# Yahoo! UI Library

### Container 2.8.1

Yahoo! UI Library > container > Overlay.js (source view)
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    (function () {

        /**
        * Overlay is a Module that is absolutely positioned above the page flow. It
        * has convenience methods for positioning and sizing, as well as options for
        * controlling zIndex and constraining the Overlay's position to the current
        * visible viewport. Overlay also contains a dynamicly generated IFRAME which
        * is placed beneath it for Internet Explorer 6 and 5.x so that it will be
        * properly rendered above SELECT elements.
        * @namespace YAHOO.widget
        * @class Overlay
        * @extends YAHOO.widget.Module
        * @param {String} el The element ID representing the Overlay <em>OR</em>
        * @param {HTMLElement} el The element representing the Overlay
        * @param {Object} userConfig The configuration object literal containing
        * the configuration that should be set for this Overlay. See configuration
        * documentation for more details.
        * @constructor
        */
        YAHOO.widget.Overlay = function (el, userConfig) {
            YAHOO.widget.Overlay.superclass.constructor.call(this, el, userConfig);
        };

        var Lang = YAHOO.lang,
            CustomEvent = YAHOO.util.CustomEvent,
            Module = YAHOO.widget.Module,
            Event = YAHOO.util.Event,
            Dom = YAHOO.util.Dom,
            Config = YAHOO.util.Config,
            UA = YAHOO.env.ua,
            Overlay = YAHOO.widget.Overlay,

            _SUBSCRIBE = "subscribe",
            _UNSUBSCRIBE = "unsubscribe",
            _CONTAINED = "contained",

            m_oIFrameTemplate,

            /**
            * Constant representing the name of the Overlay's events
            * @property EVENT_TYPES
            * @private
            * @final
            * @type Object
            */
            EVENT_TYPES = {
                "BEFORE_MOVE": "beforeMove",
                "MOVE": "move"
            },

            /**
            * Constant representing the Overlay's configuration properties
            * @property DEFAULT_CONFIG
            * @private
            * @final
            * @type Object
            */
            DEFAULT_CONFIG = {

                "X": {
                    key: "x",
                    validator: Lang.isNumber,
                    suppressEvent: true,
                    supercedes: ["iframe"]
                },

                "Y": {
                    key: "y",
                    validator: Lang.isNumber,
                    suppressEvent: true,
                    supercedes: ["iframe"]
                },

                "XY": {
                    key: "xy",
                    suppressEvent: true,
                    supercedes: ["iframe"]
                },

                "CONTEXT": {
                    key: "context",
                    suppressEvent: true,
                    supercedes: ["iframe"]
                },

                "FIXED_CENTER": {
                    key: "fixedcenter",
                    value: false,
                    supercedes: ["iframe", "visible"]
                },

                "WIDTH": {
                    key: "width",
                    suppressEvent: true,
                    supercedes: ["context", "fixedcenter", "iframe"]
                },

                "HEIGHT": {
                    key: "height",
                    suppressEvent: true,
                    supercedes: ["context", "fixedcenter", "iframe"]
                },

                "AUTO_FILL_HEIGHT" : {
                    key: "autofillheight",
                    supercedes: ["height"],
                    value:"body"
                },

                "ZINDEX": {
                    key: "zindex",
                    value: null
                },

                "CONSTRAIN_TO_VIEWPORT": {
                    key: "constraintoviewport",
                    value: false,
                    validator: Lang.isBoolean,
                    supercedes: ["iframe", "x", "y", "xy"]
                },

                "IFRAME": {
                    key: "iframe",
                    value: (UA.ie == 6 ? true : false),
                    validator: Lang.isBoolean,
                    supercedes: ["zindex"]
                },

                "PREVENT_CONTEXT_OVERLAP": {
                    key: "preventcontextoverlap",
                    value: false,
                    validator: Lang.isBoolean,
                    supercedes: ["constraintoviewport"]
                }

            };

        /**
        * The URL that will be placed in the iframe
        * @property YAHOO.widget.Overlay.IFRAME_SRC
        * @static
        * @final
        * @type String
        */
        Overlay.IFRAME_SRC = "javascript:false;";

        /**
        * Number representing how much the iframe shim should be offset from each
        * side of an Overlay instance, in pixels.
        * @property YAHOO.widget.Overlay.IFRAME_SRC
        * @default 3
        * @static
        * @final
        * @type Number
        */
        Overlay.IFRAME_OFFSET = 3;

        /**
        * Number representing the minimum distance an Overlay instance should be
        * positioned relative to the boundaries of the browser's viewport, in pixels.
        * @property YAHOO.widget.Overlay.VIEWPORT_OFFSET
        * @default 10
        * @static
        * @final
        * @type Number
        */
        Overlay.VIEWPORT_OFFSET = 10;

        /**
        * Constant representing the top left corner of an element, used for
        * configuring the context element alignment
        * @property YAHOO.widget.Overlay.TOP_LEFT
        * @static
        * @final
        * @type String
        */
        Overlay.TOP_LEFT = "tl";

        /**
        * Constant representing the top right corner of an element, used for
        * configuring the context element alignment
        * @property YAHOO.widget.Overlay.TOP_RIGHT
        * @static
        * @final
        * @type String
        */
        Overlay.TOP_RIGHT = "tr";

        /**
        * Constant representing the top bottom left corner of an element, used for
        * configuring the context element alignment
        * @property YAHOO.widget.Overlay.BOTTOM_LEFT
        * @static
        * @final
        * @type String
        */
        Overlay.BOTTOM_LEFT = "bl";

        /**
        * Constant representing the bottom right corner of an element, used for
        * configuring the context element alignment
        * @property YAHOO.widget.Overlay.BOTTOM_RIGHT
        * @static
        * @final
        * @type String
        */
        Overlay.BOTTOM_RIGHT = "br";

        Overlay.PREVENT_OVERLAP_X = {
            "tltr": true,
            "blbr": true,
            "brbl": true,
            "trtl": true
        };

        Overlay.PREVENT_OVERLAP_Y = {
            "trbr": true,
            "tlbl": true,
            "bltl": true,
            "brtr": true
        };

        /**
        * Constant representing the default CSS class used for an Overlay
        * @property YAHOO.widget.Overlay.CSS_OVERLAY
        * @static
        * @final
        * @type String
        */
        Overlay.CSS_OVERLAY = "yui-overlay";

        /**
        * Constant representing the default hidden CSS class used for an Overlay. This class is
        * applied to the overlay's outer DIV whenever it's hidden.
        *
        * @property YAHOO.widget.Overlay.CSS_HIDDEN
        * @static
        * @final
        * @type String
        */
        Overlay.CSS_HIDDEN = "yui-overlay-hidden";

        /**
        * Constant representing the default CSS class used for an Overlay iframe shim.
        *
        * @property YAHOO.widget.Overlay.CSS_IFRAME
        * @static
        * @final
        * @type String
        */
        Overlay.CSS_IFRAME = "yui-overlay-iframe";

        /**
         * Constant representing the names of the standard module elements
         * used in the overlay.
         * @property YAHOO.widget.Overlay.STD_MOD_RE
         * @static
         * @final
         * @type RegExp
         */
        Overlay.STD_MOD_RE = /^\s*?(body|footer|header)\s*?$/i;

        /**
        * A singleton CustomEvent used for reacting to the DOM event for
        * window scroll
        * @event YAHOO.widget.Overlay.windowScrollEvent
        */
        Overlay.windowScrollEvent = new CustomEvent("windowScroll");

        /**
        * A singleton CustomEvent used for reacting to the DOM event for
        * window resize
        * @event YAHOO.widget.Overlay.windowResizeEvent
        */
        Overlay.windowResizeEvent = new CustomEvent("windowResize");

        /**
        * The DOM event handler used to fire the CustomEvent for window scroll
        * @method YAHOO.widget.Overlay.windowScrollHandler
        * @static
        * @param {DOMEvent} e The DOM scroll event
        */
        Overlay.windowScrollHandler = function (e) {
            var t = Event.getTarget(e);

            // - Webkit (Safari 2/3) and Opera 9.2x bubble scroll events from elements to window
            // - FF2/3 and IE6/7, Opera 9.5x don't bubble scroll events from elements to window
            // - IE doesn't recognize scroll registered on the document.
            //
            // Also, when document view is scrolled, IE doesn't provide a target,
            // rest of the browsers set target to window.document, apart from opera
            // which sets target to window.
            if (!t || t === window || t === window.document) {
                if (UA.ie) {

                    if (! window.scrollEnd) {
                        window.scrollEnd = -1;
                    }

                    clearTimeout(window.scrollEnd);

                    window.scrollEnd = setTimeout(function () {
                        Overlay.windowScrollEvent.fire();
                    }, 1);

                } else {
                    Overlay.windowScrollEvent.fire();
                }
            }
        };

