cc/CCDelayBasedTimeSource.h

   1 // Copyright 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 #ifndef CCDelayBasedTimeSource_h
   6 #define CCDelayBasedTimeSource_h
   7
   8 #include "CCTimeSource.h"
   9 #include "CCTimer.h"
  10 #include <wtf/PassRefPtr.h>
  11
  12 namespace cc {
  13
  14 class CCThread;
  15
  16 // This timer implements a time source that achieves the specified interval
  17 // in face of millisecond-precision delayed callbacks and random queueing delays.
  18 class CCDelayBasedTimeSource : public CCTimeSource, CCTimerClient {
  19 public:
  20     static PassRefPtr<CCDelayBasedTimeSource> create(double intervalSeconds, CCThread*);
  21
  22     virtual ~CCDelayBasedTimeSource() { }
  23
  24     virtual void setClient(CCTimeSourceClient* client) OVERRIDE { m_client = client; }
  25
  26     // CCTimeSource implementation
  27     virtual void setTimebaseAndInterval(double timebase, double intervalSeconds) OVERRIDE;
  28
  29     virtual void setActive(bool) OVERRIDE;
  30     virtual bool active() const OVERRIDE { return m_state != STATE_INACTIVE; }
  31
  32     // Get the last and next tick times.
  33     virtual double lastTickTime() OVERRIDE;
  34     virtual double nextTickTimeIfActivated() OVERRIDE;
  35
  36     // CCTimerClient implementation.
  37     virtual void onTimerFired() OVERRIDE;
  38
  39     // Virtual for testing.
  40     virtual double monotonicTimeNow() const;
  41
  42 protected:
  43     CCDelayBasedTimeSource(double interval, CCThread*);
  44     double nextTickTarget(double now);
  45     void postNextTickTask(double now);
  46
  47     enum State {
  48         STATE_INACTIVE,
  49         STATE_STARTING,
  50         STATE_ACTIVE,
  51     };
  52
  53     struct Parameters {
  54         Parameters(double interval, double tickTarget)
  55             : interval(interval), tickTarget(tickTarget)
  56         { }
  57         double interval;
  58         double tickTarget;
  59     };
  60
  61     CCTimeSourceClient* m_client;
  62     bool m_hasTickTarget;
  63     double m_lastTickTime;
  64
  65     // m_currentParameters should only be written by postNextTickTask.
  66     // m_nextParameters will take effect on the next call to postNextTickTask.
  67     // Maintaining a pending set of parameters allows nextTickTime() to always
  68     // reflect the actual time we expect onTimerFired to be called.
  69     Parameters m_currentParameters;
  70     Parameters m_nextParameters;
  71
  72     State m_state;
  73     CCThread* m_thread;
  74     CCTimer m_timer;
  75 };
  76
  77 }
  78 #endif // CCDelayBasedTimeSource_h