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 <string>
   9
  10 #include "base/memory/weak_ptr.h"
  11 #include "base/values.h"
  12 #include "cc/base/cc_export.h"
  13
  14 namespace base {
  15 namespace debug {
  16 class TracedValue;
  17 }
  18 class SingleThreadTaskRunner;
  19 }
  20
  21 namespace cc {
  22
  23 class CC_EXPORT TimeSourceClient {
  24  public:
  25   virtual void OnTimerTick() = 0;
  26
  27  protected:
  28   virtual ~TimeSourceClient() {}
  29 };
  30
  31 // This timer implements a time source that achieves the specified interval
  32 // in face of millisecond-precision delayed callbacks and random queueing
  33 // delays. DelayBasedTimeSource uses base::TimeTicks::Now as its timebase.
  34 class CC_EXPORT DelayBasedTimeSource
  35     : public base::RefCounted<DelayBasedTimeSource> {
  36  public:
  37   static scoped_refptr<DelayBasedTimeSource> Create(
  38       base::TimeDelta interval, base::SingleThreadTaskRunner* task_runner);
  39
  40   virtual void SetClient(TimeSourceClient* client);
  41
  42   // TimeSource implementation
  43   virtual void SetTimebaseAndInterval(base::TimeTicks timebase,
  44                                       base::TimeDelta interval);
  45   base::TimeDelta Interval() const { return next_parameters_.interval; }
  46
  47   virtual base::TimeTicks SetActive(bool active);
  48   virtual bool Active() const;
  49
  50   // Get the last and next tick times. NextTickTime() returns null when
  51   // inactive.
  52   virtual base::TimeTicks LastTickTime() const;
  53   virtual base::TimeTicks NextTickTime() const;
  54
  55   // Virtual for testing.
  56   virtual base::TimeTicks Now() const;
  57
  58   virtual void AsValueInto(base::debug::TracedValue* dict) const;
  59
  60  protected:
  61   DelayBasedTimeSource(base::TimeDelta interval,
  62                        base::SingleThreadTaskRunner* task_runner);
  63   virtual ~DelayBasedTimeSource();
  64
  65   virtual std::string TypeString() const;
  66
  67   base::TimeTicks NextTickTarget(base::TimeTicks now);
  68   void PostNextTickTask(base::TimeTicks now);
  69   void OnTimerFired();
  70
  71   struct Parameters {
  72     Parameters(base::TimeDelta interval, base::TimeTicks tick_target)
  73         : interval(interval), tick_target(tick_target) {}
  74     base::TimeDelta interval;
  75     base::TimeTicks tick_target;
  76   };
  77
  78   TimeSourceClient* client_;
  79   base::TimeTicks last_tick_time_;
  80
  81   // current_parameters_ should only be written by PostNextTickTask.
  82   // next_parameters_ will take effect on the next call to PostNextTickTask.
  83   // Maintaining a pending set of parameters allows NextTickTime() to always
  84   // reflect the actual time we expect OnTimerFired to be called.
  85   Parameters current_parameters_;
  86   Parameters next_parameters_;
  87
  88   bool active_;
  89
  90   base::SingleThreadTaskRunner* task_runner_;
  91   base::WeakPtrFactory<DelayBasedTimeSource> weak_factory_;
  92
  93  private:
  94   friend class base::RefCounted<DelayBasedTimeSource>;
  95   DISALLOW_COPY_AND_ASSIGN(DelayBasedTimeSource);
  96 };
  97
  98 // DelayBasedTimeSource uses base::TimeTicks::HighResNow as its timebase.
  99 class DelayBasedTimeSourceHighRes : public DelayBasedTimeSource {
 100  public:
 101   static scoped_refptr<DelayBasedTimeSourceHighRes> Create(
 102         base::TimeDelta interval, base::SingleThreadTaskRunner* task_runner);
 103
 104   base::TimeTicks Now() const override;
 105
 106  protected:
 107   DelayBasedTimeSourceHighRes(base::TimeDelta interval,
 108                               base::SingleThreadTaskRunner* task_runner);
 109   ~DelayBasedTimeSourceHighRes() override;
 110
 111   std::string TypeString() const override;
 112
 113  private:
 114   DISALLOW_COPY_AND_ASSIGN(DelayBasedTimeSourceHighRes);
 115 };
 116
 117 }  // namespace cc
 118
 119 #endif  // CC_SCHEDULER_DELAY_BASED_TIME_SOURCE_H_