Allow explicit inherit in matched declarations cache

https://bugs.webkit.org/show_bug.cgi?id=260199
rdar://113902520

Reviewed by Alan Baradlay.

If explicit inherit is involved we just need to apply it on top of the cached value.

* Source/WebCore/style/ElementRuleCollector.cpp:
(WebCore::Style::ElementRuleCollector::addMatchedProperties):
* Source/WebCore/style/PropertyCascade.cpp:
(WebCore::Style::PropertyCascade::addMatch):

Check for explicit inherit if needed.

* Source/WebCore/style/PropertyCascade.h:
* Source/WebCore/style/StyleResolver.cpp:
(WebCore::Style::Resolver::applyMatchedProperties):

Canonical link: https://commits.webkit.org/266986@main

Source/WebCore/style/ElementRuleCollector.cpp

@@ -671,12 +671,7 @@ void ElementRuleCollector::addMatchedProperties(MatchedProperties&& matchedPrope
             if (current.isInherited())
                 continue;
 
-            // If the property value is explicitly inherited, we need to apply further non-inherited properties
-            // as they might override the value inherited here. For this reason we don't allow declarations with
-            // explicitly inherited properties to be cached.
             auto& value = *current.value();
-            if (isValueID(value, CSSValueInherit))
-                return false;
 
             // The value currentColor has implicitely the same side effect. It depends on the value of color,
             // which is an inherited value, making the non-inherited property implicitly inherited.

Source/WebCore/style/PropertyCascade.cpp

@@ -221,27 +221,33 @@ bool PropertyCascade::addMatch(const MatchedProperties& matchedProperties, Casca
 
             if (m_includedProperties.containsAll(allProperties()))
                 return true;
-            if (m_includedProperties.contains(PropertyType::Inherited) && current.isInherited())
-                return true;
-            if (m_includedProperties.contains(PropertyType::NonInherited) && !current.isInherited())
-                return true;
 
             // If we have applied this property for some reason already we must apply anything that overrides it.
             if (hasProperty(propertyID, *current.value()))
                 return true;
 
-            if (m_includedProperties.contains(PropertyType::VariableReference)) {
-                if (current.value()->hasVariableReferences())
-                    return true;
-                // Apply all deferred properties if we have applied any. They may override the ones we already applied.
-                if (propertyID >= firstDeferredProperty && m_lastIndexForDeferred)
-                    return true;
-            }
             if (m_includedProperties.containsAny({ PropertyType::AfterAnimation, PropertyType::AfterTransition })) {
                 if (shouldApplyAfterAnimation(current)) {
                     m_animationLayer->overriddenProperties.add(propertyID);
                     return true;
                 }
+                return false;
+            }
+
+            if (m_includedProperties.contains(PropertyType::Inherited) && current.isInherited())
+                return true;
+            if (m_includedProperties.contains(PropertyType::ExplicitlyInherited) && isValueID(*current.value(), CSSValueInherit))
+                return true;
+            if (m_includedProperties.contains(PropertyType::NonInherited) && !current.isInherited())
+                return true;
+
+            // Apply all deferred properties if we have applied any. They may override the ones we already applied.
+            if (propertyID >= firstDeferredProperty && m_lastIndexForDeferred)
+                return true;
+
+            if (m_includedProperties.contains(PropertyType::VariableReference)) {
+                if (current.value()->hasVariableReferences())
+                    return true;
             }
 
             return false;

Source/WebCore/style/PropertyCascade.h

@@ -42,9 +42,10 @@ class PropertyCascade {
     enum class PropertyType : uint8_t {
         NonInherited = 1 << 0,
         Inherited = 1 << 1,
-        VariableReference = 1 << 2,
-        AfterAnimation = 1 << 3,
-        AfterTransition = 1 << 4
+        ExplicitlyInherited = 1 << 2,
+        VariableReference = 1 << 3,
+        AfterAnimation = 1 << 4,
+        AfterTransition = 1 << 5
     };
     static constexpr OptionSet<PropertyType> allProperties() { return { PropertyType::NonInherited,  PropertyType::Inherited }; }
 

Source/WebCore/style/StyleResolver.cpp

@@ -620,7 +620,10 @@ void Resolver::applyMatchedProperties(State& state, const MatchResult& matchResu
         // element context. This is fast and saves memory by reusing the style data structures.
         style.copyNonInheritedFrom(*cacheEntry->renderStyle);
 
-        if (parentStyle.inheritedEqual(*cacheEntry->parentRenderStyle) && !isAtShadowBoundary(element)) {
+        bool hasExplicitlyInherited = cacheEntry->renderStyle->hasExplicitlyInheritedProperties();
+        bool inheritedStyleEqual = parentStyle.inheritedEqual(*cacheEntry->parentRenderStyle) && !isAtShadowBoundary(element);
+
+        if (inheritedStyleEqual && !hasExplicitlyInherited) {
             InsideLink linkStatus = state.style()->insideLink();
             // If the cache item parent style has identical inherited properties to the current parent style then the
             // resulting style will be identical too. We copy the inherited properties over from the cache and are done.
@@ -635,9 +638,11 @@ void Resolver::applyMatchedProperties(State& state, const MatchResult& matchResu
             return;
         }
 
-        includedProperties = { PropertyCascade::PropertyType::Inherited };
-
-        if (!parentStyle.inheritedCustomPropertiesEqual(*cacheEntry->parentRenderStyle))
+        if (!inheritedStyleEqual)
+            includedProperties.add(PropertyCascade::PropertyType::Inherited);
+        if (hasExplicitlyInherited)
+            includedProperties.add(PropertyCascade::PropertyType::ExplicitlyInherited);
+        if (!inheritedStyleEqual && !parentStyle.inheritedCustomPropertiesEqual(*cacheEntry->parentRenderStyle))
             includedProperties.add(PropertyCascade::PropertyType::VariableReference);
     }