specifing visual for X11 window

Hello,
I've been working on an OpenGL vo module for G2.
What I need is a way to make sure the window that is passed to the 
config function is usable for OpenGL.
The best idea I had so far was adding a XVisualInfo* part to 
vo_instance_t and if it's set the window will be created using this visual.
Would this be acceptable / do you have any other ideas (except creating 
the window in the vo module, this would give the same mess as in G1).

Greetings,
Reimar Döffinger