color-complement for defface (was: Eliminating a couple of independent face definitions)

[Ted Zlatanov <tzz@lifelogs.com>]

On Fri, 04 Feb 2011 11:26:49 +0100 Julien Danjou <julien@danjou.info> wrote: 

JD> On Thu, Feb 03 2011, Drew Adams wrote:
>> FWIW, for this I simply use the complements of the light-background default
>> colors as the dark-background colors.  That is not necessarily ideal, but it at
>> least is reasonable and consistent.  It is also very quick to do, given some
>> code (e.g. hexrgb.el or palette.el) that quickly gives you color complements.

JD> color.el included in Emacs 24 as `color-complement' so you can even use
JD> it in your defface directly, I think.

It would be nice if an example of that usage was part of the manual.
Even better would be if defining a face could automatically use the
complement (e.g. by setting the background to 'complement).

Julien, do you want to propose a patch to the manual?

Does anyone have comments on a defface modification to let
color-complement pick the background automatically if requested?  I
don't know how hard that would be to write, but I want to know if it's
even acceptable.

Thanks
Ted