Track the region where text is painted.

Source/core/rendering/InlineTextBox.cpp

 /*
  * (C) 1999 Lars Knoll (knoll@kde.org)
  * (C) 2000 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 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 393 matching lines @@
         context->clip(shadowRect);
 
         extraOffset = FloatSize(0, 2 * textRect.height() + max(0.0f, shadowOffset.height()) + shadowBlur);
         shadowOffset -= extraOffset;
     }
 
     context->setShadow(shadowOffset, shadowBlur, shadowColor, context->fillColorSpace());
     return extraOffset;
 }
 
-static void paintTextWithShadows(GraphicsContext* context, const Font& font, const TextRun& textRun, const AtomicString& emphasisMark, int emphasisMarkOffset, int startOffset, int endOffset, int truncationPoint, const FloatPoint& textOrigin,
-                                 const FloatRect& boxRect, const ShadowData* shadow, bool stroked, bool horizontal)
+static void paintTextWithShadows(GraphicsContext* context, const Font& font, const TextRun& textRun,
+                                 const AtomicString& emphasisMark, int emphasisMarkOffset,
+                                 int startOffset, int endOffset, int truncationPoint,
+                                 const FloatPoint& textOrigin, const FloatRect& boxRect,
+                                 const ShadowData* shadow, bool stroked, bool horizontal)
 {
     Color fillColor = context->fillColor();
     ColorSpace fillColorSpace = context->fillColorSpace();
     bool opaque = fillColor.alpha() == 255;
     if (!opaque)
         context->setFillColor(Color::black, fillColorSpace);
 
+    TextRunPaintInfo textRunPaintInfo(textRun);
+    textRunPaintInfo.bounds = boxRect;
     do {
         IntSize extraOffset;
         if (shadow)
             extraOffset = roundedIntSize(InlineTextBox::applyShadowToGraphicsContext(context, shadow, boxRect, stroked, opaque, horizontal));
         else if (!opaque)
             context->setFillColor(fillColor, fillColorSpace);
 
         if (startOffset <= endOffset) {
+            textRunPaintInfo.from = startOffset;
+            textRunPaintInfo.to = endOffset;
             if (emphasisMark.isEmpty())
-                context->drawText(font, textRun, textOrigin + extraOffset, startOffset, endOffset);
+                context->drawText(font, textRunPaintInfo, textOrigin + extraOffset);
             else
-                context->drawEmphasisMarks(font, textRun, emphasisMark, textOrigin + extraOffset + IntSize(0, emphasisMarkOffset), startOffset, endOffset);
+                context->drawEmphasisMarks(font, textRunPaintInfo, emphasisMark, textOrigin + extraOffset + IntSize(0, emphasisMarkOffset));
         } else {
             if (endOffset > 0) {
+                textRunPaintInfo.from = 0;
+                textRunPaintInfo.to = endOffset;
                 if (emphasisMark.isEmpty())
-                    context->drawText(font, textRun, textOrigin + extraOffset,  0, endOffset);
+                    context->drawText(font, textRunPaintInfo, textOrigin + extraOffset);
                 else
-                    context->drawEmphasisMarks(font, textRun, emphasisMark, textOrigin + extraOffset + IntSize(0, emphasisMarkOffset),  0, endOffset);
+                    context->drawEmphasisMarks(font, textRunPaintInfo, emphasisMark, textOrigin + extraOffset + IntSize(0, emphasisMarkOffset));
             }
             if (startOffset < truncationPoint) {
+                textRunPaintInfo.from = startOffset;
+                textRunPaintInfo.to = truncationPoint;
                 if (emphasisMark.isEmpty())
-                    context->drawText(font, textRun, textOrigin + extraOffset, startOffset, truncationPoint);
+                    context->drawText(font, textRunPaintInfo, textOrigin + extraOffset);
                 else
-                    context->drawEmphasisMarks(font, textRun, emphasisMark, textOrigin + extraOffset + IntSize(0, emphasisMarkOffset),  startOffset, truncationPoint);
+                    context->drawEmphasisMarks(font, textRunPaintInfo, emphasisMark, textOrigin + extraOffset + IntSize(0, emphasisMarkOffset));
             }
         }
 
         if (!shadow)
             break;
 
         if (shadow->next() || stroked || !opaque)
             context->restore();
         else
             context->clearShadow();
@@ skipping 1172 matching lines @@
 
 void InlineTextBox::reportMemoryUsage(MemoryObjectInfo* memoryObjectInfo) const
 {
     MemoryClassInfo info(memoryObjectInfo, this, WebCoreMemoryTypes::Rendering);
     InlineBox::reportMemoryUsage(memoryObjectInfo);
     info.addMember(m_prevTextBox, "prevTextBox");
     info.addMember(m_nextTextBox, "nextTextBox");
 }
 
 } // namespace WebCore