Take Accept-Language into account in CJK font fallback for Android/Win

third_party/WebKit/Source/platform/fonts/AcceptLanguagesResolver.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 "platform/fonts/AcceptLanguagesResolver.h"
+
+#include "platform/Language.h"
+#include "platform/text/LocaleToScriptMapping.h"
+#include <unicode/locid.h>
+
+namespace blink {
+
+UScriptCode AcceptLanguagesResolver::m_preferredHanScript = USCRIPT_COMMON;
+const char* AcceptLanguagesResolver::m_preferredHanSkFontMgrLocale = nullptr;
+
+// SkFontMgr requires script-based locale names, like "zh-Hant" and "zh-Hans",
+// instead of "zh-CN" and "zh-TW".
+static const char* toSkFontMgrLocaleForHan(UScriptCode script)
+{
+    switch (script) {
+    case USCRIPT_KATAKANA_OR_HIRAGANA:
+        return "ja-jp";
+    case USCRIPT_HANGUL:
+        return "ko-kr";
+    case USCRIPT_SIMPLIFIED_HAN:
+        return "zh-Hans";
+    case USCRIPT_TRADITIONAL_HAN:
+        return "zh-Hant";
+    default:
+        ASSERT_NOT_REACHED();
+        return nullptr;
+    }
+}
+
+void AcceptLanguagesResolver::acceptLanguagesChanged(
+    const String& acceptLanguages)
+{
+    // Use the UI locale if it can disambiguate the Unified Han.
+    // Historically we use ICU on Windows. crbug.com/586520
+#if OS(WIN)
+    // Since Chrome synchronizes the ICU default locale with its UI locale,
+    // this ICU locale tells the current UI locale of Chrome.
+    m_preferredHanScript = scriptCodeForHanFromLocale(
+        icu::Locale::getDefault().getName(), '_');
+#else
+    m_preferredHanScript = scriptCodeForHanFromLocale(defaultLanguage());
+#endif
+    if (m_preferredHanScript != USCRIPT_COMMON) {
+        // We don't need additional locale if defaultLanguage() can disambiguate
+        // since it's always passed to matchFamilyStyleCharacter() separately.
+        m_preferredHanSkFontMgrLocale = nullptr;
+        return;
+    }
+
+    updateFromAcceptLanguages(acceptLanguages);
+}
+
+void AcceptLanguagesResolver::updateFromAcceptLanguages(
+    const String& acceptLanguages)
+{
+    // Use the first acceptLanguages that can disambiguate.
+    Vector<String> languages;
+    acceptLanguages.split(',', languages);
+    for (String token : languages) {
+        token = token.stripWhiteSpace();
+        m_preferredHanScript = scriptCodeForHanFromLocale(token);
+        if (m_preferredHanScript != USCRIPT_COMMON) {
+            m_preferredHanSkFontMgrLocale = toSkFontMgrLocaleForHan(
+                m_preferredHanScript);
+            return;
+        }
+    }
+
+    m_preferredHanScript = USCRIPT_COMMON;
+    m_preferredHanSkFontMgrLocale = nullptr;
+}
+
+} // namespace blink