Qt VNC Server for non-Qt Quick apps

My app uses QtPainter graphics, another one uses Qt Widgets. I heard of Qt VNC Server and hoped I could use it too, but then I realized that it supports only Qt Quick based UI. I would need Qt VNC Server for

• a projection solution that does not require using Qt Quick
• the projection of the content of a selected QWindow. With this, I could use it with QWidgets even if it would not be possible to project a single widget 
• with this, I would also not need to change the src code on in the UI level. Calling some specific API would still be OK
• a self-contained projection solution in my app. This is possible in the current Qt VNC Server and this is a very cool feature
• I think, the use cases for my end-users are the same as when the current Qt VNC Server is used