Make compositingState explicit

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 3db81e33e92bb8b428490476965e92164f5d84e0..51cd6ed9277bd853adc45c6870e6118cb4b9d19d 100644
--- a/Source/core/rendering/RenderLayer.cpp
+++ b/Source/core/rendering/RenderLayer.cpp
@@ -217,11 +217,10 @@ bool RenderLayer::canRender3DTransforms() const
 
 bool RenderLayer::paintsWithFilters() const
 {
-    // FIXME: Eventually there will be more factors than isComposited() to decide whether or not to render the filter
     if (!renderer()->hasFilter())
         return false;
 
-    if (!isComposited())
+    if (compositingState() != PaintsIntoOwnBacking)
         return true;
 
     if (!m_compositedLayerMapping || !m_compositedLayerMapping->canCompositeFilters())
@@ -308,7 +307,7 @@ void RenderLayer::updateLayerPositions(RenderGeometryMap* geometryMap, UpdateLay
 
     // Clear the IsCompositingUpdateRoot flag once we've found the first compositing layer in this update.
     bool isUpdateRoot = (flags & IsCompositingUpdateRoot);
-    if (isComposited())
+    if (compositedLayerMapping())
         flags &= ~IsCompositingUpdateRoot;
 
     if (useRegionBasedColumns() && renderer()->isInFlowRenderFlowThread()) {
@@ -322,7 +321,7 @@ void RenderLayer::updateLayerPositions(RenderGeometryMap* geometryMap, UpdateLay
     for (RenderLayer* child = firstChild(); child; child = child->nextSibling())
         child->updateLayerPositions(geometryMap, flags);
 
-    if ((flags & UpdateCompositingLayers) && isComposited()) {
+    if ((flags & UpdateCompositingLayers) && compositedLayerMapping()) {
         CompositedLayerMapping::UpdateAfterLayoutFlags updateFlags = CompositedLayerMapping::CompositingChildrenOnly;
         if (flags & NeedsFullRepaintInBacking)
             updateFlags |= CompositedLayerMapping::NeedsFullRepaint;
@@ -835,7 +834,7 @@ void RenderLayer::updatePagination()
     m_isPaginated = false;
     m_enclosingPaginationLayer = 0;
 
-    if (isComposited() || !parent())
+    if (compositedLayerMapping() || !parent())
         return; // FIXME: We will have to deal with paginated compositing layers someday.
                 // FIXME: For now the RenderView can't be paginated.  Eventually printing will move to a model where it is though.
 
@@ -1145,7 +1144,7 @@ bool RenderLayer::updateLayerPosition()
             localPoint += offset;
         }
     } else if (parent()) {
-        if (isComposited()) {
+        if (compositedLayerMapping()) {
             // FIXME: Composited layers ignore pagination, so about the best we can do is make sure they're offset into the appropriate column.
             // They won't split across columns properly.
             LayoutSize columnOffset;
@@ -1277,13 +1276,17 @@ static inline const RenderLayer* compositingContainer(const RenderLayer* layer)
     return layer->isNormalFlowOnly() ? layer->parent() : layer->ancestorStackingContainer();
 }
 
+// FIXME: having two different functions named enclosingCompositingLayer and enclosingCompositingLayerForRepaint
+// is error-prone and misleading for reading code that uses these functions - especially compounded with
+// the includeSelf option. It is very likely that some call sites of this function actually mean to use
+// enclosingCompositingLayerForRepaint().
 RenderLayer* RenderLayer::enclosingCompositingLayer(bool includeSelf) const
 {
-    if (includeSelf && isComposited())
+    if (includeSelf && compositedLayerMapping())
         return const_cast<RenderLayer*>(this);
 
     for (const RenderLayer* curr = compositingContainer(this); curr; curr = compositingContainer(curr)) {
-        if (curr->isComposited())
+        if (curr->compositedLayerMapping())
             return const_cast<RenderLayer*>(curr);
     }
 
@@ -1292,11 +1295,11 @@ RenderLayer* RenderLayer::enclosingCompositingLayer(bool includeSelf) const
 
