Bug 809273 - Add code for handling dual buffers in ContentHost. r=nrc

gfx/layers/CompositorTypes.h

@@ -101,6 +101,8 @@ struct TextureFactoryIdentifier
 typedef uint32_t TextureIdentifier;
 const TextureIdentifier TextureFront = 1;
 const TextureIdentifier TextureBack = 2;
+const TextureIdentifier TextureOnWhiteFront = 3;
+const TextureIdentifier TextureOnWhiteBack = 4;
 
 /**
  * Information required by the compositor from the content-side for creating or

gfx/layers/composite/ContentHost.cpp

@@ -31,6 +31,8 @@ ContentHostBase::DestroyFrontHost()
 {
   MOZ_ASSERT(!mTextureHost || mTextureHost->GetDeAllocator(),
              "We won't be able to destroy our SurfaceDescriptor");
+  MOZ_ASSERT(!mTextureHostOnWhite || mTextureHostOnWhite->GetDeAllocator(),
+             "We won't be able to destroy our SurfaceDescriptor");
   mTextureHost = nullptr;
   mTextureHostOnWhite = nullptr;
 }
@@ -213,15 +215,19 @@ ContentHostSingleBuffered::EnsureTextureHost(TextureIdentifier aTextureId,
                                              ISurfaceAllocator* aAllocator,
                                              const TextureInfo& aTextureInfo)
 {
-  MOZ_ASSERT(aTextureId == TextureFront);
+  MOZ_ASSERT(aTextureId == TextureFront ||
-  mNewFrontHost = TextureHost::CreateTextureHost(aSurface.type(),
+             aTextureId == TextureOnWhiteFront);
-                                                 aTextureInfo.mTextureHostFlags,
+  RefPtr<TextureHost> *newHost =
-                                                 aTextureInfo.mTextureFlags);
+    (aTextureId == TextureFront) ? &mNewFrontHost : &mNewFrontHostOnWhite;
 
-  mNewFrontHost->SetBuffer(new SurfaceDescriptor(aSurface), aAllocator);
+  *newHost = TextureHost::CreateTextureHost(aSurface.type(),
+                                            aTextureInfo.mTextureHostFlags,
+                                            aTextureInfo.mTextureFlags);
+
+  (*newHost)->SetBuffer(new SurfaceDescriptor(aSurface), aAllocator);
   Compositor* compositor = GetCompositor();
   if (compositor) {
-    mNewFrontHost->SetCompositor(compositor);
+    (*newHost)->SetCompositor(compositor);
   }
 
   return true;
@@ -232,7 +238,10 @@ ContentHostSingleBuffered::DestroyTextures()
 {
   MOZ_ASSERT(!mNewFrontHost || mNewFrontHost->GetDeAllocator(),
              "We won't be able to destroy our SurfaceDescriptor");
+  MOZ_ASSERT(!mNewFrontHostOnWhite || mNewFrontHostOnWhite->GetDeAllocator(),
+             "We won't be able to destroy our SurfaceDescriptor");
   mNewFrontHost = nullptr;
+  mNewFrontHostOnWhite = nullptr;
 
   // don't touch mTextureHost, we might need it for compositing
 }
@@ -254,9 +263,14 @@ ContentHostSingleBuffered::UpdateThebes(const ThebesBufferData& aData,
     DestroyFrontHost();
     mTextureHost = mNewFrontHost;
     mNewFrontHost = nullptr;
+    if (mNewFrontHostOnWhite) {
+      mTextureHostOnWhite = mNewFrontHostOnWhite;
+      mNewFrontHostOnWhite = nullptr;
+    }
   }
 
   MOZ_ASSERT(mTextureHost);
+  MOZ_ASSERT(!mNewFrontHostOnWhite, "New white host without a new black?");
 
