RE: default for read-face-name

[Drew Adams]

> Please see how STRING-DESCRIBING-DEFAULT is used in `customize-face'
> where "all faces" means that nil returned from `read-face-name'
> forces it to use all faces.

I don't see how that is a problem.  Is such an implementation required?  Can't
`customize-face' easily be made to use all faces without such a hack?

> We could keep this functionality and also allow specifying the default
> face like you proposed.  It is possible to distinguish two cases
> by checking if STRING-DESCRIBING-DEFAULT is a string (to be 
> used in prompt) or a face (for the default value).

I would prefer to have two separate parameters, if you insist on retaining
STRING-DESCRIBING-DEFAULT as it is (for `customize-face').  In that case, please
just add DEFAULT as a normal default value: a face name.

I disagree with having a default value for completion be other than a string.
In the case of `read-face-name', the DEFAULT arg should be a face name.
Completion accepts a string (strings) as the default (defaults) and returns a
string.  Let's stick to that approach.

You might argue in favor of allowing a face so as to allow a face spec - or even
a list of faces (symbols or specs) that are to be combined.  I disagree with
such complexity here.  I would prefer a simple DEFAULT: a face name (string).