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

output_ <<= ~output + qtf;

if (!sb && !tsb) { //Both are still zero if view has nothing.
    _output.ScrollEnd();
    _sbConst = _output_.GetSbTotal() - _output_.GetSb(); //_sbConst is a member var initialized here to contain the magic number
} else {
    ASSERT(_sbConst > 0);
    if (tsb - sb != _sbConst) _output_.SetSb(sb);
    else _output_.ScrollEnd();
}