ci(pytest): focus_force() crashes on Linux/X11 in python3.9 headless environments

So use focus_set() instead.

Author: amilcarlucas

ardupilot_methodic_configurator/frontend_tkinter_parameter_editor.py

@@ -940,7 +940,7 @@ def ask_user_choice(title: str, message: str, options: list[str]) -> ExperimentC
             # Show dialog at correct position and make it modal
             # On macOS, grab_set() causes UI freeze (issue #1264), so skip it
             if sys_platform != "darwin":
-                dialog.focus_force()
+                dialog.focus_set()  # focus_force() crashes on Linux/X11 in python3.9 headless environments
                 dialog.grab_set()
 
             # Set focus after dialog is shown and modal

ardupilot_methodic_configurator/frontend_tkinter_parameter_editor_table.py

@@ -990,7 +990,7 @@ def _center_and_focus_window(self, window: Union[tk.Toplevel, tk.Tk]) -> None:
 
         # On macOS, grab_set() causes UI freeze (issue #1264), so skip it
         if sys_platform != "darwin":
-            window.focus_force()
+            window.focus_set()  # focus_force() crashes on Linux/X11 in python3.9 headless environments
             window.grab_set()
 
     def _confirm_parameter_addition(self, param_name: str) -> bool:

ardupilot_methodic_configurator/frontend_tkinter_usage_popup_window.py

@@ -114,9 +114,11 @@ def finalize_setup_popupwindow(
             popup_window.root.deiconify()
             popup_window.root.lift()
             popup_window.root.update()  # Ensure the window is fully rendered before setting focus
-            # Defer focus_force to after the event loop has processed the deiconify/lift,
-            # avoiding a segfault in Python 3.9 on Linux (X11) in headless environments.
-            popup_window.root.after(1, popup_window.root.focus_force)
+            # Use focus_set() instead of focus_force(): focus_force() calls XSetInputFocus
+            # directly via X11, which causes a segfault in Python 3.9 on Linux in headless
+            # environments. focus_set() only updates Tk's internal focus state, avoiding the crash.
+            # grab_set() below ensures modality regardless.
+            popup_window.root.focus_set()
 
             # On macOS, grab_set() causes UI freeze (issue #1264), so skip it
             # On Windows/Linux, make the popup modal and give it focus