Re: master 6458e16: New mode outline-cycle-minor-mode with Orgmode-like TAB cycling on headings

[Juri Linkov <juri@linkov.net>]

> This is very welcome functionality (and the highlighting as well).
> I wonder if we really need the new minor modes, tho, instead of just
> sticking to the new `outline-minor-mode-cycle` and
> `outline-minor-mode-highlight` variables (which we could make into
> `defcustom`s).

One example (mostly for demonstration purposes) currently is
in etc/compilation.txt. whose Local Variables contains just:

  ;;; eval: (outline-cycle-highlight-minor-mode)

Initially I implemented this only with variables and without modes
like you suggested:

  ;;; outline-minor-mode-cycle: t
  ;;; outline-minor-mode-highlight: t
  ;;; eval: (outline-minor-mode 1)

But then thought that maybe with a mode would be more concise and convenient.

I'm fine with removing these modes after analyzing more use cases.

> IOW, I wonder if there are many use cases where users will want to have
> some `outline-minor-mode` buffers with cycling and others without.

Here's is a list of use cases where I tried to use outline-minor-mode
with cycling, and somewhere also with highlighting.

1. (add-hook 'Man-cooked-hook 'outline-cycle-highlight-minor-mode)
   where manual page sections could be highlighted with outline faces.

2. (add-hook 'diff-mode-hook 'outline-cycle-minor-mode)

3. (add-hook 'emacs-lisp-mode-hook 'outline-cycle-minor-mode)
   without outline highlighting to not overwrite major mode faces

4. (advice-add 'xref--insert-xrefs :after
            (lambda (&rest _args)
              (setq-local outline-regexp "/")
              (outline-cycle-minor-mode +1)))
   using file names as headings where S-TAB could provide
   an overview of all found files

But none of them require to disable cycling.  I don't know where
outline-minor-mode without cycling would be needed.  Maybe in
external packages that implement own cycling in outline-minor-mode
like in https://debbugs.gnu.org/41198#99