.mix(thisWinUI.FlipView, WinJS.Utilities.createEventProperties(
        thisWinUI.FlipView.datasourceCountChangedEvent,
        thisWinUI.FlipView.pageVisibilityChangedEvent,
        thisWinUI.FlipView.pageSelectedEvent,
        thisWinUI.FlipView.pageCompletedEvent));
    WinJS.Class.mix(thisWinUI.FlipView, WinJS.UI.DOMEventMixin);

    var strings = {
        get badAxis() { return WinJS.Resources._getWinJSString("ui/badAxis").value; },
        get badCurrentPage() { return WinJS.Resources._getWinJSString("ui/badCurrentPage").value; },
        get noitemsManagerForCount() { return WinJS.Resources._getWinJSString("ui/noitemsManagerForCount").value; },
        get badItemSpacingAmount() { return WinJS.Resources._getWinJSString("ui/badItemSpacingAmount").value; },
        get navigationDuringStateChange() { return WinJS.Resources._getWinJSString("ui/flipViewNavigationDuringStateChange").value; },
        get panningContainerAriaLabel() { return WinJS.Resources._getWinJSString("ui/flipViewPanningContainerAriaLabel").value; }
    };

})(WinJS);


(function flipperPageManagerInit(WinJS) {
    "use strict";

    var thisWinUI = WinJS.UI;

    // Utilities are private and global pointer will be deleted so we need to cache it locally
    var utilities = WinJS.Utilities;

    var animations = WinJS.UI.Animation;

    var leftBufferAmount = 500,
        itemSelectedEventDelay = 250;

    var strings = {
        get badCurrentPage() { return WinJS.Resources._getWinJSString("ui/badCurrentPage").value; }
    };

    function isFlipper(element) {
        var control = element.winControl;
        if (control && control instanceof WinJS.UI.FlipView) {
            return true;
        }

        return false;
    }

    function flipperPropertyChanged(e) {
        var element = e.srcElement;
        if (element.winControl && element.tabIndex >= 0) {
            element.winControl._pageManager._updateTabIndex(element.tabIndex);
            element.tabIndex = -1;
        }

        if (e.propertyName === "dir" || e.propertyName === "style.direction") {
            var that = element.winControl;
            if (that && that instanceof WinJS.UI.FlipView) {
                that._pageManager._rtl = window.getComputedStyle(that._pageManager._flipperDiv, null).direction === "rtl";
                that._pageManager.resized();
            }
        }
    }

    WinJS.Namespace.define("WinJS.UI", {

        // Definition of our private utility
        _FlipPageManager: WinJS.Class.define(
            function _FlipPageManager_ctor(flipperDiv, panningDiv, panningDivContainer, itemsManager, itemSpacing, buttonVisibilityHandler) {
                // Construction
                this._visibleElements = [];
                this._flipperDiv = flipperDiv;
                this._panningDiv = panningDiv;
                this._panningDivContainer = panningDivContainer;
                this._buttonVisibilityHandler = buttonVisibilityHandler;
                this._currentPage = null;
                this._rtl = window.getComputedStyle(this._flipperDiv, null).direction === "rtl";
                this._itemsManager = itemsManager;
                this._itemSpacing = itemSpacing;
                this._tabIndex = (flipperDiv.tabIndex !== undefined && flipperDiv.tabIndex >= 0 ? flipperDiv.tabIndex : 0);
                flipperDiv.tabIndex = -1;
                this._tabManager = new WinJS.UI.TabContainer(this._panningDivContainer);
                this._tabManager.tabIndex = this._tabIndex;
                this._lastSelectedPage = null;
                this._lastSelectedElement = null;
                this._bufferSize = thisWinUI._FlipPageManager.flipPageBufferCount;
                this._cachedSize = -1;

                var that = this;
                this._panningDiv.addEventListener("keydown", function (event) {
                    if (that._blockTabs && event.keyCode === utilities.Key.tab) {
                        event.stopImmediatePropagation();
                        event.preventDefault();
                    }
                }, true);
                this._flipperDiv.addEventListener("focus", function (event) {
                    if (event.srcElement === that._flipperDiv) {
                        if (that._currentPage.element) {
                            try {
                                that._currentPage.element.setActive();
                            } catch (e) { }
                        }
                    }
                }, false);
                this._flipperDiv.attachEvent("onpropertychange", flipperPropertyChanged, false);
                this._panningDiv.addEventListener("activate", function (event) {
                    that._hasFocus = true;
                }, true);
                this._panningDiv.addEventListener("deactivate", function (event) {
                    that._hasFocus = false;
                }, true);
                this._panningDivContainer.addEventListener("MSManipulationStateChanged", function (event) {
                    that._manipulationState = event.currentState;
                    if (event.currentState === 0) {
                        that._itemSettledOn();
                    }
                }, true);
            },
            {
                // Public Methods

                initialize: function (initialIndex, horizontal) {
                    var currPage = null;
                    // Every call to offsetWidth/offsetHeight causes an switch from Script to Layout which affects
                    // the performance of the control. The values will be cached and will be updated when a resize occurs.
                    this._panningDivContainerOffsetWidth = this._panningDivContainer.offsetWidth;
                    this._panningDivContainerOffsetHeight = this._panningDivContainer.offsetHeight;

                    this._horizontal = horizontal;
                    if (!this._currentPage) {
                        this._bufferAriaStartMarker = document.createElement("div");
                        this._bufferAriaStartMarker.id = this._bufferAriaStartMarker.uniqueID;
                        this._panningDiv.appendChild(this._bufferAriaStartMarker);

                        this._currentPage = this._createFlipPage(null, this);
                        currPage = this._currentPage;
                        this._panningDiv.appendChild(currPage.pageRoot);

                        // flipPageBufferCount is added here twice. 
                        // Once for the buffer prior to the current item, and once for the buffer ahead of the current item.
                        var pagesToInit = 2 * this._bufferSize;
                        for (var i = 0; i < pagesToInit; i++) {
                            currPage = this._createFlipPage(currPage, this);
                            this._panningDiv.appendChild(currPage.pageRoot);
                        }

                        this._bufferAriaEndMarker = document.createElement("div");
                        this._bufferAriaEndMarker.id = this._bufferAriaEndMarker.uniqueID;
                        this._panningDiv.appendChild(this._bufferAriaEndMarker);
                    }

                    this._prevMarker = this._currentPage.prev.prev;

                    if (this._itemsManager) {
                        this.setNewItemsManager(this._itemsManager, initialIndex);
                    }
                },

                setOrientation: function (horizontal) {
                    if (this._notificationsEndedSignal) {
                        var that = this;
                        this._notificationsEndedSignal.promise.done(function() {
                            that._notificationsEndedSignal = null;
                            that.setOrientation(horizontal);
                        });
                        return;
                    }

                    if (horizontal !== this._horizontal) {
                        this._isOrientationChanging = true;
                        this._horizontal = horizontal;
                        this._forEachPage(function (curr) {
                            var currStyle = curr.pageRoot.style;
                            currStyle.left = "0px";
                            currStyle.top = "0px";
                        });
                        this._panningDivContainer.scrollLeft = 0;
                        this._panningDivContainer.scrollTop = 0;
                        var containerStyle = this._panningDivContainer.style;
                        containerStyle["overflow-x"] = "hidden";
                        containerStyle["overflow-y"] = "hidden";

                        var that = this;
                        requestAnimationFrame(function () {
                            that._isOrientationChanging = false;
                            containerStyle["overflow-x"] = that._horizontal ? "scroll" : "hidden";
                            containerStyle["overflow-y"] = that._horizontal ? "hidden" : "scroll";
                            that._ensureCentered();
                        });
                    }
                },

                resetState: function (initialIndex) {
                    msWriteProfilerMark("WinJS.UI.FlipView:resetState,info");
                    if (initialIndex !== 0) {
                        var indexValid = this.jumpToIndex(initialIndex, true);
                        if (!indexValid && WinJS.validation) {
                            throw new WinJS.ErrorFromName("WinJS.UI.FlipView.BadCurrentPage", strings.badCurrentPage);
                        }
                        return indexValid;
                    } else {
                        this._resetBuffer(null, true);
                        var that = this;
                        var work = WinJS.Promise.wrap(true);
                        if (this._itemsManager) {
                            work = that._itemsManager._firstItem().then(function (e) {
                                that._currentPage.setElement(e);
                                return that._fetchPreviousItems(true).
                                    then(function () {
                                        return that._fetchNextItems();
                                    }).then(function () {
                                        that._setButtonStates();
                                    });
                            });
                        }
                        return work.then(function () {
                            that._tabManager.childFocus = that._currentPage.element;
                            that._ensureCentered();
                            that._itemSettledOn();
                        });
                    }
                },

                setNewItemsManager: function (manager, initialIndex) {
                    this._itemsManager = manager;
                    var that = this;
                    return this.resetState(initialIndex).then(function () {
                        // resetState already configures the tabManager, calls _ensureCentered and _itemSettledOn when the initial index is 0
                        if (initialIndex !== 0) {
                            that._tabManager.childFocus = that._currentPage.element;
                            that._ensureCentered();
                            that._itemSettledOn();
                        }
                    });
                },

                currentIndex: function () {
                    if (!this._itemsManager) {
                        return 0;
                    }
                    var index = 0;
                    var element = (this._navigationAnimationRecord ? this._navigationAnimationRecord.newCurrentElement : this._currentPage.element);
                    if (element) {
                        var item = this._itemsManager.itemObject(element);
                        if (item) {
                            index = item.index;
                        }
                    }
                    return index;
                },

                resetScrollPos: function () {
                    this._ensureCentered();
                },

                scrollPosChanged: function () {
                    if (!this._itemsManager || !this._currentPage.element || this._isOrientationChanging) {
                        return;
                    }

                    var newPos = this._viewportStart(),
                        bufferEnd = (this._lastScrollPos > newPos ? this._getTailOfBuffer() : this._getHeadOfBuffer());

                    if (newPos === this._lastScrollPos) {
                        return;
                    }

                    while (this._currentPage.element && this._itemStart(this._currentPage) > newPos && this._currentPage.prev.element) {
                        this._currentPage = this._currentPage.prev;
                        this._fetchOnePrevious(bufferEnd.prev);
                        bufferEnd = bufferEnd.prev;
                    }

                    while (this._currentPage.element && this._itemEnd(this._currentPage) <= newPos && this._currentPage.next.element) {
                        this._currentPage = this._currentPage.next;
                        this._fetchOneNext(bufferEnd.next);
                        bufferEnd = bufferEnd.next;
                    }
                    this._setButtonStates();
                    this._checkElementVisibility(false);
                    this._blockTabs = true;
                    this._lastScrollPos = newPos;
                    this._tabManager.childFocus = this._currentPage.pageRoot;
                    this._setListEnds();

                    if (!this._manipulationState && this._viewportOnItemStart()) {
                        // Setup a timeout to invoke _itemSettledOn in cases where the scroll position is changed, and the control 
                        // does not know when it has settled on an item (e.g. 1-finger swipe with narrator touch).
                        this._currentPage.element.setAttribute("aria-setsize", this._cachedSize);
                        this._currentPage.element.setAttribute("aria-posinset", this.currentIndex() + 1);
                        this._timeoutPageSelection();
                    }
                },

                itemRetrieved: function (real, placeholder) {
                    var that = this;
                    this._forEachPage(function (curr) {
                        if (curr.element === placeholder) {
                            if (curr === that._currentPage || curr === that._currentPage.next) {
                                that._changeFlipPage(curr, placeholder, real);
                            } else {
                                curr.setElement(real, true);
                            }
                            return true;
                        }
                    });
                    if (this._navigationAnimationRecord) {
                        var animatingElements = this._navigationAnimationRecord.elementContainers;
                        for (var i = 0, len = animatingElements.length; i < len; i++) {
                            if (animatingElements[i].element === placeholder) {
                                that._changeFlipPage(animatingElements[i], placeholder, real);
                                animatingElements[i].element = real;
                            }
                        }
                    }
                    this._checkElementVisibility(false);
                },

                resized: function () {
                    this._panningDivContainerOffsetWidth = this._panningDivContainer.offsetWidth;
                    this._panningDivContainerOffsetHeight = this._panningDivContainer.offsetHeight;
                    var that = this;
                    this._forEachPage(function (curr) {
                        curr.pageRoot.style.width = that._panningDivContainerOffsetWidth + "px";
                        curr.pageRoot.style.height = that._panningDivContainerOffsetHeight + "px";
                    });

                    // Call _ensureCentered to adjust all the width/height of the pages in the buffer
                    this._ensureCentered();
                    msWriteProfilerMark("WinJS.UI.FlipView:resize,StopTM");
                },

                jumpToIndex: function (index, forceJump) {
                    // If we force jumping to an index, we are not interested in making sure that there is distance
                    // between the current and the new index.
                    if (!forceJump) {
                        if (!this._itemsManager || !this._currentPage.element || index < 0) {
                            return WinJS.Promise.wrap(false);
                        }

                        // If we have to keep our pages in memory, we need to iterate through every single item from our current position to the desired target
                        var i,
                            currIndex = this._itemsManager.itemObject(this._currentPage.element).index,
                            distance = Math.abs(index - currIndex);

                        if (distance === 0) {
                            return WinJS.Promise.wrap(false);
                        }
                    }

                    var tail = WinJS.Promise.wrap(true);
                    var that = this;

                    tail = tail.then(function () {
                        var itemPromise = that._itemsManager._itemPromiseAtIndex(index);
                        return WinJS.Promise.join({
                            element: that._itemsManager._itemFromItemPromise(itemPromise),
                            item: itemPromise
                        }).then(function (v) {
                            var elementAtIndex = v.element;

                            // Reset the buffer regardless of whether we have elementAtIndex or not
                            that._resetBuffer(elementAtIndex, forceJump);

                            if (!elementAtIndex) {
                                return false;
                            }

                            that._currentPage.setElement(elementAtIndex);
                            return that._fetchNextItems().
                                then(function () {
                                    return that._fetchPreviousItems(true);
                                }).
                                then(function () {
                                    return true;
                                });
                        });
                    });
                    tail = tail.then(function (v) {
                        that._setButtonStates();
                        return v;
                    });

                    return tail;
                },

                startAnimatedNavigation: function (goForward, cancelAnimationCallback, completionCallback) {
                    if (this._currentPage.element) {
                        var outgoingPage = this._currentPage,
                            incomingPage = (goForward ? this._currentPage.next : this._currentPage.prev);

                        if (incomingPage.element) {
                            if (this._hasFocus) {
                                try {
                                    // Give focus to the panning div ONLY if anything inside the flipview control currently has
                                    // focus; otherwise, it will be lost when the current page is animated during the navigation.
                                    this._panningDiv.setActive();
                                } catch (e) { }
                            }
                            this._navigationAnimationRecord = {};
                            this._navigationAnimationRecord.goForward = goForward;
                            this._navigationAnimationRecord.cancelAnimationCallback = cancelAnimationCallback;
                            this._navigationAnimationRecord.completionCallback = completionCallback;
                            this._navigationAnimationRecord.oldCurrentPage = outgoingPage;
                            this._navigationAnimationRecord.newCurrentPage = incomingPage;
                            var outgoingElement = outgoingPage.element;
                            var incomingElement = incomingPage.element;
                            this._navigationAnimationRecord.newCurrentElement = incomingElement;

                            // When a page element is animated during a navigation, it is temporarily appended on a different container during the animation (see _createDiscardablePage).
                            // However, updates in the data source can happen (change, remove, insert, etc) during the animation affecting the element that is being animated.
                            // Therefore, the page object also maintains the elementUniqueID, and the functions that deal with re-building the internal buffer (shifting/remove/etc)
                            // do all the comparissons, based on the page.elementUniqueID that way even if the element of the page is being animated, we are able to restore/discard it
                            // into the internal buffer back in the correct place.
                            outgoingPage.setElement(null, true);
                            outgoingPage.elementUniqueID = outgoingElement.uniqueID;
                            incomingPage.setElement(null, true);
                            incomingPage.elementUniqueID = incomingElement.uniqueID;

                            var outgoingFlipPage = this._createDiscardablePage(outgoingElement),
                                incomingFlipPage = this._createDiscardablePage(incomingElement);

                            outgoingFlipPage.pageRoot.itemIndex = this._itemsManager.itemObject(outgoingElement).index;
                            incomingFlipPage.pageRoot.itemIndex = outgoingFlipPage.pageRoot.itemIndex + (goForward ? 1 : -1);
                            outgoingFlipPage.pageRoot.style.position = "absolute";
                            incomingFlipPage.pageRoot.style.position = "absolute";
                            outgoingFlipPage.pageRoot.style.zIndex = 1;
                            incomingFlipPage.pageRoot.style.zIndex = 2;
                            this._itemStart(outgoingFlipPage, 0, 0);
                            this._itemStart(incomingFlipPage, 0, 0);
                            this._blockTabs = true;
                            this._visibleElements.push(incomingElement);
                            this._announceElementVisible(incomingElement);
                            this._navigationAnimationRecord.elementContainers = [outgoingFlipPage, incomingFlipPage];
                            return {
                                outgoing: outgoingFlipPage,
                                incoming: incomingFlipPage
                            };
                        }
                    }
                    return null;
                },

                endAnimatedNavigation: function (goForward, outgoing, incoming) {
                    if (this._navigationAnimationRecord &&
                        this._navigationAnimationRecord.oldCurrentPage &&
                        this._navigationAnimationRecord.newCurrentPage) {
                        var outgoingRemoved = this._restoreAnimatedElement(this._navigationAnimationRecord.oldCurrentPage, outgoing);
                        this._restoreAnimatedElement(this._navigationAnimationRecord.newCurrentPage, incoming);
                        if (!outgoingRemoved) {
                            // Advance only when the element in the current page was not removed because if it did, all the pages
                            // were shifted.
                            this._viewportStart(this._itemStart(goForward ? this._currentPage.next : this._currentPage.prev));
                        }
                        this._navigationAnimationRecord = null;
                        this._itemSettledOn();
                    }
                },

                startAnimatedJump: function (index, cancelAnimationCallback, completionCallback) {
                    if (this._currentPage.element) {
                        var oldElement = this._currentPage.element;
                        var oldIndex = this._itemsManager.itemObject(oldElement).index;
                        var that = this;
                        
                        return that.jumpToIndex(index).then(function (v) {
                            if (!v) {
                                return null;
                            }
                            that._navigationAnimationRecord = {};
                            that._navigationAnimationRecord.cancelAnimationCallback = cancelAnimationCallback;
                            that._navigationAnimationRecord.completionCallback = completionCallback;
                            that._navigationAnimationRecord.oldCurrentPage = null;
                            that._forEachPage(function (curr) {
                                if (curr.element === oldElement) {
                                    that._navigationAnimationRecord.oldCurrentPage = curr;
                                    return true;
                                }
                            });
                            that._navigationAnimationRecord.newCurrentPage = that._currentPage;
                            if (that._navigationAnimationRecord.newCurrentPage === that._navigationAnimationRecord.oldCurrentPage) {
                                return null;
                            }
                            var newElement = that._currentPage.element;
                            that._navigationAnimationRecord.newCurrentElement = newElement;

                            // When a page element is animated during a jump, it is temporarily appended on a different container during the animation (see _createDiscardablePage).
                            // However, updates in the data source can happen (change, remove, insert, etc) during the animation affecting the element that is being animated.
                            // Therefore, the page object also maintains the elementUniqueID, and the functions that deal with re-building the internal buffer (shifting/remove/etc)
                            // do all the comparissons, based on the page.elementUniqueID that way even if the element of the page is being animated, we are able to restore/discard it
                            // into the internal buffer back in the correct place.
                            that._currentPage.setElement(null, true);
                            that._currentPage.elementUniqueID = newElement.uniqueID;

                            if (that._navigationAnimationRecord.oldCurrentPage) {
                                that._navigationAnimationRecord.oldCurrentPage.setElement(null, true);
                            }

                            var oldFlipPage = that._createDiscardablePage(oldElement),
                                newFlipPage = that._createDiscardablePage(newElement);
                            oldFlipPage.pageRoot.itemIndex = oldIndex;
                            newFlipPage.pageRoot.itemIndex = index;
                            oldFlipPage.pageRoot.style.position = "absolute";
                            newFlipPage.pageRoot.style.position = "absolute";
                            oldFlipPage.pageRoot.style.zIndex = 1;
                            newFlipPage.pageRoot.style.zIndex = 2;
                            that._itemStart(oldFlipPage, 0, 0);
                            that._itemStart(newFlipPage, that._itemSize(that._currentPage), 0);
                            that._visibleElements.push(newElement);
                            that._announceElementVisible(newElement);
                            that._navigationAnimationRecord.elementContainers = [oldFlipPage, newFlipPage];
                            that._blockTabs = true;
                            return {
                                oldPage: oldFlipPage,
                                newPage: newFlipPage
                            };
                        });
                    }

                    return WinJS.Promise.wrap(null);
                },

                endAnimatedJump: function (oldCurr, newCurr) {
                    if (this._navigationAnimationRecord.oldCurrentPage) {
                        this._navigationAnimationRecord.oldCurrentPage.setElement(oldCurr.element, true);
                    } else {
                        oldCurr.element.parentNode.removeChild(oldCurr.element);
                    }
                    this._navigationAnimationRecord.newCurrentPage.setElement(newCurr.element, true);
                    this._navigationAnimationRecord = null;
                    this._ensureCentered();
                    this._itemSettledOn();
                },

                inserted: function (element, prev, next, animateInsertion) {
                    var curr = this._prevMarker,
                        passedCurrent = false,
                        elementSuccessfullyPlaced = false;

                    if (animateInsertion) {
                        this._createAnimationRecord(element.uniqueID, null);
                        this._getAnimationRecord(element).inserted = true;
                    }

                    if (!prev) {
                        if (!next) {
                            this._currentPage.setElement(element);
                        } else {
                            while (curr.next !== this._prevMarker && curr.elementUniqueID !== next.uniqueID) {
                                if (curr === this._currentPage) {
                                    passedCurrent = true;
                                }
                                curr = curr.next;
                            }

                            // We never should go past current if prev is null/undefined.
                            //#DBG _ASSERT(!passedCurrent);

                            if (curr.elementUniqueID === next.uniqueID && curr !== this._prevMarker) {
                                curr.prev.setElement(element);
                                elementSuccessfullyPlaced = true;
                            } else {
                                this._itemsManager.releaseItem(element);
                            }
                        }
                    } else {
                        do {
                            if (curr === this._currentPage) {
                                passedCurrent = true;
                            }
                            if (curr.elementUniqueID === prev.uniqueID) {
                                elementSuccessfullyPlaced = true;
                                var pageShifted = curr,
                                    lastElementMoved = element,
                                    lastElementMovedUniqueID = element.uniqueID,
                                    temp;
                                if (passedCurrent) {
                                    while (pageShifted.next !== this._prevMarker) {
                                        temp = pageShifted.next.element;
                                        lastElementMovedUniqueID = pageShifted.next.elementUniqueID;
                                        pageShifted.next.setElement(lastElementMoved, true);
                                        if (!lastElementMoved && lastElementMovedUniqueID) {
                                            // Shift the uniqueID of the page manually since its element is being animated.
                                            // This page  will not contain the element until the animation completes.
                                            pageShifted.next.elementUniqueID = lastElementMovedUniqueID;
                                        }
                                        lastElementMoved = temp;
                                        pageShifted = pageShifted.next;
                                    }
                                } else {
                                    if (curr.elementUniqueID === curr.next.elementUniqueID && curr.elementUniqueID) {
                                        pageShifted = curr.next;
                                    }
                                    while (pageShifted.next !== this._prevMarker) {
                                        temp = pageShifted.element;
                                        lastElementMovedUniqueID = pageShifted.elementUniqueID;
                                        pageShifted.setElement(lastElementMoved, true);
                                        if (!lastElementMoved && lastElementMovedUniqueID) {
                                            // Shift the uniqueID of the page manually since its element is being animated.
                                            // This page  will not contain the element until the animation completes.
                                            pageShifted.elementUniqueID = lastElementMovedUniqueID;
                                        }
                                        lastElementMoved = temp;
                                        pageShifted = pageShifted.prev;
                                    }
                                }
                                if (lastElementMoved) {
                                    var reused = false;
                                    this._forEachPage(function (curr) {
                                        if (lastElementMoved.uniqueID === curr.elementUniqueID) {
                                            reused = true;
                                            return true;
                                        }
                                    });
                                    if (!reused) {
                                        this._itemsManager.releaseItem(lastElementMoved);
                                    }
                                }
                                break;
                            }
                            curr = curr.next;
                        } while (curr !== this._prevMarker);
                    }

                    this._getAnimationRecord(element).successfullyMoved = elementSuccessfullyPlaced;
                    this._setButtonStates();
                },

                changed: function (newVal, element) {
                    var curr = this._prevMarker;
                    var that = this;
                    this._forEachPage(function (curr) {
                        if (curr.elementUniqueID === element.uniqueID) {
                            var record = that._animationRecords[curr.elementUniqueID];
                            record.changed = true;
                            record.oldElement = element;
                            record.newElement = newVal;
                            curr.element = newVal; // We set curr's element field here so that next/prev works, but we won't update the visual until endNotifications
                            curr.elementUniqueID = newVal.uniqueID;
                            that._animationRecords[newVal.uniqueID] = record;
                            return true;
                        }
                    });

                    if (this._navigationAnimationRecord && this._navigationAnimationRecord.elementContainers) {
                        for (var i = 0, len = this._navigationAnimationRecord.elementContainers.length; i < len; i++) {
                            var page = this._navigationAnimationRecord.elementContainers[i];
                            if (page && page.elementUniqueID === element.uniqueID) {
                                page.element = newVal;
                                page.elementUniqueID = newVal.uniqueID;
                            }
                        }

                        var newElement = this._navigationAnimationRecord.newCurrentElement;
                        if (newElement && newElement.uniqueID === element.uniqueID) {
                            this._navigationAnimationRecord.newCurrentElement = newVal;
                        }
                    }
                },

                moved: function (element, prev, next) {
                    var record = this._getAnimationRecord(element);

                    if (!record) {
                        /*#DBG
                        // When a moved notification is received, and it doesn't have a record, it shouldn't be in the buffer
                        this._forEachPage(function (curr) {
                            _ASSERT(curr.element !== element);
                        });
                        #DBG*/
                        record = this._createAnimationRecord(element.uniqueID);
                    }

                    record.moved = true;
                    this.removed(element, false, false);
                    if (prev || next) {
                        this.inserted(element, prev, next, false);
                    } else {
                        record.successfullyMoved = false;
                    }
                },

                removed: function (element, mirage, animateRemoval) {
                    var that = this;
                    var prevMarker = this._prevMarker;
                    var work = WinJS.Promise.wrap();

                    if (mirage) {
                        var clearNext = false;
                        this._forEachPage(function (curr) {
                            if (curr.elementUniqueID === element.uniqueID || clearNext) {
                                curr.setElement(null, true);
                                clearNext = true;
                            }
                        });
                        this._setButtonStates();
                        return;
                    }

                    if (animateRemoval) {
                        var record = this._getAnimationRecord(element);
                        if (record) {
                            record.removed = true;
                        }
                    }
                    if (this._currentPage.elementUniqueID === element.uniqueID) {
                        if (this._currentPage.next.elementUniqueID) {
                            this._shiftLeft(this._currentPage);
                            this._ensureCentered();
                        } else if (this._currentPage.prev.elementUniqueID) {
                            this._shiftRight(this._currentPage);
                        } else {
                            this._currentPage.setElement(null, true);
                        }
                    } else if (prevMarker.elementUniqueID === element.uniqueID) {
                        if (prevMarker.next.element) {
                            work = this._itemsManager._previousItem(prevMarker.next.element).
                                then(function (e) {
                                    if (e === element) {
                                        // Because the VDS and Binding.List can send notifications in 
                                        // different states we accomodate this here by fixing the case 
                                        // where VDS hasn't yet removed an item when it sends a removed
                                        // or moved notification.
                                        //
                                        e = that._itemsManager._previousItem(e);
                                    }
                                    return e;
                                }).
                                then(function (e) {
                                    prevMarker.setElement(e, true);
                                });
                        } else {
                            prevMarker.setElement(null, true);
                        }
                    } else if (prevMarker.prev.elementUniqueID === element.uniqueID) {
                        if (prevMarker.prev.prev && prevMarker.prev.prev.element) {
                            work = this._itemsManager._nextItem(prevMarker.prev.prev.element).
                                then(function (e) {
                                    if (e === element) {
                                        // Because the VDS and Binding.List can send notifications in 
                                        // different states we accomodate this here by fixing the case 
                                        // where VDS hasn't yet removed an item when it sends a removed
                                        // or moved notification.
                                        //
                                        e = that._itemsManager._nextItem(e);
                                    }
                                    return e;
                                }).
                                then(function (e) {
                                    prevMarker.prev.setElement(e, true);
                                });
                        } else {
                            prevMarker.prev.setElement(null, true);
                        }
                    } else {
                        var curr = this._currentPage.prev,
                            handled = false;
                        while (curr !== prevMarker && !handled) {
                            if (curr.elementUniqueID === element.uniqueID) {
                                this._shiftRight(curr);
                                handled = true;
                            }

                            curr = curr.prev;
                        }

                        curr = this._currentPage.next;
                        while (curr !== prevMarker && !handled) {
                            if (curr.elementUniqueID === element.uniqueID) {
                                this._shiftLeft(curr);
                                handled = true;
                            }

                            curr = curr.next;
                        }
                    }

                    return work.then(function () {
                        that._setButtonStates();
                    });
                },

                reload: function () {
                    this.resetState(0);
                },

                getItemSpacing: function () {
                    return this._itemSpacing;
                },

                setItemSpacing: function (space) {
                    this._itemSpacing = space;
                    this._ensureCentered();
                },

                notificationsStarted: function () {
                    msWriteProfilerMark("WinJS.UI.FlipView:changeNotifications,StartTM");
                    this._notificationsStarted = this._notificationsStarted || 0;
                    this._notificationsStarted++;
                    this._notificationsEndedSignal = new WinJS._Signal();
                    this._temporaryKeys = [];
                    this._animationRecords = {};
                    var that = this;
                    this._forEachPage(function (curr) {
                        that._createAnimationRecord(curr.elementUniqueID, curr);
                    });

                    // Since the current item is defined as the left-most item in the view, the only possible elements that can be in view at any time are
                    // the current item and the item proceeding it. We'll save these two elements for animations during the notificationsEnded cycle
                    this._animationRecords.currentPage = this._currentPage.element;
                    this._animationRecords.nextPage = this._currentPage.next.element;
                },

                notificationsEnded: function () {
                    // The animations are broken down into three parts.
                    // First, we move everything back to where it was before the changes happened. Elements that were inserted between two pages won't have their flip pages moved.
                    // Next, we figure out what happened to the two elements that used to be in view. If they were removed/moved, they get animated as appropriate in this order:
                    // removed, moved
                    // Finally, we figure out how the items that are now in view got there, and animate them as necessary, in this order: moved, inserted.
                    // The moved animation of the last part is joined with the moved animation of the previous part, so in the end it is:
                    // removed -> moved items in view + moved items not in view -> inserted.
                    var that = this;
                    var animationPromises = [];
                    this._forEachPage(function (curr) {
                        var record = that._getAnimationRecord(curr.element);
                        if (record) {
                            if (record.changed) {
                                record.oldElement.removedFromChange = true;
                                animationPromises.push(that._changeFlipPage(curr, record.oldElement, record.newElement));
                            }
                            record.newLocation = curr.location;
                            that._itemStart(curr, record.originalLocation);
                            if (record.inserted) {
                                curr.elementRoot.style.opacity = 0.0;
                            }
                        }
                    });

                    function flipPageFromElement(element) {
                        var flipPage = null;
                        that._forEachPage(function (curr) {
                            if (curr.element === element) {
                                flipPage = curr;
                                return true;
                            }
                        });
                        return flipPage;
                    }

                    function animateOldViewportItemRemoved(record, item) {
                        var removedPage = that._createDiscardablePage(item);
                        that._itemStart(removedPage, record.originalLocation);
                        animationPromises.push(that._deleteFlipPage(removedPage));
                    }

                    function animateOldViewportItemMoved(record, item) {
                        var newLocation = record.originalLocation,
                            movedPage;
                        if (!record.successfullyMoved) {
                            // If the old visible item got moved, but the next/prev of that item don't match up with anything
                            // currently in our flip page buffer, we need to figure out in which direction it moved.
                            // The exact location doesn't matter since we'll be deleting it anyways, but we do need to
                            // animate it going in the right direction.
                            movedPage = that._createDiscardablePage(item);
                            var indexMovedTo = that._itemsManager.itemObject(item).index;
                            var newCurrentIndex = (that._currentPage.element ? that._itemsManager.itemObject(that._currentPage.element).index : 0);
                            newLocation += (newCurrentIndex > indexMovedTo ? -100 * that._bufferSize : 100 * that._bufferSize);
                        } else {
                            movedPage = flipPageFromElement(item);
                            newLocation = record.newLocation;
                        }
                        that._itemStart(movedPage, record.originalLocation);
                        animationPromises.push(that._moveFlipPage(movedPage, function () {
                            that._itemStart(movedPage, newLocation);
                        }));
                    }

                    var oldCurrent = this._animationRecords.currentPage,
                        oldCurrentRecord = this._getAnimationRecord(oldCurrent),
                        oldNext = this._animationRecords.nextPage,
                        oldNextRecord = this._getAnimationRecord(oldNext);
                    if (oldCurrentRecord && oldCurrentRecord.changed) {
                        oldCurrent = oldCurrentRecord.newElement;
                    }
                    if (oldNextRecord && oldNextRecord.changed) {
                        oldNext = oldNextRecord.newElement;
                    }

                    if (oldCurrent !== this._currentPage.element || oldNext !== this._currentPage.next.element) {
                        if (oldCurrentRecord && oldCurrentRecord.removed) {
                            animateOldViewportItemRemoved(oldCurrentRecord, oldCurrent);
                        }
                        if (oldNextRecord && oldNextRecord.removed) {
                            animateOldViewportItemRemoved(oldNextRecord, oldNext);
                        }
                    }

                    function joinAnimationPromises() {
                        if (animationPromises.length === 0) {
                            animationPromises.push(WinJS.Promise.wrap());
                        }

                        return WinJS.Promise.join(animationPromises);
                    }
                    this._blockTabs = true;
                    joinAnimationPromises().then(function () {
                        animationPromises = [];
                        if (oldCurrentRecord && oldCurrentRecord.moved) {
                            animateOldViewportItemMoved(oldCurrentRecord, oldCurrent);
                        }
                        if (oldNextRecord && oldNextRecord.moved) {
                            animateOldViewportItemMoved(oldNextRecord, oldNext);
                        }
                        var newCurrRecord = that._getAnimationRecord(that._currentPage.element),
                            newNextRecord = that._getAnimationRecord(that._currentPage.next.element);
                        that._forEachPage(function (curr) {
                            var record = that._getAnimationRecord(curr.element);
                            if (record) {
                                if (!record.inserted) {
                                    if (record.originalLocation !== record.newLocation) {
                                        if ((record !== oldCurrentRecord && record !== oldNextRecord) ||
                                            (record === oldCurrentRecord && !oldCurrentRecord.moved) ||
                                            (record === oldNextRecord && !oldNextRecord.moved)) {
                                            animationPromises.push(that._moveFlipPage(curr, function () {
                                                that._itemStart(curr, record.newLocation);
                                            }));
                                        }
                                    }
                                } else if (record !== newCurrRecord && record !== newNextRecord) {
                                    curr.elementRoot.style.opacity = 1.0;
                                }
                            }
                        });
                        joinAnimationPromises().then(function () {
                            animationPromises = [];
                            if (newCurrRecord && newCurrRecord.inserted) {
                                animationPromises.push(that._insertFlipPage(that._currentPage));
                            }
                            if (newNextRecord && newNextRecord.inserted) {
                                animationPromises.push(that._insertFlipPage(that._currentPage.next));
                            }
                            joinAnimationPromises().then(function () {
                                that._checkElementVisibility(false);
                                that._itemSettledOn();
                                that._setListEnds();
                                that._notificationsStarted--;
                                if (that._notificationsStarted === 0) {
                                    that._notificationsEndedSignal.complete();
                                }
                                msWriteProfilerMark("WinJS.UI.FlipView:changeNotifications,StopTM");
                            });
                        });
                    });
                },

                // Private methods

                _timeoutPageSelection: function () {
                    var that = this;
                    if (this._lastTimeoutRequest) {
                        this._lastTimeoutRequest.cancel();
                    }
                    this._lastTimeoutRequest = WinJS.Promise.timeout(itemSelectedEventDelay).then(function () {
                        that._itemSettledOn();
                    });
                },

                _updateTabIndex: function (newIndex) {
                    this._forEachPage(function (curr) {
                        if (curr.element) {
                            curr.element.tabIndex = newIndex;
                        }
                    });
                    this._tabIndex = newIndex;
                    this._tabManager.tabIndex = newIndex;
                },

                _getAnimationRecord: function (element) {
                    return (element ? this._animationRecords[element.uniqueID] : null);
                },

                _createAnimationRecord: function (elementUniqueID, flipPage) {
                    if (elementUniqueID) {
                        var record = this._animationRecords[elementUniqueID] = {
                            removed: false,
                            changed: false,
                            inserted: false
                        };

                        if (flipPage) {
                            record.originalLocation = flipPage.location;
                        }

                        return record;
                    }
                },

                _resetBuffer: function (elementToSave, skipReleases) {
                    var head = this._currentPage,
                        curr = head;
                    do {
                        if ((curr.element && curr.element === elementToSave) || skipReleases) {
                            curr.setElement(null, true);
                        } else {
                            curr.setElement(null);
                        }
                        curr = curr.next;
                    } while (curr !== head);
                },

                _getHeadOfBuffer: function () {
                    return this._prevMarker.prev;
                },

                _getTailOfBuffer: function () {
                    return this._prevMarker;
                },

                _insertNewFlipPage: function (prevElement) {
                    var newPage = this._createFlipPage(prevElement, this);
                    this._panningDiv.appendChild(newPage.pageRoot);
                    return newPage;
                },

                _fetchNextItems: function () {
                    var tail = WinJS.Promise.wrap(this._currentPage);
                    var that = this;

                    for (var i = 0; i < this._bufferSize; i++) {
                        tail = tail.then(function (curr) {
                            if (curr.next === that._prevMarker) {
                                that._insertNewFlipPage(curr);
                            }
                            if (curr.element) {
                                return that._itemsManager._nextItem(curr.element).
                                    then(function (element) {
                                        curr.next.setElement(element);
                                        return curr.next;
                                    });
                            } else {
                                curr.next.setElement(null);
                                return curr.next;
                            }
                        });
                    }

                    return tail;
                },

                _fetchOneNext: function (target) {
                    var prevElement = target.prev.element;
                    // If the target we want to fill with the next item is the end of the circular buffer but we want to keep everything in memory, we've got to increase the buffer size
                    // so that we don't reuse prevMarker.
                    if (this._prevMarker === target) {
                        this._prevMarker = this._prevMarker.next;
                    }
                    if (!prevElement) {
                        target.setElement(null);
                        return;
                    }
                    var that = this;
                    return this._itemsManager._nextItem(prevElement).
                        then(function (element) {
                            target.setElement(element);
                            that._movePageAhead(target.prev, target);
                        });
                },

                _fetchPreviousItems: function (setPrevMarker) {
                    var that = this;

                    var tail = WinJS.Promise.wrap(this._currentPage);

                    for (var i = 0; i < this._bufferSize; i++) {
                        tail = tail.then(function (curr) {
                            if (curr.element) {
                                return that._itemsManager._previousItem(curr.element).
                                    then(function (element) {
                                        curr.prev.setElement(element);
                                        return curr.prev;
                                    });
                            } else {
                                curr.prev.setElement(null);
                                return curr.prev;
                            }
                        });
                    }

                    return tail.then(function (curr) {
                        if (setPrevMarker) {
                            that._prevMarker = curr;
                        }
                    });
                },

                _fetchOnePrevious: function (target) {
                    var nextElement = target.next.element;

                    // If the target we want to fill with the previous item is the end of the circular buffer but we want to keep everything in memory, we've got to increase the buffer size
                    // so that we don't reuse prevMarker. We'll add a new element to be prevMarker's prev, then set prevMarker to point to that new element.
                    if (this._prevMarker === target.next) {
                        this._prevMarker = this._prevMarker.prev;
                    }
                    if (!nextElement) {
                        target.setElement(null);
                        return WinJS.Promise.wrap();
                    }
                    var that = this;
                    return this._itemsManager._previousItem(nextElement).
                        then(function (element) {
                            target.setElement(element);
                            that._movePageBehind(target.next, target);
                        });
                },

                _setButtonStates: function () {
                    if (this._currentPage.prev.element) {
                        this._buttonVisibilityHandler.showPreviousButton();
                    } else {
                        this._buttonVisibilityHandler.hidePreviousButton();
                    }

                    if (this._currentPage.next.element) {
                        this._buttonVisibilityHandler.showNextButton();
                    } else {
                        this._buttonVisibilityHandler.hideNextButton();
                    }
                },

                _ensureCentered: function (delayBoundariesSet) {
                    this._itemStart(this._currentPage, leftBufferAmount * this._viewportSize());
                    var curr = this._currentPage;
                    while (curr !== this._prevMarker) {
                        this._movePageBehind(curr, curr.prev);
                        curr = curr.prev;
                    }

                    curr = this._currentPage;
                    while (curr.next !== this._prevMarker) {
                        this._movePageAhead(curr, curr.next);
                        curr = curr.next;
                    }
                    var boundariesSet = false;
                    if (this._lastScrollPos && !delayBoundariesSet) {
                        this._setListEnds();
                        boundariesSet = true;
                    }
                    this._lastScrollPos = this._itemStart(this._currentPage);
                    this._viewportStart(this._lastScrollPos);
                    this._checkElementVisibility(true);
                    this._setupSnapPoints();
                    if (!boundariesSet) {
                        this._setListEnds();
                    }
                },

                _shiftLeft: function (startingPoint) {
                    var curr = startingPoint,
                        nextEl = null;
                    while (curr !== this._prevMarker && curr.next !== this._prevMarker) {
                        nextEl = curr.next.element;
                        if (!nextEl && curr.next.elementUniqueID) {
                            // Shift the uniqueID of the page manually since its element is being animated.
                            // This page  will not contain the element until the animation completes.
                            curr.elementUniqueID = curr.next.elementUniqueID;
                        }
                        curr.next.setElement(null, true);
                        curr.setElement(nextEl, true);
                        curr = curr.next;
                    }
                    if (curr !== this._prevMarker && curr.prev.element) {
                        var that = this;
                        return this._itemsManager._nextItem(curr.prev.element).
                            then(function (element) {
                                curr.setElement(element);
                                that._createAnimationRecord(curr.elementUniqueID, curr);
                            });
                    }
                },

                _shiftRight: function (startingPoint) {
                    var curr = startingPoint,
                        prevEl = null;
                    while (curr !== this._prevMarker) {
                        prevEl = curr.prev.element;
                        if (!prevEl && curr.prev.elementUniqueID) {
                            // Shift the uniqueID of the page manually since its element is being animated.
                            // This page  will not contain the element until the animation completes.
                            curr.elementUniqueID = curr.prev.elementUniqueID;
                        }
                        curr.prev.setElement(null, true);
                        curr.setElement(prevEl, true);
                        curr = curr.prev;
                    }
                    if (curr.next.element) {
                        var that = this;
                        return this._itemsManager._previousItem(curr.next.element).
                            then(function (element) {
                                curr.setElement(element);
                                that._createAnimationRecord(curr.elementUniqueID, curr);
                            });
                    }
                },

                _checkElementVisibility: function (viewWasReset) {
                    var i,
                        len;
                    if (viewWasReset) {
                        var currentElement = this._currentPage.element;
                        for (i = 0, len = this._visibleElements.length; i < len; i++) {
                            if (this._visibleElements[i] !== currentElement) {
                                this._announceElementInvisible(this._visibleElements[i]);
                            }
                        }

                        this._visibleElements = [];
                        if (currentElement) {
                            this._visibleElements.push(currentElement);
                            this._announceElementVisible(currentElement);
                        }
                    } else {
                        // Elements that have been removed completely from the flipper still need to raise pageVisibilityChangedEvents if they were visible prior to being removed,
                        // so before going through all the elements we go through the ones that we knew were visible and see if they're missing a parentNode. If they are,
                        // the elements were removed and we announce them as invisible.
                        for (i = 0, len = this._visibleElements.length; i < len; i++) {
                            if (!this._visibleElements[i].parentNode || this._visibleElements[i].removedFromChange) {
                                this._announceElementInvisible(this._visibleElements[i]);
                            }
                        }
                        this._visibleElements = [];
                        var that = this;
                        this._forEachPage(function (curr) {
                            var element = curr.element;
                            if (element) {
                                if (that._itemInView(curr)) {
                                    that._visibleElements.push(element);
                                    that._announceElementVisible(element);
                                } else {
                                    that._announceElementInvisible(element);
                                }
                            }
                        });
                    }
                },

                _announceElementVisible: function (element) {
                    if (element && !element.visible) {
                        element.visible = true;

                        var event = document.createEvent("CustomEvent");
                        msWriteProfilerMark("WinJS.UI.FlipView:pageVisibilityChangedEvent(visible:true),info");
                        event.initCustomEvent(thisWinUI.FlipView.pageVisibilityChangedEvent, true, false, { source: this._flipperDiv, visible: true });

                        element.dispatchEvent(event);
                    }
                },

                _announceElementInvisible: function (element) {
                    if (element && element.visible) {
                        element.visible = false;

                        // Elements that have been removed from the flipper still need to fire invisible events, but they can't do that without being in the DOM.
                        // To fix that, we add the element back into the flipper, fire the event, then remove it.
                        var addedToDomForEvent = false;
                        if (!element.parentNode) {
                            addedToDomForEvent = true;
                            this._panningDivContainer.appendChild(element);
                        }

                        var event = document.createEvent("CustomEvent");
                        msWriteProfilerMark("WinJS.UI.FlipView:pageVisibilityChangedEvent(visible:false),info");
                        event.initCustomEvent(thisWinUI.FlipView.pageVisibilityChangedEvent, true, false, { source: this._flipperDiv, visible: false });

                        element.dispatchEvent(event);
                        if (addedToDomForEvent) {
                            this._panningDivContainer.removeChild(element);
                        }
                    }
                },

                _createDiscardablePage: function (content) {
                    var pageDivs = this._createPageContainer(),
                        page = {
                            pageRoot: pageDivs.root,
                            elementRoot: pageDivs.elementContainer,
                            discardable: true,
                            element: content,
                            elementUniqueID: content.uniqueID,
                            discard: function () {
                                if (page.pageRoot.parentNode) {
                                    page.pageRoot.parentNode.removeChild(page.pageRoot);
                                }
                                if (page.element.parentNode) {
                                    page.elementRoot.removeChild(page.element);
                                }
                            }
                        };
                    page.pageRoot.style.top = "0px";
                    page.elementRoot.appendChild(content);
                    this._panningDiv.appendChild(page.pageRoot);
                    return page;
                },

                _createPageContainer: function () {
                    var width = this._panningDivContainerOffsetWidth,
                        height = this._panningDivContainerOffsetHeight,
                        parentDiv = document.createElement("div"),
                        pageStyle = parentDiv.style,
                        flexBox = document.createElement("div");
                    flexBox.className = "win-item";
                    pageStyle.position = "absolute";
                    pageStyle.overflow = "hidden";
                    pageStyle.width = width + "px";
                    pageStyle.height = height + "px";

                    parentDiv.appendChild(flexBox);
                    return {
                        root: parentDiv,
                        elementContainer: flexBox
                    };
                },

                _createFlipPage: function (prev, manager) {
                    var page = {};
                    page.element = null;
                    page.elementUniqueID = null;

                    // The flip pages are managed as a circular doubly-linked list. this.currentItem should always refer to the current item in view, and this._prevMarker marks the point 
                    // in the list where the last previous item is stored. Why a circular linked list?
                    // The virtualized flipper reuses its flip pages. When a new item is requested, the flipper needs to reuse an old item from the buffer. In the case of previous items,
                    // the flipper has to go all the way back to the farthest next item in the buffer and recycle it (which is why having a .prev pointer on the farthest previous item is really useful),
                    // and in the case of the next-most item, it needs to recycle next's next (ie, the this._prevMarker). The linked structure comes in really handy when iterating through the list
                    // and separating out prev items from next items (like removed and ensureCentered do). If we were to use a structure like an array it would be pretty messy to do that and still
                    // maintain a buffer of recyclable items.
                    if (!prev) {
                        page.next = page;
                        page.prev = page;
                    } else {
                        page.prev = prev;
                        page.next = prev.next;
                        page.next.prev = page;
                        prev.next = page;
                    }
                    var pageContainer = this._createPageContainer();
                    page.elementRoot = pageContainer.elementContainer;
                    page.elementRoot.style["-ms-overflow-style"] = "auto";
                    page.pageRoot = pageContainer.root;

                    // Sets the element to display in this flip page
                    page.setElement = function (element, isReplacement) {
                        if (element === undefined) {
                            element = null;
                        }
                        if (element === page.element) {
                            if (!element) {
                                // If there are data source updates during the animation (e.g. item removed), a page element can be set to null when the shiftLeft/Right functions
                                // call this function with a null element. However, since the element in the page is in the middle of an animation its page.elementUniqueID
                                // is still set, so we need to explicitly clear its value so that when the animation completes, the animated element is not 
                                // restored back into the internal buffer.
                                page.elementUniqueID = null;
                            }
                            return;
                        }
                        if (page.element) {
                            if (!isReplacement) {
                                manager._itemsManager.releaseItem(page.element);
                            }
                        }
                        page.element = element;
                        page.elementUniqueID = (element ? element.uniqueID : null);
                        utilities.empty(page.elementRoot);

                        if (page.element) {
                            if (!isFlipper(page.element)) {
                                page.element.tabIndex = manager._tabIndex;
                                page.element.setAttribute("role", "option");
                                page.element.setAttribute("aria-selected", false);
                                if (!page.element.id) {
                                    page.element.id = page.element.uniqueID;
                                }

                                var setAriaFlowAttributeIfIDChanged = function (element, target, attributeName) {
                                    var record = manager._itemsManager._recordFromElement(element, true);
                                    record && record.renderComplete.then(function () {
                                        var completeElement = record.element;
                                        if (target && completeElement && target.getAttribute(attributeName) !== completeElement.id) {
                                            target.setAttribute(attributeName, completeElement.id);
                                        }
                                    });
                                };

                                var setFlowAttribute = function (source, target, attributeName, isStaticID) {
                                    source.setAttribute(attributeName, target.id);

                                    if (!isStaticID) {
                                        // Update aria flow attribute if the element id changed in renderComplete
                                        setAriaFlowAttributeIfIDChanged(target, source, attributeName);
                                    }
                                }

                                var isEnd = !page.next.element || page === manager._prevMarker.prev;
                                if (isEnd) {
                                    setFlowAttribute(page.element, manager._bufferAriaEndMarker, "aria-flowto", true);
                                    setFlowAttribute(manager._bufferAriaEndMarker, page.element, "x-ms-aria-flowfrom");
                                }

                                if (page !== manager._prevMarker && page.prev.element) {
                                    setFlowAttribute(page.prev.element, page.element, "aria-flowto");
                                    setFlowAttribute(page.element, page.prev.element, "x-ms-aria-flowfrom");
                                }
                                if (page.next !== manager._prevMarker && page.next.element) {
                                    setFlowAttribute(page.element, page.next.element, "aria-flowto");
                                    setFlowAttribute(page.next.element, page.element, "x-ms-aria-flowfrom");
                                }

                                if (!page.prev.element) {
                                    setFlowAttribute(page.element, manager._bufferAriaStartMarker, "x-ms-aria-flowfrom", true);
                                    // aria-flowto in the start marker is configured in itemSettledOn to point to the current page in view
                                }
                            }
                            page.elementRoot.appendChild(page.element);
                        }
                    };

                    return page;
                },

                _itemInView: function (flipPage) {
                    return this._itemEnd(flipPage) > this._viewportStart() && this._itemStart(flipPage) < this._viewportEnd();
                },

                _viewportStart: function (newValue) {
                    if (this._horizontal) {
                        if (newValue === undefined) {
                            return this._panningDivContainer.scrollLeft;
                        }
                        this._panningDivContainer.scrollLeft = newValue;
                    } else {
                        if (newValue === undefined) {
                            return this._panningDivContainer.scrollTop;
                        }

                        this._panningDivContainer.scrollTop = newValue;
                    }
                },

                _viewportEnd: function () {
                    var element = this._panningDivContainer;
                    if (this._horizontal) {
                        if (this._rtl) {
                            return this._viewportStart() + this._panningDivContainerOffsetWidth;
                        } else {
                            return element.scrollLeft + this._panningDivContainerOffsetWidth;
                        }
                    } else {
                        return element.scrollTop + this._panningDivContainerOffsetHeight;
                    }
                },

                _viewportSize: function () {
                    return this._horizontal ? this._panningDivContainerOffsetWidth : this._panningDivContainerOffsetHeight;
                },

                _itemStart: function (flipPage, newValue) {
                    if (newValue === undefined) {
                        return flipPage.location;
                    }

                    if (this._horizontal) {
                        flipPage.pageRoot.style.left = (this._rtl ? -newValue : newValue) + "px";
                    } else {
                        flipPage.pageRoot.style.top = newValue + "px";
                    }

                    flipPage.location = newValue;
                },

                _itemEnd: function (flipPage) {
                    return (this._horizontal ? flipPage.location + this._panningDivContainerOffsetWidth : flipPage.location + this._panningDivContainerOffsetHeight) + this._itemSpacing;
                },

                _itemSize: function (flipPage) {
                    return this._horizontal ? this._panningDivContainerOffsetWidth : this._panningDivContainerOffsetHeight;
                },

                _movePageAhead: function (referencePage, pageToPlace) {
                        var delta = this._itemSize(referencePage) + this._itemSpacing;
                        this._itemStart(pageToPlace, this._itemStart(referencePage) + delta);
                },

                _movePageBehind: function (referencePage, pageToPlace) {
                    var delta = this._itemSize(referencePage) + this._itemSpacing;
                    this._itemStart(pageToPlace, this._itemStart(referencePage) - delta);
                },

                _setupSnapPoints: function () {
                    var containerStyle = this._panningDivContainer.style;
                    containerStyle["-ms-scroll-snap-type"] = "mandatory";
                    var viewportSize = this._viewportSize();
                    var snapInterval = viewportSize + this._itemSpacing;
                    var propertyName = "-ms-scroll-snap-points";
                    var startSnap = 0;
                    var currPos = this._itemStart(this._currentPage);
                    startSnap = currPos % (viewportSize + this._itemSpacing);
                    containerStyle[(this._horizontal ? propertyName + "-x" : propertyName + "-y")] = "snapInterval(" + startSnap + "px, " + snapInterval + "px)";
                },

                _setListEnds: function () {
                    if (this._currentPage.element) {
                        var containerStyle = this._panningDivContainer.style,
                            startScroll = 0,
                            endScroll = 0,
                            startNonEmptyPage = this._getTailOfBuffer(),
                            endNonEmptyPage = this._getHeadOfBuffer(),
                            startBoundaryStyle = "-ms-scroll-limit-" + (this._horizontal ? "x-min" : "y-min"),
                            endBoundaryStyle = "-ms-scroll-limit-" + (this._horizontal ? "x-max" : "y-max");

                        while (!endNonEmptyPage.element) {
                            endNonEmptyPage = endNonEmptyPage.prev;

                            // We started at the item before prevMarker (going backwards), so we will exit if all
                            // the pages in the buffer are empty.
                            if (endNonEmptyPage == this._prevMarker.prev) {
                                break;
                            }
                        }

                        while (!startNonEmptyPage.element) {
                            startNonEmptyPage = startNonEmptyPage.next;

                            // We started at prevMarker (going forward), so we will exit if all the pages in the
                            // buffer are empty.
                            if (startNonEmptyPage == this._prevMarker) {
                                break;
                            }
                        }

                        endScroll = this._itemStart(endNonEmptyPage);
                        startScroll = this._itemStart(startNonEmptyPage);
                        containerStyle[startBoundaryStyle] = startScroll + "px";
                        containerStyle[endBoundaryStyle] = endScroll + "px";
                    }
                },

                _viewportOnItemStart: function () {
                    return this._itemStart(this._currentPage) === this._viewportStart();
                },

                _restoreAnimatedElement: function (oldPage, discardablePage) {
                    var removed = true;
                    // Restore the element in the old page only if it still matches the uniqueID, and the page
                    // does not have new updated content. If the element was removed, it won't be restore in the
                    // old page.
                    if (oldPage.elementUniqueID === discardablePage.element.uniqueID && !oldPage.element) {
                        oldPage.setElement(discardablePage.element, true);
                        removed = false;
                    } else {
                        // Iterate through the pages to see if the element was moved
                        this._forEachPage(function (curr) {
                            if (curr.elementUniqueID === discardablePage.elementUniqueID && !curr.element) {
                                curr.setElement(discardablePage.element, true);
                                removed = false;
                            }
                        });
                    }
                    return removed;
                },

                _itemSettledOn: function () {
                    if (this._lastTimeoutRequest) {
                        this._lastTimeoutRequest.cancel();
                        this._lastTimeoutRequest = null;
                    }

                    var that = this;
                    // setImmediate needed to be able to register for the pageselected event after instantiating the control and still get the event
                    setImmediate(function () {
                        if (that._viewportOnItemStart()) {
                            that._blockTabs = false;
                            if (that._currentPage.element) {
                                if (that._hasFocus) {
                                    try {
                                        that._currentPage.element.setActive();
                                        that._tabManager.childFocus = that._currentPage.element;
                                    } catch (e) { }
                                }
                                if (that._lastSelectedElement !== that._currentPage.element) {
                                    if (that._lastSelectedPage && that._lastSelectedPage.element && !isFlipper(that._lastSelectedPage.element)) {
                                        that._lastSelectedPage.element.setAttribute("aria-selected", false);
                                    }
                                    that._lastSelectedPage = that._currentPage;
                                    that._lastSelectedElement = that._currentPage.element;
                                    if (!isFlipper(that._currentPage.element)) {
                                        that._currentPage.element.setAttribute("aria-selected", true);
                                    }

                                    // setImmediate needed in case a navigation is triggered inside the pageselected listener
                                    setImmediate(function () {
                                        if (that._currentPage.element) {
                                            var event = document.createEvent("CustomEvent");
                                            event.initCustomEvent(thisWinUI.FlipView.pageSelectedEvent, true, false, { source: that._flipperDiv });
                                            msWriteProfilerMark("WinJS.UI.FlipView:pageSelectedEvent,info");
                                            that._currentPage.element.dispatchEvent(event);

                                            // Fire the pagecompleted event when the render completes if we are still looking  at the same element.
                                            // Check that the current element is not null, since the app could've triggered a navigation inside the 
                                            // pageselected event handler.
                                            var originalElement = that._currentPage.element;
                                            if (originalElement) {
                                                var record = that._itemsManager._recordFromElement(originalElement, true);
                                                if (record) {
                                                    record.renderComplete.then(function () {
                                                        if (originalElement === that._currentPage.element) {
                                                            that._currentPage.element.setAttribute("aria-setsize", that._cachedSize);
                                                            that._currentPage.element.setAttribute("aria-posinset", that.currentIndex() + 1);
                                                            that._bufferAriaStartMarker.setAttribute("aria-flowto", that._currentPage.element.id);
                                                            event = document.createEvent("CustomEvent");
                                                            event.initCustomEvent(thisWinUI.FlipView.pageCompletedEvent, true, false, { source: that._flipperDiv });
                                                            msWriteProfilerMark("WinJS.UI.FlipView:pageCompletedEvent,info");
                                                            that._currentPage.element.dispatchEvent(event);
                                                        }
                                                    });
                                                }
                                            }
                                        }
                                    });
                                }
                            }
                        }
                    });
                },

                _forEachPage: function (callback) {
                    var go = true;
                    var curr = this._prevMarker;
                    while (go) {
                        if (callback(curr)) {
                            break;
                        }
                        curr = curr.next;
                        go = (curr !== this._prevMarker);
                    }
                },

                _changeFlipPage: function (page, oldElement, newElement) {
                    page.element = null;
                    if (page.setElement) {
                        page.setElement(newElement, true);
                    } else {
                        // Discardable pages that are created for animations aren't full fleged pages, and won't have some of the functions a normal page would.
                        // changeFlipPage will be called on them when an item that's animating gets fetched. When that happens, we need to replace its element
                        // manually, then center it.
                        oldElement.parentNode.removeChild(oldElement);
                        page.elementRoot.appendChild(newElement);
                    }

                    var style = oldElement.style;
                    style.position = "absolute";
                    style.left = "0px";
                    style.top = "0px";
                    style.opacity = 1.0;

                    page.pageRoot.appendChild(oldElement);
                    oldElement.style.left = Math.max(0, (page.pageRoot.offsetWidth - oldElement.offsetWidth) / 2) + "px";
                    oldElement.style.top = Math.max(0, (page.pageRoot.offsetHeight - oldElement.offsetHeight) / 2) + "px";

                    return WinJS.Promise.timeout().then(function () {
                        return animations.fadeOut(oldElement).then(function () {
                            oldElement.parentNode.removeChild(oldElement);
                        });
                    });
                },

                _deleteFlipPage: function (page) {
                    page.elementRoot.style.opacity = 0;
                    var animation = animations.createDeleteFromListAnimation([page.elementRoot]);


                    return WinJS.Promise.timeout().then(function () {
                        return animation.execute().then(function () {
                            if (page.discardable) {
                                page.discard();
                            }
                        });
                    });
                },

                _insertFlipPage: function (page) {
                    page.elementRoot.style.opacity = 1.0;
                    var animation = animations.createAddToListAnimation([page.elementRoot]);

                    return WinJS.Promise.timeout().then(function () {
                        return animation.execute().then(function () {
                            if (page.discardable) {
                                page.discard();
                            }
                        });
                    });
                },

                _moveFlipPage: function (page, move) {
                    var animation = animations.createRepositionAnimation(page.pageRoot);

                    return WinJS.Promise.timeout().then(function () {
                        move();
                        return animation.execute().then(function () {
                            if (page.discardable) {
                                page.discard();
                            }
                        });
                    });
                }
            }, {
                supportedForProcessing: false,
            }
        )
    });

    thisWinUI._FlipPageManager.flipPageBufferCount = 2; // The number of items that should surround the current item as a buffer at any time
})(WinJS);


(function animationHelperInit(global, WinJS, undefined) {
    "use strict";


var utilities = WinJS.Utilities,
    Promise = WinJS.Promise,
    Signal = WinJS._Signal,
    Animation = WinJS.UI.Animation;

var AnimationStage = {
    waiting: 0,
    remove: 1,
    move: 2,
    add: 3,
    done: 4
};

var gridReflowOutgoingDuration = 80;
var gridReflowIncomingDuration = 366;
var gridReflowTimeoutBuffer = 50;
function gridReflowOutgoingTransition() {
    return "transform " + gridReflowOutgoingDuration + "ms linear " + WinJS.UI._libraryDelay + "ms";
}

function gridReflowIncomingTransition() {
    return "transform " + gridReflowIncomingDuration + "ms cubic-bezier(0.1, 0.9, 0.2, 1) " + WinJS.UI._libraryDelay + "ms";
}

function _ListviewAnimationStage() {
    this._affectedItems = {};
    this._running = false;
}

_ListviewAnimationStage.prototype = {
    stageCompleted: function () {
        if (!this._completed) {
            var itemKeys = Object.keys(this._affectedItems);
            for (var i = 0, len = itemKeys.length; i < len; i++) {
                var element = this._affectedItems[itemKeys[i]].element;
                if (element._currentAnimationStage === this) {
                    // An item can be moved between stages, so the currentAnimationStage should only be cleared if this stage is the right stage
                    element._animating = false;
                    delete element._currentAnimationStage;
                }
            }
        }
        this._completed = true;
        this._running = false;
    },

    /*#DBG
    // _ListviewAnimationStage is an abstract class; these functions need to be implemented by the subclasses.
    // mergeStage is called by the animation tracker. The stages being merged should be instances of the same class.
    mergeStage: function () {
        _ASSERT(false);
    },

    animateStage: function () {
        _ASSERT(false);
    },

    cancel: function() {
    },

    replaceItemInStage: function (oldItem, newItem) {
        _ASSERT(false);
    },
    #DBG*/

    clearAnimationProperties: function (item) {
        item.style.transition = "";
        item.style.animationName = "";
        item.style.transform = "";
        item.style.opacity = 1.0;
    },

    removeItemFromStage: function (item) {
        if (!item.parentNode) {
            this.clearAnimationProperties(item);
        }
        item._animating = false;
        delete item._currentAnimationStage;
        delete this._affectedItems[item.uniqueID];
    },

    running: function () {
        return this._running;
    }
};

function _ListviewAnimationRemoveStage(itemsRemoved, canvas, rtl) {
    var itemIDs = Object.keys(itemsRemoved);
    this._affectedItems = {};
    this._targetSurface = canvas;
    this._positionProperty = (rtl ? "right" : "left");

    for (var i = 0, len = itemIDs.length; i < len; i++) {
        var itemID = itemIDs[i],
            itemData = itemsRemoved[itemID],
            itemAnimationStage = itemData.element._currentAnimationStage,
            skipItemAnimation = false;

        if (itemAnimationStage && !itemAnimationStage.running()) {
            // An item can already be attached to a different animation stage.
            // Remove animations take precedence over the other two animation stages.
            // If an item is in an add stage and is now being removed and that add animation hasn't played yet,
            // then it's okay to just skip the item's animation entirely.
            itemAnimationStage.removeItemFromStage(itemsRemoved[itemID].element);
            if (itemAnimationStage instanceof _ListviewAnimationAddStage) {
                skipItemAnimation = true;
                if (itemData.element.parentNode) {
                    itemData.element.parentNode.removeChild(itemData.element);
                }
            }
        }

        itemData.element._animating = true;
        if (!skipItemAnimation) {
            itemData.element._currentAnimationStage = this;
            this._affectedItems[itemID] = itemsRemoved[itemID];
        }
    }
}

_ListviewAnimationRemoveStage.prototype = new _ListviewAnimationStage();
_ListviewAnimationRemoveStage.prototype.mergeStage = function (stage) {
    var newItemIDs = Object.keys(stage._affectedItems);
    for (var i = 0, len = newItemIDs.length; i < len; i++) {
        var itemID = newItemIDs[i],
            itemData = stage._affectedItems[itemID];
        this._affectedItems[itemID] = itemData;
        itemData.element._currentAnimationStage = this;
    }
};

_ListviewAnimationRemoveStage.prototype.animateStage = function () {
    this._running = true;
    var itemIDs = Object.keys(this._affectedItems),
        items = [];
    if (itemIDs.length === 0) {
        return Promise.wrap();
    }

    msWriteProfilerMark("WinJS.UI.ListView.Animation:remove,StartTM");
    var that = this;
    function done() {
        if (!that._canceled) {
            for (var i = 0, len = itemIDs.length; i < len; i++) {
                var item = that._affectedItems[itemIDs[i]].element;
                if (item.parentNode) {
                    item.parentNode.removeChild(item);
                    item.style.opacity = 1.0;
                }
            }
        }
        that.stageCompleted();
    }

    for (var j = 0, lenJ = itemIDs.length; j < lenJ; j++) {
        // It's necessary to set the opacity of every item being removed to 0 here.
        // The deleteFromList animation will reset the item's opacity to 1.0 for the sake of animation,
        // but once that animation is finished it will clean up every state it put on the item and reset the
        // item back to its original style. If the opacity isn't set, the item will briefly flicker back
        // on screen at full size+opacity until the cleanup code in done() runs.
        var item = that._affectedItems[itemIDs[j]].element;
        item.style.opacity = 0.0;
        if (item.parentNode !== this._targetSurface) {
            this._targetSurface.appendChild(item);
        }
        items.push(item);
    }

    // One way or another, these promises are finishing. If something goes wrong with the animations, things will still be okay.
    var animationPromise = Animation.createDeleteFromListAnimation(items).execute().then(done, done);

    msWriteProfilerMark("WinJS.UI.ListView.Animation:remove(removed:" + items.length + "),info");
    msWriteProfilerMark("WinJS.UI.ListView.Animation:remove,StopTM");
    return animationPromise;
};

_ListviewAnimationRemoveStage.prototype.replaceItemInStage = function (oldItem, newItem) {
    if (!this._running) {
        _prepareReplacement(this, oldItem, newItem);
        this._affectedItems[newItem.uniqueID] = { element: newItem }; 
    }

    oldItem._animating = false;
    delete oldItem._currentAnimationStage;
    this.removeItemFromStage(oldItem);
};

_ListviewAnimationRemoveStage.prototype.cancel = function () {
    var itemIDs = Object.keys(this._affectedItems);
    for (var i = 0, len = itemIDs.length; i < len; i++) {
        var item = this._affectedItems[itemIDs[i]].element;
        this.clearAnimationProperties(item);
        if (item.parentNode) {
            item.parentNode.removeChild(item);
        }
    }
    this._affectedItems = [];
    this._canceled = true;
};

// The listview has two types of move animations: A Reflow animation, and a fade transition between the two views.
// A fade transition will play if there are variably sized items in or near the viewport. Reflows will play at all other times.
// The problem is that one move may be triggered using reflow, and another using fade (it's a very rare scenario, but possible).
// When this happens, the fade transition should take precedence. If the old move animation used fades, then the new one will use
// it too.
function _ListviewAnimationMoveStage(itemsMoved, gridLayout, useFadeAnimation, canvas, rtl, canvasHeight, totalItemHeight) {
    msWriteProfilerMark("WinJS.UI.ListView.Animation:moveConstructor,StartTM");

    // The itemsMoved parameter passed to the move stage must map items to their old+new locations.
    this._affectedItems = {};
    this._targetSurface = canvas;
    this._positionProperty = (rtl ? "right" : "left");
    this._useFadeAnimation = useFadeAnimation;
    this._gridLayout = gridLayout;
    this._rtl = rtl;
    // Canvas height and totalItemHeight are only used in a grid reflow animation, and as such will only be defined when that animation is being created
    this._canvasHeight = canvasHeight;
    this._totalItemHeight = totalItemHeight;

    var itemIDs = Object.keys(itemsMoved);
    for (var i = 0, len = itemIDs.length; i < len; i++) {
        var itemID = itemIDs[i],
            itemData = itemsMoved[itemID],
            itemAnimationStage = itemData.element._currentAnimationStage,
            skipItemAnimation = false,
            itemCameFromRunningMoveAnimation = false;

        if (itemAnimationStage) {
            // An item can already be attached to a different animation stage.
            // Moved items should never have a removed stage animation attached to them. 
            // If the moved item has another move stage attached to it, there can be two possibilities:
            //  1 - The animation is already running. If this happens, the animation tracker will automatically handle
            //      the chaining of the old move animation and this new one. The item's animation stage just needs to be
            //      updated to point to this new stage instead.
            //  2 - The animation hasn't yet run. If this is the case, the item is still in its original position before any
            //      move animations were queued up. In this case, this new stage will take the old stage's record of the item's
            //      old location, remove the item from the old stage, and animate the item going from oldRecordLoc to newRecordLoc.
            // If the moved item has an add animation attached to it, there are two cases:
            //  1 - Animation is not yet running. If that's the case, this stage won't animate the item being moved, but will
            //      move that item instantly to its final location and leave the item's stage alone.
            //  2 - Animation is already running. In this case, the move animation should play once this item is done
            //      animating in. This stage will remove the item from the old add stage and prepare to animate it.
            //      The tracker will handle firing the move animation at the appropriate time.
            //#DBG _ASSERT(!(itemAnimationStage instanceof _ListviewAnimationRemoveStage));
            if (!itemAnimationStage.running()) {
                if (itemAnimationStage instanceof _ListviewAnimationMoveStage) {
                    var oldMoveData = itemAnimationStage._affectedItems[itemID],
                        newMoveData = itemsMoved[itemID];
                    newMoveData.oldRow = oldMoveData.oldRow;
                    newMoveData.oldColumn = oldMoveData.oldColumn;
                    newMoveData.oldLeft = oldMoveData.oldLeft;
                    newMoveData.oldTop = oldMoveData.oldTop;
                    itemAnimationStage.removeItemFromStage(itemsMoved[itemID].element);
                    this._useFadeAnimation = this._useFadeAnimation || itemAnimationStage._useFadeAnimation;
                } else if (itemAnimationStage instanceof _ListviewAnimationAddStage) {
                    skipItemAnimation = true;
                    itemAnimationStage.updateItemLocation (itemsMoved[itemID]);
                }
            } else if (itemAnimationStage instanceof _ListviewAnimationMoveStage) {
                itemCameFromRunningMoveAnimation = true;
            }
        }

        itemData.element._animating = true;
        if (!skipItemAnimation) {
            if (!itemCameFromRunningMoveAnimation) {
                // If an item came from a running move animation, we don't want to change its top/left properties mid animation.
                var elementStyle = itemData.element.style;
                elementStyle[this._positionProperty] = itemData.oldLeft + "px";
                elementStyle.top = itemData.oldTop + "px";
            }
            this._affectedItems[itemID] = itemsMoved[itemID];
            itemData.element._currentAnimationStage = this;
        }
    }

    // This cancelAnimation function is the default cancel for move stages. If a move stage hasn't begun yet, it's clear to just reposition elements immediately.
    // When the stage begins with whatever move animation should actually play, this default cancelAnimation function will be overwritten by a cancel function
    // specific to that move animation.
    this.cancelAnimation = function () {
        for (var i = 0, len = itemIDs.length; i < len; i++) {
            var itemData = this._affectedItems[itemIDs[i]];
            if (itemData) {
                var element = itemData.element;
                element.style.top = itemData.top + "px";
                element.style[this._positionProperty] = itemData.left + "px";
            }
        }
        this.stageCompleted();
    }

    msWriteProfilerMark("WinJS.UI.ListView.Animation:moveConstructor,StopTM");
}

_ListviewAnimationMoveStage.prototype = new _ListviewAnimationStage();
_ListviewAnimationMoveStage.prototype.mergeStage = function (stage) {
    this._useFadeAnimation = this._useFadeAnimation || stage._useFadeAnimation;
    var newItemIDs = Object.keys(stage._affectedItems);
    for (var i = 0, len = newItemIDs.length; i < len; i++) {
        // There shouldn't be any duplicate items in this merge. Items with two move stages would have been handled
        // in the second stage's constructor.
        var itemID = newItemIDs[i];
        if (!this._affectedItems[itemID]) {
            this._affectedItems[itemID] = stage._affectedItems[itemID];
            this._affectedItems[itemID].element._currentAnimationStage = this;
        }
    }
};

_ListviewAnimationMoveStage.prototype.animateStage = function () {
    this._running = true;
    var itemIDs = Object.keys(this._affectedItems);
    if (itemIDs.length === 0) {
        return Promise.wrap();
    }

    var that = this;
    function done() {
        that.stageCompleted();
    }

    var animation = (this._gridLayout ? (this._useFadeAnimation ? this.createFadeReflowAnimation (itemIDs) : this.createGridReflowAnimation (itemIDs)) : this.createListReflowAnimation (itemIDs));
    return animation.then(done, done);
};

_ListviewAnimationMoveStage.prototype.createGridReflowAnimation = function (itemIDs) {
    msWriteProfilerMark("WinJS.UI.ListView.Animation:moveGridReflow,StartTM");
    var reflowingMoves = [];
    var reflowingMoveData = [];
    var remainingMoves = [];
    var remainingMoveData = [];
    var incomingColumnInfo = [];
    var i = 0;
    var len = 0;

    function updateColumnInfo(goingDown, row, column) {
        if (!incomingColumnInfo[column]) {
            incomingColumnInfo[column] = {};
        }

        var columnInfo = incomingColumnInfo[column];
        if (goingDown && (columnInfo.maxRow === undefined || columnInfo.maxRow < row)) {
            columnInfo.maxRow = row;
        } else if (!goingDown && (columnInfo.minRow === undefined || columnInfo.minRow > row)) {
            columnInfo.minRow = row;
        }
    }
    // The move animations work using transitions on position transforms.
    // Once all items' move deltas have been calculated, they're moved to their final location.
    // That means that all offsets to old positions need to be relative to their final location, not their original.
    for (var i = 0, len = itemIDs.length; i < len; i++) {
        var itemData = this._affectedItems[itemIDs[i]];
        var leftOffset = itemData.oldLeft - itemData.left;
        var topOffset = itemData.oldTop - itemData.top;

        // This final offset check is necessary in the event of move stages being merged repeatedly. An item may have moved, but then been moved back
        // before the first move stage could animate.
        if (leftOffset !== 0 || topOffset !== 0) {
            leftOffset = (this._rtl ? -leftOffset : leftOffset);
            if (itemData.oldColumn !== undefined && itemData.oldColumn !== itemData.column) {
                var outgoingEndOffset;
                if (itemData.oldColumn > itemData.column) {
                    outgoingEndOffset = -this._canvasHeight + itemData.oldTop - itemData.top;
                    updateColumnInfo(false, itemData.row, itemData.column);
                } else {
                    outgoingEndOffset = this._canvasHeight + itemData.oldTop - itemData.top;
                    updateColumnInfo(true, itemData.row, itemData.column);
                }
                reflowingMoves.push(itemData.element);
                reflowingMoveData.push({
                    outgoingLeftOffset: leftOffset,
                    outgoingStartOffset: itemData.oldTop - itemData.top,
                    outgoingEndOffset: outgoingEndOffset,
                    column: itemData.column,
                    goingDown: (itemData.oldColumn < itemData.column)
                });
            } else {
                remainingMoves.push(itemData.element);
                remainingMoveData.push({ oldLeftOffset: leftOffset, oldTopOffset: itemData.oldTop - itemData.top });
            }
        }
        var element = itemData.element;
        element.style.top = itemData.top + "px";
        element.style[this._positionProperty] = itemData.left + "px";
    }
    var signal = new WinJS._Signal(),
        moveData;

    for (i = 0, len = reflowingMoves.length; i < len; i++) {
        moveData = reflowingMoveData[i];
        reflowingMoves[i].style.transform = "translate(" + moveData.outgoingLeftOffset + "px, " + moveData.outgoingStartOffset + "px)";
        var columnInfo = incomingColumnInfo[moveData.column];
        if (moveData.goingDown) {
            moveData.incomingStartOffset = -this._totalItemHeight * (columnInfo.maxRow + 1);
        } else {
            moveData.incomingStartOffset = this._canvasHeight - (columnInfo.minRow * this._totalItemHeight);
        }
    }
    for (i = 0, len = remainingMoves.length; i < len; i++) {
        moveData = remainingMoveData[i];
        remainingMoves[i].style.transform = "translate(" + moveData.oldLeftOffset + "px, " + moveData.oldTopOffset + "px)";
    }

    var that = this;
    var finishedOutgoing = false;
    var finishedIncoming = false;
    var elementsRemovedFromStage = {};
    var secondStageEventHandler = null;

    function forceRecalculateLayout() {
        // Force trident to resolve the styles. This allows us to change the styles (transform/opacity/etc)
        // of the element and then transition from those styles to a new set of styles. Without this the
        // intermediate styles are ignored and it uses the original styles as the starting point.
        for (i = 0, len = reflowingMoves.length; i < len; i++) {
            window.getComputedStyle(reflowingMoves[i], null).transform;
        }
        for (i = 0, len = remainingMoves.length; i < len; i++) {
            window.getComputedStyle(remainingMoves[i], null).transform;
        }
    }

    function onOutgoingEnd(eventObject) {
        if (eventObject && eventObject.srcElement !== reflowingMoves[0]) {
            return;
        }
        if (!finishedOutgoing) {
            finishedOutgoing = true;
            reflowingMoves[0].removeEventListener("transitionend", onOutgoingEnd, false);
            playRemainingMoves();
        }
    }

    function animationsComplete(eventObject) {
        if (!finishedIncoming) {
            if (eventObject && eventObject.srcElement !== secondStageEventHandler) {
                // If this callback is triggered via an animation playing inside of an animating element, then we want to ignore the
                // event and keep waiting.
                return;
            }
            finishedIncoming = true;
            for (i = 0, len = reflowingMoves.length; i < len; i++) {
                if (!elementsRemovedFromStage[reflowingMoves[i].uniqueID]) {
                    reflowingMoves[i].style.transition = "";
                    reflowingMoves[i].style.transform = "";
                }
            }
            if (reflowingMoves.length > 0) {
                reflowingMoves[0].removeEventListener("transitionend", onOutgoingEnd, false);
            }
            for (i = 0, len = remainingMoves.length; i < len; i++) {
                if (!elementsRemovedFromStage[remainingMoves[i].uniqueID]) {
                    remainingMoves[i].style.transition = "";
                    remainingMoves[i].style.transform = "";
                }
            }
            if (secondStageEventHandler) {
                secondStageEventHandler.removeEventListener("transitionend", animationsComplete, false);
            }
            signal.complete();
        }
    }


/*
These transitions use watchdog timeouts to catch abandonment scenarios.
The watchdog timeout is set to the expected end of the action, plus a little extra time to ensure that when the action completes normally,
the completion event fires ahead of the watchdog.

Since setTimeout doesn't wait for the next animation frame to start, we schedule the watchdog timer as a series of timeouts.
The first timeout is for a fixed small amount of time. This guarantees that the first timeout will not expire
until the first render pass is complete and the animation has started.
At that point, we can schedule the real timeout, and this one will not fire prematurely. 
*/
    function setTimeoutAfterTTFF(callback, delay) {
        setTimeout(function() {
            setTimeout(callback, delay);
        }, gridReflowTimeoutBuffer);
    }

    function playRemainingMoves() {
        if (that._canceled) {
            return;
        }
        if (remainingMoves.length === 0 && reflowingMoves.length === 0) {
            animationsComplete();
        } else {
            msWriteProfilerMark("WinJS.UI.ListView.Animation:moveGridReflowRemaining,StartTM");
            // Since the move animation is broken down into two parts, we need to check each element to see if it's been removed from this animation via
            // removeItemFromStage. removeItemFromStage is called when an element is discarded through virtualization logic.
            for (i = 0, len = reflowingMoves.length; i < len; i++) {
                if (!elementsRemovedFromStage[reflowingMoves[i].uniqueID]) {
                    reflowingMoves[i].style.transition = "";
                    reflowingMoves[i].style.transform = "translate(0px, " + reflowingMoveData[i].incomingStartOffset + "px)";
                }
            }

            forceRecalculateLayout();
            var eventHandlingElement;
            var incomingTransition = gridReflowIncomingTransition();
            for (i = 0, len = reflowingMoves.length; i < len; i++) {
                if (!elementsRemovedFromStage[reflowingMoves[i].uniqueID]) {
                    eventHandlingElement = reflowingMoves[i];
                    reflowingMoves[i].style.transition = incomingTransition;
                    reflowingMoves[i].style.transform = "translate(0px, 0px)";
                }
            }
            for (i = 0, len = remainingMoves.length; i < len; i++) {
                if (!elementsRemovedFromStage[remainingMoves[i].uniqueID]) {
                    eventHandlingElement = remainingMoves[i];
                    remainingMoves[i].style.transition = incomingTransition;
                    remainingMoves[i].style.transform = "translate(0px, 0px)";
                }
            }
            if (eventHandlingElement) {
                secondStageEventHandler = eventHandlingElement;
                eventHandlingElement.addEventListener("transitionend", animationsComplete, false);
                setTimeoutAfterTTFF(animationsComplete, gridReflowIncomingDuration);
            } else {
                animationsComplete();
            }

            msWriteProfilerMark("WinJS.UI.ListView.Animation:moveGridReflowRemaining,StopTM");
        }
    }

    if (reflowingMoves.length > 0) {
        forceRecalculateLayout();
        var outgoingTransition = gridReflowOutgoingTransition();
        for (i = 0, len = reflowingMoves.length; i < len; i++) {
            reflowingMoves[i].style.transition = outgoingTransition;
            moveData = reflowingMoveData[i];
            reflowingMoves[i].style.transform = "translate(" + moveData.outgoingLeftOffset + "px, " + moveData.outgoingEndOffset + "px)";
        }
        reflowingMoves[0].addEventListener("transitionend", onOutgoingEnd, false);
        setTimeoutAfterTTFF(onOutgoingEnd, gridReflowOutgoingDuration);
    } else {
        playRemainingMoves();
    }

    msWriteProfilerMark("WinJS.UI.ListView.Animation:moveGridReflow:(reflowing:" + reflowingMoves.length + ", moving: " + remainingMoves.length + "),info");

    
    this.cancelAnimation = function() {
        animationsComplete();
    };

    this.removeItemFromStage = function(item) {
        // If this version of removeItemFromStage is called, then it means an item has been recycled (other animation stages will only call
        // removeItemFromStage when a new stage is created using that item AND the item's old animation stage hadn't yet been started). When this happens
        // we need to mark the item as removed so it doesn't get animated in any later move stages. removeItemFromStage will clear any animation properties that might've been set on that element.
        elementsRemovedFromStage[item.uniqueID] = true;
        _ListviewAnimationMoveStage.prototype.removeItemFromStage.call(this, item);
    };

    msWriteProfilerMark("WinJS.UI.ListView.Animation:moveGridReflow,StopTM");
    return signal.promise;
};

_ListviewAnimationMoveStage.prototype.createListReflowAnimation = function (itemIDs) {
    msWriteProfilerMark("WinJS.UI.ListView.Animation:moveListReflow,StartTM");

    var that = this;
    function done() {
        that.stageCompleted();
    }

    var items = [],
        i, len;
    for (i = 0, len = itemIDs.length; i < len; i++) {
        items.push(this._affectedItems[itemIDs[i]].element);
    }

    var animation = Animation.createDeleteFromListAnimation ([], items);

    for (i = 0, len = itemIDs.length; i < len; i++) {
        var itemData = this._affectedItems[itemIDs[i]];
        itemData.element.style[this._positionProperty] = itemData.left + "px";
        itemData.element.style.top = itemData.top + "px";
    }

    var that = this;
    this.cancelAnimation = function() {
        for (i = 0, len = items.length; i < len; i++) {
            that.clearAnimationProperties(items[i]);
        }
        done();
    };
    msWriteProfilerMark("WinJS.UI.ListView.Animation:moveListReflow:(moving:" + items.length + "),info");

    var animationPromise = animation.execute().then(done, done);

    msWriteProfilerMark("WinJS.UI.ListView.Animation:moveListReflow,StopTM");
    return animationPromise;
};

_ListviewAnimationMoveStage.prototype.createFadeReflowAnimation = function (itemIDs) {
    var movedItems = [],
        moveData = [],
        i, len;
    for (i = 0, len = itemIDs.length; i < len; i++) {
        // This check is only necessary for the fade animation. In horizontal grid layout with
        // variably sized items, the items' left and top properties will stay the same,
        // but their row/column will change, so endLayout will treat the item as an affected item.
        // This check will filter out the items that never moved.
        var itemData = this._affectedItems[itemIDs[i]];
        if (itemData.oldLeft !== itemData.left || itemData.oldTop !== itemData.top) {
            movedItems.push(itemData.element);
            moveData.push(itemData);
        }
    }

    if (movedItems.length === 0) {
        return Promise.wrap();
    }
    msWriteProfilerMark("WinJS.UI.ListView.Animation:moveFadeReflow,StartTM");

    msWriteProfilerMark("WinJS.UI.ListView.Animation:moveFadeReflow(moving: " + movedItems.length + "),info");

    var signal = new WinJS._Signal();
    var that = this;
    function done() {
        signal.complete();
    }
    function moveItems() {
        msWriteProfilerMark("WinJS.UI.ListView.Animation:moveFadeReflow:move,StartTM");
        for (i = 0, len = movedItems.length; i < len; i++) {
            var itemStyle = movedItems[i].style,
                itemData = moveData[i];
            itemStyle[that._positionProperty] = itemData.left + "px";
            itemStyle.top = itemData.top + "px";
        }
        WinJS.UI.Animation.fadeIn(movedItems).then(done, done);
        msWriteProfilerMark("WinJS.UI.ListView.Animation:moveFadeReflow:move,StopTM");
    }

    WinJS.UI.Animation.fadeOut(movedItems).then(moveItems, moveItems);

    this.cancelAnimation = function () {
        msWriteProfilerMark("WinJS.UI.ListView.Animation:moveFadeReflow:move,StartTM");
        for (i = 0, len = movedItems.length; i < len; i++) {
            var itemStyle = movedItems[i].style,
                itemData = moveData[i];
            that.clearAnimationProperties(movedItems[i]);
            itemStyle[that._positionProperty] = itemData.left + "px";
            itemStyle.top = itemData.top + "px";
        }

        msWriteProfilerMark("WinJS.UI.ListView.Animation:moveFadeReflow:move,StopTM");
        done();
    };

    msWriteProfilerMark("WinJS.UI.ListView.Animation:moveFadeReflow,StopTM");
    return signal.promise;
};

function _prepareReplacement(newStage, oldItem, newItem) {
    newItem._currentAnimationStage = newStage;
    newItem._animating = true;
    newItem.style.position = oldItem.style.position;
    newItem.style.left = oldItem.offsetLeft + "px";
    newItem.style.top = oldItem.offsetTop + "px";
}

_ListviewAnimationMoveStage.prototype.replaceItemInStage = function (oldItem, newItem) {
    if (!this._running) {
        _prepareReplacement(this, oldItem, newItem);
        this._affectedItems[newItem.uniqueID] = this._affectedItems[oldItem.uniqueID]; 
        this._affectedItems[newItem.uniqueID].element = newItem;
    }

    oldItem._animating = false;
    delete oldItem._currentAnimationStage;
    this.removeItemFromStage(oldItem);
};

_ListviewAnimationMoveStage.prototype.cancel = function () {
    this.cancelAnimation();
    this._affectedItems = [];
    this._canceled = true;
};

function _ListviewAnimationAddStage(itemsAdded, canvas, rtl) {
    // The itemsMoved parameter passed to the move stage must map items to their old+new locations.
    var itemIDs = Object.keys(itemsAdded);
    this._affectedItems = {};
    this._targetSurface = canvas;
    this._positionProperty = (rtl ? "right" : "left");

    for (var i = 0, len = itemIDs.length; i < len; i++) {
        var itemID = itemIDs[i],
            itemData = itemsAdded[itemID],
            itemAnimationStage = itemData.element._currentAnimationStage,
            skipItemAnimation = false;

        if (itemAnimationStage) {
            // An item can already be attached to a different animation stage.
            // If an item is already attached to a remove stage, we'll follow this logic:
            // - If remove animation is running, queue up add animation
            // - If remove animation isn't running, cancel remove animation for that item and don't play add.
            // Added items should never be attached to a move stage
            // Added items should never be attached to another add stage
            //#DBG _ASSERT(!(itemAnimationStage instanceof _ListviewAnimationMoveStage));
            //#DBG _ASSERT(!(itemAnimationStage instanceof _ListviewAnimationAddStage));
            if (itemAnimationStage instanceof _ListviewAnimationRemoveStage) {
                if (!itemAnimationStage.running()) {
                    itemAnimationStage.removeItemFromStage(itemsAdded[itemID].element);
                    skipItemAnimation = true;
                }
            }
        }
        
        itemData.element._animating = true;
        if (!skipItemAnimation) {
            this._affectedItems[itemID] = itemsAdded[itemID];
            itemData.element._currentAnimationStage = this;
        }
    }
}

_ListviewAnimationAddStage.prototype = new _ListviewAnimationStage();
_ListviewAnimationAddStage.prototype.mergeStage = function (stage) {
    var newItemIDs = Object.keys(stage._affectedItems);
    for (var i = 0, len = newItemIDs.length; i < len; i++) {
        // There shouldn't be any duplicate items in this merge.
        var itemID = newItemIDs[i];
        if (!this._affectedItems[itemID]) {
            this._affectedItems[itemID] = stage._affectedItems[itemID];
            this._affectedItems[itemID].element._currentAnimationStage = this;
        }
    }
};

_ListviewAnimationAddStage.prototype.animateStage = function () {
    this._running = true;
    var itemIDs = Object.keys(this._affectedItems),
        items = [];

    if (itemIDs.length === 0 || this._canceled) {
        return Promise.wrap();
    }
    msWriteProfilerMark("WinJS.UI.ListView.Animation:add,StartTM");

    var that = this;

    function done() {
        that.stageCompleted();
    }
    
    for (var i = 0, len = itemIDs.length; i < len; i++) {
        var item = this._affectedItems[itemIDs[i]].element;
        item.style.opacity = 1.0;
        if (!item.parentNode) {
            this._targetSurface.appendChild(item);
        }
        items.push(item);
    }

    msWriteProfilerMark("WinJS.UI.ListView.Animation:add(added:" + items.length + "),info");

    var animationPromise = Animation.createAddToListAnimation(items).execute().then(done, done);
    msWriteProfilerMark("WinJS.UI.ListView.Animation:add,StopTM");
    return animationPromise;
};

// updateItemLocation will be called by the move animation stage.
// It will only be called if an item waiting to be added gets moved before its animation plays.
_ListviewAnimationAddStage.prototype.updateItemLocation = function (itemData) {
    itemData.element.style[this._positionProperty] = itemData.left + "px";
    itemData.element.style.top = itemData.top + "px";
};

_ListviewAnimationAddStage.prototype.replaceItemInStage = function (oldItem, newItem) {
    if (!this._running) {
        newItem._currentAnimationStage = this;
        newItem._animating = true;
        newItem._insertedItemAwaitingLayout = true;
        newItem.style.opacity = 0.0;
        this._affectedItems[newItem.uniqueID] = { element: newItem }; 
    }

    oldItem._animating = false;
    delete oldItem._currentAnimationStage;
    this.removeItemFromStage(oldItem);
};

_ListviewAnimationAddStage.prototype.cancel = function () {
    var affectedItems = this._affectedItems,
        itemIDs = Object.keys(affectedItems);
    for (var i = 0, len = itemIDs.length; i < len; i++) {
        this.clearAnimationProperties(affectedItems[itemIDs[i]].element);
    }
    this.stageCompleted();
    this._canceled = true;
};

function _ListViewAnimationTracker(removeStage, moveStage, addStage, oldTracker) {
    var startRemoveStage = true;

    this._removeStage = removeStage;
    this._moveStage = moveStage;
    this._addStage = addStage;
    this._started = false;
    this._stopped = false;
    this._currentStage = AnimationStage.waiting;
    this._animationsSignal = new Signal();

    if (oldTracker && !oldTracker.done()) {
        if (oldTracker.waiting()) {
            removeStage.mergeStage(oldTracker._removeStage);
            moveStage.mergeStage(oldTracker._moveStage);
            addStage.mergeStage(oldTracker._addStage);
            this._waitingPromise = oldTracker._waitingPromise;
            this._waitingPromise.then(waitComplete, waitComplete);
            startRemoveStage = false;
        } else {
            var oldTrackerStage = oldTracker.getCurrentStage();
            switch (oldTrackerStage) {
                case AnimationStage.remove:
                    moveStage.mergeStage(oldTracker._moveStage);
                    // Fallthrough is intentional here. If the old tracker was on the remove stage, then the new one
                    // needs to merge the move+add stages of the old tracker
                case AnimationStage.move: 
                    addStage.mergeStage(oldTracker._addStage);
                    break;
            }

            // If the old tracker was in its remove stage, the tracker can play its remove animations while the older animation is still running.
            if (oldTrackerStage !== AnimationStage.remove) {
                startRemoveStage = false;
            }
        }
        oldTracker.stopAnimations();
    }

    this._oldTracker = oldTracker;
    if (startRemoveStage) {
        this.startAnimations(oldTracker && oldTracker._waitingPromise);
    } else {
        var waitComplete = this.waitingComplete.bind(this);
        this._waitingPromise = oldTracker._waitingPromise;
        this._waitingPromise.then(waitComplete, waitComplete);
    }
}

_ListViewAnimationTracker.prototype = {
    getCompletionPromise: function () {
        if (this._done) {
            return Promise.wrap();
        }

        return this._animationsSignal.promise;
    },

    waitingComplete: function () {
        if (!this._stopped) {
            this.startAnimations();
        }
    },

    nextStage: function () {
        this._waitingPromise = null;
        this._currentStage++;

        if (this._stopped) {
            return;
        }

        var targetStage = (this._currentStage === AnimationStage.move ? this._moveStage : (this._currentStage === AnimationStage.add ? this._addStage : null));

        if (targetStage) {
            this._waitingPromise = targetStage.animateStage();
            var that = this;
            var moveToNext = function () {
                that.nextStage();
            }
            this._waitingPromise.then(moveToNext, moveToNext); 
        } else {
            this._animationsSignal.complete();
        }
    },

    startAnimations: function (previousAnimationPromise) {
        if (this._started) {
            return;
        }
        this._started = true;
        this._currentStage = AnimationStage.remove;
        this._waitingPromise = Promise.join([previousAnimationPromise, this._removeStage.animateStage()]);
        var moveToNext = this.nextStage.bind(this);
        this._waitingPromise.then(moveToNext, moveToNext);
    },

    stopAnimations: function () {
        this._stopped = true;
        this._animationsSignal.complete();
    },

    cancelAnimations: function () {
        this._stopped = true;
        if (this._currentStage === AnimationStage.waiting) {
            this._oldTracker.cancelAnimations();
        }
        if (this._currentStage < AnimationStage.move) {
            this._removeStage.cancel();
        }
        if (this._currentStage < AnimationStage.add) {
            this._moveStage.cancel();
        }
        if (this._currentStage < AnimationStage.done) {
            this._addStage.cancel();
        }
        this._animationsSignal.complete();
    },

    getCurrentStage: function () {
        return this._currentStage;
    },

    done: function () {
        return this._currentStage === AnimationStage.done || this._stopped;
    },

    waiting: function () {
        return this._currentStage === AnimationStage.waiting;
    }
};

WinJS.Namespace.define("WinJS.UI", {
    _ListViewAnimationHelper: {
        fadeInElement: function (element) {
            return Animation.fadeIn(element);
        },

        fadeOutElement: function (element) {
            return Animation.fadeOut(element);
        },

        animateListFadeBetween: function (oldAnimationTracker, canvas, rtl, affectedItems, inserted, removed) {
            return new _ListViewAnimationTracker(new _ListviewAnimationRemoveStage(removed, canvas, rtl), 
                                                 new _ListviewAnimationMoveStage(affectedItems, true, true, canvas, rtl), 
                                                 new _ListviewAnimationAddStage(inserted, canvas, rtl), oldAnimationTracker);
        },

        animateEntrance: function (canvas, firstEntrance) {
            return Animation.enterContent(canvas, [{left: firstEntrance ? "100px" : "40px", top: "0px"}]);
        },

        animateReflow: function (oldAnimationTracker, canvas, rtl, affectedItems, inserted, removed, canvasHeight, totalItemHeight) {
            return new _ListViewAnimationTracker(new _ListviewAnimationRemoveStage(removed, canvas, rtl), 
                                                 new _ListviewAnimationMoveStage(affectedItems, true, false, canvas, rtl, canvasHeight, totalItemHeight),
                                                 new _ListviewAnimationAddStage(inserted, canvas, rtl), oldAnimationTracker);
        },

        animateListReflow: function (oldAnimationTracker, canvas, rtl, affectedItems, inserted, removed) {
            return new _ListViewAnimationTracker(new _ListviewAnimationRemoveStage(removed, canvas, rtl), 
                                                 new _ListviewAnimationMoveStage(affectedItems, false, false, canvas, rtl),
                                                 new _ListviewAnimationAddStage(inserted, canvas, rtl), oldAnimationTracker);
        }
    }
});

})(this, WinJS);

(function browseModeInit(global, WinJS, undefined) {
    "use strict";

    var utilities = WinJS.Utilities,
        Promise = WinJS.Promise,
        Animation = WinJS.UI.Animation,
        AnimationHelper = WinJS.UI._ListViewAnimationHelper;

    var SwipeBehaviorState = {
        started: 0,
        dragging: 1,
        selecting: 2,
        selectSpeedBumping: 3,
        speedBumping: 4,
        rearranging: 5,
        completed: 6,

        selected: function (state) {
            return state === this.selecting || state === this.selectSpeedBumping;
        }
    };

    var RELEASE_TIMEOUT = 500;
    var PT_TOUCH = 2;

    function getElementWithClass(parent, className) {
        return parent.querySelector("." + className);
    }

    function releaseWhen(winRTObject, predicate) {
        if (!winRTObject) { return; }

        if (predicate(winRTObject)) {
            try {
                msReleaseWinRTObject(winRTObject);
            }
            catch (e) {
                // double-release throws, and in this scenario we are OK with just
                // ignoring that
            }
        }
        else {
            setTimeout(function () { releaseWhen(winRTObject, predicate); }, RELEASE_TIMEOUT);
        }
    }

    // This component is responsible for handling input in Browse Mode. 
    // When the user clicks on an item in this mode itemInvoked event is fired.
    WinJS.Namespace.define("WinJS.UI", {
        _getCursorPos: function (eventObject) {
            var docElement = document.documentElement;

            return {
                left: eventObject.clientX + (document.body.dir === "rtl" ? -docElement.scrollLeft : docElement.scrollLeft),
                top: eventObject.clientY + docElement.scrollTop
            };
        },

        _getElementsByClasses: function (parent, classes) {
            var retVal = []

            for (var i = 0, len = classes.length; i < len; i++) {
                var element = getElementWithClass(parent, classes[i]);
                if (element) {
                    retVal.push(element);
                }
            }
            return retVal;
        },

        _SelectionMode: function (modeSite) {
            this.initialize(modeSite);
        }
    });

    WinJS.UI._SelectionMode.prototype = {
        _dispose: function () {
            releaseWhen(this.cachedRecognizer, function (reco) { return !reco.isActive; });
            this.cachedRecognizer = null;
        },
        initialize: function (modeSite) {
            this.site = modeSite;
            this.pressedItem = null;
            this.pressedIndex = WinJS.UI._INVALID_INDEX;
            this.pressedPosition = null;

            this._work = [];
            this.animations = {};
            this.keyboardNavigationHandlers = {};
            this.keyboardAcceleratorHandlers = {};

            function createArrowHandler(direction, clampToBounds) {
                var handler = function (oldFocus) {
                    var items = modeSite._view.items;
                    return modeSite._layout.getKeyboardNavigatedItem(oldFocus, items.wrapperAt(oldFocus), direction);
                };
                handler.clampToBounds = clampToBounds;
                return handler;
            }

            var Key = utilities.Key,
                that = this;
            this.keyboardNavigationHandlers[Key.upArrow] = createArrowHandler(Key.upArrow);
            this.keyboardNavigationHandlers[Key.downArrow] = createArrowHandler(Key.downArrow);
            this.keyboardNavigationHandlers[Key.leftArrow] = createArrowHandler(Key.leftArrow);
            this.keyboardNavigationHandlers[Key.rightArrow] = createArrowHandler(Key.rightArrow);
            this.keyboardNavigationHandlers[Key.pageUp] = createArrowHandler(Key.pageUp, true);
            this.keyboardNavigationHandlers[Key.pageDown] = createArrowHandler(Key.pageDown, true);
            this.keyboardNavigationHandlers[Key.home] = function () {
                return Promise.wrap(0);
            };
            this.keyboardNavigationHandlers[Key.end] = function () {
                // The two views need to treat their ends a bit differently. Scroll view is virtualized and will allow one to jump
                // to the end of the list, but incremental view requires that the item be loaded before it can be jumped to.
                // Due to that limitation, we need to ask the view what its final item is and jump to that. The incremental view
                // will give the final loaded item, while the scroll view will give count - 1.
                return that.site._view.finalItem();
            };

            this.keyboardAcceleratorHandlers[Key.a] = function () {
                if (that.site._multiSelection()) {
                    that.site._selection.selectAll();
                }
            };

            setTimeout(function () {
                if (!that.cachedRecognizer && !that.site._isZombie()) {
                    that.cachedRecognizer = that.createGestureRecognizer();
                }
            }, 500);
        },

        staticMode: function SelectionMode_staticMode() {
            return this.site._tap === WinJS.UI.TapBehavior.none && this.site._selectionMode === WinJS.UI.SelectionMode.none;
        },

        togglePressed: function SelectionMode_togglePressed(add) {
            if (!this.staticMode()) {
                // If we are adding the pressed effect do it immediately because we
                // already delayed it but if we are removing it add the delay here.
                if (add) {
                    msWriteProfilerMark("WinJS.UI.ListView:applyPressedUI,info");
                    utilities.addClass(this.pressedItem, WinJS.UI._pressedClass);

                    // Shrink by 97.5% unless that is larger than 7px in either direction. In that case we cap the 
                    // scale so that it is no larger than 7px in either direction. We keep the scale uniform in both x
                    // and y directions. Note that this scale cap only works if getItemPosition returns synchronously
                    // which it does for the built in layouts.
                    var scale = 0.975;
                    var maxPixelsToShrink = 7;
                    this.site._layout.getItemPosition(this.pressedIndex).then(function (pos) {
                        if (pos.contentWidth > 0) {
                            scale = Math.max(scale, (1 - (maxPixelsToShrink / pos.contentWidth)));
                        }
                        if (pos.contentHeight > 0) {
                            scale = Math.max(scale, (1 - (maxPixelsToShrink / pos.contentHeight)));
                        }
                    }, function() {
                        // Swallow errors in case data source changes
                    });

                    this.pressedItem.style.transform = "scale(" + scale + "," + scale + ")";
                } else {
                    var element = this.pressedItem;
                    setImmediate(function () {
                        if (utilities.hasClass(element, WinJS.UI._pressedClass)) {
                            msWriteProfilerMark("WinJS.UI.ListView:removePressedUI,info");
                            utilities.removeClass(element, WinJS.UI._pressedClass);
                            Animation.pointerUp(element);
                        }
                    });
                }
            }
        },

        // In single selection mode, in addition to itemIndex's selection state being toggled,
        // all other items will become deselected
        _toggleItemSelection: function SelectionMode_toggleItemSelection(itemIndex) {
            var site = this.site,
                selection = this.site._selection,
                selected = selection._isIncluded(itemIndex);

            if (site._selectionMode === WinJS.UI.SelectionMode.single) {
                if (!selected) {
                    selection.set(itemIndex);
                } else {
                    selection.clear();
                }
            } else {
                if (!selected) {
                    selection.add(itemIndex);
                } else {
                    selection.remove(itemIndex);
                }
            }
        },

        handleTap: function SelectionMode_handleTap(itemIndex) {
            var site = this.site,
                selection = site._selection;

            if (site._selectionAllowed() && site._selectOnTap()) {
                if (site._tap === WinJS.UI.TapBehavior.toggleSelect) {
                    this._toggleItemSelection(itemIndex);
                } else {
                    // site._tap === WinJS.UI.TapBehavior.directSelect so ensure only itemIndex is selected
                    if (site._selectionMode === WinJS.UI.SelectionMode.multi || !selection._isIncluded(itemIndex)) {
                        selection.set(itemIndex);
                    }
                }
            }
        },

        handleSwipeBehavior: function SelectionMode_handleSwipeBehavior(itemIndex) {
            var site = this.site;

            if (site._selectionAllowed()) {
                this._toggleItemSelection(itemIndex);
            }
        },

        itemUnrealized: function SelectionMode_itemUnrealized(index) {
            if (this.pressedIndex === index) {
                this.resetPointerDownState();
            }
        },

        fireInvokeEvent: function SelectionMode_fireInvokeEvent(itemIndex, itemElement) {
            if (itemElement &&
                this.site._tap !== WinJS.UI.TapBehavior.none &&
                itemIndex !== WinJS.UI._INVALID_INDEX) {

                var listBinding = this.site.itemDataSource.createListBinding(),
                    itemPromise = listBinding.fromIndex(itemIndex);

                itemPromise.then(function (item) {
                    listBinding.release();
                });

                var eventObject = document.createEvent("CustomEvent");
                eventObject.initCustomEvent("iteminvoked", true, true, {
                    itemPromise: itemPromise,
                    itemIndex: itemIndex
                });

                // If preventDefault was not called, call the default action on the site
                if (itemElement.dispatchEvent(eventObject)) {
                    this.site._defaultInvoke(itemIndex);
                }
            }
        },

        selectionAllowed: function SelectionMode_selectionAllowed(itemIndex) {
            var site = this.site;
            if (site._selectionAllowed() && (site._selectOnTap() || site._swipeBehavior === WinJS.UI.SwipeBehavior.select)) {
                var selected = site._selection._isIncluded(itemIndex),
                    single = !site._multiSelection(),
                    newSelection = site._selection._cloneSelection();

                if (selected) {
                    if (single) {
                        newSelection.clear();
                    } else {
                        newSelection.remove(itemIndex);
                    }
                } else {
                    if (single) {
                        newSelection.set(itemIndex);
                    } else {
                        newSelection.add(itemIndex);
                    }
                }

                var eventObject = document.createEvent("CustomEvent"),
                    newSelectionUpdated = Promise.wrap(),
                    completed = false,
                    preventTap = false,
                    included;

                eventObject.initCustomEvent("selectionchanging", true, true, {
                    newSelection: newSelection,
                    preventTapBehavior: function () {
                        preventTap = true;
                    },
                    setPromise: function (promise) {
                        /// <signature helpKeyword="WinJS.UI.BrowseMode.selectionchanging.setPromise">
                        /// <summary locid="WinJS.UI.BrowseMode.selectionchanging.setPromise">
                        /// Used to inform the ListView that asynchronous work is being performed, and that this
                        /// event handler should not be considered complete until the promise completes.
                        /// </summary>
                        /// <param name="promise" type="WinJS.Promise" locid="WinJS.UI.BrowseMode.selectionchanging.setPromise_p:promise">
                        /// The promise to wait for.
                        /// </param>
                        /// </signature>

                        newSelectionUpdated = promise;
                    }
                });

                var defaultBehavior = site._element.dispatchEvent(eventObject);

                newSelectionUpdated.then(function () {
                    completed = true;
                    included = newSelection._isIncluded(itemIndex);
                    newSelection.clear();
                });

                var canSelect = defaultBehavior && completed && (selected || included);

                return {
                    canSelect: canSelect,
                    canTapSelect: canSelect && !preventTap
                };
            } else {
                return {
                    canSelect: false,
                    canTapSelect: false
                };
            }
        },

        prepareItem: function SelectionMode_prepareItem(pressedIndex, pressedElement, selected) {
            var that = this,
                site = this.site;

            if (!selected) {
                (this.animations[pressedIndex] || Promise.wrap()).then(function () {
                    if (!that.site._isZombie()) {
                        var items = site._view.items,
                            itemData = items.itemDataAt(pressedIndex),
                            pressedElement = itemData.element,
                            wrapper = itemData.wrapper;

                        utilities.addClass(wrapper, WinJS.UI._swipeClass);

                        if (!WinJS.UI._isSelectionRenderer(wrapper)) {
                            site._renderSelection(wrapper, pressedElement, true);

                            utilities.removeClass(wrapper, WinJS.UI._selectedClass);

                            var nodes = wrapper.querySelectorAll(WinJS.UI._selectionPartsSelector);
                            for (var i = 0, len = nodes.length; i < len; i++) {
                                nodes[i].style.opacity = 0;
                            }
                        }
                    }
                });
            } else {
                var wrapper = site._view.items.itemDataAt(pressedIndex).wrapper;
                utilities.addClass(wrapper, WinJS.UI._swipeClass);
            }
        },

        clearItem: function SelectionMode_clearItem(pressedIndex, selected) {
            var site = this.site,
                itemData = site._view.items.itemDataAt(pressedIndex);

            if (itemData) {
                var wrapper = itemData.wrapper;

                utilities.removeClass(wrapper, WinJS.UI._swipeClass);

                site._renderSelection(wrapper, itemData.element, selected, true);
            }
        },

        isInteractive: function SelectionMode_isInteractive(element) {
            if (element.parentNode) {
                var matches = element.parentNode.querySelectorAll(".win-interactive, .win-interactive *");
                for (var i = 0, len = matches.length; i < len; i++) {
                    if (matches[i] === element) {
                        return true;
                    }
                }
            }
            return false;
        },

        resetPointerDownState: function SelectionMode_resetPointerDownState() {
            if (this.gestureRecognizer) {
                this.endSelfRevealGesture();
                this.endSwipeBehavior(true);
            }

            if (this.pressedItem) {
                this.togglePressed(false);
                this.pressedItem = null;
            }

            this.removeSelectionHint();

            this.pressedIndex = WinJS.UI._INVALID_INDEX;
            this.pointerId = null;
            this.waitingForGot = false;
        },

        onMSPointerDown: function SelectionMode_onMSPointerDown(eventObject) {
            msWriteProfilerMark("WinJS.UI.ListView:MSPointerDown,StartTM");
            var site = this.site,
                that = this,
                items = site._view.items,
                touchInput = (eventObject.pointerType === PT_TOUCH),
                leftButton,
                rightButton;

            if (WinJS.Utilities.hasWinRT) {
                // xButton is true when you've x-clicked with a mouse or pen. Otherwise it is false.
                var currentPoint = this.getCurrentPoint(eventObject);
                var pointProps = currentPoint.properties;
                if (!(touchInput || pointProps.isInverted || pointProps.isEraser || pointProps.isMiddleButtonPressed)) {
                    rightButton = pointProps.isRightButtonPressed;
                    leftButton = !rightButton && pointProps.isLeftButtonPressed;
                } else {
                    leftButton = rightButton = false;
                }
            } else {
                // xButton is true when you've x-clicked with a mouse. Otherwise it is false.
                leftButton = (eventObject.button === WinJS.UI._LEFT_MSPOINTER_BUTTON);
                rightButton = (eventObject.button === WinJS.UI._RIGHT_MSPOINTER_BUTTON);
            }

            this.swipeBehaviorState = null;
            var swipeEnabled = site._swipeBehavior === WinJS.UI.SwipeBehavior.select,
                swipeBehavior = touchInput && swipeEnabled,
                isInteractive = this.isInteractive(eventObject.srcElement),
                currentPressedIndex = items.index(eventObject.srcElement),
                mustSetCapture = !isInteractive && currentPressedIndex !== WinJS.UI._INVALID_INDEX;

            if ((touchInput || leftButton || (site._selectionAllowed() && swipeEnabled && rightButton)) && this.pressedIndex === WinJS.UI._INVALID_INDEX && !isInteractive) {
                this.pressedIndex = currentPressedIndex;

                if (this.pressedIndex !== WinJS.UI._INVALID_INDEX) {
                    this.pressedPosition = WinJS.UI._getCursorPos(eventObject);

                    var allowed = this.selectionAllowed(this.pressedIndex);
                    this.canSelect = allowed.canSelect;
                    this.canTapSelect = allowed.canTapSelect;

                    this.swipeBehaviorSelectionChanged = false;
                    this.selectionHint = null;

                    this.pressedItem = items.wrapperAt(this.pressedIndex);

                    this.togglePressed(true);

                    if (swipeBehavior && this.canSelect) {
                        // Record the swipe start location on down because the first move could be far from the down 
                        // location. Store the position off the pointerpoint since GestureRecognizer will not give us
                        // the delta they only give us the new location.
                        this.swipeBehaviorStart = this.getCurrentPoint(eventObject).position[this.site._layout.horizontal ? "y" : "x"];
                        this.startSwipeBehavior();
                    }

                    if (this.canSelect) {
                        this.addSelectionHint();
                    }

