Skeleton implementation of CSS Properties and Values API

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

+// Copyright 2016 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/PropertyRegistration.h"
+
+#include "core/css/CSSSyntaxDescriptor.h"
+#include "core/css/CSSVariableReferenceValue.h"
+#include "core/css/PropertyDescriptor.h"
+#include "core/css/PropertyRegistry.h"
+#include "core/css/parser/CSSVariableParser.h"
+#include "core/dom/Document.h"
+#include "core/dom/ExceptionCode.h"
+#include "core/dom/StyleChangeReason.h"
+
+namespace blink {
+
+static bool computationallyIdempotent(const CSSValue& value)
+{
+    // TODO(timloh): Implement this
+    return true;
+}
+
+void PropertyRegistration::registerProperty(ExecutionContext* executionContext, const PropertyDescriptor& descriptor, ExceptionState& exceptionState)
+{
+    // Bindings code ensures these are set.
+    DCHECK(descriptor.hasName());
+    DCHECK(descriptor.hasInherits());
+    DCHECK(descriptor.hasSyntax());
+
+    String name = descriptor.name();
+    if (!CSSVariableParser::isValidVariableName(name)) {
+        exceptionState.throwDOMException(SyntaxError, "The name provided is not a valid custom property name.");
+        return;
+    }
+    AtomicString atomicName(name);
+    Document* document = toDocument(executionContext);
+    PropertyRegistry& registry = *document->propertyRegistry();
+    if (registry.registration(atomicName)) {
+        exceptionState.throwDOMException(InvalidModificationError, "The name provided has already been registered.");
+        return;
+    }
+
+    CSSSyntaxDescriptor syntaxDescriptor(descriptor.syntax());
+    if (!syntaxDescriptor.isValid()) {
+        exceptionState.throwDOMException(SyntaxError, "The syntax provided is not a valid custom property syntax.");
+        return;
+    }
+
+    if (descriptor.hasInitialValue()) {
+        const CSSValue* initial = syntaxDescriptor.parse(descriptor.initialValue());
+        if (!initial) {
+            exceptionState.throwDOMException(SyntaxError, "The initial value provided does not parse for the given syntax.");
+            return;
+        }
+        if (!computationallyIdempotent(*initial)) {
+            exceptionState.throwDOMException(SyntaxError, "The initial value provided is not computationally idempotent.");
+            return;
+        }
+        registry.registerProperty(atomicName, syntaxDescriptor, descriptor.inherits(), initial);
+    } else {
+        if (!syntaxDescriptor.isTokenStream()) {
+            exceptionState.throwDOMException(SyntaxError, "An initial value must be provided if the syntax is not '*'");
+            return;
+        }
+        registry.registerProperty(atomicName, syntaxDescriptor, descriptor.inherits(), nullptr);
+    }
+
+    // TODO(timloh): Invalidate only elements with this custom property set
+    document->setNeedsStyleRecalc(SubtreeStyleChange, StyleChangeReasonForTracing::create(StyleChangeReason::PropertyRegistration));
+}
+
+void PropertyRegistration::unregisterProperty(ExecutionContext* executionContext, const String& property, ExceptionState& exceptionState)
+{
+    Document* document = toDocument(executionContext);
+    PropertyRegistry& registry = *document->propertyRegistry();
+    AtomicString atomicProperty(property);
+    if (!registry.registration(atomicProperty)) {
+        exceptionState.throwDOMException(NotFoundError, "CSS.unregisterProperty() called with non-registered property " + property);
+        return;
+    }
+    registry.unregisterProperty(atomicProperty);
+
+    document->setNeedsStyleRecalc(SubtreeStyleChange, StyleChangeReasonForTracing::create(StyleChangeReason::PropertyUnregistration));
+}
+
+} // namespace blink