Menubar and dock gone after hiding a fullscreen widget on the Mac OS X - Cocoa

#include <QtGui>

class Widget : public QWidget
{
        Q_OBJECT
public:
        Widget()
        {
                QTimer::singleShot(3000, this, SLOT(testSlot()));
                QTimer::singleShot(5000, this, SLOT(testSlot2()));
                QTimer::singleShot(7000, this, SLOT(testSlot3()));
        }

public slots:
        void testSlot()
        {
                hide();
        }

        void testSlot2()
        {
                dialog = new QDialog(0);
                dialog->showFullScreen();
        }

        void testSlot3()
        {
                dialog->hide();
                show();
        }

private:
        QDialog *dialog ;
};


#include "main.moc"

int main(int argc, char **argv)
{
    QApplication app(argc, argv);
    Widget box;
    box.show();
    return app.exec();    
}