        /**
        * The DOM event handler used to fire the CustomEvent for window resize
        * @method YAHOO.widget.Overlay.windowResizeHandler
        * @static
        * @param {DOMEvent} e The DOM resize event
        */
        Overlay.windowResizeHandler = function (e) {

            if (UA.ie) {
                if (! window.resizeEnd) {
                    window.resizeEnd = -1;
                }

                clearTimeout(window.resizeEnd);

                window.resizeEnd = setTimeout(function () {
                    Overlay.windowResizeEvent.fire();
                }, 100);
            } else {
                Overlay.windowResizeEvent.fire();
            }
        };

        /**
        * A boolean that indicated whether the window resize and scroll events have
        * already been subscribed to.
        * @property YAHOO.widget.Overlay._initialized
        * @private
        * @type Boolean
        */
        Overlay._initialized = null;

        if (Overlay._initialized === null) {
            Event.on(window, "scroll", Overlay.windowScrollHandler);
            Event.on(window, "resize", Overlay.windowResizeHandler);
            Overlay._initialized = true;
        }

        /**
         * Internal map of special event types, which are provided
         * by the instance. It maps the event type to the custom event
         * instance. Contains entries for the "windowScroll", "windowResize" and
         * "textResize" static container events.
         *
         * @property YAHOO.widget.Overlay._TRIGGER_MAP
         * @type Object
         * @static
         * @private
         */
        Overlay._TRIGGER_MAP = {
            "windowScroll" : Overlay.windowScrollEvent,
            "windowResize" : Overlay.windowResizeEvent,
            "textResize"   : Module.textResizeEvent
        };

        YAHOO.extend(Overlay, Module, {

            /**
             * <p>
             * Array of default event types which will trigger
             * context alignment for the Overlay class.
             * </p>
             * <p>The array is empty by default for Overlay,
             * but maybe populated in future releases, so classes extending
             * Overlay which need to define their own set of CONTEXT_TRIGGERS
             * should concatenate their super class's prototype.CONTEXT_TRIGGERS
             * value with their own array of values.
             * </p>
             * <p>
             * E.g.:
             * <code>CustomOverlay.prototype.CONTEXT_TRIGGERS = YAHOO.widget.Overlay.prototype.CONTEXT_TRIGGERS.concat(["windowScroll"]);</code>
             * </p>
             *
             * @property CONTEXT_TRIGGERS
             * @type Array
             * @final
             */
            CONTEXT_TRIGGERS : [],

            /**
            * The Overlay initialization method, which is executed for Overlay and
            * all of its subclasses. This method is automatically called by the
            * constructor, and  sets up all DOM references for pre-existing markup,
            * and creates required markup if it is not already present.
            * @method init
            * @param {String} el The element ID representing the Overlay <em>OR</em>
            * @param {HTMLElement} el The element representing the Overlay
            * @param {Object} userConfig The configuration object literal
            * containing the configuration that should be set for this Overlay.
            * See configuration documentation for more details.
            */
            init: function (el, userConfig) {

                /*
                     Note that we don't pass the user config in here yet because we
                     only want it executed once, at the lowest subclass level
                */

                Overlay.superclass.init.call(this, el/*, userConfig*/);

                this.beforeInitEvent.fire(Overlay);

                Dom.addClass(this.element, Overlay.CSS_OVERLAY);

                if (userConfig) {
                    this.cfg.applyConfig(userConfig, true);
                }

                if (this.platform == "mac" && UA.gecko) {

                    if (! Config.alreadySubscribed(this.showEvent,
                        this.showMacGeckoScrollbars, this)) {

                        this.showEvent.subscribe(this.showMacGeckoScrollbars,
                            this, true);

                    }

                    if (! Config.alreadySubscribed(this.hideEvent,
                        this.hideMacGeckoScrollbars, this)) {

                        this.hideEvent.subscribe(this.hideMacGeckoScrollbars,
                            this, true);

                    }
                }

                this.initEvent.fire(Overlay);
            },

            /**
            * Initializes the custom events for Overlay which are fired
            * automatically at appropriate times by the Overlay class.
            * @method initEvents
            */
            initEvents: function () {

                Overlay.superclass.initEvents.call(this);

                var SIGNATURE = CustomEvent.LIST;

                /**
                * CustomEvent fired before the Overlay is moved.
                * @event beforeMoveEvent
                * @param {Number} x x coordinate
                * @param {Number} y y coordinate
                */
                this.beforeMoveEvent = this.createEvent(EVENT_TYPES.BEFORE_MOVE);
                this.beforeMoveEvent.signature = SIGNATURE;

                /**
                * CustomEvent fired after the Overlay is moved.
                * @event moveEvent
                * @param {Number} x x coordinate
                * @param {Number} y y coordinate
                */
                this.moveEvent = this.createEvent(EVENT_TYPES.MOVE);
                this.moveEvent.signature = SIGNATURE;

            },

            /**
            * Initializes the class's configurable properties which can be changed
            * using the Overlay's Config object (cfg).
            * @method initDefaultConfig
            */
            initDefaultConfig: function () {

                Overlay.superclass.initDefaultConfig.call(this);

                var cfg = this.cfg;

                // Add overlay config properties //

                /**
                * The absolute x-coordinate position of the Overlay
                * @config x
                * @type Number
                * @default null
                */
                cfg.addProperty(DEFAULT_CONFIG.X.key, {

                    handler: this.configX,
                    validator: DEFAULT_CONFIG.X.validator,
                    suppressEvent: DEFAULT_CONFIG.X.suppressEvent,
                    supercedes: DEFAULT_CONFIG.X.supercedes

                });

                /**
                * The absolute y-coordinate position of the Overlay
                * @config y
                * @type Number
                * @default null
                */
                cfg.addProperty(DEFAULT_CONFIG.Y.key, {

                    handler: this.configY,
                    validator: DEFAULT_CONFIG.Y.validator,
                    suppressEvent: DEFAULT_CONFIG.Y.suppressEvent,
                    supercedes: DEFAULT_CONFIG.Y.supercedes

                });

                /**
                * An array with the absolute x and y positions of the Overlay
                * @config xy
                * @type Number[]
                * @default null
                */
                cfg.addProperty(DEFAULT_CONFIG.XY.key, {
                    handler: this.configXY,
                    suppressEvent: DEFAULT_CONFIG.XY.suppressEvent,
                    supercedes: DEFAULT_CONFIG.XY.supercedes
                });

                /**
                * <p>
                * The array of context arguments for context-sensitive positioning.
                * </p>
                *
                * <p>
                * The format of the array is: <code>[contextElementOrId, overlayCorner, contextCorner, arrayOfTriggerEvents (optional), xyOffset (optional)]</code>, the
                * the 5 array elements described in detail below:
                * </p>
                *
                * <dl>
                * <dt>contextElementOrId &#60;String|HTMLElement&#62;</dt>
                * <dd>A reference to the context element to which the overlay should be aligned (or it's id).</dd>
                * <dt>overlayCorner &#60;String&#62;</dt>
                * <dd>The corner of the overlay which is to be used for alignment. This corner will be aligned to the
                * corner of the context element defined by the "contextCorner" entry which follows. Supported string values are:
                * "tr" (top right), "tl" (top left), "br" (bottom right), or "bl" (bottom left).</dd>
                * <dt>contextCorner &#60;String&#62;</dt>
                * <dd>The corner of the context element which is to be used for alignment. Supported string values are the same ones listed for the "overlayCorner" entry above.</dd>
                * <dt>arrayOfTriggerEvents (optional) &#60;Array[String|CustomEvent]&#62;</dt>
                * <dd>
                * <p>
                * By default, context alignment is a one time operation, aligning the Overlay to the context element when context configuration property is set, or when the <a href="#method_align">align</a>
                * method is invoked. However, you can use the optional "arrayOfTriggerEvents" entry to define the list of events which should force the overlay to re-align itself with the context element.
                * This is useful in situations where the layout of the document may change, resulting in the context element's position being modified.
                * </p>
                * <p>
                * The array can contain either event type strings for events the instance publishes (e.g. "beforeShow") or CustomEvent instances. Additionally the following
                * 3 static container event types are also currently supported : <code>"windowResize", "windowScroll", "textResize"</code> (defined in <a href="#property__TRIGGER_MAP">_TRIGGER_MAP</a> private property).
                * </p>
                * </dd>
                * <dt>xyOffset &#60;Number[]&#62;</dt>
                * <dd>
                * A 2 element Array specifying the X and Y pixel amounts by which the Overlay should be offset from the aligned corner. e.g. [5,0] offsets the Overlay 5 pixels to the left, <em>after</em> aligning the given context corners.
                * NOTE: If using this property and no triggers need to be defined, the arrayOfTriggerEvents property should be set to null to maintain correct array positions for the arguments.
                * </dd>
                * </dl>
                *
                * <p>
                * For example, setting this property to <code>["img1", "tl", "bl"]</code> will
                * align the Overlay's top left corner to the bottom left corner of the
                * context element with id "img1".
                * </p>
                * <p>
                * Setting this property to <code>["img1", "tl", "bl", null, [0,5]</code> will
                * align the Overlay's top left corner to the bottom left corner of the
                * context element with id "img1", and then offset it by 5 pixels on the Y axis (providing a 5 pixel gap between the bottom of the context element and top of the overlay).
                * </p>
                * <p>
                * Adding the optional trigger values: <code>["img1", "tl", "bl", ["beforeShow", "windowResize"], [0,5]]</code>,
                * will re-align the overlay position, whenever the "beforeShow" or "windowResize" events are fired.
                * </p>
                *
                * @config context
                * @type Array
                * @default null
                */
                cfg.addProperty(DEFAULT_CONFIG.CONTEXT.key, {
                    handler: this.configContext,
                    suppressEvent: DEFAULT_CONFIG.CONTEXT.suppressEvent,
                    supercedes: DEFAULT_CONFIG.CONTEXT.supercedes
                });

