Implement ShadowRoot.delegatesFocus 4/4 (match CSS :focus for shadow host)

Source/core/dom/ContainerNode.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2013 Apple Inc. 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
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
@@ skipping 1066 matching lines @@
             document().styleEngine().pseudoStateChangedForElement(CSSSelector::PseudoFocus, *toElement(this));
         else if (computedStyle()->affectedByFocus())
             setNeedsStyleRecalc(LocalStyleChange, StyleChangeReasonForTracing::createWithExtraData(StyleChangeReason::PseudoClass, StyleChangeExtraData::Focus));
     }
 
     LayoutTheme::theme().controlStateChanged(*layoutObject(), FocusControlState);
 }
 
 void ContainerNode::setFocus(bool received)
 {
+    // Recurse up the shadow trees to mark shadow hosts if it matches :focus.

[hayato, 2015/06/12 04:37:57]

Could you add a layout test which involves a dom mutation?

If a focused element is moved to somewhere, the focus state of each nodes are
set (or unset) correctly?

[kochi, 2015/06/12 07:34:17]

Added 'focus-with-dom-mutation.html' layout test which tests :focus
state is properly cleared when focused element is moved out of shadow tree.

+    if (isInShadowTree() && shadowHost()->shadowRoot())

[hayato, 2015/06/12 04:37:57]

Not intuitive to me. Is this checking that `this` is in an author shadow tree or
not?

[kochi, 2015/06/12 07:34:17]

Yes, it's author shadow only.
Updated the comment and moved the TODO comment below (line 1093) here.

+        shadowHost()->setFocus(received);
+
+    // If this is an author shadow host and indirectly focused (has focused element within
+    // its shadow root), update focus.
+    // TODO(kochi): Handle UA shadow which marks multiple nodes as focused such as
+    // <input type="date"> the same way as author shadow.
+    if (document().focusedElement() && document().focusedElement() != this) {
+        Element* host = toElement(this);

[hayato, 2015/06/12 04:37:57]

1. Looks isElementNode() is used in L1112.
 `this` is always Element here?

2. `host` looks confusing name to me since `this` is not always a shadow host,
at least until 1098.

[kochi, 2015/06/12 07:34:17]

1. Good catch.  I guess no one is calling setFocus() on Node or ContainerNode,
but adding isElementNode() here looks correct to me.  The same bug existed for
the old tabStop implementation.

2. replaced toElement() for both occurrences.

+        if (host->shadowRoot())
+            received = received && host->shadowRoot()->delegatesFocus();
+    }
+
     if (focused() == received)
         return;
 
     Node::setFocus(received);
 
     focusStateChanged();
 
     if (layoutObject() || received)
         return;
 
     // If :focus sets display: none, we lose focus but still need to recalc our style.

[hayato, 2015/06/12 04:37:57]

Looks focusStateChanged() and the code around here are very similar. Can we
remove duplication?

[kochi, 2015/06/12 07:34:17]

I'm afraid their conditions are subtly different and they can't be simplified
by unifying, just more complex.

     if (isElementNode() && toElement(this)->childrenOrSiblingsAffectedByFocus() && styleChangeType() < SubtreeStyleChange)
         document().styleEngine().pseudoStateChangedForElement(CSSSelector::PseudoFocus, *toElement(this));
     else
         setNeedsStyleRecalc(LocalStyleChange, StyleChangeReasonForTracing::createWithExtraData(StyleChangeReason::PseudoClass, StyleChangeExtraData::Focus));
 }
 
 void ContainerNode::setActive(bool down)
 {
     if (down == active())
         return;
@@ skipping 399 matching lines @@
         return true;
 
     if (node->isElementNode() && toElement(node)->shadow())
         return true;
 
     return false;
 }
 #endif
 
 } // namespace blink