Self-explanatory.
Done in r12680, please close if this works for you.
PS: I think we should make the readonly flag server driven so that if the server has the flag set, all clients are forced to be readonly. Should be easy to add too.
r12691 contains minor tray menu fixes and adds support for the readonly flag server side. (+ doc updates in r12692)
Not heard back. Closing.
this ticket has been moved to: https://github.com/Xpra-org/xpra/issues/1208