Use correct cascading order for Shadow DOM v1

third_party/WebKit/Source/core/css/resolver/StyleResolver.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, 2013 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 369 matching lines @@
 
 void StyleResolver::clearStyleSharingList()
 {
     m_styleSharingLists.resize(0);
 }
 
 static inline ScopedStyleResolver* scopedResolverFor(const Element& element)
 {
     // Ideally, returning element->treeScope().scopedStyleResolver() should be
     // enough, but ::cue and custom pseudo elements like ::-webkit-meter-bar pierce
-    // through a shadow dom boundary, yet they are not part of m_treeBoundaryCrossingRules.
+    // through a shadow dom boundary, yet they are not part of m_treeBoundaryCrossingScopes.
     // The assumption here is that these rules only pierce through one boundary and
     // that the scope of these elements do not have a style resolver due to the fact
     // that VTT scopes and UA shadow trees don't have <style> elements. This is
     // backed up by the ASSERTs below.
     //
     // FIXME: Make ::cue and custom pseudo elements part of boundary crossing rules
     // when moving those rules to ScopedStyleResolver as part of issue 401359.
 
     TreeScope* treeScope = &element.treeScope();
     if (ScopedStyleResolver* resolver = treeScope->scopedStyleResolver()) {
         ASSERT(element.shadowPseudoId().isEmpty());
         ASSERT(!element.isVTTElement());
         return resolver;
     }
 
     treeScope = treeScope->parentTreeScope();
     if (!treeScope)
         return nullptr;
     if (element.shadowPseudoId().isEmpty() && !element.isVTTElement())
         return nullptr;
     return treeScope->scopedStyleResolver();
 }
 
+static void matchHostRules(const Element& element, ElementRuleCollector& collector)
+{
+    ElementShadow* shadow = element.shadow();
+    if (!shadow)
+        return;
+
+    for (ShadowRoot* shadowRoot = shadow->oldestShadowRoot(); shadowRoot; shadowRoot = shadowRoot->youngerShadowRoot()) {
+        if (!shadowRoot->numberOfStyles())
+            continue;
+        if (ScopedStyleResolver* resolver = shadowRoot->scopedStyleResolver()) {
+            collector.clearMatchedRules();
+            resolver->collectMatchingShadowHostRules(collector);
+            collector.sortAndTransferMatchedRules();
+            collector.finishAddingAuthorRulesForTreeScope();
+        }
+    }
+}
+
+static void matchElementScopeRules(const Element& element, ScopedStyleResolver* elementScopeResolver, ElementRuleCollector& collector)
+{
+    if (elementScopeResolver) {
+        collector.clearMatchedRules();
+        elementScopeResolver->collectMatchingAuthorRules(collector);
+        elementScopeResolver->collectMatchingTreeBoundaryCrossingRules(collector);
+        collector.sortAndTransferMatchedRules();
+    }
+
+    if (element.isStyledElement() && element.inlineStyle() && !collector.isCollectingForPseudoElement()) {

[rune, 2016/03/18 12:04:12]

Adding inline style here means we'll have inline style between /deep/ rules from
outer scope and :host rules in the case where you have mixed v0/v1. Is that the
intention?

Could you point to were the final decision/spec for the v1 cascade order was?

[kochi, 2016/03/22 08:16:59]

Yes, in v0/v1 mix, /deep/ wins against inline style.

The spec is not in the final state, but this issue is the resolution so far:
https://github.com/w3c/webcomponents/issues/316
I'm working on upstreaming to CSS scoping spec with Tab.

Adding a v1 shadow on v0 site will break in various degree, we don't have to
care
about cases when adding v1 breaks v0 site (hopefully:) ).

