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

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 1556 matching lines @@
     return parent->locateNamespacePrefix(namespaceToLocate);
 
   return nullAtom;
 }
 
 const AtomicString Element::imageSourceURL() const {
   return getAttribute(srcAttr);
 }
 
 bool Element::layoutObjectIsNeeded(const ComputedStyle& style) {
-  return style.display() != EDisplay::None &&
-         style.display() != EDisplay::Contents;
+  if (style.display() == EDisplay::None)
+    return false;
+
+  if (style.display() == EDisplay::Contents)
+    return isPseudoElement();

[rune, 2017/03/13 10:29:50]

What layout object is needed and created for the ::before element in "::before {
display:contents; content: "PASS"}"?

[emilio, 2017/03/13 13:28:31]

Whoops, this is leftover from the previous approach. It'll arrive to
LayoutObject::createObject and return null there (no LayoutObject needed). This
part can be reverted completely.

+
+  return true;
 }
 
 LayoutObject* Element::createLayoutObject(const ComputedStyle& style) {
   return LayoutObject::createObject(this, style);
 }
 
 Node::InsertionNotificationRequest Element::insertedInto(
     ContainerNode* insertionPoint) {
   // need to do superclass processing first so isConnected() is true
   // by the time we reach updateId
@@ skipping 408 matching lines @@
     if (localChange != NoChange) {
       layoutObject->setStyle(newStyle.get());
     } else {
       // Although no change occurred, we use the new style so that the cousin
       // style sharing code won't get fooled into believing this style is the
       // same.
       // FIXME: We may be able to remove this hack, see discussion in
       // https://codereview.chromium.org/30453002/
       layoutObject->setStyleInternal(newStyle.get());
     }
-  } else if (localChange != NoChange &&
-             shouldStoreNonLayoutObjectComputedStyle(*newStyle)) {
-    storeNonLayoutObjectComputedStyle(newStyle);
+  } else {
+    if (localChange != NoChange) {
+      if (shouldStoreNonLayoutObjectComputedStyle(*newStyle))
+        storeNonLayoutObjectComputedStyle(newStyle);
+      else if (hasRareData())
+        elementRareData()->clearComputedStyle();
+    }
   }
 
   if (getStyleChangeType() >= SubtreeStyleChange)
     return Force;
 
   if (change > Inherit || localChange > Inherit)
     return max(localChange, change);
 
   if (localChange < IndependentInherit) {
     if (oldStyle->hasChildDependentFlags()) {
@@ skipping 1154 matching lines @@
     ElementRareData& rareData = ensureElementRareData();
     if (!rareData.computedStyle())
       rareData.setComputedStyle(
           document().styleForElementIgnoringPendingStylesheets(this));
     elementStyle = rareData.computedStyle();
   }
 
   if (!pseudoElementSpecifier)
     return elementStyle;
 
-  if (ComputedStyle* pseudoElementStyle =
+  if (ComputedStyle* cached =
           elementStyle->getCachedPseudoStyle(pseudoElementSpecifier))
-    return pseudoElementStyle;
+    return cached;

[rune, 2017/03/13 10:29:50]

This and the code below duplicates the code in Element::pseudoStyle(). Couldn't
you call pseudoStyle() here instead?

[emilio, 2017/03/13 13:28:31]

No, I can't. We use pseudoStyleForElement instead of getUncachedPseudoStyle,
which makes a difference when calling getComputedStyle(foo, ":internal-pseudo").

 
-  // TODO(ecobos): Passing two times elementStyle may be wrong, though we don't
-  // support display: contents elements' pseudo-elements yet, so this is not a
-  // problem for now.
+  const ComputedStyle* layoutParentStyle = elementStyle;
+  if (hasDisplayContentsStyle()) {
+    LayoutObject* parentLayoutObject =
+        LayoutTreeBuilderTraversal::parentLayoutObject(*this);
+    if (parentLayoutObject)
+      layoutParentStyle = parentLayoutObject->style();
+  }
+
   RefPtr<ComputedStyle> result =
       document().ensureStyleResolver().pseudoStyleForElement(
-          this, PseudoStyleRequest(pseudoElementSpecifier,
-                                   PseudoStyleRequest::ForComputedStyle),
-          elementStyle, elementStyle);
+          this,
+          PseudoStyleRequest(pseudoElementSpecifier,
+                             PseudoStyleRequest::ForComputedStyle),
+          elementStyle, layoutParentStyle);
   DCHECK(result);
   return elementStyle->addCachedPseudoStyle(result.release());
 }
 
 const ComputedStyle* Element::nonLayoutObjectComputedStyle() const {
   if (layoutObject() || !hasRareData())
     return nullptr;
 
   return elementRareData()->computedStyle();
 }
@@ skipping 63 matching lines @@
   PseudoElement* element = pseudoElement(pseudoId);
 
   if (element && (change == UpdatePseudoElements ||
                   element->shouldCallRecalcStyle(change))) {
     if (pseudoId == PseudoIdFirstLetter && updateFirstLetter(element))
       return;
 
