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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 // This file provides the ScrollingAction object, which scrolls a page | |
6 // from top to bottom: | |
7 // 1. var action = new __ScrollingAction(callback) | |
8 // 2. action.start(element_to_scroll) | |
9 'use strict'; | |
10 | |
11 (function() { | |
12 var MAX_SCROLL_LENGTH_PIXELS = 5000; | |
13 | |
14 var getTimeMs = (function() { | |
15 if (window.performance) | |
16 return (performance.now || | |
17 performance.mozNow || | |
18 performance.msNow || | |
19 performance.oNow || | |
20 performance.webkitNow).bind(window.performance); | |
21 else | |
22 return function() { return new Date().getTime(); }; | |
23 })(); | |
24 | |
25 var requestAnimationFrame = (function() { | |
26 return window.requestAnimationFrame || | |
27 window.webkitRequestAnimationFrame || | |
28 window.mozRequestAnimationFrame || | |
29 window.oRequestAnimationFrame || | |
30 window.msRequestAnimationFrame || | |
31 function(callback) { | |
32 window.setTimeout(callback, 1000 / 60); | |
33 }; | |
34 })().bind(window); | |
35 | |
36 /** | |
37 * Scrolls a given element down a certain amount to emulate user scrolling. | |
38 * Uses smooth scrolling capabilities provided by the platform, if available. | |
39 * @constructor | |
40 */ | |
41 function SmoothScrollDownGesture(opt_element) { | |
42 this.element_ = opt_element || document.body; | |
43 }; | |
44 | |
45 function min(a, b) { | |
46 if (a > b) { | |
47 return b; | |
48 } | |
49 return a; | |
50 }; | |
51 | |
52 function getBoundingVisibleRect(el) { | |
53 var bound = el.getBoundingClientRect(); | |
54 var rect = { top: bound.top, | |
55 left: bound.left, | |
56 width: bound.width, | |
57 height: bound.height }; | |
58 var outsideHeight = (rect.top + rect.height) - window.innerHeight; | |
59 var outsideWidth = (rect.left + rect.width) - window.innerWidth; | |
60 | |
61 if (outsideHeight > 0) { | |
62 rect.height -= outsideHeight; | |
63 } | |
64 if (outsideWidth > 0) { | |
65 rect.width -= outsideWidth; | |
66 } | |
67 return rect; | |
68 }; | |
69 | |
70 SmoothScrollDownGesture.prototype.start = function(distance, callback) { | |
71 this.callback_ = callback; | |
72 if (window.chrome && | |
73 chrome.gpuBenchmarking && | |
74 chrome.gpuBenchmarking.smoothScrollBy) { | |
75 var rect = getBoundingVisibleRect(this.element_); | |
76 chrome.gpuBenchmarking.smoothScrollBy(distance, function() { | |
77 callback(); | |
78 }, rect.left + rect.width / 2, rect.top + rect.height / 2); | |
79 return; | |
80 } | |
81 | |
82 var SCROLL_DELTA = 100; | |
83 this.element_.scrollTop += SCROLL_DELTA; | |
84 requestAnimationFrame(callback); | |
85 }; | |
86 | |
87 // This class scrolls a page from the top to the bottom once. | |
88 // | |
89 // The page is scrolled down by a set of scroll gestures. These gestures | |
90 // correspond to a reading gesture on that platform. | |
91 // | |
92 // start -> startPass_ -> ...scrolling... -> onGestureComplete_ -> | |
93 // -> startPass_ -> .. scrolling... -> onGestureComplete_ -> callback_ | |
94 function ScrollingAction(opt_callback) { | |
95 var self = this; | |
96 | |
97 this.beginMeasuringHook = function() {} | |
98 this.endMeasuringHook = function() {} | |
99 | |
100 this.callback_ = opt_callback; | |
101 } | |
102 | |
103 ScrollingAction.prototype.getRemainingScrollDistance_ = function() { | |
104 var clientHeight; | |
105 // clientHeight is "special" for the body element. | |
106 if (this.element_ == document.body) | |
107 clientHeight = window.innerHeight; | |
108 else | |
109 clientHeight = this.element_.clientHeight; | |
110 | |
111 return this.scrollHeight_ - this.element_.scrollTop - clientHeight; | |
112 } | |
113 | |
114 ScrollingAction.prototype.start = function(opt_element) { | |
115 // Assign this.element_ here instead of constructor, because the constructor | |
116 // ensures this method will be called after the document is loaded. | |
117 this.element_ = opt_element || document.body; | |
118 // Some pages load more content when you scroll to the bottom. Record | |
119 // the original element height here and only scroll to that point. | |
120 // -1 to allow for rounding errors on scaled viewports (like mobile). | |
121 this.scrollHeight_ = Math.min(MAX_SCROLL_LENGTH_PIXELS, | |
122 this.element_.scrollHeight - 1); | |
123 requestAnimationFrame(this.startPass_.bind(this)); | |
124 }; | |
125 | |
126 ScrollingAction.prototype.startPass_ = function() { | |
127 this.element_.scrollTop = 0; | |
128 | |
129 this.beginMeasuringHook(); | |
130 | |
131 this.gesture_ = new SmoothScrollDownGesture(this.element_); | |
132 this.gesture_.start(this.getRemainingScrollDistance_(), | |
133 this.onGestureComplete_.bind(this)); | |
134 }; | |
135 | |
136 ScrollingAction.prototype.getResults = function() { | |
137 return this.renderingStats_; | |
138 } | |
139 | |
140 ScrollingAction.prototype.onGestureComplete_ = function(timestamp) { | |
141 // If the scrollHeight went down, only scroll to the new scrollHeight. | |
142 // -1 to allow for rounding errors on scaled viewports (like mobile). | |
143 this.scrollHeight_ = Math.min(this.scrollHeight_, | |
144 this.element_.scrollHeight - 1); | |
145 | |
146 if (this.getRemainingScrollDistance_() > 0) { | |
147 this.gesture_.start(this.getRemainingScrollDistance_(), | |
148 this.onGestureComplete_.bind(this)); | |
149 return; | |
150 } | |
151 | |
152 this.endMeasuringHook(); | |
153 | |
154 // We're done. | |
155 if (this.callback_) | |
156 this.callback_(); | |
157 }; | |
158 | |
159 window.__ScrollingAction = ScrollingAction; | |
160 window.__ScrollingAction_GetBoundingVisibleRect = getBoundingVisibleRect; | |
161 })(); | |
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