Optimize Complex Text Shaping and Caching

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 12 matching lines @@
  */
 
 #ifndef Font_h
 #define Font_h
 
 #include "platform/PlatformExport.h"
 #include "platform/fonts/FontDescription.h"
 #include "platform/fonts/FontFallbackList.h"
 #include "platform/fonts/SimpleFontData.h"
 #include "platform/fonts/TextBlob.h"
+#include "platform/text/TabSize.h"
 #include "platform/text/TextDirection.h"
 #include "platform/text/TextPath.h"
 #include "wtf/HashMap.h"
 #include "wtf/HashSet.h"
 #include "wtf/MathExtras.h"
 #include "wtf/unicode/CharacterNames.h"
 
 // "X11/X.h" defines Complex to 0 and conflicts
 // with Complex value in CodePath enum.
 #ifdef Complex
@@ skipping 55 matching lines @@
     int emphasisMarkAscent(const AtomicString&) const;
     int emphasisMarkDescent(const AtomicString&) const;
     int emphasisMarkHeight(const AtomicString&) const;
 
     const SimpleFontData* primaryFont() const;
     const FontData* fontDataAt(unsigned) const;
 
     GlyphData glyphDataForCharacter(UChar32&, bool mirror, bool normalizeSpace = false, FontDataVariant = AutoVariant) const;
     CodePath codePath(const TextRunPaintInfo&) const;
 
+    // Whether the font supports shaping word by word instead of shaping the
+    // full run in one go. Allows better caching for fonts where space cannot
+    // participate in kerning and/or ligatures.
+    bool canShapeWordByWord() const;
+
+    void setCanShapeWordByWordForTesting(bool b)
+    {
+        m_canShapeWordByWord = b;
+        m_shapeWordByWordComputed = true;
+    }
+
 private:
     enum ForTextEmphasisOrNot { NotForTextEmphasis, ForTextEmphasis };
 
     // Returns the total advance.
     float buildGlyphBuffer(const TextRunPaintInfo&, GlyphBuffer&, const GlyphData* emphasisData = nullptr) const;
     PassTextBlobPtr buildTextBlob(const GlyphBuffer&) const;
     void paintGlyphs(SkCanvas*, const SkPaint&, const SimpleFontData*, const Glyph glyphs[], unsigned numGlyphs,
         const SkPoint pos[], const FloatRect& textRect, float deviceScaleFactor) const;
     void paintGlyphsHorizontal(SkCanvas*, const SkPaint&, const SimpleFontData*, const Glyph glyphs[], unsigned numGlyphs,
         const SkScalar xpos[], SkScalar constY, const FloatRect& textRect, float deviceScaleFactor) const;
     void drawGlyphs(SkCanvas*, const SkPaint&, const SimpleFontData*, const GlyphBuffer&, unsigned from, unsigned numGlyphs,
         const FloatPoint&, const FloatRect& textRect, float deviceScaleFactor) const;
     void drawTextBlob(SkCanvas*, const SkPaint&, const SkTextBlob*, const SkPoint& origin) const;
     void drawGlyphBuffer(SkCanvas*, const SkPaint&, const TextRunPaintInfo&, const GlyphBuffer&, const FloatPoint&, float deviceScaleFactor) const;
     float floatWidthForSimpleText(const TextRun&, HashSet<const SimpleFontData*>* fallbackFonts = 0, FloatRect* glyphBounds = 0) const;
     int offsetForPositionForSimpleText(const TextRun&, float position, bool includePartialGlyphs) const;
     FloatRect selectionRectForSimpleText(const TextRun&, const FloatPoint&, int h, int from, int to, bool accountForGlyphBounds) const;
 
     bool getEmphasisMarkGlyphData(const AtomicString&, GlyphData&) const;
 
     float floatWidthForComplexText(const TextRun&, HashSet<const SimpleFontData*>* fallbackFonts, FloatRect* glyphBounds) const;
     int offsetForPositionForComplexText(const TextRun&, float position, bool includePartialGlyphs) const;
     FloatRect selectionRectForComplexText(const TextRun&, const FloatPoint&, int h, int from, int to) const;
 
+    bool computeCanShapeWordByWord() const;
+
     friend struct SimpleShaper;
 
 public:
     FontSelector* fontSelector() const;
 
     void willUseFontData(UChar32) const;
 
     bool loadingCustomFonts() const;
     bool isFallbackValid() const;
 
 private:
     bool shouldSkipDrawing() const
     {
         return m_fontFallbackList && m_fontFallbackList->shouldSkipDrawing();
     }
 
     FontDescription m_fontDescription;
     mutable RefPtr<FontFallbackList> m_fontFallbackList;
+    mutable unsigned m_canShapeWordByWord : 1;
+    mutable unsigned m_shapeWordByWordComputed : 1;
 };
 
 inline Font::~Font()
 {
 }
 
 inline const SimpleFontData* Font::primaryFont() const
 {
     ASSERT(m_fontFallbackList);
     return m_fontFallbackList->primarySimpleFontData(m_fontDescription);
@@ skipping 21 matching lines @@
     // to the next tab stop is less than that, advance an additional tab stop.
     if (distanceToTabStop < fontDescription().letterSpacing())
         distanceToTabStop += baseTabWidth;
 
     return distanceToTabStop;
 }
 
 } // namespace blink
 
 #endif