MDL-10604:

[moodle-linuxchix.git] / lib / yui / event / event.js

/*
Copyright (c) 2006, Yahoo! Inc. All rights reserved.
Code licensed under the BSD License:
http://developer.yahoo.net/yui/license.txt
version: 0.12.2
*/
/**
 * The CustomEvent class lets you define events for your application
 * that can be subscribed to by one or more independent component.
 *
 * @param {String}  type The type of event, which is passed to the callback
 *                  when the event fires
 * @param {Object}  oScope The context the event will fire from.  "this" will
 *                  refer to this object in the callback.  Default value: 
 *                  the window object.  The listener can override this.
 * @param {boolean} silent pass true to prevent the event from writing to
 *                  the debugsystem
 * @param {int}     signature the signature that the custom event subscriber
 *                  will receive. YAHOO.util.CustomEvent.LIST or 
 *                  YAHOO.util.CustomEvent.FLAT.  The default is
 *                  YAHOO.util.CustomEvent.LIST.
 * @namespace YAHOO.util
 * @class CustomEvent
 * @constructor
 */
YAHOO.util.CustomEvent = function(type, oScope, silent, signature) {

    /**
     * The type of event, returned to subscribers when the event fires
     * @property type
     * @type string
     */
    this.type = type;

    /**
     * The scope the the event will fire from by default.  Defaults to the window 
     * obj
     * @property scope
     * @type object
     */
    this.scope = oScope || window;

    /**
     * By default all custom events are logged in the debug build, set silent
     * to true to disable debug outpu for this event.
     * @property silent
     * @type boolean
     */
    this.silent = silent;

    /**
     * Custom events support two styles of arguments provided to the event
     * subscribers.  
     * <ul>
     * <li>YAHOO.util.CustomEvent.LIST: 
     *   <ul>
     *   <li>param1: event name</li>
     *   <li>param2: array of arguments sent to fire</li>
     *   <li>param3: <optional> a custom object supplied by the subscriber</li>
     *   </ul>
     * </li>
     * <li>YAHOO.util.CustomEvent.FLAT
     *   <ul>
     *   <li>param1: the first argument passed to fire.  If you need to
     *           pass multiple parameters, use and array or object literal</li>
     *   <li>param2: <optional> a custom object supplied by the subscriber</li>
     *   </ul>
     * </li>
     * </ul>
     *   @property signature
     *   @type int
     */
    this.signature = signature || YAHOO.util.CustomEvent.LIST;

    /**
     * The subscribers to this event
     * @property subscribers
     * @type Subscriber[]
     */
    this.subscribers = [];

    if (!this.silent) {
    }

    var onsubscribeType = "_YUICEOnSubscribe";

    // Only add subscribe events for events that are not generated by 
    // CustomEvent
    if (type !== onsubscribeType) {

        /**
         * Custom events provide a custom event that fires whenever there is
         * a new subscriber to the event.  This provides an opportunity to
         * handle the case where there is a non-repeating event that has
         * already fired has a new subscriber.  
         *
         * @event subscribeEvent
         * @type YAHOO.util.CustomEvent
         * @param {Function} fn The function to execute
         * @param {Object}   obj An object to be passed along when the event 
         *                       fires
         * @param {boolean|Object}  override If true, the obj passed in becomes 
         *                                   the execution scope of the listener.
         *                                   if an object, that object becomes the
         *                                   the execution scope.
         */
        this.subscribeEvent = 
                new YAHOO.util.CustomEvent(onsubscribeType, this, true);

    } 
};

/**
 * Subscriber listener sigature constant.  The LIST type returns three
 * parameters: the event type, the array of args passed to fire, and
 * the optional custom object
 * @property YAHOO.util.CustomEvent.LIST
 * @static
 * @type int
 */
YAHOO.util.CustomEvent.LIST = 0;

/**
 * Subscriber listener sigature constant.  The FLAT type returns two
 * parameters: the first argument passed to fire and the optional 
 * custom object
 * @property YAHOO.util.CustomEvent.FLAT
 * @static
 * @type int
 */
YAHOO.util.CustomEvent.FLAT = 1;

YAHOO.util.CustomEvent.prototype = {

    /**
     * Subscribes the caller to this event
     * @method subscribe
     * @param {Function} fn        The function to execute
     * @param {Object}   obj       An object to be passed along when the event 
     *                             fires
     * @param {boolean|Object}  override If true, the obj passed in becomes 
     *                                   the execution scope of the listener.
     *                                   if an object, that object becomes the
     *                                   the execution scope.
     */
    subscribe: function(fn, obj, override) {
        if (this.subscribeEvent) {
            this.subscribeEvent.fire(fn, obj, override);
        }

        this.subscribers.push( new YAHOO.util.Subscriber(fn, obj, override) );
    },

    /**
     * Unsubscribes the caller from this event
     * @method unsubscribe
     * @param {Function} fn  The function to execute
     * @param {Object}   obj  The custom object passed to subscribe (optional)
     * @return {boolean} True if the subscriber was found and detached.
     */
    unsubscribe: function(fn, obj) {
        var found = false;
        for (var i=0, len=this.subscribers.length; i<len; ++i) {
            var s = this.subscribers[i];
            if (s && s.contains(fn, obj)) {
                this._delete(i);
                found = true;
            }
        }

        return found;
    },

    /**
     * Notifies the subscribers.  The callback functions will be executed
     * from the scope specified when the event was created, and with the 
     * following parameters:
     *   <ul>
     *   <li>The type of event</li>
     *   <li>All of the arguments fire() was executed with as an array</li>
     *   <li>The custom object (if any) that was passed into the subscribe() 
     *       method</li>
     *   </ul>
     * @method fire 
     * @param {Object*} arguments an arbitrary set of parameters to pass to 
     *                            the handler.
     * @return {boolean} false if one of the subscribers returned false, 
     *                   true otherwise
     */
    fire: function() {
        var len=this.subscribers.length;
        if (!len && this.silent) {
            return true;
        }

