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/* -*- Mode: C++; tab-width: 2; 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 */
#ifndef mozilla_widget_VsyncDispatcher_h
#define mozilla_widget_VsyncDispatcher_h
#include "mozilla/DataMutex.h"
#include "mozilla/TimeStamp.h"
#include "nsISupportsImpl.h"
#include "nsTArray.h"
#include "mozilla/RefPtr.h"
#include "VsyncSource.h"
namespace mozilla {
class VsyncObserver {
// The method is called when a vsync occurs.
// In general, this vsync notification will occur on the hardware vsync
// thread from VsyncSource. But it might also be called on PVsync ipc thread
// if this notification is cross process. Thus all observer should check the
// thread model before handling the real task.
virtual void NotifyVsync(const VsyncEvent& aVsync) = 0;
VsyncObserver() = default;
virtual ~VsyncObserver() = default;
}; // VsyncObserver
class VsyncDispatcher;
// Used to dispatch vsync events in the parent process to compositors.
// When the compositor is in-process, CompositorWidgets own a
// CompositorVsyncDispatcher, and directly attach the compositor's observer
// to it.
// When the compositor is out-of-process, the CompositorWidgetDelegate owns
// the vsync dispatcher instead. The widget receives vsync observer/unobserve
// commands via IPDL, and uses this to attach a CompositorWidgetVsyncObserver.
// This observer forwards vsync notifications (on the vsync thread) to a
// dedicated vsync I/O thread, which then forwards the notification to the
// compositor thread in the compositor process.
class CompositorVsyncDispatcher final : public VsyncObserver {
NS_INLINE_DECL_THREADSAFE_REFCOUNTING(CompositorVsyncDispatcher, override)
explicit CompositorVsyncDispatcher(RefPtr<VsyncDispatcher> aVsyncDispatcher);
// Called on the vsync thread when a hardware vsync occurs
void NotifyVsync(const VsyncEvent& aVsync) override;
// Compositor vsync observers must be added/removed on the compositor thread
void SetCompositorVsyncObserver(VsyncObserver* aVsyncObserver);
void Shutdown();
virtual ~CompositorVsyncDispatcher();
void ObserveVsync(bool aEnable);
RefPtr<VsyncDispatcher> mVsyncDispatcher;
Mutex mCompositorObserverLock MOZ_UNANNOTATED;
RefPtr<VsyncObserver> mCompositorVsyncObserver;
bool mDidShutdown;
// Dispatch vsync events to various observers. This is used by:
// - CompositorVsyncDispatcher
// - Parent process refresh driver timers
// - IPC for content process refresh driver timers (VsyncParent <->
// VsyncMainChild)
// - IPC for content process worker requestAnimationFrame (VsyncParent <->
// VsyncWorkerChild)
// This class is only used in the parent process.
// There is one global vsync dispatcher which is managed by gfxPlatform.
// On Linux Wayland, there is also one vsync source and vsync dispatcher per
// widget.
// A vsync dispatcher can swap out its underlying VsyncSource. This happens, for
// example, when the layout.frame_rate pref is modified, causing us to switch
// between hardware vsync and software vsync.
class VsyncDispatcher final {
explicit VsyncDispatcher(gfx::VsyncSource* aVsyncSource);
// Please check CompositorVsyncDispatcher::NotifyVsync().
void NotifyVsync(const VsyncEvent& aVsync);
// Swap out the underlying vsync source. Can be called on any thread.
// aVsyncSource must be non-null.
void SetVsyncSource(gfx::VsyncSource* aVsyncSource);
// Always non-null.
RefPtr<gfx::VsyncSource> GetCurrentVsyncSource();
TimeDuration GetVsyncRate();
// Add a vsync observer to this dispatcher. This is a no-op if the observer is
// already registered. Can be called from any thread.
void AddVsyncObserver(VsyncObserver* aVsyncObserver);
// Remove a vsync observer from this dispatcher. This is a no-op if the
// observer is not registered. Can be called from any thread.
void RemoveVsyncObserver(VsyncObserver* aVsyncObserver);
// Add and remove an observer for vsync which can only be notified on the
// main thread. Note that keeping an observer registered means vsync will keep
// firing, which may impact power usage. So this is intended only for "short
// term" vsync observers.
// These methods must be called on the parent process main thread, and the
// observer will likewise be notified on the parent process main thread.
void AddMainThreadObserver(VsyncObserver* aObserver);
void RemoveMainThreadObserver(VsyncObserver* aObserver);
virtual ~VsyncDispatcher();
// Can be called on any thread.
void UpdateVsyncStatus();
// Can only be called on the main thread.
void NotifyMainThreadObservers(VsyncEvent aEvent);
struct State {
explicit State(gfx::VsyncSource* aVsyncSource)
: mCurrentVsyncSource(aVsyncSource) {}
State(State&&) = default;
~State() = default;
nsTArray<RefPtr<VsyncObserver>> mObservers;
nsTArray<RefPtr<VsyncObserver>> mMainThreadObservers;
VsyncId mLastVsyncIdSentToMainThread;
VsyncId mLastMainThreadProcessedVsyncId;
// Always non-null.
RefPtr<gfx::VsyncSource> mCurrentVsyncSource;
// The number of skipped vsyncs since the last non-skipped vsync.
// Reset to zero every n vsyncs, where n is given by the pref
// gfx.display.frame-rate-divisor.
int32_t mVsyncSkipCounter = 0;
bool mIsObservingVsync = false;
DataMutex<State> mState;
} // namespace mozilla
#endif // mozilla_widget_VsyncDispatcher_h