Add per-fragment early-out for getCharNumAtPosition

Source/core/rendering/svg/SVGTextQuery.cpp

Index: Source/core/rendering/svg/SVGTextQuery.cpp
diff --git a/Source/core/rendering/svg/SVGTextQuery.cpp b/Source/core/rendering/svg/SVGTextQuery.cpp
index fe7f7c08c3b9c361b9321c7fc1b1a00aac61f0bf..60d90c1795a81c32cda65dfa24a795b37fe81090 100644
--- a/Source/core/rendering/svg/SVGTextQuery.cpp
+++ b/Source/core/rendering/svg/SVGTextQuery.cpp
@@ -508,6 +508,18 @@ static inline void calculateGlyphBoundaries(SVGTextQuery::Data* queryData, const
     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);
@@ -545,6 +557,11 @@ bool SVGTextQuery::characterNumberAtPositionCallback(Data* queryData, const SVGT
 {
     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;