(CANCELED) Improve performance of large option list with CJK text

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

 /*
  * Copyright (C) 2000 Lars Knoll (knoll@kde.org)
  *           (C) 2000 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2003, 2006, 2007, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Holger Hans Peter Freyther
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
@@ skipping 66 matching lines @@
     void update(PassRefPtrWillBeRawPtr<FontSelector>) const;
 
     enum CustomFontNotReadyAction { DoNotPaintIfFontNotReady, UseFallbackIfFontNotReady };
     bool drawText(SkCanvas*, const TextRunPaintInfo&, const FloatPoint&, float deviceScaleFactor, const SkPaint&) const;
     bool drawBidiText(SkCanvas*, const TextRunPaintInfo&, const FloatPoint&, CustomFontNotReadyAction, float deviceScaleFactor, const SkPaint&) const;
     void drawEmphasisMarks(SkCanvas*, const TextRunPaintInfo&, const AtomicString& mark, const FloatPoint&, float deviceScaleFactor, const SkPaint&) const;
 
     // Glyph bounds will be the minimum rect containing all glyph strokes, in coordinates using
     // (<text run x position>, <baseline position>) as the origin.
     float width(const TextRun&, HashSet<const SimpleFontData*>* fallbackFonts = nullptr, FloatRect* glyphBounds = nullptr) const;
+    float widthForUnbrokenRun(const TextRun&) const;

[drott, 2015/12/16 13:17:39]

This method and its implementation, i.e. new splitting logic, should not be in
Font.h. Rather I think we should have something in CachingWordShaper that allows
as to use the m_singleCharMap of ShapeCache for the CJK case.

If possible, I'd like to avoid "by character" special casing. Could we use
FontDescription.locale() for the distinction of what kind of splitting we do in
the CachingWordShaper?

 
     int offsetForPosition(const TextRun&, float position, bool includePartialGlyphs) const;
     FloatRect selectionRectForText(const TextRun&, const FloatPoint&, int h, int from = 0, int to = -1, bool accountForGlyphBounds = false) const;
 
     // Metrics that we query the FontFallbackList for.
     const FontMetrics& fontMetrics() const
     {
         RELEASE_ASSERT(primaryFont());
         return primaryFont()->fontMetrics();
     }
@@ skipping 106 matching lines @@
     // if the distance to the next tab stop is less than that, advance an additional tab stop.
     if (distanceToTabStop < std::max(fontDescription().letterSpacing(), LayoutUnit::epsilon()))
         distanceToTabStop += baseTabWidth;
 
     return distanceToTabStop;
 }
 
 } // namespace blink
 
 #endif