blink fonts: Load Android SkFontMgr on Linux.

third_party/WebKit/Source/platform/fonts/skia/FontCacheSkia.cpp

Index: third_party/WebKit/Source/platform/fonts/skia/FontCacheSkia.cpp
diff --git a/third_party/WebKit/Source/platform/fonts/skia/FontCacheSkia.cpp b/third_party/WebKit/Source/platform/fonts/skia/FontCacheSkia.cpp
index a97fbbf87aa2ebec7e7fe74f866f0355c8f7f237..d454c7bf64999190b07ebd31510e7520cd3f82ea 100644
--- a/third_party/WebKit/Source/platform/fonts/skia/FontCacheSkia.cpp
+++ b/third_party/WebKit/Source/platform/fonts/skia/FontCacheSkia.cpp
@@ -31,6 +31,7 @@
 #include "SkFontMgr.h"
 #include "SkStream.h"
 #include "SkTypeface.h"
+#include "platform/Language.h"
 #include "platform/fonts/AlternateFontFamily.h"
 #include "platform/fonts/FontCache.h"
 #include "platform/fonts/FontDescription.h"
@@ -87,6 +88,51 @@ static PassRefPtr<SkTypeface> typefaceForFontconfigInterfaceIdAndTtcIndex(int fo
 
 namespace blink {
 
+// SkFontMgr requires script-based locale names, like "zh-Hant" and "zh-Hans",
+// instead of "zh-CN" and "zh-TW".
+static CString toSkFontMgrLocale(const String& locale)
+{
+    if (!locale.startsWith("zh", TextCaseInsensitive))
+        return locale.ascii();
+
+    switch (localeToScriptCodeForFontSelection(locale)) {
+    case USCRIPT_SIMPLIFIED_HAN:
+        return "zh-Hans";
+    case USCRIPT_TRADITIONAL_HAN:
+        return "zh-Hant";
+    default:
+        return locale.ascii();
+    }
+}
+
+
+#if OS(ANDROID) || OS(LINUX)
+// This function is called on android or when we are emulating android fonts on linux and the
+// embedder has overriden the default fontManager with WebFontRendering::setSkiaFontMgr.
+// static
+AtomicString FontCache::getFamilyNameForCharacter(SkFontMgr* fm, UChar32 c, const FontDescription& fontDescription)
+{
+    ASSERT(fm);
+
+    const char* bcp47Locales[2];
+    int localeCount = 0;
+    CString defaultLocale = toSkFontMgrLocale(defaultLanguage());
+    bcp47Locales[localeCount++] = defaultLocale.data();
+    CString fontLocale;
+    if (!fontDescription.locale().isEmpty()) {
+        fontLocale = toSkFontMgrLocale(fontDescription.locale());
+        bcp47Locales[localeCount++] = fontLocale.data();
+    }
+    RefPtr<SkTypeface> typeface = adoptRef(fm->matchFamilyStyleCharacter(0, SkFontStyle(), bcp47Locales, localeCount, c));
+    if (!typeface)
+        return emptyAtom;
+
+    SkString skiaFamilyName;
+    typeface->getFamilyName(&skiaFamilyName);
+    return skiaFamilyName.c_str();
+}
+#endif
+
 void FontCache::platformInit()
 {
 }
@@ -227,6 +273,14 @@ PassRefPtr<SkTypeface> FontCache::createTypeface(const FontDescription& fontDesc
     }
 #endif
 
+#if OS(LINUX)
+    // On linux if the fontManager has been overridden then we should be calling the embedder
+    // provided font Manager rather than calling SkTypeface::CreateFromName which may redirect the
+    // call to the default font Manager.
+    if (m_fontManager)
+        return adoptRef(m_fontManager->legacyCreateTypeface(name.data(), style));

[bungeman-chromium, 2016/02/29 22:48:50]

This is a little bit sneaky, but I think this should instead be

m_fontManager->matchFamilyStyle(name.data(), fontStyle(fontDescription))

It appears that legacyCreateTypeface was chosen here to mirror what
CreateFromName below would do. However, there is no real need to be limited that
way. By using matchFamilyStyle you should get better weight selection (and
probably better fallback).

The CreateFromName call below eventually should be a call to matchFamilyStyle on
the default font manager (and I think this is now possible, I'll have to see
what changes).

[Khushal, 2016/03/01 18:52:43]

You're right, I was trying to be consistent with the other uses of font manager
but I guess its not necessary. The legacyCreateTypeface for the
SkFontMgr_android currently routes the call to matchFamilyStyle itself so there
is no need to have this indirection. The SkFontHost_fontconfig implementation
though returns null for matchFamilyStyle and we have to use
legacyCreateTypeface.

+#endif
+
     // FIXME: Use m_fontManager, SkFontStyle and matchFamilyStyle instead of
     // CreateFromName on all platforms.
     return adoptRef(SkTypeface::CreateFromName(name.data(), static_cast<SkTypeface::Style>(style)));