XPRA_OPENGL_DOUBLE_BUFFERED=1 needs re-testing with python3, see ticket:1469#comment:8
Seems to work on all the systems I've tried it on (was already enabled on win32), so r23323 enables it by default.
Something did need re-testing with the latest GTK3: #2466 (repaint was needed)
this ticket has been moved to: https://github.com/Xpra-org/xpra/issues/2350