                /**
                * Determines whether or not the Overlay should be anchored
                * to the center of the viewport.
                *
                * <p>This property can be set to:</p>
                *
                * <dl>
                * <dt>true</dt>
                * <dd>
                * To enable fixed center positioning
                * <p>
                * When enabled, the overlay will
                * be positioned in the center of viewport when initially displayed, and
                * will remain in the center of the viewport whenever the window is
                * scrolled or resized.
                * </p>
                * <p>
                * If the overlay is too big for the viewport,
                * it's top left corner will be aligned with the top left corner of the viewport.
                * </p>
                * </dd>
                * <dt>false</dt>
                * <dd>
                * To disable fixed center positioning.
                * <p>In this case the overlay can still be
                * centered as a one-off operation, by invoking the <code>center()</code> method,
                * however it will not remain centered when the window is scrolled/resized.
                * </dd>
                * <dt>"contained"<dt>
                * <dd>To enable fixed center positioning, as with the <code>true</code> option.
                * <p>However, unlike setting the property to <code>true</code>,
                * when the property is set to <code>"contained"</code>, if the overlay is
                * too big for the viewport, it will not get automatically centered when the
                * user scrolls or resizes the window (until the window is large enough to contain the
                * overlay). This is useful in cases where the Overlay has both header and footer
                * UI controls which the user may need to access.
                * </p>
                * </dd>
                * </dl>
                *
                * @config fixedcenter
                * @type Boolean | String
                * @default false
                */
                cfg.addProperty(DEFAULT_CONFIG.FIXED_CENTER.key, {
                    handler: this.configFixedCenter,
                    value: DEFAULT_CONFIG.FIXED_CENTER.value,
                    validator: DEFAULT_CONFIG.FIXED_CENTER.validator,
                    supercedes: DEFAULT_CONFIG.FIXED_CENTER.supercedes
                });

                /**
                * CSS width of the Overlay.
                * @config width
                * @type String
                * @default null
                */
                cfg.addProperty(DEFAULT_CONFIG.WIDTH.key, {
                    handler: this.configWidth,
                    suppressEvent: DEFAULT_CONFIG.WIDTH.suppressEvent,
                    supercedes: DEFAULT_CONFIG.WIDTH.supercedes
                });

                /**
                * CSS height of the Overlay.
                * @config height
                * @type String
                * @default null
                */
                cfg.addProperty(DEFAULT_CONFIG.HEIGHT.key, {
                    handler: this.configHeight,
                    suppressEvent: DEFAULT_CONFIG.HEIGHT.suppressEvent,
                    supercedes: DEFAULT_CONFIG.HEIGHT.supercedes
                });

                /**
                * Standard module element which should auto fill out the height of the Overlay if the height config property is set.
                * Supported values are "header", "body", "footer".
                *
                * @config autofillheight
                * @type String
                * @default null
                */
                cfg.addProperty(DEFAULT_CONFIG.AUTO_FILL_HEIGHT.key, {
                    handler: this.configAutoFillHeight,
                    value : DEFAULT_CONFIG.AUTO_FILL_HEIGHT.value,
                    validator : this._validateAutoFill,
                    supercedes: DEFAULT_CONFIG.AUTO_FILL_HEIGHT.supercedes
                });

                /**
                * CSS z-index of the Overlay.
                * @config zIndex
                * @type Number
                * @default null
                */
                cfg.addProperty(DEFAULT_CONFIG.ZINDEX.key, {
                    handler: this.configzIndex,
                    value: DEFAULT_CONFIG.ZINDEX.value
                });

                /**
                * True if the Overlay should be prevented from being positioned
                * out of the viewport.
                * @config constraintoviewport
                * @type Boolean
                * @default false
                */
                cfg.addProperty(DEFAULT_CONFIG.CONSTRAIN_TO_VIEWPORT.key, {

                    handler: this.configConstrainToViewport,
                    value: DEFAULT_CONFIG.CONSTRAIN_TO_VIEWPORT.value,
                    validator: DEFAULT_CONFIG.CONSTRAIN_TO_VIEWPORT.validator,
                    supercedes: DEFAULT_CONFIG.CONSTRAIN_TO_VIEWPORT.supercedes

                });

                /**
                * @config iframe
                * @description Boolean indicating whether or not the Overlay should
                * have an IFRAME shim; used to prevent SELECT elements from
                * poking through an Overlay instance in IE6.  When set to "true",
                * the iframe shim is created when the Overlay instance is intially
                * made visible.
                * @type Boolean
                * @default true for IE6 and below, false for all other browsers.
                */
                cfg.addProperty(DEFAULT_CONFIG.IFRAME.key, {

                    handler: this.configIframe,
                    value: DEFAULT_CONFIG.IFRAME.value,
                    validator: DEFAULT_CONFIG.IFRAME.validator,
                    supercedes: DEFAULT_CONFIG.IFRAME.supercedes

                });

                /**
                * @config preventcontextoverlap
                * @description Boolean indicating whether or not the Overlay should overlap its
                * context element (defined using the "context" configuration property) when the
                * "constraintoviewport" configuration property is set to "true".
                * @type Boolean
                * @default false
                */
                cfg.addProperty(DEFAULT_CONFIG.PREVENT_CONTEXT_OVERLAP.key, {
                    value: DEFAULT_CONFIG.PREVENT_CONTEXT_OVERLAP.value,
                    validator: DEFAULT_CONFIG.PREVENT_CONTEXT_OVERLAP.validator,
                    supercedes: DEFAULT_CONFIG.PREVENT_CONTEXT_OVERLAP.supercedes
                });
            },

            /**
            * Moves the Overlay to the specified position. This function is
            * identical to calling this.cfg.setProperty("xy", [x,y]);
            * @method moveTo
            * @param {Number} x The Overlay's new x position
            * @param {Number} y The Overlay's new y position
            */
            moveTo: function (x, y) {
                this.cfg.setProperty("xy", [x, y]);
            },

            /**
            * Adds a CSS class ("hide-scrollbars") and removes a CSS class
            * ("show-scrollbars") to the Overlay to fix a bug in Gecko on Mac OS X
            * (https://bugzilla.mozilla.org/show_bug.cgi?id=187435)
            * @method hideMacGeckoScrollbars
            */
            hideMacGeckoScrollbars: function () {
                Dom.replaceClass(this.element, "show-scrollbars", "hide-scrollbars");
            },

            /**
            * Adds a CSS class ("show-scrollbars") and removes a CSS class
            * ("hide-scrollbars") to the Overlay to fix a bug in Gecko on Mac OS X
            * (https://bugzilla.mozilla.org/show_bug.cgi?id=187435)
            * @method showMacGeckoScrollbars
            */
            showMacGeckoScrollbars: function () {
                Dom.replaceClass(this.element, "hide-scrollbars", "show-scrollbars");
            },

            /**
             * Internal implementation to set the visibility of the overlay in the DOM.
             *
             * @method _setDomVisibility
             * @param {boolean} visible Whether to show or hide the Overlay's outer element
             * @protected
             */
            _setDomVisibility : function(show) {
                Dom.setStyle(this.element, "visibility", (show) ? "visible" : "hidden");
                var hiddenClass = Overlay.CSS_HIDDEN;

                if (show) {
                    Dom.removeClass(this.element, hiddenClass);
                } else {
                    Dom.addClass(this.element, hiddenClass);
                }
            },

            // BEGIN BUILT-IN PROPERTY EVENT HANDLERS //
            /**
            * The default event handler fired when the "visible" property is
            * changed.  This method is responsible for firing showEvent
            * and hideEvent.
            * @method configVisible
            * @param {String} type The CustomEvent type (usually the property name)
            * @param {Object[]} args The CustomEvent arguments. For configuration
            * handlers, args[0] will equal the newly applied value for the property.
            * @param {Object} obj The scope object. For configuration handlers,
            * this will usually equal the owner.
            */
            configVisible: function (type, args, obj) {

                var visible = args[0],
                    currentVis = Dom.getStyle(this.element, "visibility"),
                    effect = this.cfg.getProperty("effect"),
                    effectInstances = [],
                    isMacGecko = (this.platform == "mac" && UA.gecko),
                    alreadySubscribed = Config.alreadySubscribed,
                    eff, ei, e, i, j, k, h,
                    nEffects,
                    nEffectInstances;

                if (currentVis == "inherit") {
                    e = this.element.parentNode;

                    while (e.nodeType != 9 && e.nodeType != 11) {
                        currentVis = Dom.getStyle(e, "visibility");

