QMenu does no open when a main window which contains QQuickWidget is shown is fullscreen mode

#include <QApplication>
#include<QMainWindow>
#include <QMenu>
#include <QMenuBar>
#include <QQuickWidget>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    QMainWindow w;

    QAction *actionNew = new QAction(&w);
    actionNew->setText("New");

    QMenuBar *menuBar = new QMenuBar(&w);

    QMenu *menuFile = new QMenu(menuBar);
    menuFile->setTitle("File");

    menuBar->addAction(menuFile->menuAction());
    menuFile->addAction(actionNew);

    w.setMenuBar(menuBar);

    w.setCentralWidget(new QQuickWidget);

    w.showFullScreen();

    return a.exec();
}