This may help with testing and with things like #916, #917.
It shouldn't be too hard to make a simple win32 client using pywin32 + opengl. Doing so would also help to ensure that the separation between the gtk client, ui client class and platform code is clean.
Here's some example code:
Things like the clipboard are due to be re-written anyway (#812), and sound is out of process already. The keyboard support can't be too difficult either.
See also: #1569 python3 opengl client
The code is now much more modular: see ticket:1569#comment:2.
this ticket has been moved to: https://github.com/Xpra-org/xpra/issues/921