Subject: bug#21507: 25.0.50: (global-SOME-MINOR-MODE) not affecting fundamental mode buffers

From: Kaushal Modi <[email-masked]>
Date: Thu, 17 Sep 2015 12:15:46 -0400

Hi,

I recently was debugging an issue with my globalized minor mode and auto
generated Fundamental mode buffers created by different pacakages. I
brought up that problem over at emacs.SE:
http://emacs.stackexchange.com/q/16693/115

The below code summarizes what I learnt. The code can be eval'ed in an
emacs -Q session to recreate the issue I am seeing.

Please review the below code, eval and run it and proceed with my
explanation after the code.

;; my1-mode - init value nil - enabled using its global variant
(define-minor-mode my1-mode
  :init-value nil
  :lighter " my1")
(defun turn-on-my1-mode () (my1-mode 1))
(define-globalized-minor-mode global-my1-mode my1-mode turn-on-my1-mode)
(global-my1-mode)

;; my2-mode - init value nil - enabled using setq-default
(define-minor-mode my2-mode
  :init-value nil
  :lighter " my2")
(defun turn-on-my2-mode () (my2-mode 1))
(define-globalized-minor-mode global-my2-mode my2-mode turn-on-my2-mode)
(setq-default my2-mode t)

;; my3-mode - init value t (so enabled by default)
(define-minor-mode my3-mode
  :init-value t
  :lighter " my3")

;; Now call `get-buffer-create' that creates a buffer with Fundamental
major mode
(with-current-buffer (get-buffer-create "*temp*")
  (insert "Hello"))
(split-window-right)
(switch-to-buffer "*temp*")

---

My minor mode is of the type my1-mode above where the init value is nil but
I enable it in my config using (global-my1-mode).

The global enabling of my1-mode is seen everywhere, all the newly created
buffers except for the cases where a package would create some sort of temp
buffer using `get-buffer-create'. Such buffers would be in Fundamental mode
by default and I noticed that the (global-my1-mode) had no effect on those
buffers.

If I tweak my minor mode to be of my2-mode (change the init value to t)or
my3-mode (force the init value to t using setq-default) types above, then
my minor mode gets enabled globally in true sense (even in buffers created
using get-create-buffer).

In essence, setting the init value as t is not the same as enabling a
globalized minor mode.

Is this by design?

--
Kaushal Modi