You should also investigate SDL. It works under windows/linux/max/beos. It provides basic low level 2d and opengl access across the board including a software rendering if necessary. Support libraries include audio, threading, files io and cdrom access.

It''s pretty sweet, and you can theoreticly cross compile to windows or vise versa.

http://www.libsdl.org/

Good luck

Wait, let''s be careful here.

I reffered to glx as being the functions glX*(), a set
of functions which `glue'' OpenGL to XLib.

This has the same exact principal as glw*() functions
that glue OpenGL to Windows'' native gui language (which
I''m assuming you know quite well).

If you review the glx intro document:

http://www.sun.com/software/graphics/OpenGL/manpages/glXIntro.html;$sessionid$22Q4NEIAAE3WRAMTA1LU4GQ

(Sorry that''s the best one I could find at the moment online)

It shows you how to use XLib''s calls to select a Visual
create a Window (all using XLib calls) and then create
an OpenGL context and bind it (using glX calls).

Now remember with that all done you are pretty
much set up for the OpenGL stuff. Now when yer program
runs, you need to call Xlib functions to fetch XEvents
(aka messages for Windows coders) and handle them.

One more important thing GLX != glX, because GLX
is a specific implmentation (ie UTAH GLX). For example
UTAH GLX is used for Linux/X 3d graphics acceleration
(this information may be outof date, they might be using
something different now and possibly intigrated into
XFree 4.x.

So if you want to get GLX hardware acceleration info you
might want to start looking at UTAH GLX:

http://utah-glx.sourceforge.net/

They have a GLX HOWTO there that might help you get
hardware acceleration set up.

Note I was told once Voodoo cards use a simpler
driver in XFree 3.x (double check on that though).
Most newer 3d accelerated cards need XFree 4.x though.