Emacs Parent Modes List

Question

In emacs, can I get a list of parent modes for a derived mode?

I found derived-mode-p, but this only allows me to check whether the mode is derived from another.

Answer 1

Each symbol has a list of properties , and for derived modes, this list includes a component derived-mode-parentthat indicates which mode it was received from. It seems to be just one character.

(define-derived-mode nst-mode text-mode "Testing")
=> nst-mode

(get 'nst-mode 'derived-mode-parent)
=> text-mode

I do not see how there can be more than one parent.

Here is a daemon parental transit chain.

(define-derived-mode rope nil "Victim of mouse")
(define-derived-mode mouse rope "Victim of cat")
(define-derived-mode cat mouse "Victim of dog")
(define-derived-mode dog cat "Enough already")

(let ((mode 'dog) parents)
  (while mode
    (setq parents (cons mode parents)
          mode (get mode 'derived-mode-parent)))
  (reverse parents))

=> (dog cat mouse rope)

... or, just for fun, a recursive version:

(defun derived-mode-parents (mode)
  (and mode
    (cons mode (derived-mode-parents
          (get mode 'derived-mode-parent)))))

(derived-mode-parents 'dog)
=> (dog cat mouse rope)