GNU Screen equivalent for X11 aplications

Question

What is the X11 equivalent of GNU Screen for X11 applications? I know there is VNC, possibly RDP and other candidates, but last week when tuning up my VNC config I've stumbled upon a project, that was basically screen for X11 applications, i.e. you could start remote app wrapped in it, log out of the X11 session and later return to the application. Unluckily this wasn't a direct google hit and I cannot find it in the google history now. Any idea, what the name/url of the project might be ?

Answer 1

There's xpra, which is pretty much the first result under "screen for X".