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