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

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

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2007 David Smith (catfish.man@gmail.com)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc.
  * All rights reserved.
  * Copyright (C) Research In Motion Limited 2010. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 282 matching lines @@
   unsigned remainingLength = oldText.length() - length;
 
   // Construct a text fragment for the text after the first letter.
   // This text fragment might be empty.
   LayoutTextFragment* remainingText;
 
   if (nextLayoutObject->node()) {
     remainingText = new LayoutTextFragment(
         nextLayoutObject->node(), oldText.impl(), length, remainingLength);
   } else {
+    PseudoElement* owningPseudo = nextLayoutObject->ownerPseudoElement();
     remainingText = LayoutTextFragment::createAnonymous(
-        *this, oldText.impl(), length, remainingLength);
+        owningPseudo ? *owningPseudo : *this, oldText.impl(), length,
+        remainingLength);

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

I don't understand this. What is an ownerPseudoElement? Is it something specific
to first-letter?

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

So this is specific to first-letter because first-letter does this hacky thing
where it splits a text fragment into two. If that fragment happens to be
generated content inside a display: contents pseudo-element, we lost track of
the only hint that allows us to find them.

Perhaps I can take advantage of generated content always creating a text
fragment and mutate it instead, which may be cleaner and remove a bunch of
complexity. Let me try that.

Also, if we can guarantee that those LayoutObjects don't go away, we could just
track generated content in a std::vector<LayoutObject*> inside the
pseudo-element when it's a display: contents pseudo, but that sounds flacky.

   }
 
   remainingText->setFirstLetterPseudoElement(this);
   remainingText->setIsRemainingTextLayoutObject(true);
   remainingText->setStyle(nextLayoutObject->mutableStyle());
 
   if (remainingText->node())
     remainingText->node()->setLayoutObject(remainingText);
 
   m_remainingTextLayoutObject = remainingText;
@@ skipping 34 matching lines @@
 
     // We only manage the style for the generated content items.
     if (!child->isText() && !child->isQuote() && !child->isImage())
       continue;
 
     child->setPseudoStyle(layoutObject->mutableStyle());
   }
 }
 
 }  // namespace blink