Re: master fe7c015b20: Support XFCE in wallpaper.el

[Eli Zaretskii]

> From: Stefan Kangas <stefankangas@gmail.com>
> Date: Tue, 27 Sep 2022 13:01:11 -0400
> Cc: visuweshm@gmail.com, thievol@posteo.net, luangruo@yahoo.com, 
>       emacs-devel@gnu.org
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> >> +If the value is a function, it will be evaluated only when
> >> +needed.  For example:
> >
> > What does it mean "only when needed" in this context?
> 
> I wrote this rather quickly.
> 
> Is "only when a %-spec needs it" more clear?  It should probably say
> "called" instead of "evaluated", too.

First I think you should use "substitution", not "value", because
that's how the SPECIFICATION alist is described:

  SPECIFICATION is an alist mapping format specification characters
  to their substitutions.

And then I'd suggest something like

  If the substitution for a specification character is a function, the
  function will be called only if FORMAT uses that character.