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

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

Index: third_party/WebKit/Source/core/dom/PseudoElement.cpp
diff --git a/third_party/WebKit/Source/core/dom/PseudoElement.cpp b/third_party/WebKit/Source/core/dom/PseudoElement.cpp
index 02b89a54b169f147c2a60c54cb20da313e7c778a..4d282aa87bb1ff0e59d3a6d94316b9c4ff661749 100644
--- a/third_party/WebKit/Source/core/dom/PseudoElement.cpp
+++ b/third_party/WebKit/Source/core/dom/PseudoElement.cpp
@@ -27,6 +27,7 @@
 #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"
@@ -121,20 +122,23 @@ void PseudoElement::attachLayoutTree(const AttachContext& context) {
 
   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());
+
+  LayoutObject* parentLayoutObject = layoutObject();
+  if (!parentLayoutObject)
+    parentLayoutObject = LayoutTreeBuilderTraversal::parentLayoutObject(*this);
 
-  for (const ContentData* content = style.contentData(); content;
+  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 {
@@ -147,21 +151,59 @@ bool PseudoElement::layoutObjectIsNeeded(const ComputedStyle& style) {
   return pseudoElementLayoutObjectIsNeeded(&style);
 }
 
-void PseudoElement::didRecalcStyle() {
-  if (!layoutObject())
-    return;
+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() {
   // 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;
-
-    child->setPseudoStyle(layoutObject->mutableStyle());
+  if (LayoutObject* layoutObject = this->layoutObject()) {
+    updateGeneratedContentStyleIn(layoutObject, layoutObject->mutableStyle());
+  } else if (hasDisplayContentsStyle()) {
+    DCHECK(m_pseudoId == PseudoIdBefore || m_pseudoId == PseudoIdAfter);
+
+    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);
   }
 }