                        if (currentVis != "inherit") {
                            break;
                        }

                        e = e.parentNode;
                    }

                    if (currentVis == "inherit") {
                        currentVis = "visible";
                    }
                }

                if (effect) {
                    if (effect instanceof Array) {
                        nEffects = effect.length;

                        for (i = 0; i < nEffects; i++) {
                            eff = effect[i];
                            effectInstances[effectInstances.length] =
                                eff.effect(this, eff.duration);

                        }
                    } else {
                        effectInstances[effectInstances.length] =
                            effect.effect(this, effect.duration);
                    }
                }

                if (visible) { // Show
                    if (isMacGecko) {
                        this.showMacGeckoScrollbars();
                    }

                    if (effect) { // Animate in
                        if (visible) { // Animate in if not showing
                            if (currentVis != "visible" || currentVis === "") {
                                this.beforeShowEvent.fire();
                                nEffectInstances = effectInstances.length;

                                for (j = 0; j < nEffectInstances; j++) {
                                    ei = effectInstances[j];
                                    if (j === 0 && !alreadySubscribed(
                                            ei.animateInCompleteEvent,
                                            this.showEvent.fire, this.showEvent)) {

                                        /*
                                             Delegate showEvent until end
                                             of animateInComplete
                                        */

                                        ei.animateInCompleteEvent.subscribe(
                                         this.showEvent.fire, this.showEvent, true);
                                    }
                                    ei.animateIn();
                                }
                            }
                        }
                    } else { // Show
                        if (currentVis != "visible" || currentVis === "") {
                            this.beforeShowEvent.fire();

                            this._setDomVisibility(true);

                            this.cfg.refireEvent("iframe");
                            this.showEvent.fire();
                        } else {
                            this._setDomVisibility(true);
                        }
                    }
                } else { // Hide

                    if (isMacGecko) {
                        this.hideMacGeckoScrollbars();
                    }

                    if (effect) { // Animate out if showing
                        if (currentVis == "visible") {
                            this.beforeHideEvent.fire();

                            nEffectInstances = effectInstances.length;
                            for (k = 0; k < nEffectInstances; k++) {
                                h = effectInstances[k];

                                if (k === 0 && !alreadySubscribed(
                                    h.animateOutCompleteEvent, this.hideEvent.fire,
                                    this.hideEvent)) {

                                    /*
                                         Delegate hideEvent until end
                                         of animateOutComplete
                                    */

                                    h.animateOutCompleteEvent.subscribe(
                                        this.hideEvent.fire, this.hideEvent, true);

                                }
                                h.animateOut();
                            }

                        } else if (currentVis === "") {
                            this._setDomVisibility(false);
                        }

                    } else { // Simple hide

                        if (currentVis == "visible" || currentVis === "") {
                            this.beforeHideEvent.fire();
                            this._setDomVisibility(false);
                            this.hideEvent.fire();
                        } else {
                            this._setDomVisibility(false);
                        }
                    }
                }
            },

            /**
            * Fixed center event handler used for centering on scroll/resize, but only if
            * the overlay is visible and, if "fixedcenter" is set to "contained", only if
            * the overlay fits within the viewport.
            *
            * @method doCenterOnDOMEvent
            */
            doCenterOnDOMEvent: function () {
                var cfg = this.cfg,
                    fc = cfg.getProperty("fixedcenter");

                if (cfg.getProperty("visible")) {
                    if (fc && (fc !== _CONTAINED || this.fitsInViewport())) {
                        this.center();
                    }
                }
            },

            /**
             * Determines if the Overlay (including the offset value defined by Overlay.VIEWPORT_OFFSET)
             * will fit entirely inside the viewport, in both dimensions - width and height.
             *
             * @method fitsInViewport
             * @return boolean true if the Overlay will fit, false if not
             */
            fitsInViewport : function() {
                var nViewportOffset = Overlay.VIEWPORT_OFFSET,
                    element = this.element,
                    elementWidth = element.offsetWidth,
                    elementHeight = element.offsetHeight,
                    viewportWidth = Dom.getViewportWidth(),
                    viewportHeight = Dom.getViewportHeight();

                return ((elementWidth + nViewportOffset < viewportWidth) && (elementHeight + nViewportOffset < viewportHeight));
            },

            /**
            * The default event handler fired when the "fixedcenter" property
            * is changed.
            * @method configFixedCenter
            * @param {String} type The CustomEvent type (usually the property name)
            * @param {Object[]} args The CustomEvent arguments. For configuration
            * handlers, args[0] will equal the newly applied value for the property.
            * @param {Object} obj The scope object. For configuration handlers,
            * this will usually equal the owner.
            */
            configFixedCenter: function (type, args, obj) {

                var val = args[0],
                    alreadySubscribed = Config.alreadySubscribed,
                    windowResizeEvent = Overlay.windowResizeEvent,
                    windowScrollEvent = Overlay.windowScrollEvent;

                if (val) {
                    this.center();

                    if (!alreadySubscribed(this.beforeShowEvent, this.center)) {
                        this.beforeShowEvent.subscribe(this.center);
                    }

                    if (!alreadySubscribed(windowResizeEvent, this.doCenterOnDOMEvent, this)) {
                        windowResizeEvent.subscribe(this.doCenterOnDOMEvent, this, true);
                    }

                    if (!alreadySubscribed(windowScrollEvent, this.doCenterOnDOMEvent, this)) {
                        windowScrollEvent.subscribe(this.doCenterOnDOMEvent, this, true);
                    }

                } else {
                    this.beforeShowEvent.unsubscribe(this.center);

                    windowResizeEvent.unsubscribe(this.doCenterOnDOMEvent, this);
                    windowScrollEvent.unsubscribe(this.doCenterOnDOMEvent, this);
                }
            },

            /**
            * The default event handler fired when the "height" property is changed.
            * @method configHeight
            * @param {String} type The CustomEvent type (usually the property name)
            * @param {Object[]} args The CustomEvent arguments. For configuration
            * handlers, args[0] will equal the newly applied value for the property.
            * @param {Object} obj The scope object. For configuration handlers,
            * this will usually equal the owner.
            */
            configHeight: function (type, args, obj) {

                var height = args[0],
                    el = this.element;

                Dom.setStyle(el, "height", height);
                this.cfg.refireEvent("iframe");
            },

            /**
             * The default event handler fired when the "autofillheight" property is changed.
             * @method configAutoFillHeight
             *
             * @param {String} type The CustomEvent type (usually the property name)
             * @param {Object[]} args The CustomEvent arguments. For configuration
             * handlers, args[0] will equal the newly applied value for the property.
             * @param {Object} obj The scope object. For configuration handlers,
             * this will usually equal the owner.
             */
            configAutoFillHeight: function (type, args, obj) {
                var fillEl = args[0],
                    cfg = this.cfg,
                    autoFillHeight = "autofillheight",
                    height = "height",
                    currEl = cfg.getProperty(autoFillHeight),
                    autoFill = this._autoFillOnHeightChange;

                cfg.unsubscribeFromConfigEvent(height, autoFill);
                Module.textResizeEvent.unsubscribe(autoFill);
                this.changeContentEvent.unsubscribe(autoFill);

                if (currEl && fillEl !== currEl && this[currEl]) {
                    Dom.setStyle(this[currEl], height, "");
                }

                if (fillEl) {
                    fillEl = Lang.trim(fillEl.toLowerCase());

                    cfg.subscribeToConfigEvent(height, autoFill, this[fillEl], this);
                    Module.textResizeEvent.subscribe(autoFill, this[fillEl], this);
                    this.changeContentEvent.subscribe(autoFill, this[fillEl], this);

                    cfg.setProperty(autoFillHeight, fillEl, true);
                }
            },

            /**
            * The default event handler fired when the "width" property is changed.
            * @method configWidth
            * @param {String} type The CustomEvent type (usually the property name)
            * @param {Object[]} args The CustomEvent arguments. For configuration
            * handlers, args[0] will equal the newly applied value for the property.
            * @param {Object} obj The scope object. For configuration handlers,
            * this will usually equal the owner.
            */
            configWidth: function (type, args, obj) {

                var width = args[0],
                    el = this.element;

                Dom.setStyle(el, "width", width);
                this.cfg.refireEvent("iframe");
            },

