The Framebuffer Configuration Extension

The framebuffer configuration extension, SGIX_fbconfig, provides three new features:

It introduces a new way to describe the capabilities of a GLX drawable, that is, to describe the resolution of color buffer components and the type and size of ancillary buffers by providing a GLXFBConfig construct.
It relaxes the "similarity" requirement when associating a current context with a drawable.
It supports RGBA rendering to one- and two-component windows and GLX pixmaps as well as pbuffers.

Caution: This extension is an SGIX (experimental) extension. The interface may change, or some other details of the extension may change.