Bug 1228877 - Make nsStyleContext::HasChildThatUsesGrandancestorStyle by setting bit on grandchild's parent instead of grandchild. r=xidorn

--HG--
extra : commitid : 2tUmogO3bzN

layout/style/nsRuleNode.cpp

@@ -1703,29 +1703,18 @@ nsRuleNode::PropagateGrandancestorBit(nsStyleContext* aContext,
 {
   MOZ_ASSERT(aContext);
   MOZ_ASSERT(aContextInheritedFrom &&
-             aContextInheritedFrom != aContext &&
-             aContextInheritedFrom != aContext->GetParent(),
-             "aContextInheritedFrom must be an ancestor of aContext's parent");
+             aContextInheritedFrom != aContext,
+             "aContextInheritedFrom must be an ancestor of aContext");
 
-  aContext->AddStyleBit(NS_STYLE_USES_GRANDANCESTOR_STYLE);
-
-  nsStyleContext* context = aContext->GetParent();
+  for (nsStyleContext* context = aContext->GetParent();
+       context != aContextInheritedFrom;
+       context = context->GetParent()) {
     if (!context) {
-    return;
-  }
-
-  for (;;) {
-    nsStyleContext* parent = context->GetParent();
-    if (!parent) {
       MOZ_ASSERT(false, "aContextInheritedFrom must be an ancestor of "
                         "aContext's parent");
       break;
     }
-    if (parent == aContextInheritedFrom) {
-      break;
-    }
-    context->AddStyleBit(NS_STYLE_USES_GRANDANCESTOR_STYLE);
-    context = parent;
+    context->AddStyleBit(NS_STYLE_CHILD_USES_GRANDANCESTOR_STYLE);
   }
 }
 
@@ -8040,7 +8029,7 @@ nsRuleNode::ComputePositionData(void* aStartStruct,
     if (MOZ_LIKELY(parentContext)) {
       nsStyleContext* grandparentContext = parentContext->GetParent();
       if (MOZ_LIKELY(grandparentContext)) {
-        aContext->AddStyleBit(NS_STYLE_USES_GRANDANCESTOR_STYLE);
+        parentContext->AddStyleBit(NS_STYLE_CHILD_USES_GRANDANCESTOR_STYLE);
       }
       pos->mAlignSelf =
         parentPos->ComputedAlignSelf(parentContext->StyleDisplay(),
@@ -8100,7 +8089,7 @@ nsRuleNode::ComputePositionData(void* aStartStruct,
     if (MOZ_LIKELY(parentContext)) {
       nsStyleContext* grandparentContext = parentContext->GetParent();
       if (MOZ_LIKELY(grandparentContext)) {
-        aContext->AddStyleBit(NS_STYLE_USES_GRANDANCESTOR_STYLE);
+        parentContext->AddStyleBit(NS_STYLE_CHILD_USES_GRANDANCESTOR_STYLE);
       }
       pos->mJustifySelf =
         parentPos->ComputedJustifySelf(parentContext->StyleDisplay(),

layout/style/nsStyleContext.cpp

@@ -389,29 +389,6 @@ nsStyleContext::FindChildWithRules(const nsIAtom* aPseudoTag,
   return result.forget();
 }
 
-/* static */ bool
-nsStyleContext::ListContainsStyleContextThatUsesGrandancestorStyle(const nsStyleContext* aHead)
-{
-  if (aHead) {
-    const nsStyleContext* child = aHead;
-    do {
-      if (child->UsesGrandancestorStyle()) {
-        return true;
-      }
-      child = child->mNextSibling;
-    } while (child != aHead);
-  }
-
-  return false;
-}
-
-bool
-nsStyleContext::HasChildThatUsesGrandancestorStyle() const
-{
-  return ListContainsStyleContextThatUsesGrandancestorStyle(mEmptyChild) ||
-         ListContainsStyleContextThatUsesGrandancestorStyle(mChild);
-}
-
 const void* nsStyleContext::StyleData(nsStyleStructID aSID)
 {
   const void* cachedData = GetCachedStyleData(aSID);
@@ -1567,8 +1544,8 @@ nsStyleContext::LogStyleContextTree(bool aFirst, uint32_t aStructs)
   if (IsStyleIfVisited()) {
     flags.AppendLiteral("IS_STYLE_IF_VISITED ");
   }
-  if (UsesGrandancestorStyle()) {
-    flags.AppendLiteral("USES_GRANDANCESTOR_STYLE ");
+  if (HasChildThatUsesGrandancestorStyle()) {
+    flags.AppendLiteral("CHILD_USES_GRANDANCESTOR_STYLE ");
   }
   if (IsShared()) {
     flags.AppendLiteral("IS_SHARED ");

layout/style/nsStyleContext.h

@@ -247,21 +247,16 @@ public:
     }
   }
 
-  // Does this style context, or any of its descendants, have any style values
-  // that were computed based on this style context's grandparent style context
-  // or any of the grandparent's ancestors?
-  bool UsesGrandancestorStyle() const
-    { return !!(mBits & NS_STYLE_USES_GRANDANCESTOR_STYLE); }
+  // Does any descendant of this style context have any style values
+  // that were computed based on this style context's ancestors?
+  bool HasChildThatUsesGrandancestorStyle() const
+    { return !!(mBits & NS_STYLE_CHILD_USES_GRANDANCESTOR_STYLE); }
 
   // Is this style context shared with a sibling or cousin?
   // (See nsStyleSet::GetContext.)
   bool IsShared() const
     { return !!(mBits & NS_STYLE_IS_SHARED); }
 
-  // Does this style context have any children that return true for
-  // UsesGrandancestorStyle()?
-  bool HasChildThatUsesGrandancestorStyle() const;
-
   // Tell this style context to cache aStruct as the struct for aSID
   void SetStyle(nsStyleStructID aSID, void* aStruct);
 
@@ -474,10 +469,6 @@ private:
 
   void ApplyStyleFixups(bool aSkipParentDisplayBasedStyleFixup);
 
-  // Helper function for HasChildThatUsesGrandancestorStyle.
-  static bool ListContainsStyleContextThatUsesGrandancestorStyle(
-                                                   const nsStyleContext* aHead);
-
 #ifdef DEBUG
   struct AutoCheckDependency {
 

layout/style/nsStyleStruct.h

@@ -62,8 +62,8 @@ struct nsStyleVisibility;
 #define NS_STYLE_RELEVANT_LINK_VISITED     0x004000000
 // See nsStyleContext::IsStyleIfVisited
 #define NS_STYLE_IS_STYLE_IF_VISITED       0x008000000
-// See nsStyleContext::UsesGrandancestorStyle
-#define NS_STYLE_USES_GRANDANCESTOR_STYLE  0x010000000
+// See nsStyleContext::HasChildThatUsesGrandancestorStyle
+#define NS_STYLE_CHILD_USES_GRANDANCESTOR_STYLE 0x010000000
 // See nsStyleContext::IsShared
 #define NS_STYLE_IS_SHARED                 0x020000000
 // See nsStyleContext::AssertStructsNotUsedElsewhere