+        // Inline style is immutable as long as there is no CSSOM wrapper.
+        bool isInlineStyleCacheable = !element.inlineStyle()->isMutable();
+        collector.addElementStyleProperties(element.inlineStyle(), isInlineStyleCacheable);
+    }
+
+    collector.finishAddingAuthorRulesForTreeScope();
+}
+
+static bool shouldCheckScope(const Element& element, const Node& scopingNode, bool isInnerTreeScope)
+{
+    if (isInnerTreeScope && element.treeScope() != scopingNode.treeScope()) {
+        // Check if |element| may be affected by a ::content rule in |scopingNode|'s style.
+        // If |element| is a descendant of a shadow host which is ancestral to |scopingNode|,
+        // the |element| should be included for rule collection.
+        // Skip otherwise.
+        const TreeScope* scope = &scopingNode.treeScope();
+        while (scope && scope->parentTreeScope() != &element.treeScope())
+            scope = scope->parentTreeScope();
+        Element* shadowHost = scope ? scope->rootNode().shadowHost() : nullptr;
+        return shadowHost && element.isDescendantOf(shadowHost);
+    }
+
+    // When |element| can be distributed to |scopingNode| via <shadow>, ::content rule can match,
+    // thus the case should be included.
+    if (!isInnerTreeScope && scopingNode.parentOrShadowHostNode() == element.treeScope().rootNode().parentOrShadowHostNode())
+        return true;
+
+    // Obviously cases when ancestor scope has /deep/ or ::shadow rule should be included.
+    // Skip otherwise.
+    return scopingNode.treeScope().scopedStyleResolver()->hasDeepOrShadowSelector();
+}
+
+void StyleResolver::matchScopedRules(const Element& element, ElementRuleCollector& collector)
+{
+    // Match rules from treeScopes in the reverse tree-of-trees order, since the
+    // cascading order for normal rules is such that when comparing rules from
+    // different shadow trees, the rule from the tree which comes first in the
+    // tree-of-trees order wins. From other treeScopes than the element's own
+    // scope, only tree-boundary-crossing rules may match.
+
+    ScopedStyleResolver* elementScopeResolver = scopedResolverFor(element);
+    bool matchElementScopeDone = !elementScopeResolver && !element.inlineStyle();
+
+    // TODO(kochi): This loops through m_treeBoundaryCrossingScopes because to handle
+    // Shadow DOM V0 documents as well. In pure V1 document only have to go through
+    // the chain of scopes for assigned slots. Add fast path for pure V1 document.
+    for (auto it = m_treeBoundaryCrossingScopes.rbegin(); it != m_treeBoundaryCrossingScopes.rend(); ++it) {
+        const TreeScope& scope = (*it)->treeScope();
+        ScopedStyleResolver* resolver = scope.scopedStyleResolver();
+        ASSERT(resolver);
+
+        bool isInnerTreeScope = element.treeScope().isInclusiveAncestorOf(scope);
+        if (!shouldCheckScope(element, **it, isInnerTreeScope))
+            continue;
+
+        if (!matchElementScopeDone && scope.isInclusiveAncestorOf(element.treeScope())) {
+
+            matchElementScopeDone = true;
+
+            // At this point, the iterator has either encountered the scope for the element
+            // itself (if that scope has boundary-crossing rules), or the iterator has moved
+            // to a scope which appears before the element's scope in the tree-of-trees order.
+            // Try to match all rules from the element's scope.
+
+            matchElementScopeRules(element, elementScopeResolver, collector);
+            if (resolver == elementScopeResolver) {
+                // Boundary-crossing rules already collected in matchElementScopeRules.
+                continue;
+            }
+        }
+
+        collector.clearMatchedRules();
+        resolver->collectMatchingTreeBoundaryCrossingRules(collector);
+        collector.sortAndTransferMatchedRules();
+        collector.finishAddingAuthorRulesForTreeScope();
+    }
+
+    if (!matchElementScopeDone)
+        matchElementScopeRules(element, elementScopeResolver, collector);
+}
+
 void StyleResolver::matchAuthorRules(const Element& element, ElementRuleCollector& collector)
 {
+    if (!element.document().styleEngine().useCascadeOrderForShadowDOMV1()) {
+        matchAuthorRulesV0(element, collector);
+        return;
+    }
+
+    ASSERT(RuntimeEnabledFeatures::shadowDOMV1Enabled());
+    matchHostRules(element, collector);
+    matchScopedRules(element, collector);
+}
+
+void StyleResolver::matchAuthorRulesV0(const Element& element, ElementRuleCollector& collector)
+{
     collector.clearMatchedRules();
 
