Negative SVGTransform scale values should be correctly stringified

https://bugs.webkit.org/show_bug.cgi?id=264752 rdar://problem/118656892 Reviewed by Said Abou-Hallawa. This patch is to align WebKit with Blink / Chromium and partially with Gecko / Firefox. Merge: https://chromium.googlesource.com/chromium/blink/+/8a7252a2602bd8067c83d48c8fd525ef322708c2 Before this patch, SVGTransformValue::appendScale used AffineTransform::{x,y}Scale}, which computed transform scale values by computing norm of projected unit vectors. However, that would always return positive values, even if negative scale values were specified. This patch changes the implementation to use `a` and `d` values instead. This is valid, as the scale matrix is guaranteed to be in the below simple form when the transform has type `SVG_TRANSFORM_SCALE`. |xscale 0 0| | 0 yscale 0| * Source/WebCore/svg/SVGTransformValue.h: (appendScale): * LayoutTests/svg/transforms/negative-scale-value.html: Add Test Case * LayoutTests/svg/transforms/negative-scale-value-expected.txt: Add Test Case Expectation Canonical link: https://commits.webkit.org/272885@main
WebKit · Jan 11, 2024 · 2efdea0 · 2efdea0
1 parent 9abc579
commit 2efdea0
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Showing 3 changed files with 28 additions and 2 deletions.
diff --git a/LayoutTests/svg/transforms/negative-scale-value-expected.txt b/LayoutTests/svg/transforms/negative-scale-value-expected.txt
@@ -0,0 +1,10 @@
+SVG scale transform with negative scale values should be correctly converted to strings.
+
+On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
+
+
+PASS g.getAttribute('transform') is "scale(-2 -4)"
+PASS successfullyParsed is true
+
+TEST COMPLETE
+
diff --git a/LayoutTests/svg/transforms/negative-scale-value.html b/LayoutTests/svg/transforms/negative-scale-value.html
@@ -0,0 +1,15 @@
+<!DOCTYPE HTML>
+<script src='../../resources/js-test.js'></script>
+<script>
+description("SVG scale transform with negative scale values should be correctly converted to strings.");
+
+var svg = document.createElementNS('http://www.w3.org/2000/svg', 'svg');
+var g = document.createElementNS('http://www.w3.org/2000/svg', 'g');
+var transform = svg.createSVGTransform();
+transform.setScale(-2, -4);
+
+var list = g.transform.baseVal;
+list.appendItem(transform);
+
+shouldBeEqualToString("g.getAttribute('transform')", "scale(-2 -4)");
+</script>
diff --git a/Source/WebCore/svg/SVGTransformValue.h b/Source/WebCore/svg/SVGTransformValue.h
@@ -1,7 +1,8 @@
 /*
  * Copyright (C) 2004, 2005, 2008 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005 Rob Buis <buis@kde.org>
- * Copyright (C) 2019 Apple Inc. All rights reserved.
+ * Copyright (C) 2019-2024 Apple Inc. 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
@@ -264,7 +265,7 @@ class SVGTransformValue {
 
     void appendScale(StringBuilder& builder) const
     {
-        appendFixedPrecisionNumbers(builder, m_matrix->value().xScale(), m_matrix->value().yScale());
+        appendFixedPrecisionNumbers(builder, m_matrix->a(), m_matrix->d());
     }
 
     void appendRotate(StringBuilder& builder) const