File: event/js/synthetic.js

/**
 * Define new DOM events that can be subscribed to from Nodes.
 *
 * @module event
 * @submodule event-synthetic
 */
var CustomEvent = Y.CustomEvent,
    DOMMap   = Y.Env.evt.dom_map,
    toArray  = Y.Array,
    YLang    = Y.Lang,
    isObject = YLang.isObject,
    isString = YLang.isString,
    isArray  = YLang.isArray,
    query    = Y.Selector.query,
    noop     = function () {};
 
/**
 * <p>The triggering mechanism used by SyntheticEvents.</p>
 *
 * <p>Implementers should not instantiate these directly.  Use the Notifier
 * provided to the event's implemented <code>on(node, sub, notifier)</code> or
 * <code>delegate(node, sub, notifier, filter)</code> methods.</p>
 *
 * @class SyntheticEvent.Notifier
 * @constructor
 * @param handle {EventHandle} the detach handle for the subscription to an
 *              internal custom event used to execute the callback passed to
 *              on(..) or delegate(..)
 * @param emitFacade {Boolean} take steps to ensure the first arg received by
 *              the subscription callback is an event facade
 * @private
 * @since 3.2.0
 */
function Notifier(handle, emitFacade) {
    this.handle     = handle;
    this.emitFacade = emitFacade;
}
 
/**
 * <p>Executes the subscription callback, passing the firing arguments as the
 * first parameters to that callback. For events that are configured with
 * emitFacade=true, it is common practice to pass the triggering DOMEventFacade
 * as the first parameter.  Barring a proper DOMEventFacade or EventFacade
 * (from a CustomEvent), a new EventFacade will be generated.  In that case, if
 * fire() is called with a simple object, it will be mixed into the facade.
 * Otherwise, the facade will be prepended to the callback parameters.</p>
 *
 * <p>For notifiers provided to delegate logic, the first argument should be an
 * object with a &quot;currentTarget&quot; property to identify what object to
 * default as 'this' in the callback.  Typically this is gleaned from the
 * DOMEventFacade or EventFacade, but if configured with emitFacade=false, an
 * object must be provided.  In that case, the object will be removed from the
 * callback parameters.</p>
 *
 * <p>Additional arguments passed during event subscription will be
 * automatically added after those passed to fire().</p>
 *
 * @method fire
 * @param {EventFacade|DOMEventFacade|any} e (see description)
 * @param {any[]} [arg*] additional arguments received by all subscriptions
 * @private
 */
Notifier.prototype.fire = function (e) {
    // first arg to delegate notifier should be an object with currentTarget
    var args     = toArray(arguments, 0, true),
        handle   = this.handle,
        ce       = handle.evt,
        sub      = handle.sub,
        thisObj  = sub.context,
        delegate = sub.filter,
        event    = e || {},
        ret;
 
    if (this.emitFacade) {
        if (!e || !e.preventDefault) {
            event = ce._getFacade();
 
            if (isObject(e) && !e.preventDefault) {
                Y.mix(event, e, true);
                args[0] = event;
            } else {
                args.unshift(event);
            }
        }
 
        event.type    = ce.type;
        event.details = args.slice();
 
        if (delegate) {
            event.container = ce.host;
        }
    } else if (delegate && isObject(e) && e.currentTarget) {
        args.shift();
    }
 
    sub.context = thisObj || event.currentTarget || ce.host;
    ret = ce.fire.apply(ce, args);
 
    // have to handle preventedFn and stoppedFn manually because
    // Notifier CustomEvents are forced to emitFacade=false
    if (e.prevented && ce.preventedFn) {
        ce.preventedFn.apply(ce, args);
    }
 
    if (e.stopped && ce.stoppedFn) {
        ce.stoppedFn.apply(ce, args);
    }
 
    sub.context = thisObj; // reset for future firing
 
    // to capture callbacks that return false to stopPropagation.
    // Useful for delegate implementations
    return ret;
};
 
