[md8z]

You need to double buffer the clients or you will still get flickering and noticeable redraw. You can see this with older X clients. It actually is a protocol issue because X was explicitly designed to do this.

You are presenting this as if it's some kind of decision between "break compatibility" and "start from scratch" when really those are a lot closer than you think. Realistically, most of the X server is still overdue for a major rewrite/refactor. But I really doubt anyone would ever volunteer to do that work at this point.

[vidarh]

No, you don't need to double buffer the clients if the clients are properly designed and flush the request queue cautiously rather than willy-nilly, and the server takes a minimum of care rather than just stupidly processing requests one by one. None of the clients I use give flickering or noticeable redraw.

There may certainly be cases where it'd be harder to avoid, but realistically this hasn't been a problem for most X users for decades. Of course I'm not doubting that it is a problem for some, but it's not for me and haven't been since the 90's.