# Yahoo! UI Library

### event-custom 3.0.0

Yahoo! UI Library > event-custom > event-custom.js (source view)
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    /**
     * Custom event engine, DOM event listener abstraction layer, synthetic DOM
     * events.
     * @module event-custom
     * @submodule event-custom-base
     */

    /**
     * Return value from all subscribe operations
     * @class EventHandle
     * @constructor
     * @param evt {CustomEvent} the custom event
     * @param sub {Subscriber} the subscriber
     */

    // var onsubscribeType = "_event:onsub",
    var AFTER = 'after',
        CONFIGS = [
            'broadcast',
            'bubbles',
            'context',
            'contextFn',
            'currentTarget',
            'defaultFn',
            'details',
            'emitFacade',
            'fireOnce',
            'host',
            'preventable',
            'preventedFn',
            'queuable',
            'silent',
            'stoppedFn',
            'target',
            'type'
        ],

        YUI3_SIGNATURE = 9,
        YUI_LOG = 'yui:log';

    Y.EventHandle = function(evt, sub) {

        /**
         * The custom event
         * @type CustomEvent
         */
        this.evt = evt;

        /**
         * The subscriber object
         * @type Subscriber
         */
        this.sub = sub;
    };

    Y.EventHandle.prototype = {

        /**
         * Detaches this subscriber
         * @method detach
         */
        detach: function() {
            var evt = this.evt, i;
            if (evt) {
                // Y.log('EventHandle.detach: ' + this.sub, 'info', 'Event');
                if (Y.Lang.isArray(evt)) {
                    for (i=0; i<evt.length; i++) {
                        evt[i].detach();
                    }
                } else {
                    evt._delete(this.sub);
                }
            }
        }
    };

    /**
     * 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 o configuration object
     * @class CustomEvent
     * @constructor
     */
    Y.CustomEvent = function(type, o) {

        // if (arguments.length > 2) {
    // this.log('CustomEvent context and silent are now in the config', 'warn', 'Event');
        // }

        o = o || {};

        this.id = Y.stamp(this);

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

        /**
         * The context the the event will fire from by default.  Defaults to the YUI
         * instance.
         * @property context
         * @type object
         */
        this.context = Y;

        this.logSystem = (type == YUI_LOG);

        /**
         * If 0, this event does not broadcast.  If 1, the YUI instance is notified
         * every time this event fires.  If 2, the YUI instance and the YUI global
         * (if event is enabled on the global) are notified every time this event
         * fires.
         * @property broadcast
         * @type int
         */
        // this.broadcast = 0;

        /**
         * 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 = this.logSystem;

        /**
         * Specifies whether this event should be queued when the host is actively
         * processing an event.  This will effect exectution order of the callbacks
         * for the various events.
         * @property queuable
         * @type boolean
         * @default false
         */
        // this.queuable = false;

        /**
         * The subscribers to this event
         * @property subscribers
         * @type Subscriber{}
         */
        this.subscribers = {};

        /**
         * 'After' subscribers
         * @property afters
         * @type Subscriber{}
         */
        this.afters = {};

        /**
         * This event has fired if true
         *
         * @property fired
         * @type boolean
         * @default false;
         */
        // this.fired = false;

        /**
         * An array containing the arguments the custom event
         * was last fired with.
         * @property firedWith
         * @type Array
         */
        // this.firedWith;

        /**
         * This event should only fire one time if true, and if
         * it has fired, any new subscribers should be notified
         * immediately.
         *
         * @property fireOnce
         * @type boolean
         * @default false;
         */
        // this.fireOnce = false;

        /**
         * Flag for stopPropagation that is modified during fire()
         * 1 means to stop propagation to bubble targets.  2 means
         * to also stop additional subscribers on this target.
         * @property stopped
         * @type int
         */
        // this.stopped = 0;

        /**
         * Flag for preventDefault that is modified during fire().
         * if it is not 0, the default behavior for this event
         * @property prevented
         * @type int
         */
        // this.prevented = 0;

        /**
         * Specifies the host for this custom event.  This is used
         * to enable event bubbling
         * @property host
         * @type EventTarget
         */
        // this.host = null;

        /**
         * The default function to execute after event listeners
         * have fire, but only if the default action was not
         * prevented.
         * @property defaultFn
         * @type Function
         */
        // this.defaultFn = null;

        /**
         * The function to execute if a subscriber calls
         * stopPropagation or stopImmediatePropagation
         * @property stoppedFn
         * @type Function
         */
        // this.stoppedFn = null;

        /**
         * The function to execute if a subscriber calls
         * preventDefault
         * @property preventedFn
         * @type Function
         */
        // this.preventedFn = null;

        /**
         * Specifies whether or not this event's default function
         * can be cancelled by a subscriber by executing preventDefault()
         * on the event facade
         * @property preventable
         * @type boolean
         * @default true
         */
        this.preventable = true;