     CascadeOrder cascadeOrder = 0;
     WillBeHeapVector<RawPtrWillBeMember<ScopedStyleResolver>, 8> resolversInShadowTree;
     collectScopedResolversForHostedShadowTrees(element, resolversInShadowTree);
 
     // Apply :host and :host-context rules from inner scopes.
     for (int j = resolversInShadowTree.size() - 1; j >= 0; --j)
         resolversInShadowTree.at(j)->collectMatchingShadowHostRules(collector, ++cascadeOrder);
 
@@ skipping 52 matching lines @@
             if (isAuto) {
                 state.setHasDirAutoAttribute(true);
                 collector.addElementStyleProperties(textDirection == LTR ? leftToRightDeclaration() : rightToLeftDeclaration());
             }
         }
     }
 
     matchAuthorRules(*state.element(), collector);
 
     if (state.element()->isStyledElement()) {
-        if (state.element()->inlineStyle()) {
+        // For Shadow DOM V1, inline style is already collected in matchScopedRules().
+        if (!state.element()->document().styleEngine().useCascadeOrderForShadowDOMV1() && state.element()->inlineStyle()) {
             // Inline style is immutable as long as there is no CSSOM wrapper.
             bool isInlineStyleCacheable = !state.element()->inlineStyle()->isMutable();
             collector.addElementStyleProperties(state.element()->inlineStyle(), isInlineStyleCacheable);
         }
 
         // Now check SMIL animation override style.
         if (includeSMILProperties && state.element()->isSVGElement())
             collector.addElementStyleProperties(toSVGElement(state.element())->animatedSMILStyleProperties(), false /* isCacheable */);
     }
 
     collector.finishAddingAuthorRulesForTreeScope();
 }
 
-static bool shouldCheckScope(const Element& element, const Node& scopingNode, bool isInnerTreeScope)
-{
-    if (isInnerTreeScope && element.treeScope() != scopingNode.treeScope()) {
-        // Check if |element| may be affected by a ::content rule in |scopingNode|'s style.
-        // If |element| is a descendant of a shadow host which is ancestral to |scopingNode|,
-        // the |element| should be included for rule collection.
-        // Skip otherwise.
-        const TreeScope* scope = &scopingNode.treeScope();
-        while (scope && scope->parentTreeScope() != &element.treeScope())
-            scope = scope->parentTreeScope();
-        Element* shadowHost = scope ? scope->rootNode().shadowHost() : nullptr;
-        return shadowHost && element.isDescendantOf(shadowHost);
-    }
-
-    // When |element| can be distributed to |scopingNode| via <shadow>, ::content rule can match,
-    // thus the case should be included.
-    if (!isInnerTreeScope && scopingNode.parentOrShadowHostNode() == element.treeScope().rootNode().parentOrShadowHostNode())
-        return true;
-
-    // Obviously cases when ancestor scope has /deep/ or ::shadow rule should be included.
-    // Skip otherwise.
-    return scopingNode.treeScope().scopedStyleResolver()->hasDeepOrShadowSelector();
-}
-
 void StyleResolver::collectTreeBoundaryCrossingRules(const Element& element, ElementRuleCollector& collector)
 {
     if (m_treeBoundaryCrossingScopes.isEmpty())
         return;
 
     // When comparing rules declared in outer treescopes, outer's rules win.
     CascadeOrder outerCascadeOrder = m_treeBoundaryCrossingScopes.size() * 2;
     // When comparing rules declared in inner treescopes, inner's rules win.
     CascadeOrder innerCascadeOrder = m_treeBoundaryCrossingScopes.size();
 
@@ skipping 1076 matching lines @@
     visitor->trace(m_uncommonAttributeRuleSet);
     visitor->trace(m_watchedSelectorsRules);
     visitor->trace(m_treeBoundaryCrossingScopes);
     visitor->trace(m_styleSharingLists);
     visitor->trace(m_pendingStyleSheets);
     visitor->trace(m_document);
 #endif
 }
 
 } // namespace blink