/**
 * Manager object for synthetic event subscriptions to aggregate multiple synths on the
 * same node without colliding with actual DOM subscription entries in the global map of
 * DOM subscriptions.  Also facilitates proper cleanup on page unload.
 *
 * @class SynthRegistry
 * @constructor
 * @param el {HTMLElement} the DOM element
 * @param yuid {String} the yuid stamp for the element
 * @param key {String} the generated id token used to identify an event type +
 *                     element in the global DOM subscription map.
 * @private
 */
function SynthRegistry(el, yuid, key) {
    this.handles = [];
    this.el      = el;
    this.key     = key;
    this.domkey  = yuid;
}
 
SynthRegistry.prototype = {
    constructor: SynthRegistry,
 
    // A few object properties to fake the CustomEvent interface for page
    // unload cleanup.  DON'T TOUCH!
    type      : '_synth',
    fn        : noop,
    capture   : false,
 
    /**
     * Adds a subscription from the Notifier registry.
     *
     * @method register
     * @param handle {EventHandle} the subscription
     * @since 3.4.0
     */
    register: function (handle) {
        handle.evt.registry = this;
        this.handles.push(handle);
    },
 
    /**
     * Removes the subscription from the Notifier registry.
     *
     * @method _unregisterSub
     * @param sub {Subscription} the subscription
     * @since 3.4.0
     */
    unregister: function (sub) {
        var handles = this.handles,
            events = DOMMap[this.domkey],
            i;
 
        for (i = handles.length - 1; i >= 0; --i) {
            if (handles[i].sub === sub) {
                handles.splice(i, 1);
                break;
            }
        }
 
        // Clean up left over objects when there are no more subscribers.
        if (!handles.length) {
            delete events[this.key];
            if (!Y.Object.size(events)) {
                delete DOMMap[this.domkey];
            }
        }
    },
 
    /**
     * Used by the event system's unload cleanup process.  When navigating
     * away from the page, the event system iterates the global map of element
     * subscriptions and detaches everything using detachAll().  Normally,
     * the map is populated with custom events, so this object needs to
     * at least support the detachAll method to duck type its way to
     * cleanliness.
     *
     * @method detachAll
     * @private
     * @since 3.4.0
     */
    detachAll : function () {
        var handles = this.handles,
            i = handles.length;
 
        while (--i >= 0) {
            handles[i].detach();
        }
    }
};
 
/**
 * <p>Wrapper class for the integration of new events into the YUI event
 * infrastructure.  Don't instantiate this object directly, use
 * <code>Y.Event.define(type, config)</code>.  See that method for details.</p>
 *
 * <p>Properties that MAY or SHOULD be specified in the configuration are noted
 * below and in the description of <code>Y.Event.define</code>.</p>
 *
 * @class SyntheticEvent
 * @constructor
 * @param cfg {Object} Implementation pieces and configuration
 * @since 3.1.0
 * @in event-synthetic
 */
function SyntheticEvent() {
    this._init.apply(this, arguments);
}
 
Y.mix(SyntheticEvent, {
    Notifier: Notifier,
    SynthRegistry: SynthRegistry,
 
    /**
     * Returns the array of subscription handles for a node for the given event
     * type.  Passing true as the third argument will create a registry entry
     * in the event system's DOM map to host the array if one doesn't yet exist.
     *
     * @method getRegistry
     * @param node {Node} the node
     * @param type {String} the event
     * @param create {Boolean} create a registration entry to host a new array
     *                  if one doesn't exist.
     * @return {Array}
     * @static
     * @protected
     * @since 3.2.0
     */
    getRegistry: function (node, type, create) {
        var el     = node._node,
            yuid   = Y.stamp(el),
            key    = 'event:' + yuid + type + '_synth',
            events = DOMMap[yuid];
 
        if (create) {
            if (!events) {
                events = DOMMap[yuid] = {};
            }
            if (!events[key]) {
                events[key] = new SynthRegistry(el, yuid, key);
            }
        }
 