        /**
         * Specifies whether or not a subscriber can stop the event propagation
         * via stopPropagation(), stopImmediatePropagation(), or halt()
         * @property bubbles
         * @type boolean
         * @default true
         */
        this.bubbles = true;

        /**
         * Supports multiple options for listener signatures in order to
         * port YUI 2 apps.
         * @property signature
         * @type int
         * @default 9
         */
        this.signature = YUI3_SIGNATURE;

        // this.hasSubscribers = false;

        // this.hasAfters = false;

        /**
         * If set to true, the custom event will deliver an EventFacade object
         * that is similar to a DOM event object.
         * @property emitFacade
         * @type boolean
         * @default false
         */
        // this.emitFacade = false;

        this.applyConfig(o, true);

        // this.log("Creating " + this.type);

    };

    Y.CustomEvent.prototype = {

        /**
         * Apply configuration properties.  Only applies the CONFIG whitelist
         * @method applyConfig
         * @param o hash of properties to apply
         * @param force {boolean} if true, properties that exist on the event
         * will be overwritten.
         */
        applyConfig: function(o, force) {
            if (o) {
                Y.mix(this, o, force, CONFIGS);
            }
        },

        _on: function(fn, context, args, when) {

            if (!fn) {
                this.log("Invalid callback for CE: " + this.type);
            }

            var s = new Y.Subscriber(fn, context, args, when);

            if (this.fireOnce && this.fired) {
                Y.later(0, this, Y.bind(this._notify, this, s, this.firedWith));
            }

            if (when == AFTER) {
                this.afters[s.id] = s;
                this.hasAfters = true;
            } else {
                this.subscribers[s.id] = s;
                this.hasSubscribers = true;
            }

            return new Y.EventHandle(this, s);

        },

        /**
         * Listen for this event
         * @method subscribe
         * @param {Function} fn        The function to execute
         * @return {EventHandle|EventTarget} unsubscribe handle or a
         * chainable event target depending on the 'chain' config.
         * @deprecated use on
         */
        subscribe: function(fn, context) {
            Y.log('ce.subscribe deprecated, use "on"', 'warn', 'deprecated');
            var a = (arguments.length > 2) ? Y.Array(arguments, 2, true): null;
            return this._on(fn, context, a, true);
        },

        /**
         * Listen for this event
         * @method on
         * @param {Function} fn        The function to execute
         * @return {EventHandle|EventTarget} unsubscribe handle or a
         * chainable event target depending on the 'chain' config.
         */
        on: function(fn, context) {
            var a = (arguments.length > 2) ? Y.Array(arguments, 2, true): null;
            return this._on(fn, context, a, true);
        },

        /**
         * Listen for this event after the normal subscribers have been notified and
         * the default behavior has been applied.  If a normal subscriber prevents the
         * default behavior, it also prevents after listeners from firing.
         * @method after
         * @param {Function} fn        The function to execute
         * @return {EventHandle|EventTarget} unsubscribe handle or a
         * chainable event target depending on the 'chain' config.
         */
        after: function(fn, context) {
            var a = (arguments.length > 2) ? Y.Array(arguments, 2, true): null;
            return this._on(fn, context, a, AFTER);
        },

        /**
         * Detach listeners.
         * @method detach
         * @param {Function} fn  The subscribed function to remove, if not supplied
         *                       all will be removed
         * @param {Object}   context The context object passed to subscribe.
         * @return {int|EventTarget} returns a chainable event target
         * or the number of subscribers unsubscribed.
         */
        detach: function(fn, context) {
            // unsubscribe handle
            if (fn && fn.detach) {
                return fn.detach();
            }

            var found = 0, subs = this.subscribers, i, s;

            for (i in subs) {
                if (subs.hasOwnProperty(i)) {
                    s = subs[i];
                    if (s && (!fn || fn === s.fn)) {
                        this._delete(s);
                        found++;
                    }
                }
            }

            return found;
        },

        /**
         * Detach listeners.
         * @method unsubscribe
         * @param {Function} fn  The subscribed function to remove, if not supplied
         *                       all will be removed
         * @param {Object}   context The context object passed to subscribe.
         * @return {boolean|EventTarget} returns a chainable event target
         * or a boolean for legacy detach support.
         * @deprecated use detach
         */
        unsubscribe: function() {
            return this.detach.apply(this, arguments);
        },

        /**
         * Notify a single subscriber
         * @method _notify
         * @param s {Subscriber} the subscriber
         * @param args {Array} the arguments array to apply to the listener
         * @private
         */
        _notify: function(s, args, ef) {

            this.log(this.type + "->" + "sub: " +  s.id);

            var ret;

            ret = s.notify(args, this);

            if (false === ret || this.stopped > 1) {
                this.log(this.type + " cancelled by subscriber");
                return false;
            }

            return true;
        },

        /**
         * Logger abstraction to centralize the application of the silent flag
         * @method log
         * @param msg {string} message to log
         * @param cat {string} log category
         */
        log: function(msg, cat) {
            if (!this.silent) {
                Y.log(this.id + ': ' + msg, cat || "info", "event");
            }
        },

