Bug 1267438 - Use the layer's scrolled clip during compositor hit testing. r=mstange

MozReview-Commit-ID: 2nodwaZHeWZ

--HG--
extra : rebase_source : 4a61e20fa5ea6de457132aa7e06c27e48286f28c
extra : source : 6618e805fce8e1b45241783d8ba3b5bec5ad182a
extra : histedit_source : 4b27d55d0f26de7a13ef741feef9df6f8e6c4f13

gfx/layers/LayerMetricsWrapper.h

@@ -372,10 +372,14 @@ public:
 
     Maybe<ParentLayerIntRect> result;
 
-    // The layer can have a clip rect, which is considered to apply
-    // only to the bottommost LayerMetrics.
+    // The layer can have a clip rect and a scrolled clip, which are considered
+    // to apply only to the bottommost LayerMetricsWrapper.
+    // TODO: These actually apply in a different coordinate space than the
+    // scroll clip of the bottommost metrics, so we shouldn't be intersecting
+    // them with the scroll clip; bug 1269537 tracks fixing this.
     if (AtBottomLayer()) {
       result = mLayer->GetClipRect();
+      result = IntersectMaybeRects(result, mLayer->GetScrolledClipRect());
     }
 
     // The scroll metadata can have a clip rect as well.

gfx/layers/Layers.cpp

@@ -851,6 +851,12 @@ Layer::CalculateScissorRect(const RenderTargetIntRect& aCurrentScissorRect)
   return currentClip.Intersect(scissor);
 }
 
+Maybe<ParentLayerIntRect>
+Layer::GetScrolledClipRect() const
+{
+  return mScrolledClip ? Some(mScrolledClip->GetClipRect()) : Nothing();
+}
+
 const ScrollMetadata&
 Layer::GetScrollMetadata(uint32_t aIndex) const
 {

gfx/layers/Layers.h

@@ -1302,6 +1302,7 @@ public:
   gfx::CompositionOp GetMixBlendMode() const { return mMixBlendMode; }
   const Maybe<ParentLayerIntRect>& GetClipRect() const { return mClipRect; }
   const Maybe<LayerClip>& GetScrolledClip() const { return mScrolledClip; }
+  Maybe<ParentLayerIntRect> GetScrolledClipRect() const;
   uint32_t GetContentFlags() { return mContentFlags; }
   const gfx::IntRect& GetLayerBounds() const { return mLayerBounds; }
   const LayerIntRegion& GetVisibleRegion() const { return mVisibleRegion; }