Ah, ok. In that case, I *would* suggest special-casing this in GL,
simply always drawing cs 0 first, because it is *the* logical place to
put the bg vob.
I'd strongly prefer using something symbolic, like Vob.BEGINNING
as the name of the coordsys, or something?
[ reorg'd for answers]
I'd
prefer to think about the bg vob as non-magical, just being a big
rectangle of some color, so that it could be also used to render the
background of e.g. cells.
Not really doable since glClear is quite a bit faster than rastering
a rectangle.