1 files changed, 69 insertions, 0 deletions
diff --git a/gfx/layers/SampleTime.h b/gfx/layers/SampleTime.h
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+++ b/gfx/layers/SampleTime.h
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_layers_SampleTime_h
+#define mozilla_layers_SampleTime_h
+
+#include "mozilla/TimeStamp.h"
+
+namespace mozilla {
+namespace layers {
+
+/**
+ * When compositing frames, there is usually a "sample time" associated
+ * with the frame, which may be derived from vsync or controlled by a test.
+ * This class encapsulates that and tracks where the sample time comes from,
+ * as the desired behaviour may vary based on the time source.
+ */
+class SampleTime {
+ public:
+  enum TimeType {
+    // Uninitialized sample time.
+    eNull,
+    // Time comes from a vsync tick, possibly adjusted by a vsync interval.
+    eVsync,
+    // Time comes from a "now" timestamp
+    eNow,
+    // Time is set by a test
+    eTest,
+  };
+
+  SampleTime();
+  static SampleTime FromVsync(const TimeStamp& aTime);
+  static SampleTime FromNow();
+  static SampleTime FromTest(const TimeStamp& aTime);
+
+  bool IsNull() const;
+  TimeType Type() const;
+  const TimeStamp& Time() const;
+
+  // These operators just compare the timestamps
+  bool operator==(const SampleTime& aOther) const;
+  bool operator!=(const SampleTime& aOther) const;
+  bool operator<(const SampleTime& aOther) const;
+  bool operator<=(const SampleTime& aOther) const;
+  bool operator>(const SampleTime& aOther) const;
+  bool operator>=(const SampleTime& aOther) const;
+  // These return a new SampleTime with the same type as this one, but the
+  // time adjusted by the provided TimeDuration
+  SampleTime operator+(const TimeDuration& aDuration) const;
+  SampleTime operator-(const TimeDuration& aDuration) const;
+  // This just produces the time difference between the two SampleTimes,
+  // ignoring the type.
+  TimeDuration operator-(const SampleTime& aOther) const;
+
+ private:
+  // Private constructor; use one of the static FromXXX methods instead.
+  SampleTime(TimeType aType, const TimeStamp& aTime);
+
+  TimeType mType;
+  TimeStamp mTime;
+};
+
+}  // namespace layers
+}  // namespace mozilla
+
+#endif  // mozilla_layers_SampleTime_h