{
other_trace_corner_approx = curr_other_trace_corner_approx;
other_trace_line = curr_other_trace_line;
prev_corner_side = curr_prev_corner_side;
other_prev_trace_line = curr_other_prev_trace_line;
<BUG>}
}
}
else
{
return null;</BUG>
}

{
if (trace_polyline.corner_count() < 3) return null;
curr_prev_end_corner = trace_polyline.corner(trace_polyline.corner_count() - 3);
--end_line_no;