                    // Even though we are calling msSetPointerCapture we may not recieve Pointer Capture. This can happen
                    // when the Semantic Zoom control calls msSetPointerCapture after us. When this happens we need to
                    // reset the pointer down state. We detect this scenario by recieving an MSPointerOut before an 
                    // MSGotPointerCapture event.
                    this.waitingForGot = true;

                    this.pointerId = eventObject.pointerId;
                    this.pointerRightButton = rightButton;
                    this.pointerTriggeredSRG = false;

                    if (this.gestureRecognizer) {
                        this.gestureRecognizer.processDownEvent(this.getCurrentPoint(eventObject));
                    }

                    mustSetCapture = false;
                    if (touchInput) {
                        try {
                            site._canvasProxy.msSetPointerCapture(eventObject.pointerId);
                        } catch (e) {
                            this.resetPointerDownState();
                            msWriteProfilerMark("WinJS.UI.ListView:MSPointerDown,StopTM");
                            return;
                        }
                    }

                    // Stop MSPointerDown from moving focus which is quite expensive sometimes
                    eventObject.preventDefault();
                }
            }

            if (mustSetCapture) {
                if (touchInput) {
                    try {
                        // Move pointer capture to avoid hover visual on second finger
                        site._canvasProxy.msSetPointerCapture(eventObject.pointerId);
                    } catch (e) {
                        msWriteProfilerMark("WinJS.UI.ListView:MSPointerDown,StopTM");
                        return;
                    }
                }
            }

            // Once the shift selection pivot is set, it remains the same until the user
            // performs a left- or right-click without holding the shift key down.
            if ((leftButton || rightButton) && !touchInput &&               // Left or right mouse/pen click
                    site._selectionAllowed() && site._multiSelection() &&   // Multi selection enabled
                    this.pressedIndex !== WinJS.UI._INVALID_INDEX &&        // A valid item was clicked
                    site._selection._getFocused() !== WinJS.UI._INVALID_INDEX && site._selection._pivot === WinJS.UI._INVALID_INDEX) {
                site._selection._pivot = site._selection._getFocused();
            }

            msWriteProfilerMark("WinJS.UI.ListView:MSPointerDown,StopTM");
        },

        // Play the self-reveal gesture (SRG) animation which jiggles the item to reveal the selection hint behind it
        startSelfRevealGesture: function SelectionMode_startSelfRevealGesture(eventObject) {
            if (eventObject.holdingState === Windows.UI.Input.HoldingState.started && this.canSelect &&
                    this.site._swipeBehavior === WinJS.UI.SwipeBehavior.select) {
                msWriteProfilerMark("WinJS.UI.ListView:playSelfRevealGesture,info");

                var that = this;
                var site = this.site,
                    Animation = WinJS.UI.Animation,
                    index = this.pressedIndex,
                    element = site._view.items.wrapperAt(index),
                    selected = site._selection._isIncluded(index);

                var swipeReveal = function () {
                    var top,
                        left;

                    if (site._layout.horizontal) {
                        top = WinJS.UI._VERTICAL_SWIPE_SELF_REVEAL_GESTURE + "px";
                        left = "0px";
                    } else {
                        top = "0px";
                        left = (site._rtl() ? "" : "-") + WinJS.UI._HORIZONTAL_SWIPE_SELF_REVEAL_GESTURE + "px";
                    }

                    return Animation.swipeReveal(element, { top: top, left: left });
                }

                var swipeHide = function () {
                    return Animation.swipeReveal(element, { top: "0px", left: "0px" });
                }

                var cleanUp = function (selectionHint) {
                    if (!that.site._isZombie()) {
                        if (selectionHint) {
                            that.removeSelectionHint(selectionHint);
                        }
                        that.clearItem(index, site._selection._isIncluded(index));
                    }
                }

                // Cancels the SRG animation by stopping the item at its current location. Leaves the item in the "prepared"
                // state.
                var freezeAnimation = function () {
                    // Replace the SRG animation with a no-op animation. The no-op animation works by moving the item to its current location.
                    var transformationMatrix = window.getComputedStyle(element).transform.slice(4, -1).split(", "),
                        left = transformationMatrix[4] + "px",
                        top = transformationMatrix[5] + "px";

                    that.selfRevealGesture._promise.cancel();
                    Animation.swipeReveal(element, { top: top, left: left });
                }

                // Immediately begins the last phase of the SRG animation which animates the item back to its original location
                var finishAnimation = function () {
                    that.selfRevealGesture._promise.cancel();
                    var selectionHint = that.selectionHint;
                    that.selectionHint = null;
                    return swipeHide().then(function () {
                        cleanUp(selectionHint);
                    });
                }

                this.prepareItem(index, element, selected);
                this.showSelectionHintCheckmark();

                this.pointerTriggeredSRG = true;
                this.selfRevealGesture = {
                    freezeAnimation: freezeAnimation,
                    finishAnimation: finishAnimation,
                    _promise: swipeReveal().
                        then(swipeHide).
                        then(function () {
                            that.hideSelectionHintCheckmark();
                            cleanUp();
                            that.selfRevealGesture = null;
                        })
                };
            }
        },

        endSelfRevealGesture: function SelectionMode_endSelfRevealGesture() {
            if (this.selfRevealGesture) {
                this.selfRevealGesture.finishAnimation();
                this.selfRevealGesture = null;
            }
        },

        onMSPointerMove: function SelectionMode_onMSPointerMove(eventObject) {
            if (this.pointerId === eventObject.pointerId) {
                if (this.gestureRecognizer) {
                    this.gestureRecognizer.processMoveEvents(this.getIntermediatePoints(eventObject));
                }
            }
        },

        onclick: function SelectionMode_onclick(eventObject) {
            if (!this.skipClick) {
                // Handle the UIA invoke action on an item. this.skipClick is false which tells us that we received a click
                // event without an associated MSPointerUp event. This means that the click event was triggered thru UIA 
                // rather than thru the GUI.
                var index = this.site._view.items.index(eventObject.srcElement);

                if (utilities.hasClass(eventObject.srcElement, WinJS.UI._itemClass) && index !== WinJS.UI._INVALID_INDEX) {
                    var allowed = this.selectionAllowed(index);
                    if (allowed.canTapSelect) {
                        this.handleTap(index);
                    }
                    this.fireInvokeEvent(index, eventObject.srcElement);
                }
            }
        },

        _releasedElement: function SelectionMode_releasedElement(eventObject) {
            return document.elementFromPoint(eventObject.clientX, eventObject.clientY);
        },

        onMSPointerUp: function SelectionMode_onMSPointerUp(eventObject) {
            msWriteProfilerMark("WinJS.UI.ListView:MSPointerUp,StartTM");

            this.skipClick = true;
            var that = this;
            var swipeEnabled = this.site._swipeBehavior === WinJS.UI.SwipeBehavior.select;
            setImmediate(function () {
                that.skipClick = false;
            });

            if (this.gestureRecognizer) {
                this.gestureRecognizer.processUpEvent(this.getCurrentPoint(eventObject));
            }

            try {
                // Release the pointer capture to allow in air touch pointers to be reused for multiple interactions
                this.site._canvasProxy.msReleasePointerCapture(eventObject.pointerId);
            } catch (e) {
                // This can throw if SeZo had capture or if the pointer was not already captured
            }

            var site = this.site,
                currentFocus = site._selection._getFocused(),
                touchInput = (eventObject.pointerType === PT_TOUCH),
                items = site._view.items,
                releasedElement = this._releasedElement(eventObject),
                releasedIndex = items.index(releasedElement);

            if (this.pointerId === eventObject.pointerId) {
                if (this.pressedItem) {
                    this.togglePressed(false);
                }

                if (this.pressedItem && !touchInput && this.pressedIndex === releasedIndex) {
                    if (!eventObject.shiftKey) {
                        // Reset the shift selection pivot when the user clicks w/o pressing shift
                        site._selection._pivot = WinJS.UI._INVALID_INDEX;
                    }

                    if (eventObject.shiftKey) {
                        // Shift selection should work when shift or shift+ctrl are depressed for both left- and right-click
                        if (site._selectionAllowed() && site._multiSelection() && site._selection._pivot !== WinJS.UI._INVALID_INDEX) {
                            site._selection.set({
                                firstIndex: Math.min(this.pressedIndex, site._selection._pivot),
                                lastIndex: Math.max(this.pressedIndex, site._selection._pivot)
                            });
                        }
                    } else if (eventObject.ctrlKey || (site._selectionAllowed() && swipeEnabled && this.pointerRightButton)) {
                        // Swipe emulation
                        this.handleSwipeBehavior(this.pressedIndex);
                    }
                }

                if (this.pressedItem && this.swipeBehaviorState !== SwipeBehaviorState.completed) {
                    var upPosition = WinJS.UI._getCursorPos(eventObject);
                    var isTap = Math.abs(upPosition.left - this.pressedPosition.left) <= WinJS.UI._TAP_END_THRESHOLD &&
                            Math.abs(upPosition.top - this.pressedPosition.top) <= WinJS.UI._TAP_END_THRESHOLD;

                    this.endSelfRevealGesture();
                    this.clearItem(this.pressedIndex, this.isSelected(this.pressedIndex));

                    // We do not care whether or not the pressed and released indices are equivalent when the user is using touch. The only time they won't be is if the user
                    // tapped the edge of an item and the pressed animation shrank the item such that the user's finger was no longer over it. In this case, the item should
                    // be considered tapped.
                    // However, if the user is using touch then we must perform an extra check. Sometimes we receive MSPointerUp events when the user intended to pan or swipe.
                    // This extra check ensures that these intended pans/swipes aren't treated as taps.
                    if (!this.pointerRightButton && !this.pointerTriggeredSRG && !eventObject.ctrlKey && !eventObject.shiftKey &&
                            ((touchInput && isTap) ||
                            (!touchInput && this.pressedIndex === releasedIndex))) {
                        this.pressedItem = items.wrapperAt(this.pressedIndex);
                        if (this.canTapSelect) {
                            this.handleTap(this.pressedIndex);
                        }
                        this.fireInvokeEvent(this.pressedIndex, this.pressedItem);
                    }
                }

                if (this.pressedIndex !== WinJS.UI._INVALID_INDEX) {
                    site._changeFocus(this.pressedIndex, true, false, true);
                }

                this.resetPointerDownState();
            }

            msWriteProfilerMark("WinJS.UI.ListView:MSPointerUp,StopTM");
        },

        onMSPointerOut: function SelectionMode_onMSPointerOut(eventObject) {
            if (this.waitingForGot && eventObject.pointerType === PT_TOUCH && this.pointerId === eventObject.pointerId) {
                this.resetPointerDownState();
            }
        },

        onMSPointerCancel: function SelectionMode_onMSPointerCancel(eventObject) {
            if (this.pointerId === eventObject.pointerId) {
                msWriteProfilerMark("WinJS.UI.ListView:MSPointerCancel,info");
                this.resetPointerDownState();
            }
        },

        onMSGotPointerCapture: function SelectionMode_onMSGotPointerCapture(eventObject) {
            if (this.pointerId === eventObject.pointerId) {
                this.waitingForGot = false;
                msWriteProfilerMark("WinJS.UI.ListView:MSGotPointerCapture,info");
            }
        },

        onMSLostPointerCapture: function SelectionMode_onMSLostPointerCapture(eventObject) {
            if (this.pointerId === eventObject.pointerId && eventObject.target === this.site._canvasProxy) {
                msWriteProfilerMark("WinJS.UI.ListView:MSLostPointerCapture,info");
                this.resetPointerDownState();
            }
        },

        // In order for ListView to play nicely with other UI controls such as the app bar, it calls preventDefault on
        // contextmenu events. It does this only when selection is enabled, the event occurred on or within an item, and
        // the event did not occur on an interactive element.
        onContextMenu: function SelectionMode_onContextMenu(eventObject) {
            var itemWrapperElement = this.site._view.items.wrapperFrom(eventObject.srcElement);

            if (this.site._selectionAllowed() && itemWrapperElement && !this.isInteractive(eventObject.srcElement)) {
                eventObject.preventDefault();
            }
        },

        onMSHoldVisual: function SelectionMode_onMSHoldVisual(eventObject) {
            if (!this.isInteractive(eventObject.srcElement)) {
                eventObject.preventDefault();
            }
        },

        onDataChanged: function SelectionMode_onDataChanged() {
            this.resetPointerDownState();
        },

        createGestureRecognizer: function SelectionMode_createGestureRecognizer() {
            if (WinJS.Utilities.hasWinRT) {
                var recognizer = new Windows.UI.Input.GestureRecognizer();
                var settings = Windows.UI.Input.GestureSettings;
                recognizer.gestureSettings = settings.hold | settings.crossSlide | settings.manipulationTranslateX | settings.manipulationTranslateY;
                recognizer.showGestureFeedback = false;

                var that = this;
                recognizer.addEventListener("crosssliding", function (eventObject) {
                    that.dispatchSwipeBehavior(eventObject);
                });
                recognizer.addEventListener("manipulationstarted", function (eventObject) {
                    that.manipulationStarted(eventObject);
                });
                recognizer.addEventListener("holding", function (eventObject) {
                    that.startSelfRevealGesture(eventObject);
                });

                return recognizer;
            } else {
                return null;
            }
        },

        getCurrentPoint: function SelectionMode_getCurrentPoint(eventObject) {
            return Windows.UI.Input.PointerPoint.getCurrentPoint(eventObject.pointerId);
        },

        getIntermediatePoints: function SelectionMode_getIntermediatePoints(eventObject) {
            return Windows.UI.Input.PointerPoint.getIntermediatePoints(eventObject.pointerId);
        },

        startSwipeBehavior: function SelectionMode_startSwipeBehavior() {
            if (WinJS.UI._PerfMeasurement_setCachedRecognizerStatus && this.cachedRecognizer) {
                WinJS.UI._PerfMeasurement_setCachedRecognizerStatus(this.cachedRecognizer.isActive);
            }

            if (!this.cachedRecognizer || this.cachedRecognizer.isActive) {
                releaseWhen(this.cachedRecognizer, function (reco) { return !reco.isActive; });
                this.cachedRecognizer = this.createGestureRecognizer();
            }

            this.gestureRecognizer = this.cachedRecognizer;
            if (this.gestureRecognizer) {
                var thresholds = {
                    rearrangeStart: null
                };

                if (this.site._layout.horizontal) {
                    thresholds.selectionStart = WinJS.UI._VERTICAL_SWIPE_SELECTION_THRESHOLD;
                    thresholds.speedBumpStart = WinJS.UI._VERTICAL_SWIPE_SPEED_BUMP_START;
                    thresholds.speedBumpEnd = WinJS.UI._VERTICAL_SWIPE_SPEED_BUMP_END;
                } else {
                    thresholds.selectionStart = WinJS.UI._HORIZONTAL_SWIPE_SELECTION_THRESHOLD;
                    thresholds.speedBumpStart = WinJS.UI._HORIZONTAL_SWIPE_SPEED_BUMP_START;
                    thresholds.speedBumpEnd = WinJS.UI._HORIZONTAL_SWIPE_SPEED_BUMP_END;
                }

                thresholds.speedBumpStart += thresholds.selectionStart;
                thresholds.speedBumpEnd += thresholds.speedBumpStart;
                this.gestureRecognizer.crossSlideThresholds = thresholds;

                this.gestureRecognizer.crossSlideHorizontally = !this.site._layout.horizontal;
            }
        },

        manipulationStarted: function SelectionMode_manipulationStarted(eventObject) {
            this.resetPointerDownState();
        },

        animateSelectionChange: function SelectionMode_animateSelectionChange(select) {
            var that = this,
                pressedItem = this.pressedItem;

            function toggleClasses() {
                var classOperation = select ? "addClass" : "removeClass";
                utilities[classOperation](pressedItem, WinJS.UI._selectedClass);
                if (that.selectionHint) {
                    var hintCheckMark = getElementWithClass(that.selectionHint, WinJS.UI._selectionHintClass);
                    if (hintCheckMark) {
                        utilities[classOperation](hintCheckMark, WinJS.UI._revealedClass);
                    }
                }
            }

            this.swipeBehaviorSelectionChanged = true;
            this.swipeBehaviorSelected = select;

            var elementsToShowHide = WinJS.UI._getElementsByClasses(this.pressedItem, [WinJS.UI._selectionBorderContainerClass, WinJS.UI._selectionBackgroundClass]);

            if (!select) {
                elementsToShowHide = elementsToShowHide.concat(WinJS.UI._getElementsByClasses(this.pressedItem, [WinJS.UI._selectionCheckmarkBackgroundClass, WinJS.UI._selectionCheckmarkClass]));
            }

            msWriteProfilerMark("WinJS.UI.ListView:" + (select ? "hitSelectThreshold" : "hitUnselectThreshold") + ",info");

            this.applyUIInBatches(function () {
                msWriteProfilerMark("WinJS.UI.ListView:" + (select ? "apply" : "remove") + "SelectionVisual,info");
                var opacity = (select ? 1 : 0);
                for (var i = 0; i < elementsToShowHide.length; i++) {
                    elementsToShowHide[i].style.opacity = opacity;
                }

                toggleClasses();
            });
        },

        isSelected: function SelectionMode_isSelected(index) {
            return (!this.swipeBehaviorSelectionChanged && this.site._selection._isIncluded(index)) || (this.swipeBehaviorSelectionChanged && this.swipeBehaviorSelected);
        },

        endSwipeBehavior: function SelectionMode_endSwipeBehavior(animateBack) {
            var that = this;

            this.flushUIBatches();

            var selectionHint = this.selectionHint;
            this.selectionHint = null;

            if (this.gestureRecognizer) {
                this.gestureRecognizer.completeGesture();
                this.gestureRecognizer = null;
            }

            return new Promise(function (complete) {
                var pressedIndex = that.pressedIndex,
                    selected = that.isSelected(pressedIndex);

                function cleanUp() {
                    if (!that.site._isZombie()) {
                        that.clearItem(pressedIndex, that.site._selection._isIncluded(pressedIndex));
                        if (selectionHint) {
                            that.removeSelectionHint(selectionHint);
                        }
                        delete that.animations[pressedIndex];

                        complete();
                    }
                }

                if (!that.pressedItem) {
                    complete();
                } else if (animateBack) {
                    if (selected) {
                        var elementsToShowHide = WinJS.UI._getElementsByClasses(that.pressedItem, [WinJS.UI._selectionCheckmarkClass, WinJS.UI._selectionCheckmarkBackgroundClass]);
                        for (var i = 0; i < elementsToShowHide.length; i++) {
                            elementsToShowHide[i].style.opacity = 1;
                        }
                    }
                    that.animations[pressedIndex] = Animation.swipeSelect(that.pressedItem, []);
                    that.animations[pressedIndex].then(cleanUp, cleanUp);
                } else {
                    cleanUp();
                }
            });
        },

        dispatchSwipeBehavior: function SelectionMode_dispatchSwipeBehavior(eventObject) {
            if (this.pressedItem) {
                if (this.swipeBehaviorState !== eventObject.crossSlidingState) {
                    if (eventObject.crossSlidingState === SwipeBehaviorState.started) {
                        msWriteProfilerMark("WinJS.UI.ListView:crossSlidingStarted,info");
                        var site = this.site,
                            items = site._view.items,
                            pressedElement = items.itemAt(this.pressedIndex),
                            selected = site._selection._isIncluded(this.pressedIndex);

                        if (this.selfRevealGesture) {
                            this.selfRevealGesture.freezeAnimation();
                            this.selfRevealGesture = null;
                        } else if (this.canSelect) {
                            this.prepareItem(this.pressedIndex, pressedElement, selected);
                        }

                        if (utilities.hasClass(pressedElement, WinJS.UI._pressedClass)) {
                            utilities.removeClass(pressedElement, WinJS.UI._pressedClass);
                        }

                        this.swipeBehaviorTransform = "";
                        this.showSelectionHintCheckmark();
                    } else if (eventObject.crossSlidingState === SwipeBehaviorState.completed) {
                        msWriteProfilerMark("WinJS.UI.ListView:crossSlidingCompleted,info");
                        var that = this,
                            site = this.site,
                            selection = site._selection,
                            pressedIndex = this.pressedIndex,
                            swipeBehaviorSelectionChanged = this.swipeBehaviorSelectionChanged,
                            swipeBehaviorSelected = this.swipeBehaviorSelected;


                        // snap back and remove addional elements
                        this.endSwipeBehavior(true);
                        if (swipeBehaviorSelectionChanged) {
                            if (site._selectionAllowed() && site._swipeBehavior === WinJS.UI.SwipeBehavior.select) {
                                if (site._selectionMode === WinJS.UI.SelectionMode.single) {
                                    if (swipeBehaviorSelected) {
                                        selection.set(pressedIndex);
                                    } else if (selection._isIncluded(pressedIndex)) {
                                        selection.remove(pressedIndex);
                                    }
                                } else {
                                    if (swipeBehaviorSelected) {
                                        selection.add(pressedIndex);
                                    } else if (selection._isIncluded(pressedIndex)) {
                                        selection.remove(pressedIndex);
                                    }
                                }
                            }
                        }
                    } else if (SwipeBehaviorState.selected(eventObject.crossSlidingState) && !SwipeBehaviorState.selected(this.swipeBehaviorState) && this.canSelect) {
                        this.animateSelectionChange(!this.site._selection._isIncluded(this.pressedIndex));
                    } else if (!SwipeBehaviorState.selected(eventObject.crossSlidingState) && SwipeBehaviorState.selected(this.swipeBehaviorState) && this.canSelect) {
                        this.animateSelectionChange(this.site._selection._isIncluded(this.pressedIndex));
                    }
                    this.swipeBehaviorState = eventObject.crossSlidingState;
                }

                if (eventObject.crossSlidingState !== SwipeBehaviorState.completed) {
                    // When swiping we get many pointer move events to update the UI. To save the CPU and layout work
                    // we only do one transform per animation frame.
                    this.crossSlideTransformOffset = Math.floor(eventObject.position[this.site._layout.horizontal ? "y" : "x"]) - this.swipeBehaviorStart;
                    this.applyUIInBatches(this._processTransform.bind(this));
                }
            }
        },

        _processTransform: function SelectionMode_processTransform() {
            if (this.pressedItem && +this.crossSlideTransformOffset === this.crossSlideTransformOffset) {
                msWriteProfilerMark("WinJS.UI.ListView:applyCrossSlideTransform,info");
                var transform = "translate" + (this.site._layout.horizontal ? "Y" : "X") + "(" + this.crossSlideTransformOffset + "px)";
                this.pressedItem.style.transform = this.swipeBehaviorTransform + " " + transform;
                this.crossSlideTransformOffset = null;
            }
        },

        applyUIInBatches: function SelectionMode_applyUIInBatches(work) {
            var that = this;
            this._work.push(work);

            if (!this._paintedThisFrame) {
                applyUI();
            }

            function applyUI() {
                if (that._work.length > 0) {
                    that.flushUIBatches();
                    that._paintedThisFrame = requestAnimationFrame(applyUI.bind(that));
                } else {
                    that._paintedThisFrame = null;
                }
            }
        },

        flushUIBatches: function SelectionMode_flushUIBatches() {
            if (this._work.length > 0) {
                var workItems = this._work;
                this._work = [];

                for (var i = 0; i < workItems.length; i++) {
                    workItems[i]();
                }
            }
        },

        showSelectionHintCheckmark: function SelectionMode_showSelectionHintCheckmark() {
            if (this.selectionHint) {
                var hintCheckMark = getElementWithClass(this.selectionHint, WinJS.UI._selectionHintClass);
                if (hintCheckMark) {
                    hintCheckMark.style.display = 'block';
                }
            }
        },

        hideSelectionHintCheckmark: function SelectionMode_hideSelectionHintCheckmark() {
            if (this.selectionHint) {
                var hintCheckMark = getElementWithClass(this.selectionHint, WinJS.UI._selectionHintClass);
                if (hintCheckMark) {
                    hintCheckMark.style.display = 'none';
                }
            }
        },

        addSelectionHint: function SelectionMode_addSelectionHint() {
            var selectionHint = this.selectionHint = document.createElement("div");
            selectionHint.className = WinJS.UI._wrapperClass + " " + WinJS.UI._footprintClass;

            if (!this.site._selection._isIncluded(this.pressedIndex)) {
                var element = document.createElement("div");
                element.className = WinJS.UI._selectionHintClass;
                element.innerText = WinJS.UI._SELECTION_CHECKMARK;
                element.style.display = 'none';
                this.selectionHint.appendChild(element);
            }

            var that = this;
            this.site._layout.getItemPosition(this.pressedIndex).then(function (pos) {
                if (!that.site._isZombie() && that.selectionHint && that.selectionHint === selectionHint) {
                    var style = selectionHint.style;
                    var cssText = ";position:absolute;" +
                        (that.site._rtl() ? "right:" : "left:") + pos.left + "px;top:" +
                        pos.top + "px;width:" + pos.contentWidth + "px;height:" + pos.contentHeight + "px";
                    style.cssText += cssText;
                    that.site._itemCanvas.insertBefore(that.selectionHint, that.pressedItem);
                }
            }, function() {
                // Swallow errors in case data source changes
            });
        },

        removeSelectionHint: function SelectionMode_removeSelectionHint(selectionHint) {
            if (!selectionHint) {
                selectionHint = this.selectionHint;
                this.selectionHint = null;
            }
            if (selectionHint && selectionHint.parentNode) {
                selectionHint.parentNode.removeChild(selectionHint);
            }
        },

        onDragStart: function SelectionMode_onDragStart(eventObject) {
            eventObject.preventDefault();
        },

        onKeyDown: function SelectionMode_onKeyDown(eventObject) {
            if (eventObject.altKey) {
                return;
            }

            var that = this,
                site = this.site,
                swipeEnabled = site._swipeBehavior === WinJS.UI.SwipeBehavior.select,
                view = site._view,
                oldFocus = site._selection._getFocused(),
                handled = true,
                handlerName,
                ctrlKeyDown = eventObject.ctrlKey;

            function setNewFocus(newFocus, skipSelection, clampToBounds) {
                // We need to get the final item in the view so that we don't try setting focus out of bounds.
                return view.finalItem().then(function (maxIndex) {
                    var moveView = true,
                        invalidIndex = false;
                    // Since getKeyboardNavigatedItem is purely geometry oriented, it can return us out of bounds numbers, so this check is necessary
                    if (clampToBounds) {
                        newFocus = Math.max(0, Math.min(maxIndex, newFocus));
                    } else if (newFocus < 0 || newFocus > maxIndex) {
                        invalidIndex = true;
                    }
                    if (!invalidIndex && oldFocus !== newFocus) {
                        var navigationEvent = document.createEvent("CustomEvent");
                        navigationEvent.initCustomEvent("keyboardnavigating", true, true, {
                            oldFocus: oldFocus,
                            newFocus: newFocus
                        });
                        var changeFocus = that.site._element.dispatchEvent(navigationEvent);
                        if (changeFocus) {
                            site._changeFocus(newFocus, skipSelection, ctrlKeyDown, false, true);
                            moveView = false;
                        }
                    }

                    // When a key is pressed, we want to make sure the current focus is in view. If the keypress is changing to a new valid index,
                    // _changeFocus will handle moving the viewport for us. If the focus isn't moving, though, we need to put the view back on
                    // the current item ourselves and call setFocused(oldFocus, true) to make sure that the listview knows the focused item was
                    // focused via keyboard and renders the rectangle appropriately.
                    if (moveView) {
                        site._selection._setFocused(oldFocus, true);
                        site.ensureVisible(oldFocus);
                    }
                    if (invalidIndex) {
                        return WinJS.UI._INVALID_INDEX;
                    } else {
                        return newFocus;
                    }
                });
            }

            var Key = utilities.Key,
                keyCode = eventObject.keyCode;

            if (!this.isInteractive(eventObject.srcElement)) {
                if (eventObject.ctrlKey && !eventObject.altKey && !eventObject.shiftKey && this.keyboardAcceleratorHandlers[keyCode]) {
                    this.keyboardAcceleratorHandlers[keyCode]();
                }

                if (this.keyboardNavigationHandlers[keyCode]) {
                    this.keyboardNavigationHandlers[keyCode](oldFocus).then(function (index) {
                        var clampToBounds = that.keyboardNavigationHandlers[keyCode].clampToBounds;
                        if (eventObject.shiftKey && site._selectionAllowed() && site._multiSelection()) {
                            // Shift selection should work when shift or shift+ctrl are depressed
                            if (site._selection._pivot === WinJS.UI._INVALID_INDEX) {
                                site._selection._pivot = oldFocus;
                            }
                            setNewFocus(index, true, clampToBounds).then(function (newFocus) {
                                if (newFocus !== WinJS.UI._INVALID_INDEX) {
                                    site._selection.set({
                                        firstIndex: Math.min(newFocus, site._selection._pivot),
                                        lastIndex: Math.max(newFocus, site._selection._pivot)
                                    });
                                }
                            });
                        } else {
                            site._selection._pivot = WinJS.UI._INVALID_INDEX;
                            setNewFocus(index, false, clampToBounds);
                        }
                    });
                } else if (!eventObject.ctrlKey && keyCode === Key.enter) {
                    var item = site._view.items.itemAt(oldFocus);
                    if (item) {
                        this.pressedIndex = oldFocus;
                        this.pressedItem = item;

                        var allowed = this.selectionAllowed(oldFocus);
                        if (allowed.canTapSelect) {
                            this.handleTap(oldFocus);
                        }
                        this.fireInvokeEvent(oldFocus, this.pressedItem);

                        // Check if fireInvokeEvent changed the data source, which caused pressedItem to become null
                        if (this.pressedItem) {
                            this.pressedItem = null;
                            this.pressedIndex = WinJS.UI._INVALID_INDEX;
                            this.site._changeFocus(oldFocus, true, ctrlKeyDown, false, true);
                        }
                    }
                } else if (eventObject.ctrlKey && keyCode === Key.enter ||
                        (swipeEnabled && eventObject.shiftKey && keyCode === Key.F10) ||
                        (swipeEnabled && keyCode === Key.menu) ||
                        keyCode === Key.space) {
                    // Swipe emulation
                    this.handleSwipeBehavior(oldFocus);
                    this.site._changeFocus(oldFocus, true, ctrlKeyDown, false, true);
                } else if (keyCode === Key.escape && this.site._selection.count() > 0) {
                    site._selection._pivot = WinJS.UI._INVALID_INDEX;
                    site._selection.clear();
                } else {
                    handled = false;
                }

                if (handled) {
                    eventObject.stopPropagation();
                    eventObject.preventDefault();
                }
            }

            if (keyCode === Key.tab) {
                this.site._keyboardFocusInbound = true;
            }
        }
    };

    WinJS.Namespace.define("WinJS.UI", {
        _DataTransfer: function () {
            this.formatsMap = {};
            this.dropEffect = "move";
        }
    });

    WinJS.UI._DataTransfer.prototype = {
        setData: function DataTransfer_setData(format, data) {
            this.formatsMap[format] = data;
        },

        getData: function DataTransfer_getData(format) {
            return this.formatsMap[format];
        },

        count: function DataTransfer_count() {
            return Object.keys(this.formatsMap).length;
        }
    };
})(this, WinJS);

(function constantsInit(global, WinJS, undefined) {
    "use strict";

    var thisWinUI = WinJS.UI;
    thisWinUI._listViewClass = "win-listview";
    thisWinUI._viewportClass = "win-viewport";
    thisWinUI._rtlListViewClass = "win-rtl";
    thisWinUI._horizontalClass = "win-horizontal";
    thisWinUI._verticalClass = "win-vertical";
    thisWinUI._scrollableClass = "win-surface";
    thisWinUI._proxyClass = "_win-proxy";
    thisWinUI._backdropClass = "win-backdrop";
    thisWinUI._itemClass = "win-item";
    thisWinUI._wrapperClass = "win-container";
    thisWinUI._footprintClass = "win-footprint";
    thisWinUI._groupsClass = "win-groups";
    thisWinUI._selectedClass = "win-selected";
    thisWinUI._swipeableClass = "win-swipeable";
    thisWinUI._swipeClass = "win-swipe";
    thisWinUI._selectionBorderContainerClass = "win-selectionbordercontainer";
    thisWinUI._selectionBorderClass = "win-selectionborder";
    thisWinUI._selectionBorderTopClass = "win-selectionbordertop";
    thisWinUI._selectionBorderRightClass = "win-selectionborderright";
    thisWinUI._selectionBorderBottomClass = "win-selectionborderbottom";
    thisWinUI._selectionBorderLeftClass = "win-selectionborderleft";
    thisWinUI._selectionBackgroundClass = "win-selectionbackground";
    thisWinUI._selectionCheckmarkClass = "win-selectioncheckmark";
    thisWinUI._selectionCheckmarkBackgroundClass = "win-selectioncheckmarkbackground";
    thisWinUI._selectionPartsSelector = ".win-selectionbordercontainer, .win-selectionbackground, .win-selectioncheckmark, .win-selectioncheckmarkbackground";
    thisWinUI._pressedClass = "win-pressed";
    thisWinUI._headerClass = "win-groupheader";
    thisWinUI._progressClass = "win-progress";
    thisWinUI._selectionHintClass = "win-selectionhint";
    thisWinUI._revealedClass = "win-revealed";
    thisWinUI._itemFocusClass = "win-focused";
    thisWinUI._itemFocusOutlineClass = "win-focusedoutline";
    thisWinUI._zoomingXClass = "win-zooming-x";
    thisWinUI._zoomingYClass = "win-zooming-y";
    
    thisWinUI._INVALID_INDEX = -1;
    thisWinUI._UNINITIALIZED = -1;

    thisWinUI._LEFT_MSPOINTER_BUTTON = 0;
    thisWinUI._RIGHT_MSPOINTER_BUTTON = 2;

    thisWinUI._TAP_END_THRESHOLD = 10;
    
    thisWinUI._DEFAULT_PAGES_TO_LOAD = 5;
    thisWinUI._DEFAULT_PAGE_LOAD_THRESHOLD = 2;
    thisWinUI._INCREMENTAL_CANVAS_PADDING = 100;

    thisWinUI._DEFERRED_ACTION = 500;

    // For horizontal layouts
    thisWinUI._VERTICAL_SWIPE_SELECTION_THRESHOLD = 39;
    thisWinUI._VERTICAL_SWIPE_SPEED_BUMP_START = 0;
    thisWinUI._VERTICAL_SWIPE_SPEED_BUMP_END = 127;
    thisWinUI._VERTICAL_SWIPE_SELF_REVEAL_GESTURE = 15;

    // For vertical layouts
    thisWinUI._HORIZONTAL_SWIPE_SELECTION_THRESHOLD = 27;
    thisWinUI._HORIZONTAL_SWIPE_SPEED_BUMP_START = 0;
    thisWinUI._HORIZONTAL_SWIPE_SPEED_BUMP_END = 150;
    thisWinUI._HORIZONTAL_SWIPE_SELF_REVEAL_GESTURE = 23;

    thisWinUI._SELECTION_CHECKMARK = "\uE081";

    thisWinUI._LISTVIEW_PROGRESS_DELAY = 2000;
})(this, WinJS);

(function errorMessagesInit(global, WinJS, undefined) {
    "use strict";

    WinJS.Namespace.define("WinJS.UI._strings", {

        layoutIsInvalid: {
            get: function () { return WinJS.Resources._getWinJSString("ui/layoutIsInvalid").value; }
        },

        modeIsInvalid: {
            get: function () { return WinJS.Resources._getWinJSString("ui/modeIsInvalid").value; }
        },

        loadingBehaviorIsInvalid: {
            get: function () { return WinJS.Resources._getWinJSString("ui/loadingBehaviorIsInvalid").value; }
        },

        pagesToLoadIsInvalid: {
            get: function () { return WinJS.Resources._getWinJSString("ui/pagesToLoadIsInvalid").value; }
        },

        pagesToLoadThresholdIsInvalid: {
            get: function () { return WinJS.Resources._getWinJSString("ui/pagesToLoadThresholdIsInvalid").value; }
        },

        automaticallyLoadPagesIsInvalid: {
            get: function () { return WinJS.Resources._getWinJSString("ui/automaticallyLoadPagesIsInvalid").value; }
        },

        layoutNotInitialized: {
            get: function () { return WinJS.Resources._getWinJSString("ui/layoutNotInitialized").value; }
        },

        invalidTemplate: {
            get: function () { return WinJS.Resources._getWinJSString("ui/invalidTemplate").value; }
        }

    });

})(this, WinJS);

(function groupsContainerInit(global, WinJS, undefined) {
    "use strict";

    var utilities = WinJS.Utilities,
    Promise = WinJS.Promise;

    // This component is responsible for dividing the items into groups and storing the information about these groups.
    WinJS.Namespace.define("WinJS.UI", {
        _GroupsContainer: function (listView, groupDataSource) {
            this._listView = listView;
            this.groupDataSource = groupDataSource;
            this.groups = [];
            this.groupsStage = [];
            this.pendingChanges = [];
            this.dirty = true;

            var that = this,
            notificationHandler = {
                beginNotifications: function GroupsContainer_beginNotifications() {
                    that._listView._versionManager.beginNotifications();
                },

                endNotifications: function GroupsContainer_endNotifications() {
                    //#DBG _ASSERT(that.assertValid());
                    that._listView._versionManager.endNotifications();

                    if (that._listView._ifZombieDispose()) { return; }

                    if (!that.ignoreChanges && that._listView._groupsChanged) {
                        that._listView._scheduleUpdate();
                    }
                },

                indexChanged: function GroupsContainer_indexChanged(item, newIndex, oldIndex) {
                    that._listView._versionManager.receivedNotification();

                    if (that._listView._ifZombieDispose()) { return; }

                    this.scheduleUpdate();
                },

                itemAvailable: function GroupsContainer_itemAvailable(item, placeholder) {
                },

                countChanged: function GroupsContainer_countChanged(newCount, oldCount) {
                    that._listView._versionManager.receivedNotification();

                    if (that._listView._ifZombieDispose()) { return; }

                    this.scheduleUpdate();
                },

                changed: function GroupsContainer_changed(newItem, oldItem) {
                    that._listView._versionManager.receivedNotification();

                    if (that._listView._ifZombieDispose()) { return; }

                    //#DBG _ASSERT(newItem.key == oldItem.key);
                    var groupEntry = that.stageObject.fromKey(newItem.key);
                    if (groupEntry) {
                        groupEntry.group.userData = newItem;
                        groupEntry.group.startIndex = newItem.firstItemIndexHint;
                        //#DBG _ASSERT(that.assertValid());
                        this.markToRemove(groupEntry.group);
                    }

                    this.scheduleUpdate();
                },

                removed: function GroupsContainer_removed(itemHandle, mirage) {
                    that._listView._versionManager.receivedNotification();

                    if (that._listView._ifZombieDispose()) { return; }

                    var groupEntry = that.stageObject.fromHandle(itemHandle);
                    if (groupEntry) {
                        that.groupsStage.splice(groupEntry.index, 1);
                        var index = that.groups.indexOf(groupEntry.group, groupEntry.index);

                        if (index > -1) {
                            that.groups.splice(index, 1);
                        }

                        //#DBG _ASSERT(that.assertValid());
                        this.markToRemove(groupEntry.group);
                    }

                    this.scheduleUpdate();
                },

                inserted: function GroupsContainer_inserted(itemPromise, previousHandle, nextHandle) {
                    that._listView._versionManager.receivedNotification();

                    if (that._listView._ifZombieDispose()) { return; }

                    var notificationHandler = this;
                    itemPromise.retain().then(function (item) {
                        //#DBG _ASSERT(!that.stageObject.fromKey(item.key))

                        var index = notificationHandler.findIndex(previousHandle, nextHandle);
                        if (index !== -1) {
                            var newGroup = {
                                key: item.key,
                                startIndex: item.firstItemIndexHint,
                                userData: item,
                                handle: itemPromise.handle
                            };
                            newGroup.startFound = Promise.wrap(newGroup);

                            that.groupsStage.splice(index, 0, newGroup);
                            that._updateGroupsView();
                        }
                        notificationHandler.scheduleUpdate();
                    });
                    that.pendingChanges.push(itemPromise);
                },

                moved: function GroupsContainer_moved(itemPromise, previousHandle, nextHandle) {
                    that._listView._versionManager.receivedNotification();

                    if (that._listView._ifZombieDispose()) { return; }

                    var notificationHandler = this;
                    itemPromise.then(function (item) {
                        var newIndex = notificationHandler.findIndex(previousHandle, nextHandle),
                            groupEntry = that.stageObject.fromKey(item.key);

                        if (groupEntry) {
                            that.groupsStage.splice(groupEntry.index, 1);

                            if (newIndex !== -1) {
                                if (groupEntry.index < newIndex) {
                                    newIndex--;
                                }

                                groupEntry.group.key = item.key;
                                groupEntry.group.userData = item;
                                groupEntry.group.startIndex = item.firstItemIndexHint;
                                that.groupsStage.splice(newIndex, 0, groupEntry.group);
                            }

                            that._updateGroupsView();
                        } else if (newIndex !== -1) {
                            var newGroup = {
                                key: item.key,
                                startIndex: item.firstItemIndexHint,
                                userData: item,
                                handle: itemPromise.handle
                            };
                            newGroup.startFound = Promise.wrap(newGroup);
                            that.groupsStage.splice(newIndex, 0, newGroup);
                            that._updateGroupsView();
                            itemPromise.retain();
                        }

                        //#DBG _ASSERT(that.assertValid());
                        notificationHandler.scheduleUpdate();
                    });
                    that.pendingChanges.push(itemPromise);
                },

                reload: function GroupsContainer_reload() {
                    that._listView._versionManager.receivedNotification();

                    if (that._listView._ifZombieDispose()) {
                        return;
                    }

                    for (var i = 0, len = that.groups.length; i < len; i++) {
                        this.removeElements(that.groups[i]);
                    }

                    // Set the lengths to zero to clear the arrays, rather than setting = [], which re-instantiates
                    that.groups.length = 0;
                    that.groupsStage.length = 0;
                    delete that.pinnedItem;
                    delete that.pinnedOffset;
                    this.scheduleUpdate();
                },

                markToRemove: function GroupsContainer_markToRemove(group) {
                    if (group.elements) {
                        var elements = group.elements;
                        group.elements = null;
                        group.left = -1;
                        group.width = -1;
                        group.decorator = null;

                        that._listView._groupsToRemove[elements.header.uniqueID] = elements.header;
                        that._listView._groupsToRemove[elements.group.uniqueID] = elements.group;
                    }
                },

                scheduleUpdate: function GroupsContainer_scheduleUpdate() {
                    that.dirty = true;
                    if (!that.ignoreChanges) {
                        that._listView._groupsChanged = true;
                    }
                },

                findIndex: function GroupsContainer_findIndex(previousHandle, nextHandle) {
                    var index = -1,
                        groupEntry;

                    if (previousHandle) {
                        groupEntry = that.stageObject.fromHandle(previousHandle);
                        if (groupEntry) {
                            index = groupEntry.index + 1;
                        }
                    }

                    if (index === -1 && nextHandle) {
                        groupEntry = that.stageObject.fromHandle(nextHandle);
                        if (groupEntry) {
                            index = groupEntry.index;
                        }
                    }

                    return index;
                },

                removeElements: function GroupsContainer_removeElements(group) {
                    if (group.elements) {
                        var canvas = that._listView._canvas;
                        canvas.removeChild(group.elements.header);
                        canvas.removeChild(group.elements.group);
                        group.elements = null;
                        group.left = -1;
                        group.width = -1;
                    }
                }
            };

            this.listBinding = this.groupDataSource.createListBinding(notificationHandler);

            // This object is used to call a few functions below in a context that redirects
            // references to the "groups" array to the "groupsStage" array
            // This saves us from having to duplicate these functions.
            // Note that we don't redirect the "dirty" property because we don't want that bit
            // flipped when we modify groupsStage.
            this.stageObject = {
                groups: that.groupsStage,
                groupFrom: function () {
                    return that.groupFrom.apply(that.stageObject, arguments);
                },
                groupFromImpl: function () {
                    return that.groupFromImpl.apply(that.stageObject, arguments);
                },
                fromKey: function () {
                    return that.fromKey.apply(that.stageObject, arguments);
                },
                fromHandle: function () {
                    return that.fromHandle.apply(that.stageObject, arguments);
                }
            };
        }
    });

    WinJS.UI._GroupsContainer.prototype = {
        _updateGroupsView: function GroupsContainer_updateGroupsView() {
            var that = this;
            this.groups = [];

            this.groupsStage.forEach(function (group) {
                if (group.userData !== undefined) {
                    that.groups.push(group);
                }
            });
        },

        addItem: function GroupsContainer_addItem(itemIndex, itemPromise) {
            var that = this;
            return this.ensureFirstGroup().then(function () {
                return itemPromise;
            }).then(function (item) {
                if (!item) {
                    return WinJS.Promise.cancel;
                }

                var currentIndex = that.groupFromItem.call(that.stageObject, itemIndex);

                var currentGroup = null,
                    currentGroupKey = null,
                    nextGroup = null,
                    previousGroup = null;

                if (currentIndex !== null) {
                    currentGroup = that.groupsStage[currentIndex];
                    currentGroupKey = currentGroup.key;

                    if (currentIndex + 1 < that.groupsStage.length) {
                        nextGroup = that.groupsStage[currentIndex + 1];
                    }
                    if (currentIndex > 0) {
                        previousGroup = that.groupsStage[currentIndex - 1];
                    }
                }

                var newGroupKey = item.groupKey;
                //#DBG _ASSERT(newGroupKey);
                if (currentGroupKey && newGroupKey === currentGroupKey) {
                    if (itemIndex < currentGroup.startIndex) {
                        currentGroup.startIndex = itemIndex;
                        that.dirty = true;
                    }
                    //#DBG _ASSERT(that.assertValid());
                    // The item belongs to the current group
                    return currentGroup.startFound;
                    // Maybe the item belongs to the next group. This can happen when the beginning of the next group is still not known (nextGroup.startFound !== undefined).
                } else if (nextGroup && nextGroup.key === newGroupKey) {
                    return nextGroup.startFound;
                } else if (previousGroup && previousGroup.key === newGroupKey) {
                    return previousGroup.startFound;
                } else {
                    // The item belongs to a new group
                    var newGroup = {
                        key: newGroupKey,
                        startIndex: itemIndex
                    };
                    that.addGroup.call(that.stageObject, currentGroup, currentIndex, newGroup);
                    //#DBG _ASSERT(that.assertValid());
                    newGroup.startFound = that.listBinding.fromKey(newGroupKey, { groupMemberKey: item.key, groupMemberIndex: itemIndex });
                    newGroup.handle = newGroup.startFound.handle;
                    newGroup.startFound.retain().then(function (newGroupData) {
                        if (newGroupData) {
                            newGroup.userData = newGroupData;
                            newGroup.startIndex = newGroupData.firstItemIndexHint;
                            that._updateGroupsView();

                            that.dirty = true;
                            //#DBG _ASSERT(that.assertValid());
                            return newGroup;
                        } else {
                            return WinJS.Promise.cancel;
                        }
                    }).then(null, function (err) {
                        for (var i = 0, len = that.groupsStage.length; i < len; i++) {
                            if (that.groupsStage[i] === newGroup) {
                                that.groupsStage.splice(i, 1);
                                break;
                            }
                        }
                        return WinJS.Promise.wrapError(err);
                    });
                    return newGroup.startFound;
                }
            });
        },

        ensureFirstGroup: function GroupsContainer_ensureFirstGroup() {
            var that = this;

            function firstGroupLoaded() {
                return that.groups.length > 0 && that.groups[0].startIndex === 0;
            }

            if (firstGroupLoaded()) {
                return Promise.wrap();
            }

            var itemPromise = this.listBinding.first().retain();
            return itemPromise.then(function (firstGroupData) {
                if (firstGroupData) {
                    if (firstGroupLoaded()) {
                        // Somebody loaded the first group before us so we don't need to retain it
                        itemPromise.release();
                    } else {
                        var newGroup = {
                            key: firstGroupData.key,
                            startIndex: firstGroupData.firstItemIndexHint,
                            userData: firstGroupData,
                            handle: firstGroupData.handle
                        };
                        newGroup.startFound = Promise.wrap(newGroup);
                        that.groups.unshift(newGroup);
                        that.groupsStage.unshift(newGroup);
                        that.dirty = true;

                        //#DBG _ASSERT(that.assertValid());

                        return newGroup;
                    }
                } else {
                    return WinJS.Promise.cancel;
                }
            });
        },

        addGroup: function GroupsContainer_addGroup(currentGroup, currentIndex, toInsert) {
            if (currentGroup) {
                this.groups.splice((currentGroup.startIndex < toInsert.startIndex ? currentIndex + 1 : currentIndex), 0, toInsert);
            } else {
                this.groups.unshift(toInsert);
            }

            this.dirty = true;
        },

        groupFromImpl: function GroupsContainer_groupFromImpl(fromGroup, toGroup, comp) {
            if (toGroup < fromGroup) {
                return null;
            }

            var center = fromGroup + Math.floor((toGroup - fromGroup) / 2),
                centerGroup = this.groups[center];

            if (comp(centerGroup, center)) {
                return this.groupFromImpl(fromGroup, center - 1, comp);
            } else if (center < toGroup && !comp(this.groups[center + 1], center + 1)) {
                return this.groupFromImpl(center + 1, toGroup, comp);
            } else {
                return center;
            }
        },

        groupFrom: function GroupsContainer_groupFrom(comp) {
            //#DBG _ASSERT(this.assertValid());
            if (this.groups.length > 0) {
                var lastGroupIndex = this.groups.length - 1,
                    lastGroup = this.groups[lastGroupIndex];

                if (!comp(lastGroup, lastGroupIndex)) {
                    return lastGroupIndex;
                } else {
                    return this.groupFromImpl(0, this.groups.length - 1, comp);
                }
            } else {
                return null;
            }
        },

        groupFromItem: function GroupsContainer_groupFromItem(itemIndex) {
            return this.groupFrom(function (group) {
                return itemIndex < group.startIndex;
            });
        },

        groupFromOffset: function GroupsContainer_groupFromOffset(offset) {
            //#DBG _ASSERT(this.assertValid());
            return this.groupFrom(function (group, groupIndex) {
                //#DBG _ASSERT(group.offset !== undefined);
                return offset < group.offset;
            });
        },

        group: function GroupsContainer_getGroup(index) {
            return this.groups[index];
        },

        length: function GroupsContainer_length() {
            return this.groups.length;
        },

        renderGroup: function GroupsContainer_renderGroup(index) {
            var group = this.groups[index],
                renderedHeaderPromise,
                renderedGroupPromise;

            if (this._listView.groupHeaderTemplate) {
                renderedHeaderPromise = this._listView._headersPool.renderItemAsync(Promise.wrap(group.userData));
                renderedGroupPromise = this._listView._groupsPool.renderItemAsync(Promise.wrap(null));
                return Promise.join({ header: renderedHeaderPromise, group: renderedGroupPromise });
            } else {
                return Promise.wrap(null);
            }
        },

        setDomElements: function GroupsContainer_setDomElements(index, headerElement, groupElement) {
            var group = this.groups[index];
            //#DBG _ASSERT(!group.elements);
            group.elements = {
                header: headerElement,
                group: groupElement
            };
        },

        removeElements: function GroupsContainer_removeElements() {
            var canvas = this._listView._canvas,
                elements = this._listView._groupsToRemove || {},
                keys = Object.keys(elements);

            for (var i = 0, len = keys.length; i < len; i++) {
                var element = elements[keys[i]];
                canvas.removeChild(element);
            }

            this._listView._groupsToRemove = {};
        },

        resetGroups: function GroupsContainer_resetGroups() {
            var groupsStage = this.groupsStage.slice(0);

            for (var i = 0, len = groupsStage.length; i < len; i++) {
                var group = groupsStage[i];

                group.startFound.cancel();
                if (this.listBinding && group.userData) {
                    this.listBinding.releaseItem(group.userData);
                }
            }

            // Set the lengths to zero to clear the arrays, rather than setting = [], which re-instantiates
            this.groups.length = 0;
            this.groupsStage.length = 0;
            delete this.pinnedItem;
            delete this.pinnedOffset;
            this.dirty = true;
        },

        pinItem: function GroupsContainer_pinItem(item, offset) {
            this.pinnedItem = item;
            this.pinnedOffset = offset ? offset.offset : null;
            this.dirty = true;
        },

        cleanUp: function GroupsContainer_cleanUp() {
            if (this.listBinding) {
                for (var i = 0, len = this.groups.length; i < len; i++) {
                    var group = this.groups[i];
                    if (group.userData) {
                        this.listBinding.releaseItem(group.userData);
                    }
                }
                this.listBinding.release();
            }
        },

        _dispose: function GroupsContainer_dispose() {
            this.cleanUp();
        },

        /*#DBG
        assertValid: function () {
        if (WinJS.validation) {
        if (this.groups.length) {
        var prevIndex = this.groups[0].startIndex,
        prevKey = this.groups[0].key,
        keys = {};

        //#DBG _ASSERT(prevIndex === 0);
        keys[prevKey] = true;

        for (var i = 1, len = this.groups.length; i < len; i++) {
        var group = this.groups[i];
        //#DBG _ASSERT(group.startIndex > prevIndex);
        prevIndex = group.startIndex;

        //#DBG _ASSERT(!keys[group.key]);
        keys[group.key] = true;

        prevKey = group.key;
        }
        }
        }
        return  true;
        },
        #DBG*/

        groupOf: function GroupsContainer_groupOf(item) {
            return item ? this.addItem(item.index, item) : Promise.wrap();
        },

        synchronizeGroups: function GroupsContainer_synchronizeGroups() {
            var that = this;

            function done() {
                that.ignoreChanges = false;
            }

            this.pendingChanges = [];
            this.ignoreChanges = true;
            return this.groupDataSource.invalidateAll().then(function () {
                return Promise.join(that.pendingChanges);
            }).then(function () {
                if (that._listView._ifZombieDispose()) {
                    return WinJS.Promise.cancel;
                }
            }).then(done, done);
        },

        fromKey: function GroupsContainer_fromKey(key) {
            for (var i = 0, len = this.groups.length; i < len; i++) {
                var group = this.groups[i];
                if (group.key === key) {
                    return {
                        group: group,
                        index: i
                    }
                }
            }
            return null;
        },

        fromHandle: function GroupsContainer_fromHandle(handle) {
            for (var i = 0, len = this.groups.length; i < len; i++) {
                var group = this.groups[i];
                if (group.handle === handle) {
                    return {
                        group: group,
                        index: i
                    }
                }
            }
            return null;
        },

        purgeDecorator: function GroupsContainer_purgeDecorator(index) {
            var group = this.groups[this.groupFromItem(index)];
            if (group) {
                group.decorator = null;
            }
        },

        purgeDecorators: function GroupsContainer_purgeDecorators() {
            for (var i = 0, len = this.groups.length; i < len; i++) {
                this.groups[i].decorator = null;
            }
        }
    };

    WinJS.UI._NoGroups = function (listView) {
        this._listView = listView;
        this.groups = [{ startIndex: 0}];
        this.dirty = true;

        this.synchronizeGroups = function () {
            return WinJS.Promise.wrap();
        };

        this.addItem = function (itemIndex, itemPromise) {
            return WinJS.Promise.wrap(this.groups[0]);
        };

        this.resetGroups = function () {
            this.groups = [{ startIndex: 0}];
            delete this.pinnedItem;
            delete this.pinnedOffset;
            this.dirty = true;
        };

        this.renderGroup = function () {
            return WinJS.Promise.wrap(null);
        };

        this.purgeDecorator = function () {
            this.groups[0].decorator = null;
        };

        this.purgeDecorators = function () {
            this.groups[0].decorator = null;
        };
    };

    WinJS.UI._NoGroups.prototype = WinJS.UI._GroupsContainer.prototype;

})(this, WinJS);

(function horizontalGropuedGridLayoutInit(global, WinJS, undefined) {
    "use strict";


var utilities = WinJS.Utilities,
    Key = utilities.Key,
    Promise = WinJS.Promise,
    Signal = WinJS._Signal,
    Animation = WinJS.UI.Animation,
    AnimationHelper = WinJS.UI._ListViewAnimationHelper;

function getDimension(element, property) {
    return WinJS.Utilities.convertToPixels(element, window.getComputedStyle(element, null)[property]);
}


// This component is responsible for calculating items' positions in horizontal grid mode.
WinJS.Namespace.define("WinJS.UI", {
    Layout: WinJS.Class.define(function Layout_ctor(options) {
        /// <signature helpKeyword="WinJS.UI.Layout.Layout">
        /// <summary locid="WinJS.UI.Layout.constructor">
        /// Creates a new Layout object.
        /// </summary>
        /// <param name="options" type="Object" locid="WinJS.UI.Layout.constructor_p:options">
        /// The set of options to be applied initially to the new Layout object.
        /// </param>
        /// <returns type="WinJS.UI.Layout" locid="WinJS.UI.Layout.constructor_returnValue">
        /// The new Layout object.
        /// </returns>
        /// </signature>
    }),

    _getMargins: function Layout_getMargins(element) {
        return {
            left: getDimension(element, "marginLeft"),
            right: getDimension(element, "marginRight"),
            top: getDimension(element, "marginTop"),
            bottom: getDimension(element, "marginBottom")
        };
    },

    _LayoutCommon: WinJS.Class.derive(WinJS.UI.Layout, function (options) {
    }, {
        init: function _LayoutCommon_init() {
            /// <signature helpKeyword="WinJS.UI._LayoutCommon.init">
            /// <summary locid="WinJS.UI._LayoutCommon.init">
            /// This method supports the Windows Library for JavaScript infrastructure and is not intended to be used directly from your code.
            /// </summary>
            /// </signature>
            this._disableBackdrop = false;
            this._trackedAnimation = null;
            this._items = {};
            this.reset();
        },

        setSite: function _LayoutCommon_setSite(layoutSite) {
            /// <signature helpKeyword="WinJS.UI._LayoutCommon.setSite">
            /// <summary locid="WinJS.UI._LayoutCommon.setSite">
            /// This method supports the Windows Library for JavaScript infrastructure and is not intended to be used directly from your code.
            /// </summary>
            /// <param name="layoutSite" locid="WinJS.UI._LayoutCommon.setSite_p:layoutSite">
            /// 
            /// </param>
            /// </signature>
            this._site = layoutSite;
        },

        /// <field type="Boolean" locid="WinJS.UI._LayoutCommon.disableBackdrop" helpKeyword="WinJS.UI._LayoutCommon.disableBackdrop">
        /// Gets or sets a value that indicates whether the layout should disable the backdrop feature
        /// which avoids blank areas while panning in a virtualized list.
        /// </field>
        disableBackdrop: {
            get: function () {
                return this._disableBackdrop;
            },
            set: function (value) {
                if (value) {
                    // Hide the existing backdrop elements
                    if (this._backdropBefore && this._backdropBefore.parentNode) {
                        this._backdropBefore.parentNode.removeChild(this._backdropBefore);
                    }
                    if (this._backdropAfter && this._backdropAfter.parentNode) {
                        this._backdropAfter.parentNode.removeChild(this._backdropAfter);
                    }
                }
                return this._disableBackdrop = value;
            }
        },

        /// <field type="String" locid="WinJS.UI._LayoutCommon.backdropColor" helpKeyword="WinJS.UI._LayoutCommon.backdropColor">
        /// Gets or sets the fill color for the default pattern used for the backdrops.
        /// The default value is "rgba(155,155,155,0.23)".
        /// </field>
        backdropColor: {
            get: function _LayoutCommon_backdropColor_get() {
                return this._backdropColor || "rgba(155,155,155,0.23)";
            },
            set: function _LayoutCommon_backdropColor_set(color) {
                this._backdropColor = color;

                // Reset the canvas to null so a new background-image is created via canvas
                this._backdropCanvas = null;

                // Hide the existing backdrop so a quick pan after this changes doesn't show the previous backdrop
                if (this._backdropBefore && this._backdropBefore.parentNode) {
                    this._backdropBefore.parentNode.removeChild(this._backdropBefore);
                }
                if (this._backdropAfter && this._backdropAfter.parentNode) {
                    this._backdropAfter.parentNode.removeChild(this._backdropAfter);
                }
            }
        },

        reset: function _LayoutCommon_reset() {
            /// <signature helpKeyword="WinJS.UI._LayoutCommon.reset">
            /// <summary locid="WinJS.UI._LayoutCommon.reset">
            /// This method supports the Windows Library for JavaScript infrastructure and is not intended to be used directly from your code. 
            /// </summary>
            /// </signature>
            if (this._trackedAnimation) {
                this._trackedAnimation.cancelAnimations();
            }

            this._measuring = null; 
            this._totalItemWidth = WinJS.UI._UNINITIALIZED;
            this._totalItemHeight = WinJS.UI._UNINITIALIZED;
            this._itemWidth = WinJS.UI._UNINITIALIZED;
            this._itemHeight = WinJS.UI._UNINITIALIZED;
            this._totalHeaderWidth = WinJS.UI._UNINITIALIZED;
            this._totalHeaderHeight = WinJS.UI._UNINITIALIZED;
            this._itemsPerColumn = WinJS.UI._UNINITIALIZED;
            this._itemMargins = {
                left: 0,
                right: 0,
                top: 0,
                bottom: 0,
                horizontal: 0,
                vertical: 0
            };
            if (this._item0PositionPromise) {
                this._item0PositionPromise.cancel();
                this._item0PositionPromise = null;
            }
            this._backdropCanvas = null;
            this._headerPaddingAndBorder = 0;
            this._headerMargins = {
                left: 0,
                right: 0,
                top: 0
            };
            this._canvasScrollBounds = {
                left: 0,
                right: 0,
            };

            this._cachedInserted = [];
            if (this._cachedRemoved) {
                this._cachedRemoved.forEach(function (element) {
                    if (element.parentNode) {
                        element.parentNode.removeChild(element);
                    }
                });
            }
            this._cachedRemoved = [];
            this._cachedItemRecords = {};
            this._dataModifiedPromise = null;

            if (this._site) {
                if (this._site._groups) {
                    this._site._groups.purgeDecorators();
                }

                this._site.itemSurface.style.clip = "auto";
            }
        },
        
        /// <field type="Function" locid="WinJS.UI._LayoutCommon.itemInfo" helpKeyword="WinJS.UI._LayoutCommon.itemInfo">
        /// Determines the size of the item and whether
        /// the item should be placed in a new column.
        /// </field>
        itemInfo: {
            enumerable: true, 
            get: function () {
                return this._itemSize;
            },
            set: function (itemSize) {
                this._itemSize = itemSize;
                this._invalidateLayout();
            }
        },

        _invalidateLayout: function _LayoutCommon_invalidateLayout() {
            if (this._site) {
                this._site.invalidateLayout();
            }
        },

        _getSize: function _LayoutCommon_getSize(group) {
            if (this._totalItemWidth === WinJS.UI._UNINITIALIZED || this._totalItemHeight === WinJS.UI._UNINITIALIZED) {
                var size;
                if (this._itemSize) {
                    size = (typeof this._itemSize === "function" ? this._itemSize() : this._itemSize);
                } else {
                    // Normalize the getGroupInfo result because it already includes the margins.
                    size = {
                        width: this._getGroupInfo(group).cellWidth - this._itemMargins.horizontal,
                        height: this._getGroupInfo(group).cellHeight - this._itemMargins.vertical
                    };
                }
                this._itemWidth = size.width;
                this._itemHeight = size.height;
                this._totalItemWidth = this._itemWidth + this._itemMargins.horizontal;
                this._totalItemHeight = this._itemHeight + this._itemMargins.vertical;
            }
        },

        _getItemWidth: function _LayoutCommon_getItemWidth(group) {
            this._getSize(group);
            return this._itemWidth;
        },
        
        _getItemHeight: function _LayoutCommon_getItemHeight(group) {
            this._getSize(group);
            return this._itemHeight;
        },
        
        _getTotalItemWidth: function _LayoutCommon_getTotalItemWidth(group) {
            this._getSize(group);
            return this._totalItemWidth;
        },

        _getTotalItemHeight: function _LayoutCommon_getTotalItemHeight(group) {
            this._getSize(group);
            return this._totalItemHeight;
        },

        _getItemInfo: function _LayoutCommon_getItemInfo(index) {
            var cached = this._items[index];
            if (!cached) {
                this._items[index] = cached = {};
            }
            return cached;
        },

        _purgeItemCache: function _LayoutCommon_purgeItemCache(begin, end) {
            var keys = Object.keys(this._items)
            for (var i = 0, len = keys.length; i < len; i++) {
                var index = parseInt(keys[i], 10);
                if (index < begin || index >= end) {
                    delete this._items[index];
                }
            }
        },

        _addElements: function _LayoutCommon_addElements(scratch, element) {
            var wrapper = document.createElement("div");
            utilities.addClass(wrapper, WinJS.UI._wrapperClass);

            // This function clones element returned by itemAtIndex and adds them to viewport.
            // Element is cloned in order to avoid changes to element stored in ItemsManager cache.
            var retVal = [wrapper, element.cloneNode(true)];
            for (var i = 0, len = retVal.length; i < len; i++) {
                scratch.appendChild(retVal[i]);
            }
            return retVal;
        },

        _addHeader: function _LayoutCommon_addHeader(scratch, header) {
            utilities.addClass(header, WinJS.UI._headerClass);

            scratch.appendChild(header);

            return header;
        },

        _measureHeaders: function _LayoutCommon_measureHeaders(header) {
            var width = utilities.getContentWidth(header);
            this._totalHeaderWidth = utilities.getTotalWidth(header);
            this._totalHeaderHeight = utilities.getTotalHeight(header);
            this._headerMargins = WinJS.UI._getMargins(header);
            this._headerPaddingAndBorder = this._totalHeaderWidth - width - this._headerMargins.left - this._headerMargins.right;
        },

        _noHeaders: function _LayoutCommon_noHeaders(headers) {
            this._totalHeaderWidth = this._totalHeaderHeight = this._headerPaddingAndBorder = 0;
            this._headerMargins = {
                left: 0,
                right: 0,
                top: 0
            };
        },
        
        _isEmpty: function _LayoutCommon_isEmpty(count) {
            if (+count === count) {
                return Promise.wrap(count === 0);
            } else {
                return this._site._itemsManager.dataSource.getCount().then(function (count) {
                    return count === 0;
                });
            }
        },

        _initialized: function _LayoutCommon_initialized() {
            return this._measuring;
        },

        _initializeBase: function _LayoutCommon_initializeBase(count) {
            var that = this;
            if (!this._measuring) {
                return this._isEmpty(count).then(function (isEmpty) {
                    if (!isEmpty) {
                        return that._site._groups.ensureFirstGroup().then(function () {
                            return that._measureItems();
                        });
                    } else {
                        return false;
                    }
                });
            } else {
                return this._measuring;
            }
        },

        _measureMargin: function _LayoutCommon_measureMargin(elements) {
            var wrapper = elements[0];

            this._itemMargins = WinJS.UI._getMargins(wrapper);
            this._itemMargins.horizontal = this._itemMargins.left + this._itemMargins.right;
            this._itemMargins.vertical = this._itemMargins.top + this._itemMargins.bottom;
        },

        _measureItem: function _LayoutCommon_measureItem(elements) {
            var element = elements[1];

            if (element.offsetWidth !== 0 && element.offsetHeight !== 0) {
                var totalItemWidth = utilities.getTotalWidth(element),
                    totalItemHeight = utilities.getTotalHeight(element);

                this._itemWidth = totalItemWidth;
                this._itemHeight = totalItemHeight;
                this._totalItemWidth = totalItemWidth + this._itemMargins.horizontal;
                this._totalItemHeight = totalItemHeight + this._itemMargins.vertical;

                return true;
            } else {
                return false;
            }
        },

        _measureItems: function _LayoutCommon_measureItems() {
            if (!this._measuring) {
                var that = this,
                    viewport = that._site.viewport;

                this._measuring = new Promise(function (complete) {
                    var scratch = document.createElement("div");

                    function error() {
                        complete(false);
                    }

                    function computeSizeOfRendered(element, itemResult) {
                        if (element) {
                            var elements = [],
                                header;

                            var measure = function (newGroup) {
                                if (that._site._isZombie()) {
                                    error();
                                    return;
                                }

                                viewport.appendChild(scratch);
                                that._measureMargin(elements);

                                if (!that._multiSize(newGroup) && !that._measureItem(elements)) {
                                    viewport.removeChild(scratch);
                                    error();
                                    return;
                                }

                                if (header) {
                                    that._measureHeaders(header);
                                } else {
                                    that._noHeaders();
                                }

                                viewport.removeChild(scratch);
                                complete(true);
                            }

                            that._site._groupOf(itemResult).then(function (newGroup) {
                                if (newGroup.userData && that._site._groupHeaderTemplate) {
                                    var rendered = WinJS.UI._normalizeRendererReturn(that._site._groupHeaderTemplate(Promise.wrap(newGroup.userData)));
                                    rendered.then(function (headerRecord) {
                                        elements = that._addElements(scratch, element);
                                        header = that._addHeader(scratch, headerRecord.element);
                                        measure(newGroup);
                                    }, error);
                                } else {
                                    elements = that._addElements(scratch, element);
                                    measure(newGroup);
                                }
                            }, error);
                        } else {
                            error();
                        }
                    }
                    
                    Promise.join({
                        element: that._site._itemsManager._itemAtIndex(0),
                        item: that._site._itemsManager._itemPromiseAtIndex(0)
                    }).then(function (v) {
                        computeSizeOfRendered(v.element, v.item);
                    }, error);
                }); 
            }
            return this._measuring;
        },

        _adjustDirection: function _LayoutCommon_adjustDirection(keyPressed) {
            if (this._site.rtl) {
                if (keyPressed === Key.leftArrow) {
                    keyPressed = Key.rightArrow;
                } else if (keyPressed === Key.rightArrow) {
                    keyPressed = Key.leftArrow;
                }
            }
            return keyPressed;
        },

        _setZIndex: function _LayoutCommon_setZIndex(items, zIndex) {
            for (var i = 0, len = items.length; i < len; i++) {
                items[i].style.zIndex = zIndex;
            }
        },

        getKeyboardNavigatedItem: function _LayoutCommon_getKeyboardNavigatedItem(itemIndex, element, keyPressed) {
            /// <signature helpKeyword="WinJS.UI._LayoutCommon.getKeyboardNavigatedItem">
            /// <summary locid="WinJS.UI._LayoutCommon.getKeyboardNavigatedItem">
            /// This method supports the Windows Library for JavaScript infrastructure and is not intended to be used directly from your code.
            /// </summary>
            /// <param name="itemIndex" locid="WinJS.UI._LayoutCommon.setSite_p:itemIndex"></param>
            /// <param name="element" locid="WinJS.UI._LayoutCommon.setSite_p:element"></param>
            /// <param name="keyPressed" locid="WinJS.UI._LayoutCommon.setSite_p: keyPressed"></param>
            /// </signature>
            var scrollbarPos = this._site.scrollbarPos,
                viewportLength = this._site.viewportSize[this.horizontal ? "width" : "height"],
                offsetProp = this.horizontal ? "offsetWidth" : "offsetHeight",
                currentItemLength = (element ? element[offsetProp] : 0),
                that = this;

            if (keyPressed === Key.pageUp) {
                return new Promise(function (complete) {
                    that.calculateFirstVisible(scrollbarPos, true).then(function (firstElementOnPage) {
                        if (itemIndex !== firstElementOnPage) {
                            complete(firstElementOnPage);
                        } else {
                            that.calculateFirstVisible(Math.max(0, scrollbarPos - viewportLength + currentItemLength), false).then(function (newFocus) {
                                // This check is necessary for items that are larger than the viewport
                                complete(newFocus < itemIndex ? newFocus : itemIndex - 1);
                            });
                        }
                    });
                });
            } else {
                //#DBG _ASSERT(keyPressed === Key.pageDown);
                return new Promise(function (complete) {
                    that.calculateLastVisible(scrollbarPos + viewportLength - 1, true).then(function (lastElementOnPage) {
                        if (itemIndex !== lastElementOnPage) {
                            complete(lastElementOnPage);
                        } else {
                            that.calculateLastVisible(scrollbarPos + 2 * viewportLength - currentItemLength - 1, false).then(function (newFocus) {
                                // This check is necessary for items that are larger than the viewport
                                complete(newFocus > itemIndex ? newFocus : itemIndex + 1);
                            });
                        }
                    });
                });
            }
        },

        /// <field type="Function" locid="WinJS.UI._LayoutCommon.groupInfo" helpKeyword="WinJS.UI._LayoutCommon.groupInfo">
        /// Indicates whether a group has variable-sized items.
        /// </field>
        groupInfo: {
            enumerable: true, 
            get: function () {
                return this._groupInfo;
            },
            set: function (groupInfo) {
                this._groupInfo = groupInfo;
                this._invalidateLayout();
            }
        },

        _multiSize: function _LayoutCommon_multiSize(group) {
            return this._groupInfo && this._getGroupInfo(group).enableCellSpanning;
        },

        _getGroupInfo: function _LayoutCommon_getGroupInfo(group) {
            var groupInfo = (typeof this._groupInfo === "function" ? this._groupInfo(group.userData) : this._groupInfo),
                margins = this._itemMargins,
                adjustedInfo = null;

            if (groupInfo) {
                adjustedInfo = {
                    enableCellSpanning: groupInfo.enableCellSpanning,
                    cellWidth: groupInfo.cellWidth + margins.horizontal,
                    cellHeight: groupInfo.cellHeight + margins.vertical
                };
            }
            return adjustedInfo;
        },

        updateBackdrop: function _LayoutCommon_updateBackdrop(count) {
            /// <signature helpKeyword="WinJS.UI._LayoutCommon.updateBackdrop">
            /// <summary locid="WinJS.UI._LayoutCommon.updateBackdrop">
            /// This method supports the Windows Library for JavaScript infrastructure and is not intended to be used directly from your code.
            /// </summary>
            /// <param name="count" locid="WinJS.UI._LayoutCommon.updateBackdrop_p:count"></param>
            /// </signature>

            if (this._disableBackdrop) {
                return;
            }

            // Create the backdrops and reinsert them into the surface if necessary
            if (!this._backdropBefore) {
                this._backdropBefore = document.createElement('div');
                this._backdropBefore.setAttribute("aria-hidden", "true");
                this._backdropBefore.className = WinJS.UI._backdropClass;
            }
            if (!this._backdropBefore.parentNode) {
                this._site.surface.insertBefore(this._backdropBefore, this._site.surface.firstElementChild);
            }
            if (!this._backdropAfter) {
                this._backdropAfter = document.createElement('div');
                this._backdropAfter.setAttribute("aria-hidden", "true");
                this._backdropAfter.className = WinJS.UI._backdropClass;
            }
            if (!this._backdropAfter.parentNode) {
                this._site.surface.insertBefore(this._backdropAfter, this._site.surface.firstElementChild);
            }

            var backdropBefore = this._backdropBefore;
            var backdropAfter = this._backdropAfter;

            if (count === 0) {
                // Empty list so hide the backdrops
                backdropBefore.style.height = "0px";
                backdropAfter.style.height = "0px";
                backdropBefore.style.width = "0px";
                backdropAfter.style.width = "0px";
            } else {
                // If the viewport size has changed (snap/resize) the item may have changed size. For example items
                // are 100% width in the vertical list view. In this case we need to redraw the background image.
                var viewPortSizeKey = this._site.viewportSize.height + "x" + this._site.viewportSize.width;
                if (this._viewPortSizeKey !== viewPortSizeKey) {
                    this._viewPortSizeKey = viewPortSizeKey;
                    if (this._item0PositionPromise) {
                        this._item0PositionPromise.cancel();
                        this._item0PositionPromise = null;
                    }
                    this._backdropCanvas = null;
                }

                if (!this._item0PositionPromise) {
                    this._item0PositionPromise = this.getItemPosition(0);
                }

                var that = this;
                this._item0PositionPromise.then(function (pos) {
                    var itemMargins = that._itemMargins;

                    var left = that._site.rtl ? "right" : "left";
                    var right = that._site.rtl ? "left" : "right";

                    // For multisize instead of using the first item size use the slot size of the first group.
                    var groupInfo;
                    if (typeof that._groupInfo === "function") {
                        var group0 = that._getGroup(0);
                        if (group0) {
                            groupInfo = that.groupInfo(group0.userData);
                        }
                    } else {
                        groupInfo = that._groupInfo;
                    }

                    if (groupInfo && groupInfo.cellHeight && groupInfo.cellWidth) {
                        pos.contentWidth = groupInfo.cellWidth;
                        pos.contentHeight = groupInfo.cellHeight;
                        pos.totalWidth = groupInfo.cellWidth + itemMargins.right + itemMargins.left;
                        pos.totalHeight = groupInfo.cellHeight + itemMargins.top + itemMargins.bottom;
                    }

                    if (!that._backdropCanvas) {
                        that._backdropCanvas = document.createElement("canvas");
                        that._backdropCanvas.width = pos.totalWidth;
                        that._backdropCanvas.height = pos.totalHeight;
                        var ctx = that._backdropCanvas.getContext("2d");
                        ctx.fillStyle = that.backdropColor;
                        if (that.horizontal) {
                            ctx.fillRect(itemMargins[left], itemMargins.top, pos.contentWidth, pos.contentHeight);
                        } else {
                            ctx.fillRect(itemMargins.left, itemMargins.top, pos.contentWidth, pos.contentHeight);
                        }

                        var backgroundImage = "url(" + that._backdropCanvas.toDataURL("image/png") + ")";
                        backdropBefore.style.backgroundImage = backgroundImage;
                        backdropAfter.style.backgroundImage = backgroundImage;
                    }

                    // Find the start of the first item realized and the end of the last item realized. Scroll view
                    // does not leave holes between realized ranges so 2 backdrops are sufficent.
                    var itemsStart;
                    var itemsEnd;

                    Object.keys(that._items).forEach(function (index) {
                        var itemData = that._items[index];
                        if (itemData && itemData.element && itemData.element.parentNode) {
                            if (that.horizontal) {
                                itemsStart = (+itemsStart === itemsStart) ? Math.min(itemData.left, itemsStart) : itemData.left;
                                itemsEnd = (+itemsEnd === itemsEnd) ? Math.max(itemData.left + itemData.width, itemsEnd) : (itemData.left + itemData.width);
                            }
                            else {
                                itemsStart = (+itemsStart === itemsStart) ? Math.min(itemData.top, itemsStart) : itemData.top;
                                itemsEnd = (+itemsEnd === itemsEnd) ? Math.max(itemData.top + itemData.height, itemsEnd) : (itemData.top + itemData.height);
                            }
                        }
                    });

                    if (that.horizontal) {
                        var usableSurfaceHeight = that._site.viewportSize.height - that._site._surfaceMargins.top - that._site._surfaceMargins.bottom;
                        // These orgins represent the origin for a single backdrop that spans the whole list
                        var backdropOriginY = pos.top;
                        // Unable to use pos.left because it is a dynamic value that changes with group/item pinning 
                        // and we cache the value in that._item0PositionPromise. Instead use header margin, header 
                        // width or 0 which is used in item positioning.
                        var item0Offset = that._groupHeaderPosition === "top" ? that._headerMargin : that._totalHeaderWidth;
                        var backdropOriginX = Math.max(0, item0Offset);
                        var placeholderRows = Math.floor((usableSurfaceHeight - backdropOriginY) / pos.totalHeight);
                        if (that.maxRows) {
                            placeholderRows = Math.min(that.maxRows, placeholderRows);
                        }
                        placeholderRows = Math.max(1, placeholderRows);
                        // This width/height is if there was a single backdrop across the whole list
                        var width = that._site._surfaceLength - itemMargins[left];
                        var height = placeholderRows * pos.totalHeight;

                        itemsStart = (+itemsStart === itemsStart) ? Math.max(0, itemsStart) : 0;
                        itemsEnd = (+itemsEnd === itemsEnd) ? Math.max(0, itemsEnd + itemMargins[left] + itemMargins[right]) : 0;

                        backdropOriginX = Math.max(backdropOriginX, that._site._surfaceScrollLimitMin);
                        itemsEnd = Math.max(itemsEnd, that._site._surfaceScrollLimitMin);

                        // We place one backdrop before the realized items (itemsStart) and one after the realized items (itemsEnd)
                        backdropBefore.style.cssText += ";" + left + ":" + backdropOriginX + "px;top:" + backdropOriginY + "px;width:" +
                            Math.max(0, (itemsStart - backdropOriginX)) + "px;height:" + height + "px";
                        backdropAfter.style.cssText += ";" + left + ":" + itemsEnd + "px;top:" + backdropOriginY + "px;width:" +
                            Math.max(0, (width - itemsEnd)) + "px;height:" + height + "px";
                    } else {
                        var usableSurfaceWidth = that._site.viewportSize.width - that._site._surfaceMargins[left] - that._site._surfaceMargins[right];
                        // These orgins represent the origin for a single backdrop that spans the whole list
                        var backdropOriginX = pos.left;
                        var backdropOriginY = Math.max(0, pos.top);
                        var placeholderColumns = Math.floor((usableSurfaceWidth - backdropOriginX) / pos.totalWidth);
                        placeholderColumns = Math.max(1, placeholderColumns);
                        // This width/height is if there was a single backdrop across the whole list
                        var height = that._site._surfaceLength - itemMargins.top;
                        var width = placeholderColumns * pos.totalWidth;

                        itemsStart = (+itemsStart === itemsStart) ? Math.max(0, itemsStart) : 0;
                        itemsEnd = (+itemsEnd === itemsEnd) ? Math.max(0, itemsEnd + itemMargins.top + itemMargins.bottom) : 0;

                        backdropOriginY = Math.max(backdropOriginY, that._site._surfaceScrollLimitMin);
                        itemsEnd = Math.max(itemsEnd, that._site._surfaceScrollLimitMin);

                        // We place one backdrop before the realized items (itemsStart) and one after the realized items (itemsEnd)
                        backdropBefore.style.cssText += ";top:" + backdropOriginY + "px;" + left + ":" + backdropOriginX + "px;height:" +
                            Math.max(0, (itemsStart - backdropOriginY)) + "px;width:" + width + "px";
                        backdropAfter.style.cssText += ";top:" + itemsEnd + "px;" + left + ":" + backdropOriginX + "px;height:" +
                            Math.max(0, (height - itemsEnd)) + "px;width:" +  width + "px";
                    }
                }, function () {
                    // Error occurred because the promise was canceled or data source was reset so hide the backdrop
                    // since we do not know the correct location of the items.
                    backdropBefore.style.height = "0px";
                    backdropAfter.style.height = "0px";
                    backdropBefore.style.width = "0px";
                    backdropAfter.style.width = "0px";
                });
            }
        }
    })
});

function FixedSizeDecorator() {
}

FixedSizeDecorator.prototype = {
    getGroupSize: function (layout, group, groupIndex, itemsCount) {
        return Math.ceil(itemsCount / layout._itemsPerColumn) * layout._getTotalItemWidth(group) + layout._headerSlot.cx;
    },
    
    calcItemPosition: function (layout, group, groupIndex, index) {
        var coordinates = layout._indexToCoordinate(index - group.startIndex),
            pos = {
                left: group.offset + layout._headerSlot.cx + coordinates.column * layout._getTotalItemWidth(group),
                top: layout._headerSlot.cy + coordinates.row * layout._getTotalItemHeight(group),
                contentWidth: layout._getItemWidth(group),
                contentHeight:  layout._getItemHeight(group),
                totalWidth: layout._getTotalItemWidth(group),
                totalHeight: layout._getTotalItemHeight(group),
                row: coordinates.row,
                column: coordinates.column
            };

        pos.offset = pos.left;

        return Promise.wrap(pos);
    },

    itemOffset: function (layout, group, index) {
        var coordinates = layout._indexToCoordinate(index - group.startIndex);
        return coordinates.column * layout._getTotalItemWidth(group);
    },

    itemFromOffset: function (layout, group, groupIndex, offset, wholeItem, last) {
        if (wholeItem) {
            offset += (last ? -1 : 1) * (layout._getTotalItemWidth(group) - 1);
        }
        return (Math.max(0, Math.floor((offset - group.offset - layout._headerSlot.cx) / layout._getTotalItemWidth(group))) + last) * layout._itemsPerColumn - last;
    },

    getKeyboardNavigatedItem: function (layout, group, groupSize, index, element, keyPressed) {
        return new Promise(function (complete) {
            var currentColumn = Math.floor((index - group.startIndex) / layout._itemsPerColumn),
                currentRow = (index - group.startIndex) % layout._itemsPerColumn;
            
            switch (keyPressed) {
            case Key.upArrow:
                complete({ index: (currentRow === 0 ? index : index - 1) });
                break;
            case Key.downArrow:
                var isLastIndexOfGroup = index === group.startIndex + groupSize - 1,
                    inLastRow = currentRow === layout._itemsPerColumn - 1;
                complete({ index: (isLastIndexOfGroup || inLastRow ? index : index + 1) });
                break;
            case Key.leftArrow:
                complete(currentColumn > 0 ? { index: index - layout._itemsPerColumn } : { group: -1 });
                break;
            case Key.rightArrow:
                var newIndex = index + layout._itemsPerColumn,
                    lastIndexOfGroup = group.startIndex + groupSize - 1,
                    lastColumn = Math.floor((lastIndexOfGroup - group.startIndex) / layout._itemsPerColumn);
                if (lastColumn === currentColumn) {
                    complete({ group: 1 });
                } else {
                    complete(newIndex <= lastIndexOfGroup ? { index: newIndex } : { index: lastIndexOfGroup });
                }
                break;
            default:
                WinJS.UI._LayoutCommon.prototype.getKeyboardNavigatedItem.call(layout, index, element, keyPressed).then(function (newIndex) {
                    complete({ index: newIndex });
                });
                break;
            }
        });
    },

    getLogicalIndex: function (layout, group, groupIndex, wholeItem, x, y, last) {
        var groupSize = layout._getItemsCount(group, groupIndex),
            startIndex = group.startIndex,
            index = this.itemFromOffset(layout, group, groupIndex, x, false, last),
            row = Math.min(layout._itemsPerColumn - 1, Math.floor((y - layout._headerSlot.cy) / layout._getTotalItemHeight(group)));

        return Math.min(startIndex + index + row, startIndex + groupSize - 1);
    }
};

/*#DBG
function dumpMap(occupancyMap, itemsPerColumn, inMapIndex, groupIndex) {
    var lastColumn = Math.floor((occupancyMap.length - 1) / itemsPerColumn);
    _TRACE("Group "+groupIndex+". Map length = " + occupancyMap.length + " lastColumn=" + lastColumn);

    var text = "    ";
    for (var c = 0; c <= Math.min(999, lastColumn); c++) {
        var column = c.toString();
        text += " " + ("000".substr(0, 3 - column.length)) + column + ".";
    }
    _TRACE(text);
    for (var r = 0; r < itemsPerColumn; r++) {
        text = r + " [ ";
        for (c = 0; c <= lastColumn; c++) {
            var i = c * itemsPerColumn + r;
            text += (i === inMapIndex ? "*" : " ");
            var entry = occupancyMap[i];
            if (entry) {
                var index = entry.index.toString();
                text += ("000".substr(0, 3 - index.length)) + index + "|";
            } else {
                text += "___|";
            }
        }
        text += " ]";
        _TRACE(text);
    }
}
#DBG*/

function VariableSizeDecorator() {
    this.occupancyMap = [];
    this.lastAdded = 0;
    this.adding = [];
    this.slotsPerColumn = 0;
}

VariableSizeDecorator.prototype = {

    getGroupSize: function (layout, group, groupIndex, itemsCount) {
        if (this.occupancyMap.length === 0 && group.cachedSize) {
            return group.cachedSize;
        } 

        var measuredItems = 0,
            groupInfo = layout._getGroupInfo(group);

        if (this.occupancyMap.length > 0) {
            measuredItems = Math.ceil(this.occupancyMap.length / this.slotsPerColumn) * groupInfo.cellWidth;
            itemsCount -= this.getOccupancyMapItemCount();
        } else {
            measuredItems = 0;
        }

        var otherItems = Math.ceil(itemsCount / this.slotsPerColumn) * groupInfo.cellWidth + layout._headerSlot.cx;
        group.cachedSize = measuredItems + otherItems;
        return group.cachedSize;
    },

    getOccupancyMapItemCount: function () {
        var index = -1;

        // Use forEach as the map may be sparse
        this.occupancyMap.forEach(function (item) {
            if (item.index > index) {
                index = item.index;
            }
        });

        return index + 1;
    },
    
    coordinateToIndex: function (layout, c, r) {
        return c * this.slotsPerColumn + r;
    },

    markSlotAsFull: function (layout, index, itemEntry) {
        var coordinates = layout._indexToCoordinate(index, this.slotsPerColumn);
        for (var r = coordinates.row, toRow = coordinates.row + itemEntry.rows; r < toRow; r++) {
            for (var c = coordinates.column, toColumn = coordinates.column + itemEntry.columns; c < toColumn; c++) {
                this.occupancyMap[this.coordinateToIndex(layout, c, r)] = itemEntry;
            }
        }
    },

    isSlotEmpty: function (layout, itemSize, row, column) {
        for (var r = row, toRow = row + itemSize.rows; r < toRow; r++) {
            for (var c = column, toColumn = column + itemSize.columns; c < toColumn; c++) {
                if ((r >= this.slotsPerColumn) || (this.occupancyMap[this.coordinateToIndex(layout, c, r)] !== undefined)) {
                    return false;
                }
            }
        }
        return true;
    },

    findEmptySlot: function (layout, startIndex, itemSize, newColumn) {
        var coordinates = layout._indexToCoordinate(startIndex, this.slotsPerColumn),
            startRow = coordinates.row,
            lastColumn = Math.floor((this.occupancyMap.length - 1) / this.slotsPerColumn);

        if (newColumn) {
            for (var c = coordinates.column + 1; c <= lastColumn; c++) {
                if (this.isSlotEmpty(layout, itemSize, 0, c)) {
                    return this.coordinateToIndex(layout, c, 0);
                }
            }
        } else {
            for (var c = coordinates.column; c <= lastColumn; c++) {
                for (var r = startRow; r < this.slotsPerColumn; r++) {
                    if (this.isSlotEmpty(layout, itemSize, r, c)) {
                        return this.coordinateToIndex(layout, c, r);
                    }
                }
                startRow = 0;
            }
        }

        return (lastColumn + 1) * this.slotsPerColumn;
    },

    findItem: function (index) {
        for (var inMapIndex = index, len = this.occupancyMap.length; inMapIndex < len; inMapIndex++) {
            var entry = this.occupancyMap[inMapIndex];
            if (entry && entry.index === index) {
                return inMapIndex;
            }
        }
        return inMapIndex;
    },

    getItemSize: function (layout, group, element, index) {
        var added;

        var wrapper = element.parentNode;

        //#DBG _ASSERT(utilities.hasClass(wrapper, WinJS.UI._wrapperClass));
        //#DBG _ASSERT(utilities.hasClass(element, WinJS.UI._itemClass));

        if (!wrapper.parentNode) {
            added = true;
            layout._site.surface.appendChild(wrapper);
        }

        var itemWidth = utilities.getTotalWidth(element),
            itemHeight = utilities.getTotalHeight(element),
            totalItemWidth = itemWidth + layout._itemMargins.horizontal,
            totalItemHeight = itemHeight + layout._itemMargins.vertical;

        if (added) {
            layout._site.surface.removeChild(wrapper);
        }

        var groupInfo = layout._getGroupInfo(group);
        return {
            index: index,
            contentWidth: itemWidth,
            contentHeight: itemHeight,
            columns: Math.max(1, Math.ceil(totalItemWidth / groupInfo.cellWidth)),
            rows: Math.min(this.slotsPerColumn, Math.max(1, Math.ceil(totalItemHeight / groupInfo.cellHeight)))
        };
    },


    addItemToMap: function (layout, group, index) {
        var that = this;

        function add(mapEntry, newColumn) {
            var inMapIndex = that.findEmptySlot(layout, that.lastAdded, mapEntry, newColumn);
            that.lastAdded = inMapIndex;
            that.markSlotAsFull(layout, inMapIndex, mapEntry);
            layout._site._groups.dirty = true;
            return inMapIndex;
        }

        return new Promise(function (complete) {
            var mapEntry, newColumn;

            if (layout._itemSize && typeof layout._itemSize === "function") {
                var size = layout._itemSize(group.startIndex + index);
                if (size.width && size.height) {
                    var groupInfo = layout._getGroupInfo(group);
                    mapEntry = {
                        index: index,
                        contentWidth: size.width,
                        contentHeight: size.height,
                        columns: Math.max(1, Math.ceil(size.width / groupInfo.cellWidth)),
                        rows: Math.min(that.slotsPerColumn, Math.max(1, Math.ceil(size.height / groupInfo.cellHeight)))
                    };
                }

                newColumn = size.newColumn;
            } 

            if (mapEntry) {
                var inMapIndex = add(mapEntry, newColumn);
                complete(inMapIndex);
            } else {
                var processElement = function (element) {
                    if (!layout._site._isZombie()) {
                        inMapIndex = add(that.getItemSize(layout, group, element, index), newColumn);
                        complete(inMapIndex);
                    }
                }
            
                layout._site._itemsManager._itemAtIndex(group.startIndex + index).then(processElement);
            }
        });
    },

    ensureInMap: function (layout, group, index) {
        var that = this;
        if (index >= this.adding.length) {
            for (var i = this.adding.length; i < index; i++) {
                this.ensureInMap(layout, group, i);
            }
            var previous = index > 0 ? this.adding[index - 1] : Promise.wrap();
            this.adding[index] = previous.then(function () {
                return that.addItemToMap(layout, group, index);
            });
        }
        return this.adding[index];
    },

    calcItemPosition: function (layout, group, groupIndex, index) {
        var that = this;
        return new Promise(function (complete) {
            that.ensureInMap(layout, group, index - group.startIndex).then( function (inMapIndex) {
                layout._updateOffsets();
                var groupInfo = layout._getGroupInfo(group),
                    itemEntry = that.occupancyMap[inMapIndex],
                    coordinates = layout._indexToCoordinate(inMapIndex, that.slotsPerColumn),
                    pos = {
                        left: group.offset + layout._headerSlot.cx + coordinates.column * groupInfo.cellWidth,
                        top: layout._headerSlot.cy + coordinates.row * groupInfo.cellHeight,
                        contentWidth: itemEntry.contentWidth,
                        contentHeight: itemEntry.contentHeight, 
                        totalWidth: itemEntry.columns * groupInfo.cellWidth,
                        totalHeight: itemEntry.rows * groupInfo.cellHeight,
                        row: coordinates.row,
                        column: coordinates.column
                    };
                
                pos.offset = pos.left;

                complete(pos);
            });
        });
    },

    itemOffset: function (layout, group, index) {
        var inMapIndex = this.findItem(index - group.startIndex),
            coordinates = layout._indexToCoordinate(inMapIndex, this.slotsPerColumn),
            groupInfo = layout._getGroupInfo(group);
        return coordinates.column * groupInfo.cellWidth;
    },

    itemFromOffset: function (layout, group, groupIndex, offset, wholeItem, last) {
        offset -= group.offset + layout._headerSlot.cx + ((last ? 1 : -1) * layout._itemMargins[last ? "left" : "right"]);

        return this.indexFromOffset(layout, group, groupIndex, offset, wholeItem, last).item;
    },

    indexFromOffset: function (layout, group, groupIndex, adjustedOffset, wholeItem, last) {
        var measuredWidth = 0,
            lastItem = 0,
            groupInfo = layout._getGroupInfo(group),
            index = 0;

        if (this.occupancyMap.length > 0) {
            lastItem = this.getOccupancyMapItemCount() - 1;
            measuredWidth = Math.ceil((this.occupancyMap.length - 1) / this.slotsPerColumn) * groupInfo.cellWidth;

            if (adjustedOffset < measuredWidth) {
                var counter = this.slotsPerColumn,
                    index = (Math.max(0, Math.floor(adjustedOffset / groupInfo.cellWidth)) + last) * this.slotsPerColumn - last;
                while (!this.occupancyMap[index] && counter-- > 0) {
                    index += (last > 0 ? -1 : 1);
                }
                return {
                    index: index,
                    item: this.occupancyMap[index].index
                }
            } else {
                index = this.occupancyMap.length - 1;
            }
        }

        return {
            index: index,
            item: lastItem + (Math.max(0, Math.floor((adjustedOffset - measuredWidth) / groupInfo.cellWidth)) + last) * this.slotsPerColumn - last
        };
    },

    getKeyboardNavigatedItem: function (layout, group, groupSize, index, element, keyPressed) {
        if (keyPressed === Key.upArrow ||
            keyPressed === Key.downArrow ||
            keyPressed === Key.leftArrow ||
            keyPressed === Key.rightArrow) {
            var that = this,
                originalIndex = index;

            index -= group.startIndex;

            var newIndex, inMap, inMapIndex;
            if (this.lastAdjacent === index) {
                inMapIndex = this.lastInMapIndex;
            } else {
                inMapIndex = this.findItem(index);
            }

            do {
                var column = Math.floor(inMapIndex / this.slotsPerColumn),
                    row = inMapIndex - column * this.slotsPerColumn,
                    lastColumn = Math.floor((this.occupancyMap.length - 1) / this.slotsPerColumn),
                    entry,
                    c;

                switch (keyPressed) {
                    case Key.upArrow:
                        if (row > 0) {
                            inMapIndex--;
                        } else {
                            return Promise.wrap({ index: originalIndex });
                        }
                        break;
                    case Key.downArrow:
                        if (row + 1 < this.slotsPerColumn) {
                            inMapIndex++;
                        } else {
                            return Promise.wrap({ index: originalIndex });
                        }
                        break;
                    case Key.leftArrow:
                        inMapIndex = (column > 0 ? inMapIndex - this.slotsPerColumn : -1);
                        break;
                    case Key.rightArrow:
                        inMapIndex = (column < lastColumn ? inMapIndex + this.slotsPerColumn : this.occupancyMap.length);
                        break;
                }

                inMap = inMapIndex >= 0 && inMapIndex < this.occupancyMap.length;
                if (inMap) {
                    newIndex = that.occupancyMap[inMapIndex] ? that.occupancyMap[inMapIndex].index : undefined;
                }

            } while (inMap && (index === newIndex || newIndex === undefined));

            this.lastAdjacent = newIndex;
            this.lastInMapIndex = inMapIndex;

            return Promise.wrap(inMap ? { index: group.startIndex + newIndex } : { group: inMapIndex < 0 ? -1 : 1 });
        } else {
            return new Promise(function (complete) {
                WinJS.UI._LayoutCommon.prototype.getKeyboardNavigatedItem.call(layout, index, element, keyPressed).then(function (newIndex) {
                    complete({ index: newIndex });
                });
            });
        }
    },

    getLogicalIndex: function (layout, group, groupIndex, wholeItem, x, y, last) {
        var groupSize = layout._getItemsCount(group, groupIndex),
            startIndex = group.startIndex,
            itemIndex = 0;

        if (this.occupancyMap.length > 0) {
            var adjustedX = (x -= group.offset + layout._headerSlot.cx);
            var result = this.indexFromOffset(layout, group, groupIndex, adjustedX, wholeItem, last);

            var counter = Math.min(this.slotsPerColumn - 1, Math.floor((y - layout._headerSlot.cy) / layout._getTotalItemHeight(group))),
                    curr = result.index;
            while (this.occupancyMap[curr] && counter-- > 0) {
                curr++;
            }
            if (!this.occupancyMap[curr]) {
                curr--;
            }

            itemIndex = this.occupancyMap[curr].index;
        }

        return Math.min(startIndex + itemIndex, startIndex + groupSize - 1);
    }
};


WinJS.Namespace.define("WinJS.UI", {
    HeaderPosition: {
        left: "left",
        top: "top"
    },

    GridLayout: WinJS.Class.derive(WinJS.UI._LayoutCommon, function (options) {
        /// <signature helpKeyword="WinJS.UI.GridLayout">
        /// <summary locid="WinJS.UI.GridLayout">
        /// Creates a new GridLayout.
        /// </summary>
        /// <param name="options" type="Object" locid="WinJS.UI.GridLayout_p:options">
        /// The set of properties and values to apply to the new GridLayout.
        /// </param>
        /// <returns type="WinJS.UI.GridLayout" locid="WinJS.UI.GridLayout_returnValue">
        /// The new GridLayout.
        /// </returns>
        /// </signature>
        this.init();
        this._groupHeaderPosition = WinJS.UI.HeaderPosition.top;
        this._itemsPerColumn = WinJS.UI._UNINITIALIZED;
        WinJS.UI.setOptions(this, options);
    }, {
        /// <field type="Boolean" hidden="true" locid="WinJS.UI.GridLayout.horizontal" helpKeyword="WinJS.UI.GridLayout.horizontal">
        /// Gets a value that indicates whether items are laid out horizontally.
        /// This property always returns true for GridLayout.
        /// </field>
        horizontal: {
            enumerable: true, 
            get: function () {
                return true;
            }
        },
        
        /// <field type="String" oamOptionsDatatype="WinJS.UI.GridLayout.HeaderPosition" locid="WinJS.UI.GridLayout.groupHeaderPosition" helpKeyword="WinJS.UI.GridLayout.groupHeaderPosition">
        /// Gets or sets the position of group headers relative to their items.
        /// The default value is "top".
        /// </field>
        groupHeaderPosition: {
            enumerable: true, 
            get: function () {
                return this._groupHeaderPosition;
            },
            set: function (position) {
                this._groupHeaderPosition = position;
                this._invalidateLayout();
            }
        },


        /// <field type="Number" integer="true" locid="WinJS.UI.GridLayout.maxRows" helpKeyword="WinJS.UI.GridLayout.maxRows">
        /// The maximum number of rows that the ListView displays.
        /// </field>
        maxRows: {
            enumerable: true, 
            get: function () {
                return this._maxRows;
            },
            set: function (maxRows) {
                this._maxRows = maxRows;
                this._invalidateLayout();
                
                // If we have itemsPerColumn, recompute it with the new maxRows setting
                if (this._itemsPerColumn !== WinJS.UI._UNINITIALIZED) {
                    this._itemsPerColumn = this._computeItemsPerColumn();
                }
            }
        },

        _initialize: function GridLayout_initialize(count) {
            var that = this
            return this._initializeBase(count).then(function (initialized) {
                if (initialized) {
                    that._rtl = that._site.rtl;
                    var positionProperty = that._rtl ? "right" : "left";
                    if (positionProperty != that._positionProperty) {
                        that._items = {};
                    }
                    that._positionProperty = positionProperty;

                    var surfaceMargin = that._site._surfaceMargins;
                    that._surfaceMargin = surfaceMargin[positionProperty];
                    that._headerMargin = that._headerMargins[positionProperty];
                    if (that._groupHeaderPosition === "top") {
                        that._headerSlot = {
                            cx: that._headerMargin,
                            cy: that._totalHeaderHeight
                        };
                    } else {
                        //#DBG _ASSERT(that._groupHeaderPosition === "left");
                        that._headerSlot = {
                            cx: that._totalHeaderWidth,
                            cy: 0
                        };
                    }
                }
                return initialized;
            });
        },

        startLayout: function GridLayout_startLayout(beginScrollPosition, endScrollPosition, count) {
            /// <signature helpKeyword="WinJS.UI.GridLayout.startLayout">
            /// <summary locid="WinJS.UI.startLayout">
            /// This method supports the Windows Library for JavaScript infrastructure and is not intended to be used directly from your code. 
            /// </summary>
            /// <param name="beginScrollPosition" locid="WinJS.UI.GridLayout.startLayout_p:beginScrollPosition">
            /// 
            /// </param>
            /// <param name="endScrollPosition" locid="WinJS.UI.GridLayout.startLayout_p:endScrollPosition">
            /// 
            /// </param>
            /// <param name="count" locid="WinJS.UI.GridLayout.startLayout_p:count">
            /// 
            /// </param>
            /// </signature>
            var that = this;

            if (count) {
                this._count = count;
                return this._initialize(count).then(function (initialized) {
                    if (initialized) {
                        var dataModifiedPromise = that._dataModifiedPromise ? that._dataModifiedPromise : Promise.wrap();
                        return dataModifiedPromise.then(function () {
                            return that._site._groups.ensureFirstGroup().then(function () {
                                that._itemsPerColumn = WinJS.UI._UNINITIALIZED;
                                // GridLayout needs to cancel animations when it's resized while animations are playing. To do that, we cache the last calculated surface height
                                // and recalculate it every time startLayout is called. If there's a difference and animations are playing, cancel them.
                                var surfaceMargins = that._site._surfaceMargins,
                                    surfaceHeight = that._site.viewportSize.height - surfaceMargins.top - surfaceMargins.bottom;
                                if (that._oldSurfaceHeight !== surfaceHeight && that._trackedAnimation) {
                                    that._trackedAnimation.cancelAnimations();
                                    that._site.itemSurface.style.clip = "auto";
                                }
                                that._oldSurfaceHeight = surfaceHeight;
                                var currentScrollLocation = that._site.scrollbarPos,
                                    animationRangePromise = Promise.wrap(),
                                    animationRangeBegin = Math.max(beginScrollPosition, currentScrollLocation - that._site.viewportSize.width),
                                    animationRangeEnd = Math.min(endScrollPosition, currentScrollLocation + 2 * that._site.viewportSize.width);

                                if (that._site.loadingBehavior !== "incremental") {
                                    animationRangePromise = Promise.join([that.calculateFirstVisible(animationRangeBegin, false), that.calculateLastVisible(animationRangeEnd, false)]).then(function(indices) {
                                        that._viewAnimationRange = {
                                            start: indices[0],
                                            end: indices[1]
                                        };
                                    });
                                }
                                return animationRangePromise.then(function() {
                                    // In incremental mode, startLayout needs to give a range of whole items, and not round up if there isn't enough space in the scroll range.
                                    var incremental = (that._site.loadingBehavior === "incremental");
                                    return that.calculateFirstVisible(beginScrollPosition, incremental).then(function (begin) {
                                        return that.calculateLastVisible(endScrollPosition, incremental).then(function (last) {
                                            var end = last + 1;
                                            that._purgeItemCache(begin, end);

                                            return {
                                                beginIndex: begin,
                                                endIndex: end
                                            };
                                        });
                                    });
                                });
                            });
                        });
                    } else {
                        return null;
                    }
                });
            } else {
                return Promise.wrap(null);
            }
        },

        _getCanvasWidth: function GridLayout_getCanvasWidth(count) {
            var groupIndex = this._site._groups.length() - 1,
                lastGroup = this._getGroup(groupIndex);
            
            return lastGroup.offset + this._decorateGroup(lastGroup).getGroupSize(this, lastGroup, groupIndex, count - lastGroup.startIndex);
        },

        _getGroupType: function GridLayout_getGroupType(group) {
            return group.decorator instanceof VariableSizeDecorator ? "variable" : "fixed";
        },

        getScrollbarRange: function GridLayout_getScrollbarRange(count) {
            /// <signature helpKeyword="WinJS.UI.GridLayout.getScrollbarRange">
            /// <summary locid="WinJS.UI.GridLayout.getScrollbarRange">
            /// This method supports the Windows Library for JavaScript infrastructure and is not intended to be used directly from your code. 
            /// </summary>
            /// <param name="count" locid="WinJS.UI.GridLayout.getScrollbarRange_p:count">
            ///  
            /// </param>
            /// </signature>
            var that = this;
            return this._initialize(count).then(function (initialized) {
                if (initialized) {
                    that._updateOffsets();
                    var firstGroup = that._getGroup(0),
                        canvasWidth = that._getCanvasWidth(count);
                    that._canvasScrollBounds.left = firstGroup.offset;
                    that._canvasScrollBounds.right = canvasWidth;
                    return {
                        beginScrollPosition: firstGroup.offset,
                        endScrollPosition: canvasWidth
                    };
                } else {
                    that._canvasScrollBounds.left = 0;
                    that._canvasScrollBounds.right = 0;
                    return {
                        beginScrollPosition: 0,
                        endScrollPosition: 0
                    };
                }
            });
        },

        getKeyboardNavigatedItem: function GridLayout_getKeyboardNavigatedItem(itemIndex, element, keyPressed) {
            /// <signature helpKeyword="WinJS.UI.GridLayout.getKeyboardNavigatedItem">
            /// <summary locid="WinJS.UI.GridLayout.getKeyboardNavigatedItem">
            /// This method supports the Windows Library for JavaScript infrastructure and is not intended to be used directly from your code.
            /// </summary>
            /// <param name="itemIndex" locid="WinJS.UI.GridLayout.getKeyboardNavigatedItem_p:itemIndex">
            /// 
            /// </param>
            /// <param name="element" locid="WinJS.UI.GridLayout.getKeyboardNavigatedItem_p:element">
            /// 
            /// </param>
            /// <param name="keyPressed" locid="WinJS.UI.GridLayout.getKeyboardNavigatedItem_p:keyPressed">
            /// 
            /// </param>
            /// </signature>
            if (!this._initialized()) {
                return Promise.wrap(-1);
            }

            var that = this;
            return new Promise(function (complete) {

                var groupIndex = that._site._groups.groupFromItem(itemIndex),
                    group = that._site._groups.group(groupIndex);

                // In the case that we ask the data source for information about the groups
                // and it throws up it's hands (basically we don't have any items and are
                // asking about stale data), we can safely just report -1, indicating to 
                // select nothing.
                //
                if (groupIndex === null) {
                    complete(-1);
                    return;
                }
                
                that._measureItems().then(function() {
                    that._decorateGroup(group).getKeyboardNavigatedItem(that, group, that._getItemsCount(group, groupIndex), itemIndex, element, that._adjustDirection(keyPressed)).then(function (newPosition) {
                        if (newPosition.group) {
                            var newGroupIndex = groupIndex + newPosition.group,
                                newGroup = that._site._groups.group(newGroupIndex);
                            
                            if (newGroupIndex < 0) {
                                complete(-1);
                            } else if (newGroupIndex >= that._site._groups.length()) {
                                complete(that._count);
                            } else {
                                var oldGroupType = that._getGroupType(group),
                                    newGroupType = that._getGroupType(newGroup),
                                    oldItemsPerColumn = (oldGroupType === "variable" ? group.decorator.slotsPerColumn : that._itemsPerColumn),
                                    oldCoordinates = that._indexToCoordinate(itemIndex - group.startIndex, oldItemsPerColumn),
                                    newGroupCount = that._getItemsCount(newGroup, newGroupIndex),
                                    lastItemIndex = newGroup.startIndex + newGroupCount - 1,
                                    coords = null;

                                if (oldGroupType === "fixed" && newGroupType === "fixed") {
                                    // We're moving between two fixed-size groups, so select the parallel item
                                    if (newPosition.group < 0) {
                                        var lastItemCoordinates = that._indexToCoordinate(lastItemIndex - newGroup.startIndex);
                                        coords = (lastItemCoordinates.row >= oldCoordinates.row ? (lastItemIndex - (lastItemCoordinates.row - oldCoordinates.row)) : lastItemIndex);
                                    } else {
                                        coords = (newGroupCount > oldCoordinates.row ? (newGroup.startIndex + oldCoordinates.row) : lastItemIndex);
                                    }
                                } else {
                                    // We're moving to or from a variable-size group, so select the first or last item
                                    coords = newPosition.group < 0 ? lastItemIndex : newGroup.startIndex;
                                }

