Improve shaping segmentation for grapheme cluster based font fallback

third_party/WebKit/Source/platform/fonts/FontFallbackIterator.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef FontFallbackIterator_h
 #define FontFallbackIterator_h
 
 #include "platform/fonts/FontDataRange.h"
 #include "wtf/HashMap.h"
 #include "wtf/PassRefPtr.h"
@@ skipping 21 matching lines @@
     // Returns whether a list of all remaining characters to be shaped is
     // needed.  Needed by the FontfallbackIterator in order to check whether a
     // font from a segmented range should be loaded.
     bool needsHintList() const;
 
     bool hasNext() const { return m_fallbackStage != OutOfLuck; };
 
     // Some system fallback APIs (Windows, Android) require a character, or a
     // portion of the string to be passed.  On Mac and Linux, we get a list of
     // fonts without passing in characters.
-    const SimpleFontData* next(const Vector<UChar32>& hintList);
+    const FontDataRange next(const Vector<UChar32>& hintList);
 
 private:
     FontFallbackIterator(const FontDescription&, PassRefPtr<FontFallbackList>);
+    bool rangeContributesForHint(const Vector<UChar32> hintList, const FontDataRange&);
+    bool alreadyLoadingRangeForHintChar(UChar32 hintChar);
     void willUseRange(const AtomicString& family, const FontDataRange&);
 
-    const SimpleFontData* uniqueSystemFontForHint(UChar32 hint);
+    const PassRefPtr<SimpleFontData> uniqueSystemFontForHint(UChar32 hint);
 
     const FontDescription& m_fontDescription;
     RefPtr<FontFallbackList> m_fontFallbackList;
     int m_currentFontDataIndex;
     unsigned m_segmentedIndex;
 
     enum FallbackStage {
         FontGroupFonts,
         SegmentedFace,
         PreferencesFonts,
         SystemFonts,
         OutOfLuck
     };
 
     FallbackStage m_fallbackStage;
     const FontFamily* m_currentFamily;
     HashMap<UChar32, RefPtr<SimpleFontData>> m_visitedSystemFonts;
+    Vector<FontDataRange> m_loadingCustomFontForRanges;
 };
 
 } // namespace blink
 
 #endif