Use a programmatic approach to disable animations.

.github/workflows/ci.yml

@@ -195,9 +195,7 @@ jobs:
 
           - backend: linux
             runs-on: ubuntu-latest
-            pre-command: |
-              sudo apt-get update -y && sudo apt-get install -y python3-gi python3-gi-cairo gir1.2-gtk-3.0 python3-dev libgirepository1.0-dev libcairo2-dev pkg-config libfuse2
-              gsettings set org.gnome.desktop.interface enable-animations false
+            pre-command: sudo apt-get update -y && sudo apt-get install -y python3-gi python3-gi-cairo gir1.2-gtk-3.0 python3-dev libgirepository1.0-dev libcairo2-dev pkg-config libfuse2
             briefcase-run-prefix: 'xvfb-run -a -s "-screen 0 2048x1536x24"'
 
           - backend: windows

gtk/tests_backend/widgets/base.py

@@ -1,9 +1,8 @@
 import asyncio
-import warnings
 
 from pytest import skip
 
-from toga_gtk.libs import Gio, Gtk
+from toga_gtk.libs import Gtk
 
 from .properties import toga_color, toga_font
 
@@ -15,15 +14,9 @@ def __init__(self, widget):
         self.native = widget._impl.native
         assert isinstance(self.native, self.native_class)
 
-        # Check if GTK UI animations are enabled.
-        settings = Gio.Settings(schema="org.gnome.desktop.interface")
-        if settings.get_boolean("enable-animations"):
-            warnings.warn(
-                "GTK UI animations are enabled; any tests failures are likely "
-                "caused by this. Run `gsettings set org.gnome.desktop.interface "
-                "enable-animations false` to disable animations.",
-                RuntimeWarning,
-            )
+        # Ensure that the theme isn't using animations for the widget.
+        settings = Gtk.Settings.get_for_screen(self.native.get_screen())
+        settings.set_property("gtk-enable-animations", False)
 
     def assert_container(self, container):
         container_native = container._impl.container