cc/scheduler/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_SCHEDULER_DELAY_BASED_TIME_SOURCE_H_
   6 #define CC_SCHEDULER_DELAY_BASED_TIME_SOURCE_H_
   7
   8 #include "base/memory/weak_ptr.h"
   9 #include "cc/base/cc_export.h"
  10 #include "cc/scheduler/time_source.h"
  11
  12 namespace cc {
  13
  14 class Thread;
  15
  16 // This timer implements a time source that achieves the specified interval
  17 // in face of millisecond-precision delayed callbacks and random queueing
  18 // delays.
  19 class CC_EXPORT DelayBasedTimeSource : public TimeSource {
  20  public:
  21   static scoped_refptr<DelayBasedTimeSource> Create(base::TimeDelta interval,
  22                                                     Thread* thread);
  23
  24   virtual void SetClient(TimeSourceClient* client) OVERRIDE;
  25
  26   // TimeSource implementation
  27   virtual void SetTimebaseAndInterval(base::TimeTicks timebase,
  28                                       base::TimeDelta interval) OVERRIDE;
  29
  30   virtual void SetActive(bool active) OVERRIDE;
  31   virtual bool Active() const OVERRIDE;
  32
  33   // Get the last and next tick times. nextTimeTime() returns null when
  34   // inactive.
  35   virtual base::TimeTicks LastTickTime() OVERRIDE;
  36   virtual base::TimeTicks NextTickTime() OVERRIDE;
  37
  38   // Virtual for testing.
  39   virtual base::TimeTicks Now() const;
  40
  41  protected:
  42   DelayBasedTimeSource(base::TimeDelta interval, Thread* thread);
  43   virtual ~DelayBasedTimeSource();
  44
  45   base::TimeTicks NextTickTarget(base::TimeTicks now);
  46   void PostNextTickTask(base::TimeTicks now);
  47   void OnTimerFired();
  48
  49   enum State {
  50     STATE_INACTIVE,
  51     STATE_STARTING,
  52     STATE_ACTIVE,
  53   };
  54
  55   struct Parameters {
  56     Parameters(base::TimeDelta interval, base::TimeTicks tick_target)
  57         : interval(interval), tick_target(tick_target) {}
  58     base::TimeDelta interval;
  59     base::TimeTicks tick_target;
  60   };
  61
  62   TimeSourceClient* client_;
  63   bool has_tick_target_;
  64   base::TimeTicks last_tick_time_;
  65
  66   // current_parameters_ should only be written by PostNextTickTask.
  67   // next_parameters_ will take effect on the next call to PostNextTickTask.
  68   // Maintaining a pending set of parameters allows NextTickTime() to always
  69   // reflect the actual time we expect OnTimerFired to be called.
  70   Parameters current_parameters_;
  71   Parameters next_parameters_;
  72
  73   State state_;
  74
  75   Thread* thread_;
  76   base::WeakPtrFactory<DelayBasedTimeSource> weak_factory_;
  77   DISALLOW_COPY_AND_ASSIGN(DelayBasedTimeSource);
  78 };
  79
  80 }  // namespace cc
  81
  82 #endif  // CC_SCHEDULER_DELAY_BASED_TIME_SOURCE_H_