tests: Add tests for stickyness

The test tests how sticky windows and their transient-for dialog windows
behave together.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3870>

src/tests/meson.build

@@ -736,6 +736,7 @@ stacking_tests = [
   'sloppy-focus',
   'sloppy-focus-pointer-rest',
   'sloppy-focus-auto-raise',
+  'sticky',
   'strut-monitor-changes'
 ]
 

src/tests/stacking/sticky.metatest

@@ -0,0 +1,48 @@
+num_workspaces 2
+activate_workspace 0
+
+new_client w wayland
+create w/1
+show w/1
+stick w/1
+create w/2
+set_parent w/2 1
+show w/2
+wait
+assert_stacking_showing w/1 w/2
+
+activate_workspace 1
+assert_stacking_showing w/1 w/2
+
+unstick w/1
+assert_sticky w/1 false
+assert_sticky w/2 false
+wait
+
+activate_workspace 0
+dispatch
+assert_stacking_showing
+
+quit_client w
+
+new_client x x11
+
+create x/1
+show x/1
+stick x/1
+create x/2
+set_parent x/2 1
+show x/2
+wait
+assert_stacking_showing x/1 x/2
+
+activate_workspace 1
+assert_stacking_showing x/1 x/2
+
+unstick x/1
+
+activate_workspace 0
+dispatch
+assert_stacking_showing
+
+quit_client x