[Xcb] xcb and protocol versions

[Jeremy A. Kolb]

Oops, sent this to xorg at lists.freedesktop.org not xorg@:

Hi,
 
Wondering if anyone has any insight on this problem.
 
I'm trying to think of ways to handle protocol revisions in xcb.  Are 
there guidelines about what is allowed/not allowed for protocol revisions?  
Most of the extension revisions I've seen add events or new 
requests/replies, these are all very easy to deal with.  The one big 
question (has the most implications on the client-side library) is:
 
Are requests/replies ever extended (more bits over the wire) in newer 
revisions?
 
I am unsure how to handle the case where the client uses a 
request from an older version of the extension that has now changed its 
signature in a later version of xcb.
 
Thanks,
Jeremy