Index: resources/bookmark_manager/js/cr/eventtarget.js |
=================================================================== |
--- resources/bookmark_manager/js/cr/eventtarget.js (revision 0) |
+++ resources/bookmark_manager/js/cr/eventtarget.js (revision 0) |
@@ -0,0 +1,96 @@ |
+// Copyright (c) 2010 The Chromium Authors. All rights reserved. |
+// Use of this source code is governed by a BSD-style license that can be |
+// found in the LICENSE file. |
+ |
+cr.define('cr', function() { |
+ |
+ // TODO(arv): object.handleEvent |
+ |
+ function EventTarget() { |
+ } |
+ |
+ EventTarget.prototype = { |
+ |
+ /** |
+ * Adds an event listener to the target. |
+ * @param {string} type The name of the event. |
+ * @param {!Function|{handleEvent:Function}} handler The handler for the |
+ * event. This is called when the event is dispatched. |
+ */ |
+ addEventListener: function(type, handler) { |
+ if (!this.listeners_) |
+ this.listeners_ = {__proto__: null}; |
+ if (!(type in this.listeners_)) { |
+ this.listeners_[type] = [handler]; |
+ } else { |
+ var handlers = this.listeners_[type]; |
+ if (handlers.indexOf(handler) < 0) |
+ handlers.push(handler); |
+ } |
+ }, |
+ |
+ /** |
+ * Removes an event listener from the target. |
+ * @param {string} type The name of the event. |
+ * @param {!Function|{handleEvent:Function}} handler The handler for the |
+ * event. |
+ */ |
+ removeEventListener: function(type, handler) { |
+ if (!this.listeners_) |
+ return; |
+ if (type in this.listeners_) { |
+ var handlers = this.listeners_[type]; |
+ var index = handlers.indexOf(handler); |
+ if (index >= 0) { |
+ // Clean up if this was the last listener. |
+ if (handlers.length == 1) |
+ delete this.listeners_[type]; |
+ else |
+ handlers.splice(index, 1); |
+ } |
+ } |
+ }, |
+ |
+ /** |
+ * Dispatches an event and calls all the listeners that are listening to |
+ * the type of the event. |
+ * @param {!cr.event.Event} event The event to dispatch. |
+ * @return {boolean} Whether the default action was prevented. If someone |
+ * calls preventDefault on the event object then this returns false. |
+ */ |
+ dispatchEvent: function(event) { |
+ if (!this.listeners_) |
+ return true; |
+ |
+ // Since we are using DOM Event objects we need to override some of the |
+ // properties and methods so that we can emulate this correctly. |
+ var self = this; |
+ event.__defineGetter__('target', function() { |
+ return self; |
+ }); |
+ event.preventDefault = function() { |
+ this.returnValue = false; |
+ }; |
+ |
+ var type = event.type; |
+ var prevented = 0; |
+ if (type in this.listeners_) { |
+ // Clone to prevent removal during dispatch |
+ var handlers = this.listeners_[type].concat(); |
+ for (var i = 0, handler; handler = handlers[i]; i++) { |
+ if (handler.handleEvent) |
+ prevented |= handler.handleEvent.call(handler, event) === false; |
+ else |
+ prevented |= handler.call(this, event) === false; |
+ } |
+ } |
+ |
+ return !prevented && event.returnValue; |
+ } |
+ }; |
+ |
+ // Export |
+ return { |
+ EventTarget: EventTarget |
+ }; |
+}); |