Make compositingState explicit

Source/core/rendering/RenderLayerBacking.cpp

Index: Source/core/rendering/RenderLayerBacking.cpp
diff --git a/Source/core/rendering/RenderLayerBacking.cpp b/Source/core/rendering/RenderLayerBacking.cpp
index 5a16fab63c2b8c1f7d4ce94fb24d7b6615220379..a0f76968043339707e6a1ad456d7010092fdc67e 100644
--- a/Source/core/rendering/RenderLayerBacking.cpp
+++ b/Source/core/rendering/RenderLayerBacking.cpp
@@ -694,7 +694,7 @@ void RenderLayerBacking::updateGraphicsLayerGeometry()
         m_backgroundLayer->setOffsetFromRenderer(m_graphicsLayer->offsetFromRenderer());
     }
 
-    if (m_owningLayer->reflectionLayer() && m_owningLayer->reflectionLayer()->isComposited()) {
+    if (m_owningLayer->reflectionLayer() && m_owningLayer->reflectionLayer()->backing()) {
         RenderLayerBacking* reflectionBacking = m_owningLayer->reflectionLayer()->backing();
         reflectionBacking->updateGraphicsLayerGeometry();
 
@@ -1192,9 +1192,16 @@ float RenderLayerBacking::compositingOpacity(float rendererOpacity) const
         if (!curr->isStackingContainer())
             continue;
 
-        // If we found a compositing layer, we want to compute opacity
-        // relative to it. So we can break here.
-        if (curr->isComposited())
+        // If we found a composited layer, regardless of whether it actually
+        // paints into it, we want to compute opacity relative to it. So we can
+        // break here.
+        //
+        // FIXME: with grouped backings, a composited descendant will have to
+        //        continue past the grouped (squashed) layers that its parents
+        //        may contribute to. This whole confusion can be avoided by
+        //        specifying explicitly the composited ancestor where we would
+        //        stop accumulating opacity.
+        if (curr->compositingState() == PaintsIntoOwnBacking || curr->compositingState() == HasOwnBackingButPaintsIntoAncestor)
             break;
 
         finalOpacity *= curr->renderer()->opacity();
@@ -1332,7 +1339,7 @@ static bool hasVisibleNonCompositingDescendant(RenderLayer* parent)
         size_t listSize = normalFlowList->size();
         for (size_t i = 0; i < listSize; ++i) {
             RenderLayer* curLayer = normalFlowList->at(i);
-            if (!curLayer->isComposited()
+            if (!curLayer->backing()
                 && (curLayer->hasVisibleContent() || hasVisibleNonCompositingDescendant(curLayer)))
                 return true;
         }
@@ -1347,7 +1354,7 @@ static bool hasVisibleNonCompositingDescendant(RenderLayer* parent)
             size_t listSize = negZOrderList->size();
             for (size_t i = 0; i < listSize; ++i) {
                 RenderLayer* curLayer = negZOrderList->at(i);
-                if (!curLayer->isComposited()
+                if (!curLayer->backing()
                     && (curLayer->hasVisibleContent() || hasVisibleNonCompositingDescendant(curLayer)))
                     return true;
             }
@@ -1357,7 +1364,7 @@ static bool hasVisibleNonCompositingDescendant(RenderLayer* parent)
             size_t listSize = posZOrderList->size();
             for (size_t i = 0; i < listSize; ++i) {
                 RenderLayer* curLayer = posZOrderList->at(i);
-                if (!curLayer->isComposited()
+                if (!curLayer->backing()
                     && (curLayer->hasVisibleContent() || hasVisibleNonCompositingDescendant(curLayer)))
                     return true;
             }
@@ -1368,6 +1375,9 @@ static bool hasVisibleNonCompositingDescendant(RenderLayer* parent)
 }
 
 // Conservative test for having no rendered children.
+// FIXME: By name the implementation is correct. But the code that uses this function means something
+//        very slightly different - the implementation needs to also include composited descendants that
+//        don't paint into their own backing, and instead paint into this backing.
 bool RenderLayerBacking::hasVisibleNonCompositingDescendantLayers() const
 {
     return hasVisibleNonCompositingDescendant(m_owningLayer);