Bug 1170966 - Check quad's effective region before drawing. r=nical, a=me

gfx/layers/opengl/CompositorOGL.cpp

@@ -607,6 +607,8 @@ CompositorOGL::BeginFrame(const nsIntRegion& aInvalidRegion,
     *aRenderBoundsOut = rect;
   }
 
+  mRenderBoundsOut = rect;
+
   GLint width = rect.width;
   GLint height = rect.height;
 
@@ -950,6 +952,19 @@ CompositorOGL::DrawQuad(const Rect& aRect,
     DrawVRDistortion(aRect, aClipRect, aEffectChain, aOpacity, aTransform);
     return;
   }
+
+  // XXX: This doesn't handle 3D transforms. It also doesn't handled rotated
+  //      quads. Fix me.
+  Rect destRect = aTransform.TransformBounds(aRect);
+  mPixelsFilled += destRect.width * destRect.height;
+
+  // Do a simple culling if this rect is out of target buffer.
+  // Inflate a small size to avoid some numerical imprecision issue.
+  destRect.Inflate(1, 1);
+  if (!mRenderBoundsOut.Intersects(destRect)) {
+    return;
+  }
+
   LayerScope::DrawBegin();
 
   Rect clipRect = aClipRect;
@@ -999,13 +1014,6 @@ CompositorOGL::DrawQuad(const Rect& aRect,
     maskType = MaskType::MaskNone;
   }
 
-  {
-    // XXX: This doesn't handle 3D transforms. It also doesn't handled rotated
-    //      quads. Fix me.
-    const Rect destRect = aTransform.TransformBounds(aRect);
-    mPixelsFilled += destRect.width * destRect.height;
-  }
-
   // Determine the color if this is a color shader and fold the opacity into
   // the color since color shaders don't have an opacity uniform.
   Color color;

gfx/layers/opengl/CompositorOGL.h

@@ -457,6 +457,8 @@ private:
   FenceHandle mReleaseFenceHandle;
   ShaderProgramOGL *mCurrentProgram;
 
+  gfx::Rect mRenderBoundsOut;
+
   CompositorOGLVRObjects mVR;
 };