                                complete(coords);
                            }
                        } else {
                            complete(newPosition.index);
                        }
                    });
                 });
            });
        },

        _indexToCoordinate: /*@varargs*/ function GridLayout_indexToCoordinate(index, itemsPerColumn) {
            itemsPerColumn = itemsPerColumn || this._itemsPerColumn;
            var column = Math.floor(index / itemsPerColumn);
            return {
                column: column,
                row: index - column * itemsPerColumn
            };
        },

        _calcItemPosition: function GridLayout_calcItemPosition(index, groupIndex) {
            this._updateOffsets();

            var that = this,
                group = this._getGroup(groupIndex);

            return this._decorateGroup(group).calcItemPosition(this, group, groupIndex, index);
        },

        prepareItem: function GridLayout_prepareItem(element) {
            /// <signature helpKeyword="WinJS.UI.GridLayout.prepareItem">
            /// <summary locid="WinJS.UI.GridLayout.prepareItem">
            /// This method supports the Windows Library for JavaScript infrastructure and is not intended to be used directly from your code.
            /// </summary>
            /// <param name="element" locid="WinJS.UI.GridLayout.prepareItem_p:element">
            /// 
            /// </param>
            /// </signature>

            // Do nothing because position absolute is already set in CSS.
        },

        prepareHeader: function GridLayout_prepareHeader(element) {
            /// <signature helpKeyword="WinJS.UI.GridLayout.prepareHeader">
            /// <summary locid="WinJS.UI.GridLayout.prepareHeader">
            /// This method supports the Windows Library for JavaScript infrastructure and is not intended to be used directly from your code.
            /// </summary>
            /// <param name="element" locid="WinJS.UI.GridLayout.prepareHeader_p:element">
            /// 
            /// </param>
            /// </signature>

            // Do nothing because position absolute is already set in CSS.
        },

        releaseItem: function GridLayout_releaseItem(item, newItem) {
            /// <signature helpKeyword="WinJS.UI.GridLayout.releaseItem">
            /// <summary locid="WinJS.UI.GridLayout.releaseItem">
            /// This method supports the Windows Library for JavaScript infrastructure and is not intended to be used directly from your code.
            /// </summary>
            /// <param name="item" locid="WinJS.UI.GridLayout.releaseItem_p:item">
            /// 
            /// </param>
            /// <param name="newItem" locid="WinJS.UI.GridLayout.releaseItem_p:newItem">
            /// 
            /// </param>
            /// </signature>
            if (item._currentAnimationStage) {
                if (newItem) {
                    item._currentAnimationStage.replaceItemInStage(item, newItem);
                } else {
                    item._animating = false;
                    item._currentAnimationStage.removeItemFromStage(item);
                }
            }
        },

        layoutItem: function GridLayout_layoutItem(itemIndex, element) {
            /// <signature helpKeyword="WinJS.UI.GridLayout.layoutItem">
            /// <summary locid="WinJS.UI.GridLayout.layoutItem">
            /// This method supports the Windows Library for JavaScript infrastructure and is not intended to be used directly from your code. 
            /// </summary>
            /// <param name="itemIndex" locid="WinJS.UI.GridLayout.layoutItem_p:itemIndex">
            ///  
            /// </param>
            /// <param name="element" locid="WinJS.UI.GridLayout.layoutItem_p:element">
            ///  
            /// </param>
            /// </signature>
            var that = this,
                groupIndex = this._site._groups.groupFromItem(itemIndex);

            this._calcItemPosition(itemIndex, groupIndex).then(function (itemPos) {
                var itemData = that._getItemInfo(itemIndex);
                
                if (itemData.left !== itemPos.left || itemData.top !== itemPos.top || itemData.width != itemPos.contentWidth || itemData.height != itemPos.contentHeight || element !== itemData.element) {
                    var oldTop = (itemData.element === element ? itemData.top : undefined),
                        oldLeft = (itemData.element === element ? itemData.left : undefined);
                    itemData.element = element;
                    itemData.left = itemPos.left;
                    itemData.top = itemPos.top;
                    itemData.width = itemPos.contentWidth;
                    itemData.height = itemPos.contentHeight;
                    itemData.row = itemPos.row;
                    itemData.column = itemPos.column;

                    var cachedRecord = that._cachedItemRecords[element.uniqueID];
                    if (cachedRecord) {
                        cachedRecord.left = itemData.left;
                        cachedRecord.top = itemData.top;
                        cachedRecord.itemIndex = itemIndex;
                        if (!cachedRecord.appearedInView) {
                            // The row+column properties of a record are only used for determining whether the animation played on the element
                            // should be a reflow across columns, or just a move. Since elements just appearing in view shouldn't move between columns,
                            // we only update the row/col properties of records that didn't appear, that way the animation helper won't detect
                            // a column change on an appeared item and animate it.
                            cachedRecord.row = itemData.row;
                            cachedRecord.column = itemData.column;
                        } else {
                            // When an item is laid out, has an animation record, and appearedInView is true, it hasn't had a chance to
                            // animate in from the bottom of the view yet. We need to update its left/top and its record's oldLeft/Top
                            // so that it gets animated properly when coming into view.
                            cachedRecord.oldLeft = itemData.left;
                            cachedRecord.oldTop = itemData.top + (that._itemsPerColumn * that._totalItemHeight);
                            element.style.cssText += ";" + that._positionProperty + ":" + cachedRecord.left + "px;top:" + that._cachedItemRecords[element.uniqueID].oldTop;
                        }
                    }

                    if (!element._animating && !cachedRecord) {
                        // When an element isn't marked as animating, and no animation record exists for it, it's still not necessarily safe to animate.
                        // If a lot of elements are being deleted, we can run into cases where new items that we've never seen before need to be realized and put
                        // in the view. If an item falls into the animation range and has no record, we'll set up a special record for it and animate it coming in from the bottom
                        // of the view.
                        if (that._dataModifiedPromise && itemIndex >= that._viewAnimationRange.start && itemIndex <= that._viewAnimationRange.end) {
                            that._cachedItemRecords[element.uniqueID] = {
                                oldTop: itemData.top + (that._itemsPerColumn * that._totalItemHeight),
                                oldLeft: itemData.left,
                                row: itemData.row,
                                column: itemData.column,
                                top: itemData.top,
                                left: itemData.left,
                                element: element,
                                itemIndex: itemIndex,
                                appearedInView: true
                            };
                            // Since this item just appeared in the view and we're going to animate it coming in from the bottom, we set its opacity to zero because it'll be moved to the bottom of the listview
                            // but can still be visible since the canvas region's clip style isn't set until endLayout
                            element.style.cssText += ";" + that._positionProperty + ":" + itemPos.left + "px;top:" + that._cachedItemRecords[element.uniqueID].oldTop + "px;width:" + itemPos.contentWidth + "px;height:" + itemPos.contentHeight + "px; opacity: 0";
                        } else {
                            // Setting the left, top, width, and height via cssText is approximately 50% faster than setting each one individually.
                            // Start with semicolon since cssText does not end in one even if you provide one at the end.
                            element.style.cssText += ";" + that._positionProperty + ":" + itemPos.left + "px;top:" + itemPos.top + "px;width:" + itemPos.contentWidth + "px;height:" + itemPos.contentHeight + "px";
                        }
                    }

                    // When an element is laid out again while animating but doesn't have a cached record, that means that enough changes have occurred to
                    // make that element outside of the range of usual animations (that range is found in the dataModified handler). We don't want to move the
                    // element instantly, since while it may be outside of the range of visible indices, it may still be visible because it's in the midst
                    // of a move animation. We'll instead make a new record for this element and let endLayout animate it again.
                    if (element._animating && !cachedRecord) {
                        that._cachedItemRecords[element.uniqueID] = {
                            oldTop: oldTop,
                            oldLeft: oldLeft,
                            row: itemData.row,
                            column: itemData.column,
                            top: itemData.top,
                            left: itemData.left,
                            element: element,
                            itemIndex: itemIndex 
                        };
                    }
                }
            });
        },

        layoutHeader: function GridLayout_layoutHeader(groupIndex, element) {
            /// <signature helpKeyword="WinJS.UI.GridLayout.layoutHeader">
            /// <summary locid="WinJS.UI.GridLayout.layoutHeader">
            /// This method supports the Windows Library for JavaScript infrastructure and is not intended to be used directly from your code.
            /// </summary>
            /// <param name="groupIndex" locid="WinJS.UI.GridLayout.layoutHeader_p:groupIndex">
            /// 
            /// </param>
            /// <param name="element" locid="WinJS.UI.GridLayout.layoutHeader_p:element">
            /// 
            /// </param>
            /// </signature>
            this._updateOffsets();

            var groups = this._site._groups,
                group = groups.group(groupIndex),
                nextGroup = (groupIndex + 1 < groups.length() ? groups.group(groupIndex + 1) : null),
                left = group.offset,
                width;

            //#DBG _ASSERT(group.offset !== undefined);

            if (this._groupHeaderPosition === "top") {
                if (nextGroup) {
                    width = nextGroup.offset;
                } else {
                    // This is the last group, so derive the header width from the canvas width
                    width = this._canvasScrollBounds.right;
                }

                width -= group.offset + this._headerMargin + this._headerPaddingAndBorder;
            }

            if (group.left !== left || group.width !== width) {
                var style = element.style;

                style[this._positionProperty] = left + "px";
                style.width = (width ? width + "px" : "");

                group.left = left;
                group.width = width;
            }
        },

        endLayout: function GridLayout_endLayout() {
            /// <signature helpKeyword="WinJS.UI.GridLayout.endLayout">
            /// <summary locid="WinJS.UI.GridLayout.endLayout">
            /// This method supports the Windows Library for JavaScript infrastructure and is not intended to be used directly from your code. 
            /// </summary>
            /// </signature>
            if (!this._animateEndLayout) {
                return;
            }
            var dataModifiedPromise = this._dataModifiedPromise ? this._dataModifiedPromise : Promise.wrap();
            this._dataModifiedPromise = null;
            this._animateEndLayout = false;
            var that = this;

            var endLayoutPromise = dataModifiedPromise.then(function () {
                var i, len, element;
                if (that._site.animationsDisabled) {
                    for (i = 0, len = that._cachedInserted.length; i < len; i++) {
                        that._cachedInserted[i].style.opacity = 1.0;
                    }
                    for (i = 0, len = that._cachedRemoved.length; i < len; i++) {
                        element = that._cachedRemoved[i];
                        if (element.parentNode) {
                            element.parentNode.removeChild(element);
                        }
                    }
                    var cachedRecordKeys = Object.keys(that._cachedItemRecords);
                    for (i = 0, len = cachedRecordKeys.length; i < len; i++) {
                        var itemRecord = that._cachedItemRecords[cachedRecordKeys[i]];
                        if (itemRecord.element) {
                            if (itemRecord.oldLeft !== itemRecord.left || itemRecord.oldTop !== itemRecord.top) {
                                if (itemRecord.left !== undefined) {
                                    itemRecord.element.style[that._positionProperty] = itemRecord.left + "px";
                                }
                                if (itemRecord.top !== undefined) {
                                    itemRecord.element.style.top = itemRecord.top + "px";
                                }
                            }

                            if (itemRecord.appearedInView) {
                                itemRecord.element.style.opacity = 1;
                            }
                        }
                    }
                    that._cachedInserted = [];
                    that._cachedRemoved = [];
                    that._cachedItemRecords = {};
                    return;
                }

                var affectedItems = {},
                    groups = that._site._groups,
                    animationSignal = new Signal(),
                    variablySizedItemsFound = false,
                    cachedRecordKeys = Object.keys(that._cachedItemRecords);

                var insertedMap = {},
                    removedMap = {};
                for (i = 0, len = that._cachedInserted.length; i < len; i++) {
                    element = that._cachedInserted[i];
                    var itemRecord = that._cachedItemRecords[element.uniqueID];
                    if (itemRecord) {
                        element.style.cssText += ";" + that._positionProperty + ":" + itemRecord.left + "px;top:" + itemRecord.top + "px;";
                    }
                    insertedMap[element.uniqueID] = { element: element };
                }
                for (i = 0, len = that._cachedRemoved.length; i < len; i++) {
                    element = that._cachedRemoved[i];
                    removedMap[element.uniqueID] = { element: element };
                }
                var appearingItems = [];
                for (i = 0, len = cachedRecordKeys.length; i < len; i++) {
                    var itemRecord = that._cachedItemRecords[cachedRecordKeys[i]];
                    if (itemRecord.element) {
                        var itemID = itemRecord.element.uniqueID;
                        if (!insertedMap[itemID] && !removedMap[itemID]) {
                            variablySizedItemsFound = variablySizedItemsFound || that._multiSize(groups.group(groups.groupFromItem(itemRecord.itemIndex)));
                            if ((itemRecord.oldRow !== itemRecord.row || itemRecord.oldColumn !== itemRecord.column || itemRecord.oldLeft !== itemRecord.left || itemRecord.oldTop !== itemRecord.top)) {
                                // The itemData object can be reused by the ListView, but item records are recreated every time a change happens. The stages
                                // need unchanging records to function properly, so we give it the itemRecord.
                                affectedItems[itemID] = itemRecord;
                                itemRecord.element._animating = true;
                            }

                            if (itemRecord.appearedInView && !insertedMap[itemID]) {
                                appearingItems.push(itemRecord.element);
                            }
                        }
                    }
                }

                // If items are appearing from out of no where in uniform/grouped grids, we'll set their opacity to 1 since they'll be hidden by the clipping set up a little later.
                // Multisized items that appear will have no where to fade out from, so we leave their opacity as 0 so they just fade in when animated
                if (!variablySizedItemsFound) {
                    for (i = 0, len = appearingItems.length; i < len; i++) {
                        appearingItems[i].style.opacity = 1;
                    }
                }

                if (variablySizedItemsFound) {
                    that._trackedAnimation = AnimationHelper.animateListFadeBetween(that._trackedAnimation, that._site.surface, that._site.rtl, affectedItems, insertedMap, removedMap);
                } else {
                    var itemSurface = that._site.itemSurface,
                        itemStart = that._headerSlot.cy,
                        itemEnd = that._itemsPerColumn * that._totalItemHeight + itemStart;

                    // Some columns may have been deleted, and we don't want them to be clipped. Here we calculate what the max clipping should be
                    if (that._itemsPerColumn === 1) {
                        that._trackedAnimation = AnimationHelper.animateListReflow(that._trackedAnimation, itemSurface, that._site.rtl, affectedItems, insertedMap, removedMap);
                    } else {
                        that._trackedAnimation = AnimationHelper.animateReflow(that._trackedAnimation, itemSurface, that._site.rtl, affectedItems, insertedMap, removedMap, itemEnd - itemStart, that._totalItemHeight);
                    }
                    itemSurface.style.clip = "rect(" + itemStart + "px,auto," + itemEnd + "px,auto)";
                }

                function trackerDone() {
                    if (!that._site._isZombie()) {
                        // It's important to reset the surface clip once animations are done. We don't want to clip an item that's at the bottom row and being selected via cross slide when the ListView is static
                        that._site.itemSurface.style.clip = "auto";
                        that._trackedAnimation = null;
                        animationSignal.complete();
                    }
                }
                that._trackedAnimation.getCompletionPromise().then(trackerDone, trackerDone);

                that._cachedInserted = [];
                that._cachedRemoved = [];
                that._cachedItemRecords = {};

                return animationSignal.promise;
            });

            return {
                animationPromise: endLayoutPromise
            };
        },

        _groupFromOffset: function GridLayout_groupFromOffset(offset) {
            this._updateOffsets();
            return offset < this._getGroup(0).offset ? 0 : this._site._groups.groupFromOffset(offset);
        },

        _getGroup: function GridLayout_getGroup(groupIndex) {
            return this._site._groups.group(groupIndex);
        },

        _getItemsCount: function GridLayout_getItemsCount(group, groupIndex) {
            if (groupIndex + 1 < this._site._groups.length()) {
                return this._site._groups.group(groupIndex + 1).startIndex - group.startIndex;
            } else {
                return this._count - group.startIndex;
            }
        },

        calculateFirstVisible: function GridLayout_calculateFirstVisible(beginScrollPosition, wholeItem) {
            /// <signature helpKeyword="WinJS.UI.GridLayout.calculateFirstVisible">
            /// <summary locid="WinJS.UI.GridLayout.calculateFirstVisible">
            /// This method supports the Windows Library for JavaScript infrastructure and is not intended to be used directly from your code.
            /// </summary>
            /// <param name="beginScrollPosition" locid="WinJS.UI.GridLayout.calculateFirstVisible_p:beginScrollPosition">
            /// 
            /// </param>
            /// <param name="wholeItem" locid="WinJS.UI.GridLayout.calculateFirstVisible_p:wholeItem">
            /// 
            /// </param>
            /// </signature>
            var that = this;
            return this._initialize().then(function (initialized) {
                if (initialized) {
                    beginScrollPosition -= that._surfaceMargin;
                    var groupIndex = that._groupFromOffset(beginScrollPosition),
                        group = that._site._groups.group(groupIndex),
                        groupSize = that._getItemsCount(group, groupIndex),
                        startIndex = group.startIndex;

                    if (!wholeItem) {
                        beginScrollPosition += that._itemMargins[that._site.rtl ? "left" : "right"];
                    }
                    var index = that._decorateGroup(group).itemFromOffset(that, group, groupIndex, beginScrollPosition, wholeItem, 0);
                    return Math.min(startIndex + index, startIndex + groupSize - 1);
                } else {
                    return Promise.wrapError(new WinJS.ErrorFromName("WinJS.UI.LayoutNotInitialized", WinJS.UI._strings.layoutNotInitialized));
                }
            });
        },

        calculateLastVisible: function GridLayout_calculateLastVisible(endScrollPosition, wholeItem) {
            /// <signature helpKeyword="WinJS.UI.GridLayout.calculateLastVisible">
            /// <summary locid="WinJS.UI.GridLayout.calculateLastVisible">
            /// This method supports the Windows Library for JavaScript infrastructure and is not intended to be used directly from your code.
            /// </summary>
            /// <param name="endScrollPosition" locid="WinJS.UI.GridLayout.calculateLastVisible_p:endScrollPosition">
            /// 
            /// </param>
            /// <param name="wholeItem" locid="WinJS.UI.GridLayout.calculateLastVisible_p:wholeItem">
            /// 
            /// </param>
            /// </signature>
            var that = this;
            return this._initialize().then(function (initialized) {
                if (initialized) {
                    var offset = endScrollPosition - that._surfaceMargin,
                        groupIndex = that._groupFromOffset(offset),
                        group = that._site._groups.group(groupIndex),
                        groupSize = that._getItemsCount(group, groupIndex),
                        startIndex = group.startIndex,
                        groupOffset;
                    if (offset - group.offset >= that._headerSlot.cx) {
                        if (!wholeItem) {
                            offset -= that._itemMargins[that._site.rtl ? "right" : "left"];
                        }
                        var index = that._decorateGroup(group).itemFromOffset(that, group, groupIndex, offset, wholeItem, 1);
                        return Math.min(startIndex + index, startIndex + groupSize - 1);
                    } else {
                        return Math.max(0, startIndex - 1);
                    }
                } else {
                    return Promise.wrapError(new WinJS.ErrorFromName("WinJS.UI.LayoutNotInitialized", WinJS.UI._strings.layoutNotInitialized));
                }
            });
        },

        hitTest: function GridLayout_hitTest(x, y) {
            /// <signature helpKeyword="WinJS.UI.GridLayout.hitTest">
            /// <summary locid="WinJS.UI.GridLayout.hitTest">
            /// This method supports the Windows Library for JavaScript infrastructure and is not intended to be used directly from your code.
            /// </summary>
            /// <param name="x" locid="WinJS.UI.GridLayout.hitTest_p:x">
            /// 
            /// </param>
            /// <param name="y" locid="WinJS.UI.GridLayout.hitTest_p:y">
            /// 
            /// </param>
            /// </signature>
            if (this._count) {
                x -= this._surfaceMargin;
                if (this._rtl) {
                    x = this._getCanvasWidth(this._count) - x;
                }
                var groups = this._site._groups;
                for (var i = 0, len = groups.length() ; i < len; i++) {
                    if (x < groups.group(i).offset) {
                        break;
                    }
                }
                var groupIndex = i - 1,
                    group = groups.group(groupIndex);
                if (group) {
                    var decorator = this._decorateGroup(group);
                    return decorator.getLogicalIndex(this, group, groupIndex, false, x, y, 0);
                } else {
                    if (groupIndex < 0) {
                        return 0;
                    } else {
                        var lastGroupIndex = groups.length() - 1,
                            lastGroup = groups.group(lastGroupIndex),
                            lastGroupSize = this._getItemsCount(lastGroup, lastGroupIndex);
                        return lastGroup.startIndex + lastGroupSize - 1;
                    }
                }
            } else {
                return -1;
            }
        },

        getItemPosition: function GridLayout_getItemPosition(itemIndex) {
            /// <signature helpKeyword="WinJS.UI.GridLayout.getItemPosition">
            /// <summary locid="WinJS.UI.GridLayout.getItemPosition">
            /// This method supports the Windows Library for JavaScript infrastructure and is not intended to be used directly from your code.
            /// </summary>
            /// <param name="itemIndex" locid="WinJS.UI.GridLayout.getItemPosition_p:itemIndex">
            /// 
            /// </param>
            /// </signature>
            var that = this;
            return this._initialize().then(function (initialized) {
                if (initialized) {
                    var itemPromise = that._site._itemsManager._itemPromiseAtIndex(itemIndex);
                    return that._site._groupOf(itemPromise).then(
                        function () {
                            itemPromise.cancel();
                            var groupIndex = that._site._groups.groupFromItem(itemIndex);
                            return that._calcItemPosition(itemIndex, groupIndex);
                        },
                        function (e) {
                            itemPromise.cancel();
                            return WinJS.Promise.wrapError(e);
                        }
                    );
                } else {
                    return Promise.wrapError(new WinJS.ErrorFromName("WinJS.UI.LayoutNotInitialized", WinJS.UI._strings.layoutNotInitialized));
                }
            });
        },

        _computeItemsPerColumn: function GridLayout_computeItemsPerColumn(group) {
            var surfaceMargin = this._site._surfaceMargins,
                surfaceHeight = this._site.viewportSize.height - surfaceMargin.top - surfaceMargin.bottom,
                groupInfo = this._getGroupInfo(group),
                itemsPerColumn = Math.floor((surfaceHeight - this._headerSlot.cy) / (groupInfo && groupInfo.enableCellSpanning ? groupInfo.cellHeight : this._getTotalItemHeight(group)));

            if (this._maxRows) {
                itemsPerColumn = Math.min(itemsPerColumn, this._maxRows);
            }

            itemsPerColumn = Math.max(itemsPerColumn, 1);
            return itemsPerColumn;
        },

        _decorateGroup: function GridLayout_decorateGroup(group) {
            if (!group.decorator) {
                if (this._multiSize(group)) {
                    group.decorator = new VariableSizeDecorator();
                    group.decorator.slotsPerColumn = this._computeItemsPerColumn(group);
                } else {
                    group.decorator = new FixedSizeDecorator();
                }
            }

            if (this._itemsPerColumn === WinJS.UI._UNINITIALIZED && group.decorator instanceof FixedSizeDecorator) {
                this._itemsPerColumn = this._computeItemsPerColumn(group);
            }

            return group.decorator;
        },

        itemsAdded: function GridLayout_itemsAdded(elements) {
            /// <signature helpKeyword="WinJS.UI.GridLayout.itemsAdded">
            /// <summary locid="WinJS.UI.GridLayout.itemsAdded">
            /// This method supports the Windows Library for JavaScript infrastructure and is not intended to be used directly from your code.
            /// </summary>
            /// <param name="elements" locid="WinJS.UI.itemsAdded_p:elements">
            /// 
            /// </param>
            /// </signature>
            this._dataModified(elements, []);
        },

        itemsRemoved: function GridLayout_itemsRemoved(elements) {
            /// <signature helpKeyword="WinJS.UI.GridLayout.itemsRemoved">
            /// <summary locid="WinJS.UI.GridLayout.itemsRemoved">
            /// This method supports the Windows Library for JavaScript infrastructure and is not intended to be used directly from your code.
            /// </summary>
            /// <param name="elements" locid="WinJS.UI.itemsRemoved_p:elements">
            /// 
            /// </param>
            /// </signature>
            this._dataModified([], elements);
        },

        itemsMoved: function GridLayout_itemsMoved() {
            /// <signature helpKeyword="WinJS.UI.GridLayout.itemsMoved">
            /// <summary locid="WinJS.UI.GridLayout.itemsMoved">
            /// This method supports the Windows Library for JavaScript infrastructure and is not intended to be used directly from your code.
            /// </summary>
            /// </signature>
            this._dataModified([], []);
        },

        _dataModified: function GridLayout_dataModified(inserted, removed) {
            var i, len;
            for (i = 0, len = inserted.length; i < len; i++) {
                this._cachedInserted.push(inserted[i]);
            }
            for (i = 0, len = removed.length; i < len; i++) {
                this._cachedRemoved.push(removed[i]);
            }

            // If the layout's already been cached (or being cached) in this cycle, skip this datamodified run
            if (this._dataModifiedPromise) {
                return;
            }

            var currentPromise = new Signal();
            this._dataModifiedPromise = currentPromise.promise;
            this._animateEndLayout = true;
            function completePromise() {
                currentPromise.complete();
            }
            if (this._initialized()) {
                var that = this;
                this._isEmpty().then(function (isEmpty) {
                    if (!isEmpty) {
                        var animationRangePromise = Promise.wrap();
                        if (that._site.loadingBehavior === "incremental") {
                            var viewportSize = that._site.viewportSize.width,
                                firstPromise = that.calculateFirstVisible(Math.max(0, that._site.scrollbarPos - viewportSize), false),
                                lastPromise = that.calculateLastVisible(that._site.scrollbarPos + 2 * viewportSize - 1, false);

                            animationRangePromise = Promise.join([firstPromise, lastPromise]).then(function (indices) {
                                that._viewAnimationRange = {
                                    start: indices[0],
                                    end: indices[1]
                                };
                            });
                        }
                        animationRangePromise.then(function () {
                            if (that._viewAnimationRange) {
                                var firstNearbyItem = that._viewAnimationRange.start - 1,
                                    lastNearbyItem = that._viewAnimationRange.end + that._cachedRemoved.length + 1;
                                for (i = firstNearbyItem; i < lastNearbyItem; i++) {
                                    var itemData = that._getItemInfo(i);
                                    if (itemData && itemData.element) {
                                        if (!that._cachedItemRecords[itemData.element.uniqueID]) {
                                            that._cachedItemRecords[itemData.element.uniqueID] = {
                                                oldRow: itemData.row,
                                                row: itemData.row,
                                                oldColumn: itemData.column,
                                                column: itemData.column,
                                                oldLeft: itemData.left,
                                                oldTop: itemData.top,
                                                left: itemData.left,
                                                top: itemData.top,
                                                element: itemData.element,
                                                itemIndex: i
                                            };
                                        }
                                    }
                                }
                            }
                            completePromise();
                        }, completePromise);
                    } else {
                        completePromise();
                    }
                }, completePromise);
            } else {
                completePromise();
            }
        },

        _updateOffsets: function GridLayout_updateOffsets() {
            if (this._site._groups.dirty) {
                var count = this._site._groups.length();

                if (count) {
                    var previousGroup;

                    for (var i = 0; i < count; i++) {
                        var group = this._site._groups.group(i);

                        if (previousGroup) {
                            var itemsCount = group.startIndex - previousGroup.startIndex;
                            group.offset = previousGroup.offset + this._decorateGroup(previousGroup).getGroupSize(this, previousGroup, i - 1, itemsCount);
                            group.absoluteOffset = group.offset;
                        } else {
                            group.offset = 0;
                        }

                        previousGroup = group;
                    }

                    if (this._site._groups.pinnedItem !== undefined) {
                        var pinnedGroupIndex = this._site._groups.groupFromItem(this._site._groups.pinnedItem),
                            pinnedGroup = this._site._groups.group(pinnedGroupIndex),
                            pinnedCoordinates = this._indexToCoordinate(this._site._groups.pinnedItem - pinnedGroup.startIndex),
                            pinnedGroupOffset = this._site._groups.pinnedOffset - this._headerSlot.cx - this._decorateGroup(pinnedGroup).itemOffset(this, pinnedGroup, this._site._groups.pinnedItem),
                            correction = pinnedGroupOffset - pinnedGroup.offset;

                        for (i = 0; i < count; i++) {
                            this._site._groups.group(i).offset += correction;
                        }
                    }
                }

                this._site._groups.dirty = false;
            }
        }
    })
});
})(this, WinJS);

(function incrementalViewInit(global, WinJS, undefined) {
    "use strict";


var utilities = WinJS.Utilities,
    Promise = WinJS.Promise;

// Incremental View doesn't use virtualization. It creates all the items immediately but it creates 
// only a small set of items - a chunk. By default there are 50 items in a chunk. When the user 
// scrolls to the last item the next chunk of items is created.
WinJS.Namespace.define("WinJS.UI", {
    _IncrementalView: function (viewSite) {
        this.site = viewSite;
        this.items = new WinJS.UI._ItemsContainer(viewSite);
        this.lastPageBegin = 0;
        this.lastItem = -1;
        this.loadingInProgress = false;
        this.realizePass = 1;
        this.pagesToLoad = WinJS.UI._DEFAULT_PAGES_TO_LOAD;
        this.pagesToLoadThreshold = WinJS.UI._DEFAULT_PAGE_LOAD_THRESHOLD;
        this.automaticallyLoadPages = true;
        this.resetView();
        this.firstLayoutPass = true;
        this.firstIndexDisplayed = -1;
        this.lastIndexDisplayed = -1;
        this.runningAnimations = null;
        this.animating = false;
        this.lastAnimatedPass = -1;
        this.loadingItems = false;
        this.renderCompletePromise = Promise.wrap();
        this.insertedElements = [];
    }
});
WinJS.UI._IncrementalView.prototype = {
    addItem: function IncrementalView_addItem(fragment, itemIndex, currentPass, finishCallback) {
        var that = this;

        var itemAvailable = function (element) {
            if (that.site._isZombie()) {
                return;
            }

            var record = that.site._itemsManager._recordFromElement(element);
            var renderComplete = record.renderComplete;

            var wrapper = element.parentNode;
            if (wrapper.parentNode !== fragment) {
                fragment.appendChild(wrapper);
            }

            function configure() {
                if (that.site._isSelected(itemIndex)) {
                    that.site._renderSelection(wrapper, element, true, true);
                }

                if (that.site._isInsertedItem(record.itemPromise)) {
                    wrapper.style.opacity = 0;
                    that.insertedElements.push(wrapper);
                }

                that.items.setItemAt(itemIndex, {
                    element: element,
                    itemsManagerRecord: record,
                    wrapper: wrapper
                });

                that.site._layout.layoutItem(itemIndex, wrapper);

                finishCallback(renderComplete);
            }

            function nextItemSibling(element) {
                var curr = element.nextSibling;
                while (curr && !utilities.hasClass(curr, WinJS.UI._wrapperClass)) {
                    curr = curr.nextSibling;
                }
                return curr;
            }

            function insert(wrapper, insertBefore) {
                if (that.realizePass === currentPass) {
                    if (insertBefore) {
                        fragment.insertBefore(wrapper, insertBefore);
                    } else {
                        fragment.appendChild(wrapper);
                    }

                    configure();
                } else {
                    finishCallback(renderComplete);
                }
            }

            if (wrapper.parentNode !== fragment) {
                if (itemIndex === 0) {
                    insert(wrapper);
                } else {
                    that.items.requestItem(itemIndex - 1).then(function (previousItem) {
                        if (that.site._isZombie()) {
                            return;
                        }

                        insert(wrapper, nextItemSibling(that.items.wrapperAt(itemIndex - 1)));
                    });
                }
            } else if (that.realizePass === currentPass) {
                configure();
            } else {
                finishCallback(renderComplete);
            }
        };

        this.site._itemsManager._itemAtIndex(itemIndex).
            then(itemAvailable, function (err) { finishCallback(); return WinJS.Promise.wrapError(err); });
    },

    checkRenderStatus: function () {
        if (!this.loadingItems && !this.animating) {
            this.site._raiseViewComplete();
        }
    },

    realizeItems: function IncrementalView_realizeItem(fragment, begin, end, count, currentPass, finishCallback) {
        var that = this,
            counter = end - begin,
            renderCompletePromises = [];

        this.hideProgressBar();
        this.loadingItems = true;
        function callCallback(renderCompletePromise) {
            renderCompletePromises.push(renderCompletePromise);
            if (--counter === 0) {
                if (that.realizePass === currentPass) {
                    that.renderCompletePromise = Promise.join(renderCompletePromises);
                    if (that.insertedElements.length) {
                        that.site._layout.itemsAdded(that.insertedElements);
                    }
                    var endLayoutResult = that.site._layout.endLayout(),
                        wasFirstLayout = that.firstLayoutPass,
                        finished = false,
                        animationPromise;

                    that.site._clearInsertedItems();
                    that.insertedElements = [];

                    if (that.firstLayoutPass) {
                        that.runningAnimations = Promise.join([that.runningAnimations, that.site._animateListEntrance(!that.firstEntranceAnimated)]);
                        that.firstLayoutPass = false;
                        that.firstEntranceAnimated = true;
                    }
                    if (endLayoutResult) {
                        if (endLayoutResult.newEndIndex) {
                            that.realizeItems(fragment, end, Math.min(count, endLayoutResult.newEndIndex), count, currentPass, finishCallback);
                        }

                        animationPromise = endLayoutResult.animationPromise;
                    }    
                    finished = !endLayoutResult || !endLayoutResult.newEndIndex;
                    if (finished) {
                        that.site._raiseViewLoaded();
                    }

                    if (animationPromise || wasFirstLayout) {
                        that.animating = true;
                        that.lastAnimatedPass = currentPass;
                    }
                    that.renderCompletePromise.then(function() {
                        if (that.realizePass === currentPass) {
                            that.loadingItems = false;
                            that.updateAriaOnItems(count);
                        }
                     });

                    that.runningAnimations = Promise.join([that.runningAnimations, animationPromise]).then(function() {
                        return Promise.timeout();
                    });
                    that.runningAnimations.then(function () {
                        if (that.lastAnimatedPass === currentPass) {
                            that.animating = false;
                            that.runningAnimations = null;
                        }
                    });

                    Promise.join([that.renderCompletePromise, that.runningAnimations]).then(function () {
                        if (that.realizePass === currentPass || that.lastAnimatedPass === currentPass) {
                            that.checkRenderStatus();
                        }
                    });

                    if (finished) {
                        finishCallback(end - 1);
                    }
                }
            }
        }

        if (counter !== 0) {
            for (var itemIndex = begin; itemIndex < end; itemIndex++) {
                var itemData = this.items.itemDataAt(itemIndex);
                if (!itemData || itemData.removed) {
                    this.addItem(fragment, itemIndex, currentPass, callCallback);
                } else {
                    // Item already exists. Only position needs to be updated 
                    this.site._layout.layoutItem(itemIndex, itemData.wrapper);
                    callCallback(that.site._itemsManager._recordFromElement(itemData.element).renderComplete);
                }
            }
        } else {
            finishCallback(end - 1);
        }
    },

    loadNextChunk: function IncrementalView_loadNextChunk(callback) {
        if (!this.loadingInProgress) {
            var that = this,
                currentPass = ++this.realizePass;

            this.loadingInProgress = true;

            var done = function (realizeItemsCalled) {
                that.hideProgressBar();
                that.loadingInProgress = false;
                callback(realizeItemsCalled);
            };

            var noRange = function (count) {
                that.site._layout.endLayout();
                that.site._clearInsertedItems();
                done(false);
            };
            
            this.site._itemsCount().then(function (count) {
                if (!that.destroyed && that.realizePass === currentPass) {
                    if (count > that.lastItem + 1) {
                        var viewportLength = that.site._getViewportLength();

                        that.site._layout.startLayout(0, that.pagesToLoad * viewportLength - 1, count).then(function (initialRange) {
                            that.calculateDisplayedItems(count).then(function () {
                                if (initialRange) {
                                    var itemsPerChunk = initialRange.endIndex - initialRange.beginIndex,
                                        chunksToLoad = Math.max(0, Math.ceil(that.lastItem / itemsPerChunk)) + 1,
                                        totalItems = Math.min(count, itemsPerChunk * chunksToLoad);
                                    that.site._layout.startLayout(0, chunksToLoad * that.pagesToLoad * viewportLength - 1, totalItems).then(function (range) {
                                        if (range) {
                                            var begin = that.lastItem + 1;

                                            that.lastPageBegin = begin;
                                            that.lastItem = range.endIndex - 1;

                                            that.realizeItems(that.site._itemCanvas, begin, range.endIndex, totalItems, currentPass, function (finalItem) {
                                                if (that.realizePass === currentPass) {
                                                    that.lastItem = finalItem;
                                                    that.updateScrollbar(count);
                                                }
                                                done(true);
                                            });
                                        } else {
                                            noRange(count);
                                        }
                                    });
                                } else {
                                    noRange(count);
                                }
                            });
                        });
                    } else {
                        that.calculateDisplayedItems(count).then(function () {
                            done(false);
                        });
                    }
                } else {
                    that.calculateDisplayedItems(count).then(function () {
                        done(false);
                    });
                }
            });
        }
    },

    updateItems: function IncrementalView_updateItems(callback, refreshView) {
        var that = this,
            currentPass = this.realizePass,
            scrollbarPos = this.site.scrollPosition,
            viewportLength = this.site._getViewportLength();

        function noRange(count) {
            that.hideProgressBar();

            if (!count) {
                var endLayoutResult = that.site._layout.endLayout();
                that.site._clearInsertedItems();
                if (endLayoutResult && endLayoutResult.animationPromise) {
                    that.animating = true;
                    that.lastAnimatedPass = currentPass;
                    that.runningAnimations = that.runningAnimations ? Promise.join([that.runningAnimations, endLayoutResult.animationPromise]) : endLayoutResult.animationPromise;
                    that.runningAnimations.then(function () {
                        if (that.lastAnimatedPass === currentPass) {
                            that.animating = false;
                            that.runningAnimations = null;
                            that.checkRenderStatus();
                        }
                    });
                } else {
                    that.checkRenderStatus();
                }
                that.loadingInProgress = false;
            }

            callback(true);
        }

        this.site._itemsCount().then(function (count) {
            if (!that.destroyed && that.realizePass === currentPass) {
                currentPass = ++that.realizePass;
                that.site._layout.startLayout(0, that.pagesToLoad * viewportLength - 1, count).then(function (initialRange) {
                    that.calculateDisplayedItems(Math.min(count, that.lastItem + 1)).then(function () {
                        if (initialRange) {
                            var itemsPerChunk = initialRange.endIndex - initialRange.beginIndex,
                                chunksLoaded = Math.max(1, Math.ceil(that.lastItem / itemsPerChunk)),
                                totalItems = Math.min(count, itemsPerChunk * chunksLoaded);
                            that.site._layout.startLayout(0, chunksLoaded * that.pagesToLoad * viewportLength - 1, totalItems).then(function (range) {
                                if (that.site._isZombie()) {
                                    return;
                                }

                                if (range && range.beginIndex < range.endIndex) {
                                    var end = Math.min(range.endIndex, totalItems);
                                    if (refreshView) {
                                        var canvas = that.site._itemCanvas,
                                            items = that.items;

                                        items.eachIndex(function (index) {
                                            if ((index < 0) || (index > (end - 1))) {
                                                var wrapper = items.wrapperAt(index);
                                                canvas.removeChild(wrapper);
                                                items.removeItem(index);
                                            }
                                        });
                                    }
                                    that.loadingInProgress = true;
                                    that.realizeItems(that.site._itemCanvas, 0, end, totalItems, currentPass, function (finalItem) {
                                        if (that.realizePass === currentPass) {
                                            that.loadingInProgress = false;
                                            that.lastItem = finalItem;
                                            that.updateScrollbar(count);
                                        }
                                        callback(true);
                                    });
                                } else {
                                    noRange(count);
                                }
                            });
                        } else {
                            noRange(count);
                        }
                    });
                });
            }
        });
    },

    download: function IncrementalView_download(action, callback) {
        var that = this;

        if (this.site._cachedCount === WinJS.UI._UNINITIALIZED || this.lastItem === WinJS.UI._UNINITIALIZED) {
            this.showProgressBar();
        }

        this.site._raiseViewLoading();
        action(function (realizeItemsCalled) {
            if (!realizeItemsCalled) {
                that.site._raiseViewComplete();
            }
        });
    },

    loadNextPages: function IncrementalView_loadNextPages() {
        this.download(this.loadNextChunk.bind(this));
        this.checkProgressBarVisibility();
    },

    checkProgressBarVisibility: function IncrementalView_checkProgressBarVisibility() {
        if (this.site._isZombie()) {
            return;
        }

        var viewportLength = this.site._getViewportLength(),
            scrollBarPos = this.site.scrollPosition;

            if (this.site._cachedCount > this.lastItem + 1 && this.loadingInProgress &&
                scrollBarPos >= this.site._canvas[this.site._layout.horizontal ? "offsetWidth" : "offsetHeight"] - viewportLength) {
                this.showProgressBar(); 
            }
    },

    showProgressBar: function IncrementalView_showProgressBar() {
        var barX = "50%",
            barY = "50%",
            parent = this.site._element;
        if (this.lastItem !== WinJS.UI._UNINITIALIZED) {
            parent = this.site._canvas;
            var padding = WinJS.UI._INCREMENTAL_CANVAS_PADDING / 2;
            if (this.site._layout.horizontal) {
                barX = "calc(100% - " + padding + "px)";
            } else {
                barY = "calc(100% - " + padding + "px)";
            }
        }

        this.site._showProgressBar(parent, barX, barY);
    },

    calculateDisplayedItems: function (count) {
        var that = this;
        
        function setUpdateMarkersPromise(promise) {
            if (that.updateMarkersPromise) {
                that.updateMarkersPromise.cancel();
            }
            that.updateMarkersPromise = promise;
        }
        
        if (count !== 0) {
            var scrollbarPos = this.site.scrollPosition,
                firstPromise = this.site.layout.calculateFirstVisible(scrollbarPos, false),
                lastPromise = this.site.layout.calculateLastVisible(scrollbarPos + this.site._getViewportLength() - 1, false);

            firstPromise.then(function (first) {
                that.firstIndexDisplayed = first;
            });

            lastPromise.then(function (last) {
                that.lastIndexDisplayed = last;
            });

            return WinJS.Promise.join([firstPromise, lastPromise]).then(function(v) {
                 setUpdateMarkersPromise(that.updateAriaMarkers(count, that.firstIndexDisplayed, that.lastIndexDisplayed));
                return WinJS.Promise.wrap(v);
            }, function (error) {
                var name = (error.length > 0 ? error[0].name : "");
                if (name !== "WinJS.UI.LayoutNotInitialized") {
                    return WinJS.Promise.wrapError(error);
                } else {
                    // If the ListView is invisible (LayoutNotInitialized), eat the exception
                    return WinJS.Promise.wrap();
                }
            });
        } else {
            this.firstIndexDisplayed = -1;
            this.lastIndexDisplayed = -1;
            setUpdateMarkersPromise(this.updateAriaMarkers(count, this.firstIndexDisplayed, this.lastIndexDisplayed));
            return WinJS.Promise.wrap();
        }
    },

    hideProgressBar: function IncrementalView_hideProgressBar() {
        this.site._hideProgressBar();
    },

    scrollbarAtEnd: function IncrementalView_scrollbarAtEnd(scrollbarPos, scrollLength, viewportSize) {
        var viewportLength = this.site._getViewportLength(),
            last = this.items.wrapperAt(this.lastItem),
            lastOffset = 0;

        if (last) {
            lastOffset =  last[ this.site._layout.horizontal ? "offsetLeft" : "offsetTop"]; 
        }

        return (scrollbarPos + viewportLength) > (lastOffset - viewportLength * this.pagesToLoadThreshold);
    },

    finalItem: function IncrementalView_finalItem() {
        return Promise.wrap(this.lastItem);
    },

    onScroll: function IncrementalView_onScroll(scrollbarPos, scrollLength, viewportSize) {
        this.checkProgressBarVisibility();

        if (this.scrollbarAtEnd(scrollbarPos, scrollLength, viewportSize) && this.automaticallyLoadPages) {
            this.download(this.loadNextChunk.bind(this));
        } else {
            var that = this;
            this.site._itemsCount().then(function (count) {
                return that.calculateDisplayedItems(count);
            }).then(function() {
                if (that.animating || that.loadingItems) {
                    that.site._raiseViewLoaded();
                } else {
                    that.site._raiseViewComplete();
                }
            });
        }
    },

    onResize: function IncrementalView_onResize(scrollbarPos, viewportSize) {
        this.download(this.updateItems.bind(this));
    },

    reset: function IncrementalView_reset() {
        var site = this.site;
        this.firstIndexDisplayed = -1;
        this.lastIndexDisplayed = -1;
        this.loadingInProgress = false;
        this.firstLayoutPass = true;
        this.runningAnimations = null;
        this.animating = false;
        this.loadingItems = false;
        this.lastItem = -1;
        site._unsetFocusOnItem();
        if (site._currentMode().onDataChanged) {
            site._currentMode().onDataChanged();
        }

        this.items.each(function (index, item) {
            site._itemsManager.releaseItem(item);
        });

        this.items.removeItems();
        site._resetCanvas();

        this.insertedElements = [];
        site._clearInsertedItems();
    },

    reload: function IncrementalView_reload() {
        this.download(this.loadNextChunk.bind(this));
    },

    resetView: function IncrementalView_resetView() {
        this.site.scrollPosition = 0;
    },

    refresh: function IncrementalView_refresh(scrollbarPos, scrollLength, viewportSize, newCount) {
        var that = this,
            end = Math.min(this.lastItem + 1, newCount);

        this.lastItem = end - 1;
        that.updateScrollbar(newCount);

        var canvas = this.site._itemCanvas,
            items = this.items;

        this.download(function (callback) {
            that.updateItems(function () {
                if (that.scrollbarAtEnd(scrollbarPos, scrollLength, viewportSize) && (newCount > end) && that.automaticallyLoadPages) {
                    that.loadNextChunk(callback);
                } else {
                    that.calculateDisplayedItems(newCount).then(function () {
                        callback(newCount);
                    });
                }
            }, true);
        });
    },

    updateScrollbar: function IncrementalView_updateScrollbar(count) {
        var that = this,
            length = Math.min(count, (this.lastItem !== -1 ? this.lastItem + 1 : count));
        
        if (length) {
            return this.site._layout.getScrollbarRange(length).then(
                function (range) {
                    that.site._setCanvasLength(range.beginScrollPosition, (length < count ?  WinJS.UI._INCREMENTAL_CANVAS_PADDING : 0) + range.endScrollPosition);
                },
                function () {
                    that.site._setCanvasLength(0, 0);
                }
            );
        } else {
            this.site._setCanvasLength(0, 0);
            return Promise.wrap();
        }
    },
    
    // Sets the ARIA attributes on each item
    updateAriaOnItems: function IncrementalView_updateAriaOnItems(count) {
        if (this.site._isZombie()) { return; }
        
        if (count > 0) {
            this.site._createAriaMarkers();
            var that = this;
            var startMarker = this.site._ariaStartMarker,
                endMarker = this.site._ariaEndMarker,
                firstItem = this.items.itemAt(0);
                
            WinJS.UI._ensureId(firstItem);
            WinJS.UI._setAttribute(firstItem, "x-ms-aria-flowfrom", startMarker.id);
            
            this.items.each(function (index, item, itemData) {
                var nextItem = that.items.itemAt(index + 1);

                if (nextItem) {
                    // We aren't at the last item so flow to the next one
                    WinJS.UI._ensureId(nextItem);
                    WinJS.UI._setFlow(item, nextItem);
                } else {
                    // We're at the last item so flow to the end marker
                    WinJS.UI._setAttribute(item, "aria-flowto", endMarker.id);
                }
                
                WinJS.UI._setAttribute(item, "role", that.site._itemRole);
                WinJS.UI._setAttribute(item, "aria-setsize", count);
                WinJS.UI._setAttribute(item, "aria-posinset", index + 1);
                WinJS.UI._setAttribute(item, "tabIndex", that.site._tabIndex);
            });
        }
    },
    
    // Sets aria-flowto on _ariaStartMarker and x-ms-aria-flowfrom on _ariaEndMarker. The former
    // points to the first visible item and the latter points to the last visible item.
    updateAriaMarkers: function IncrementalView_updateAriaMarkers(count, firstIndexDisplayed, lastIndexDisplayed) {
        if (this.site._isZombie()) { return Promise.wrap(); }
        
        this.site._createAriaMarkers();
        var that = this;
        var startMarker = this.site._ariaStartMarker,
            endMarker = this.site._ariaEndMarker;
        
        if (count === 0) {
            WinJS.UI._setFlow(startMarker, endMarker);
            return Promise.wrap();
        } else if (firstIndexDisplayed !== -1 && lastIndexDisplayed !== -1) {
            return Promise.join([this.items.requestItem(firstIndexDisplayed), this.items.requestItem(lastIndexDisplayed)]).done(function (v) {
                if (that.site._isZombie()) { return; }
                var firstVisibleItem = v[0],
                    lastVisibleItem = v[1];
                WinJS.UI._ensureId(firstVisibleItem);
                WinJS.UI._ensureId(lastVisibleItem);
                
                WinJS.UI._setAttribute(startMarker, "aria-flowto", firstVisibleItem.id);
                WinJS.UI._setAttribute(endMarker, "x-ms-aria-flowfrom", lastVisibleItem.id);
            });
        } else {
            return Promise.wrap();
        }
    },
    
    // Update the ARIA attributes on item that are needed so that Narrator can announce it.
    // item must be in the items container.
    updateAriaForAnnouncement: function IncrementalView_updateAriaForAnnouncement(item, count) {
        var index = this.items.index(item);
        //#DBG _ASSERT(index !== WinJS.UI._INVALID_INDEX);
        
        WinJS.UI._setAttribute(item, "role", this.site._itemRole);
        WinJS.UI._setAttribute(item, "aria-setsize", count);
        WinJS.UI._setAttribute(item, "aria-posinset", index + 1);
    },

    cleanUp: function IncrementalView_cleanUp() {
        var itemsManager = this.site._itemsManager;
        this.items.each(function (index, item) {
            itemsManager.releaseItem(item);
        });
        this.lastItem = -1;
        this.site._unsetFocusOnItem();
        this.items.removeItems();
        this.site._resetCanvas();
        this.destroyed = true;
    }
};

})(this, WinJS);

(function itemsContainerInit(global, WinJS, undefined) {
    "use strict";

var utilities = WinJS.Utilities,
    Promise = WinJS.Promise;

WinJS.Namespace.define("WinJS.UI", {
    _ItemsContainer: function (site) {
        this.site = site;
        this._itemData = {};
        this.dataIndexToLayoutIndex = {};
        this.waitingItemRequests = {};
        this.placeholders = {};
    }
});

WinJS.UI._ItemsContainer.prototype = {
    requestItem: function ItemsContainer_requestItem(itemIndex) {
        if (!this.waitingItemRequests[itemIndex]) {
            this.waitingItemRequests[itemIndex] = [];
        }

        var that = this;
        var promise = new Promise(function (complete, error) {
            var itemData = that._itemData[itemIndex];
            if (itemData && !itemData.detached && itemData.element) {
                complete(itemData.element);
            } else {
                that.waitingItemRequests[itemIndex].push(complete);
            }
        });

        return promise;
    },

    removeItem: function (index) {
        /*#DBG
        delete WinJS.Utilities.data(this._itemData[index].element).itemData;
        delete WinJS.Utilities.data(this._itemData[index].element).itemsContainer;
        #DBG*/
        delete this._itemData[index];
    },

    removeItems: function ItemsContainer_removeItems() {
        /*#DBG
        var that = this;
        Object.keys(this._itemData).forEach(function (k) {
            delete WinJS.Utilities.data(that._itemData[k].element).itemData;
            delete WinJS.Utilities.data(that._itemData[k].element).itemsContainer;
        });
        #DBG*/
        this._itemData = {};
        this.placeholders = {};
        this.waitingItemRequests = {};
    },
    
    setPlaceholderAt: function ItemsContainer_setPlaceholderAt(itemIndex, placeholder) {
        this.placeholders[itemIndex] = placeholder;
    },

    setItemAt: function ItemsContainer_setItemAt(itemIndex, itemData) {
        /*#DBG
        if (itemData.itemsManagerRecord.released) {
            throw "ACK! Attempt to use a released itemsManagerRecord";
        }
        var oldItemData = WinJS.Utilities.data(itemData.element).itemData;
        if (oldItemData || WinJS.Utilities.data(itemData.element).itemsContainer) {
            if (oldItemData.itemsManagerRecord.item.index !== itemIndex) {
                throw "ACK! Attempted use of already in-use element";
            }
        }
        WinJS.Utilities.data(itemData.element).itemData = itemData;
        WinJS.Utilities.data(itemData.element).itemsContainer = this;
        #DBG*/
        //#DBG _ASSERT(itemData.element && (itemData.element instanceof HTMLElement));
        //#DBG _ASSERT(!this._itemData[itemIndex]);
        this._itemData[itemIndex] = itemData;
        if (!itemData.detached) {
            this.notify(itemIndex, itemData);
        }
    },

    notify: function ItemsContainer_notify(itemIndex, itemData) {
        if (this.waitingItemRequests[itemIndex]) {
            var requests = this.waitingItemRequests[itemIndex];
            for (var i = 0; i < requests.length; i++) {
                requests[i](itemData.element);
            }

            this.waitingItemRequests[itemIndex] = [];
        }
        if (this.placeholders[itemIndex]) {
            delete this.placeholders[itemIndex];
        }
    },

    elementAvailable: function ItemsContainer_elementAvailable(itemIndex) {
        var itemData = this._itemData[itemIndex];
        itemData.detached = false;
        this.notify(itemIndex, itemData);
    },


    itemAt: function ItemsContainer_itemAt(itemIndex) {
        var itemData = this._itemData[itemIndex];
        return itemData ? itemData.element : null;
    },

    itemDataAt: function ItemsContainer_itemDataAt(itemIndex) {
        return this._itemData[itemIndex];
    },
    
    wrapperAt: function ItemsContainer_wrapperAt(itemIndex) {
        var itemData = this._itemData[itemIndex];
        return itemData ? itemData.wrapper : null;
    },
    
    wrapperFrom: function ItemsContainer_wrapperFrom(element) {
        var canvas = this.site._itemCanvas,
            viewport = this.site._viewport;

        while (element && element.parentNode && element.parentNode !== canvas && element.parentNode !== viewport) {
            element = element.parentNode;
        }

        return (element && utilities.hasClass(element, WinJS.UI._wrapperClass) ? element : null);
    },

    index: function ItemsContainer_index(element) {
        var item = this.wrapperFrom(element);
        if (item) {
            for (var index in this._itemData) {
                if (this._itemData[index].wrapper === item) {
                    return parseInt(index, 10);
                }
            }
        }

        return WinJS.UI._INVALID_INDEX;
    },

    each: function ItemsContainer_each(callback) {
        for (var index in this._itemData) {
            if (this._itemData.hasOwnProperty(index)) {
                var itemData = this._itemData[index];
                //#DBG _ASSERT(itemData);
                callback(parseInt(index, 10), itemData.element, itemData);
            }
        }
    },

    eachIndex: function ItemsContainer_each(callback) {
        for (var index in this._itemData) {
            callback(parseInt(index, 10))
        }
    },

    setLayoutIndices: function ItemsContainer_setLayoutIndices(indices) {
        this.dataIndexToLayoutIndex = indices;
    },

    getLayoutIndex: function ItemsContainer_getLayoutIndex(dataIndex) {
        var layoutIndex = this.dataIndexToLayoutIndex[dataIndex];
        return layoutIndex === undefined ? dataIndex : layoutIndex;
    }
};
})(this, WinJS);

(function itemsPoolInit(global, WinJS, undefined) {
    "use strict";

var utilities = WinJS.Utilities,
    Promise = WinJS.Promise;

function getListView(element) {
    while (element && !utilities.hasClass(element, WinJS.UI._listViewClass)) {
        element = element.parentNode;
    }
    return element ? element.winControl : null;
}

// This is onpropertychange handler. attachEvent handlers leak stuff referenced by closures so this function is global and doesn't use a closure to access ListView or an item.
function itemPropertyChange() {
    if (event.propertyName === "aria-selected") {
        var wrapper = event.srcElement.parentNode,
            selected = event.srcElement.getAttribute("aria-selected") === "true";

        // Only respond to aria-selected changes coming from UIA. This check relies on the fact that, in renderSelection, we update the selection visual before aria-selected.
        if (wrapper && (selected !== WinJS.UI._isSelectionRenderer(wrapper))) {
            var listView = getListView(wrapper.parentNode);
            if (listView) {
                var index = listView._view.items.index(wrapper),
                    selection = listView.selection;

                if (listView._selectionAllowed()) {
                    if (selected) {
                        selection[listView._selectionMode === WinJS.UI.SelectionMode.single ? "set" : "add"](index);
                    } else {
                        selection.remove(index);
                    }
                }

                if (selection._isIncluded(index) !== selected) {
                    // If a selectionchanging event handler rejected the selection change, revert aria-selected
                    event.srcElement.setAttribute("aria-selected", !selected);
                }
            }
        }
    }
}

WinJS.Namespace.define("WinJS.UI", {
    _itemPropertyChange: itemPropertyChange
});

// Default renderer for Listview
var trivialHtmlRenderer = WinJS.UI.simpleItemRenderer(function (item) {
    if (utilities._isDOMElement(item.data)) {
        return item.data;
    }

    var data = item.data;
    if (data === undefined) {
        data = "undefined";
    } else if (data === null) {
        data = "null";
    } else if (typeof data === "object") {
        data = JSON.stringify(data);
    }

    var element = document.createElement("span");
    element.innerText = data.toString();
    return element;
});

WinJS.Namespace.define("WinJS.UI", {
    _trivialHtmlRenderer: trivialHtmlRenderer,
    _ElementsPool: function (site, itemClass, prepareMethodName) {
        this.init(site, itemClass, prepareMethodName);
    }
});

var canceledPromise = WinJS.Promise.wrapError(new WinJS.ErrorFromName("Canceled"));

WinJS.UI._ElementsPool.prototype = {
    init: function (site, itemClass, prepareMethodName) {
        this.site = site;
        this.itemClass = itemClass;
        this.prepareMethodName = prepareMethodName;
        this.entries = [];
        this.uidToEntry = {};
        this.renderer = WinJS.UI._trivialHtmlRenderer;
        this.release = null;
    },

    setRenderer: function (newRenderer) {
        if (!newRenderer) {
            if (WinJS.validation) {
                throw new WinJS.ErrorFromName("WinJS.UI.ListView.invalidTemplate", WinJS.UI._strings.invalidTemplate);
            }
            this.renderer = trivialHtmlRenderer;
        } else if (typeof newRenderer === "function") {
            this.renderer = newRenderer;
        } else if (typeof newRenderer === "object") {
            if (WinJS.validation && !newRenderer.renderItem) {
                throw new WinJS.ErrorFromName("WinJS.UI.ListView.invalidTemplate", WinJS.UI._strings.invalidTemplate);
            }
            this.renderer = newRenderer.renderItem;
        }
    },

    renderItemAsync: function (itemPromise, oldElement) {
        var entry,
            recycledElement;

        if (oldElement) {
            recycledElement = oldElement;
        } else {
            entry = this.getEntry();
            recycledElement = entry ? entry.element : null;
        }

        var itemForRendererPromise = itemPromise.then(function (item) {
            return item || canceledPromise;
        });

        var rendered = WinJS.Promise.as(this.renderer(itemForRendererPromise, recycledElement)).
            then(WinJS.UI._normalizeRendererReturn);

        var that = this;
        return rendered.then(function (v) {
            that.itemRendered(v.element, recycledElement, entry);
            return v;
        });
    },
    
    renderItemSync: function (itemPromise) {
        var entry = this.getEntry();
        var recycledElement = entry ? entry.element : null;
        var rendered = this.renderer(itemPromise, recycledElement);
        this.itemRendered(rendered.element, recycledElement, entry);
        return rendered;
    },

    itemRendered: function (element, recycledElement, entry) {
        if (element) {
            if (element !== recycledElement) {
                this.setUpItem(element);
            } else {
                this.resetItem(recycledElement, entry);
                if (entry) {
                    this.entries.splice(entry.index, 1);
                    delete this.uidToEntry[recycledElement.uniqueID];
                }
            }
        }
    },

    setUpItem: function (element) {
        if (this.itemClass) {
            utilities.addClass(element, this.itemClass);
        }
        if (this.prepareMethodName) {
            this.site._layout[this.prepareMethodName](element);
        }
    },

    prepareForReuse: function (recycledElement) {
    },

    resetItem: function (recycledElement, entry) {
        if (entry && entry.display) {
            recycledElement.style.display = entry.display;
        }
    },

    getEntry: function () {
        for(var i = this.entries.length - 1; i >= 0; i--) {
            var object = this.entries[i];
            if (!object.removed) {
                object.removed = true;
                this.prepareForReuse(object.element);
                object.element.id = "";
                return {
                    element: object.element,
                    data: object.data,
                    display: object.display,
                    index: i
                };
            }
        } 
        return null;
    },

    remove: function (element) {
        var entry = this.uidToEntry[element.uniqueID];
        if (entry) {
            entry.removed = true;
        }
    },

    add: function (data, element, display) {
        if (this.release) {
            this.release(data, element);
        }

        /*#DBG
        if (WinJS.Utilities.data(element).itemData
            || WinJS.Utilities.data(element).itemsContainer
            || WinJS.Utilities.data(element).itemsManagerRecord) {
            throw "ACK! Attempt to put something into the pool that wasn't properly released";
        }
        #DBG*/

        var entry = {
            element: element,
            display: display,
            removed: false
        };
        this.entries.push(entry);
        this.uidToEntry[element.uniqueID] = entry;
    },

    clear: function () {
        for (var i = 0, len = this.entries.length; i < len; i++) {
            var entry = this.entries[i],
                element = entry.element,
                parentNode = entry.element.parentNode;

            if (!entry.removed && parentNode) {
                parentNode.removeChild(element);
            }
        }
        this.entries = [];
        this.uidToEntry = {};
    }
};

WinJS.Namespace.define("WinJS.UI", {
    _ItemsPool: WinJS.Class.derive(WinJS.UI._ElementsPool, function (site) {
        this.init(site);
    },{
        setUpItem: function (element) {
            var wrapper = this.site._wrappersPool.renderItemSync().element;

            this.site._renderSelection(wrapper, element, false, true);

            wrapper.insertBefore(element, wrapper.firstElementChild);
            utilities.addClass(element, WinJS.UI._itemClass);

            this.site._layout.prepareItem(element);
            this.site._layout.prepareItem(wrapper);
            
            element.attachEvent("onpropertychange", itemPropertyChange);
        },
        prepareForReuse: function (recycledElement) {
            var wrapper = recycledElement.parentNode;
            if (wrapper) {
                this.site._wrappersPool.remove(wrapper);
            }
        },
        resetItem: function (recycledElement, entry) {
            var wrapper = recycledElement.parentNode;
            if (wrapper) {
                this.site._renderSelection(wrapper, recycledElement, false, true);
            } else {
                this.setUpItem(recycledElement);
            }
        }
    }, {
        supportedForProcessing: false,
    })
});

})(this, WinJS);

(function listLayoutInit(global, WinJS, undefined) {
    "use strict";


var utilities = WinJS.Utilities,
    Promise = WinJS.Promise,
    Signal = WinJS._Signal,
    AnimationHelper = WinJS.UI._ListViewAnimationHelper;

// This component is responsible for calculating items' positions in list mode. 
WinJS.Namespace.define("WinJS.UI", {
    ListLayout: WinJS.Class.derive(WinJS.UI._LayoutCommon, function (options) {
        /// <signature helpKeyword="WinJS.UI.ListLayout">
        /// <summary locid="WinJS.UI.ListLayout">
        /// Creates a new ListLayout object.
        /// </summary>
        /// <param name="options" type="Object" locid="WinJS.UI.ListLayout_p:options">
        /// The set of properties and values to apply to the new ListLayout.
        /// </param>
        /// <returns type="WinJS.UI.ListLayout" locid="WinJS.UI.ListLayout_returnValue">
        /// The new ListLayout object.
        /// </returns>
        /// </signature>
        this.init();
        this._cachedItemRecords = {};
    }, {        
        /// <field type="Boolean" hidden="true" locid="WinJS.UI.ListLayout.horizontal" helpKeyword="WinJS.UI.ListLayout.horizontal">
        /// Gets a value that indicates whether items are laid out horizontally.
        /// This property always returns false for ListLayout.
        /// </field>
        horizontal: {
            enumerable: true, 
            get: function () {
                return false;
            }
        },

        getKeyboardNavigatedItem: function (itemIndex, element, keyPressed) {
            /// <signature helpKeyword="WinJS.UI.ListLayout.getKeyboardNavigatedItem">
            /// <summary locid="WinJS.UI.ListLayout.getKeyboardNavigatedItem">
            /// This API supports the Windows Library for JavaScript infrastructure and is not intended to be used directly from your code.
            /// </summary>
            /// <param name="itemIndex" locid="WinJS.UI.ListLayout.getKeyboardNavigatedItem_p:itemIndex">
            /// 
            /// </param>
            /// <param name="element" locid="WinJS.UI.ListLayout.getKeyboardNavigatedItem_p:element">
            /// 
            /// </param>
            /// <param name="keyPressed" locid="WinJS.UI.ListLayout.getKeyboardNavigatedItem_p:keyPressed">
            /// 
            /// </param>
            /// </signature>
            if (!this._initialized()) {
                return Promise.wrap(-1);
            }

            keyPressed = this._adjustDirection(keyPressed);

            var newIndex;
            switch (keyPressed) {
            case WinJS.Utilities.Key.upArrow:
            case WinJS.Utilities.Key.leftArrow:
                newIndex = itemIndex - 1;
                break;
            case WinJS.Utilities.Key.downArrow:
            case WinJS.Utilities.Key.rightArrow:
                newIndex = itemIndex + 1;
                break;
            default:
                return WinJS.UI._LayoutCommon.prototype.getKeyboardNavigatedItem.call(this, itemIndex, element, keyPressed);
            }
            
            return Promise.wrap(newIndex);
        },

        setSite: function (layoutSite) {
            /// <signature helpKeyword="WinJS.UI.ListLayout.setSite">
            /// <summary locid="WinJS.UI.ListLayout.setSite">
            /// This API supports the Windows Library for JavaScript infrastructure and is not intended to be used directly from your code.
            /// </summary>
            /// <param name="layoutSite" locid="WinJS.UI.ListLayout.setSite_p:layoutSite">
            /// 
            /// </param>
            /// </signature>
            this._site = layoutSite;
        },

        getScrollbarRange: function (count) {
            /// <signature helpKeyword="WinJS.UI.ListLayout.getScrollbarRange">
            /// <summary locid="WinJS.UI.ListLayout.getScrollbarRange">
            /// This API supports the Windows Library for JavaScript infrastructure and is not intended to be used directly from your code. 
            /// </summary>
            /// <param name="count" locid="WinJS.UI.ListLayout.getScrollbarRange_p:count">
            ///  
            /// </param>
            /// </signature>
            var that = this;
            return this._initialize(count).then(function (initialized) {
                if (initialized) {
                    return {
                        beginScrollPosition: 0,
                        endScrollPosition: count * that._totalItemHeight
                    };
                } else {
                    return {
                        beginScrollPosition: 0,
                        endScrollPosition: 0
                    };
                }
            });
        },

        getItemPosition: function (itemIndex) {
            /// <signature helpKeyword="WinJS.UI.ListLayout.getItemPosition">
            /// <summary locid="WinJS.UI.ListLayout.getItemPosition">
            /// This API supports the Windows Library for JavaScript infrastructure and is not intended to be used directly from your code.
            /// </summary>
            /// <param name="itemIndex" locid="WinJS.UI.ListLayout.getItemPosition_p:itemIndex">
            /// 
            /// </param>
            /// </signature>
            var that = this;
            return this._initialize().then(function (initialized) {
                if (initialized) {
                    var pos = that._calcItemPosition(itemIndex);

                    pos.contentWidth = that._width;
                    pos.contentHeight = that._itemHeight;
                    pos.totalWidth = that._site.viewportSize.width;
                    pos.totalHeight = that._totalItemHeight;

                    return pos;
                } else {
                    return Promise.wrapError(new WinJS.ErrorFromName("WinJS.UI.LayoutNotInitialized", WinJS.UI._strings.layoutNotInitialized));
                }
            });
        },

        _initialize: function (count) {
            var that = this
            return this._initializeBase(count).then(function (initialized) {
                if (initialized) {
                    //#DBG _ASSERT(that._totalItemWidth > 0 && that._itemWidth > 0);
                    var overhead = that._totalItemWidth - that._itemWidth;
                    that._width = that._site.viewportSize.width - overhead;

                    var surfaceMargin = that._site._surfaceMargins;
                    that._surfaceMargin = surfaceMargin.top;
                }
                return initialized;
            });
        },

        startLayout: function (beginScrollPosition, endScrollPosition, count) {
            /// <signature helpKeyword="WinJS.UI.ListLayout.startLayout">
            /// <summary locid="WinJS.UI.ListLayout.startLayout">
            /// This API supports the Windows Library for JavaScript infrastructure and is not intended to be used directly from your code. 
            /// </summary>
            /// <param name="beginScrollPosition" locid="WinJS.UI.ListLayout.startLayout_p:beginScrollPosition">
            ///  
            /// </param>
            /// <param name="endScrollPosition" locid="WinJS.UI.ListLayout.startLayout_p:endScrollPosition">
            ///  
            /// </param>
            /// <param name="count" locid="WinJS.UI.ListLayout.startLayout_p:count">
            ///  
            /// </param>
            /// </signature>
            var that = this;
            if (count) {
                this._count = count;
                return this._initialize(count).then(function (initialized) {
                    if (initialized) {
                        var dataModifiedPromise = that._dataModifiedPromise ? that._dataModifiedPromise : Promise.wrap();
                        return dataModifiedPromise.then(function () {
                            // In incremental mode, startLayout needs to give a range of whole items, and not round up if there isn't enough space in the scroll range.
                            var incremental = (that._site.loadingBehavior === "incremental");
                            return that.calculateFirstVisible(beginScrollPosition, incremental).then(function (begin) {
                                return that.calculateLastVisible(endScrollPosition, incremental).then(function (last) {
                                    var end = last + 1;
                                    that._purgeItemCache(begin, end);
                                    return {
                                        beginIndex: begin,
                                        endIndex: end
                                    };
                                });
                            });
                        });
                    } else {
                        return null;
                    }
                });
            } else {
                return Promise.wrap(null);
            }
        },

        prepareItem: function (element) {
            /// <signature helpKeyword="WinJS.UI.ListLayout.prepareItem">
            /// <summary locid="WinJS.UI.ListLayout.prepareItem">
            /// This API supports the Windows Library for JavaScript infrastructure and is not intended to be used directly from your code.
            /// </summary>
            /// <param name="element" locid="WinJS.UI.ListLayout.prepareItem_p:element">
            /// 
            /// </param>
            /// </signature>

            // Do nothing because position absolute is already set in CSS.
        },

        prepareHeader: function (element) {
            /// <signature helpKeyword="WinJS.UI.ListLayout.prepareHeader">
            /// <summary locid="WinJS.UI.ListLayout.prepareHeader">
            /// This API supports the Windows Library for JavaScript infrastructure and is not intended to be used directly from your code.
            /// </summary>
            /// <param name="element" locid="WinJS.UI.ListLayout.prepareHeader_p:element">
            ///  
            /// </param>
            /// </signature>

            // Do nothing because position absolute is already set in CSS.
        },

        releaseItem: function (item, newItem) {
            /// <signature helpKeyword="WinJS.UI.ListLayout.releaseItem">
            /// <summary locid="WinJS.UI.ListLayout.releaseItem">
            /// This API supports the Windows Library for JavaScript infrastructure and is not intended to be used directly from your code.
            /// </summary>
            /// <param name="item" locid="WinJS.UI.ListLayout.releaseItem_p:item">
            /// 
            /// </param>
            /// <param name="newItem" locid="WinJS.UI.ListLayout.releaseItem_p:newItem">
            /// 
            /// </param>
            /// </signature>
            item._animating = false;
        },

        layoutItem: function (itemIndex, element) {
            /// <signature helpKeyword="WinJS.UI.ListLayout.layoutItem">
            /// <summary locid="WinJS.UI.ListLayout.layoutItem">
            /// This API supports the Windows Library for JavaScript infrastructure and is not intended to be used directly from your code. 
            /// </summary>
            /// <param name="itemIndex" locid="WinJS.UI.ListLayout.layoutItem_p:itemIndex">
            ///  
            /// </param>
            /// <param name="element" locid="WinJS.UI.ListLayout.layoutItem_p:element">
            ///  
            /// </param>
            /// </signature>
            var itemPos = this._calcItemPosition(itemIndex),
                itemData = this._getItemInfo(itemIndex);

            if (itemData.top !== itemPos.top || itemData.width !== this._width || itemData.height != this._itemHeight || element !== itemData.element) {
                var oldTop = (itemData.element === element ? itemData.top : undefined);
                itemData.element = element;
                itemData.top = itemPos.top;
                itemData.width = this._width;
                itemData.height = this._itemHeight;

                var cachedRecord = this._cachedItemRecords[element.uniqueID];
                if (cachedRecord) {
                    cachedRecord.left = itemData.left;
                    cachedRecord.top = itemData.top;
                }

                var style = element.style;
                if (!element._animating && !cachedRecord) {
                    // When an element isn't marked as animating, and no animation record exists for it, it's still not necessarily safe to animate.
                    // If a lot of elements are being deleted, we can run into cases where new items that we've never seen before need to be realized and put
                    // in the view. If an item falls into the animation range and has no record, we'll set up a special record for it and animate it coming in from the bottom
                    // of the view.
                    if (this._dataModifiedPromise && itemIndex >= this._viewAnimationRange.start && itemIndex <= this._viewAnimationRange.end) {
                        this._cachedItemRecords[element.uniqueID] = {
                            oldTop: itemData.top + this._site.viewportSize.height * 2,
                            oldLeft: itemData.left,
                            row: itemData.row,
                            column: itemData.column,
                            top: itemData.top,
                            left: itemData.left,
                            element: element,
                            itemIndex: itemIndex,
                            appearedInView: true
                        };
                        // Since this item just appeared in the view and we're going to animate it coming in from the bottom, we set its opacity to zero because it'll be moved to the bottom of the listview
                        // but can still be visible since the canvas region's clip style isn't set until endLayout
                        style.cssText += ";left:0px;top:" + this._cachedItemRecords[element.uniqueID].oldTop + "px;width:" + this._width + "px;height:" + this._itemHeight + "px; opacity: 0";
                    } else {
                        // Setting the left, top, width, and height via cssText is approximately 50% faster than setting each one individually.
                        // Start with semicolon since cssText does not end in one even if you provide one at the end.
                        style.cssText += ";left:0px;top:" + itemPos.top + "px;width:" + this._width + "px;height:" + this._itemHeight + "px";
                    }
                }

                // When an element is laid out again while animating but doesn't have a cached record, that means that enough changes have occurred to
                // make that element outside of the range of usual animations (that range is found in the dataModified handler). We don't want to move the
                // element instantly, since while it may be outside of the range of visible indices, it may still be visible because it's in the midst
                // of a move animation. We'll instead make a new record for this element and let endLayout animate it again.
                if (element._animating && !cachedRecord) {
                    this._cachedItemRecords[element.uniqueID] = {
                        oldTop: oldTop,
                        top: itemData.top,
                        element: element
                    };
                }
            }
        },

        layoutHeader: function (groupIndex, element) {
            /// <signature helpKeyword="WinJS.UI.ListLayout.layoutHeader">
            /// <summary locid="WinJS.UI.ListLayout.layoutHeader">
            /// This API supports the Windows Library for JavaScript infrastructure and is not intended to be used directly from your code.
            /// </summary>
            /// <param name="groupIndex" locid="WinJS.UI.ListLayout.layoutHeader_p:groupIndex">
            /// 
            /// </param>
            /// <param name="element" locid="WinJS.UI.ListLayout.layoutHeader_p:element">
            /// 
            /// </param>
            /// </signature>
            element.style.display = "none";
        },

        itemsAdded: function (elements) {
            /// <signature helpKeyword="WinJS.UI.ListLayout.itemsAdded">
            /// <summary locid="WinJS.UI.ListLayout.itemsAdded">
            /// This API supports the Windows Library for JavaScript infrastructure and is not intended to be used directly from your code.
            /// </summary>
            /// <param name="elements" locid="WinJS.UI.ListLayout_p:elements">
            /// 
            /// </param>
            /// </signature>
            this._dataModified(elements, []);
        },

        itemsRemoved: function (elements) {
            /// <signature helpKeyword="WinJS.UI.ListLayout.itemsRemoved">
            /// <summary locid="WinJS.UI.ListLayout.itemsRemoved">
            /// This API supports the Windows Library for JavaScript infrastructure and is not intended to be used directly from your code.
            /// </summary>
            /// <param name="elements" locid="WinJS.UI.itemsRemoved_p:elements">
            /// 
            /// </param>
            /// </signature>
            this._dataModified([], elements);
        },

        itemsMoved: function GridLayout_itemsMoved() {
            /// <signature helpKeyword="WinJS.UI.ListLayout.itemsMoved">
            /// <summary locid="WinJS.UI.ListLayout.itemsMoved">
            /// This API supports the Windows Library for JavaScript infrastructure and is not intended to be used directly from your code.
            /// </summary>
            /// </signature>
            this._dataModified([], []);
        },

        _dataModified: function (inserted, removed) {
            var i, len;
            for (i = 0, len = inserted.length; i < len; i++) {
                this._cachedInserted.push(inserted[i]);
            }
            for (i = 0, len = removed.length; i < len; i++) {
                this._cachedRemoved.push(removed[i]);
            }

            // If the layout's already been cached in this cycle, skip this datamodified run
            if (this._dataModifiedPromise) {
                return;
            }

            var currentPromise = new Signal();
            this._dataModifiedPromise = currentPromise.promise;
            this._animateEndLayout = true;
            if (this._initialized()) {
                var that = this;
                this._isEmpty().then(function (isEmpty) {
                    if (!isEmpty) {
                        var viewportSize = that._site.viewportSize.height,
                            firstPromise = that.calculateFirstVisible(Math.max(0, that._site.scrollbarPos - viewportSize), false),
                            lastPromise = that.calculateLastVisible(that._site.scrollbarPos + 2 * viewportSize - 1, false);

                        WinJS.Promise.join([firstPromise, lastPromise]).done(function (indices) {
                                var firstNearbyItem = indices[0],
                                    lastNearbyItem = indices[1] + that._cachedRemoved.length;

                                that._viewAnimationRange = {
                                    start: firstNearbyItem,
                                    end: lastNearbyItem
                                };
                                for (var i = firstNearbyItem - 1; i <= lastNearbyItem; i++) {
                                    var itemData = that._getItemInfo(i);
                                    if (itemData && itemData.element) {
                                        if (!that._cachedItemRecords[itemData.element.uniqueID]) {
                                            that._cachedItemRecords[itemData.element.uniqueID] = {
                                                oldLeft: itemData.left,
                                                oldTop: itemData.top,
                                                left: itemData.left,
                                                top: itemData.top,
                                                element: itemData.element
                                            };
                                        }
                                    }
                                }
                                currentPromise.complete();
                            }, 
                            function (error) {
                                currentPromise.complete();
                                var layoutNotInitialized;
                                if (Array.isArray(error)) {
                                    layoutNotInitialized = error.some(function (e) { return e && e.name === "WinJS.UI.LayoutNotInitialized"; });
                                } else {
                                    layoutNotInitialized = error.name === "WinJS.UI.LayoutNotInitialized";
                                }
                                if (!layoutNotInitialized) {
                                    return WinJS.Promise.wrapError(error);
                                }
                            }
                        );
                    } else {
                        currentPromise.complete();
                    }
                });
            } else {
                currentPromise.complete();
            }
        },

        endLayout: function () {
            /// <signature helpKeyword="WinJS.UI.ListLayout.endLayout">
            /// <summary locid="WinJS.UI.ListLayout.endLayout">
            /// This API supports the Windows Library for JavaScript infrastructure and is not intended to be used directly from your code. 
            /// </summary>
            /// </signature>
            if (!this._animateEndLayout) {
                return;
            }
            var dataModifiedPromise = this._dataModifiedPromise ? this._dataModifiedPromise : Promise.wrap();
            this._dataModifiedPromise = null;
            this._animateEndLayout = false;
            var that = this;

            var endLayoutPromise = dataModifiedPromise.then(function () {
                var i, len, element;
                if (that._site.animationsDisabled) {
                    for (i = 0, len = that._cachedInserted.length; i < len; i++) {
                        that._cachedInserted[i].style.opacity = 1.0;
                    }
                    for (i = 0, len = that._cachedRemoved.length; i < len; i++) {
                        element = that._cachedRemoved[i];
                        if (element.parentNode) {
                            element.parentNode.removeChild(element);
                        }
                    }
                    var cachedRecordKeys = Object.keys(that._cachedItemRecords);
                    for (i = 0, len = cachedRecordKeys.length; i < len; i++) {
                        var itemRecord = that._cachedItemRecords[cachedRecordKeys[i]];
                        if (itemRecord.element) {
                            if (itemRecord.oldLeft !== itemRecord.left || itemRecord.oldTop !== itemRecord.top) {
                                if (itemRecord.left !== undefined) {
                                    itemRecord.element.style.left = itemRecord.left + "px";
                                }
                                if (itemRecord.top !== undefined) {
                                    itemRecord.element.style.top = itemRecord.top + "px";
                                }
                            }

                            if (itemRecord.appearedInView) {
                                itemRecord.element.style.opacity = 1;
                            }
                        }
                    }
                    that._cachedInserted = [];
                    that._cachedRemoved = [];
                    that._cachedItemRecords = {};

                    return;
                }

                var affectedItems = {},
                    animationSignal = new Signal(),
                    cachedRecordKeys = Object.keys(that._cachedItemRecords),
                    insertedElements = [],
                    removedElements = [];

                for (i = 0, len = that._cachedRemoved.length; i < len; i++) {
                    element = that._cachedRemoved[i];
                    element.style.opacity = 0.0;
                    element._removed = true;
                    removedElements.push(element);
                }

                for (i = 0, len = that._cachedInserted.length; i < len; i++) {
                    element = that._cachedInserted[i];
                    if (!element._removed) {
                        element.style.opacity = 1;
                        var itemRecord = that._cachedItemRecords[element.uniqueID];
                        if (itemRecord) {
                            element.style.cssText += ";top:" + itemRecord.top + "px;";
                        }
                        element._inserted = true;
                        insertedElements.push(element);
                    }
                }

                var movingElements = [],
                    moveData = [];
                for (i = 0, len = cachedRecordKeys.length; i < len; i++) {
                    var itemRecord = that._cachedItemRecords[cachedRecordKeys[i]];
                    if (itemRecord.element) {
                        var element = itemRecord.element;
                        if ((itemRecord.oldLeft !== itemRecord.left || itemRecord.oldTop !== itemRecord.top) && !element._inserted && !element._removed) {
                            // The itemData object is reused by the ListView, but item records are recreated every time a change happens. The stages
                            // need unchanging records to function properly.
                            movingElements.push(element);
                            moveData.push({left: itemRecord.left, top: itemRecord.top});
                            itemRecord.element._animating = true;
                        }

                        if (itemRecord.appearedInView && !element._inserted && !element._removed) {
                            element.style.opacity = 1;
                        }
                    }
                }

                var animation = WinJS.UI.Animation._createUpdateListAnimation(insertedElements, removedElements, movingElements);
                for (i = 0, len = insertedElements.length; i < len; i++) {
                    insertedElements[i]._currentAnimation = animation;
                    insertedElements[i]._inserted = null;
                }
                for (i = 0, len = removedElements.length; i < len; i++) {
                    removedElements[i]._currentAnimation = animation;
                    removedElements[i]._removed = null;
                }
                for (i = 0, len = movingElements.length; i < len; i++) {
                    movingElements[i].style.left = moveData[i].left + "px";
                    movingElements[i].style.top = moveData[i].top + "px";
                    movingElements[i]._currentAnimation = animation;
                }
                function done() {
                    for (i = 0, len = insertedElements.length; i < len; i++) {
                        if (insertedElements[i]._currentAnimation === animation) {
                            insertedElements[i]._currentAnimation = null;
                            insertedElements[i]._animating = false;
                        }
                    }
                    for (i = 0, len = removedElements.length; i < len; i++) {
                        if (removedElements[i]._currentAnimation === animation) {
                            removedElements[i]._currentAnimation = null;
                            removedElements[i]._animating = false;
                            if (removedElements[i].parentNode) {
                                removedElements[i].parentNode.removeChild(removedElements[i]);
                            }
                        }
                    }
                    for (i = 0, len = movingElements.length; i < len; i++) {
                        if (movingElements[i]._currentAnimation === animation) {
                            movingElements[i]._currentAnimation = null;
                            movingElements[i]._animating = false;
                        }
                    }

                    if (!that._site._isZombie()) {
                        animationSignal.complete();
                    }
                }
                animation.execute().then(done, done);
                that._cachedInserted = [];
                that._cachedRemoved = [];
                that._cachedItemRecords = {};
                return animationSignal.promise;
            });

            return {
                animationPromise: endLayoutPromise
            };
        },

        _calcItemPosition: function (index) {
            return {
                top: index * this._totalItemHeight,
                left: 0,
                offset: 0
            };
        },

        calculateFirstVisible: function (beginScrollPosition, wholeItem) {
            /// <signature helpKeyword="WinJS.UI.ListLayout.calculateFirstVisible">
            /// <summary locid="WinJS.UI.ListLayout.calculateFirstVisible">
            /// This API supports the Windows Library for JavaScript infrastructure and is not intended to be used directly from your code.
            /// </summary>
            /// <param name="beginScrollPosition" locid="WinJS.UI.ListLayout.calculateFirstVisible_p:beginScrollPosition">
            /// 
            /// </param>
            /// <param name="wholeItem" locid="WinJS.UI.ListLayout.calculateFirstVisible_p:wholeItem">
            /// 
            /// </param>
            /// </signature>
            var that = this;
            return this._initialize().then(function (initialized) {
                if (initialized) {
                    if (!wholeItem) {
                        beginScrollPosition += that._itemMargins.bottom;
                    }
                    return Math.max(-1, Math.min(that._count - 1, Math[wholeItem ? "ceil" : "floor"](beginScrollPosition / that._totalItemHeight)));
                } else {
                    return Promise.wrapError(new WinJS.ErrorFromName("WinJS.UI.LayoutNotInitialized", WinJS.UI._strings.layoutNotInitialized));
                }
            });
        },

        calculateLastVisible: function (endScrollPosition, wholeItem) {
            /// <signature helpKeyword="WinJS.UI.ListLayout.calculateLastVisible">
            /// <summary locid="WinJS.UI.ListLayout.calculateLastVisible">
            /// This API supports the Windows Library for JavaScript infrastructure and is not intended to be used directly from your code.
            /// </summary>
            /// <param name="endScrollPosition" locid="WinJS.UI.ListLayout.calculateLastVisible_p:endScrollPosition">
            /// 
            /// </param>
            /// <param name="wholeItem" locid="WinJS.UI.ListLayout.calculateLastVisible_p:wholeItem">
            /// 
            /// </param>
            /// </signature>
            var that = this;
            return this._initialize().then(function (initialized) {
                if (initialized) {
                    if (!wholeItem) {
                        endScrollPosition -= that._itemMargins.top;
                    }
                    var lastPossibleIndex = Math[wholeItem ? "floor" : "ceil"]((endScrollPosition + 1) / that._totalItemHeight) - 1;
                    return Math.max(-1, Math.min(lastPossibleIndex, that._count - 1));
                } else {
                    return Promise.wrapError(new WinJS.ErrorFromName("WinJS.UI.LayoutNotInitialized", WinJS.UI._strings.layoutNotInitialized));
                }
            });
        },

        hitTest: function (x, y) {
            /// <signature helpKeyword="WinJS.UI.ListLayout.hitTest">
            /// <summary locid="WinJS.UI.ListLayout.hitTest">
            /// This API supports the Windows Library for JavaScript infrastructure and is not intended to be used directly from your code.
            /// </summary>
            /// <param name="x" locid="WinJS.UI.ListLayout.hitTest_p:x">
            /// 
            /// </param>
            /// <param name="y" locid="WinJS.UI.ListLayout.hitTest_p:y">
            /// 
            /// </param>
            /// </signature>
            return Math.floor(y / this._totalItemHeight);
        }
    })
});

})(this, WinJS);

(function listViewImplInit(global, WinJS, undefined) {
    "use strict";

var DISPOSE_TIMEOUT = 1000;
var controlsToDispose = [];
var disposeControlTimeout;
function disposeControls() {
    controlsToDispose = controlsToDispose.filter(function (c) {
        if (c._isZombie()) {
            c._dispose();
            return false;
        } else {
            return true;
        }
    });
}
function scheduleForDispose(lv) {
    controlsToDispose.push(lv);
    disposeControlTimeout && disposeControlTimeout.cancel();
    disposeControlTimeout = WinJS.Promise.timeout(DISPOSE_TIMEOUT).then(disposeControls);
}

function ensureId(element) {
    if (!element.id) {
        element.id = element.uniqueID;
    }
}

function setFlow(from, to) {
    WinJS.UI._setAttribute(from, "aria-flowto", to.id);
    WinJS.UI._setAttribute(to, "x-ms-aria-flowfrom", from.id);
}

// Only set the attribute if its value has changed
function setAttribute(element, attribute, value) {
    if (element.getAttribute(attribute) !== "" + value) {
        element.setAttribute(attribute, value);
    }
}

WinJS.Namespace.define("WinJS.UI", {
    _disposeControls: disposeControls,
    _ensureId: ensureId,
    _setFlow: setFlow,
    _setAttribute: setAttribute
});

var thisWinUI = WinJS.UI,
    utilities = WinJS.Utilities,
    Promise = WinJS.Promise,
    AnimationHelper = WinJS.UI._ListViewAnimationHelper;

    var strings = {
        get notCompatibleWithSemanticZoom() { return WinJS.Resources._getWinJSString("ui/notCompatibleWithSemanticZoom").value; },
        get listViewInvalidItem() { return WinJS.Resources._getWinJSString("ui/listViewInvalidItem").value; },
        get listViewViewportAriaLabel() { return WinJS.Resources._getWinJSString("ui/listViewViewportAriaLabel").value; }
    };

    var requireSupportedForProcessing = WinJS.Utilities.requireSupportedForProcessing;

// ListView implementation

function elementListViewHandler(eventName, caseSensitive, capture) {
    return {
        name: (caseSensitive ? eventName : eventName.toLowerCase()),
        handler: function (eventObject) {
            var srcElement = eventObject.srcElement;
            if (srcElement) {
                var that = srcElement.winControl;
                if (that && that instanceof WinJS.UI.ListView) {
                    that["_on" + eventName](eventObject);
                }
            }
        },
        capture: capture
    };
}

var ZoomableView = WinJS.Class.define(function ZoomableView_ctor(listView) {
    // Constructor

    this._listView = listView;
}, {
    // Public methods

    getPanAxis: function () {
        return this._listView._getPanAxis();
    },

    configureForZoom: function (isZoomedOut, isCurrentView, triggerZoom, prefetchedPages) {
        this._listView._configureForZoom(isZoomedOut, isCurrentView, triggerZoom, prefetchedPages);
    },

    setCurrentItem: function (x, y) {
        this._listView._setCurrentItem(x, y);
    },

    getCurrentItem: function () {
        return this._listView._getCurrentItem();
    },

    beginZoom: function () {
        this._listView._beginZoom();
    },

    positionItem: function (item, position) {
        return this._listView._positionItem(item, position);
    },

    endZoom: function (isCurrentView) {
        this._listView._endZoom(isCurrentView);
    }
});

WinJS.Namespace.define("WinJS.UI", {
        /// <field locid="WinJS.UI.ListView.SelectionMode" helpKeyword="WinJS.UI.SelectionMode">
        /// Specifies the selection mode for a ListView.
        /// </field>
    SelectionMode: {
        /// <field locid="WinJS.UI.ListView.SelectionMode.none" helpKeyword="WinJS.UI.SelectionMode.none">
        /// Items cannot be selected.
        /// </field>
        none: "none",
        /// <field locid="WinJS.UI.ListView.SelectionMode.single" helpKeyword="WinJS.UI.SelectionMode.single">
        /// A single item may be selected.
        /// </field>
        single: "single",
        /// <field locid="WinJS.UI.ListView.SelectionMode.multi" helpKeyword="WinJS.UI.SelectionMode.multi">
        /// Multiple items may be selected.
        /// </field>
        multi: "multi"
    },

     /// <field locid="WinJS.UI.ListView.TapBehavior" helpKeyword="WinJS.UI.TapBehavior">
     /// Specifies how items in a ListView respond to the tap interaction.
     /// </field>
    TapBehavior: {
        /// <field locid="WinJS.UI.ListView.TapBehavior.directSelect" helpKeyword="WinJS.UI.TapBehavior.directSelect">
        /// Tapping the item invokes it and selects it. Navigating to the item with the keyboard changes the
        /// the selection so that the focused item is the only item that is selected.
        /// </field>
        directSelect: "directSelect",
        /// <field locid="WinJS.UI.ListView.TapBehavior.toggleSelect" helpKeyword="WinJS.UI.TapBehavior.toggleSelect">
        /// Tapping the item invokes it. If the item was selected, tapping it clears the selection. If the item wasn't
        /// selected, tapping the item selects it.
        /// Navigating to the item with the keyboard does not select or invoke it.
        /// </field>
        toggleSelect: "toggleSelect",
        /// <field locid="WinJS.UI.ListView.TapBehavior.invokeOnly" helpKeyword="WinJS.UI.TapBehavior.invokeOnly">
        /// Tapping the item invokes it. Navigating to the item with keyboard does not select it or invoke it.
        /// </field>
        invokeOnly: "invokeOnly",
        /// <field locid="WinJS.UI.ListView.TapBehavior.none" helpKeyword="WinJS.UI.TapBehavior.none">
        /// Nothing happens.
        /// </field>
        none: "none"
    },
    
    /// <field locid="WinJS.UI.ListView.SwipeBehavior" helpKeyword="WinJS.UI.SwipeBehavior">
    /// Specifies whether items are selected when the user performs a swipe interaction.
    /// </field>
    SwipeBehavior: {
        /// <field locid="WinJS.UI.ListView.SwipeBehavior.select" helpKeyword="WinJS.UI.SwipeBehavior.select">
        /// The swipe interaction selects the items touched by the swipe.
        /// </field>
        select: "select",
        /// <field locid="WinJS.UI.ListView.SwipeBehavior.none" helpKeyword="WinJS.UI.SwipeBehavior.none">
        /// The swipe interaction does not change which items are selected.
        /// </field>
        none: "none"
    },

    /// <field locid="WinJS.UI.ListView.ListViewAnimationType" helpKeyword="WinJS.UI.ListViewAnimationType">
    /// Specifies whether the ListView animation is an entrance animation or a transition animation.
    /// </field>
    ListViewAnimationType: {
        /// <field locid="WinJS.UI.ListView.ListViewAnimationType.entrance" helpKeyword="WinJS.UI.ListViewAnimationType.entrance">
        /// The animation plays when the ListView is first displayed.
        /// </field>
        entrance: "entrance",
        /// <field locid="WinJS.UI.ListView.ListViewAnimationType.contentTransition" helpKeyword="WinJS.UI.ListViewAnimationType.contentTransition">
        /// The animation plays when the ListView is changing its content.
        /// </field>
        contentTransition: "contentTransition"
    },

    /// <summary locid="WinJS.UI.ListView">
    /// Displays items in a customizable list or grid.
    /// </summary>
    /// <icon src="ui_winjs.ui.listview.12x12.png" width="12" height="12" />
    /// <icon src="ui_winjs.ui.listview.16x16.png" width="16" height="16" />
    /// <htmlSnippet><![CDATA[<div data-win-control="WinJS.UI.ListView"></div>]]></htmlSnippet>
    /// <event name="contentanimating" bubbles="true" locid="WinJS.UI.ListView_e:contentanimating">Raised when the ListView is about to play an entrance or a transition animation.</event>
    /// <event name="iteminvoked" bubbles="true" locid="WinJS.UI.ListView_e:iteminvoked">Raised when the user taps or clicks an item.</event>
    /// <event name="selectionchanging" bubbles="true" locid="WinJS.UI.ListView_e:selectionchanging">Raised before items are selected or deselected.</event>
    /// <event name="selectionchanged" bubbles="true" locid="WinJS.UI.ListView_e:selectionchanged">Raised after items are selected or deselected.</event>
    /// <event name="loadingstatechanged" bubbles="true" locid="WinJS.UI.ListView_e:loadingstatechanged">Raised when the loading state changes.</event>
    /// <event name="keyboardnavigating" bubbles="true" locid="WinJS.UI.ListView_e:keyboardnavigating">Raised when the focused item changes.</event>
    /// <part name="listView" class="win-listview" locid="WinJS.UI.ListView_part:listView">The entire ListView control.</part>
    /// <part name="viewport" class="win-viewport" locid="WinJS.UI.ListView_part:viewport">The viewport of the ListView. </part>
    /// <part name="surface" class="win-surface" locid="WinJS.UI.ListView_part:surface">The scrollable region of the ListView.</part>
    /// <part name="item" class="win-item" locid="WinJS.UI.ListView_part:item">An item in the ListView.</part>
    /// <part name="selectionbackground" class="win-selectionbackground" locid="WinJS.UI.ListView_part:selectionbackground">The background of a selection checkmark.</part>
    /// <part name="selectioncheckmark" class="win-selectioncheckmark" locid="WinJS.UI.ListView_part:selectioncheckmark">A selection checkmark.</part>
    /// <part name="groupHeader" class="win-groupheader" locid="WinJS.UI.ListView_part:groupHeader">The header of a group.</part>
    /// <part name="progressbar" class="win-progress" locid="WinJS.UI.ListView_part:progressbar">The progress indicator of the ListView.</part>
    /// <resource type="javascript" src="//Microsoft.WinJS.1.0/js/base.js" shared="true" />
    /// <resource type="javascript" src="//Microsoft.WinJS.1.0/js/ui.js" shared="true" />
    /// <resource type="css" src="//Microsoft.WinJS.1.0/css/ui-dark.css" shared="true" />
    ListView: WinJS.Class.define(function ListView_ctor(element, options) {
        /// <signature helpKeyword="WinJS.UI.ListView.ListView">
        /// <summary locid="WinJS.UI.ListView.constructor">
        /// Creates a new ListView.
        /// </summary>
        /// <param name="element" domElement="true" locid="WinJS.UI.ListView.constructor_p:element">
        /// The DOM element that hosts the ListView control.
        /// </param>
        /// <param name="options" type="Object" locid="WinJS.UI.ListView.constructor_p:options">
        /// An object that contains one or more property/value pairs to apply to the new control.
        /// Each property of the options object corresponds to one of the control's properties or events.
        /// Event names must begin with "on". For example, to provide a handler for the selectionchanged event,
        /// add a property named "onselectionchanged" to the options object and set its value to the event handler.
        /// </param>
        /// <returns type="WinJS.UI.ListView" locid="WinJS.UI.ListView.constructor_returnValue">
        /// The new ListView.
        /// </returns>
        /// </signature>
        msWriteProfilerMark("WinJS.UI.ListView:constructor,StartTM");
        element = element || document.createElement("div");
        options = options || {};

        // Attaching JS control to DOM element
        element.winControl = this;
        this._versionManager = null;
        this._canvasLength = 0;
        this._scrollLimitMin = 0;
        this._insertedItems = {};
        this._element = element;
        this._startProperty = null;
        this._scrollProperty = null;
        this._scrollLength = null;
        this._scrolling = false;
        this._zooming = false;
        this._pinching = false;
        this._itemsManager = null;
        this._canvas = null;
        this._itemCanvas = null;
        this._cachedCount = WinJS.UI._UNINITIALIZED;
        this._loadingState = this._LoadingState.complete;
        this._firstTimeDisplayed = true;
        this._currentScrollPosition = 0;
        this._lastScrollPosition = 0;
        this._notificationHandlers = [];
        this._viewportWidth = WinJS.UI._UNINITIALIZED;
        this._viewportHeight = WinJS.UI._UNINITIALIZED;
        this._manipulationState = MSManipulationEvent.MS_MANIPULATION_STATE_STOPPED;
        this._groupsToRemove = {};
        this._setupInternalTree();
        this._isCurrentZoomView = true;
        // The view needs to be initialized after the internal tree is setup, because the view uses the canvas node immediately to insert an element in its constructor
        this._view = new WinJS.UI._ScrollView(this);
        this._selection = new WinJS.UI._SelectionManager(this);
        this._createTemplates();
        this._wrappersPool = new WinJS.UI._ElementsPool(this);
        var that = this;
        this._wrappersPool.setRenderer(function (itemPromise, recycledElement) {
            if (recycledElement) {
                recycledElement.innerText = "";
                WinJS.Utilities.removeClass(recycledElement, WinJS.UI._selectedClass);
                return { element: recycledElement };
            }
            else {
                return { element: that._wrapperTemplate.cloneNode(true) };
            }
        });
        this._itemsPool = new WinJS.UI._ItemsPool(this);
        this._headersPool = new WinJS.UI._ElementsPool(this, WinJS.UI._headerClass, "prepareHeader");
        this._groupsPool = new WinJS.UI._ElementsPool(this);
        this._groupsPool.setRenderer(function (groupItemPromise, recycledElement) {
            return WinJS.Promise.wrap(recycledElement || document.createElement("div"));
        });
        if (!options.itemDataSource) {
            var list = new WinJS.Binding.List();
            this._dataSource = list.dataSource;
        } else {
            this._dataSource = options.itemDataSource;
        }
        this._selectionMode = WinJS.UI.SelectionMode.multi;
        this._tap = WinJS.UI.TapBehavior.invokeOnly;
        this._swipeBehavior = WinJS.UI.SwipeBehavior.select;
        this._mode = new WinJS.UI._SelectionMode(this);

        // Call after swipeBehavior and modes are set
        this._setSwipeClass();

        this._updateAriaRoles();
        this._tabIndex = (this._element.tabIndex !== undefined && this._element.tabIndex >= 0) ? this._element.tabIndex : 0;
        this._element.tabIndex = -1;
        this._tabManager.tabIndex = this._tabIndex;
        if (this._element.style.position !== "absolute" && this._element.style.position !== "relative") {
            this._element.style.position = "relative";
        }
        this._groups = new WinJS.UI._NoGroups(this);
        this._scrollToPriority = thisWinUI.ListView._ScrollToPriority.medium;
        this._scrollToPromise = Promise.wrap(0);
        this._updateItemsManager();
        this._updateLayout(new WinJS.UI.GridLayout());
        this._attachEvents();

        this._runningInit = true;
        this._incrementalViewOptions = {};
        WinJS.UI.setOptions(this, options);
        this._runningInit = false;

        this._refresh(0);
        msWriteProfilerMark("WinJS.UI.ListView:constructor,StopTM");
    }, {
        // Public properties

        /// <field type="HTMLElement" domElement="true" hidden="true" locid="WinJS.UI.ListView.element" helpKeyword="WinJS.UI.ListView.element">
        /// Gets the DOM element that hosts the ListView.
        /// </field>
        element: {
            get: function () { return this._element; }
        },

        /// <field type="WinJS.UI.Layout" locid="WinJS.UI.ListView.layout" helpKeyword="WinJS.UI.ListView.layout">
        /// Gets or sets an object that controls the layout of the ListView.
        /// </field>
        layout: {
            get: function () {
                return this._layout;
            },
            set: function (layoutObject) {
                this._updateLayout(layoutObject);

                if (!this._runningInit) {
                    this._view.reset();
                    this._updateItemsManager();
                    this._refresh(0);
                }
            }
        },

        /// <field type="Number" integer="true" locid="WinJS.UI.ListView.pagesToLoad" helpKeyword="WinJS.UI.ListView.pagesToLoad" isAdvanced="true">
        /// Gets or sets the number of pages to load when the user scrolls beyond the
        /// threshold specified by the pagesToLoadThreshold property if
        /// the loadingBehavior property is set to incremental.
        /// </field>
        pagesToLoad: {
            get: function () {
                return this._view.pagesToLoad;
            },
            set: function (newValue) {
                if ((typeof newValue === "number") && (newValue > 0)) {
                    this._incrementalViewOptions.pagesToLoad = newValue;
                    if (this._view instanceof WinJS.UI._IncrementalView) {
                        this._view.pagesToLoad = newValue;
                        this._refresh(0);
                    }
                    return;
                }
                throw new WinJS.ErrorFromName("WinJS.UI.ListView.PagesToLoadIsInvalid", WinJS.UI._strings.pagesToLoadIsInvalid);
            }
        },

        /// <field type="Number" integer="true" locid="WinJS.UI.ListView.pagesToLoadThreshold" helpKeyword="WinJS.UI.ListView.pagesToLoadThreshold" isAdvanced="true">
        /// Gets or sets the threshold (in pages) for initiating an incremental load. When the last visible item is
        /// within the specified number of pages from the end of the loaded portion of the list,
        /// and if automaticallyLoadPages is true and loadingBehavior is set to "incremental",
        /// the ListView initiates an incremental load.
        /// </field>
        pagesToLoadThreshold: {
            get: function () {
                return this._view.pagesToLoadThreshold;
            },
            set: function (newValue) {
                if ((typeof newValue === "number") && (newValue > 0)) {
                    this._incrementalViewOptions.pagesToLoadThreshold = newValue;
                    if (this._view instanceof WinJS.UI._IncrementalView) {
                        this._view.pagesToLoadThreshold = newValue;
                        this._refresh(0);
                    }
                    return;
                }
                throw new WinJS.ErrorFromName("WinJS.UI.ListView.PagesToLoadThresholdIsInvalid", WinJS.UI._strings.pagesToLoadThresholdIsInvalid);
            }
        },

        /// <field type="Object" locid="WinJS.UI.ListView.groupDataSource" helpKeyword="WinJS.UI.ListView.groupDataSource">
        /// Gets or sets the data source that contains the groups for the items in the itemDataSource.
        /// </field>
        groupDataSource: {
            get: function () {
                return this._groupDataSource;
            },
            set: function (newValue) {
                msWriteProfilerMark("WinJS.UI.ListView:set_groupDataSource,info");

                var that = this;
                
                function groupStatusChanged(eventObject) {
                    if (eventObject.detail === thisWinUI.DataSourceStatus.failure) {
                        that.itemDataSource = null;
                        that.groupDataSource = null;
                    }
                }

                if (this._groupDataSource && this._groupDataSource.removeEventListener) {
                    this._groupDataSource.removeEventListener("statuschanged", groupStatusChanged, false);
                }
                    
                this._groupDataSource = newValue;

                if (this._groupDataSource && this._groupDataSource.addEventListener) {
                    this._groupDataSource.addEventListener("statuschanged", groupStatusChanged, false);
                }

                if (this._groups) {
                    this._groups.cleanUp();
                }
                if (newValue) {
                    this._groups = new WinJS.UI._GroupsContainer(this, newValue);
                    utilities.addClass(this._element, WinJS.UI._groupsClass);
                } else {
                    this._groups = new WinJS.UI._NoGroups(this);
                    utilities.removeClass(this._element, WinJS.UI._groupsClass);
                }

                if (!this._runningInit) {
                    this._cancelRealize();
                    this._layout.reset();
                    this._refresh(0);
                }
            }
        },

        /// <field type="Boolean" locid="WinJS.UI.ListView.automaticallyLoadPages" helpKeyword="WinJS.UI.ListView.automaticallyLoadPages">
        /// Gets or sets a value that indicates whether the next set of pages is automatically loaded
        /// when the user scrolls beyond the number of pages specified by the
        /// pagesToLoadThreshold property.
        /// </field>
        automaticallyLoadPages: {
            get: function () {
                return this._view.automaticallyLoadPages;
            },
            set: function (newValue) {
                if (typeof newValue === "boolean") {
                    this._incrementalViewOptions.automaticallyLoadPages = newValue;
                    if (this._view instanceof WinJS.UI._IncrementalView) {
                        this._view.automaticallyLoadPages = newValue;
                    }
                    return;
                }
                throw new WinJS.ErrorFromName("WinJS.UI.ListView.AutomaticallyLoadPagesIsInvalid", WinJS.UI._strings.automaticallyLoadPagesIsInvalid);
            }
        },

        /// <field type="String" oamOptionsDatatype="WinJS.UI.ListView.LoadingBehavior" locid="WinJS.UI.ListView.loadingBehavior" helpKeyword="WinJS.UI.ListView.loadingBehavior">
        /// Gets or sets a value that determines how many data items are loaded into the DOM.
        /// </field>
        loadingBehavior: {
            get: function () {
                return (this._view instanceof WinJS.UI._IncrementalView) ? "incremental" : "randomAccess";  
            },
            set: function (newValue) {
                if (typeof newValue === "string") {
                    if (newValue.match(/^(incremental|randomaccess)$/i)) {
                        if (this._view) {
                            this._view.cleanUp();
                        }

                    var that = this;
                    this._versionManager.unlocked.then(function () {
                        if (newValue === "incremental") {
                            that._view = new WinJS.UI._IncrementalView(that);
                            WinJS.UI.setOptions(that._view, that._incrementalViewOptions);
                        } else {
                            that._view = new WinJS.UI._ScrollView(that);
                        }

                        that._setLayoutSite();

                        that._refresh(0);
                    });

                        return;
                    }
                }
                throw new WinJS.ErrorFromName("WinJS.UI.ListView.LoadingBehaviorIsInvalid", WinJS.UI._strings.loadingBehaviorIsInvalid);
            }
        },
        
        /// <field type="String" oamOptionsDatatype="WinJS.UI.ListView.SelectionMode" locid="WinJS.UI.ListView.selectionMode" helpKeyword="WinJS.UI.ListView.selectionMode">
        /// Gets or sets a value that specifies how many ListView items the user can select: "none", "single", or "multi".
        /// </field>
        selectionMode: {
            get: function () {
                return this._selectionMode;
            },
            set: function (newMode) {
                if (typeof newMode === "string") {
                    if (newMode.match(/^(none|single|multi)$/)) {
                        this._selectionMode = newMode;
                        this._element.setAttribute("aria-multiselectable", this._multiSelection());
                        this._updateAriaRoles();
                        this._setSwipeClass();
                        return;
                    }
                }
                throw new WinJS.ErrorFromName("WinJS.UI.ListView.ModeIsInvalid", WinJS.UI._strings.modeIsInvalid);
            }
        },
        
        /// <field type="String" oamOptionsDatatype="WinJS.UI.ListView.TapBehavior" locid="WinJS.UI.ListView.tapBehavior" helpKeyword="WinJS.UI.ListView.tapBehavior">
        /// Gets or sets how the ListView reacts when the user taps or clicks an item.
        /// The tap or click can invoke the item, select it and invoke it, or have no
        /// effect.
        /// </field>
        tapBehavior: {
            get: function () {
                return this._tap;
            },
            set: function (tap) {
                this._tap = tap;
                this._updateAriaRoles();
            }
        },
        
        /// <field type="String" oamOptionsDatatype="WinJS.UI.ListView.SwipeBehavior" locid="WinJS.UI.ListView.swipeBehavior" helpKeyword="WinJS.UI.ListView.swipeBehavior">
        /// Gets or sets how the ListView reacts to the swipe interaction.
        /// The swipe gesture can select the swiped items or it can
        /// have no effect on the current selection.
        /// </field>
        swipeBehavior: {
            get: function () {
                return this._swipeBehavior;
            },
            set: function (swipeBehavior) {
                this._swipeBehavior = swipeBehavior;
                this._setSwipeClass();
            }
        },

        /// <field type="Object" locid="WinJS.UI.ListView.itemDataSource" helpKeyword="WinJS.UI.ListView.itemDataSource">
        /// Gets or sets the data source that provides items for the ListView.
        /// </field>
        itemDataSource: {
            get: function () {
                return this._itemsManager.dataSource;
            },
            set: function (newData) {
                msWriteProfilerMark("WinJS.UI.ListView:set_itemDataSource,info");
                this._dataSource = newData || new WinJS.Binding.List().dataSource;

                if (!this._runningInit) {
                    this._selection._reset();
                    this._cancelRealize();
                    this._layout.reset();
                    this._updateItemsManager();
                    this._refresh(0);
                }
            }
        },

