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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 */
#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 {
typedef mozilla::VsyncDispatcher VsyncDispatcher;
// 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();
virtual ~VsyncSource();
// 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 */