Implements CSSPropertyAPI for the font-variation-settings property.

third_party/WebKit/Source/core/css/properties/CSSPropertyAPIFontVariationSettings.cpp

+// Copyright 2017 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/properties/CSSPropertyAPIFontVariationSettings.h"
+
+#include "core/css/CSSFontVariationValue.h"
+#include "core/css/CSSValueList.h"
+#include "core/css/parser/CSSParserContext.h"
+#include "core/css/parser/CSSPropertyParserHelpers.h"
+#include "platform/RuntimeEnabledFeatures.h"
+
+namespace blink {
+
+namespace {
+
+CSSFontVariationValue* consumeFontVariationTag(CSSParserTokenRange& range) {
+  // Feature tag name consists of 4-letter characters.
+  static const unsigned tagNameLength = 4;
+
+  const CSSParserToken& token = range.consumeIncludingWhitespace();
+  // Feature tag name comes first
+  if (token.type() != StringToken)
+    return nullptr;
+  if (token.value().length() != tagNameLength)
+    return nullptr;
+  AtomicString tag = token.value().toAtomicString();
+  for (unsigned i = 0; i < tagNameLength; ++i) {
+    // Limits the range of characters to 0x20-0x7E, following the tag name rules
+    // defined in the OpenType specification.
+    UChar character = tag[i];
+    if (character < 0x20 || character > 0x7E)
+      return nullptr;
+  }
+
+  double tagValue = 0;
+  if (!CSSPropertyParserHelpers::consumeNumberRaw(range, tagValue))
+    return nullptr;
+  return CSSFontVariationValue::create(tag, clampTo<float>(tagValue));
+}
+
+}  // namespace
+
+const CSSValue* CSSPropertyAPIFontVariationSettings::parseSingleValue(
+    CSSParserTokenRange& range,
+    const CSSParserContext& context) {
+  DCHECK(RuntimeEnabledFeatures::cssVariableFontsEnabled());
+  if (range.peek().id() == CSSValueNormal)
+    return CSSPropertyParserHelpers::consumeIdent(range);
+  CSSValueList* variationSettings = CSSValueList::createCommaSeparated();
+  do {
+    CSSFontVariationValue* fontVariationValue = consumeFontVariationTag(range);
+    if (!fontVariationValue)
+      return nullptr;
+    variationSettings->append(*fontVariationValue);
+  } while (CSSPropertyParserHelpers::consumeCommaIncludingWhitespace(range));
+  return variationSettings;
+}
+
+}  // namespace blink