        /**
         * Notifies the subscribers.  The callback functions will be executed
         * from the context 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() {
            if (this.fireOnce && this.fired) {
                this.log('fireOnce event: ' + this.type + ' already fired');
                return true;
            } else {

                var args = Y.Array(arguments, 0, true);

                this.fired = true;
                this.firedWith = args;

                if (this.emitFacade) {
                    return this.fireComplex(args);
                } else {
                    return this.fireSimple(args);
                }
            }
        },

        fireSimple: function(args) {
            if (this.hasSubscribers || this.hasAfters) {
                this._procSubs(Y.merge(this.subscribers, this.afters), args);
            }
            this._broadcast(args);
            return this.stopped ? false : true;
        },

        // Requires the event-custom-complex module for full funcitonality.
        fireComplex: function(args) {
            args[0] = args[0] || {};
            return this.fireSimple(args);
        },

        _procSubs: function(subs, args, ef) {
            var s, i;
            for (i in subs) {
                if (subs.hasOwnProperty(i)) {
                    s = subs[i];
                    if (s && s.fn) {
                        if (false === this._notify(s, args, ef)) {
                            this.stopped = 2;
                        }
                        if (this.stopped == 2) {
                            return false;
                        }
                    }
                }
            }

            return true;
        },

        _broadcast: function(args) {
            if (!this.stopped && this.broadcast) {

                var a = Y.Array(args);
                a.unshift(this.type);

                if (this.host !== Y) {
                    Y.fire.apply(Y, a);
                }

                if (this.broadcast == 2) {
                    Y.Global.fire.apply(Y.Global, a);
                }
            }
        },

        /**
         * Removes all listeners
         * @method unsubscribeAll
         * @return {int} The number of listeners unsubscribed
         * @deprecated use detachAll
         */
        unsubscribeAll: function() {
            return this.detachAll.apply(this, arguments);
        },

        /**
         * Removes all listeners
         * @method detachAll
         * @return {int} The number of listeners unsubscribed
         */
        detachAll: function() {
            return this.detach();
        },

        /**
         * @method _delete
         * @param subscriber object
         * @private
         */
        _delete: function(s) {
            if (s) {
                delete s.fn;
                delete s.context;
                delete this.subscribers[s.id];
                delete this.afters[s.id];
            }
        }
    };

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

    /**
     * Stores the subscriber information to be used when the event fires.
     * @param {Function} fn       The wrapped function to execute
     * @param {Object}   context  The value of the keyword 'this' in the listener
     * @param {Array} args*       0..n additional arguments to supply the listener
     *
     * @class Subscriber
     * @constructor
     */
    Y.Subscriber = function(fn, context, args) {

        /**
         * The callback that will be execute when the event fires
         * This is wrapped by Y.rbind if obj was supplied.
         * @property fn
         * @type Function
         */
        this.fn = fn;

        /**
         * Optional 'this' keyword for the listener
         * @property context
         * @type Object
         */
        this.context = context;

        /**
         * Unique subscriber id
         * @property id
         * @type String
         */
        this.id = Y.stamp(this);

        /**
         * Additional arguments to propagate to the subscriber
         * @property args
         * @type Array
         */
        this.args = args;

        /**
         * Custom events for a given fire transaction.
         * @property events
         * @type {EventTarget}
         */
        this.events = null;

    };

    Y.Subscriber.prototype = {

        _notify: function(c, args, ce) {
            var a = this.args, ret;
            switch (ce.signature) {
                case 0:
                    ret = this.fn.call(c, ce.type, args, c);
                    break;
                case 1:
                    ret = this.fn.call(c, args[0] || null, c);
                    break;
                default:
                    if (a || args) {
                        args = args || [];
                        a = (a) ? args.concat(a) : args;
                        ret = this.fn.apply(c, a);
                    } else {
                        ret = this.fn.call(c);
                    }
            }

            return ret;
        },

        /**
         * Executes the subscriber.
         * @method notify
         * @param args {Array} Arguments array for the subscriber
         * @param ce {CustomEvent} The custom event that sent the notification
         */
        notify: function(args, ce) {
            var c = this.context,
                ret = true;

            if (!c) {
                c = (ce.contextFn) ? ce.contextFn() : ce.context;
            }

            // only catch errors if we will not re-throw them.
            if (Y.config.throwFail) {
                ret = this._notify(c, args, ce);
            } else {
                try {
                    ret = this._notify(c, args, ce);
                } catch(e) {
                    Y.error(this + ' failed: ' + e.message, e);
                }
            }

            return ret;
        },

        /**
         * 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} context optional 'this' keyword for the listener
         * @return {boolean} true if the supplied arguments match this
         *                   subscriber's signature.
         */
        contains: function(fn, context) {
            if (context) {
                return ((this.fn == fn) && this.context == context);
            } else {
                return (this.fn == fn);
            }
        }

    };

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