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 trace_event {
  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:
  36   static scoped_ptr<DelayBasedTimeSource> Create(
  37       base::TimeDelta interval,
  38       base::SingleThreadTaskRunner* task_runner) {
  39     return make_scoped_ptr(new DelayBasedTimeSource(interval, task_runner));
  40   }
  41
  42   virtual ~DelayBasedTimeSource();
  43
  44   virtual void SetClient(TimeSourceClient* client);
  45
  46   // TimeSource implementation
  47   virtual void SetTimebaseAndInterval(base::TimeTicks timebase,
  48                                       base::TimeDelta interval);
  49   base::TimeDelta Interval() const { return next_parameters_.interval; }
  50
  51   virtual base::TimeTicks SetActive(bool active);
  52   virtual bool Active() const;
  53
  54   // Get the last and next tick times. NextTickTime() returns null when
  55   // inactive.
  56   virtual base::TimeTicks LastTickTime() const;
  57   virtual base::TimeTicks NextTickTime() const;
  58
  59   // Virtual for testing.
  60   virtual base::TimeTicks Now() const;
  61
  62   virtual void AsValueInto(base::trace_event::TracedValue* dict) const;
  63
  64  protected:
  65   DelayBasedTimeSource(base::TimeDelta interval,
  66                        base::SingleThreadTaskRunner* task_runner);
  67
  68   virtual std::string TypeString() const;
  69
  70   base::TimeTicks NextTickTarget(base::TimeTicks now);
  71   void PostNextTickTask(base::TimeTicks now);
  72   void OnTimerFired();
  73
  74   struct Parameters {
  75     Parameters(base::TimeDelta interval, base::TimeTicks tick_target)
  76         : interval(interval), tick_target(tick_target) {}
  77     base::TimeDelta interval;
  78     base::TimeTicks tick_target;
  79   };
  80
  81   TimeSourceClient* client_;
  82   base::TimeTicks last_tick_time_;
  83
  84   // current_parameters_ should only be written by PostNextTickTask.
  85   // next_parameters_ will take effect on the next call to PostNextTickTask.
  86   // Maintaining a pending set of parameters allows NextTickTime() to always
  87   // reflect the actual time we expect OnTimerFired to be called.
  88   Parameters current_parameters_;
  89   Parameters next_parameters_;
  90
  91   bool active_;
  92
  93   base::SingleThreadTaskRunner* task_runner_;
  94   base::WeakPtrFactory<DelayBasedTimeSource> weak_factory_;
  95
  96  private:
  97   DISALLOW_COPY_AND_ASSIGN(DelayBasedTimeSource);
  98 };
  99
 100 }  // namespace cc
 101
 102 #endif  // CC_SCHEDULER_DELAY_BASED_TIME_SOURCE_H_