Is it possible to detect when DirectX/OGL/Vulkan application starts drawing to a Win32 window?

I want to detect such thing, but cannot find any info is it actually possible.

Are you asking as a user trying to find out on your own system? Or as an app developer trying to write an app which does this for others?

PresentMon can tell you as a user. It is open-source, so theoretically you'd be able to incorporate its core into another application.

I am working on my UI framework and potentially think about possibility that my window can be used as render target for another game engine, for ex.

And I just want to switch off my own embedded rendering for my window in that case just not to waste resources and made conflicts. The same as WPF does when someone start rendering to its Window (I don`t know how it handle such cases exactly, maybe there are more simple way to do it using Win API)