QDialog 设置成圆角

void paintEvent(QPaintEvent *event)
{
    Q_UNUSED(event);
    QBitmap bmp(this->size());
    bmp.fill();
    QPainter p(&bmp);
    p.setPen(Qt::NoPen);
    p.setBrush(Qt::black);
    p.drawRoundedRect(bmp.rect(),15,20);
    setMask(bmp);
}