> This is fun and all, but if you lose your connection, your windows will go away and your program will usually exit.

Interestingly, that is xlib's behavior moreso than inherent in the protocol. xlib assumes connection lost is a fatal event, but if you're doing your own socket, you can choose to do this differently. (or, even with xlib, you can throw an exception from the connection lost callback and regain control before letting it abort)

Some server state is lost, but it is possible, with some care, to recreate that from your client upon reconnecting. You can even connect to a different server and somewhat seamlessly migrate windows over.

But yeah it isn't commonly done.