Make compositingState explicit (re-land #2 with bogus ASSERT removed)

A lot of code uses isComposited() and compositedLayerMapping()
as booleans to check the compositing state of a RenderLayer or
RenderObject. However, in the code there are actually 3 different
states:

(1) not composited (paints into CompositedLayerMapping of a
    composited ancestor)
(2) paints into own CompositedLayerMapping
(3) has its own CompositedLayerMapping but actually still paints
    into composited ancestor.

Furthermore, upcoming changes to compositing will add a
fourth state:

(4) paints into a GraphicsLayer that is shared by a group of
    layers.

This patch removes isComposited() boolean check, and
replaces it with compositingState() that returns an enum.

Most call sites outside of RenderLayer, CompositedLayerMapping,
and RenderLayerCompositor have been updated to reflect
what states they really intended to check for.  Remaining call
sites have been replaced with the compositedLayerMapping()
accessor for now, which is exactly equivalent to the old
isComposited() boolean, and those sites will be updated in
follow-up patches.

BUG=261605
R=jamesr@chromium.org, jchaffraix@chromium.org, vollick@chromium.org

Review URL: https://codereview.chromium.org/24921002

git-svn-id: svn://svn.chromium.org/blink/trunk@159118 bbb929c8-8fbe-4397-9dbb-9b2b20218538

Source/core/css/CSSComputedStyleDeclaration.cpp

@@ -1616,7 +1616,8 @@ PassRefPtr<RenderStyle> CSSComputedStyleDeclaration::computeRenderStyle(CSSPrope
     Node* styledNode = this->styledNode();
     ASSERT(styledNode);
     RenderObject* renderer = styledNode->renderer();
-    if (renderer && renderer->isComposited() && !RuntimeEnabledFeatures::webAnimationsCSSEnabled() && AnimationController::supportsAcceleratedAnimationOfProperty(propertyID)) {
+    if (renderer && renderer->compositingState() == PaintsIntoOwnBacking
+        && !RuntimeEnabledFeatures::webAnimationsCSSEnabled() && AnimationController::supportsAcceleratedAnimationOfProperty(propertyID)) {
         AnimationUpdateBlock animationUpdateBlock(renderer->animation());
         if (m_pseudoElementSpecifier && !styledNode->isPseudoElement()) {
             // FIXME: This cached pseudo style will only exist if the animation has been run at least once.

Source/core/inspector/InspectorLayerTreeAgent.cpp

@@ -204,7 +204,7 @@ void InspectorLayerTreeAgent::getLayers(ErrorString* errorString, const int* nod
 
 void InspectorLayerTreeAgent::buildLayerIdToNodeIdMap(ErrorString* errorString, RenderLayer* root, LayerIdToNodeIdMap& layerIdToNodeIdMap)
 {
-    if (root->isComposited()) {
+    if (root->compositedLayerMapping()) {
         if (Node* node = root->renderer()->generatingNode()) {
             GraphicsLayer* graphicsLayer = root->compositedLayerMapping()->childForSuperlayers();
             layerIdToNodeIdMap.set(graphicsLayer->platformLayer()->id(), idForNode(errorString, node));

Source/core/page/FrameView.cpp

@@ -1255,7 +1255,7 @@ void FrameView::updateCanBlitOnScrollRecursively()
 bool FrameView::contentsInCompositedLayer() const
 {
     RenderView* renderView = this->renderView();
-    if (renderView && renderView->isComposited()) {
+    if (renderView && renderView->compositingState() == PaintsIntoOwnBacking) {
         GraphicsLayer* layer = renderView->layer()->compositedLayerMapping()->mainGraphicsLayer();
         if (layer && layer->drawsContent())
             return true;
@@ -1372,10 +1372,10 @@ bool FrameView::scrollContentsFastPath(const IntSize& scrollDelta, const IntRect
         ASSERT(renderer->hasLayer());
         RenderLayer* layer = toRenderBoxModelObject(renderer)->layer();
 
-        // Composited layers may still actually paint into their ancestor.
-        // If that happens, the viewport constrained object needs to be
-        // repainted on scroll.
-        if (layer->isComposited() && !layer->compositedLayerMapping()->paintsIntoCompositedAncestor())
+        // Layers that paint into their ancestor or into a grouped backing will still need
+        // to apply a repaint invalidation. If the layer paints into its own backing, then
+        // it does not need repainting just to scroll.
+        if (layer->compositingState() == PaintsIntoOwnBacking)
             continue;
 
         if (layer->viewportConstrainedNotCompositedReason() == RenderLayer::NotCompositedForBoundsOutOfView