        var args=[], ret=true, i;

        for (i=0; i<arguments.length; ++i) {
            args.push(arguments[i]);
        }

        var argslength = args.length;

        if (!this.silent) {
        }

        for (i=0; i<len; ++i) {
            var s = this.subscribers[i];
            if (s) {
                if (!this.silent) {
                }

                var scope = s.getScope(this.scope);

                if (this.signature == YAHOO.util.CustomEvent.FLAT) {
                    var param = null;
                    if (args.length > 0) {
                        param = args[0];
                    }
                    ret = s.fn.call(scope, param, s.obj);
                } else {
                    ret = s.fn.call(scope, this.type, args, s.obj);
                }
                if (false === ret) {
                    if (!this.silent) {
                    }

                    //break;
                    return false;
                }
            }
        }

        return true;
    },

    /**
     * Removes all listeners
     * @method unsubscribeAll
     */
    unsubscribeAll: function() {
        for (var i=0, len=this.subscribers.length; i<len; ++i) {
            this._delete(len - 1 - i);
        }
    },

    /**
     * @method _delete
     * @private
     */
    _delete: function(index) {
        var s = this.subscribers[index];
        if (s) {
            delete s.fn;
            delete s.obj;
        }

        // delete this.subscribers[index];
        this.subscribers.splice(index, 1);
    },

    /**
     * @method toString
     */
    toString: function() {
         return "CustomEvent: " + "'" + this.type  + "', " + 
             "scope: " + this.scope;

    }
};

/////////////////////////////////////////////////////////////////////

/**
 * Stores the subscriber information to be used when the event fires.
 * @param {Function} fn       The function to execute
 * @param {Object}   obj      An object to be passed along when the event fires
 * @param {boolean}  override If true, the obj passed in becomes the execution
 *                            scope of the listener
 * @class Subscriber
 * @constructor
 */
YAHOO.util.Subscriber = function(fn, obj, override) {

    /**
     * The callback that will be execute when the event fires
     * @property fn
     * @type function
     */
    this.fn = fn;

    /**
     * An optional custom object that will passed to the callback when
     * the event fires
     * @property obj
     * @type object
     */
    this.obj = obj || null;

    /**
     * The default execution scope for the event listener is defined when the
     * event is created (usually the object which contains the event).
     * By setting override to true, the execution scope becomes the custom
     * object passed in by the subscriber.  If override is an object, that 
     * object becomes the scope.
     * @property override
     * @type boolean|object
     */
    this.override = override;

};

/**
 * Returns the execution scope for this listener.  If override was set to true
 * the custom obj will be the scope.  If override is an object, that is the
 * scope, otherwise the default scope will be used.
 * @method getScope
 * @param {Object} defaultScope the scope to use if this listener does not
 *                              override it.
 */
YAHOO.util.Subscriber.prototype.getScope = function(defaultScope) {
    if (this.override) {
        if (this.override === true) {
            return this.obj;
        } else {
            return this.override;
        }
    }
    return defaultScope;
};

/**
 * Returns true if the fn and obj match this objects properties.
 * Used by the unsubscribe method to match the right subscriber.
 *
 * @method contains
 * @param {Function} fn the function to execute
 * @param {Object} obj an object to be passed along when the event fires
 * @return {boolean} true if the supplied arguments match this 
 *                   subscriber's signature.
 */
YAHOO.util.Subscriber.prototype.contains = function(fn, obj) {
    if (obj) {
        return (this.fn == fn && this.obj == obj);
    } else {
        return (this.fn == fn);
    }
};

/**
 * @method toString
 */
YAHOO.util.Subscriber.prototype.toString = function() {
    return "Subscriber { obj: " + (this.obj || "")  + 
           ", override: " +  (this.override || "no") + " }";
};

/**
 * The Event Utility provides utilities for managing DOM Events and tools
 * for building event systems
 *
 * @module event
 * @title Event Utility
 * @namespace YAHOO.util
 * @requires yahoo
 */

// The first instance of Event will win if it is loaded more than once.
if (!YAHOO.util.Event) {

/**
 * The event utility provides functions to add and remove event listeners,
 * event cleansing.  It also tries to automatically remove listeners it
 * registers during the unload event.
 *
 * @class Event
 * @static
 */
    YAHOO.util.Event = function() {

        /**
         * True after the onload event has fired
         * @property loadComplete
         * @type boolean
         * @static
         * @private
         */
        var loadComplete =  false;

        /**
         * Cache of wrapped listeners
         * @property listeners
         * @type array
         * @static
         * @private
         */
        var listeners = [];

        /**
         * User-defined unload function that will be fired before all events
         * are detached
         * @property unloadListeners
         * @type array
         * @static
         * @private
         */
        var unloadListeners = [];

        /**
         * Cache of DOM0 event handlers to work around issues with DOM2 events
         * in Safari
         * @property legacyEvents
         * @static
         * @private
         */
        var legacyEvents = [];

        /**
         * Listener stack for DOM0 events
         * @property legacyHandlers
         * @static
         * @private
         */
        var legacyHandlers = [];

        /**
         * The number of times to poll after window.onload.  This number is
         * increased if additional late-bound handlers are requested after
         * the page load.
         * @property retryCount
         * @static
         * @private
         */
        var retryCount = 0;

        /**
         * onAvailable listeners
         * @property onAvailStack
         * @static
         * @private
         */
        var onAvailStack = [];

        /**
         * Lookup table for legacy events
         * @property legacyMap
         * @static
         * @private
         */
        var legacyMap = [];