 RenderLayer* RenderLayer::enclosingCompositingLayerForRepaint(bool includeSelf) const
 {
-    if (includeSelf && isComposited() && !compositedLayerMapping()->paintsIntoCompositedAncestor())
+    if (includeSelf && compositingState() == PaintsIntoOwnBacking)
         return const_cast<RenderLayer*>(this);
 
     for (const RenderLayer* curr = compositingContainer(this); curr; curr = compositingContainer(curr)) {
-        if (curr->isComposited() && !curr->compositedLayerMapping()->paintsIntoCompositedAncestor())
+        if (curr->compositingState() == PaintsIntoOwnBacking)
             return const_cast<RenderLayer*>(curr);
     }
 
@@ -1334,7 +1337,7 @@ RenderLayer* RenderLayer::enclosingFilterLayer(bool includeSelf) const
 RenderLayer* RenderLayer::enclosingFilterRepaintLayer() const
 {
     for (const RenderLayer* curr = this; curr; curr = curr->parent()) {
-        if ((curr != this && curr->requiresFullLayerImageForFilters()) || curr->isComposited() || curr->isRootLayer())
+        if ((curr != this && curr->requiresFullLayerImageForFilters()) || curr->compositingState() == PaintsIntoOwnBacking || curr->isRootLayer())
             return const_cast<RenderLayer*>(curr);
     }
     return 0;
@@ -1365,7 +1368,7 @@ void RenderLayer::setFilterBackendNeedsRepaintingInRect(const LayoutRect& rect)
     FloatQuad repaintQuad(rectForRepaint);
     LayoutRect parentLayerRect = renderer()->localToContainerQuad(repaintQuad, parentLayer->renderer()).enclosingBoundingBox();
 
-    if (parentLayer->isComposited()) {
+    if (parentLayer->compositedLayerMapping()) {
         parentLayer->setBackingNeedsRepaintInRect(parentLayerRect);
         return;
     }
@@ -1396,7 +1399,7 @@ bool RenderLayer::hasAncestorWithFilterOutsets() const
 
 RenderLayer* RenderLayer::clippingRootForPainting() const
 {
-    if (isComposited())
+    if (compositedLayerMapping())
         return const_cast<RenderLayer*>(this);
 
     const RenderLayer* current = this;
@@ -1407,7 +1410,7 @@ RenderLayer* RenderLayer::clippingRootForPainting() const
         current = compositingContainer(current);
         ASSERT(current);
         if (current->transform()
-            || (current->isComposited() && !current->compositedLayerMapping()->paintsIntoCompositedAncestor())
+            || (current->compositingState() == PaintsIntoOwnBacking)
         )
             return const_cast<RenderLayer*>(current);
     }
@@ -1442,11 +1445,11 @@ bool RenderLayer::isTransparent() const
 
 RenderLayer* RenderLayer::transparentPaintingAncestor()
 {
-    if (isComposited())
+    if (compositedLayerMapping())
         return 0;
 
     for (RenderLayer* curr = parent(); curr; curr = curr->parent()) {
-        if (curr->isComposited())
+        if (curr->compositedLayerMapping())
             return 0;
         if (curr->isTransparent())
             return curr;
@@ -1885,7 +1888,7 @@ bool RenderLayer::usesCompositedScrolling() const
     if (box && (box->isIntristicallyScrollable(VerticalScrollbar) || box->isIntristicallyScrollable(HorizontalScrollbar)))
         return false;
 
-    return isComposited() && compositedLayerMapping()->scrollingLayer();
+    return compositedLayerMapping() && compositedLayerMapping()->scrollingLayer();
 }
 
 bool RenderLayer::needsCompositedScrolling() const
@@ -2516,7 +2519,7 @@ static bool paintForFixedRootBackground(const RenderLayer* layer, RenderLayer::P
 
