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

[Robert Pluim <rpluim@gmail.com>]

>>>>> On Tue, 25 Apr 2023 21:00:08 +0300, Eli Zaretskii <eliz@gnu.org> said:

    >> >> 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?
    >> 
    >> How the user would be able to use 'outline-show-branches'
    >> in the custom function, and not to use 'outline-hide-entry'?

    Eli> Sorry, I don't understand the question and its relevance.  Maybe
    Eli> Robert does.

In the current implementation, the user is free to write a function
that uses any of the outline-show/hide functions to get the effect
they desire. If we replace that with just a predicate function, then
theyʼre effectively restricted to `outline-hide-entry' and
`outline-show-subtree'.

I guess we could add `predicate', to be checked before
`custom-function', if set. If we do that, we definitely need to
document which outline functions are available. 100% backwards
compatible as well 😄

Robert
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