1 files changed, 119 insertions, 0 deletions
diff --git a/gfx/thebes/VsyncSource.h b/gfx/thebes/VsyncSource.h
new file mode 100644
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+++ b/gfx/thebes/VsyncSource.h
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+/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * 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 GFX_VSYNCSOURCE_H
+#define GFX_VSYNCSOURCE_H
+
+#include "nsTArray.h"
+#include "mozilla/DataMutex.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/Mutex.h"
+#include "mozilla/TimeStamp.h"
+#include "nsISupportsImpl.h"
+#include "mozilla/layers/LayersTypes.h"
+
+namespace mozilla {
+class VsyncDispatcher;
+class VsyncObserver;
+struct VsyncEvent;
+
+class VsyncIdType {};
+typedef layers::BaseTransactionId<VsyncIdType> VsyncId;
+
+namespace gfx {
+
+// Controls how and when to enable/disable vsync. Lives as long as the
+// gfxPlatform does on the parent process
+class VsyncSource {
+  NS_INLINE_DECL_THREADSAFE_REFCOUNTING(VsyncSource)
+
+  typedef mozilla::VsyncDispatcher VsyncDispatcher;
+
+ public:
+  VsyncSource();
+
+  // Notified when this display's vsync callback occurs, on the vsync thread
+  // Different platforms give different aVsyncTimestamp values.
+  // macOS: TimeStamp::Now() or the output time of the previous vsync
+  //        callback, whichever is older.
+  // Windows: It's messy, see gfxWindowsPlatform.
+  // Android: TODO
+  //
+  // @param aVsyncTimestamp  The time of the Vsync that just occured. Needs to
+  //     be at or before the time of the NotifyVsync call.
+  // @param aOutputTimestamp  The estimated timestamp at which drawing will
+  //     appear on the screen, if the drawing happens within a certain
+  //     (unknown) budget. Useful for Audio/Video sync. On platforms where
+  //     this timestamp is provided by the system (macOS), it is a much more
+  //     stable and consistent timing source than the time at which the vsync
+  //     callback is called.
+  virtual void NotifyVsync(const TimeStamp& aVsyncTimestamp,
+                           const TimeStamp& aOutputTimestamp);
+
+  // Can be called on any thread.
+  // Adding the same dispatcher multiple times will increment a count.
+  // This means that the sequence "Add, Add, Remove" has the same behavior as
+  // "Add, Remove, Add".
+  void AddVsyncDispatcher(VsyncDispatcher* aDispatcher);
+  void RemoveVsyncDispatcher(VsyncDispatcher* aDispatcher);
+
+  virtual TimeDuration GetVsyncRate();
+
+  // These should all only be called on the main thread
+  virtual void EnableVsync() = 0;
+  virtual void DisableVsync() = 0;
+  virtual bool IsVsyncEnabled() = 0;
+  virtual void Shutdown() = 0;
+
+  // Returns the rate of the fastest enabled VsyncSource or Nothing().
+  static Maybe<TimeDuration> GetFastestVsyncRate();
+
+ protected:
+  virtual ~VsyncSource();
+
+ private:
+  // Can be called on any thread
+  void UpdateVsyncStatus();
+
+  struct DispatcherRefWithCount {
+    // The dispatcher.
+    RefPtr<VsyncDispatcher> mDispatcher;
+    // The number of add calls minus the number of remove calls for this
+    // dispatcher. Should always be > 0 as long as this dispatcher is in
+    // mDispatchers.
+    size_t mCount = 0;
+  };
+
+  struct State {
+    // The set of VsyncDispatchers which are registered with this source.
+    // At the moment, the length of this array is always zero or one.
+    // The ability to register multiple dispatchers is not used yet; it is
+    // intended for when we have one dispatcher per widget.
+    nsTArray<DispatcherRefWithCount> mDispatchers;
+
+    // The vsync ID which we used for the last vsync event.
+    VsyncId mVsyncId;
+  };
+
+  DataMutex<State> mState;
+};
+
+}  // namespace gfx
+
+struct VsyncEvent {
+  VsyncId mId;
+  TimeStamp mTime;
+  TimeStamp mOutputTime;  // estimate
+
+  VsyncEvent(const VsyncId& aId, const TimeStamp& aVsyncTime,
+             const TimeStamp& aOutputTime)
+      : mId(aId), mTime(aVsyncTime), mOutputTime(aOutputTime) {}
+  VsyncEvent() = default;
+};
+
+}  // namespace mozilla
+
+#endif /* GFX_VSYNCSOURCE_H */