 void RenderLayer::paintLayer(GraphicsContext* context, const LayerPaintingInfo& paintingInfo, PaintLayerFlags paintFlags)
 {
-    if (isComposited()) {
+    if (compositingState() != NotComposited) {
         // The updatingControlTints() painting pass goes through compositing layers,
         // but we need to ensure that we don't cache clip rects computed with the wrong root in this case.
         if (context->updatingControlTints() || (paintingInfo.paintBehavior & PaintBehaviorFlattenCompositingLayers)) {
@@ -4316,7 +4319,7 @@ IntRect RenderLayer::calculateLayerBounds(const RenderLayer* ancestorLayer, cons
     const_cast<RenderLayer*>(this)->updateLayerListsIfNeeded();
 
     if (RenderLayer* reflection = reflectionLayer()) {
-        if (!reflection->isComposited()) {
+        if (!reflection->compositedLayerMapping()) {
             IntRect childUnionBounds = reflection->calculateLayerBounds(this, 0, descendantFlags);
             unionBounds.unite(childUnionBounds);
         }
@@ -4328,11 +4331,14 @@ IntRect RenderLayer::calculateLayerBounds(const RenderLayer* ancestorLayer, cons
     LayerListMutationDetector mutationChecker(const_cast<RenderLayer*>(this));
 #endif
 
+    // FIXME: Descendants that are composited should not necessarily be skipped, if they don't paint into their own
+    // separate backing. Instead, they ought to contribute to the bounds of the layer we're trying to compute.
+    // This applies to all z-order lists below.
     if (Vector<RenderLayer*>* negZOrderList = this->negZOrderList()) {
         size_t listSize = negZOrderList->size();
         for (size_t i = 0; i < listSize; ++i) {
             RenderLayer* curLayer = negZOrderList->at(i);
-            if (flags & IncludeCompositedDescendants || !curLayer->isComposited()) {
+            if (flags & IncludeCompositedDescendants || !curLayer->compositedLayerMapping()) {
                 IntRect childUnionBounds = curLayer->calculateLayerBounds(this, 0, descendantFlags);
                 unionBounds.unite(childUnionBounds);
             }
@@ -4343,7 +4349,7 @@ IntRect RenderLayer::calculateLayerBounds(const RenderLayer* ancestorLayer, cons
         size_t listSize = posZOrderList->size();
         for (size_t i = 0; i < listSize; ++i) {
             RenderLayer* curLayer = posZOrderList->at(i);
-            if (flags & IncludeCompositedDescendants || !curLayer->isComposited()) {
+            if (flags & IncludeCompositedDescendants || !curLayer->compositedLayerMapping()) {
                 IntRect childUnionBounds = curLayer->calculateLayerBounds(this, 0, descendantFlags);
                 unionBounds.unite(childUnionBounds);
             }
@@ -4354,7 +4360,7 @@ IntRect RenderLayer::calculateLayerBounds(const RenderLayer* ancestorLayer, cons
         size_t listSize = normalFlowList->size();
         for (size_t i = 0; i < listSize; ++i) {
             RenderLayer* curLayer = normalFlowList->at(i);
-            if (flags & IncludeCompositedDescendants || !curLayer->isComposited()) {
+            if (flags & IncludeCompositedDescendants || !curLayer->compositedLayerMapping()) {
                 IntRect curAbsBounds = curLayer->calculateLayerBounds(this, 0, descendantFlags);
                 unionBounds.unite(curAbsBounds);
             }
@@ -4407,6 +4413,21 @@ void RenderLayer::clearClipRects(ClipRectsType typeToClear)
     }
 }
 
+CompositingState RenderLayer::compositingState() const
+{
+    // This is computed procedurally so there is no redundant state variable that
+    // can get out of sync from the real actual compositing state.
+
+    if (!m_compositedLayerMapping)
+        return NotComposited;
+
+    if (m_compositedLayerMapping && compositedLayerMapping()->paintsIntoCompositedAncestor())
+        return HasOwnBackingButPaintsIntoAncestor;
+
+    ASSERT(m_compositedLayerMapping);
+    return PaintsIntoOwnBacking;
+}
+
 CompositedLayerMapping* RenderLayer::ensureCompositedLayerMapping()
 {
     if (!m_compositedLayerMapping) {
@@ -4468,7 +4489,7 @@ GraphicsLayer* RenderLayer::layerForScrollCorner() const
 
