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1// Copyright (c) 2011 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/** @fileoverview EventTracker is a simple class that manages the addition and
6 *  removal of DOM event listeners. In particular, it keeps track of all
7 *  listeners that have been added and makes it easy to remove some or all of
8 *  them without requiring all the information again. This is particularly
9 *  handy when the listener is a generated function such as a lambda or the
10 *  result of calling Function.bind.
11 */
12
13// Use an anonymous function to enable strict mode just for this file (which
14// will be concatenated with other files when embedded in Chrome)
15var EventTracker = (function() {
16  'use strict';
17
18  /**
19   *  Create an EventTracker to track a set of events.
20   *  EventTracker instances are typically tied 1:1 with other objects or
21   *  DOM elements whose listeners should be removed when the object is disposed
22   *  or the corresponding elements are removed from the DOM.
23   *  @constructor
24   */
25  function EventTracker() {
26    /**
27     *  @type {Array.<EventTracker.Entry>}
28     *  @private
29     */
30    this.listeners_ = [];
31  }
32
33  /**
34   * The type of the internal tracking entry.
35   *  @typedef {{node: !Node,
36   *            eventType: string,
37   *            listener: Function,
38   *            capture: boolean}}
39   */
40  EventTracker.Entry;
41
42  EventTracker.prototype = {
43    /**
44     * Add an event listener - replacement for Node.addEventListener.
45     * @param {!Node} node The DOM node to add a listener to.
46     * @param {string} eventType The type of event to subscribe to.
47     * @param {Function} listener The listener to add.
48     * @param {boolean} capture Whether to invoke during the capture phase.
49     */
50    add: function(node, eventType, listener, capture) {
51      var h = {
52        node: node,
53        eventType: eventType,
54        listener: listener,
55        capture: capture
56      };
57      this.listeners_.push(h);
58      node.addEventListener(eventType, listener, capture);
59    },
60
61    /**
62     * Remove any specified event listeners added with this EventTracker.
63     * @param {!Node} node The DOM node to remove a listener from.
64     * @param {string} eventType The type of event to remove.
65     */
66    remove: function(node, eventType) {
67      this.listeners_ = this.listeners_.filter(function(h) {
68        if (h.node == node && h.eventType == eventType) {
69          EventTracker.removeEventListener_(h);
70          return false;
71        }
72        return true;
73      });
74    },
75
76    /**
77     * Remove all event listeners added with this EventTracker.
78     */
79    removeAll: function() {
80      this.listeners_.forEach(EventTracker.removeEventListener_);
81      this.listeners_ = [];
82    }
83  };
84
85  /**
86   * Remove a single event listener given it's tracker entry.  It's up to the
87   * caller to ensure the entry is removed from listeners_.
88   * @param {EventTracker.Entry} h The entry describing the listener to remove.
89   * @private
90   */
91  EventTracker.removeEventListener_ = function(h) {
92    h.node.removeEventListener(h.eventType, h.listener, h.capture);
93  };
94
95  return EventTracker;
96})();
97
98