Implement CSS4 pseudo-class :dir()

third_party/WebKit/Source/core/css/SelectorChecker.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 2004-2005 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2006, 2007 Nicholas Shanks (webkit@nickshanks.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
  * Copyright (C) 2007, 2008 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (c) 2011, Code Aurora Forum. All rights reserved.
  * Copyright (C) Research In Motion Limited 2011. All rights reserved.
@@ skipping 931 matching lines @@
                 value = toVTTElement(element).language();
             else
                 value = element.computeInheritedLanguage();
             const AtomicString& argument = selector.argument();
             if (value.isEmpty() || !value.startsWith(argument, TextCaseASCIIInsensitive))
                 break;
             if (value.length() != argument.length() && value[argument.length()] != '-')
                 break;
             return true;
         }
+    case CSSSelector::PseudoDir:
+        {
+            // TODO(ramya.v): Need to check the exact direction element is rendered.
+            AtomicString value;
+            TextDirection dir = LTR;
+            if (m_mode == ResolvingStyle)
+                dir = context.elementStyle->direction();

[esprehn, 2016/02/12 05:13:41]

how does this work? The elementStyle is the one being created right now, we
haven't figured out what values apply yet.

+            else if (element.ensureComputedStyle())
+                dir = element.ensureComputedStyle()->direction();

[esprehn, 2016/02/12 05:13:41]

ensureComputedStyle() is non-trivial, always do 

if (ComputedStyle* style = element.ensureComputedStyle()) {
  // use style here
}

I don't think this is right though, you can't compute the style in a detached
subtree, and this would cause a style resolve from inside querySelector for
display none elements, or use stale style for displayed elements giving you back
the wrong value.

+            switch (dir) {
+            case LTR:
+                value = "ltr";

[esprehn, 2016/02/12 05:13:41]

we should just atomize these with a DEFINE_STATIC_LOCAL(AtomicString, ltrAtom,
"ltr") and then the check below will usually be very fast since authors will
write dir(ltr)

+                break;
+            case RTL:
+                value = "rtl";
+                break;
+            default:
+                break;
+            }
+            const AtomicString& argument = selector.argument();
+            if (value.isEmpty() || !equalIgnoringCase(value, argument))

[esprehn, 2016/02/12 05:13:41]

should this use ascii case? this file is inconsistent, I'm not sure when we're
supposed to be using ascii these days.

+                break;
+            return true;
+        }
     case CSSSelector::PseudoFullScreen:
         // While a Document is in the fullscreen state, and the document's current fullscreen
         // element is an element in the document, the 'full-screen' pseudoclass applies to
         // that element. Also, an <iframe>, <object> or <embed> element whose child browsing
         // context's Document is in the fullscreen state has the 'full-screen' pseudoclass applied.
         if (isHTMLFrameElementBase(element) && element.containsFullScreenElement())
             return true;
         return Fullscreen::isActiveFullScreenElement(element);
     case CSSSelector::PseudoFullScreenAncestor:
         return element.containsFullScreenElement();
@@ skipping 235 matching lines @@
 }
 
 bool SelectorChecker::matchesFocusPseudoClass(const Element& element)
 {
     if (InspectorInstrumentation::forcePseudoState(const_cast<Element*>(&element), CSSSelector::PseudoFocus))
         return true;
     return element.focused() && isFrameFocused(element);
 }
 
 }