QSplashScreen: On Linux the splashscreen is not always visible

#include <QtWidgets>

int main(int argc, char **argv)
{
QApplication a(argc, argv);
QMainWindow mw;
QPixmap pix(200, 200);
pix.fill(Qt::red);
QPainter p(&pix);
p.setBrush(Qt::blue);
p.drawRect(20,20,50,50);
p.end();
QSplashScreen splash(pix); //, Qt::WindowStaysOnTopHint);
splash.show();
a.processEvents();
splash.raise();
splash.finish(&mw);
a.processEvents();
QTimer::singleShot(5000, &mw, SLOT(show()));
return a.exec();
}