Qt：实现顶层窗体圆角_qt 圆角窗口弹窗-CSDN博客 

    setWindowFlags(Qt::FramelessWindowHint);
    QBitmap bmp(this->size());
    bmp.fill();
    QPainter p(&bmp);
    p.setPen(Qt::NoPen);
    p.setBrush(Qt::black);
    p.setRenderHint(QPainter::Antialiasing);
    p.drawRoundedRect(bmp.rect(), 15, 15); //四个角都是圆弧
    setMask(bmp);