server, client and general GLX extensions and version numbers

[Tomas Carnecky]

Brian Paul wrote:
> Most GLX extensions require both client and server-side support, but
> some are client-side only (like GLX_ARB_get_proc_address) and some are
> server-side only (can't think of any off-hand).
> 

While we're at it, the OpenGL code on Wine also needs to query GL/GLX to
see which extensions are supported, and because of buggy (proprietary
ATI) drivers some workarounds are necessary.

Where is it defined how to correctly test whether an extension is
supported? I haven't seen in any spec that either the client, server or
global extension string should be queried. So, is it true that, for
example, to test for GLX_ARB_get_proc_address the client extension
string can be used on all drivers or can a driver choose to support this
extension only if the 'global' extension strings contains this string?
The same for the versions: can I count on GLX_ARB_get_proc_address if
the client version is >=1.4 or does the global version need to be >=1.4?

thanks
tom