        /**
         * Counter for auto id generation
         * @property counter
         * @static
         * @private
         */
        var counter = 0;

        return { // PREPROCESS

            /**
             * The number of times we should look for elements that are not
             * in the DOM at the time the event is requested after the document
             * has been loaded.  The default is 200@amp;50 ms, so it will poll
             * for 10 seconds or until all outstanding handlers are bound
             * (whichever comes first).
             * @property POLL_RETRYS
             * @type int
             * @static
             * @final
             */
            POLL_RETRYS: 200,

            /**
             * The poll interval in milliseconds
             * @property POLL_INTERVAL
             * @type int
             * @static
             * @final
             */
            POLL_INTERVAL: 20,

            /**
             * Element to bind, int constant
             * @property EL
             * @type int
             * @static
             * @final
             */
            EL: 0,

            /**
             * Type of event, int constant
             * @property TYPE
             * @type int
             * @static
             * @final
             */
            TYPE: 1,

            /**
             * Function to execute, int constant
             * @property FN
             * @type int
             * @static
             * @final
             */
            FN: 2,

            /**
             * Function wrapped for scope correction and cleanup, int constant
             * @property WFN
             * @type int
             * @static
             * @final
             */
            WFN: 3,

            /**
             * Object passed in by the user that will be returned as a 
             * parameter to the callback, int constant
             * @property OBJ
             * @type int
             * @static
             * @final
             */
            OBJ: 3,

            /**
             * Adjusted scope, either the element we are registering the event
             * on or the custom object passed in by the listener, int constant
             * @property ADJ_SCOPE
             * @type int
             * @static
             * @final
             */
            ADJ_SCOPE: 4,

            /**
             * Safari detection is necessary to work around the preventDefault
             * bug that makes it so you can't cancel a href click from the 
             * handler.  There is not a capabilities check we can use here.
             * @property isSafari
             * @private
             * @static
             */
            isSafari: (/Safari|Konqueror|KHTML/gi).test(navigator.userAgent),

            /**
             * IE detection needed to properly calculate pageX and pageY.  
             * capabilities checking didn't seem to work because another 
             * browser that does not provide the properties have the values 
             * calculated in a different manner than IE.
             * @property isIE
             * @private
             * @static
             */
            isIE: (!this.isSafari && !navigator.userAgent.match(/opera/gi) && 
                    navigator.userAgent.match(/msie/gi)),

            /**
             * poll handle
             * @property _interval
             * @private
             */
            _interval: null,

            /**
             * @method startInterval
             * @static
             * @private
             */
            startInterval: function() {
                if (!this._interval) {
                    var self = this;
                    var callback = function() { self._tryPreloadAttach(); };
                    this._interval = setInterval(callback, this.POLL_INTERVAL);
                    // this.timeout = setTimeout(callback, i);
                }
            },

            /**
             * Executes the supplied callback when the item with the supplied
             * id is found.  This is meant to be used to execute behavior as
             * soon as possible as the page loads.  If you use this after the
             * initial page load it will poll for a fixed time for the element.
             * The number of times it will poll and the frequency are
             * configurable.  By default it will poll for 10 seconds.
             *
             * @method onAvailable
             *
             * @param {string}   p_id the id of the element to look for.
             * @param {function} p_fn what to execute when the element is found.
             * @param {object}   p_obj an optional object to be passed back as
             *                   a parameter to p_fn.
             * @param {boolean}  p_override If set to true, p_fn will execute
             *                   in the scope of p_obj
             *
             * @static
             */
            onAvailable: function(p_id, p_fn, p_obj, p_override) {
                onAvailStack.push( { id:         p_id, 
                                     fn:         p_fn, 
                                     obj:        p_obj, 
                                     override:   p_override, 
                                     checkReady: false    } );

                retryCount = this.POLL_RETRYS;
                this.startInterval();
            },

            /**
             * Works the same way as onAvailable, but additionally checks the
             * state of sibling elements to determine if the content of the
             * available element is safe to modify.
             *
             * @method onContentReady
             *
             * @param {string}   p_id the id of the element to look for.
             * @param {function} p_fn what to execute when the element is ready.
             * @param {object}   p_obj an optional object to be passed back as
             *                   a parameter to p_fn.
             * @param {boolean}  p_override If set to true, p_fn will execute
             *                   in the scope of p_obj
             *
             * @static
             */
            onContentReady: function(p_id, p_fn, p_obj, p_override) {
                onAvailStack.push( { id:         p_id, 
                                     fn:         p_fn, 
                                     obj:        p_obj, 
                                     override:   p_override,
                                     checkReady: true      } );

                retryCount = this.POLL_RETRYS;
                this.startInterval();
            },

            /**
             * Appends an event handler
             *
             * @method addListener
             *
             * @param {Object}   el        The html element to assign the 
             *                             event to
             * @param {String}   sType     The type of event to append
             * @param {Function} fn        The method the event invokes
             * @param {Object}   obj    An arbitrary object that will be 
             *                             passed as a parameter to the handler
             * @param {boolean}  override  If true, the obj passed in becomes
             *                             the execution scope of the listener
             * @return {boolean} True if the action was successful or defered,
             *                        false if one or more of the elements 
             *                        could not have the listener attached,
             *                        or if the operation throws an exception.
             * @static
             */
            addListener: function(el, sType, fn, obj, override) {

                if (!fn || !fn.call) {
                    return false;
                }

                // The el argument can be an array of elements or element ids.
                if ( this._isValidCollection(el)) {
                    var ok = true;
                    for (var i=0,len=el.length; i<len; ++i) {
                        ok = this.on(el[i], 
                                       sType, 
                                       fn, 
                                       obj, 
                                       override) && ok;
                    }
                    return ok;

