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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)
     15 var 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 && (!eventType || (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