How to define keymap for minor mode correctly

Question

I'd like to define custom mode for improvements that suits to any program mode. And I need to define key-bindings for all this modes. I choose to use define-minor-mode with :keymap to declare key bindings with minimum effort.

I'd like to bind comment-or-uncomment-region to "C-;" The kbd macro gave me [67108923] magic number for this key sequence.

I've wrote sample that doesn't work

(define-minor-mode
  my-mode
  nil nil
 :keymap '(
   ( [67108923] . comment-or-uncomment-region )
  )
)

I've registered mode, toggled it on, but pressing С-; produces notifications that the key sequence is not defined

After that I've wrote in the scratch buffer and evaluate simple global-set-key that performed in expected way.

(global-set-key [67108923] 'comment-or-uncomment-region )

Now pressing C-; produces expected comment-or-oncomment-region behavior.

I've tried to debug the issue with searching to function info via C-h f. It produces strange output, comment-or-oncomment-region is bound twice to different key sequences:

It is bound to C - ;, C-;

First one appears and disappears with the minor mode toggling, other emerge from global-set-key invocation.

How can it be, if I've used the same key definition for both maps? What details I have missed?

Answer 1

1. Just create a keymap normally, using make-sparse-keymap, and name it my-mode-map --- you're done. No need for :keymap arg to define-minor-mode.

2. Or use the keymap you create using make-sparse-keymap as the value of :keymap, if you like. (But no need to, since it is named as the minor mode expects: my-mode-map.)

3. But why not just use a global binding, via global-set-key? Why do you even need this to be a minor-mode binding?

Answer 2

Don't use the magic number. IOW use [?\C-\;], so it can be understood by humans. And I agree with Drew:

(defvar my-mode-map
  (let ((map (make-sparse-keymap)))
    (define-key map [?\C-\;] 'comment-or-uncomment-region)
    map))

(define-minor-mode my-mode
  "blabla"
  nil nil nil
  <add code, if any>)

Oh, and one more thing: why would you prefer C-; over the standard M-; binding?