history_set_pos
if (!history_set_pos(off) || history(h, &ev, H_CURR) != 0)
int history_set_pos(int);
history_set_pos(1);
if ((ret = history_set_pos(-1)) != 0)
if ((ret = history_set_pos(1)) != 1)
history_set_pos(0);
history_set_pos(1);
history_set_pos(1);