            /**
            * The default event handler fired when the "zIndex" property is changed.
            * @method configzIndex
            * @param {String} type The CustomEvent type (usually the property name)
            * @param {Object[]} args The CustomEvent arguments. For configuration
            * handlers, args[0] will equal the newly applied value for the property.
            * @param {Object} obj The scope object. For configuration handlers,
            * this will usually equal the owner.
            */
            configzIndex: function (type, args, obj) {

                var zIndex = args[0],
                    el = this.element;

                if (! zIndex) {
                    zIndex = Dom.getStyle(el, "zIndex");
                    if (! zIndex || isNaN(zIndex)) {
                        zIndex = 0;
                    }
                }

                if (this.iframe || this.cfg.getProperty("iframe") === true) {
                    if (zIndex <= 0) {
                        zIndex = 1;
                    }
                }

                Dom.setStyle(el, "zIndex", zIndex);
                this.cfg.setProperty("zIndex", zIndex, true);

                if (this.iframe) {
                    this.stackIframe();
                }
            },

            /**
            * The default event handler fired when the "xy" property is changed.
            * @method configXY
            * @param {String} type The CustomEvent type (usually the property name)
            * @param {Object[]} args The CustomEvent arguments. For configuration
            * handlers, args[0] will equal the newly applied value for the property.
            * @param {Object} obj The scope object. For configuration handlers,
            * this will usually equal the owner.
            */
            configXY: function (type, args, obj) {

                var pos = args[0],
                    x = pos[0],
                    y = pos[1];

                this.cfg.setProperty("x", x);
                this.cfg.setProperty("y", y);

                this.beforeMoveEvent.fire([x, y]);

                x = this.cfg.getProperty("x");
                y = this.cfg.getProperty("y");

                YAHOO.log(("xy: " + [x, y]), "iframe");

                this.cfg.refireEvent("iframe");
                this.moveEvent.fire([x, y]);
            },

            /**
            * The default event handler fired when the "x" property is changed.
            * @method configX
            * @param {String} type The CustomEvent type (usually the property name)
            * @param {Object[]} args The CustomEvent arguments. For configuration
            * handlers, args[0] will equal the newly applied value for the property.
            * @param {Object} obj The scope object. For configuration handlers,
            * this will usually equal the owner.
            */
            configX: function (type, args, obj) {

                var x = args[0],
                    y = this.cfg.getProperty("y");

                this.cfg.setProperty("x", x, true);
                this.cfg.setProperty("y", y, true);

                this.beforeMoveEvent.fire([x, y]);

                x = this.cfg.getProperty("x");
                y = this.cfg.getProperty("y");

                Dom.setX(this.element, x, true);

                this.cfg.setProperty("xy", [x, y], true);

                this.cfg.refireEvent("iframe");
                this.moveEvent.fire([x, y]);
            },

            /**
            * The default event handler fired when the "y" property is changed.
            * @method configY
            * @param {String} type The CustomEvent type (usually the property name)
            * @param {Object[]} args The CustomEvent arguments. For configuration
            * handlers, args[0] will equal the newly applied value for the property.
            * @param {Object} obj The scope object. For configuration handlers,
            * this will usually equal the owner.
            */
            configY: function (type, args, obj) {

                var x = this.cfg.getProperty("x"),
                    y = args[0];

                this.cfg.setProperty("x", x, true);
                this.cfg.setProperty("y", y, true);

                this.beforeMoveEvent.fire([x, y]);

                x = this.cfg.getProperty("x");
                y = this.cfg.getProperty("y");

                Dom.setY(this.element, y, true);

                this.cfg.setProperty("xy", [x, y], true);

                this.cfg.refireEvent("iframe");
                this.moveEvent.fire([x, y]);
            },

            /**
            * Shows the iframe shim, if it has been enabled.
            * @method showIframe
            */
            showIframe: function () {

                var oIFrame = this.iframe,
                    oParentNode;

                if (oIFrame) {
                    oParentNode = this.element.parentNode;

                    if (oParentNode != oIFrame.parentNode) {
                        this._addToParent(oParentNode, oIFrame);
                    }
                    oIFrame.style.display = "block";
                }
            },

            /**
            * Hides the iframe shim, if it has been enabled.
            * @method hideIframe
            */
            hideIframe: function () {
                if (this.iframe) {
                    this.iframe.style.display = "none";
                }
            },

            /**
            * Syncronizes the size and position of iframe shim to that of its
            * corresponding Overlay instance.
            * @method syncIframe
            */
            syncIframe: function () {

                var oIFrame = this.iframe,
                    oElement = this.element,
                    nOffset = Overlay.IFRAME_OFFSET,
                    nDimensionOffset = (nOffset * 2),
                    aXY;

                if (oIFrame) {
                    // Size <iframe>
                    oIFrame.style.width = (oElement.offsetWidth + nDimensionOffset + "px");
                    oIFrame.style.height = (oElement.offsetHeight + nDimensionOffset + "px");

                    // Position <iframe>
                    aXY = this.cfg.getProperty("xy");

                    if (!Lang.isArray(aXY) || (isNaN(aXY[0]) || isNaN(aXY[1]))) {
                        this.syncPosition();
                        aXY = this.cfg.getProperty("xy");
                    }
                    Dom.setXY(oIFrame, [(aXY[0] - nOffset), (aXY[1] - nOffset)]);
                }
            },

            /**
             * Sets the zindex of the iframe shim, if it exists, based on the zindex of
             * the Overlay element. The zindex of the iframe is set to be one less
             * than the Overlay element's zindex.
             *
             * <p>NOTE: This method will not bump up the zindex of the Overlay element
             * to ensure that the iframe shim has a non-negative zindex.
             * If you require the iframe zindex to be 0 or higher, the zindex of
             * the Overlay element should be set to a value greater than 0, before
             * this method is called.
             * </p>
             * @method stackIframe
             */
            stackIframe: function () {
                if (this.iframe) {
                    var overlayZ = Dom.getStyle(this.element, "zIndex");
                    if (!YAHOO.lang.isUndefined(overlayZ) && !isNaN(overlayZ)) {
                        Dom.setStyle(this.iframe, "zIndex", (overlayZ - 1));
                    }
                }
            },

            /**
            * The default event handler fired when the "iframe" property is changed.
            * @method configIframe
            * @param {String} type The CustomEvent type (usually the property name)
            * @param {Object[]} args The CustomEvent arguments. For configuration
            * handlers, args[0] will equal the newly applied value for the property.
            * @param {Object} obj The scope object. For configuration handlers,
            * this will usually equal the owner.
            */
            configIframe: function (type, args, obj) {

                var bIFrame = args[0];

                function createIFrame() {

                    var oIFrame = this.iframe,
                        oElement = this.element,
                        oParent;

                    if (!oIFrame) {
                        if (!m_oIFrameTemplate) {
                            m_oIFrameTemplate = document.createElement("iframe");

                            if (this.isSecure) {
                                m_oIFrameTemplate.src = Overlay.IFRAME_SRC;
                            }

                            /*
                                Set the opacity of the <iframe> to 0 so that it
                                doesn't modify the opacity of any transparent
                                elements that may be on top of it (like a shadow).
                            */
                            if (UA.ie) {
                                m_oIFrameTemplate.style.filter = "alpha(opacity=0)";
                                /*
                                     Need to set the "frameBorder" property to 0
                                     supress the default <iframe> border in IE.
                                     Setting the CSS "border" property alone
                                     doesn't supress it.
                                */
                                m_oIFrameTemplate.frameBorder = 0;
                            }
                            else {
                                m_oIFrameTemplate.style.opacity = "0";
                            }

                            m_oIFrameTemplate.style.position = "absolute";
                            m_oIFrameTemplate.style.border = "none";
                            m_oIFrameTemplate.style.margin = "0";
                            m_oIFrameTemplate.style.padding = "0";
                            m_oIFrameTemplate.style.display = "none";
                            m_oIFrameTemplate.tabIndex = -1;
                            m_oIFrameTemplate.className = Overlay.CSS_IFRAME;
                        }

                        oIFrame = m_oIFrameTemplate.cloneNode(false);
                        oIFrame.id = this.id + "_f";
                        oParent = oElement.parentNode;

                        var parentNode = oParent || document.body;

                        this._addToParent(parentNode, oIFrame);
                        this.iframe = oIFrame;
                    }

                    /*
                         Show the <iframe> before positioning it since the "setXY"
                         method of DOM requires the element be in the document
                         and visible.
                    */
                    this.showIframe();

                    /*
                         Syncronize the size and position of the <iframe> to that
                         of the Overlay.
                    */
                    this.syncIframe();
                    this.stackIframe();

                    // Add event listeners to update the <iframe> when necessary
                    if (!this._hasIframeEventListeners) {
                        this.showEvent.subscribe(this.showIframe);
                        this.hideEvent.subscribe(this.hideIframe);
                        this.changeContentEvent.subscribe(this.syncIframe);

