Partial implementation of CSSVariablesMap for CSS Variables CSSOM

Source/core/css/CSSComputedStyleDeclaration.h

 /*
  * Copyright (C) 2004 Zack Rusin <zack@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2008, 2012 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Lesser General Public License for more details.
  *
  * You should have received a copy of the GNU Lesser General Public
  * License along with this library; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  * 02110-1301  USA
  */
 
 #ifndef CSSComputedStyleDeclaration_h
 #define CSSComputedStyleDeclaration_h
 
 #include "core/css/CSSStyleDeclaration.h"
+#include "core/css/CSSVariablesMap.h"
 #include "core/rendering/style/RenderStyleConstants.h"
-#include <wtf/RefPtr.h>
-#include <wtf/text/WTFString.h>
+#include "wtf/HashMap.h"
+#include "wtf/RefPtr.h"
+#include "wtf/text/AtomicString.h"
+#include "wtf/text/AtomicStringHash.h"
+#include "wtf/text/WTFString.h"
 
 namespace WebCore {
 
 class CSSPrimitiveValue;
 class CSSValueList;
 class Color;
 class MutableStylePropertySet;
 class Node;
 class RenderObject;
 class RenderStyle;
@@ skipping 54 matching lines @@
     virtual String getPropertyShorthand(const String& propertyName);
     virtual bool isPropertyImplicit(const String& propertyName);
     virtual void setProperty(const String& propertyName, const String& value, const String& priority, ExceptionCode&);
     virtual String removeProperty(const String& propertyName, ExceptionCode&);
     virtual String cssText() const;
     virtual void setCssText(const String&, ExceptionCode&);
     virtual PassRefPtr<CSSValue> getPropertyCSSValueInternal(CSSPropertyID);
     virtual String getPropertyValueInternal(CSSPropertyID);
     virtual void setPropertyInternal(CSSPropertyID, const String& value, bool important, ExceptionCode&);
 
+    virtual PassRefPtr<CSSVariablesMap> var() OVERRIDE { return CSSVariablesMap::create(this); }

[esprehn, 2013/07/10 02:42:11]

This isn't correct, you need to keep it in a member variable. For example I can
do: s = getComputedStyle(...); s.var.expando = 1; assert (s.var.expando  == 1);
but since you return a brand new one every time expando will disappear.

[alancutter (OOO until 2018), 2013/07/10 11:18:13]

CSSStyleDeclaration now has a RefPtr to CSSVariablesMap. The map now has a raw
pointer to CSSStyleDeclaration that gets nullified on style's destruction.

It's still possible to lose access to the same CSSVariablesMap JavaScript object
via the el.style.var pathway should the style declaration get deallocated during
the page's lifetime. This is perhaps an issue with style in general as any
expando declared on the style object would also be lost.

I had attempted a static mapping from CSSStyleDeclaration to CSSVariablesMap to
avoid adding extra weight onto the style declaration classes but this approach
is not as robust as the one you had suggested in IRC which is what I've
implemented here.

+    const HashMap<AtomicString, String>* variableMap() const;
+    virtual unsigned variableCount() const OVERRIDE;
+    virtual String variableValue(const AtomicString& name) const OVERRIDE;
+    virtual void setVariableValue(const AtomicString& name, const String& value, ExceptionCode&) OVERRIDE;
+    virtual bool removeVariable(const AtomicString& name) OVERRIDE;
+    virtual void clearVariables(ExceptionCode&) OVERRIDE;
+
     virtual bool cssPropertyMatches(CSSPropertyID, const CSSValue*) const OVERRIDE;
 
     PassRefPtr<CSSValue> valueForShadow(const ShadowData*, CSSPropertyID, const RenderStyle*) const;
     PassRefPtr<CSSPrimitiveValue> currentColorOrValidColor(RenderStyle*, const Color&) const;
     PassRefPtr<SVGPaint> adjustSVGPaintForCurrentColor(PassRefPtr<SVGPaint>, RenderStyle*) const;
 
     PassRefPtr<CSSValue> valueForFilter(const RenderObject*, const RenderStyle*) const;
 
     PassRefPtr<CSSValueList> getCSSPropertyValuesForShorthandProperties(const StylePropertyShorthand&) const;
     PassRefPtr<CSSValueList> getCSSPropertyValuesForSidesShorthand(const StylePropertyShorthand&) const;
     PassRefPtr<CSSValueList> getBackgroundShorthandValue() const;
     PassRefPtr<CSSValueList> getCSSPropertyValuesForGridShorthand(const StylePropertyShorthand&) const;
 
     RefPtr<Node> m_node;
     PseudoId m_pseudoElementSpecifier;
     bool m_allowVisitedStyle;
     unsigned m_refCount;
 };
 
 } // namespace WebCore
 
 #endif // CSSComputedStyleDeclaration_h