Add per-fragment early-out for getCharNumAtPosition

Source/core/rendering/svg/SVGTextQuery.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 490 matching lines @@
 
     SVGTextMetrics metrics = SVGTextMetrics::measureCharacterRange(queryData->textRenderer, fragment.characterOffset + startPosition, 1);
     extent.setSize(FloatSize(metrics.width(), metrics.height()));
 
     AffineTransform fragmentTransform;
     fragment.buildFragmentTransform(fragmentTransform, SVGTextFragment::TransformIgnoringTextLength);
 
     extent = fragmentTransform.mapRect(extent);
 }
 
+static inline FloatRect calculateFragmentBoundaries(const RenderSVGInlineText& textRenderer, const SVGTextFragment& fragment)
+{
+    float scalingFactor = textRenderer.scalingFactor();
+    ASSERT(scalingFactor);
+    float baseline = textRenderer.scaledFont().fontMetrics().floatAscent() / scalingFactor;
+
+    AffineTransform fragmentTransform;
+    FloatRect fragmentRect(fragment.x, fragment.y - baseline, fragment.width, fragment.height);
+    fragment.buildFragmentTransform(fragmentTransform);
+    return fragmentTransform.mapRect(fragmentRect);

[fs, 2014/06/27 14:16:04]

(Pondered putting these last four lines in a method on SVGTextFragment - only
saw one additional user of this exact sequence though. Holler if you'd like me
to do that change.)

+}
+
 bool SVGTextQuery::extentOfCharacterCallback(Data* queryData, const SVGTextFragment& fragment) const
 {
     ExtentOfCharacterData* data = static_cast<ExtentOfCharacterData*>(queryData);
 
     int startPosition = data->position;
     int endPosition = startPosition + 1;
     if (!mapStartEndPositionsIntoFragmentCoordinates(queryData, fragment, startPosition, endPosition))
         return false;
 
     calculateGlyphBoundaries(queryData, fragment, startPosition, data->extent);
@@ skipping 17 matching lines @@
     {
     }
 
     FloatPoint position;
 };
 
 bool SVGTextQuery::characterNumberAtPositionCallback(Data* queryData, const SVGTextFragment& fragment) const
 {
     CharacterNumberAtPositionData* data = static_cast<CharacterNumberAtPositionData*>(queryData);
 
+    // Test the query point against the bounds of the entire fragment first.
+    FloatRect fragmentExtents = calculateFragmentBoundaries(*queryData->textRenderer, fragment);
+    if (!fragmentExtents.contains(data->position))
+        return false;
+
     // Iterate through the glyphs in this fragment, and check if their extents
     // contain the query point.
     FloatRect extent;
     const Vector<SVGTextMetrics>& textMetrics = queryData->textRenderer->layoutAttributes()->textMetricsValues();
     unsigned textMetricsOffset = fragment.metricsListOffset;
     unsigned fragmentOffset = 0;
     while (fragmentOffset < fragment.length) {
         calculateGlyphBoundaries(queryData, fragment, fragmentOffset, extent);
         if (extent.contains(data->position)) {
             // Compute the character offset of the glyph within the text box
@@ skipping 14 matching lines @@
         return -1;
 
     CharacterNumberAtPositionData data(position);
     if (!executeQuery(&data, &SVGTextQuery::characterNumberAtPositionCallback))
         return -1;
 
     return data.processedCharacters;
 }
 
 }