Improve getFallbackFamily() for Unified Han Ideographs on Windows

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 17 matching lines @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #include "config.h"
 #include "platform/fonts/win/FontFallbackWin.h"
 
 #include "platform/fonts/FontCache.h"
 #include "SkFontMgr.h"
 #include "SkTypeface.h"
 #include "wtf/HashMap.h"
+#include "wtf/StringExtras.h"
 #include "wtf/text/StringHash.h"
 #include "wtf/text/WTFString.h"
 #include <limits>
 #include <unicode/locid.h>
 #include <unicode/uchar.h>
 
 namespace blink {
 
 namespace {
 
@@ skipping 37 matching lines @@
 
     static const FontMap fontMap[] = {
         { USCRIPT_HEBREW, L"courier new" },
         { USCRIPT_ARABIC, L"courier new" },
     };
 
     for (size_t i = 0; i < WTF_ARRAY_LENGTH(fontMap); ++i)
         scriptFontMap[fontMap[i].script] = fontMap[i].family;
 }
 
+static UScriptCode scriptCodeForUnifiedHanFromDefaultLocale()

[drott, 2015/09/04 08:26:15]

I think it would be helpful if you would give this function argument(s) and
either mock icu::Locale or give this function language, country and script
arguments and write a couple of unit tests that show the improvement?

This would make it more clear to understand what is getting improved. It's not
100% clear to me from the CL description what where the cases in which our
previous algorithm lead to less than optimal resolutions.

+{
+    // Since Chrome synchronizes the ICU default locale with its UI locale,
+    // this ICU locale tells the current UI locale of Chrome.
+    const icu::Locale& locale = icu::Locale::getDefault();
+
+    // ICU default locale may have country as an empty string or differently.
+    // Avoid fullName comparisons for Japanese and Korean where language()
+    // can safely disambiguate.
+    if (strcasecmp(locale.getLanguage(), icu::Locale::getJapanese().getLanguage()) == 0)
+        return USCRIPT_HIRAGANA;
+    if (strcasecmp(locale.getLanguage(), icu::Locale::getKorean().getLanguage()) == 0)
+        return USCRIPT_HANGUL;
+
+    const icu::Locale& traditionalChinese = icu::Locale::getTraditionalChinese();
+    if (strcasecmp(locale.getLanguage(), traditionalChinese.getLanguage()) == 0
+        && (strcasecmp(locale.getCountry(), traditionalChinese.getCountry()) == 0
+            || strcasecmp(locale.getCountry(), "HK") == 0
+            || strcasecmp(locale.getScript(), "Hant") == 0)) {
+        return USCRIPT_TRADITIONAL_HAN;
+    }
+
+    // For other locales, use the simplified Chinese font for Han.
+    return USCRIPT_SIMPLIFIED_HAN;
+}
+
 void initializeScriptFontMap(ScriptToFontMap& scriptFontMap, SkFontMgr* fontManager)
 {
     struct FontMap {
         UScriptCode script;
         const UChar* family;
     };
 
     static const FontMap fontMap[] = {
         {USCRIPT_LATIN, L"times new roman"},
         {USCRIPT_GREEK, L"times new roman"},
@@ skipping 104 matching lines @@
         while (*familyPtr) {
             if (isFontPresent(*familyPtr, fontManager)) {
                 scriptFontMap[script] = *familyPtr;
                 break;
             }
             ++familyPtr;
         }
     }
 
     // Initialize the locale-dependent mapping.
-    // Since Chrome synchronizes the ICU default locale with its UI locale,
-    // this ICU locale tells the current UI locale of Chrome.
-    icu::Locale locale = icu::Locale::getDefault();
-    const UChar* localeFamily = 0;
-    if (locale == icu::Locale::getJapanese()) {
-        localeFamily = scriptFontMap[USCRIPT_HIRAGANA];
-    } else if (locale == icu::Locale::getKorean()) {
-        localeFamily = scriptFontMap[USCRIPT_HANGUL];
-    } else if (locale == icu::Locale::getTraditionalChinese()) {
-        localeFamily = scriptFontMap[USCRIPT_TRADITIONAL_HAN];
-    } else {
-        // For other locales, use the simplified Chinese font for Han.
-        localeFamily = scriptFontMap[USCRIPT_SIMPLIFIED_HAN];
-    }
+    const UChar* localeFamily = scriptFontMap[scriptCodeForUnifiedHanFromDefaultLocale()];
     if (localeFamily)
         scriptFontMap[USCRIPT_HAN] = localeFamily;
 }
 
 // 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)
 {
@@ skipping 168 matching lines @@
             family = L"lucida sans unicode";
         }
     }
 
     if (scriptChecked)
         *scriptChecked = script;
     return family;
 }
 
 } // namespace blink