                } else if (typeof el == "string") {
                    var oEl = this.getEl(el);
                    // If the el argument is a string, we assume it is 
                    // actually the id of the element.  If the page is loaded
                    // we convert el to the actual element, otherwise we 
                    // defer attaching the event until onload event fires

                    // check to see if we need to delay hooking up the event 
                    // until after the page loads.
                    if (oEl) {
                        el = oEl;
                    } else {
                        // defer adding the event until the element is available
                        this.onAvailable(el, function() {
                           YAHOO.util.Event.on(el, sType, fn, obj, override);
                        });

                        return true;
                    }
                }

                // Element should be an html element or an array if we get 
                // here.
                if (!el) {
                    return false;
                }

                // we need to make sure we fire registered unload events 
                // prior to automatically unhooking them.  So we hang on to 
                // these instead of attaching them to the window and fire the
                // handles explicitly during our one unload event.
                if ("unload" == sType && obj !== this) {
                    unloadListeners[unloadListeners.length] =
                            [el, sType, fn, obj, override];
                    return true;
                }


                // if the user chooses to override the scope, we use the custom
                // object passed in, otherwise the executing scope will be the
                // HTML element that the event is registered on
                var scope = el;
                if (override) {
                    if (override === true) {
                        scope = obj;
                    } else {
                        scope = override;
                    }
                }

                // wrap the function so we can return the obj object when
                // the event fires;
                var wrappedFn = function(e) {
                        return fn.call(scope, YAHOO.util.Event.getEvent(e), 
                                obj);
                    };

                var li = [el, sType, fn, wrappedFn, scope];
                var index = listeners.length;
                // cache the listener so we can try to automatically unload
                listeners[index] = li;

                if (this.useLegacyEvent(el, sType)) {
                    var legacyIndex = this.getLegacyIndex(el, sType);

                    // Add a new dom0 wrapper if one is not detected for this
                    // element
                    if ( legacyIndex == -1 || 
                                el != legacyEvents[legacyIndex][0] ) {

                        legacyIndex = legacyEvents.length;
                        legacyMap[el.id + sType] = legacyIndex;

                        // cache the signature for the DOM0 event, and 
                        // include the existing handler for the event, if any
                        legacyEvents[legacyIndex] = 
                            [el, sType, el["on" + sType]];
                        legacyHandlers[legacyIndex] = [];

                        el["on" + sType] = 
                            function(e) {
                                YAHOO.util.Event.fireLegacyEvent(
                                    YAHOO.util.Event.getEvent(e), legacyIndex);
                            };
                    }

                    // add a reference to the wrapped listener to our custom
                    // stack of events
                    //legacyHandlers[legacyIndex].push(index);
                    legacyHandlers[legacyIndex].push(li);

                } else {
                    try {
                        this._simpleAdd(el, sType, wrappedFn, false);
                    } catch(e) {
                        // handle an error trying to attach an event.  If it fails
                        // we need to clean up the cache
                        this.removeListener(el, sType, fn);
                        return false;
                    }
                }

                return true;
                
            },

            /**
             * When using legacy events, the handler is routed to this object
             * so we can fire our custom listener stack.
             * @method fireLegacyEvent
             * @static
             * @private
             */
            fireLegacyEvent: function(e, legacyIndex) {
                var ok = true;

                var le = legacyHandlers[legacyIndex];
                for (var i=0,len=le.length; i<len; ++i) {
                    var li = le[i];
                    if ( li && li[this.WFN] ) {
                        var scope = li[this.ADJ_SCOPE];
                        var ret = li[this.WFN].call(scope, e);
                        ok = (ok && ret);
                    }
                }

                return ok;
            },

            /**
             * Returns the legacy event index that matches the supplied 
             * signature
             * @method getLegacyIndex
             * @static
             * @private
             */
            getLegacyIndex: function(el, sType) {
                var key = this.generateId(el) + sType;
                if (typeof legacyMap[key] == "undefined") { 
                    return -1;
                } else {
                    return legacyMap[key];
                }
            },

            /**
             * Logic that determines when we should automatically use legacy
             * events instead of DOM2 events.
             * @method useLegacyEvent
             * @static
             * @private
             */
            useLegacyEvent: function(el, sType) {
                if (!el.addEventListener && !el.attachEvent) {
                    return true;
                } else if (this.isSafari) {
                    if ("click" == sType || "dblclick" == sType) {
                        return true;
                    }
                }
                return false;
            },
                    
            /**
             * Removes an event handler
             *
             * @method removeListener
             *
             * @param {Object} el the html element or the id of the element to 
             * assign the event to.
             * @param {String} sType the type of event to remove.
             * @param {Function} fn the method the event invokes.  If fn is
             * undefined, then all event handlers for the type of event are 
             * removed.
             * @return {boolean} true if the unbind was successful, false 
             * otherwise.
             * @static
             */
            removeListener: function(el, sType, fn) {
                var i, len;

                // The el argument can be a string
                if (typeof el == "string") {
                    el = this.getEl(el);
                // The el argument can be an array of elements or element ids.
                } else if ( this._isValidCollection(el)) {
                    var ok = true;
                    for (i=0,len=el.length; i<len; ++i) {
                        ok = ( this.removeListener(el[i], sType, fn) && ok );
                    }
                    return ok;
                }

                if (!fn || !fn.call) {
                    //return false;
                    return this.purgeElement(el, false, sType);
                }

                if ("unload" == sType) {

                    for (i=0, len=unloadListeners.length; i<len; i++) {
                        var li = unloadListeners[i];
                        if (li && 
                            li[0] == el && 
                            li[1] == sType && 
                            li[2] == fn) {
                                unloadListeners.splice(i, 1);
                                return true;
                        }
                    }

                    return false;
                }

                var cacheItem = null;