        return (events && events[key]) || null;
    },
 
    /**
     * Alternate <code>_delete()</code> method for the CustomEvent object
     * created to manage SyntheticEvent subscriptions.
     *
     * @method _deleteSub
     * @param sub {Subscription} the subscription to clean up
     * @private
     * @since 3.2.0
     */
    _deleteSub: function (sub) {
        if (sub && sub.fn) {
            var synth = this.eventDef,
                method = (sub.filter) ? 'detachDelegate' : 'detach';
 
            this._subscribers = [];
 
            if (CustomEvent.keepDeprecatedSubs) {
                this.subscribers = {};
            }
 
            synth[method](sub.node, sub, this.notifier, sub.filter);
            this.registry.unregister(sub);
 
            delete sub.fn;
            delete sub.node;
            delete sub.context;
        }
    },
 
    prototype: {
        constructor: SyntheticEvent,
 
        /**
         * Construction logic for the event.
         *
         * @method _init
         * @protected
         */
        _init: function () {
            var config = this.publishConfig || (this.publishConfig = {});
 
            // The notification mechanism handles facade creation
            this.emitFacade = ('emitFacade' in config) ?
                                config.emitFacade :
                                true;
            config.emitFacade  = false;
        },
 
        /**
         * <p>Implementers MAY provide this method definition.</p>
         *
         * <p>Implement this function if the event supports a different
         * subscription signature.  This function is used by both
         * <code>on()</code> and <code>delegate()</code>.  The second parameter
         * indicates that the event is being subscribed via
         * <code>delegate()</code>.</p>
         *
         * <p>Implementations must remove extra arguments from the args list
         * before returning.  The required args for <code>on()</code>
         * subscriptions are</p>
         * <pre><code>[type, callback, target, context, argN...]</code></pre>
         *
         * <p>The required args for <code>delegate()</code>
         * subscriptions are</p>
         *
         * <pre><code>[type, callback, target, filter, context, argN...]</code></pre>
         *
         * <p>The return value from this function will be stored on the
         * subscription in the '_extra' property for reference elsewhere.</p>
         *
         * @method processArgs
         * @param args {Array} parmeters passed to Y.on(..) or Y.delegate(..)
         * @param delegate {Boolean} true if the subscription is from Y.delegate
         * @return {any}
         */
        processArgs: noop,
 
        /**
         * <p>Implementers MAY override this property.</p>
         *
         * <p>Whether to prevent multiple subscriptions to this event that are
         * classified as being the same.  By default, this means the subscribed
         * callback is the same function.  See the <code>subMatch</code>
         * method.  Setting this to true will impact performance for high volume
         * events.</p>
         *
         * @property preventDups
         * @type {Boolean}
         * @default false
         */
        //preventDups  : false,
 
        /**
         * <p>Implementers SHOULD provide this method definition.</p>
         *
         * Implementation logic for subscriptions done via <code>node.on(type,
         * fn)</code> or <code>Y.on(type, fn, target)</code>.  This
         * function should set up the monitor(s) that will eventually fire the
         * event.  Typically this involves subscribing to at least one DOM
         * event.  It is recommended to store detach handles from any DOM
         * subscriptions to make for easy cleanup in the <code>detach</code>
         * method.  Typically these handles are added to the <code>sub</code>
         * object.  Also for SyntheticEvents that leverage a single DOM
         * subscription under the hood, it is recommended to pass the DOM event
         * object to <code>notifier.fire(e)</code>.  (The event name on the
         * object will be updated).
         *
         * @method on
         * @param node {Node} the node the subscription is being applied to
         * @param sub {Subscription} the object to track this subscription
         * @param notifier {SyntheticEvent.Notifier} call notifier.fire(..) to
         *              trigger the execution of the subscribers
         */
        on: noop,
 
        /**
         * <p>Implementers SHOULD provide this method definition.</p>
         *
         * <p>Implementation logic for detaching subscriptions done via
         * <code>node.on(type, fn)</code>.  This function should clean up any
         * subscriptions made in the <code>on()</code> phase.</p>
         *
         * @method detach
         * @param node {Node} the node the subscription was applied to
         * @param sub {Subscription} the object tracking this subscription
         * @param notifier {SyntheticEvent.Notifier} the Notifier used to
         *              trigger the execution of the subscribers
         */
        detach: noop,
 
