Using bevy to render to an existing OpenGL surface

[weiznich]

I'm currently doing some experimentation to render something into a fixed surface into an existing QT application using rust. For that I'm using a QtOpenGLWidget as render able surface. I was able to render to this surface from rust using the gl and egli crate and low level OpenGL calls. I see that as demonstration such a rendering setup is possible.

Now I'm investigating if it's possible to use more high level crates for this. As bevy offers quite a lot of functionality I might want to need later, it would be interesting to get it to work there. By default bevy seems to create it's own window and renders everything there. There is this example that shows how to setup a bevy instance without creating a window. Also there is #4838 that discusses how to use an existing window, which seems to be somehow related to what I want to do. Even with that resources I fail to put together the pieces to make this work. So my question is whether that's even possible and if it's possible where to look for more information about this topic.