        /// <field type="Object" locid="WinJS.UI.ListView.itemTemplate" helpKeyword="WinJS.UI.ListView.itemTemplate" potentialValueSelector="[data-win-control='WinJS.Binding.Template']">
        /// Gets or sets the templating function that creates the DOM elements
        /// for each item in the itemDataSource. Each item can contain multiple
        /// DOM elements, but we recommend that it have a single root element.
        /// </field>
        itemTemplate: {
            get: function () {
                return this._itemsPool.renderer;
            },
            set: function (newRenderer) {
                this._itemsPool.setRenderer(newRenderer);

                if (!this._runningInit) {
                    this._cancelRealize();
                    this._layout.reset();
                    this._updateItemsManager();
                    this._refresh(0);
                }
            }
        },

        /// <field type="Function" locid="WinJS.UI.ListView.resetItem" helpKeyword="WinJS.UI.ListView.resetItem">
        /// Gets or sets the function that is called when the ListView recycles the
        /// element representation of an item.
        /// </field>
        resetItem: {
            get: function () {
                return this._itemsPool.release;
            },
            set: function (release) {
                this._itemsPool.release = release;
            }
        },

        /// <field type="Object" locid="WinJS.UI.ListView.groupHeaderTemplate" helpKeyword="WinJS.UI.ListView.groupHeaderTemplate" potentialValueSelector="[data-win-control='WinJS.Binding.Template']">
        /// Gets or sets the templating function that creates the DOM elements
        /// for each group header in the groupDataSource. Each group header
        /// can contain multiple elements, but it must have a single root element.
        /// </field>
        groupHeaderTemplate: {
            get: function () {
                return this._headersPool.renderer;
            },
            set: function (newRenderer) {
                this._headersPool.setRenderer(newRenderer);

                if (!this._runningInit) {
                    this._cancelRealize();
                    this._layout.reset();
                    this._refresh(0);
                }
            }
        },

        /// <field type="Function" locid="WinJS.UI.ListView.resetGroupHeader" helpKeyword="WinJS.UI.ListView.resetGroupHeader" isAdvanced="true">
        /// Gets or sets the function that is called when the ListView recycles the DOM element representation
        /// of a group header.
        /// </field>
        resetGroupHeader: {
            get: function () {
                return this._headersPool.release;
            },
            set: function (release) {
                this._headersPool.release = release;
            }
        },

        /// <field type="String" hidden="true" locid="WinJS.UI.ListView.loadingState" helpKeyword="WinJS.UI.ListView.loadingState">
        /// Gets a value that indicates whether the ListView is still loading or whether
        /// loading is complete.  This property can return one of these values:
        /// "itemsLoading", "viewPortLoaded", "itemsLoaded", or "complete".
        /// </field>
        loadingState: {
            get: function () {
                return this._loadingState;
            }
        },

        /// <field type="Object" locid="WinJS.UI.ListView.selection" helpKeyword="WinJS.UI.ListView.selection" isAdvanced="true">
        /// Gets an ISelection object that contains the currently selected items.
        /// </field>
        selection: {
            get: function () {
                return this._selection;
            }
        },

        /// <field type="Number" integer="true" locid="WinJS.UI.ListView.indexOfFirstVisible" helpKeyword="WinJS.UI.ListView.indexOfFirstVisible" isAdvanced="true">
        /// Gets or sets the first visible item. When setting this property, the ListView scrolls so that the
        /// item with the specified index is at the top of the list.
        /// </field>
        indexOfFirstVisible: {
            get: function () {
                return this._view.firstIndexDisplayed;
            },

            set: function (itemIndex) {
                if (itemIndex < 0) {
                    return;
                }

                this._raiseViewLoading(true);

                var that = this,
                    count;

                this._scrollToPriority = thisWinUI.ListView._ScrollToPriority.high;
                this._scrollToPromise = Promise.timeout().then(function () {
                    if (that._isZombie()) {
                        return WinJS.Promise.cancel;
                    }

                    return that._itemsCount();
                }).then(function (itemsCount) {
                    count = itemsCount;
                    if (count === 0) {
                        return Promise.wrapError(new WinJS.ErrorFromName("WinJS.UI.LayoutNotInitialized", WinJS.UI._strings.layoutNotInitialized));
                    }
                    return that._getItemOffset(itemIndex);
                }).then(function (range) {
                    return that._view.updateScrollbar(count, true).then(function () { return range; });
                }).then(function (range) {
                    return that._correctRangeInFirstColumn(range);
                }).then(function (range) {
                    range = that._convertFromCanvasCoordinates(range);

                    var begin = Math.max(0, range.begin);
                    that.scrollPosition = begin;
                    that._lastScrollPosition = begin;
                    that._view.refresh(
                        begin,
                        that._viewport[that._scrollLength],
                        that._getViewportSize(),
                        that._cachedCount
                    );

                    return range.begin;
                }).then(null, function(error) {
                    // If the ListView is invisible (LayoutNotInitialized), eat the exception
                    if (error.name !== "WinJS.UI.LayoutNotInitialized") {
                        return WinJS.Promise.wrapError(error);
                    }
                });
            }
        },

        /// <field type="Number" integer="true" readonly="true" locid="WinJS.UI.ListView.indexOfLastVisible" helpKeyword="WinJS.UI.ListView.indexOfLastVisible" isAdvanced="true">
        /// Gets the index of the last visible item.
        /// </field>
        indexOfLastVisible: {
            get: function () {
                return this._view.lastIndexDisplayed;
            }
        },

        /// <field type="Object" locid="WinJS.UI.ListView.currentItem" helpKeyword="WinJS.UI.ListView.currentItem" isAdvanced="true">
        /// Gets or sets an object that indicates which item should get keyboard focus and its focus status.
        /// The object has these properties:
        /// index: the index of the item in the itemDataSource.
        /// key: the key of the item in the itemDataSource.
        /// hasFocus: when getting this property, this value is true if the item already has focus; otherwise, it's false.
        /// When setting this property, set this value to true if the item should get focus immediately; otherwise, set it to
        /// false and the item will get focus eventually.
        /// showFocus: true if the item displays the focus rectangle; otherwise, false.
        /// </field>
        currentItem: {
            get: function () {
                var item = this._view.items.itemAt(this._selection._getFocused()),
                    key = null,
                    focusVisible = false;
                if (item) {
                    key = this._itemsManager._recordFromElement(item).item.key;
                    focusVisible = !!item.parentNode.querySelector("." + thisWinUI._itemFocusOutlineClass);
                }
                return {
                    index: this._selection._getFocused(),
                    key: key,
                    hasFocus: !!this._hasKeyboardFocus,
                    showFocus: focusVisible
                };
            },

            set: function (data) {
                this._hasKeyboardFocus = data.hasFocus || this._hasKeyboardFocus;  
                var that = this;
                function setItemFocused(item, isInTree,  itemIndex) {
                    var drawKeyboardFocus = !!data.showFocus && that._hasKeyboardFocus;
                    that._unsetFocusOnItem(isInTree);
                    that._selection._setFocused(itemIndex, drawKeyboardFocus);
                    if (that._hasKeyboardFocus) {
                        that._keyboardFocusInbound = drawKeyboardFocus;
                        that._setFocusOnItem(itemIndex);
                    } else {
                        that._tabManager.childFocus = (isInTree ? item : null);
                    }
                }

                if (data.key && this._dataSource.itemFromKey) {
                    if (this.oldCurrentItemKeyFetch) {
                        this.oldCurrentItemKeyFetch.cancel();
                    }

                    this.oldCurrentItemKeyFetch = this._dataSource.itemFromKey(data.key).then(function (item) {
                        that.oldCurrentItemKeyFetch = null;
                        if (item) {
                            var element = that._view.items.itemAt(item.index);
                            setItemFocused(element, !!element, item.index);
                        }
                    });
                } else {
                    if (data.index !== undefined) {
                        var focusedIndex = data.index,
                        focusedItem = this._view.items.itemAt(focusedIndex);
                        setItemFocused(focusedItem, !!focusedItem, focusedIndex);
                    }
                }
            }
        },

        /// <field type="Object" locid="WinJS.UI.ListView.zoomableView" helpKeyword="WinJS.UI.ListView.zoomableView" isAdvanced="true">
        /// Gets a ZoomableView. This API supports the SemanticZoom infrastructure
        /// and is not intended to be used directly from your code.
        /// </field>
        zoomableView: {
            get: function () {
                if (!this._zoomableView) {
                    this._zoomableView = new ZoomableView(this);
                }

                return this._zoomableView;
            }
        },

        // Public methods
        elementFromIndex: function (itemIndex) {
            /// <signature helpKeyword="WinJS.UI.ListView.elementFromIndex">
            /// <summary locid="WinJS.UI.ListView.elementFromIndex">
            /// Returns the DOM element that represents the item at the specified index.
            /// </summary>
            /// <param name="itemIndex" type="Number" integer="true" locid="WinJS.UI.ListView.elementFromIndex_p:itemIndex">
            /// The index of the item.
            /// </param>
            /// <returns type="Object" domElement="true" locid="WinJS.UI.ListView.elementFromIndex_returnValue">
            /// The DOM element that represents the specified item.
            /// </returns>
            /// </signature>

            return this._view.items.itemAt(itemIndex);
        },

        indexOfElement: function (element) {
            /// <signature helpKeyword="WinJS.UI.ListView.indexOfElement">
            /// <summary locid="WinJS.UI.ListView.indexOfElement">
            /// Returns the index of the item that the specified DOM element displays.
            /// </summary>
            /// <param name="element" type="HTMLElement" domElement="true" locid="WinJS.UI.ListView.indexOfElement_p:element">
            /// The DOM element that displays the item.
            /// </param>
            /// <returns type="Number" integer="true" locid="WinJS.UI.ListView.indexOfElement_returnValue">
            /// The index of item that the specified DOM element displays.
            /// </returns>
            /// </signature>

            return this._view.items.index(element);
        },

        ensureVisible: function ListView_ensureVisible(itemIndex) {
            /// <signature helpKeyword="WinJS.UI.ListView.ensureVisible">
            /// <summary locid="WinJS.UI.ListView.ensureVisible">
            /// Makes the specified item visible. The ListView scrolls to the item if needed.
            /// </summary>
            /// <param name="itemIndex" type="Number" integer="true" locid="WinJS.UI.ListView.ensureVisible_p:itemIndex">
            /// The index of the item to bring into view.
            /// </param>
            /// </signature>
            if (itemIndex < 0) {
                return Promise.wrap();
            }

            this._raiseViewLoading(true);

            var that = this,
                count;

            this._itemsCount().then(function (itemsCount) {
                count = itemsCount;
                if (count === 0) {
                    return Promise.wrapError(new WinJS.ErrorFromName("WinJS.UI.LayoutNotInitialized", WinJS.UI._strings.layoutNotInitialized));
                }
                return that._getItemOffset(itemIndex);
            }).then(function (range) {
                if (range.begin < 0) {
                    that._groups.pinItem();
                    return that._getItemOffset(itemIndex);
                } else {
                    return range;
                }
            }).then(function (range) {
                return that._view.updateScrollbar(count, true).then(function () { return range; });
            }).then(function (range) {
                return that._correctRangeInFirstColumn(range);
            }).then(function (range) {
                var left = that._viewportScrollPosition,
                    right = left + that._getViewportLength(),
                    newPosition = that._viewportScrollPosition;

                range = that._convertFromCanvasCoordinates(range);

                if (range.begin < left) {
                    newPosition = range.begin;
                } else if (range.end > right) {
                    newPosition = range.end - that._getViewportLength();
                }

                newPosition = Math.max(0, newPosition);
                if (newPosition !== left) {
                    that.scrollPosition = newPosition;
                    that._lastScrollPosition = newPosition;
                }

                that._view.refresh(
                    newPosition,
                    that._viewport[that._scrollLength],
                    that._getViewportSize(),
                    that._cachedCount
                );
            }).then(null, function (error) {
                // If the ListView is invisible (LayoutNotInitialized), eat the exception
                if (error.name !== "WinJS.UI.LayoutNotInitialized") {
                    return WinJS.Promise.wrapError(error);
                }
            });
        },

        loadMorePages: function ListView_loadMorePages() {
            /// <signature helpKeyword="WinJS.UI.ListView.loadMorePages">
            /// <summary locid="WinJS.UI.ListView.loadMorePages">
            /// Loads the next set of pages if the ListView object's loadingBehavior is set to incremental.
            /// </summary>
            /// </signature>
            if (this._view instanceof WinJS.UI._IncrementalView) {
                this._view.loadNextPages();
            }
        },

        recalculateItemPosition: function ListView_recalculateItemPosition() {
            /// <signature helpKeyword="WinJS.UI.ListView.recalculateItemPosition">
            /// <summary locid="WinJS.UI.ListView.recalculateItemPosition">
            /// Repositions all the visible items in the ListView to adjust for items whose sizes have changed. Most apps won't ever need to call this method.
            /// </summary>
            /// </signature>
            var that = this;
            this._versionManager.unlocked.then(function () {
                that._itemMargins = null;
                that._canvasMargins = null;
                that._cachedRTL = null;
                that._cancelRealize();
                that._layout.reset();
                that._resizeViewport();
                that._groups.pinItem();
                that._groups.purgeDecorators();
                that._view.reload(that.scrollPosition);
            });
        },

        forceLayout: function ListView_forceLayout() {
            /// <signature helpKeyword="WinJS.UI.ListView.forceLayout">
            /// <summary locid="WinJS.UI.ListView.forceLayout">
            /// Forces the ListView to update its layout. Use this function when making the ListView visible again
            /// after you set its style.display property to "none".
            /// </summary>
            /// </signature>
            msWriteProfilerMark("WinJS.UI.ListView:forceLayoutRequested,info");
            this._clearInsertedItems();
            if (this._updater) {
                this._updater.removedElements = [];
            }
            var that = this;
            this._versionManager.unlocked.then(function () {
                msWriteProfilerMark("WinJS.UI.ListView:forceLayout,info");
                that._itemMargins = null;
                that._canvasMargins = null;
                that._cachedRTL = null;
                that._layout.reset();
                that._view.reset();
                that._resizeViewport();
                var currentScrollPosition = that._viewportScrollPosition;

                if (currentScrollPosition !== that._lastScrollPosition) {
                    that.scrollPosition = that._lastScrollPosition;
                }
                that._forceReload = true;
                that._scheduleUpdate();
            });
        },

        _viewportScrollPosition: {
            get: function () {
                this._currentScrollPosition = this._viewport[this._scrollProperty];
                return this._currentScrollPosition;
            },
            set: function (value) {
                this._viewport[this._scrollProperty] = value;
                this._currentScrollPosition = value;
            }
        },

        _canvasStart: {
            get: function () {
                if (this._rtl() && this._horizontal()) {
                    return this._canvas.style["right"];
                } else {
                    return this._canvas.style[this._startProperty];
                }
            },
            set: function (value) {
                if (this._rtl() && this._horizontal()) {
                    this._canvas.style["right"] = value;
                } else {
                    this._canvas.style[this._startProperty] = value;
                }
            }
        },
        
        /// <field type="Number" integer="true" locid="WinJS.UI.ListView.scrollPosition" helpKeyword="WinJS.UI.ListView.scrollPosition">
        /// Gets or sets the position of the ListView's scrollbar.
        /// </field>
        scrollPosition: {
            get: function () {
                //#DBG _ASSERT(this._lastScrollPosition >= 0);
                return this._currentScrollPosition;
            },
            set: function (newPosition) {
                this._viewportScrollPosition = newPosition;
            }
        },

        _isInsertedItem: function ListView_isInsertedItem(itemPromise) {
            return !!this._insertedItems[itemPromise.handle];
        },

        _clearInsertedItems: function ListView_clearInsertedItems() {
            var keys = Object.keys(this._insertedItems);
            for (var i = 0, len = keys.length; i < len; i++) {
                this._insertedItems[keys[i]].release();
            }
            this._insertedItems = {};
        },

        // Private methods
        _cancelRealize: function () {
            this._view && this._view._cancelRealize && this._view._cancelRealize();
        },

        _refreshHandler: function () {
            var that = this;
            function onRefresh() {
                if (that._isZombie()) { return; }

                that._refreshTimer = false;
                that._itemMargins = null;
                that._canvasMargins = null;
                that._cachedRTL = null;                
                // Retrieve the values before DOM modifications occur
                that._getCanvasMargins();
                that._rtl();
                
                if (!that._firstTimeDisplayed) {
                    that._view.reset();
                    that._cancelRealize();
                }

                //#DBG _ASSERT(that._scrollToPriority !== thisWinUI.ListView._ScrollToPriority.uninitialized);
                var promise = that._scrollToPromise;
                that._scrollToPriority = thisWinUI.ListView._ScrollToPriority.uninitialized;
                that._scrollToPromise = null;

                promise.then(function (position) {
                    position = Math.max(0, position);
                    if (that._lastScrollPosition !== position) {
                        that._lastScrollPosition = position;
                        that.scrollPosition = position;
                    }
                    that._view.reload(position);
                    that._setFocusOnItem(that._selection._getFocused());
                });
            }

            if (this._isZombie()) { return; }

            // If we're displaying for the first time, or there were no items visible in the view, we can skip the fade out animation
            // and go straight to the refresh. _view.items._itemData.length is the most trustworthy way to find how many items are visible.
            if (this._firstTimeDisplayed || Object.keys(this._view.items._itemData).length === 0) {
                onRefresh();
                this._firstTimeDisplayed = false;
            } else {
                this._fadeOutViewport(onRefresh);
            }
        },

        _refresh: function (position) {
            // Give a higher priority to requests that reset the scroll position
            var priority = (position === 0 ? thisWinUI.ListView._ScrollToPriority.medium : thisWinUI.ListView._ScrollToPriority.low);
            if (!this._scrollToPromise || priority > this._scrollToPriority) {
                if (this._scrollToPromise) {
                    this._scrollToPromise.cancel();
                }
                this._scrollToPriority = priority;
                this._scrollToPromise = Promise.wrap(position);
            }

            if (!this._refreshTimer) {
                this._refreshTimer = true;

                this._raiseViewLoading();

                var that = this;
                setImmediate(function () {
                    that._refreshHandler();
                });
            }
        },

        _resetItemCanvas: function () {
            // The item canvas MUST have style.position = absolute, otherwise clipping will not be done.
            this._itemCanvas = document.createElement("div");
            this._canvas.appendChild(this._itemCanvas);
            var positionProp = this._rtl() ? "right" : "left";
            this._itemCanvas.style.cssText = "position: absolute; " + positionProp + ": 0px; top: 0px; width: 100%; height: 100%;";
            this._tabManager = new WinJS.UI.TabContainer(this._itemCanvas);
            function tabManagerHandler(eventName) {
                return {
                    name: eventName,
                    handler: function (eventObject) {
                        that["_" + eventName](eventObject);
                    },
                    capture: false
                };
            }

            var itemCanvasEvents = [
                tabManagerHandler("onTabEnter"),
                tabManagerHandler("onTabExit")
            ];
            var that = this;
            itemCanvasEvents.forEach(function (itemCanvasEvent) {
                that._itemCanvas.addEventListener(itemCanvasEvent.name, itemCanvasEvent.handler, false);
            });
            this._tabManager.tabIndex = this._tabIndex;
        },

        _resetCanvas: function () {
            utilities.empty(this._canvas);
            this._groupsToRemove = {};
            // We reset the itemCanvas on _resetCanvas in case a ListView client uses two separate custom layouts, and each layout
            // changes different styles on the itemCanvas without resetting it.
            this._canvas.appendChild(this._canvasProxy);
            this._resetItemCanvas();
        },

        _setupInternalTree: function ListView_setupInternalTree() {

            utilities.addClass(this._element, WinJS.UI._listViewClass);
            utilities[this._rtl() ? "addClass" : "removeClass"](this._element, WinJS.UI._rtlListViewClass);

            this._element.innerHTML =
                '<div tabIndex="-1" role="group" class="' + WinJS.UI._viewportClass + ' ' + WinJS.UI._horizontalClass + '">' +
                    '<div class="' + WinJS.UI._scrollableClass + '">' +
                        // Create a proxy element inside the canvas so that during an MSPointerDown event we can call
                        // msSetPointerCapture on it. This allows hover to not be passed to it which saves a large invalidation.
                        '<div class="' + WinJS.UI._proxyClass + '"></div>' +
                    '</div>' +
                '</div>' + 
                // The keyboard event helper is a dummy node that allows us to keep getting keyboard events when a virtualized element
                // gets discarded. It has to be positioned in the center of the viewport, though, otherwise calling .focus() on it
                // can move our viewport around when we don't want it moved.
                // The keyboard event helper element will be skipped in the tab order if it doesn't have width+height set on it.
                '<div aria-hidden="true" style="position:absolute;left:50%;top:50%;">' +
                    '<div aria-hidden="true" style="width:0px; height:0px;"></div>' +
                '</div>';

            this._viewport = this._element.firstElementChild;
            this._viewport.setAttribute("aria-label", strings.listViewViewportAriaLabel);
            this._canvas = this._viewport.firstElementChild;
            this._canvasProxy = this._canvas.firstElementChild;
            this._keyboardEventsHelper = this._viewport.nextElementSibling.firstElementChild;
            this._tabIndex = this._element.tabIndex !== undefined ? this._element.tabIndex : 0;
            this._tabEventsHelper = new WinJS.UI.TabContainer(this._keyboardEventsHelper.parentNode);
            this._tabEventsHelper.tabIndex = this._tabIndex;
            this._resetItemCanvas();

            this._progressBar = document.createElement("progress");
            utilities.addClass(this._progressBar, WinJS.UI._progressClass);
            this._progressBar.style.position = "absolute";
            this._progressBar.max = 100;
        },

        _unsetFocusOnItem: function ListView_unsetFocusOnItem(newFocusExists) {
            if (this._tabManager.childFocus) {
                this._clearFocusRectangle(this._tabManager.childFocus);
            }
            if (this._isZombie()) {
                return;    
            }
            if (!newFocusExists) {
                // _setFocusOnItem may run asynchronously so prepare the keyboardEventsHelper
                // to receive focus.
                if (this._tabManager.childFocus) {
                    this._tabManager.childFocus = null;
                }

                this._keyboardEventsHelper._shouldHaveFocus = false;
                this._tabEventsHelper.childFocus = this._keyboardEventsHelper;
                // If the viewport has focus, leave it there. This will prevent focus from jumping
                // from the viewport to the keyboardEventsHelper when scrolling with Narrator Touch.
                if (document.activeElement !== this._viewport && this._hasKeyboardFocus) {
                    this._keyboardEventsHelper._shouldHaveFocus = true;
                    this._keyboardEventsHelper.focus();
                }
            }
            this._itemFocused = false;
        },

        _setFocusOnItem: function ListView_setFocusOnItem(index) {
            if (this._focusRequest) {
                this._focusRequest.cancel();
            }
            if (this._isZombie()) {
                return;    
            }
            var that = this;
            this._focusRequest = this._view.items.requestItem(index).then(function(item) {
                if (that._isZombie()) {
                    return;    
                }
                that._tabEventsHelper.childFocus = null;

                if (that._tabManager.childFocus !== item) {
                    that._tabManager.childFocus = item;
                }
                that._focusRequest = null;
                if (that._hasKeyboardFocus && !that._itemFocused) {
                    if (that._selection._keyboardFocused()) {
                        that._drawFocusRectangle(item);
                    }
                    //#DBG _ASSERT(that._cachedCount !== WinJS.UI._UNINITIALIZED);
                    // The requestItem promise just completed so _cachedCount will
                    // be initialized.
                    that._view.updateAriaForAnnouncement(item, that._cachedCount);
                    
                    // Some consumers of ListView listen for item invoked events and hide the listview when an item is clicked.
                    // Since keyboard interactions rely on async operations, sometimes an invoke event can be received before we get
                    // to item.setActive(), and the listview will be made invisible. If that happens and we call item.setActive(), an exception
                    // is raised for trying to focus on an invisible item. Checking visibility is non-trivial, so it's best
                    // just to catch the exception and ignore it.
                    try {
                        that._itemFocused = true;
                        item.setActive();
                    } catch (error) { }
                }
            });
        },

        _attachEvents: function ListView_attachEvents() {
            var that = this;
            
            function listViewHandler(eventName, caseSensitive, capture) {
                return {
                    name: (caseSensitive ? eventName : eventName.toLowerCase()),
                    handler: function (eventObject) {
                        that["_on" + eventName](eventObject);
                    },
                    capture: capture
                };
            }

            function modeHandler(eventName, caseSensitive, capture) {
                return {
                    capture: capture,
                    name: (caseSensitive ? eventName : eventName.toLowerCase()),
                    handler: function (eventObject) {
                        var currentMode = that._mode,
                            name = "on" + eventName;
                        if (currentMode[name]) {
                            currentMode[name](eventObject);
                        }
                    }
                };
            }

            var elementEventsAttached = [
                elementListViewHandler("Resize"),
                elementListViewHandler("PropertyChange")
            ];

            // Event handlers that must be added using attachEvent
            elementEventsAttached.forEach(function (elementEvent) {
                that._element.attachEvent("on" + elementEvent.name, elementEvent.handler);
            });

            // KeyDown handler needs to be added explicitly via addEventListener instead of using the above attachEvent.
            // If it's not added via addEventListener, the eventObject given to us on event does not have the functions stopPropagation() and preventDefault().
            var events = [
                modeHandler("MSPointerDown", true),
                modeHandler("MSPointerMove", true),
                modeHandler("click", true),
                modeHandler("MSPointerUp", true),
                modeHandler("MSGotPointerCapture", true),
                modeHandler("MSLostPointerCapture", true),
                modeHandler("MSHoldVisual", true),
                modeHandler("MSPointerOut", true),
                modeHandler("MSPointerCancel", true),
                modeHandler("DragStart"),
                modeHandler("ContextMenu")
            ];
            events.forEach(function (eventHandler) {
                that._viewport.addEventListener(eventHandler.name, eventHandler.handler, false);
            });
            
            // Focus and Blur events need to be handled during the capturing phase, they do not bubble.
            var elementEvents = [
                listViewHandler("Focus", false, true),
                listViewHandler("Blur", false, true),
                modeHandler("KeyDown")
            ];
            elementEvents.forEach(function (eventHandler) {
                that._element.addEventListener(eventHandler.name, eventHandler.handler, !!eventHandler.capture);
            });

            var viewportEvents = [
                listViewHandler("MSManipulationStateChanged", true),
                listViewHandler("Scroll")
            ];
            viewportEvents.forEach(function (viewportEvent) {
                that._viewport.addEventListener(viewportEvent.name, viewportEvent.handler, false);
            });

            this._keyboardEventsHelper.parentNode.addEventListener("onTabEnter", this._onTabEnter.bind(this), false);
            this._keyboardEventsHelper.parentNode.addEventListener("onTabExit", this._onTabExit.bind(this), false);
        },

        _updateItemsManager: function ListView_updateItemsManager() {
            var that = this,
                notificationHandler = {
                    // Following methods are used by ItemsManager
                    beginNotifications: function ListView_beginNotifications() {
                    },

                    changed: function ListView_changed(newItem, oldItem, oldItemObject) {
                        if (that._ifZombieDispose()) { return; }

                        that._createUpdater();

                        //#DBG _ASSERT(utilities._isDOMElement(newItem));

                        var elementInfo = that._updater.elements[oldItem.uniqueID];
                        if (elementInfo) {
                            var selected = that.selection._isIncluded(elementInfo.index);
                            if (oldItem !== newItem) {
                                if (that._tabManager.childFocus === oldItem || that._updater.newFocusedItem === oldItem) {
                                    that._updater.newFocusedItem = newItem;
                                    that._tabManager.childFocus = null;
                                }

                                var next = oldItem.nextElementSibling;
                                elementInfo.wrapper.removeChild(oldItem);
                                that._setAriaSelected(newItem, selected);
                                elementInfo.wrapper.insertBefore(newItem, next);
                                that._view.items.setItemAt(elementInfo.newIndex, {
                                    element: newItem,
                                    display: elementInfo.display,
                                    wrapper: elementInfo.wrapper,
                                    itemsManagerRecord: elementInfo.itemsManagerRecord
                                });
                                delete that._updater.elements[oldItem.uniqueID];
                                that._updater.elements[newItem.uniqueID] = {
                                    item: newItem,
                                    wrapper: elementInfo.wrapper,
                                    index: elementInfo.index,
                                    newIndex: elementInfo.newIndex,
                                    display: elementInfo.display,
                                    itemsManagerRecord: elementInfo.itemsManagerRecord
                                };
                            } else {
                                that._renderSelection(elementInfo.wrapper, newItem, selected, true);
                            }
                            that._updater.changed = true;
                            that._groups.purgeDecorator(elementInfo.index);
                        } else {
                            var placeholder = that._updater.placeholders[oldItem.uniqueID];
                            if (placeholder) {
                                that._updater.placeholders[oldItem.uniqueID].element = newItem;
                                that._updater.changed = true;
                            }
                        }
                        for (var i = 0, len = that._notificationHandlers.length; i < len; i++) {
                            that._notificationHandlers[i].changed(newItem, oldItem);
                        }
                    },

                    removed: function ListView_removed(item, mirage, handle) {
                        if (that._ifZombieDispose()) { return; }

                        that._createUpdater();

                        function removeFromSelection(index) {
                            var firstRange = that._updater.selectionFirst[index],
                                lastRange = that._updater.selectionLast[index],
                                range = firstRange || lastRange;

                            if (range) {
                                delete that._updater.selectionFirst[range.oldFirstIndex];
                                delete that._updater.selectionLast[range.oldLastIndex];
                                that._updater.selectionChanged = true;
                            }
                        }

                        if (item) {
                            var index,
                                elementInfo = that._updater.elements[item.uniqueID],
                                itemObject = that._itemsManager.itemObject(item);

                            if (elementInfo) {
                                index = elementInfo.index;

                                // We track removed elements for animation purposes (layout
                                // component consumes this).
                                //
                                that._updater.removedElements.push(elementInfo.wrapper);

                                // The view can't access the data from the itemsManager
                                // anymore, so we need to flag the itemData that it
                                // has been removed.
                                //
                                var itemData = that._view.items.itemDataAt(index);
                                itemData.removed = true;

                                /*#DBG
                                delete elementInfo.itemsManagerRecord.updater;
                                #DBG*/
                                delete that._updater.elements[item.uniqueID];
                            } else {
                                index = itemObject && itemObject.index;
                            }
                            if (+index === index) {
                                that._groups.purgeDecorator(index);
                            }

                            var placeholder = that._updater.placeholders[item.uniqueID];
                            if (placeholder) {
                                delete that._updater.placeholders[item.uniqueID];
                            }

                            if (that._updater.oldFocus === index) {
                                that._updater.newFocus = index; // If index is too high, it'll be fixed in endNotifications
                                that._updater.focusedItemRemoved = true;
                            }

                            removeFromSelection(index);
                        } else {
                            var index = that._updater.selectionHandles[handle];
                            if (index === +index) {
                                removeFromSelection(index);
                            }
                        }

                        if (that._groups.pinnedItem === index) {
                            that._groups.pinItem();
                        }
                        that._updater.changed = true;
                    },

                    indexChanged: function ListView_indexChanged(item, newIndex, oldIndex) {
                        // We should receive at most one indexChanged notification per oldIndex
                        // per notification cycle.
                        if (that._ifZombieDispose()) { return; }

                        that._createUpdater();

                        if (item) {
                            var elementInfo = that._updater.elements[item.uniqueID];
                            if (elementInfo) {
                                elementInfo.newIndex = newIndex;
                                that._updater.changed = true;
                            }
                            that._updater.itemsMoved = true;
                            var placeholder = that._updater.placeholders[item.uniqueID];
                            if (placeholder) {
                                placeholder.newIndex = newIndex;
                                that._updater.changed = true;
                            }
                        }
                        if (that._updater.oldFocus === oldIndex) {
                            that._updater.newFocus = newIndex;
                            that._updater.changed = true;
                        }

                        if (that._updater.oldSelectionPivot === oldIndex) {
                            that._updater.newSelectionPivot = newIndex;
                            that._updater.changed = true;
                        }
                        
                        var range = that._updater.selectionFirst[oldIndex];
                        if (range) {
                            range.newFirstIndex = newIndex;
                            that._updater.changed = true;
                        }
                        range = that._updater.selectionLast[oldIndex];
                        if (range) {
                            range.newLastIndex = newIndex;
                            that._updater.changed = true;
                        }
                        if (that._groups.pinnedItem === oldIndex) {
                            that._groups.pinItem();
                        }
                        that._groups.purgeDecorator(oldIndex);
                    },

                    endNotifications: function ListView_endNotifications() {
                        that._update();
                    },

                    itemAvailable: function ListView_itemAvailable(item, placeholder) {
                        var index = that._itemsManager.itemObject(item).index;

                        if (that._view.items.placeholders[index]) {
                            delete that._view.items.placeholders[index];
                        }

                        if (that._updater && that._updater.placeholders[placeholder.uniqueID]) {
                            delete that._updater.placeholders[placeholder.uniqueID];
                        }
                    },

                    inserted: function ListView_inserted(itemPromise) {
                        if (that._ifZombieDispose()) { return; }

                        that._createUpdater();
                        that._updater.changed = true;
                        itemPromise.retain();
                        that._insertedItems[itemPromise.handle] = itemPromise;
                    },

                    moved: function ListView_moved(item, previous, next, itemPromise) {
                        if (that._ifZombieDispose()) { return; }

                        that._createUpdater();

                        if (item) {
                            that._updater.itemsMoved = true;
                        }

                        var index = that._updater.selectionHandles[itemPromise.handle];
                        if (index === +index) {
                            var firstRange = that._updater.selectionFirst[index],
                                lastRange = that._updater.selectionLast[index],
                                range = firstRange || lastRange;

                            if (range && range.oldFirstIndex !== range.oldLastIndex) {
                                delete that._updater.selectionFirst[range.oldFirstIndex];
                                delete that._updater.selectionLast[range.oldLastIndex];
                                that._updater.selectionChanged = true;
                                that._updater.changed = true;
                            }
                        }
                    },

                    countChanged: function ListView_countChanged(newCount, oldCount) {
                        if (that._ifZombieDispose()) { return; }

                        //#DBG _ASSERT(newCount !== undefined);
                        that._cachedCount = newCount;
                        if (newCount < oldCount) {
                            // no change, but the creation of the updater signals that things need to get refreshed
                            that._createUpdater();
                            that._updater.updateScrollbar = true;
                        } else if ((that._view.lastIndexDisplayed + 1) === oldCount) {
                            that._createUpdater();
                            that._updater.changed = true;
                        }
                    },

                    reload: function () {
                        if (that._ifZombieDispose()) { return; }

                        // Inform scroll view that a realization pass is coming so that it doesn't restart the 
                        // realization pass itself.
                        that._cancelRealize();
                        that._raiseViewLoading();
                        that._fadeOutViewport(function () {
                            that._selection._reset();
                            that._updateItemsManager();
                            that._view.reset();
                            that._view.reload(that.scrollPosition);
                        });
                    }
                };

            function statusChanged(eventObject) {
                if (eventObject.detail === thisWinUI.DataSourceStatus.failure) {
                    that.itemDataSource = null;
                    that.groupDataSource = null;
                }
            }

            if (this._versionManager) {
                this._versionManager._dispose();
            }

            this._versionManager = new WinJS.UI._VersionManager();
            this._updater = null;

            var ranges = this._selection.getRanges();
            this._selection._selected.clear();

            if (this._itemsManager) {

                if (this._itemsManager.dataSource && this._itemsManager.dataSource.removeEventListener) {
                    this._itemsManager.dataSource.removeEventListener("statuschanged", statusChanged, false);
                }

                this._clearInsertedItems();
                this._itemsManager.release();
            }

            if (this._itemsCountPromise) {
                this._itemsCountPromise.cancel();
                this._itemsCountPromise = null;
            }
            this._cachedCount = WinJS.UI._UNINITIALIZED;

            this._itemsManager = thisWinUI._createItemsManager(
                this._dataSource, 
                function (itemPromise, oldElement) { return that._itemsPool.renderItemAsync(itemPromise, oldElement); },
                notificationHandler, 
                {
                    ownerElement: this._element,
                    versionManager: this._versionManager,
                    resetItem: function (item, element) {
                        if (that.resetItem) {
                            return that.resetItem(item, element);
                        }
                        return null;
                    },
                    indexInView: function(index) {
                        return (index >= that.indexOfFirstVisible && index <= that.indexOfLastVisible);
                    }
                });

            if (this._dataSource.addEventListener) {
                this._dataSource.addEventListener("statuschanged", statusChanged, false);
            }

            this._selection._selected.set(ranges);
        },

        _createUpdater: function ListView_createUpdater() {
            if (!this._updater) {
                this._versionManager.beginUpdating();

                // Inform scroll view that a realization pass is coming so that it doesn't restart the 
                // realization pass itself.
                this._cancelRealize();

                var updater = {
                    changed: false,
                    elements: {},
                    placeholders: {},
                    selectionFirst: {},
                    selectionLast: {},
                    selectionHandles: {},
                    oldSelectionPivot: WinJS.UI._INVALID_INDEX,
                    newSelectionPivot: WinJS.UI._INVALID_INDEX,
                    removedElements: [],
                    selectionChanged: false,
                    oldFocus: WinJS.UI._INVALID_INDEX,
                    newFocus: WinJS.UI._INVALID_INDEX,
                    hadKeyboardFocus: this._hasKeyboardFocus,
                    itemsMoved: false,
                    lastVisible: this.indexOfLastVisible
                };

                this._view.items.each(function (index, item, itemData) {
                    /*#DBG
                    if (itemData.itemsManagerRecord.released) {
                        throw "ACK! found released data in items collection";
                    }
                    itemData.itemsManagerRecord.updater = updater;
                    #DBG*/
                    updater.elements[item.uniqueID] = {
                        item: item,
                        wrapper: itemData.wrapper,
                        index: index,
                        newIndex: index,
                        display: itemData.display,
                        itemsManagerRecord: itemData.itemsManagerRecord
                    };
                });

                var placeholders = this._view.items.placeholders,
                    keys = Object.keys(placeholders);
                for (var i = 0, len = keys.length; i < len; i++) {
                    var index = parseInt(keys[i], 10),
                        item = placeholders[index];
                    updater.placeholders[item.uniqueID] = {
                        element: item,
                        index: index,
                        newIndex: index
                    };
                }

                var selection = this._selection._selected._ranges;
                for (i = 0, len = selection.length; i < len; i++) {
                    var range = selection[i];
                    var newRange = {
                        newFirstIndex: selection[i].firstIndex,
                        oldFirstIndex: selection[i].firstIndex,
                        newLastIndex: selection[i].lastIndex,
                        oldLastIndex: selection[i].lastIndex
                    };
                    updater.selectionFirst[newRange.oldFirstIndex] = newRange;
                    updater.selectionLast[newRange.oldLastIndex] = newRange;
                    updater.selectionHandles[range.firstPromise.handle] = newRange.oldFirstIndex;
                    updater.selectionHandles[range.lastPromise.handle] = newRange.oldLastIndex;
                }
                updater.oldSelectionPivot = this._selection._pivot;
                updater.newSelectionPivot = updater.oldSelectionPivot;
                updater.oldFocus = this._selection._getFocused();
                updater.newFocus = updater.oldFocus;

                this._updater = updater;
            }
        },

        _correctScrollbarPos: function () {
            var current = this.scrollPosition;
            var viewportLength = this._getViewportLength();
            var canvasMargins = this._getCanvasMargins();
            var maxScrollbarPos = this._canvasLength - viewportLength +
                (this._layout.horizontal ? (canvasMargins.right + canvasMargins.left) : (canvasMargins.top + canvasMargins.bottom));

            if (current > maxScrollbarPos) {
                return Math.max(0, maxScrollbarPos);
            } else {
                return current;
            }
        },

        _synchronize: function ListView_synchronize() {
            var updater = this._updater;
            this._updater = null;
            var groupsChanged = this._groupsChanged;
            this._groupsChanged = false;

            /*#DBG
            if (updater) {
                for (i in updater.elements) {
                    if (updater.elements.hasOwnProperty(i)) {
                        var elementInfo = updater.elements[i];
                        delete elementInfo.itemsManagerRecord.updater;
                    }
                }
            }
            #DBG*/

            if (updater && updater.changed) {
                this._resizeViewport();
                if (updater.itemsMoved) {
                    this._layout.itemsMoved();
                }
                if (updater.removedElements.length) {
                    this._layout.itemsRemoved(updater.removedElements);
                }
                this._view.items.setLayoutIndices({});

                if (this._currentMode().onDataChanged) {
                    this._currentMode().onDataChanged();
                }

                var newSelection = [];
                for (var i in updater.selectionFirst) {
                    if (updater.selectionFirst.hasOwnProperty(i)) {
                        var range = updater.selectionFirst[i];
                        updater.selectionChanged = updater.selectionChanged || ((range.newLastIndex - range.newFirstIndex) != (range.oldLastIndex - range.oldFirstIndex));
                        if (range.newFirstIndex <= range.newLastIndex) {
                            newSelection.push({
                                firstIndex: range.newFirstIndex,
                                lastIndex: range.newLastIndex
                            });
                        }
                    }
                }

                if (updater.selectionChanged) {
                    var newSelectionItems = new WinJS.UI._Selection(this, newSelection);

                    // We do not allow listeners to cancel the selection
                    // change because the cancellation would also have to
                    // prevent the deletion.
                    this._selection._fireSelectionChanging(newSelectionItems);
                    this._selection._selected.set(newSelection);
                    this._selection._fireSelectionChanged();
                    newSelectionItems.clear();
                } else {
                    this._selection._selected.set(newSelection);
                }
                this._selection._updateCount(this._cachedCount);
                updater.newSelectionPivot = Math.min(this._cachedCount - 1, updater.newSelectionPivot);
                this._selection._pivot = (updater.newSelectionPivot >= 0 ? updater.newSelectionPivot : WinJS.UI._INVALID_INDEX);
                updater.newFocus = Math.max(0, Math.min(this._cachedCount - 1, updater.newFocus));
                this._selection._setFocused(updater.newFocus, this._selection._keyboardFocused());

                var newItems = {};
                for (i in updater.elements) {
                    if (updater.elements.hasOwnProperty(i)) {
                        var elementInfo = updater.elements[i];
                        /*#DBG
                        if (elementInfo.itemsManagerRecord.released) {
                            throw "ACK! attempt to put released record into list of items for ScrollView";
                        }
                        #DBG*/
                        newItems[elementInfo.newIndex] = {
                            element: elementInfo.item,
                            display: elementInfo.display,
                            wrapper: elementInfo.wrapper,
                            itemsManagerRecord: elementInfo.itemsManagerRecord
                        };
                    }
                }
                this._view.items._itemData = newItems;

                var newPlaceholders = {};
                for (i in updater.placeholders) {
                    if (updater.placeholders.hasOwnProperty(i)) {
                        var placeholder = updater.placeholders[i];
                        newPlaceholders[placeholder.newIndex] = placeholder.element;
                    }
                }
                this._view.items.placeholders = newPlaceholders;

                if (updater.focusedItemRemoved) {
                    this._itemFocused = false;
                    this._setFocusOnItem(this._selection._getFocused());
                } else if (updater.newFocusedItem) {
                    // We need to restore the value of _hasKeyboardFocus because a changed item
                    // gets removed from the DOM at the time of the notification. If the item
                    // had focus at that time, then our value of _hasKeyboardFocus will have changed.
                    this._hasKeyboardFocus = updater.hadKeyboardFocus;
                    this._itemFocused = false;
                    this._setFocusOnItem(this._selection._getFocused());
                }

                var that = this;
                return this._groups.synchronizeGroups().then(function () {
                    // Once the groups have been synchronized, we call layout.getItemPosition on the last visible item so that multisize layout
                    // computes a new occupancy map before calling updateScrollbar.
                    var lastVisible = Math.min(that._cachedCount - 1, updater.lastVisible),
                        layoutPromise = (lastVisible > 0 ? that._layout.getItemPosition(lastVisible) : Promise.wrap());
                    return layoutPromise.then(function () {
                        return (updater.updateScrollbar ? that._view.updateScrollbar(that._cachedCount, true) : Promise.wrap());
                    });
                }).then(function () {
                    var newScrollbarPos = that._correctScrollbarPos();
                    newScrollbarPos = Math.max(0, newScrollbarPos);
                    if (that._lastScrollPosition !== newScrollbarPos) {

                        that._lastScrollPosition = newScrollbarPos;
                        that.scrollPosition = newScrollbarPos;
                    }
                    that._versionManager.endUpdating();
                    return newScrollbarPos;
                });
            } else if (groupsChanged) {
                var that = this;
                return this._groups.synchronizeGroups().then(function () {
                    updater && that._versionManager.endUpdating();
                    return Promise.wrap(that.scrollPosition);
                });
            } else {
                updater && this._versionManager.endUpdating();

                return Promise.wrap(this.scrollPosition);
            }
        },

        _update: function ListView_update() {
            if (this._ifZombieDispose()) { return; }

            var that = this;
            if (this._versionManager.noOutstandingNotifications) {
                if (this._forceReload) {
                    this._forceReload = false;
                    this._cancelRealize();
                    this._synchronize().then(function (scrollbarPos) {
                        that._view.reload(scrollbarPos)
                    });
                } else if (this._updater || this._groupsChanged) {
                    this._cancelRealize();
                    this._synchronize().then(function (scrollbarPos) {
                        that._view.refresh(
                            scrollbarPos,
                            that._viewport[that._scrollLength],
                            that._getViewportSize(),
                            that._cachedCount
                        );
                    });
                } 
            }
        },

        _scheduleUpdate: function ListView_scheduleUpdate() {
            if (!this._updateTimer) {
                this._updateTimer = true;

                this._raiseViewLoading();

                var that = this;
                setImmediate(function () {
                    that._updateTimer = false;
                    that._update();
                });
            }
        },

        _registerNotificationHandler: function (handler) {
            this._notificationHandlers.push(handler);     
        },
        
        _unregisterNotificationHandler: function (handler) {
            for (var i = 0, len = this._notificationHandlers.length; i < len; i++) {
                if (this._notificationHandlers[i] === handler) {
                    this._notificationHandlers.splice(i, 1);
                    break;
                }
            }
        },

        _setLayoutSite: function () {
            var that = this,
                layoutSite = Object.create({
                invalidateLayout: function () {
                    that._refresh(that.scrollPosition);
                },
                _isZombie: function () {
                    return that._isZombie();
                }
                }, {
                _itemsManager: {
                    enumerable: true, 
                    get: function () { 
                        return that._itemsManager;
                    }
                }, 
                rtl: {
                    enumerable: true, 
                    get: function () { 
                        return that._rtl();
                    }
                }, 
                surface: {
                    enumerable: true, 
                    get: function () { 
                        return that._canvas;
                    }
                },
                itemSurface: {
                    enumerable: true,
                    get: function () {
                        return that._itemCanvas;
                    }
                },
                viewport: {
                    enumerable: true, 
                    get: function () { 
                        return that._viewport;
                    }
                }, 
                _groupOf: {
                    enumerable: true, 
                    get: function () {
                        return that._groups.groupOf.bind(that._groups);
                    }
                }, 
                _groupHeaderTemplate: {
                    enumerable: true, 
                    get: function () { 
                        return that.groupHeaderTemplate;
                    }
                }, 
                _groups: {
                    enumerable: true, 
                    get: function () { 
                        return that._groups;
                    }
                },
                scrollbarPos: {
                    enumerable: true, 
                    get: function () { 
                        return that.scrollPosition;
                    }
                },
                _surfaceLength: {
                    enumerable: true,
                    get: function () {
                        return that._getCanvasLength();
                    }
                },
                _surfaceScrollLimitMin: {
                    enumerable: true,
                    get: function () {
                        return that._getScrollLimitMin();
                    }
                },
                _surfaceMargins: {
                    enumerable: true,
                    get: function () {
                        return that._getCanvasMargins();
                    }
                },
                viewportSize: {
                    enumerable: true, 
                    get: function () { 
                        return that._getViewportSize();
                    }
                },
                loadingBehavior: {
                    enumerable: true, 
                    get: function () { 
                        return that.loadingBehavior;
                    }
                },
                animationsDisabled: {
                    enumerable: true, 
                    get: function () { 
                        return that._animationsDisabled();
                    }
                }
            });

            this._layout.setSite(layoutSite);
        },

        _updateLayout: function ListView_updateLayout(layoutObject) {
            var hadPreviousLayout = false;
            if (this._layout) {
                // The old layout is reset here in case it was in the middle of animating when the layout got changed. Reset
                // will cancel out the animations.
                this._cancelRealize();
                this._layout.reset();
                hadPreviousLayout = true;
            }

            if (layoutObject && typeof layoutObject.type === "function") {
                var LayoutCtor = requireSupportedForProcessing(layoutObject.type);
                this._layout = new LayoutCtor(layoutObject);
            } else if (layoutObject && layoutObject.setSite) {
                this._layout = layoutObject;
            } else {
                this._layout = new WinJS.UI.GridLayout(layoutObject);
            }
            
            this._unsetFocusOnItem();
            this._setFocusOnItem(0);
            this._selection._setFocused(0);
            this._setLayoutSite();

            if (this._layout.horizontal) {
                this._startProperty = "left";
                this._scrollProperty = "scrollLeft";
                this._scrollLength = "scrollWidth";
                utilities.addClass(this._viewport, WinJS.UI._horizontalClass);
                utilities.removeClass(this._viewport, WinJS.UI._verticalClass);
                if (hadPreviousLayout) {
                    this._viewport.scrollTop = 0;
                }
            } else {
                this._startProperty = "top";
                this._scrollProperty = "scrollTop";
                this._scrollLength = "scrollHeight";
                utilities.addClass(this._viewport, WinJS.UI._verticalClass);
                utilities.removeClass(this._viewport, WinJS.UI._horizontalClass);
                if (hadPreviousLayout) {
                    this._viewport.scrollLeft = 0;
                }
            }
        },

        _currentMode: function ListView_currentMode() {
            return this._mode;
        },

        _setSwipeClass: function ListView_setSwipeClass() {
            // We apply an -ms-touch-action style to block panning and swiping from occurring at the same time. It is
            // possible to pan in the margins between items and on lists without the swipe ability.
            if (this._currentMode() instanceof WinJS.UI._SelectionMode && this._selectionAllowed() && this._swipeBehavior === WinJS.UI.SwipeBehavior.select) {
                utilities.addClass(this._element, WinJS.UI._swipeableClass);
            } else {
                utilities.removeClass(this._element, WinJS.UI._swipeableClass);
            }
        },

        _resizeViewport: function ListView_resizeViewport() {
            this._viewportWidth = WinJS.UI._UNINITIALIZED;
            this._viewportHeight = WinJS.UI._UNINITIALIZED;
        },

        _onResize: function ListView_onResize() {
            setImmediate((function() {
                if (this._isZombie()) { return; }
                // If these values are uninitialized there is already a realization pass pending.
                if (this._viewportWidth !== WinJS.UI._UNINITIALIZED && this._viewportHeight !== WinJS.UI._UNINITIALIZED) {
                    if ((this._previousWidth !== this._element.offsetWidth) ||
                        (this._previousHeight !== this._element.offsetHeight)) {
                        this._previousWidth = this._element.offsetWidth;
                        this._previousHeight = this._element.offsetHeight;

                        this._resizeViewport();

                        this._groups.pinItem();
                        this._groups.purgeDecorators();
                        this._raiseViewLoading();
                        this._view.onResize(this.scrollPosition, this._getViewportSize());
                    }
                }
            }).bind(this));
        },

        _onFocus: function ListView_onFocus(event) {
            this._hasKeyboardFocus = true;
            var that = this;
            function moveFocusToItem(keyboardFocused) {
                that._changeFocus(that._selection._getFocused(), true, false, false, keyboardFocused);
            }
            // The keyboardEventsHelper object can get focus through three ways: We give it focus explicitly, in which case _shouldHaveFocus will be true,
            // or the item that should be focused isn't in the viewport, so keyboard focus could only go to our helper. The third way happens when
            // focus was already on the keyboard helper and someone alt tabbed away from and eventually back to the app. In the second case, we want to navigate
            // back to the focused item via changeFocus(). In the third case, we don't want to move focus to a real item. We differentiate between cases two and three
            // by checking if the flag _keyboardFocusInbound is true. It'll be set to true when the tab manager notifies us about the user pressing tab
            // to move focus into the listview.
            if (event.srcElement === this._keyboardEventsHelper) {
                if (!this._keyboardEventsHelper._shouldHaveFocus && this._keyboardFocusInbound) {
                    moveFocusToItem(true);
                } else {
                    this._keyboardEventsHelper._shouldHaveFocus = false;
                }
            } else if (event.srcElement === this._element) {
                // If someone explicitly calls .focus() on the listview element, we need to route focus to the item that should be focused
                moveFocusToItem();
            } else {
                this._tabEventsHelper.childFocus = null;
                // In the event that .focus() is explicitly called on an element, we need to figure out what item got focus and set our state appropriately.
                var items = this._view.items,
                    itemRootElement = items.wrapperFrom(event.srcElement);
                
                // itemRootElement will be null when the element that is getting focus isn't part of a list item (e.g. this._canvas, this._viewport)
                if (this._keyboardFocusInbound && itemRootElement && event.srcElement.parentNode === itemRootElement) {
                    this._drawFocusRectangle(itemRootElement);
                }

                if (itemRootElement && this._tabManager.childFocus !== itemRootElement) {
                    var index = items.index(itemRootElement);
                    
                    //#DBG _ASSERT(index !== WinJS.UI._INVALID_INDEX);
                    this._selection._setFocused(index, this._keyboardFocusInbound);
                    this._keyboardFocusInbound = false;
                    var item = items.itemAt(index);
                    this._tabManager.childFocus = item;

                    if (that._updater) {
                        var elementInfo = that._updater.elements[item.uniqueID],
                            focusIndex = index;
                        if (elementInfo && elementInfo.newIndex) {
                            focusIndex = elementInfo.newIndex;
                        }

                        that._updater.oldFocus = focusIndex;
                        that._updater.newFocus = focusIndex;
                    } 
                }
            }
        },

        _onBlur: function ListView_onBlur(event) {
            this._hasKeyboardFocus = false;
            this._itemFocused = false;
            var itemRootElement = this._view.items.wrapperFrom(event.srcElement);
            if (itemRootElement) {
                this._clearFocusRectangle(itemRootElement);
            }
            if (this._focusRequest) {
                // If we're losing focus and we had an outstanding focus request, that means the focused item isn't realized. To enable the user to tab back
                // into the listview, we'll make the keyboardEventsHelper tabbable for this scenario.
                this._tabEventsHelper.childFocus = this._keyboardEventsHelper;
            }
        },

        _onMSManipulationStateChanged: function ListView_onMSManipulationStateChanged(ev) {
            this._manipulationState = ev.currentState;
        },

        _pendingScroll: false,

        _onScroll: function ListView_onScroll() {
            if (!this._zooming && !this._pendingScroll) {
                this._checkScroller();
            }
        },

        _checkScroller: function ListView_checkScroller() {
            if (this._isZombie()) { return; }

            var currentScrollPosition = this._viewportScrollPosition;
            if (currentScrollPosition !== this._lastScrollPosition) {
                this._pendingScroll = setTimeout(this._checkScroller.bind(this), 16);

                var direction = (currentScrollPosition < this._lastScrollPosition) ? "left" : "right";
                currentScrollPosition = Math.max(0, currentScrollPosition);
                this._lastScrollPosition = currentScrollPosition;
                this._raiseViewLoading(true);
                this._view.onScroll(
                    this._lastScrollPosition,
                    this._viewport[this._scrollLength],
                    direction,
                    this._getViewportSize());
            } else {
                this._pendingScroll = null;
            }
        },

        _onTabEnter: function ListView_onTabEnter() {
            this._keyboardFocusInbound = true;
        },

        _onTabExit: function ListView_onTabExit() {
            this._keyboardFocusInbound = false;
        },

        _onPropertyChange: function ListView_onPropertyChange() {
            if ((event.propertyName === "dir") || (event.propertyName === "style.direction")) {
                this._cachedRTL = null;
                utilities[this._rtl() ? "addClass" : "removeClass"](this._element, WinJS.UI._rtlListViewClass);
                
                this._lastScrollPosition = 0;
                this.scrollPosition = 0;
                
                this.forceLayout();
            }

            if (event.propertyName === "tabIndex") {
                var newTabIndex = this._element.tabIndex;
                if (newTabIndex >= 0) {
                    this._view.items.each(function (index, item, itemData) {
                        item.tabIndex = newTabIndex;
                    });
                    this._tabIndex = newTabIndex;
                    this._tabManager.tabIndex = newTabIndex;
                    this._tabEventsHelper.tabIndex = newTabIndex;
                    this._element.tabIndex = -1;
                }
            }
        },

        _getCanvasMargins: function ListView_getCanvasMargins() {
            if (!this._canvasMargins) {
                this._canvasMargins = WinJS.UI._getMargins(this._canvas);
            }
            return this._canvasMargins;
        },

        _convertFromCanvasCoordinates: function ListView_convertFromCanvasCoordinates(coordinates) {
            function fix(field, offset) {
                if (coordinates[field] !== undefined) {
                    coordinates[field] += offset;
                }
            }

            var offset;
            if (this._horizontal()) {
                offset = this._getCanvasMargins()[this._rtl() ? "right" : "left"];
                fix("left", offset);
            } else {
                offset = this._getCanvasMargins().top;
                fix("top", offset);
            }
            fix("begin", offset);
            fix("end", offset);

            return coordinates;
        },

        // Methods in the site interface used by ScrollView
        _getViewportSize: function ListView_getViewportSize() {
            if (this._viewportWidth === WinJS.UI._UNINITIALIZED || this._viewportHeight === WinJS.UI._UNINITIALIZED) {
                this._viewportWidth = Math.max(0, utilities.getContentWidth(this._element));
                this._viewportHeight = Math.max(0, utilities.getContentHeight(this._element));

                this._previousWidth = this._element.offsetWidth;
                this._previousHeight = this._element.offsetHeight;
            }
            return {
                width: this._viewportWidth,
                height: this._viewportHeight
            };
        },

        _itemsCount: function ListView_itemsCount() {
            if (this._cachedCount !== WinJS.UI._UNINITIALIZED) {
                return Promise.wrap(this._cachedCount);
            } else {
                var that = this;
                this._itemsCountPromise = this._itemsManager.dataSource.getCount().then(
                    function (count) {
                        if (count === thisWinUI.CountResult.unknown) {
                            count = 0;
                        }
                        that._cachedCount = count;
                        that._selection._updateCount(that._cachedCount);
                        return count;
                    },
                    function () {
                        return WinJS.Promise.cancel;
                    }
                );
                return this._itemsCountPromise;
            }
        },

        _isSelected: function ListView_isSelected(index) {
            return this._selection._isIncluded(index);
        },

        _LoadingState: {
            itemsLoading: "itemsLoading",
            viewPortLoaded: "viewPortLoaded",
            itemsLoaded: "itemsLoaded",
            complete: "complete"
        },

        _raiseViewLoading: function ListView_raiseViewLoading(scrolling) {
            if (this._loadingState !== this._LoadingState.itemsLoading) {
                this._scrolling = !!scrolling;
            }
            this._setViewState(this._LoadingState.itemsLoading, null);            
        },

        _raiseViewPortLoaded: function ListView_raiseViewPortLoaded() {
            if (!this._scheduledForDispose) {
                scheduleForDispose(this);
                this._scheduledForDispose = true;
            }
            this._setViewState(this._LoadingState.viewPortLoaded, null);
        },

        _raiseViewLoaded: function ListView_raiseViewLoaded() {
            var detail = {
                scrolling: this._scrolling
            };
            this._setViewState(this._LoadingState.itemsLoaded, detail);            
        },

        _raiseViewComplete: function ListView_raiseViewComplete() {
            if (!this._view.animating) {
                /*#DBG
                this._checkForOverlap();
                #DBG*/
                this._setViewState(this._LoadingState.complete, null);
            }
        },

        _setViewState: function ListView_setViewState(state, detail) {
            if (state !== this._loadingState) {
                // We can go from any state to itemsLoading but the rest of the states transitions must follow this
                // order: itemsLoading -> viewPortLoaded -> itemsLoaded -> complete.
                // Recursively set the previous state until you hit the current state or itemsLoading.
                switch (state) {
                    case this._LoadingState.viewPortLoaded:
                        this._setViewState(this._LoadingState.itemsLoading);
                        break;

                    case this._LoadingState.itemsLoaded:
                        this._setViewState(this._LoadingState.viewPortLoaded);
                        break;

                    case this._LoadingState.complete:
                        this._setViewState(this._LoadingState.itemsLoaded);
                        break;
                }

                if (this.loadingBehavior === "incremental" &&
                    (state === this._LoadingState.itemsLoaded || state == this._LoadingState.complete)) {
                    detail = detail || {};
                    detail.numItemsLoaded = this._view.lastItem + 1;
                }

                msWriteProfilerMark("WinJS.UI.ListView:loadingStateChanged:" + state + ",info");
                this._loadingState = state;
                var eventObject = document.createEvent("CustomEvent");
                eventObject.initCustomEvent("loadingstatechanged", true, false, detail);
                this._element.dispatchEvent(eventObject);
            }  
        },
        /*#DBG
        _checkForOverlap: function ListView_checkForOverlap(){
            if (WinJS.UI.ListView._internalValidation){
                // This checks against overlapping tiles in list view. It is slow (N^2) and is only used when we want
                // extra validation.
                var finishedCheckingHeaders = false;
                var existing = [];
                var elementToTest = this._canvas.firstChild;
                while (elementToTest) {
                    var computedStyle = window.getComputedStyle(elementToTest);
                    if (WinJS.Utilities.hasClass(elementToTest, WinJS.UI._wrapperClass) || WinJS.Utilities.hasClass(elementToTest, WinJS.UI._headerClass)) {
                        if (computedStyle.position === "absolute" && computedStyle.opacity === "1") {
                            var clientRect = elementToTest.getBoundingClientRect();
                            var left = clientRect.left;
                            var top = clientRect.top;
                            var right = clientRect.right;
                            var bottom = clientRect.bottom

                            for (var i = 0; i < existing.length; i++) {
                                var previous = existing[i];
                                var prevLeft = previous.left;
                                var prevTop = previous.top;
                                var prevRight = previous.right;
                                var prevBottom = previous.bottom;

                                var overlapX = (left < prevRight && right > prevLeft);
                                var overlapY = (top < prevBottom && bottom > prevTop);

                                _ASSERT(!(overlapX && overlapY));
                            }

                            existing.push({
                                element: elementToTest,
                                left: left,
                                top: top,
                                right: right,
                                bottom: bottom
                            });
                        }
                    }
                    elementToTest = elementToTest.nextSibling;
                    if (!elementToTest && !finishedCheckingHeaders) {
                        elementToTest = this._itemCanvas.firstChild;
                        finishedCheckingHeaders = true;
                    }
                }
            }
        },
        #DBG*/
        _createTemplates: function ListView_createTemplates() {

            function createNodeWithClass(className, skipAriaHidden) {
                var element = document.createElement("div");
                element.className = className;
                if (!skipAriaHidden) {
                    element.setAttribute("aria-hidden", true);
                }
                return element;
            }

            var selectionBorder = createNodeWithClass(WinJS.UI._selectionBorderContainerClass);
            selectionBorder.appendChild(createNodeWithClass(WinJS.UI._selectionBorderClass + " " + WinJS.UI._selectionBorderTopClass));
            selectionBorder.appendChild(createNodeWithClass(WinJS.UI._selectionBorderClass + " " + WinJS.UI._selectionBorderRightClass));
            selectionBorder.appendChild(createNodeWithClass(WinJS.UI._selectionBorderClass + " " + WinJS.UI._selectionBorderBottomClass));
            selectionBorder.appendChild(createNodeWithClass(WinJS.UI._selectionBorderClass + " " + WinJS.UI._selectionBorderLeftClass));
            
            this._selectionTemplate = [];
            this._selectionTemplate.push(createNodeWithClass(WinJS.UI._selectionBackgroundClass));
            this._selectionTemplate.push(selectionBorder);
            this._selectionTemplate.push(createNodeWithClass(WinJS.UI._selectionCheckmarkBackgroundClass));
            var checkmark = createNodeWithClass(WinJS.UI._selectionCheckmarkClass);
            checkmark.innerText = WinJS.UI._SELECTION_CHECKMARK;
            this._selectionTemplate.push(checkmark);

            this._wrapperTemplate = createNodeWithClass(WinJS.UI._wrapperClass, true);
        },

        // Methods used by SelectionManager
        _renderSelection: function ListView_renderSelection(wrapper, element, selected, aria) {
            // Update the selection rendering if necessary
            if (selected !== WinJS.UI._isSelectionRenderer(wrapper)) {
                if (selected) {
                    wrapper.insertBefore(this._selectionTemplate[0].cloneNode(true), wrapper.firstElementChild);

                    for (var i = 1, len = this._selectionTemplate.length; i < len; i++) {
                        wrapper.appendChild(this._selectionTemplate[i].cloneNode(true));
                    }
                } else {
                    var nodes = wrapper.querySelectorAll(WinJS.UI._selectionPartsSelector);
                    for (var i = 0, len = nodes.length; i < len; i++) {
                        wrapper.removeChild(nodes[i]);
                    }
                }

                utilities[selected ? "addClass" : "removeClass"](wrapper, WinJS.UI._selectedClass);
            }

            // To allow itemPropertyChange to work properly, aria needs to be updated after the selection visuals are added to the wrapper
            if (aria) {
                this._setAriaSelected(element, selected);
            }
        },

        _updateSelection: function ListView_updateSelection() {
            var indices = this._selection.getIndices(),
                selectAll = this._selection.isEverything(),
                selectionMap = {};

            if (!selectAll) {
                for (var i = 0, len = indices.length ; i < len; i++) {
                    var index = indices[i];
                    selectionMap[index] = true;
                }
            }

            var that = this;
            this._view.items.each(function (index, element, itemData) {
                if (!utilities.hasClass(itemData.wrapper, thisWinUI._swipeClass)) {
                    var selected = selectAll || !!selectionMap[index];
                    that._renderSelection(itemData.wrapper, element, selected, true);
                }
            });
        },

        _getViewportLength: function ListView_getViewportLength() {
            return this._getViewportSize()[this._horizontal() ? "width" : "height"];
        },

        _getCanvasLength: function () {
            return this._canvasLength;
        },

        _getScrollLimitMin: function() {
            return this._scrollLimitMin;
        },

        _setCanvasLength: function (begin, end) {
            var length = end;
            begin = Math.max(0, begin);

            // Cache the canvas length before the right margin and scrollLimit extensions because getCanvasLength()
            // is used to figure out how far items go.
            this._canvasLength = length;

            // Margin right and bottom are not supportedChildren inside an overflow scroll parent. To make them work
            // we just add extra length to win-surface.
            var unsupportedMargin = this._horizontal() ? (this._rtl() ? "left" : "right") : "bottom";
            length += this._getCanvasMargins()[unsupportedMargin];

            if (begin > 0) {
                // The msScrollLimitXMin and msScrollLimitYMin styles only works if the 
                // content length (including margins) - scroll limit min >= viewport length.
                var margin = this._horizontal() ? (this._rtl() ? "right" : "left") : "top";
                length = Math.max(length, (begin + this._getViewportLength() - this._getCanvasMargins()[margin]));
            }

            this._canvas.style[this._horizontal() ? "width" : "height"] = length + "px";
            this._canvas.style[!this._horizontal() ? "width" : "height"] = "";

            this._scrollLimitMin = begin;
            this._viewport.style[this._horizontal() ? "msScrollLimitXMin" : "msScrollLimitYMin"] = begin + "px";
        },
        
        _horizontal: function ListView_horizontal() {
            return this._scrollProperty === "scrollLeft";
        },
        
        _rtl: function ListView_rtl() {
            if (typeof this._cachedRTL !== "boolean") {
                this._cachedRTL = window.getComputedStyle(this._element, null).direction === "rtl";
            }
            return this._cachedRTL;
        },

        _showProgressBar: function ListView_showProgressBar(parent, x, y) {
            var progressBar = this._progressBar,
                progressStyle = progressBar.style;

            if (!progressBar.parentNode) {
                this._fadingProgressBar = false;
                if (this._progressIndicatorDelayTimer) {
                    this._progressIndicatorDelayTimer.cancel();
                }
                var that = this;
                this._progressIndicatorDelayTimer = Promise.timeout(WinJS.UI._LISTVIEW_PROGRESS_DELAY).then(function () {
                    if (!that._isZombie()) {
                        parent.appendChild(progressBar);
                        AnimationHelper.fadeInElement(progressBar);
                        that._progressIndicatorDelayTimer = null;
                    }
                });
            }
            progressStyle[this._rtl() ? "right" : "left"] = x;
            progressStyle.top = y;
        },

        _hideProgressBar: function ListView_hideProgressBar() {
            if (this._progressIndicatorDelayTimer) {
                this._progressIndicatorDelayTimer.cancel();
                this._progressIndicatorDelayTimer = null;
            }

            var progressBar = this._progressBar;
            if (progressBar.parentNode && !this._fadingProgressBar) {
                this._fadingProgressBar = true;
                var that = this;
                AnimationHelper.fadeOutElement(progressBar).then(function () {
                    if (progressBar.parentNode) {
                        progressBar.parentNode.removeChild(progressBar);
                    }
                    that._fadingProgressBar = false;
                });
            }
        },

        _getPanAxis: function () {
            return this._horizontal() ? "horizontal" : "vertical";
        },

        _configureForZoom: function (isZoomedOut, isCurrentView, triggerZoom, pagesToPrefetch) {
            if (WinJS.validation) {
                if (!this._view.realizePage || typeof this._view.begin !== "number") {
                    throw new WinJS.ErrorFromName("WinJS.UI.ListView.NotCompatibleWithSemanticZoom", strings.notCompatibleWithSemanticZoom);
                }
            }

            this._isZoomedOut = isZoomedOut;
            this._disableEntranceAnimation = !isCurrentView;

            this._isCurrentZoomView = isCurrentView;

            this._triggerZoom = triggerZoom;
        },

        _setCurrentItem: function (x, y) {
            // First, convert the position into canvas coordinates
            if (this._horizontal()) {
                x += (
                    this._rtl() ?
                        this._canvas.offsetWidth - this._viewportWidth - this.scrollPosition :
                        this.scrollPosition
                );
            } else {
                y += this.scrollPosition;
            }

            var index = this._layout.hitTest(x, y);

            if (index >= 0) {
                if (this._hasKeyboardFocus) {
                    this._changeFocus(index, true, false, true);
                } else {
                    this._changeFocusPassively(index);
                }
            }
        },

        _getCurrentItem: function () {
            var indexFocused = this._selection._getFocused();
            
            if (typeof indexFocused !== "number") {
                // Do a hit-test in the viewport center
                this._setCurrentItem(0.5 * this._viewportWidth, 0.5 * this._viewportHeight);

                indexFocused = this._selection._getFocused();
            }

            var that = this;
            var promisePosition = this._getItemOffsetPosition(indexFocused).
                    then(function (posCanvas) {
                        var scrollOffset = parseInt(that._canvasStart, 10);

                        posCanvas[that._startProperty] += scrollOffset;

                        return posCanvas;
                    });

            return Promise.join({ 
                item: this._dataSource.itemFromIndex(indexFocused), 
                position: promisePosition 
            });
        },

        _beginZoom: function () {
            this._zooming = true;

            // Hide the scrollbar and extend the content beyond the ListView viewport

            var horizontal = this._horizontal(),
                scrollOffset = -this.scrollPosition;

            utilities.addClass(this._viewport, horizontal ? WinJS.UI._zoomingXClass : WinJS.UI._zoomingYClass);
            this._canvasStart = scrollOffset + "px";
            utilities.addClass(this._viewport, horizontal ? WinJS.UI._zoomingYClass : WinJS.UI._zoomingXClass);
        },

        _positionItem: function (item, position) {
            var that = this;
            function positionItemAtIndex(index) {
                return that._getItemOffsetPosition(index).then(function positionItemAtIndex_then_ItemOffsetPosition(posCanvas) {
                    var horizontal = that._horizontal(),
                        canvasSize = that._canvas[horizontal ? "offsetWidth" : "offsetHeight"],
                        viewportSize = (horizontal ? that._viewportWidth : that._viewportHeight),
                        scrollPosition;

                    // Align the leading edge
                    var start = position[that._startProperty],
                        startMax = viewportSize - (horizontal ? posCanvas.width : posCanvas.height);

                    // Ensure the item ends up within the viewport
                    start = Math.max(0, Math.min(startMax, start));

                    scrollPosition = posCanvas[that._startProperty] - start;
                    

                    // Ensure the scroll position is valid
                    var adjustedScrollPosition = Math.max(0, Math.min(canvasSize - viewportSize, scrollPosition)),
                    scrollAdjustment = adjustedScrollPosition - scrollPosition;

                    scrollPosition = adjustedScrollPosition;

                    // Since a zoom is in progress, adjust the div position
                    var scrollOffset = -scrollPosition;
                    that._canvasStart = scrollOffset + "px";

                    if (that._hasKeyboardFocus) {
                        that._changeFocus(index, true);
                    } else {
                        that._changeFocusPassively(index);
                    }

                    that._raiseViewLoading(true);
                    that._view.realizePage(scrollPosition, true);

                    return (
                        horizontal ?
                            { x: scrollAdjustment, y : 0 } :
                            { x: 0, y : scrollAdjustment }
                    );
                });
            }

            var itemIndex = 0;
            if (item) {
                itemIndex = (this._isZoomedOut ? item.groupIndexHint : item.firstItemIndexHint);
            }

            if (typeof itemIndex === "number") {
                return positionItemAtIndex(itemIndex);
            } else {
                // We'll need to obtain the index from the data source
                var itemPromise;

                var key = (this._isZoomedOut ? item.groupKey : item.firstItemKey);
                if (typeof key === "string" && this._dataSource.itemFromKey) {
                    itemPromise = this._dataSource.itemFromKey(key, (this._isZoomedOut ? {
                        groupMemberKey: item.key,
                        groupMemberIndex: item.index
                    } : null));
                } else {
                    var description = (this._isZoomedOut ? item.groupDescription : item.firstItemDescription);

                    if (WinJS.validation) {
                        if (description === undefined) {
                            throw new WinJS.ErrorFromName("WinJS.UI.ListView.InvalidItem", strings.listViewInvalidItem);
                        }
                    }

                    itemPromise = this._dataSource.itemFromDescription(description);
                }
               
                return itemPromise.
                    then(function (item) {
                        return Promise.timeout().
                            then(function () {
                                return positionItemAtIndex(item.index);
                            });
                    });
            }
        },

        _endZoom: function (isCurrentView) {
            // Crop the content again and re-enable the scrollbar

            var horizontal = this._horizontal(),
                scrollOffset = parseInt(this._canvasStart, 10);

            utilities.removeClass(this._viewport, WinJS.UI._zoomingYClass);
            utilities.removeClass(this._viewport, WinJS.UI._zoomingXClass);

            this._canvasStart = "0px";

            this.scrollPosition = -scrollOffset;

            this._disableEntranceAnimation = !isCurrentView;

            this._isCurrentZoomView = isCurrentView;
            this._zooming = false;

            var that = this;
            setImmediate(function () {
                if (that._view.realizePage) {
                    that._view.realizePage(that.scrollPosition, false);
                }
            });
        },

        _getItemOffsetPosition: function (index) {
            var items = this._view.items,
                elementAtIndex = items.itemAt(index);

            function elementOffsetPosition(element, index) {
                var elementRoot = items.wrapperAt(index),
                    left = elementRoot.offsetLeft + element.offsetLeft,
                    width = element.offsetWidth;

                if (that._rtl()) {
                    left = that._canvasLength - left - width; //offsetRight equivalent
                }

                return {
                    left: left,
                    top: elementRoot.offsetTop + element.offsetTop,
                    width: width,
                    height: element.offsetHeight
                };
            }

            var that = this;
            return new Promise(function (complete) {
                // See if an element already exists for the item, in which case it has been positioned
                if (elementAtIndex) {
                    complete(elementOffsetPosition(elementAtIndex, index));
                } else {
                    that._itemsCount().then(function (count) {
                        that._layout.startLayout(0, that._getViewportLength() - 1, count).then(function () {
                            var promisePosition = that._getItemOffset(index).then(
                                    function () {
                                        return that._layout.getItemPosition(index);
                                    },
                                    function (error) {
                                        if (error.name !== "WinJS.UI.LayoutNotInitialized") {
                                            return WinJS.Promise.wrapError(error);
                                        } else {
                                            return WinJS.Promise.cancel;
                                        }
                                    }),
                                indexRealized = that._view.begin,
                                elementRealized = items.itemAt(indexRealized),
                                promiseResult;

                            // Otherwise, see if there's at least one item that has been realized
                            if (elementRealized) {
                                // There is, so use the heuristic that its offsets relative to its computed position are likely to
                                // be the same as those of the item at the given index.
                                var offsetPosRealized = elementOffsetPosition(elementRealized, indexRealized);

                                promiseResult = Promise.join([promisePosition, that._layout.getItemPosition(indexRealized)]).then(function (results) {
                                    var pos = that._convertFromCanvasCoordinates(results[0]),
                                        posRealized = results[1];

                                    return {
                                        left: pos.left + (offsetPosRealized.left - posRealized.left),
                                        top: pos.top + (offsetPosRealized.top - posRealized.top),
                                        width: offsetPosRealized.width,
                                        height: offsetPosRealized.height
                                    };
                                });
                            } else {
                                // There's no way to determine the offsets, just return the calculated position
                                promiseResult = promisePosition.then(function (pos) {
                                    return {
                                        left: pos.left,
                                        top: pos.top,
                                        width: pos.totalWidth,
                                        height: pos.totalHeight
                                    };
                                });
                            }

                            promiseResult.then(function (result) {
                                that._layout.endLayout();
                                complete(result);
                            });
                        });
                    });
                }
            });
        },

        _changeFocus: function (newFocus, skipSelection, ctrlKeyDown, skipEnsureVisible, keyboardFocused) {
            //#DBG _ASSERT(newFocus !== -1);
            if (this._isZombie()) {
                return;    
            }
            var targetItem = this._view.items.itemAt(newFocus);
            this._unsetFocusOnItem(!!targetItem);
            this._hasKeyboardFocus = true;
            this._selection._setFocused(newFocus, keyboardFocused);
            if (!skipEnsureVisible) {
                this.ensureVisible(newFocus);
            }
            
            // _selection.set() needs to know which item has focus so we
            // must call it after _selection._setFocused() has been called.
            if (!skipSelection && this._selectFocused(ctrlKeyDown)) {
                this._selection.set(newFocus);
            }
            this._setFocusOnItem(newFocus);
        },
        
        // Updates ListView's internal focus state and, if ListView currently has focus, moves
        // Trident's focus to the item at index newFocus.
        // Similar to _changeFocus except _changeFocusPassively doesn't:
        // - ensure the item is selected or visible
        // - set Trident's focus to newFocus when ListView doesn't have focus
        _changeFocusPassively: function (newFocus) {
            //#DBG _ASSERT(newFocus !== -1);

            var targetItem = this._view.items.itemAt(newFocus);
            this._unsetFocusOnItem(!!targetItem);
            this._selection._setFocused(newFocus);
            this._setFocusOnItem(newFocus);
        },

        _drawFocusRectangle: function (item) {
            var wrapper = utilities.hasClass(item, WinJS.UI._wrapperClass) ? item : item.parentNode;
            //#DBG _ASSERT(utilities.hasClass(wrapper, WinJS.UI._wrapperClass));
            if (wrapper.querySelector("." + thisWinUI._itemFocusOutlineClass)) {
                return;
            }
            utilities.addClass(wrapper, thisWinUI._itemFocusClass);
            var outline = document.createElement("div");
            outline.className = thisWinUI._itemFocusOutlineClass;
            wrapper.appendChild(outline);
        },

        _clearFocusRectangle: function (item) {
            if (!item || this._isZombie()) {
                return;
            }
            
            if (!utilities.hasClass(item, WinJS.UI._wrapperClass) && !item.parentNode) {
                return;
            }
            
            var wrapper = utilities.hasClass(item, WinJS.UI._wrapperClass) ? item : item.parentNode;
            //#DBG _ASSERT(utilities.hasClass(wrapper, WinJS.UI._wrapperClass));
            utilities.removeClass(wrapper, thisWinUI._itemFocusClass);
            var outline = wrapper.querySelector("." + thisWinUI._itemFocusOutlineClass);
            if (outline) {
                outline.parentNode.removeChild(outline);
            }
        },

        _defaultInvoke: function (itemIndex) {
            if (this._isZoomedOut) {
                this._changeFocusPassively(itemIndex);
                this._triggerZoom();
            }
        },

        _selectionAllowed: function ListView_selectionAllowed() {
            return this._selectionMode !== WinJS.UI.SelectionMode.none;
        },

        _multiSelection: function ListView_multiSelection() {
            return this._selectionMode === WinJS.UI.SelectionMode.multi;
        },

        _selectOnTap: function ListView_selectOnTap() {
            return this._tap === WinJS.UI.TapBehavior.toggleSelect || this._tap === WinJS.UI.TapBehavior.directSelect;
        },

        _selectFocused: function ListView_selectFocused(ctrlKeyDown) {
            return this._tap === WinJS.UI.TapBehavior.directSelect && this._selectionMode === WinJS.UI.SelectionMode.multi && !ctrlKeyDown;
        },

        _dispose: function () {
            if (!this._disposed) {
                this._disposed = true;
                var clear = function clear(e) {
                    e && (e.innerText = "");
                }

                this._view && this._view._dispose && this._view._dispose();
                this._mode && this._mode._dispose && this._mode._dispose();
                this._groups && this._groups._dispose && this._groups._dispose();
                this._selection && this._selection._dispose && this._selection._dispose();

                this._groupsPool && this._groupsPool.clear();
                this._wrappersPool && this._wrappersPool.clear();
                this._itemsPool && this._itemsPool.clear();
                this._headersPool && this._headersPool.clear();

                this._itemsCountPromise && this._itemsCountPromise.cancel();
                this._versionManager && this._versionManager._dispose();
                this._clearInsertedItems();
                this._itemsManager && this._itemsManager.release();

                clear(this._viewport);
                clear(this._itemCanvas);
                clear(this._canvas);
                clear(this._canvasProxy);

                this._versionManager = null;
                this._view = null;
                this._wrappersPool = null;
                this._itemsPool = null;
                this._headersPool = null;
                this._groupsPool = null;
                this._mode = null;
                this._element = null;
                this._viewport = null;
                this._itemsManager = null;
                this._canvas = null;
                this._canvasProxy = null;
                this._itemCanvas = null;
                this._itemsCountPromise = null;
            }
        },

        _isZombie: function () {
            // determines if this ListView is no longer in the DOM or has been cleared
            //
            return this._disposed || !(this.element.firstElementChild && document.body.contains(this.element));
        },
        
        _ifZombieDispose: function () {
            var zombie = this._isZombie();
            if (zombie && !this._disposed) {
                scheduleForDispose(this);
            }
            return zombie;
        },

        _animationsDisabled: function () {
            if (this._viewportWidth === 0 || this._viewportHeight === 0) {
                return true;
            }

            return !WinJS.UI.isAnimationEnabled();
        },

        _fadeOutViewport: function ListView_fadeOutViewport(complete) {
            if (this._animationsDisabled()) {
                complete();
                return;
            }

            if (!this._fadingViewportOut) {
                if (this._waitingEntranceAnimationPromise) {
                    this._waitingEntranceAnimationPromise.cancel();
                    this._waitingEntranceAnimationPromise = null;
                }
                var eventDetails = this._fireAnimationEvent(WinJS.UI.ListViewAnimationType.contentTransition);
                this._firedAnimationEvent = true;
                if (!eventDetails.prevented) {
                    this._fadingViewportOut = true;
                    var that = this;
                    this._viewport.style["-ms-overflow-style"] = "none";
                    AnimationHelper.fadeOutElement(this._viewport).then(function () {
                        if (that._isZombie()) { return; }
                        that._fadingViewportOut = false;
                        that._viewport.style.opacity = 1.0;
                        complete();
                    });
                } else {
                    this._disableEntranceAnimation = true;
                    this._viewport.style.opacity = 1.0;
                    complete();
                }
            }
        },

        _animateListEntrance: function (firstTime) {
            var eventDetails = {
                prevented: false,
                animationPromise: Promise.wrap()
            };
            var that = this;
            function resetViewOpacity() {
                that._canvas.style.opacity = 1;
                that._viewport.style["-ms-overflow-style"] = "";
            }

            if (this._disableEntranceAnimation || this._animationsDisabled()) {
                resetViewOpacity();
                if (this._waitingEntranceAnimationPromise) {
                    this._waitingEntranceAnimationPromise.cancel();
                    this._waitingEntranceAnimationPromise = null;
                }
                return Promise.wrap();
            }

            if (!this._firedAnimationEvent) {
                eventDetails = this._fireAnimationEvent(WinJS.UI.ListViewAnimationType.entrance);
            } else {
                this._firedAnimationEvent = false;
            }

            if (eventDetails.prevented) {
                resetViewOpacity();
                return Promise.wrap();
            } else {
                if (this._waitingEntranceAnimationPromise) {
                    this._waitingEntranceAnimationPromise.cancel();
                }
                this._canvas.style.opacity = 0;
                this._viewport.style["-ms-overflow-style"] = "none";
                this._waitingEntranceAnimationPromise = eventDetails.animationPromise.then(function () {
                    if (!that._isZombie()) {
                        that._canvas.style.opacity = 1;
                        return AnimationHelper.animateEntrance(that._viewport, firstTime).then(function () {
                            if (!that._isZombie()) {
                                that._viewport.style["-ms-overflow-style"] = "";
                                that._waitingEntranceAnimationPromise = null;
                            }
                        });
                    }
                });
                return this._waitingEntranceAnimationPromise;
            }
        },

        _fireAnimationEvent: function (type) {
            var animationEvent = document.createEvent("CustomEvent"),
                animationPromise = Promise.wrap();

            animationEvent.initCustomEvent("contentanimating", true, true, {
                type: type
            });
            if (type === WinJS.UI.ListViewAnimationType.entrance) {
                animationEvent.detail.setPromise = function (delayPromise) {
                    animationPromise = delayPromise;
                };
            }
            var prevented = !this._element.dispatchEvent(animationEvent);
            return {
                prevented: prevented,
                animationPromise: animationPromise
            }
        },
        
        // If they don't yet exist, create the start and end markers which are required
        // by Narrator's aria-flowto/flowfrom implementation. They mark the start and end
        // of ListView's set of out-of-order DOM elements and so they must surround the
        // headers and groups in the DOM.
        _createAriaMarkers: function ListView_createAriaMarkers() {
            if (!this._ariaStartMarker) {
                this._ariaStartMarker = document.createElement("div");
                this._ariaStartMarker.id = this._ariaStartMarker.uniqueID;
                this._viewport.insertBefore(this._ariaStartMarker, this._canvas);
            }
            if (!this._ariaEndMarker) {
                this._ariaEndMarker = document.createElement("div");
                this._ariaEndMarker.id = this._ariaEndMarker.uniqueID;
                this._viewport.insertBefore(this._ariaEndMarker, this._canvas.nextSibling);
            }
        },

        // If the ListView is in static mode, then the roles of the list and items should be "list" and "listitem", respectively.
        // Otherwise, the roles should be "listbox" and "option." If the ARIA roles are out of sync with the ListView's
        // static/interactive state, update the role of the ListView and the role of each realized item.
        _updateAriaRoles: function ListView_updateAriaRoles() {
            var that = this;
            var listRole = this._element.getAttribute("role"),
                expectedListRole,
                expectedItemRole;

            if (this._currentMode().staticMode()) {
                expectedListRole = "list";
                expectedItemRole = "listitem";
            } else {
                expectedListRole = "listbox";
                expectedItemRole = "option";
            }

            if (listRole !== expectedListRole || this._itemRole !== expectedItemRole) {
                this._element.setAttribute("role", expectedListRole);
                this._itemRole = expectedItemRole;
                this._view.items.each(function (index, itemElement, itemData) {
                    itemElement.setAttribute("role", that._itemRole);
                });
            }
        },
        
        // Avoids unnecessary UIA selection events by only updating aria-selected if it has changed 
        _setAriaSelected: function ListView_setAriaSelected(itemElement, isSelected) {
            var ariaSelected = (itemElement.getAttribute("aria-selected") === "true");
            
            if (isSelected !== ariaSelected) {
                itemElement.setAttribute("aria-selected", isSelected);
            }
        },

        _groupsEnabled: function () {
            return this._groups.groupDataSource;
        },

        _getItemOffset: function ListView_getItemOffset(itemIndex) {
            var that = this;
            return this._layout.getItemPosition(itemIndex).then(function (pos) {
                that._groups.pinItem(itemIndex, pos);
                var margins = that._getItemMargins();
                if (that._layout.horizontal) {
                    var rtl = that._rtl();
                    return {
                        begin: pos.left - margins[rtl ? "left" : "right"],
                        end: pos.left + pos.totalWidth + margins[rtl ? "right" : "left"]
                    };

                } else {
                    return {
                        begin: pos.top - margins.bottom,
                        end: pos.top + pos.totalHeight + margins.top
                    };
                }
            });
        },

        _getItemMargins: function ListView_getItemMargins() {
            if (!this._itemMargins) {
                var item = this._itemCanvas.querySelector("." + WinJS.UI._wrapperClass),
                    cleanup;

                if (!item) {
                    item = document.createElement("div"),
                    utilities.addClass(item, WinJS.UI._wrapperClass);
                    this._viewport.appendChild(item);

                    cleanup = true;
                }

                this._itemMargins = WinJS.UI._getMargins(item);

                if (cleanup) {
                    this._viewport.removeChild(item);
                }
            }
            return this._itemMargins;
        },

        _correctRangeInFirstColumn: function ListView_correctRangeInFirstColumn(range) {
            var that = this;
            return this._getItemOffset(0).then(function (firstRange) {
                if (firstRange.begin === range.begin) {
                    if (that._horizontal()) {
                        range.begin = -that._getCanvasMargins()[that._rtl() ? "right" : "left"];
                    } else {
                        range.begin = -that._getCanvasMargins().top;
                    }
                }
                return range;
            });
        }
    }, {
        // Static members
        
        triggerDispose: function () {
            /// <signature helpKeyword="WinJS.UI.ListView.triggerDispose">
            /// <summary locid="WinJS.UI.ListView.triggerDispose">
            /// Triggers the ListView disposal service manually. In normal operation this is triggered
            /// at ListView instantiation. However in some scenarios it may be appropriate to run
            /// the disposal service manually.
            /// </summary>
            /// </signature>
            WinJS.UI._disposeControls();
        },

        _ScrollToPriority: {
            uninitialized: 0,
            low: 1,
            medium: 2,
            high: 3
        }
    }),

    _isSelectionRenderer: function ListView_isSelectionRenderer(wrapper) {
        // The tree is changed at pointerDown but _selectedClass is added only when the user drags an item below the selection threshold so checking for _selectedClass is not reliable.
        return wrapper.querySelectorAll(WinJS.UI._selectionPartsSelector).length > 0;
    }
});

WinJS.Class.mix(thisWinUI.ListView, WinJS.Utilities.createEventProperties(
    "iteminvoked",
    "selectionchanging",
    "selectionchanged",
    "loadingstatechanged",
    "keyboardnavigating",
    "contentanimating"));
WinJS.Class.mix(thisWinUI.ListView, WinJS.UI.DOMEventMixin);


})(this, WinJS);


(function scrollViewInit(global, WinJS, undefined) {
    "use strict";

var utilities = WinJS.Utilities,
    Promise = WinJS.Promise;
    
// Virtualized scroll view
WinJS.Namespace.define("WinJS.UI", {
    _ScrollView: function (listView) {
        this.listView = listView;
        this.items = new WinJS.UI._ItemsContainer(listView);
        this.pagesToPrefetch = WinJS.UI._ScrollView._pagesToPreload;
        this.begin = 0;
        this.end = 0;
        this.realizePass = 1;
        this.firstLayoutPass = true;
        this.firstIndexDisplayed = -1;
        this.lastIndexDisplayed = -1;
        this.runningAnimations = null;
        this.animating = false;
        this.loadingItems = false;
        this.renderCompletePromise = Promise.wrap();
        this._insertedElements = [];

        // These variables help determine if we can skip updateItem calls onScroll.
        this.cleanStartIndex = -1;
        this.cleanEndIndex = -1;
    }
});

// OK to skip a frame, but don't skip two...
//
WinJS.UI._ScrollView._maxTimePerRealizeFrame = 40;
WinJS.UI._ScrollView._maxTimePerRealizeFrameWhenPanning = 50;
WinJS.UI._ScrollView._maxTimePerRealizeFrameInit = 250;
WinJS.UI._ScrollView._pagesToPreload = 2;
WinJS.UI._ScrollView._preloadEdges = true;
WinJS.UI._ScrollView._retryTimeForAriaSetupDuringZoom = 500;

WinJS.UI._TimeBasedQueue = WinJS.Class.define(
    function _TimeBasedQueue_ctor(options) {
        this._work = [];
        this._lowPriorityWork = [];
        this._paused = 0;
        options = options || {};
        this._duration = options.duration || WinJS.UI._ScrollView._maxTimePerRealizeFrame;
        this.isBusy = options.isBusy;
    },
    {
        duration: {
            get: function () {
                return this._duration;
            },
            set: function (val) {
                if (val !== this._duration) {
                    this._duration = val;
                    if (this._running && !this._paused) {
                        this.pause();
                        setImmediate(this.resume.bind(this));
                    }
                }
            }
        },
        cancel: function TimeBasedQueue_cancel() {
            this._work = [];
            this._lowPriorityWork = [];
        },
        push: function TimeBasedQueue_push(workUnit, lowPriority) {
            if (lowPriority) {
                this._lowPriorityWork.push(workUnit);
            } else {
                this._work.push(workUnit);
            }
            if (this._started && !this._running) {
                this.start();
            }
        },
        start: function TimeBasedQueue_start(startDuration) {
            if (!this._running && !this._paused) {
                this._running = true;
                this._started = true;
                if (startDuration) {
                    // Do initial run synchronously to avoid any yielding to the browser in the case of small amounts
                    // of work.
                    this._run(startDuration);
                } else {
                    setImmediate(this._run.bind(this));
                }
            }
        },
        pause: function TimeBasedQueue_pause() {
            this._paused++;
        },
        resume: function TimeBasedQueue_resume() {
            //#DBG _ASSERT(this._paused);
            this._paused--;
            this.start();
        },
        _run: function TimeBasedQueue_run(duration) {
            // If we are busy doing other things wait for a bit and try again
            if (this.isBusy && this.isBusy() && (this._work.length > 0 || this._lowPriorityWork.length > 0)) {
                setTimeout(this._run.bind(this), 16);
                return;
            }

            duration = duration || this.duration;
            var start = new Date();
            do {
                if (!this._paused && (this._work.length > 0 || this._lowPriorityWork.length > 0)) {
                    var workUnit = (this._work.length > 0 ? this._work.shift() : this._lowPriorityWork.shift());
                    workUnit();
                } else {
                    this._running = false;
                    return;
                }
            } while (!(this.isBusy && this.isBusy()) && (new Date() - start) < duration);

            setImmediate(this._run.bind(this));
        }
    }, {
        supportedForProcessing: false,
    }
);

WinJS.UI._ScrollView.prototype = {

    _dispose: function ScrollView_dispose() {
        this.cleanUp();
        this.items = null;
        this.renderCompletePromise && this.renderCompletePromise.cancel();
        this.renderCompletePromise = null;
    },

    createItem: function ScrollView_createItem(itemIndex, available, unavailable) {
        var that = this;
        var itemPromise = that.listView._itemsManager._itemPromiseAtIndex(itemIndex);
        var elementPromise = that.listView._groups.addItem(itemIndex, itemPromise).
            then(function () {
                return that.listView._itemsManager._itemFromItemPromise(itemPromise);
            }).then(
                function (element) {
                    if (element) {
                        return available(itemIndex, element, that.listView._itemsManager._recordFromElement(element));
                    } else {
                        unavailable(itemIndex);
                    }
                },
                function (err) {
                    unavailable(itemIndex);
                    return WinJS.Promise.wrapError(err);
                }
            );

        return elementPromise;
    },

    addItem: function ScrollView_addItem(fragment, itemIndex, element, currentPass) {
        /*#DBG
        if (!WinJS.Utilities.data(element).itemsManagerRecord || WinJS.Utilities.data(element).removeElementMapRecord) {
            throw "ACK! Attempt to add an item to the scrollview which hasn't yet been realized";
        }
        #DBG*/

        if (this.realizePass === currentPass) {
            var layoutIndex = this.items.getLayoutIndex(itemIndex);
            if (layoutIndex !== WinJS.UI._INVALID_INDEX) {

                var record = this.listView._itemsManager._recordFromElement(element);
                var wrapper = element.parentNode;

                if (this.listView._isSelected(itemIndex)) {
                    this.listView._renderSelection(wrapper, element, true, true);
                }

                this.items.setItemAt(itemIndex, {
                    wrapper: wrapper,
                    element: element,
                    detached: true,
                    itemsManagerRecord: record,
                    visible: true
                });

                this.listView._layout.layoutItem(layoutIndex, wrapper);
            }
        }
    },

    finalItem: function ScrollView_finalItem() {
        return this.listView._itemsCount().then(function (count) {
            return count - 1;
        });
    },

    hideItem: function ScrollView_hideItem(itemData, wrapper) {
        if (itemData.display === undefined) {
            itemData.display = wrapper.style.display;
            wrapper.style.display = "none";
        }
    },

    updateItem: function ScrollView_updateItem(itemIndex, itemIsReadyCallback) {
        var that = this,
            itemPromise = that.listView._itemsManager._itemPromiseAtIndex(itemIndex);

        return that.listView._groups.addItem(itemIndex, itemPromise).then(
            function () {
                // Update can happen before an item promise completes when there are placeholders
                itemPromise.cancel();

                var layoutIndex = that.items.getLayoutIndex(itemIndex),
                    itemData = that.items.itemDataAt(itemIndex),
                    wrapper = itemData.wrapper;

                if (layoutIndex !== WinJS.UI._INVALID_INDEX) {
                    that.listView._layout.layoutItem(layoutIndex, wrapper);
                    if (itemData.display !== undefined) {
                        wrapper.style.display = itemData.display;
                        itemData.display = undefined;
                    }
                }
                else {
                    that.hideItem(itemData, wrapper);
                }

                itemIsReadyCallback(itemIndex, itemData.element, itemData.itemsManagerRecord);
            },
            function (e) {
                itemPromise.cancel();
                return WinJS.Promise.wrapError(e);
            }
        );
    },

    updateCleanIndexRange: function ScrollView_updateCleanIndexRange(itemIndex) {
        // This function allows us to remember which elements we have called UpdateIndex on
        // after a forceLayout so we do not have to do it again.
        if (this.cleanStartIndex - 1 === itemIndex) {
            this.cleanStartIndex = itemIndex;
        } else if (this.cleanEndIndex + 1 === itemIndex) {
            this.cleanEndIndex = itemIndex;
        } else if (itemIndex < this.cleanStartIndex || itemIndex > this.cleanEndIndex) {
            this.cleanStartIndex = this.cleanEndIndex = itemIndex;
        }
    },

    realizeItems: function ScrollView_realizeItems(fragment, begin, end, count, currentPass, scrollbarPos, direction) {
        var perfId = "WinJS.UI.ListView:realizeItems(" + begin + "-" + end + ")";
        msWriteProfilerMark(perfId + ",StartTM");
        direction = direction || "right";

        var counter = end - begin;
        var firstInView;
        var lastInView;
        var inViewCounter;
        var renderCompletePromises = [];
        var loadingSignal = new WinJS._Signal();
        var viewportItemsRealized = new WinJS._Signal();
        var allItemsRealized = new WinJS._Signal();

        var that = this;

        var work;
        var pinnedItemIndex = this.listView._groups.pinnedItem;
        var waitForStart = (+pinnedItemIndex === pinnedItemIndex ? pinnedItemIndex : 0);
        var waitForEnd = waitForStart;
        var readyWaitForStart = waitForStart;
        var readyWaitForEnd = waitForEnd;

        if (waitForStart < that.cleanStartIndex || waitForEnd > that.cleanEndIndex) {
            this._resetLayoutState();
        }

        var newElements = {};
        var updatedElements = {};

        this.loadingItems = true;

        var initComplete = Promise.join([
            this.listView.layout.calculateFirstVisible(scrollbarPos, false),
            this.listView.layout.calculateLastVisible(scrollbarPos + this.listView._getViewportLength() - 1, false)
        ]);
        initComplete.then(function (indices) {
            var showProgress = true;
            for (var i = indices[0]; i <= indices[1]; i++) {
                if (that.items.itemAt(i)) {
                    showProgress = false;
                    break;
                }
            }

            if (that.firstLayoutPass) {
                that.listView._canvas.style.opacity = 0;
            } else {
                if (showProgress) {
                    that.listView._showProgressBar(that.listView._element, "50%", "50%");
                } else {
                    that.listView._hideProgressBar();
                }
            }
        });

        function itemIsReady(itemIndex, element, itemsManagerRecord) {
            renderCompletePromises.push(itemsManagerRecord.renderComplete);

            return delivered(itemIndex);
        }

        function appendItemsToDom(startIndex, endIndex) {
            if (that.listView._isZombie()) { return; }

            var firstIndexInDom = -1;
            var lastIndexInDom = -1;
            var itemIndex;
            for (itemIndex = startIndex; itemIndex <= endIndex; itemIndex++) {
                var itemData = that.items.itemDataAt(itemIndex);
                if (itemData) {
                    var element = itemData.element;
                    var wrapper = element.parentNode;
                    if (wrapper.parentNode !== fragment) {
                        fragment.appendChild(wrapper);
                    }

                    if (firstIndexInDom === -1) {
                        firstIndexInDom = lastIndexInDom = itemIndex;
                    } else {
                        firstIndexInDom = Math.min(firstIndexInDom, itemIndex);
                        lastIndexInDom = Math.max(lastIndexInDom, itemIndex);
                    }

                    // elementAvailable needs to be called after fragment.appendChild. elementAvailable fulfills a promise for items requested
                    // by the keyboard focus handler. That handler will explicitly call .focus() on the element, so in order for
                    // the focus handler to work, the element needs to be in a tree prior to focusing.
                    that.items.elementAvailable(itemIndex);
                }
            }

            if (firstIndexInDom !== -1) {
                // Update the headers in batches as well
                that.updateHeaders(that.listView._canvas, firstIndexInDom, lastIndexInDom + 1, true);

            }
        }

        function removeGaps(first, last, begin, end) {
            // If we realized items 0 through 20 and then scrolled so that items 25 - 30 are on screen when we 
            // append them to the dom we should remove items 0 - 20 from the dom so there are no gaps between the
            // two realized spots.

