I see, I do not know much about the internal workings of Wayland. The problem I do see though is that screen recording is an essential feature that has been neglected for years due to the lack of a standard.
> This is a really bad idea, don't do this.
While I agree that getting window positions may be questionable, providing a human readable title for the streams that have been selected seems obvious, yet is missing.
> syncing issues with window sizes being reported incorrectly
This seems rather theoretical to me, while of course true, I doubt it is going to matter in practice.
> It's also a misuse of the screencasting API.
Hmm, do you think there is a better solution, that isn't giving up and having each desktop environment do its own thing?
> If you want to do this right now then you'll have to integrate with the specifics of the window manager or shell. There is no way around it, I really doubt you will get much interest in doing it another way.
This is also my conclusion, alas it's not happening and one of the reasons why I think Wayland is not quite there yet.