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// Copyright 2005 The Closure Library Authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS-IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
/**
* @fileoverview Implementation of EventTarget as defined by W3C DOM 2/3.
*
* @author arv@google.com (Erik Arvidsson) [Original implementation]
* @author pupius@google.com (Daniel Pupius) [Port to use goog.events]
* @see ../demos/eventtarget.html
*/
/**
* Namespace for events
*/
goog.provide('goog.events.EventTarget');
goog.require('goog.Disposable');
goog.require('goog.events');
/**
* Inherit from this class to give your object the ability to dispatch events.
* Note that this class provides event <em>sending</em> behaviour, not event
* receiving behaviour: your object will be able to broadcast events, and other
* objects will be able to listen for those events using goog.events.listen().
*
* <p>The name "EventTarget" reflects the fact that this class implements the
* <a href="http://www.w3.org/TR/DOM-Level-2-Events/events.html">
* EventTarget interface</a> as defined by W3C DOM 2/3, with a few differences:
* <ul>
* <li>Event objects do not have to implement the Event interface. An object
* is treated as an event object if it has a 'type' property.
* <li>You can use a plain string instead of an event object; an event-like
* object will be created with the 'type' set to the string value.
* </ul>
*
* <p>Unless propagation is stopped, an event dispatched by an EventTarget
* will bubble to the parent returned by <code>getParentEventTarget</code>.
* To set the parent, call <code>setParentEventTarget</code> or override
* <code>getParentEventTarget</code> in a subclass. Subclasses that don't
* support changing the parent should override the setter to throw an error.
*
* <p>Example usage:
* <pre>
* var source = new goog.events.EventTarget();
* function handleEvent(event) {
* alert('Type: ' + e.type + '\nTarget: ' + e.target);
* }
* goog.events.listen(source, 'foo', handleEvent);
* ...
* source.dispatchEvent({type: 'foo'}); // will call handleEvent
* // or source.dispatchEvent('foo');
* ...
* goog.events.unlisten(source, 'foo', handleEvent);
*
* // You can also use the Listener interface:
* var listener = {
* handleEvent: function(event) {
* ...
* }
* };
* goog.events.listen(source, 'bar', listener);
* </pre>
*
* @constructor
* @extends {goog.Disposable}
*/
goog.events.EventTarget = function() {
goog.Disposable.call(this);
};
goog.inherits(goog.events.EventTarget, goog.Disposable);
/**
* Used to tell if an event is a real event in goog.events.listen() so we don't
* get listen() calling addEventListener() and vice-versa.
* @type {boolean}
* @private
*/
goog.events.EventTarget.prototype.customEvent_ = true;
/**
* Parent event target, used during event bubbling.
* @type {goog.events.EventTarget?}
* @private
*/
goog.events.EventTarget.prototype.parentEventTarget_ = null;
/**
* Returns the parent of this event target to use for bubbling.
*
* @return {goog.events.EventTarget} The parent EventTarget or null if there
* is no parent.
*/
goog.events.EventTarget.prototype.getParentEventTarget = function() {
return this.parentEventTarget_;
};
/**
* Sets the parent of this event target to use for bubbling.
*
* @param {goog.events.EventTarget?} parent Parent EventTarget (null if none).
*/
goog.events.EventTarget.prototype.setParentEventTarget = function(parent) {
this.parentEventTarget_ = parent;
};
/**
* Adds an event listener to the event target. The same handler can only be
* added once per the type. Even if you add the same handler multiple times
* using the same type then it will only be called once when the event is
* dispatched.
*
* Supported for legacy but use goog.events.listen(src, type, handler) instead.
*
* @param {string} type The type of the event to listen for.
* @param {Function|Object} handler The function to handle the event. The
* handler can also be an object that implements the handleEvent method
* which takes the event object as argument.
* @param {boolean=} opt_capture In DOM-compliant browsers, this determines
* whether the listener is fired during the capture or bubble phase
* of the event.
* @param {Object=} opt_handlerScope Object in whose scope to call the listener.
*/
goog.events.EventTarget.prototype.addEventListener = function(
type, handler, opt_capture, opt_handlerScope) {
goog.events.listen(this, type, handler, opt_capture, opt_handlerScope);
};
/**
* Removes an event listener from the event target. The handler must be the
* same object as the one added. If the handler has not been added then
* nothing is done.
* @param {string} type The type of the event to listen for.
* @param {Function|Object} handler The function to handle the event. The
* handler can also be an object that implements the handleEvent method
* which takes the event object as argument.
* @param {boolean=} opt_capture In DOM-compliant browsers, this determines
* whether the listener is fired during the capture or bubble phase
* of the event.
* @param {Object=} opt_handlerScope Object in whose scope to call the listener.
*/
goog.events.EventTarget.prototype.removeEventListener = function(
type, handler, opt_capture, opt_handlerScope) {
goog.events.unlisten(this, type, handler, opt_capture, opt_handlerScope);
};
/**
* Dispatches an event (or event like object) and calls all listeners
* listening for events of this type. The type of the event is decided by the
* type property on the event object.
*
* If any of the listeners returns false OR calls preventDefault then this
* function will return false. If one of the capture listeners calls
* stopPropagation, then the bubble listeners won't fire.
*
* @param {string|Object|goog.events.Event} e Event object.
* @return {boolean} If anyone called preventDefault on the event object (or
* if any of the handlers returns false this will also return false.
*/
goog.events.EventTarget.prototype.dispatchEvent = function(e) {
return goog.events.dispatchEvent(this, e);
};
/**
* Unattach listeners from this object. Classes that extend EventTarget may
* need to override this method in order to remove references to DOM Elements
* and additional listeners, it should be something like this:
* <pre>
* MyClass.prototype.disposeInternal = function() {
* MyClass.superClass_.disposeInternal.call(this);
* // Dispose logic for MyClass
* };
* </pre>
* @override
* @protected
*/
goog.events.EventTarget.prototype.disposeInternal = function() {
goog.events.EventTarget.superClass_.disposeInternal.call(this);
goog.events.removeAll(this);
this.parentEventTarget_ = null;
};
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