commit 569552b3a36058798b33a0e5660748c6242bddc9
parent 2da8eb3289c7d7e4f44fbf20c37c7abb41a0c2d9
Author: Emilio Cobos Álvarez <emilio@crisal.io>
Date: Wed, 5 Nov 2025 22:10:53 +0000
Bug 1997351 - More explicitly deal with singular matrices in getCTM and getScreenCTM. r=jrmuizel
This is much like bug 1992972, but a bit more general.
The issue in this case is that GetViewBoxTransform() is singular,
because of the zero viewport height:
https://searchfox.org/firefox-main/rev/cb52781342cc905eda923d009fc0b678f3a8c8c6/dom/svg/SVGViewportElement.cpp#162-164
Returning an identity matrix there seems a bit sketchy since it is used
in intermediate computations. Instead, deal with singular transforms at
the end of the process.
Differential Revision: https://phabricator.services.mozilla.com/D271409
Diffstat:
2 files changed, 34 insertions(+), 0 deletions(-)
diff --git a/dom/svg/SVGGraphicsElement.cpp b/dom/svg/SVGGraphicsElement.cpp
@@ -121,6 +121,9 @@ already_AddRefed<SVGMatrix> SVGGraphicsElement::GetCTM() {
currentDoc->FlushPendingNotifications(FlushType::Layout);
}
gfx::Matrix m = SVGContentUtils::GetCTM(this);
+ if (m.IsSingular()) {
+ m = {};
+ }
return do_AddRef(new SVGMatrix(ThebesMatrix(m)));
}
@@ -130,6 +133,9 @@ already_AddRefed<SVGMatrix> SVGGraphicsElement::GetScreenCTM() {
currentDoc->FlushPendingNotifications(FlushType::Layout);
}
gfx::Matrix m = SVGContentUtils::GetScreenCTM(this);
+ if (m.IsSingular()) {
+ m = {};
+ }
return do_AddRef(new SVGMatrix(ThebesMatrix(m)));
}
diff --git a/testing/web-platform/tests/svg/types/scripted/SVGGraphicsElement.getCTM-empty-viewBox.html b/testing/web-platform/tests/svg/types/scripted/SVGGraphicsElement.getCTM-empty-viewBox.html
@@ -0,0 +1,28 @@
+<!doctype html>
+<title>SVGGraphicsElement.getCTM and co with empty viewbox</title>
+<link rel="author" href="mailto:emilio@crisal.io" title="Emilio Cobos Álvarez">
+<link rel="author" href="https://mozilla.com" title="Mozilla">
+<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1997351">
+<link rel="help" href="https://svgwg.org/svg2-draft/types.html#InterfaceSVGGraphicsElement" />
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<div id="container" style="width: 500px; height: 0px;">
+ <svg width="100%" height="100%" xmlns:xlink="http://www.w3.org/1999/xlink">
+ <defs></defs>
+ <g class="viewport">
+ </g>
+ </svg>
+</div>
+<script>
+ function assert_identity(m, prefix) {
+ assert_equals(m.a, 1, prefix + "a");
+ assert_equals(m.d, 1, prefix + "d");
+ for (let member of ["b", "c", "e", "f"]) {
+ assert_equals(m[member], 0, prefix + member);
+ }
+ }
+ test(function () {
+ assert_identity(document.querySelector(".viewport").getCTM(), "getCTM: ");
+ assert_identity(document.querySelector(".viewport").getScreenCTM(), "getScreenCTM: ");
+ });
+</script>
