Following up #2341, we now wait for the init thread to complete (r21937). See also #2415 and #2411 We could try to accept the client connections first and later update the client with the new list of codecs.
Warning: the code to update the tray menu is a bit iffy, we monkey patch the packet handler to update the tray menu when the encoding attributes are received.
Ensure we can use 'png' and 'jpeg' early, even before the threaded initialization has completed: r24341.
this ticket has been moved to: https://github.com/Xpra-org/xpra/issues/2414