        /**
         * <p>Implementers SHOULD provide this method definition.</p>
         *
         * <p>Implementation logic for subscriptions done via
         * <code>node.delegate(type, fn, filter)</code> or
         * <code>Y.delegate(type, fn, container, filter)</code>.  Like with
         * <code>on()</code> above, this function should monitor the environment
         * for the event being fired, and trigger subscription execution by
         * calling <code>notifier.fire(e)</code>.</p>
         *
         * <p>This function receives a fourth argument, which is the filter
         * used to identify which Node's are of interest to the subscription.
         * The filter will be either a boolean function that accepts a target
         * Node for each hierarchy level as the event bubbles, or a selector
         * string.  To translate selector strings into filter functions, use
         * <code>Y.delegate.compileFilter(filter)</code>.</p>
         *
         * @method delegate
         * @param node {Node} the node the subscription is being applied to
         * @param sub {Subscription} the object to track this subscription
         * @param notifier {SyntheticEvent.Notifier} call notifier.fire(..) to
         *              trigger the execution of the subscribers
         * @param filter {String|Function} Selector string or function that
         *              accepts an event object and returns null, a Node, or an
         *              array of Nodes matching the criteria for processing.
         * @since 3.2.0
         */
        delegate       : noop,
 
        /**
         * <p>Implementers SHOULD provide this method definition.</p>
         *
         * <p>Implementation logic for detaching subscriptions done via
         * <code>node.delegate(type, fn, filter)</code> or
         * <code>Y.delegate(type, fn, container, filter)</code>.  This function
         * should clean up any subscriptions made in the
         * <code>delegate()</code> phase.</p>
         *
         * @method detachDelegate
         * @param node {Node} the node the subscription was applied to
         * @param sub {Subscription} the object tracking this subscription
         * @param notifier {SyntheticEvent.Notifier} the Notifier used to
         *              trigger the execution of the subscribers
         * @param filter {String|Function} Selector string or function that
         *              accepts an event object and returns null, a Node, or an
         *              array of Nodes matching the criteria for processing.
         * @since 3.2.0
         */
        detachDelegate : noop,
 
        /**
         * Sets up the boilerplate for detaching the event and facilitating the
         * execution of subscriber callbacks.
         *
         * @method _on
         * @param args {Array} array of arguments passed to
         *              <code>Y.on(...)</code> or <code>Y.delegate(...)</code>
         * @param delegate {Boolean} true if called from
         * <code>Y.delegate(...)</code>
         * @return {EventHandle} the detach handle for this subscription
         * @private
         * since 3.2.0
         */
        _on: function (args, delegate) {
            var handles  = [],
                originalArgs = args.slice(),
                extra    = this.processArgs(args, delegate),
                selector = args[2],
                method   = delegate ? 'delegate' : 'on',
                nodes, handle;
 
            // Can't just use Y.all because it doesn't support window (yet?)
            nodes = (isString(selector)) ?
                query(selector) :
                toArray(selector || Y.one(Y.config.win));
 
            if (!nodes.length && isString(selector)) {
                handle = Y.on('available', function () {
                    Y.mix(handle, Y[method].apply(Y, originalArgs), true);
                }, selector);
 
                return handle;
            }
 
            Y.Array.each(nodes, function (node) {
                var subArgs = args.slice(),
                    filter;
 
                node = Y.one(node);
 
                if (node) {
                    if (delegate) {
                        filter = subArgs.splice(3, 1)[0];
                    }
 
                    // (type, fn, el, thisObj, ...) => (fn, thisObj, ...)
                    subArgs.splice(0, 4, subArgs[1], subArgs[3]);
 
                    if (!this.preventDups ||
                        !this.getSubs(node, args, null, true))
                    {
                        handles.push(this._subscribe(node, method, subArgs, extra, filter));
                    }
                }
            }, this);
 
            return (handles.length === 1) ?
                handles[0] :
                new Y.EventHandle(handles);
        },
 