     // Need to clear the cached style if the PseudoElement wants a recalc so it
     // computes a new style.
     if (element->needsStyleRecalc())
-      layoutObject()->mutableStyle()->removeCachedPseudoStyle(pseudoId);
+      mutableComputedStyle()->removeCachedPseudoStyle(pseudoId);
 
     // PseudoElement styles hang off their parent element's style so if we
     // needed a style recalc we should Force one on the pseudo.  FIXME: We
     // should figure out the right text sibling to pass.
     element->recalcStyle(change == UpdatePseudoElements ? Force : change);
 
     // Wait until our parent is not displayed or
     // pseudoElementLayoutObjectIsNeeded is false, otherwise we could
     // continuously create and destroy PseudoElements when
     // LayoutObject::isChildAllowed on our parent returns false for the
     // PseudoElement's layoutObject for each style recalc.
-    if (!layoutObject() ||
-        !pseudoElementLayoutObjectIsNeeded(
-            layoutObject()->getCachedPseudoStyle(pseudoId)))
+    if (!canHaveGeneratedPseudo(pseudoId) ||
+        !pseudoElementLayoutObjectIsNeeded(pseudoStyle(pseudoId)))
       elementRareData()->setPseudoElement(pseudoId, nullptr);
   } else if (pseudoId == PseudoIdFirstLetter && element &&
              change >= UpdatePseudoElements &&
              !FirstLetterPseudoElement::firstLetterTextLayoutObject(*element)) {
     // This can happen if we change to a float, for example. We need to cleanup
     // the first-letter pseudoElement and then fix the text of the original
     // remaining text layoutObject.  This can be seen in Test 7 of
     // fast/css/first-letter-removed-added.html
     elementRareData()->setPseudoElement(pseudoId, nullptr);
   } else if (change >= UpdatePseudoElements) {
@@ skipping 16 matching lines @@
     // incorrect results due to setting the first letter back.
     if (remainingTextLayoutObject)
       element->reattachLayoutTree();
     else
       elementRareData()->setPseudoElement(PseudoIdFirstLetter, nullptr);
     return true;
   }
   return false;
 }
 
+ComputedStyle* Element::pseudoStyle(PseudoId pseudoId) const {
+  ComputedStyle* style = mutableComputedStyle();
+  DCHECK(pseudoId < FirstInternalPseudoId);
+  if (!style->hasPseudoStyle(pseudoId))
+    return nullptr;
+
+  if (ComputedStyle* cached = style->getCachedPseudoStyle(pseudoId))
+    return cached;
+  RefPtr<ComputedStyle> uncached = getUncachedPseudoStyle(pseudoId);
+  if (uncached)
+    return style->addCachedPseudoStyle(uncached.release());
+  return nullptr;
+}
+
+PassRefPtr<ComputedStyle> Element::getUncachedPseudoStyle(
+    PseudoId pseudoId) const {
+  if (pseudoId == PseudoIdBefore || pseudoId == PseudoIdAfter) {
+    LayoutObject* parentLayoutObject = layoutObject();
+    if (!parentLayoutObject && hasDisplayContentsStyle()) {
+      parentLayoutObject =
+          LayoutTreeBuilderTraversal::parentLayoutObject(*this);
+    }
+    if (!parentLayoutObject)
+      return nullptr;
+    return document().ensureStyleResolver().pseudoStyleForElement(
+        const_cast<Element*>(this), PseudoStyleRequest(pseudoId),
+        computedStyle(), parentLayoutObject->style());
+  }
+  if (!layoutObject())
+    return nullptr;
+  return layoutObject()->getUncachedPseudoStyle(PseudoStyleRequest(pseudoId));
+}
+
+// For display: contents elements, we still need to generate ::before and
+// ::after, but the rest of the pseudo-elements should only be used for elements
+// with an actual layout object.
+bool Element::canHaveGeneratedPseudo(PseudoId pseudoId) const {
+  if (hasDisplayContentsStyle())
+    return pseudoId == PseudoIdBefore || pseudoId == PseudoIdAfter;
+  return !!layoutObject();
+}
+
 void Element::createPseudoElementIfNeeded(PseudoId pseudoId) {
   if (isPseudoElement())
     return;
 
   // Document::ensureStyleResolver is not inlined and shows up on profiles,
   // avoid it here.
   PseudoElement* element =
       document().styleEngine().ensureResolver().createPseudoElementIfNeeded(
           *this, pseudoId);
   if (!element)
@@ skipping 845 matching lines @@
 }
 
 DEFINE_TRACE_WRAPPERS(Element) {
   if (hasRareData()) {
     visitor->traceWrappers(elementRareData());
   }
   ContainerNode::traceWrappers(visitor);
 }
 
 }  // namespace blink