            // Walk backwards from the beginning and if we find an item which is missing remove the rest
            var foundMissing = false;
            while (first >= begin) {
                foundMissing = testGap(first, foundMissing);
                first--;
            }

            // Walk forwards from the end and if we find an item which is missing remove the rest
            foundMissing = false;
            while (last <= end) {
                foundMissing = testGap(last, foundMissing);
                last++;
            }

            function testGap(itemIndex, foundMissing) {
                // This helper method is called for each index and once an item is missing from the dom
                // it removes any future one it encounters.
                var itemData = that.items.itemDataAt(itemIndex);
                if (itemData) {
                    var element = itemData.element;
                    var wrapper = element.parentNode;
                    if (wrapper.parentNode !== fragment) {
                        return true;
                    } else if (foundMissing) {
                        wrapper.parentNode.removeChild(wrapper);
                        return true;
                    } else {
                        return false;
                    }
                } else {
                    return true;
                }
            }
        }

        function delivered(index) {
            var retVal = null;
            if (index >= firstInView && index <= lastInView) {
                if (--inViewCounter === 0) {
                    if (that.realizePass === currentPass) {
                        appendItemsToDom(firstInView, lastInView);
                        removeGaps(firstInView, lastInView, begin, end);
                        that.updateBackdrop(count);
                        // Set the scroll bar to an initial guess
                        that.updateScrollbar(count);

                        if (that.firstLayoutPass) {
                            work.duration = WinJS.UI._ScrollView._maxTimePerRealizeFrame;

                            // Entrance animation does not work unless it is in a timeout
                            var entranceAnimation = Promise.timeout().then(function () {
                                if (that.listView._isZombie()) { return; }

                                return that.listView._animateListEntrance(!that.firstEntranceAnimated);
                            });
                            that.runningAnimations = Promise.join([that.runningAnimations, entranceAnimation]);
                            that.firstLayoutPass = false;
                            that.firstEntranceAnimated = true;
                            that.animating = true;
                        }

                        viewportItemsRealized.complete();
                    }
                }
            }

            counter--;

            if (that.realizePass === currentPass && inViewCounter <= 0 && (counter % (lastInView - firstInView + 1) === 0)) {
                // We have another page worth of data.
                appendItemsToDom(begin, end - 1);
                that.updateBackdrop(count);
            }

            if (counter === 0) {
                that.renderCompletePromise = Promise.join(renderCompletePromises).then(null, function (e) {
                    var error = Array.isArray(e) && e.some(function (item) { return item && !(item instanceof Error && item.name === "Canceled"); });
                    if (error) {
                        // rethrow
                        return Promise.wrapError(e);
                    }
                });

                if (that.realizePass === currentPass) {
                    //#DBG _ASSERT(Object.keys(newElements).length === 0);
                    //#DBG _ASSERT(Object.keys(updatedElements).length === 0);

                    if (that._insertedElements.length) {
                        that.listView._layout.itemsAdded(that._insertedElements);
                    }
                    var endLayoutResult = that.listView._layout.endLayout(),
                        animationPromise;
                    that._insertedElements = [];
                    that.listView._clearInsertedItems();

                    if (endLayoutResult) {
                        if (endLayoutResult.newEndIndex) {
                            retVal = that.realizeItems(fragment, end, Math.min(count, endLayoutResult.newEndIndex), end, currentPass, scrollbarPos).allItemsRealized;
                        }

                        animationPromise = endLayoutResult.animationPromise;
                    }

                    if (animationPromise) {
                        that.animating = true;
                    }
                    that.renderCompletePromise.then(function () {
                        if (that.realizePass === currentPass) {
                            that.loadingItems = false;
                        }
                    });
                    that.runningAnimations = Promise.join([that.runningAnimations, animationPromise]).then(function () {
                        return Promise.timeout();
                    });
                    // Delay the animation completed code until endLayout is finished. If endLayout triggers another animation, then
                    // realizePass will be updated and this promise will be invalid.
                    that.runningAnimations.then(function () {
                        if (that.realizePass === currentPass) {
                            that.animating = false;
                            that.runningAnimations = null;
                        }
                    });

                    Promise.join([that.renderCompletePromise, that.runningAnimations]).then(function () {
                        if (that.listView._isZombie()) { return WinJS.Promise.cancel; }

                        if (that.realizePass === currentPass && !that.loadingItems && !that.animating) {
                            loadingSignal.complete();
                        }
                    });

                    allItemsRealized.complete();
                }
            }
            return retVal;
        }

        function newItemIsReady(itemIndex, element, itemsManagerRecord) {
            var wrapper = element.parentNode;

            if (that.realizePass === currentPass) {
                if (that.listView._isInsertedItem(itemsManagerRecord.itemPromise)) {
                    // Start element at opacity 0 so it can fade in.
                    wrapper.style.opacity = 0;
                    that._insertedElements.push(wrapper);
                }

                //#DBG _ASSERT(!itemsManagerRecord.released);
                newElements[itemIndex] = itemsManagerRecord;
                processWaitingElements(itemIndex);
                itemsManagerRecord.itemPromise.then(function () {
                    processReadyWaiting();
                });
            }
        }

        function processReadyWaiting() {
            function tryQueueReadyWork(itemIndex) {
                var itemData = that.items.itemDataAt(itemIndex);
                var record = itemData.itemsManagerRecord;
                if (record.pendingReady) {
                    work.push(function () {
                        if (that.listView._isZombie()) {
                            return;
                        }
                        if (record.pendingReady) {
                            record.pendingReady();
                        }
                    }, (itemIndex < that.firstIndexDisplayed || itemIndex > that.lastIndexDisplayed));
                    return true;
                } else if (record.readyComplete) {
                    return true;
                }
                return false;
            }

            if (currentPass === that.realizePass) {
                while (waitForEnd > readyWaitForEnd && tryQueueReadyWork(readyWaitForEnd)) {
                    if (readyWaitForEnd === readyWaitForStart) {
                        readyWaitForStart--;
                    }

                    readyWaitForEnd++;
                }

                while (waitForStart < readyWaitForStart && tryQueueReadyWork(readyWaitForStart)) {
                    readyWaitForStart--;
                }
            }
        }

        function processWaitingElements(itemIndex) {
            var processedOne = false;
            if (itemIndex === waitForStart || itemIndex === waitForEnd) {

                var tryProcessingElement = function (itemIndex) {
                    if (newElements[itemIndex]) {
                        var itemsManagerRecord = newElements[itemIndex];
                        //#DBG _ASSERT(!itemsManagerRecord.released);
                        var element = itemsManagerRecord.element;
                        delete newElements[itemIndex];
                        that.addItem(fragment, itemIndex, element, currentPass);
                        itemIsReady(itemIndex, element, itemsManagerRecord);
                        that.updateCleanIndexRange(itemIndex);
                    } else if (updatedElements[itemIndex]) {
                        var updateFunction = updatedElements[itemIndex];
                        delete updatedElements[itemIndex];
                        updateFunction();
                    } else {
                        return false;
                    }
                    return true;
                }

                if (tryProcessingElement(waitForEnd)) {
                    if (waitForStart === waitForEnd) {
                        waitForStart--;
                        queueProcessWaiting(waitForStart);
                    }

                    processedOne = true;
                    waitForEnd++;
                    queueProcessWaiting(waitForEnd);
                } else if (tryProcessingElement(waitForStart)) {
                    processedOne = true;
                    waitForStart--;
                    queueProcessWaiting(waitForStart);
                }

                if (processedOne) {
                    that.listView._hideProgressBar();
                }
            }

            function queueProcessWaiting(itemIndex) {
                work.push(function () {
                    processWaitingElements(itemIndex);
                });
            }
        }

        if (counter > 0) {
            var itemsRealizedPromise = initComplete.then(function (v) {
                var buffer = [];
                var createCount = 0;
                var updateCount = 0;
                var cleanCount = 0;
                firstInView = v[0] || begin;
                lastInView = v[1] || end - 1;
                //#DBG _ASSERT(lastInView < end);
                inViewCounter = lastInView - firstInView + 1;
                that.firstIndexDisplayed = firstInView;
                that.lastIndexDisplayed = lastInView;

                var queueWork = function (itemIndex) {
                    return function ScrollView_realizeItemsWork() {
                        if (that.listView._isZombie()) {
                            return;
                        }

                        var itemData = that.items.itemDataAt(itemIndex);
                        if (!itemData) {
                            createCount++;
                            buffer.push(that.createItem(itemIndex, newItemIsReady, delivered));
                        } else {
                            updatedElements[itemIndex] = function () {
                                if (itemIndex > that.cleanEndIndex || itemIndex < that.cleanStartIndex) {
                                    updateCount++;
                                    // Skip calling updateItem if there was no reason to update since the last full
                                    // realizepage or if the item has already been updated.
                                    that.updateItem(itemIndex, itemIsReady);
                                    that.updateCleanIndexRange(itemIndex);
                                } else {
                                    cleanCount++;
                                    itemIsReady(itemIndex, itemData.element, itemData.itemsManagerRecord);
                                }

                                itemData.itemsManagerRecord.itemPromise.then(function () {
                                    processReadyWaiting();
                                });
                            };
                            processWaitingElements(itemIndex);
                        }
                    };
                };

                var isCurrentZoomView = that.listView._isCurrentZoomView;
                WinJS.UI._ScrollView._inViewWorking = WinJS.UI._ScrollView._inViewWorking || 0;

                var startDuration = 0;
                var duration;
                if (isCurrentZoomView) {
                    WinJS.UI._ScrollView._inViewWorking++;

                    if (that.firstLayoutPass) {
                        // Use long duration during initialization since it does not impact scrolling
                        duration = WinJS.UI._ScrollView._maxTimePerRealizeFrameInit;
                        startDuration = WinJS.UI._ScrollView._maxTimePerRealizeFrameInit;
                    } else if (that.listView._manipulationState === MSManipulationEvent.MS_MANIPULATION_STATE_STOPPED) {
                        startDuration = WinJS.UI._ScrollView._maxTimePerRealizeFrame / 4;
                    } else {
                        startDuration = WinJS.UI._ScrollView._maxTimePerRealizeFrameWhenPanning;
                        duration = WinJS.UI._ScrollView._maxTimePerRealizeFrameWhenPanning;
                    }
                }

                work = new WinJS.UI._TimeBasedQueue({
                    isBusy: function () {
                        // when listview is disposed, we just let the queue drain
                        if (that.listView._disposed) { return false; }

                        // Do not work on the hidden listviews when there is work to be done for the visible listviews
                        return that.listView._versionManager.locked || (!isCurrentZoomView && WinJS.UI._ScrollView._inViewWorking > 0);
                    },
                    duration: duration
                });

                //#DBG work._startVersion = that.listView._versionManager.version;

                // Pause the itemsManager from performing ready work while the queue is running
                that.listView._itemsManager._workQueue.pause();

                // Create a promise to wrap the work in the queue. When the queue gets to the last item we can mark
                // the work promise complete and if the work promise is canceled we cancel the queue.
                var queueWorkComplete;
                var workPromise = new WinJS.Promise(function (c, e, p) {
                    queueWorkComplete = function () {
                        work.push(function () {
                            if (that.listView._isZombie()) {
                                c(WinJS.Promise.cancel);
                            }
                            c();
                        });
                    };
                }).then(function () {
                    if (isCurrentZoomView) {
                        WinJS.UI._ScrollView._inViewWorking--;
                    }
                    that.listView._versionManager.clearCancelOnNotification(cancelToken);
                    that.listView._itemsManager._workQueue.resume();
                }, function (err) {
                    if (isCurrentZoomView) {
                        WinJS.UI._ScrollView._inViewWorking--;
                    }

                    that.listView._versionManager.clearCancelOnNotification(cancelToken);
                    work.cancel();
                    that.listView._itemsManager && that.listView._itemsManager._workQueue.resume();

                    loadingSignal.cancel();
                    viewportItemsRealized.cancel();
                    allItemsRealized.cancel();

                    return WinJS.Promise.wrapError(err);
                });

                var promiseToCancel = new WinJS.Promise(function () { });
                promiseToCancel.then(null, function () {
                    workPromise.cancel();
                    if (currentPass === that.realizePass) {
                        setImmediate(function () {
                            if (that.listView._isZombie()) { return; }

                            // The work can be canceled by a beginNotification in ItemsManager or GroupsContainer. The 
                            // ListView will call cancelRealize if the notification requires synchronization work. In 
                            // that case the realization pass will be started by the ListView. However if cancelRealize 
                            // was not called we need to resume the realization pass ourselves.
                            that.listView._versionManager.unlocked.then(function () {
                                if (currentPass === that.realizePass) {
                                    that.realizePage(scrollbarPos, true, direction);
                                }
                            });
                        });
                    }
                });

                var cancelToken = that.listView._versionManager.cancelOnNotification(promiseToCancel);

                // Always build in the direction we are moving
                if (direction === "left") {
                    for (var itemIndex = lastInView; itemIndex >= firstInView; itemIndex--) {
                        work.push(queueWork(itemIndex));
                    }
                } else {
                    for (var itemIndex = firstInView; itemIndex <= lastInView; itemIndex++) {
                        work.push(queueWork(itemIndex));
                    }
                }

                var startPromise;
                if (waitForStart < firstInView || waitForEnd > lastInView) {
                    if (direction === "left") {
                        waitForStart = waitForEnd = lastInView;
                    } else {
                        waitForStart = waitForEnd = firstInView;
                    }
                    readyWaitForEnd = readyWaitForStart = waitForStart;

                    startPromise = that.listView._layout.getItemPosition(waitForStart).then(function (position) {
                        that.listView._groups.pinItem(waitForStart, position);
                        work.start(startDuration);
                    });
                } else {
                    work.start(startDuration);
                    startPromise = WinJS.Promise.as();
                }

                viewportItemsRealized.promise.then(function () {
                    function queueRight() {
                        for (var itemIndex = lastInView + 1; itemIndex < end; itemIndex++) {
                            work.push(queueWork(itemIndex), true);
                        }
                    }

                    function queueLeft() {
                        // Always build the left side in the direction away from the center.
                        for (var itemIndex = firstInView - 1; itemIndex >= begin; itemIndex--) {
                            work.push(queueWork(itemIndex), true);
                        }
                    }

                    if (direction === "left") {
                        queueLeft();
                        queueRight();
                        allItemsRealized.promise.then(function () {
                            queueWorkComplete();
                        });
                    }
                    else {
                        queueRight();
                        queueLeft();
                        allItemsRealized.promise.then(function () {
                            queueWorkComplete();
                        });
                    }
                });

                return workPromise.then(function () {
                    msWriteProfilerMark(perfId + ":complete(created:" + createCount + " updated:" + updateCount + "),info");
                    return WinJS.Promise.join(buffer);
                }, function realizePageCanceled(err) {
                    msWriteProfilerMark(perfId + ":canceled(created:" + createCount + " updated:" + updateCount + " clean:" + cleanCount + "),info");
                    startPromise.cancel();
                    //#DBG _ASSERT(err.name === "Canceled");
                    var newElementsKeys = Object.keys(newElements);
                    for (var i = 0, len = newElementsKeys.length; i < len; i++) {
                        var newElement = newElements[newElementsKeys[i]].element;
                        if (that.listView._itemsPool.release) {
                            var data = that.listView._itemsManager._recordFromElement(newElement).item;
                            that.listView._itemsPool.release(data, newElement);
                        }
                        that.listView._itemsManager.releaseItem(newElement);
                        var wrapper = newElement.parentNode;
                        if (wrapper.parentNode) {
                            wrapper.parentNode.removeChild(wrapper);
                        }
                        var indexOfElement = that._insertedElements.indexOf(wrapper);
                        if (indexOfElement !== -1) {
                            wrapper.style.opacity = 1;
                            that._insertedElements.splice(indexOfElement, 1);
                        }
                    }
                    newElements = {};
                    updatedElements = {};
                    return WinJS.Promise.wrapError(err);
                });
            });

            msWriteProfilerMark(perfId + ",StopTM");
            return {
                viewportItemsRealized: viewportItemsRealized.promise,
                allItemsRealized: itemsRealizedPromise,
                loadingCompleted: Promise.join([itemsRealizedPromise, loadingSignal.promise])
            };
        }
        else {
            msWriteProfilerMark(perfId + ",StopTM");
            return {
                viewportItemsRealized: Promise.wrap(),
                allItemsRealized: Promise.wrap(),
                loadingCompleted: Promise.wrap()
            };
        }
    },

    addHeader: function ScrollView_addHeader(fragment, groupIndex) {
        var that = this;
        return this.listView._groups.renderGroup(groupIndex).then(function (results) {
            if (results) {
                var header = results.header,
                    group = results.group;

                //#DBG _ASSERT(header && header.element && group && group.element);
                if (header.element.parentNode !== fragment) {
                    fragment.appendChild(header.element);
                }

                if (group.element.parentNode !== fragment) {
                    fragment.appendChild(group.element);
                }

                that.listView._groups.setDomElements(groupIndex, header.element, group.element);

                that.listView._layout.layoutHeader(groupIndex, header.element);
            }
        });
    },

    updateHeader: function ScrollView_updateHeader(group, groupIndex) {
        this.listView._layout.layoutHeader(groupIndex, group.elements.header);
    },

    updateHeaders: function ScrollView_updateHeaders(fragment, begin, end, hideOthers) {
        var that = this;

        function updateGroup(index) {
            var group = that.listView._groups.group(index);
            if (group) {
                if (group.elements) {
                    that.updateHeader(group, index);
                    // Show the header if it has been hidden.
                    group.elements.header.style.opacity = 1;
                } else {
                    that.addHeader(fragment, index);
                }
            }
        }

        var groupStart = this.listView._groups.groupFromItem(begin),
            groupIndex = groupStart,
            groupEnd = this.listView._groups.groupFromItem(end - 1);
        if (groupIndex !== null) {
            //#DBG _ASSERT(groupEnd !== null);
            for (; groupIndex <= groupEnd; groupIndex++) {
                updateGroup(groupIndex);
            }

            if (hideOthers) {
                // We call update headers at the same time as realizing a page of items. This allows the headers on the
                // current page to be shown when the items on the current page are shown instead of after all the pages
                // are done. We do not currently animate the headers to new locations on insert/remove events. To avoid
                // overlapping the headers we need to hide the group headers that fall outside of our index range. These
                // groups may have moved or been removed.
                var listView = this.listView;
                for (var i = 0, len = listView._groups.groups.length; i < len; i++) {
                    var group = listView._groups.groups[i];
                    if (group.elements && (i < groupStart || i > groupEnd)) {
                        group.elements.header.style.opacity = 0;
                    }
                }

                // Some groups may have "changed" because their count/start index changed. We need to remove those so
                // they do not overlap as well.
                listView._groups.removeElements();
            }
        }
    },

    purgePlaceholders: function ScrollView_purgePlaceholders() {
        var im = this.listView._itemsManager,
            placeholders = this.items.placeholders;

        var keys = Object.keys(placeholders);
        for (var i = 0, len = keys.length; i < len; i++) {
            var index = parseInt(keys[i], 10);
            if (index < this.begin || index >= this.end) {
                var item = placeholders[index];
                delete placeholders[index];
                im.releaseItem(item);
            }
        }
    },

    updateBackdrop: function ScrollView_updateBackdrop(count) {
        if (this.listView._layout.updateBackdrop) {
            this.listView._layout.updateBackdrop(count);
        }
    },

    addItemsToPool: function ScrollView_addItemsToPool(count) {
        var listView = this.listView,
            im = listView._itemsManager,
            items = this.items,
            keys = Object.keys(items),
            focusedItemPurged = false,
            len,
            i,
            mode = listView._currentMode();
        var removedItem = false;
        var that = this;

        items.eachIndex(function (index) {
            if (index < that.begin || index >= that.end) {
                if (listView._selection._getFocused() === index) {
                    listView._unsetFocusOnItem();
                    focusedItemPurged = true;
                }
                var itemData = items.itemDataAt(index),
                    item = itemData.element,
                    wrapper = itemData.wrapper;

                if (wrapper.parentNode) {
                    wrapper.parentNode.removeChild(wrapper);
                    removedItem = true;
                }

                if (mode.itemUnrealized) {
                    mode.itemUnrealized(index);
                }

                listView._layout.releaseItem(wrapper);

                var indexOfElement = that._insertedElements.indexOf(wrapper);
                if (indexOfElement !== -1) {
                    wrapper.style.opacity = 1;
                    that._insertedElements.splice(indexOfElement, 1);
                }

                items.removeItem(index);
                var data = itemData.itemsManagerRecord.item;

                // If this wasn't released by the itemsManager already, then
                // we remove it. This handles the special case of delete
                // occuring on an item that is outside of the current view, but
                // has not been cleaned up yet.
                //
                if (!itemData.removed) {
                    im.releaseItem(item);
                }

                listView._itemsPool.add(data, item);
                listView._wrappersPool.add(null, wrapper, itemData.display);
            }
        });

        if (focusedItemPurged) {
            // If the focused item was purged, we'll still want to focus on it if it comes into view sometime in the future.
            // calling _setFocusOnItem once the item is removed from this.items will set up a promise that will be fulfilled
            // if the item ever gets reloaded
            listView._setFocusOnItem(listView._selection._getFocused());
        }

        if (removedItem) {
            this.updateBackdrop(count);
        }
    },

    addHeadersToPool: function ScrollView_addHeadersToPool() {
        var listView = this.listView,
            beginGroup = listView._groups.groupFromItem(this.begin);

        if (beginGroup !== null) {
            var endGroup = listView._groups.groupFromItem(this.end - 1);
            for (var i = 0, len = listView._groups.groups.length; i < len; i++) {
                var group = listView._groups.groups[i];
                if (group.elements && (i < beginGroup || i > endGroup)) {
                    var headerElement = group.elements.header,
                        groupElement = group.elements.group;

                    if (headerElement.parentNode) {
                        headerElement.parentNode.removeChild(headerElement);
                    }
                    if (groupElement.parentNode) {
                        groupElement.parentNode.removeChild(groupElement);
                    }
                    listView._headersPool.add(group.userData, headerElement);
                    listView._groupsPool.add(null, groupElement);
                    delete group.elements;
                    delete group.left;
                    delete group.top;
                }
            }
        }
    },

    // This function removes items which are outside of current viewport and prefetched area
    purgeItems: function ScrollView_purgeItems() {
        if (this.listView._disposed) { return; }

        this.listView._itemsPool.clear();
        this.listView._wrappersPool.clear();
        this.listView._headersPool.clear();
        this.listView._groupsPool.clear();
    },

    clearDeferTimeout: function ScrollView_clearDeferTimeout() {
        if (this.deferTimeout) {
            this.deferTimeout.cancel();
            this.deferTimeout = null;
        }
        if (this.deferAriaCancelToken !== -1) {
            this.listView._versionManager.clearCancelOnNotification(this.deferAriaCancelToken);
            this.deferAriaCancelToken = -1;
        }
    },

    deferAriaSetup: function ScrollView_deferAriaSetup(count, begin, end) {
        msWriteProfilerMark("WinJS.UI.ListView:aria initialize,StartTM");
        var that = this;
        
        function calcLastRealizedIndexInGroup(groupIndex) {
            var groups = that.listView._groups,
                nextGroup = groups.group(groupIndex + 1);
            return (nextGroup ? Math.min(nextGroup.startIndex - 1, end - 1) : end - 1);
        }

        function deferAriaWorker() {
            if (that.listView._zooming || that.listView._pinching) {
                //To improve SeZo's zoom animation and pinch detection perf, we want to ensure unimportant task 
                //is only run while zooming or pinching is in progress
                return Promise.timeout(WinJS.UI._ScrollView._retryTimeForAriaSetupDuringZoom).then(deferAriaWorker);
            } else {
                deferAriaWorkerImpl();
                return Promise.wrap();
            }
        }

        function deferAriaWorkerImpl() {
            if (that.listView._isZombie()) { return; }
            
            msWriteProfilerMark("WinJS.UI.ListView:aria work,StartTM");
            that.listView._createAriaMarkers();
            var startMarker = that.listView._ariaStartMarker,
                endMarker = that.listView._ariaEndMarker,
                item = that.items.itemAt(begin),
                // These are only used when the ListView is using groups
                groups,
                groupIndex,
                group,
                lastRealizedIndexInGroup;
            
            if (count > 0) {
                item.detachEvent("onpropertychange", WinJS.UI._itemPropertyChange);
                WinJS.UI._ensureId(item);
                if (that.listView._groupsEnabled()) {
                    groups = that.listView._groups;
                    groupIndex = groups.groupFromItem(begin);
                    group = groups.group(groupIndex);
                    lastRealizedIndexInGroup = calcLastRealizedIndexInGroup(groupIndex);
                    WinJS.UI._ensureId(group.elements.header);
                    WinJS.UI._setAttribute(group.elements.header, "x-ms-aria-flowfrom", startMarker.id);
                    WinJS.UI._setFlow(group.elements.header, item);
                } else {
                    WinJS.UI._setAttribute(item, "x-ms-aria-flowfrom", startMarker.id);
                }

                that.deferTimeout = null;
                that.listView._versionManager.clearCancelOnNotification(that.deferAriaCancelToken);
                that.deferAriaCancelToken = -1;

                that.items.each(function (index, item, itemData) {
                    var nextItem = that.items.itemAt(index + 1);

                    if (nextItem) {
                        nextItem.detachEvent("onpropertychange", WinJS.UI._itemPropertyChange);
                        WinJS.UI._ensureId(nextItem);
                    }

                    WinJS.UI._setAttribute(item, "role", that.listView._itemRole);
                    WinJS.UI._setAttribute(item, "aria-setsize", count);
                    WinJS.UI._setAttribute(item, "aria-posinset", index + 1);
                    if (item.tabIndex !== that.listView._tabIndex) {
                        item.tabIndex = that.listView._tabIndex;
                    }

                    if (that.listView._groupsEnabled()) {
                        if (index === lastRealizedIndexInGroup) {
                            var nextGroup = groups.group(groupIndex + 1);

                            // If group is the last realized group, then nextGroup won't exist in the DOM.
                            // When this is the case, nextItem shouldn't exist.
                            //#DBG _ASSERT(nextGroup && nextGroup.elements || !nextItem);
                            if (nextGroup && nextGroup.elements) {
                                WinJS.UI._ensureId(nextGroup.elements.header);
                                WinJS.UI._setFlow(item, nextGroup.elements.header);
                                WinJS.UI._setFlow(nextGroup.elements.header, nextItem);
                            } else {
                                // We're at the last group so flow to the end marker
                                WinJS.UI._setAttribute(item, "aria-flowto", endMarker.id);
                            }

                            WinJS.UI._setAttribute(group.elements.group, "aria-hidden", true);

                            groupIndex++;
                            group = nextGroup;
                            lastRealizedIndexInGroup = calcLastRealizedIndexInGroup(groupIndex);
                        } else {
                            // This is not the last item in the group so flow to the next item
                            //#DBG _ASSERT(nextItem);
                            WinJS.UI._setFlow(item, nextItem);
                        }
                    } else if (nextItem) {
                        // Groups are disabled so as long as we aren't at the last item, flow to the next one
                        WinJS.UI._setFlow(item, nextItem);
                    } else {
                        // Groups are disabled and we're at the last item, so flow to the end marker
                        WinJS.UI._setAttribute(item, "aria-flowto", endMarker.id);
                    }
                    item.attachEvent("onpropertychange", WinJS.UI._itemPropertyChange);
                });
            }
            msWriteProfilerMark("WinJS.UI.ListView:aria work,StopTM");
        }

        this.clearDeferTimeout();
        if (this.listView._isZombie()) { return; }

        this.deferTimeout = WinJS.Promise.timeout(WinJS.UI._DEFERRED_ACTION).then(deferAriaWorker);
        this.deferAriaCancelToken = this.listView._versionManager.cancelOnNotification(this.deferTimeout);
        msWriteProfilerMark("WinJS.UI.ListView:aria initialize,StopTM");
    },
    
    // Sets aria-flowto on _ariaStartMarker and x-ms-aria-flowfrom on _ariaEndMarker. The former
    // points to either the first visible group header or the first visible item. The latter points
    // to the last visible item.
    updateAriaMarkers: function ScrollView_updateAriaMarkers(count, firstIndexDisplayed, lastIndexDisplayed) {
        this.listView._createAriaMarkers();
        var startMarker = this.listView._ariaStartMarker,
            endMarker = this.listView._ariaEndMarker;
        
        if (count === 0) {
            WinJS.UI._setFlow(startMarker, endMarker);
        } else if (firstIndexDisplayed !== -1 && lastIndexDisplayed !== -1) {
            var firstVisibleItem = this.items.itemAt(firstIndexDisplayed),
                lastVisibleItem = this.items.itemAt(lastIndexDisplayed);
            
            if (firstVisibleItem && lastVisibleItem) {
                WinJS.UI._ensureId(firstVisibleItem);
                WinJS.UI._ensureId(lastVisibleItem);
                
                // Set startMarker's flowto
                if (this.listView._groupsEnabled()) {
                    var groups = this.listView._groups,
                        firstVisibleGroup = groups.group(groups.groupFromItem(firstIndexDisplayed));

                    if (firstVisibleGroup.elements) {
                        WinJS.UI._ensureId(firstVisibleGroup.elements.header);
                        
                        if (firstIndexDisplayed === firstVisibleGroup.startIndex) {
                            WinJS.UI._setAttribute(startMarker, "aria-flowto", firstVisibleGroup.elements.header.id);
                        } else {
                            WinJS.UI._setAttribute(startMarker, "aria-flowto", firstVisibleItem.id);
                        }
                    }
                } else {
                    WinJS.UI._setAttribute(startMarker, "aria-flowto", firstVisibleItem.id);
                }
                
                // Set endMarker's flowfrom
                WinJS.UI._setAttribute(endMarker, "x-ms-aria-flowfrom", lastVisibleItem.id);
            }
        }
    },
    
    // Update the ARIA attributes on item that are needed so that Narrator can announce it.
    // item must be in the items container.
    updateAriaForAnnouncement: function ScrollView_updateAriaForAnnouncement(item, count) {
        var index = this.items.index(item);
        //#DBG _ASSERT(index !== WinJS.UI._INVALID_INDEX);

        WinJS.UI._setAttribute(item, "role", this.listView._itemRole);
        WinJS.UI._setAttribute(item, "aria-setsize", count);
        WinJS.UI._setAttribute(item, "aria-posinset", index + 1);
    },

    _resetLayoutState: function ScrollView_resetLayoutState() {
        this.cleanStartIndex = -1;
        this.cleanEndIndex = -1;
    },

    realizePage: function ScrollView_realizePage(scrollbarPos, forceRelayout, direction) {
        msWriteProfilerMark("WinJS.UI.ListView:realizePage(" + forceRelayout + "),StartTM");

        // It's safe to skip realizePage, so we just queue up the last request to run when the version manager
        // get unlocked.
        //
        if (this.listView._versionManager.locked) {
            var that = this;
            this.listView._versionManager.unlocked.then(function () {
                return WinJS.Promise.timeout();
            }).then(function () {
                if (!that.listView._isZombie()) {
                    that.realizePage(scrollbarPos, forceRelayout, direction);
                }
            });
            msWriteProfilerMark("WinJS.UI.ListView:realizePage,StopTM");
            return;
        }
        this.listView._versionManager.onunlocked = null;

        var start_pageRealized = WinJS.log && new Date();

        if (forceRelayout) {
            this._resetLayoutState();
        }

        var that = this,
            itemsManager = this.listView._itemsManager,
            viewportLength = that.listView._getViewportLength(),
            viewBoundsSignal = new WinJS._Signal(),
            pageRealizedSignal = new WinJS._Signal();

        function calculateDisplayedItems(count) {
            if (count) {
                Promise.join([
                    that.listView.layout.calculateFirstVisible(scrollbarPos, false),
                    that.listView.layout.calculateLastVisible(scrollbarPos + viewportLength - 1, false)
                ]).then(
                    function (indices) {
                        that.firstIndexDisplayed = indices[0];
                        that.lastIndexDisplayed = indices[1];
                        viewBoundsSignal.complete();
                    },
                    function () {
                        that.firstIndexDisplayed = -1;
                        that.lastIndexDisplayed = -1;
                        viewBoundsSignal.complete();
                    }
                );
            } else {
                that.firstIndexDisplayed = -1;
                that.lastIndexDisplayed = -1;
                viewBoundsSignal.complete();
            }
        }

        function viewPortPageRealized() {
            that.listView._hideProgressBar();
            that.listView._raiseViewPortLoaded();

            if (that.listView.scrollPosition <= 0) {
                // If the user hit the beginning of the list apply the fix immediately
                that.fixScrollbarRange(that.listView.scrollPosition);
            }

            WinJS.log && WinJS.log((new Date()) - start_pageRealized, "winjs viewPortPageRealized", "perf");
        }

        function pageRealized(count) {
            that.listView._hideProgressBar();
            viewBoundsSignal.promise.then(function () {
                that.updateAriaMarkers(count, that.firstIndexDisplayed, that.lastIndexDisplayed);
                
                that.listView._raiseViewLoaded();

                WinJS.log && WinJS.log((new Date()) - start_pageRealized, "winjs pageRealized", "perf");

                pageRealizedSignal.complete();
            });
        }

        this.listView._raiseViewLoading();
        if (this.firstLayoutPass) {
            this.listView._showProgressBar(this.listView._element, "50%", "50%");
        }

        this.listView._itemsCount().then(function (count) {
            if (!that.destroyed) {
                var loadingSignal = new WinJS._Signal();

                that.listView._groups.dirty = true;

                // While the zoom animation is played we want to minimize the # of pages 
                // being fetched to improve TtFF for SeZo scenarios
                var pagesToPrefetch = that.pagesToPrefetch;
                if (that.listView._zooming) {
                    pagesToPrefetch = 0;
                }

                var beginningOffset = scrollbarPos - pagesToPrefetch * viewportLength;
                var endingOffset = scrollbarPos + (1 + pagesToPrefetch) * viewportLength;

                // If we are near the beginning of the scroll region or the end of the scroll region
                // shift the beginning and ending offsets so we still always get 1 + (2 * pagesToPrefetch) items.
                // This helps the initial scroll so that many items do not have to be created.
                if (beginningOffset < 0) {
                    if (WinJS.UI._ScrollView._preloadEdges) {
                        endingOffset -= beginningOffset;
                    }
                    beginningOffset = 0;
                }
                else {
                    var maxOffset = that.listView._getCanvasLength();

                    //#DBG _ASSERT(typeof maxOffset === "number");

                    // Now deal with the case where we are at the end of the canvas.
                    if (endingOffset > maxOffset && WinJS.UI._ScrollView._preloadEdges) {
                        // We could set endingOffset equal to maxOffset but it is not needed.
                        beginningOffset = Math.max(0, beginningOffset - (endingOffset - maxOffset));
                    }
                }

                that.listView._layout.startLayout(beginningOffset, endingOffset - 1, count).then(
                    function (range) {
                        var currentPass = that.realizePass,
                            endLayoutResult,
                            checkRenderStatus = false;

                        if (range) {
                            var begin = Math.max(0, range.beginIndex);
                            var end = Math.min(count, range.endIndex);

                            var firstPromise;
                            var lastPromise;
                            if (!count) {
                                that.firstIndexDisplayed = -1;
                                that.lastIndexDisplayed = -1;
                                that.updateBackdrop(count);
                                firstPromise = WinJS.Promise.wrap(-1);
                                lastPromise = WinJS.Promise.wrap(-1);
                            } else {
                                firstPromise = that.listView.layout.calculateFirstVisible(scrollbarPos, false);
                                lastPromise = that.listView.layout.calculateLastVisible(scrollbarPos + viewportLength - 1, false);
                            }

                            WinJS.Promise.join([firstPromise, lastPromise]).then(function (indices) {
                                var firstInView = indices[0];
                                var lastInView = indices[1];

                                if ((forceRelayout || begin !== that.begin || end !== that.end || firstInView !== that._previousFirstInView || lastInView !== that._previousLastInView) && (begin < end) && (beginningOffset < endingOffset)) {
                                    that._cancelRealize();
                                    // _cancelRealize changes the realizePass and resets begin/end
                                    currentPass = that.realizePass;
                                    that.begin = begin;
                                    that.end = end;
                                    that._previousFirstInView = firstInView;
                                    that._previousLastInView = lastInView;

                                    that.purgePlaceholders();
                                    that.addItemsToPool(count);

                                    var realizeWork = that.realizeItems(
                                        that.listView._itemCanvas,
                                        that.begin,
                                        that.end,
                                        count,
                                        currentPass,
                                        scrollbarPos,
                                        direction);
                                    that.lastRealizePass = realizeWork.allItemsRealized;

                                    realizeWork.viewportItemsRealized.then(viewPortPageRealized);

                                    realizeWork.allItemsRealized.then(
                                        function () {
                                            if (that.realizePass === currentPass) {
                                                that.listView._groups.removeElements();

                                                // We couldn't call this earlier with addItemsToPool() because we had to wait for all of the
                                                // groups to be realized before deciding which groups/headers are no longer needed.
                                                that.addHeadersToPool();

                                                that.updateHeaders(that.listView._canvas, that.begin, that.end);

                                                that.updateScrollbar(count);

                                                // Items outside of current viewport and prefetched area can be removed
                                                that.purgeItems();
                                            
                                                that.deferAriaSetup(count, that.begin, that.end);

                                                calculateDisplayedItems(count);

                                                pageRealized(count);

                                                that.lastRealizePass = null;
                                            }
                                        },
                                        function (e) {
                                            if (that.realizePass === currentPass) {
                                                that.lastRealizePass = null;
                                                that.begin = -1;
                                                that.end = -1;
                                            }
                                            return WinJS.Promise.wrapError(e);
                                        });

                                    realizeWork.loadingCompleted.then(function () {
                                        loadingSignal.complete();
                                    });

                                } else if (that.lastRealizePass === null) {
                                    // We are currently in the "itemsLoading" state and need to get back to "complete". The 
                                    // previous realize pass has been completed so proceed to the other states.
                                    calculateDisplayedItems(count);
                                    endLayoutResult = that.listView._layout.endLayout();
                                    that.listView._clearInsertedItems();
                                    that.updateScrollbar(count);
                                    viewPortPageRealized();
                                    pageRealized(count);
                                    checkRenderStatus = true;
                                }
                            }, function () {
                                calculateDisplayedItems(count);
                                endLayoutResult = that.listView._layout.endLayout();
                                that.listView._clearInsertedItems();
                                that.updateScrollbar(count);
                                viewPortPageRealized();
                                pageRealized(count);
                                checkRenderStatus = true;
                            });
                        } else {
                            calculateDisplayedItems(count);
                            endLayoutResult = that.listView._layout.endLayout();
                            that.listView._clearInsertedItems();
                            that.listView._groups.removeElements();
                            that.updateBackdrop(count);
                            viewPortPageRealized();
                            pageRealized(count);
                            checkRenderStatus = true;
                        }

                        if (endLayoutResult && endLayoutResult.animationPromise) {
                            that.animating = true;
                            that.runningAnimations = Promise.join([that.runningAnimations, endLayoutResult.animationPromise]);
                            that.runningAnimations.then(function () {
                                if (that.realizePass === currentPass) {
                                    that.animating = false;
                                    that.runningAnimations = null;
                                    if (!that.loadingItems && !that.animating) {
                                        loadingSignal.complete();
                                    }
                                }
                            });
                        } else if (checkRenderStatus) {
                            loadingSignal.complete();
                        }
                    },
                    function () {
                        calculateDisplayedItems(count);
                        that.listView._clearInsertedItems();
                        viewPortPageRealized();
                        pageRealized(count);
                    }
                );

                Promise.join([pageRealizedSignal.promise, loadingSignal.promise]).
                    then(function () {
                        that.listView._raiseViewComplete();
                    });
            }
        });
        msWriteProfilerMark("WinJS.UI.ListView:realizePage,StopTM");
    },

    onScroll: function ScrollView_onScroll(scrollbarPos, scrollLength, direction, viewportSize) {
        this.realizePage(scrollbarPos, false, direction);
    },

    onResize: function ScrollView_onResize(scrollbarPos, viewportSize) {
        this.realizePage(scrollbarPos, true);
    },

    _cancelRealize: function ScrollView_cancelRealize() {
        this.clearDeferTimeout();
        this.realizePass++;

        var last = this.lastRealizePass;
        if (last) {
            this.lastRealizePass = null;
            this.begin = -1;
            this.end = -1;
            last.cancel();
        }
    },

    reset: function ScrollView_reset() {
        this._cancelRealize();
        // when in the zombie state, we let disposal cleanup the ScrollView state
        //
        if (!this.listView._isZombie()) {
            var itemData = this.items.itemDataAt(0);
            if (itemData && itemData.display !== undefined) {
                itemData.element.style.display = itemData.display;
            }
            this.firstIndexDisplayed = -1;
            this.lastIndexDisplayed = -1;
            this.runningAnimations = null;
            this.animating = false;
            this.loadingItems = false;

            var listView = this.listView;
            this.firstLayoutPass = true;
            listView._unsetFocusOnItem();
            if (listView._currentMode().onDataChanged) {
                listView._currentMode().onDataChanged();
            }

            this.items.each(function (index, item) {
                listView._itemsManager.releaseItem(item);
            });

            this.items.removeItems();
            listView._groups.resetGroups();
            listView._resetCanvas();

            this._insertedElements = [];
            listView._clearInsertedItems();
        }
    },

    reload: function ScrollView_reload(scrollbarPos) {
        if (this.listView._isZombie()) { return; }

        this.realizePage(scrollbarPos, true);
    },

    refresh: function ScrollView_refresh(scrollbarPos, scrollLength, viewportSize, newCount) {
        if (this.listView._isZombie()) { return; }

        this.realizePage(scrollbarPos, true);
    },

    updateScrollbar: function ScrollView_updateScrollbar(count) {
        var that = this;

        if (count > 0) {
            return this.listView._layout.getScrollbarRange(count).then(
                function (range) {
                    that.listView._setCanvasLength(range.beginScrollPosition, range.endScrollPosition);
                    that.updateBackdrop(count);
                },
                function () {
                    that.listView._setCanvasLength(0, 0);
                    that.updateBackdrop(0);
                }
            );
        } else {
            this.listView._setCanvasLength(0, 0);
            that.updateBackdrop(count);
            return Promise.wrap();
        }
    },

    update: function ScrollView_update(count) {
        this.listView._layout.update(count);
        this.listView._groups.dirty = true;
    },

    fixScrollbarRange: function ScrollView_fixScrollbarRange(scrollbarPos) {
        var that = this,
            fixedPos = scrollbarPos;
        if (this.listView._groups.length() && this.listView._groups.group(0).offset) {

            this.updateScrollbar(this.listView._cachedCount);

            this.listView._layout.calculateFirstVisible(scrollbarPos).then(function (firstDisplayed) {
                that.listView._layout.getItemPosition(firstDisplayed).then(function (position) {
                    that.listView._layout.getScrollbarRange().then(function (scrollbarRange) {
                        if (scrollbarRange.beginScrollPosition < 0) {
                            var start = position[that.listView._startProperty],
                                itemPos = start - scrollbarRange.beginScrollPosition;

                            that.listView._groups.pinItem(firstDisplayed, { offset: itemPos });

                            that.listView._lastScrollPosition = itemPos;
                            that.listView.scrollPosition = itemPos;
                            that.realizePage(itemPos, true);
                        }
                    });
                });
            });
        }
    },

    cleanUp: function ScrollView_cleanUp() {
        this._cancelRealize();
        this.runningAnimations && this.runningAnimations.cancel();
        var itemsManager = this.listView._itemsManager;
        this.items.each(function (index, item) {
            itemsManager.releaseItem(item);
        });
        this.listView._unsetFocusOnItem();
        this.items.removeItems();
        this.listView._groups.resetGroups();
        this.listView._resetCanvas();

        this.destroyed = true;
    }
};
})(this, WinJS);

(function selectionManagerInit(global, WinJS, undefined) {
    "use strict";

var utilities = WinJS.Utilities,
    Promise = WinJS.Promise;

WinJS.Namespace.define("WinJS.UI", {
    _ItemSet: WinJS.Class.define(function _ItemSet_ctor(listView, ranges, count) {
        this._listView = listView;
        this._ranges = ranges;
        this._itemsCount = count;
    }),

    getItemsFromRanges: function (dataSource, ranges) {
        var listBinding = dataSource.createListBinding(),
            promises = [];

        function getIndices() {
            var indices = [];
            for (var i = 0, len = ranges.length; i < len; i++) {
                var range = ranges[i];
                for (var j = range.firstIndex; j <= range.lastIndex; j++) {
                    indices.push(j);
                }
            }
            return Promise.wrap(indices);
        }

        return getIndices().then(function (indices) {
            for (var i = 0; i < indices.length; i++) {
                promises.push(listBinding.fromIndex(indices[i]));
            }

            return WinJS.Promise.join(promises).then(function (items) {
                listBinding.release();
                return items;
            });
        });
    }
});

WinJS.UI._ItemSet.prototype = {
    getRanges: function () {
        var ranges = [];
        for (var i = 0, len = this._ranges.length; i < len; i++) {
            var range = this._ranges[i];
            ranges.push({
                firstIndex: range.firstIndex,
                lastIndex: range.lastIndex,
                firstKey: range.firstKey,
                lastKey: range.lastKey
            });
        }
        return ranges;
    },

    getItems: function () {
        return WinJS.UI.getItemsFromRanges(this._listView._itemsManager.dataSource, this._ranges);
    },

    isEverything: function () {
        return this.count() === this._itemsCount;
    },

    count: function () {
        var count = 0;
        for (var i = 0, len = this._ranges.length; i < len; i++) {
            var range = this._ranges[i];
            count += range.lastIndex - range.firstIndex + 1;
        }
        return count;
    },

    getIndices: function () {
        var indices = [];
        for (var i = 0, len = this._ranges.length; i < len; i++) {
            var range = this._ranges[i];
            for (var n = range.firstIndex; n <= range.lastIndex; n++) {
                indices.push(n);
            }
        }
        return indices;
    }
};

function isEverythingRange(ranges) {
    return ranges && ranges.firstIndex === 0 && ranges.lastIndex === Number.MAX_VALUE;
}

WinJS.Namespace.define("WinJS.UI", {
    _Selection: WinJS.Class.derive(WinJS.UI._ItemSet, function (listView, indexesAndRanges) {
        this._listView = listView;
        this._itemsCount = -1;
        this._ranges = [];
        if (indexesAndRanges) {
            this.set(indexesAndRanges);
        }
    }, {
        clear: function () {
            /// <signature helpKeyword="WinJS.UI._Selection.prototype.clear">
            /// <summary locid="WinJS.UI._Selection.prototype.clear">
            /// Clears the selection.
            /// </summary>
            /// <returns type="Promise" locid="WinJS.UI._Selection.prototype.clear_returnValue">
            /// A Promise that is fulfilled when the clear operation completes.
            /// </returns>
            /// </signature>

            this._releaseRanges(this._ranges);
            this._ranges = [];
            return Promise.wrap();
        },

        set: function (items) {
            /// <signature helpKeyword="WinJS.UI._Selection.prototype.set">
            /// <summary locid="WinJS.UI._Selection.prototype.set">
            /// Clears the current selection and replaces it with the specified items.
            /// </summary>
            /// <param name="items" locid="WinJS.UI._Selection.prototype.set_items">
            /// The indexes or keys of the items that make up the selection.
            /// You can provide different types of objects for the items parameter:
            /// you can specify an index, a key, or a range of indexes.
            /// It can also be an array that contains one or more of these objects.
            /// </param>
            /// <returns type="Promise" locid="WinJS.UI._Selection.prototype.set_returnValue">
            /// A Promise that is fulfilled when the operation completes.
            /// </returns>
            /// </signature>

            // A range with lastIndex set to Number.MAX_VALUE used to mean selectAll. Passing such range to set was equivalent to selectAll. This code preserves this behavior.
            if (!isEverythingRange(items)) {
                this._releaseRanges(this._ranges);
                this._ranges = [];

                var that = this;
                return this._execute("_set", items).then(function () {
                    that._ranges.sort(function (left, right) {
                        return left.firstIndex - right.firstIndex;
                    });
                    return that._ensureKeys();
                }).then(function () {
                    return that._ensureCount();
                });
            } else {
                return this.selectAll();
            }
        },

        add: function (items) {
            /// <signature helpKeyword="WinJS.UI._Selection.prototype.add">
            /// <summary locid="WinJS.UI._Selection.prototype.add">
            /// Adds one or more items to the selection.
            /// </summary>
            /// <param name="items" locid="WinJS.UI._Selection.prototype.add_items">
            /// The indexes or keys of the items to add.
            /// You can provide different types of objects for the items parameter:
            /// you can specify an index, a key, or a range of indexes.
            /// It can also be an array that contains one or more of these objects.
            /// </param>
            /// <returns type="Promise" locid="WinJS.UI._Selection.prototype.add_returnValue">
            /// A Promise that is fulfilled when the operation completes.
            /// </returns>
            /// </signature>

            if (!isEverythingRange(items)) {
                var that = this;
                return this._execute("_add", items).then(function () {
                    return that._ensureKeys();
                }).then(function () {
                    return that._ensureCount();
                });
            } else {
                return this.selectAll();
            }
        },

        remove: function (items) {
            /// <signature helpKeyword="WinJS.UI._Selection.prototype.remove">
            /// <summary locid="WinJS.UI._Selection.prototype.remove">
            /// Removes the specified items from the selection.
            /// </summary>
            /// <param name="items" locid="WinJS.UI._Selection.prototype.remove_items">
            /// The indexes or keys of the items to remove. You can provide different types of objects for the items parameter:
            /// you can specify an index, a key, or a range of indexes.
            /// It can also be an array that contains one or more of these objects.
            /// </param>
            /// <returns type="Promise" locid="WinJS.UI._Selection.prototype.remove_returnValue">
            /// A Promise that is fulfilled when the operation completes.
            /// </returns>
            /// </signature>

            var that = this;
            return this._execute("_remove", items).then(function () {
                return that._ensureKeys();
            });
        },

        selectAll: function () {
            /// <signature helpKeyword="WinJS.UI._Selection.prototype.selectAll">
            /// <summary locid="WinJS.UI._Selection.prototype.selectAll">
            /// Adds all the items in the ListView to the selection.
            /// </summary>
            /// <returns type="Promise" locid="WinJS.UI._Selection.prototype.selectAll_returnValue">
            /// A Promise that is fulfilled when the operation completes.
            /// </returns>
            /// </signature>

            var that = this;
            return that._ensureCount().then(function () {
                var range = {
                    firstIndex: 0,
                    lastIndex: that._itemsCount - 1,
                };
                that._retainRange(range);
                that._releaseRanges(that._ranges);
                that._ranges = [range];
                return that._ensureKeys();
            });
        },

        /*#DBG
        _assertValid: function () {
            for (var i = 0, len = this._ranges.length; i < len; i++) {
                var range = this._ranges[i];
                _ASSERT(range.firstIndex <= range.lastIndex);
                _ASSERT(!i || this._ranges[i - 1].lastIndex < range.firstIndex);
            }
            return true;
        },
        #DBG*/

        _execute: function (operation, items) {
            var that = this,
                keysSupported = !!that._getListBinding().fromKey,
                array = Array.isArray(items) ? items : [items],
                promises = [Promise.wrap()];

            function toRange(type, first, last) {
                var retVal = {};
                retVal["first" + type] = first;
                retVal["last" + type] = last;
                return retVal;
            }

            function handleKeys(range) {
                var binding = that._getListBinding();

                var promise = Promise.join([binding.fromKey(range.firstKey), binding.fromKey(range.lastKey)]).then(function (items) {
                    if (items[0] && items[1]) {
                        range.firstIndex = items[0].index;
                        range.lastIndex = items[1].index;
                        that[operation](range);
                    }
                    return range;
                });
                promises.push(promise);
            }

            for (var i = 0, len = array.length; i < len; i++) {
                var item = array[i];
                if (typeof item === "number") {
                    this[operation](toRange("Index", item, item));
                } else if (item) {
                    if (keysSupported && item.key !== undefined) {
                        handleKeys(toRange("Key", item.key, item.key));
                    } else if (keysSupported && item.firstKey !== undefined && item.lastKey !== undefined) {
                        handleKeys(toRange("Key", item.firstKey, item.lastKey));
                    } else if (item.index !== undefined && typeof item.index === "number") {
                        this[operation](toRange("Index", item.index, item.index));
                    } else if (item.firstIndex !== undefined && item.lastIndex !== undefined &&
                            typeof item.firstIndex === "number" && typeof item.lastIndex === "number") {
                                this[operation](toRange("Index", item.firstIndex, item.lastIndex));
                            }
                }
            }

            return Promise.join(promises);
        },

        _set: function (range) {
            this._retainRange(range);
            this._ranges.push(range);
        },

        _add: function (newRange) {
            var that = this,
                prev = null,
                range,
                inserted;

            var merge = function (left, right) {
                if (right.lastIndex > left.lastIndex) {
                    left.lastIndex = right.lastIndex;
                    left.lastKey = right.lastKey;
                    if (left.lastPromise) {
                        left.lastPromise.release();
                    }
                    left.lastPromise = that._getListBinding().fromIndex(left.lastIndex).retain();
                }
            }

            for (var i = 0, len = this._ranges.length; i < len; i++) {
                range = this._ranges[i];
                if (newRange.firstIndex < range.firstIndex) {
                    var mergeWithPrev = prev && newRange.firstIndex < (prev.lastIndex + 1);
                    if (mergeWithPrev) {
                        inserted = i - 1;
                        merge(prev, newRange);
                    } else {
                        this._insertRange(i, newRange);
                        inserted = i;
                    }
                    break;
                } else if (newRange.firstIndex === range.firstIndex) {
                    merge(range, newRange);
                    inserted = i;
                    break;
                }
                prev = range;
            }

            if (inserted === undefined) {
                var last = this._ranges.length ? this._ranges[this._ranges.length - 1] : null,
                    mergeWithLast = last && newRange.firstIndex < (last.lastIndex + 1);
                if (mergeWithLast) {
                    merge(last, newRange);
                } else {
                    this._retainRange(newRange);
                    this._ranges.push(newRange);
                }
            } else {
                prev = null;
                for (i = inserted + 1, len = this._ranges.length; i < len; i++) {
                    range = this._ranges[i];
                    if (newRange.lastIndex < range.firstIndex) {
                        mergeWithPrev = prev && prev.lastIndex > newRange.lastIndex;
                        if (mergeWithPrev) {
                            merge(this._ranges[inserted], prev);
                        }
                        this._removeRanges(inserted + 1, i - inserted - 1);
                        break;
                    } else if (newRange.lastIndex === range.firstIndex) {
                        merge(this._ranges[inserted], range);
                        this._removeRanges(inserted + 1, i - inserted);
                        break;
                    }
                    prev = range;
                }
                if (i >= len) {
                    merge(this._ranges[inserted], this._ranges[len - 1]);
                    this._removeRanges(inserted + 1, len - inserted - 1);
                }
            }
        },

        _remove: function (toRemove) {
            var that = this;

            function retainPromise(index) {
                return that._getListBinding().fromIndex(index).retain();
            }

            // This method is called when a range needs to be unselected.  It is inspecting every range in the current selection comparing 
            // it to the range which is being unselected and it is building an array of new selected ranges
            var ranges = [];
            for (var i = 0, len = this._ranges.length; i < len; i++) {
                var range = this._ranges[i];
                if (range.lastIndex < toRemove.firstIndex || range.firstIndex > toRemove.lastIndex) {
                    // No overlap with the unselected range
                    ranges.push(range);
                } else if (range.firstIndex < toRemove.firstIndex && range.lastIndex >= toRemove.firstIndex && range.lastIndex <= toRemove.lastIndex) {
                    // The end of this range is being unselected
                    ranges.push({
                        firstIndex: range.firstIndex,
                        firstKey: range.firstKey,
                        firstPromise: range.firstPromise,
                        lastIndex: toRemove.firstIndex - 1,
                        lastPromise: retainPromise(toRemove.firstIndex - 1)
                    });
                    range.lastPromise.release();
                } else if (range.lastIndex > toRemove.lastIndex && range.firstIndex >= toRemove.firstIndex && range.firstIndex <= toRemove.lastIndex) {
                    // The beginning of this range is being unselected
                    ranges.push({
                        firstIndex: toRemove.lastIndex + 1,
                        firstPromise: retainPromise(toRemove.lastIndex + 1),
                        lastIndex: range.lastIndex,
                        lastKey: range.lastKey,
                        lastPromise: range.lastPromise
                    });
                    range.firstPromise.release();
                } else if (range.firstIndex < toRemove.firstIndex && range.lastIndex > toRemove.lastIndex) {
                    // The middle part of this range is being unselected
                    ranges.push({
                        firstIndex: range.firstIndex,
                        firstKey: range.firstKey,
                        firstPromise: range.firstPromise,
                        lastIndex: toRemove.firstIndex - 1,
                        lastPromise: retainPromise(toRemove.firstIndex - 1),
                    });
                    ranges.push({
                        firstIndex: toRemove.lastIndex + 1,
                        firstPromise: retainPromise(toRemove.lastIndex + 1),
                        lastIndex: range.lastIndex,
                        lastKey: range.lastKey,
                        lastPromise: range.lastPromise
                    });
                } else {
                    // The whole range is being unselected
                    //#DBG _ASSERT(range.firstIndex >= toRemove.firstIndex && range.lastIndex <= toRemove.lastIndex);
                    range.firstPromise.release();
                    range.lastPromise.release();
                }
            }
            this._ranges = ranges;
        },

        _ensureKeys: function () {
            var promises = [Promise.wrap()];
            var that = this;

            var ensureKey = function (which, range) {
                var keyProperty = which + "Key";

                if (!range[keyProperty]) {
                    var promise = range[which + "Promise"];
                    promise.then(function (item) {
                        if (item) {
                            range[keyProperty] = item.key;
                        }
                    });
                    return promise;
                } else {
                    return Promise.wrap();
                }
            }

            for (var i = 0, len = this._ranges.length; i < len; i++) {
                var range = this._ranges[i];
                promises.push(ensureKey("first", range));
                promises.push(ensureKey("last", range));
            }

            Promise.join(promises).then(function () {
                that._ranges = that._ranges.filter(function (range) {
                    return range.firstKey && range.lastKey;
                });
            });
            return Promise.join(promises);
        },

        _mergeRanges: function (target, source) {
            //#DBG _ASSERT(!target.lastPromise && !source.lastPromise);
            target.lastIndex = source.lastIndex;
            target.lastKey = source.lastKey;
        },

        _isIncluded: function (index) {
            if (this.isEverything()) {
                return true;
            } else {
                for (var i = 0, len = this._ranges.length; i < len; i++) {
                    var range = this._ranges[i];
                    if (range.firstIndex <= index && index <= range.lastIndex) {
                        return true;
                    }
                }
                return false;
            }
        },

        _ensureCount: function () {
            var that = this;
            return this._listView._itemsCount().then(function (count) {
                that._itemsCount = count;
            });
        },

        _insertRange: function (index, newRange) {
            this._retainRange(newRange);
            this._ranges.splice(index, 0, newRange);
        },

        _removeRanges: function (index, howMany) {
            for (var i = 0; i < howMany; i++) {
                this._releaseRange(this._ranges[index + i]);
            }
            this._ranges.splice(index, howMany);
        },

        _retainRange: function (range) {
            if (!range.firstPromise) {
                range.firstPromise = this._getListBinding().fromIndex(range.firstIndex).retain();
            }
            if (!range.lastPromise) {
                range.lastPromise = this._getListBinding().fromIndex(range.lastIndex).retain();
            }
        },

        _retainRanges: function () {
            for (var i = 0, len = this._ranges.length; i < len; i++) {
                this._retainRange(this._ranges[i]);
            }
        },

        _releaseRange: function (range) {
            range.firstPromise.release();
            range.lastPromise.release();
        },

        _releaseRanges: function (ranges) {
            for (var i = 0, len = ranges.length; i < len; ++i) {
                this._releaseRange(ranges[i]);
            }
        },

        _getListBinding: function () {
            return this._listView._itemsManager._listBinding;
        }
    }, {
        supportedForProcessing: false,
    })
});


// This component is responsible for holding selection state
WinJS.Namespace.define("WinJS.UI", {
    _SelectionManager: function (listView) {
        this._listView = listView;
        this._selected = new WinJS.UI._Selection(this._listView);
        this._pivot = WinJS.UI._INVALID_INDEX;
        this._focused = 0;
        this._pendingChange = Promise.wrap();
    }
}, {
    /* empty */
}, {
    supportedForProcessing: false,
});

WinJS.UI._SelectionManager.prototype = {
    count: function () {
        /// <signature helpKeyword="WinJS.UI._SelectionManager.prototype.count">
        /// <summary locid="WinJS.UI._SelectionManager.prototype.count">
        /// Returns the number of items in the selection.
        /// </summary>
        /// <returns type="Number" locid="WinJS.UI._SelectionManager.prototype.count_returnValue">
        /// The number of items in the selection.
        /// </returns>
        /// </signature>
        return this._selected.count();
    },

    getIndices: function () {
        /// <signature helpKeyword="WinJS.UI._SelectionManager.prototype.getIndices">
        /// <summary locid="WinJS.UI._SelectionManager.prototype.getIndices">
        /// Returns a list of the indexes for the items in the selection.
        /// </summary>
        /// <returns type="Array" locid="WinJS.UI._SelectionManager.prototype.getIndices_returnValue">
        /// The list of indexes for the items in the selection as an array of Number objects.
        /// </returns>
        /// </signature>
        return this._selected.getIndices();
    },

    getItems: function () {
        /// <signature helpKeyword="WinJS.UI._SelectionManager.prototype.getItems">
        /// <summary locid="WinJS.UI._SelectionManager.prototype.getItems">
        /// Returns an array that contains the items in the selection.
        /// </summary>
        /// <returns type="Promise" locid="WinJS.UI._SelectionManager.prototype.getItems_returnValue">
        /// A Promise that contains an array of the requested IItem objects.
        /// </returns>
        /// </signature>

        return this._selected.getItems();
    },

    getRanges: function () {
        /// <signature helpKeyword="WinJS.UI._SelectionManager.prototype.getRanges">
        /// <summary locid="WinJS.UI._SelectionManager.prototype.getRanges">
        /// Gets an array of the index ranges for the selected items.
        /// </summary>
        /// <returns type="Array" locid="WinJS.UI._SelectionManager.prototype.getRanges_returnValue">
        /// An array that contains an ISelectionRange object for each index range in the selection.
        /// </returns>
        /// </signature>
        return this._selected.getRanges();
    },

    isEverything: function () {
        /// <signature helpKeyword="WinJS.UI._SelectionManager.prototype.isEverything">
        /// <summary locid="WinJS.UI._SelectionManager.prototype.isEverything">
        /// Returns a value that indicates whether the selection contains every item in the data source.
        /// </summary>
        /// <returns type="Boolean" locid="WinJS.UI._SelectionManager.prototype.isEverything_returnValue">
        /// true if the selection contains every item in the data source; otherwise, false.
        /// </returns>
        /// </signature>
        return this._selected.isEverything();
    },

    set: function (items) {
        /// <signature helpKeyword="WinJS.UI._SelectionManager.prototype.set">
        /// <summary locid="WinJS.UI._SelectionManager.prototype.set">
        /// Clears the current selection and replaces it with the specified items. 
        /// </summary>
        /// <param name="items" locid="WinJS.UI._SelectionManager.prototype.set_items">
        /// The indexes or keys of the items that make up the selection. 
        /// You can provide different types of objects for the items parameter: 
        /// you can specify an index, a key, or a range of indexes. 
        /// It can also be an array that contains one or more of these objects.  
        /// </param>
        /// <returns type="Promise" locid="WinJS.UI._SelectionManager.prototype.set_returnValue">
        /// A Promise that is fulfilled when the operation completes. 
        /// </returns>
        /// </signature>
        var that = this,
            signal = new WinJS._Signal();
        return this._synchronize(signal).then(function () {
            var newSelection = new WinJS.UI._Selection(that._listView);
            return newSelection.set(items).then(
                function () {
                    that._set(newSelection);
                    signal.complete();
                },
                function (error) {
                    newSelection.clear();
                    signal.complete();
                    return WinJS.Promise.wrapError(error);
                }
            );
        });
    },

    clear: function () {
        /// <signature helpKeyword="WinJS.UI._SelectionManager.prototype.clear">
        /// <summary locid="WinJS.UI._SelectionManager.prototype.clear">
        /// Clears the selection.
        /// </summary>
        /// <returns type="Promise" locid="WinJS.UI._SelectionManager.prototype.clear_returnValue">
        /// A Promise that is fulfilled when the clear operation completes.  
        /// </returns>
        /// </signature>

        var that = this,
            signal = new WinJS._Signal();
        return this._synchronize(signal).then(function () {
            var newSelection = new WinJS.UI._Selection(that._listView);
            return newSelection.clear().then(
                function () {
                    that._set(newSelection);
                    signal.complete();
                },
                function (error) {
                    newSelection.clear();
                    signal.complete();
                    return WinJS.Promise.wrapError(error);
                }
            );
        });
    },

    add: function (items) {
        /// <signature helpKeyword="WinJS.UI._SelectionManager.prototype.add">
        /// <summary locid="WinJS.UI._SelectionManager.prototype.add">
        /// Adds one or more items to the selection. 
        /// </summary>
        /// <param name="items" locid="WinJS.UI._SelectionManager.prototype.add_items">
        /// The indexes or keys of the items to add. 
        /// You can provide different types of objects for the items parameter: 
        /// you can specify an index, a key, or a range of indexes. 
        /// It can also be an array that contains one or more of these objects. 
        /// </param>
        /// <returns type="Promise" locid="WinJS.UI._SelectionManager.prototype.add_returnValue">
        /// A Promise that is fulfilled when the operation completes. 
        /// </returns>
        /// </signature>
        var that = this,
            signal = new WinJS._Signal();
        return this._synchronize(signal).then(function () {
            var newSelection = that._cloneSelection();
            return newSelection.add(items).then(
                function () {
                    that._set(newSelection);
                    signal.complete();
                },
                function (error) {
                    newSelection.clear();
                    signal.complete();
                    return WinJS.Promise.wrapError(error);
                }
            );
        });
    },

    remove: function (items) {
        /// <signature helpKeyword="WinJS.UI._SelectionManager.prototype.remove">
        /// <summary locid="WinJS.UI._SelectionManager.prototype.remove">
        /// Removes the specified items from the selection. 
        /// </summary>
        /// <param name="items" locid="WinJS.UI._SelectionManager.prototype.remove_items">
        /// The indexes or keys of the items to remove. You can provide different types of objects for the items parameter: 
        /// you can specify an index, a key, or a range of indexes. 
        /// It can also be an array that contains one or more of these objects.  
        /// </param>
        /// <returns type="Promise" locid="WinJS.UI._SelectionManager.prototype.remove_returnValue">
        /// A Promise that is fulfilled when the operation completes. 
        /// </returns>
        /// </signature>
        var that = this,
            signal = new WinJS._Signal();
        return this._synchronize(signal).then(function () {
            var newSelection = that._cloneSelection();
            return newSelection.remove(items).then(
                function () {
                    that._set(newSelection);
                    signal.complete();
                },
                function (error) {
                    newSelection.clear();
                    signal.complete();
                    return WinJS.Promise.wrapError(error);
                }
            );
        });
    },

    selectAll: function () {
        /// <signature helpKeyword="WinJS.UI._SelectionManager.prototype.selectAll">
        /// <summary locid="WinJS.UI._SelectionManager.prototype.selectAll">
        /// Adds all the items in the ListView to the selection. 
        /// </summary>
        /// <returns type="Promise" locid="WinJS.UI._SelectionManager.prototype.selectAll_returnValue">
        /// A Promise that is fulfilled when the operation completes.  
        /// </returns>
        /// </signature>
        var that = this,
            signal = new WinJS._Signal();
        return this._synchronize(signal).then(function () {
            var newSelection = new WinJS.UI._Selection(that._listView);
            return newSelection.selectAll().then(
                function () {
                    that._set(newSelection);
                    signal.complete();
                },
                function (error) {
                    newSelection.clear();
                    signal.complete();
                    return WinJS.Promise.wrapError(error);
                }
            );
        });
    },

    _synchronize: function(signal) {
        var that = this;
        return this._listView._versionManager.unlocked.then(function () {
            var currentPendingChange = that._pendingChange;
            that._pendingChange = WinJS.Promise.join([currentPendingChange, signal.promise]).then(function () { });
            return currentPendingChange;
        }); 
    },

    _reset: function () {
        this._pivot = WinJS.UI._INVALID_INDEX;
        this._setFocused(0, this._keyboardFocused());
        this._pendingChange.cancel();
        this._pendingChange = Promise.wrap();
        this._selected.clear();
        this._selected = new WinJS.UI._Selection(this._listView);
    },
    
    _dispose: function () {
        this._selected.clear();
        this._selected = null;
        this._listView = null;
    },

    _set: function (newSelection) {
        var that = this;
        this._fireSelectionChanging(newSelection).then(function (approved) {
            if (approved) {
                that._selected.clear();
                that._selected = newSelection;
                that._listView._updateSelection();
                that._fireSelectionChanged();
            } else {
                newSelection.clear();
            }
        });
    },

    _fireSelectionChanging: function (newSelection) {
        var eventObject = document.createEvent("CustomEvent"),
            newSelectionUpdated = Promise.wrap();

        eventObject.initCustomEvent("selectionchanging", true, true, {
            newSelection: newSelection,
            preventTapBehavior: function () {
            },
            setPromise: function (promise) {
                /// <signature helpKeyword="WinJS.UI.SelectionManager.selectionchanging.setPromise">
                /// <summary locid="WinJS.UI.SelectionManager.selectionchanging.setPromise">
                /// Used to inform the ListView that asynchronous work is being performed, and that this
                /// event handler should not be considered complete until the promise completes. 
                /// </summary>
                /// <param name="promise" type="WinJS.Promise" locid="WinJS.UI.SelectionManager.selectionchanging.setPromise_p:promise">
                /// The promise to wait for.
                /// </param>
                /// </signature>
                
                newSelectionUpdated = promise;
            }
        });

        var approved = this._listView._element.dispatchEvent(eventObject);
        return newSelectionUpdated.then(function () {
            return approved;
        });
    },

    _fireSelectionChanged: function () {
        var eventObject = document.createEvent("CustomEvent");
        eventObject.initCustomEvent("selectionchanged", true, false, null);
        this._listView._element.dispatchEvent(eventObject);
    },

    _getFocused: function () {
        return this._focused;
    },

    _setFocused: function (index, keyboardFocused) {
        this._focused = index;
        this._focusedByKeyboard = keyboardFocused;
    },

    _keyboardFocused: function() {
        return this._focusedByKeyboard;
    },

    _updateCount: function (count) {
        this._selected._itemsCount = count;
    },

    _isIncluded: function (index) {
        return this._selected._isIncluded(index);
    },

    _cloneSelection: function () {
        var newSelection = new WinJS.UI._Selection(this._listView);
        newSelection._ranges = this._selected.getRanges();
        newSelection._itemsCount = this._selected._itemsCount;
        newSelection._retainRanges();
        return newSelection;
    }
};

})(this, WinJS);

(function datePickerInit(WinJS, undefined) {
    "use strict";

    // Constants definition
    var DEFAULT_DAY_PATTERN = 'day', 
        DEFAULT_MONTH_PATTERN = '{month.full}',
        DEFAULT_YEAR_PATTERN = 'year.full';

    var strings = {
        get selectDay() { return WinJS.Resources._getWinJSString("ui/selectDay").value; },
        get selectMonth() { return WinJS.Resources._getWinJSString("ui/selectMonth").value; },
        get selectYear() { return WinJS.Resources._getWinJSString("ui/selectYear").value; },
    };

    var yearFormatCache = {};

    function newFormatter(pattern, calendar, defaultPattern) {
        var dtf = Windows.Globalization.DateTimeFormatting;
        pattern = !pattern ? defaultPattern : pattern;
        var c = new dtf.DateTimeFormatter(pattern);
        if (calendar) {
            return new dtf.DateTimeFormatter(pattern, c.languages, c.geographicRegion, calendar, c.clock);
        }
        return c;
    };

    function formatCacheLookup(pattern, calendar, defaultPattern) {
        var pat = yearFormatCache[pattern];
        if (!pat) {
            pat = yearFormatCache[pattern] = {};
        }
        var cal = pat[calendar];
        if (!cal) {
            cal = pat[calendar] = {};
        }
        var def = cal[defaultPattern];
        if (!def) {
            def = cal[defaultPattern] = {};
            def.formatter = newFormatter(pattern, calendar, defaultPattern);
            def.years = {};
        }
        return def;
    }

    function formatYear(pattern, calendar, defaultPattern, datePatterns, order, cal) {
        var cache = formatCacheLookup(pattern, calendar, defaultPattern);
        var y = cache.years[cal.year + "-" + cal.era];
        if (!y) { 
            y = cache.formatter.format(cal.getDateTime());
            cache.years[cal.year + "-" + cal.era] = y;
        }
        return y;
    }

    function formatMonth(pattern, calendar, defaultPattern, cal) {
        var cache = formatCacheLookup(pattern, calendar, defaultPattern);
        // can't cache actual month names because the hebrew calendar varies
        // the month name depending on religious holidays and leap months.
        //
        return  cache.formatter.format(cal.getDateTime());
    }

    function formatDay(pattern, calendar, defaultPattern, cal) {
        var cache = formatCacheLookup(pattern, calendar, defaultPattern);
        // can't cache actual day names because the format may include the day of the week,
        // which, of course, varies from month to month.
        //
        return cache.formatter.format(cal.getDateTime());
    }

    function newCal(calendar) {
        var glob = Windows.Globalization;
        var c = new glob.Calendar();
        if (calendar) {
            return new glob.Calendar(c.languages, calendar, c.getClock());
        }
        return c;
    };

    function yearDiff(start, end) {
        var yearCount = 0;

        if (start.era == end.era) {
            yearCount = end.year - start.year;
        }
        else {
            while (start.era !== end.era || start.year !== end.year) {
                yearCount++;
                start.addYears(1);
            }
        }
        return yearCount;
    }

    WinJS.Namespace.define("WinJS.UI", {
        /// <summary locid="WinJS.UI.DatePicker">Allows users to pick a date value.</summary>
        /// <name locid="WinJS.UI.DatePicker_name">Date Picker</name>
        /// <icon src="ui_winjs.ui.datepicker.12x12.png" width="12" height="12" />
        /// <icon src="ui_winjs.ui.datepicker.16x16.png" width="16" height="16" />
        /// <htmlSnippet><![CDATA[<div data-win-control="WinJS.UI.DatePicker"></div>]]></htmlSnippet>
        /// <event name="change" locid="WinJS.UI.DatePicker_e:change">Occurs when the current date changes.</event>
        /// <resource type="javascript" src="//Microsoft.WinJS.1.0/js/base.js" shared="true" />
        /// <resource type="javascript" src="//Microsoft.WinJS.1.0/js/ui.js" shared="true" />
        /// <resource type="css" src="//Microsoft.WinJS.1.0/css/ui-dark.css" shared="true" />
        DatePicker: WinJS.Class.define(function DatePicker_ctor(element, options) {
            /// <signature helpKeyword="WinJS.UI.DatePicker.DatePicker">
            /// <summary locid="WinJS.UI.DatePicker.constructor">Initializes a new instance of the DatePicker control</summary>
            /// <param name="element" type="HTMLElement" domElement="true" locid="WinJS.UI.DatePicker.constructor_p:element">
            /// The DOM element associated with the DatePicker control.
            /// </param>
            /// <param name="options" type="Object" locid="WinJS.UI.DatePicker.constructor_p:options">
            /// The set of options to be applied initially to the DatePicker control.
            /// </param>
            /// <returns type="WinJS.UI.DatePicker" locid="WinJS.UI.DatePicker.constructor_returnValue">A constructed DatePicker control.</returns>
            /// </signature>

            // Default to current date
            this._currentDate = new Date();

            // Default to +/- 100 years
            this._minYear = this._currentDate.getFullYear() - 100;
            this._maxYear = this._currentDate.getFullYear() + 100;
            this._datePatterns = {
                date: null,
                month: null,
                year: null
            };
            
            element = element || document.createElement("div");
            element.winControl = this;

            // Set options BEFORE setting the element, so they can influence things
            WinJS.UI.setOptions(this, options);
            this._init(element);
        }, {
            _information: null,
            _currentDate: null,
            _calendar: null,
            _disabled: false,
            _dateElement: null,
            _dateControl: null,
            _monthElement: null,
            _monthControl: null,
            _minYear: null,
            _maxYear: null,
            _yearElement: null,
            _yearControl: null,
            _datePatterns: { 
                date : null,
                month : null,
                year : null
            },

            _addAccessibilityAttributes: function () {
                //see http://www.w3.org/TR/wai-aria/rdf_model.png for details
                this._domElement.setAttribute("role", "group");

                this._dateElement.setAttribute("aria-label", strings.selectDay);
                this._monthElement.setAttribute("aria-label", strings.selectMonth);
                this._yearElement.setAttribute("aria-label", strings.selectYear);
            },

            _addControlsInOrder: function () {
                var e = this._domElement;
                var u = WinJS.Utilities;
                var that = this;
                var orderIndex = 0; // don't use forEach's index, because "era" is in the list
                that._information.order.forEach(function (s) {
                    switch (s) {
                        case "month":
                            e.appendChild(that._monthElement);
                            u.addClass(that._monthElement, "win-order" + (orderIndex++));
                            break;
                        case "date":
                            e.appendChild(that._dateElement);
                            u.addClass(that._dateElement, "win-order" + (orderIndex++));
                            break;
                        case "year":
                            e.appendChild(that._yearElement);
                            u.addClass(that._yearElement, "win-order" + (orderIndex++));
                            break;
                    }
                });
            },

            _createControlElements: function () {
                this._monthElement = document.createElement("select");
                this._monthElement.className = "win-datepicker-month";
                this._dateElement = document.createElement("select");
                this._dateElement.className = "win-datepicker-date";
                this._yearElement = document.createElement("select");
                this._yearElement.className = "win-datepicker-year";
            },

            _createControls: function () {
                var that = this;

                var info = this._information;
                var index = info.getIndex(this.current);

                if (info.forceLanguage) {
                    this._domElement.setAttribute("lang", info.forceLanguage);
                    this._domElement.setAttribute("dir", info.isRTL ? "rtl" : "ltr");
                }

                
                this._yearControl = new WinJS.UI._Select(this._yearElement, {
                    dataSource: this._information.years,
                    disabled: this.disabled,
                    index: index.year
                });

                this._monthControl = new WinJS.UI._Select(this._monthElement, {
                    dataSource: this._information.months(index.year),
                    disabled: this.disabled,
                    index: index.month
                });

                this._dateControl = new WinJS.UI._Select(this._dateElement, {
                    dataSource: this._information.dates(index.year, index.month),
                    disabled: this.disabled,
                    index: index.date
                });

                this._wireupEvents();
            },

            /// <field type="String" locid="WinJS.UI.DatePicker.calendar" helpKeyword="WinJS.UI.DatePicker.calendar">Gets or sets the calendar to use.</field>
            calendar: {
                get: function () {
                    return this._calendar;
                },
                set: function (value) {
                    this._calendar = value;
                    this._setElement(this._domElement);
                }
            },
            
            /// <field type="Date" locid="WinJS.UI.DatePicker.current" helpKeyword="WinJS.UI.DatePicker.current">Gets or sets the current date of the DatePicker.</field>
            current: {
                get: function () { 
                    var d = this._currentDate;
                    var y = d.getFullYear();
                    return new Date(Math.max(Math.min(this.maxYear, y), this.minYear), d.getMonth(), d.getDate(), 12, 0, 0, 0);
                },
                set: function (value) {
                    var newDate;
                    if (typeof (value) === "string") {
                        newDate = new Date(Date.parse(value));
                        newDate.setHours(12, 0, 0, 0);
                    }
                    else {
                        newDate = value;
                    }

                    var oldDate = this._currentDate;
                    if (oldDate != newDate) {
                        this._currentDate = newDate;
                        this._updateDisplay();
                    }
                }
            },

            /// <field type="Boolean" locid="WinJS.UI.DatePicker.disabled" helpKeyword="WinJS.UI.DatePicker.disabled">Specifies whether the DatePicker is disabled.</field>
            disabled: {
                get: function () { return this._disabled; },
                set: function (value) {
                    if (this._disabled !== value) {
                        this._disabled = value;
                        // all controls get populated at the same time, so any check is OK
                        //
                        if (this._yearControl) {
                            this._monthControl.setDisabled(value);
                            this._dateControl.setDisabled(value);
                            this._yearControl.setDisabled(value);
                        }
                    }
                }
            },

            /// <field type="String" locid="WinJS.UI.DatePicker.datePattern" helpKeyword="WinJS.UI.DatePicker.datePattern">Gets or sets the display pattern for the date.</field>
            datePattern: {
                get: function () { return this._datePatterns.date; },
                set: function (value) {
                    if (this._datePatterns.date !== value) {
                        this._datePatterns.date = value;
                        this._init();
                    }
                }
            },


            /// <field type="HTMLElement" domElement="true" hidden="true" locid="WinJS.UI.DatePicker.element" helpKeyword="WinJS.UI.DatePicker.element">
            /// Gets the DOM element for the DatePicker.
            /// </field>
            element: {
                get: function () { return this._domElement; }
            },

            _setElement: function (element) {
                this._domElement = this._domElement || element;
                if (!this._domElement) { return; }
                
                WinJS.Utilities.empty(this._domElement);
                WinJS.Utilities.addClass(this._domElement, "win-datepicker");

                this._updateInformation();

                this._createControlElements();
                this._addControlsInOrder();
                this._createControls();
                this._addAccessibilityAttributes();
            },

            /// <field type="Number" integer="true" locid="WinJS.UI.DatePicker.minYear" helpKeyword="WinJS.UI.DatePicker.minYear">Gets or sets the minimum Gregorian year available for picking.</field>
            minYear: {
                get: function () {
                    return this._information.getDate({year:0, month:0, date:0}).getFullYear();
                },
                set: function (value) {
                    if (this._minYear !== value) {
                        this._minYear = value;
                        if (value > this._maxYear) {
                            this._maxYear = value;
                        }
                        this._updateInformation();
                        if (this._yearControl) {
                            this._yearControl.dataSource = this._information.years;
                        }

                        this._updateDisplay();
                    }
                }
            },

            /// <field type="Number" integer="true" locid="WinJS.UI.DatePicker.maxYear" helpKeyword="WinJS.UI.DatePicker.maxYear">Gets or sets the maximum Gregorian year available for picking.</field>
            maxYear: {
                get: function () { 
                    var index = {
                        year: this._information.years.getLength() - 1
                    };
                    index.month = this._information.months(index.year).getLength() - 1;
                    index.date = this._information.dates(index.year, index.month).getLength() - 1;
                    return this._information.getDate(index).getFullYear();
                },
                set: function (value) {
                    if (this._maxYear !== value) {
                        this._maxYear = value;
                        if (value < this._minYear) {
                            this._minYear = value;
                        }
                        this._updateInformation();
                        if (this._yearControl) {
                            this._yearControl.dataSource = this._information.years;
                        }

                        this._updateDisplay();
                    }
                }
            },

            /// <field type="String" locid="WinJS.UI.DatePicker.monthPattern" helpKeyword="WinJS.UI.DatePicker.monthPattern">Gets or sets the display pattern for the month.</field>
            monthPattern: {
                get: function () { return this._datePatterns.month; },
                set: function (value) {
                    if (this._datePatterns.month !== value) {
                        this._datePatterns.month = value;
                        this._init();
                    }
                }
            },

            _updateInformation: function () {
                // since "year" in the date ctor can be two digit (85 == 1985), we need
                // to force "full year" to capture dates < 100 a.d.
                //
                var min = new Date(this._minYear, 0, 1, 12, 0, 0);
                var max = new Date(this._maxYear, 11, 31, 12, 0, 0);
                min.setFullYear(this._minYear);
                max.setFullYear(this._maxYear);

                this._information = WinJS.UI.DatePicker.getInformation(min, max, this._calendar, this._datePatterns);
            },
            
            _init: function (element) {
                this._setElement(element);
            },

            _updateDisplay: function () {
                if (!this._domElement)
                    return;

                // all controls get populated at the same time, so any check is OK
                //
                if (this._yearControl) {
                    //Render display index based on constraints (minYear and maxYear constraints)
                    //Will not modify current date
                    var index = this._information.getIndex(this.current);
                
                    this._yearControl.index = index.year;
                    this._monthControl.dataSource = this._information.months(index.year);
                    this._monthControl.index = index.month;
                    this._dateControl.dataSource = this._information.dates(index.year, index.month);
                    this._dateControl.index = index.date;
                }
            },

            _wireupEvents: function () {
                var that = this;
                function changed() {
                    that._currentDate = that._information.getDate({ year: that._yearControl.index, month: that._monthControl.index, date: that._dateControl.index }, that._currentDate);
                    var index = that._information.getIndex(that._currentDate);
                    
                    // Changing the month (or year, if the current date is 2/29) changes the day range, and could have made the day selection invalid
                    that._monthControl.dataSource = that._information.months(index.year)
                    that._monthControl.index = index.month;
                    that._dateControl.dataSource = that._information.dates(index.year, index.month);
                    that._dateControl.index = index.date;
                }

                this._dateElement.addEventListener("change", changed, false);
                this._monthElement.addEventListener("change", changed, false);
                this._yearElement.addEventListener("change", changed, false);
            },

            /// <field type="String" locid="WinJS.UI.DatePicker.yearPattern" helpKeyword="WinJS.UI.DatePicker.yearPattern">Gets or sets the display pattern for year.</field>
            yearPattern: {
                get: function () { return this._datePatterns.year; },
                set: function (value) {
                    if (this._datePatterns.year !== value) {
                        this._datePatterns.year = value;
                        this._init();
                    }
                }
            },
        }, {
            _getInformationWinRT: function (startDate, endDate, calendar, datePatterns) {
                datePatterns = datePatterns || { date: DEFAULT_DAY_PATTERN, month: DEFAULT_MONTH_PATTERN, year: DEFAULT_YEAR_PATTERN };

                var tempCal = newCal(calendar);
                var monthCal = newCal(calendar);
                var dayCal = newCal(calendar);

                tempCal.setToMin();
                var minDateTime = tempCal.getDateTime();
                tempCal.setToMax();
                var maxDateTime = tempCal.getDateTime();

                function clamp(date) {
                    return new Date(Math.min(new Date(Math.max(minDateTime, date)), maxDateTime));;
                }

                tempCal.hour = 12;

                startDate = clamp(startDate);
                endDate = clamp(endDate);

                tempCal.setDateTime(endDate);
                var end = { year: tempCal.year, era: tempCal.era };

                tempCal.setDateTime(startDate);
                var minYear = tempCal.year;
                var yearLen = 0;

                yearLen = yearDiff(tempCal, end) + 1;

                // Explicity use a template that's equivalent to a longdate template 
                // as longdate/shortdate can be overriden by the user
                var dateformat = formatCacheLookup("day month.full year", calendar).formatter;
                var localdatepattern = dateformat.patterns[0];
                var isRTL = localdatepattern.charCodeAt(0) === 8207;
                var order = ["date", "month", "year"];

                var indexes = {
                    month: localdatepattern.indexOf("{month"),
                    date: localdatepattern.indexOf("{day"),
                    year: localdatepattern.indexOf("{year")
                };
                order.sort(function (a, b) {
                    if (indexes[a] < indexes[b]) { return -1; }
                    else if (indexes[a] > indexes[b]) { return 1; }
                    else { return 0; }
                });

                var yearSource = (function () {
                    return {
                        getLength: function () { return yearLen; },
                        getValue: function (index) { 
                            tempCal.setDateTime(startDate);
                            tempCal.addYears(index);

                            return formatYear(datePatterns.year, calendar, DEFAULT_YEAR_PATTERN, datePatterns, order, tempCal);
                        }
                    }
                })();

                var monthSource = function (yearIndex) {
                    monthCal.setDateTime(startDate);
                    monthCal.addYears(yearIndex);

                    return {
                        getLength: function () { return monthCal.numberOfMonthsInThisYear; },
                        getValue: function (index) {
                            monthCal.month = monthCal.firstMonthInThisYear + index;
                            return formatMonth(datePatterns.month, calendar, DEFAULT_MONTH_PATTERN, monthCal);
                        }
                    };
                };
                
                var dateSource = function (yearIndex, monthIndex) {
                    dayCal.setDateTime(startDate);
                    dayCal.addYears(yearIndex);
                    dayCal.month = Math.max(Math.min(monthIndex + dayCal.firstMonthInThisYear, dayCal.firstMonthInThisYear + dayCal.numberOfMonthsInThisYear - 1), dayCal.firstMonthInThisYear);
                    dayCal.day = dayCal.firstDayInThisMonth;

                    return {
                        getLength: function () { return dayCal.numberOfDaysInThisMonth; },
                        getValue: function (index) {
                            dayCal.day = dayCal.firstDayInThisMonth;
                            dayCal.addDays(index);
                            return formatDay(datePatterns.date, calendar, DEFAULT_DAY_PATTERN, dayCal);
                        }
                    };
                };

                return {
                    isRTL: isRTL,
                    forceLanguage: dateformat.resolvedLanguage,

                    order: order,
                    
                    getDate: function (index, lastDate) {
                        var lastCal;

                        if (lastDate) {
                            tempCal.setDateTime(lastDate);
                            lastCal = { year: tempCal.year, month: tempCal.month, day: tempCal.day };
                        }

                        var c = tempCal;
                        c.setDateTime(startDate);
                        c.addYears(index.year);
                        var guessMonth = Math.max(Math.min(index.month + c.firstMonthInThisYear, c.firstMonthInThisYear + c.numberOfMonthsInThisYear - 1), c.firstMonthInThisYear);
                        if (lastCal && lastCal.year !== c.year) {
                            guessMonth = Math.max(Math.min(lastCal.month, c.firstMonthInThisYear + c.numberOfMonthsInThisYear - 1), c.firstMonthInThisYear);
                        }
                        c.month = guessMonth;
                        var guessDay = Math.max(Math.min(index.date + c.firstDayInThisMonth, c.firstDayInThisMonth + c.numberOfDaysInThisMonth - 1), c.firstDayInThisMonth);
                        if (lastCal && (lastCal.year !== c.year || lastCal.month !== c.month)) {
                            guessDay = Math.max(Math.min(lastCal.day, c.firstDayInThisMonth + c.numberOfDaysInThisMonth - 1), c.firstDayInThisMonth);
                        }
                        c.day = c.firstDayInThisMonth;
                        c.addDays(guessDay - c.firstDayInThisMonth);
                        return c.getDateTime();
                    },
                    getIndex: function (date) {
                        var curDate = clamp(date);
                        tempCal.setDateTime(curDate);
                        var cur = { year: tempCal.year, era: tempCal.era };

                        var yearIndex = 0;

                        tempCal.setDateTime(startDate);
                        tempCal.month = 1;
                        yearIndex = yearDiff(tempCal, cur);

                        tempCal.setDateTime(curDate);
                        var monthIndex = tempCal.month - tempCal.firstMonthInThisYear;
                        var dateIndex = tempCal.day - tempCal.firstDayInThisMonth;

                        var index = { 
                            year: yearIndex, 
                            month: monthIndex, 
                            date: dateIndex
                        };

                        return index;
                    },
                    years: yearSource,
                    months: monthSource,
                    dates: dateSource
                };
                
            },

            _getInformationJS: function (startDate, endDate) {
                var minYear = startDate.getFullYear();
                var maxYear = endDate.getFullYear();
                var yearSource = {
                    getLength: function () { return Math.max(0, maxYear - minYear + 1); },
                    getValue: function (index) { return minYear + index; }
                };

                var months = ["January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"];
                var monthSource = function (yearIndex) {
                    return {
                        getLength: function () { return months.length; },
                        getValue: function (index) { return months[index]; },
                        getMonthNumber: function (index) { return Math.min(index, months.length - 1); }
                    };
                };

                var dateSource = function (yearIndex, monthIndex) {
                    var temp = new Date();
                    var year = yearSource.getValue(yearIndex);
                    // The +1 is needed to make using a day of 0 work correctly
                    var month = monthIndex + 1; // index is always correct, unlike getMonth which changes when the date is invalid
                    temp.setFullYear(year, month, 0);

                    var maxValue = temp.getDate();
                
                    return {
                        getLength: function () { return maxValue; },
                        getValue: function (index) { return "" + (index + 1); },
                        getDateNumber: function (index) { return Math.min(index + 1, maxValue); }
                    };
                };

                return {
                    order: ["month", "date", "year"],
                    
                    getDate: function (index) {
                        return new Date(
                            yearSource.getValue(index.year), 
                            monthSource(index.year).getMonthNumber(index.month), 
                            dateSource(index.year, index.month).getDateNumber(index.date),
                            12, 0
                        );
                    },
                    getIndex: function (date) {
                        var yearIndex = 0;
                        var year = date.getFullYear();
                        if (year < minYear) {
                            yearIndex = 0;
                        }
                        else if (year > this.maxYear) {
                            yearIndex = yearSource.getLength() - 1;
                        }
                        else {
                            yearIndex = date.getFullYear() - minYear;
                        }
                        
                        var monthIndex = Math.min(date.getMonth(), monthSource(yearIndex).getLength());
                        
                        var dateIndex = Math.min(date.getDate() - 1, dateSource(yearIndex, monthIndex).getLength());
                        
                        return { 
                            year: yearIndex, 
                            month: monthIndex, 
                            date: dateIndex
                        };
                    },
                    years: yearSource,
                    months: monthSource,
                    dates: dateSource
                };
            }
        })
    });


    if (WinJS.Utilities.hasWinRT) {
        WinJS.UI.DatePicker.getInformation = WinJS.UI.DatePicker._getInformationWinRT;
    }
    else {
        WinJS.UI.DatePicker.getInformation = WinJS.UI.DatePicker._getInformationJS;
    }


    WinJS.Class.mix(WinJS.UI.DatePicker, WinJS.Utilities.createEventProperties("change"));
    WinJS.Class.mix(WinJS.UI.DatePicker, WinJS.UI.DOMEventMixin);
    
})(WinJS);


(function timePickerInit(WinJS, undefined) {
    "use strict";

    // Constants definition
    var DEFAULT_MINUTE_PATTERN = "{minute.integer(2)}",
        DEFAULT_HOUR_PATTERN = "{hour.integer(1)}",
        DEFAULT_PERIOD_PATTERN = "{period.abbreviated(2)}";

    var strings = {
        get selectHour() { return WinJS.Resources._getWinJSString("ui/selectHour").value; },
        get selectMinute() { return WinJS.Resources._getWinJSString("ui/selectMinute").value; },
        get selectAMPM() { return WinJS.Resources._getWinJSString("ui/selectAMPM").value; },
    };

    WinJS.Namespace.define("WinJS.UI", {
        /// <summary locid="WinJS.UI.TimePicker">Allows users to select time values.</summary>
        /// <name locid="WinJS.UI.TimePicker_name">Time Picker</name>
        /// <icon src="ui_winjs.ui.timepicker.12x12.png" width="12" height="12" />
        /// <icon src="ui_winjs.ui.timepicker.16x16.png" width="16" height="16" />
        /// <htmlSnippet><![CDATA[<div data-win-control="WinJS.UI.TimePicker"></div>]]></htmlSnippet>
        /// <event name="change" locid="WinJS.UI.TimePicker_e:change">Occurs when the time changes.</event>
        /// <resource type="javascript" src="//Microsoft.WinJS.1.0/js/base.js" shared="true" />
        /// <resource type="javascript" src="//Microsoft.WinJS.1.0/js/ui.js" shared="true" />
        /// <resource type="css" src="//Microsoft.WinJS.1.0/css/ui-dark.css" shared="true" />
        TimePicker: WinJS.Class.define(function TimePicker_ctor(element, options) {
            /// <signature helpKeyword="WinJS.UI.TimePicker.TimePicker">
            /// <summary locid="WinJS.UI.TimePicker.constructor">Initializes a new instance of the TimePicker control</summary>
            /// <param name="element" type="HTMLElement" domElement="true" locid="WinJS.UI.TimePicker.constructor_p:element">
            /// The DOM element associated with the TimePicker control.
            /// </param>
            /// <param name="options" type="Object" locid="WinJS.UI.TimePicker.constructor_p:options">
            /// The set of options to be applied initially to the TimePicker control.
            /// </param>
            /// <returns type="WinJS.UI.TimePicker" locid="WinJS.UI.TimePicker.constructor_returnValue">A constructed TimePicker control.</returns>
            /// </signature>

            // Default to current time
            this._currentTime = WinJS.UI.TimePicker._sentinelDate();

            element = element || document.createElement("div");
            element.winControl = this;
            this._timePatterns = {
                minute: null,
                hour: null,
                period: null
            };
            WinJS.UI.setOptions(this, options);
            this._init(element);
        }, {
            _currentTime: null,
            _clock: null,
            _disabled: false,
            _hourElement: null,
            _hourControl: null,
            _minuteElement: null,
            _minuteControl: null,
            _ampmElement: null,
            _ampmControl: null,
            _minuteIncrement: 1,
            _timePatterns: {
                minute: null,
                hour: null,
                period: null
            },
            _information: null,

            _addAccessibilityAttributes: function () {
                //see http://www.w3.org/TR/wai-aria/rdf_model.png for details
                this._domElement.setAttribute("role", "group");

                this._hourElement.setAttribute("aria-label", strings.selectHour);
                this._minuteElement.setAttribute("aria-label", strings.selectMinute);
                if (this._ampmElement) {
                    this._ampmElement.setAttribute("aria-label", strings.selectAMPM);
                }
            },

            _addControlsInOrder: function (info) {
                var that = this;
                var u = WinJS.Utilities;
                info.order.forEach(function (s, index) {
                    switch (s) {
                        case "hour":
                            that._domElement.appendChild(that._hourElement);
                            u.addClass(that._hourElement, "win-order" + index);
                            break;
                        case "minute":
                            that._domElement.appendChild(that._minuteElement);
                            u.addClass(that._minuteElement, "win-order" + index);
                            break;
                        case "period":
                            if (that._ampmElement) {
                                that._domElement.appendChild(that._ampmElement);
                                u.addClass(that._ampmElement, "win-order" + index);
                            }
                            break;
                    }
                });
            },

            /// <field type="String" locid="WinJS.UI.TimePicker.clock" helpKeyword="WinJS.UI.TimePicker.clock">Gets or sets the type of clock to display (12HourClock or 24HourClock). It defaults to the user setting.</field>
            clock: {
                get: function () {
                    return this._clock;
                },
                set: function (value) {
                    if (this._clock !== value) {
                        this._clock = value;
                        this._init();
                    }
                }
            },

            /// <field type="Date" locid="WinJS.UI.TimePicker.current" helpKeyword="WinJS.UI.TimePicker.current">Gets or sets the current date (and time) of the TimePicker.</field>
            current: {
                get: function () {
                    var cur = this._currentTime;
                    if (cur) {
                        var time = WinJS.UI.TimePicker._sentinelDate();
                        time.setHours(cur.getHours()); // accounts for AM/PM
                        time.setMinutes(this._getMinutesIndex(cur) * this.minuteIncrement);
                        time.setSeconds(0);
                        time.setMilliseconds(0);
                        return time;
                    }
                    else {
                        return cur;
                    }
                },
                set: function (value) {
                    var that = this;
                    var newTime;
                    if (typeof (value) === "string") {
                        newTime = WinJS.UI.TimePicker._sentinelDate();
                        newTime.setTime(Date.parse(newTime.toDateString() + " " + value));
                    }
                    else {
                        newTime = value;
                    }

                    var oldTime = this.currentTime;
                    if (oldTime !== newTime) {
                        this._currentTime = newTime;

                        this._updateDisplay();
                    }
                }
            },

            /// <field type="Boolean" locid="WinJS.UI.TimePicker.disabled" helpKeyword="WinJS.UI.TimePicker.disabled">Specifies whether the TimePicker is disabled.</field>
            disabled: {
                get: function () { return this._disabled; },
                set: function (value) {
                    if (this._disabled !== value) {
                        this._disabled = value;
                        if (this._hourControl) {
                            this._hourControl.setDisabled(value);
                            this._minuteControl.setDisabled(value);
                        }
                        if (this._ampmControl) {
                            this._ampmControl.setDisabled(value);
                        }
                    }
                }
            },

            /// <field type="HTMLElement" domElement="true" hidden="true" locid="WinJS.UI.TimePicker.element" helpKeyword="WinJS.UI.TimePicker.element">
            /// Gets the DOM element for the TimePicker.
            /// </field>
            element: {
                get: function () { return this._domElement; }
            },


            _init: function (element) {
                this._setElement(element);
                this._updateDisplay();
            },

            /// <field type="String" locid="WinJS.UI.TimePicker.hourPattern" helpKeyword="WinJS.UI.TimePicker.hourPattern">Gets or sets the display pattern for the hour.</field>
            hourPattern: {
                get: function () { return this._timePatterns.hour.pattern; },
                set: function (value) {
                    if (this._timePatterns.hour !== value) {
                        this._timePatterns.hour = value;
                        this._init();
                    }
                }

            },

            _getHoursAmpm: function (time) {
                var hours24 = time.getHours();
                if (this._ampmElement) {
                    if (hours24 === 0) {
                        return { hours: 12, ampm: 0 };
                    }
                    else if (hours24 < 12) {
                        return { hours: hours24, ampm: 0 };
                    }
                    return { hours: hours24 - 12, ampm: 1 };
                }

                return { hours: hours24 };
            },

            _getHoursIndex: function (hours) {
                if (this._ampmElement && hours === 12) {
                    return 0;
                }
                return hours;
            },

            _getMinutesIndex: function (time) {
                return parseInt(time.getMinutes() / this.minuteIncrement);
            },

            /// <field type="Number" integer="true" locid="WinJS.UI.TimePicker.minuteIncrement" helpKeyword="WinJS.UI.TimePicker.minuteIncrement">Gets or sets the minute increment. For example, "15" specifies that the TimePicker minute control should display only the choices 00, 15, 30, 45.</field>
            minuteIncrement: {
                //prevent divide by 0, and leave user's input intact
                get: function () { return Math.max(1, Math.abs(this._minuteIncrement | 0) % 60); },
                set: function (value) {
                    if (this._minuteIncrement != value) {
                        this._minuteIncrement = value;
                        this._init();
                    }
                }

            },

            /// <field type="String" locid="WinJS.UI.TimePicker.minutePattern" helpKeyword="WinJS.UI.TimePicker.minutePattern">Gets or sets the display pattern for the minute.</field>
            minutePattern: {
                get: function () { return this._timePatterns.minute.pattern; },
                set: function (value) {
                    if (this._timePatterns.minute !== value) {
                        this._timePatterns.minute = value;
                        this._init();
                    }
                }
            },

            /// <field type="String" locid="WinJS.UI.TimePicker.periodPattern" helpKeyword="WinJS.UI.TimePicker.periodPattern">Gets or sets the display pattern for the period.</field>
            periodPattern: {
                get: function () { return this._timePatterns.period.pattern; },
                set: function (value) {

                    if (this._timePatterns.period !== value) {
                        this._timePatterns.period = value;
                        this._init();
                    }
                }
            },

            _setElement: function (element) {
                this._domElement = this._domElement || element;
                if (!this._domElement) { return; }

                var info = WinJS.UI.TimePicker.getInformation(this.clock, this.minuteIncrement, this._timePatterns);
                this._information = info;

                if (info.forceLanguage) {
                    this._domElement.setAttribute("lang", info.forceLanguage);
                    this._domElement.setAttribute("dir", info.isRTL ? "rtl" : "ltr");
                }

                WinJS.Utilities.empty(this._domElement);
                WinJS.Utilities.addClass(this._domElement, "win-timepicker");

                this._hourElement = document.createElement("select");
                WinJS.Utilities.addClass(this._hourElement, "win-timepicker-hour");

                this._minuteElement = document.createElement("select");
                WinJS.Utilities.addClass(this._minuteElement, "win-timepicker-minute");

                this._ampmElement = null;
                if (info.clock === "12HourClock") {
                    this._ampmElement = document.createElement("select");
                    WinJS.Utilities.addClass(this._ampmElement, "win-timepicker-period");
                }

                this._addControlsInOrder(info);

                var that = this;

                var hoursAmpm = this._getHoursAmpm(this.current);
                this._hourControl = new WinJS.UI._Select(this._hourElement, {
                    dataSource: this._getInfoHours(),
                    disabled: this.disabled,
                    index: this._getHoursIndex(hoursAmpm.hours)
                });
                this._minuteControl = new WinJS.UI._Select(this._minuteElement, {
                    dataSource: info.minutes,
                    disabled: this.disabled,
                    index: this._getMinutesIndex(this.current)
                });
                this._ampmControl = null;
                if (this._ampmElement) {
                    this._ampmControl = new WinJS.UI._Select(this._ampmElement, {
                        dataSource: info.periods,
                        disabled: this.disabled,
                        index: hoursAmpm.ampm
                    });
                }

                this._wireupEvents();
                this._updateValues();
                this._addAccessibilityAttributes();
            },

            _getInfoHours: function () {
                return this._information.hours;
            },

            _updateLayout: function () {
                if (!this._domElement)
                    return;
                this._updateValues();
            },

            _updateValues: function () {
                if (this._hourControl) {
                    var hoursAmpm = this._getHoursAmpm(this.current);
                    if (this._ampmControl) {
                        this._ampmControl.index = hoursAmpm.ampm;
                    }
                    this._hourControl.index = this._getHoursIndex(hoursAmpm.hours);
                    this._minuteControl.index = this._getMinutesIndex(this.current);
                }
            },

            _updateDisplay: function () {
                //Render display index based on constraints (minuteIncrement)
                //Will not modify current time

                var hoursAmpm = this._getHoursAmpm(this.current);

                if (this._ampmControl) {
                    this._ampmControl.index = hoursAmpm.ampm;
                }

                if (this._hourControl) {
                    this._hourControl.index = this._getHoursIndex(hoursAmpm.hours);
                    this._minuteControl.index = this._getMinutesIndex(this.current);
                }
            },

            _wireupEvents: function () {
                var that = this;

                var fixupHour = function () {
                    var hour = that._hourControl.index;
                    if (that._ampmElement) {
                        if (that._ampmControl.index === 1) {
                            if (hour !== 12) {
                                hour += 12;
                            }
                        }
                    }
                    return hour;
                };

                var changed = function () {
                    var hour = fixupHour();
                    that._currentTime.setHours(hour);

                    that._currentTime.setMinutes(that._minuteControl.index * that.minuteIncrement);
                };

                this._hourElement.addEventListener("change", changed, false);
                this._minuteElement.addEventListener("change", changed, false);
                if (this._ampmElement) {
                    this._ampmElement.addEventListener("change", changed, false);
                }
            }
        }, {
            _sentinelDate: function () {
                // This is July 15th, 2011 as our sentinel date. There are no known
                //  daylight savings transitions that happened on that date.
                var current = new Date();
                return new Date(2011, 6, 15, current.getHours(), current.getMinutes());
            },
            _getInformationWinRT: function (clock, minuteIncrement, timePatterns) {
                var newFormatter = function (pattern, defaultPattern) {
                    var dtf = Windows.Globalization.DateTimeFormatting;
                    pattern = !pattern ? defaultPattern : pattern;
                    var formatter = new dtf.DateTimeFormatter(pattern);
                    if (clock) {
                        formatter = dtf.DateTimeFormatter(pattern, formatter.languages, formatter.geographicRegion, formatter.calendar, clock);
                    }
                    return formatter;
                }

                var glob = Windows.Globalization;
                var calendar = new glob.Calendar();
                if (clock) {
                    calendar = new glob.Calendar(calendar.languages, calendar.getCalendarSystem(), clock);
                }
                calendar.setDateTime(WinJS.UI.TimePicker._sentinelDate());

                var computedClock = calendar.getClock();
                var numberOfHours = 24;
                numberOfHours = calendar.numberOfHoursInThisPeriod;

                var periods = (function () {
                    var periodFormatter = newFormatter(timePatterns.period, DEFAULT_PERIOD_PATTERN);
                    return {
                        getLength: function () { return 2; },
                        getValue: function (index) {
                            var date = WinJS.UI.TimePicker._sentinelDate();
                            if (index == 0) {
                                date.setHours(1);
                                var am = periodFormatter.format(date);
                                return am;
                            }
                            if (index == 1) {
                                date.setHours(13);
                                var pm = periodFormatter.format(date);
                                return pm;
                            }
                            return null;
                        }
                    };
                })();

                // Determine minute format from the DateTimeFormatter
                var minutes = (function (index) {
                    var minuteFormatter = newFormatter(timePatterns.minute, DEFAULT_MINUTE_PATTERN);
                    var now = WinJS.UI.TimePicker._sentinelDate();
                    return {
                        getLength: function () { return 60 / minuteIncrement; },
                        getValue: function (index) {
                            var display = index * minuteIncrement;
                            now.setMinutes(display);
                            return minuteFormatter.format(now);
                        }
                    };
                })();


                // Determine hour format from the DateTimeFormatter
                var hours = (function (index) {
                    var hourFormatter = newFormatter(timePatterns.hour, DEFAULT_HOUR_PATTERN);
                    var now = WinJS.UI.TimePicker._sentinelDate();
                    return {
                        getLength: function () { return numberOfHours },
                        getValue: function (index) {
                            now.setHours(index);
                            return hourFormatter.format(now);
                        }
                    }
                })();

                // Determine the order of the items from the DateTimeFormatter.
                // "hour minute" also returns the period (if needed).
                //
                var hourMinuteFormatter = newFormatter("hour minute");
                var pattern = hourMinuteFormatter.patterns[0];
                var order = ["hour", "minute"];

                var indexes = {
                    period: pattern.indexOf("{period"),
                    hour: pattern.indexOf("{hour"),
                    minute: pattern.indexOf("{minute")
                };
                if (indexes.period > -1) {
                    order.push("period");
                }


                var DateTimeFormatter = Windows.Globalization.DateTimeFormatting.DateTimeFormatter;
                var dtf = new DateTimeFormatter("month.full", Windows.Globalization.ApplicationLanguages.languages, "ZZ", "GregorianCalendar", "24HourClock");
                var pat = dtf.patterns[0];
                var isRTL = pat.charCodeAt(0) === 8207;

                if (isRTL) {
                    var temp = indexes.hour;
                    indexes.hour = indexes.minute;
                    indexes.minute = temp;
                }

                order.sort(function (a, b) {
                    if (indexes[a] < indexes[b]) { return -1; }
                    else if (indexes[a] > indexes[b]) { return 1; }
                    else { return 0; }
                });

                return { minutes: minutes, hours: hours, clock: computedClock, periods: periods, order: order, forceLanguage: hourMinuteFormatter.resolvedLanguage, isRTL: isRTL };
            },
            _getInformationJS: function (clock, minuteIncrement) {
                var hours = [12, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11];

                var minutes = new Object();
                minutes.getLength = function () { return 60 / minuteIncrement; }
                minutes.getValue = function (index) {
                    var display = index * minuteIncrement;
                    if (display < 10) {
                        return "0" + display.toString();
                    }
                    else {
                        return display.toString();
                    }
                };

                var order = ["hour", "minute", "period"];
                if (clock === "24HourClock") {
                    hours = ["00", "01", "02", "03", "04", "05", "06", "07", "08", "09", 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23];
                    order = ["hour", "minute"];
                }
                return { minutes: minutes, hours: hours, clock: clock || "12HourClock", periods: ["AM", "PM"], order: order };
            }
        })
    });

    if (WinJS.Utilities.hasWinRT) {
        WinJS.UI.TimePicker.getInformation = WinJS.UI.TimePicker._getInformationWinRT;
    }
    else {
        WinJS.UI.TimePicker.getInformation = WinJS.UI.TimePicker._getInformationJS;
    }

    WinJS.Class.mix(WinJS.UI.TimePicker, WinJS.Utilities.createEventProperties("change"));
    WinJS.Class.mix(WinJS.UI.TimePicker, WinJS.UI.DOMEventMixin);

})(WinJS);

(function selectInit(WinJS, undefined) {
    "use strict";

    var encodeHtmlRegEx = /[^\w .,-]/g;
    var stringDirectionRegEx = /&#820[67];/g;
    function encodeHtml(str) {
        return str.replace(encodeHtmlRegEx, function (m) {
            return "&#" + m.charCodeAt(0) + ";";
        });
    };
    function stripDirectionMarker(str) {
        return str.replace(stringDirectionRegEx, "");
    }
    function stockGetValue(index) { return this[index]; }
    function stockGetLength() { return this.length; }
    function fixDataSource(dataSource) {
        if (!dataSource.getValue) {
            dataSource.getValue = stockGetValue
        }

        if (!dataSource.getLength) {
            dataSource.getLength = stockGetLength
        }
        return dataSource;
    }
    WinJS.Namespace.define("WinJS.UI", {
        _Select: WinJS.Class.define(function _Select_ctor(element, options) {
            // This is an implementation detail of the TimePicker and DatePicker, designed
            // to provide a primitive "data bound" select control. This is not designed to
            // be used outside of the TimePicker and DatePicker controls.
            //

            this._dataSource = fixDataSource(options.dataSource);
            this._index = options.index || 0;

            this._domElement = element;
            // Mark this as a tab stop
            this._domElement.tabIndex = 0;

            if (options.disabled) {
                this.setDisabled(options.disabled);
            }

            var that = this;
            this._domElement.addEventListener("change", function (e) {
                //Should be set to _index to prevent events from firing twice
                that._index = that._domElement.selectedIndex;
            }, false);

            //update runtime accessibility value after initialization
            this._createSelectElement();
        }, {
            _index: 0,
            _dataSource: null,

            dataSource: {
                get: function () { return this._dataSource; },
                set: function (value) {
                    this._dataSource = fixDataSource(value);

                    //Update layout as data source change
                    if (this._domElement) {
                        this._createSelectElement();
                    }
                }
            },

            setDisabled: function (disabled) {
                if (disabled) {
                    this._domElement.setAttribute("disabled", "disabled");
                }
                else {
                    this._domElement.removeAttribute("disabled");
                }
            },

            _createSelectElement: function () {
                var dataSourceLength = this._dataSource.getLength();
                var text = "";
                for (var i = 0; i < dataSourceLength; i++) {
                    var value = "" + this._dataSource.getValue(i);
                    var escaped = encodeHtml(value);
                    // WinRT localization often tags the strings with reading direction. We want this
                    // for display text (escaped), but don't want this in the value space, as it
                    // only present for display.
                    //
                    var stripped = stripDirectionMarker(escaped);
                    text += "<option value='" + stripped + "'>" + escaped + "</option>";
                }
                WinJS.Utilities.setInnerHTMLUnsafe(this._domElement, text);
                this._domElement.selectedIndex = this._index;
            },

            index: {
                get: function () {
                    return Math.max(0, Math.min(this._index, this._dataSource.getLength() - 1));
                },
                set: function (value) {
                    if (this._index !== value) {
                        this._index = value;

                        var d = this._domElement;
                        if (d && d.selectedIndex !== value) {
                            d.selectedIndex = value;
                        }
                    }
                }
            },

            value: {
                get: function () {
                    return this._dataSource.getValue(this.index);
                }
            }
        })
    })
})(WinJS);

(function ratingInit(global) {
    "use strict";


var utilities = WinJS.Utilities;

var strings = {
    get averageRating() { return WinJS.Resources._getWinJSString("ui/averageRating").value; },
    get clearYourRating() { return WinJS.Resources._getWinJSString("ui/clearYourRating").value; },
    get tentativeRating() { return WinJS.Resources._getWinJSString("ui/tentativeRating").value; },
    get tooltipStringsIsInvalid() { return WinJS.Resources._getWinJSString("ui/tooltipStringsIsInvalid").value; },
    get unrated() { return WinJS.Resources._getWinJSString("ui/unrated").value; },
    get userRating() { return WinJS.Resources._getWinJSString("ui/userRating").value; },
};

// Constants definition
var DEFAULT_MAX_RATING = 5,
    DEFAULT_DISABLED = false,
    CANCEL = "cancel",
    CHANGE = "change",
    PREVIEW_CHANGE = "previewchange",
    MOUSE_LBUTTON = 0, // Event attribute to indicate a mouse left click 
    PT_TOUCH = 2, // Pointer type to indicate a touch event
    PT_PEN = 3, // Pointer type to indicate a pen event
    PT_MOUSE = 4; // Pointer type to indicate a mouse event

var hiddenAverageRatingCss = "padding-left: 0px; padding-right: 0px; border-left: 0px; border-right: 0px; -ms-flex: none; display: none";

// CSS class names
var msRating = "win-rating",
    msRatingEmpty = "win-star win-empty",
    msRatingAverageEmpty = "win-star win-average win-empty",
    msRatingAverageFull = "win-star win-average win-full",
    msRatingUserEmpty = "win-star win-user win-empty",
    msRatingUserFull = "win-star win-user win-full",
    msRatingTentativeEmpty = "win-star win-tentative win-empty",
    msRatingTentativeFull = "win-star win-tentative win-full",
    msRatingDisabled = "win-disabled",
    msAverage = "win-average",
    msUser = "win-user";

// Rating control implementation
WinJS.Namespace.define("WinJS.UI", {
    /// <summary locid="WinJS.UI.Rating">
    /// The Rating control allows users to give a number on a scale of 1 to maxRating (5 is the default).
    /// </summary>
    /// <icon src="ui_winjs.ui.rating.12x12.png" width="12" height="12" />
    /// <icon src="ui_winjs.ui.rating.16x16.png" width="16" height="16" />
    /// <htmlSnippet><![CDATA[<div data-win-control="WinJS.UI.Rating"></div>]]></htmlSnippet>
    /// <event name="previewchange" bubbles="false" locid="WinJS.UI.Rating_e:previewchange">Raised when the user chooses a new tentative rating but hasn't commited the change.</event>
    /// <event name="cancel" bubbles="false" locid="WinJS.UI.Rating_e:cancel">Raised when the user finishes interacting with the rating control without committing a tentative rating.</event>
    /// <event name="change" bubbles="false" locid="WinJS.UI.Rating_e:change">Raised when the user commits a change to the userRating.</event>
    /// <part name="rating" class="win-rating" locid="WinJS.UI.Rating_part:rating">The entire Rating control.</part>
    /// <part name="average-empty" class="win-star win-average win-empty" locid="WinJS.UI.Rating_part:average-empty">The empty star when the Rating control shows the average rating.</part>
    /// <part name="average-full" class="win-star win-average win-full" locid="WinJS.UI.Rating_part:average-full">The full star when the Rating control shows the average rating.</part>
    /// <part name="user-empty" class="win-star win-user win-empty" locid="WinJS.UI.Rating_part:user-empty">The empty star when the Rating control shows the user rating.</part>
    /// <part name="user-full" class="win-star win-user win-full" locid="WinJS.UI.Rating_part:user-full">The full star when the Rating control shows the user rating.</part>
    /// <part name="tentative-empty" class="win-star win-tentative win-empty" locid="WinJS.UI.Rating_part:tentative-empty">The empty star when the Rating control shows the tentative rating.</part>
    /// <part name="tentative-full" class="win-star win-tentative win-full" locid="WinJS.UI.Rating_part:tentative-full">The full star when the Rating control shows the tentative rating.</part>
    /// <part name="disabled-empty" class="win-star win-disabled win-empty" locid="WinJS.UI.Rating_part:disabled-empty">The empty star when the control is disabled.</part>
    /// <part name="disabled-full" class="win-star win-disabled win-full" locid="WinJS.UI.Rating_part:disabled-full">The full star when the control is disabled.</part>
    /// <resource type="javascript" src="//Microsoft.WinJS.1.0/js/base.js" shared="true" />
    /// <resource type="javascript" src="//Microsoft.WinJS.1.0/js/ui.js" shared="true" />
    /// <resource type="css" src="//Microsoft.WinJS.1.0/css/ui-dark.css" shared="true" />
    Rating: WinJS.Class.define(function Rating_ctor(element, options) {
        /// <signature helpKeyword="WinJS.UI.Rating.Rating">
        /// <summary locid="WinJS.UI.Rating.constructor">
        /// Creates a new Rating.
        /// </summary>
        /// <param name="element" domElement="true" locid="WinJS.UI.Rating.constructor_p:element">
        /// The DOM element that hosts the new Rating.
        /// </param>
        /// <param name="options" type="Object" locid="WinJS.UI.Rating.constructor_p:options">
        /// An object that contains one or more property/value pairs to apply to the new control.
        /// Each property of the options object corresponds to one of the control's properties or events.
        /// Event names must begin with "on". For example, to provide a handler for the cancel event,
        /// add a property named "oncancel" to the options object and set its value to the event handler.
        /// This parameter is optional.
        /// </param>
        /// <returns type="WinJS.UI.Rating" locid="WinJS.UI.Rating.constructor_returnValue">
        /// The new Rating.
        /// </returns>
        /// </signature>
        element = element || document.createElement("div");
        options = options || {};
        this._element = element;
        
        //initialize properties with default value
        this._userRating = 0;
        this._averageRating = 0;
        this._disabled = DEFAULT_DISABLED;
        this._enableClear = true;
        this._tooltipStrings = [];

        this._controlUpdateNeeded = false;
        this._setControlSize(options.maxRating);
        if (!options.tooltipStrings) {
            this._updateTooltips(null);
        }
        WinJS.UI.setOptions(this, options);
        this._controlUpdateNeeded = true;
        this._forceLayout();

        // Remember ourselves
        element.winControl = this;
        this._events();
    }, {
        /// <field type="Number" integer="true" locid="WinJS.UI.Rating.maxRating" helpKeyword="WinJS.UI.Rating.maxRating">
        /// Gets or sets the maximum possible rating value. The default is 5.
        /// </field>
        maxRating: {
            get: function () {
                return this._maxRating;
            },
            set: function (value) {
                this._setControlSize(value);
                this._forceLayout();
            }
        },

        /// <field type="Number" integer="true" locid="WinJS.UI.Rating.userRating" helpKeyword="WinJS.UI.Rating.userRating">
        /// Gets or sets the user's rating. This value must be between greater than or equal to zero and less than or equal to the maxRating.
        /// </field>
        userRating: {
            get: function () {
                return this._userRating;
            },
            set: function (value) {
                // Coerce value to a positive integer between 0 and maxRating
                this._userRating = Math.max(0, Math.min(Number(value) >> 0, this._maxRating));
                this._updateControl();
            }
        },

        /// <field type="Number" locid="WinJS.UI.Rating.averageRating" helpKeyword="WinJS.UI.Rating.averageRating">
        /// Gets or sets the average rating as a float value. This value must be [equal to zero] OR [greater than or equal to 1 AND less than or equal to the maxRating].
        /// </field>
        averageRating: {
            get: function () {
                return this._averageRating;
            },
            set: function (value) {
                // Coerce value to either 0 or a positive float between 1 and maxRating
                this._averageRating = (Number(value) < 1) ? 0 : Math.min(Number(value) || 0, this._maxRating);
                if (this._averageRatingElement) { // After the control has been created..
                    this._ensureAverageMSStarRating(); // ..ensure correct msStarRating is given to 'average-rating' star.
                }
                this._updateControl();
            }
        },

        /// <field type="Boolean" locid="WinJS.UI.Rating.disabled" helpKeyword="WinJS.UI.Rating.disabled">
        /// Gets or sets a value that specifies whether the control is disabled. When the control is disabled, the user can't specify a
        /// new rating or modify an existing rating.
        /// </field>
        disabled: {
            get: function () {
                return this._disabled;
            },
            set: function (value) {
                this._disabled = !!value;
                if (this._disabled) {
                    this._clearTooltips();
                }
                this._updateTabIndex();
                this._updateControl();
            }
        },

