Improve getFallbackFamily() for Unified Han Ideographs on Windows

Source/platform/fonts/win/FontFallbackWin.cpp

Index: Source/platform/fonts/win/FontFallbackWin.cpp
diff --git a/Source/platform/fonts/win/FontFallbackWin.cpp b/Source/platform/fonts/win/FontFallbackWin.cpp
index a7f5be4cdc1052d3035da781586990baa85dbd20..0ba9eb1c35571978d89d5fc1b91e0008871912cb 100644
--- a/Source/platform/fonts/win/FontFallbackWin.cpp
+++ b/Source/platform/fonts/win/FontFallbackWin.cpp
@@ -35,6 +35,7 @@
 #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>
@@ -92,6 +93,32 @@ void initializeScriptMonospaceFontMap(ScriptToFontMap& scriptFontMap, SkFontMgr*
         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 {
@@ -216,20 +243,7 @@ void initializeScriptFontMap(ScriptToFontMap& scriptFontMap, SkFontMgr* fontMana
     }
 
     // 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;
 }