QQuickWidget::grabFrameBuffer does not work when format multisample is set

//代码占位符
void Widget::init() 
{ 
   m_quickWidget = new QQuickWidget(this);
   QSurfaceFormat format;
   format.setSamples(8); 
   m_quickWidget->setFormat(format); 
  QUrl source("qrc:/rotatingsquare.qml"); 
  m_quickWidget->resize(300,300); 
  m_quickWidget->setResizeMode(QQuickWidget::SizeRootObjectToView );
   m_quickWidget->setSource(source); 
  connect(ui->pushButton, &QPushButton::clicked, this, &Widget::grabBuffer);
 } 
void Widget::grabBuffer() 
{
   QImage image = m_quickWidget->grabFramebuffer(); 
   saveToFile(this, &image); 
}