move_it_by_lines (&it, min (PTRDIFF_MAX, nlines));
/* We could have some display or overlay string at ZV,
in which case it.vpos will be nonzero now, while
move_it_by_lines (&it, min (PTRDIFF_MAX, nlines));
/* We could have some display or overlay string at ZV,
in which case it.vpos will be nonzero now, while