Can you please post what's reported by Help->System Information... dialog?
Use the Copy to Clipboard button

Seems like a minor bug to me, what's the behavior if you set back the main screen to laptop with Windows(instead of unplugging HDMI cable)?

Thank you!

If I use win+P to set it to the main screen to laptop only, a black screen will also appear.

Looking forward to your reply!

I captured the event using QAbstractNativeEventFilter, but I haven’t found a suitable way to reconnect the context later. Thanks!
bool nativeEventFilter(const QByteArray& event_type, void* message, long* result)
{
#ifdef Q_OS_WIN
if (event_type == "windows_generic_MSG")
{
MSG* msg = reinterpret_cast<MSG*>(message);
if (msg->message == WM_DISPLAYCHANGE)
{
QMetaObject::invokeMethod(this, "SlotDisplayChanged", Qt::QueuedConnection);
}
}
#endif
}

I fixed the issue by recreating a new Aspect_NeutralWindow(). Thanks!

That's good news you could fix this issue. Can you share your changes with a pull request to Mayo project?
Maybe this will be helpful to the users, thanks!