From 4e27d07ff289bde0066fe5126e6b761f0ad76d73 Mon Sep 17 00:00:00 2001
From: Matthew Olsson <matthewcolsson@gmail.com>
Date: Sun, 11 Feb 2024 14:21:35 -0700
Subject: [PATCH] LibWeb: Use initial value for animation start if it does not
 exist

This fixes an issue where a property could not be animated unless the
element had a specified value for that property somewhere in its
styling.
---
 Userland/Libraries/LibWeb/CSS/StyleComputer.cpp | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/Userland/Libraries/LibWeb/CSS/StyleComputer.cpp b/Userland/Libraries/LibWeb/CSS/StyleComputer.cpp
index 5b8b8de5be..54fea1edef 100644
--- a/Userland/Libraries/LibWeb/CSS/StyleComputer.cpp
+++ b/Userland/Libraries/LibWeb/CSS/StyleComputer.cpp
@@ -923,6 +923,9 @@ ErrorOr<void> StyleComputer::collect_animation_into(JS::NonnullGCPtr<Animations:
 
         auto resolved_end_property = resolve_property(end_property.value());
 
+        if (resolved_end_property && !resolved_start_property)
+            resolved_start_property = CSS::property_initial_value(document().realm(), it.key);
+
         if (!resolved_start_property || !resolved_end_property)
             continue;