                // The index is a hidden parameter; needed to remove it from
                // the method signature because it was tempting users to
                // try and take advantage of it, which is not possible.
                var index = arguments[3];
  
                if ("undefined" == typeof index) {
                    index = this._getCacheIndex(el, sType, fn);
                }

                if (index >= 0) {
                    cacheItem = listeners[index];
                }

                if (!el || !cacheItem) {
                    return false;
                }


                if (this.useLegacyEvent(el, sType)) {
                    var legacyIndex = this.getLegacyIndex(el, sType);
                    var llist = legacyHandlers[legacyIndex];
                    if (llist) {
                        for (i=0, len=llist.length; i<len; ++i) {
                            li = llist[i];
                            if (li && 
                                li[this.EL] == el && 
                                li[this.TYPE] == sType && 
                                li[this.FN] == fn) {
                                    llist.splice(i, 1);
                                    break;
                            }
                        }
                    }

                } else {
                    try {
                        this._simpleRemove(el, sType, cacheItem[this.WFN], false);
                    } catch(e) {
                        return false;
                    }
                }

                // removed the wrapped handler
                delete listeners[index][this.WFN];
                delete listeners[index][this.FN];
                listeners.splice(index, 1);

                return true;

            },

            /**
             * Returns the event's target element
             * @method getTarget
             * @param {Event} ev the event
             * @param {boolean} resolveTextNode when set to true the target's
             *                  parent will be returned if the target is a 
             *                  text node.  @deprecated, the text node is
             *                  now resolved automatically
             * @return {HTMLElement} the event's target
             * @static
             */
            getTarget: function(ev, resolveTextNode) {
                var t = ev.target || ev.srcElement;
                return this.resolveTextNode(t);
            },

            /**
             * In some cases, some browsers will return a text node inside
             * the actual element that was targeted.  This normalizes the
             * return value for getTarget and getRelatedTarget.
             * @method resolveTextNode
             * @param {HTMLElement} node node to resolve
             * @return {HTMLElement} the normized node
             * @static
             */
            resolveTextNode: function(node) {
                // if (node && node.nodeName && 
                        // "#TEXT" == node.nodeName.toUpperCase()) {
                if (node && 3 == node.nodeType) {
                    return node.parentNode;
                } else {
                    return node;
                }
            },

            /**
             * Returns the event's pageX
             * @method getPageX
             * @param {Event} ev the event
             * @return {int} the event's pageX
             * @static
             */
            getPageX: function(ev) {
                var x = ev.pageX;
                if (!x && 0 !== x) {
                    x = ev.clientX || 0;

                    if ( this.isIE ) {
                        x += this._getScrollLeft();
                    }
                }

                return x;
            },

            /**
             * Returns the event's pageY
             * @method getPageY
             * @param {Event} ev the event
             * @return {int} the event's pageY
             * @static
             */
            getPageY: function(ev) {
                var y = ev.pageY;
                if (!y && 0 !== y) {
                    y = ev.clientY || 0;

                    if ( this.isIE ) {
                        y += this._getScrollTop();
                    }
                }

                return y;
            },

            /**
             * Returns the pageX and pageY properties as an indexed array.
             * @method getXY
             * @param {Event} ev the event
             * @return {[x, y]} the pageX and pageY properties of the event
             * @static
             */
            getXY: function(ev) {
                return [this.getPageX(ev), this.getPageY(ev)];
            },

            /**
             * Returns the event's related target 
             * @method getRelatedTarget
             * @param {Event} ev the event
             * @return {HTMLElement} the event's relatedTarget
             * @static
             */
            getRelatedTarget: function(ev) {
                var t = ev.relatedTarget;
                if (!t) {
                    if (ev.type == "mouseout") {
                        t = ev.toElement;
                    } else if (ev.type == "mouseover") {
                        t = ev.fromElement;
                    }
                }

                return this.resolveTextNode(t);
            },

            /**
             * Returns the time of the event.  If the time is not included, the
             * event is modified using the current time.
             * @method getTime
             * @param {Event} ev the event
             * @return {Date} the time of the event
             * @static
             */
            getTime: function(ev) {
                if (!ev.time) {
                    var t = new Date().getTime();
                    try {
                        ev.time = t;
                    } catch(e) { 
                        return t;
                    }
                }

                return ev.time;
            },

            /**
             * Convenience method for stopPropagation + preventDefault
             * @method stopEvent
             * @param {Event} ev the event
             * @static
             */
            stopEvent: function(ev) {
                this.stopPropagation(ev);
                this.preventDefault(ev);
            },

            /**
             * Stops event propagation
             * @method stopPropagation
             * @param {Event} ev the event
             * @static
             */
            stopPropagation: function(ev) {
                if (ev.stopPropagation) {
                    ev.stopPropagation();
                } else {
                    ev.cancelBubble = true;
                }
            },

            /**
             * Prevents the default behavior of the event
             * @method preventDefault
             * @param {Event} ev the event
             * @static
             */
            preventDefault: function(ev) {
                if (ev.preventDefault) {
                    ev.preventDefault();
                } else {
                    ev.returnValue = false;
                }
            },
             
            /**
             * Finds the event in the window object, the caller's arguments, or
             * in the arguments of another method in the callstack.  This is
             * executed automatically for events registered through the event
             * manager, so the implementer should not normally need to execute
             * this function at all.
             * @method getEvent
             * @param {Event} e the event parameter from the handler
             * @return {Event} the event 
             * @static
             */
            getEvent: function(e) {
                var ev = e || window.event;

                if (!ev) {
                    var c = this.getEvent.caller;
                    while (c) {
                        ev = c.arguments[0];
                        if (ev && Event == ev.constructor) {
                            break;
                        }
                        c = c.caller;
                    }
                }

                return ev;
            },

            /**
             * Returns the charcode for an event
             * @method getCharCode
             * @param {Event} ev the event
             * @return {int} the event's charCode
             * @static
             */
            getCharCode: function(ev) {
                return ev.charCode || ev.keyCode || 0;
            },

