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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 http://mozilla.org/MPL/2.0/. */
+
+#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 {
+ NS_INLINE_DECL_PURE_VIRTUAL_REFCOUNTING
+
+ public:
+ // 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;
+
+ protected:
+ 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)
+
+ public:
+ 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();
+
+ private:
+ 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 {
+ NS_INLINE_DECL_THREADSAFE_REFCOUNTING(VsyncDispatcher)
+
+ public:
+ 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);
+
+ private:
+ 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