Refactor ImageHost to allow acquiring the current TextureSource without locking the underlying TextureHost. (bug 1365879 part 8, r=mattwoodrow)

gfx/layers/composite/ImageHost.cpp

@@ -195,23 +195,12 @@ ImageHost::Composite(Compositor* aCompositor,
                      const nsIntRegion* aVisibleRegion,
                      const Maybe<gfx::Polygon>& aGeometry)
 {
-  HostLayerManager* lm = GetLayerManager();
-  if (!lm) {
+  RenderInfo info;
+  if (!PrepareToRender(aCompositor, &info)) {
     return;
   }
 
-  int imageIndex = ChooseImageIndex();
-  if (imageIndex < 0) {
-    return;
-  }
-
-  if (uint32_t(imageIndex) + 1 < mImages.Length()) {
-    lm->CompositeUntil(mImages[imageIndex + 1].mTimeStamp + TimeDuration::FromMilliseconds(BIAS_TIME_MS));
-  }
-
-  TimedImage* img = &mImages[imageIndex];
-  img->mTextureHost->SetTextureSourceProvider(aCompositor);
-  SetCurrentTextureHost(img->mTextureHost);
+  TimedImage* img = info.img;
 
   {
     AutoLockCompositableHost autoLock(this);
@@ -250,20 +239,6 @@ ImageHost::Composite(Compositor* aCompositor,
       diagnosticFlags |= DiagnosticFlags::YCBCR;
     }
 
-    if (mLastFrameID != img->mFrameID || mLastProducerID != img->mProducerID) {
-      if (mAsyncRef) {
-        ImageCompositeNotificationInfo info;
-        info.mImageBridgeProcessId = mAsyncRef.mProcessId;
-        info.mNotification = ImageCompositeNotification(
-          mAsyncRef.mHandle,
-          img->mTimeStamp, lm->GetCompositionTime(),
-          img->mFrameID, img->mProducerID);
-        static_cast<LayerManagerComposite*>(aLayer->GetLayerManager())->
-            AppendImageCompositeNotification(info);
-      }
-      mLastFrameID = img->mFrameID;
-      mLastProducerID = img->mProducerID;
-    }
     aEffectChain.mPrimaryEffect = effect;
     gfx::Rect pictureRect(0, 0, img->mPictureRect.width, img->mPictureRect.height);
     BigImageIterator* it = mCurrentTextureSource->AsBigImageIterator();
@@ -327,6 +302,67 @@ ImageHost::Composite(Compositor* aCompositor,
     }
   }
 
+  FinishRendering(info);
+}
+
+bool
+ImageHost::PrepareToRender(TextureSourceProvider* aProvider, RenderInfo* aOutInfo)
+{
+  HostLayerManager* lm = GetLayerManager();
+  if (!lm) {
+    return false;
+  }
+
+  int imageIndex = ChooseImageIndex();
+  if (imageIndex < 0) {
+    return false;
+  }
+
+  if (uint32_t(imageIndex) + 1 < mImages.Length()) {
+    lm->CompositeUntil(mImages[imageIndex + 1].mTimeStamp + TimeDuration::FromMilliseconds(BIAS_TIME_MS));
+  }
+
+  TimedImage* img = &mImages[imageIndex];
+  img->mTextureHost->SetTextureSourceProvider(aProvider);
+  SetCurrentTextureHost(img->mTextureHost);
+
+  aOutInfo->imageIndex = imageIndex;
+  aOutInfo->img = img;
+  aOutInfo->host = mCurrentTextureHost;
+  return true;
+}
+
+RefPtr<TextureSource>
+ImageHost::AcquireTextureSource(const RenderInfo& aInfo)
+{
+  MOZ_ASSERT(aInfo.host == mCurrentTextureHost);
+  if (!aInfo.host->AcquireTextureSource(mCurrentTextureSource)) {
+    return nullptr;
+  }
+  return mCurrentTextureSource.get();
+}
+
+void
+ImageHost::FinishRendering(const RenderInfo& aInfo)
+{
+  HostLayerManager* lm = GetLayerManager();
+  TimedImage* img = aInfo.img;
+  int imageIndex = aInfo.imageIndex;
+
+  if (mLastFrameID != img->mFrameID || mLastProducerID != img->mProducerID) {
+    if (mAsyncRef) {
+      ImageCompositeNotificationInfo info;
+      info.mImageBridgeProcessId = mAsyncRef.mProcessId;
+      info.mNotification = ImageCompositeNotification(
+        mAsyncRef.mHandle,
+        img->mTimeStamp, lm->GetCompositionTime(),
+        img->mFrameID, img->mProducerID);
+      lm->AppendImageCompositeNotification(info);
+    }
+    mLastFrameID = img->mFrameID;
+    mLastProducerID = img->mProducerID;
+  }
+
   // Update mBias last. This can change which frame ChooseImage(Index) would
   // return, and we don't want to do that until we've finished compositing
   // since callers of ChooseImage(Index) assume the same image will be chosen

