Add FontCache API for retrieving prioritized fallback fonts

third_party/WebKit/Source/platform/fonts/mac/FontCacheMac.mm

 /*
  * Copyright (C) 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Nicholas Shanks <webkit@nickshanks.com>
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
@@ skipping 35 matching lines @@
 
 // Forward declare Mac SPIs.
 // Request for public API: rdar://13803570
 @interface NSFont (WebKitSPI)
 + (NSFont*)findFontLike:(NSFont*)font forString:(NSString*)string withRange:(NSRange)range inLanguage:(id)useNil;
 + (NSFont*)findFontLike:(NSFont*)font forCharacter:(UniChar)uc inLanguage:(id)useNil;
 @end
 
 namespace blink {
 
+// Unfortunately, these chosen font names require a bit of experimentation and
+// researching on the respective platforms as to what works best and is widely
+// available. They may require further tuning after OS updates. Mozilla's
+// choices in the gfxPlatformMac::GetCommonFallbackFonts method collects some of
+// the outcome of this experimentation.
+const char* kColorEmojiFontsMac[] = { "Apple Color Emoji" };
+const char* kTextEmojiFontsMac[] = { "Hiragino Kaku Gothic ProN", "Zapf Dingbats", "Apple Symbols" };
+const char* kSymbolsAndMathFontsMac[] = { "Menlo", "Arial Unicode MS" };
+
 static void invalidateFontCache()
 {
     if (!isMainThread()) {
         Platform::current()->mainThread()->taskRunner()->postTask(BLINK_FROM_HERE, bind(&invalidateFontCache));
         return;
     }
     FontCache::fontCache()->invalidate();
 }
 
 static void fontCacheRegisteredFontsChangedNotificationCallback(CFNotificationCenterRef, void* observer, CFStringRef name, const void *, CFDictionaryRef)
@@ skipping 143 matching lines @@
     // Out-of-process loading occurs for registered fonts stored in non-system locations.
     // When loading fails, we do not want to use the returned FontPlatformData since it will not have
     // a valid SkTypeface.
     OwnPtr<FontPlatformData> platformData = adoptPtr(new FontPlatformData(platformFont, size, syntheticBold, syntheticItalic, fontDescription.orientation()));
     if (!platformData->typeface()) {
         return nullptr;
     }
     return platformData.release();
 }
 
+const Vector<AtomicString> FontCache::platformFontListForFallbackPriority(FontFallbackPriority fallbackPriority) const
+{
+    Vector<AtomicString> returnVector;
+    switch (fallbackPriority) {
+    case FontFallbackPriority::EmojiEmoji:
+        for (size_t i = 0; i < WTF_ARRAY_LENGTH(kColorEmojiFontsMac); ++i)
+            returnVector.append(kColorEmojiFontsMac[i]);
+        break;
+    case FontFallbackPriority::EmojiText:
+        for (size_t i = 0; i < WTF_ARRAY_LENGTH(kTextEmojiFontsMac); ++i)
+            returnVector.append(kTextEmojiFontsMac[i]);
+        break;
+    case FontFallbackPriority::Math:
+    case FontFallbackPriority::Symbols:
+        for (size_t i = 0; i < WTF_ARRAY_LENGTH(kSymbolsAndMathFontsMac); ++i)
+            returnVector.append(kSymbolsAndMathFontsMac[i]);
+        break;
+    default:
+        ASSERT_NOT_REACHED();
+    }
+    return returnVector;
+}
+
 } // namespace blink