/* matrix is of size window_size + 1 on each side. */
struct matrix_elt *matrix,
int window_size, int lines_below,
int *draw_cost, int *old_draw_cost,
/* matrix is of size window_size + 1 on each side. */
struct matrix_elt *matrix,
int window_size, int lines_below,
int *draw_cost, int *old_draw_cost,