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 beece9ac5117ea616115251c495916159347e1f6..f3ff63ff599f24bbb7e2e6bc1828262c8cd0a562 100644
--- a/Source/core/rendering/RenderLayerCompositor.cpp
+++ b/Source/core/rendering/RenderLayerCompositor.cpp
@@ -186,6 +186,7 @@ struct CompositingRecursionData {
     CompositingRecursionData(RenderLayer* compAncestor, bool testOverlap)
         : m_compositingAncestor(compAncestor)
         , m_subtreeIsCompositing(false)
+        , m_hasCompositedBlendingDescendants(false)
         , m_testingOverlap(testOverlap)
 #ifndef NDEBUG
         , m_depth(0)
@@ -196,6 +197,7 @@ 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)
@@ -205,6 +207,7 @@ struct CompositingRecursionData {
 
     RenderLayer* m_compositingAncestor;
     bool m_subtreeIsCompositing;
+    bool m_hasCompositedBlendingDescendants;
     bool m_testingOverlap;
 #ifndef NDEBUG
     int m_depth;
@@ -949,6 +952,15 @@ void RenderLayerCompositor::computeCompositingRequirements(RenderLayer* ancestor
     if (overlapMap && childRecursionData.m_compositingAncestor && !childRecursionData.m_compositingAncestor->isRootLayer())
         addToOverlapMap(*overlapMap, layer, absBounds, haveComputedBounds);
 
+    // According to http://dev.w3.org/fxtf/compositing-1/#csscompositingrules_CSS,
+    // an element that has blending applied must blend with all the underlying
+    // content of the stacking context [CSS21] that element belongs to.
+    // We should isolate the stacking contexts containing accelerated blending descendants
+    layer->setHasCompositedBlendingDescendants(childRecursionData.m_hasCompositedBlendingDescendants);
+
+    if (layer->hasCompositedBlendingDescendants() && !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;
@@ -975,6 +987,9 @@ 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);
 
@@ -1554,6 +1569,7 @@ bool RenderLayerCompositor::requiresOwnBackingStore(const RenderLayer* layer, co
         | CompositingReasonMaskWithCompositedDescendants
         | CompositingReasonFilterWithCompositedDescendants
         | CompositingReasonBlendingWithCompositedDescendants
+        | CompositingReasonIsolateCompositedDescendants
         | CompositingReasonPreserve3D; // preserve-3d has to create backing store to ensure that 3d-transformed elements intersect.
     return layer->compositingReasons() & indirectReasonsThatNeedBacking;
 }
@@ -1687,6 +1703,9 @@ const char* RenderLayerCompositor::logReasonsForCompositing(const RenderLayer* l
     if (reasons & CompositingReasonRoot)
         return "root";
 
+    if (reasons & CompositingReasonIsolateCompositedDescendants)
+        return "isolate composited descendants";
+
     return "";
 }
 #endif
@@ -1881,6 +1900,8 @@ CompositingReasons RenderLayerCompositor::subtreeReasonsForCompositing(RenderObj
     if (hasCompositedDescendants) {
         if (layer->transform())
             subtreeReasons |= CompositingReasonTransformWithCompositedDescendants;
+        if (layer->hasCompositedBlendingDescendants() && layer->stackingNode()->isStackingContext())
+            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());