                        this._hasIframeEventListeners = true;
                    }
                }

                function onBeforeShow() {
                    createIFrame.call(this);
                    this.beforeShowEvent.unsubscribe(onBeforeShow);
                    this._iframeDeferred = false;
                }

                if (bIFrame) { // <iframe> shim is enabled

                    if (this.cfg.getProperty("visible")) {
                        createIFrame.call(this);
                    } else {
                        if (!this._iframeDeferred) {
                            this.beforeShowEvent.subscribe(onBeforeShow);
                            this._iframeDeferred = true;
                        }
                    }

                } else {    // <iframe> shim is disabled
                    this.hideIframe();

                    if (this._hasIframeEventListeners) {
                        this.showEvent.unsubscribe(this.showIframe);
                        this.hideEvent.unsubscribe(this.hideIframe);
                        this.changeContentEvent.unsubscribe(this.syncIframe);

                        this._hasIframeEventListeners = false;
                    }
                }
            },

            /**
             * Set's the container's XY value from DOM if not already set.
             *
             * Differs from syncPosition, in that the XY value is only sync'd with DOM if
             * not already set. The method also refire's the XY config property event, so any
             * beforeMove, Move event listeners are invoked.
             *
             * @method _primeXYFromDOM
             * @protected
             */
            _primeXYFromDOM : function() {
                if (YAHOO.lang.isUndefined(this.cfg.getProperty("xy"))) {
                    // Set CFG XY based on DOM XY
                    this.syncPosition();
                    // Account for XY being set silently in syncPosition (no moveTo fired/called)
                    this.cfg.refireEvent("xy");
                    this.beforeShowEvent.unsubscribe(this._primeXYFromDOM);
                }
            },

            /**
            * The default event handler fired when the "constraintoviewport"
            * property is changed.
            * @method configConstrainToViewport
            * @param {String} type The CustomEvent type (usually the property name)
            * @param {Object[]} args The CustomEvent arguments. For configuration
            * handlers, args[0] will equal the newly applied value for
            * the property.
            * @param {Object} obj The scope object. For configuration handlers,
            * this will usually equal the owner.
            */
            configConstrainToViewport: function (type, args, obj) {
                var val = args[0];

                if (val) {
                    if (! Config.alreadySubscribed(this.beforeMoveEvent, this.enforceConstraints, this)) {
                        this.beforeMoveEvent.subscribe(this.enforceConstraints, this, true);
                    }
                    if (! Config.alreadySubscribed(this.beforeShowEvent, this._primeXYFromDOM)) {
                        this.beforeShowEvent.subscribe(this._primeXYFromDOM);
                    }
                } else {
                    this.beforeShowEvent.unsubscribe(this._primeXYFromDOM);
                    this.beforeMoveEvent.unsubscribe(this.enforceConstraints, this);
                }
            },

             /**
            * The default event handler fired when the "context" property
            * is changed.
            *
            * @method configContext
            * @param {String} type The CustomEvent type (usually the property name)
            * @param {Object[]} args The CustomEvent arguments. For configuration
            * handlers, args[0] will equal the newly applied value for the property.
            * @param {Object} obj The scope object. For configuration handlers,
            * this will usually equal the owner.
            */
            configContext: function (type, args, obj) {

                var contextArgs = args[0],
                    contextEl,
                    elementMagnetCorner,
                    contextMagnetCorner,
                    triggers,
                    offset,
                    defTriggers = this.CONTEXT_TRIGGERS;

                if (contextArgs) {

                    contextEl = contextArgs[0];
                    elementMagnetCorner = contextArgs[1];
                    contextMagnetCorner = contextArgs[2];
                    triggers = contextArgs[3];
                    offset = contextArgs[4];

                    if (defTriggers && defTriggers.length > 0) {
                        triggers = (triggers || []).concat(defTriggers);
                    }

                    if (contextEl) {
                        if (typeof contextEl == "string") {
                            this.cfg.setProperty("context", [
                                    document.getElementById(contextEl),
                                    elementMagnetCorner,
                                    contextMagnetCorner,
                                    triggers,
                                    offset],
                                    true);
                        }

                        if (elementMagnetCorner && contextMagnetCorner) {
                            this.align(elementMagnetCorner, contextMagnetCorner, offset);
                        }

                        if (this._contextTriggers) {
                            // Unsubscribe Old Set
                            this._processTriggers(this._contextTriggers, _UNSUBSCRIBE, this._alignOnTrigger);
                        }

                        if (triggers) {
                            // Subscribe New Set
                            this._processTriggers(triggers, _SUBSCRIBE, this._alignOnTrigger);
                            this._contextTriggers = triggers;
                        }
                    }
                }
            },

            /**
             * Custom Event handler for context alignment triggers. Invokes the align method
             *
             * @method _alignOnTrigger
             * @protected
             *
             * @param {String} type The event type (not used by the default implementation)
             * @param {Any[]} args The array of arguments for the trigger event (not used by the default implementation)
             */
            _alignOnTrigger: function(type, args) {
                this.align();
            },

            /**
             * Helper method to locate the custom event instance for the event name string
             * passed in. As a convenience measure, any custom events passed in are returned.
             *
             * @method _findTriggerCE
             * @private
             *
             * @param {String|CustomEvent} t Either a CustomEvent, or event type (e.g. "windowScroll") for which a
             * custom event instance needs to be looked up from the Overlay._TRIGGER_MAP.
             */
            _findTriggerCE : function(t) {
                var tce = null;
                if (t instanceof CustomEvent) {
                    tce = t;
                } else if (Overlay._TRIGGER_MAP[t]) {
                    tce = Overlay._TRIGGER_MAP[t];
                }
                return tce;
            },

            /**
             * Utility method that subscribes or unsubscribes the given
             * function from the list of trigger events provided.
             *
             * @method _processTriggers
             * @protected
             *
             * @param {Array[String|CustomEvent]} triggers An array of either CustomEvents, event type strings
             * (e.g. "beforeShow", "windowScroll") to/from which the provided function should be
             * subscribed/unsubscribed respectively.
             *
             * @param {String} mode Either "subscribe" or "unsubscribe", specifying whether or not
             * we are subscribing or unsubscribing trigger listeners
             *
             * @param {Function} fn The function to be subscribed/unsubscribed to/from the trigger event.
             * Context is always set to the overlay instance, and no additional object argument
             * get passed to the subscribed function.
             */
            _processTriggers : function(triggers, mode, fn) {
                var t, tce;

                for (var i = 0, l = triggers.length; i < l; ++i) {
                    t = triggers[i];
                    tce = this._findTriggerCE(t);
                    if (tce) {
                        tce[mode](fn, this, true);
                    } else {
                        this[mode](t, fn);
                    }
                }
            },

            // END BUILT-IN PROPERTY EVENT HANDLERS //
            /**
            * Aligns the Overlay to its context element using the specified corner
            * points (represented by the constants TOP_LEFT, TOP_RIGHT, BOTTOM_LEFT,
            * and BOTTOM_RIGHT.
            * @method align
            * @param {String} elementAlign  The String representing the corner of
            * the Overlay that should be aligned to the context element
            * @param {String} contextAlign  The corner of the context element
            * that the elementAlign corner should stick to.
            * @param {Number[]} xyOffset Optional. A 2 element array specifying the x and y pixel offsets which should be applied
            * after aligning the element and context corners. For example, passing in [5, -10] for this value, would offset the
            * Overlay by 5 pixels along the X axis (horizontally) and -10 pixels along the Y axis (vertically) after aligning the specified corners.
            */
            align: function (elementAlign, contextAlign, xyOffset) {

                var contextArgs = this.cfg.getProperty("context"),
                    me = this,
                    context,
                    element,
                    contextRegion;

                function doAlign(v, h) {

                    var alignX = null, alignY = null;

                    switch (elementAlign) {

                        case Overlay.TOP_LEFT:
                            alignX = h;
                            alignY = v;
                            break;

                        case Overlay.TOP_RIGHT:
                            alignX = h - element.offsetWidth;
                            alignY = v;
                            break;

                        case Overlay.BOTTOM_LEFT:
                            alignX = h;
                            alignY = v - element.offsetHeight;
                            break;

                        case Overlay.BOTTOM_RIGHT:
                            alignX = h - element.offsetWidth;
                            alignY = v - element.offsetHeight;
                            break;
                    }

                    if (alignX !== null && alignY !== null) {
                        if (xyOffset) {
                            alignX += xyOffset[0];
                            alignY += xyOffset[1];
                        }
                        me.moveTo(alignX, alignY);
                    }
                }

                if (contextArgs) {
                    context = contextArgs[0];
                    element = this.element;
                    me = this;

                    if (! elementAlign) {
                        elementAlign = contextArgs[1];
                    }

                    if (! contextAlign) {
                        contextAlign = contextArgs[2];
                    }

                    if (!xyOffset && contextArgs[4]) {
                        xyOffset = contextArgs[4];
                    }

                    if (element && context) {
                        contextRegion = Dom.getRegion(context);

