Take Accept-Language into account in CJK font fallback for Windows

third_party/WebKit/Source/platform/fonts/win/FontFallbackWin.cpp

 /*
  * Copyright (c) 2006, 2007, 2008, 2009, 2010, 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 212 matching lines @@
     // this ICU locale tells the current UI locale of Chrome.
     UScriptCode hanScript = scriptCodeForHanFromLocale(
         icu::Locale::getDefault().getName(), '_');
     // For other locales, use the simplified Chinese font for Han.
     const UChar* localeFamily = scriptFontMap[hanScript == USCRIPT_COMMON
         ? USCRIPT_SIMPLIFIED_HAN : hanScript];
     if (localeFamily)
         scriptFontMap[USCRIPT_HAN] = localeFamily;
 }
 
+static UScriptCode scriptForHan(UScriptCode contentScript,
+    const AtomicString& contentLocale)
+{
+    UScriptCode script = scriptCodeForHanFromLocale(contentScript, contentLocale);
+    if (script != USCRIPT_COMMON)
+        return script;
+    script = FontCache::preferredScriptForHan();
+    if (script != USCRIPT_COMMON)
+        return script;
+    return USCRIPT_HAN;
+}
+
 // There are a lot of characters in USCRIPT_COMMON that can be covered
 // by fonts for scripts closely related to them. See
 // http://unicode.org/cldr/utility/list-unicodeset.jsp?a=[:Script=Common:]
 // FIXME: make this more efficient with a wider coverage
 UScriptCode getScriptBasedOnUnicodeBlock(int ucs4)
 {
     UBlockCode block = ublock_getCode(ucs4);
     switch (block) {
     case UBLOCK_CJK_SYMBOLS_AND_PUNCTUATION:
         return USCRIPT_HAN;
@@ skipping 158 matching lines @@
     // For the full-width ASCII characters (U+FF00 - U+FF5E), use the font for
     // Han (determined in a locale-dependent way above). Full-width ASCII
     // characters are rather widely used in Japanese and Chinese documents and
     // they're fully covered by Chinese, Japanese and Korean fonts.
     if (0xFF00 < character && character < 0xFF5F)
         script = USCRIPT_HAN;
 
     if (script == USCRIPT_COMMON)
         script = getScriptBasedOnUnicodeBlock(character);
 
-    // For unified-Han scripts, try the lang attribute.
-    if (script == USCRIPT_HAN) {
-        script = scriptCodeForHanFromLocale(contentScript, contentLocale);
-        // Use the UI locale if it is still ambiguous.
-        if (script == USCRIPT_COMMON)
-            script = USCRIPT_SIMPLIFIED_HAN;
-    }
+    // For unified-Han scripts, try the lang attribute, system, or
+    // accept-languages.
+    if (script == USCRIPT_HAN)
+        script = scriptForHan(contentScript, contentLocale);
 
     family = getFontFamilyForScript(script, generic, fontManager);
     // Another lame work-around to cover non-BMP characters.
     // If the font family for script is not found or the character is
     // not in BMP (> U+FFFF), we resort to the hard-coded list of
     // fallback fonts for now.
     if (!family || character > 0xFFFF) {
         int plane = character >> 16;
         switch (plane) {
         case 1:
@@ skipping 14 matching lines @@
             family = L"lucida sans unicode";
         }
     }
 
     if (scriptChecked)
         *scriptChecked = script;
     return family;
 }
 
 } // namespace blink