        /**
         * Creates a new Notifier object for use by this event's
         * <code>on(...)</code> or <code>delegate(...)</code> implementation
         * and register the custom event proxy in the DOM system for cleanup.
         *
         * @method _subscribe
         * @param node {Node} the Node hosting the event
         * @param method {String} "on" or "delegate"
         * @param args {Array} the subscription arguments passed to either
         *              <code>Y.on(...)</code> or <code>Y.delegate(...)</code>
         *              after running through <code>processArgs(args)</code> to
         *              normalize the argument signature
         * @param extra {any} Extra data parsed from
         *              <code>processArgs(args)</code>
         * @param filter {String|Function} the selector string or function
         *              filter passed to <code>Y.delegate(...)</code> (not
         *              present when called from <code>Y.on(...)</code>)
         * @return {EventHandle}
         * @private
         * @since 3.2.0
         */
        _subscribe: function (node, method, args, extra, filter) {
            var dispatcher = new Y.CustomEvent(this.type, this.publishConfig),
                handle     = dispatcher.on.apply(dispatcher, args),
                notifier   = new Notifier(handle, this.emitFacade),
                registry   = SyntheticEvent.getRegistry(node, this.type, true),
                sub        = handle.sub;
 
            sub.node   = node;
            sub.filter = filter;
            if (extra) {
                this.applyArgExtras(extra, sub);
            }
 
            Y.mix(dispatcher, {
                eventDef     : this,
                notifier     : notifier,
                host         : node,       // I forget what this is for
                currentTarget: node,       // for generating facades
                target       : node,       // for generating facades
                el           : node._node, // For category detach
 
                _delete      : SyntheticEvent._deleteSub
            }, true);
 
            handle.notifier = notifier;
 
            registry.register(handle);
 
            // Call the implementation's "on" or "delegate" method
            this[method](node, sub, notifier, filter);
 
            return handle;
        },
 
        /**
         * <p>Implementers MAY provide this method definition.</p>
         *
         * <p>Implement this function if you want extra data extracted during
         * processArgs to be propagated to subscriptions on a per-node basis.
         * That is to say, if you call <code>Y.on('xyz', fn, xtra, 'div')</code>
         * the data returned from processArgs will be shared
         * across the subscription objects for all the divs.  If you want each
         * subscription to receive unique information, do that processing
         * here.</p>
         *
         * <p>The default implementation adds the data extracted by processArgs
         * to the subscription object as <code>sub._extra</code>.</p>
         *
         * @method applyArgExtras
         * @param extra {any} Any extra data extracted from processArgs
         * @param sub {Subscription} the individual subscription
         */
        applyArgExtras: function (extra, sub) {
            sub._extra = extra;
        },
 
        /**
         * Removes the subscription(s) from the internal subscription dispatch
         * mechanism.  See <code>SyntheticEvent._deleteSub</code>.
         *
         * @method _detach
         * @param args {Array} The arguments passed to
         *                  <code>node.detach(...)</code>
         * @private
         * @since 3.2.0
         */
        _detach: function (args) {
            // Can't use Y.all because it doesn't support window (yet?)
            // TODO: Does Y.all support window now?
            var target = args[2],
                els    = (isString(target)) ?
                            query(target) : toArray(target),
                node, i, len, handles, j;
 
            // (type, fn, el, context, filter?) => (type, fn, context, filter?)
            args.splice(2, 1);
 
            for (i = 0, len = els.length; i < len; ++i) {
                node = Y.one(els[i]);
 
                if (node) {
                    handles = this.getSubs(node, args);
 
                    if (handles) {
                        for (j = handles.length - 1; j >= 0; --j) {
                            handles[j].detach();
                        }
                    }
                }
            }
        },
 
