third_party/WebKit/Source/core/animation/AnimationClock.cpp

   1 /*
   2  * Copyright (c) 2014, Google Inc. All rights reserved.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
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  10  *     * Redistributions in binary form must reproduce the above
  11  * copyright notice, this list of conditions and the following disclaimer
  12  * in the documentation and/or other materials provided with the
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  14  *     * Neither the name of Google Inc. nor the names of its
  15  * contributors may be used to endorse or promote products derived from
  16  * this software without specific prior written permission.
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  29  */
  30
  31 #include "config.h"
  32 #include "core/animation/AnimationClock.h"
  33
  34 #include "wtf/CurrentTime.h"
  35 #include <math.h>
  36
  37 namespace {
  38
  39 // FIXME: This is an approximation of time between frames, used when
  40 // ticking the animation clock outside of animation frame callbacks.
  41 // Ideally this would be generated by the compositor.
  42 const double approximateFrameTime = 1 / 60.0;
  43
  44 }
  45
  46 namespace blink {
  47
  48 unsigned AnimationClock::s_currentTask = 0;
  49
  50 void AnimationClock::updateTime(double time)
  51 {
  52     if (time > m_time)
  53         m_time = time;
  54     m_currentTask = s_currentTask;
  55 }
  56
  57 double AnimationClock::currentTime()
  58 {
  59     if (m_currentTask != s_currentTask) {
  60         const double currentTime = m_monotonicallyIncreasingTime();
  61         if (m_time < currentTime) {
  62             // Advance to the first estimated frame after the current time.
  63             const double frameShift = fmod(currentTime - m_time, approximateFrameTime);
  64             const double newTime = currentTime + (approximateFrameTime - frameShift);
  65             ASSERT(newTime >= currentTime);
  66             ASSERT(newTime <= currentTime + approximateFrameTime);
  67             updateTime(newTime);
  68         } else {
  69             m_currentTask = s_currentTask;
  70         }
  71     }
  72     return m_time;
  73 }
  74
  75 void AnimationClock::resetTimeForTesting(double time)
  76 {
  77     m_time = time;
  78     m_currentTask = 0;
  79     s_currentTask = 0;
  80 }
  81
  82 }