I am working on a minor mode that adds functionality to outline-minor-mode associated with different major modes (e.g. emacs-lisp-mode, fortran-mode).

This is the minor mode file taxocalc.el

;; taxocask.el
(require 'taxocask-elisp)

(defun taxocask-activate ()
   "Activates the minor mode" 

(defun taxocask-deactivate ()
   "Reverts to default outline settings." 

(define-minor-mode taxocask-minor-mode
  "Enhances visibility of heading levels and text emphasis."
  :init-value nil
  :lighter " Taxocask"

  (if taxocask-minor-mode

    ;; [ELSE] Rvert the functionality provided by minor mode
    (taxocask-deactivate)) )

(defun taxocask-enable ()
  "Enables `taxocask-minor-mode'."
  (taxocask-minor-mode 1))

(defun taxocask-disable ()
  "Disables `taxocask-minor-mode'."
  (taxocask-minor-mode 0))

(provide 'taxocask)

This is the contents of taxocalc-elisp.el.

;; taxocalc-elisp.el

(defun taxocask-elisp-view ()
  "Viewing emacs-lisp outline structures."
  (define-key emacs-lisp-mode-map (kbd "H-o s") #'outline-show-subtree)
  (define-key emacs-lisp-mode-map (kbd "H-o i") #'outline-show-children)
  (define-key emacs-lisp-mode-map (kbd "H-o k") #'outline-show-branches)
  (define-key emacs-lisp-mode-map (kbd "H-o e") #'outline-show-entry) )

(provide 'taxocask-elisp)

I am struggling to see how the mode be activated for elisp files. I want to allow the user to enable outline-miner-mode in an emacs lisp file (.el), at which point taxocask-elisp is also activated.

1 Answer 1


You would (add-hook 'emacs-lisp-mode-hook FUNC) and in that FUNC function you would (add-hook 'outline-minor-mode-hook 'taxocask-minor-mode nil t)

That non-nil LOCAL argument means you're only doing something with outline-minor-mode-hook in the current buffer.

Edit: Assuming you actually want to toggle your mode on and off in alignment with outline-minor-mode-hook you'll want that hook function to be something which tests outline-minor-mode.

Like this:

(add-hook 'emacs-lisp-mode-hook 'foo--enable)

(defun foo--enable ()
  "Enable tracking of `outline-minor-mode' in current buffer."
  (add-hook 'outline-minor-mode-hook 'foo--toggle-with-outline-minor-mode
            nil :local))

(defun foo--toggle-with-outline-minor-mode ()
  "Toggle `foo-mode' with `outline-minor-mode' buffer-locally."
  (foo-mode (if outline-minor-mode 1 0)))

(define-minor-mode foo-mode
  "Foo mode."
  :init-value nil
  (if foo-mode
      (message "Foo enabled.")
    (message "Foo disabled.")))
  • Meaning the use of (add-hook 'emacs-lisp-mode-hook #'taxocask-elisp-view) in taxocask.el ? And in taxocask-elisp-view add (add-hook 'outline-minor-mode-hook 'taxocask-minor-mode nil t) ?
    – Dilna
    Commented Jun 5, 2023 at 0:39
  • I also need a call to (taxocask-activate). How should this be ?
    – Dilna
    Commented Jun 5, 2023 at 0:50
  • I am unsure what to do to make the minor mode word. I have put a call to (taxocask-activate) which is designed to activate the minor mode capability but do not know what to put in it. Your generic suggestion (add-hook 'emacs-lisp-mode-hook FUNC) is not specific enough for me to understand exactly what to do and to what FUNC actually refers to.
    – Dilna
    Commented Jun 5, 2023 at 17:33
  • I've added a generic example.
    – phils
    Commented Jun 5, 2023 at 23:21
  • Much appreciated. Would I need to call anything specific in the condition (if foo-mode ? Or is the hook for the function 'foo--enable enough to activate foo-minor-mode whenever an elisp file is loaded ?
    – Dilna
    Commented Jun 6, 2023 at 5:21

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