Invalidation set features recognized left of adjacent.

Source/core/css/RuleFeature.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 2004-2005 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2006, 2007 Nicholas Shanks (webkit@nickshanks.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
  * Copyright (C) 2007, 2008 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (c) 2011, Code Aurora Forum. All rights reserved.
  * Copyright (C) Research In Motion Limited 2011. All rights reserved.
@@ skipping 103 matching lines @@
 }
 
 void RuleFeature::trace(Visitor* visitor)
 {
     visitor->trace(rule);
 }
 
 // This method is somewhat conservative in what it accepts.
 RuleFeatureSet::InvalidationSetMode RuleFeatureSet::invalidationSetModeForSelector(const CSSSelector& selector)
 {
-    bool foundDescendantRelation = false;
+    bool foundCombinator = false;
     bool foundIdent = false;
     for (const CSSSelector* component = &selector; component; component = component->tagHistory()) {
 
         if (component->match() == CSSSelector::Class || component->match() == CSSSelector::Id
             || (component->match() == CSSSelector::Tag && component->tagQName().localName() != starAtom)
             || component->isAttributeSelector() || component->isCustomPseudoElement()) {
-            if (!foundDescendantRelation)
+            if (!foundCombinator)
                 foundIdent = true;
         } else if (component->pseudoType() == CSSSelector::PseudoHost || component->pseudoType() == CSSSelector::PseudoAny) {
             if (const CSSSelectorList* selectorList = component->selectorList()) {
                 for (const CSSSelector* selector = selectorList->first(); selector; selector = CSSSelectorList::next(*selector)) {
                     InvalidationSetMode hostMode = invalidationSetModeForSelector(*selector);
                     if (hostMode == UseSubtreeStyleChange)
-                        return foundDescendantRelation ? UseLocalStyleChange : UseSubtreeStyleChange;
-                    if (!foundDescendantRelation && hostMode == AddFeatures)
+                        return foundCombinator ? UseLocalStyleChange : UseSubtreeStyleChange;
+                    if (!foundCombinator && hostMode == AddFeatures)
                         foundIdent = true;
                 }
             }
         } else if (!isSkippableComponentForInvalidation(*component)) {
-            return foundDescendantRelation ? UseLocalStyleChange : UseSubtreeStyleChange;
+            return foundCombinator ? UseLocalStyleChange : UseSubtreeStyleChange;
         }
-        switch (component->relation()) {
-        case CSSSelector::Descendant:
-        case CSSSelector::Child:
-        case CSSSelector::ShadowPseudo:
-        case CSSSelector::ShadowDeep:
-            foundDescendantRelation = true;
-            // Fall through!
-        case CSSSelector::SubSelector:
-        case CSSSelector::DirectAdjacent:
-        case CSSSelector::IndirectAdjacent:
-            continue;
-        default:
-            // All combinators should be handled above.
-            ASSERT_NOT_REACHED();
-            return UseLocalStyleChange;
-        }
+        if (component->relation() != CSSSelector::SubSelector)
+            foundCombinator = true;
     }
     return foundIdent ? AddFeatures : UseLocalStyleChange;
 }
 
 void RuleFeatureSet::extractInvalidationSetFeature(const CSSSelector& selector, InvalidationSetFeatures& features)
 {
     if (selector.match() == CSSSelector::Tag)
         features.tagName = selector.tagQName().localName();
     else if (selector.match() == CSSSelector::Id)
         features.id = selector.value();
@@ skipping 23 matching lines @@
     if (selector.match() == CSSSelector::Id)
         return &ensureIdInvalidationSet(selector.value());
     if (selector.match() == CSSSelector::PseudoClass) {
         CSSSelector::PseudoType pseudo = selector.pseudoType();
         if (pseudo == CSSSelector::PseudoHover || pseudo == CSSSelector::PseudoActive || pseudo == CSSSelector::PseudoFocus)
             return &ensurePseudoInvalidationSet(pseudo);
     }
     return 0;
 }
 
+// Given a selector, update the descendant invalidation sets for the features found
+// in the selector. The first step is to extract the features from the rightmost
+// compound selector (extractInvalidationSetFeatures). Secondly, those features will be
+// added to the invalidation sets for the features found in the other compound selectors
+// (addFeaturesToInvalidationSets).
+
 RuleFeatureSet::InvalidationSetMode RuleFeatureSet::updateInvalidationSets(const CSSSelector& selector)
 {
     InvalidationSetMode mode = invalidationSetModeForSelector(selector);
     if (mode != AddFeatures)
         return mode;
 
     InvalidationSetFeatures features;
     if (const CSSSelector* current = extractInvalidationSetFeatures(selector, features))
         addFeaturesToInvalidationSets(*current, features);
     return AddFeatures;
@@ skipping 24 matching lines @@
             features.wholeSubtree = true;
             return current->tagHistory();
         case CSSSelector::Descendant:
         case CSSSelector::Child:
             return current->tagHistory();
         }
     }
     return 0;
 }
 
+// Add features extracted from the rightmost compound selector to descendant invalidation
+// sets for features found in other compound selectors.
+//
+// Style invalidation is currently supported for descendants only, not for sibling subtrees.
+// We use wholeSubtree invalidation for features found left of adjacent combinators as
+// SubtreeStyleChange will force sibling subtree recalc in
+// ContainerNode::checkForChildrenAdjacentRuleChanges.
+//
+// As we encounter a descendant type of combinator, the features only need to be checked
+// against descendants in the same subtree only. Hence wholeSubtree is reset to false.
+
 void RuleFeatureSet::addFeaturesToInvalidationSets(const CSSSelector& selector, InvalidationSetFeatures& features)
 {
     for (const CSSSelector* current = &selector; current; current = current->tagHistory()) {
         if (DescendantInvalidationSet* invalidationSet = invalidationSetForSelector(*current)) {
             if (features.treeBoundaryCrossing)
                 invalidationSet->setTreeBoundaryCrossing();
             if (features.wholeSubtree) {
                 invalidationSet->setWholeSubtreeInvalid();
             } else {
                 if (!features.id.isEmpty())
@@ skipping 265 matching lines @@
     visitor->trace(uncommonAttributeRules);
     visitor->trace(m_classInvalidationSets);
     visitor->trace(m_attributeInvalidationSets);
     visitor->trace(m_idInvalidationSets);
     visitor->trace(m_pseudoInvalidationSets);
     visitor->trace(m_styleInvalidator);
 #endif
 }
 
 } // namespace blink