Improve shaping segmentation for grapheme cluster based font fallback

third_party/WebKit/Source/platform/fonts/shaping/HarfBuzzFace.h

 /*
  * Copyright (c) 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.
  */
 
 #ifndef HarfBuzzFace_h
 #define HarfBuzzFace_h
 
 #include "wtf/HashMap.h"
 #include "wtf/PassRefPtr.h"
 #include "wtf/RefCounted.h"
 #include "wtf/RefPtr.h"
+#include "wtf/text/CharacterNames.h"
 
 #include <hb.h>
 
 namespace blink {
 
 class FontPlatformData;
 
 class HarfBuzzFace : public RefCounted<HarfBuzzFace> {
 public:
     static const hb_tag_t vertTag;
     static const hb_tag_t vrt2Tag;
 
     static PassRefPtr<HarfBuzzFace> create(FontPlatformData* platformData, uint64_t uniqueID)
     {
         return adoptRef(new HarfBuzzFace(platformData, uniqueID));
     }
     ~HarfBuzzFace();
 
-    hb_font_t* createFont() const;
+    // In order to support the restricting effect of unicode-range optionally a
+    // range restriction can be passed in, which will restrict which glyphs we
+    // return in the harfBuzzGetGlyph function.
+    hb_font_t* createFont(unsigned rangeFrom = 0, unsigned rangeTo = kMaxCodepoint) const;
     hb_face_t* face() const { return m_face; }
 
 private:
     HarfBuzzFace(FontPlatformData*, uint64_t);
 
     hb_face_t* createFace();
 
     FontPlatformData* m_platformData;
     uint64_t m_uniqueID;
     hb_face_t* m_face;
     WTF::HashMap<uint32_t, uint16_t>* m_glyphCacheForFaceCacheEntry;
 };
 
 } // namespace blink
 
 namespace WTF {
 
 template<typename T> struct OwnedPtrDeleter;
 template<> struct OwnedPtrDeleter<hb_font_t> {
     static void deletePtr(hb_font_t* font)
     {
         if (font)
             hb_font_destroy(font);
     }
 };
 
 } // namespace WTF
 
 #endif // HarfBuzzFace_h