Bug 1180118 - Part 1: Add a method to match a single nsCSSSelector (without pseudo-elements) against an Element. r=bzbarsky

layout/style/StyleRule.h

@@ -159,6 +159,12 @@ public:
   void ToString(nsAString& aString, mozilla::CSSStyleSheet* aSheet,
                 bool aAppend = false) const;
 
+#ifdef DEBUG
+  bool IsRestrictedSelector() const {
+    return PseudoType() == nsCSSPseudoElements::ePseudo_NotPseudoElement;
+  }
+#endif
+
 private:
   void AddPseudoClassInternal(nsPseudoClassList *aPseudoClass);
   nsCSSSelector* Clone(bool aDeepNext, bool aDeepNegations) const;

layout/style/nsCSSRuleProcessor.cpp

@@ -2293,6 +2293,36 @@ static bool SelectorMatches(Element* aElement,
 
 #undef STATE_CHECK
 
+/* static */ bool
+nsCSSRuleProcessor::RestrictedSelectorMatches(
+    Element* aElement,
+    nsCSSSelector* aSelector,
+    TreeMatchContext& aTreeMatchContext)
+{
+  MOZ_ASSERT(aSelector->IsRestrictedSelector(),
+             "aSelector must not have a pseudo-element");
+
+  // We match aSelector as if :visited and :link both match visited and
+  // unvisited links.
+
+  NodeMatchContext nodeContext(EventStates(),
+                               nsCSSRuleProcessor::IsLink(aElement));
+  if (nodeContext.mIsRelevantLink) {
+    aTreeMatchContext.SetHaveRelevantLink();
+  }
+  aTreeMatchContext.ResetForUnvisitedMatching();
+  bool matches = SelectorMatches(aElement, aSelector, nodeContext,
+                                 aTreeMatchContext, SelectorMatchesFlags::NONE);
+  if (nodeContext.mIsRelevantLink) {
+    aTreeMatchContext.ResetForVisitedMatching();
+    if (SelectorMatches(aElement, aSelector, nodeContext, aTreeMatchContext,
+                        SelectorMatchesFlags::NONE)) {
+      matches = true;
+    }
+  }
+  return matches;
+}
+
 // Right now, there are four operators:
 //   ' ', the descendant combinator, is greedy
 //   '~', the indirect adjacent sibling combinator, is greedy

layout/style/nsCSSRuleProcessor.h

@@ -112,6 +112,21 @@ public:
    */
   static bool IsLink(mozilla::dom::Element* aElement);
 
+  /**
+   * Returns true if the given aElement matches aSelector.
+   * Like nsCSSRuleProcessor.cpp's SelectorMatches (and unlike
+   * SelectorMatchesTree), this does not check an entire selector list
+   * separated by combinators.
+   *
+   * :visited and :link will match both visited and non-visited links,
+   * as if aTreeMatchContext->mVisitedHandling were eLinksVisitedOrUnvisited.
+   *
+   * aSelector is restricted to not containing pseudo-elements.
+   */
+  static bool RestrictedSelectorMatches(mozilla::dom::Element* aElement,
+                                        nsCSSSelector* aSelector,
+                                        TreeMatchContext& aTreeMatchContext);
+
   // nsIStyleRuleProcessor
   virtual void RulesMatching(ElementRuleProcessorData* aData) override;