            /**
             * Locating the saved event handler data by function ref
             *
             * @method _getCacheIndex
             * @static
             * @private
             */
            _getCacheIndex: function(el, sType, fn) {
                for (var i=0,len=listeners.length; i<len; ++i) {
                    var li = listeners[i];
                    if ( li                 && 
                         li[this.FN] == fn  && 
                         li[this.EL] == el  && 
                         li[this.TYPE] == sType ) {
                        return i;
                    }
                }

                return -1;
            },

            /**
             * Generates an unique ID for the element if it does not already 
             * have one.
             * @method generateId
             * @param el the element to create the id for
             * @return {string} the resulting id of the element
             * @static
             */
            generateId: function(el) {
                var id = el.id;

                if (!id) {
                    id = "yuievtautoid-" + counter;
                    ++counter;
                    el.id = id;
                }

                return id;
            },

            /**
             * We want to be able to use getElementsByTagName as a collection
             * to attach a group of events to.  Unfortunately, different 
             * browsers return different types of collections.  This function
             * tests to determine if the object is array-like.  It will also 
             * fail if the object is an array, but is empty.
             * @method _isValidCollection
             * @param o the object to test
             * @return {boolean} true if the object is array-like and populated
             * @static
             * @private
             */
            _isValidCollection: function(o) {
                // this.logger.debug(o.constructor.toString())
                // this.logger.debug(typeof o)

                return ( o                    && // o is something
                         o.length             && // o is indexed
                         typeof o != "string" && // o is not a string
                         !o.tagName           && // o is not an HTML element
                         !o.alert             && // o is not a window
                         typeof o[0] != "undefined" );

            },

            /**
             * @private
             * @property elCache
             * DOM element cache
             * @static
             */
            elCache: {},

            /**
             * We cache elements bound by id because when the unload event 
             * fires, we can no longer use document.getElementById
             * @method getEl
             * @static
             * @private
             */
            getEl: function(id) {
                return document.getElementById(id);
            },

            /**
             * Clears the element cache
             * @deprecated Elements are not cached any longer
             * @method clearCache
             * @static
             * @private
             */
            clearCache: function() { },

            /**
             * hook up any deferred listeners
             * @method _load
             * @static
             * @private
             */
            _load: function(e) {
                loadComplete = true;
                var EU = YAHOO.util.Event;
                // Remove the listener to assist with the IE memory issue, but not
                // for other browsers because FF 1.0x does not like it.
                if (this.isIE) {
                    EU._simpleRemove(window, "load", EU._load);
                }
            },

            /**
             * Polling function that runs before the onload event fires, 
             * attempting to attach to DOM Nodes as soon as they are 
             * available
             * @method _tryPreloadAttach
             * @static
             * @private
             */
            _tryPreloadAttach: function() {

                if (this.locked) {
                    return false;
                }

                this.locked = true;


                // keep trying until after the page is loaded.  We need to 
                // check the page load state prior to trying to bind the 
                // elements so that we can be certain all elements have been 
                // tested appropriately
                var tryAgain = !loadComplete;
                if (!tryAgain) {
                    tryAgain = (retryCount > 0);
                }

                // onAvailable
                var notAvail = [];
                for (var i=0,len=onAvailStack.length; i<len ; ++i) {
                    var item = onAvailStack[i];
                    if (item) {
                        var el = this.getEl(item.id);

                        if (el) {
                            // The element is available, but not necessarily ready
                            // @todo verify IE7 compatibility
                            // @todo should we test parentNode.nextSibling?
                            // @todo re-evaluate global content ready
                            if ( !item.checkReady || 
                                    loadComplete || 
                                    el.nextSibling ||
                                    (document && document.body) ) {

                                var scope = el;
                                if (item.override) {
                                    if (item.override === true) {
                                        scope = item.obj;
                                    } else {
                                        scope = item.override;
                                    }
                                }
                                item.fn.call(scope, item.obj);
                                //delete onAvailStack[i];
                                // null out instead of delete for Opera
                                onAvailStack[i] = null;
                            }
                        } else {
                            notAvail.push(item);
                        }
                    }
                }

                retryCount = (notAvail.length === 0) ? 0 : retryCount - 1;

                if (tryAgain) {
                    // we may need to strip the nulled out items here
                    this.startInterval();
                } else {
                    clearInterval(this._interval);
                    this._interval = null;
                }

                this.locked = false;

                return true;

            },

            /**
             * Removes all listeners attached to the given element via addListener.
             * Optionally, the node's children can also be purged.
             * Optionally, you can specify a specific type of event to remove.
             * @method purgeElement
             * @param {HTMLElement} el the element to purge
             * @param {boolean} recurse recursively purge this element's children
             * as well.  Use with caution.
             * @param {string} sType optional type of listener to purge. If
             * left out, all listeners will be removed
             * @static
             */
            purgeElement: function(el, recurse, sType) {
                var elListeners = this.getListeners(el, sType);
                if (elListeners) {
                    for (var i=0,len=elListeners.length; i<len ; ++i) {
                        var l = elListeners[i];
                        // can't use the index on the changing collection
                        //this.removeListener(el, l.type, l.fn, l.index);
                        this.removeListener(el, l.type, l.fn);
                    }
                }

                if (recurse && el && el.childNodes) {
                    for (i=0,len=el.childNodes.length; i<len ; ++i) {
                        this.purgeElement(el.childNodes[i], recurse, sType);
                    }
                }
            },

