gfx/layers/SampleTime.h

   1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* vim: set ts=8 sts=2 et sw=2 tw=80: */
   3 /* This Source Code Form is subject to the terms of the Mozilla Public
   4  * License, v. 2.0. If a copy of the MPL was not distributed with this
   5  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   6
   7 #ifndef mozilla_layers_SampleTime_h
   8 #define mozilla_layers_SampleTime_h
   9
  10 #include "mozilla/TimeStamp.h"
  11
  12 namespace mozilla {
  13 namespace layers {
  14
  15 /**
  16  * When compositing frames, there is usually a "sample time" associated
  17  * with the frame, which may be derived from vsync or controlled by a test.
  18  * This class encapsulates that and tracks where the sample time comes from,
  19  * as the desired behaviour may vary based on the time source.
  20  */
  21 class SampleTime {
  22  public:
  23   enum TimeType {
  24     // Uninitialized sample time.
  25     eNull,
  26     // Time comes from a vsync tick, possibly adjusted by a vsync interval.
  27     eVsync,
  28     // Time comes from a "now" timestamp
  29     eNow,
  30     // Time is set by a test
  31     eTest,
  32   };
  33
  34   SampleTime();
  35   static SampleTime FromVsync(const TimeStamp& aTime);
  36   static SampleTime FromNow();
  37   static SampleTime FromTest(const TimeStamp& aTime);
  38
  39   bool IsNull() const;
  40   TimeType Type() const;
  41   const TimeStamp& Time() const;
  42
  43   // These operators just compare the timestamps
  44   bool operator==(const SampleTime& aOther) const;
  45   bool operator!=(const SampleTime& aOther) const;
  46   bool operator<(const SampleTime& aOther) const;
  47   bool operator<=(const SampleTime& aOther) const;
  48   bool operator>(const SampleTime& aOther) const;
  49   bool operator>=(const SampleTime& aOther) const;
  50   // These return a new SampleTime with the same type as this one, but the
  51   // time adjusted by the provided TimeDuration
  52   SampleTime operator+(const TimeDuration& aDuration) const;
  53   SampleTime operator-(const TimeDuration& aDuration) const;
  54   // This just produces the time difference between the two SampleTimes,
  55   // ignoring the type.
  56   TimeDuration operator-(const SampleTime& aOther) const;
  57
  58  private:
  59   // Private constructor; use one of the static FromXXX methods instead.
  60   SampleTime(TimeType aType, const TimeStamp& aTime);
  61
  62   TimeType mType;
  63   TimeStamp mTime;
  64 };
  65
  66 }  // namespace layers
  67 }  // namespace mozilla
  68
  69 #endif  // mozilla_layers_SampleTime_h