let gui_set_wp_bottom (main_ui:Design.main_window_extension_points) b =
let old = Wp_parameters.Bottom.get () in
if b <> old then
begin
Wp_parameters.Bottom.set b;
let str = if b then "enable" else "disable" in
main_ui#annot_window#buffer#insert
("[wp] "^str^" using 'bottom' in next WP computations\n")
end