"Garrett D'Amore" <garrett_damore@tadpole.com> writes:

> > And then there are things like the FFB which support multiple colour
> > depths on the same screen.
> 
> Hmm... so its not a linear framebuffer I guess?  Or does it use some
> weird combination of indexing and 24bpp?

I suspect the latter. There are a number of devices like this; for
example, the DEC TGA with a Bt463 can run in a 32bpp mode where the
top 4 bits of each pixel are an index into a table which determines
whether the lower 24 bits are direct RGB color, RGB colors
gamma-mapped through the palette memory (either of those in 24-bit or
12-bit mode), or whether some N-bit subset of the 24 bits is indexed
in palette memory (and there's enough palette memory to do both
gamma-mapping and 8-bit indexing at the same time). The design is
pretty clearly targeted at directly supporting X Windows primitives
and at supporting each window having its own potential color universe.

In practice, the easiest thing to do seems to be to pick 8-bit indexed
or direct RGB and totally ignore the rest of the complicated
functionality.

        - Nathan