Source/core/page/animation/AnimationBase.cpp

@@ -555,8 +555,9 @@ void AnimationBase::freezeAtTime(double t)
     else
         m_pauseTime = m_startTime + t - m_animation->delay();
 
-    // It is possible that m_isAccelerated is true and m_object->isComposited() is false, because of style change.
-    if (m_object && m_object->isComposited() && isAccelerated())
+    // It is possible that m_isAccelerated is true and m_object->compositingState() is NotComposited, because of style change.
+    // So, both conditions need to be checked.
+    if (m_object && m_object->compositingState() == PaintsIntoOwnBacking && isAccelerated())
         toRenderBoxModelObject(m_object)->suspendAnimations(m_pauseTime);
 }
 

Source/core/page/animation/ImplicitAnimation.cpp

@@ -104,7 +104,7 @@ void ImplicitAnimation::getAnimatedStyle(RefPtr<RenderStyle>& animatedStyle)
 
 void ImplicitAnimation::startAnimation(double timeOffset)
 {
-    if (m_object && m_object->isComposited())
+    if (m_object && m_object->compositingState() == PaintsIntoOwnBacking)
         m_isAccelerated = toRenderBoxModelObject(m_object)->startTransition(timeOffset, m_animatingProperty, m_fromStyle.get(), m_toStyle.get());
 }
 
@@ -113,7 +113,7 @@ void ImplicitAnimation::pauseAnimation(double timeOffset)
     if (!m_object)
         return;
 
-    if (m_object && m_object->isComposited() && isAccelerated())
+    if (m_object && m_object->compositingState() == PaintsIntoOwnBacking && isAccelerated())
         toRenderBoxModelObject(m_object)->transitionPaused(timeOffset, m_animatingProperty);
 
     // Restore the original (unanimated) style
@@ -123,7 +123,7 @@ void ImplicitAnimation::pauseAnimation(double timeOffset)
 
 void ImplicitAnimation::endAnimation()
 {
-    if (m_object && m_object->isComposited() && isAccelerated())
+    if (m_object && m_object->compositingState() == PaintsIntoOwnBacking && isAccelerated())
         toRenderBoxModelObject(m_object)->transitionFinished(m_animatingProperty);
     m_isAccelerated = false;
 }

Source/core/page/animation/KeyframeAnimation.cpp

@@ -239,7 +239,7 @@ bool KeyframeAnimation::hasAnimationForProperty(CSSPropertyID property) const
 
 void KeyframeAnimation::startAnimation(double timeOffset)
 {
-    if (m_object && m_object->isComposited())
+    if (m_object && m_object->compositingState() == PaintsIntoOwnBacking)
         m_isAccelerated = toRenderBoxModelObject(m_object)->startAnimation(timeOffset, m_animation.get(), m_keyframes);
 }
 
@@ -248,7 +248,7 @@ void KeyframeAnimation::pauseAnimation(double timeOffset)
     if (!m_object)
         return;
 
-    if (m_object && m_object->isComposited() && isAccelerated())
+    if (m_object && m_object->compositingState() == PaintsIntoOwnBacking && isAccelerated())
         toRenderBoxModelObject(m_object)->animationPaused(timeOffset, m_keyframes.animationName());
 
     // Restore the original (unanimated) style
@@ -261,7 +261,7 @@ void KeyframeAnimation::endAnimation()
     if (!m_object)
         return;
 
-    if (m_object && m_object->isComposited() && isAccelerated())
+    if (m_object && m_object->compositingState() == PaintsIntoOwnBacking && isAccelerated())
         toRenderBoxModelObject(m_object)->animationFinished(m_keyframes.animationName());
     m_isAccelerated = false;
 

