Refactor BlendMode into a separate class.

Source/core/rendering/RenderLayer.cpp

Index: Source/core/rendering/RenderLayer.cpp
diff --git a/Source/core/rendering/RenderLayer.cpp b/Source/core/rendering/RenderLayer.cpp
index aa8d0e1601e68c17665463eacacb33799dc2366d..ad18f1a836f964af6f7d7312c0b261adfb01a62f 100644
--- a/Source/core/rendering/RenderLayer.cpp
+++ b/Source/core/rendering/RenderLayer.cpp
@@ -111,8 +111,6 @@ RenderLayer::RenderLayer(RenderLayerModelObject* renderer)
     , m_isUnclippedDescendant(false)
     , m_isRootLayer(renderer->isRenderView())
     , m_usedTransparency(false)
-    , m_childLayerHasBlendMode(false)
-    , m_childLayerHasBlendModeStatusDirty(false)
     , m_visibleContentStatusDirty(true)
     , m_hasVisibleContent(false)
     , m_visibleDescendantStatusDirty(false)
@@ -124,7 +122,6 @@ RenderLayer::RenderLayer(RenderLayerModelObject* renderer)
     , m_containsDirtyOverlayScrollbars(false)
     , m_canSkipRepaintRectsUpdateOnScroll(renderer->isTableCell())
     , m_hasFilterInfo(false)
-    , m_blendMode(blink::WebBlendModeNormal)
     , m_renderer(renderer)
     , m_parent(0)
     , m_previous(0)
@@ -136,6 +133,7 @@ RenderLayer::RenderLayer(RenderLayerModelObject* renderer)
     , m_enclosingPaginationLayer(0)
     , m_repainter(renderer)
     , m_clipper(renderer)
+    , m_blendInfo(renderer)
 {
     updateStackingNode();
 
@@ -515,30 +513,6 @@ void RenderLayer::updateLayerPositionsAfterScroll(RenderGeometryMap* geometryMap
         geometryMap->popMappingsToAncestor(parent());
 }
 
-bool RenderLayer::hasBlendMode() const
-{
-    return RuntimeEnabledFeatures::cssCompositingEnabled() && renderer()->hasBlendMode();
-}
-
-void RenderLayer::updateBlendMode()
-{
-    if (!RuntimeEnabledFeatures::cssCompositingEnabled())
-        return;
-
-    bool hadBlendMode = m_blendMode != blink::WebBlendModeNormal;
-    blink::WebBlendMode newBlendMode = renderer()->style()->blendMode();
-    if (newBlendMode != m_blendMode) {
-        m_blendMode = newBlendMode;
-
-        // Only update the flag if a blend mode is set or unset.
-        if (parent() && (!hadBlendMode || !hasBlendMode()))
-            parent()->dirtyAncestorChainBlendedDescendantStatus();
-
-        if (hasCompositedLayerMapping())
-            compositedLayerMapping()->setBlendMode(newBlendMode);
-    }
-}
-
 void RenderLayer::updateTransform()
 {
     // hasTransform() on the renderer is also true when there is transform-style: preserve-3d or perspective set,
@@ -758,33 +732,6 @@ void RenderLayer::setAncestorChainHasVisibleDescendant()
     }
 }
 
-void RenderLayer::dirtyAncestorChainBlendedDescendantStatus()
-{
-    for (RenderLayer* layer = this; layer; layer = layer->parent()) {
-        if (layer->m_childLayerHasBlendModeStatusDirty)
-            break;
-
-        layer->m_childLayerHasBlendModeStatusDirty = true;
-
-        if (layer->stackingNode()->isStackingContext())
-            break;
-    }
-}
-
-void RenderLayer::setAncestorChainBlendedDescendant()
-{
-    for (RenderLayer* layer = this; layer; layer = layer->parent()) {
-        if (!layer->m_childLayerHasBlendModeStatusDirty && layer->childLayerHasBlendMode())
-            break;
-
-        layer->m_childLayerHasBlendMode = true;
-        layer->m_childLayerHasBlendModeStatusDirty = false;
-
-        if (layer->stackingNode()->isStackingContext())
-            break;
-    }
-}
-
 void RenderLayer::updateHasUnclippedDescendant()
 {
     TRACE_EVENT0("blink_rendering", "RenderLayer::updateHasUnclippedDescendant");
@@ -858,19 +805,21 @@ void RenderLayer::updateDescendantDependentFlags()
         m_hasOutOfFlowPositionedDescendantDirty = false;
     }
 
