Re: master 2ef6f943abd: Add option to control default outlining in 'C-h b'

[Eli Zaretskii <eliz@gnu.org>]

> From: Juri Linkov <juri@linkov.net>
> Cc: Robert Pluim <rpluim@gmail.com>,  michael_heerdegen@web.de,
>   emacs-devel@gnu.org,  orontee@gmail.com
> Date: Tue, 25 Apr 2023 19:51:31 +0300
> 
> >>     >> This code and the defcustom is new in emacs-29, so we can still change
> >>     >> it to be a predicate instead. At least we should document is better
> >> 
> >>     Eli> Agreed.  Patches welcome.
> >> 
> >> I assumed you were agreeing to the code change, which looks like this:
> >
> > No objections, unless some code is already using this with a function
> > that doesn't return a boolean.
> >
> > Matthias, Juri: any objections or comments?
> 
> I guess the decision was delegated to the users
> because there is a choice what to do with the outline.
> Beside 'outline-hide-entry', there is also 'outline-show-branches'
> used by 'subtree-is-long' and 'subtree-has-long-lines'.
> 
> So I see no reason to remove 'custom-function'.
> What could be done instead is to add a new choice
> 'custom-predicate'.

The suggestion is not to remove custom-function.  The suggestion is to
require that the function returns a boolean, to mean whether to hide
or not to hide a heading, instead of requesting that the function
itself hides/unhides the headings.

What is the purpose of requesting a custom function to actually
hide/unhide the headings, i.e. to know enough about the structure and
internal details of Outline mode to do its job?