Source/core/page/scrolling/ScrollingCoordinator.cpp

@@ -159,7 +159,7 @@ static void clearPositionConstraintExceptForLayer(GraphicsLayer* layer, Graphics
 
 static WebLayerPositionConstraint computePositionConstraint(const RenderLayer* layer)
 {
-    ASSERT(layer->isComposited());
+    ASSERT(layer->compositedLayerMapping());
     do {
         if (layer->renderer()->style()->position() == FixedPosition) {
             const RenderObject* fixedPositionObject = layer->renderer();
@@ -169,7 +169,10 @@ static WebLayerPositionConstraint computePositionConstraint(const RenderLayer* l
         }
 
         layer = layer->parent();
-    } while (layer && !layer->isComposited());
+
+        // Composited layers that inherit a fixed position state will be positioned with respect to the nearest compositedLayerMapping's GraphicsLayer.
+        // So, once we find a layer that has its own compositedLayerMapping, we can stop searching for a fixed position RenderObject.
+    } while (layer && layer->compositedLayerMapping());
     return WebLayerPositionConstraint();
 }
 
@@ -806,12 +809,12 @@ bool ScrollingCoordinator::hasVisibleSlowRepaintViewportConstrainedObjects(Frame
             return true;
         RenderLayer* layer = toRenderBoxModelObject(viewportConstrainedObject)->layer();
         // Any explicit reason that a fixed position element is not composited shouldn't cause slow scrolling.
-        if (!layer->isComposited() && layer->viewportConstrainedNotCompositedReason() == RenderLayer::NoNotCompositedReason)
+        if (layer->compositingState() != PaintsIntoOwnBacking && layer->viewportConstrainedNotCompositedReason() == RenderLayer::NoNotCompositedReason)
             return true;
 
         // Composited layers that actually paint into their enclosing ancestor
         // must also force main thread scrolling.
-        if (layer->isComposited() && layer->compositedLayerMapping()->paintsIntoCompositedAncestor())
+        if (layer->compositingState() == HasOwnBackingButPaintsIntoAncestor)
             return true;
     }
     return false;

Source/core/rendering/CompositedLayerMapping.cpp

@@ -696,7 +696,7 @@ void CompositedLayerMapping::updateGraphicsLayerGeometry()
         m_backgroundLayer->setOffsetFromRenderer(m_graphicsLayer->offsetFromRenderer());
     }
 
-    if (m_owningLayer->reflectionLayer() && m_owningLayer->reflectionLayer()->isComposited()) {
+    if (m_owningLayer->reflectionLayer() && m_owningLayer->reflectionLayer()->compositedLayerMapping()) {
         CompositedLayerMapping* reflectionCompositedLayerMapping = m_owningLayer->reflectionLayer()->compositedLayerMapping();
         reflectionCompositedLayerMapping->updateGraphicsLayerGeometry();
 
@@ -1197,9 +1197,16 @@ float CompositedLayerMapping::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();
@@ -1337,7 +1344,7 @@ 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->compositedLayerMapping()
                 && (curLayer->hasVisibleContent() || hasVisibleNonCompositingDescendant(curLayer)))
                 return true;
         }
@@ -1352,7 +1359,7 @@ 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->compositedLayerMapping()
                     && (curLayer->hasVisibleContent() || hasVisibleNonCompositingDescendant(curLayer)))
                     return true;
             }
@@ -1362,7 +1369,7 @@ 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->compositedLayerMapping()
                     && (curLayer->hasVisibleContent() || hasVisibleNonCompositingDescendant(curLayer)))
                     return true;
             }
@@ -1372,7 +1379,9 @@ static bool hasVisibleNonCompositingDescendant(RenderLayer* parent)
     return false;
 }
 
-// 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 CompositedLayerMapping::hasVisibleNonCompositingDescendantLayers() const
 {
     return hasVisibleNonCompositingDescendant(m_owningLayer);

Source/core/rendering/CompositingState.h

@@ -0,0 +1,25 @@
+// Copyright 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CompositingState_h
+#define CompositingState_h
+
+namespace WebCore {
+
+enum CompositingState {
+    // The layer paints into its enclosing composited ancestor.
+    NotComposited = 0,
+
+    // The layer is composited, but its contents still paint into enclosing composited ancestor.
+    // In this state, repaint invalidations must be sent to the enclosing composited ancestor.
+    // Typically this happens when a layer's properties need to be represented in the compositor
+    // output data structures, but it doesn't actually have any other reasons to be composited.
+    HasOwnBackingButPaintsIntoAncestor = 1,
+
+    PaintsIntoOwnBacking = 2,
+};
+
+} // namespace WebCore
+
+#endif // CompositingState_h

