xwayland: Set libX11 error handlers to no-ops before terminating

We might not be the only entity holding on to the X11 GdkDisplay,
meaning the X11 connection will stay alive indefinitely, e.g. if the gjs
context has some reference to it.

Avoid running into issues due to X11 connection errors by setting the
libX11 handlers to no-ops, so when we are terminating; that means the
GDK X11 connection can stay "alive" until its too late, and we'll just
silently ignore any connection errors that may happen due to the
lingering GDK display reference.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1822>

src/wayland/meta-xwayland.c

@@ -607,6 +607,12 @@ x_io_error (Display *display)
   return 0;
 }
 
+static int
+x_io_error_noop (Display *display)
+{
+  return 0;
+}
+
 #ifdef HAVE_XSETIOERROREXITHANDLER
 static void
 x_io_error_exit (Display *display,
@@ -619,6 +625,12 @@ x_io_error_exit (Display *display,
   manager->xserver_grace_period_id =
     g_idle_add (shutdown_xwayland_cb, manager);
 }
+
+static void
+x_io_error_exit_noop (Display *display,
+                      void    *data)
+{
+}
 #endif
 
 void
@@ -1264,10 +1276,19 @@ meta_xwayland_connection_release (MetaXWaylandConnection *connection)
 void
 meta_xwayland_shutdown (MetaXWaylandManager *manager)
 {
+#ifdef HAVE_XSETIOERROREXITHANDLER
+  MetaX11Display *x11_display = meta_get_display ()->x11_display;
+#endif
   char path[256];
 
   g_cancellable_cancel (manager->xserver_died_cancellable);
 
+  XSetIOErrorHandler (x_io_error_noop);
+#ifdef HAVE_XSETIOERROREXITHANDLER
+  XSetIOErrorExitHandler (meta_x11_display_get_xdisplay (x11_display),
+                          x_io_error_exit_noop, NULL);
+#endif
+
   snprintf (path, sizeof path, "%s%d", X11_TMP_UNIX_PATH,
             manager->public_connection.display_index);
   unlink (path);