Add font fallback support to SkFontMgr_fontconfig.

src/ports/SkFontMgr_fontconfig.cpp

Index: src/ports/SkFontMgr_fontconfig.cpp
diff --git a/src/ports/SkFontMgr_fontconfig.cpp b/src/ports/SkFontMgr_fontconfig.cpp
index b54835d1be68d07e73e11d5531509d47c217b206..3b08ff4bb753df4bcc3ec7bb076ded56057a9712 100644
--- a/src/ports/SkFontMgr_fontconfig.cpp
+++ b/src/ports/SkFontMgr_fontconfig.cpp
@@ -106,6 +106,7 @@ public:
     SkAutoFc(T* obj) : SkAutoTCallVProc<T, FcTDestroy<T, P> >(obj) {}
 };
 
+typedef SkAutoFc<FcCharSet, FcCharSetDestroy> SkAutoFcCharSet;
 typedef SkAutoFc<FcConfig, FcConfigDestroy> SkAutoFcConfig;
 typedef SkAutoFc<FcFontSet, FcFontSetDestroy> SkAutoFcFontSet;
 typedef SkAutoFc<FcLangSet, FcLangSetDestroy> SkAutoFcLangSet;
@@ -650,17 +651,35 @@ protected:
         return false;
     }
 
-    static bool ValidPattern(FcPattern* pattern) {
+    static bool FontAccessible(FcPattern* font) {
         // FontConfig can return fonts which are unreadable.
-        const char* filename = get_string(pattern, FC_FILE, NULL);
+        const char* filename = get_string(font, FC_FILE, NULL);
         if (NULL == filename) {
             return false;
         }
         return sk_exists(filename, kRead_SkFILE_Flag);
     }
 
-    static bool FontMatches(FcPattern* font, FcPattern* pattern) {
-        return ValidPattern(font) && AnyMatching(font, pattern, FC_FAMILY);
+    static bool FontFamilyNameMatches(FcPattern* font, FcPattern* pattern) {
+        return AnyMatching(font, pattern, FC_FAMILY);
+    }
+
+    static bool FontContainsCharacter(FcPattern* font, uint32_t character) {
+        FcResult result;
+        FcCharSet* matchCharSet;
+        for (int charSetId = 0; ; ++charSetId) {
+            result = FcPatternGetCharSet(font, FC_CHARSET, charSetId, &matchCharSet);
+            if (FcResultNoId == result) {
+                break;
+            }
+            if (FcResultMatch != result) {

[mtklein, 2014/08/28 21:32:23]

// just a sanity check

[bungeman-skia, 2014/09/09 19:06:17]

Acknowledged.

+                continue;
+            }
+            if (FcCharSetHasChar(matchCharSet, character)) {
+                return true;
+            }
+        }
+        return false;
     }
 
     virtual SkFontStyleSet* onMatchFamily(const char familyName[]) const SK_OVERRIDE {
@@ -698,9 +717,9 @@ protected:
             }
 
             for (int fontIndex = 0; fontIndex < allFonts->nfont; ++fontIndex) {
-                if (FontMatches(allFonts->fonts[fontIndex], matchPattern)) {
-                    FcFontSetAdd(matches,
-                                 FcFontRenderPrepare(fFC, pattern, allFonts->fonts[fontIndex]));
+                FcPattern* font = allFonts->fonts[fontIndex];
+                if (FontAccessible(font) && FontFamilyNameMatches(font, matchPattern)) {
+                    FcFontSetAdd(matches, FcFontRenderPrepare(fFC, pattern, font));
                 }
             }
         }
@@ -742,12 +761,49 @@ protected:
         }
 
         FcResult result;
-        SkAutoFcPattern match(FcFontMatch(fFC, pattern, &result));
-        if (NULL == match || !FontMatches(match, matchPattern)) {
+        SkAutoFcPattern font(FcFontMatch(fFC, pattern, &result));
+        if (NULL == font || !FontAccessible(font) || !FontFamilyNameMatches(font, matchPattern)) {
+            return NULL;
+        }
+
+        return createTypefaceFromFcPattern(font);
+    }
+
+    virtual SkTypeface* onMatchFamilyStyleCharacter(const char familyName[],
+                                                    const SkFontStyle& style,
+                                                    const char bpc47[],

[mtklein, 2014/08/28 21:32:23]

/* may be NULL*/ ?

[bungeman-skia, 2014/09/09 19:06:17]

This sort of comment needs to be over in SkFontMgr.h. I'll keep it in mind.

+                                                    uint32_t character) const SK_OVERRIDE
+    {
+        FCLocker lock;
+
+        SkAutoFcPattern pattern(FcPatternCreate());
+        if (NULL == pattern) {

[mtklein, 2014/08/28 21:32:23]

add SkASSERT(pattern) ?

[bungeman-skia, 2014/09/09 19:06:17]

Done.

+            return NULL;
+        }
+
+        FcPatternAddString(pattern, FC_FAMILY, (FcChar8*)familyName);
+        fcpattern_from_skfontstyle(style, pattern);
+
+        SkAutoFcCharSet charSet(FcCharSetCreate());

[mtklein, 2014/08/28 21:32:23]

No null check?

[bungeman-skia, 2014/09/09 19:06:17]

Done.

+        FcCharSetAddChar(charSet, character);
+        FcPatternAddCharSet(pattern, FC_CHARSET, charSet);
+
+        if (bpc47) {
+            SkAutoFcLangSet langSet(FcLangSetCreate());

[mtklein, 2014/08/28 21:32:23]

...

[bungeman-skia, 2014/09/09 19:06:17]

Done.

+            FcLangSetAdd(langSet, (const FcChar8*)bpc47);
+            FcPatternAddLangSet(pattern, FC_LANG, langSet);
+        }
+
+        FcConfigSubstitute(fFC, pattern, FcMatchPattern);
+        FcDefaultSubstitute(pattern);
+
+        FcResult result;
+        SkAutoFcPattern font(FcFontMatch(fFC, pattern, &result));
+        if (NULL == font || !FontAccessible(font) || !FontContainsCharacter(font, character)) {
             return NULL;
         }
 
-        return createTypefaceFromFcPattern(match);
+        return createTypefaceFromFcPattern(font);
     }
 
     virtual SkTypeface* onMatchFaceStyle(const SkTypeface* typeface,