Source/core/rendering/RenderBox.cpp

@@ -1257,7 +1257,8 @@ static bool isCandidateForOpaquenessTest(RenderBox* childBox)
     if (!childBox->width() || !childBox->height())
         return false;
     if (RenderLayer* childLayer = childBox->layer()) {
-        if (childLayer->isComposited())
+        // FIXME: perhaps this could be less conservative?
+        if (childLayer->compositingState() != NotComposited)
             return false;
         // FIXME: Deal with z-index.
         if (!childStyle->hasAutoZIndex())
@@ -1352,9 +1353,13 @@ void RenderBox::paintClippingMask(PaintInfo& paintInfo, const LayoutPoint& paint
     if (!paintInfo.shouldPaintWithinRoot(this) || style()->visibility() != VISIBLE || paintInfo.phase != PaintPhaseClippingMask || paintInfo.context->paintingDisabled())
         return;
 
-    if (!layer() || !layer()->isComposited())
+    if (!layer() || layer()->compositingState() != PaintsIntoOwnBacking)
         return;
 
+    // We should never have this state in this function. A layer with a mask
+    // should have always created its own backing if it became composited.
+    ASSERT(layer()->compositingState() != HasOwnBackingButPaintsIntoAncestor);
+
     LayoutRect paintRect = LayoutRect(paintOffset, size());
     paintInfo.context->fillRect(pixelSnappedIntRect(paintRect), Color::black);
 }

Source/core/rendering/RenderBoxModelObject.cpp

@@ -102,49 +102,49 @@ bool RenderBoxModelObject::hasAcceleratedCompositing() const
 bool RenderBoxModelObject::startTransition(double timeOffset, CSSPropertyID propertyId, const RenderStyle* fromStyle, const RenderStyle* toStyle)
 {
     ASSERT(hasLayer());
-    ASSERT(isComposited());
+    ASSERT(compositingState() == PaintsIntoOwnBacking);
     return layer()->compositedLayerMapping()->startTransition(timeOffset, propertyId, fromStyle, toStyle);
 }
 
 void RenderBoxModelObject::transitionPaused(double timeOffset, CSSPropertyID propertyId)
 {
     ASSERT(hasLayer());
-    ASSERT(isComposited());
+    ASSERT(compositingState() == PaintsIntoOwnBacking);
     layer()->compositedLayerMapping()->transitionPaused(timeOffset, propertyId);
 }
 
 void RenderBoxModelObject::transitionFinished(CSSPropertyID propertyId)
 {
     ASSERT(hasLayer());
-    ASSERT(isComposited());
+    ASSERT(compositingState() == PaintsIntoOwnBacking);
     layer()->compositedLayerMapping()->transitionFinished(propertyId);
 }
 
 bool RenderBoxModelObject::startAnimation(double timeOffset, const CSSAnimationData* animation, const KeyframeList& keyframes)
 {
     ASSERT(hasLayer());
-    ASSERT(isComposited());
+    ASSERT(compositingState() == PaintsIntoOwnBacking);
     return layer()->compositedLayerMapping()->startAnimation(timeOffset, animation, keyframes);
 }
 
 void RenderBoxModelObject::animationPaused(double timeOffset, const String& name)
 {
     ASSERT(hasLayer());
-    ASSERT(isComposited());
+    ASSERT(compositingState() == PaintsIntoOwnBacking);
     layer()->compositedLayerMapping()->animationPaused(timeOffset, name);
 }
 
 void RenderBoxModelObject::animationFinished(const String& name)
 {
     ASSERT(hasLayer());
-    ASSERT(isComposited());
+    ASSERT(compositingState() == PaintsIntoOwnBacking);
     layer()->compositedLayerMapping()->animationFinished(name);
 }
 
 void RenderBoxModelObject::suspendAnimations(double time)
 {
     ASSERT(hasLayer());
-    ASSERT(isComposited());
+    ASSERT(compositingState() == PaintsIntoOwnBacking);
     layer()->compositedLayerMapping()->suspendAnimations(time);
 }
 
@@ -985,7 +985,7 @@ bool RenderBoxModelObject::fixedBackgroundPaintsInLocalCoordinates() const
         return false;
 
     RenderLayer* rootLayer = view()->layer();
-    if (!rootLayer || !rootLayer->isComposited())
+    if (!rootLayer || rootLayer->compositingState() == NotComposited)
         return false;
 
     return rootLayer->compositedLayerMapping()->backgroundLayerPaintsFixedRootBackground();