gfx/layers/composite/ImageHost.h

@@ -90,6 +90,31 @@ public:
 
   bool IsOpaque();
 
+  struct RenderInfo {
+    int imageIndex;
+    TimedImage* img;
+    RefPtr<TextureHost> host;
+
+    RenderInfo() : imageIndex(-1), img(nullptr)
+    {}
+  };
+
+  // Acquire rendering information for the current frame.
+  bool PrepareToRender(TextureSourceProvider* aProvider, RenderInfo* aOutInfo);
+
+  // Acquire the TextureSource for the currently prepared frame.
+  RefPtr<TextureSource> AcquireTextureSource(const RenderInfo& aInfo);
+
+  // Send ImageComposite notifications and update the ChooseImage bias.
+  void FinishRendering(const RenderInfo& aInfo);
+
+  // This should only be called inside a lock, or during rendering. It is
+  // infallible to enforce this.
+  TextureHost* CurrentTextureHost() const {
+    MOZ_ASSERT(mCurrentTextureHost);
+    return mCurrentTextureHost;
+  }
+
 protected:
   // ImageComposite
   virtual TimeStamp GetCompositionTime() const override;

gfx/layers/composite/LayerManagerComposite.cpp

@@ -1406,6 +1406,15 @@ LayerManagerComposite::AutoAddMaskEffect::~AutoAddMaskEffect()
   mCompositable->RemoveMaskEffect();
 }
 
+bool
+LayerManagerComposite::IsCompositingToScreen() const
+{
+  if (!mCompositor) {
+    return true;
+  }
+  return !mCompositor->GetTargetContext();
+}
+
 LayerComposite::LayerComposite(LayerManagerComposite *aManager)
   : HostLayer(aManager)
   , mCompositeManager(aManager)

gfx/layers/composite/LayerManagerComposite.h

@@ -132,6 +132,18 @@ public:
     aNotifications->AppendElements(Move(mImageCompositeNotifications));
   }
 
+  void AppendImageCompositeNotification(const ImageCompositeNotificationInfo& aNotification)
+  {
+    // Only send composite notifications when we're drawing to the screen,
+    // because that's what they mean.
+    // Also when we're not drawing to the screen, DidComposite will not be
+    // called to extract and send these notifications, so they might linger
+    // and contain stale ImageContainerParent pointers.
+    if (IsCompositingToScreen()) {
+      mImageCompositeNotifications.AppendElement(aNotification);
+    }
+  }
+
   /**
    * LayerManagerComposite provides sophisticated debug overlays
    * that can request a next frame.
@@ -164,6 +176,9 @@ public:
   virtual bool AlwaysScheduleComposite() const {
     return false;
   }
+  virtual bool IsCompositingToScreen() const {
+    return false;
+  }
 
   void RecordPaintTimes(const PaintTiming& aTiming);
   void RecordUpdateTime(float aValue);
@@ -290,6 +305,7 @@ public:
     CreateOptimalMaskDrawTarget(const IntSize &aSize) override;
 
   virtual const char* Name() const override { return ""; }
+  virtual bool IsCompositingToScreen() const override;
 
   bool AlwaysScheduleComposite() const override;
 
@@ -386,19 +402,6 @@ public:
 
   bool AsyncPanZoomEnabled() const override;
 
-public:
-  void AppendImageCompositeNotification(const ImageCompositeNotificationInfo& aNotification)
-  {
-    // Only send composite notifications when we're drawing to the screen,
-    // because that's what they mean.
-    // Also when we're not drawing to the screen, DidComposite will not be
-    // called to extract and send these notifications, so they might linger
-    // and contain stale ImageContainerParent pointers.
-    if (!mCompositor->GetTargetContext()) {
-      mImageCompositeNotifications.AppendElement(aNotification);
-    }
-  }
-
 public:
   virtual TextureFactoryIdentifier GetTextureFactoryIdentifier() override
   {