Track the region where text is painted.

Source/core/platform/graphics/Font.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2003, 2006, 2010, 2011 Apple Inc. All rights reserved.
  *
  * 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
  * version 2 of the License, or (at your option) any later version.
@@ skipping 138 matching lines @@
     // being reasonably safe (because inherited fonts in the render tree pick up the new
     // style anyway. Other copies are transient, e.g., the state in the GraphicsContext, and
     // won't stick around long enough to get you in trouble). Still, this is pretty disgusting,
     // and could eventually be rectified by using RefPtrs for Fonts themselves.
     if (!m_fontFallbackList)
         m_fontFallbackList = FontFallbackList::create();
     m_fontFallbackList->invalidate(fontSelector);
     m_typesettingFeatures = computeTypesettingFeatures();
 }
 
-void Font::drawText(GraphicsContext* context, const TextRun& run, const FloatPoint& point, int from, int to, CustomFontNotReadyAction customFontNotReadyAction) const
+void Font::drawText(GraphicsContext* context, const TextRunPaintInfo& runInfo, const FloatPoint& point, CustomFontNotReadyAction customFontNotReadyAction) const
 {
     // Don't draw anything while we are using custom fonts that are in the process of loading,
     // except if the 'force' argument is set to true (in which case it will use a fallback
     // font).
     if (loadingCustomFonts() && customFontNotReadyAction == DoNotPaintIfFontNotReady)
         return;
     
-    to = (to == -1 ? run.length() : to);
-
-    CodePath codePathToUse = codePath(run);
+    CodePath codePathToUse = codePath(runInfo.run);
     // FIXME: Use the fast code path once it handles partial runs with kerning and ligatures. See http://webkit.org/b/100050
-    if (codePathToUse != Complex && typesettingFeatures() && (from || to != run.length()))
+    if (codePathToUse != Complex && typesettingFeatures() && (runInfo.from || runInfo.to != runInfo.run.length()))
         codePathToUse = Complex;
 
     if (codePathToUse != Complex)
-        return drawSimpleText(context, run, point, from, to);
+        return drawSimpleText(context, runInfo, point);
 
-    return drawComplexText(context, run, point, from, to);
+    return drawComplexText(context, runInfo, point);
 }
 
-void Font::drawEmphasisMarks(GraphicsContext* context, const TextRun& run, const AtomicString& mark, const FloatPoint& point, int from, int to) const
+void Font::drawEmphasisMarks(GraphicsContext* context, const TextRunPaintInfo& runInfo, const AtomicString& mark, const FloatPoint& point) const
 {
     if (loadingCustomFonts())
         return;
 
-    if (to < 0)
-        to = run.length();
-
-    CodePath codePathToUse = codePath(run);
+    CodePath codePathToUse = codePath(runInfo.run);
     // FIXME: Use the fast code path once it handles partial runs with kerning and ligatures. See http://webkit.org/b/100050
-    if (codePathToUse != Complex && typesettingFeatures() && (from || to != run.length()))
+    if (codePathToUse != Complex && typesettingFeatures() && (runInfo.from || runInfo.to != runInfo.run.length()))
         codePathToUse = Complex;
 
     if (codePathToUse != Complex)
-        drawEmphasisMarksForSimpleText(context, run, mark, point, from, to);
+        drawEmphasisMarksForSimpleText(context, runInfo, mark, point);
     else
-        drawEmphasisMarksForComplexText(context, run, mark, point, from, to);
+        drawEmphasisMarksForComplexText(context, runInfo, mark, point);
 }
 
 float Font::width(const TextRun& run, HashSet<const SimpleFontData*>* fallbackFonts, GlyphOverflow* glyphOverflow) const
 {
     CodePath codePathToUse = codePath(run);
     if (codePathToUse != Complex) {
         // The complex path is more restrictive about returning fallback fonts than the simple path, so we need an explicit test to make their behaviors match.
         if (!canReturnFallbackFontsForComplexText())
             fallbackFonts = 0;
         // The simple path can optimize the case where glyph overflow is not observable.
@@ skipping 591 matching lines @@
 
     // Additional word-separator characters listed in CSS Text Level 3 Editor's Draft 3 November 2010.
     if (c == ethiopicWordspace || c == aegeanWordSeparatorLine || c == aegeanWordSeparatorDot
         || c == ugariticWordDivider || c == tibetanMarkIntersyllabicTsheg || c == tibetanMarkDelimiterTshegBstar)
         return false;
 
     return true;
 }
 
 }