From c5d1ec4dea5fd795eb96cbb8211e9116284dc2e0 Mon Sep 17 00:00:00 2001
From: Tim Ledbetter <timledbetter@gmail.com>
Date: Sat, 17 Feb 2024 08:09:53 +0000
Subject: [PATCH] LibWeb/CSS: Ensure length is absolute before converting to
 pixels

Previously, creating a DOMMatrix with a transform that contained
non-absolute units would cause a crash.
---
 Tests/LibWeb/Text/expected/geometry/dommatrix-create.txt | 1 +
 Tests/LibWeb/Text/input/geometry/dommatrix-create.html   | 3 +++
 Userland/Libraries/LibWeb/CSS/Transformation.cpp         | 6 ++++--
 3 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/Tests/LibWeb/Text/expected/geometry/dommatrix-create.txt b/Tests/LibWeb/Text/expected/geometry/dommatrix-create.txt
index 517e542d47..f7e5a57630 100644
--- a/Tests/LibWeb/Text/expected/geometry/dommatrix-create.txt
+++ b/Tests/LibWeb/Text/expected/geometry/dommatrix-create.txt
@@ -16,3 +16,4 @@
 16. Exception: SyntaxError
 17. Exception: SyntaxError
 18. Exception: SyntaxError
+19. Exception: SyntaxError
diff --git a/Tests/LibWeb/Text/input/geometry/dommatrix-create.html b/Tests/LibWeb/Text/input/geometry/dommatrix-create.html
index 2ea5513b1b..270a5a198f 100644
--- a/Tests/LibWeb/Text/input/geometry/dommatrix-create.html
+++ b/Tests/LibWeb/Text/input/geometry/dommatrix-create.html
@@ -64,5 +64,8 @@
 
         // 18. Creating a DOMMatrix with CSS transform string with error
         testPart(() => new DOMMatrix('matrix(1.0, 2.0deg, 3.0, 4.0, 5.0, 6.0)'));
+
+        // 19. Creating a DOMMatrix with CSS transform string with non-absolute units should fail
+        testPart(() => new DOMMatrix('translate(1em, 1em)'));
     });
 </script>
diff --git a/Userland/Libraries/LibWeb/CSS/Transformation.cpp b/Userland/Libraries/LibWeb/CSS/Transformation.cpp
index 12ca2d215f..1ca1aa957a 100644
--- a/Userland/Libraries/LibWeb/CSS/Transformation.cpp
+++ b/Userland/Libraries/LibWeb/CSS/Transformation.cpp
@@ -24,8 +24,10 @@ ErrorOr<Gfx::FloatMatrix4x4> Transformation::to_matrix(Optional<Painting::Painta
             [&](CSS::LengthPercentage const& value) -> ErrorOr<float> {
                 if (paintable_box.has_value())
                     return value.resolved(paintable_box->layout_node(), reference_length).to_px(paintable_box->layout_node()).to_float();
-                if (value.is_length())
-                    return value.length().absolute_length_to_px().to_float();
+                if (value.is_length()) {
+                    if (auto const& length = value.length(); length.is_absolute())
+                        return length.absolute_length_to_px().to_float();
+                }
                 return Error::from_string_literal("Transform contains non absolute units");
             },
             [&](CSS::AngleOrCalculated const& value) -> ErrorOr<float> {