#include <QApplication>
#include <QtWidgets>

class MainWindow : public QMainWindow
{
public:
    MainWindow(QWidget *parent = nullptr) : QMainWindow{parent} {
        sb.setMaximum(99999);
        sb.setValue(12345);
        
        sbNoButton.setMaximum(99999);
        sbNoButton.setValue(12345);
        sbNoButton.setButtonSymbols(QAbstractSpinBox::NoButtons);
        
        hLayout.addWidget(&sb);
        hLayout.addWidget(&sbNoButton);
        hLayout.addStretch(1);
        
        vLayout.addLayout(&hLayout);
        vLayout.addWidget(&debug);
        
        central.setLayout(&vLayout);
        setCentralWidget(&central);
    };
protected:
    void resizeEvent(QResizeEvent *event) override {
        debug.clear();
        QString s;
        QDebug out{&s};
        out << " sb size: \t" << sb.size()
            << "\t sbNoButton size: \t" << sbNoButton.size() << "\n";
        out << "sb hint: \t" << sb.sizeHint()
            << "\t sbNoButton hint: \t" << sbNoButton.sizeHint() << "\n";
        out << "sb min. hint: \t" << sb.minimumSizeHint()
            << "\t sbNoButton min. hint: \t" << sbNoButton.minimumSizeHint() << "\n";
        out << "sb min.: \t" << sb.minimumSize()
            << "\t sbNoButton min.: \t" << sbNoButton.minimumSize() << "\n";

        debug.append(s);
        QMainWindow::resizeEvent(event);
    };
private:
    QSpinBox sb;
    QSpinBox sbNoButton;
    QHBoxLayout hLayout;
    QVBoxLayout vLayout;
    QTextEdit debug;
    QWidget central;
};

int main(int argc, char *argv[])
{
    //QApplication::setStyle(QStyleFactory::create("Windows"));
    QApplication::setStyle(QStyleFactory::create("windows11"));
    QApplication a(argc, argv);

    MainWindow w;
    //w.setWindowTitle("Windows Style");
    w.setWindowTitle("Windows 11 Style");
    w.show();    return a.exec();
}