Re: Themes (was: Re: pGnus)

[vroonhof@math.ethz.ch]

> >> I don't know anyone who is working on adding themes to Custom, though.
> 
> > And just to iterate the point once again for third parties wanting to
> > code; I have been considering it for some time. I even have a patch
> > for an old custom version that implements a "site" custom theme.
> 
> Could you define what exactly you mean with themes in context of emacs/gnus?

A theme is basically a group of settings of variables. The two main
examples I am thinking of are
   1. The set of customizations made my the site administator.
   2. A set of customizations that define a consistent look (colors,
      fonts, etc). This is where the name comes from.

Theme support for custom I define in three levels.
   i). Low level. Allow Custom to keep track of which (variable .
   setting) pairs came from which theme. Note that custom already does 
   part of this in the 'set,saved,standard' scheme.
   ii). Medium level. Allow loading of themes and allow overiding of
   individual settings.
   iii). User interface.
   iv). User interface for Defining a theme.

I already implemented this for the limited case of 1. above. This with 
regard to the fact that "Reset to Standard" is almost never what you
want. You want "Reset to before I started messing with it." == "Reset
to site".

What I learned from that
a.  level i) support is easy to do, thanks to the quality of Per's code.
  It is a simple exention of the 'set,saved,standard' scheme.
b.   In this case iii) was easy too because of the remarks above.
     There is still a hierarchy, it just reads
     set,saved,site,standard' now. It will probably be more
     difficulties if you allow the dependencies to be a tree instead
     of the stack.
c. The hard part is in getting the override in ii) right, which is
   needed to implement 'reset' on level iii).
d. For iv). I required manual editing of the produced custom file.

Jan