mix-blend-mode implementation for accelerated layers - blink part

Source/core/rendering/RenderLayerCompositor.cpp

Index: Source/core/rendering/RenderLayerCompositor.cpp
diff --git a/Source/core/rendering/RenderLayerCompositor.cpp b/Source/core/rendering/RenderLayerCompositor.cpp
index d8e9ddc4be06c9625b0d8fde53686a22829d9a09..22937c72b4216774d79c33989bec77034e3d49c5 100644
--- a/Source/core/rendering/RenderLayerCompositor.cpp
+++ b/Source/core/rendering/RenderLayerCompositor.cpp
@@ -177,6 +177,7 @@ struct CompositingRecursionData {
     CompositingRecursionData(RenderLayer* compAncestor, bool testOverlap)
         : m_compositingAncestor(compAncestor)
         , m_subtreeIsCompositing(false)
+        , m_hasCompositedBlendingDescendants(false)

[enne (OOO), 2013/11/11 21:52:46]

Can you rename this to make it more clear? At first blush I would expect this to
be true if there was a composited blending descendant anywhere.  It's really
"hasUnisolatedCompositedBlendingDescendant"? I'm not sure if there's a better
way to make it clear that this is a more localized setting.  I could also
suggest something like "promoteAncestorStackingLayerDueToIsolation"?

[rosca, 2013/11/12 20:27:07]

I think hasUnisolatedCompositedBlendingDescendant looks good. Thanks.

         , m_testingOverlap(testOverlap)
 #ifndef NDEBUG
         , m_depth(0)
@@ -187,6 +188,7 @@ struct CompositingRecursionData {
     CompositingRecursionData(const CompositingRecursionData& other)
         : m_compositingAncestor(other.m_compositingAncestor)
         , m_subtreeIsCompositing(other.m_subtreeIsCompositing)
+        , m_hasCompositedBlendingDescendants(other.m_hasCompositedBlendingDescendants)
         , m_testingOverlap(other.m_testingOverlap)
 #ifndef NDEBUG
         , m_depth(other.m_depth + 1)
@@ -196,6 +198,7 @@ struct CompositingRecursionData {
 
     RenderLayer* m_compositingAncestor;
     bool m_subtreeIsCompositing;
+    bool m_hasCompositedBlendingDescendants;
     bool m_testingOverlap;
 #ifndef NDEBUG
     int m_depth;
@@ -909,6 +912,11 @@ void RenderLayerCompositor::computeCompositingRequirements(RenderLayer* ancestor
     if (overlapMap && childRecursionData.m_compositingAncestor && !childRecursionData.m_compositingAncestor->isRootLayer())
         addToOverlapMap(*overlapMap, layer, absBounds, haveComputedBounds);
 
+    layer->setRequiresIsolationForCompositedStackingContext(childRecursionData.m_hasCompositedBlendingDescendants);
+
+    if (layer->requiresIsolationForCompositedStackingContext() && !layer->stackingNode()->isStackingContext())
+        currentRecursionData.m_hasCompositedBlendingDescendants = true;
+
     // Now check for reasons to become composited that depend on the state of descendant layers.
     CompositingReasons subtreeCompositingReasons = subtreeReasonsForCompositing(layer->renderer(), childRecursionData.m_subtreeIsCompositing, anyDescendantHas3DTransform);
     reasonsToComposite |= subtreeCompositingReasons;
@@ -935,6 +943,9 @@ void RenderLayerCompositor::computeCompositingRequirements(RenderLayer* ancestor
     if (childRecursionData.m_subtreeIsCompositing)
         currentRecursionData.m_subtreeIsCompositing = true;
 
+    if (willBeComposited && layer->hasBlendMode())
+        currentRecursionData.m_hasCompositedBlendingDescendants = true;
+
     // Set the flag to say that this SC has compositing children.
     layer->setHasCompositingDescendant(childRecursionData.m_subtreeIsCompositing);
 
@@ -1712,6 +1723,8 @@ CompositingReasons RenderLayerCompositor::subtreeReasonsForCompositing(RenderObj
     if (hasCompositedDescendants) {
         if (layer->transform())
             subtreeReasons |= CompositingReasonTransformWithCompositedDescendants;
+        if (layer->requiresIsolationForCompositedStackingContext() && layer->stackingNode()->isStackingContext())

[enne (OOO), 2013/11/11 21:52:46]

It's a little awkward to set a "requires ... for stacking context" flag on a
layer that doesn't create a stacking context and then ignore that later.  Could
you only set this flag in cases where the layer actually is isolated and is a
stacking context?

[rosca, 2013/11/12 20:27:07]

Yes, done. In this case I think it's more appropriate to call it
shouldIsolateCompositedDescendants and ASSERT everywhere to make sure it's only
set for stacking contexts.

+            subtreeReasons |= CompositingReasonIsolateCompositedDescendants;
 
         // If the implementation of createsGroup changes, we need to be aware of that in this part of code.
         ASSERT((renderer->isTransparent() || renderer->hasMask() || renderer->hasFilter() || renderer->hasBlendMode()) == renderer->createsGroup());