[badsectoracula]

> This comment isn't really correct all, it's not possible to do that with the architecture of X.

Sorry but i do not think you understood my comment at all considering what you wrote. What i wrote is for the X server to pretend the other clients do not exist, which is something it already can do (at least for a single client, if what harporoeder wrote about putting all untrusted clients to a single domain is correct) and...

> you can't really fail anything because errors are usually treated as fatal in Xlib and most clients don't bother with error handling in Xlib

...any errors would be the same as if the other clients didn't exist and handled the same way.

Also the important bit is that you cannot do what i describe right now with the released / existing Xorg, but there is already enough functionality there to show that it is possible if the Xorg server was modified to enable it. This isn't something you can switch on with some configuration or make a couple of lines code change, it does need some effort to implement the necessary functionality and that effort combined with the lack of anyone really needing it is the main reason why it isn't already done.