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QCoreApplication::setAttribute(Qt::AA_EnableHighDpiScaling);
QGuiApplication app(argc, argv);
auto font = app.font();
QFontInfo fi(font.defaultFamily());
font.setPointSizeF(fi.pointSizeF());
app.setFont(font);
QQmlApplicationEngine engine;
engine.load(QUrl(QLatin1String("qrc:/main.qml")));
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QFont font = ui->pushButton->font();
font.setPointSize(16);
ui->pushButton->setFont(font);