QDialogButtonBox buttonBox;
    
    auto printFocusChain = [&]{
        for (auto *button : buttonBox.buttons())
            qDebug() << button->previousInFocusChain() << button << button->nextInFocusChain();
    };
    
    QDialogButtonBox::ButtonRole roles[] = { QDialogButtonBox::AcceptRole, QDialogButtonBox::AcceptRole, QDialogButtonBox::AcceptRole };
    for (auto role : roles) {
        static int i = 0;
        auto *button = new QPushButton(QString("%1").arg(++i));
        button->setObjectName(button->text());
        QObject::connect(button, &QPushButton::clicked, [=]{
            qDebug() << button->text();
            printFocusChain();
        });
        buttonBox.addButton(button, role);
    }
    
    printFocusChain();
  
    QTimer::singleShot(200, [&]{
        printFocusChain();
    });
    
    buttonBox.show();