#include <QtWidgets>

int main(int argc, char **argv)
{
    QApplication app(argc,argv);
    // spin boxes with range: [0..99] and 2 decimal places
    QDoubleSpinBox *spinbox1 = new QDoubleSpinBox();
    QDoubleSpinBox *spinbox2 = new QDoubleSpinBox();
    QHBoxLayout *testlayout = new QHBoxLayout();
    testlayout->addWidget(spinbox1);
    testlayout->addWidget(spinbox2);
    testlayout->addStretch();
    QWidget testwidget;
    testwidget.setLayout(testlayout);
    testwidget.show();
    spinbox2->setMinimum(spinbox2->minimum()); // <- ensures correct size hint

    return app.exec();
}