void CustomListWidget :: mouseMoveEvent (QMouseEvent * event)
{
    int y_pos = event->y();
    int diff = last_y_pos - y_pos;
    if(diff == 0)
        return;
    
    if((last_diff != -1) && ((diff < 0) != (last_diff < 0)))
    {
        last_y_pos = y_pos;
    }
    
    last_diff = diff;
    verticalScrollBar()->setValue(verticalScrollBar()->value() + diff); // move scrollbar here
    last_y_pos = y_pos;
    QListWidget::mouseMoveEvent(event);
}

void CustomListWidget :: mousePressEvent (QMouseEvent * event)
{
    int y_pos = event->y();
    last_diff = -1;
    last_y_pos = y_pos;
    QListWidget::mousePressEvent(event);
    
}