        /**
         * Returns the detach handles of subscriptions on a node that satisfy a
         * search/filter function.  By default, the filter used is the
         * <code>subMatch</code> method.
         *
         * @method getSubs
         * @param node {Node} the node hosting the event
         * @param args {Array} the array of original subscription args passed
         *              to <code>Y.on(...)</code> (before
         *              <code>processArgs</code>
         * @param filter {Function} function used to identify a subscription
         *              for inclusion in the returned array
         * @param first {Boolean} stop after the first match (used to check for
         *              duplicate subscriptions)
         * @return {EventHandle[]} detach handles for the matching subscriptions
         */
        getSubs: function (node, args, filter, first) {
            var registry = SyntheticEvent.getRegistry(node, this.type),
                handles  = [],
                allHandles, i, len, handle;
 
            if (registry) {
                allHandles = registry.handles;
 
                if (!filter) {
                    filter = this.subMatch;
                }
 
                for (i = 0, len = allHandles.length; i < len; ++i) {
                    handle = allHandles[i];
                    if (filter.call(this, handle.sub, args)) {
                        if (first) {
                            return handle;
                        } else {
                            handles.push(allHandles[i]);
                        }
                    }
                }
            }
 
            return handles.length && handles;
        },
 
        /**
         * <p>Implementers MAY override this to define what constitutes a
         * &quot;same&quot; subscription.  Override implementations should
         * consider the lack of a comparator as a match, so calling
         * <code>getSubs()</code> with no arguments will return all subs.</p>
         *
         * <p>Compares a set of subscription arguments against a Subscription
         * object to determine if they match.  The default implementation
         * compares the callback function against the second argument passed to
         * <code>Y.on(...)</code> or <code>node.detach(...)</code> etc.</p>
         *
         * @method subMatch
         * @param sub {Subscription} the existing subscription
         * @param args {Array} the calling arguments passed to
         *                  <code>Y.on(...)</code> etc.
         * @return {Boolean} true if the sub can be described by the args
         *                  present
         * @since 3.2.0
         */
        subMatch: function (sub, args) {
            // Default detach cares only about the callback matching
            return !args[1] || sub.fn === args[1];
        }
    }
}, true);
 
Y.SyntheticEvent = SyntheticEvent;
 
