Re: Adding olivetti to GNU ELPA

[Joost Kremers <joostkremers@fastmail.fm>]

On Tue, May 14 2019, Paul W. Rankin wrote:
>    (cond ((<= emacs-major-version 24)
>           (add-hook 'window-configuration-change-hook
>                     'olivetti--??? t t))
>          ((<= emacs-major-version 26)
>           (add-hook 'window-configuration-change-hook
>                     'olivetti--??? t t)
>           (add-hook 'window-size-change-functions
>                     'olivetti--??? t t))
>          ((<= 27 emacs-major-version)
>           (add-hook 'window-size-change-functions
>                     'olivetti--??? t t)))

I have no idea if this helps (I'm not entirely sure if I correctly 
understand the issues you're facing), but FWIW, this is what I do 
in `visual-fill-column-mode` 
<https://github.com/joostkremers/visual-fill-column>, which must 
solve essentially the same problem:

```
(defun visual-fill-column-mode--enable ()
  "Set up `visual-fill-column-mode' for the current buffer."
  (add-hook 'window-configuration-change-hook 
  #'visual-fill-column--adjust-window 'append 'local)
  (if (>= emacs-major-version 26)
      (add-hook 'window-size-change-functions 
      #'visual-fill-column--adjust-frame 'append))
  (visual-fill-column--adjust-window))
```

So I use `window-configuration-change-hook` in every Emacs version 
and `window-size-change-functions` in Emacs >= 26. ISTR that it's 
not possible to forego `window-configuration-change-hook` in Emacs 
26, but I can't remember why...

I have at least one report of this working on Emacs 27, but I must 
admit that I'm running Emacs 26 myself, so perhaps there are 
problems this particular user doesn't care about.

`visual-fill-column--adjust-frame simply calls 
`visual-fill-column--adjust-window` for every window on the 
relevant frame. In Emacs 27, this function must be in the global 
part of `window-size-change-functions`, because Emacs 27 changed 
the way the local part is called. `visual-fill-column-mode` could 
of course be adapted to use the local part of the hook, but there 
are more hooks involved with window size/config changes in Emacs 
27 and I haven't looked into which ones I should use.

 `visual-fill-column--adjust-window` does the following:

```
(defun visual-fill-column--adjust-window ()
  "Adjust the window margins and fringes."
  ;; Only run when we're really looking at a buffer that has 
  v-f-c-mode enabled. See #22.
  (when (buffer-local-value 'visual-fill-column-mode 
  (window-buffer (selected-window)))
    (set-window-fringes (get-buffer-window (current-buffer)) nil 
    nil visual-fill-column-fringes-outside-margins)
    (if (>= emacs-major-version 25)
        (set-window-parameter (get-buffer-window (current-buffer)) 
        'split-window #'visual-fill-column-split-window))
    (visual-fill-column--set-margins)))
```

So it has additional code for Emacs >= 25 to set the window 
parameter `split-window` to `visual-fill-column-split-window`, 
which unsets the margins before calling `split-window`.

In addition, there is a function 
`visual-fill-column-split-window-sensibly`, which can be used as 
the value of `split-window-preferred-function`. It handles virtual 
splitting of windows with wide margins.

HTH


--
Joost Kremers
Life has its moments