CSS Properties and Values API: Use initial value where appropriate for var()

third_party/WebKit/Source/core/css/resolver/CSSVariableResolver.cpp

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/css/resolver/CSSVariableResolver.h"
 
 #include "core/CSSPropertyNames.h"
 #include "core/CSSValueKeywords.h"
 #include "core/StyleBuilderFunctions.h"
 #include "core/StylePropertyShorthand.h"
@@ skipping 17 matching lines @@
 {
     if (range.atEnd())
         return false;
     ASSERT(range.peek().type() == CommaToken);
     range.consume();
     return resolveTokenRange(range, result);
 }
 
 CSSVariableData* CSSVariableResolver::valueForCustomProperty(AtomicString name)
 {
-    // TODO(timloh): Registered properties shouldn't return nullptr in failure
-    // cases (aside from cycles?), but instead return the initial/inherited value.
     if (m_variablesSeen.contains(name)) {
         m_cycleStartPoints.add(name);
         return nullptr;
     }
 
-    if (!m_styleVariableData)
-        return nullptr;
-    CSSVariableData* variableData = m_styleVariableData->getVariable(name);
+    DCHECK(m_registry || !RuntimeEnabledFeatures::cssVariables2Enabled());
+    const PropertyRegistry::Registration* registration = m_registry ? m_registry->registration(name) : nullptr;
+
+    CSSVariableData* variableData = nullptr;
+    if (m_styleVariableData)
+        variableData = m_styleVariableData->getVariable(name);
     if (!variableData)
-        return nullptr;
+        return registration ? registration->initialVariableData() : nullptr;
     if (!variableData->needsVariableResolution())
         return variableData;
+
     RefPtr<CSSVariableData> newVariableData = resolveCustomProperty(name, *variableData);
-
-    DCHECK(m_registry || !RuntimeEnabledFeatures::cssVariables2Enabled());
-    if (m_registry) {
-        const PropertyRegistry::Registration* registration = m_registry->registration(name);
-        if (registration) {
-            const CSSValue* parsedValue = nullptr;
-            if (newVariableData) {
-                parsedValue = newVariableData->parseForSyntax(registration->syntax());
-                if (parsedValue)
-                    parsedValue = &StyleBuilderConverter::convertRegisteredPropertyValue(m_styleResolverState, *parsedValue);
-                else
-                    newVariableData = nullptr;
-            }
-            m_styleVariableData->setVariable(name, newVariableData);
-            m_styleVariableData->setRegisteredInheritedProperty(name, parsedValue);
-            return newVariableData.get();
+    if (registration) {
+        const CSSValue* parsedValue = nullptr;
+        if (newVariableData) {
+            parsedValue = newVariableData->parseForSyntax(registration->syntax());
+            if (parsedValue)
+                parsedValue = &StyleBuilderConverter::convertRegisteredPropertyValue(m_styleResolverState, *parsedValue);
+            else
+                newVariableData = nullptr;
         }
+        m_styleVariableData->setVariable(name, newVariableData);
+        m_styleVariableData->setRegisteredInheritedProperty(name, parsedValue);
+        if (!newVariableData)
+            return registration->initialVariableData();

[Timothy Loh, 2016/09/22 10:01:25]

We could alternatively set the initial values into the maps instead of nullptr
(which already means initial values). I don't think there's much difference so I
left it as setting nullptr.

[meade_UTC10, 2016/09/23 01:16:50]

seems fine as is.

+        return newVariableData.get();
     }
 
     m_styleVariableData->setVariable(name, newVariableData);
     return newVariableData.get();
 }
 
 PassRefPtr<CSSVariableData> CSSVariableResolver::resolveCustomProperty(AtomicString name, const CSSVariableData& variableData)
 {
     ASSERT(variableData.needsVariableResolution());
 
@@ skipping 149 matching lines @@
 CSSVariableResolver::CSSVariableResolver(const StyleResolverState& state)
     : m_styleResolverState(state)
     , m_styleVariableData(state.style()->variables())
     , m_registry(state.document().propertyRegistry())
 {
 }
 
 DEFINE_TRACE(CSSVariableResolver) { visitor->trace(m_registry); }
 
 } // namespace blink