How can I embed my mpv window in other application now?
At some point it needed a custom interface and the ability to reconfigure itself on the fly.
Adding in a GUI was not a reasonable option.
We ended up writing a GUI (in gtk) then using Xembed to embed the other process and communicate via a Unix socket.
What would have been a major rewrite (and likely a port to a different language) ended up being a few a days project and worked beautifully.
It really showed me how powerful X11 really was.
[1]: https://learn.microsoft.com/en-us/windows/win32/api/winuser/...