core: Avoid focusing windows on map during grabs

Normally, mutter implicitly allows a window being shown to take
focus. This is normally desired, except it steals input from
GNOME Shell self. Avoid focusing the just shown window in those
situations.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2878>

src/core/window.c

@@ -1990,6 +1990,15 @@ window_state_on_map (MetaWindow *window,
       return;
     }
 
+  /* Do not focus window on map if input is already taken by the
+   * compositor.
+   */
+  if (!meta_display_windows_are_interactable (window->display))
+    {
+      *takes_focus = FALSE;
+      return;
+    }
+
   /* Terminal usage may be different; some users intend to launch
    * many apps in quick succession or to just view things in the new
    * window while still interacting with the terminal.  In that case,