        /// <field type="Boolean" locid="WinJS.UI.Rating.enableClear" helpKeyword="WinJS.UI.Rating.enableClear">
        /// Gets or sets whether the control lets the user clear the rating.
        /// </field>
        enableClear: {
            get: function () {
                return this._enableClear;
            },
            set: function (value) {
                this._enableClear = !!value;
                this._setAriaValueMin();
                this._updateControl();
            }
        },

        /// <field type="Array" locid="WinJS.UI.Rating.tooltipStrings" helpKeyword="WinJS.UI.Rating.tooltipStrings">
        /// Gets or sets a set of descriptions to show for rating values in the tooltip. The array must
        /// contain a string for each available rating value, and it can contain an optional string
        /// (at the end of the array) for the clear rating option.
        /// </field>
        tooltipStrings: {
            get: function () {
                return this._tooltipStrings;
            },
            set: function (value) {
                if (typeof value !== "object") {
                    throw new WinJS.ErrorFromName("WinJS.UI.Rating.TooltipStringsIsInvalid", strings.tooltipStringsIsInvalid);
                }
                this._updateTooltips(value);
                this._updateAccessibilityRestState();
            }
        },

        /// <field type="HTMLElement" domElement="true" hidden="true" locid="WinJS.UI.Rating.element" helpKeyword="WinJS.UI.Rating.element">
        /// Gets the DOM element that hosts the Rating.
        /// </field>
        element: {
            get: function () {
                return this._element;
            }
        },

        addEventListener: function (eventName, eventCallBack, capture) {
            /// <signature helpKeyword="WinJS.UI.Rating.addEventListener">
            /// <summary locid="WinJS.UI.Rating.addEventListener">
            /// Registers an event handler for the specified event.
            /// </summary>
            /// <param name="eventName" type="String" locid="WinJS.UI.Rating.addEventListener_p:eventName">The name of the event.</param>
            /// <param name="eventCallback" type="Function" locid="WinJS.UI.Rating.addEventListener_p:eventCallback">The event handler function to associate with this event.</param>
            /// <param name="capture" type="Boolean" locid="WinJS.UI.Rating.addEventListener_p:capture">Set to true to register the event handler for the capturing phase; set to false to register for the bubbling phase.</param>
            /// </signature>

            this._element.addEventListener(eventName, eventCallBack, capture);
        },

        removeEventListener: function (eventName, eventCallBack, capture) {
            /// <signature helpKeyword="WinJS.UI.Rating.removeEventListener">
            /// <summary locid="WinJS.UI.Rating.removeEventListener">
            /// Unregisters an event handler for the specified event.
            /// </summary>
            /// <param name="eventName" type="String" locid="WinJS.UI.Rating.removeEventListener_p:eventName">The name of the event.</param>
            /// <param name="eventCallback" type="Function" locid="WinJS.UI.Rating.removeEventListener_p:eventCallback">The event handler function to remove.</param>
            /// <param name="capture" type="Boolean" locid="WinJS.UI.Rating.removeEventListener_p:capture">Set to true to unregister the event handler for the capturing phase; otherwise, set to false to unregister the event handler for the bubbling phase.</param>
            /// </signature>

            return this._element.removeEventListener(eventName, eventCallBack, capture);
        },

        _forceLayout: function () {
            if (!this._controlUpdateNeeded) {
                return;
            }

            // Disable incremental update during redraw, postpone till all properties set
            var updateNeeded = false;
            this._updateControl = function () {
                updateNeeded = true;
            };

            // Coerce userRating and averageRating to conform to maxRating
            this.userRating = this._userRating;
            this.averageRating = this._averageRating; 

            // Reset properties
            this._lastEventWasChange = false;
            this._lastEventWasCancel = false;
            this._tentativeRating = -1;
            this._captured = false;
            this._ariaChangeEnabled = true;
            this._pointerDownFocus = false;
            this._elements = [];
            this._toolTips = [];
            this._clearElement = null;

            // Element that is used for showing average rating
            this._averageRatingElement = null;
            this._elementWidth = null;
            this._elementPadding = null;
            this._elementBorder = null;
            this._floatingValue = 0;

            this._createControl();
            this._setAccessibilityProperties();

            delete this._updateControl;
            if (updateNeeded) {
                this._updateControl();
            }

        },

        // Hide the help star if the control is not showing average rating
        _hideAverageRating: function () {
            if (!this._averageRatingHidden) {
                this._averageRatingHidden = true;
                this._averageRatingElement.style.cssText = hiddenAverageRatingCss;
            }
        },

        _createControl: function () {
            // rating control could have more than one class name
            utilities.addClass(this._element, msRating);

            var html = "";
            this._averageRatingHidden = true;
            // create control
            for (var i = 0; i <= this._maxRating; i++) {
                if (i === this._maxRating) {
                    html = html + "<div class='" + msRatingAverageFull + "' style='" + hiddenAverageRatingCss + "'></div>";
                }
                else {
                    html = html + "<div class='" + msRatingUserEmpty + "'></div>";
                }
            }
            this._element.innerHTML = html;
            var oneStar = this._element.firstElementChild;
            var i = 0;
            while (oneStar) {
                this._elements[i] = oneStar;
                if (i < this._maxRating){ 
                    WinJS.Utilities.data(oneStar).msStarRating = i + 1;
                } 
                oneStar = oneStar.nextElementSibling;
                i++;
            }
            this._averageRatingElement = this._elements[this._maxRating];
            this._ensureAverageMSStarRating();

            // add focus capability relative to element's position in the document
            this._updateTabIndex();
        },

        _setAriaValueMin: function () {
            this._element.setAttribute("aria-valuemin", this._enableClear ? 0 : 1);
        },

        _setAccessibilityProperties: function () {
            this._element.setAttribute("role", "slider");
            this._element.setAttribute("aria-valuemax", this._maxRating);
            this._setAriaValueMin();
            this._updateAccessibilityRestState();
        },

        _getText: function (number) {
            var string = this._tooltipStrings[number];
            if (string) {
                var tempDiv =  document.createElement("div");
                tempDiv.innerHTML = string;
                return tempDiv.innerText;
            } else if (number === this._maxRating) {
                return strings.clearYourRating;
            } else {
                return number + 1;
            }
        },

        _updateAccessibilityRestState: function () {
            var element = this._element;
            this._ariaChangeEnabled = false;
            element.setAttribute("aria-readOnly", this._disabled);

            if (this._userRating !== 0) {
                element.setAttribute("aria-valuenow", this._userRating);
                element.setAttribute("aria-label", strings.userRating);
                element.setAttribute("aria-valuetext", this._getText(this._userRating - 1));
            } else if (this._averageRating !== 0) {
                element.setAttribute("aria-valuenow", this._averageRating);
                element.setAttribute("aria-label", strings.averageRating);
                element.setAttribute("aria-valuetext", this._averageRating);
            } else {
                element.setAttribute("aria-valuenow", strings.unrated);
                element.setAttribute("aria-label", strings.userRating);
                element.setAttribute("aria-valuetext", strings.unrated);
            }
            this._ariaChangeEnabled = true;
        },

        _updateAccessibilityHoverState: function () {
            var element = this._element;
            this._ariaChangeEnabled = false;
            element.setAttribute("aria-readOnly", this._disabled);

            if (this._tentativeRating > 0) {
                element.setAttribute("aria-label", strings.tentativeRating);
                element.setAttribute("aria-valuenow", this._tentativeRating);
                element.setAttribute("aria-valuetext", this._getText(this._tentativeRating - 1));
            } else if (this._tentativeRating === 0) {
                element.setAttribute("aria-valuenow", strings.unrated);
                element.setAttribute("aria-label", strings.tentativeRating);
                element.setAttribute("aria-valuetext", this._getText(this._maxRating));
            } else {
                //shouldn't get here
                element.setAttribute("aria-valuenow", strings.unrated);
                element.setAttribute("aria-label", strings.tentativeRating);
                element.setAttribute("aria-valuetext", strings.unrated);
            }
            this._ariaChangeEnabled = true;
        },

        _ensureTooltips: function () {
            if (this.disabled) {
                return;
            }

            if (this._toolTips.length === 0) {
                for (var i = 0; i < this._maxRating; i++) {
                    this._toolTips[i] = new WinJS.UI.Tooltip(this._elements[i]);
                }
            }
        },

        // decrement tentative rating by one
        _decrementRating: function () {
            this._closeTooltip();
            var firePreviewChange = true;
            if ((this._tentativeRating === 0) || ((this._tentativeRating === -1) && (this._userRating === 0))) {
                firePreviewChange = false;
            } else {
                if (this._tentativeRating > 0) {
                    this._tentativeRating--;
                } else if (this._tentativeRating === -1) {
                    if (this._userRating !== 0) {
                        if (this._userRating > 0) {
                            this._tentativeRating = this._userRating - 1;
                        } else {
                            this._tentativeRating = 0;
                        }
                    } else {
                        this._tentativeRating = 0;
                    }
                }

                if ((this._tentativeRating === 0) && !this._enableClear) {
                    this._tentativeRating = 1;
                    firePreviewChange = false;
                }
            }

            this._showTentativeRating(firePreviewChange, "keyboard");
        },

        _events: function () {
            var that = this;
            function ratingHandler(eventName) {
                return {
                    name: eventName,
                    lowerCaseName: eventName.toLowerCase(),
                    handler: function (event) {
                        var fn = that["_on" + eventName];
                        if (fn) {
                            fn.apply(that, [event]);
                        }
                    }
                };
            }

            var eventsRegisteredInLowerCase = [
                    ratingHandler("KeyDown"),
                    ratingHandler("Blur"),
                    ratingHandler("Focus")
                    ];
            var events = [
                    ratingHandler("MSPointerCancel"),
                    ratingHandler("MSPointerDown"),
                    ratingHandler("MSPointerMove"),
                    ratingHandler("MSPointerOver"),
                    ratingHandler("MSPointerUp"),
                    ratingHandler("MSPointerOut"),
                    ratingHandler("DOMNodeInserted"),
                    ratingHandler("DOMAttrModified")
                    ];

            var i;
            for (i = 0; i < eventsRegisteredInLowerCase.length; ++i) {
                this._element.addEventListener(eventsRegisteredInLowerCase[i].lowerCaseName, eventsRegisteredInLowerCase[i].handler, false);
            }
            for (i = 0; i < events.length; ++i) {
                this._element.addEventListener(events[i].name, events[i].handler, false);
            }
        },

        _onDOMNodeInserted: function (eventObject) {
            if (eventObject.target === this._element) {
                this._recalculateStarProperties();
                this._updateControl();
            }
        },

        _recalculateStarProperties: function () {
            var j = 0;
            // If the average rating is 1 we do not have correct padding on the first star so we are reading it from the second star
            // When we create average rating star we are creating it from 2 divs - stars. The first one is the average rating star the second one is the regular rating star. 
            // If the average rating is 1 we are creating that rating on the following way - The first part of star 
            // (without right padding, right border) is average rating star - the second part is regular star that does not have left padding and left border anymore 
            // (we set on 0 to create average rating star). In that situation the average rating star has correct left padding and left border.
            if (this._averageRating === 1) {
                j = 1;
            }
            var style = this._elements[j].currentStyle;
            this._elementWidth = style.width;
            if (this._element.currentStyle.direction === "rtl") {
                this._elementPadding = style.paddingRight;
                this._elementBorder = style.borderRight;
            } else {
                this._elementPadding = style.paddingLeft;
                this._elementBorder = style.borderLeft;
            }
        },

        // Hide the help star if the control is not showing average rating
        _hideAverageStar: function () {
            // check if this average rating control
            if (this._averageRating !== 0) {
                // hide the empty star
                this._resetAverageStar(false);
            }
        },

        // increase tentative rating by one
        _incrementRating: function () {
            this._closeTooltip();
            var firePreviewChange = true;
            if ((this._tentativeRating === this._maxRating) || ((this._tentativeRating === -1) && (this._userRating === this._maxRating))) {
                firePreviewChange = false;
            }

            if (this._tentativeRating !== -1) {
                if (this._tentativeRating < this._maxRating) {
                    this._tentativeRating++;
                }
            } else {
                if (this._userRating !== 0) {
                    if (this._userRating < this._maxRating) {
                        this._tentativeRating = this._userRating + 1;
                    } else {
                        this._tentativeRating = this._maxRating;
                    }
                } else {
                    this._tentativeRating = 1;
                }
            }
            this._showTentativeRating(firePreviewChange, "keyboard");
        },

        _onDOMAttrModified: function (eventObject) {
            var attrName = eventObject.attrName;
            if ((attrName === "dir") || (attrName === "style.direction")) {
                this._resetAverageStar(true);
                this._updateControl();
            // We need to update the control when aria-valuenow is set and we are not in the middle of an interaction.
            } else if (!this._disabled && (attrName === "aria-valuenow") && this._ariaChangeEnabled) {
                var attrNode = this._element.getAttributeNode("aria-valuenow");
                if (attrNode !== null) {
                    this.userRating = attrNode.nodeValue;
                    this._tentativeRating = this._userRating;
                    this._raiseEvent(CHANGE, this._userRating);
                }
            }
        },

        _onMSPointerCancel: function (eventObject) {
            this._showCurrentRating();
            if (!this._lastEventWasChange) {
                this._raiseEvent(CANCEL, null);
            }
        },

        _onMSPointerDown: function (eventObject) {
            if (eventObject.pointerType === PT_MOUSE && eventObject.button !== MOUSE_LBUTTON) { 
                return; // Ignore any mouse clicks that are not left clicks.
            }
            if (!this._captured) { // Rating Control does not support multi-touch, ignore mspointerdown messages if the control already has capture.
                this._pointerDownAt = { x: eventObject.clientX, y: eventObject.clientY };
                this._pointerDownFocus = true;
                if (!this._disabled) {
                    // Only capture the event when active to support block panning
                    this._element.msSetPointerCapture(eventObject.pointerId);
                    this._captured = true;

                    if (eventObject.pointerType === PT_TOUCH) {
                        this._tentativeRating = WinJS.Utilities.data(eventObject.srcElement).msStarRating || 0;
                        // change states for all stars
                        this._setStarClasses(msRatingTentativeFull, this._tentativeRating, msRatingTentativeEmpty);
                        this._hideAverageStar();
                        this._updateAccessibilityHoverState();
                        this._openTooltip("touch");
                        this._raiseEvent(PREVIEW_CHANGE, this._tentativeRating);
                    } else {
                        this._openTooltip("mousedown");
                    }
                }
            }
        },

        _onPointerMove: function (eventObject, tooltipType) {
            // Manual hit-test because we capture the pointer
            // If the pointer is already down, we use its information.
            var pointerAt = this._pointerDownAt || { x: eventObject.clientX, y: eventObject.clientY };

            var star;
            var hit = document.msElementsFromPoint(eventObject.clientX, pointerAt.y);
            if (hit) {
                for (var i = 0, len = hit.length; i < len; i++) {
                    var item = hit[i];
                    if (item.getAttribute("role") === "tooltip") {
                        return;
                    }
                    if (WinJS.Utilities.hasClass(item, "win-star")) {
                        star = item;
                        break;
                    }
                }
            }
            var starNum;
            if (star && (star.parentElement === this._element)) {
                starNum = WinJS.Utilities.data(star).msStarRating || 0;
            }
            else {
                var left = 0, right = this.maxRating;
                if (this._element.currentStyle.direction === "rtl") {
                    left = right;
                    right = 0;
                }
                if (eventObject.clientX < pointerAt.x) {
                    starNum = left;
                }
                else {
                    starNum = right;
                }
            }

            var firePreviewChange = false;
            var newTentativeRating = Math.min(Math.ceil(starNum), this._maxRating);
            if ((newTentativeRating === 0) && !this._enableClear) {
                newTentativeRating = 1;
            }
            if (newTentativeRating !== this._tentativeRating) {
                this._closeTooltip();
                firePreviewChange = true;
            }

            this._tentativeRating = newTentativeRating;
            this._showTentativeRating(firePreviewChange, tooltipType);
        },

        _onMSPointerMove: function (eventObject) {
            if (this._captured) {
                if (eventObject.pointerType === PT_TOUCH) {
                    this._onPointerMove(eventObject, "touch");
                } else {
                    this._onPointerMove(eventObject, "mousedown");
                }
            }
        },

        _onMSPointerOver: function (eventObject) {
            if (!this._disabled && (eventObject.pointerType === PT_PEN || eventObject.pointerType === PT_MOUSE)) {
                this._onPointerMove(eventObject, "mouseover");
            }
        },

        _onMSPointerUp: function (eventObject) {
            if (this._captured) {
                this._element.msReleasePointerCapture(eventObject.pointerId);
                this._captured = false;
                this._onUserRatingChanged();
            }
            this._pointerDownAt = null;
        },

        _onBlur: function () {
            if (!this._captured) {
                this._onUserRatingChanged();
                if (!this._lastEventWasChange && !this._lastEventWasCancel) {
                    this._raiseEvent(CANCEL, null);
                }
            }
        },

        _onFocus: function () {
            if (!this._pointerDownFocus) {
                // if the control is read only don't hover stars
                if (!this._disabled) {
                    // change states for all previous stars
                    // but only if user didnt vote
                    if (this._userRating === 0) {
                        for (var i = 0; i < this._maxRating; i++) {
                            this._elements[i].className = msRatingTentativeEmpty;
                        }
                    }
                    // hide the help star
                    this._hideAverageStar();
                }

                if (this._userRating !== 0) {
                    this._raiseEvent(PREVIEW_CHANGE, this._userRating);
                } else {
                    this._raiseEvent(PREVIEW_CHANGE, 0);
                }
                this._tentativeRating = this._userRating;
            }
            this._pointerDownFocus = false;
        },

        _onKeyDown: function (eventObject) {
            var Key = utilities.Key;
            var keyCode = eventObject.keyCode;
            var rtlString = this._element.currentStyle.direction;
            var handled = true;
            switch (keyCode) {
                case Key.enter: // Enter
                    this._onUserRatingChanged();
                    break;
                case Key.tab: //Tab
                    this._onUserRatingChanged();
                    handled = false;
                    break;
                case Key.escape: // escape
                    this._showCurrentRating();

                    if (!this._lastEventWasChange) {
                        this._raiseEvent(CANCEL, null);
                    }

                    break;
                case Key.leftArrow: // Arrow Left
                    if (rtlString === "rtl") {
                        this._incrementRating();
                    } else {
                        this._decrementRating();
                    }
                    break;
                case Key.upArrow: // Arrow Up
                    this._incrementRating();
                    break;
                case Key.rightArrow: // Arrow Right
                    if (rtlString === "rtl") {
                        this._decrementRating();
                    } else {
                        this._incrementRating();
                    }
                    break;
                case Key.downArrow: // Arrow Down
                    this._decrementRating();
                    break;
                default:
                    var number = 0;
                    if ((keyCode >= Key.num0) && (keyCode <= Key.num9)) {
                        number = Key.num0;
                    } else if ((keyCode >= Key.numPad0) && (keyCode <= Key.numPad9)) {
                        number = Key.numPad0;
                    }

                    if (number > 0) {
                        var firePreviewChange = false;
                        var newTentativeRating = Math.min(keyCode - number, this._maxRating);
                        if ((newTentativeRating === 0) && !this._enableClear) {
                            newTentativeRating = 1;
                        }
                        if (newTentativeRating !== this._tentativeRating) {
                            this._closeTooltip();
                            firePreviewChange = true;
                        }
                        this._tentativeRating = newTentativeRating;
                        this._showTentativeRating(firePreviewChange, "keyboard");
                    } else {
                        handled = false;
                    }
            }

            if (handled) {
                eventObject.stopPropagation();
                eventObject.preventDefault();
            }
        },

        _onMSPointerOut: function (eventObject) {
            if (!this._captured && !utilities.eventWithinElement(this._element, eventObject)) {
                this._showCurrentRating();
                if (!this._lastEventWasChange) {
                    // only fire cancel event if we move out of the rating control, and if
                    // user did not change rating on the control
                    this._raiseEvent(CANCEL, null);
                }
            }
        },

        _onUserRatingChanged: function () {
            if (!this._disabled) {
                this._closeTooltip();
                // Only submit a change event if the user has altered the rating control value via PREVIEWCHANGE event.
                if (this._userRating !== this._tentativeRating && !this._lastEventWasCancel && !this._lastEventWasChange) {  
                    this.userRating = this._tentativeRating;
                    this._raiseEvent(CHANGE, this._userRating);
                } else {
                    this._updateControl();
                }
            }
        },

        _raiseEvent: function (eventName, tentativeRating) {
            if (!this._disabled) {
                this._lastEventWasChange = (eventName === CHANGE);
                this._lastEventWasCancel = (eventName === CANCEL);
                if (document.createEvent) {
                    var event = document.createEvent("CustomEvent");
                    event.initCustomEvent(eventName, false, false, { tentativeRating: tentativeRating });
                    this._element.dispatchEvent(event);
                }
            }
        },

        _resetNextElement: function (prevState) {
            if (this._averageRatingElement.nextSibling !== null) {
                var style = this._averageRatingElement.nextSibling.style;
                style.msFlexPositive = 1; style.msFlexNegative = 1;
                var direction = this._element.currentStyle.direction;
                if (prevState) {
                    if (direction === "rtl") {
                        direction = "ltr";
                    } else {
                        direction = "rtl";
                    }
                }
                if (direction === "rtl") {
                    style.paddingRight = this._elementPadding;
                    style.borderRight = this._elementBorder;
                    style.direction = "rtl";
                } else {
                    style.paddingLeft = this._elementPadding;
                    style.borderLeft = this._elementBorder;
                    style.direction = "ltr";
                }
                style.backgroundPosition = "left";
                style.backgroundSize = "100% 100%";
                style.width = this._resizeStringValue(this._elementWidth, 1, style.width);
            }
        },

        _resetAverageStar: function (prevState) {
            this._resetNextElement(prevState);
            this._hideAverageRating();
        },

        _resizeStringValue: function (string, factor, curString) {
            var number = parseFloat(string);
            if (isNaN(number)) {
                if (curString !== null) {
                    return curString
                } else {
                    return string;
                }
            }
            var unit = string.substring(number.toString(10).length);
            number = number * factor;
            return (number + unit);
        },

        _setControlSize: function (value) {
            // Coerce value to a positive integer between 0 and maxRating
            // if negative default to DEFAULT_MAX_RATING
            var maxRating = (Number(value) || DEFAULT_MAX_RATING) >> 0;
            this._maxRating = maxRating > 0 ? maxRating : DEFAULT_MAX_RATING;
        },

        _updateTooltips: function (value) {
            var i, max = 0;
            if (value !== null) {
                max = ((value.length <= this._maxRating + 1) ? value.length : this._maxRating + 1);
                for (i = 0; i < max; i++) {
                    this._tooltipStrings[i] = value[i];
                }
            } else {
                for (i = 0; i < this._maxRating; i++) {
                    this._tooltipStrings[i] = i + 1;
                }
                this._tooltipStrings[this._maxRating] = strings.clearYourRating;
            }
        },

        _updateTabIndex: function () {
            this._element.tabIndex = (this._disabled ? "-1" : "0");
        },

        _setStarClasses: function (classNameBeforeThreshold, threshold, classNameAfterThreshold) {
            for (var i = 0; i < this._maxRating; i++) {
                if (i < threshold) {
                    this._elements[i].className = classNameBeforeThreshold;
                } else {
                    this._elements[i].className = classNameAfterThreshold;
                }
            }
        },

        // Average rating star is created from 2 divs:
        // In the first div the glyph starts from the beginning in the direction of the control
        // In the second div the glyph starts from the beginning in the opposite direction
        // That way we are making the average star look like one glyph
        _updateAverageStar: function () {
            var style = this._averageRatingElement.style;
            var nextStyle = this._averageRatingElement.nextSibling.style;
            if (this._element.currentStyle.direction == "rtl") {
                style.backgroundPosition = "right";
                style.paddingRight = this._elementPadding;
                style.borderRight = this._elementBorder;
                nextStyle.paddingRight = "0px";
                nextStyle.borderRight = "0px";
                nextStyle.direction = "ltr";
            } else {
                style.backgroundPosition = "left";
                nextStyle.backgroundPosition = "right";
                style.paddingLeft = this._elementPadding;
                style.borderLeft = this._elementBorder;
                nextStyle.paddingLeft = "0px";
                nextStyle.borderLeft = "0px";
                nextStyle.direction = "rtl";
            }
            style.width = this._resizeStringValue(this._elementWidth, this._floatingValue, style.width);
            style.msFlexPositive = this._floatingValue; style.msFlexNegative = this._floatingValue;
            style.backgroundSize = (100 / this._floatingValue) + "% 100%";
            style.display = this._averageRatingElement.nextSibling.currentStyle.display;
            this._averageRatingHidden = false;
            nextStyle.msFlexPositive = 1 - this._floatingValue; nextStyle.msFlexNegative = 1 - this._floatingValue;
            nextStyle.width = this._resizeStringValue(this._elementWidth, 1 - this._floatingValue, nextStyle.width);
            nextStyle.backgroundSize = (100 / (1 - this._floatingValue)) + "% 100%";
        },

        // show current rating
        _showCurrentRating: function () {
            this._closeTooltip();
            // reset tentative rating
            this._tentativeRating = -1;
            // if the control is read only then we didn't change anything on hover
            if (!this._disabled) {
                this._updateControl();
            }
            this._updateAccessibilityRestState();
        },

        _showTentativeRating: function (firePreviewChange, tooltipType) {
            // if the control is read only don't hover stars
            if ((!this._disabled) && (this._tentativeRating >= 0)) {
                this._setStarClasses(msRatingTentativeFull, this._tentativeRating, msRatingTentativeEmpty);

                // hide the empty star
                this._hideAverageStar();
            }

            this._updateAccessibilityHoverState();

            if (firePreviewChange) {
                this._openTooltip(tooltipType);
                this._raiseEvent(PREVIEW_CHANGE, this._tentativeRating);
            }
        },

        _openTooltip: function (tooltipType) {
            if (this.disabled) {
                return;
            }

            this._ensureTooltips();
            if (this._tentativeRating > 0) {
                this._toolTips[this._tentativeRating - 1].innerHTML = this._tooltipStrings[this._tentativeRating - 1];
                this._toolTips[this._tentativeRating - 1].open(tooltipType);
            } else if (this._tentativeRating === 0) {
                this._clearElement = document.createElement("div");
                var distance = this._elements[0].offsetWidth + parseInt(this._elementPadding, 10);
                if (this._element.currentStyle.direction === "ltr") {
                    distance *= -1;
                }
                this._clearElement.style.cssText ="visiblity:hidden; position:absolute; width:0px; height:100%; left:" + distance + "px; top:0px;";
                this._elements[0].appendChild(this._clearElement);
                this._toolTips[this._maxRating] = new WinJS.UI.Tooltip(this._clearElement);
                this._toolTips[this._maxRating].innerHTML = this._tooltipStrings[this._maxRating];
                this._toolTips[this._maxRating].open(tooltipType);
            }
        },

        _closeTooltip: function (tooltipType) {
            if (this._toolTips.length !== 0) {
                if (this._tentativeRating > 0) {
                    this._toolTips[this._tentativeRating - 1].close();
                } else if (this._tentativeRating === 0) {
                    if (this._clearElement !== null) {
                        this._toolTips[this._maxRating].close();
                        this._elements[0].removeChild(this._clearElement);
                        this._clearElement = null;
                    }
                }
            }
        },

        _clearTooltips: function () {
            if (this._toolTips && this._toolTips.length !== 0) {
                for (var i = 0; i < this._maxRating; i++) {
                    this._toolTips[i].innerHTML = null;
                }
            }
        },

        _appendClass: function (classNameToBeAdded) {
            for (var i = 0; i <= this._maxRating; i++) {
                utilities.addClass(this._elements[i], classNameToBeAdded);
            }
        },

        _setClasses: function (classNameBeforeThreshold, threshold, classNameAfterThreshold) {
            for (var i = 0; i < this._maxRating; i++) {
                if (i < threshold) {
                    this._elements[i].className = classNameBeforeThreshold;
                } else {
                    this._elements[i].className = classNameAfterThreshold;
                }
            }
        },

        _ensureAverageMSStarRating: function() {
            WinJS.Utilities.data(this._averageRatingElement).msStarRating = Math.ceil(this._averageRating); 
        },

        _updateControl: function () {
            if (!this._controlUpdateNeeded) {
                return;
            }

            // check for average rating (if user rating is specified then we are not showing average rating)
            if ((this._averageRating !== 0) && (this._userRating === 0)) {
                if ((this._averageRating >= 1) && (this._averageRating <= this._maxRating)) { // Display average rating
                    this._setClasses(msRatingAverageFull, this._averageRating - 1, msRatingAverageEmpty);
                    this._averageRatingElement.className = msRatingAverageFull;

                    for (var i = 0; i < this._maxRating; i++) {
                        // check if it is average star
                        if ((i < this._averageRating) && ((i + 1) >= this._averageRating)) {
                            this._resetNextElement(false);

                            this._element.insertBefore(this._averageRatingElement, this._elements[i]);

                            this._floatingValue = this._averageRating - i;
                            this._elementWidth = this._elements[i].currentStyle.width;

                            if (this._element.currentStyle.direction == "rtl") {
                                this._elementPadding = this._elements[i].currentStyle.paddingRight;
                                this._elementBorder = this._elements[i].currentStyle.borderRight;
                            } else {
                                this._elementPadding = this._elements[i].currentStyle.paddingLeft;
                                this._elementBorder = this._elements[i].currentStyle.borderLeft;
                            }

                            this._updateAverageStar();
                        }
                    }
                }
            }

            // check if it is user rating control
            if (this._userRating !== 0) {
                if ((this._userRating >= 1) && (this._userRating <= this._maxRating)) { // Display user rating.
                    this._setClasses(msRatingUserFull, this._userRating, msRatingUserEmpty);
                    
                    // hide average star
                    this._resetAverageStar(false);
                }
            }

            // update stars if the rating is not set
            if ((this._userRating === 0) && (this._averageRating === 0)) { // Display empty rating
                this._setClasses(msRatingEmpty, this._maxRating);

                // hide average star
                this._resetAverageStar(false);
            }

            if (this.disabled) { // Display disabled rating.
                this._appendClass(msRatingDisabled);
            }

            // update classes to differentiate average rating vs user rating
            // If the userRating is 0 and averageRating is 0 we would like to treat that rating control as user rating control (not as average rating control).
            if ((this._averageRating !== 0) && (this._userRating === 0)) {
                this._appendClass(msAverage);
            } else {
                this._appendClass(msUser);
            }

            this._updateAccessibilityRestState();
        }
    })
});

// Rating support for "on"<eventName> properties
WinJS.Class.mix(WinJS.UI.Rating, WinJS.Utilities.createEventProperties(
    CANCEL,
    CHANGE,
    PREVIEW_CHANGE));

})(this, WinJS);
(function toggleInit(global) {
    "use strict";

    // Constants definition
    var MOUSE_LBUTTON = 0; // left button of the mouse

    var strings = {
        get on() { return WinJS.Resources._getWinJSString("ui/on").value; },
        get off() { return WinJS.Resources._getWinJSString("ui/off").value; },
    };

    // CSS class names
    var msToggle = "win-toggleswitch";
    var msToggleSwitch = "win-switch";
    var msToggleTitle = "win-title";
    var msToggleLabel = "win-label";
    var msToggleOn = "win-on";
    var msToggleOff = "win-off";
    var msToggleDisabled = "win-disabled";
    var msToggleHidden = "win-hidden";
    var msFocusHide = "win-focus-hide";

    var Control = WinJS.Class.define(null, {
        raiseEvent: function (type, eventProperties) {
            this.dispatchEvent(type, eventProperties);
        }
    });

    var utilities = WinJS.Utilities;

    function reloadChangeHandler(event) {
        if (event.propertyName === "defaultValue") {
            var that = event.srcElement.winControl;
            that.checked = that._switchElement.valueAsNumber;
        }
    };

    WinJS.Class.mix(Control, WinJS.UI.DOMEventMixin);

    WinJS.Namespace.define("WinJS.UI", {
        /// <summary locid="WinJS.UI.ToggleSwitch">
        /// A control that lets the user switch an option on or off.
        /// </summary>
        /// <icon src="ui_winjs.ui.toggleswitch.12x12.png" width="12" height="12" />
        /// <icon src="ui_winjs.ui.toggleswitch.16x16.png" width="16" height="16" />
        /// <htmlSnippet><![CDATA[<div data-win-control="WinJS.UI.ToggleSwitch"></div>]]></htmlSnippet>
        /// <event name="change" bubbles="true" locid="WinJS.UI.ToggleSwitch_e:change">Raised when the switch is flipped to on (checked is set to true) or off (checked is set to false). </event>
        /// <part name="toggle" class="win-toggleSwitch" locid="WinJS.UI.ToggleSwitch_part:toggle">The entire ToggleSwitch control.</part>
        /// <part name="switch" class="win-switch" locid="WinJS.UI.ToggleSwitch_part:switch">The slider that enables the user to switch the state of the ToggleSwitch.</part>
        /// <part name="title" class="win-title" locid="WinJS.UI.ToggleSwitch_part:title">The main text for the ToggleSwitch control.</part>
        /// <part name="label-on" class="win-on" locid="WinJS.UI.ToggleSwitch_part:label-on">The text for when the switch is on.</part>
        /// <part name="label-off" class="win-off" locid="WinJS.UI.ToggleSwitch_part:label-off:">The text for when the switch is off.</part>
        /// <resource type="javascript" src="//Microsoft.WinJS.1.0/js/base.js" shared="true" />
        /// <resource type="javascript" src="//Microsoft.WinJS.1.0/js/ui.js" shared="true" />
        /// <resource type="css" src="//Microsoft.WinJS.1.0/css/ui-dark.css" shared="true" />
        ToggleSwitch: WinJS.Class.derive(Control, function (element, options) {
            /// <signature helpKeyword="WinJS.UI.ToggleSwitch.ToggleSwitch">
            /// <summary locid="WinJS.UI.ToggleSwitch.constructor">
            /// Creates a new ToggleSwitch.
            /// </summary>
            /// <param name="element" domElement="true" locid="WinJS.UI.ToggleSwitch.constructor_p:element">
            /// The DOM element that hosts the ToggleSwitch.
            /// </param>
            /// <param name="options" type="Object" locid="WinJS.UI.ToggleSwitch.constructor_p:options">
            /// An object that contains one or more property/value pairs to apply to the new control.
            /// Each property of the options object corresponds to one of the control's properties or events.
            /// Event names must begin with "on". For example, to provide a handler for the change event,
            /// add a property named "onchange" to the options object and set its value to the event handler.
            /// This parameter is optional.
            /// </param>
            /// <returns type="WinJS.UI.ToggleSwitch" locid="WinJS.UI.ToggleSwitch.constructor_returnValue">
            /// The new ToggleSwitch.
            /// </returns>
            /// </signature>

            element = element || document.createElement("div");

            var toggle = utilities.data(element).toggle;
            if (toggle) {
                return toggle;
            }

            // Elements
            this._domElement = null;
            this._switchElement = null;
            this._titleElement = null;
            this._labelGridElement = null;
            this._labelOnElement = null;
            this._labelOffElement = null;


            // Strings
            this._labelOn = strings.on;
            this._labelOff = strings.off;

            // Variable
            this._spaceKeyDown = false;
            
            this._gesture = new MSGesture(); // Add the gesture object before creating the listeners in _setElement for gesture events handling
            this._shouldHideFocus = false; // This variable is needed to prevent focus rect from showing between the time during pointer down and focus happens.
            this._pointerId = 0;
            this._hasCapture = false;

            this._setElement(element);
            this._setDefaultOptions();
            WinJS.UI.setOptions(this, options);
            element.winControl = this;
            utilities.data(element).toggle = this;
        }, {
            // Properties

            /// <field type="Boolean" locid="WinJS.UI.ToggleSwitch.checked" helpKeyword="WinJS.UI.ToggleSwitch.checked">
            /// Gets or sets whether the control is on (checked is set to true) or off (checked is set to false).
            /// </field>
            checked: {
                get: function () {
                    return this._checked;
                },
                set: function (value) {
                    this._setChecked(value);
                }
            },
            /// <field type="Boolean" locid="WinJS.UI.ToggleSwitch.disabled" helpKeyword="WinJS.UI.ToggleSwitch.disabled">
            /// Gets or sets a value that specifies whether the control is disabled.
            /// </field>
            disabled: {
                get: function () {
                    return this._switchElement.disabled;
                },
                set: function (value) {
                    var disabled = !!value; // Sanitize for a bool
                    this._switchElement.disabled = disabled; // This is necessary to apply the css to the toggle 'switch' 
                    if (disabled == true) { // This is necessary to apply the css to the toggle 'label' and 'title' 
                        utilities.addClass(this._labelOnElement, msToggleDisabled);
                        utilities.addClass(this._labelOffElement, msToggleDisabled);
                        utilities.addClass(this._titleElement, msToggleDisabled); 
                    } else {
                        utilities.removeClass(this._labelOnElement, msToggleDisabled);
                        utilities.removeClass(this._labelOffElement, msToggleDisabled);  
                        utilities.removeClass(this._titleElement, msToggleDisabled);
                    }
                    this._switchElement.setAttribute("aria-disabled", disabled);
                }
            },
            /// <field type="HTMLElement" domElement="true" hidden="true" locid="WinJS.UI.ToggleSwitch.element" helpKeyword="WinJS.UI.ToggleSwitch.element">
            /// The DOM element that hosts the ToggleSwitch control.
            /// </field>
            element: {
                get: function () { return this._domElement; }
            },
            /// <field type="String" locid="WinJS.UI.ToggleSwitch.labelOn" helpKeyword="WinJS.UI.ToggleSwitch.labelOn">
            /// Gets or sets the text that displays when the control is on (checked is set to true). The default value is "On".
            /// </field>
            labelOn: {
                get: function () {
                    return this._labelOn;
                },
                set: function (value) {
                    this._labelOn = value;
                    this._labelOnElement.innerHTML = this._labelOn;
                }
            },
            /// <field type="String" locid="WinJS.UI.ToggleSwitch.labelOff" helpKeyword="WinJS.UI.ToggleSwitch.labelOff">
            /// Gets or sets the text that displays when the control is off (checked is set to false). The default value is "Off".
            /// </field>
            labelOff: {
                get: function () {
                    return this._labelOff;
                },
                set: function (value) {
                    this._labelOff = value;
                    this._labelOffElement.innerHTML = this._labelOff;
                }
            },

            /// <field type="String" locid="WinJS.UI.ToggleSwitch.title" helpKeyword="WinJS.UI.ToggleSwitch.title">
            /// Gets or sets the main text for the ToggleSwitch control. This text is always displayed, regardless of whether
            /// the control is switched on or off.
            /// </field>
            title: {
                get: function () {
                    return this._titleElement.innerHTML;
                },
                set: function (value) {
                    this._titleElement.innerHTML = value;
                }
            },

            _addControlsInOrder: function () {
                this._domElement.appendChild(this._titleElement);
                this._labelGridElement.appendChild(this._labelOnElement);
                this._labelGridElement.appendChild(this._labelOffElement);              
                this._labelGridElement.appendChild(this._switchElement);
                this._domElement.appendChild(this._labelGridElement);
            },

            _setChecked: function (value) {
                value = !!value; // Sanitize the value
                if (value !== this._checked) {
                    this._checked = value;
                    if (this._checked) { // On state
                        utilities.removeClass(this._domElement, msToggleOff);
                        utilities.addClass(this._domElement, msToggleOn);
                        utilities.addClass(this._labelOffElement, msToggleHidden);
                        utilities.removeClass(this._labelOnElement, msToggleHidden);
                        this._switchElement.valueAsNumber = 1; // Update the slider visual
                    } else { // Off state
                        utilities.removeClass(this._domElement, msToggleOn);
                        utilities.addClass(this._domElement, msToggleOff);
                        utilities.addClass(this._labelOnElement, msToggleHidden);
                        utilities.removeClass(this._labelOffElement, msToggleHidden);
                        this._switchElement.valueAsNumber = 0; // Update the slider visual
                    }
                    this._switchElement.setAttribute("aria-checked", this._checked); // Update accessibility information
                }
            },

            _setDefaultOptions: function () {
                this.labelOn = strings.on;
                this.labelOff = strings.off;
                this.title = "";
                this.checked = false;
                this.disabled = false;
            },

            _setElement: function (element) {
                this._domElement = element;
                utilities.addClass(this._domElement, msToggle);
                utilities.addClass(this._domElement, msToggleOff);

                this._titleElement = document.createElement("div");
                this._titleElement.setAttribute("id", this._titleElement.uniqueID);
                this._titleElement.setAttribute("role", "note");
                utilities.addClass(this._titleElement, msToggleTitle);

                this._switchElement = document.createElement("input");
                this._switchElement.type = "range";
                this._switchElement.max = 1;
                this._switchElement.step = 1;
                this._switchElement.setAttribute("role", "checkbox");
                this._switchElement.setAttribute("aria-labelledby", this._titleElement.id);
                utilities.addClass(this._switchElement, msToggleSwitch);

                this._labelGridElement = document.createElement("div");
                this._labelGridElement.style.display = "-ms-grid";

                this._labelOnElement = document.createElement("div");
                utilities.addClass(this._labelOnElement, msToggleLabel);

                this._labelOffElement = document.createElement("div");
                utilities.addClass(this._labelOffElement, msToggleLabel);  

                this._addControlsInOrder();

                this._wireupEvents();
            },


            _valueHandler: function (fTapped) {
                var oldValue = this._checked;
                if (fTapped) {
                    this.checked = !this.checked;
                } else {
                    this.checked = this._switchElement.valueAsNumber;
                }

                if (oldValue !== this._checked) {
                    this.raiseEvent("change");
                }
            },

            _wireupEvents: function () {
                var that = this;
                var pointerUpHandler = function (event) {
                    if (event.pointerId == that._pointerId) {
                        that._valueHandler(false);
                    }
                };
                var spaceDownHandler = function (event) {
                    if (event.keyCode === utilities.Key.space) { // Spacebar
                        if (!that._spaceKeyDown) {
                            that._switchElement.valueAsNumber = (that._switchElement.valueAsNumber + 1) % 2;
                            that._spaceKeyDown = true;
                        }
                        event.preventDefault();
                    }
                };
                var keyUpHandler = function (event) {
                    if (event.keyCode === utilities.Key.space || (event.keyCode >= utilities.Key.end && event.keyCode <= utilities.Key.downArrow)) { // Spacebar and arrow, home/end key
                        that._valueHandler(false);
                        if (event.keyCode === utilities.Key.space) { //  Additional step for spacebar
                            that._spaceKeyDown = false;
                        }
                    }
                };
                var tapHandler = function () {
                    that._valueHandler(true);
                };
                var cancelHandler = function () {
                    that._switchElement.valueAsNumber = that.checked;
                    that._spaceKeyDown = false; // Reset flag on spaceKey
                };
                var dragHandler = function (event) {
                    if (!that._switchElement.disabled) {
                        // touch or the left button of mouse is down
                        if (!that._hasCapture && event.type == "MSGestureChange") {
                            try {
                                that._switchElement.msSetPointerCapture(that._pointerId);
                                that._hasCapture = true;
                            } catch (err) {}
                        }
                        else if (that._hasCapture && event.type == "MSGestureEnd") {
                            try {
                                that._hasCapture = false;
                            } catch (err) {}
                        }
                    }
                };
                var trackTap = function (event) {
                    if (!that._switchElement.disabled && (event.pointerType === event.MSPOINTER_TYPE_TOUCH || event.pointerType === event.MSPOINTER_TYPE_PEN || event.button === MOUSE_LBUTTON) ) {
                        if (!that._hasCapture) {
                            try {
                                // since toggle only needs to track one finger,
                                // it's better to reset the old pointerId and only track one
                                that._gesture.stop(); 
                                that._gesture.target = event.target;
                                that._gesture.addPointer(event.pointerId);
                                that._pointerId = event.pointerId;
                            } catch (err) {}
                        }
                        // Prevent default behavior for these events
                        event.preventDefault();
                        switchFocus();
                    }
                };
                var onDOMAttrModified = function (event) {
                    if (event.attrName === "aria-checked") {
                        var attrNode = that._switchElement.getAttributeNode("aria-checked");
                        if (attrNode !== null) {                            
                            var oldValue = that._checked;
                            
                            if (attrNode.nodeValue === "true") { // "nodeValue" is a string
                                that._setChecked(true);
                            }
                            else {
                                that._setChecked(false);
                            }
                            
                            if (oldValue !== that._checked) {
                                that.raiseEvent("change");
                            }        
                        }       
                    }
                };
                var switchFocus = function () {
                    that._switchElement.focus();
                    that._shouldHideFocus = false;
                };
                var dismissFocusRect = function () {
                    utilities.addClass(that._switchElement, msFocusHide);
                    that._shouldHideFocus = true;
                };
                var enableFocusRect = function () {
                    if (!that._shouldHideFocus) {
                        utilities.removeClass(that._switchElement, msFocusHide);
                    }
                };
                this._switchElement.addEventListener("MSPointerCancel", cancelHandler, false);
                this._switchElement.addEventListener("MSLostPointerCapture", cancelHandler, false);
                this._switchElement.addEventListener("MSPointerUp", pointerUpHandler, false);
                this._switchElement.addEventListener("MSGestureChange", dragHandler, false);
                this._switchElement.addEventListener("MSGestureEnd", dragHandler, false);
                this._switchElement.addEventListener("MSGestureTap", tapHandler, false);
                this._switchElement.addEventListener("keydown", spaceDownHandler, false);
                this._switchElement.addEventListener("keyup", keyUpHandler, false);
                this._switchElement.attachEvent("onpropertychange", reloadChangeHandler);
                this._switchElement.addEventListener("change", function (ev) { ev.stopPropagation(); }, true); // Stop the change event from bubbling up and fire our own change event when the user interaction is done.

                this._switchElement.addEventListener("MSPointerDown", trackTap, false); // Use the gesture object so we could listen to tap events
                this._switchElement.addEventListener("DOMAttrModified", onDOMAttrModified, false); // Listen to DOMAttrModified for aria-checked change
                this._switchElement.addEventListener("blur", function() { enableFocusRect(); cancelHandler(); }, false); 
                this._domElement.addEventListener("focus", switchFocus, true);
                this._domElement.addEventListener("MSPointerDown", dismissFocusRect, true);
            },

            addEventListener: function (eventName, eventCallBack, capture) {
                /// <signature helpKeyword="WinJS.UI.ToggleSwitch.addEventListener">
                /// <summary locid="WinJS.UI.ToggleSwitch.addEventListener">
                /// Registers an event handler for the specified event.
                /// </summary>
                /// <param name="eventName" type="String" locid="WinJS.UI.ToggleSwitch.addEventListener_p:eventName">The name of the event.</param>
                /// <param name="eventCallback" type="Function" locid="WinJS.UI.ToggleSwitch.addEventListener_p:eventCallback">The event handler function to associate with this event.</param>
                /// <param name="capture" type="Boolean" locid="WinJS.UI.ToggleSwitch.addEventListener_p:capture">Set to true to register the event handler for the capturing phase; set to false to register for the bubbling phase.</param>
                /// </signature>
                if (eventName == "change") {
                    // Set the capture to be false explicitly because we want the change events for Toggle to be listened only in bubble up phase
                    // Therefore, the change events would only happen when users have finished their actions.
                    capture = false;
                }
                this._domElement.addEventListener(eventName, eventCallBack, capture);
                
            },

            removeEventListener: function (eventName, eventCallBack, capture) {
                /// <signature helpKeyword="WinJS.UI.ToggleSwitch.removeEventListener">
                /// <summary locid="WinJS.UI.ToggleSwitch.removeEventListener">
                /// Unregisters an event handler for the specified event.
                /// </summary>
                /// <param name="eventName" type="String" locid="WinJS.UI.ToggleSwitch.removeEventListener_p:eventName">The name of the event.</param>
                /// <param name="eventCallback" type="Function" locid="WinJS.UI.ToggleSwitch.removeEventListener_p:eventCallback">The event handler function to remove.</param>
                /// <param name="capture" type="Boolean" locid="WinJS.UI.ToggleSwitch.removeEventListener_p:capture">Set to true to unregister the event handler for the capturing phase; otherwise, set to false to unregister the event handler for the bubbling phase.</param>
                /// </signature>
                if (eventName == "change") {
                    // Set the capture to be false explicitly because we only allow the user to add change events that are listened to in bubble up phase.
                    // Therefore it is not possible to remove a change event that is listened to in the capture phase.
                    capture = false;
                } 
                return this._domElement.removeEventListener(eventName, eventCallBack, capture);
            }
        })
    });

WinJS.Class.mix(WinJS.UI.ToggleSwitch, WinJS.Utilities.createEventProperties("change"));

})(WinJS);
// Semantic Zoom control
(function semanticZoomInit(global) {
    "use strict";


    var Utilities = WinJS.Utilities,
        UI = WinJS.UI;

    var strings = {
        get invalidZoomFactor() { return WinJS.Resources._getWinJSString("ui/invalidZoomFactor").value; },
    };

    // Private statics

    var sezoButtonClass = "win-semanticzoom-button";
    var sezoButtonLocationClass = "win-semanticzoom-button-location";
    var sezoButtonShowDuration = 3000;
    var sezoButtonMouseMoveThreshold = 8;     

    var semanticZoomClass = "win-semanticzoom";
    var semanticZoomActiveClass = "win-semanticzoomactive";

    var zoomChangedEvent = "zoomchanged";

    var bounceFactor = 1.05;
    var defaultZoomFactor = 0.65; // Value used by the shell
    // If we change these we need to update the metadata for the zoomFactor property as well.
    var maxZoomFactor = 0.8;
    var minZoomFactor = 0.2;

    var canvasSizeMax = 4096;

    var outgoingOpacityTransitionDuration = 0.333;
    var incomingOpacityTransitionDuration = 0.333;
    var outgoingScaleTransitionDuration = 0.333;
    var incomingScaleTransitionDuration = 0.333;
    var zoomAnimationDuration = outgoingOpacityTransitionDuration * 1000;
    var zoomAnimationTTFFBuffer = 50;
    // PS 846107 - TransitionEnd event not being fired occassionally if duration is not same
    var bounceInDuration = 0.333;
    var bounceBackDuration = 0.333;
    var easeOutBezier = "cubic-bezier(0.1,0.9,0.2,1)";

    function buildTransition(prop, duration, timing) {
        return prop + " " + duration + "s " + timing + " " + WinJS.UI._libraryDelay + "ms";
    }
    function outgoingElementTransition() {
        return buildTransition("transform", outgoingScaleTransitionDuration, "ease-in-out") + ", " +
               buildTransition("opacity", outgoingOpacityTransitionDuration, "ease-in-out");
    }

    function incomingElementTransition() {
        return buildTransition("transform", incomingScaleTransitionDuration, "ease-in-out") + ", " +
               buildTransition("opacity", incomingOpacityTransitionDuration, "ease-in-out");
    }

    function bounceInTransition() {
        return buildTransition("transform", bounceInDuration, easeOutBezier);
    }

    function bounceBackTransition() {
        return buildTransition("transform", bounceBackDuration, easeOutBezier);
    }

    var pinchDistanceCount = 2;
    var zoomOutGestureDistanceChangeFactor = 0.2;
    var zoomInGestureDistanceChangeFactor = 0.45;

    var zoomAnimationTimeout = 1000;

    // The semantic zoom has to piece together information from a variety of separate events to get an understanding of the current
    // manipulation state. Since these events are altogether separate entities, we have to put a delay between the end of one event
    // to allow time for another event to come around. For example, when we handle MSLostPointerCapture events, we need
    // to wait because DManip might be taking over. If it is, we'll receive an MSManipulationStateChanged event soon,
    // and so we don't want to reset our state back, and need give that event a chance to fire.
    var eventTimeoutDelay = 50;

    var PinchDirection = {
        none: 0,
        zoomedIn: 1,
        zoomedOut: 2
    };

    var PT_TOUCH = 2;
    var PT_PEN = 3;
    var PT_MOUSE = 4;

    function getDimension(element, property) {
        return WinJS.Utilities.convertToPixels(element, property);
    }

    function scaleElement(element, scale) {
        if (WinJS.UI.isAnimationEnabled()) {
            element.style["transform"] = "scale(" + scale + ")";
        }
    }

    var origin = { x: 0, y: 0 };

    function translateElement(element, offset) {
        if (WinJS.UI.isAnimationEnabled()) {
            element.style["transform"] = "translate(" + offset.x + "px, " + offset.y + "px)";
        }
    }

    function onSemanticZoomResize(ev) {
        var control = ev.srcElement && ev.srcElement.winControl;
        if (control && !control._resizing) {
            control._onResize();
        }
    }

    function onSemanticZoomPropertyChanged(ev) {
        var control = ev.srcElement && ev.srcElement.winControl;
        if (control && control instanceof WinJS.UI.SemanticZoom) {
            control._onPropertyChanged(ev);
        }
    }

    WinJS.Namespace.define("WinJS.UI", {

        /// <summary locid="WinJS.UI.SemanticZoom">
        /// Enables the user to zoom between two different views supplied by two child controls.
        /// One child control supplies the zoomed-out view and the other provides the zoomed-in view.
        /// </summary>
        /// <icon src="ui_winjs.ui.semanticzoom.12x12.png" width="12" height="12" />
        /// <icon src="ui_winjs.ui.semanticzoom.16x16.png" width="16" height="16" />
        /// <htmlSnippet supportsContent="true"><![CDATA[<div data-win-control="WinJS.UI.SemanticZoom"><div class="zoomedInContainer" data-win-control="WinJS.UI.ListView"></div><div class="zoomedOutContainer" data-win-control="WinJS.UI.ListView"></div></div>]]></htmlSnippet>
        /// <part name="semanticZoom" class="win-semanticzoom" locid="WinJS.UI.SemanticZoom_part:semanticZoom">The entire SemanticZoom control.</part>
        /// <resource type="javascript" src="//Microsoft.WinJS.1.0/js/base.js" shared="true" />
        /// <resource type="javascript" src="//Microsoft.WinJS.1.0/js/ui.js" shared="true" />
        /// <resource type="css" src="//Microsoft.WinJS.1.0/css/ui-dark.css" shared="true" />
        SemanticZoom: WinJS.Class.define(function SemanticZoom_ctor(element, options) {
            /// <signature helpKeyword="WinJS.UI.SemanticZoom.SemanticZoom">
            /// <summary locid="WinJS.UI.SemanticZoom.constructor">
            /// Creates a new SemanticZoom.
            /// </summary>
            /// <param name="element" domElement="true" locid="WinJS.UI.SemanticZoom.constructor_p:element">
            /// The DOM element that hosts the SemanticZoom.
            /// </param>
            /// <param name="options" type="object" locid="WinJS.UI.SemanticZoom.constructor_p:options">
            /// An object that contains one or more property/value pairs to apply to the new control.
            /// Each property of the options object corresponds to one of the control's properties or events. This parameter is optional.
            /// </param>
            /// <returns type="WinJS.UI.SemanticZoom" locid="WinJS.UI.SemanticZoom.constructor_returnValue">
            /// The new SemanticZoom control.
            /// </returns>
            /// </signature>

            var that = this;

            this._element = element;
            this._element.winControl = this;
            Utilities.addClass(this._element, semanticZoomClass);
            this._element.setAttribute("role", "ms-semanticzoomcontainer");
            var ariaLabel = this._element.getAttribute("aria-label");
            if (!ariaLabel) {
                this._element.setAttribute("aria-label", "");
            }

            options = options || {};
            this._zoomedOut = !!options.zoomedOut || !!options.initiallyZoomedOut || false;
            this._enableButton = true;
            if (options.enableButton !== undefined) {
                this._enableButton = !!options.enableButton;
            }

            this._element.setAttribute("aria-checked", this._zoomedOut.toString());
            this._zoomFactor = Utilities._clamp(options.zoomFactor, minZoomFactor, maxZoomFactor, defaultZoomFactor);

            var identity = function (item) { return item; };
            this._zoomedInItem = options.zoomedInItem || identity;
            this._zoomedOutItem = options.zoomedOutItem || identity;

            if (WinJS.validation) {
                if (options._zoomFactor && options._zoomFactor !== this._zoomFactor) {
                    throw new WinJS.ErrorFromName("WinJS.UI.SemanticZoom.InvalidZoomFactor", strings.invalidZoomFactor);
                }
            }

            this._locked = false;

            this._zoomInProgress = false;
            this._isBouncingIn = false;
            this._isBouncing = false;
            this._zooming = false;
            this._aligning = false;
            this._gesturing = false;
            this._gestureEnding = false;
            this._buttonShown = false;

            // Initialize the control

            this._initialize();
            this._configure();

            // Register event handlers

            this._element.attachEvent("onresize", onSemanticZoomResize);
            this._element.attachEvent("onpropertychange", onSemanticZoomPropertyChanged, false);
            this._element.addEventListener("mousewheel", this._onMouseWheel.bind(this), true);
            this._element.addEventListener("keydown", this._onKeyDown.bind(this), true);
            this._element.addEventListener("MSPointerDown", this._onPointerDown.bind(this), this._isListView);
            this._element.addEventListener("MSPointerMove", this._onPointerMove.bind(this), true);
            this._element.addEventListener("MSPointerOut", this._onPointerOut.bind(this), true);
            this._element.addEventListener("MSPointerCancel", this._onPointerCancel.bind(this), true);
            this._element.addEventListener("MSPointerUp", this._onPointerUp.bind(this), false);
            this._hiddenElement.addEventListener("MSGotPointerCapture", this._onGotPointerCapture.bind(this), false);
            this._hiddenElement.addEventListener("MSLostPointerCapture", this._onLostPointerCapture.bind(this), false);
            this._element.addEventListener("click", this._onClick.bind(this), true);
            this._canvasIn.addEventListener("transitionend", this._onCanvasTransitionEnd.bind(this), false);
            this._canvasOut.addEventListener("transitionend", this._onCanvasTransitionEnd.bind(this), false);
            this._resetPointerRecords();

            // Get going
            this._onResizeImpl();

            WinJS.UI._setOptions(this, options, true);

            // Present the initial view
            setImmediate(function () {
                that._setVisibility();
            });
        }, {
            // Public members

            /// <field type="HTMLElement" domElement="true" hidden="true" locid="WinJS.UI.SemanticZoom.element" helpKeyword="WinJS.UI.SemanticZoom.element">
            /// The DOM element that hosts the SemanticZoom control.
            /// </field>
            element: {
                get: function () {
                    return this._element;
                }
            },

            /// <field type="Boolean" locid="WinJS.UI.SemanticZoom.enableButton" helpKeyword="WinJS.UI.SemanticZoom.enableButton">
            /// Gets or sets a value that specifies whether the semantic zoom button should be displayed or not
            /// </field>
            enableButton: {
                get: function () {
                    return this._enableButton;
                },
                set: function (value) {
                    var newValue = !!value;
                    if (this._enableButton !== newValue) {
                        this._enableButton = newValue;
                        if (newValue) {
                            this._createSemanticZoomButton();
                        } else {
                            this._removeSemanticZoomButton();
                        }
                    }
                }
            },

            /// <field type="Boolean" locid="WinJS.UI.SemanticZoom.zoomedOut" helpKeyword="WinJS.UI.SemanticZoom.zoomedOut">
            /// Gets or sets a value that specifies whether the zoomed out view is currently displayed.
            /// </field>
            zoomedOut: {
                get: function () {
                    return this._zoomedOut;
                },
                set: function (value) {
                    this._zoom(!!value, { x: 0.5 * this._sezoClientWidth, y : 0.5 * this._sezoClientHeight }, false);
                }
            },

            /// <field type="Number" locid="WinJS.UI.SemanticZoom.zoomFactor" helpKeyword="WinJS.UI.SemanticZoom.zoomFactor" minimum="0.2" maximum="0.8">
            /// Gets or sets a value between 0.2 and 0.85 that specifies the scale of the zoomed out view. The default is 0.65.
            /// </field>
            zoomFactor: {
                get: function () {
                    return this._zoomFactor;
                },
                set: function (value) {
                    var oldValue = this._zoomFactor;
                    var newValue = Utilities._clamp(value, minZoomFactor, maxZoomFactor, defaultZoomFactor);
                    if (oldValue !== newValue) {
                        this._zoomFactor = newValue;
                        this._onResize();
                    }
                }
            },

            /// <field type="Boolean" locid="WinJS.UI.SemanticZoom.locked" helpKeyword="WinJS.UI.SemanticZoom.locked">
            /// Gets or sets a value that indicates whether SemanticZoom is locked and zooming between views is disabled.
            /// </field>
            locked: {
                get: function () {
                    return this._locked;
                },
                set: function (value) {
                    this._locked = !!value;
                }
            },

            forceLayout: function () {
                /// <signature helpKeyword="WinJS.UI.SemanticZoom.forceLayout">
                /// <summary locid="WinJS.UI.SemanticZoom.forceLayout">
                /// Forces the SemanticZoom to update its layout. Use this function when making the SemanticZoom visible again
                /// after its style.display property had been set to "none".
                /// </summary>
                /// </signature>
                this._onResizeImpl();
            },

            // Private members

            _initialize: function () {
                // initialize the semantic zoom, parent the child controls

                // Zoomed in and zoomed out controls must be on the first two child elements

                var children = Utilities.children(this._element);
                this._elementIn = children[0];
                this._elementOut = children[1];

                // Ensure the child controls have the same height as the SemanticZoom element

                this._elementIn.style.height = this._elementOut.style.height = this._element.offsetHeight + "px";

                // Create the child controls if they haven't been created already

                UI.processAll(this._elementIn);
                UI.processAll(this._elementOut);

                this._viewIn = this._elementIn.winControl.zoomableView;
                this._viewOut = this._elementOut.winControl.zoomableView;
                this._elementInIsListView = this._elementIn.winControl instanceof WinJS.UI.ListView;
                this._elementOutIsListView = this._elementOut.winControl instanceof WinJS.UI.ListView;
                this._isListView = this._elementInIsListView && this._elementOutIsListView;

                // Remove the children and place them beneath new divs that will serve as canvases and viewports

                this._element.removeChild(this._elementOut);
                this._element.removeChild(this._elementIn);
                this._element.innerHTML = "";
                this._cropViewport = document.createElement("div");
                this._element.appendChild(this._cropViewport);
                this._viewportIn = document.createElement("div");
                this._viewportOut = document.createElement("div");
                this._cropViewport.appendChild(this._viewportIn);
                this._cropViewport.appendChild(this._viewportOut);

                this._canvasIn = document.createElement("div");
                this._canvasOut = document.createElement("div");
                this._viewportIn.appendChild(this._canvasIn);
                this._viewportOut.appendChild(this._canvasOut);
                this._canvasIn.appendChild(this._elementIn);
                this._canvasOut.appendChild(this._elementOut);

                if (this._enableButton) {
                    this._createSemanticZoomButton();
                } 
                
                this._hiddenElement = document.createElement("div");
                this._hiddenElement.tabIndex = -1;
                this._hiddenElement.visibility = "hidden";
                this._hiddenElement.setAttribute("aria-hidden", "true");
                this._element.appendChild(this._hiddenElement);

                this._setLayout(this._element, "relative", "hidden");
                this._setLayout(this._cropViewport, "absolute", "hidden");
                this._setLayout(this._viewportIn, "absolute", "hidden");
                this._setLayout(this._viewportOut, "absolute", "hidden");
                this._setLayout(this._canvasIn, "absolute", "hidden");
                this._setLayout(this._canvasOut, "absolute", "hidden");


                this._elementIn.style.position = "absolute";
                this._elementOut.style.position = "absolute";
            },

            _createSemanticZoomButton: function () {
                this._sezoButton = document.createElement("button");
                this._sezoButton.className = sezoButtonClass + " " + sezoButtonLocationClass + " " + (this._rtl() ? "rtl" : "ltr");
                this._sezoButton.tabIndex = -1;
                this._sezoButton.style.visibility = "hidden";
                this._element.appendChild(this._sezoButton);

                //register the appropriate events for display the sezo button
                this._sezoButton.addEventListener("click", this._onSeZoButtonZoomOutClick.bind(this), false);
                this._element.addEventListener("scroll", this._onSeZoChildrenScroll.bind(this), true);
                this._element.addEventListener("MSPointerHover", this._onPenHover.bind(this), false);
            },

            _removeSemanticZoomButton: function () {
                if (this._sezoButton) {
                    this._element.removeChild(this._sezoButton);
                    this._sezoButton = null;
                }
            },

            _configure: function () {
                // Configure the controls for zooming
                var axisIn = this._viewIn.getPanAxis(),
                    axisOut = this._viewOut.getPanAxis();
                this._pansHorizontallyIn = (axisIn === "horizontal" || axisIn === "both");
                this._pansVerticallyIn = (axisIn === "vertical" || axisIn === "both");
                this._pansHorizontallyOut = (axisOut === "horizontal" || axisOut === "both");
                this._pansVerticallyOut = (axisOut === "vertical" || axisOut === "both");

                if (this._zoomInProgress) {
                    return;
                }

                var pagesToPrefetchIn = 1 / this._zoomFactor - 1,
                    pagesToPrefetchOut = bounceFactor - 1;

                this._setLayout(this._elementIn, "absolute", "visible");
                this._setLayout(this._elementOut, "absolute", "visible");
                this._viewIn.configureForZoom(false, !this._zoomedOut, this._zoomFromCurrent.bind(this, true), pagesToPrefetchIn);
                this._viewOut.configureForZoom(true, this._zoomedOut, this._zoomFromCurrent.bind(this, false), pagesToPrefetchOut);
                this._pinching = false;
                this._pinchGesture = 0;
                this._canvasLeftIn = 0;
                this._canvasTopIn = 0;
                this._canvasLeftOut = 0;
                this._canvasTopOut = 0;

                // Set scales and opacity
                if (this._zoomedOut) {
                    scaleElement(this._canvasIn, this._zoomFactor);
                } else {
                    scaleElement(this._canvasOut, 1 / this._zoomFactor);
                }
 
                var styleViewportIn = this._viewportIn.style,
                    styleViewportOut = this._viewportOut.style,
                    styleCanvasIn = this._canvasIn.style,
                    styleCanvasOut = this._canvasOut.style;

                styleCanvasIn.opacity = (this._zoomedOut ? 0 : 1);
                styleCanvasOut.opacity = (this._zoomedOut ? 1 : 0);

                // Enable animation
                if (WinJS.UI.isAnimationEnabled()) {
                    styleViewportIn["transition-property"] = "transform";
                    styleViewportIn["transition-duration"] = "0s";
                    styleViewportIn["transition-timing-function"] = "linear";

                    styleViewportOut["transition-property"] = "transform";
                    styleViewportOut["transition-duration"] = "0s";
                    styleViewportOut["transition-timing-function"] = "linear";
                }
            },

            _onPropertyChanged: function (ev) {
                if (ev.propertyName === "aria-checked") {
                    var newValue = this._element.getAttribute("aria-checked");
                    var zoomedOut = newValue === "true";
                    if (this._zoomedOut !== zoomedOut) {
                        var that = this;
                        setImmediate(function () {
                            that.zoomedOut = zoomedOut;
                        });
                    }
                }
            },

            _onResizeImpl: function () {
                this._resizing = this._resizing || 0;
                this._resizing++;
                try {
                    var positionElement = function (element, left, top, width, height) {
                        var style = element.style;
                        style.left = left + "px";
                        style.top = top + "px";
                        style.width = width + "px";
                        style.height = height + "px";
                    };

                    var sezoComputedStyle = window.getComputedStyle(this._element, null),
                        sezoPaddingLeft = getDimension(this._element, sezoComputedStyle["paddingLeft"]),
                        sezoPaddingRight = getDimension(this._element, sezoComputedStyle["paddingRight"]),
                        sezoPaddingTop = getDimension(this._element, sezoComputedStyle["paddingTop"]),
                        sezoPaddingBottom = getDimension(this._element, sezoComputedStyle["paddingBottom"]),
                        viewportWidth = this._element.clientWidth - sezoPaddingLeft - sezoPaddingRight,
                        viewportHeight = this._element.clientHeight - sezoPaddingTop - sezoPaddingBottom,
                        scaleFactor = 1 / this._zoomFactor;

                    
                    if (this._viewportWidth === viewportWidth && this._viewportHeight === viewportHeight) {
                        return;
                    }
                    this._sezoClientHeight = this._element.clientHeight;
                    this._sezoClientWidth = this._element.clientWidth;
                    this._viewportWidth = viewportWidth;
                    this._viewportHeight = viewportHeight;
                    
                    this._configure();

                    var multiplierIn = 2 * scaleFactor - 1,
                        canvasInWidth = Math.min(canvasSizeMax, (this._pansHorizontallyIn ? multiplierIn : 1) * viewportWidth),
                        canvasInHeight = Math.min(canvasSizeMax, (this._pansVerticallyIn ? multiplierIn : 1) * viewportHeight);

                    this._canvasLeftIn = 0.5 * (canvasInWidth - viewportWidth);
                    this._canvasTopIn = 0.5 * (canvasInHeight - viewportHeight);
                    positionElement(this._cropViewport, sezoPaddingLeft, sezoPaddingTop, viewportWidth, viewportHeight);
                    positionElement(this._viewportIn, 0, 0, viewportWidth, viewportHeight);
                    positionElement(this._canvasIn, -this._canvasLeftIn, -this._canvasTopIn, canvasInWidth, canvasInHeight);
                    positionElement(this._elementIn, this._canvasLeftIn, this._canvasTopIn, viewportWidth, viewportHeight);

                    var multiplierOut = 2 * bounceFactor - 1,
                        canvasOutWidth = (this._pansHorizontallyOut ? multiplierOut : 1) * viewportWidth,
                        canvasOutHeight = (this._pansVerticallyOut ? multiplierOut : 1) * viewportHeight;

                    this._canvasLeftOut = 0.5 * (canvasOutWidth - viewportWidth);
                    this._canvasTopOut = 0.5 * (canvasOutHeight - viewportHeight);
                    positionElement(this._viewportOut, 0, 0, viewportWidth, viewportHeight);
                    positionElement(this._canvasOut, -this._canvasLeftOut, -this._canvasTopOut, canvasOutWidth, canvasOutHeight);
                    positionElement(this._elementOut, this._canvasLeftOut, this._canvasTopOut, viewportWidth, viewportHeight);
                } finally {
                    this._resizing--;
                }
            },

            _onResize: function () {
                this._onResizeImpl();
            },

            _onMouseMove: function (ev) {
                if (this._zooming ||
                     (!this._lastMouseX && !this._lastMouseY) ||
                     (ev.screenX === this._lastMouseX && ev.screenY === this._lastMouseY)) {
                    this._lastMouseX = ev.screenX;
                    this._lastMouseY = ev.screenY;
                    return;
                }

                if (Math.abs(ev.screenX - this._lastMouseX) <= sezoButtonMouseMoveThreshold &&
                    Math.abs(ev.screenY - this._lastMouseY) <= sezoButtonMouseMoveThreshold) {
                    return;
                }

                this._lastMouseX = ev.screenX;
                this._lastMouseY = ev.screenY;

                this._displayButton();
            },

            _displayButton: function () {
                clearTimeout(this._dismissButtonTimer);
                this._showSemanticZoomButton();

                var that = this;
                this._dismissButtonTimer = setTimeout(function () {
                    that._hideSemanticZoomButton();
                }, sezoButtonShowDuration);
            },

            _showSemanticZoomButton: function () {
                if (this._buttonShown) {
                    return;
                }

                if (this._sezoButton && !this._zoomedOut) {
                    WinJS.UI.Animation.fadeIn(this._sezoButton);
                    this._sezoButton.style.visibility = "visible";
                }
                this._buttonShown = true;
            },

            _hideSemanticZoomButton: function (immediately) {
                if (!this._buttonShown) {
                    return;
                }

                if (this._sezoButton) {
                    if (!immediately) {
                        WinJS.UI.Animation.fadeOut(this._sezoButton);
                    }
                    this._sezoButton.style.visibility = "hidden";
                }
                this._buttonShown = false;
            },

            _onSeZoChildrenScroll: function (ev) {
                if (ev.target !== this.element) {
                    this._hideSemanticZoomButton(true);
                }
            },

            _onMouseWheel: function (ev) {
                if (ev.ctrlKey) {
                    this._zoom(ev.wheelDelta < 0, this._getPointerLocation(ev));

                    ev.stopPropagation();
                    ev.preventDefault();
                }
            },

            _onPenHover: function (ev) {
                if (ev.pointerType === PT_PEN) {
                    this._displayButton();
                }
            },

            _onSeZoButtonZoomOutClick: function (ev) {
                this._hideSemanticZoomButton();
                this._zoom(true, { x: 0.5 * this._sezoClientWidth, y : 0.5 * this._sezoClientHeight }, false);
            },

            _onKeyDown: function (ev) {
                var handled = false;

                if (ev.ctrlKey) {
                    var Key = Utilities.Key;

                    switch (ev.keyCode) {
                        case Key.add:
                        case Key.equal:
                            this._zoom(false);
                            handled = true;
                            break;

                        case Key.subtract:
                        case Key.dash:
                            this._zoom(true);
                            handled = true;
                            break;
                    }
                }

                if (handled) {
                    ev.stopPropagation();
                    ev.preventDefault();
                }
            },

            _createPointerRecord: function (ev) {
                var location = this._getPointerLocation(ev);

                var newRecord = {};
                newRecord.startX = newRecord.currentX = location.x;
                newRecord.startY = newRecord.currentY = location.y;

                this._pointerRecords[ev.pointerId] = newRecord;
                this._pointerCount = Object.keys(this._pointerRecords).length;

                return newRecord;
            },

            _deletePointerRecord: function (id) {
                var record = this._pointerRecords[id];

                delete this._pointerRecords[id];
                this._pointerCount = Object.keys(this._pointerRecords).length;

                if (this._pointerCount !== 2) {
                    this._pinching = false;
                }

                return record;
            },

            _handlePointerDown: function (ev) {
                this._createPointerRecord(ev);

                // When we get more than one pointer, we need to explicitly set msPointerCapture on every pointer we've got to the SemanticZoom.
                // This will fire lostCapture events on any descendant elements that had called setCapture earlier (for example, ListView items),
                // and let the hosted control know that the pointer is no longer under its control.
                var targetSurface = this._element;
                var contactKeys = Object.keys(this._pointerRecords);

                for (var i = 0, len = contactKeys.length; i < len; i++) {
                    try {
                        this._hiddenElement.msSetPointerCapture(contactKeys[i] | 0);
                    } catch (e) {
                        this._resetPointerRecords();
                        return;
                    }
                }


                ev.stopImmediatePropagation();
                ev.cancelBubble = true;
            },

            _handleFirstPointerDown: function (ev) {
                this._resetPointerRecords();
                this._createPointerRecord(ev);
                this._startedZoomedOut = this._zoomedOut;
            },

            // SeZo wants to prevent clicks while it is playing the bounce animation
            // This can happen when user try to pinch out on the zoomed out view
            // and lift the finger up on the same item
            _onClick: function (ev) {
                if (ev.srcElement !== this._element) {
                    if (this._isBouncing) {
                        ev.stopImmediatePropagation();
                    }
                }
            },

            // To optimize perf for ListView and to support more than 2 contact points
            // for custom control, we wire up pointerDown routine for listview during capture
            // but during bubbling phase for everythign else
            _onPointerDown: function (ev) {
                if (ev.pointerType !== PT_TOUCH) {
                    return;
                }

                if (this._pointerCount === 0) {
                    this._handleFirstPointerDown(ev);
                } else {
                    this._handlePointerDown(ev);
                }
            },

            // SemanticZoom uses MSPointerMove messages to recognize a pinch. It has to use pointer messages instead of GestureUpdate for a few reasons:
            // 1 - MSGestureUpdate events' scale property (the property that determines pinches) is based on a scalar value. We want our pinch threshold to be pixel based
            // 2 - MSGestureUpdate events' scale property doesn't work when multiple contacts are on multiple surfaces. When that happens .scale will always stay 1.0.
            _onPointerMove: function (ev) {
                if (ev.pointerType === PT_MOUSE || ev.pointerType === PT_PEN) {
                    this._onMouseMove(ev);
                    return;
                }

                if (ev.pointerType !== PT_TOUCH) {
                    return;
                }

                function distance(startX, startY, endX, endY) {
                    return Math.sqrt((endX - startX) * (endX - startX) + (endY - startY) * (endY - startY));
                }

                function midpoint(point1, point2) {
                    return {
                        x: (0.5 * (point1.currentX + point2.currentX)) | 0,
                        y: (0.5 * (point1.currentY + point2.currentY)) | 0
                    };
                }

                var pointerRecord = this._pointerRecords[ev.pointerId],
                    location = this._getPointerLocation(ev);

                // We listen to MSPointerDown on the bubbling phase of its event, but listen to MSPointerMove on the capture phase.
                // MSPointerDown can be stopped from bubbling if the underlying control doesn't want the SemanticZoom to interfere for whatever reason.
                // When that happens, we won't have a pointer record for the event we just got, so there's no sense in doing additional processing.
                if (!pointerRecord) {
                    return;
                }
                pointerRecord.currentX = location.x;
                pointerRecord.currentY = location.y;
                
                if (this._pointerCount === 2) {
                    this._pinching = true;

                    // The order in which these contacts are stored and retrieved from contactKeys is unimportant.  Any two points will suffice."
                    var contactKeys = Object.keys(this._pointerRecords),
                        point1 = this._pointerRecords[contactKeys[0]],
                        point2 = this._pointerRecords[contactKeys[1]];
                    this._currentMidPoint = midpoint(point1, point2);
                    var contactDistance = distance(point1.currentX, point1.currentY, point2.currentX, point2.currentY);
                    var that = this;
                    var processPinchGesture = function (zoomingOut) {
                        var pinchDirection = (zoomingOut ? PinchDirection.zoomedOut : PinchDirection.zoomedIn),
                            gestureReversed = (zoomingOut ? (that._pinchedDirection === PinchDirection.zoomedIn && !that._zoomingOut) : (that._pinchedDirection === PinchDirection.zoomedOut && that._zoomingOut)),
                            canZoomInGesturedDirection = (zoomingOut ? !that._zoomedOut : that._zoomedOut);
                        if (that._pinchedDirection === PinchDirection.none) {
                            if (canZoomInGesturedDirection) {
                                that._isBouncingIn = false;
                                that._zoom(zoomingOut, midpoint(point1, point2), true);
                                that._pinchedDirection = pinchDirection;
                            } else if (!that._isBouncingIn) {
                                that._playBounce(true, midpoint(point1, point2));
                            }
                        } else if (gestureReversed) {
                            var deltaFromStart = that._lastPinchDistance / that._lastPinchStartDistance;
                            var deltaFromLast = that._lastLastPinchDistance / that._lastPinchDistance;
                            if ((zoomingOut && deltaFromStart > zoomOutGestureDistanceChangeFactor) ||
                                (!zoomingOut && deltaFromLast > zoomInGestureDistanceChangeFactor)) {
                                that._zoom(zoomingOut, midpoint(point1, point2), true);
                                that._pinchedDirection = pinchDirection;
                            }
                        }

                    };
                    this._updatePinchDistanceRecords(contactDistance);
                    if (this._pinchDistanceCount >= pinchDistanceCount) {
                        if (!this._zooming && !this._isBouncing) {
                            msWriteProfilerMark("WinJS.UI.SemanticZoom:EndPinchDetection,info");
                            processPinchGesture(this._lastPinchDirection === PinchDirection.zoomedOut);
                        }
                    }
                        
                    // When two or more pointers are down, we want to hide all of their move events from the underlying view.
                    ev.stopImmediatePropagation();
                } else if (this._pointerCount > 2) {
                        // When more than two pointers are down, we're not going to interpret that as a pinch, so we reset the distance we'd recorded when it was
                        // just two pointers down.
                    this._resetPinchDistanceRecords();
                    ev.stopImmediatePropagation();
                }
                
                // If the pointerCount isn't 2, we're no longer making a pinch. This generally happens if you try pinching, find you can't zoom in the pinched direction,
                // then release one finger. When that happens we need to animate back to normal state.
                if (this._pointerCount !== 2 && this._isBouncingIn) {
                    this._playBounce(false);
                }
            },

            _onPointerOut: function (ev) {
                if (ev.pointerType !== PT_TOUCH || ev.srcElement !== this._element) {
                    return;
                }

                this._completePointerUp(ev);
            },

            _onPointerUp: function (ev) {
                this._releasePointerCapture(ev);
                this._completePointerUp(ev);
                this._completeZoomingIfTimeout();
            },

            _onPointerCancel: function (ev) {
                this._releasePointerCapture(ev);
                this._completePointerUp(ev);
                this._completeZoomingIfTimeout();
            },

            _onGotPointerCapture: function (ev) {
                var pointerRecord = this._pointerRecords[ev.pointerId];
                if (pointerRecord) {
                    pointerRecord.dirty = false;
                }
            },

            _onLostPointerCapture: function (ev) {
                var pointerRecord = this._pointerRecords[ev.pointerId];
                if (pointerRecord) {
                    // If we lose capture on an element, there are three things that could be happening:
                    // 1 - Independent Manipulations are taking over. If that's the case, we should be getting an MSManipulationStateChanged event soon.
                    // 2 - Capture is just moving around inside of the semantic zoom region. We should get a got capture event soon, so we'll want to preserve this record.
                    // 3 - Capture got moved outside of the semantic zoom region. We'll destroy the pointer record if this happens.
                    pointerRecord.dirty = true;
                    var that = this;
                    WinJS.Promise.timeout(eventTimeoutDelay).then(function () {
                        if (pointerRecord.dirty) {
                            // If the timeout completed and the record is still dirty, we can discard it
                            that._completePointerUp(ev);
                        }
                    });
                }
            },

            _updatePinchDistanceRecords: function (contactDistance) {
                var that = this;
                function updatePinchDirection(direction) {
                    if (that._lastPinchDirection === direction) {
                        that._pinchDistanceCount++;
                    } else {
                        that._pinchGesture++;
                        that._pinchDistanceCount = 0;
                        that._lastPinchStartDistance = contactDistance;
                    }
                    that._lastPinchDirection = direction;
                    that._lastPinchDistance = contactDistance;
                    that._lastLastPinchDistance = that._lastPinchDistance;
                }

                if (this._lastPinchDistance === -1) {
                    msWriteProfilerMark("WinJS.UI.SemanticZoom:StartPinchDetection,info");
                    this._lastPinchDistance = contactDistance;
                } else {
                    if (this._lastPinchDistance !== contactDistance) {
                        if (this._lastPinchDistance > contactDistance) {
                            updatePinchDirection(PinchDirection.zoomedOut);
                        } else {
                            updatePinchDirection(PinchDirection.zoomedIn);
                        }
                    }
                }
            },

            _zoomFromCurrent: function (zoomOut) {
                this._zoom(zoomOut, null, false, true);
            },

            _zoom: function (zoomOut, zoomCenter, gesture, centerOnCurrent) {
                msWriteProfilerMark("WinJS.UI.SemanticZoom:StartZoom(zoomOut=" + zoomOut + "),info");

                this._clearTimeout(this._completeZoomTimer);
                this._clearTimeout(this._TTFFTimer);

                this._hideSemanticZoomButton();
                this._resetPinchDistanceRecords();

                if (this._locked || this._gestureEnding) {
                    return;
                }

                if (this._zoomInProgress) {
                    if (this._gesturing === !gesture) {
                        return;
                    }

                    if (zoomOut !== this._zoomingOut) {
                        // Reverse the zoom that's currently in progress
                        this._startAnimations(zoomOut);
                    }
                } else if (zoomOut !== this._zoomedOut) {
                    this._zooming = true;
                    this._aligning = true;
                    this._gesturing = !!gesture;

                    if (zoomCenter) {	   
                        (zoomOut ? this._viewIn : this._viewOut).setCurrentItem(zoomCenter.x, zoomCenter.y);
                    }

                    this._zoomInProgress = true;

                    (zoomOut ? this._viewportOut : this._viewportIn).style.visibility = "visible";

                    this._viewIn.beginZoom();
                    this._viewOut.beginZoom();

                    // To simplify zoomableView implementations, only call getCurrentItem between beginZoom and endZoom
                    if (centerOnCurrent) {
                        var that = this;
                        (zoomOut ? this._viewIn : this._viewOut).getCurrentItem().then(function (current) {
                            var position = current.position;

                            // Pass in current item to avoid calling getCurrentItem again
                            that._prepareForZoom(zoomOut, {
                                x: that._rtl() ? (that._sezoClientWidth - position.left - 0.5 * position.width) : position.left + 0.5 * position.width,
                                y: position.top + 0.5 * position.height
                            }, WinJS.Promise.wrap(current));
                        });
                    } else {
                        this._prepareForZoom(zoomOut, zoomCenter || {});
                    }
                }
            },

            _prepareForZoom: function (zoomOut, zoomCenter, completedCurrentItem) {
                msWriteProfilerMark("WinJS.UI.SemanticZoom:prepareForZoom,StartTM");
                var that = this;
                var centerX = zoomCenter.x,
                    centerY = zoomCenter.y;
                   

                if (typeof centerX !== "number" || !this._pansHorizontallyIn || !this._pansHorizontallyOut) {
                    centerX = 0.5 * this._sezoClientWidth;
                }

                if (typeof centerY !== "number" || !this._pansVerticallyIn || !this._pansVerticallyOut) {
                    centerY = 0.5 * this._sezoClientHeight;
                }

                function setZoomCenters(adjustmentIn, adjustmentOut) {
                    that._canvasIn.style["transform-origin"] = (that._canvasLeftIn + centerX - adjustmentIn.x) + "px " + (that._canvasTopIn + centerY - adjustmentIn.y) + "px";
                    that._canvasOut.style["transform-origin"] = (that._canvasLeftOut + centerX - adjustmentOut.x) + "px " + (that._canvasTopOut + centerY - adjustmentOut.y) + "px";
                }

                setZoomCenters(origin, origin);

                this._alignViews(zoomOut, centerX, centerY, completedCurrentItem).then(function (adjustment) {
                    that._aligning = false;
                    that._gestureEnding = false;
                    if (!that._zooming && !that._gesturing) {
                        that._completeZoom();
                    }
                });

                this._zoomingOut = zoomOut;
                msWriteProfilerMark("WinJS.UI.SemanticZoom:prepareForZoom,StopTM");
                setImmediate(function () {
                    that._startAnimations(zoomOut);
                });
            },

            _alignViews: function (zoomOut, centerX, centerY, completedCurrentItem) {
                var multiplier = (1 - this._zoomFactor),
                    rtl = this._rtl(),
                    offsetLeft = multiplier * (rtl ? this._viewportWidth - centerX: centerX),
                    offsetTop = multiplier * centerY;

                var that = this;
                if (zoomOut) {
                    var item = completedCurrentItem || this._viewIn.getCurrentItem();
                    if (item) {
                        return item.then(function (current) {
                            var positionIn = current.position,
                            positionOut = {
                                left: positionIn.left * that._zoomFactor + offsetLeft,
                                top: positionIn.top * that._zoomFactor + offsetTop,
                                width: positionIn.width * that._zoomFactor,
                                height: positionIn.height * that._zoomFactor
                            };

                            return that._viewOut.positionItem(that._zoomedOutItem(current.item), positionOut);
                        });
                    }
                } else {
                    var item2 = completedCurrentItem || this._viewOut.getCurrentItem();
                    if (item2) {
                        return item2.then(function (current) {
                            var positionOut = current.position,
                            positionIn = {
                                left: (positionOut.left - offsetLeft) / that._zoomFactor,
                                top: (positionOut.top - offsetTop) / that._zoomFactor,
                                width: positionOut.width / that._zoomFactor,
                                height: positionOut.height / that._zoomFactor
                            };

                            return that._viewIn.positionItem(that._zoomedInItem(current.item), positionIn);
                        });
                    }
                }

                return new WinJS.Promise(function () { return { x: 0, y: 0 }; });
            },

            _startAnimations: function (zoomOut) {
                this._zoomingOut = zoomOut;

                if (WinJS.UI.isAnimationEnabled()) {
                    msWriteProfilerMark("WinJS.UI.SemanticZoom:ZoomAnimation,StartTM");
                    this._canvasIn.style["transition"] = (zoomOut ? outgoingElementTransition() : incomingElementTransition());
                    this._canvasOut.style["transition"] = (zoomOut ? incomingElementTransition() : outgoingElementTransition());
                }

                scaleElement(this._canvasIn, (zoomOut ? this._zoomFactor : 1));
                scaleElement(this._canvasOut, (zoomOut ? 1 : 1 / this._zoomFactor));
                this._canvasIn.style.opacity = (zoomOut ? 0 : 1);
                this._canvasOut.style.opacity = (zoomOut ? 1 : 0);

                if (!WinJS.UI.isAnimationEnabled()) {
                    this._zooming = false;
                    this._completeZoom();
                } else {
                    this.setTimeoutAfterTTFF(this._onZoomAnimationComplete.bind(this), zoomAnimationDuration);
                }
            },

            _onBounceAnimationComplete: function () {
                if (!this._isBouncingIn) {
                    this._completeZoom();
                }
            },

            _onZoomAnimationComplete: function () {
                    msWriteProfilerMark("WinJS.UI.SemanticZoom:ZoomAnimation,StopTM");
                    this._zooming = false;
                    if (!this._aligning && !this._gesturing && !this._gestureEnding) {
                        this._completeZoom();
                    }
            },

            _onCanvasTransitionEnd: function (ev) {
                if ((ev.srcElement === this._canvasOut || ev.srcElement === this._canvasIn) && this._isBouncing) {
                    this._onBounceAnimationComplete();
                    return;
                }

                if (ev.srcElement === this._canvasIn && ev.propertyName === "transform") {
                    this._onZoomAnimationComplete();
                }
            },

            _clearTimeout: function (timer) {
                if (timer) {
                    clearTimeout(timer);
                }
            },

            _completePointerUp: function (ev) {
                var id = ev.pointerId;
                var pointerRecord = this._pointerRecords[id];
                if (pointerRecord) {
                    this._deletePointerRecord(id);
                    if (this._isBouncingIn) {
                        this._playBounce(false);
                    }


                    if (this._pointerCount === 0) {
                        // if we are not zooming and if there's any single pending pinch gesture detected that's not being triggered (fast pinch), process them now
                        if (this._pinchGesture === 1 && !this._zooming && this._lastPinchDirection !== PinchDirection.none && this._pinchDistanceCount < pinchDistanceCount) {
                            this._zoom(this._lastPinchDirection === PinchDirection.zoomedOut, this._currentMidPoint, false);
                            this._pinchGesture = 0;
                            this._attemptRecordReset();
                            return;
                        }

                        if (this._pinchedDirection !== PinchDirection.none) {
                            this._gesturing = false;
                            if (!this._aligning && !this._zooming) {
                                this._completeZoom();
                            }
                        }
                        this._pinchGesture = 0;
                        this._attemptRecordReset();
                    }
                }
            },

            setTimeoutAfterTTFF: function (callback, delay) {
                var that = this;
                that._TTFFTimer = setTimeout(function () {
                    that._TTFFTimer = setTimeout(callback, delay);
                }, zoomAnimationTTFFBuffer);
            },

            _completeZoomingIfTimeout: function () {
                if (this._pointerCount !== 0) {
                    return;
                }

                var that = this;
                if (this._zoomInProgress || this._isBouncing) {
                    that._completeZoomTimer = setTimeout(function () {
                           that._completeZoom();
                    }, zoomAnimationTimeout);
                }
            },

            _completeZoom: function () {
                if (this._isBouncing) {
                    if (this._zoomedOut) {
                        this._viewOut.endZoom(true);
                    } else {
                        this._viewIn.endZoom(true);
                    }
                    this._isBouncing = false;
                    return;
                }


                if (!this._zoomInProgress) {
                    return;
                }

                msWriteProfilerMark("WinJS.UI.SemanticZoom:CompleteZoom,info");

                this._clearTimeout(this._completeZoomTimer);
                this._clearTimeout(this._TTFFTimer);

                this._gestureEnding = false;

                this._viewIn.endZoom(!this._zoomingOut);
                this._viewOut.endZoom(this._zoomingOut);

                this._zoomInProgress = false;

                var zoomChanged = false;
                if (this._zoomingOut !== this._zoomedOut) {
                    this._zoomedOut = !!this._zoomingOut;
                    this._element.setAttribute("aria-checked", this._zoomedOut.toString());
                    zoomChanged = true;
                }

                this._setVisibility();

                if (zoomChanged) {
                    // Dispatch the zoomChanged event
                    var ev = document.createEvent("CustomEvent");
                    ev.initCustomEvent(zoomChangedEvent, true, true, this._zoomedOut);
                    this._element.dispatchEvent(ev);

                    if (this._isActive) {
                        // If the element is no longer a valid focus target, it will throw, we
                        // simply won't do anything in this case
                        try {
                            (this._zoomedOut ? this._elementOut : this._elementIn).setActive();
                        } catch (e) {}
                    }
                }

                msWriteProfilerMark("WinJS.UI.SemanticZoom:CompleteZoom_Custom,info");
            },

            _isActive: function () {
                var element = document.activeElement;
                while ((element = element.parentElement)) {
                    if (element === this._element) {
                        return true;
                    }
                }
                return false;
            },

            _setLayout: function (element, position, overflow) {
                var style = element.style;
                style.position = position;
                style.overflow = overflow;
            },

            _setVisibility: function () {
                function setVisibility(element, isVisible) {
                    element.style.visibility = (isVisible ? "visible" : "hidden");
                }
                setVisibility(this._viewportIn, !this._zoomedOut);
                setVisibility(this._viewportOut, this._zoomedOut);
            },

            _resetPointerRecords: function () {
                this._pinchedDirection = PinchDirection.none;
                this._pointerCount = 0;
                this._pointerRecords = {};
                this._resetPinchDistanceRecords();
            },

            _releasePointerCapture: function (ev) {
                var id = ev.pointerId;
                try {
                    // Release the pointer capture since they are going away, to allow in air touch pointers 
                    // to be reused for multiple interactions
                    this._hiddenElement.msReleasePointerCapture(id);
                } catch (e) {
                    // This can throw if the pointer was not already captured
                }
            },

            _attemptRecordReset: function () {
                if (this._recordResetPromise) {
                    this._recordResetPromise.cancel();
                }

                var that = this;
                this._recordResetPromise = WinJS.Promise.timeout(eventTimeoutDelay).then(function () {
                    if (that._pointerCount === 0) {
                        that._resetPointerRecords();
                        that._recordResetPromise = null;
                    }
                });
            },

            _resetPinchDistanceRecords: function () {
                this._lastPinchDirection = PinchDirection.none;
                this._lastPinchDistance = -1;
                this._lastLastPinchDistance = -1;
                this._pinchDistanceCount = 0;
                this._currentMidPoint = null;
            },

            _getPointerLocation: function (ev) {
                // Get pointer location returns co-ordinate in the sezo control co-ordinate space
                var sezoBox = { left: 0, top: 0 };
                try {
                    sezoBox = this._element.getBoundingClientRect();
                }
                catch (err) { }  // an exception can be thrown if SeZoDiv is no longer available

                var sezoComputedStyle = window.getComputedStyle(this._element, null),
                    sezoPaddingLeft = getDimension(this._element, sezoComputedStyle["paddingLeft"]),
                    sezoPaddingTop = getDimension(this._element, sezoComputedStyle["paddingTop"]),
                    sezoBorderLeft = getDimension(this._element, sezoComputedStyle["borderLeftWidth"]);

                return {
                    x: +ev.clientX === ev.clientX ? (ev.clientX - sezoBox.left - sezoPaddingLeft - sezoBorderLeft) : 0,
                    y: +ev.clientY === ev.clientY ? (ev.clientY - sezoBox.top - sezoPaddingTop - sezoPaddingTop) : 0
                };
            },

            _playBounce: function (beginBounce, center) {
                if (!WinJS.UI.isAnimationEnabled()) {
                    return;
                }

                if (this._isBouncingIn === beginBounce) {
                    return;
                }

                this._clearTimeout(this._completeZoomTimer);
                this._clearTimeout(this._TTFFTimer);
                this._isBouncing = true;
                this._isBouncingIn = beginBounce;
                if (beginBounce) {
                    this._bounceCenter = center;
                } else {
                    this._aligned = true;
                }

                var targetElement = (this._zoomedOut ? this._canvasOut : this._canvasIn);
                var adjustmentX = (this._zoomedOut ? this._canvasLeftOut : this._canvasLeftIn);
                var adjustmentY = (this._zoomedOut ? this._canvasTopOut : this._canvasTopIn);
                targetElement.style["transform-origin"] = (adjustmentX + this._bounceCenter.x) + "px " + (adjustmentY + this._bounceCenter.y) + "px";
                targetElement.style["transition"] = beginBounce ? bounceInTransition() : bounceBackTransition();

                if (!this._zoomedOut) {
                    this._viewIn.beginZoom();
                } else {
                    this._viewOut.beginZoom();
                }

                var scale = (beginBounce ? (this._zoomedOut ? 2 - bounceFactor : bounceFactor) : 1);

                scaleElement(targetElement, scale);

                this.setTimeoutAfterTTFF(this._onBounceAnimationComplete.bind(this), zoomAnimationDuration);
            },

            _rtl: function () {
                return window.getComputedStyle(this._element, null).direction === "rtl";
            },

            _pinching: {
                set: function (value) {
                    if (this._elementInIsListView) {
                        this._elementIn.winControl._pinching = value;
                    }

                    if (this._elementOutIsListView) {
                        this._elementOut.winControl._pinching = value;
                    }
                }
            }
        })
    });

    // The Semantic Zoom processes its own descendents
    UI.SemanticZoom.isDeclarativeControlContainer = true;

    WinJS.Class.mix(WinJS.UI.SemanticZoom, WinJS.Utilities.createEventProperties("zoomchanged"));
    WinJS.Class.mix(WinJS.UI.SemanticZoom, WinJS.UI.DOMEventMixin);


})(this);

/// <dictionary>animatable,appbar,appbars,divs,Flyout,Flyouts,iframe,Statics,unfocus,unselectable</dictionary>
(function overlayInit(WinJS) {
    "use strict";

    var thisWinUI = WinJS.UI;
    var utilities = thisWinUI.Utilities;

    // Class Names
    var overlayClass   = "win-overlay";
    var hideFocusClass = "win-hidefocus";   // Prevents the element from showing a focus rect

    // Helper to get DOM elements from input single object or array or IDs/toolkit/dom elements
    function _resolveElements(elements) {
        // No input is just an empty array
        if (!elements) {
            return [];
        }

        // Make sure it's in array form.
        if (typeof elements === "string" || !elements || !elements.length) {
            elements = [elements];
        }

        // Make sure we have a DOM element for each one, (could be string id name or toolkit object)
        var i,
            realElements = [];
        for (i = 0; i < elements.length; i++) {
            if (elements[i]) {
                if (typeof elements[i] === "string") {
                    var element = document.getElementById(elements[i]);
                    if (element) {
                        realElements.push(element);
                    }
                } else if (elements[i].element) {
                    realElements.push(elements[i].element);
                } else {
                    realElements.push(elements[i]);
                }
            }
        }

        return realElements;
    }

    // Helpers for keyboard showing related events
    function _allOverlaysCallback(event, command) {
        var elements = document.querySelectorAll("." + overlayClass);
        if (elements) {
            var len = elements.length;
            for (var i = 0; i < len; i++) {
                var element = elements[i];
                var control = element.winControl;
                if (control) {
                    control[command](event);
                }
            }
        }
    }
    
    WinJS.Namespace.define("WinJS.UI", {
        _Overlay: WinJS.Class.define(
        function _Overlay_ctor(element, options) {
            /// <signature helpKeyword="WinJS.UI._Overlay">
            /// <summary locid="WinJS.UI._Overlay">
            /// Constructs the Overlay control and associates it with the underlying DOM element.
            /// </summary>
            /// <param name="element" type="HTMLElement" domElement="true" locid="WinJS.UI._Overlay_p:element">
            /// The DOM element to be associated with the Overlay control.
            /// </param>
            /// <param name="options" type="Object" domElement="false" locid="WinJS.UI._Overlay_p:options">
            /// The set of options to be applied initially to the Overlay control.
            /// </param>
            /// <returns type="WinJS.UI._Overlay" locid="WinJS.UI._Overlay_returnValue">A fully constructed Overlay control.</returns>
            /// </signature>
            this._baseOverlayConstructor(element, options);
        }, {
            // Command Animations to Queue
            _queuedToShow: [],
            _queuedToHide: [],
            _queuedCommandAnimation: false,

            // Functions/properties
            _baseOverlayConstructor: function (element, options) {
                // Make sure there's an input element
                if (!element) {
                    element = document.createElement("div");
                }

                // Check to make sure we weren't duplicated
                var overlay = element.winControl;
                if (overlay) {
                    throw new WinJS.ErrorFromName("WinJS.UI._Overlay.DuplicateConstruction", strings.duplicateConstruction);
                }

                this._element = element;
                this._sticky = false;
                this._doNext = "";
                
                this._element.style.visibility = "hidden";
                this._element.style.opacity = 0;

                // Remember ourselves
                element.winControl = this;

                // Attach our css class
                WinJS.Utilities.addClass(this._element, overlayClass);

                // We don't want to be selectable, set UNSELECTABLE
                var unselectable = this._element.getAttribute("unselectable");
                if (unselectable === null || unselectable === undefined) {
                    this._element.setAttribute("unselectable", "on");
                }

                // Base animation is popIn/popOut
                this._currentAnimateIn = this._baseAnimateIn;
                this._currentAnimateOut = this._baseAnimateOut;

                if (options) {
                    WinJS.UI.setOptions(this, options);
                }
            },

            /// <field type="HTMLElement" domElement="true" readonly="true" hidden="true" locid="WinJS.UI._Overlay.element" helpKeyword="WinJS.UI._Overlay.element">The DOM element the Overlay is attached to</field>
            element: {
                get: function () {
                    return this._element;
                }
            },

            /// <field type="Boolean" locid="WinJS.UI._Overlay.disabled" helpKeyword="WinJS.UI._Overlay.disabled">Disable an Overlay, setting or getting the HTML disabled attribute.  When disabled the Overlay will no longer display with show(), and will hide if currently visible.</field>
            disabled: {
                get: function () {
                    // Ensure it's a boolean because we're using the DOM element to keep in-sync
                    return !!this._element.disabled;
                },
                set: function (value) {
                    // Force this check into a boolean because our current state could be a bit confused since we tie to the DOM element
                    value = !!value;
                    var oldValue = !!this._element.disabled;
                    if (oldValue !== value) {
                        this._element.disabled = value;
                        if (!this.hidden && this._element.disabled) {
                            this._hideOrDismiss();
                        }
                    }
                }
            },

            show: function () {
                /// <signature helpKeyword="WinJS.UI._Overlay.show">
                /// <summary locid="WinJS.UI._Overlay.show">
                /// Shows the Overlay, if hidden, regardless of other state
                /// </summary>
                /// </signature>
                // call private show to distinguish it from public version
                this._show();
            },

            _show: function() {
                // We call our base _baseShow because AppBar may need to override show
                this._baseShow();
            },

            hide: function () {
                /// <signature helpKeyword="WinJS.UI._Overlay.hide">
                /// <summary locid="WinJS.UI._Overlay.hide">
                /// Hides the Overlay, if visible, regardless of other state
                /// </summary>
                /// </signature>
                // call private hide to distinguish it from public version
                this._hide();
            },

            _hide: function() {
                // We call our base _baseHide because AppBar may need to override hide
                this._baseHide();
            },

            // Is the overlay "hidden"?
            /// <field type="Boolean" hidden="true" locid="WinJS.UI._Overlay.hidden" helpKeyword="WinJS.UI._Overlay.hidden">Read only, true if an overlay is currently not visible.</field>
            hidden: {
                get: function () {
                    return (this._element.style.visibility === "hidden" ||
                            this._element.winAnimating === "hiding" ||
                            this._doNext === "hide" || 
                            this._fakeHide);
                }
            },

            addEventListener: function (type, listener, useCapture) {
                /// <signature helpKeyword="WinJS.UI._Overlay.addEventListener">
                /// <summary locid="WinJS.UI._Overlay.addEventListener">
                /// Add an event listener to the DOM element for this Overlay
                /// </summary>
                /// <param name="type" type="String" locid="WinJS.UI._Overlay.addEventListener_p:type">Required. Event type to add, "beforehide", "afterhide", "beforeshow", or "aftershow"</param>
                /// <param name="listener" type="Function" locid="WinJS.UI._Overlay.addEventListener_p:listener">Required. The event handler function to associate with this event.</param>
                /// <param name="useCapture" type="Boolean" locid="WinJS.UI._Overlay.addEventListener_p:useCapture">Optional. True, register for the event capturing phase.  False for the event bubbling phase.</param>
                /// </signature>
                return this._element.addEventListener(type, listener, useCapture);
            },

            removeEventListener: function (type, listener, useCapture) {
                /// <signature helpKeyword="WinJS.UI._Overlay.removeEventListener">
                /// <summary locid="WinJS.UI._Overlay.removeEventListener">
                /// Remove an event listener to the DOM element for this Overlay
                /// </summary>
                /// <param name="type" type="String" locid="WinJS.UI._Overlay.removeEventListener_p:type">Required. Event type to remove, "beforehide", "afterhide", "beforeshow", or "aftershow"</param>
                /// <param name="listener" type="Function" locid="WinJS.UI._Overlay.removeEventListener_p:listener">Required. The event handler function to associate with this event.</param>
                /// <param name="useCapture" type="Boolean" locid="WinJS.UI._Overlay.removeEventListener_p:useCapture">Optional. True, register for the event capturing phase.  False for the event bubbling phase.</param>
                /// </signature>
                return this._element.removeEventListener(type, listener, useCapture);
            },

            _baseShow: function () {
                // If we are already animating, just remember this for later
                if (this._animating || this._keyboardShowing || this._keyboardHiding) {
                    this._doNext = "show";
                    return false;
                }

                // "hiding" would need to cancel.
                if (this._element.style.visibility !== "visible" || this._fakeHide) {
                    // Let us know we're showing.
                    this._element.winAnimating = "showing";

                    // Hiding, but not none
                    this._element.style.display = "";
                    if (!this._fakeHide) {
                        this._element.style.visibility = "hidden";
                    }

                    // In case their event is going to manipulate commands, see if there are
                    // any queued command animations we can handle while we're still hidden.
                    if (this._queuedCommandAnimation) {
                        this._showAndHideFast(this._queuedToShow, this._queuedToHide);
                        this._queuedToShow = [];
                        this._queuedToHide = [];
                    }

                    // Send our "beforeShow" event
                    this._sendEvent(thisWinUI._Overlay.beforeShow);

                    // Need to measure
                    this._findPosition();

                    // Make sure it's visible, and fully opaque.
                    // Do the popup thing, sending event afterward.
                    var that = this;
                    this._currentAnimateIn().
                    then(function () {
                        that._baseEndShow();
                    }, function (err) {
                        that._baseEndShow();
                    });
                    this._fakeHide = false;
                    return true;
                }
                return false;
            },

            // Flyout in particular will need to measure our positioning.
            _findPosition: function() {
            },

            _baseEndShow: function () {
                // Make sure it's visible after showing
                this._element.setAttribute("aria-hidden", "false");

                this._element.winAnimating = "";
                                
                // Do our derived classes show stuff
                this._endShow();

                // We're shown now
                if (this._doNext === "show") {
                    this._doNext = "";
                }

                // After showing, send the after showing event
                this._sendEvent(thisWinUI._Overlay.afterShow);

                // If we had something queued, do that
                var that = this;
                setImmediate(function () { that._checkDoNext(); });
            },

            _endShow: function () {
                // Nothing by default
            },

            _baseHide: function () {
                // If we are already animating, just remember this for later
                if (this._animating || this._keyboardShowing) {
                    this._doNext = "hide";
                    return false;
                }

                // In the unlikely event we're between the hiding keyboard and the resize events, just snap it away:
                if (this._keyboardHiding) {
                    // use the "uninitialized" flag
                    this._element.style.visibility = "";
                }

                // "showing" would need to queue up.
                if (this._element.style.visibility !== "hidden") {
                    // Let us know we're hiding, accessibility as well.
                    this._element.winAnimating = "hiding";
                    this._element.setAttribute("aria-hidden", "true");

                    // Send our "beforeHide" event
                    this._sendEvent(thisWinUI._Overlay.beforeHide);
                    
                    // If we our visibility is empty, then this is the first time, just hide it
                    if (this._element.style.visibility === "") {
                        // Initial hiding, just hide it
                        this._element.style.opacity = 0;
                        this._baseEndHide();
                    } else {
                        // Make sure it's hidden, and fully transparent.
                        var that = this;
                        this._currentAnimateOut().
                        then(function () {
                            that._baseEndHide();
                        }, function (err) {
                            that._baseEndHide();
                        });
                    }
                    return true;
                }
                this._fakeHide = false;

                return false;
            },

            _baseEndHide: function () {
                // Make sure animation is finished
                this._element.style.visibility = "hidden";
                this._element.style.display = "none";
                this._element.winAnimating = "";

                // In case their event is going to manipulate commands, see if there
                // are any queued command animations we can handle now we're hidden.
                if (this._queuedCommandAnimation) {
                    this._showAndHideFast(this._queuedToShow, this._queuedToHide);
                    this._queuedToShow = [];
                    this._queuedToHide = [];
                }

                // We're hidden now
                if (this._doNext === "hide") {
                    this._doNext = "";
                }

                // After hiding, send our "afterHide" event
                this._sendEvent(thisWinUI._Overlay.afterHide);

                // If we had something queued, do that.  This has to be after
                // the afterHide event in case it triggers a show() and they
                // have something to do in beforeShow that requires afterHide first.
                var that = this;
                setImmediate(function () { that._checkDoNext(); });
            },

            _checkDoNext: function () {
                // Do nothing if we're still animating
                if (this._animating || this._keyboardShowing || this._keyboardHiding) {
                    return;
                }

                if (this._doNext === "hide") {
                    // Do hide first because animating commands would be easier
                    this._hide();
                    this._doNext = "";
                } else if (this._queuedCommandAnimation) {
                    // Do queued commands before showing if possible
                    this._showAndHideQueue();
                } else if (this._doNext === "show") {
                    // Show last so that we don't unnecessarily animate commands
                    this._show();
                    this._doNext = "";
                }
            },

            // Default animations
            _baseAnimateIn: function () {
                this._element.style.opacity = 0;
                this._element.style.visibility = "visible";
                // touch opacity so that IE fades from the 0 we just set to 1
                window.getComputedStyle(this._element, null).opacity;
                return WinJS.UI.Animation.fadeIn(this._element);
            },

            _baseAnimateOut: function () {
                this._element.style.opacity = 1;
                // touch opacity so that IE fades from the 1 we just set to 0
                window.getComputedStyle(this._element, null).opacity;
                return WinJS.UI.Animation.fadeOut(this._element);
            },

            _animating: {
                get: function () {
                    // Ensure it's a boolean because we're using the DOM element to keep in-sync
                    return !!this._element.winAnimating;
                }
            },

            // Send one of our events
            _sendEvent: function (eventName) {                
                var event = document.createEvent("CustomEvent");
                event.initEvent(eventName, true, true, {});
                this._element.dispatchEvent(event);
            },

            // Show commands
            _showCommands: function (commands, immediate) {
                var showHide = this._resolveCommands(commands);
                this._showAndHideCommands(showHide.commands, [], immediate);
            },

            // Hide commands
            _hideCommands: function (commands, immediate) {
                var showHide = this._resolveCommands(commands);
                this._showAndHideCommands([], showHide.commands, immediate);
            },

            // Hide commands
            _showOnlyCommands: function (commands, immediate) {
                var showHide = this._resolveCommands(commands);
                this._showAndHideCommands(showHide.commands, showHide.others, immediate);
            },

            _showAndHideCommands: function (showCommands, hideCommands, immediate) {
                // Immediate is "easy"
                if (immediate || (this.hidden && !this._animating)) {
                    // Immediate mode (not animated)
                    this._showAndHideFast(showCommands, hideCommands);
                    // Need to remove them from queues, but others could be queued
                    this._removeFromQueue(showCommands, this._queuedToShow);
                    this._removeFromQueue(hideCommands, this._queuedToHide);
                } else {
                    // Queue Commands
                    this._updateAnimateQueue(showCommands, this._queuedToShow, this._queuedToHide);
                    this._updateAnimateQueue(hideCommands, this._queuedToHide, this._queuedToShow);
                }
            },

            _removeFromQueue: function (commands, queue) {
                // remove commands from queue.
                var count;
                for (count = 0; count < commands.length; count++) {
                    // Remove if it was in queue
                    var countQ;
                    for (countQ = 0; countQ < queue.length; countQ++) {
                        if (queue[countQ] === commands[count]) {
                            queue.splice(countQ, 1);
                            break;
                        }
                    }
                }
            },