 bool RenderLayer::paintsWithTransform(PaintBehavior paintBehavior) const
 {
-    return transform() && ((paintBehavior & PaintBehaviorFlattenCompositingLayers) || !isComposited());
+    return transform() && ((paintBehavior & PaintBehaviorFlattenCompositingLayers) || compositingState() != PaintsIntoOwnBacking);
 }
 
 bool RenderLayer::backgroundIsKnownToBeOpaqueInRect(const LayoutRect& localRect) const
@@ -4519,7 +4540,7 @@ bool RenderLayer::listBackgroundIsKnownToBeOpaqueInRect(const Vector<RenderLayer
 
     for (Vector<RenderLayer*>::const_reverse_iterator iter = list->rbegin(); iter != list->rend(); ++iter) {
         const RenderLayer* childLayer = *iter;
-        if (childLayer->isComposited())
+        if (childLayer->compositedLayerMapping())
             continue;
 
         if (!childLayer->canUseConvertToLayerCoords())
@@ -4776,7 +4797,7 @@ void RenderLayer::repaintIncludingDescendants()
 
 void RenderLayer::setBackingNeedsRepaint()
 {
-    ASSERT(isComposited());
+    ASSERT(compositedLayerMapping());
     compositedLayerMapping()->setContentsNeedDisplay();
 }
 
@@ -4784,8 +4805,8 @@ void RenderLayer::setBackingNeedsRepaintInRect(const LayoutRect& r)
 {
     // https://bugs.webkit.org/show_bug.cgi?id=61159 describes an unreproducible crash here,
     // so assert but check that the layer is composited.
-    ASSERT(isComposited());
-    if (!isComposited()) {
+    ASSERT(compositedLayerMapping());
+    if (!compositedLayerMapping()) {
         // If we're trying to repaint the placeholder document layer, propagate the
         // repaint to the native view system.
         LayoutRect absRect(r);
@@ -5002,7 +5023,7 @@ inline bool RenderLayer::needsCompositingLayersRebuiltForClip(const RenderStyle*
 inline bool RenderLayer::needsCompositingLayersRebuiltForOverflow(const RenderStyle* oldStyle, const RenderStyle* newStyle) const
 {
     ASSERT(newStyle);
-    return !isComposited() && oldStyle && (oldStyle->overflowX() != newStyle->overflowX()) && ancestorStackingContainer()->hasCompositingDescendant();
+    return !compositedLayerMapping() && oldStyle && (oldStyle->overflowX() != newStyle->overflowX()) && ancestorStackingContainer()->hasCompositingDescendant();
 }
 
 inline bool RenderLayer::needsCompositingLayersRebuiltForFilters(const RenderStyle* oldStyle, const RenderStyle* newStyle, bool didPaintWithFilters) const
@@ -5046,7 +5067,7 @@ void RenderLayer::updateFilters(const RenderStyle* oldStyle, const RenderStyle*
     updateOrRemoveFilterClients();
     // During an accelerated animation, both WebKit and the compositor animate properties.
     // However, WebKit shouldn't ask the compositor to update its filters if the compositor is performing the animation.
-    bool shouldUpdateFilters = isComposited() && !renderer()->animation()->isRunningAcceleratedAnimationOnRenderer(renderer(), CSSPropertyWebkitFilter);
+    bool shouldUpdateFilters = compositedLayerMapping() && !renderer()->animation()->isRunningAcceleratedAnimationOnRenderer(renderer(), CSSPropertyWebkitFilter);
     if (shouldUpdateFilters)
         compositedLayerMapping()->updateFilters(renderer()->style());
     updateOrRemoveFilterEffectRenderer();
@@ -5092,7 +5113,7 @@ void RenderLayer::styleChanged(StyleDifference, const RenderStyle* oldStyle)
         || needsCompositingLayersRebuiltForOverflow(oldStyle, newStyle)
         || needsCompositingLayersRebuiltForFilters(oldStyle, newStyle, didPaintWithFilters))
         compositor()->setCompositingLayersNeedRebuild();
-    else if (isComposited())
+    else if (compositedLayerMapping())
         compositedLayerMapping()->updateGraphicsLayerGeometry();
 }