Re: About the :distant-foreground face attribute

[Eli Zaretskii <eliz@gnu.org>]

> From: Chong Yidong <cyd@gnu.org>
> Cc: jan.h.d@swipnet.se,  emacs-devel@gnu.org
> Date: Fri, 10 Jan 2014 00:15:00 +0800
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> >> The analogy would be if there was a :low-color-foreground face attribute
> >> which would override :foreground on low-color displays.  That would be
> >> ugly, as I hope you agree.
> >
> > I'm not sure I see the ugliness, please elaborate.
> 
> One face attribute should govern one aspect of how the face is
> displayed.  In some cases, it may be hard to avoid having multiple
> attributes with overlapping effects, but the results are not pretty.
> For example, the interactions between :family, :foundry and :font have
> been a source of annoyance over the years.  Introducing another such
> situation should, in my view, be avoided as far as possible.
> 
> An example of a face attribute that handles things right is the :height
> attribute.  An absolute height is given by an integer, while a relative
> height can be specified by a float.  Allowing both in a single attribute
> is good, because absolute height and the relative height are just
> different ways to specify height.  We don't have a :height and a
> separate :relative-height attribute.

If you are arguing for a change in the syntax of :foreground such that
it could convey the information about both the "normal" color, and the
alternate color to be used when the background is too similar to that
"normal" color, then I agree it will probably be a nicer and cleaner
feature.  But that means :foreground will no longer be a simple
string, but some more complex data structure, e.g. a list.

> If I cannot convince anyone that there is a problem here, then forget
> it.

Don't give up just yet ;-)

The solution should be able to cope with the need to dynamically
decide which color is used as a foreground, based on the current
background.  It also needs to support the possibility that a face will
want to force use of a specific fixed foreground color, regardless of
the background.  (Jan, did I miss some additional requirements?)  If
you can propose a cleaner solution that satisfies these requirements,
please do, and let's discuss that.