Index: chrome/browser/resources/touch_ntp/eventtracker.js |
diff --git a/chrome/browser/resources/touch_ntp/eventtracker.js b/chrome/browser/resources/touch_ntp/eventtracker.js |
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+// Copyright (c) 2011 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. |
+ |
+/** @fileoverview EventTracker is a simple class that manages the addition and |
+ * removal of DOM event listeners. In particular, it keeps track of all |
+ * listeners that have been added and makes it easy to remove some or all of |
+ * them without requiring all the information again. This is particularly |
+ * handy when the listener is a generated function such as a lambda or the |
+ * result of calling Function.bind. The goal of this class is to make it |
+ * easier to avoid memory leaks caused by DOM<->JS cycles - removing event |
+ * listeners breakes the DOM->JS part of the cycle. |
+ */ |
+ |
+// Use an anonymous function to enable strict mode just for this file (which |
+// will be concatenated with other files when embedded in Chrome) |
+var EventTracker = (function() { |
+ 'use strict'; |
+ |
+ /** |
+ * Create an EventTracker to track a set of events. |
+ * EventTracker instances are typically tied 1:1 with other objects or |
+ * DOM elements whose listeners should be removed when the object is disposed |
+ * or the corresponding elements are removed from the DOM. |
+ * @constructor |
+ */ |
+ function EventTracker() { |
+ /** |
+ * @type {Array.<EventTracker.Entry>} |
+ * @private |
+ */ |
+ this.listeners_ = []; |
+ } |
+ |
+ /** |
+ * The type of the internal tracking entry. |
+ * @typedef {{node: !Node, |
+ * eventType: string, |
+ * listener: Function, |
+ * capture: boolean}} |
+ */ |
+ EventTracker.Entry; |
+ |
+ EventTracker.prototype = { |
+ /** |
+ * Add an event listener - replacement for Node.addEventListener. |
+ * @param {!Node} node The DOM node to add a listener to. |
+ * @param {string} eventType The type of event to subscribe to. |
+ * @param {Function} listener The listener to add. |
+ * @param {boolean} capture Whether to invoke during the capture phase. |
+ */ |
+ add: function(node, eventType, listener, capture) { |
+ var h = { |
+ node: node, |
+ eventType: eventType, |
+ listener: listener, |
+ capture: capture |
+ }; |
+ this.listeners_.push(h); |
+ node.addEventListener(eventType, listener, capture); |
+ }, |
+ |
+ /** |
+ * Remove any specified event listeners added with this EventTracker. |
+ * @param {!Node} node The DOM node to remove a listener from. |
+ * @param {string} eventType The type of event to remove. |
+ */ |
+ remove: function(node, eventType) { |
+ this.listeners_ = this.listeners_.filter(function(h) { |
+ if (h.node == node && h.eventType == eventType) { |
+ EventTracker.removeEventListener_(h); |
+ return false; |
+ } |
+ return true; |
+ }); |
+ }, |
+ |
+ /** |
+ * Remove all event listeners added with this EventTracker. |
+ */ |
+ removeAll: function() { |
+ this.listeners_.forEach(EventTracker.removeEventListener_); |
+ this.listeners_ = []; |
+ } |
+ }; |
+ |
+ /** |
+ * Remove a single event listener given it's tracker entry. It's up to the |
+ * caller to ensure the entry is removed from listeners_. |
+ * @param {EventTracker.Entry} h The entry describing the listener to remove. |
+ * @private |
+ */ |
+ EventTracker.removeEventListener_ = function(h) { |
+ h.node.removeEventListener(h.eventType, h.listener, h.capture); |
+ }; |
+ |
+ return EventTracker; |
+})(); |
+ |