/**
+ * Provides stackable (z-index) support for Widgets through an extension.
+ *
+ * @module widget-stack
+ */
+ var L = Y.Lang,
+ UA = Y.UA,
+ Node = Y.Node,
+ Widget = Y.Widget,
+
+ ZINDEX = "zIndex",
+ SHIM = "shim",
+ VISIBLE = "visible",
+
+ BOUNDING_BOX = "boundingBox",
+
+ RENDER_UI = "renderUI",
+ BIND_UI = "bindUI",
+ SYNC_UI = "syncUI",
+
+ OFFSET_WIDTH = "offsetWidth",
+ OFFSET_HEIGHT = "offsetHeight",
+ PARENT_NODE = "parentNode",
+ FIRST_CHILD = "firstChild",
+
+ WIDTH = "width",
+ HEIGHT = "height",
+ PX = "px",
+
+ // HANDLE KEYS
+ SHIM_DEFERRED = "shimdeferred",
+ SHIM_RESIZE = "shimresize",
+
+ // Events
+ VisibleChange = "visibleChange",
+ WidthChange = "widthChange",
+ HeightChange = "heightChange",
+ ShimChange = "shimChange",
+ ZIndexChange = "zIndexChange",
+ ContentUpdate = "contentUpdate",
+
+ // CSS
+ STACKED = "stacked";
+
+ /**
+ * Widget extension, which can be used to add stackable (z-index) support to the
+ * base Widget class along with a shimming solution, through the
+ * <a href="Base.html#method_build">Base.build</a> method.
+ *
+ * @class WidgetStack
+ * @param {Object} User configuration object
+ */
+ function Stack(config) {
+ this._stackNode = this.get(BOUNDING_BOX);
+ this._stackHandles = {};
+
+ // WIDGET METHOD OVERLAP
+ Y.after(this._renderUIStack, this, RENDER_UI);
+ Y.after(this._syncUIStack, this, SYNC_UI);
+ Y.after(this._bindUIStack, this, BIND_UI);
+ }
+
+ // Static Properties
+ /**
+ * Static property used to define the default attribute
+ * configuration introduced by WidgetStack.
+ *
+ * @property WidgetStack.ATTRS
+ * @type Object
+ * @static
+ */
+ Stack.ATTRS = {
+ /**
+ * @attribute shim
+ * @type boolean
+ * @default false, for all browsers other than IE6, for which a shim is enabled by default.
+ *
+ * @description Boolean flag to indicate whether or not a shim should be added to the Widgets
+ * boundingBox, to protect it from select box bleedthrough.
+ */
+ shim: {
+ value: (UA.ie == 6)
+ },
+
+ /**
+ * @attribute zIndex
+ * @type number
+ * @default 0
+ * @description The z-index to apply to the Widgets boundingBox. Non-numerical values for
+ * zIndex will be converted to 0
+ */
+ zIndex: {
+ value:0,
+ setter: function(val) {
+ return this._setZIndex(val);
+ }
+ }
+ };
+
+ /**
+ * The HTML parsing rules for the WidgetStack class.
+ *
+ * @property WidgetStack.HTML_PARSER
+ * @static
+ * @type Object
+ */
+ Stack.HTML_PARSER = {
+ zIndex: function(contentBox) {
+ return contentBox.getStyle(ZINDEX);
+ }
+ };
+
+ /**
+ * Default class used to mark the shim element
+ *
+ * @property WidgetStack.SHIM_CLASS_NAME
+ * @type String
+ * @static
+ * @default "yui-widget-shim"
+ */
+ Stack.SHIM_CLASS_NAME = Widget.getClassName(SHIM);
+
+ /**
+ * Default class used to mark the boundingBox of a stacked widget.
+ *
+ * @property WidgetStack.STACKED_CLASS_NAME
+ * @type String
+ * @static
+ * @default "yui-widget-stacked"
+ */
+ Stack.STACKED_CLASS_NAME = Widget.getClassName(STACKED);
+
+ /**
+ * Default markup template used to generate the shim element.