-    if (m_childLayerHasBlendModeStatusDirty) {
-        m_childLayerHasBlendMode = false;
+    if (m_blendInfo.childLayerHasBlendModeStatusDirty()) {
+        m_blendInfo.setChildLayerHasBlendMode(false);
         for (RenderLayer* child = firstChild(); child; child = child->nextSibling()) {
             if (!child->stackingNode()->isStackingContext())
                 child->updateDescendantDependentFlags();
 
-            bool childLayerHasBlendMode = child->paintsWithBlendMode() || (child->m_childLayerHasBlendMode && !child->stackingNode()->isStackingContext());
-            m_childLayerHasBlendMode |= childLayerHasBlendMode;
+            bool childLayerHasBlendMode = child->paintsWithBlendMode()
+                || (child->blendInfo().childLayerHasBlendModeWhileDirty() && !child->stackingNode()->isStackingContext());

[Julien - ping for review, 2013/12/10 00:55:09]

We should *never* allow the flag to be queried dirty. Is this really needed in
the current code?

[dsinclair, 2013/12/10 16:59:12]

The current code does require this at the moment.  If you look in
RenderLayer::styleChanged on line ~3932 we do: 

    if (RuntimeEnabledFeatures::cssCompositingEnabled())
        updateBlendMode();

updateBlendMode() will call to dirtyAncestorChainBlendDescendantStatus() which
sets the dirty flag to true.

Then on line ~3934 (the next call) we call updateDescendentDependentFlags()
which has this chunk of code which, on line ~808 above, specifically checks if
the status is dirty before doing any work. So, currently, I need to be able to
get the blend mode while it's dirty as otherwise it will ASSERT and blowup.

The current code works because it's all operating on internal m_* values. After
splitting it into it's own class is where it causes the weirdness.

+
+            m_blendInfo.updateChildLayerHasBlendMode(childLayerHasBlendMode);

[Julien - ping for review, 2013/12/10 00:55:09]

A better way to handle that would be to store this in a local variable and set
it at the end. This would remove the need for updateChildLayerHasBlendMode.

[dsinclair, 2013/12/13 16:53:59]

Done.

 
-            if (m_childLayerHasBlendMode)
+            if (m_blendInfo.childLayerHasBlendModeWhileDirty())
                 break;
         }
-        m_childLayerHasBlendModeStatusDirty = false;
+        m_blendInfo.setChildLayerHasBlendModeStatusDirty(false);
     }
 
     if (m_visibleContentStatusDirty) {
@@ -1336,7 +1285,7 @@ LayoutRect RenderLayer::paintingExtent(const RenderLayer* rootLayer, const Layou
 
 void RenderLayer::beginTransparencyLayers(GraphicsContext* context, const RenderLayer* rootLayer, const LayoutRect& paintDirtyRect, PaintBehavior paintBehavior)
 {
-    bool createTransparencyLayerForBlendMode = m_stackingNode->isStackingContext() && m_childLayerHasBlendMode;
+    bool createTransparencyLayerForBlendMode = m_stackingNode->isStackingContext() && m_blendInfo.childLayerHasBlendMode();
     if (context->paintingDisabled() || ((paintsWithTransparency(paintBehavior) || paintsWithBlendMode() || createTransparencyLayerForBlendMode) && m_usedTransparency))
         return;
 