                        switch (contextAlign) {

                            case Overlay.TOP_LEFT:
                                doAlign(contextRegion.top, contextRegion.left);
                                break;

                            case Overlay.TOP_RIGHT:
                                doAlign(contextRegion.top, contextRegion.right);
                                break;

                            case Overlay.BOTTOM_LEFT:
                                doAlign(contextRegion.bottom, contextRegion.left);
                                break;

                            case Overlay.BOTTOM_RIGHT:
                                doAlign(contextRegion.bottom, contextRegion.right);
                                break;
                        }
                    }
                }
            },

            /**
            * The default event handler executed when the moveEvent is fired, if the
            * "constraintoviewport" is set to true.
            * @method enforceConstraints
            * @param {String} type The CustomEvent type (usually the property name)
            * @param {Object[]} args The CustomEvent arguments. For configuration
            * handlers, args[0] will equal the newly applied value for the property.
            * @param {Object} obj The scope object. For configuration handlers,
            * this will usually equal the owner.
            */
            enforceConstraints: function (type, args, obj) {
                var pos = args[0];

                var cXY = this.getConstrainedXY(pos[0], pos[1]);
                this.cfg.setProperty("x", cXY[0], true);
                this.cfg.setProperty("y", cXY[1], true);
                this.cfg.setProperty("xy", cXY, true);
            },

            /**
             * Shared implementation method for getConstrainedX and getConstrainedY.
             *
             * <p>
             * Given a coordinate value, returns the calculated coordinate required to
             * position the Overlay if it is to be constrained to the viewport, based on the
             * current element size, viewport dimensions, scroll values and preventoverlap
             * settings
             * </p>
             *
             * @method _getConstrainedPos
             * @protected
             * @param {String} pos The coordinate which needs to be constrained, either "x" or "y"
             * @param {Number} The coordinate value which needs to be constrained
             * @return {Number} The constrained coordinate value
             */
            _getConstrainedPos: function(pos, val) {

                var overlayEl = this.element,

                    buffer = Overlay.VIEWPORT_OFFSET,

                    x = (pos == "x"),

                    overlaySize      = (x) ? overlayEl.offsetWidth : overlayEl.offsetHeight,
                    viewportSize     = (x) ? Dom.getViewportWidth() : Dom.getViewportHeight(),
                    docScroll        = (x) ? Dom.getDocumentScrollLeft() : Dom.getDocumentScrollTop(),
                    overlapPositions = (x) ? Overlay.PREVENT_OVERLAP_X : Overlay.PREVENT_OVERLAP_Y,

                    context = this.cfg.getProperty("context"),

                    bOverlayFitsInViewport = (overlaySize + buffer < viewportSize),
                    bPreventContextOverlap = this.cfg.getProperty("preventcontextoverlap") && context && overlapPositions[(context[1] + context[2])],

                    minConstraint = docScroll + buffer,
                    maxConstraint = docScroll + viewportSize - overlaySize - buffer,

                    constrainedVal = val;

                if (val < minConstraint || val > maxConstraint) {
                    if (bPreventContextOverlap) {
                        constrainedVal = this._preventOverlap(pos, context[0], overlaySize, viewportSize, docScroll);
                    } else {
                        if (bOverlayFitsInViewport) {
                            if (val < minConstraint) {
                                constrainedVal = minConstraint;
                            } else if (val > maxConstraint) {
                                constrainedVal = maxConstraint;
                            }
                        } else {
                            constrainedVal = minConstraint;
                        }
                    }
                }

                return constrainedVal;
            },

            /**
             * Helper method, used to position the Overlap to prevent overlap with the
             * context element (used when preventcontextoverlap is enabled)
             *
             * @method _preventOverlap
             * @protected
             * @param {String} pos The coordinate to prevent overlap for, either "x" or "y".
             * @param {HTMLElement} contextEl The context element
             * @param {Number} overlaySize The related overlay dimension value (for "x", the width, for "y", the height)
             * @param {Number} viewportSize The related viewport dimension value (for "x", the width, for "y", the height)
             * @param {Object} docScroll  The related document scroll value (for "x", the scrollLeft, for "y", the scrollTop)
             *
             * @return {Number} The new coordinate value which was set to prevent overlap
             */
            _preventOverlap : function(pos, contextEl, overlaySize, viewportSize, docScroll) {

                var x = (pos == "x"),

                    buffer = Overlay.VIEWPORT_OFFSET,

                    overlay = this,

                    contextElPos   = ((x) ? Dom.getX(contextEl) : Dom.getY(contextEl)) - docScroll,
                    contextElSize  = (x) ? contextEl.offsetWidth : contextEl.offsetHeight,

                    minRegionSize = contextElPos - buffer,
                    maxRegionSize = (viewportSize - (contextElPos + contextElSize)) - buffer,

                    bFlipped = false,

                    flip = function () {
                        var flippedVal;

                        if ((overlay.cfg.getProperty(pos) - docScroll) > contextElPos) {
                            flippedVal = (contextElPos - overlaySize);
                        } else {
                            flippedVal = (contextElPos + contextElSize);
                        }

                        overlay.cfg.setProperty(pos, (flippedVal + docScroll), true);

                        return flippedVal;
                    },

                    setPosition = function () {

                        var displayRegionSize = ((overlay.cfg.getProperty(pos) - docScroll) > contextElPos) ? maxRegionSize : minRegionSize,
                            position;

                        if (overlaySize > displayRegionSize) {
                            if (bFlipped) {
                                /*
                                     All possible positions and values have been
                                     tried, but none were successful, so fall back
                                     to the original size and position.
                                */
                                flip();
                            } else {
                                flip();
                                bFlipped = true;
                                position = setPosition();
                            }
                        }

                        return position;
                    };

                setPosition();

                return this.cfg.getProperty(pos);
            },

            /**
             * Given x coordinate value, returns the calculated x coordinate required to
             * position the Overlay if it is to be constrained to the viewport, based on the
             * current element size, viewport dimensions and scroll values.
             *
             * @param {Number} x The X coordinate value to be constrained
             * @return {Number} The constrained x coordinate
             */
            getConstrainedX: function (x) {
                return this._getConstrainedPos("x", x);
            },

            /**
             * Given y coordinate value, returns the calculated y coordinate required to
             * position the Overlay if it is to be constrained to the viewport, based on the
             * current element size, viewport dimensions and scroll values.
             *
             * @param {Number} y The Y coordinate value to be constrained
             * @return {Number} The constrained y coordinate
             */
            getConstrainedY : function (y) {
                return this._getConstrainedPos("y", y);
            },

            /**
             * Given x, y coordinate values, returns the calculated coordinates required to
             * position the Overlay if it is to be constrained to the viewport, based on the
             * current element size, viewport dimensions and scroll values.
             *
             * @param {Number} x The X coordinate value to be constrained
             * @param {Number} y The Y coordinate value to be constrained
             * @return {Array} The constrained x and y coordinates at index 0 and 1 respectively;
             */
            getConstrainedXY: function(x, y) {
                return [this.getConstrainedX(x), this.getConstrainedY(y)];
            },

            /**
            * Centers the container in the viewport.
            * @method center
            */
            center: function () {

                var nViewportOffset = Overlay.VIEWPORT_OFFSET,
                    elementWidth = this.element.offsetWidth,
                    elementHeight = this.element.offsetHeight,
                    viewPortWidth = Dom.getViewportWidth(),
                    viewPortHeight = Dom.getViewportHeight(),
                    x,
                    y;

                if (elementWidth < viewPortWidth) {
                    x = (viewPortWidth / 2) - (elementWidth / 2) + Dom.getDocumentScrollLeft();
                } else {
                    x = nViewportOffset + Dom.getDocumentScrollLeft();
                }

                if (elementHeight < viewPortHeight) {
                    y = (viewPortHeight / 2) - (elementHeight / 2) + Dom.getDocumentScrollTop();
                } else {
                    y = nViewportOffset + Dom.getDocumentScrollTop();
                }

                this.cfg.setProperty("xy", [parseInt(x, 10), parseInt(y, 10)]);
                this.cfg.refireEvent("iframe");

                if (UA.webkit) {
                    this.forceContainerRedraw();
                }
            },

            /**
            * Synchronizes the Panel's "xy", "x", and "y" properties with the
            * Panel's position in the DOM. This is primarily used to update
            * position information during drag & drop.
            * @method syncPosition
            */
            syncPosition: function () {

                var pos = Dom.getXY(this.element);

                this.cfg.setProperty("x", pos[0], true);
                this.cfg.setProperty("y", pos[1], true);
                this.cfg.setProperty("xy", pos, true);

            },

            /**
            * Event handler fired when the resize monitor element is resized.
            * @method onDomResize
            * @param {DOMEvent} e The resize DOM event
            * @param {Object} obj The scope object
            */
            onDomResize: function (e, obj) {

                var me = this;

