Added function to check Saver window is always at the front

c/app

@@ -221,6 +221,19 @@ static void calc_max_coords_for_current_mode_and_sprite(void)
   calc_to_nearest_even_number(bottom_edge);
 }
 
+/* Open a large black window that covers the screen */
+static void ensure_saver_window_at_front(void)
+{
+  wimp_wstate   state;
+
+  wimp_get_wind_state(main_handle, &state);
+  if (state.o.behind != -1)
+  {
+    state.o.behind = -1;
+    wimpt_noerr(wimp_open_wind(&state.o));
+  }
+}
+
 /***************************************************************************/
 
 /* Read the current sprite size */
@@ -404,6 +417,7 @@ static void plot_moving_routine(void)
 /* Which sprite plot are we on ? */
 static void sprite_plot_routine(void)
 {
+  ensure_saver_window_at_front();
   if (intro_done == FALSE)
     plot_intro_animation();
   else