            _updateAnimateQueue: function (addCommands, toQueue, fromQueue) {
                // Add addCommands to toQueue and remove addCommands from fromQueue.
                var count;
                for (count = 0; count < addCommands.length; count++) {
                    // See if it's already in toQueue
                    var countQ;
                    for (countQ = 0; countQ < toQueue.length; countQ++) {
                        if (toQueue[countQ] === addCommands[count]) {
                            break;
                        }
                    }
                    if (countQ === toQueue.length) {
                        // Not found, add it
                        toQueue[countQ] = addCommands[count];
                    }
                    // Remove if it was in fromQueue
                    for (countQ = 0; countQ < fromQueue.length; countQ++) {
                        if (fromQueue[countQ] === addCommands[count]) {
                            fromQueue.splice(countQ, 1);
                            break;
                        }
                    }
                }
                // If we haven't queued the actual animation
                if (!this._queuedCommandAnimation) {
                    // If not already animating, we'll need to call _checkDoNext
                    if (!this._animating) {
                        var that = this;
                        setImmediate(function () { that._checkDoNext(); });
                    }
                    this._queuedCommandAnimation = true;
                }
            },

            // show/hide commands without doing any animation.
            _showAndHideFast: function (showCommands, hideCommands) {
                var count;
                for (count = 0; count < showCommands.length; count++) {
                    if (showCommands[count] && showCommands[count].style) {
                        showCommands[count].style.visibility = "";
                        showCommands[count].style.display = "";
                    }
                }
                for (count = 0; count < hideCommands.length; count++) {
                    if (hideCommands[count] && hideCommands[count].style) {
                        hideCommands[count].style.visibility = "hidden";
                        hideCommands[count].style.display = "none";
                    }
                }
            },

            // show and hide the queued commands, perhaps animating if overlay isn't hidden.
            _showAndHideQueue: function () {
                // Only called if not currently animating.
                // We'll be done with the queued stuff when we return.
                this._queuedCommandAnimation = false;

                // Shortcut if hidden
                if (this.hidden) {
                    this._showAndHideFast(this._queuedToShow, this._queuedToHide);
                    // Might be something else to do
                    var that = this;
                    setImmediate(function () { that._checkDoNext(); });
                } else {
                    // Animation has 3 parts:  "hiding", "showing", and "moving"
                    // PVL has "addToList" and "deleteFromList", both of which allow moving parts.
                    // So we'll set up "add" for showing, and use "delete" for "hiding" + moving,
                    // then trigger both at the same time.
                    var showCommands = this._queuedToShow;
                    var hideCommands = this._queuedToHide;
                    var siblings = this._findSiblings(showCommands.concat(hideCommands));

                    // Don't animate ones that don't need animated
                    var count;
                    for (count = 0; count < showCommands.length; count++) {
                        // If this one's not real or not attached, skip it
                        if (!showCommands[count] ||
                            !showCommands[count].style ||
                            !document.body.contains(showCommands[count])) {
                            // Not real, skip it
                            showCommands.splice(count, 1);
                            count--;
                        } else if (showCommands[count].style.visibility !== "hidden" && showCommands[count].style.opacity !== "0") {
                            // Don't need to animate this one, already visible, so now it's a sibling
                            siblings.push(showCommands[count]);
                            showCommands.splice(count, 1);
                            count--;
                        }
                    }
                    for (count = 0; count < hideCommands.length; count++) {
                        // If this one's not real or not attached, skip it
                        if (!hideCommands[count] ||
                            !hideCommands[count].style ||
                            !document.body.contains(hideCommands[count]) ||
                            hideCommands[count].style.visibility === "hidden" ||
                            hideCommands[count].style.opacity === "0") {
                            // Don't need to animate this one, not real, or it's hidden,
                            // so don't even need it as a sibling.
                            hideCommands.splice(count, 1);
                            count--;
                        }
                    }

                    // Now we have the show, hide & siblings lists
                    var showAnimated = null,
                        hideAnimated = null;

                    // Hide commands first, with siblings if necessary, 
                    // so that the showing commands don't disrupt the hiding commands position.
                    if (hideCommands.length > 0) {
                        hideAnimated = WinJS.UI.Animation.createDeleteFromListAnimation(hideCommands, showCommands.length === 0 ? siblings : undefined);
                    }
                    if (showCommands.length > 0) {
                        showAnimated = WinJS.UI.Animation.createAddToListAnimation(showCommands, siblings);
                    }

                    // Update hiding commands
                    for (count = 0; count < hideCommands.length; count++) {
                        // Need to fix our position
                        var rectangle = hideCommands[count].getBoundingClientRect(),
                            style = window.getComputedStyle(hideCommands[count]);

                        // Use the bounding box, adjusting for margins
                        hideCommands[count].style.top = (rectangle.top - parseFloat(style.marginTop)) + "px";
                        hideCommands[count].style.left = (rectangle.left - parseFloat(style.marginLeft)) + "px";
                        hideCommands[count].style.opacity = 0;
                        hideCommands[count].style.position = "fixed";
                    }

                    // Mark as animating
                    this._element.winAnimating = "rearranging";

                    // Start hiding animations
                    // Hide needs extra cleanup when done
                    var promise = null;
                    if (hideAnimated) {
                        promise = hideAnimated.execute();
                    }

                    // Update showing commands,
                    // After hiding commands so that the hiding ones fade in the right place.
                    for (count = 0; count < showCommands.length; count++) {
                        showCommands[count].style.visibility = "";
                        showCommands[count].style.display = "";
                        showCommands[count].style.opacity = 1;
                    }

                    // Start showing animations
                    if (showAnimated) {
                        var newPromise = showAnimated.execute();
                        if (promise) {
                            promise = WinJS.Promise.join([promise, newPromise]);
                        } else {
                            promise = newPromise;
                        }
                    }

                    // Hook end animations
                    var that = this;
                    if (promise) {
                        // Needed to animate
                        promise.done(function () { that._endAnimateCommands(hideCommands); },
                                     function () { that._endAnimateCommands(hideCommands); });
                    } else {
                        // Already positioned correctly
                        setImmediate(function () { that._endAnimateCommands([]); });
                    }
                }

                // Done, clear queues
                this._queuedToShow = [];
                this._queuedToHide = [];
            },

            // Once animation is complete, ensure that the commands are display:none
            // and check if there's another animation to start.
            _endAnimateCommands: function(hideCommands) {
                // Update us
                var count;
                for (count = 0; count < hideCommands.length; count++) {
                    // Force us back into our appbar so that we can show again correctly
                    hideCommands[count].style.position = "";
                    hideCommands[count].getBoundingClientRect();
                    // Now make us really hidden
                    hideCommands[count].style.visibility = "hidden";
                    hideCommands[count].style.display = "none";
                    hideCommands[count].style.opacity = 1;
                }
                // Done animating
                this._element.winAnimating = "";

                // Might be something else to do
                this._checkDoNext();
            },

            // Resolves our commands
            _resolveCommands: function (commands) {
                // First make sure they're all DOM elements.
                commands = _resolveElements(commands);

                // Now make sure they're all in this container
                var result = {};
                result.commands = [];
                result.others = [];
                var allCommands = this.element.querySelectorAll(".win-command");
                var countAll, countIn;
                for (countAll = 0; countAll < allCommands.length; countAll++) {
                    var found = false;
                    for (countIn = 0; countIn < commands.length; countIn++) {
                        if (commands[countIn] === allCommands[countAll]) {
                            result.commands.push(allCommands[countAll]);
                            commands.splice(countIn, 1);
                            found = true;
                            break;
                        }
                    }
                    if (!found) {
                        result.others.push(allCommands[countAll]);
                    }
                }
                return result;
            },

            // Find siblings, all DOM elements now.
            // This is all .win-commands that are NOT in our commands array.
            _findSiblings: function (commands) {
                // Now make sure they're all in this container
                var siblings = [];
                var allCommands = this.element.querySelectorAll(".win-command");
                var countAll, countIn;
                for (countAll = 0; countAll < allCommands.length; countAll++) {
                    var found = false;
                    for (countIn = 0; countIn < commands.length; countIn++) {
                        if (commands[countIn] === allCommands[countAll]) {
                            commands.splice(countIn, 1);
                            found = true;
                            break;
                        }
                    }
                    if (!found) {
                        siblings.push(allCommands[countAll]);
                    }
                }
                return siblings;
            },

            _baseResize: function (event) {
                // Could be an orientation change
                if (WinJS.Utilities.hasWinRT) {
                    var newState = Windows.UI.ViewManagement.ApplicationView.value;
                    if (this._currentViewState !== newState) {
                        this._currentViewState = newState;
                        if (!this._sticky) {
                            this._hideOrDismiss();
                        }
                    }
                }

                // Call specific resize
                this._resize(event);
            },

            _hideOrDismiss: function () {
                var element = this._element;
                if (element && WinJS.Utilities.hasClass(element, "win-settingsflyout")) {
                    this._dismiss();
                } else {
                    this.hide();
                }
            },

            _resize: function (event) {
                // Nothing by default
            },

            _checkScrollPosition: function (event) {
                // Nothing by default
            },

            _showingKeyboard: function (event) {
                // Nothing by default
            },

            _hidingKeyboard: function (event) {
                // Nothing by default
            },

            // Verify that this HTML AppBar only has AppBar/MenuCommands.
            _verifyCommandsOnly: function (element, type) {
                if (element) {
                    var commands = element.children;
                    for (var i = 0; i < commands.length; i++) {
                        // If constructed they have win-command class, otherwise they have data-win-control
                        if (!WinJS.Utilities.hasClass(commands[i], "win-command") &&
                        commands[i].getAttribute("data-win-control") !== type) {
                            // Wasn't tagged with class or AppBar/MenuCommand, not an AppBar/MenuCommand
                            throw new WinJS.ErrorFromName("WinJS.UI._Overlay.MustContainCommands", strings.mustContainCommands);
                        }
                    }
                }
            },
            
            // Sets focus on what we think is the last tab stop. If nothing is focusable will
            // try to set focus on itself.
            _focusOnLastFocusableElementOrThis: function () {
                if (!this._focusOnLastFocusableElement()) {
                    // Nothing is focusable.  Set focus to this.
                    thisWinUI._Overlay._trySetActive(this._element);
                }
            },
            
            // Sets focus to what we think is the last tab stop. This element must have
            // a firstDiv with tabIndex equal to the lowest tabIndex in the element
            // and a finalDiv with tabIndex equal to the highest tabIndex in the element.
            // Also the firstDiv must be its first child and finalDiv be its last child.
            // Returns true if successful, false otherwise.
            _focusOnLastFocusableElement: function () {
                var _elms = this._element.getElementsByTagName("*");

                // There should be at least the firstDiv & finalDiv
                if (_elms.length < 2) {
                    return false;
                }

                // Get the tabIndex set to the finalDiv (which is the highest)
                var _highestTabIndex = thisWinUI._Overlay._getHighestTabIndexInList(_elms);
                var _nextHighestTabIndex = 0;

                // Try all tabIndex 0 first. After this conditional the _highestTabIndex
                // should be equal to the highest positive tabIndex.
                if (_highestTabIndex === 0) {
                    for (var i = _elms.length - 2; i > 0; i--) {
                        if (_elms[i].tabIndex === _highestTabIndex) {
                            _elms[i].focus();
                            
                            if (_elms[i] === document.activeElement) {
                                thisWinUI._Overlay._trySelect(_elms[i]);
                                return true;
                            }
                        } else if (_nextHighestTabIndex < _elms[i].tabIndex) {
                            _nextHighestTabIndex = _elms[i].tabIndex;
                        }
                    }
                    
                    _highestTabIndex     = _nextHighestTabIndex;
                    _nextHighestTabIndex = 0;
                }
                
                // If there are positive tabIndices, set focus to the element with the highest tabIndex.
                // Keep trying with the next highest tabIndex until all tabIndices have been exhausted.
                // Otherwise set focus to the last focusable element in DOM order.
                while (_highestTabIndex) {
                    for (i = _elms.length - 2; i > 0; i--) {
                        if (_elms[i].tabIndex === _highestTabIndex) {
                            _elms[i].focus();
                            
                            if (_elms[i] === document.activeElement) {
                                thisWinUI._Overlay._trySelect(_elms[i]);
                                return true;
                            }
                        } else if ((_nextHighestTabIndex < _elms[i].tabIndex) && (_elms[i].tabIndex < _highestTabIndex)) {
                            // Here if _nextHighestTabIndex < _elms[i].tabIndex < _highestTabIndex
                            _nextHighestTabIndex = _elms[i].tabIndex;
                        }
                    }
                    
                    // We weren't able to set focus to anything at that tabIndex
                    // If we found a lower valid tabIndex, try that now
                    _highestTabIndex     = _nextHighestTabIndex;
                    _nextHighestTabIndex = 0;
                }

                // Wasn't able to set focus to anything with a tabIndex, try everything now
                for (i = _elms.length - 2; i > 0; i--) {
                    _elms[i].focus();

                    if (_elms[i] === document.activeElement) {
                        thisWinUI._Overlay._trySelect(_elms[i]);
                        return true;
                    }
                }
                
                return false;
            },
            
            // Sets focus on what we think is the first tab stop. If nothing is focusable will
            // try to set focus on itself.
            _focusOnFirstFocusableElementOrThis: function () {
                if (!this._focusOnFirstFocusableElement()) {
                    // Nothing is focusable.  Set focus to this.
                    thisWinUI._Overlay._trySetActive(this._element);
                }
            },
            
            // Sets focus to what we think is the first tab stop. This element must have
            // a firstDiv with tabIndex equal to the lowest tabIndex in the element
            // and a finalDiv with tabIndex equal to the highest tabIndex in the element.
            // Also the firstDiv must be its first child and finalDiv be its last child.
            // Returns true if successful, false otherwise.
            _focusOnFirstFocusableElement: function () {
                var _elms = this._element.getElementsByTagName("*");

                // There should be at least the firstDiv & finalDiv
                if (_elms.length < 2) {
                    return false;
                }

                // Get the tabIndex set to the firstDiv (which is the lowest)
                var _lowestTabIndex = thisWinUI._Overlay._getLowestTabIndexInList(_elms);
                var _nextLowestTabIndex = 0;

                // If there are positive tabIndices, set focus to the element with the lowest tabIndex.
                // Keep trying with the next lowest tabIndex until all tabIndices have been exhausted.
                // Otherwise set focus to the first focusable element in DOM order.
                while (_lowestTabIndex) {
                    for (var i = 1; i < _elms.length - 1; i++) {
                        if (_elms[i].tabIndex === _lowestTabIndex) {
                            _elms[i].focus();

                            if (_elms[i] === document.activeElement) {
                                thisWinUI._Overlay._trySelect(_elms[i]);
                                return true;
                            }
                        } else if ((_lowestTabIndex < _elms[i].tabIndex)
                                && ((_elms[i].tabIndex < _nextLowestTabIndex) || (_nextLowestTabIndex === 0))) {
                            // Here if _lowestTabIndex < _elms[i].tabIndex < _nextLowestTabIndex
                            _nextLowestTabIndex = _elms[i].tabIndex;
                        }
                    }
                    
                    // We weren't able to set focus to anything at that tabIndex
                    // If we found a higher valid tabIndex, try that now
                    _lowestTabIndex     = _nextLowestTabIndex;
                    _nextLowestTabIndex = 0;
                } 
                
                // Wasn't able to set focus to anything with a positive tabIndex, try everything now.
                // This is where things with tabIndex of 0 will be tried.
                for (i = 1; i < _elms.length - 1; i++) {
                    _elms[i].focus();

                    if (_elms[i] === document.activeElement) {
                        thisWinUI._Overlay._trySelect(_elms[i]);
                        return true;
                    }
                }
                
                return false;
            },

            _addFlyoutEventHandlers: function (isFlyoutOrSettings) {
                // Set up global event handlers for all overlays
                if (!thisWinUI._Overlay._flyoutEdgeLightDismissEvent) {
                    // Dismiss on blur & resize
                    window.addEventListener("blur", thisWinUI._Overlay._checkBlur, false);

                    // Be careful so it behaves in designer as well.
                    if (WinJS.Utilities.hasWinRT) {
                        // Catch edgy events too
                        var commandUI = Windows.UI.Input.EdgeGesture.getForCurrentView();
                        commandUI.addEventListener("starting", thisWinUI._Overlay._hideAllFlyouts);
                        commandUI.addEventListener("completed", function edgyMayHideFlyouts() {
                            if (!thisWinUI._Overlay._rightMouseMightEdgy) {
                                thisWinUI._Overlay._hideAllFlyouts();
                            }
                        });

                        // Also need to react to keyboard
                        var inputPane = Windows.UI.ViewManagement.InputPane.getForCurrentView();
                        inputPane.addEventListener("showing", function (event) { _allOverlaysCallback(event, "_showingKeyboard"); });
                        inputPane.addEventListener("hiding", function (event) { _allOverlaysCallback(event, "_hidingKeyboard"); });
                        window.addEventListener("resize", function (event) { _allOverlaysCallback(event, "_baseResize"); });
                        document.addEventListener("scroll", function (event) { _allOverlaysCallback(event, "_checkScrollPosition"); });
                    }

                    thisWinUI._Overlay._flyoutEdgeLightDismissEvent = true;
                }

                // Each overlay tracks it's own view state
                if (WinJS.Utilities.hasWinRT) {
                    // Cache current state
                    this._currentViewState = Windows.UI.ViewManagement.ApplicationView.value;
                }

                // Individual handlers for Flyouts only
                if (isFlyoutOrSettings) {
                    // Need to hide ourselves if we lose focus
                    var that = this;
                    this._element.addEventListener("focusout", function (e) { thisWinUI._Overlay._hideIfLostFocus(that, e); }, false);

                    // Attempt to flag right clicks that may turn into edgy
                    this._element.addEventListener("MSPointerDown", thisWinUI._Overlay._checkRightClickDown, true);
                    this._element.addEventListener("MSPointerUp", thisWinUI._Overlay._checkRightClickUp, true);
                }
            }
        })
    });

    // Statics
    thisWinUI._Overlay._clickEatingAppBarDiv = false;
    thisWinUI._Overlay._clickEatingFlyoutDiv = false;
    thisWinUI._Overlay._flyoutEdgeLightDismissEvent = false;

    thisWinUI._Overlay._hideFlyouts = function (testElement, notSticky) {
        var elements = testElement.querySelectorAll(".win-flyout,.win-settingsflyout");
        var len = elements.length;
        for (var i = 0; i < len; i++) {
            var element = elements[i];
            if (element.style.visibility !== "hidden") {
                var flyout = element.winControl;
                if (flyout && (!notSticky || !flyout._sticky)) {
                    flyout._hideOrDismiss();
                }
            }
        }
    };

    thisWinUI._Overlay._hideAllFlyouts = function () {
        thisWinUI._Overlay._hideFlyouts(document, true);
    };

    thisWinUI._Overlay._createClickEatingDivTemplate = function (divClass, hideClickEatingDivFunction) {
        var clickEatingDiv = document.createElement("section");
        WinJS.Utilities.addClass(clickEatingDiv, divClass);
        clickEatingDiv.addEventListener("MSPointerUp", function (event) { thisWinUI._Overlay._checkSameClickEatingPointerUp(event, true); }, true);
        clickEatingDiv.addEventListener("MSPointerDown", function (event) { thisWinUI._Overlay._checkClickEatingPointerDown(event, true); }, true);
        clickEatingDiv.addEventListener("click", hideClickEatingDivFunction, true);
        // Tell Aria that it's clickable
        clickEatingDiv.setAttribute("role", "menuitem");
        clickEatingDiv.setAttribute("aria-label", strings.closeOverlay);
        // Prevent CED from removing any current selection
        clickEatingDiv.setAttribute("unselectable", "on");
        document.body.appendChild(clickEatingDiv);
        return clickEatingDiv;
    };

    // Used by AppBar, and Settings Pane
    thisWinUI._Overlay._createClickEatingDivAppBar = function () {
        if (!thisWinUI._Overlay._clickEatingAppBarDiv) {
            thisWinUI._Overlay._clickEatingAppBarDiv = thisWinUI._Overlay._createClickEatingDivTemplate(thisWinUI._Overlay._clickEatingAppBarClass, thisWinUI._Overlay._handleAppBarClickEatingClick);
        }
    };

    // Used by Flyout and Menu
    thisWinUI._Overlay._createClickEatingDivFlyout = function () {
        if (!thisWinUI._Overlay._clickEatingFlyoutDiv) {
            thisWinUI._Overlay._clickEatingFlyoutDiv = thisWinUI._Overlay._createClickEatingDivTemplate(thisWinUI._Overlay._clickEatingFlyoutClass, thisWinUI._Overlay._handleFlyoutClickEatingClick);
        }
    };

    // All click-eaters eat "down" clicks so that we can still eat
    // the "up" click that'll come later.
    thisWinUI._Overlay._checkClickEatingPointerDown = function (event, stopPropogation) {
        var target = event.currentTarget;
        if (target) {
            try {
                // Remember pointer id and remember right mouse
                target._winPointerId = event.pointerId;
                // Cache right mouse if that was what happened
                target._winRightMouse = (event.button === 2);
            } catch (e) { }
        }

        if (stopPropogation && !target._winRightMouse) {
            event.stopPropagation();
            event.preventDefault();
        }
    };

    // Make sure that if we have an up we had an earlier down of the same kind
    thisWinUI._Overlay._checkSameClickEatingPointerUp = function (event, stopPropogation) {
        var result = false,
            rightMouse = false,
            target = event.currentTarget;

        // Same pointer we were watching?
        try {
            if (target && target._winPointerId === event.pointerId) {
                // Same pointer
                result = true;
                rightMouse = target._winRightMouse;
                // For click-eaters, don't count right click the same because edgy will dismiss
                if (rightMouse && stopPropogation) {
                    result = false;
                }
            }
        } catch (e) { }


        if (stopPropogation && !rightMouse) {
            event.stopPropagation();
            event.preventDefault();
        }

        return result;
    };
    
    // If they click on a click eating div, even with a right click,
    // touch or anything, then we want to light dismiss that layer.
    thisWinUI._Overlay._handleAppBarClickEatingClick = function (event) {
        event.stopPropagation();
        event.preventDefault();
        
        thisWinUI.AppBar._hideLightDismissAppBars(null, false);
        thisWinUI._Overlay._hideClickEatingDivAppBar();
        thisWinUI._Overlay._hideAllFlyouts();
    };

    // If they click on a click eating div, even with a right click,
    // touch or anything, then we want to light dismiss that layer.
    thisWinUI._Overlay._handleFlyoutClickEatingClick = function (event) {
        event.stopPropagation();
        event.preventDefault();
        
        // Don't light dismiss AppBars because edgy will do that as needed,
        // so flyouts only.
        thisWinUI._Overlay._hideClickEatingDivFlyout();
        thisWinUI._Overlay._hideAllFlyouts();
    };

    thisWinUI._Overlay._checkRightClickDown = function (event) {
        thisWinUI._Overlay._checkClickEatingPointerDown(event, false);
    };

    thisWinUI._Overlay._checkRightClickUp = function (event) {
        if (thisWinUI._Overlay._checkSameClickEatingPointerUp(event, false)) {
            // It was a right click we may want to eat.
            thisWinUI._Overlay._rightMouseMightEdgy = true;
            setImmediate(function () { thisWinUI._Overlay._rightMouseMightEdgy = false; });
        }
    };

    thisWinUI._Overlay._showClickEatingDivAppBar = function () {
        setImmediate(function() { thisWinUI._Overlay._clickEatingAppBarDiv.style.display = "block"; });
    };

    thisWinUI._Overlay._hideClickEatingDivAppBar = function () {
        setImmediate(function() { thisWinUI._Overlay._clickEatingAppBarDiv.style.display = "none"; });
    };

    thisWinUI._Overlay._showClickEatingDivFlyout = function () {
        setImmediate(function() { thisWinUI._Overlay._clickEatingFlyoutDiv.style.display = "block"; });
    };

    thisWinUI._Overlay._hideClickEatingDivFlyout = function () {
        setImmediate(function() { thisWinUI._Overlay._clickEatingFlyoutDiv.style.display = "none"; });
    };

    thisWinUI._Overlay._isFlyoutVisible = function() {
        if (!thisWinUI._Overlay._clickEatingFlyoutDiv) {
            return false;
        }
        return (thisWinUI._Overlay._clickEatingFlyoutDiv.style.display === "block");
    };

    thisWinUI._Overlay._hideIfLostFocus = function (overlay, focusEvent) {
        // If we're still showing we haven't really lost focus
        if (overlay.hidden || overlay.element.winAnimating === "showing" || overlay._sticky) {
            return;
        }
        // If the active thing is within our element, we haven't lost focus
        var active = document.activeElement;
        if (overlay._element && overlay._element.contains(active)) {
            return;
        }
        // Settings don't dismiss if they spawned a flyout
        if (WinJS.Utilities.hasClass(overlay._element, "win-settingsflyout")) {
            // If the active thing is a flyout, then don't dismiss us.
            var control = thisWinUI._Overlay._getParentControlUsingClassName(active, "win-flyout");
            if (control) {
                return;
            }
        }
        // Do not hide focus if focus moved to a CED. Let the click handler on the CED take care of hiding us.
        if (active &&
            (WinJS.Utilities.hasClass(active, thisWinUI._Overlay._clickEatingFlyoutClass) ||
             WinJS.Utilities.hasClass(active, thisWinUI._Overlay._clickEatingAppBarClass))) {
            return;
        }

        overlay._hideOrDismiss();
    };

    // Want to hide flyouts on blur.
    // We get blur if we click off the window, including to an iframe within our window.
    // Both blurs call this function, but fortunately document.hasFocus is true if either
    // the document window or our iframe window has focus.
    thisWinUI._Overlay._checkBlur = function (focusEvent) {
        if (!document.hasFocus()) {
            // The document doesn't have focus, so they clicked off the app, so light dismiss.
            thisWinUI._Overlay._hideAllFlyouts();
            thisWinUI.AppBar._hideLightDismissAppBars(null, false);
        } else {
            if ((thisWinUI._Overlay._clickEatingFlyoutDiv &&
                 thisWinUI._Overlay._clickEatingFlyoutDiv.style.display === "block") || 
                (thisWinUI._Overlay._clickEatingAppBarDiv &&
                 thisWinUI._Overlay._clickEatingAppBarDiv.style.display === "block")){
                // We were trying to unfocus the window, but document still has focus,
                // so make sure the iframe that took the focus will check for blur next time.
                // We don't have to do this if the click eating div is hidden because then
                // there would be no flyout or appbar needing light dismiss.
                var active = document.activeElement;
                if (active && active.tagName === "IFRAME" && !active.msLightDismissBlur) {
                    // This will go away when the IFRAME goes away, and we only create one
                    active.msLightDismissBlur = active.addEventListener("blur", thisWinUI._Overlay._checkBlur, false);
                }
            }
        }
    };

    // Try to set us as active
    thisWinUI._Overlay._trySetActive = function (element) {
        if (!element || !element.setActive || !document.body || !document.body.contains(element)) {
            return false;
        }
        try {
            element.setActive();
        } catch (err) {
            return false;
        }
        return (element === document.activeElement);
    };

    // Try to select the text so keyboard can be used.
    thisWinUI._Overlay._trySelect = function (element) {
        try {
            if (element && element.select) {
                element.select();
            }
        } catch (e) { }
    };

    // Prevent the document.activeElement from showing focus
    thisWinUI._Overlay._addHideFocusClass = function (element) {
        if (element) {
            WinJS.Utilities.addClass(element, hideFocusClass);
            element.addEventListener("focusout", thisWinUI._Overlay._removeHideFocusClass, false);
        }
    };

    // Allow the event.target (element that is losing focus) to show focus next time it gains focus
    thisWinUI._Overlay._removeHideFocusClass = function (event) {
        // Make sure we really lost focus and was not just an App switch
        var target = event.target;
        if (target && target !== document.activeElement) {
            WinJS.Utilities.removeClass(target, hideFocusClass);
            event.target.removeEventListener("focusout", thisWinUI._Overlay._removeHideFocusClass, false);
        }
    };

    // Returns the lowest positive tabIndex in a list of elements.
    // Returns 0 if there are no positive tabIndices.
    thisWinUI._Overlay._getLowestTabIndexInList = function (elements) {
        var lowestTabIndex = 0;
        var elmTabIndex;
        for (var i = 0; i < elements.length; i++) {
            elmTabIndex = parseInt(elements[i].getAttribute("tabIndex"), 10);
            if ((0 < elmTabIndex) 
             && ((elmTabIndex < lowestTabIndex) || !lowestTabIndex)) {
                lowestTabIndex = elmTabIndex;
            }
        }
        
        return lowestTabIndex;
    };

    // Returns 0 if any element is explicitly set to 0. (0 is the highest tabIndex)
    // Returns the highest tabIndex in the list of elements.
    // Returns 0 if there are no positive tabIndices.
    thisWinUI._Overlay._getHighestTabIndexInList = function (elements) {
        var highestTabIndex = 0;
        var elmTabIndex;
        for (var i = 0; i < elements.length; i++) {
            elmTabIndex = parseInt(elements[i].getAttribute("tabIndex"), 10);
            if (elmTabIndex === 0) {
                return elmTabIndex;
            } else if (highestTabIndex < elmTabIndex) {
                highestTabIndex = elmTabIndex;
            }
        }
        
        return highestTabIndex;
    };
    
    thisWinUI._Overlay._getParentControlUsingClassName = function (element, className) {
        while (element && element !== document.body) {
            if (WinJS.Utilities.hasClass(element, className)) {
                return element.winControl;
            }
            element = element.parentNode;
        }
        return null;
    };

    // Global keyboard hiding offset
    thisWinUI._Overlay._keyboardInfo = {
        // Determine if the keyboard is visible or not.
        get _visible() {
            return (WinJS.Utilities.hasWinRT && Windows.UI.ViewManagement.InputPane.getForCurrentView().occludedRect.height > 0);
        },

        // See if we have to reserve extra space for the IHM
        get _extraOccluded() {
            var occluded = WinJS.Utilities.hasWinRT ? Windows.UI.ViewManagement.InputPane.getForCurrentView().occludedRect.height : 0;

            // Nothing occluded if not visible.
            if (occluded && !thisWinUI._Overlay._keyboardInfo._isResized) {
                // View hasn't been resized, need to return occluded height.
                return occluded;
            }

            // View already has space for keyboard or there's no keyboard
            return 0;
        },

        // See if the view has been resized to fit a keyboard
        get _isResized() {
            // Compare ratios.  Very different includes IHM space.
            var heightRatio = document.documentElement.clientHeight / window.innerHeight,
                widthRatio = document.documentElement.clientWidth / window.innerWidth;

            // If they're nearly identical, then the view hasn't been resized for the IHM
            // Only check one bound because we know the IHM will make it shorter, not skinnier.
            return (widthRatio / heightRatio < 0.99);
        },

        // Get the top of our visible area in terms of document.documentElement.
        get _visibleDocTop() {
            return window.pageYOffset - document.documentElement.scrollTop;
        },

        // Get the bottom of our visible area.
        get _visibleDocBottom() {
            return thisWinUI._Overlay._keyboardInfo._visibleDocTop + thisWinUI._Overlay._keyboardInfo._visibleDocHeight;
        },

        // Get the visible height, minus any needed keyboard occlusion.
        get _visibleDocHeight() {
            return window.innerHeight - thisWinUI._Overlay._keyboardInfo._extraOccluded;
        },

        // Get offset of visible window from bottom.
        get _visibleDocBottomOffset() {
            return document.documentElement.clientHeight - thisWinUI._Overlay._keyboardInfo._visibleDocBottom;
        },

        // Get total length of the IHM showPanel animation
        get _animationShowLength() {
            if (!WinJS.Utilities.hasWinRT) {
                return 0;
            }

            var a = Windows.UI.Core.AnimationMetrics,
                animationDescription = new a.AnimationDescription(a.AnimationEffect.showPanel, a.AnimationEffectTarget.primary);
            var animations = animationDescription.animations;
            var max = 0;
            for (var i = 0; i < animations.size; i++) {
                var animation = animations[i];
                max = Math.max(max, animation.delay + animation.duration);
            }
            return max;
        }
    };

    // Classes other objects use
    thisWinUI._Overlay._clickEatingAppBarClass = "win-appbarclickeater";
    thisWinUI._Overlay._clickEatingFlyoutClass = "win-flyoutmenuclickeater";
    
    // Padding for IHM timer to allow for first scroll event
    thisWinUI._Overlay._scrollTimeout = 150;

    // Events
    thisWinUI._Overlay.beforeShow = "beforeshow";
    thisWinUI._Overlay.beforeHide = "beforehide";
    thisWinUI._Overlay.afterShow = "aftershow";
    thisWinUI._Overlay.afterHide = "afterhide";

    thisWinUI._Overlay.commonstrings = {
        get cannotChangeCommandsWhenVisible() { return WinJS.Resources._getWinJSString("ui/cannotChangeCommandsWhenVisible").value; },
        get cannotChangeHiddenProperty() { return WinJS.Resources._getWinJSString("ui/cannotChangeHiddenProperty").value; }
    };
    
    var strings = {
        get duplicateConstruction() { return WinJS.Resources._getWinJSString("ui/duplicateConstruction").value; },
        get mustContainCommands() { return WinJS.Resources._getWinJSString("ui/mustContainCommands").value; },
        get closeOverlay() { return WinJS.Resources._getWinJSString("ui/closeOverlay").value; },
    };
    
    WinJS.Class.mix(WinJS.UI._Overlay, WinJS.Utilities.createEventProperties("beforeshow", "aftershow", "beforehide", "afterhide"));
    WinJS.Class.mix(WinJS.UI._Overlay, WinJS.UI.DOMEventMixin);
})(WinJS);
   

// Glyph Enumeration
/// <dictionary>Segoe</dictionary>
(function appBarIconInit(WinJS) {
    "use strict";

    var glyphs = ["previous",
                    "next",
                    "play",
                    "pause",
                    "edit",
                    "save",
                    "clear",
                    "delete",
                    "remove",
                    "add",
                    "cancel",
                    "accept",
                    "more",
                    "redo",
                    "undo",
                    "home",
                    "up",
                    "forward",
                    "right",
                    "back",
                    "left",
                    "favorite",
                    "camera",
                    "settings",
                    "video",
                    "sync",
                    "download",
                    "mail",
                    "find",
                    "help",
                    "upload",
                    "emoji",
                    "twopage",
                    "leavechat",
                    "mailforward",
                    "clock",
                    "send",
                    "crop",
                    "rotatecamera",
                    "people",
                    "closepane",
                    "openpane",
                    "world",
                    "flag",
                    "previewlink",
                    "globe",
                    "trim",
                    "attachcamera",
                    "zoomin",
                    "bookmarks",
                    "document",
                    "protecteddocument",
                    "page",
                    "bullets",
                    "comment",
                    "mail2",
                    "contactinfo",
                    "hangup",
                    "viewall",
                    "mappin",
                    "phone",
                    "videochat",
                    "switch",
                    "contact",
                    "rename",
                    "pin",
                    "musicinfo",
                    "go",
                    "keyboard",
                    "dockleft",
                    "dockright",
                    "dockbottom",
                    "remote",
                    "refresh",
                    "rotate",
                    "shuffle",
                    "list",
                    "shop",
                    "selectall",
                    "orientation",
                    "import",
                    "importall",
                    "browsephotos",
                    "webcam",
                    "pictures",
                    "savelocal",
                    "caption",
                    "stop",
                    "showresults",
                    "volume",
                    "repair",
                    "message",
                    "page2",
                    "calendarday",
                    "calendarweek",
                    "calendar",
                    "characters",
                    "mailreplyall",
                    "read",
                    "link",
                    "accounts",
                    "showbcc",
                    "hidebcc",
                    "cut",
                    "attach",
                    "paste",
                    "filter",
                    "copy",
                    "emoji2",
                    "important",
                    "mailreply",
                    "slideshow",
                    "sort",
                    "manage",
                    "allapps",
                    "disconnectdrive",
                    "mapdrive",
                    "newwindow",
                    "openwith",
                    "contactpresence",
                    "priority",
                    "uploadskydrive",
                    "gototoday",
                    "font",
                    "fontcolor",
                    "contact2",
                    "folder",
                    "audio",
                    "placeholder",
                    "view",
                    "setlockscreen",
                    "settile",
                    "cc",
                    "stopslideshow",
                    "permissions",
                    "highlight",
                    "disableupdates",
                    "unfavorite",
                    "unpin",
                    "openlocal",
                    "mute",
                    "italic",
                    "underline",
                    "bold",
                    "movetofolder",
                    "likedislike",
                    "dislike",
                    "like",
                    "alignright",
                    "aligncenter",
                    "alignleft",
                    "zoom",
                    "zoomout",
                    "openfile",
                    "otheruser",
                    "admin",
                    "street",
                    "map",
                    "clearselection",
                    "fontdecrease",
                    "fontincrease",
                    "fontsize",
                    "cellphone",
                    "reshare",
                    "tag",
                    "repeatone",
                    "repeatall",
                    "outlinestar",
                    "solidstar",
                    "calculator",
                    "directions",
                    "target",
                    "library",
                    "phonebook",
                    "memo",
                    "microphone",
                    "postupdate",
                    "backtowindow",
                    "fullscreen",
                    "newfolder",
                    "calendarreply",
                    "unsyncfolder",
                    "reporthacked",
                    "syncfolder",
                    "blockcontact",
                    "switchapps",
                    "addfriend",
                    "touchpointer",
                    "gotostart",
                    "zerobars",
                    "onebar",
                    "twobars",
                    "threebars",
                    "fourbars"];

    // Provide properties to grab resources for each of the icons
    /// <summary locid="WinJS.UI.AppBarIcon">
    /// The AppBarIcon enumeration provides a set of glyphs for use with the AppBarCommand icon property.
    /// </summary>
    WinJS.Namespace.define("WinJS.UI.AppBarIcon",
        glyphs.reduce(function (fixedIcons, item) {
            fixedIcons[item] = { get: function () { return WinJS.Resources._getWinJSString("ui/appBarIcons/" + item).value; } };
            return fixedIcons;
        }, {}));
})(WinJS);
// AppBarCommand
/// <dictionary>appbar,appbars,Flyout,Flyouts,onclick,Statics</dictionary>
(function appBarCommandInit(WinJS) {
    "use strict";

    var thisWinUI = WinJS.UI;

    // Class Names
    var appBarCommandClass = "win-command",
        appBarCommandGlobalClass = "win-global",
        appBarCommandSelectionClass = "win-selection",
        typeSeparator = "separator",
        typeButton = "button",
        typeToggle = "toggle",
        typeFlyout = "flyout",
        sectionSelection = "selection",
        sectionGlobal = "global",
        wideSize = 1024;

    function _handleClick(event) {
        var command = this.winControl;
        if (command) {
            if (command._type === typeToggle) {
                command.selected = !command.selected;
            } else if (command._type === typeFlyout && command._flyout) {
                var parentAppBar = thisWinUI._Overlay._getParentControlUsingClassName(this, "win-appbar");
                var placement = "top";
                if (parentAppBar && parentAppBar.placement === "top") {
                    placement = "bottom";
                }
                var flyout = command._flyout;
                // Flyout may not have processAll'd, so this may be a DOM object
                if (typeof flyout === "string") {
                    flyout = document.getElementById(flyout);
                }
                if (!flyout.show) {
                    flyout = flyout.winControl;
                }
                if (flyout && flyout.show) {
                    flyout.show(this, placement);
                }
            }
            if (command.onclick) {
                command.onclick(event);
            }
        }
    }

    WinJS.Namespace.define("WinJS.UI", {
        /// <summary locid="WinJS.UI.AppBarCommand">
        /// AppBarCommands provide button, toggle button, flyout button, or separator functionality for AppBars.
        /// </summary>
        /// <icon src="ui_winjs.ui.appbarcommand.12x12.png" width="12" height="12" />
        /// <icon src="ui_winjs.ui.appbarcommand.16x16.png" width="16" height="16" />
        /// <htmlSnippet><![CDATA[<button data-win-control="WinJS.UI.AppBarCommand" data-win-options="{type:'button',label:'Button'}"></button>]]></htmlSnippet>
        /// <part name="appBarCommand" class="win-command" locid="WinJS.UI.AppBarCommand_part:appBarCommand">The AppBarCommand control itself</part>
        /// <part name="appBarCommandIcon" class="win-commandicon" locid="WinJS.UI.AppBarCommand_part:appBarCommandIcon">The AppBarCommand's icon box</part>
        /// <part name="appBarCommandImage" class="win-commandimage" locid="WinJS.UI.AppBarCommand_part:appBarCommandImage">The AppBarCommand's icon's image formatting</part>
        /// <part name="appBarCommandRing" class="win-commandring" locid="WinJS.UI.AppBarCommand_part:appBarCommandRing">The AppBarCommand's icon's ring</part>
        /// <part name="appBarCommandLabel" class="win-label" locid="WinJS.UI.AppBarCommand_part:appBarCommandLabel">The AppBarCommand's label</part>
        /// <resource type="javascript" src="//Microsoft.WinJS.1.0/js/base.js" shared="true" />
        /// <resource type="javascript" src="//Microsoft.WinJS.1.0/js/ui.js" shared="true" />
        /// <resource type="css" src="//Microsoft.WinJS.1.0/css/ui-dark.css" shared="true" />
        AppBarCommand: WinJS.Class.define(function AppBarCommand_ctor(element, options) {
            /// <signature helpKeyword="WinJS.UI.AppBarCommand.AppBarCommand">
            /// <summary locid="WinJS.UI.AppBarCommand.constructor">
            /// Constructs the AppBarCommand control
            /// </summary>
            /// <param name="element" domElement="true" locid="WinJS.UI.AppBarCommand.constructor_p:element">
            /// The DOM element to be associated with the AppBarCommand control.  AppBarCommand will create one if null.
            /// </param>
            /// <param name="options" type="Object" locid="WinJS.UI.AppBarCommand.constructor_p:options">
            /// The set of options to be applied initially to the AppBarCommand control.
            /// </param>
            /// <returns type="WinJS.UI.AppBarCommand" locid="WinJS.UI.AppBarCommand.constructor_returnValue">
            /// A AppBarCommand control.
            /// </returns>
            /// </signature>

            // Check to make sure we weren't duplicated
            if (element && element.winControl) {
                throw new WinJS.ErrorFromName("WinJS.UI.AppBarCommand.DuplicateConstruction", strings.duplicateConstruction);
            }

            // Don't blow up if they didn't pass options
            if (!options) {
                options = {};
            } 

            // Need a type before we can create our element
            if (!options.type) {
                this._type = typeButton;
            } 
            
            // Go ahead and create it, separators look different than buttons
            // Don't forget to use passed in element if one was provided.
            this._element = element;
            
            if (options.type === typeSeparator) {
                this._createSeparator();
            } else {
                // This will also set the icon & label
                this._createButton();
            }

            // Remember ourselves
            this._element.winControl = this;

            // Attach our css class
            WinJS.Utilities.addClass(this._element, appBarCommandClass);

            if (options.onclick) {
                this.onclick = options.onclick;
            }
            // We want to handle some clicks
            options.onclick = _handleClick;
            
            WinJS.UI.setOptions(this, options);

            if (!options.section) {
                this._setSection(options.section);
            }

            if (this._type === typeToggle && !options.selected) {
                this.selected = false;
            }
            
            // Clean up ARIA if needed
            if (this._type !== typeSeparator) {
                // Make sure we have an ARIA role
                var role = this._element.getAttribute("role");
                if (role === null || role === "" || role === undefined) {
                    role = "menuitem";
                    if (this._type === typeToggle) {
                        role = "menuitemcheckbox";
                    }
                    this._element.setAttribute("role", role);
                    if (this._type === typeFlyout) {
                        this._element.setAttribute("aria-haspopup", true);
                    }
                }
                // Label should've been set by label, but if it was missed for some reason:
                var label = this._element.getAttribute("aria-label");
                if (label === null || label === "" || label === undefined) {
                    this._element.setAttribute("aria-label", strings.ariaLabel);
                }
            }
        }, {
            /// <field type="String" locid="WinJS.UI.AppBarCommand.id" helpKeyword="WinJS.UI.AppBarCommand.id" isAdvanced="true">The Id of the AppBarCommand.</field>
            id: {
                get: function () {
                    return this._element.id;
                }, 
                
                set: function(value) {
                    // we allow setting first time only. otherwise we ignore it.
                    if (value && !this._element.id) {
                        this._element.id = value;
                    }
                }
            },

            /// <field type="String" defaultValue="button" readonly="true" oamOptionsDatatype="WinJS.UI.AppBarCommand.type" locid="WinJS.UI.AppBarCommand.type" helpKeyword="WinJS.UI.AppBarCommand.type" isAdvanced="true">The Type of the AppBarCommand, possible values are "button", "toggle", "flyout", or "separator"</field>
            type: {
                get: function () {
                    return this._type;
                }, 
                set: function (value) {
                    // we allow setting first time only. otherwise we ignore it.
                    if (!this._type) {
                        if (value !== typeButton && value !== typeFlyout && value !== typeToggle && value !== typeSeparator) {
                            this._type = typeButton;
                        } else {
                            this._type = value;
                        }
                    }
                }
            },

            /// <field type="String" locid="WinJS.UI.AppBarCommand.label" helpKeyword="WinJS.UI.AppBarCommand.label">The label of the AppBarCommand</field>
            label: {
                get: function () {
                    return this._label;
                },
                set: function (value) {
                    this._label = value;
                    if (this._labelSpan) {
                        this._labelSpan.innerText = this.label;
                    }

                    // Ensure that we have a tooltip, by updating already-constructed tooltips.  Separators won't have these:
                    if (!this.tooltip && this._tooltipControl) {
                        this._tooltip = this.label;
                        this._tooltipControl.innerHTML = this.label;
                    }

                    // Update aria-label
                    this._element.setAttribute("aria-label", this.label);

                    // Check if we need to suppress the tooltip
                    this._testIdenticalTooltip();
                }
            },

            /// <field type="String" locid="WinJS.UI.AppBarCommand.icon" helpKeyword="WinJS.UI.AppBarCommand.icon">The icon of the AppBarCommand</field>
            icon: {
                get: function () {
                    return this._icon;
                },
                set: function (value) {
                    if (value) {
                        this._icon = (WinJS.UI.AppBarIcon[value] || value);
                    } else {
                        this._icon = value;
                    }

                    if (this._imageSpan) {
                        // If the icon's a single character, presume a glyph
                        if (this._icon && this._icon.length === 1) {
                            // Set the glyph
                            this._imageSpan.innerText = this._icon;
                            this._imageSpan.style.backgroundImage = "";
                            this._imageSpan.style.msHighContrastAdjust = "";
                        } else {
                            // Must be an image, set that
                            this._imageSpan.innerText = "";
                            this._imageSpan.style.backgroundImage = this._icon;
                            this._imageSpan.style.msHighContrastAdjust = "none";
                        }
                    }
                }
            },

            /// <field type="Function" locid="WinJS.UI.AppBarCommand.onclick" helpKeyword="WinJS.UI.AppBarCommand.onclick">The click event to call when the AppBarCommand is invoked</field>
            onclick: {
                get: function () {
                    return this._onclick;
                },
                set: function (value) {
                    if (value && typeof value !== "function") {
                        throw new WinJS.ErrorFromName("WinJS.UI.AppBarCommand.BadClick", WinJS.Resources._formatString(strings.badClick, "AppBarCommand"));
                    }
                    this._onclick = value;
                }
            },

            /// <field type="Object" locid="WinJS.UI.AppBarCommand.flyout" helpKeyword="WinJS.UI.AppBarCommand.flyout">For flyout type AppBarCommands, get returns the WinJS.UI.Flyout that this command invokes.  Set may also use the String id of the flyout to invoke, the DOM object of the flyout, or the flyout object itself</field>
            flyout: {
                get: function () {
                    // Resolve it to the flyout
                    var flyout = this._flyout;
                    if (typeof flyout === "string") {
                        flyout = document.getElementById(flyout);
                    }
                    // If it doesn't have a .element, then we need to getControl on it
                    if (flyout && !flyout.element) {
                        flyout = flyout.winControl;
                    }

                    return flyout;
                },
                set: function (value) {
                    // Need to update aria-owns with the new ID.
                    var id = value;
                    if (id && typeof id !== "string") {
                        // Our controls have .element properties
                        if (id.element) {
                            id = id.element;
                        }
                        // Hope it's a DOM element, get ID from DOM element
                        if (id) {
                            if (id.id) {
                                id = id.id;
                            } else {
                                // No id, have to fake one
                                id.id = id.uniqueID;
                                id = id.id;
                            }
                        }
                    }
                    if (typeof id === "string") {
                        this._element.setAttribute("aria-owns", id);
                    }

                    // Remember it
                    this._flyout = value;
                }
            },

            /// <field type="String" defaultValue="global" oamOptionsDatatype="WinJS.UI.AppBarCommand.section" locid="WinJS.UI.AppBarCommand.section" helpKeyword="WinJS.UI.AppBarCommand.section">Set or get the section to place the button in, either "global" or "selection"</field>
            section: {
                get: function () {
                    return this._section;
                },
                set: function (value) {
                    // we allow settings section only one time 
                    if (!this._section || (window.Windows && Windows.ApplicationModel && Windows.ApplicationModel.DesignMode.designModeEnabled)) {
                        this._setSection(value);
                    }
                }
            },

            /// <field type="String" locid="WinJS.UI.AppBarCommand.tooltip" helpKeyword="WinJS.UI.AppBarCommand.tooltip">The tooltip text of the AppBarCommand</field>
            tooltip: {
                get: function () {
                    return this._tooltip;
                },
                set: function (value) {
                    this._tooltip = value;

                    // Update already-constructed tooltips.  Separators won't have these:
                    if (this._tooltipControl) {
                        this._tooltipControl.innerHTML = this._tooltip;
                    }

                    // Check if we need to suppress the tooltip
                    this._testIdenticalTooltip();
                }
            },

            /// <field type="Boolean" locid="WinJS.UI.AppBarCommand.selected" helpKeyword="WinJS.UI.AppBarCommand.selected">Set or get the selected state of a toggle button</field>
            selected: {
                get: function () {
                    // Ensure it's a boolean because we're using the DOM element to keep in-sync
                    return this._element.getAttribute("aria-checked") === "true";
                },
                set: function (value) {
                    this._element.setAttribute("aria-checked", value);
                }
            },

            /// <field type="HTMLElement" domElement="true" readonly="true" hidden="true" locid="WinJS.UI.AppBarCommand.element" helpKeyword="WinJS.UI.AppBarCommand.element">The DOM element the AppBarCommad is attached to</field>
            element: {
                get: function () {
                    return this._element;
                }
            },

            /// <field type="Boolean" locid="WinJS.UI.AppBarCommand.disabled" helpKeyword="WinJS.UI.AppBarCommand.disabled">Disable a command. It will get or set the HTML disabled attribute.</field>
            disabled: {
                get: function () {
                    // Ensure it's a boolean because we're using the DOM element to keep in-sync
                    return !!this._element.disabled;
                },
                set: function (value) {
                    this._element.disabled = value;
                }
            },

            /// <field type="Boolean" hidden="true" locid="WinJS.UI.AppBarCommand.hidden" helpKeyword="WinJS.UI.AppBarCommand.hidden">Determine if a command is currently hidden.</field>
            hidden: {
                get: function () {
                    // Ensure it's a boolean because we're using the DOM element to keep in-sync
                    return this._element.style.visibility === "hidden";
                },
                set: function (value) {
                    var appbarControl = thisWinUI._Overlay._getParentControlUsingClassName(this._element, "win-appbar");
                    if (appbarControl && !appbarControl.hidden) {
                        throw new WinJS.ErrorFromName("WinJS.UI.AppBarCommand.CannotChangeHiddenProperty", WinJS.Resources._formatString(thisWinUI._Overlay.commonstrings.cannotChangeHiddenProperty, "AppBar"));
                    }
                    
                    var style = this._element.style;
                    if (value) {
                        style.visibility = "hidden";
                        style.display = "none";
                    } else {
                        style.visibility = "";
                        style.display = "inline-block";
                    }
                }
            },

            addEventListener: function (type, listener, useCapture) {
                /// <signature helpKeyword="WinJS.UI.AppBarCommand.addEventListener">
                /// <summary locid="WinJS.UI.AppBarCommand.addEventListener">
                /// Add an event listener to the DOM element for this command
                /// </summary>
                /// <param name="type" type="String" locid="WinJS.UI.AppBarCommand.addEventListener_p:type">Required. Event type to add.</param>
                /// <param name="listener" type="Function" locid="WinJS.UI.AppBarCommand.addEventListener_p:listener">Required. The event handler function to associate with this event.</param>
                /// <param name="useCapture" type="Boolean" locid="WinJS.UI.AppBarCommand.addEventListener_p:useCapture">Optional. True, register for the event capturing phase.  False for the event bubbling phase.</param>
                /// </signature>
                return this._element.addEventListener(type, listener, useCapture);
            },

            removeEventListener: function (type, listener, useCapture) {
                /// <signature helpKeyword="WinJS.UI.AppBarCommand.removeEventListener">
                /// <summary locid="WinJS.UI.AppBarCommand.removeEventListener">
                /// Remove an event listener to the DOM element for this command
                /// </summary>
                /// <param name="type" type="String" locid="WinJS.UI.AppBarCommand.removeEventListener_p:type">Required. Event type to remove.</param>
                /// <param name="listener" type="Function" locid="WinJS.UI.AppBarCommand.removeEventListener_p:listener">Required. The event handler function to associate with this event.</param>
                /// <param name="useCapture" type="Boolean" locid="WinJS.UI.AppBarCommand.removeEventListener_p:useCapture">Optional. True, register for the event capturing phase.  False for the event bubbling phase.</param>
                /// </signature>
                return this._element.removeEventListener(type, listener, useCapture);
            },

            /// <field type="String" locid="WinJS.UI.AppBarCommand.extraClass" helpKeyword="WinJS.UI.AppBarCommand.extraClass" isAdvanced="true">Adds an extra CSS class during construction.</field>
            extraClass: {
                get: function () {
                    return this._extraClass;
                },
                set: function (value) {
                    if (this._extraClass) {
                        WinJS.Utilities.removeClass(this._element, this._extraClass);
                    }
                    this._extraClass = value;
                    WinJS.Utilities.addClass(this._element, this._extraClass);
                }
            },

            // Private
            _testIdenticalTooltip: function () {
                this._hideIfWide = (this._label === this._tooltip);
            },

            _createSeparator: function () {
                // Make sure there's an input element
                if (!this._element) {
                    this._element = document.createElement("hr");
                } else {
                    // Verify the input was an hr
                    if (this._element.tagName !== "HR") {
                        throw new WinJS.ErrorFromName("WinJS.UI.AppBarCommand.BadHrElement", strings.badHrElement);
                    }
                }
            },

            _createButton: function () {
                // Make sure there's an input element
                if (!this._element) {
                    this._element = document.createElement("button");
                } else {
                    // Verify the input was a button
                    if (this._element.tagName !== "BUTTON") {
                        throw new WinJS.ErrorFromName("WinJS.UI.AppBarCommand.BadButtonElement", strings.badButtonElement);
                    }
                    // Make sure it has a type="button"
                    var type = this._element.getAttribute("type");
                    if (type === null || type === "" || type === undefined) {
                        this._element.setAttribute("type", "button");
                    }
                    this._element.innerHtml = "";
                }

                // AppBarCommand buttons need to look like this:
                //// <button type="button" onclick="" class="win-command win-global">
                ////      <span class="win-commandicon win-commandring"><span class="win-commandimage">&#xE0D5;</span></span><span class="win-label">Command 1</span>
                //// Or This:
                ////      <span class="win-commandicon win-commandring"><span class="win-commandimage" style="background-image:url('customimage.png')"></span></span><span class="win-label">Command 1</span>
                //// </button>
                this._element.type = "button";
                this._iconSpan = document.createElement("span");
                this._iconSpan.setAttribute("aria-hidden", "true");
                this._iconSpan.className = "win-commandicon win-commandring";
                this._iconSpan.tabIndex = -1;
                this._element.appendChild(this._iconSpan);
                this._imageSpan = document.createElement("span");
                this._imageSpan.setAttribute("aria-hidden", "true");
                this._imageSpan.className = "win-commandimage";
                this._imageSpan.tabIndex = -1;
                this._iconSpan.appendChild(this._imageSpan);
                this._labelSpan = document.createElement("span");
                this._labelSpan.setAttribute("aria-hidden", "true");
                this._labelSpan.className = "win-label";
                this._labelSpan.tabIndex = -1;
                this._element.appendChild(this._labelSpan);
                // 'win-global' or 'win-selection' are added later by caller.
                // Label and icon are added later by caller.

                // Attach a tooltip - Note: we're going to stomp on it's setControl so we don't have to make another DOM element to hang it off of.
                // This private _tooltipControl attribute is used by other pieces, changing the name could break them.
                this._tooltipControl = new WinJS.UI.Tooltip(this._element);
                var that = this;
                this._tooltipControl.addEventListener("beforeopen", function () {
                    if (that._hideIfWide && window.innerWidth >= wideSize) {
                        that._tooltipControl.close();
                    }
                }, false);
                
                // Hide the modern focus rect on click or touch
                var that = this;
                this._element.addEventListener("MSPointerDown", function () { thisWinUI._Overlay._addHideFocusClass(that._element); }, false);
            },
            
            _setSection: function (section) {
                if (!section) {
                    section = sectionGlobal;
                }
                if (this._section) {
                    // Remove the old section class
                    if (this._section === sectionGlobal) {
                        WinJS.Utilities.removeClass(this._element, appBarCommandGlobalClass);
                    } else if (this.section === sectionSelection) {
                        WinJS.Utilities.removeClass(this._element, appBarCommandSelectionClass);
                    }
                }
                // Add the new section class
                this._section = section;
                if (section === sectionGlobal) {
                    WinJS.Utilities.addClass(this._element, appBarCommandGlobalClass);
                } else if (section === sectionSelection) {
                    WinJS.Utilities.addClass(this._element, appBarCommandSelectionClass);
                }
            }
        })
    });

    // Statics
    
    var strings = {
        get ariaLabel() { return WinJS.Resources._getWinJSString("ui/appBarCommandAriaLabel").value; },
        get duplicateConstruction() { return WinJS.Resources._getWinJSString("ui/duplicateConstruction").value; },
        get badClick() { return WinJS.Resources._getWinJSString("ui/badClick").value; },
        get badHrElement() { return WinJS.Resources._getWinJSString("ui/badHrElement").value; },
        get badButtonElement() { return WinJS.Resources._getWinJSString("ui/badButtonElement").value; }
    };

})(WinJS);

// AppBar
/// <dictionary>appbar,appBars,Flyout,Flyouts,iframe,Statics,unfocus,WinJS</dictionary>
(function appBarInit(WinJS) {
    "use strict";

    var thisWinUI = WinJS.UI;

    // Class Names
    var commandClass        = "win-commandlayout",
        appBarClass         = "win-appbar",
        settingsFlyoutClass = "win-settingsflyout",
        topClass            = "win-top",
        bottomClass         = "win-bottom";

    var firstDivClass       = "win-firstdiv",
        finalDivClass       = "win-finaldiv";

    // Constants for placement
    var appBarPlacementTop    = "top",
        appBarPlacementBottom = "bottom";

    // Constants for layout
    var appBarLayoutCustom   = "custom",
        appBarLayoutCommands = "commands";

    // Hook into event
    var appBarCommandEvent = false;
    var edgyHappening      = null;

    // Handler for the edgy starting/completed/cancelled events
    function _completedEdgy(e) {
        // If we had a right click on a flyout, ignore it.
        if (thisWinUI._Overlay._rightMouseMightEdgy &&
            e.kind === Windows.UI.Input.EdgeGestureKind.mouse) {
            return;
        }
        if (edgyHappening) {
            // Edgy was happening, just skip it
            edgyHappening = null;
        } else {
            // Edgy wasn't happening, so toggle
            var keyboardInvoked = e.kind === Windows.UI.Input.EdgeGestureKind.keyboard;
            WinJS.UI.AppBar._toggleAppBarEdgy(keyboardInvoked);
        }
    }

    function _startingEdgy() {
        if (!edgyHappening) {
            // Edgy wasn't happening, so toggle & start it
            edgyHappening = WinJS.UI.AppBar._toggleAppBarEdgy(false);
        }
    }

    function _canceledEdgy() {
        // Shouldn't get here unless edgy was happening.
        // Undo whatever we were doing.
        var bars = _getDynamicBarsForEdgy();
        if (edgyHappening === "showing") {
            _hideAllBars(bars, false);
        } else if (edgyHappening === "hiding") {
            _showAllBars(bars, false);
        }
        edgyHappening = null;
    }

    function _allManipulationChanged(event) {
        var elements = document.querySelectorAll("." + appBarClass);
        if (elements) {
            var len = elements.length;
            for (var i = 0; i < len; i++) {
                var element = elements[i];
                var appbar = element.winControl;
                if (appbar && !element.disabled) {
                    appbar._manipulationChanged(event);
                }
            }
        }
    }

    // Get all the non-sticky bars and return them.
    // Returns array of AppBar objects.
    // The array also has _hidden and/or _visible set if ANY are hidden of visible.
    function _getDynamicBarsForEdgy() {
        var elements = document.querySelectorAll("." + appBarClass);
        var len = elements.length;
        var AppBars = [];
        AppBars._visible = false;
        AppBars._hidden = false;
        for (var i = 0; i < len; i++) {
            var element = elements[i];
            if (element.disabled) {
                // Skip disabled AppBars
                continue;
            }
            var AppBar = element.winControl;
            if (AppBar) {
                AppBars.push(AppBar);
                // Middle of animation is different than animated
                if (AppBar._element.winAnimating) {
                    // If animating, look at showing/hiding
                    if (AppBar._element.winAnimating === "hiding") {
                        AppBars._hidden = true;
                    } else {
                        AppBars._visible = true;
                    }
                } else {
                    // Not animating, so use "hidden"
                    if (AppBar._element.style.visibility === "hidden") {
                        AppBars._hidden = true;
                    } else {
                        AppBars._visible = true;
                    }
                }
            }
        }

        return AppBars;
    }

    // Show or hide all bars
    function _hideAllBars(bars, keyboardInvoked) {
        var len = bars.length;
        for (var i = 0; i < len; i++) {
            bars[i]._keyboardInvoked = keyboardInvoked;
            bars[i].hide();
        }
    }
    
    function _showAllBars(bars, keyboardInvoked) {
        var len = bars.length;
        for (var i = 0; i < len; i++) {
            bars[i]._keyboardInvoked = keyboardInvoked;
            bars[i]._doNotFocus = false;
            bars[i]._show();
        }
    }

    // On "Esc" key press hide all flyouts and light dismiss AppBars.
    function _handleKeyDown(event) {
        if (event.key === "Esc") {
            event.preventDefault();
            event.stopPropagation();
            thisWinUI._Overlay._hideAllFlyouts();
            thisWinUI.AppBar._hideLightDismissAppBars(null, true);
        }
    }

    // Sets focus to the last AppBar in the provided appBars array with given placement.
    // Returns true if focus was set.  False otherwise.
    function _setFocusToPreviousAppBarHelper(startIndex, appBarPlacement, appBars) {
        for (var i = startIndex; i >= 0; i--) {
            if (appBars[i].winControl
             && appBars[i].winControl.placement === appBarPlacement
             && !appBars[i].winControl.hidden
             && appBars[i].winControl._focusOnLastFocusableElement
             && appBars[i].winControl._focusOnLastFocusableElement()) {
                return true;
            }
        }
        return false;
    }
    
    // Sets focus to the last AppBar in the provided appBars array with other placement.
    // Returns true if focus was set.  False otherwise.
    function _setFocusToPreviousAppBarHelperNeither(startIndex, appBars) {
        for (var i = startIndex; i >= 0; i--) {
            if (appBars[i].winControl
             && appBars[i].winControl.placement != appBarPlacementBottom
             && appBars[i].winControl.placement != appBarPlacementTop
             && !appBars[i].winControl.hidden
             && appBars[i].winControl._focusOnLastFocusableElement
             && appBars[i].winControl._focusOnLastFocusableElement()) {
                return true;
            }
        }
        return false;
    }
    
    // Sets focus to the last tab stop of the previous AppBar
    // AppBar tabbing order:
    //    1) Bottom AppBars
    //    2) Top AppBars
    //    3) Other AppBars
    // DOM order is respected, because an AppBar should not have a defined tabIndex
    function _setFocusToPreviousAppBar() {
        var appBars = document.querySelectorAll("." + appBarClass);
        if (!appBars.length) {
            return;
        }
        
        var thisAppBarIndex = 0;
        for(var i = 0; i < appBars.length; i++) {
            if (appBars[i] === this.parentElement) {
                thisAppBarIndex = i;
                break;
            }
        }

        var appBarControl = this.parentElement.winControl;
        if (appBarControl.placement === appBarPlacementBottom) {
            // Bottom appBar: Focus order: (1)previous bottom appBars (2)other appBars (3)top appBars (4)bottom appBars
            if (thisAppBarIndex && _setFocusToPreviousAppBarHelper(thisAppBarIndex - 1, appBarPlacementBottom, appBars)) { return; }
            if (_setFocusToPreviousAppBarHelperNeither(appBars.length - 1, appBars)) { return; }
            if (_setFocusToPreviousAppBarHelper(appBars.length - 1, appBarPlacementTop, appBars)) { return; }
            if (_setFocusToPreviousAppBarHelper(appBars.length - 1, appBarPlacementBottom, appBars)) { return; }
        } else if (appBarControl.placement === appBarPlacementTop) {
            // Top appBar: Focus order: (1)previous top appBars (2)bottom appBars (3)other appBars (4)top appBars
            if (thisAppBarIndex && _setFocusToPreviousAppBarHelper(thisAppBarIndex - 1, appBarPlacementTop, appBars)) { return; }
            if (_setFocusToPreviousAppBarHelper(appBars.length - 1, appBarPlacementBottom, appBars)) { return; }
            if (_setFocusToPreviousAppBarHelperNeither(appBars.length - 1, appBars)) { return; }
            if (_setFocusToPreviousAppBarHelper(appBars.length - 1, appBarPlacementTop, appBars)) { return; }
        } else {
            // Other appBar: Focus order: (1)previous other appBars (2)top appBars (3)bottom appBars (4)other appBars
            if (thisAppBarIndex && _setFocusToPreviousAppBarHelperNeither(thisAppBarIndex - 1, appBars)) { return; }
            if (_setFocusToPreviousAppBarHelper(appBars.length - 1, appBarPlacementTop, appBars)) { return; }
            if (_setFocusToPreviousAppBarHelper(appBars.length - 1, appBarPlacementBottom, appBars)) { return; }
            if (_setFocusToPreviousAppBarHelperNeither(appBars.length - 1, appBars)) { return; }
        }
    }
    
    // Sets focus to the first AppBar in the provided appBars array with given placement.
    // Returns true if focus was set.  False otherwise.
    function _setFocusToNextAppBarHelper(startIndex, appBarPlacement, appBars) {
        for (var i = startIndex; i < appBars.length; i++) {
            if (appBars[i].winControl
             && appBars[i].winControl.placement === appBarPlacement
             && !appBars[i].winControl.hidden
             && appBars[i].winControl._focusOnFirstFocusableElement
             && appBars[i].winControl._focusOnFirstFocusableElement()) {
                return true;
            }
        }
        return false;
    }
    
    // Sets focus to the first AppBar in the provided appBars array with other placement.
    // Returns true if focus was set.  False otherwise.
    function _setFocusToNextAppBarHelperNeither(startIndex, appBars) {
        for (var i = startIndex; i < appBars.length; i++) {
            if (appBars[i].winControl
             && appBars[i].winControl.placement != appBarPlacementBottom
             && appBars[i].winControl.placement != appBarPlacementTop
             && !appBars[i].winControl.hidden
             && appBars[i].winControl._focusOnFirstFocusableElement
             && appBars[i].winControl._focusOnFirstFocusableElement()) {
                return true;
            }
        }
        return false;
    }
    
    // Sets focus to the first tab stop of the next AppBar
    // AppBar tabbing order:
    //    1) Bottom AppBars
    //    2) Top AppBars
    //    3) Other AppBars
    // DOM order is respected, because an AppBar should not have a defined tabIndex
    function _setFocusToNextAppBar() {
        var appBars = document.querySelectorAll("." + appBarClass);
        
        var thisAppBarIndex = 0;
        for(var i = 0; i < appBars.length; i++) {
            if (appBars[i] === this.parentElement) {
                thisAppBarIndex = i;
                break;
            }
        }

        var appBarControl = this.parentElement.winControl;
        if (this.parentElement.winControl.placement === appBarPlacementBottom) {
            // Bottom appBar: Focus order: (1)next bottom appBars (2)top appBars (3)other appBars (4)bottom appBars
            if (_setFocusToNextAppBarHelper(thisAppBarIndex + 1, appBarPlacementBottom, appBars)) { return; }
            if (_setFocusToNextAppBarHelper(0, appBarPlacementTop, appBars)) { return; }
            if (_setFocusToNextAppBarHelperNeither(0, appBars)) { return; }
            if (_setFocusToNextAppBarHelper(0, appBarPlacementBottom, appBars)) { return; }
        } else if (this.parentElement.winControl.placement === appBarPlacementTop) {
            // Top appBar: Focus order: (1)next top appBars (2)other appBars (3)bottom appBars (4)top appBars
            if (_setFocusToNextAppBarHelper(thisAppBarIndex + 1, appBarPlacementTop, appBars)) { return; }
            if (_setFocusToNextAppBarHelperNeither(0, appBars)) { return; }
            if (_setFocusToNextAppBarHelper(0, appBarPlacementBottom, appBars)) { return; }
            if (_setFocusToNextAppBarHelper(0, appBarPlacementTop, appBars)) { return; }
        } else {
            // Other appBar: Focus order: (1)next other appBars (2)bottom appBars (3)top appBars (4)other appBars
            if (_setFocusToNextAppBarHelperNeither(thisAppBarIndex + 1, appBars)) { return; }
            if (_setFocusToNextAppBarHelper(0, appBarPlacementBottom, appBars)) { return; }
            if (_setFocusToNextAppBarHelper(0, appBarPlacementTop, appBars)) { return; }
            if (_setFocusToNextAppBarHelperNeither(0, appBars)) { return; }
        }
    }
    
    // Updates the firstDiv & finalDiv of all visible AppBars
    function _updateAllAppBarsFirstAndFinalDiv() {
        var appBars = document.querySelectorAll("." + appBarClass);
        
        for(var i = 0; i < appBars.length; i++) {
            if (appBars[i].winControl
             && !appBars[i].winControl.hidden
             && appBars[i].winControl._updateFirstAndFinalDiv) {
                appBars[i].winControl._updateFirstAndFinalDiv();
            }
        }
    }
    
    // Returns true if a visible non-sticky (light dismiss) AppBar is found in the document
    function _isThereVisibleNonStickyBar() {
        var appBars = document.querySelectorAll("." + appBarClass);
        for (var i = 0; i < appBars.length; i++) {
            var appBarControl = appBars[i].winControl;
            if (appBarControl && !appBarControl.sticky &&
                (!appBarControl.hidden || appBarControl._element.winAnimating === "showing")) {
                return true;
            }
        }

        return false;
    }

    // Hide all light dismiss AppBars if what has focus is not part of a AppBar or flyout.
    function _hideIfAllAppBarsLostFocus() {
        if (!thisWinUI.AppBar._isAppBarOrChild(document.activeElement)) {
            thisWinUI.AppBar._hideLightDismissAppBars(null, false);
            // Ensure that sticky appbars clear cached focus after light dismiss are dismissed, which moved focus.
            thisWinUI.AppBar._ElementWithFocusPreviousToAppBar = null;
        }
    }
    
    // If the previous focus was not a AppBar or CED, store it in the cache
    // (_isAppBarOrChild tests CED for us).
    function _checkStorePreviousFocus(focusEvent) {
        if (focusEvent.relatedTarget 
         && focusEvent.relatedTarget.focus 
         && !thisWinUI.AppBar._isAppBarOrChild(focusEvent.relatedTarget)) {
            _storePreviousFocus(focusEvent.relatedTarget);
        }
    }
    
    // Cache the previous focus information
    function _storePreviousFocus(element) {
        if (element) {
            thisWinUI.AppBar._ElementWithFocusPreviousToAppBar = element;
        }
    }
    
    // Try to return focus to what had focus before.
    // If successfully return focus to a textbox, restore the selection too.
    function _restorePreviousFocus() {
        thisWinUI._Overlay._trySetActive(thisWinUI.AppBar._ElementWithFocusPreviousToAppBar);
    }
            
    WinJS.Namespace.define("WinJS.UI", {
        /// <summary locid="WinJS.UI.AppBar">
        /// The AppBar control provides a surface for AppBarCommands or other information that the user can show or hide.
        /// </summary>
        /// <icon src="ui_winjs.ui.appbar.12x12.png" width="12" height="12" />
        /// <icon src="ui_winjs.ui.appbar.16x16.png" width="16" height="16" />
        /// <htmlSnippet supportsContent="true"><![CDATA[<div data-win-control="WinJS.UI.AppBar">
        /// <button data-win-control="WinJS.UI.AppBarCommand" data-win-options="{id:'',label:'example',icon:'back',type:'button',onclick:null,section:'global'}"></button>
        /// </div>]]></htmlSnippet>
        /// <event name="beforeshow" locid="WinJS.UI.AppBar_e:beforeshow">Raised just before showing an AppBar.</event>
        /// <event name="aftershow" locid="WinJS.UI.AppBar_e:aftershow">Raised immediately after an AppBar is fully shown.</event>
        /// <event name="beforehide" locid="WinJS.UI.AppBar_e:beforehide">Raised just before hiding an AppBar.</event>
        /// <event name="afterhide" locid="WinJS.UI.AppBar_e:afterhide">Raised immediately after an AppBar is fully hidden.</event>
        /// <part name="appbar" class="win-commandlayout" locid="WinJS.UI.AppBar_part:appbar">The AppBar control itself</part>
        /// <part name="appBarCustom" class="win-appbar" locid="WinJS.UI.AppBar_part:appBarCustom">Style for a custom layout appbar</part>
        /// <resource type="javascript" src="//Microsoft.WinJS.1.0/js/base.js" shared="true" />
        /// <resource type="javascript" src="//Microsoft.WinJS.1.0/js/ui.js" shared="true" />
        /// <resource type="css" src="//Microsoft.WinJS.1.0/css/ui-dark.css" shared="true" />
        AppBar: WinJS.Class.derive(WinJS.UI._Overlay, function (element, options) {
            /// <signature helpKeyword="WinJS.UI.AppBar.AppBar">
            /// <summary locid="WinJS.UI.AppBar.constructor">
            /// Constructs the AppBar control
            /// </summary>
            /// <param name="element" type="HTMLElement" domElement="true" locid="WinJS.UI.AppBar.constructor_p:element">
            /// The DOM element to be associated with the AppBar control.
            /// </param>
            /// <param name="options" type="Object" locid="WinJS.UI.AppBar.constructor_p:options">
            /// The set of options to be applied initially to the AppBar control.
            /// </param>
            /// <returns type="WinJS.UI.AppBar" locid="WinJS.UI.AppBar.constructor_returnValue">
            /// A constructed AppBar control.
            /// </returns>
            /// </signature>

            // Simplify checking later
            if (!options) {
                options = {};
            }

            // validate that if they didn't set commands, but want command
            // layout that the HTML only contains commands.  Do this first
            // so that we don't leave partial AppBars in the DOM.
            if (options.layout !== appBarLayoutCustom && !options.commands) {
                this._verifyCommandsOnly(element, "WinJS.UI.AppBarCommand");
            }

            // Call the base overlay constructor helper
            this._baseOverlayConstructor(element, options);
            
            // Make a click eating div
            thisWinUI._Overlay._createClickEatingDivAppBar();

            // Attach our css class,
            WinJS.Utilities.addClass(this._element, appBarClass);
            // Also may need a command class if not a custom layout appbar
            if (options.layout !== appBarLayoutCustom) {
                WinJS.Utilities.addClass(this._element, commandClass);
            }
            
            if (!options.placement) {
                // Make sure we have default placement
                this.placement = appBarPlacementBottom;
            }

            // Make sure we have an ARIA role
            var role = this._element.getAttribute("role");
            if (!role) {
                this._element.setAttribute("role", "menubar");
            }
            var label = this._element.getAttribute("aria-label");
            if (!label) {
                this._element.setAttribute("aria-label", strings.ariaLabel);
            }

            // Handle key presses (esc)
            this._element.addEventListener("keydown", _handleKeyDown, false);

            // Attach event handler
            if (!appBarCommandEvent) {
                // We'll trigger on invoking.  Could also have invoked or canceled
                // Eventually we may want click up on invoking and drop back on invoked.
                // Check for namespace so it'll behave in the designer.
                if (WinJS.Utilities.hasWinRT) {
                    var commandUI = Windows.UI.Input.EdgeGesture.getForCurrentView();
                    commandUI.addEventListener("starting", _startingEdgy);
                    commandUI.addEventListener("completed", _completedEdgy);
                    commandUI.addEventListener("canceled", _canceledEdgy);
                }

                // Need to know if the IHM is done scrolling
                document.addEventListener("MSManipulationStateChanged", _allManipulationChanged, false);

                appBarCommandEvent = true;
            }

            // Make sure flyout event handlers are hooked up (this aids light dismiss)
            this._addFlyoutEventHandlers(false);

            // Need to store what had focus before
            this._element.addEventListener("focusin", function (event) { _checkStorePreviousFocus(event); }, false);

            // Need to hide ourselves if we lose focus
            this._element.addEventListener("focusout", function (event) { _hideIfAllAppBarsLostFocus(); }, false);
 
            return this;
        }, {
            // Public Properties

            /// <field type="String" defaultValue="bottom" oamOptionsDatatype="WinJS.UI.AppBar.placement" locid="WinJS.UI.AppBar.placement" helpKeyword="WinJS.UI.AppBar.placement">The placement of the AppBar on the display.  Values are "top" or "bottom".</field>
            placement: {
                get: function () {
                    return this._placement;
                },
                set: function (value) {
                    // In designer we may have to move it
                    var wasShown = false;
                    if (window.Windows && Windows.ApplicationModel && Windows.ApplicationModel.DesignMode.designModeEnabled && !this.hidden) {
                        this._hide();
                        wasShown = true;
                    }

                    if (!this.hidden) {
                        throw new WinJS.ErrorFromName("WinJS.UI.AppBar.CannotChangePlacementWhenVisible", strings.cannotChangePlacementWhenVisible);
                    }

                    // Set placement
                    this._placement = value;

                    // Clean up win-top, win-bottom styles
                    if (this._placement === appBarPlacementTop) {
                        WinJS.Utilities.addClass(this._element, topClass);
                        WinJS.Utilities.removeClass(this._element, bottomClass);
                    } else if (this._placement === appBarPlacementBottom) {
                        WinJS.Utilities.removeClass(this._element, topClass);
                        WinJS.Utilities.addClass(this._element, bottomClass);
                    } else {
                        WinJS.Utilities.removeClass(this._element, topClass);
                        WinJS.Utilities.removeClass(this._element, bottomClass);
                    }

                    // Make sure our animations are correct
                    this._assignAnimations();

                    // Show again if we hid ourselves for the designer
                    if (wasShown) {
                        this._show();
                    }
                }
            },

            /// <field type="String" defaultValue="commands" oamOptionsDatatype="WinJS.UI.AppBar.layout" locid="WinJS.UI.AppBar.layout" helpKeyword="WinJS.UI.AppBar.layout">The layout of the AppBar contents, either "commands" or "custom".</field>
            layout: {
                get: function () {
                    // Defaults to commands if not set
                    return this._layout ? this._layout : appBarLayoutCommands;
                },
                set: function (value) {
                    if (value !== appBarLayoutCommands && value !== appBarLayoutCustom) {
                        throw new WinJS.ErrorFromName("WinJS.UI.AppBar.BadLayout", strings.badLayout);
                    }

                    // In designer we may have to redraw it
                    var wasShown = false;
                    if (window.Windows && Windows.ApplicationModel && Windows.ApplicationModel.DesignMode.designModeEnabled && !this.hidden) {
                        this._hide();
                        wasShown = true;
                    }

                    if (!this.hidden) {
                        throw new WinJS.ErrorFromName("WinJS.UI.AppBar.CannotChangeLayoutWhenVisible", strings.cannotChangeLayoutWhenVisible);
                    }

                    // Set layout
                    this._layout = value;

                    // Update our classes
                    if (this._layout === appBarLayoutCommands) {
                        // Add the appbar css class back
                        WinJS.Utilities.addClass(this._element, commandClass);
                    } else {
                        // Remove the appbar css class
                        WinJS.Utilities.removeClass(this._element, commandClass);
                    }

                    // Show again if we hid ourselves for the designer
                    if (wasShown) {
                        this._show();
                    }
                }
            },

            /// <field type="Boolean" locid="WinJS.UI.AppBar.sticky" isAdvanced="true" helpKeyword="WinJS.UI.AppBar.sticky">Whether the AppBar is sticky.</field>
            sticky: {
                get: function () {
                    return this._sticky;
                },
                set: function (value) {
                    // If it doesn't change, do nothing
                    if (this._sticky === !!value) {
                        return;
                    }

                    this._sticky = !!value;

                    // Note: caller has to call .show() if they also want it visible

                    // Show or hide the click eating div based on sticky value
                    if (!this.hidden && this._element.style.visibility === "visible") {
                        // May have changed sticky state for keyboard navigation
                        _updateAllAppBarsFirstAndFinalDiv();

                        // Ensure that the click eating div is in the correct state
                        if (this._sticky) {
                            if (!_isThereVisibleNonStickyBar()) {
                                thisWinUI._Overlay._hideClickEatingDivAppBar();
                            }
                        } else {
                            thisWinUI._Overlay._showClickEatingDivAppBar();
                            
                            if (this._shouldStealFocus()) {
                                _storePreviousFocus(document.activeElement);
                                this._setFocusToAppBar();
                            }
                        }
                    }
                }
            },

            /// <field type="Array" locid="WinJS.UI.AppBar.commands" helpKeyword="WinJS.UI.AppBar.commands" isAdvanced="true">The Commands for the AppBar, contains an array of AppBarCommand options.</field>
            commands: {
                set: function (value) {
                    // Fail if trying to set when visible
                    if (!this.hidden) {
                        throw new WinJS.ErrorFromName("WinJS.UI.AppBar.CannotChangeCommandsWhenVisible", WinJS.Resources._formatString(thisWinUI._Overlay.commonstrings.cannotChangeCommandsWhenVisible, "AppBar"));
                    }

                    // Start from scratch
                    this._element.innerHTML = "";

                    // In case they had only one...
                    if (!Array.isArray(value)) {
                        value = [value];
                    }

                    // Add commands
                    var len = value.length;
                    for (var i = 0; i < len; i++) {
                        this._addCommand(value[i]);
                    }
                }
            },

            
            getCommandById: function (id) {
                /// <signature helpKeyword="WinJS.UI.AppBar.getCommandById">
                /// <summary locid="WinJS.UI.AppBar.getCommandById">
                /// Retrieve the command with the specified ID from this AppBar.  If more than one command is found, all are returned.
                /// </summary>
                /// <param name="id" type="String" locid="WinJS.UI.AppBar.getCommandById_p:id">Id of the command to return.</param>
                /// <returns type="object" locid="WinJS.UI.AppBar.getCommandById_returnValue">The command found, an array of commands if more than one have the same id, or null if no command is found with that id.</returns>
                /// </signature>
                var commands = this.element.querySelectorAll("#" + id);
                for (var count = 0; count < commands.length; count++) {
                    // Any elements we generated this should succeed for,
                    // but remove missing ones just to be safe.
                    commands[count] = commands[count].winControl;
                    if (!commands[count]) {
                        commands.splice(count, 1);
                    }
                }

                if (commands.length === 1) {
                    return commands[0];
                } else if (commands.length === 0) {
                    return null;
                }

                return commands;
            },

            
            showCommands: function (commands) {
                /// <signature helpKeyword="WinJS.UI.AppBar.showCommands">
                /// <summary locid="WinJS.UI.AppBar.showCommands">
                /// Show commands within this AppBar
                /// </summary>
                /// <param name="commands" type="Array" locid="WinJS.UI.AppBar.showCommands_p:commands">Required. Command or Commands to show, either String, DOM elements, or WinJS objects.</param>
                /// </signature>
                if (!commands) {
                    throw new WinJS.ErrorFromName("WinJS.UI.AppBar.RequiresCommands", strings.requiresCommands);
                }

                this._showCommands(commands);
            },

           
            hideCommands: function (commands) {
                /// <signature helpKeyword="WinJS.UI.AppBar.hideCommands">
                /// <summary locid="WinJS.UI.AppBar.hideCommands">
                /// Hide commands within this AppBar
                /// </summary>
                /// <param name="commands" type="Array" locid="WinJS.UI.AppBar.hideCommands_p:commands">Required. Command or Commands to hide, either String, DOM elements, or WinJS objects.</param>
                /// </signature>
                if (!commands) {
                    throw new WinJS.ErrorFromName("WinJS.UI.AppBar.RequiresCommands", strings.requiresCommands);
                }

                this._hideCommands(commands);
            },

            
            showOnlyCommands: function (commands) {
                /// <signature helpKeyword="WinJS.UI.AppBar.showOnlyCommands">
                /// <summary locid="WinJS.UI.AppBar.showOnlyCommands">
                /// Show the specified commands, hiding all of the others in the AppBar.
                /// </summary>
                /// <param name="commands" type="Array" locid="WinJS.UI.AppBar.showOnlyCommands_p:commands">Required. Command or Commands to show, either String, DOM elements, or WinJS objects.</param>
                /// </signature>
                if (!commands) {
                    throw new WinJS.ErrorFromName("WinJS.UI.AppBar.RequiresCommands", strings.requiresCommands);
                }

                this._showOnlyCommands(commands);
            },

            
            show: function () {
                /// <signature helpKeyword="WinJS.UI.AppBar.show">
                /// <summary locid="WinJS.UI.AppBar.show">
                /// Shows the AppBar, if hidden, regardless of other state
                /// </summary>
                /// </signature>
                // Just wrap the private one, turning off keyboard invoked flag
                this._keyboardInvoked = false;
                this._doNotFocus = !!this.sticky;
                this._show();
            },

            _show: function () {
                // Don't do anything if disabled
                if (this.disabled) {
                    return;
                }

                // If we're covered by a keyboard we look hidden, so we may have to jump up
                if (this._keyboardObscured) {
                    // just make us look hidden so that show() gets called.
                    this._fakeHide = true;
                    this._keyboardObscured = false;
                }

                // Regardless we're going to be in a CED state
                if (!this.sticky) {
                    // Need click-eating div to be visible ASAP.
                    thisWinUI._Overlay._showClickEatingDivAppBar();
                }

                // If we are already animating, just remember this for later
                if (this._element.winAnimating) {
                    this._doNext = "show";
                    return false;
                }
                
                // We call our base _baseShow because AppBar may need to override show
                // "hiding" would need to cancel.
                this._baseShow();

                // Clean up after showing
                if (!this.sticky && _isThereVisibleNonStickyBar()) {
                    this._needToUpdateAllAppBarsInEndShow = true;
                } else {
                    this._needToUpdateAllAppBarsInEndShow = false;
                }
            },

            _endShow: function () {
                // Make sure first & final divs are right
                if (this._needToUpdateAllAppBarsInEndShow) {
                    _updateAllAppBarsFirstAndFinalDiv();
                } else {
                    this._updateFirstAndFinalDiv();
                }

                // Check if we should steal focus
                if (!this._doNotFocus && this._shouldStealFocus()) {
                    // Store what had focus if nothing currently is stored
                    if (!thisWinUI.AppBar._ElementWithFocusPreviousToAppBar) {
                        _storePreviousFocus(document.activeElement);
                    }

                    this._setFocusToAppBar();
                }
            },
            
            hide: function () {
                /// <signature helpKeyword="WinJS.UI.AppBar.hide">
                /// <summary locid="WinJS.UI.AppBar.hide">
                /// Hides the AppBar, if visible, regardless of other state
                /// </summary>
                /// </signature>
                // Just wrap the private one
                this._hide();
            },

            _hide: function () {
                // If we're covered by a keyboard we already look hidden
                if (this._keyboardObscured && !this._animating) {
                    this._keyboardObscured = false;
                    this._baseEndHide();
                } else {
                    // We call our base _baseHide because AppBar may need to override hide
                    this._baseHide();
                }

                // Determine if there are any AppBars that are visible.
                // Set the focus to the next visible AppBar.
                // If there are none, set the focus to the control stored in the cache, which
                //   is what had focus before the AppBars were given focus.
                var appBars = document.querySelectorAll("." + appBarClass);
                var areOtherAppBars = false;
                var areOtherNonStickyAppBars = false;
                var i;
                for (i = 0; i < appBars.length; i++) {
                    var appBarControl = appBars[i].winControl;
                    if (appBarControl && !appBarControl.hidden && (appBarControl !== this)) {
                        areOtherAppBars = true;

                        if (!appBarControl.sticky) {
                            areOtherNonStickyAppBars = true;
                            break;
                        }
                    }
                }
                
                var settingsFlyouts = document.querySelectorAll("." + settingsFlyoutClass);
                var areVisibleSettingsFlyouts = false;
                for (i = 0; i < settingsFlyouts.length; i++) {
                    var settingsFlyoutControl = settingsFlyouts[i].winControl;
                    if (settingsFlyoutControl && !settingsFlyoutControl.hidden) {
                        areVisibleSettingsFlyouts = true;
                        break;
                    }
                }

                if (!areOtherNonStickyAppBars && !areVisibleSettingsFlyouts) {
                    // Hide the click eating div because there are no other AppBars showing
                    thisWinUI._Overlay._hideClickEatingDivAppBar();
                }

                var that = this;
                if (!areOtherAppBars) {
                    // Set focus to what had focus before showing the AppBar
                    if (thisWinUI.AppBar._ElementWithFocusPreviousToAppBar &&
                        (!document.activeElement || thisWinUI.AppBar._isAppBarOrChild(document.activeElement))) {
                        _restorePreviousFocus();
                    }
                    // Always clear the previous focus (to prevent temporary leaking of element)
                    thisWinUI.AppBar._ElementWithFocusPreviousToAppBar = null;
                } else if (thisWinUI.AppBar._isWithinAppBarOrChild(document.activeElement, that.element)) {
                    // Set focus to next visible AppBar in DOM

                    var foundCurrentAppBar = false;
                    for (i = 0; i <= appBars.length; i++) {
                        if (i === appBars.length) {
                            i = 0;
                        }

                        var appBar = appBars[i];
                        if (appBar === this.element) {
                            foundCurrentAppBar = true;
                        } else if (foundCurrentAppBar && !appBar.winControl.hidden) {
                            appBar.winControl._keyboardInvoked = !!this._keyboardInvoked;
                            appBar.winControl._setFocusToAppBar();
                            break;
                        }
                    }
                }
                
                // If we are hiding the last lightDismiss AppBar, 
                //   then we need to update the tabStops of the other AppBars
                if (!this.sticky && !_isThereVisibleNonStickyBar()) {
                    _updateAllAppBarsFirstAndFinalDiv();
                }
                
                // Reset these values
                this._keyboardInvoked = false;
                this._doNotFocus = false;
            },

            _assignAnimations: function () {
                // Make sure the animations are correct for our current placement
                if (this._placement === appBarPlacementTop || this._placement === appBarPlacementBottom) {
                    // Top or Bottom
                    this._currentAnimateIn = this._animateSlideIn;
                    this._currentAnimateOut = this._animateSlideOut;
                } else {
                    // Default for in the middle of nowhere
                    this._currentAnimateIn = this._baseAnimateIn;
                    this._currentAnimateOut = this._baseAnimateOut;
                }
            },

            // AppBar animations
            _animateSlideIn: function () {
                var where,
                    height = this._element.offsetHeight;
                // Get top/bottoms
                this._checkPosition();
                // Get animation direction and clear other value
                if (this._placement === appBarPlacementTop) {
                    // Top Bar
                    where = { top: "-" + height + "px", left: "0px" };
                    this._element.style.bottom = "auto";
                } else {
                    // Bottom Bar
                    where = { top: height + "px", left: "0px" };
                    this._element.style.top = "auto";
                }

                this._element.style.opacity = 1;
                this._element.style.visibility = "visible";
                return WinJS.UI.Animation.showEdgeUI(this._element, where);
            },

            _animateSlideOut: function () {
                var where,
                    height = this._element.offsetHeight;
                if (this._placement === appBarPlacementTop) {
                    // Top Bar
                    where = { top: height + "px", left: "0px" };
                    // Adjust for scrolling or soft keyboard positioning
                    this._element.style.top = (this._getAdjustedTop() - height) + "px";
                } else {
                    // Bottom Bar
                    where = { top: "-" + height + "px", left: "0px" };
                    // Adjust for scrolling or soft keyboard positioning
                    this._element.style.bottom = (this._getAdjustedBottom() - height) + "px";
                }
                return WinJS.UI.Animation.showEdgeUI(this._element, where);
            },

            _isABottomAppBarInTheProcessOfShowing : function () {
                var appbars = document.querySelectorAll("." + appBarClass + "." + bottomClass);
                for (var i = 0; i < appbars.length; i++) {
                    if (appbars[i].winAnimating === "showing") {
                        return true;
                    }
                }
                
                return false;
            },
            
            // Returns true if
            //   1) This is a bottom appbar
            //   2) No appbar has focus and a bottom appbar is not in the process of showing
            //   3) What currently has focus is neither a bottom appbar nor a top appbar
            //      AND a bottom appbar is not in the process of showing.
            // Otherwise Returns false
            _shouldStealFocus : function () {
                var activeElementAppBar = thisWinUI.AppBar._isAppBarOrChild(document.activeElement);
                if (this._element === activeElementAppBar) {
                    // This appbar already has focus and we don't want to move focus 
                    // from where it currently is in this appbar.
                    return false;
                }
                if (this._placement === appBarPlacementBottom) {
                    // This is a bottom appbar
                    return true;
                } 
                
                var isBottomAppBarShowing = this._isABottomAppBarInTheProcessOfShowing();
                if (!activeElementAppBar) {
                    // Currently no appbar has focus.
                    // Return true if a bottom appbar is not in the process of showing.
                    return !isBottomAppBarShowing;
                }
                if (!activeElementAppBar.winControl) {
                    // This should not happen, but if it does we want to make sure
                    // that an AppBar ends up with focus.
                    return true;
                }
                if ((activeElementAppBar.winControl._placement !== appBarPlacementBottom)
                 && (activeElementAppBar.winControl._placement !== appBarPlacementTop)
                 && !isBottomAppBarShowing) {
                    // What currently has focus is neither a bottom appbar nor a top appbar
                    // -and-
                    // a bottom appbar is not in the process of showing.
                    return true;
                }
                return false
            },
    
            // Set focus to the passed in AppBar
            _setFocusToAppBar: function () {
                if (this._focusOnFirstFocusableElement()) {
                    // Prevent what is gaining focus from showing that it has focus,
                    // but only in the non-keyboard scenario.
                    if (!this._keyboardInvoked) {
                        thisWinUI._Overlay._addHideFocusClass(document.activeElement);
                    }
                } else {
                    // No first element, set it to appbar itself
                    thisWinUI._Overlay._trySetActive(this._element);
                }
            },
            
            _addCommand: function (command) {
                // See if it's a command already
                if (command && !command._element) {
                    // Not a command, so assume it's options for a command
                    command = new WinJS.UI.AppBarCommand(null, command);
                }
                // If we were attached somewhere else, detach us
                if (command._element.parentElement) {
                    command._element.parentElement.removeChild(command._element);
                }
                // Reattach us
                this._element.appendChild(command._element);
            },

            // Get the top of the top appbars, would be 0 if not for viewport changes.
            // "normally", top is just 0, if there's no IHM yet,
            // When keyboard first shows up, also still 0,
            // When resize happens, then we need to consider page offset - base offset
            _getAdjustedTop: function() {
                // Top is always at the top of the viewport
                return thisWinUI._Overlay._keyboardInfo._visibleDocTop;
            },

            // Get the bottom of the bottom appbars, would be 0 if not for viewport changes
            // "normally", bottom is just 0, if there's no IHM yet,
            // When keyboard first shows, need to adjust by distance of keyboard
            // When resize happens, then we need to consider page offset - base offset.
            // If the keyboard obscures the appbar we need to make sure it stays obscured.
            _getAdjustedBottom: function() {
                // Need the distance the IHM moved as well.
                return thisWinUI._Overlay._keyboardInfo._visibleDocBottomOffset;
            },
            
            _showingKeyboard: function (event) {
                // Remember keyboard showing state.
                this._keyboardObscured = false;
                this._keyboardHiding = false;

                // If we're already moved, then ignore the whole thing
                if (thisWinUI._Overlay._keyboardInfo._visible && this._alreadyInPlace()) {
                    return;
                }

                this._keyboardShowing = true;
                // If focus is in the appbar, don't cause scrolling.
                if (!this.hidden && this._element.contains(document.activeElement)) {
                    event.ensuredFocusedElementInView = true;
                }

                // Check if appbar moves or is obscured
                if (!this.hidden && this._placement !== appBarPlacementTop && thisWinUI._Overlay._isFlyoutVisible()) {
                    // Remember that we're obscured
                    this._keyboardObscured = true;
                } else {
                    // If not obscured, tag as showing and set timeout to restore us.
                    this._scrollHappened = false;
                }

                // Also set timeout regardless, so we can clean up our keyboard showing flag.
                var that = this;
                setTimeout(function (e) { that._checkKeyboardTimer(e); }, thisWinUI._Overlay._keyboardInfo._animationShowLength + thisWinUI._Overlay._scrollTimeout);
            },

            _hidingKeyboard: function (event) {
                // We won't be obscured
                this._keyboardObscured = false;
                this._keyboardShowing = false;
                this._keyboardHiding = true;

                // We'll either just reveal the current space or resize the window
                if (!thisWinUI._Overlay._keyboardInfo._isResized) {
                    // If we're visible or only fake hiding under keyboard, or already animating,
                    // then snap us to our final position.
                    if (!this.hidden || this._fakeHide || this._animating) {
                        // Not resized, update our final position immediately
                        this._checkScrollPosition();
                        this._element.style.display = "";
                        this._fakeHide = false;
                    }
                    this._keyboardHiding = false;
                }
                // Else resize should clear keyboardHiding.
            },

            _resize: function (event) {
                // If we're hidden by the keyboard, then hide bottom appbar so it doesn't pop up twice when it scrolls
                if (this._keyboardShowing) {
                    // Top is allowed to scroll off the top, but we don't want bottom to peek up when
                    // scrolled into view since we'll show it ourselves and don't want a stutter effect.
                    if (!this.hidden) {
                        if (this._placement !== appBarPlacementTop && !this._keyboardObscured) {
                            // If viewport doesn't match window, need to vanish momentarily so it doesn't scroll into view,
                            // however we don't want to toggle thie visibility="hidden" hidden flag.
                            this._element.style.display = "none";
                        }
                    }
                    // else if we're top we stay, and if there's a flyout, stay obscured by the keyboard.
                } else if (this._keyboardHiding) {
                    this._keyboardHiding = false;
                    if (!this.hidden || this._animating) {
                        // Snap to final position
                        this._checkScrollPosition();
                        this._element.style.display = "";
                        this._fakeHide = false;
                    }
                }
            },

            _checkKeyboardTimer: function () {
                if (!this._scrollHappened) {
                    this._mayEdgeBackIn();
                }
            },

            _manipulationChanged: function (event) {
                // See if we're at the not manipulating state, and we had a scroll happen,
                // which is implicitly after the keyboard animated.
                if (event.currentState === 0 && this._scrollHappened) {
                    this._mayEdgeBackIn();
                }
            },

            _mayEdgeBackIn: function (event) {
                // May need to react to IHM being resized event
                if (this._keyboardShowing) {
                    // If not top appbar or viewport isn't still at top, then need to show again
                    this._keyboardShowing = false;
                    // If obscured (flyout showing), don't change.
                    // If hidden, may be because _fakeHide was set in _resize.
                    // If bottom we have to move, or if top scrolled off screen.
                    if (!this._keyboardObscured && (!this.hidden || this._fakeHide) &&
                        (this._placement !== appBarPlacementTop || thisWinUI._Overlay._keyboardInfo._visibleDocTop !== 0)) {
                        this._doNotFocus = true;
                        this._fakeHide = true;
                        this._show();
                    } else {
                        // Ensure any animation dropped during the showing keyboard are caught up.
                        this._checkDoNext();
                    }
                }
                this._scrollHappened = false;
            },

            // _checkPosition repositions the AppBar when the soft keyboard shows up
            _checkPosition: function () {
                // Bottom's the only one needing movement
                if (this._placement === appBarPlacementBottom) {
                    this._element.style.bottom = this._getAdjustedBottom() + "px";
                } else if (this._placement === appBarPlacementTop) {
                    this._element.style.top = this._getAdjustedTop() + "px";
                }
                // else we don't touch custom positions
            },

            _checkScrollPosition: function (event) {
                // If keyboard's animating, then remember we may come in
                if (this._keyboardShowing) {
                    // Tag that it's OK to edge back in.
                    this._scrollHappened = true;
                    return;
                }

                // We only need to update if we're visible
                if (!this.hidden || this._animating) {
                    this._checkPosition();
                    // Ensure any animation dropped during the showing keyboard are caught up.
                    this._checkDoNext();
                }
            },

            _alreadyInPlace: function () {
                // See if we're already where we're supposed to be.
                if (this._placement === appBarPlacementBottom) {
                    if (parseInt(this._element.style.bottom) === this._getAdjustedBottom()) {
                        return true;
                    }
                } else if (this._placement === appBarPlacementTop) {
                    if (parseInt(this._element.style.top) === this._getAdjustedTop()) {
                        return true;
                    }
                }
                // else we don't understand custom positioning
                return false;
            },
            
            // If there is a visible non-sticky AppBar then it sets the firstDiv tabIndex to
            //   the minimum tabIndex found in the AppBars and finalDiv to the max found.
            // Otherwise sets their tabIndex to -1 so they are not tab stops.
            _updateFirstAndFinalDiv : function () {
                var appBarFirstDiv = this._element.querySelectorAll("." + firstDivClass);
                appBarFirstDiv = appBarFirstDiv.length >= 1 ? appBarFirstDiv[0] : null;
                    
                var appBarFinalDiv = this._element.querySelectorAll("." + finalDivClass);
                appBarFinalDiv = appBarFinalDiv.length >= 1 ? appBarFinalDiv[0] : null;
                
                // Remove the firstDiv & finalDiv if they are not at the appropriate locations
                if (appBarFirstDiv && (this._element.children[0] != appBarFirstDiv)) {
                    appBarFirstDiv.parentNode.removeChild(appBarFirstDiv);
                    appBarFirstDiv = null;
                }
                if (appBarFinalDiv && (this._element.children[this._element.children.length - 1] != appBarFinalDiv)) {
                    appBarFinalDiv.parentNode.removeChild(appBarFinalDiv);
                    appBarFinalDiv = null;
                }

                // Create and add the firstDiv & finalDiv if they don't already exist
                if (!appBarFirstDiv) {
                    // Add a firstDiv that will be the first child of the appBar.
                    // On focus set focus to the previous appBar.
                    // The div should only be focusable if there are visible non-sticky AppBars.
                    appBarFirstDiv = document.createElement("div");
                    // display: inline is needed so that the div doesn't take up space and cause the page to scroll on focus
                    appBarFirstDiv.style.display = "inline";
                    appBarFirstDiv.className = firstDivClass;
                    appBarFirstDiv.tabIndex = -1;
                    appBarFirstDiv.setAttribute("aria-hidden", "true");
                    appBarFirstDiv.addEventListener("focus", _setFocusToPreviousAppBar, true);
                    this._element.insertAdjacentElement("AfterBegin", appBarFirstDiv);
                }
                if (!appBarFinalDiv) {
                    // Add a finalDiv that will be the last child of the appBar.
                    // On focus set focus to the next appBar.
                    // The div should only be focusable if there are visible non-sticky AppBars.
                    appBarFinalDiv = document.createElement("div");
                    // display: inline is needed so that the div doesn't take up space and cause the page to scroll on focus
                    appBarFinalDiv.style.display = "inline";
                    appBarFinalDiv.className = finalDivClass;
                    appBarFinalDiv.tabIndex = -1;
                    appBarFinalDiv.setAttribute("aria-hidden", "true");
                    appBarFinalDiv.addEventListener("focus", _setFocusToNextAppBar, true);
                    this._element.appendChild(appBarFinalDiv);
                }
                
                // Update the tabIndex of the firstDiv & finalDiv
                if (_isThereVisibleNonStickyBar()) {
                    var elms = this._element.getElementsByTagName("*");

                    if (appBarFirstDiv) {
                        appBarFirstDiv.tabIndex = thisWinUI._Overlay._getLowestTabIndexInList(elms);
                    }
                    if (appBarFinalDiv) {
                        appBarFinalDiv.tabIndex = thisWinUI._Overlay._getHighestTabIndexInList(elms);
                    }
                } else {
                    if (appBarFirstDiv) {
                        appBarFirstDiv.tabIndex = -1;
                    }
                    if (appBarFinalDiv) {
                        appBarFinalDiv.tabIndex = -1;
                    }
                }
            }
        })
    });


    // Statics
    thisWinUI.AppBar._ElementWithFocusPreviousToAppBar = null;
    
    // Returns appbar element (or CED/sentinal) if the element or what had focus before the element (if a Flyout) is either:
    //   1) an AppBar,
    //   2) OR in the subtree of an AppBar,
    //   3) OR an AppBar click eating div.
    // Returns null otherwise.
    thisWinUI.AppBar._isAppBarOrChild = function (element) {
        // If it's null, we can't do this
        if (!element) {
            return null;
        }

        // click eating divs and sentinals should not have children
        if (WinJS.Utilities.hasClass(element, thisWinUI._Overlay._clickEatingAppBarClass) ||
            WinJS.Utilities.hasClass(element, thisWinUI._Overlay._clickEatingFlyoutClass) ||
            WinJS.Utilities.hasClass(element, firstDivClass) ||
            WinJS.Utilities.hasClass(element, finalDivClass)) {
            return element;
        }

        while (element && element !== document) {
            if (WinJS.Utilities.hasClass(element, appBarClass)) {
                return element;
            }
            if (WinJS.Utilities.hasClass(element, "win-flyout")
             && element != element.winControl._previousFocus) {
                return thisWinUI.AppBar._isAppBarOrChild(element.winControl._previousFocus);
            }

            element = element.parentNode;
        }

        return null;
    };

    // Returns true if the element or what had focus before the element (if a Flyout) is either:
    //   1) the appBar or subtree
    //   2) OR in a flyout spawned by the appBar
    // Returns false otherwise.
    thisWinUI.AppBar._isWithinAppBarOrChild = function (element, appBar) {
        if (!element || !appBar) {
            return false;
        }
        if (appBar.contains(element)) {
            return true;
        }
        var flyout = thisWinUI._Overlay._getParentControlUsingClassName(element, "win-flyout");
        return (flyout && appBar.contains(flyout._previousFocus));
    };
            
    // Overlay class calls this for global light dismiss events
    thisWinUI.AppBar._hideLightDismissAppBars = function (event, keyboardInvoked) {
        var elements = document.querySelectorAll("." + appBarClass);
        var len = elements.length;
        var AppBars = [];
        for (var i = 0; i < len; i++) {
            var AppBar = elements[i].winControl;
            if (AppBar && !AppBar.sticky && !AppBar.hidden) {
                AppBars.push(AppBar);
            }
        }

        _hideAllBars(AppBars, keyboardInvoked);
    };
    
    // Callback for AppBar Edgy Event Command
    thisWinUI.AppBar._toggleAppBarEdgy = function(keyboardInvoked) {
        var bars = _getDynamicBarsForEdgy();

        // If they're all visible hide them, otherwise show them all
        if (bars._visible && !bars._hidden) {
            _hideAllBars(bars, keyboardInvoked);
            return "hiding";
        } else {
            _showAllBars(bars, keyboardInvoked);
            return "showing";
        }
    };

    var strings = {
        get ariaLabel() { return WinJS.Resources._getWinJSString("ui/appBarAriaLabel").value; },
        get requiresCommands() { return WinJS.Resources._getWinJSString("ui/requiresCommands").value; },
        get cannotChangePlacementWhenVisible() { return WinJS.Resources._getWinJSString("ui/cannotChangePlacementWhenVisible").value; },
        get badLayout() { return WinJS.Resources._getWinJSString("ui/badLayout").value; },
        get cannotChangeLayoutWhenVisible() { return WinJS.Resources._getWinJSString("ui/cannotChangeLayoutWhenVisible").value; }
    };
})(WinJS);


/// <dictionary>appbar,Flyout,Flyouts,Statics</dictionary>
(function flyoutInit(WinJS) {
    "use strict";

    var thisWinUI = WinJS.UI;

    // Class Names
    var appBarCommandClass = "win-command";
    var flyoutClass        = "win-flyout";
    var flyoutLightClass   = "win-ui-light";
    var menuClass          = "win-menu";
    var scrollsClass       = "win-scrolls";
    
    var finalDivClass       = "win-finaldiv";
    var firstDivClass       = "win-firstdiv";

    function getDimension(element, property) {
        return parseFloat(element, window.getComputedStyle(element, null)[property]);
    }
    
    WinJS.Namespace.define("WinJS.UI", {
        /// <summary locid="WinJS.UI.Flyout">Flyout controls provide temporary surfaces for small amounts of content.</summary>
        /// <name locid="WinJS.UI.Flyout_name">Flyout</name>
        /// <icon src="ui_winjs.ui.flyout.12x12.png" width="12" height="12" />
        /// <icon src="ui_winjs.ui.flyout.16x16.png" width="16" height="16" />
        /// <htmlSnippet supportsContent="true"><![CDATA[<div data-win-control="WinJS.UI.Flyout"></div>]]></htmlSnippet>
        /// <event name="beforeshow" locid="WinJS.UI.Flyout_e:beforeshow">Raised just before showing a flyout.</event>
        /// <event name="aftershow" locid="WinJS.UI.Flyout_e:aftershow">Raised immediately after a flyout is fully shown.</event>
        /// <event name="beforehide" locid="WinJS.UI.Flyout_e:beforehide">Raised just before hiding a flyout.</event>
        /// <event name="afterhide" locid="WinJS.UI.Flyout_e:afterhide">Raised immediately after a flyout is fully hidden.</event>
        /// <part name="flyout" class="win-flyout" locid="WinJS.UI.Flyout_part:flyout">The Flyout control itself</part>
        /// <resource type="javascript" src="//Microsoft.WinJS.1.0/js/base.js" shared="true" />
        /// <resource type="javascript" src="//Microsoft.WinJS.1.0/js/ui.js" shared="true" />
        /// <resource type="css" src="//Microsoft.WinJS.1.0/css/ui-dark.css" shared="true" />
        Flyout: WinJS.Class.derive(WinJS.UI._Overlay, function (element, options) {
            /// <signature helpKeyword="WinJS.UI.Flyout.Flyout">
            /// <summary locid="WinJS.UI.Flyout.constructor">
            /// Constructs the Flyout control and associates it with the underlying DOM element.
            /// </summary>
            /// <param name="element" type="HTMLElement" domElement="true" locid="WinJS.UI.Flyout.constructor_p:element">
            /// The DOM element to be associated with the Flyout control.
            /// </param>
            /// <param name="options" type="Object" domElement="false" locid="WinJS.UI.Flyout.constructor_p:options">
            /// The set of options to be applied initially to the Flyout control.
            /// </param>
            /// <returns type="WinJS.UI.Flyout" locid="WinJS.UI.Flyout.constructor_returnValue">A fully constructed Flyout control.</returns>
            /// </signature>

            this._baseFlyoutConstructor(element, options);

            var _elms = this._element.getElementsByTagName("*");
            var firstDiv = this._addFirstDiv();
            firstDiv.tabIndex = thisWinUI._Overlay._getLowestTabIndexInList(_elms);
            var finalDiv = this._addFinalDiv();
            finalDiv.tabIndex = thisWinUI._Overlay._getHighestTabIndexInList(_elms);

            // Handle "esc" & "tab" key presses
            this._element.addEventListener("keydown", this._handleKeyDown, true);

            return this;
        }, {
            _lastMaxHeight: null,

            _baseFlyoutConstructor: function (element, options) {
                // Flyout constructor

                // We have some options with defaults
                this._placement = "auto";
                this._alignment = "center";
                
                // Call the base overlay constructor helper
                this._baseOverlayConstructor(element, options);

                // Make a click eating div
                thisWinUI._Overlay._createClickEatingDivFlyout();

                // Start flyouts hidden
                this._element.style.visibilty = "hidden";
                this._element.style.display = "none";

                // Attach our css class
                WinJS.Utilities.addClass(this._element, flyoutClass);
                WinJS.Utilities.addClass(this._element, flyoutLightClass);

                // Make sure we have an ARIA role
                var role = this._element.getAttribute("role");
                if (role === null || role === "" || role === undefined) {
                    if (WinJS.Utilities.hasClass(this._element, menuClass)) {
                        this._element.setAttribute("role", "menu");
                    } else {
                        this._element.setAttribute("role", "dialog");
                    }
                }
                var label = this._element.getAttribute("aria-label");
                if (label === null || label === "" || label === undefined) {
                    this._element.setAttribute("aria-label", strings.ariaLabel);
                }

                // Base animation is popIn, but our flyout has different arguments
                this._currentAnimateIn = this._flyoutAnimateIn;
                this._currentAnimateOut = this._flyoutAnimateOut;

