widget/VsyncDispatcher.h

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
   2 /* This Source Code Form is subject to the terms of the Mozilla Public
   3  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
   4  * You can obtain one at http://mozilla.org/MPL/2.0/. */
   5
   6 #ifndef mozilla_widget_VsyncDispatcher_h
   7 #define mozilla_widget_VsyncDispatcher_h
   8
   9 #include "mozilla/DataMutex.h"
  10 #include "mozilla/TimeStamp.h"
  11 #include "nsISupportsImpl.h"
  12 #include "nsTArray.h"
  13 #include "mozilla/RefPtr.h"
  14 #include "VsyncSource.h"
  15
  16 namespace mozilla {
  17
  18 class VsyncObserver {
  19   NS_INLINE_DECL_PURE_VIRTUAL_REFCOUNTING
  20
  21  public:
  22   // The method called when a vsync occurs. Return true if some work was done.
  23   // In general, this vsync notification will occur on the hardware vsync
  24   // thread from VsyncSource. But it might also be called on PVsync ipc thread
  25   // if this notification is cross process. Thus all observer should check the
  26   // thread model before handling the real task.
  27   virtual bool NotifyVsync(const VsyncEvent& aVsync) = 0;
  28
  29  protected:
  30   VsyncObserver() = default;
  31   virtual ~VsyncObserver() = default;
  32 };  // VsyncObserver
  33
  34 // Used to dispatch vsync events in the parent process to compositors.
  35 //
  36 // When the compositor is in-process, CompositorWidgets own a
  37 // CompositorVsyncDispatcher, and directly attach the compositor's observer
  38 // to it.
  39 //
  40 // When the compositor is out-of-process, the CompositorWidgetDelegate owns
  41 // the vsync dispatcher instead. The widget receives vsync observer/unobserve
  42 // commands via IPDL, and uses this to attach a CompositorWidgetVsyncObserver.
  43 // This observer forwards vsync notifications (on the vsync thread) to a
  44 // dedicated vsync I/O thread, which then forwards the notification to the
  45 // compositor thread in the compositor process.
  46 class CompositorVsyncDispatcher final {
  47   NS_INLINE_DECL_THREADSAFE_REFCOUNTING(CompositorVsyncDispatcher)
  48
  49  public:
  50   CompositorVsyncDispatcher();
  51   explicit CompositorVsyncDispatcher(RefPtr<gfx::VsyncSource> aVsyncSource);
  52
  53   // Called on the vsync thread when a hardware vsync occurs
  54   void NotifyVsync(const VsyncEvent& aVsync);
  55
  56   void MoveToSource(const RefPtr<gfx::VsyncSource>& aVsyncSource);
  57
  58   // Compositor vsync observers must be added/removed on the compositor thread
  59   void SetCompositorVsyncObserver(VsyncObserver* aVsyncObserver);
  60   void Shutdown();
  61
  62  private:
  63   virtual ~CompositorVsyncDispatcher();
  64   void ObserveVsync(bool aEnable);
  65
  66   RefPtr<gfx::VsyncSource> mVsyncSource;
  67   Mutex mCompositorObserverLock MOZ_UNANNOTATED;
  68   RefPtr<VsyncObserver> mCompositorVsyncObserver;
  69   bool mDidShutdown;
  70 };
  71
  72 // Dispatch vsync events to various observers. This is used by:
  73 //  - Parent process refresh driver timers
  74 //  - IPC for content process refresh driver timers (VsyncParent <->
  75 //  VsyncMainChild)
  76 //  - IPC for content process worker requestAnimationFrame (VsyncParent <->
  77 //  VsyncWorkerChild)
  78 class RefreshTimerVsyncDispatcher final {
  79   NS_INLINE_DECL_THREADSAFE_REFCOUNTING(RefreshTimerVsyncDispatcher)
  80
  81  public:
  82   explicit RefreshTimerVsyncDispatcher(gfx::VsyncSource* aVsyncSource);
  83
  84   // Please check CompositorVsyncDispatcher::NotifyVsync().
  85   void NotifyVsync(const VsyncEvent& aVsync);
  86
  87   void MoveToSource(gfx::VsyncSource* aVsyncSource);
  88
  89   // Add a vsync observer to this dispatcher. This is a no-op if the observer is
  90   // already registered. Can be called from any thread.
  91   void AddVsyncObserver(VsyncObserver* aVsyncObserver);
  92
  93   // Remove a vsync observer from this dispatcher. This is a no-op if the
  94   // observer is not registered. Can be called from any thread.
  95   void RemoveVsyncObserver(VsyncObserver* aVsyncObserver);
  96
  97  private:
  98   virtual ~RefreshTimerVsyncDispatcher();
  99   void UpdateVsyncStatus();
 100   bool NeedsVsync();
 101
 102   // We need to hold a weak ref to the vsync source we belong to in order to
 103   // notify it of our vsync requirement. The vsync source holds a RefPtr to us,
 104   // so we can't hold a RefPtr back without causing a cyclic dependency.
 105   gfx::VsyncSource* mVsyncSource;
 106   DataMutex<nsTArray<RefPtr<VsyncObserver>>> mVsyncObservers;
 107 };
 108
 109 }  // namespace mozilla
 110
 111 #endif  // mozilla_widget_VsyncDispatcher_h