Qt无边框窗口可拖动

this->setWindowFlags(Qt::FramelessWindowHint | Qt::WindowStaysOnTopHint);

QPoint m_dragPosition;

void mousePressEvent(QMouseEvent *event) 
{
  if (event->button() == Qt::LeftButton)
  {
    m_dragPosition = event->globalPos() - frameGeometry().topLeft();
    raise();
    event->accept();
  }
}
void mouseMoveEvent(QMouseEvent *event)
{
  if (event->buttons() & Qt::LeftButton)
  {
    move(event->globalPos() - m_dragPosition);
    event->accept();
  }
}