            /**
             * Returns all listeners attached to the given element via addListener.
             * Optionally, you can specify a specific type of event to return.
             * @method getListeners
             * @param el {HTMLElement} the element to inspect 
             * @param sType {string} optional type of listener to return. If
             * left out, all listeners will be returned
             * @return {Object} the listener. Contains the following fields:
             * &nbsp;&nbsp;type:   (string)   the type of event
             * &nbsp;&nbsp;fn:     (function) the callback supplied to addListener
             * &nbsp;&nbsp;obj:    (object)   the custom object supplied to addListener
             * &nbsp;&nbsp;adjust: (boolean)  whether or not to adjust the default scope
             * &nbsp;&nbsp;index:  (int)      its position in the Event util listener cache
             * @static
             */           
            getListeners: function(el, sType) {
                var elListeners = [];
                if (listeners && listeners.length > 0) {
                    for (var i=0,len=listeners.length; i<len ; ++i) {
                        var l = listeners[i];
                        if ( l  && l[this.EL] === el && 
                                (!sType || sType === l[this.TYPE]) ) {
                            elListeners.push({
                                type:   l[this.TYPE],
                                fn:     l[this.FN],
                                obj:    l[this.OBJ],
                                adjust: l[this.ADJ_SCOPE],
                                index:  i
                            });
                        }
                    }
                }

                return (elListeners.length) ? elListeners : null;
            },

            /**
             * Removes all listeners registered by pe.event.  Called 
             * automatically during the unload event.
             * @method _unload
             * @static
             * @private
             */
            _unload: function(e) {

                var EU = YAHOO.util.Event, i, j, l, len, index;

                for (i=0,len=unloadListeners.length; i<len; ++i) {
                    l = unloadListeners[i];
                    if (l) {
                        var scope = window;
                        if (l[EU.ADJ_SCOPE]) {
                            if (l[EU.ADJ_SCOPE] === true) {
                                scope = l[EU.OBJ];
                            } else {
                                scope = l[EU.ADJ_SCOPE];
                            }
                        }
                        l[EU.FN].call(scope, EU.getEvent(e), l[EU.OBJ] );
                        unloadListeners[i] = null;
                        l=null;
                        scope=null;
                    }
                }

                unloadListeners = null;

                if (listeners && listeners.length > 0) {
                    j = listeners.length;
                    while (j) {
                        index = j-1;
                        l = listeners[index];
                        if (l) {
                            EU.removeListener(l[EU.EL], l[EU.TYPE], 
                                    l[EU.FN], index);
                        } 
                        j = j - 1;
                    }
                    l=null;

                    EU.clearCache();
                }

                for (i=0,len=legacyEvents.length; i<len; ++i) {
                    // dereference the element
                    //delete legacyEvents[i][0];
                    legacyEvents[i][0] = null;

                    // delete the array item
                    //delete legacyEvents[i];
                    legacyEvents[i] = null;
                }

                legacyEvents = null;

                EU._simpleRemove(window, "unload", EU._unload);

            },

            /**
             * Returns scrollLeft
             * @method _getScrollLeft
             * @static
             * @private
             */
            _getScrollLeft: function() {
                return this._getScroll()[1];
            },

            /**
             * Returns scrollTop
             * @method _getScrollTop
             * @static
             * @private
             */
            _getScrollTop: function() {
                return this._getScroll()[0];
            },

            /**
             * Returns the scrollTop and scrollLeft.  Used to calculate the 
             * pageX and pageY in Internet Explorer
             * @method _getScroll
             * @static
             * @private
             */
            _getScroll: function() {
                var dd = document.documentElement, db = document.body;
                if (dd && (dd.scrollTop || dd.scrollLeft)) {
                    return [dd.scrollTop, dd.scrollLeft];
                } else if (db) {
                    return [db.scrollTop, db.scrollLeft];
                } else {
                    return [0, 0];
                }
            },

            /**
             * Adds a DOM event directly without the caching, cleanup, scope adj, etc
             *
             * @method _simpleAdd
             * @param {HTMLElement} el      the element to bind the handler to
             * @param {string}      sType   the type of event handler
             * @param {function}    fn      the callback to invoke
             * @param {boolen}      capture capture or bubble phase
             * @static
             * @private
             */
            _simpleAdd: function () {
                if (window.addEventListener) {
                    return function(el, sType, fn, capture) {
                        el.addEventListener(sType, fn, (capture));
                    };
                } else if (window.attachEvent) {
                    return function(el, sType, fn, capture) {
                        el.attachEvent("on" + sType, fn);
                    };
                } else {
                    return function(){};
                }
            }(),

            /**
             * Basic remove listener
             *
             * @method _simpleRemove
             * @param {HTMLElement} el      the element to bind the handler to
             * @param {string}      sType   the type of event handler
             * @param {function}    fn      the callback to invoke
             * @param {boolen}      capture capture or bubble phase
             * @static
             * @private
             */
            _simpleRemove: function() {
                if (window.removeEventListener) {
                    return function (el, sType, fn, capture) {
                        el.removeEventListener(sType, fn, (capture));
                    };
                } else if (window.detachEvent) {
                    return function (el, sType, fn) {
                        el.detachEvent("on" + sType, fn);
                    };
                } else {
                    return function(){};
                }
            }()
        };

    }();

    (function() {
        var EU = YAHOO.util.Event;

        /**
         * YAHOO.util.Event.on is an alias for addListener
         * @method on
         * @see addListener
         * @static
         */
        EU.on = EU.addListener;

