StyleResolverParentPusher can decide if it needs to push at creation time

Source/core/dom/Element.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Peter Kelly (pmk@post.com)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2007 David Smith (catfish.man@gmail.com)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2012, 2013 Apple Inc. All rights reserved.
  *           (C) 2007 Eric Seidel (eric@webkit.org)
  *
  * This library is free software; you can redistribute it and/or
@@ skipping 91 matching lines @@
 #include "wtf/text/CString.h"
 #include "wtf/text/TextPosition.h"
 
 namespace WebCore {
 
 using namespace HTMLNames;
 using namespace XMLNames;
 
 class StyleResolverParentPusher {
 public:
-    explicit StyleResolverParentPusher(Element& parent)
+    StyleResolverParentPusher(Element& parent, StyleRecalcChange change = NoChange)

[leviw_travelin_and_unemployed, 2013/11/11 18:56:15]

Since the 2nd argument isn't required, are you sure you don't still want the
explicit?

         : m_parent(parent)
         , m_pushedStyleResolver(0)
     {
+        if ((change >= Inherit || parent.childNeedsStyleRecalc()) && (parent.hasChildNodes() || parent.youngestShadowRoot())) {
+            m_pushedStyleResolver = m_parent.document().styleResolver();
+            m_pushedStyleResolver->pushParentElement(m_parent);
+        }
     }
-    void push()
-    {
-        if (m_pushedStyleResolver)
-            return;
-        m_pushedStyleResolver = m_parent.document().styleResolver();
-        m_pushedStyleResolver->pushParentElement(m_parent);
-    }
+
     ~StyleResolverParentPusher()
     {
-
         if (!m_pushedStyleResolver)
             return;
-
-        // This tells us that our pushed style selector is in a bad state,
-        // so we should just bail out in that scenario.
-        ASSERT(m_pushedStyleResolver == m_parent.document().styleResolver());
-        if (m_pushedStyleResolver != m_parent.document().styleResolver())
-            return;
-
         m_pushedStyleResolver->popParentElement(m_parent);
     }
 
 private:
     Element& m_parent;
     StyleResolver* m_pushedStyleResolver;
 };
 
 typedef Vector<RefPtr<Attr> > AttrNodeList;
 typedef HashMap<Element*, OwnPtr<AttrNodeList> > AttrNodeListMap;
@@ skipping 1206 matching lines @@
     document().removeFromTopLayer(this);
 
     if (hasRareData())
         elementRareData()->setIsInCanvasSubtree(false);
 }
 
 void Element::attach(const AttachContext& context)
 {
     ASSERT(document().inStyleRecalc());
 
-    StyleResolverParentPusher parentPusher(*this);
-
     // We've already been through detach when doing a lazyAttach, but we might
     // need to clear any state that's been added since then.
     if (hasRareData() && styleChangeType() == NeedsReattachStyleChange) {
         ElementRareData* data = elementRareData();
         data->clearComputedStyle();
         data->resetDynamicRestyleObservations();
         if (!context.resolvedStyle)
             data->resetStyleState();
     }
 
     NodeRenderingContext(this, context.resolvedStyle).createRendererForElementIfNeeded();
 
     if (RenderStyle* style = renderStyle())
         updateCallbackSelectors(0, style);
 
+    StyleResolverParentPusher pushParent(*this);
+
     createPseudoElementIfNeeded(BEFORE);
 
     // When a shadow root exists, it does the work of attaching the children.
-    if (ElementShadow* shadow = this->shadow()) {
-        parentPusher.push();
+    if (ElementShadow* shadow = this->shadow())
         shadow->attach(context);
-    } else if (firstChild())
-        parentPusher.push();
 
     ContainerNode::attach(context);
 
     createPseudoElementIfNeeded(AFTER);
     createPseudoElementIfNeeded(BACKDROP);
 
     if (hasRareData()) {
         ElementRareData* data = elementRareData();
         if (data->needsFocusAppearanceUpdateSoonAfterAttach()) {
             if (isFocusable() && document().focusedElement() == this)
@@ skipping 187 matching lines @@
 
     return max(localChange, change);
 }
 
 void Element::recalcChildStyle(StyleRecalcChange change)
 {
     ASSERT(document().inStyleRecalc());
     ASSERT(change >= Inherit || childNeedsStyleRecalc());
     ASSERT(!needsStyleRecalc());
 
-    StyleResolverParentPusher parentPusher(*this);
+    StyleResolverParentPusher pushParent(*this, change);
 
     for (ShadowRoot* root = youngestShadowRoot(); root; root = root->olderShadowRoot()) {
-        if (shouldRecalcStyle(change, root)) {
-            parentPusher.push();
+        if (shouldRecalcStyle(change, root))
             root->recalcStyle(change);
-        }
     }
 
     if (shouldRecalcStyle(change, this))
         updatePseudoElement(BEFORE, change);
 
     if (change < Force && hasRareData() && childNeedsStyleRecalc())
         checkForChildrenAdjacentRuleChanges();
 
     // This loop is deliberately backwards because we use insertBefore in the rendering tree, and want to avoid
     // a potentially n^2 loop to find the insertion point while resolving style. Having us start from the last
     // child and work our way back means in the common case, we'll find the insertion point in O(1) time.
     // Reversing this loop can lead to non-deterministic results in our code to optimize out empty whitespace
     // RenderTexts. We try to put off recalcing their style until the end to avoid this issue.
     // See crbug.com/288225
     for (Node* child = lastChild(); child; child = child->previousSibling()) {
         bool didReattach = false;
         if (child->isTextNode()) {
             didReattach = toText(child)->recalcTextStyle(change);
         } else if (child->isElementNode()) {
             Element* element = toElement(child);
-            if (shouldRecalcStyle(change, element)) {
-                parentPusher.push();
+            if (shouldRecalcStyle(change, element))
                 didReattach = element->recalcStyle(change);
-            } else if (element->supportsStyleSharing()) {
+            else if (element->supportsStyleSharing())
                 document().styleResolver()->addToStyleSharingList(*element);
-            }
         }
         if (didReattach)
             child->reattachWhitespaceSiblings();
     }
 
     if (shouldRecalcStyle(change, this)) {
         updatePseudoElement(AFTER, change);
         updatePseudoElement(BACKDROP, change);
     }
 }
@@ skipping 1861 matching lines @@
     // Before doing so, we need to resolve issues in HTMLSelectElement::recalcListItems
     // and RenderMenuList::setText. See also https://bugs.webkit.org/show_bug.cgi?id=88405
     if (hasTagName(optionTag) || hasTagName(optgroupTag))
         return false;
     if (FullscreenElementStack::isActiveFullScreenElement(this))
         return false;
     return true;
 }
 
 } // namespace WebCore