if (!no_vertical_start)
start = Line_interface::line (me, Offset (0,0), Offset (0, h));
if (!no_vertical_end)
end = Line_interface::line (me, Offset (w, 0), Offset (w,h));
if (!no_vertical_start)
start = Line_interface::line (me, Offset (0,0), Offset (0, h));
if (!no_vertical_end)
end = Line_interface::line (me, Offset (w, 0), Offset (w,h));