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/Mutex.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_THREADSAFE_REFCOUNTING(VsyncObserver)
  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;
  68   RefPtr<VsyncObserver> mCompositorVsyncObserver;
  69   bool mDidShutdown;
  70 };
  71
  72 // Dispatch vsync event to ipc actor parent and chrome RefreshTimer.
  73 class RefreshTimerVsyncDispatcher final {
  74   NS_INLINE_DECL_THREADSAFE_REFCOUNTING(RefreshTimerVsyncDispatcher)
  75
  76  public:
  77   explicit RefreshTimerVsyncDispatcher(gfx::VsyncSource::Display* aDisplay);
  78
  79   // Please check CompositorVsyncDispatcher::NotifyVsync().
  80   void NotifyVsync(const VsyncEvent& aVsync);
  81
  82   void MoveToDisplay(gfx::VsyncSource::Display* aDisplay);
  83
  84   // Set chrome process's RefreshTimer to this dispatcher.
  85   // This function can be called from any thread.
  86   void SetParentRefreshTimer(VsyncObserver* aVsyncObserver);
  87
  88   // Add or remove the content process' RefreshTimer to this dispatcher. This
  89   // will be a no-op for AddChildRefreshTimer() if the observer is already
  90   // registered.
  91   // These functions can be called from any thread.
  92   void AddChildRefreshTimer(VsyncObserver* aVsyncObserver);
  93   void RemoveChildRefreshTimer(VsyncObserver* aVsyncObserver);
  94
  95  private:
  96   virtual ~RefreshTimerVsyncDispatcher();
  97   void UpdateVsyncStatus();
  98   bool NeedsVsync();
  99
 100   // We need to hold a weak ref to the display we belong to in order to notify
 101   // it of our vsync requirement. The display holds a RefPtr to us, so we can't
 102   // hold a RefPtr back without causing a cyclic dependency.
 103   gfx::VsyncSource::Display* mDisplay;
 104   Mutex mRefreshTimersLock;
 105   RefPtr<VsyncObserver> mParentRefreshTimer;
 106   nsTArray<RefPtr<VsyncObserver>> mChildRefreshTimers;
 107 };
 108
 109 }  // namespace mozilla
 110
 111 #endif  // mozilla_widget_VsyncDispatcher_h