connect_demo :-
    send(new(P, picture('Connect Demo')), open),
    send(P, recogniser,
         click_gesture(left, '', single,
                       message(@prolog, display_box,
                               P, @event?position))).

:- pce_global(@east,  new(handle(0, h/2, any, east))).
:- pce_global(@north, new(handle(w/2, 0, any, north))).
:- pce_global(@west,  new(handle(w, h/2, any, west))).
:- pce_global(@south, new(handle(w/2, h, any, south))).

:- pce_global(@connect_recogniser,
              new(handler_group(connect_gesture(left, '', link(any)),
                                new(move_gesture)))).

display_box(P, Pos) :-
    send(P, display, new(B, box(30,30)), Pos),
    send_list(B, handle,
              [ @east, @north, @west, @south
              ]),
    send(B, recogniser, @connect_recogniser).