+ *
+ * @property WidgetStack.SHIM_TEMPLATE
+ * @type String
+ * @static
+ */
+ Stack.SHIM_TEMPLATE = '<iframe class="' + Stack.SHIM_CLASS_NAME + '" frameborder="0" title="Widget Stacking Shim" src="javascript:false" tabindex="-1" role="presentation"></iframe>';
+
+ Stack.prototype = {
+
+ /**
+ * Synchronizes the UI to match the Widgets stack state. This method in
+ * invoked after syncUI is invoked for the Widget class using YUI's aop infrastructure.
+ *
+ * @method _syncUIStack
+ * @protected
+ */
+ _syncUIStack: function() {
+ this._uiSetShim(this.get(SHIM));
+ this._uiSetZIndex(this.get(ZINDEX));
+ },
+
+ /**
+ * Binds event listeners responsible for updating the UI state in response to
+ * Widget stack related state changes.
+ * <p>
+ * This method is invoked after bindUI is invoked for the Widget class
+ * using YUI's aop infrastructure.
+ * </p>
+ * @method _bindUIStack
+ * @protected
+ */
+ _bindUIStack: function() {
+ this.after(ShimChange, this._afterShimChange);
+ this.after(ZIndexChange, this._afterZIndexChange);
+ },
+
+ /**
+ * Creates/Initializes the DOM to support stackability.
+ * <p>
+ * This method in invoked after renderUI is invoked for the Widget class
+ * using YUI's aop infrastructure.
+ * </p>
+ * @method _renderUIStack
+ * @protected
+ */
+ _renderUIStack: function() {
+ this._stackNode.addClass(Stack.STACKED_CLASS_NAME);
+ },
+
+ /**
+ * Default setter for zIndex attribute changes. Normalizes zIndex values to
+ * numbers, converting non-numerical values to 0.
+ *
+ * @method _setZIndex
+ * @protected
+ * @param {String | Number} zIndex
+ * @return {Number} Normalized zIndex
+ */
+ _setZIndex: function(zIndex) {
+ if (L.isString(zIndex)) {
+ zIndex = parseInt(zIndex, 10);
+ }
+ if (!L.isNumber(zIndex)) {
+ zIndex = 0;
+ }
+ return zIndex;
+ },
+
+ /**
+ * Default attribute change listener for the shim attribute, responsible
+ * for updating the UI, in response to attribute changes.
+ *
+ * @method _afterShimChange
+ * @protected
+ * @param {EventFacade} e The event facade for the attribute change
+ */
+ _afterShimChange : function(e) {
+ this._uiSetShim(e.newVal);
+ },
+
+ /**
+ * Default attribute change listener for the zIndex attribute, responsible
+ * for updating the UI, in response to attribute changes.
+ *
+ * @method _afterZIndexChange
+ * @protected
+ * @param {EventFacade} e The event facade for the attribute change
+ */
+ _afterZIndexChange : function(e) {
+ this._uiSetZIndex(e.newVal);
+ },
+
+ /**
+ * Updates the UI to reflect the zIndex value passed in.
+ *
+ * @method _uiSetZIndex
+ * @protected
+ * @param {number} zIndex The zindex to be reflected in the UI
+ */
+ _uiSetZIndex: function (zIndex) {
+ this._stackNode.setStyle(ZINDEX, zIndex);
+ },
+
+ /**
+ * Updates the UI to enable/disable the shim. If the widget is not currently visible,
+ * creation of the shim is deferred until it is made visible, for performance reasons.
+ *
+ * @method _uiSetShim
+ * @protected
+ * @param {boolean} enable If true, creates/renders the shim, if false, removes it.
+ */
+ _uiSetShim: function (enable) {
+ if (enable) {
+ // Lazy creation
+ if (this.get(VISIBLE)) {
+ this._renderShim();
+ } else {
+ this._renderShimDeferred();
+ }
+ } else {
+ this._destroyShim();
+ }
+ },
+
+ /**
+ * Sets up change handlers for the visible attribute, to defer shim creation/rendering
+ * until the Widget is made visible.