                Overlay.superclass.onDomResize.call(this, e, obj);

                setTimeout(function () {
                    me.syncPosition();
                    me.cfg.refireEvent("iframe");
                    me.cfg.refireEvent("context");
                }, 0);
            },

            /**
             * Determines the content box height of the given element (height of the element, without padding or borders) in pixels.
             *
             * @method _getComputedHeight
             * @private
             * @param {HTMLElement} el The element for which the content height needs to be determined
             * @return {Number} The content box height of the given element, or null if it could not be determined.
             */
            _getComputedHeight : (function() {

                if (document.defaultView && document.defaultView.getComputedStyle) {
                    return function(el) {
                        var height = null;
                        if (el.ownerDocument && el.ownerDocument.defaultView) {
                            var computed = el.ownerDocument.defaultView.getComputedStyle(el, '');
                            if (computed) {
                                height = parseInt(computed.height, 10);
                            }
                        }
                        return (Lang.isNumber(height)) ? height : null;
                    };
                } else {
                    return function(el) {
                        var height = null;
                        if (el.style.pixelHeight) {
                            height = el.style.pixelHeight;
                        }
                        return (Lang.isNumber(height)) ? height : null;
                    };
                }
            })(),

            /**
             * autofillheight validator. Verifies that the autofill value is either null
             * or one of the strings : "body", "header" or "footer".
             *
             * @method _validateAutoFillHeight
             * @protected
             * @param {String} val
             * @return true, if valid, false otherwise
             */
            _validateAutoFillHeight : function(val) {
                return (!val) || (Lang.isString(val) && Overlay.STD_MOD_RE.test(val));
            },

            /**
             * The default custom event handler executed when the overlay's height is changed,
             * if the autofillheight property has been set.
             *
             * @method _autoFillOnHeightChange
             * @protected
             * @param {String} type The event type
             * @param {Array} args The array of arguments passed to event subscribers
             * @param {HTMLElement} el The header, body or footer element which is to be resized to fill
             * out the containers height
             */
            _autoFillOnHeightChange : function(type, args, el) {
                var height = this.cfg.getProperty("height");
                if ((height && height !== "auto") || (height === 0)) {
                    this.fillHeight(el);
                }
            },

            /**
             * Returns the sub-pixel height of the el, using getBoundingClientRect, if available,
             * otherwise returns the offsetHeight
             * @method _getPreciseHeight
             * @private
             * @param {HTMLElement} el
             * @return {Float} The sub-pixel height if supported by the browser, else the rounded height.
             */
            _getPreciseHeight : function(el) {
                var height = el.offsetHeight;

                if (el.getBoundingClientRect) {
                    var rect = el.getBoundingClientRect();
                    height = rect.bottom - rect.top;
                }

                return height;
            },

            /**
             * <p>
             * Sets the height on the provided header, body or footer element to
             * fill out the height of the container. It determines the height of the
             * containers content box, based on it's configured height value, and
             * sets the height of the autofillheight element to fill out any
             * space remaining after the other standard module element heights
             * have been accounted for.
             * </p>
             * <p><strong>NOTE:</strong> This method is not designed to work if an explicit
             * height has not been set on the container, since for an "auto" height container,
             * the heights of the header/body/footer will drive the height of the container.</p>
             *
             * @method fillHeight
             * @param {HTMLElement} el The element which should be resized to fill out the height
             * of the container element.
             */
            fillHeight : function(el) {
                if (el) {
                    var container = this.innerElement || this.element,
                        containerEls = [this.header, this.body, this.footer],
                        containerEl,
                        total = 0,
                        filled = 0,
                        remaining = 0,
                        validEl = false;

                    for (var i = 0, l = containerEls.length; i < l; i++) {
                        containerEl = containerEls[i];
                        if (containerEl) {
                            if (el !== containerEl) {
                                filled += this._getPreciseHeight(containerEl);
                            } else {
                                validEl = true;
                            }
                        }
                    }

                    if (validEl) {

                        if (UA.ie || UA.opera) {
                            // Need to set height to 0, to allow height to be reduced
                            Dom.setStyle(el, 'height', 0 + 'px');
                        }

                        total = this._getComputedHeight(container);

                        // Fallback, if we can't get computed value for content height
                        if (total === null) {
                            Dom.addClass(container, "yui-override-padding");
                            total = container.clientHeight; // Content, No Border, 0 Padding (set by yui-override-padding)
                            Dom.removeClass(container, "yui-override-padding");
                        }

                        remaining = Math.max(total - filled, 0);

                        Dom.setStyle(el, "height", remaining + "px");

                        // Re-adjust height if required, to account for el padding and border
                        if (el.offsetHeight != remaining) {
                            remaining = Math.max(remaining - (el.offsetHeight - remaining), 0);
                        }
                        Dom.setStyle(el, "height", remaining + "px");
                    }
                }
            },

            /**
            * Places the Overlay on top of all other instances of
            * YAHOO.widget.Overlay.
            * @method bringToTop
            */
            bringToTop: function () {

                var aOverlays = [],
                    oElement = this.element;

                function compareZIndexDesc(p_oOverlay1, p_oOverlay2) {

                    var sZIndex1 = Dom.getStyle(p_oOverlay1, "zIndex"),
                        sZIndex2 = Dom.getStyle(p_oOverlay2, "zIndex"),

                        nZIndex1 = (!sZIndex1 || isNaN(sZIndex1)) ? 0 : parseInt(sZIndex1, 10),
                        nZIndex2 = (!sZIndex2 || isNaN(sZIndex2)) ? 0 : parseInt(sZIndex2, 10);

                    if (nZIndex1 > nZIndex2) {
                        return -1;
                    } else if (nZIndex1 < nZIndex2) {
                        return 1;
                    } else {
                        return 0;
                    }
                }

                function isOverlayElement(p_oElement) {

                    var isOverlay = Dom.hasClass(p_oElement, Overlay.CSS_OVERLAY),
                        Panel = YAHOO.widget.Panel;

                    if (isOverlay && !Dom.isAncestor(oElement, p_oElement)) {
                        if (Panel && Dom.hasClass(p_oElement, Panel.CSS_PANEL)) {
                            aOverlays[aOverlays.length] = p_oElement.parentNode;
                        } else {
                            aOverlays[aOverlays.length] = p_oElement;
                        }
                    }
                }

                Dom.getElementsBy(isOverlayElement, "DIV", document.body);

                aOverlays.sort(compareZIndexDesc);

                var oTopOverlay = aOverlays[0],
                    nTopZIndex;

                if (oTopOverlay) {
                    nTopZIndex = Dom.getStyle(oTopOverlay, "zIndex");

                    if (!isNaN(nTopZIndex)) {
                        var bRequiresBump = false;

                        if (oTopOverlay != oElement) {
                            bRequiresBump = true;
                        } else if (aOverlays.length > 1) {
                            var nNextZIndex = Dom.getStyle(aOverlays[1], "zIndex");
                            // Don't rely on DOM order to stack if 2 overlays are at the same zindex.
                            if (!isNaN(nNextZIndex) && (nTopZIndex == nNextZIndex)) {
                                bRequiresBump = true;
                            }
                        }
                        if (bRequiresBump) {
                            this.cfg.setProperty("zindex", (parseInt(nTopZIndex, 10) + 2));
                        }
                    }
                }
            },

            /**
            * Removes the Overlay element from the DOM and sets all child
            * elements to null.
            * @method destroy
            */
            destroy: function () {

                if (this.iframe) {
                    this.iframe.parentNode.removeChild(this.iframe);
                }

                this.iframe = null;

                Overlay.windowResizeEvent.unsubscribe(
                    this.doCenterOnDOMEvent, this);

                Overlay.windowScrollEvent.unsubscribe(
                    this.doCenterOnDOMEvent, this);

                Module.textResizeEvent.unsubscribe(this._autoFillOnHeightChange);

                if (this._contextTriggers) {
                    // Unsubscribe context triggers - to cover context triggers which listen for global
                    // events such as windowResize and windowScroll. Easier just to unsubscribe all
                    this._processTriggers(this._contextTriggers, _UNSUBSCRIBE, this._alignOnTrigger);
                }

                Overlay.superclass.destroy.call(this);
            },

            /**
             * Can be used to force the container to repaint/redraw it's contents.
             * <p>
             * By default applies and then removes a 1px bottom margin through the
             * application/removal of a "yui-force-redraw" class.
             * </p>
             * <p>
             * It is currently used by Overlay to force a repaint for webkit
             * browsers, when centering.
             * </p>
             * @method forceContainerRedraw
             */
            forceContainerRedraw : function() {
                var c = this;
                Dom.addClass(c.element, "yui-force-redraw");
                setTimeout(function() {
                    Dom.removeClass(c.element, "yui-force-redraw");
                }, 0);
            },

            /**
            * Returns a String representation of the object.
            * @method toString
            * @return {String} The string representation of the Overlay.
            */
            toString: function () {
                return "Overlay " + this.id;
            }

        });
    }());

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