                // Make sure flyout event handlers are hooked up
                this._addFlyoutEventHandlers(true);
            },

            /// <field type="String" locid="WinJS.UI.Flyout.anchor" helpKeyword="WinJS.UI.Flyout.anchor">The anchor element is the HTML element which the flyout originates from and is positioned relative to. You can override it with the anchor that you pass in the show() method.</field>
            anchor: {
                get: function () {
                    return this._anchor;
                },
                set: function (value) {
                    this._anchor = value;
                }
            },

            /// <field type="String" defaultValue="auto" oamOptionsDatatype="WinJS.UI.Flyout.placement" locid="WinJS.UI.Flyout.placement" helpKeyword="WinJS.UI.Flyout.placement">Default placement to be used for this flyout, overridden by placement passed in show().</field>
            placement: {
                get: function () {
                    return this._placement;
                },
                set: function (value) {
                    if (value !== "top" && value !== "bottom" && value !== "left" && value !== "right" && value !== "auto") {
                        // Not a legal placement value
                        throw new WinJS.ErrorFromName("WinJS.UI.Flyout.BadPlacement", strings.badPlacement);
                    }
                    this._placement = value;
                }
            },

            /// <field type="String" defaultValue="center" oamOptionsDatatype="WinJS.UI.Flyout.alignment" locid="WinJS.UI.Flyout.alignment" helpKeyword="WinJS.UI.Flyout.alignment">Default alignment to be used for this flyout, overridden by alignment passed in show().</field>
            alignment: {
                get: function () {
                    return this._alignment;
                },
                set: function (value) {
                    if (value !== "right" && value !== "left" && value !== "center") {
                        // Not a legal alignment value
                        throw new WinJS.ErrorFromName("WinJS.UI.Flyout.BadAlignment", strings.badAlignment);
                    }
                    this._alignment = value;
                }
            },

            show: function (anchor, placement, alignment) {
                /// <signature helpKeyword="WinJS.UI.Flyout.show">
                /// <summary locid="WinJS.UI.Flyout.show">
                /// Shows the Flyout, if hidden, regardless of other state
                /// </summary>
                /// <param name="anchor" type="HTMLElement" domElement="true" locid="WinJS.UI.Flyout.show_p:anchor">
                /// The DOM element, or ID of a DOM element to anchor the Flyout, overriding the anchor property for this time only.
                /// </param>
                /// <param name="placement" type="Object" domElement="false" locid="WinJS.UI.Flyout.show_p:placement">
                /// The placement of the Flyout to the anchor: 'auto' (default), 'top', 'bottom', 'left', or 'right'.  This parameter overrides the placement property for this show only.
                /// </param>
                /// <param name="alignment" type="Object" domElement="false" locid="WinJS.UI.Flyout.show:alignment">
                /// For 'top' or 'bottom' placement, the alignment of the Flyout to the anchor's edge: 'center' (default), 'left', or 'right'.  This parameter overrides the alignment property for this show only.
                /// </param>
                /// </signature>
                // Just call private version to make appbar flags happy
                this._show(anchor, placement, alignment);
            },

            _show: function (anchor, placement, alignment) {
                this._baseFlyoutShow(anchor, placement, alignment);
            },

            hide: function () {
                /// <signature helpKeyword="WinJS.UI.Flyout.hide">
                /// <summary locid="WinJS.UI.Flyout.hide">
                /// Hides the Flyout, if visible, regardless of other state
                /// </summary>
                /// </signature>
                // Just wrap the private one, turning off keyboard invoked flag
                this._keyboardInvoked = false;
                this._hide();
            },

            _hide: function () {
                if (this._baseHide()) {
                    // Return focus if this or the flyout CED has focus
                    var active = document.activeElement;
                    if (this._previousFocus
                       && active
                       && (this._element.contains(active) 
                           || WinJS.Utilities.hasClass(active, thisWinUI._Overlay._clickEatingFlyoutClass))
                       && this._previousFocus.focus !== undefined) {                          
                        
                        // _isAppBarOrChild may return a CED or sentinal
                        var appBar = thisWinUI.AppBar._isAppBarOrChild(this._previousFocus);
                        if (!appBar || (appBar.winControl && !appBar.winControl.hidden && !appBar.winAnimating)) {
                            // Don't move focus back to a appBar that is hidden
                            // We cannot rely on element.style.visibility because it will be visible while animating
                            var role = this._previousFocus.getAttribute("role");
                            var fHideRole = thisWinUI._Overlay._keyboardInfo._visible && !this._keyboardWasUp;
                            if (fHideRole) {
                                // Convince IHM to dismiss because it only came up after the flyout was up.
                                // Change aria role and back to get IHM to dismiss.
                                this._previousFocus.setAttribute("role", "");
                            }
                        
                            if (this._keyboardInvoked) {
                                this._previousFocus.focus();
                            } else {
                                thisWinUI._Overlay._trySetActive(this._previousFocus);
                            }
                            active = document.activeElement;

                            if (fHideRole) {
                                // Restore the role so that css is applied correctly
                                var that = this;
                                setImmediate(function () {
                                    // We clear the previousFocus so make sure it still exists
                                    if (that._previousFocus) {
                                        that._previousFocus.setAttribute("role", role);
                                    }
                                });
                            }
                        }
                        
                        // If the anchor gained focus we want to hide the focus in the non-keyboarding scenario
                        if (!this._keyboardInvoked && (this._previousFocus === active) && appBar && active) {
                            thisWinUI._Overlay._addHideFocusClass(active);
                        }
                    }
                    
                    // Clear the previousFocus after allowing role to be restored if needed
                    var that = this;
                    setImmediate(function () {
                        that._previousFocus = null;
                    });
                    
                    // Need click-eating div to be hidden if there are no other visible flyouts
                    if (!this._isThereVisibleFlyout()) {
                        thisWinUI._Overlay._hideClickEatingDivFlyout();
                    }
                }
            },

            _baseFlyoutShow: function (anchor, placement, alignment) {
                // Don't do anything if disabled
                if (this.disabled) {
                    return;
                }
                // Pick up defaults
                if (!anchor) {
                    anchor = this._anchor;
                }
                if (!placement) {
                    placement = this._placement;
                }
                if (!alignment) {
                    alignment = this._alignment;
                }

                // Dereference the anchor if necessary
                if (typeof anchor === "string") {
                    anchor = document.getElementById(anchor);
                } else if (anchor && anchor.element) {
                    anchor = anchor.element;
                }
                
                // We expect an anchor
                if (!anchor) {
                    // If we have _nextLeft, etc., then we were continuing an old animation, so that's OK
                    if (!this._retryLast) {
                        throw new WinJS.ErrorFromName("WinJS.UI.Flyout.NoAnchor", strings.noAnchor);
                    }
                    // Last call was incomplete, so use the previous _current values.
                    this._retryLast = null;
                } else {
                    // Remember the anchor so that if we lose focus we can go back
                    this._currentAnchor = anchor;
                    // Remember current values
                    this._currentPlacement = placement;
                    this._currentAlignment = alignment;
                }

                // Need click-eating div to be visible, no matter what
                if (!this._sticky) {
                    thisWinUI._Overlay._showClickEatingDivFlyout();
                }

                // If we're animating (eg baseShow is going to fail), then don't mess up our current state.
                // Queue us up to wait for current animation to finish first.
                if (this._element.winAnimating) {
                    this._doNext = "show";
                    this._retryLast = true;
                    return;
                }

                // We call our base _baseShow to handle the actual animation
                if (this._baseShow()) {
                    // (_baseShow shouldn't ever fail because we tested winAnimating above).
                    if (!WinJS.Utilities.hasClass(this.element, "win-menu")) {
                        // Verify that the firstDiv is in the correct location.
                        // Move it to the correct location or add it if not.
                        var _elms = this._element.getElementsByTagName("*"); 
                        var firstDiv = this.element.querySelectorAll(".win-first");
                        if (this.element.children.length && !WinJS.Utilities.hasClass(this.element.children[0], firstDivClass)) {
                            if (firstDiv && firstDiv.length > 0) {
                                firstDiv.item(0).parentNode.removeChild(firstDiv.item(0));
                            }

                            firstDiv = this._addFirstDiv();
                        }
                        firstDiv.tabIndex = thisWinUI._Overlay._getLowestTabIndexInList(_elms);
                        
                        // Verify that the finalDiv is in the correct location.
                        // Move it to the correct location or add it if not.
                        var finalDiv = this.element.querySelectorAll(".win-final");
                        if (!WinJS.Utilities.hasClass(this.element.children[this.element.children.length - 1], finalDivClass)) {
                            if (finalDiv && finalDiv.length > 0) {
                                finalDiv.item(0).parentNode.removeChild(finalDiv.item(0));
                            }

                            finalDiv = this._addFinalDiv();
                        }
                        finalDiv.tabIndex = thisWinUI._Overlay._getHighestTabIndexInList(_elms);
                    }

                    // Hide all other flyouts
                    this._hideAllOtherFlyouts(this);
                    
                    // Store what had focus before showing the Flyout.
                    // This must happen after we hide all other flyouts so that we store the correct element.
                    this._previousFocus = document.activeElement;
                }
            },

            _endShow: function () {                
                // Remember if the IHM was up since we may need to hide it when the flyout hides.
                // This check needs to happen after the IHM has a chance to hide itself after we force hide
                // all other visible Flyouts.
                this._keyboardWasUp = thisWinUI._Overlay._keyboardInfo._visible;
                
                if (!WinJS.Utilities.hasClass(this.element, "win-menu")) {
                    // Put focus on the first child in the Flyout
                    this._focusOnFirstFocusableElementOrThis();
                    
                    // Prevent what is gaining focus from showing that it has focus
                    thisWinUI._Overlay._addHideFocusClass(document.activeElement); 
                } else {
                    // Make sure the menu has focus, but don't show a focus rect
                    thisWinUI._Overlay._trySetActive(this._element);
                }
            },

            // Find our new flyout position.
            _findPosition: function() {
                this._nextHeight = null;
                this._keyboardMovedUs = false;
                this._hasScrolls = false;
                this._keyboardSquishedUs = 0;
                
                // Make sure menu toggles behave
                if (this._checkToggle) {
                    this._checkToggle();
                }

                // Update margins for this alignment and remove old scrolling
                this._updateAdjustments(this._currentAlignment);

                // Set up the new position, and prep the offset for showPopup
                this._getTopLeft();
                // Panning top offset is calculated top - current scroll adjustment
                this._scrollTop = this._nextTop - thisWinUI._Overlay._keyboardInfo._visibleDocTop;

                // Adjust position
                if (this._nextTop < 0) {
                    // Need to attach to bottom
                    this._element.style.bottom = "0px";
                    this._element.style.top = "auto";
                } else {
                    // Normal, attach to top
                    this._element.style.top = this._nextTop + "px";
                    this._element.style.bottom = "auto";
                }
                if (this._nextLeft < 0) {
                    // Overran right, attach to right
                    this._element.style.right = "0px";
                    this._element.style.left = "auto";
                } else {
                    // Normal, attach to left
                    this._element.style.left = this._nextLeft + "px";
                    this._element.style.right = "auto";
                }

                // Adjust height/scrollbar
                if (this._nextHeight !== null) {
                    WinJS.Utilities.addClass(this._element, scrollsClass);
                    this._lastMaxHeight = this._element.style.maxHeight;
                    this._element.style.maxHeight = this._nextHeight + "px";
                    this._nextBottom = this._nextTop + this._nextHeight;
                    this._hasScrolls = true;
                }

                // May need to adjust if the IHM is showing.
                if (thisWinUI._Overlay._keyboardInfo._visible) {
                    // Use keyboard logic
                    this._checkKeyboardFit();

                    if (this._keyboardMovedUs) {
                        this._adjustForKeyboard();
                    }
                }
            },

            // This determines our positioning.  We have 5 modes, the 1st four are explicit, the last is automatic:
            // * top - position explicitly on the top of the anchor, shrinking and adding scrollbar as needed.
            // * bottom - position explicitly below the anchor, shrinking and adding scrollbar as needed.
            // * left - position left of the anchor, shrinking and adding a vertical scrollbar as needed.
            // * right - position right of the anchor, shrinking and adding a vertical scroolbar as needed.
            // * auto - Automatic placement.
            // Auto tests the height of the anchor and the flyout.  For consistency in orientation, we imagine
            // that the anchor is placed in the vertical center of the display.  If the flyout would fit above
            // that centered anchor, then we will place the flyout vertically in relation to the anchor, otherwise
            // placement will be horizontal.
            // Vertical auto placement will be positioned on top of the anchor if room, otherwise below the anchor.
            //   - this is because touch users would be more likely to obscure flyouts below the anchor.
            // Horizontal auto placement will be positioned to the left of the anchor if room, otherwise to the right.
            //   - this is because right handed users would be more likely to obscure a flyout on the right of the anchor.
            // Auto placement will add a vertical scrollbar if necessary.
            _getTopLeft: function () {
                var anchorRawRectangle = this._currentAnchor.getBoundingClientRect(),
                    flyout = {},
                    anchor = {};

                // Adjust for the anchor's margins
                anchor.top = anchorRawRectangle.top;
                anchor.bottom = anchorRawRectangle.bottom;
                anchor.left = anchorRawRectangle.left;
                anchor.right = anchorRawRectangle.right;
                anchor.height = anchor.bottom - anchor.top;
                anchor.width = anchor.right - anchor.left;

                // Get our flyout and margins, note that getDimension calls
                // window.getComputedStyle, which ensures layout is updated.
                flyout.marginTop = getDimension(this._element, "marginTop");
                flyout.marginBottom = getDimension(this._element, "marginBottom");
                flyout.marginLeft = getDimension(this._element, "marginLeft");
                flyout.marginRight = getDimension(this._element, "marginRight");
                flyout.width = WinJS.Utilities.getTotalWidth(this._element);
                flyout.height = WinJS.Utilities.getTotalHeight(this._element);
                flyout.innerWidth = WinJS.Utilities.getContentWidth(this._element);
                flyout.innerHeight = WinJS.Utilities.getContentHeight(this._element);
                this._nextMarginPadding = (flyout.height - flyout.innerHeight);

                // Check fit for requested this._currentPlacement, doing fallback if necessary
                switch (this._currentPlacement) {
                    case "top":
                        if (!this._fitTop(anchor, flyout)) {
                            // Didn't fit, needs scrollbar
                            this._nextTop = thisWinUI._Overlay._keyboardInfo._visibleDocTop;
                            this._nextHeight = anchor.top - thisWinUI._Overlay._keyboardInfo._visibleDocTop - this._nextMarginPadding;
                        }
                        this._centerHorizontally(anchor, flyout, this._currentAlignment);
                        break;
                    case "bottom":
                        if (!this._fitBottom(anchor, flyout)) {
                            // Didn't fit, needs scrollbar
                            this._nextTop = -1;
                            this._nextHeight = thisWinUI._Overlay._keyboardInfo._visibleDocHeight - (anchor.bottom - thisWinUI._Overlay._keyboardInfo._visibleDocTop) - this._nextMarginPadding;
                        }
                        this._centerHorizontally(anchor, flyout, this._currentAlignment);
                        break;
                    case "left":
                        if (!this._fitLeft(anchor, flyout)) {
                            // Didn't fit, just shove it to edge
                            this._nextLeft = 0;
                        }
                        this._centerVertically(anchor, flyout);
                        break;
                    case "right":
                        if (!this._fitRight(anchor, flyout)) {
                            // Didn't fit,just shove it to edge
                            this._nextLeft = -1;
                        }
                        this._centerVertically(anchor, flyout);
                        break;
                    case "auto":
                        // Auto, if the anchor was in the vertical center of the display would we fit above it?
                        if (this._sometimesFitsAbove(anchor, flyout)) {
                            // It will fit above or below the anchor
                            if (!this._fitTop(anchor, flyout)) {
                                // Didn't fit above (preferred), so go below.
                                this._fitBottom(anchor, flyout);
                            }
                            this._centerHorizontally(anchor, flyout, this._currentAlignment);
                        } else {
                            // Won't fit above or below, try a side
                            if (!this._fitLeft(anchor, flyout) && 
                                !this._fitRight(anchor, flyout)) {
                                // Didn't fit left or right either, is top or bottom bigger?
                                if (this._topHasMoreRoom(anchor)) {
                                    // Top, won't fit, needs scrollbar
                                    this._nextTop = thisWinUI._Overlay._keyboardInfo._visibleDocTop;
                                    this._nextHeight = anchor.top - thisWinUI._Overlay._keyboardInfo._visibleDocTop - this._nextMarginPadding;
                                } else {
                                    // Bottom, won't fit, needs scrollbar
                                    this._nextTop = -1;
                                    this._nextHeight = thisWinUI._Overlay._keyboardInfo._visibleDocHeight - (anchor.bottom - thisWinUI._Overlay._keyboardInfo._visibleDocTop) - this._nextMarginPadding;
                                }
                                this._centerHorizontally(anchor, flyout, this._currentAlignment);
                            } else {
                                this._centerVertically(anchor, flyout);
                            }
                        }
                        break;
                    default:
                        // Not a legal this._currentPlacement value
                        throw new WinJS.ErrorFromName("WinJS.UI.Flyout.BadPlacement", strings.badPlacement);
                }

                // Remember "bottom" in case we need to consider keyboard later, only tested for top-pinned bars
                this._nextBottom = this._nextTop + flyout.height;
            },

            // If the anchor is centered vertically, would the flyout fit above it?
            _sometimesFitsAbove: function(anchor, flyout) {
                return ((thisWinUI._Overlay._keyboardInfo._visibleDocHeight - anchor.height) / 2) >= flyout.height;
            },

            _topHasMoreRoom: function(anchor) {
                return anchor.top > thisWinUI._Overlay._keyboardInfo._visibleDocHeight - anchor.bottom;
            },

            // See if we can fit in various places, fitting in the main view,
            // ignoring viewport changes, like for the IHM.
            _fitTop: function (anchor, flyout) {
                this._nextTop = anchor.top - flyout.height;
                this._nextAnimOffset = { top: "40px", left: "0px" };
                return (this._nextTop >= thisWinUI._Overlay._keyboardInfo._visibleDocTop &&
                        this._nextTop + flyout.height <= thisWinUI._Overlay._keyboardInfo._visibleDocBottom);
            },

            _fitBottom: function (anchor, flyout) {
                this._nextTop = anchor.bottom;
                this._nextAnimOffset = { top: "-40px", left: "0px" };
                return (this._nextTop >= thisWinUI._Overlay._keyboardInfo._visibleDocTop &&
                        this._nextTop + flyout.height <= thisWinUI._Overlay._keyboardInfo._visibleDocBottom);
            },

            _fitLeft: function (anchor, flyout) {
                this._nextLeft = anchor.left - flyout.width;
                this._nextAnimOffset = { top: "0px", left: "40px" };
                return (this._nextLeft >= 0 && this._nextLeft + flyout.width <= document.documentElement.clientWidth);
            },

            _fitRight: function (anchor, flyout) {
                this._nextLeft = anchor.right;
                this._nextAnimOffset = { top: "0px", left: "-40px" };
                return (this._nextLeft >= 0 && this._nextLeft + flyout.width <= document.documentElement.clientWidth);
            },

            _centerVertically: function (anchor, flyout) {
                this._nextTop = anchor.top + anchor.height / 2 - flyout.height / 2;
                if (this._nextTop < thisWinUI._Overlay._keyboardInfo._visibleDocTop) {
                    this._nextTop = thisWinUI._Overlay._keyboardInfo._visibleDocTop;
                } else if (this._nextTop + flyout.height >= thisWinUI._Overlay._keyboardInfo._visibleDocBottom) {
                    // Flag to put on bottom
                    this._nextTop = -1;
                }
            },

            _centerHorizontally: function (anchor, flyout, alignment) {
                if (alignment === "center") {
                    this._nextLeft = anchor.left + anchor.width / 2 - flyout.width / 2;
                } else if (alignment === "left") {
                    this._nextLeft = anchor.left;
                } else if (alignment === "right") {
                    this._nextLeft = anchor.right - flyout.width;
                } else {
                    throw new WinJS.ErrorFromName("WinJS.UI.Flyout.BadAlignment", strings.badAlignment);
                }
                if (this._nextLeft < 0) {
                    this._nextLeft = 0;
                } else if (this._nextLeft + flyout.width >= document.documentElement.clientWidth) {
                    // flag to put on right
                    this._nextLeft = -1;
                }
            },

            _updateAdjustments: function (alignment) {
                // Move to 0,0 in case it is off screen, so that it lays out at a reasonable size
                this._element.style.top = "0px";
                this._element.style.bottom = "auto";
                this._element.style.left = "0px";
                this._element.style.right = "auto";

                // Scrolling may not be necessary
                WinJS.Utilities.removeClass(this._element, scrollsClass);
                if (this._lastMaxHeight !== null) {
                    this._element.style.maxHeight = this._lastMaxHeight;
                    this._lastMaxHeight = null;
                }
                // Alignment
                if (alignment === "center") {
                    WinJS.Utilities.removeClass(this._element, "win-leftalign");
                    WinJS.Utilities.removeClass(this._element, "win-rightalign");
                } else if (alignment === "left") {
                    WinJS.Utilities.addClass(this._element, "win-leftalign");
                    WinJS.Utilities.removeClass(this._element, "win-rightalign");
                } else if (alignment === "right") {
                    WinJS.Utilities.addClass(this._element, "win-rightalign");
                    WinJS.Utilities.removeClass(this._element, "win-leftalign");
                }
            },

            _showingKeyboard: function (event) {
                if (this.hidden) {
                    return;
                }

                // The only way that we can be showing a keyboard when a flyout is up is because the input was
                // in the flyout itself, in which case we'll be moving ourselves.  There is no practical way
                // for the application to override this as the focused element is in our flyout.
                event.ensuredFocusedElementInView = true;

                // See if the keyboard is going to force us to move
                this._checkKeyboardFit();

                if (this._keyboardMovedUs) {
                    // Pop out immediately, then move to new spot
                    this._element.style.opacity = 0;
                    var that = this;
                    setTimeout(function () { that._adjustForKeyboard(); that._baseAnimateIn(); }, thisWinUI._Overlay._keyboardInfo._animationShowLength);
                }
            },

            _resize: function (event) {
                // If hidden and not busy animating, then nothing to do
                if (this.hidden && !this._animating) {
                    return;
                }

                // This should only happen if the IHM is dismissing,
                // the only other way is for viewstate changes, which
                // would dismiss any flyout.
                if (this._keyboardHiding) {
                    // Hiding keyboard, update our position, giving the anchor a chance to update first.
                    var that = this;
                    setImmediate(function () { that._findPosition(); });
                    this._keyboardHiding = false;
                }
            },

            _checkKeyboardFit: function () {
                // Check for moving to fit keyboard:
                // - Too Tall, above top, or below bottom.
                var height = WinJS.Utilities.getTotalHeight(this._element);
                var viewportHeight = thisWinUI._Overlay._keyboardInfo._visibleDocHeight - this._nextMarginPadding;
                if (height > viewportHeight) {
                    // Too Tall, pin to top with max height
                    this._keyboardMovedUs = true;
                    this._scrollTop = 0;
                    this._keyboardSquishedUs = viewportHeight;
                } else if (this._nextTop === -1) {
                    // Pinned to bottom counts as moved
                    this._keyboardMovedUs = true;
                } else if (this._nextTop < thisWinUI._Overlay._keyboardInfo._visibleDocTop) {
                    // Above the top of the viewport
                    this._scrollTop = 0;
                    this._keyboardMovedUs = true;
                } else if (this._nextBottom > thisWinUI._Overlay._keyboardInfo._visibleDocBottom) {
                    // Below the bottom of the viewport
                    this._scrollTop = -1;
                    this._keyboardMovedUs = true;
                }
            },

            _adjustForKeyboard: function () {
                // Keyboard moved us, update our metrics as needed
                if (this._keyboardSquishedUs) {
                    // Add scrollbar if we didn't already have scrollsClass
                    if (!this._hasScrolls) {
                        WinJS.Utilities.addClass(this._element, scrollsClass);
                        this._lastMaxHeight = this._element.style.maxHeight;
                    }
                    // Adjust height
                    this._element.style.maxHeight = this._keyboardSquishedUs + "px";
                }

                // Update top/bottom
                this._checkScrollPosition(true);
            },

            _hidingKeyboard: function (event) {
                // If we aren't visible and not animating, or haven't been repositioned, then nothing to do
                // We don't know if the keyboard moved the anchor, so _keyboardMovedUs doesn't help here
                if (this.hidden && !this._animating) {
                    return;
                }

                // Snap to the final position
                // We'll either just reveal the current space or resize the window
                if (thisWinUI._Overlay._keyboardInfo._isResized) {
                    // Flag resize that we'll need an updated position
                    this._keyboardHiding = true;
                } else {
                    // Not resized, update our final position, giving the anchor a chance to update first.
                    var that = this;
                    setImmediate(function () { that._findPosition(); });
                }
            },

            _checkScrollPosition: function (showing) {
                if (this.hidden && !showing) {
                    return;
                }

                // May need to adjust top by viewport offset
                if (this._scrollTop < 0) {
                    // Need to attach to bottom
                    this._element.style.bottom = thisWinUI._Overlay._keyboardInfo._visibleDocBottomOffset + "px";
                    this._element.style.top = "auto";
                } else {
                    // Normal, attach to top
                    this._element.style.top = (this._scrollTop + thisWinUI._Overlay._keyboardInfo._visibleDocTop) + "px";
                    this._element.style.bottom = "auto";
                }
            },

            // AppBar flyout animations
            _flyoutAnimateIn: function () {
                if (this._keyboardMovedUs){
                    return this._baseAnimateIn();
                } else {
                    this._element.style.opacity = 1;
                    this._element.style.visibility = "visible";
                    return WinJS.UI.Animation.showPopup(this._element, this._nextAnimOffset);
                }
            },

            _flyoutAnimateOut: function () {
                if (this._keyboardMovedUs) {
                    return this._baseAnimateOut();
                } else {
                    this._element.style.opacity = 0;
                    return WinJS.UI.Animation.hidePopup(this._element, this._nextAnimOffset);
                }
            },

            // Hide all other flyouts besides this one
            _hideAllOtherFlyouts: function (thisFlyout) {
                var flyouts = document.querySelectorAll(".win-flyout");
                for (var i = 0; i < flyouts.length; i++) {
                    var flyoutControl = flyouts[i].winControl;
                    if (flyoutControl && !flyoutControl.hidden && (flyoutControl !== thisFlyout)) {
                        flyoutControl.hide();
                    }
                }
            },

            // Returns true if there is a flyout in the DOM that is not hidden
            _isThereVisibleFlyout: function () {
                var flyouts = document.querySelectorAll(".win-flyout");
                for (var i = 0; i < flyouts.length; i++) {
                    var flyoutControl = flyouts[i].winControl;
                    if (flyoutControl && !flyoutControl.hidden) {
                        return true;
                    }
                }

                return false;
            },

            _handleKeyDown: function (event) {
                if (event.key === "Esc") {
                    // Show a focus rect on what we move focus to
                    event.preventDefault();
                    event.stopPropagation();
                    this.winControl._keyboardInvoked = true;
                    this.winControl._hide();
                } else if ((event.key === "Spacebar" || event.key === "Enter")
                     && (this === document.activeElement)) {
                         event.preventDefault();
                         event.stopPropagation();
                         this.winControl.hide();
                } else if (event.shiftKey && event.key === "Tab"
                      && this === document.activeElement
                      && !event.altKey && !event.ctrlKey && !event.metaKey) {
                    event.preventDefault();
                    event.stopPropagation();
                    this.winControl._focusOnLastFocusableElementOrThis();
                }
            },

            // Create and add a new first div as the first child
            _addFirstDiv: function () {
                var firstDiv = document.createElement("div");
                firstDiv.className = firstDivClass;
                firstDiv.style.display = "inline";
                firstDiv.setAttribute("role", "menuitem");
                firstDiv.setAttribute("aria-hidden", "true");

                this._element.insertAdjacentElement("AfterBegin", firstDiv);
                var that = this;
                firstDiv.addEventListener("focus", function () { that._focusOnLastFocusableElementOrThis(); }, false);
                
                return firstDiv;
            },
            
            // Create and add a new final div as the last child
            _addFinalDiv: function () {
                var finalDiv = document.createElement("div");
                finalDiv.className = finalDivClass;
                finalDiv.style.display = "inline";
                finalDiv.setAttribute("role", "menuitem");
                finalDiv.setAttribute("aria-hidden", "true");

                this._element.appendChild(finalDiv);
                var that = this;
                finalDiv.addEventListener("focus", function () { that._focusOnFirstFocusableElementOrThis(); }, false);
                
                return finalDiv;
            }
        })
    });

    // Statics

    var strings = {
        get ariaLabel() { return WinJS.Resources._getWinJSString("ui/flyoutAriaLabel").value; },
        get noAnchor() { return WinJS.Resources._getWinJSString("ui/noAnchor").value; },
        get badPlacement() { return WinJS.Resources._getWinJSString("ui/badPlacement").value; },
        get badAlignment() { return WinJS.Resources._getWinJSString("ui/badAlignment").value; }
    };

    //// Labels

    //// Errors

})(WinJS);

// Menu
/// <dictionary>Menu,Menus,Flyout,Flyouts,Statics</dictionary>
(function menuInit(WinJS) {
    "use strict";

    var thisWinUI = WinJS.UI;

    // Class Names
    var menuClass = "win-menu";
    var menuToggleClass = "win-menu-toggle";

    WinJS.Namespace.define("WinJS.UI", {
        /// <summary locid="WinJS.UI.Menu">The Menu control provides MenuCommands to the user.</summary>
        /// <name locid="WinJS.UI.Menu_name">Menu</name>
        /// <icon src="ui_winjs.ui.menu.12x12.png" width="12" height="12" />
        /// <icon src="ui_winjs.ui.menu.16x16.png" width="16" height="16" />
        /// <htmlSnippet supportsContent="true"><![CDATA[<div data-win-control="WinJS.UI.Menu">
        /// <button data-win-control="WinJS.UI.MenuCommand" data-win-options="{id:'',label:'example',type:'button',onclick:null}"></button>
        /// </div>]]></htmlSnippet>
        /// <event name="beforeshow" locid="WinJS.UI.Menu_e:beforeshow">Raised just before showing a menu.</event>
        /// <event name="aftershow" locid="WinJS.UI.Menu_e:aftershow">Raised immediately after a menu is fully shown.</event>
        /// <event name="beforehide" locid="WinJS.UI.Menu_e:beforehide">Raised just before hiding a menu.</event>
        /// <event name="afterhide" locid="WinJS.UI.Menu_e:afterhide">Raised immediately after a menu is fully hidden.</event>
        /// <part name="menu" class="win-menu" locid="WinJS.UI.Menu_part:menu">The Menu control itself</part>
        /// <resource type="javascript" src="//Microsoft.WinJS.1.0/js/base.js" shared="true" />
        /// <resource type="javascript" src="//Microsoft.WinJS.1.0/js/ui.js" shared="true" />
        /// <resource type="css" src="//Microsoft.WinJS.1.0/css/ui-dark.css" shared="true" />
        Menu: WinJS.Class.derive(WinJS.UI.Flyout, function (element, options) {
            /// <signature helpKeyword="WinJS.UI.Menu.Menu">
            /// <summary locid="WinJS.UI.Menu.constructor">
            /// Constructs the Menu control and associates it with the underlying DOM element.
            /// </summary>
            /// <param name="element" type="HTMLElement" domElement="true" locid="WinJS.UI.Menu.constructor_p:element">
            /// The DOM element to be associated with the Menu control.
            /// </param>
            /// <param name="options" type="Object" domElement="false" locid="WinJS.UI.Menu.constructor_p:options">
            /// The set of options to be applied initially to the Menu control.
            /// </param>
            /// <returns type="WinJS.UI.Menu" locid="WinJS.UI.Menu.constructor_returnValue">A fully constructed Menu control.</returns>
            /// </signature>

            // We need to be built on top of a Flyout, so stomp on the user's input
            if (!options) {
                options = {};
            }
            if (!options.commands) {
                // validate that if they didn't set commands, in which
                // case any HTML only contains commands.  Do this first
                // so that we don't leave partial Menus in the DOM.
                this._verifyCommandsOnly(element, "WinJS.UI.MenuCommand");
            }

            // Remember aria role in case base constructor changes it
            var role = element ? element.getAttribute("role") : null;
            var label = element ? element.getAttribute("aria-label") : null;

            // Call the base overlay constructor helper
            this._baseFlyoutConstructor(element, options);

            // Make sure we have an ARIA role
            if (role === null || role === "" || role === undefined) {
                this._element.setAttribute("role", "menu");
            }
            if (label === null || label === "" || label === undefined) {
                this._element.setAttribute("aria-label", strings.ariaLabel);
            }

            // Handle "esc" & "up/down" key presses
            this._element.addEventListener("keydown", this._handleKeyDown, true);

            // Attach our css class
            WinJS.Utilities.addClass(this._element, menuClass);

            // Need to set our commands, making sure we're hidden first
            this.hide();
        }, {
            // Public Properties

            /// <field type="Array" locid="WinJS.UI.Menu.commands" helpKeyword="WinJS.UI.Menu.commands" isAdvanced="true">The Commands for the Menu, contains an array of MenuCommand options.</field>
            commands: {
                set: function (value) {
                    // Fail if trying to set when visible
                    if (!this.hidden) {
                        throw new WinJS.ErrorFromName("WinJS.UI.Menu.CannotChangeCommandsWhenVisible", WinJS.Resources._formatString(thisWinUI._Overlay.commonstrings.cannotChangeCommandsWhenVisible, "Menu"));
                    }

                    // Start from scratch
                    this._element.innerHTML = "";

                    // In case they had only one...
                    if (!Array.isArray(value)) {
                        value = [value];
                    }

                    // Add commands
                    var len = value.length;
                    for (var i = 0; i < len; i++) {
                        this._addCommand(value[i]);
                    }
                }
            },

            getCommandById: function (id) {
                /// <signature helpKeyword="WinJS.UI.Menu.getCommandById">
                /// <summary locid="WinJS.UI.Menu.getCommandById">
                /// Retrieve the command with the specified ID from this Menu.  If more than one command is found, all are returned.
                /// </summary>
                /// <param name="id" type="String" locid="WinJS.UI.Menu.getCommandById_p:id">Id of the command to return.</param>
                /// <returns type="object" locid="WinJS.UI.Menu.getCommandById_returnValue">The command found, an array of commands if more than one have the same id, or null if no command is found with that id.</returns>
                /// </signature>
                var commands = this.element.querySelectorAll("#" + id);
                for (var count = 0; count < commands.length; count++) {
                    // Any elements we generated this should succeed for,
                    // but remove missing ones just to be safe.
                    commands[count] = commands[count].winControl;
                    if (!commands[count]) {
                        commands.splice(count, 1);
                    }
                }

                if (commands.length === 1) {
                    return commands[0];
                } else if (commands.length === 0) {
                    return null;
                }

                return commands;
            },

            
            showCommands: function (commands) {
                /// <signature helpKeyword="WinJS.UI.Menu.showCommands">
                /// <summary locid="WinJS.UI.Menu.showCommands">
                /// Show commands within this Menu
                /// </summary>
                /// <param name="commands" type="Array" locid="WinJS.UI.Menu.showCommands_p:commands">Required. Command or Commands to show, either String, DOM elements, or WinJS objects.</param>
                /// </signature>
                if (!commands) {
                    throw new WinJS.ErrorFromName("WinJS.UI.Menu.RequiresCommands", strings.requiresCommands);
                }

                this._showCommands(commands, true);
            },

            hideCommands: function (commands) {
                /// <signature helpKeyword="WinJS.UI.Menu.hideCommands">
                /// <summary locid="WinJS.UI.Menu.hideCommands">
                /// Hide commands within this Menu
                /// </summary>
                /// <param name="commands" type="Array" locid="WinJS.UI.Menu.hideCommands_p:commands">Required. Command or Commands to hide, either String, DOM elements, or WinJS objects.</param>
                /// </signature>
                if (!commands) {
                    throw new WinJS.ErrorFromName("WinJS.UI.Menu.RequiresCommands", strings.requiresCommands);
                }

                this._hideCommands(commands, true);
            },
 
            showOnlyCommands: function (commands) {
                /// <signature helpKeyword="WinJS.UI.Menu.showOnlyCommands">
                /// <summary locid="WinJS.UI.Menu.showOnlyCommands">
                /// Show the specified commands, hiding all of the others in the Menu.
                /// </summary>
                /// <param name="commands" type="Array" locid="WinJS.UI.Menu.showOnlyCommands_p:commands">Required. Command or Commands to show, either String, DOM elements, or WinJS objects.</param>
                /// </signature>
                if (!commands) {
                    throw new WinJS.ErrorFromName("WinJS.UI.Menu.RequiresCommands", strings.requiresCommands);
                }

                this._showOnlyCommands(commands, true);
            },

            show: function (anchor, placement, alignment) {
                /// <signature helpKeyword="WinJS.UI.Menu.show">
                /// <summary locid="WinJS.UI.Menu.show">
                /// Shows the Menu, if hidden, regardless of other state
                /// </summary>
                /// <param name="anchor" type="HTMLElement" domElement="true" locid="WinJS.UI.Menu.show_p:anchor">
                /// The DOM element, or ID of a DOM element to anchor the Menu, overriding the anchor property for this time only.
                /// </param>
                /// <param name="placement" type="object" domElement="false" locid="WinJS.UI.Menu.show_p:placement">
                /// The placement of the Menu to the anchor: 'auto' (default), 'top', 'bottom', 'left', or 'right'.  This parameter overrides the placement property for this show only.
                /// </param>
                /// <param name="alignment" type="object" domElement="false" locid="WinJS.UI.Menu.show_p:alignment">
                /// For 'top' or 'bottom' placement, the alignment of the Menu to the anchor's edge: 'center' (default), 'left', or 'right'.  This parameter overrides the alignment property for this show only.
                /// </param>
                /// </signature>
                // Just call private version to make appbar flags happy
                this._show(anchor, placement, alignment);
            },

            _show: function (anchor, placement, alignment) {
                // Before we show, we also need to check for children flyouts needing anchors
                this._checkForFlyoutCommands();

                // Call flyout show
                this._baseFlyoutShow(anchor, placement, alignment);
                
                // We need to check for toggles after we send the beforeshow event,
                // so the developer has a chance to show or hide more commands.  
                // Flyout's _findPosition will make that call.
            },

            _addCommand: function (command) {
                // See if its a command already
                if (command && !command._element) {
                    // Not a command, so assume it's options for a command
                    command = new WinJS.UI.MenuCommand(null, command);
                }
                // If we were attached somewhere else, detach us
                if (command._element.parentElement) {
                    command._element.parentElement.removeChild(command._element);
                }

                // Reattach us
                this._element.appendChild(command._element);
            },

            // Called by flyout's _findPosition so that application can update it status
            // we do the test and we can then fix this last-minute before showing.
            _checkToggle: function () {
                var toggles = this._element.querySelectorAll(".win-command[aria-checked]");
                var hasToggle = false;
                if (toggles) {
                    for (var i = 0; i < toggles.length; i++) {
                        if (toggles[i] && toggles[i].winControl && !toggles[i].winControl.hidden) {
                            // Found a visible toggle control
                            hasToggle = true;
                            break;
                        }
                    }
                }
                if (hasToggle) {
                    WinJS.Utilities.addClass(this._element, menuToggleClass);
                } else {
                    WinJS.Utilities.removeClass(this._element, menuToggleClass);
                }
            },

            _checkForFlyoutCommands: function () {
                var commands = this._element.querySelectorAll(".win-command");
                for (var count = 0; count < commands.length; count++) {
                    if (commands[count].winControl) {
                        // Remember our anchor in case it's a flyout
                        commands[count].winControl._parentFlyout = this;
                    }
                }
            },

            _handleKeyDown: function (event) {
                if (event.key === "Esc") {
                    // Show a focus rect on what we move focus to
                    this.winControl._keyboardInvoked = true;
                    this.winControl._hide();
                } else if ((event.key === "Spacebar" || event.key === "Enter")
                       && (this === document.activeElement)) {
                           event.preventDefault();
                           this.winControl.hide();
                       } else if (event.key === "Up") {
                           var that = this;
                           thisWinUI.Menu._focusOnPreviousElement(that);

                           // Prevent the page from scrolling
                           event.preventDefault();
                       } else if (event.key === "Down") {
                           that = this;
                           thisWinUI.Menu._focusOnNextElement(that);

                           // Prevent the page from scrolling
                           event.preventDefault();
                       } else if (event.key === "Tab") {
                           event.preventDefault();
                       }
            }
        })
    });
    // Statics

    // Set focus to next focusable element in the menu (loop if necessary).
    //   Note: The loop works by first setting focus to the menu itself.  If the menu is
    //         what had focus before, then we break.  Otherwise we try the first child next.
    // Focus remains on the menu if nothing is focusable.
    thisWinUI.Menu._focusOnNextElement = function (menu) {
        var _currentElement = document.activeElement;

        do {
            if (_currentElement === menu) {
                _currentElement = _currentElement.firstElementChild;
            } else {
                _currentElement = _currentElement.nextElementSibling;
            }

            if (_currentElement) {
                _currentElement.focus();
            } else {
                _currentElement = menu;
            }

        } while (_currentElement !== document.activeElement)
    };

    // Set focus to previous focusable element in the menu (loop if necessary).
    //   Note: The loop works by first setting focus to the menu itself.  If the menu is
    //         what had focus before, then we break.  Otherwise we try the last child next.
    // Focus remains on the menu if nothing is focusable.
    thisWinUI.Menu._focusOnPreviousElement = function (menu) {
        var _currentElement = document.activeElement;

        do {
            if (_currentElement === menu) {
                _currentElement = _currentElement.lastElementChild;
            } else {
                _currentElement = _currentElement.previousElementSibling;
            }

            if (_currentElement) {
                _currentElement.focus();
            } else {
                _currentElement = menu;
            }

        } while (_currentElement !== document.activeElement)
    };

    var strings = {
        get ariaLabel() { return WinJS.Resources._getWinJSString("ui/menuAriaLabel").value; },
        get requiresCommands() { return WinJS.Resources._getWinJSString("ui/requiresCommands").value; }
    };
})(WinJS);


// Menu Command
/// <dictionary>appbar,appbars,Flyout,Flyouts,onclick,Statics</dictionary>
(function menuCommandInit(WinJS) {
    "use strict";

    var thisWinUI = WinJS.UI;

    // Class Names
    var menuCommandClass = "win-command";
    var typeSeparator = "separator";
    var typeButton = "button";
    var typeToggle = "toggle";
    var typeFlyout = "flyout";

    function _handleMenuClick(event) {
        var command = this.winControl;
        if (command) {
            var hideParent = true;
            if (command._type === typeToggle) {
                command.selected = !command.selected;
            } else if (command._type === typeFlyout && command._flyout) {
                var flyout = command._flyout;
                // Flyout may not have processAll'd, so this may be a DOM object
                if (typeof flyout === "string") {
                    flyout = document.getElementById(flyout);
                }
                if (!flyout.show) {
                    flyout = flyout.winControl;
                }
                if (flyout && flyout.show) {
                    if (command._parentFlyout) {
                        hideParent = false;
                        flyout.show(command._parentFlyout._currentAnchor, command._parentFlyout._currentPlacement, command._parentFlyout._currentAlignment);
                    } else {
                        flyout.show(this);
                    }
                }
            }
            if (command.onclick) {
                command.onclick(event);
            }
            // Dismiss parent flyout
            if (hideParent && command._parentFlyout) {
                command._parentFlyout.hide();
            }
        }
    }
    
    function _handleMouseOver(event) {
        if (this && this.focus) {
            this.focus();
            
            this.addEventListener("mousemove", _handleMouseMove, false);
        }
    }
    
    function _handleMouseMove(event) {
        if (this && this.focus && this !== document.activeElement) {
            this.focus();
        }
    }
    
    function _handleMouseOut(event) {
        var that = this;
        var parentFlyout = _getParentFlyout(that);
        if (parentFlyout 
         && this === document.activeElement
         && WinJS.Utilities.hasClass(parentFlyout, "win-menu")
         && parentFlyout.focus) {
            // Menu gives focus to the menu itself
            parentFlyout.focus();
         } else if (parentFlyout 
                 && this === document.activeElement
                 && parentFlyout.children
                 && parentFlyout.children.length > 0
                 && parentFlyout.children[0]
                 && WinJS.Utilities.hasClass(parentFlyout.children[0], "win-firstdiv")
                 && parentFlyout.children[0].focus) {
            // Flyout gives focus to firstDiv
            parentFlyout.children[0].focus();
        }
        
        this.removeEventListener("mousemove", _handleMouseMove, false);
    }

    function _getParentFlyout(element) {
        while (element && !WinJS.Utilities.hasClass(element, "win-flyout")) {
            element = element.parentElement;
        }
        
        return element;
    }

    WinJS.Namespace.define("WinJS.UI", {
        /// <summary locid="WinJS.UI.MenuCommand">
        /// MenuCommands provide button, toggle button, flyout button, or separator functionality for Menus.
        /// </summary>
        /// <icon src="ui_winjs.ui.menucommand.12x12.png" width="12" height="12" />
        /// <icon src="ui_winjs.ui.menucommand.16x16.png" width="16" height="16" />
        /// <htmlSnippet><![CDATA[<button data-win-control="WinJS.UI.MenuCommand" data-win-options="{type:'button',label:'Button'}"></button>]]></htmlSnippet>
        /// <part name="MenuCommand" class="win-command" locid="WinJS.UI.MenuCommand_name">The MenuCommand control itself</part>
        /// <resource type="javascript" src="//Microsoft.WinJS.1.0/js/base.js" shared="true" />
        /// <resource type="javascript" src="//Microsoft.WinJS.1.0/js/ui.js" shared="true" />
        /// <resource type="css" src="//Microsoft.WinJS.1.0/css/ui-dark.css" shared="true" />
        MenuCommand: WinJS.Class.define(function MenuCommand_ctor(element, options) {
            /// <signature helpKeyword="WinJS.UI.AppBarCommand.MenuCommand">
            /// <summary locid="WinJS.UI.MenuCommand.constructor">
            /// Constructs the MenuCommand control
            /// </summary>
            /// <param name="element" domElement="true" locid="WinJS.UI.MenuCommand.constructor_p:element">
            /// The DOM element to be associated with the MenuCommand control.  MenuCommand will create one if null.
            /// </param>
            /// <param name="options" type="Object" locid="WinJS.UI.MenuCommand.constructor_p:options">
            /// The set of options to be applied initially to the MenuCommand control.
            /// </param>
            /// <returns type="WinJS.UI.MenuCommand" locid="WinJS.UI.MenuCommand.constructor_returnValue">
            /// A MenuCommand control.
            /// </returns>
            /// </signature>

            // Check to make sure we weren't duplicated
            if (element && element.winControl) {
                throw new WinJS.ErrorFromName("WinJS.UI.MenuCommand.DuplicateConstruction", strings.duplicateConstruction);
            }

            // Don't blow up if they didn't pass options
            if (!options) {
                options = {};
            }

            // Need a type before we can create our element
            if (!options.type) {
                this._type = typeButton;
            }

            // Go ahead and create it, separators look different than buttons
            // Don't forget to use passed in element if one was provided.
            this._element = element;
            if (options.type === typeSeparator) {
                this._createSeparator();
            } else {
                // This will also set the icon & label
                this._createButton();
            }

            // Remember ourselves
            this._element.winControl = this;

            // Attach our css class
            WinJS.Utilities.addClass(this._element, menuCommandClass);

            if (!options.selected && options.type === typeToggle) {
                // Make sure toggle's have selected false for CSS
                this.selected = false;
            }
            if (options.onclick) {
                this.onclick = options.onclick;
            }
            options.onclick = _handleMenuClick;

            WinJS.UI.setOptions(this, options);

            // Set our options
            if (this._type !== typeSeparator) {
                // Make sure we have an ARIA role
                var role = this._element.getAttribute("role");
                if (role === null || role === "" || role === undefined) {
                    role = "menuitem";
                    if (this._type === typeToggle) {
                        role = "menuitemcheckbox";
                    }
                    this._element.setAttribute("role", role);
                    if (this._type === typeFlyout) {
                        this._element.setAttribute("aria-haspopup", true);
                    }
                }
                var label = this._element.getAttribute("aria-label");
                if (label === null || label === "" || label === undefined) {
                    this._element.setAttribute("aria-label", strings.ariaLabel);
                }
            }
            
            this._element.addEventListener("mouseover", _handleMouseOver, false);
            this._element.addEventListener("mouseout", _handleMouseOut, false);            
        }, {
            /// <field type="String" locid="WinJS.UI.MenuCommand.id" helpKeyword="WinJS.UI.MenuCommand.id" isAdvanced="true">The Id of the MenuCommand.</field>
            id: {
                get: function () {
                    return this._element.id;
                },
                set: function (value) {
                    // we allow setting first time only. otherwise we ignore it.
                    if (!this._element.id) {
                        this._element.id = value;
                    }
                }
            },

            /// <field type="String" readonly="true" defaultValue="button" oamOptionsDatatype="WinJS.UI.MenuCommand.type" locid="WinJS.UI.MenuCommand.type" helpKeyword="WinJS.UI.MenuCommand.type" isAdvanced="true">The Type of the MenuCommand, possible values are "button", "toggle", "flyout", or "separator"</field>
            type: {
                get: function () {
                    return this._type;
                }, 
                set: function (value) {
                    // we allow setting first time only. otherwise we ignore it.
                    if (!this._type) {
                        if (value !== typeButton && value !== typeFlyout && value !== typeToggle && value !== typeSeparator) {
                            this._type = typeButton;
                        } else {
                            this._type = value;
                        }
                    }
                }
            },

            /// <field type="String" locid="WinJS.UI.MenuCommand.label" helpKeyword="WinJS.UI.MenuCommand.label">The label of the MenuCommand</field>
            label: {
                get: function () {
                    return this._label;
                },
                set: function (value) {
                    this._label = value;
                    this._element.innerText = this.label;

                    // Update aria-label
                    this._element.setAttribute("aria-label", this.label);
                }
            },

            /// <field type="Function" locid="WinJS.UI.MenuCommand.onclick" helpKeyword="WinJS.UI.MenuCommand.onclick">The click event to call when the MenuCommand is invoked</field>
            onclick: {
                get: function () {
                    return this._onclick;
                },
                set: function (value) {
                    if (value && typeof value !== "function") {
                        throw new WinJS.ErrorFromName("WinJS.UI.MenuCommand.BadClick", WinJS.Resources._formatString(strings.badClick, "MenuCommand"));
                    }
                    this._onclick = value;
                }
            },

            /// <field type="Object" locid="WinJS.UI.MenuCommand.flyout" helpKeyword="WinJS.UI.MenuCommand.flyout">For flyout type MenuCommands, get returns the WinJS.UI.Flyout that this command invokes.  Set may also use the String id of the flyout to invoke, the DOM object of the flyout, or the flyout object itself</field>
            flyout: {
                get: function () {
                    // Resolve it to the flyout
                    var flyout = this._flyout;
                    if (typeof flyout === "string") {
                        flyout = document.getElementById(flyout);
                    }
                    // If it doesn't have a .element, then we need to getControl on it
                    if (flyout && !flyout.element) {
                        flyout = flyout.winControl;
                    }

                    return flyout;
                },
                set: function (value) {
                    // Need to update aria-owns with the new ID.
                    var id = value;
                    if (id && typeof id !== "string") {
                        // Our controls have .element properties
                        if (id.element) {
                            id = id.element;
                        }
                        // Hope it's a DOM element, get ID from DOM element
                        if (id) {
                            if (id.id) {
                                id = id.id;
                            } else {
                                // No id, have to fake one
                                id.id = id.uniqueID;
                                id = id.id;
                            }
                        }
                    }
                    if (typeof id === "string") {
                        this._element.setAttribute("aria-owns", id);
                    }

                    // Remember it
                    this._flyout = value;
                }
            },

            /// <field type="Boolean" locid="WinJS.UI.MenuCommand.selected" helpKeyword="WinJS.UI.MenuCommand.selected">Set or get the selected state of a toggle button</field>
            selected: {
                get: function () {
                    // Ensure it's a boolean because we're using the DOM element to keep in-sync
                    return this._element.getAttribute("aria-checked") === "true";
                },
                set: function (value) {
                    this._element.setAttribute("aria-checked", !!value);
                }
            },

            /// <field type="HTMLElement" domElement="true" readonly="true" hidden="true" locid="WinJS.UI.MenuCommand.element" helpKeyword="WinJS.UI.MenuCommand.element">The DOM element the MenuCommand is attached to</field>
            element: {
                get: function () {
                    return this._element;
                }
            },

            /// <field type="Boolean" locid="WinJS.UI.MenuCommand.disabled" helpKeyword="WinJS.UI.MenuCommand.disabled">Disable a command. It will get or set the HTML disabled attribute.</field>
            disabled: {
                get: function () {
                    // Ensure it's a boolean because we're using the DOM element to keep in-sync
                    return !!this._element.disabled;
                },
                set: function (value) {
                    this._element.disabled = !!value;
                }
            },

            /// <field type="Boolean" hidden="true" locid="WinJS.UI.MenuCommand.hidden" helpKeyword="WinJS.UI.MenuCommand.hidden">Determine if a command is currently hidden.</field>
            hidden: {
                get: function () {
                    // Ensure it's a boolean because we're using the DOM element to keep in-sync
                    return this._element.style.visibility === "hidden";
                },
                set: function (value) {
                    var menuControl = thisWinUI._Overlay._getParentControlUsingClassName(this._element, "win-menu");
                    if (menuControl && !menuControl.hidden) {
                        throw new WinJS.ErrorFromName("WinJS.UI.MenuCommand.CannotChangeHiddenProperty", WinJS.Resources._formatString(thisWinUI._Overlay.commonstrings.cannotChangeHiddenProperty, "Menu"));
                    }

                    var style = this._element.style;
                    if (value) {
                        style.visibility = "hidden";
                        style.display = "none";
                    } else {
                        style.visibility = "";
                        style.display = "block";
                    }
                }
            },

            /// <field type="String" locid="WinJS.UI.MenuCommand.extraClass" isAdvanced="true" helpKeyword="WinJS.UI.MenuCommand.extraClass">Adds an extra CSS class during construction.</field>
            extraClass: {
                get: function () {
                    return this._extraClass;
                },
                set: function (value) {
                    if (this._extraClass) {
                        WinJS.Utilities.removeClass(this._element, this._extraClass);
                    }
                    this._extraClass = value;
                    WinJS.Utilities.addClass(this._element, this._extraClass);
                }
            },

            addEventListener: function (type, listener, useCapture) {
                /// <signature helpKeyword="WinJS.UI.MenuCommand.addEventListener">
                /// <summary locid="WinJS.UI.MenuCommand.addEventListener">
                /// Add an event listener to the DOM element for this command
                /// </summary>
                /// <param name="type" type="String" locid="WinJS.UI.MenuCommand.addEventListener_p:type">Required. Event type to add.</param>
                /// <param name="listener" type="Function" locid="WinJS.UI.MenuCommand.addEventListener_p:listener">Required. The event handler function to associate with this event.</param>
                /// <param name="useCapture" type="Boolean" locid="WinJS.UI.MenuCommand.addEventListener_p:useCapture">Optional. True, register for the event capturing phase.  False for the event bubbling phase.</param>
                /// </signature>
                return this._element.addEventListener(type, listener, useCapture);
            },

            removeEventListener: function (type, listener, useCapture) {
                /// <signature helpKeyword="WinJS.UI.MenuCommand.removeEventListener">
                /// <summary locid="WinJS.UI.MenuCommand.removeEventListener">
                /// Remove an event listener to the DOM element for this command
                /// </summary>
                /// <param name="type" type="String" locid="WinJS.UI.MenuCommand.removeEventListener_p:type">Required. Event type to remove.</param>
                /// <param name="listener" type="Function" locid="WinJS.UI.MenuCommand.removeEventListener_p:listener">Required. The event handler function to associate with this event.</param>
                /// <param name="useCapture" type="Boolean" locid="WinJS.UI.MenuCommand.removeEventListener_p:useCapture">Optional. True, register for the event capturing phase.  False for the event bubbling phase.</param>
                /// </signature>
                return this._element.removeEventListener(type, listener, useCapture);
            },

            // Private properties
            _createSeparator: function () {
                // Make sure there's an input element
                if (!this._element) {
                    this._element = document.createElement("hr");
                } else {
                    // Verify the input was an hr
                    if (this._element.tagName !== "HR") {
                        throw new WinJS.ErrorFromName("WinJS.UI.MenuCommand.BadHrElement", strings.badHrElement);
                    }
                }
            },

            _createButton: function () {
                // Make sure there's an input element
                if (!this._element) {
                    this._element = document.createElement("button");
                } else {
                    // Verify the input was a button
                    if (this._element.tagName !== "BUTTON") {
                        throw new WinJS.ErrorFromName("WinJS.UI.MenuCommand.BadButtonElement", strings.badButtonElement);
                    }
                    this._element.innerHtml = "";
                }

                // MenuCommand buttons need to look like this:
                //// <button type="button" onclick="" class="win-command">Command 1</button>
                this._element.type = "button";

                // 'innertext' label is added later by caller
            }
        })
    });

    // Statics

    var strings = {
        get ariaLabel() { return WinJS.Resources._getWinJSString("ui/menuCommandAriaLabel").value; },
        get duplicateConstruction() { return WinJS.Resources._getWinJSString("ui/duplicateConstruction").value; },
        get badClick() { return WinJS.Resources._getWinJSString("ui/badClick").value; },
        get badHrElement() { return WinJS.Resources._getWinJSString("ui/badHrElement").value; },
        get badButtonElement() { return WinJS.Resources._getWinJSString("ui/badButtonElement").value; }
    };

})(WinJS);


/// <dictionary>appbar,Flyout,Flyouts,registeredforsettings,SettingsFlyout,Statics,Syriac</dictionary>
(function settingsFlyoutInit(WinJS) {
    "use strict";

    var thisWinUI = WinJS.UI;

    var focusHasHitSettingsPaneOnce;
    
    // Class Names
    var settingsFlyoutClass      = "win-settingsflyout",
        fullSettingsFlyoutClassName = "." + settingsFlyoutClass,
        settingsFlyoutLightClass = "win-ui-light",
        narrowClass              = "win-narrow",
        wideClass                = "win-wide";
    
    var firstDivClass       = "win-firstdiv";
    var finalDivClass       = "win-finaldiv";

    // Constants for width
    var settingsNarrow = "narrow",
        settingsWide   = "wide";

    // Determine if the settings pane (system language) is RTL or not.
    function _shouldAnimateFromLeft() {
        if (WinJS.Utilities.hasWinRT && Windows.UI.ApplicationSettings.SettingsEdgeLocation) {
            var appSettings = Windows.UI.ApplicationSettings;
            return (appSettings.SettingsPane.edge === appSettings.SettingsEdgeLocation.left);
        } else {
            return false;
        }
    };
    
    // Get the settings control by matching the settingsCommandId
    // if no match we'll try to match element id
    function _getChildSettingsControl(parentElement, id) {
        var settingElements = parentElement.querySelectorAll(fullSettingsFlyoutClassName);
        var retValue,
            control;
        for (var i=0; i<settingElements.length; i++) {
            control = settingElements[i].winControl;
            if (control) {
                if (control.settingsCommandId === id) {
                    retValue = control;
                    break;
                }
                if (settingElements[i].id === id) {
                    retValue = retValue || control;
                }
            }
        }
        
        return retValue;
    }

    WinJS.Namespace.define("WinJS.UI", {
        /// <summary locid="WinJS.UI.SettingsFlyout">The SettingsFlyout provides access to information from the Settings pane.</summary>
        /// <name locid="WinJS.UI.SettingsFlyout_name">Settings Flyout</name>
        /// <icon src="ui_winjs.ui.settingsflyout.12x12.png" width="12" height="12" />
        /// <icon src="ui_winjs.ui.settingsflyout.16x16.png" width="16" height="16" />
        /// <htmlSnippet supportsContent="true"><![CDATA[<div data-win-control="WinJS.UI.SettingsFlyout">
        /// <div class="win-header">
        /// <button type="button" onclick="WinJS.UI.SettingsFlyout.show()" class="win-backbutton"></button>
        /// <div class="win-label">Custom Settings</div>
        /// </div>
        /// <div class="win-content">
        /// {Your Content Here}
        /// </div>
        /// </div>]]></htmlSnippet>
        /// <event name="beforeshow" locid="WinJS.UI.SettingsFlyout_e:beforeshow">Raised just before showing a SettingsFlyout.</event>
        /// <event name="aftershow" locid="WinJS.UI.SettingsFlyout_e:aftershow">Raised immediately after a SettingsFlyout is fully shown.</event>
        /// <event name="beforehide" locid="WinJS.UI.SettingsFlyout_e:beforehide">Raised just before hiding a SettingsFlyout.</event>
        /// <event name="afterhide" locid="WinJS.UI.SettingsFlyout_e:afterhide">Raised immediately after a SettingsFlyout is fully hidden.</event>
        /// <part name="settings" class="win-settingsflyout" locid="WinJS.UI.SettingsFlyout_part:settings">The SettingsFlyout control itself.</part>
        /// <resource type="javascript" src="//Microsoft.WinJS.1.0/js/base.js" shared="true" />
        /// <resource type="javascript" src="//Microsoft.WinJS.1.0/js/ui.js" shared="true" />
        /// <resource type="css" src="//Microsoft.WinJS.1.0/css/ui-dark.css" shared="true" />
        SettingsFlyout: WinJS.Class.derive(WinJS.UI._Overlay, function (element, options) {
            /// <signature helpKeyword="WinJS.UI.SettingsFlyout.SettingsFlyout">
            /// <summary locid="WinJS.UI.SettingsFlyout.constructor">Constructs a SettingsFlyout control.</summary>
            /// <param name="element" type="HTMLElement" domElement="true" locid="WinJS.UI.SettingsFlyout.constructor_p:element">
            /// The DOM element to be associated with the SettingsFlyout control.
            /// </param>
            /// <param name="options" type="Object" locid="WinJS.UI.SettingsFlyout.constructor_p:options">
            /// The set of options to be applied initially to the SettingsFlyout control.
            /// </param>
            /// <returns type="WinJS.UI.SettingsFlyout" locid="WinJS.UI.SettingsFlyout.constructor_returnValue">A constructed SettingsFlyout control.</returns>
            /// </signature>

            // Call the base overlay constructor helper
            this._baseOverlayConstructor(element, options);

            this._addFirstDiv();
            this._addFinalDiv();

            // Handle "esc" & "tab" key presses
            this._element.addEventListener("keydown", this._handleKeyDown, true);

            // Make a click eating div
            thisWinUI._Overlay._createClickEatingDivAppBar();

            // Start settings hidden
            this._element.style.visibilty = "hidden";
            this._element.style.display = "none";

            // Attach our css class
            WinJS.Utilities.addClass(this._element, settingsFlyoutClass);

            // apply the light theme styling to the win-content elements inside the SettingsFlyout
            WinJS.Utilities.query("div.win-content", this._element).
                forEach(function (e) {
                    if (!e.msMatchesSelector('.win-ui-dark, .win-ui-dark *')) {
                        WinJS.Utilities.addClass(e, settingsFlyoutLightClass);
                    }
                });

            // Make sure we have an ARIA role
            var role = this._element.getAttribute("role");
            if (role === null || role === "" || role === undefined) {
                this._element.setAttribute("role", "dialog");
            }
            var label = this._element.getAttribute("aria-label");
            if (label === null || label === "" || label === undefined) {
                this._element.setAttribute("aria-label", strings.ariaLabel);
            }

            // Make sure Flyout event handlers are hooked up
            this._addFlyoutEventHandlers(true);

            // Make sure animations are hooked up
            this._currentAnimateIn = this._animateSlideIn;
            this._currentAnimateOut = this._animateSlideOut;
        }, {
            // Public Properties

            /// <field type="String" defaultValue="narrow" oamOptionsDatatype="WinJS.UI.SettingsFlyout.width" locid="WinJS.UI.SettingsFlyout.width" helpKeyword="WinJS.UI.SettingsFlyout.width">Width of the SettingsFlyout, "narrow", or "wide".</field>
            width: {
                get: function () {
                    return this._width;
                },

                set: function (value) {
                    if (value === this._width) {
                        return;
                    }
                    // Get rid of old class
                    if (this._width === settingsNarrow) {
                        WinJS.Utilities.removeClass(this._element, narrowClass);
                    } else if (this._width === settingsWide) {
                        WinJS.Utilities.removeClass(this._element, wideClass);
                    }
                    this._width = value;

                    // Attach our new css class
                    if (this._width === settingsNarrow) {
                        WinJS.Utilities.addClass(this._element, narrowClass);
                    } else if (this._width === settingsWide) {
                        WinJS.Utilities.addClass(this._element, wideClass);
                    }
                }
            },
            
            /// <field type="String" locid="WinJS.UI.SettingsFlyout.settingsCommandId" helpKeyword="WinJS.UI.SettingsFlyout.settingsCommandId">Define the settings command Id for the SettingsFlyout control.</field>
            settingsCommandId: {
                get: function() {
                    return this._settingsCommandId;
                },
                
                set: function (value) {
                    this._settingsCommandId = value;
                }
            },

            show: function () {
                /// <signature helpKeyword="WinJS.UI.SettingsFlyout.show">
                /// <summary locid="WinJS.UI.SettingsFlyout.show">
                /// Shows the SettingsFlyout, if hidden.
                /// </summary>
                /// </signature>
                // Just call private version to make appbar flags happy

                // Don't do anything if disabled
                if (this.disabled) {
                    return;
                }

                this._show();
            },

            _show: function() {
                // We call our base _baseShow because AppBar may need to override show
                this._baseShow();
                // Need click-eating div to be visible,
                // (even if now hiding, we'll show and need click eater)
                thisWinUI._Overlay._showClickEatingDivAppBar();
            },

            _endShow: function () {
                // Clean up after showing
                this._initAfterAnimation();
            },

            _initAfterAnimation: function() {
                focusHasHitSettingsPaneOnce = 0;

                // Verify that the firstDiv and finalDiv are in the correct location.
                // Move them to the correct location or add them if they are not.
                if (!WinJS.Utilities.hasClass(this.element.children[0], firstDivClass)) {
                    var firstDiv = this.element.querySelectorAll(".win-first");
                    if (firstDiv && firstDiv.length > 0) {
                        firstDiv.item(0).parentNode.removeChild(firstDiv.item(0));
                    }

                    this._addFirstDiv();
                }

                // Set focus to the firstDiv
                if (this.element.children[0]) {
                    this.element.children[0].addEventListener("focusout", function () { focusHasHitSettingsPaneOnce = 1; }, false);
                    this.element.children[0].focus();
                }

                if (!WinJS.Utilities.hasClass(this.element.children[this.element.children.length - 1], finalDivClass)) {
                    var finalDiv = this.element.querySelectorAll(".win-final");
                    if (finalDiv && finalDiv.length > 0) {
                        finalDiv.item(0).parentNode.removeChild(finalDiv.item(0));
                    }

                    this._addFinalDiv();
                }
                
                this._setBackButtonsAriaLabel();
            },
            
            _setBackButtonsAriaLabel: function() {
                var backbuttons = this.element.querySelectorAll(".win-backbutton");
                var label;
                for (var i=0; i<backbuttons.length; i++) {
                    label = backbuttons[i].getAttribute("aria-label");
                    if (label === null || label === "" || label === undefined) {
                        backbuttons[i].setAttribute("aria-label", strings.backbuttonAriaLabel);
                    }
                }
            },
            
            hide: function () {
                /// <signature helpKeyword="WinJS.UI.SettingsFlyout.hide">
                /// <summary locid="WinJS.UI.SettingsFlyout.hide">
                /// Hides the SettingsFlyout, if visible, regardless of other state.
                /// </summary>
                /// </signature>
                // Just call private version to make appbar flags happy
                this._hide();
            },

            _hide: function () {
                if (this._baseHide()) {
                    // Need click-eating div to be hidden
                    thisWinUI._Overlay._hideClickEatingDivAppBar();
                }
            },

            // SettingsFlyout animations
            _animateSlideIn: function () {
                var animateFromLeft = _shouldAnimateFromLeft();
                var offset =  animateFromLeft ? "-100px" : "100px";
                WinJS.Utilities.query("div.win-content", this._element).
                    forEach(function(e) { WinJS.UI.Animation.enterPage(e, {left: offset})});

                var where,
                    width = this._element.offsetWidth;
                // Slide in from right side or left side?
                if (animateFromLeft) {
                    // RTL
                    where = { top: "0px", left: "-" + width + "px" };
                    this._element.style.right = "auto";
                    this._element.style.left = "0px";
                } else {
                    // From right side
                    where = { top: "0px", left: width + "px" };
                    this._element.style.right = "0px";
                    this._element.style.left = "auto";
                }

                this._element.style.opacity = 1;
                this._element.style.visibility = "visible";

                return WinJS.UI.Animation.showPanel(this._element, where);
            },

            _animateSlideOut: function () {
                var where,
                    width = this._element.offsetWidth;
                if (_shouldAnimateFromLeft()) {
                    // RTL
                    where = { top: "0px", left: width + "px" };
                    this._element.style.right = "auto";
                    this._element.style.left = "-" + width + "px";
                } else {
                    // From right side
                    where = { top: "0px", left: "-" + width + "px" };
                    this._element.style.right = "-" + width + "px";
                    this._element.style.left = "auto";
                }
                
                return WinJS.UI.Animation.showPanel(this._element, where);
            },

            _fragmentDiv: {
                get: function () {
                    return this._fragDiv;
                },

                set: function (value) {
                    this._fragDiv = value;
                }
            },

            _unloadPage: function (event) {
                var settingsControl = event.currentTarget.winControl;
                settingsControl.removeEventListener(thisWinUI._Overlay.afterHide, this._unloadPage, false);

                WinJS.Promise.as().then( function () {
                    if (settingsControl._fragmentDiv) {
                        document.body.removeChild(settingsControl._fragmentDiv);
                        settingsControl._fragmentDiv = null;
                    }
               });
            },

            _dismiss: function () {
                this.addEventListener(thisWinUI._Overlay.afterHide, this._unloadPage, false);
                this._hide();
            },

            _handleKeyDown: function (event) {
                if (event.key === "Esc") {
                    event.preventDefault();
                    event.stopPropagation();
                    this.winControl._dismiss();
                } else if ((event.key === "Spacebar" || event.key === "Enter")
                       && (this.children[0] === document.activeElement)) {
                    event.preventDefault();
                    event.stopPropagation();
                    this.winControl._dismiss();
                } else if (event.shiftKey && event.key === "Tab"
                && this.children[0] === document.activeElement) {
                    event.preventDefault();
                    event.stopPropagation();
                    var _elms = this.getElementsByTagName("*");

                    for (var i = _elms.length - 2; i >= 0; i--) {
                        _elms[i].focus();

                        if (_elms[i] === document.activeElement) {
                            break;
                        }
                    }
                }
            },

            _focusOnLastFocusableElementFromParent: function () {
                var active = document.activeElement;
                if (!focusHasHitSettingsPaneOnce || !active || !WinJS.Utilities.hasClass(active, firstDivClass)) {
                    return;
                }
                
                var _elms = this.parentElement.getElementsByTagName("*");

                // There should be at least 1 element in addition to the firstDiv & finalDiv
                if (_elms.length <= 2) {
                    return;
                }

                // Get the tabIndex set to the finalDiv (which is the highest)
                var _highestTabIndex = _elms[_elms.length - 1].tabIndex;

                // If there are positive tabIndices, set focus to the element with the highest tabIndex.
                // Otherwise set focus to the last focusable element in DOM order.
                if (_highestTabIndex) {
                    for (var i = _elms.length - 2; i > 0; i--) {
                        if (_elms[i].tabIndex === _highestTabIndex) {
                            _elms[i].focus();
                            break;
                        }
                    }
                } else {
                    for (i = _elms.length - 2; i > 0; i--) {
                        // Skip <div> with undefined tabIndex (To work around Win8 bug #622245)
                        if ((_elms[i].tagName !== "DIV") || (_elms[i].getAttribute("tabIndex") !== null)) {
                            _elms[i].focus();

                            if (_elms[i] === document.activeElement) {
                                break;
                            }
                        }
                    }
                }
            },

            _focusOnFirstFocusableElementFromParent: function () {
                var active = document.activeElement;
                if (!active || !WinJS.Utilities.hasClass(active, finalDivClass)) {
                    return;
                }
                var _elms = this.parentElement.getElementsByTagName("*");

                // There should be at least 1 element in addition to the firstDiv & finalDiv
                if (_elms.length <= 2) {
                    return;
                }

                // Get the tabIndex set to the firstDiv (which is the lowest)
                var _lowestTabIndex = _elms[0].tabIndex;

                // If there are positive tabIndices, set focus to the element with the lowest tabIndex.
                // Otherwise set focus to the first focusable element in DOM order.
                if (_lowestTabIndex) {
                    for (var i = 1; i < _elms.length - 1; i++) {
                        if (_elms[i].tabIndex === _lowestTabIndex) {
                            _elms[i].focus();
                            break;
                        }
                    }
                } else {
                    for (i = 1; i < _elms.length - 1; i++) {
                        // Skip <div> with undefined tabIndex (To work around Win8 bug #622245)
                        if ((_elms[i].tagName !== "DIV") || (_elms[i].getAttribute("tabIndex") !== null)) {
                            _elms[i].focus();

                            if (_elms[i] === document.activeElement) {
                                break;
                            }
                        }
                    }
                }
            },

            // Create and add a new first div to the beginning of the list
            _addFirstDiv: function () {
                var _elms = this._element.getElementsByTagName("*");
                var _minTab = 0;
                for (var i = 0; i < _elms.length; i++) {
                    if ((0 < _elms[i].tabIndex) && (_minTab === 0 || _elms[i].tabIndex < _minTab)) {
                        _minTab = _elms[i].tabIndex;
                    }
                }
                var firstDiv = document.createElement("div");
                firstDiv.className = firstDivClass;
                firstDiv.style.display = "inline";
                firstDiv.setAttribute("role", "menuitem");
                firstDiv.setAttribute("aria-hidden", "true");
                firstDiv.tabIndex = _minTab;
                firstDiv.addEventListener("focus", this._focusOnLastFocusableElementFromParent, false);

                this._element.insertAdjacentElement("AfterBegin", firstDiv);
            },

            // Create and add a new final div to the end of the list
            _addFinalDiv: function () {
                var _elms = this._element.getElementsByTagName("*");
                var _maxTab = 0;
                for (var i = 0; i < _elms.length; i++) {
                    if (_elms[i].tabIndex > _maxTab) {
                        _maxTab = _elms[i].tabIndex;
                    }
                }
                var finalDiv = document.createElement("div");
                finalDiv.className = finalDivClass;
                finalDiv.style.display = "inline";
                finalDiv.setAttribute("role", "menuitem");
                finalDiv.setAttribute("aria-hidden", "true");
                finalDiv.tabIndex = _maxTab;
                finalDiv.addEventListener("focus", this._focusOnFirstFocusableElementFromParent, false);

                this._element.appendChild(finalDiv);
            }
        })
    });

    // Statics
    thisWinUI.SettingsFlyout.show = function () {
        /// <signature helpKeyword="WinJS.UI.SettingsFlyout.show">
        /// <summary locid="WinJS.UI.SettingsFlyout.show_static">
        /// Activate the settings charm window.
        /// </summary>
        /// </signature>
        // Show the main settings pane
        if (WinJS.Utilities.hasWinRT) {
            Windows.UI.ApplicationSettings.SettingsPane.show();
        }
        // And hide the WWA one
        var elements = document.querySelectorAll('div[data-win-control="WinJS.UI.SettingsFlyout"]');
        var len = elements.length;
        for (var i = 0; i < len; i++) {
            var settingsFlyout = elements[i].winControl;
            if (settingsFlyout) {
                settingsFlyout._dismiss();
            }
        }
    };

    var _settingsEvent = { event: undefined };
    thisWinUI.SettingsFlyout.populateSettings = function (e) {
        /// <signature helpKeyword="WinJS.UI.SettingsFlyout.populateSettings">
        /// <summary locid="WinJS.UI.SettingsFlyout.populateSettings">
        /// Populate the settings commands to be shown in the settings charm window.
        /// </summary>
        /// <param name="e" type="Object" locid="WinJS.UI.SettingsFlyout.showSettings_p:e">
        /// The event object holding the settings commands array to be shown in the settings charm window.
        /// </param>
        /// </signature>
        _settingsEvent.event = e.detail;

        if (_settingsEvent.event.applicationcommands) {
            var n = Windows.UI.ApplicationSettings;
            Object.keys(_settingsEvent.event.applicationcommands).forEach(function (name) {
                var setting = _settingsEvent.event.applicationcommands[name];
                if (!setting.title) { setting.title = name; }
                var command = new n.SettingsCommand(name, setting.title, thisWinUI.SettingsFlyout._onSettingsCommand);
                _settingsEvent.event.e.request.applicationCommands.append(command);
            });
        }
    };

    thisWinUI.SettingsFlyout._onSettingsCommand = function (command) {
        var id = command.id;
        if (_settingsEvent.event.applicationcommands && _settingsEvent.event.applicationcommands[id]) {
            thisWinUI.SettingsFlyout.showSettings(id, _settingsEvent.event.applicationcommands[id].href);
        }
    };

    thisWinUI.SettingsFlyout.showSettings = function (id, path) {
        /// <signature helpKeyword="WinJS.UI.SettingsFlyout.showSettings">
        /// <summary locid="WinJS.UI.SettingsFlyout.showSettings">
        /// Show the SettingsFlyout using the path of the page contains the settings element and the settings element Id.
        /// </summary>
        /// </signature>
        var control = _getChildSettingsControl(document, id);
        if (control) {
            control.show();
        } else if (path) {
            var divElement = document.createElement("div");
            divElement = document.body.appendChild(divElement);
            WinJS.UI.Pages.render(path, divElement).then(function () {
                control = _getChildSettingsControl(divElement, id);
                if (control) {
                    control._fragmentDiv = divElement;
                    control.show();
                } else {
                    document.body.removeChild(divElement);
                }
            });
        } else {
            throw new WinJS.ErrorFromName("WinJS.UI.SettingsFlyout.BadReference", strings.badReference);
        }
    };
    // Application Settings Handling End

    var strings = {
        get ariaLabel() { return WinJS.Resources._getWinJSString("ui/settingsFlyoutAriaLabel").value; },
        get badReference() { return WinJS.Resources._getWinJSString("ui/badReference").value; },
        get backbuttonAriaLabel() { return WinJS.Resources._getWinJSString("ui/backbuttonarialabel").value; },
    };

    //// Labels

    //// Errors

})(WinJS);


(function tooltipInit(global) {
    "use strict";


    var lastCloseTime = 0;
    var utilities = WinJS.Utilities;
    var animation = WinJS.UI.Animation;

    // Constants definition
    var DEFAULT_PLACEMENT = "top";
    var DELAY_INITIAL_TOUCH_SHORT = 400;
    var DELAY_INITIAL_TOUCH_LONG = 1200;
    var DEFAULT_MOUSE_HOVER_TIME = 400; // 0.4 second
    var DEFAULT_MESSAGE_DURATION = 5000; // 5 secs
    var DELAY_RESHOW_NONINFOTIP_TOUCH = 0;
    var DELAY_RESHOW_NONINFOTIP_NONTOUCH = 600;
    var DELAY_RESHOW_INFOTIP_TOUCH = 400;
    var DELAY_RESHOW_INFOTIP_NONTOUCH = 600;
    var RESHOW_THRESHOLD = 200;
    var HIDE_DELAY_MAX = 300000; // 5 mins
    var OFFSET_KEYBOARD = 12;
    var OFFSET_MOUSE = 20;
    var OFFSET_TOUCH = 45;
    var OFFSET_PROGRAMMATIC_TOUCH = 20;
    var OFFSET_PROGRAMMATIC_NONTOUCH = 12;
    var SAFETY_NET_GAP = 1; // We set a 1-pixel gap between the right or bottom edge of the tooltip and the viewport to avoid possible re-layout
    var PT_TOUCH = 2; // pointer type to indicate a touch event

    var EVENTS_INVOKE = { "keyup": "", "MSPointerOver": "" },
        EVENTS_UPDATE = { "MSPointerMove": "" },
    EVENTS_DISMISS = { "MSPointerDown": "", "keydown": "", "blur": "", "MSPointerOut": "", "MSPointerCancel": "", "MSPointerUp": "" },
    EVENTS_BY_CHILD = { "MSPointerOver": "", "MSPointerOut": "" };

    // CSS class names
    var msTooltip = "win-tooltip",
    msTooltipPhantom = "win-tooltip-phantom";

    // Global attributes
    var mouseHoverTime = DEFAULT_MOUSE_HOVER_TIME,
        nonInfoTooltipNonTouchShowDelay = 2 * mouseHoverTime,
        infoTooltipNonTouchShowDelay = 2.5 * mouseHoverTime,
        messageDuration = DEFAULT_MESSAGE_DURATION,
        isLeftHanded = false;

    var hasInitWinRTSettings = false;

    // Tooltip control implementation
    WinJS.Namespace.define("WinJS.UI", {
        /// <summary locid="WinJS.UI.Tooltip">
        /// Displays a tooltip that can contain images and formatting.
        /// </summary>
        /// <icon src="ui_winjs.ui.tooltip.12x12.png" width="12" height="12" />
        /// <icon src="ui_winjs.ui.tooltip.16x16.png" width="16" height="16" />
        /// <htmlSnippet supportsContent="true"><![CDATA[<div style="display:inline-block;" data-win-control="WinJS.UI.Tooltip" data-win-options="{innerHTML:'Tooltip content goes here'}"></div>]]></htmlSnippet>
        /// <event name="beforeopen" bubbles="false" locid="WinJS.UI.Tooltip_e:beforeopen">Raised when the tooltip is about to appear.</event>
        /// <event name="opened" bubbles="false" locid="WinJS.UI.Tooltip_e:opened">Raised when the tooltip is showing.</event>
        /// <event name="beforeclose" bubbles="false" locid="WinJS.UI.Tooltip_e:beforeclose">Raised when the tooltip is about to become hidden.</event>
        /// <event name="closed" bubbles="false" locid="WinJS.UI.Tooltip_e:close">Raised when the tooltip is hidden.</event>
        /// <part name="tooltip" class="win-tooltip" locid="WinJS.UI.Tooltip_e:tooltip">The entire Tooltip control.</part>
        /// <resource type="javascript" src="//Microsoft.WinJS.1.0/js/base.js" shared="true" />
        /// <resource type="javascript" src="//Microsoft.WinJS.1.0/js/ui.js" shared="true" />
        /// <resource type="css" src="//Microsoft.WinJS.1.0/css/ui-dark.css" shared="true" />
        Tooltip: WinJS.Class.define(function Tooltip_ctor(anchorElement, options) {
            /// <signature helpKeyword="WinJS.UI.Tooltip.Tooltip">
            /// <summary locid="WinJS.UI.Tooltip.constructor">
            /// Creates a new Tooltip.
            /// </summary>
            /// <param name="element" domElement="true" locid="WinJS.UI.Tooltip.constructor_p:element">
            /// The DOM element that hosts the Tooltip.
            /// </param>
            /// <param name="options" type="Object" locid="WinJS.UI.Tooltip.constructor_p:options">
            /// An object that contains one or more property/value pairs to apply to the new control.
            /// Each property of the options object corresponds to one of the control's properties or events.
            /// Event names must begin with "on". For example, to provide a handler for the opened event,
            /// add a property named "onopened" to the options object and set its value to the event handler.
            /// This parameter is optional.
            /// </param>
            /// <returns type="WinJS.UI.Tooltip" locid="WinJS.UI.Tooltip.constructor_returnValue">
            /// The new Tooltip.
            /// </returns>
            /// </signature>
            anchorElement = anchorElement || document.createElement("div");

            var tooltip = utilities.data(anchorElement).tooltip;
            if (tooltip) {
                return tooltip;
            }

            // Set system attributes if it is in WWA, otherwise, use the default values
            if (!hasInitWinRTSettings && WinJS.Utilities.hasWinRT) { // in WWA
                var uiSettings = new Windows.UI.ViewManagement.UISettings();
                mouseHoverTime = uiSettings.mouseHoverTime;
                nonInfoTooltipNonTouchShowDelay = 2 * mouseHoverTime;
                infoTooltipNonTouchShowDelay = 2.5 * mouseHoverTime;
                messageDuration = uiSettings.messageDuration * 1000;  // uiSettings.messageDuration is in seconds.
                var handedness = uiSettings.handPreference;
                isLeftHanded = (handedness == Windows.UI.ViewManagement.HandPreference.leftHanded);
            }
            hasInitWinRTSettings = true;

            // Need to initialize properties
            this._placement = DEFAULT_PLACEMENT;
            this._infotip = false;
            this._innerHTML = null;
            this._contentElement = null;
            this._extraClass = null;
            this._lastContentType = "html";
            this._anchorElement = anchorElement;
            this._domElement = null;
            this._phantomDiv = null;
            this._triggerByOpen = false;

            // To handle keyboard navigation
            this._lastKeyOrBlurEvent = null;
            this._currentKeyOrBlurEvent = null;

            // Remember ourselves
            anchorElement.winControl = this;

            // If anchor element's title is defined, set as the default tooltip content
            if (anchorElement.title) {
                this._innerHTML = this._anchorElement.title;
                this._anchorElement.removeAttribute("title");
            }

            WinJS.UI.setOptions(this, options);
            this._events();
            utilities.data(anchorElement).tooltip = this;
        }, {
            /// <field type="String" locid="WinJS.UI.Tooltip.innerHTML" helpKeyword="WinJS.UI.Tooltip.innerHTML">
            /// Gets or sets the HTML content of the Tooltip.
            /// </field>
            innerHTML: {
                get: function () {
                    return this._innerHTML;
                },
                set: function (value) {
                    this._innerHTML = value;
                    if (this._domElement) {
                        // If we set the innerHTML to null or "" while tooltip is up, we should close it
                        if (!this._innerHTML || this._innerHTML === "") {
                            this._onDismiss();
                            return;
                        }
                        this._domElement.innerHTML = value;
                        this._position();
                    }
                    this._lastContentType = "html";
                }
            },

            /// <field type="HTMLElement" hidden="true" locid="WinJS.UI.Tooltip.element" helpKeyword="WinJS.UI.Tooltip.element">
            /// Gets or sets the DOM element that hosts the Tooltip.
            /// </field>
            element: {
                get: function () {
                    return this._anchorElement;
                }
            },

            /// <field type="HTMLElement" locid="WinJS.UI.Tooltip.contentElement" helpKeyword="WinJS.UI.Tooltip.contentElement" potentialValueSelector="div[style='display: none;']&gt;div[id], div[style='display: none;']&gt;div[class]">
            /// Gets or sets the DOM element that is the content for the ToolTip.
            /// </field>
            contentElement: {
                get: function () {
                    return this._contentElement;
                },
                set: function (value) {
                    this._contentElement = value;
                    if (this._domElement) {
                        // If we set the contentElement to null while tooltip is up, we should close it
                        if (!this._contentElement) {
                            this._onDismiss();
                            return;
                        }
                        this._domElement.innerHTML = "";
                        this._domElement.appendChild(this._contentElement);
                        this._position();
                    }
                    this._lastContentType = "element";
                }
            },

            /// <field type="String" oamOptionsDatatype="WinJS.UI.Tooltip.placement" locid="WinJS.UI.Tooltip.placement" helpKeyword="WinJS.UI.Tooltip.placement">
            /// Gets or sets the position for the Tooltip relative to its target element: top, bottom, left or right.
            /// </field>
            placement: {
                get: function () {
                    return this._placement;
                },
                set: function (value) {
                    if (value !== "top" && value !== "bottom" && value !== "left" && value !== "right") {
                        value = DEFAULT_PLACEMENT;
                    }
                    this._placement = value;
                    if (this._domElement) {
                        this._position();
                    }
                }
            },

            /// <field type="Boolean" locid="WinJS.UI.Tooltip.infotip" helpKeyword="WinJS.UI.Tooltip.infotip">
            /// Gets or sets a value that specifies whether the Tooltip is an infotip, a tooltip that contains
            /// a lot of info and should be displayed for longer than a typical Tooltip.
            /// The default value is false.
            /// </field>
            infotip: {
                get: function () {
                    return this._infotip;
                },
                set: function (value) {
                    this._infotip = !!value; //convert the value to boolean
                }
            },

            /// <field type="String" locid="WinJS.UI.Tooltip.extraClass" helpKeyword="WinJS.UI.Tooltip.extraClass" isAdvanced="true">
            /// Gets or sets additional CSS classes to apply to the Tooltip control's host element.
            /// </field>
            extraClass: {
                get: function () {
                    return this._extraClass;
                },
                set: function (value) {
                    this._extraClass = value;
                }
            },

            addEventListener: function (eventName, eventCallBack, capture) {
                /// <signature helpKeyword="WinJS.UI.Tooltip.addEventListener">
                /// <summary locid="WinJS.UI.Tooltip.addEventListener">
                /// Registers an event handler for the specified event.
                /// </summary>
                /// <param name="eventName" type="String" locid="WinJS.UI.Tooltip.addEventListener_p:eventName">The name of the event.</param>
                /// <param name="eventCallback" type="Function" locid="WinJS.UI.Tooltip.addEventListener_p:eventCallback">The event handler function to associate with this event.</param>
                /// <param name="capture" type="Boolean" locid="WinJS.UI.Tooltip.addEventListener_p:capture">Set to true to register the event handler for the capturing phase; set to false to register for the bubbling phase.</param>
                /// </signature>

                if (this._anchorElement) {
                    this._anchorElement.addEventListener(eventName, eventCallBack, capture);
                }
            },

            removeEventListener: function (eventName, eventCallBack, capture) {
                /// <signature helpKeyword="WinJS.UI.Tooltip.removeEventListener">
                /// <summary locid="WinJS.UI.Tooltip.removeEventListener">
                /// Unregisters an event handler for the specified event.
                /// </summary>
                /// <param name="eventName" type="String" locid="WinJS.UI.Tooltip.removeEventListener:eventName">The name of the event.</param>
                /// <param name="eventCallback" type="Function" locid="WinJS.UI.Tooltip.removeEventListener:eventCallback">The event handler function to remove.</param>
                /// <param name="capture" type="Boolean" locid="WinJS.UI.Tooltip.removeEventListener:capture">Set to true to unregister the event handler for the capturing phase; otherwise, set to false to unregister the event handler for the bubbling phase.</param>
                /// </signature>

                if (this._anchorElement) {
                    this._anchorElement.removeEventListener(eventName, eventCallBack, capture);
                }
            },

            open: function (type) {
                /// <signature helpKeyword="WinJS.UI.Tooltip.open">
                /// <summary locid="WinJS.UI.Tooltip.open">
                /// Shows the Tooltip.
                /// </summary>
                /// <param name="type" type="String" locid="WinJS.UI.Tooltip.open_p:type">The type of tooltip to show: "touch", "mouseover", "mousedown", or "keyboard". The default value is "mousedown".</param>
                /// </signature>

                // Open takes precedence over other triggering events
                // Once tooltip is opened using open(), it can only be closed by time out(mouseover or keyboard) or explicitly by close().
                this._triggerByOpen = true;

                if (type !== "touch" && type !== "mouseover" && type !== "mousedown" && type !== "keyboard") {
                    type = "default";
                }

                switch (type) {
                    case "touch":
                        this._onInvoke("touch", "never");
                        break;
                    case "mouseover":
                        this._onInvoke("mouse", "auto");
                        break;
                    case "keyboard":
                        this._onInvoke("keyboard", "auto");
                        break;
                    case "mousedown":
                    case "default":
                        this._onInvoke("nodelay", "never");
                        break;
                }

            },

            close: function () {
                /// <signature helpKeyword="WinJS.UI.Tooltip.close">
                /// <summary locid="WinJS.UI.Tooltip.close">
                /// Hids the Tooltip.
                /// </summary>
                /// </signature>

                this._onDismiss();
            },

            _cleanUpDOM: function () {
                if (this._domElement) {
                    document.body.removeChild(this._phantomDiv);
                    document.body.removeChild(this._domElement);
                    this._domElement = null;
                    this._phantomDiv = null;
                }
            },

            _createTooltipDOM: function () {
                this._cleanUpDOM();

                this._domElement = document.createElement("div");

                var id = this._domElement.uniqueID;
                this._domElement.setAttribute("id", id);

                // Set the direction of tooltip according to anchor element's
                var computedStyle = document.defaultView.getComputedStyle(this._anchorElement, null);
                var elemStyle = this._domElement.style;
                elemStyle.direction = computedStyle.direction;
                elemStyle.writingMode = computedStyle["writing-mode"]; // must use CSS name, not JS name

                // Make the tooltip non-focusable
                this._domElement.setAttribute("tabindex", -1);

                // Set the aria tags for accessibility
                this._domElement.setAttribute("role", "tooltip");
                this._anchorElement.setAttribute("aria-describedby", id);

                // Set the tooltip content
                if (this._lastContentType === "element") { // Last update through contentElement option
                    this._domElement.appendChild(this._contentElement);
                } else { // Last update through innerHTML option
                    this._domElement.innerHTML = this._innerHTML;
                }

                document.body.appendChild(this._domElement);
                utilities.addClass(this._domElement, msTooltip);

                // In the event of user-assigned classes, add those too
                if (this._extraClass) {
                    utilities.addClass(this._domElement, this._extraClass);
                }

                // Create a phantom div on top of the tooltip div to block all interactions
                this._phantomDiv = document.createElement("div");
                this._phantomDiv.setAttribute("tabindex", -1);
                document.body.appendChild(this._phantomDiv);
                utilities.addClass(this._phantomDiv, msTooltipPhantom);
                var zIndex = document.defaultView.getComputedStyle(this._domElement, null).zIndex + 1;
                this._phantomDiv.style.zIndex = zIndex;
            },

            _raiseEvent: function (type, eventProperties) {
                if (this._anchorElement) {
                    var customEvent = document.createEvent("CustomEvent");
                    customEvent.initCustomEvent(type, false, false, eventProperties);
                    this._anchorElement.dispatchEvent(customEvent);
                }
            },

            // Support for keyboard navigation
            _captureLastKeyBlurOrPointerOverEvent: function (event, listener) {
                listener._lastKeyOrBlurEvent = listener._currentKeyOrBlurEvent;
                switch (event.type) {
                    case "keyup":
                        if (event.key === "Shift") {
                            listener._currentKeyOrBlurEvent = null;
                        } else {
                            listener._currentKeyOrBlurEvent = "keyboard";
                        }
                        break;
                    case "blur":
                        //anchor elment no longer in focus, clear up the stack
                        listener._currentKeyOrBlurEvent = null;
                        break;
                    default:
                        break;

                }
            },

            _registerEventToListener: function (element, eventType, listener) {
                element.addEventListener(eventType,
                function (event) {
                    listener._captureLastKeyBlurOrPointerOverEvent(event, listener);
                    listener._handleEvent(event);
                },
                false);
            },

            _events: function () {
                for (var eventType in EVENTS_INVOKE) {
                    this._registerEventToListener(this._anchorElement, eventType, this);
                }
                for (var eventType in EVENTS_UPDATE) {
                    this._registerEventToListener(this._anchorElement, eventType, this);
                }
                for (eventType in EVENTS_DISMISS) {
                    this._registerEventToListener(this._anchorElement, eventType, this);
                }


            },

            _handleEvent: function (event) {
                var eventType = event.type;
                if (!this._triggerByOpen) {
                    // If the anchor element has children, we should ignore events that are caused within the anchor element
                    // Please note that we are not using event.target here as in bubbling phases from the child, the event target
                    // is usually the child
                    if (eventType in EVENTS_BY_CHILD) {
                        var elem = event.relatedTarget;

                        while (elem && elem !== this._anchorElement && elem !== document.body) {
                            try {
                                elem = elem.parentNode;
                            }
                            catch (e) {
                                if (e instanceof Error && e.message === 'Permission denied') {
                                    //Permission denied error, if we can't access the node's
                                    //information, we should not handle the event
                                    //Put this guard prior Bug 484666 is fixed
                                    return;
                                }
                                else {
                                    throw e;
                                }
                            }
                        }
                        if (elem === this._anchorElement) {
                            return;
                        }
                    }
                    if (eventType in EVENTS_INVOKE) {
                        if (event.pointerType == PT_TOUCH) {
                            this._onInvoke("touch", "never", event);
                            this._showTrigger = "touch";
                        } else {
                            var type = eventType.substring(0, 3) === "key" ? "keyboard" : "mouse";
                            this._onInvoke(type, "auto", event);
                            this._showTrigger = type;
                        }
                    } else if (eventType in EVENTS_UPDATE) {
                        this._contactPoint = { x: event.clientX, y: event.clientY };
                    } else if (eventType in EVENTS_DISMISS) {
                        var eventTrigger;
                        if (event.pointerType == PT_TOUCH) {
                            if (eventType == "MSPointerDown") {
                                return;
                            }
                            eventTrigger = "touch";
                        }
                        else {
                            eventTrigger = eventType.substring(0, 3) === "key" ? "keyboard" : "mouse";
                        }
                        if (eventType != "blur" && eventTrigger != this._showTrigger) {
                            return;
                        }
                        this._onDismiss();
                    }
                }
            },

            _onShowAnimationEnd: function () {
                if (this._shouldDismiss) {
                    return;
                }
                this._raiseEvent("opened");
                if (this._domElement) {
                    if (this._hideDelay !== "never") {
                        var that = this;
                        var delay = this._infotip ? Math.min(3 * messageDuration, HIDE_DELAY_MAX) : messageDuration;
                        this._hideDelayTimer = setTimeout(function () {
                            that._onDismiss();
                        }, delay);
                    }
                }
            },


            _onHideAnimationEnd: function () {
                document.body.removeEventListener("DOMNodeRemoved", this._removeTooltip, false);
                this._cleanUpDOM();
                // Once we remove the tooltip from the DOM, we should remove the aria tag from the anchor
                if (this._anchorElement) {
                    this._anchorElement.removeAttribute("aria-describedby");
                }
                lastCloseTime = (new Date()).getTime();
                this._triggerByOpen = false;
                this._raiseEvent("closed");
            },

            _decideOnDelay: function (type) {
                var value;
                this._useAnimation = true;

                if (type == "nodelay") {
                    value = 0;
                    this._useAnimation = false;
                }
                else {
                    var curTime = (new Date()).getTime();
                    // If the mouse is moved immediately from another anchor that has
                    // tooltip open, we should use a shorter delay
                    if (curTime - lastCloseTime <= RESHOW_THRESHOLD) {
                        if (type == "touch") {
                            value = this._infotip ? DELAY_RESHOW_INFOTIP_TOUCH : DELAY_RESHOW_NONINFOTIP_TOUCH;
                        }
                        else {
                            value = this._infotip ? DELAY_RESHOW_INFOTIP_NONTOUCH : DELAY_RESHOW_NONINFOTIP_NONTOUCH;
                        }
                        this._useAnimation = false;
                    } else if (type == "touch") {
                        value = this._infotip ? DELAY_INITIAL_TOUCH_LONG : DELAY_INITIAL_TOUCH_SHORT;
                    } else {
                        value = this._infotip ? infoTooltipNonTouchShowDelay : nonInfoTooltipNonTouchShowDelay;
                    }
                }
                return value;
            },

            // This function returns the anchor element's position in the Window coordinates.
            _getAnchorPositionFromElementWindowCoord: function () {
                var rect = this._anchorElement.getBoundingClientRect();

                return {
                    x: rect.left,
                    y: rect.top,
                    width: rect.width,
                    height: rect.height
                };
            },

            _getAnchorPositionFromPointerWindowCoord: function (contactPoint) {
                return {
                    x: contactPoint.x,
                    y: contactPoint.y,
                    width: 1,
                    height: 1
                };
            },

            _canPositionOnSide: function (placement, viewport, anchor, tip) {
                var availWidth = 0, availHeight = 0;

                switch (placement) {
                    case "top":
                        availWidth = tip.width + this._offset;
                        availHeight = anchor.y;
                        break;
                    case "bottom":
                        availWidth = tip.width + this._offset;
                        availHeight = viewport.height - anchor.y - anchor.height;
                        break;
                    case "left":
                        availWidth = anchor.x;
                        availHeight = tip.height + this._offset;
                        break;
                    case "right":
                        availWidth = viewport.width - anchor.x - anchor.width;
                        availHeight = tip.height + this._offset;
                        break;
                }
                return ((availWidth >= tip.width + this._offset) && (availHeight >= tip.height + this._offset));
            },

            _positionOnSide: function (placement, viewport, anchor, tip) {
                var left = 0, top = 0;

                switch (placement) {
                    case "top":
                    case "bottom":
                        // Align the tooltip to the anchor's center horizontally
                        left = anchor.x + anchor.width / 2 - tip.width / 2;

                        // If the left boundary is outside the window, set it to 0
                        // If the right boundary is outside the window, set it to align with the window right boundary
                        left = Math.min(Math.max(left, 0), viewport.width - tip.width - SAFETY_NET_GAP);

                        top = (placement == "top") ? anchor.y - tip.height - this._offset : anchor.y + anchor.height + this._offset;
                        break;
                    case "left":
                    case "right":
                        // Align the tooltip to the anchor's center vertically
                        top = anchor.y + anchor.height / 2 - tip.height / 2;

                        // If the top boundary is outside the window, set it to 0
                        // If the bottom boundary is outside the window, set it to align with the window bottom boundary
                        top = Math.min(Math.max(top, 0), viewport.height - tip.height - SAFETY_NET_GAP);

                        left = (placement == "left") ? anchor.x - tip.width - this._offset : anchor.x + anchor.width + this._offset;
                        break;
                }

                // Actually set the position
                this._domElement.style.left = left + "px";
                this._domElement.style.top = top + "px";

                // Set the phantom's position and size
                this._phantomDiv.style.left = left + "px";
                this._phantomDiv.style.top = top + "px";
                this._phantomDiv.style.width = tip.width + "px";
                this._phantomDiv.style.height = tip.height + "px";
            },

            _position: function (contactType) {
                var viewport = { width: 0, height: 0 };
                var anchor = { x: 0, y: 0, width: 0, height: 0 };
                var tip = { width: 0, height: 0 };

                viewport.width = document.documentElement.clientWidth;
                viewport.height = document.documentElement.clientHeight;
                if (document.defaultView.getComputedStyle(document.body, null)["writing-mode"] === "tb-rl") {
                    viewport.width = document.documentElement.clientHeight;
                    viewport.height = document.documentElement.clientWidth;
                }

                if (this._contactPoint && (contactType === "touch" || contactType === "mouse")) {
                    anchor = this._getAnchorPositionFromPointerWindowCoord(this._contactPoint);
                }
                else {
                    // keyboard or programmatic is relative to element
                    anchor = this._getAnchorPositionFromElementWindowCoord();
                }
                tip.width = this._domElement.offsetWidth;
                tip.height = this._domElement.offsetHeight;
                var fallback_order = {
                    "top": ["top", "bottom", "left", "right"],
                    "bottom": ["bottom", "top", "left", "right"],
                    "left": ["left", "right", "top", "bottom"],
                    "right": ["right", "left", "top", "bottom"]
                };
                if (isLeftHanded) {
                    fallback_order.top[2] = "right";
                    fallback_order.top[3] = "left";
                    fallback_order.bottom[2] = "right";
                    fallback_order.bottom[3] = "left";
                }

                // Try to position the tooltip according to the placement preference
                // We use this order:
                // 1. Try the preferred placement
                // 2. Try the opposite placement
                // 3. If the preferred placement is top or bottom, we should try left
                // and right (or right and left if left handed)
                // If the preferred placement is left or right, we should try top and bottom
                var order = fallback_order[this._placement];
                var length = order.length;
                for (var i = 0; i < length; i++) {
                    if (i == length - 1 || this._canPositionOnSide(order[i], viewport, anchor, tip)) {
                        this._positionOnSide(order[i], viewport, anchor, tip);
                        break;
                    }
                }
                return order[i];
            },

            _showTooltip: function (contactType) {
                // Give a chance to dismiss the tooltip before it starts to show
                if (this._shouldDismiss) {
                    return;
                }
                this._isShown = true;
                this._raiseEvent("beforeopen");

                // If the anchor is not in the DOM tree, we don't create the tooltip
                if (!this._anchorElement.parentNode) {
                    return;
                }
                if (this._shouldDismiss) {
                    return;
                }

                // If the contentElement is set to null or innerHTML set to null or "", we should NOT show the tooltip
                if (this._lastContentType === "element") { // Last update through contentElement option
                    if (!this._contentElement) {
                        this._isShown = false;
                        return;
                    }
                } else { // Last update through innerHTML option
                    if (!this._innerHTML || this._innerHTML === "") {
                        this._isShown = false;
                        return;
                    }
                }

                var that = this;
                this._removeTooltip = function (event) {
                    var current = that._anchorElement;
                    while (current) {
                        if (event.target == current) {
                            document.body.removeEventListener("DOMNodeRemoved", that._removeTooltip, false);
                            that._cleanUpDOM();
                            break;
                        }
                        current = current.parentNode;
                    }
                };

                document.body.addEventListener("DOMNodeRemoved", this._removeTooltip, false);
                this._createTooltipDOM();
                var pos = this._position(contactType);
                var that = this;
                if (this._useAnimation) {
                    animation.fadeIn(this._domElement)
                        .then(this._onShowAnimationEnd.bind(this));
                } else {
                    this._onShowAnimationEnd();
                }
            },

            _onInvoke: function (type, hide, event) {
                // Reset the dismiss flag
                this._shouldDismiss = false;

                // If the tooltip is already shown, ignore the current event
                if (this._isShown) {
                    return;
                }

                // To handle keyboard support, we only want to display tooltip on the first tab key event only
                if (event && event.type === "keyup") {
                    if (this._lastKeyOrBlurEvent == "keyboard" ||
                        !this._lastKeyOrBlurEvent && event.key !== "Tab") {
                        return;
                    }
                }

                // Set the hide delay,
                this._hideDelay = hide;

                this._contactPoint = null;
                if (event) { // Open through interaction
                    this._contactPoint = { x: event.clientX, y: event.clientY };
                    // Tooltip display offset differently for touch events and non-touch events
                    if (type == "touch") {
                        this._offset = OFFSET_TOUCH;
                    } else if (type === "keyboard") {
                        this._offset = OFFSET_KEYBOARD;
                    } else {
                        this._offset = OFFSET_MOUSE;
                    }
                } else { // Open Programmatically
                    if (type == "touch") {
                        this._offset = OFFSET_PROGRAMMATIC_TOUCH;
                    } else {
                        this._offset = OFFSET_PROGRAMMATIC_NONTOUCH;
                    }
                }

                clearTimeout(this._delayTimer);
                clearTimeout(this._hideDelayTimer);

                // Set the delay time
                var delay = this._decideOnDelay(type);
                if (delay > 0) {
                    var that = this;
                    this._delayTimer = setTimeout(function () {
                        that._showTooltip(type);
                    }, delay);
                } else {
                    this._showTooltip(type);
                }
            },

            _onDismiss: function () {
                // Set the dismiss flag so that we don't miss dismiss events
                this._shouldDismiss = true;

                // If the tooltip is already dismissed, ignore the current event
                if (!this._isShown) {
                    return;
                }

                this._isShown = false;

                // Reset tooltip state
                this._showTrigger = "mouse";

                if (this._domElement) {
                    this._raiseEvent("beforeclose");
                    if (this._useAnimation) {
                        animation.fadeOut(this._domElement)
                            .then(this._onHideAnimationEnd.bind(this));
                    } else {
                        this._onHideAnimationEnd();
                    }
                } else {
                    this._raiseEvent("beforeclose");
                    this._raiseEvent("closed");
                }
            }
        })
    });

// Tooltip support for "on"<eventName> properties
WinJS.Class.mix(WinJS.UI.Tooltip, WinJS.Utilities.createEventProperties(
    "beforeopen",
    "opened",
    "beforeclose",
    "closed"));

})(this, WinJS);
// ViewBox control
(function viewboxInit(global, undefined) {
    "use strict";

    var strings = {
        get invalidViewBoxChildren() { return WinJS.Resources._getWinJSString("ui/invalidViewBoxChildren").value; },
    };

    function onresize(control) {
        if (control && !control._resizing) {
            control._resizing = control._resizing || 0;
            control._resizing++;
            try {
                control._updateLayout();
            } finally {
                control._resizing--;
            }
        }
    }

    function onresizeBox(ev) {
        if (ev.srcElement) {
            onresize(ev.srcElement.winControl);
        }
    }

    function onresizeSizer(ev) {
        if (ev.srcElement) {
            onresize(ev.srcElement.parentElement.winControl);
        }
    }

    WinJS.Namespace.define("WinJS.UI", {
        /// <summary locid="WinJS.UI.ViewBox">
        /// Scales a single child element to fill the available space without
        /// resizing it. This control reacts to changes in the size of the container as well as
        /// changes in size of the child element. For example, a media query may result in
        /// a change in aspect ratio.
        /// </summary>
        /// <name locid="WinJS.UI.ViewBox_name">View Box</name>
        /// <icon src="ui_winjs.ui.viewbox.12x12.png" width="12" height="12" />
        /// <icon src="ui_winjs.ui.viewbox.16x16.png" width="16" height="16" />
        /// <htmlSnippet supportsContent="true"><![CDATA[<div data-win-control="WinJS.UI.ViewBox"><div>ViewBox</div></div>]]></htmlSnippet>
        /// <resource type="javascript" src="//Microsoft.WinJS.1.0/js/base.js" shared="true" />
        /// <resource type="javascript" src="//Microsoft.WinJS.1.0/js/ui.js" shared="true" />
        /// <resource type="css" src="//Microsoft.WinJS.1.0/css/ui-dark.css" shared="true" />
        ViewBox: WinJS.Class.define(
            function ViewBox_ctor(element, options) {
                /// <signature helpKeyword="WinJS.UI.ViewBox.ViewBox">
                /// <summary locid="WinJS.UI.ViewBox.constructor">Initializes a new instance of the ViewBox control</summary>
                /// <param name="element" type="HTMLElement" domElement="true" mayBeNull="true" locid="WinJS.UI.ViewBox.constructor_p:element">
                /// The DOM element that functions as the scaling box. This element fills 100% of the width and height allotted to it.
                /// </param>
                /// <param name="options" type="Object" optional="true" locid="WinJS.UI.ViewBox.constructor_p:options">
                /// The set of options to be applied initially to the ViewBox control.
                /// </param>
                /// <returns type="WinJS.UI.ViewBox" locid="WinJS.UI.ViewBox.constructor_returnValue">A constructed ViewBox control.</returns>
                /// </signature>
                this._element = element || document.createElement("div");
                var box = this.element;
                box.winControl = this;
                WinJS.Utilities.addClass(box, "win-viewbox");
                this.forceLayout();
            },
            {
                _sizer: null,
                _element: null,

                /// <field type="HTMLElement" domElement="true" hidden="true" locid="WinJS.UI.ViewBox.element" helpKeyword="WinJS.UI.ViewBox.element">
                /// Gets the DOM element that functions as the scaling box.
                /// </field>
                element: {
                    get: function () { return this._element; }
                },

                _rtl: {
                    get: function () {
                        return window.getComputedStyle(this.element).direction === "rtl";
                    }
                },

                _initialize: function () {
                    var box = this.element;
                    if (box.firstElementChild !== this._sizer) {
                        if (WinJS.validation) {
                            if (box.childElementCount != 1) {
                                throw new WinJS.ErrorFromName("WinJS.UI.ViewBox.InvalidChildren", strings.invalidViewBoxChildren);
                            }
                        }
                        if (this._sizer) {
                            this._sizer.onresize = null;
                        }
                        var sizer = box.firstElementChild;
                        this._sizer = sizer;
                        if (sizer) {
                            box.attachEvent("onresize", onresizeBox);
                            sizer.attachEvent("onresize", onresizeSizer);
                        }
                        if (box.clientWidth === 0 && box.clientHeight === 0) {
                            var that = this;
                            setImmediate(function () {
                                that._updateLayout();
                            })
                        }
                    }
                },
                _updateLayout: function () {
                    var sizer = this._sizer;
                    if (sizer) {
                        var box = this.element;
                        var w = sizer.clientWidth;
                        var h = sizer.clientHeight;
                        var bw = box.clientWidth;
                        var bh = box.clientHeight;
                        var wRatio = bw / w;
                        var hRatio = bh / h;
                        var mRatio = Math.min(wRatio, hRatio);
                        var transX = Math.abs(bw - (w * mRatio)) / 2;
                        var transY = Math.abs(bh - (h * mRatio)) / 2;
                        this._sizer.style["transform"] = "translate(" + transX + "px," + transY + "px) scale(" + mRatio + ")";
                        this._sizer.style["transform-origin"] = this._rtl ? "top right" : "top left";
                    }
                },

                forceLayout: function () {
                    this._initialize();
                    this._updateLayout();
                }
            }
        )
    });

    WinJS.Class.mix(WinJS.UI.ViewBox, WinJS.UI.DOMEventMixin);

}(this));

