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Side by Side Diff: tools/cc-frame-viewer/src/ui/event_target.js

Issue 15736032: Remove old cc-frame-viewer now that it is upstreamed into trace_viewer (Closed) Base URL: svn://svn.chromium.org/chrome/trunk/src
Patch Set: Created 7 years, 6 months ago
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1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 /**
6 * @fileoverview This contains an implementation of the EventTarget interface
7 * as defined by DOM Level 2 Events.
8 */
9 base.exportTo('ui', function() {
10
11 /**
12 * Creates a new EventTarget. This class implements the DOM level 2
13 * EventTarget interface and can be used wherever those are used.
14 * @constructor
15 */
16 function EventTarget() {
17 }
18
19 EventTarget.prototype = {
20
21 /**
22 * Adds an event listener to the target.
23 * @param {string} type The name of the event.
24 * @param {!Function|{handleEvent:Function}} handler The handler for the
25 * event. This is called when the event is dispatched.
26 */
27 addEventListener: function(type, handler) {
28 if (!this.listeners_)
29 this.listeners_ = Object.create(null);
30 if (!(type in this.listeners_)) {
31 this.listeners_[type] = [handler];
32 } else {
33 var handlers = this.listeners_[type];
34 if (handlers.indexOf(handler) < 0)
35 handlers.push(handler);
36 }
37 },
38
39 /**
40 * Removes an event listener from the target.
41 * @param {string} type The name of the event.
42 * @param {!Function|{handleEvent:Function}} handler The handler for the
43 * event.
44 */
45 removeEventListener: function(type, handler) {
46 if (!this.listeners_)
47 return;
48 if (type in this.listeners_) {
49 var handlers = this.listeners_[type];
50 var index = handlers.indexOf(handler);
51 if (index >= 0) {
52 // Clean up if this was the last listener.
53 if (handlers.length == 1)
54 delete this.listeners_[type];
55 else
56 handlers.splice(index, 1);
57 }
58 }
59 },
60
61 /**
62 * Dispatches an event and calls all the listeners that are listening to
63 * the type of the event.
64 * @param {!cr.event.Event} event The event to dispatch.
65 * @return {boolean} Whether the default action was prevented. If someone
66 * calls preventDefault on the event object then this returns false.
67 */
68 dispatchEvent: function(event) {
69 if (!this.listeners_)
70 return true;
71
72 // Since we are using DOM Event objects we need to override some of the
73 // properties and methods so that we can emulate this correctly.
74 var self = this;
75 event.__defineGetter__('target', function() {
76 return self;
77 });
78 event.preventDefault = function() {
79 this.returnValue = false;
80 };
81
82 var type = event.type;
83 var prevented = 0;
84 if (type in this.listeners_) {
85 // Clone to prevent removal during dispatch
86 var handlers = this.listeners_[type].concat();
87 for (var i = 0, handler; handler = handlers[i]; i++) {
88 if (handler.handleEvent)
89 prevented |= handler.handleEvent.call(handler, event) === false;
90 else
91 prevented |= handler.call(this, event) === false;
92 }
93 }
94
95 return !prevented && event.returnValue;
96 }
97 };
98
99 // Export
100 return {
101 EventTarget: EventTarget
102 };
103 });
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