int sb = output_.GetSb(), tsb = output_.GetSbTotal();

output_ <<= ~output_ + qtf;

if (!_sbConst) {
    output_.ScrollEnd();
    sb = output_.GetSb();
    tsb = output_.GetSbTotal();
    if (tsb > sb && tsb > output_.GetSbPage())
        _sbConst = tsb - sb;
} else {
    if (abs(tsb - sb) != _sbConst) output_.SetSb(sb);
    else output_.ScrollEnd();
}