Handle multiple fragments in the getCharNumberAtPosition SVGTextQuery

https://bugs.webkit.org/show_bug.cgi?id=257429 Reviewed by Simon Fraser. This patch aligns WebKit with Blink / Chromium and Gecko / Firefox. Merge: https://src.chromium.org/viewvc/blink?view=revision&revision=176936 The start position (and thus indirectly end position) used to compute the extents of a glyph to check against the point is computed based on the 'processedCharacter' query data state. Following state is only updated after each text box has been processed, meaning that for a text box with multiple fragments, the offset of the fragment within the box needs to be included to get the correct start/end position. * Source/WebCore/rendering/svg/SVGTextQuery.cpp: (SVGTextQuery::characterNumberAtPositionCallback): As above * LayoutTests/svg/text/getcharnumatposition-multiple-fragments.html: Add Test Case * LayoutTests/svg/text/getcharnumatposition-multiple-fragments-expected.txt: Add Test Case Expectation Canonical link: https://commits.webkit.org/264796@main
WebKit · Jun 1, 2023 · c01e3ba · c01e3ba
1 parent ab72213
commit c01e3ba
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diff --git a/LayoutTests/svg/text/getcharnumatposition-multiple-fragments-expected.txt b/LayoutTests/svg/text/getcharnumatposition-multiple-fragments-expected.txt
@@ -0,0 +1,4 @@
+AAAA
+
+PASS SVGTextContentElement.getCharNumAtPosition w/ multiple fragments per text box.
+
diff --git a/LayoutTests/svg/text/getcharnumatposition-multiple-fragments.html b/LayoutTests/svg/text/getcharnumatposition-multiple-fragments.html
@@ -0,0 +1,21 @@
+<!DOCTYPE html>
+<script src="../../resources/testharness.js"></script>
+<script src="../../resources/testharnessreport.js"></script>
+<svg height="0">
+  <defs><path id="p" d="M0,20h100"/></defs>
+  <text y="20" font-size="20" font-family="Ahem"><textPath xlink:href="#p">AAAA</textPath></text>
+</svg>
+<script>
+test(function() {
+  var text = document.querySelector('text');
+  var extents = text.getExtentOfChar(0);
+  var point = document.querySelector('svg').createSVGPoint();
+  point.x = extents.width / 2;
+  point.y = 10;
+  for (var i = 0; i < 4; ++i) {
+    assert_equals(text.getCharNumAtPosition(point), i);
+
+    point.x += extents.width;
+  }
+}, 'SVGTextContentElement.getCharNumAtPosition w/ multiple fragments per text box.');
+</script>
diff --git a/Source/WebCore/rendering/svg/SVGTextQuery.cpp b/Source/WebCore/rendering/svg/SVGTextQuery.cpp
@@ -1,5 +1,6 @@
 /*
  * Copyright (C) Research In Motion Limited 2010-2012. All rights reserved.
+ * Copyright (C) 2014 Google 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
@@ -521,16 +522,19 @@ bool SVGTextQuery::characterNumberAtPositionCallback(Data* queryData, const SVGT
 {
     CharacterNumberAtPositionData* data = static_cast<CharacterNumberAtPositionData*>(queryData);
 
+    // Offset of the fragment within the text box.
+    unsigned boxOffset = fragment.characterOffset - queryData->textBox->start();
+
     FloatRect extent;
     for (unsigned i = 0; i < fragment.length; ++i) {
-        unsigned startPosition = data->processedCharacters + i;
+        unsigned startPosition = data->processedCharacters + boxOffset + i;
         unsigned endPosition = startPosition + 1;
         if (!mapStartEndPositionsIntoFragmentCoordinates(queryData, fragment, startPosition, endPosition))
             continue;
 
         calculateGlyphBoundaries(queryData, fragment, startPosition, extent);
         if (extent.contains(data->position)) {
-            data->processedCharacters += i;
+            data->processedCharacters += i + boxOffset;
             return true;
         }
     }