void QMyWidget::paintEvent(QPaintEvent*)
    {
    QPainter painter(this);
 
    // Create font
    QFont f("Helvetica",20);
    // Set current font
    painter.setFont(f);
    // Set font color
    painter.setPen(Qt::white);
    // Get QFontMetrics reference
    QFontMetrics fm = painter.fontMetrics();
 
    QString text = "helloworld";
 
    // Calculate text center position into the screen using QFontMetrics class
    QPoint center = QPoint( ( width()-fm.width(text))/2,
                            ( height() - fm.height())/2 );
 
    // QFontMetrics::width() gives calculated text width with current QFont in QPainter
    // QFontMetrics::height() gives text height
 
    painter.drawText(center,text);
    }