Fix PostprocessRetainedLayers to not test occlusion with asynchronous clips. (bug 1148582 part 5, r=tn)

gfx/layers/Layers.cpp

@@ -929,6 +929,27 @@ Layer::GetVisibleRegionRelativeToRootLayer(nsIntRegion& aResult,
   return true;
 }
 
+Maybe<ParentLayerIntRect>
+Layer::GetCombinedClipRect() const
+{
+  Maybe<ParentLayerIntRect> clip = GetClipRect();
+
+  for (size_t i = 0; i < mFrameMetrics.Length(); i++) {
+    if (!mFrameMetrics[i].HasClipRect()) {
+      continue;
+    }
+
+    const ParentLayerIntRect& other = mFrameMetrics[i].ClipRect();
+    if (clip) {
+      clip = Some(clip.value().Intersect(other));
+    } else {
+      clip = Some(other);
+    }
+  }
+
+  return clip;
+}
+
 ContainerLayer::ContainerLayer(LayerManager* aManager, void* aImplData)
   : Layer(aManager, aImplData),
     mFirstChild(nullptr),

gfx/layers/Layers.h

@@ -1255,6 +1255,12 @@ public:
   bool IsScrollbarContainer() { return mIsScrollbarContainer; }
   Layer* GetMaskLayer() const { return mMaskLayer; }
 
+  /*
+   * Get the combined clip rect of the Layer clip and all clips on FrameMetrics.
+   * This is intended for use in Layout. The compositor needs to apply async
+   * transforms to find the combined clip.
+   */
+  Maybe<ParentLayerIntRect> GetCombinedClipRect() const;
 
   /**
    * Retrieve the root level visible region for |this| taking into account

layout/base/FrameLayerBuilder.cpp

@@ -4408,6 +4408,15 @@ InvalidateVisibleBoundsChangesForScrolledLayer(PaintedLayer* aLayer)
   }
 }
 
+static inline const Maybe<ParentLayerIntRect>&
+GetStationaryClipInContainer(Layer* aLayer)
+{
+  if (size_t metricsCount = aLayer->GetFrameMetricsCount()) {
+    return aLayer->GetFrameMetrics(metricsCount - 1).GetClipRect();
+  }
+  return aLayer->GetClipRect();
+}
+
 void
 ContainerState::PostprocessRetainedLayers(nsIntRegion* aOpaqueRegionForContainer)
 {
@@ -4434,7 +4443,7 @@ ContainerState::PostprocessRetainedLayers(nsIntRegion* aOpaqueRegionForContainer
     if (hideAll) {
       e->mVisibleRegion.SetEmpty();
     } else if (!e->mLayer->IsScrollbarContainer()) {
-      const Maybe<ParentLayerIntRect>& clipRect = e->mLayer->GetClipRect();
+      const Maybe<ParentLayerIntRect>& clipRect = GetStationaryClipInContainer(e->mLayer);
       if (clipRect && opaqueRegionForContainer >= 0 &&
           opaqueRegions[opaqueRegionForContainer].mOpaqueRegion.Contains(ParentLayerIntRect::ToUntyped(*clipRect))) {
         e->mVisibleRegion.SetEmpty();
@@ -4474,7 +4483,7 @@ ContainerState::PostprocessRetainedLayers(nsIntRegion* aOpaqueRegionForContainer
       }
 
       nsIntRegion clippedOpaque = e->mOpaqueRegion;
-      const Maybe<ParentLayerIntRect>& clipRect = e->mLayer->GetClipRect();
+      Maybe<ParentLayerIntRect> clipRect = e->mLayer->GetCombinedClipRect();
       if (clipRect) {
         clippedOpaque.AndWith(ParentLayerIntRect::ToUntyped(*clipRect));
       }