Bug 1095242. Part 3 - Make enable/disable vsync noops if already enabled/disabled. r=kats

gfx/thebes/SoftwareVsyncSource.cpp

@@ -22,7 +22,8 @@ SoftwareVsyncSource::~SoftwareVsyncSource()
 }
 
 SoftwareDisplay::SoftwareDisplay()
-  : mCurrentTaskMonitor("SoftwareVsyncCurrentTaskMonitor")
+  : mVsyncEnabled(false)
+  , mCurrentTaskMonitor("SoftwareVsyncCurrentTaskMonitor")
 {
   // Mimic 60 fps
   MOZ_ASSERT(NS_IsMainThread());
@@ -35,22 +36,32 @@ void
 SoftwareDisplay::EnableVsync()
 {
   MOZ_ASSERT(NS_IsMainThread());
-  mozilla::MonitorAutoLock lock(mCurrentTaskMonitor);
-  mVsyncEnabled = true;
-  MOZ_ASSERT(!mVsyncThread->IsRunning());
-  MOZ_RELEASE_ASSERT(mVsyncThread->Start(), "Could not start software vsync thread");
-  mCurrentVsyncTask = NewRunnableMethod(this,
-      &SoftwareDisplay::NotifyVsync,
-      mozilla::TimeStamp::Now());
-  mVsyncThread->message_loop()->PostTask(FROM_HERE, mCurrentVsyncTask);
+  if (IsVsyncEnabled()) {
+    return;
+  }
+
+  { // scope lock
+    mozilla::MonitorAutoLock lock(mCurrentTaskMonitor);
+    mVsyncEnabled = true;
+    MOZ_ASSERT(!mVsyncThread->IsRunning());
+    MOZ_RELEASE_ASSERT(mVsyncThread->Start(), "Could not start software vsync thread");
+    mCurrentVsyncTask = NewRunnableMethod(this,
+        &SoftwareDisplay::NotifyVsync,
+        mozilla::TimeStamp::Now());
+    mVsyncThread->message_loop()->PostTask(FROM_HERE, mCurrentVsyncTask);
+  }
 }
 
 void
 SoftwareDisplay::DisableVsync()
 {
   MOZ_ASSERT(NS_IsMainThread());
+  if (!IsVsyncEnabled()) {
+    return;
+  }
+
   MOZ_ASSERT(mVsyncThread->IsRunning());
-  { // Scope lock
+  { // scope lock
     mozilla::MonitorAutoLock lock(mCurrentTaskMonitor);
     mVsyncEnabled = false;
     if (mCurrentVsyncTask) {

gfx/thebes/gfxAndroidPlatform.cpp

@@ -452,12 +452,18 @@ public:
     virtual void EnableVsync() MOZ_OVERRIDE
     {
       MOZ_ASSERT(NS_IsMainThread());
+      if (IsVsyncEnabled()) {
+        return;
+      }
       mVsyncEnabled = HwcComposer2D::GetInstance()->EnableVsync(true);
     }
 
     virtual void DisableVsync() MOZ_OVERRIDE
     {
       MOZ_ASSERT(NS_IsMainThread());
+      if (!IsVsyncEnabled()) {
+        return;
+      }
       mVsyncEnabled = HwcComposer2D::GetInstance()->EnableVsync(false);
     }
 

gfx/thebes/gfxPlatformMac.cpp

@@ -448,6 +448,9 @@ public:
     virtual void EnableVsync() MOZ_OVERRIDE
     {
       MOZ_ASSERT(NS_IsMainThread());
+      if (IsVsyncEnabled()) {
+        return;
+      }
 
       // Create a display link capable of being used with all active displays
       // TODO: See if we need to create an active DisplayLink for each monitor in multi-monitor
@@ -473,6 +476,9 @@ public:
     virtual void DisableVsync() MOZ_OVERRIDE
     {
       MOZ_ASSERT(NS_IsMainThread());
+      if (!IsVsyncEnabled()) {
+        return;
+      }
 
       // Release the display link
       if (mDisplayLink) {