@@ -1350,7 +1299,7 @@ void RenderLayer::beginTransparencyLayers(GraphicsContext* context, const Render
         LayoutRect clipRect = paintingExtent(rootLayer, paintDirtyRect, paintBehavior);
         context->clip(clipRect);
         if (paintsWithBlendMode())
-            context->setCompositeOperation(context->compositeOperation(), m_blendMode);
+            context->setCompositeOperation(context->compositeOperation(), m_blendInfo.blendMode());
 
         context->beginTransparencyLayer(renderer()->opacity());
 #ifdef REVEAL_TRANSPARENCY_LAYERS
@@ -1406,8 +1355,8 @@ void RenderLayer::addChild(RenderLayer* child, RenderLayer* beforeChild)
     if (child->isSelfPaintingLayer() || child->hasSelfPaintingLayerDescendant())
         setAncestorChainHasSelfPaintingLayerDescendant();
 
-    if (child->paintsWithBlendMode() || child->childLayerHasBlendMode())
-        setAncestorChainBlendedDescendant();
+    if (child->paintsWithBlendMode() || child->blendInfo().childLayerHasBlendMode())
+        m_blendInfo.setAncestorChainBlendedDescendant();
 
     if (subtreeContainsOutOfFlowPositionedLayer(child)) {
         // Now that the out of flow positioned descendant is in the tree, we
@@ -1467,8 +1416,8 @@ RenderLayer* RenderLayer::removeChild(RenderLayer* oldChild)
     if (oldChild->m_hasVisibleContent || oldChild->m_hasVisibleDescendant)
         dirtyAncestorChainVisibleDescendantStatus();
 
-    if (oldChild->paintsWithBlendMode() || oldChild->childLayerHasBlendMode())
-        dirtyAncestorChainBlendedDescendantStatus();
+    if (oldChild->paintsWithBlendMode() || oldChild->blendInfo().childLayerHasBlendMode())
+        m_blendInfo.dirtyAncestorChainBlendedDescendantStatus();
 
     if (oldChild->isSelfPaintingLayer() || oldChild->hasSelfPaintingLayerDescendant())
         dirtyAncestorChainHasSelfPaintingLayerDescendantStatus();
@@ -2055,7 +2004,7 @@ void RenderLayer::paintLayerContents(GraphicsContext* context, const LayerPainti
 
     // Blending operations must be performed only with the nearest ancestor stacking context.
     // Note that there is no need to create a transparency layer if we're painting the root.
-    bool createTransparencyLayerForBlendMode = !renderer()->isRoot() && m_stackingNode->isStackingContext() && m_childLayerHasBlendMode;
+    bool createTransparencyLayerForBlendMode = !renderer()->isRoot() && m_stackingNode->isStackingContext() && m_blendInfo.childLayerHasBlendMode();
 
     if (createTransparencyLayerForBlendMode)
         beginTransparencyLayers(context, paintingInfo.rootLayer, paintingInfo.paintDirtyRect, paintingInfo.paintBehavior);
@@ -3655,7 +3604,7 @@ CompositedLayerMappingPtr RenderLayer::ensureCompositedLayerMapping()
         updateOrRemoveFilterEffectRenderer();
 
         if (RuntimeEnabledFeatures::cssCompositingEnabled())
-            compositedLayerMapping()->setBlendMode(m_blendMode);
+            compositedLayerMapping()->setBlendMode(m_blendInfo.blendMode());
     }
     return m_compositedLayerMapping.get();
 }
@@ -3972,7 +3921,7 @@ void RenderLayer::styleChanged(StyleDifference, const RenderStyle* oldStyle)
     updateReflectionInfo(oldStyle);
 
     if (RuntimeEnabledFeatures::cssCompositingEnabled())
-        updateBlendMode();
+        m_blendInfo.updateBlendMode();
 
     updateDescendantDependentFlags();
     updateTransform();