Bug 756606. Implement CreateRenderTargetFromSource. r=Bas

gfx/layers/d3d11/CompositorD3D11.cpp

@@ -362,7 +362,6 @@ CompositorD3D11::CreateRenderTarget(const gfx::IntRect& aRect,
   return rt;
 }
 
-// TODO[Bas] this method doesn't actually use aSource
 TemporaryRef<CompositingRenderTarget>
 CompositorD3D11::CreateRenderTargetFromSource(const gfx::IntRect &aRect,
                                               const CompositingRenderTarget* aSource)
@@ -374,6 +373,30 @@ CompositorD3D11::CreateRenderTargetFromSource(const gfx::IntRect &aRect,
   RefPtr<ID3D11Texture2D> texture;
   mDevice->CreateTexture2D(&desc, nullptr, byRef(texture));
 
+  if (aSource) {
+    const CompositingRenderTargetD3D11* sourceD3D11 =
+      static_cast<const CompositingRenderTargetD3D11*>(aSource);
+
+    D3D11_BOX srcBox;
+    srcBox.left = aRect.x;
+    srcBox.top = aRect.y;
+    srcBox.front = 0;
+    srcBox.right = aRect.XMost();
+    srcBox.bottom = aRect.YMost();
+    srcBox.back = 0;
+
+    const IntSize& srcSize = sourceD3D11->GetSize();
+    if (srcBox.right <= srcSize.width &&
+        srcBox.bottom <= srcSize.height) {
+      mContext->CopySubresourceRegion(texture, 0,
+                                      0, 0, 0,
+                                      sourceD3D11->GetD3D11Texture(), 0,
+                                      &srcBox);
+    } else {
+      NS_WARNING("Could not copy render target - source rect out of bounds");
+    }
+  }
+
   RefPtr<CompositingRenderTargetD3D11> rt =
     new CompositingRenderTargetD3D11(texture);
   rt->SetSize(IntSize(aRect.width, aRect.height));
@@ -675,8 +698,7 @@ CompositorD3D11::UpdateRenderTarget()
     return;
   }
 
-  mDefaultRT = new CompositingRenderTargetD3D11(nullptr);
-  mDevice->CreateRenderTargetView(backBuf, nullptr, byRef(mDefaultRT->mRTView));
+  mDefaultRT = new CompositingRenderTargetD3D11(backBuf);
 }
 
 bool

gfx/layers/d3d11/TextureD3D11.cpp

@@ -41,9 +41,7 @@ CreateDeprecatedTextureHostD3D11(SurfaceDescriptorType aDescriptorType,
 
 CompositingRenderTargetD3D11::CompositingRenderTargetD3D11(ID3D11Texture2D* aTexture)
 {
-  if (!aTexture) {
-    return;
-  }
+  MOZ_ASSERT(aTexture);
   
   mTextures[0] = aTexture;
 

gfx/layers/d3d11/TextureD3D11.h

@@ -50,7 +50,6 @@ class CompositingRenderTargetD3D11 : public CompositingRenderTarget,
                                      public TextureSourceD3D11
 {
 public:
-  // Use aTexture == nullptr for rendering to the window
   CompositingRenderTargetD3D11(ID3D11Texture2D* aTexture);
 
   virtual TextureSourceD3D11* AsSourceD3D11() MOZ_OVERRIDE { return this; }