+ *
+ * @method _renderShimDeferred
+ * @private
+ */
+ _renderShimDeferred : function() {
+
+ this._stackHandles[SHIM_DEFERRED] = this._stackHandles[SHIM_DEFERRED] || [];
+
+ var handles = this._stackHandles[SHIM_DEFERRED],
+ createBeforeVisible = function(e) {
+ if (e.newVal) {
+ this._renderShim();
+ }
+ };
+
+ handles.push(this.on(VisibleChange, createBeforeVisible));
+ },
+
+ /**
+ * Sets up event listeners to resize the shim when the size of the Widget changes.
+ * <p>
+ * NOTE: This method is only used for IE6 currently, since IE6 doesn't support a way to
+ * resize the shim purely through CSS, when the Widget does not have an explicit width/height
+ * set.
+ * </p>
+ * @method _addShimResizeHandlers
+ * @private
+ */
+ _addShimResizeHandlers : function() {
+
+ this._stackHandles[SHIM_RESIZE] = this._stackHandles[SHIM_RESIZE] || [];
+
+ var sizeShim = this.sizeShim,
+ handles = this._stackHandles[SHIM_RESIZE];
+
+ this.sizeShim();
+
+ handles.push(this.after(VisibleChange, sizeShim));
+ handles.push(this.after(WidthChange, sizeShim));
+ handles.push(this.after(HeightChange, sizeShim));
+ handles.push(this.after(ContentUpdate, sizeShim));
+ },
+
+ /**
+ * Detaches any handles stored for the provided key
+ *
+ * @method _detachStackHandles
+ * @param String handleKey The key defining the group of handles which should be detached
+ * @private
+ */
+ _detachStackHandles : function(handleKey) {
+ var handles = this._stackHandles[handleKey],
+ handle;
+
+ if (handles && handles.length > 0) {
+ while((handle = handles.pop())) {
+ handle.detach();
+ }
+ }
+ },
+
+ /**
+ * Creates the shim element and adds it to the DOM
+ *
+ * @method _renderShim
+ * @private
+ */
+ _renderShim : function() {
+ var shimEl = this._shimNode,
+ stackEl = this._stackNode;
+
+ if (!shimEl) {
+ shimEl = this._shimNode = this._getShimTemplate();
+ stackEl.insertBefore(shimEl, stackEl.get(FIRST_CHILD));
+
+ if (UA.ie == 6) {
+ this._addShimResizeHandlers();
+ }
+ this._detachStackHandles(SHIM_DEFERRED);
+ }
+ },
+
+ /**
+ * Removes the shim from the DOM, and detaches any related event
+ * listeners.
+ *
+ * @method _destroyShim
+ * @private
+ */
+ _destroyShim : function() {
+ if (this._shimNode) {
+ this._shimNode.get(PARENT_NODE).removeChild(this._shimNode);
+ this._shimNode = null;
+
+ this._detachStackHandles(SHIM_DEFERRED);
+ this._detachStackHandles(SHIM_RESIZE);
+ }
+ },
+
+
+ /**
+ * For IE6, synchronizes the size and position of iframe shim to that of
+ * Widget bounding box which it is protecting. For all other browsers,
+ * this method does not do anything.
+ *
+ * @method sizeShim
+ */
+ sizeShim: function () {
+ var shim = this._shimNode,
+ node = this._stackNode;
+
+ if (shim && UA.ie === 6 && this.get(VISIBLE)) {
+ shim.setStyle(WIDTH, node.get(OFFSET_WIDTH) + PX);
+ shim.setStyle(HEIGHT, node.get(OFFSET_HEIGHT) + PX);
+ }
+ },
+
+ /**
+ * Creates a cloned shim node, using the SHIM_TEMPLATE html template, for use on a new instance.
+ *
+ * @method _getShimTemplate
+ * @private
+ * @return {Node} node A new shim Node instance.
+ */
+ _getShimTemplate : function() {
+ if (!Stack._SHIM_TEMPLATE) {
+ Stack._SHIM_TEMPLATE = Node.create(Stack.SHIM_TEMPLATE);
+ }
+ return Stack._SHIM_TEMPLATE.cloneNode(true);
+ }
+ };
+
+ Y.WidgetStack = Stack;
+