screen_write_scrollregion
screen_write_scrollregion(sctx, n - 1, m - 1);
screen_write_scrollregion(ctx, 0, screen_size_y(s) - 1);
screen_write_scrollregion(&ctx, 0, sy - 1);
void screen_write_scrollregion(struct screen_write_ctx *, u_int, u_int);