Is a GLXFBConfig's type really XID?

(Incredibly low priority, spec-lawyer-y kind of issue, just writing it down for posterity.)

The GLX spec calls them XIDs, or at least, implies that the storage for a number describing an fbconfig is as big as an XID. But they don't really correspond to an XID inside the server, they're not in the resource database and they don't name an object. I think this is an artifact of the (X server) sample implementation, which allocates _visual IDs_ with the same allocator as server-owned resource IDs, and then the GLX code probably copied that when fbconfigs were added. Certainly that's what X.org did when we finally got around to implementing 1.3 (the SGI SI only went through 1.2).

I'd like Xorg to stop doing the visual ID hack described above, and allocate visuals with their own allocator. I might like the ability to say fbconfigs are in _that_ namespace, as it's unambiguous. I might especially like to say that fbconfig IDs and visual IDs are numerically equal if the visual supports GLX_WINDOW_BIT.

I guess the question here is, is the word "XID" in the GLX spec a comment about just the size of the integer, or about the namespace it came from? Is there any implementation that meaningfully differs, and could a change here possibly break an app?