transform_point(&mat, x, y, &x1, &y1);
transform_point(&mat, line->sx, line->sy, &x2, &y2);
transform_point(&mat, line->x, line->y, &x3, &y3);
transform_point(&mat, x, y, &x1, &y1);
transform_point(&mat, line->sx, line->sy, &x2, &y2);
transform_point(&mat, line->x, line->y, &x3, &y3);