Bug 1095242. Part 5: Unobserve vsync in RefreshTimerVsyncDispatcher. r=kats

widget/VsyncDispatcher.cpp

@@ -123,26 +123,61 @@ RefreshTimerVsyncDispatcher::NotifyVsync(TimeStamp aVsyncTimestamp)
 void
 RefreshTimerVsyncDispatcher::SetParentRefreshTimer(VsyncObserver* aVsyncObserver)
 {
+  MOZ_ASSERT(NS_IsMainThread());
+  { // lock scope because UpdateVsyncStatus runs on main thread and will deadlock
     MutexAutoLock lock(mRefreshTimersLock);
     mParentRefreshTimer = aVsyncObserver;
+  }
+
+  UpdateVsyncStatus();
 }
 
 void
 RefreshTimerVsyncDispatcher::AddChildRefreshTimer(VsyncObserver* aVsyncObserver)
 {
+  { // scope lock - called on pbackground thread
     MutexAutoLock lock(mRefreshTimersLock);
     MOZ_ASSERT(aVsyncObserver);
     if (!mChildRefreshTimers.Contains(aVsyncObserver)) {
       mChildRefreshTimers.AppendElement(aVsyncObserver);
     }
+  }
+
+  UpdateVsyncStatus();
 }
 
 void
 RefreshTimerVsyncDispatcher::RemoveChildRefreshTimer(VsyncObserver* aVsyncObserver)
 {
+  { // scope lock - called on pbackground thread
     MutexAutoLock lock(mRefreshTimersLock);
     MOZ_ASSERT(aVsyncObserver);
     mChildRefreshTimers.RemoveElement(aVsyncObserver);
+  }
+
+  UpdateVsyncStatus();
+}
+
+void
+RefreshTimerVsyncDispatcher::UpdateVsyncStatus()
+{
+  if (!NS_IsMainThread()) {
+    nsCOMPtr<nsIRunnable> vsyncControl = NS_NewRunnableMethod(this,
+                                           &RefreshTimerVsyncDispatcher::UpdateVsyncStatus);
+    NS_DispatchToMainThread(vsyncControl);
+    return;
+  }
+
+  gfx::VsyncSource::Display& display = gfxPlatform::GetPlatform()->GetHardwareVsync()->GetGlobalDisplay();
+  display.NotifyRefreshTimerVsyncStatus(NeedsVsync());
+}
+
+bool
+RefreshTimerVsyncDispatcher::NeedsVsync()
+{
+  MOZ_ASSERT(NS_IsMainThread());
+  MutexAutoLock lock(mRefreshTimersLock);
+  return (mParentRefreshTimer != nullptr) || !mChildRefreshTimers.IsEmpty();
 }
 
 } // namespace mozilla

widget/VsyncDispatcher.h

@@ -79,6 +79,8 @@ public:
 
 private:
   virtual ~RefreshTimerVsyncDispatcher();
+  void UpdateVsyncStatus();
+  bool NeedsVsync();
 
   Mutex mRefreshTimersLock;
   nsRefPtr<VsyncObserver> mParentRefreshTimer;