FBconfig
This extension introduces a new way to describe the capabilites of a
GLX drawable (the depth of color buffer components and the type/size of
ancillary buffers), removes the "similarity" requirement when making a
context current to a drawable, and supports RGBA rendering to one- and
two-component Windows and GLX Pixmaps.
This extension will allow the much stronger RGBA rendering semantics to
be used to render to color index windows. The red component is used to
generate the display; blue and green, if present are ignored for display
purposes.