Draws a rectangle with coordinates X1,Y1, X2,Y2 using the current pen , and fills it with the current brush . In round_rect the arguments Ex and Ey give the size of the ellipse which is used to make the corners round.
If Ex and Ey are zero then round_rect will be the
same as rect . On the other hand if Ex and Ey are
too big then round_rect will become ellipse.
?-window(_, _, win_func(_), "Rectangle demo", 100, 100, 200, 200).