[css-display] Support display: contents pseudo-elements.

third_party/WebKit/Source/core/dom/PseudoElement.cpp

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Neither the name of Google Inc. nor the names of its
  * contributors may be used to endorse or promote products derived from
  * this software without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #include "core/dom/PseudoElement.h"
 
 #include "core/dom/FirstLetterPseudoElement.h"
+#include "core/dom/NodeComputedStyle.h"
 #include "core/frame/UseCounter.h"
 #include "core/layout/LayoutObject.h"
 #include "core/layout/LayoutQuote.h"
 #include "core/probe/CoreProbes.h"
 #include "core/style/ContentData.h"
 
 namespace blink {
 
 PseudoElement* PseudoElement::create(Element* parent, PseudoId pseudoId) {
   return new PseudoElement(parent, pseudoId);
@@ skipping 74 matching lines @@
   document().adoptIfNeeded(*this);
   setParentOrShadowHostNode(0);
   removedFrom(parent);
 }
 
 void PseudoElement::attachLayoutTree(const AttachContext& context) {
   DCHECK(!layoutObject());
 
   Element::attachLayoutTree(context);
 
-  LayoutObject* layoutObject = this->layoutObject();
-  if (!layoutObject)
+  ComputedStyle* style = mutableComputedStyle();
+  if (!style || (style->styleType() != PseudoIdBefore &&
+                 style->styleType() != PseudoIdAfter))
     return;
 
-  ComputedStyle& style = layoutObject->mutableStyleRef();
-  if (style.styleType() != PseudoIdBefore && style.styleType() != PseudoIdAfter)
-    return;
-  DCHECK(style.contentData());
+  DCHECK(style->contentData());
 
-  for (const ContentData* content = style.contentData(); content;
+  LayoutObject* parentLayoutObject = layoutObject();
+  if (!parentLayoutObject)
+    parentLayoutObject = LayoutTreeBuilderTraversal::parentLayoutObject(*this);
+
+  for (const ContentData* content = style->contentData(); content;
        content = content->next()) {
-    LayoutObject* child = content->createLayoutObject(*this, style);
-    if (layoutObject->isChildAllowed(child, style)) {
-      layoutObject->addChild(child);
+    LayoutObject* child = content->createLayoutObject(*this, *style);
+    if (parentLayoutObject->isChildAllowed(child, *style)) {
+      parentLayoutObject->addChild(child);
+      DCHECK(child->isPseudoElementGeneratedContentFor(*this));
       if (child->isQuote())
         toLayoutQuote(child)->attachQuote();
     } else {
       child->destroy();
     }
   }
 }
 
 bool PseudoElement::layoutObjectIsNeeded(const ComputedStyle& style) {
   return pseudoElementLayoutObjectIsNeeded(&style);
 }
 
+static bool isGeneratedContentLike(LayoutObject* layoutObject) {

[rune, 2017/04/04 14:23:41]

Why not call it isGeneratedContent?

[emilio, 2017/04/04 15:09:18]

Sounds good to me, yeah.

+  if (!layoutObject->isAnonymous())
+    return false;
+  return layoutObject->isText() || layoutObject->isQuote() ||
+         layoutObject->isImage();
+}
+
+static void updateGeneratedContentStyleIn(LayoutObject* root,
+                                          ComputedStyle* style) {
+  for (LayoutObject* child = root; child; child = child->nextInPreOrder(root)) {
+    if (isGeneratedContentLike(child))
+      child->setPseudoStyle(style);
+  }
+}
+
 void PseudoElement::didRecalcStyle() {
-  if (!layoutObject())
-    return;
-
   // The layoutObjects inside pseudo elements are anonymous so they don't get
   // notified of recalcStyle and must have the style propagated downward
   // manually similar to LayoutObject::propagateStyleToAnonymousChildren.
-  LayoutObject* layoutObject = this->layoutObject();
-  for (LayoutObject* child = layoutObject->nextInPreOrder(layoutObject); child;
-       child = child->nextInPreOrder(layoutObject)) {
-    // We only manage the style for the generated content items.
-    if (!child->isText() && !child->isQuote() && !child->isImage())
-      continue;
+  if (LayoutObject* layoutObject = this->layoutObject()) {
+    updateGeneratedContentStyleIn(layoutObject, layoutObject->mutableStyle());
+  } else if (hasDisplayContentsStyle()) {
+    DCHECK(m_pseudoId == PseudoIdBefore || m_pseudoId == PseudoIdAfter);
 
-    child->setPseudoStyle(layoutObject->mutableStyle());
+    LayoutObject* layoutParent =
+        LayoutTreeBuilderTraversal::parentLayoutObject(*this);
+    if (!layoutParent)
+      return;
+
+    const bool isBefore = m_pseudoId == PseudoIdBefore;
+    ComputedStyle* style = mutableComputedStyle();
+    LayoutObject* child = isBefore ? layoutParent->slowFirstChild()
+                                   : layoutParent->slowLastChild();
+
+    bool foundGeneratedContent = false;
+    while (child) {
+      bool isThisPseudoContent =
+          child->isPseudoElementGeneratedContentFor(*this);
+      if (isThisPseudoContent)
+        foundGeneratedContent = true;
+      else if (foundGeneratedContent)
+        break;
+
+      if (isThisPseudoContent) {
+        updateGeneratedContentStyleIn(child, style);
+        child = isBefore ? child->nextSibling() : child->previousSibling();
+      } else {
+        child = isBefore ? child->nextInPreOrder(layoutParent)
+                         : child->previousInPreOrder(layoutParent);

[rune, 2017/04/04 14:23:41]

Why do you need to to walk descendants here?

In general, this code is hard to follow. I think it needs some documentation.
Are anonymous table layout objects handled here? How do you know the difference
between an anonymous table wrapper for generated content and one for normal dom
nodes? Are they marked as being generated for the pseudo element as well?

[emilio, 2017/04/04 15:09:18]

The idea is to handle them, yeah. Right now I don't think they're marked as
such, let me add tests for those.

+      }
+    }
+
+    DCHECK(foundGeneratedContent);
   }
 }
 
 // With PseudoElements the DOM tree and Layout tree can differ. When you attach
 // a, first-letter for example, into the DOM we walk down the Layout
 // tree to find the correct insertion point for the LayoutObject. But, this
 // means if we ask for the parentOrShadowHost Node from the first-letter
 // pseudo element we will get some arbitrary ancestor of the LayoutObject.
 //
 // For hit testing, we need the parent Node of the LayoutObject for the
@@ skipping 14 matching lines @@
   LayoutObject* ancestor = layoutObject()->parent();
   while (ancestor->isAnonymous() ||
          (ancestor->node() && ancestor->node()->isPseudoElement())) {
     DCHECK(ancestor->parent());
     ancestor = ancestor->parent();
   }
   return ancestor->node();
 }
 
 }  // namespace blink