        // YAHOO.mix(EU, YAHOO.util.EventProvider.prototype);
        // EU.createEvent("DOMContentReady");
        // EU.subscribe("DOMContentReady", EU._load);

        if (document && document.body) {
            EU._load();
        } else {
            // EU._simpleAdd(document, "DOMContentLoaded", EU._load);
            EU._simpleAdd(window, "load", EU._load);
        }
        EU._simpleAdd(window, "unload", EU._unload);
        EU._tryPreloadAttach();
    })();
}

/**
 * EventProvider is designed to be used with YAHOO.augment to wrap 
 * CustomEvents in an interface that allows events to be subscribed to 
 * and fired by name.  This makes it possible for implementing code to
 * subscribe to an event that either has not been created yet, or will
 * not be created at all.
 *
 * @Class EventProvider
 */
YAHOO.util.EventProvider = function() { };

YAHOO.util.EventProvider.prototype = {

    /**
     * Private storage of custom events
     * @property __yui_events
     * @type Object[]
     * @private
     */
    __yui_events: null,

    /**
     * Private storage of custom event subscribers
     * @property __yui_subscribers
     * @type Object[]
     * @private
     */
    __yui_subscribers: null,
    
    /**
     * Subscribe to a CustomEvent by event type
     *
     * @method subscribe
     * @param p_type     {string}   the type, or name of the event
     * @param p_fn       {function} the function to exectute when the event fires
     * @param p_obj
     * @param p_obj      {Object}   An object to be passed along when the event 
     *                              fires
     * @param p_override {boolean}  If true, the obj passed in becomes the 
     *                              execution scope of the listener
     */
    subscribe: function(p_type, p_fn, p_obj, p_override) {

        this.__yui_events = this.__yui_events || {};
        var ce = this.__yui_events[p_type];

        if (ce) {
            ce.subscribe(p_fn, p_obj, p_override);
        } else {
            this.__yui_subscribers = this.__yui_subscribers || {};
            var subs = this.__yui_subscribers;
            if (!subs[p_type]) {
                subs[p_type] = [];
            }
            subs[p_type].push(
                { fn: p_fn, obj: p_obj, override: p_override } );
        }
    },

    /**
     * Unsubscribes the from the specified event
     * @method unsubscribe
     * @param p_type {string}   The type, or name of the event
     * @param p_fn   {Function} The function to execute
     * @param p_obj  {Object}   The custom object passed to subscribe (optional)
     * @return {boolean} true if the subscriber was found and detached.
     */
    unsubscribe: function(p_type, p_fn, p_obj) {
        this.__yui_events = this.__yui_events || {};
        var ce = this.__yui_events[p_type];
        if (ce) {
            return ce.unsubscribe(p_fn, p_obj);
        } else {
            return false;
        }
    },

    /**
     * Creates a new custom event of the specified type.  If a custom event
     * by that name already exists, it will not be re-created.  In either
     * case the custom event is returned. 
     *
     * @method createEvent
     *
     * @param p_type {string} the type, or name of the event
     * @param p_config {object} optional config params.  Valid properties are:
     *
     *  <ul>
     *    <li>
     *      scope: defines the default execution scope.  If not defined
     *      the default scope will be this instance.
     *    </li>
     *    <li>
     *      silent: if true, the custom event will not generate log messages.
     *      This is false by default.
     *    </li>
     *    <li>
     *      onSubscribeCallback: specifies a callback to execute when the
     *      event has a new subscriber.  This will fire immediately for
     *      each queued subscriber if any exist prior to the creation of
     *      the event.
     *    </li>
     *  </ul>
     *
     *  @return {CustomEvent} the custom event
     *
     */
    createEvent: function(p_type, p_config) {

        this.__yui_events = this.__yui_events || {};
        var opts = p_config || {};
        var events = this.__yui_events;

        if (events[p_type]) {
        } else {

            var scope  = opts.scope  || this;
            var silent = opts.silent || null;

            var ce = new YAHOO.util.CustomEvent(p_type, scope, silent,
                    YAHOO.util.CustomEvent.FLAT);
            events[p_type] = ce;

            if (opts.onSubscribeCallback) {
                ce.subscribeEvent.subscribe(opts.onSubscribeCallback);
            }

            this.__yui_subscribers = this.__yui_subscribers || {};
            var qs = this.__yui_subscribers[p_type];

            if (qs) {
                for (var i=0; i<qs.length; ++i) {
                    ce.subscribe(qs[i].fn, qs[i].obj, qs[i].override);
                }
            }
        }

        return events[p_type];
    },

   /**
     * Fire a custom event by name.  The callback functions will be executed
     * from the scope specified when the event was created, and with the 
     * following parameters:
     *   <ul>
     *   <li>The first argument fire() was executed with</li>
     *   <li>The custom object (if any) that was passed into the subscribe() 
     *       method</li>
     *   </ul>
     * @method fireEvent
     * @param p_type    {string}  the type, or name of the event
     * @param arguments {Object*} an arbitrary set of parameters to pass to 
     *                            the handler.
     * @return {boolean} the return value from CustomEvent.fire, or null if 
     *                   the custom event does not exist.
     */
    fireEvent: function(p_type, arg1, arg2, etc) {

        this.__yui_events = this.__yui_events || {};
        var ce = this.__yui_events[p_type];

        if (ce) {
            var args = [];
            for (var i=1; i<arguments.length; ++i) {
                args.push(arguments[i]);
            }
            return ce.fire.apply(ce, args);
        } else {
            return null;
        }
    },

    /**
     * Returns true if the custom event of the provided type has been created
     * with createEvent.
     * @method hasEvent
     * @param type {string} the type, or name of the event
     */
    hasEvent: function(type) {
        if (this.__yui_events) {
            if (this.__yui_events[type]) {
                return true;
            }
        }
        return false;
    }

};