Optimize glyph positioning for SVG <textPath> layout

Source/core/rendering/svg/SVGTextLayoutEngine.cpp

 /*
  * Copyright (C) Research In Motion Limited 2010-2012. 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.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 151 matching lines @@
     return false;
 }
 
 void SVGTextLayoutEngine::beginTextPathLayout(RenderObject* object, SVGTextLayoutEngine& lineLayout)
 {
     ASSERT(object);
 
     m_inPathLayout = true;
     RenderSVGTextPath* textPath = toRenderSVGTextPath(object);
 
-    m_textPath = textPath->layoutPath();
-    if (m_textPath.isEmpty())
+    Path path = textPath->layoutPath();
+    if (path.isEmpty())
         return;
+    m_textPathCalculator = adoptPtr(new Path::PositionCalculator(path));
     m_textPathStartOffset = textPath->startOffset();
-    m_textPathLength = m_textPath.length();
+    m_textPathLength = path.length();
     if (m_textPathStartOffset > 0 && m_textPathStartOffset <= 1)
         m_textPathStartOffset *= m_textPathLength;
 
     float totalLength = 0;
     unsigned totalCharacters = 0;
 
     lineLayout.m_chunkLayoutBuilder.buildTextChunks(lineLayout.m_lineLayoutBoxes);
     const Vector<SVGTextChunk>& textChunks = lineLayout.m_chunkLayoutBuilder.textChunks();
 
     unsigned size = textChunks.size();
@@ skipping 31 matching lines @@
 
     if (lengthAdjust == SVGLengthAdjustSpacing)
         m_textPathSpacing = (desiredTextLength - totalLength) / totalCharacters;
     else
         m_textPathScaling = desiredTextLength / totalLength;
 }
 
 void SVGTextLayoutEngine::endTextPathLayout()
 {
     m_inPathLayout = false;
-    m_textPath = Path();
+    m_textPathCalculator.clear();
     m_textPathLength = 0;
     m_textPathStartOffset = 0;
     m_textPathCurrentOffset = 0;
     m_textPathSpacing = 0;
     m_textPathScaling = 1;
 }
 
 void SVGTextLayoutEngine::layoutInlineTextBox(SVGInlineTextBox* textBox)
 {
     ASSERT(textBox);
@@ skipping 178 matching lines @@
 }
 
 void SVGTextLayoutEngine::advanceToNextVisualCharacter(const SVGTextMetrics& visualMetrics)
 {
     ++m_visualMetricsListOffset;
     m_visualCharacterOffset += visualMetrics.length();
 }
 
 void SVGTextLayoutEngine::layoutTextOnLineOrPath(SVGInlineTextBox* textBox, RenderSVGInlineText* text, const RenderStyle* style)
 {
-    if (m_inPathLayout && m_textPath.isEmpty())
+    if (m_inPathLayout && !m_textPathCalculator)
         return;
 
     SVGElement* lengthContext = toSVGElement(text->parent()->node());
 
     RenderObject* textParent = text->parent();
     bool definesTextLength = textParent ? parentDefinesTextLength(textParent) : false;
 
     const SVGRenderStyle* svgStyle = style->svgStyle();
     ASSERT(svgStyle);
 
@@ skipping 111 matching lines @@
                 advanceToNextLogicalCharacter(logicalMetrics);
                 advanceToNextVisualCharacter(visualMetrics);
                 continue;
             }
 
             // Stop processing, if the next character lies behind the path.
             if (textPathOffset > m_textPathLength)
                 break;
 
             FloatPoint point;
-            bool ok = m_textPath.pointAndNormalAtLength(textPathOffset, point, angle);
+            bool ok = m_textPathCalculator->pointAndNormalAtLength(textPathOffset, point, angle);
             ASSERT_UNUSED(ok, ok);
             x = point.x();
             y = point.y();
 
             // For vertical text on path, the actual angle has to be rotated 90 degrees anti-clockwise, not the orientation angle!
             if (m_isVerticalText)
                 angle -= 90;
         } else {
             // Apply all previously calculated shift values.
             if (m_isVerticalText) {
@@ skipping 73 matching lines @@
     }
 
     if (!didStartTextFragment)
         return;
 
     // Close last open fragment, if needed.
     recordTextFragment(textBox, visualMetricsValues);
 }
 
 }