/**
 * <p>Defines a new event in the DOM event system.  Implementers are
 * responsible for monitoring for a scenario whereby the event is fired.  A
 * notifier object is provided to the functions identified below.  When the
 * criteria defining the event are met, call notifier.fire( [args] ); to
 * execute event subscribers.</p>
 *
 * <p>The first parameter is the name of the event.  The second parameter is a
 * configuration object which define the behavior of the event system when the
 * new event is subscribed to or detached from.  The methods that should be
 * defined in this configuration object are <code>on</code>,
 * <code>detach</code>, <code>delegate</code>, and <code>detachDelegate</code>.
 * You are free to define any other methods or properties needed to define your
 * event.  Be aware, however, that since the object is used to subclass
 * SyntheticEvent, you should avoid method names used by SyntheticEvent unless
 * your intention is to override the default behavior.</p>
 *
 * <p>This is a list of properties and methods that you can or should specify
 * in the configuration object:</p>
 *
 * <dl>
 *   <dt><code>on</code></dt>
 *       <dd><code>function (node, subscription, notifier)</code> The
 *       implementation logic for subscription.  Any special setup you need to
 *       do to create the environment for the event being fired--E.g. native
 *       DOM event subscriptions.  Store subscription related objects and
 *       state on the <code>subscription</code> object.  When the
 *       criteria have been met to fire the synthetic event, call
 *       <code>notifier.fire(e)</code>.  See Notifier's <code>fire()</code>
 *       method for details about what to pass as parameters.</dd>
 *
 *   <dt><code>detach</code></dt>
 *       <dd><code>function (node, subscription, notifier)</code> The
 *       implementation logic for cleaning up a detached subscription. E.g.
 *       detach any DOM subscriptions added in <code>on</code>.</dd>
 *
 *   <dt><code>delegate</code></dt>
 *       <dd><code>function (node, subscription, notifier, filter)</code> The
 *       implementation logic for subscription via <code>Y.delegate</code> or
 *       <code>node.delegate</code>.  The filter is typically either a selector
 *       string or a function.  You can use
 *       <code>Y.delegate.compileFilter(selectorString)</code> to create a
 *       filter function from a selector string if needed.  The filter function
 *       expects an event object as input and should output either null, a
 *       matching Node, or an array of matching Nodes.  Otherwise, this acts
 *       like <code>on</code> DOM event subscriptions.  Store subscription
 *       related objects and information on the <code>subscription</code>
 *       object.  When the criteria have been met to fire the synthetic event,
 *       call <code>notifier.fire(e)</code> as noted above.</dd>
 *
 *   <dt><code>detachDelegate</code></dt>
 *       <dd><code>function (node, subscription, notifier)</code> The
 *       implementation logic for cleaning up a detached delegate subscription.
 *       E.g. detach any DOM delegate subscriptions added in
 *       <code>delegate</code>.</dd>
 *
 *   <dt><code>publishConfig</code></dt>
 *       <dd>(Object) The configuration object that will be used to instantiate
 *       the underlying CustomEvent. See Notifier's <code>fire</code> method
 *       for details.</dd>
 *
 *   <dt><code>processArgs</code></dt
 *       <dd>
 *          <p><code>function (argArray, fromDelegate)</code> Optional method
 *          to extract any additional arguments from the subscription
 *          signature.  Using this allows <code>on</code> or
 *          <code>delegate</code> signatures like
 *          <code>node.on(&quot;hover&quot;, overCallback,
 *          outCallback)</code>.</p>
 *          <p>When processing an atypical argument signature, make sure the
 *          args array is returned to the normal signature before returning
 *          from the function.  For example, in the &quot;hover&quot; example
 *          above, the <code>outCallback</code> needs to be <code>splice</code>d
 *          out of the array.  The expected signature of the args array for
 *          <code>on()</code> subscriptions is:</p>
 *          <pre>
 *              <code>[type, callback, target, contextOverride, argN...]</code>
 *          </pre>
 *          <p>And for <code>delegate()</code>:</p>
 *          <pre>
 *              <code>[type, callback, target, filter, contextOverride, argN...]</code>
 *          </pre>
 *          <p>where <code>target</code> is the node the event is being
 *          subscribed for.  You can see these signatures documented for
 *          <code>Y.on()</code> and <code>Y.delegate()</code> respectively.</p>
 *          <p>Whatever gets returned from the function will be stored on the
 *          <code>subscription</code> object under
 *          <code>subscription._extra</code>.</p></dd>
 *   <dt><code>subMatch</code></dt>
 *       <dd>
 *           <p><code>function (sub, args)</code>  Compares a set of
 *           subscription arguments against a Subscription object to determine
 *           if they match.  The default implementation compares the callback
 *           function against the second argument passed to
 *           <code>Y.on(...)</code> or <code>node.detach(...)</code> etc.</p>
 *       </dd>
 * </dl>
 *
 * @method define
 * @param type {String} the name of the event
 * @param config {Object} the prototype definition for the new event (see above)
 * @param force {Boolean} override an existing event (use with caution)
 * @return {SyntheticEvent} the subclass implementation instance created to
 *              handle event subscriptions of this type
 * @static
 * @for Event
 * @since 3.1.0
 * @in event-synthetic
 */
Y.Event.define = function (type, config, force) {
    var eventDef, Impl, synth;
 
    if (type && type.type) {
        eventDef = type;
        force = config;
    } else if (config) {
        eventDef = Y.merge({ type: type }, config);
    }
 
    if (eventDef) {
        if (force || !Y.Node.DOM_EVENTS[eventDef.type]) {
            Impl = function () {
                SyntheticEvent.apply(this, arguments);
            };
            Y.extend(Impl, SyntheticEvent, eventDef);
            synth = new Impl();
 
            type = synth.type;
 
            Y.Node.DOM_EVENTS[type] = Y.Env.evt.plugins[type] = {
                eventDef: synth,
 
                on: function () {
                    return synth._on(toArray(arguments));
                },
 
                delegate: function () {
                    return synth._on(toArray(arguments), true);
                },
 
                detach: function () {
                    return synth._detach(toArray(arguments));
                }
            };
 
        }
    } else if (isString(type) || isArray(type)) {
        Y.Array.each(toArray(type), function (t) {
            Y.Node.DOM_EVENTS[t] = 1;
        });
    }
 
    return synth;
};