   // updated is in screen coordinates. Convert it to buffer coordinates.
   nsIntRegion destRegion(aUpdated);
@@ -278,6 +292,9 @@ ContentHostSingleBuffered::UpdateThebes(const ThebesBufferData& aData,
                "updated region lies across rotation boundaries!");
 
   mTextureHost->Update(*mTextureHost->GetBuffer(), &destRegion);
+  if (mTextureHostOnWhite) {
+    mTextureHostOnWhite->Update(*mTextureHostOnWhite->GetBuffer(), &destRegion);
+  }
   mInitialised = true;
 
   mBufferRect = aData.rect();
@@ -311,12 +328,19 @@ ContentHostDoubleBuffered::EnsureTextureHost(TextureIdentifier aTextureId,
     mNewFrontHost = newHost;
     return true;
   }
+  if (aTextureId == TextureOnWhiteFront) {
+    mNewFrontHostOnWhite = newHost;
+    return true;
+  }
   if (aTextureId == TextureBack) {
     mBackHost = newHost;
     mBufferRect = nsIntRect();
     mBufferRotation = nsIntPoint();
     return true;
   }
+  if (aTextureId == TextureOnWhiteBack) {
+    mBackHostOnWhite = newHost;
+  }
 
   NS_ERROR("Bad texture identifier");
   return false;
@@ -331,12 +355,24 @@ ContentHostDoubleBuffered::DestroyTextures()
     mNewFrontHost = nullptr;
   }
 
+  if (mNewFrontHostOnWhite) {
+    MOZ_ASSERT(mNewFrontHostOnWhite->GetDeAllocator(),
+               "We won't be able to destroy our SurfaceDescriptor");
+    mNewFrontHostOnWhite = nullptr;
+  }
+
   if (mBackHost) {
     MOZ_ASSERT(mBackHost->GetDeAllocator(),
                "We won't be able to destroy our SurfaceDescriptor");
     mBackHost = nullptr;
   }
 
+  if (mBackHostOnWhite) {
+    MOZ_ASSERT(mBackHostOnWhite->GetDeAllocator(),
+               "We won't be able to destroy our SurfaceDescriptor");
+    mBackHostOnWhite = nullptr;
+  }
+
   // don't touch mTextureHost, we might need it for compositing
 }
 
@@ -357,16 +393,28 @@ ContentHostDoubleBuffered::UpdateThebes(const ThebesBufferData& aData,
     DestroyFrontHost();
     mTextureHost = mNewFrontHost;
     mNewFrontHost = nullptr;
+    if (mNewFrontHostOnWhite) {
+      mTextureHostOnWhite = mNewFrontHostOnWhite;
+      mNewFrontHostOnWhite = nullptr;
+    }
   }
 
   MOZ_ASSERT(mTextureHost);
+  MOZ_ASSERT(!mNewFrontHostOnWhite, "New white host without a new black?");
   MOZ_ASSERT(mBackHost);
 
   RefPtr<TextureHost> oldFront = mTextureHost;
   mTextureHost = mBackHost;
   mBackHost = oldFront;
 
+  oldFront = mTextureHostOnWhite;
+  mTextureHostOnWhite = mBackHostOnWhite;
+  mBackHostOnWhite = oldFront;
+
   mTextureHost->Update(*mTextureHost->GetBuffer());
+  if (mTextureHostOnWhite) {
+    mTextureHostOnWhite->Update(*mTextureHostOnWhite->GetBuffer());
+  }
   mInitialised = true;
 
   mBufferRect = aData.rect();

gfx/layers/composite/ContentHost.h

@@ -125,6 +125,7 @@ protected:
   // the old one which might still be used for compositing. So we store it
   // here and move it to mTextureHost once we do the first buffer swap.
   RefPtr<TextureHost> mNewFrontHost;
+  RefPtr<TextureHost> mNewFrontHostOnWhite;
   bool mPaintWillResample;
   bool mInitialised;
 };
@@ -163,6 +164,7 @@ protected:
   // only swap it with the front buffer (mTextureHost) when we are told by the
   // content thread.
   RefPtr<TextureHost> mBackHost;
+  RefPtr<TextureHost> mBackHostOnWhite;
 };
 
 /**