It would be nice if child widget inherits all parents property with css.

#include <QtWidgets>


int main(int argc, char *argv[])

{
    QApplication app(argc, argv);
	app.setStyleSheet("  ");
      QLabel *w = new QLabel("some text");
      QPushButton *pb = new QPushButton("text", w);
      w->setFont(QFont("Arial", 45));
      w->resize(400, 300);
      w->show();
    return app.exec();
}