5.1.5 Graphical relation

Using spatials

The example below opens a picture object with two box objects that are related though a spatial object. Both boxes may be resized and moved. The spatial object ensures B1 is twice as large as B2, centered in X-direction and 10 pixels above B2.

spatial_demo :-
        new(G, handler_group(resize_gesture(left),
                                         move_gesture(left))),
        new(P, picture('Spatial Demo')),
        send(P, display, new(B1, box(100,100))),
        send(P, display, new(B2, box(50,50))),
        send_list([B1, B2], recogniser, G),
        new(_, constraint(B1, B2,
                                          spatial(xref = x+w/2, yref = y+h,
                                                          xref = x+w/2, yref = y-10,
                                                          w = w2*2, h = h2*2))),
        send(P, open).

% Start the demo

:- spatial_demo.

See also

class spatial