QMenu 二级菜单再次打开阴影消息

使用QMenu实现菜单，使用

DWMNCRENDERINGPOLICY val = DWMNCRP_ENABLED;
::DwmSetWindowAttribute(hwnd, DWMWA_NCRENDERING_POLICY, &val, sizeof(DWMNCRENDERINGPOLICY));
// This will turn OFF the shadow
// MARGINS m = {0};
 // This will turn ON the shadow
 MARGINS m = {-1};
 HRESULT hr = ::DwmExtendFrameIntoClientArea(hwnd, &m);
 if( SUCCEEDED(hr) )
{
       //do more things
}

为窗口看添加阴影，菜单有二级菜单，第一次显示二级菜单menu1，隐形显示正常，鼠标移动到其他QAction处，再显示二级菜单menu1，阴影消失

https://blog.csdn.net/weixin_39385413/article/details/107234938