Move Layout Tree Construction code into Element::rebuildLayoutTree()

third_party/WebKit/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)
  *
@@ skipping 1840 matching lines @@
         data->clearComputedStyle();
 
       if (change >= IndependentInherit) {
         if (ElementAnimations* elementAnimations = data->elementAnimations())
           elementAnimations->setAnimationStyleChange(false);
       }
     }
     if (parentComputedStyle())
       change = recalcOwnStyle(change);
     clearNeedsStyleRecalc();
+    clearNeedsReattachLayoutTree();
   }
 
   // If we reattached we don't need to recalc the style of our descendants
   // anymore.
   if ((change >= UpdatePseudoElements && change < Reattach) ||
       childNeedsStyleRecalc()) {
     SelectorFilterParentScope filterScope(*this);
     StyleSharingDepthScope sharingScope(*this);
 
     updatePseudoElement(PseudoIdBefore, change);
@@ skipping 15 matching lines @@
     // This can be seen when a child transitions from floating to
     // non-floating we have to take it into account for the first letter.
     updatePseudoElement(PseudoIdFirstLetter,
                         childNeedsStyleRecalc() ? Force : change);
 
     clearChildNeedsStyleRecalc();
   }
 
   if (hasCustomStyleCallbacks())
     didRecalcStyle(change);
-
-  if (change == Reattach)
-    reattachWhitespaceSiblingsIfNeeded(nextTextSibling);

[esprehn, 2016/10/18 02:00:10]

We don't need the nextTextSibling here anymore so we could remove the argument
in a follow up patch?

 }
 
 PassRefPtr<ComputedStyle> Element::propagateInheritedProperties(
     StyleRecalcChange change) {
   if (change != IndependentInherit)
     return nullptr;
   if (needsStyleRecalc())
     return nullptr;
   if (hasAnimations())
     return nullptr;
@@ skipping 28 matching lines @@
   StyleRecalcChange localChange =
       ComputedStyle::stylePropagationDiff(oldStyle.get(), newStyle.get());
   if (localChange == NoChange) {
     INCREMENT_STYLE_STATS_COUNTER(document().styleEngine(), stylesUnchanged, 1);
   } else {
     INCREMENT_STYLE_STATS_COUNTER(document().styleEngine(), stylesChanged, 1);
   }
 
   if (localChange == Reattach) {
     document().addNonAttachedStyle(*this, std::move(newStyle));
+    setNeedsReattachLayoutTree();
     return rebuildLayoutTree();
   }
 
   DCHECK(oldStyle);
 
   if (localChange != NoChange)
     updateCallbackSelectors(oldStyle.get(), newStyle.get());
 
   if (LayoutObject* layoutObject = this->layoutObject()) {
     if (localChange != NoChange ||
@@ skipping 23 matching lines @@
       newStyle->copyChildDependentFlagsFrom(*oldStyle);
     }
     if (oldStyle->hasPseudoElementStyle() || newStyle->hasPseudoElementStyle())
       return UpdatePseudoElements;
   }
 
   return localChange;
 }
 
 StyleRecalcChange Element::rebuildLayoutTree() {
+  DCHECK(inActiveDocument());
   AttachContext reattachContext;
   reattachContext.resolvedStyle = document().getNonAttachedStyle(*this);
   bool layoutObjectWillChange = needsAttach() || layoutObject();
+
+  // We are calling Element::rebuildLayoutTree() from inside
+  // Element::recalcOwnStyle where we set the NeedsReattachLayoutTree
+  // flag - so needsReattachLayoutTree() should always be true.
+  DCHECK(parentNode());
+  DCHECK(parentNode()->childNeedsReattachLayoutTree());
+  DCHECK(needsReattachLayoutTree());
   reattachLayoutTree(reattachContext);
-  if (layoutObjectWillChange || layoutObject())
+  // Since needsReattachLayoutTree() is always true we go into
+  // reattachLayoutTree() which reattaches all the descendant
+  // sub-trees. At this point no child should need reattaching.
+  DCHECK(!childNeedsReattachLayoutTree());
+
+  if (layoutObjectWillChange || layoutObject()) {
+    // nextTextSibling is passed on to recalcStyle from recalcDescendantStyles
+    // we can either traverse the current subtree from this node onwards
+    // or store it.
+    // The choice is between increased time and increased memory complexity.
+    reattachWhitespaceSiblingsIfNeeded(nextTextSibling());
     return Reattach;
+  }
   return ReattachNoLayoutObject;
 }
 
 void Element::updateCallbackSelectors(const ComputedStyle* oldStyle,
                                       const ComputedStyle* newStyle) {
   Vector<String> emptyVector;
   const Vector<String>& oldCallbackSelectors =
       oldStyle ? oldStyle->callbackSelectors() : emptyVector;
   const Vector<String>& newCallbackSelectors =
       newStyle ? newStyle->callbackSelectors() : emptyVector;
@@ skipping 2074 matching lines @@
 }
 
 DEFINE_TRACE_WRAPPERS(Element) {
   if (hasRareData()) {
     visitor->traceWrappers(elementRareData());
   }
   ContainerNode::traceWrappers(visitor);
 }
 
 }  // namespace blink