moving point command: next-line, previous-line, forward-char, backward-char, etc.

How to omit Ctrl key in read-only-mode?

How can I combine with read-only-mode-hook to automatically enable keybind when opening a file with read-only permissions?

  • Here is an example written Anton Johansson: by github.com/antonj/.emacs.d/blob/master/aj/… . Calling toggle-read-only will trigger his modifications assuming they have been evaluated prior thereto. Inasmuch as I knew what to look for after typing M-x find-function RET read-only-mode and perusing the code in simple.el, I Googled: emacs "read-only-mode" keymap. The link mentioned in this comment was just the first search result, so feel free to look at other results.
    – lawlist
    Commented Sep 18, 2019 at 21:41
  • @lawlist The method of using Anton Johansson is not convenient. When opening a read-only buffer, you need to execute the M-x toggle-read-only RET keybind twice to take effect. And toggle-read-only is obsolete and should be replaced with read-only-mode.
    – dongli si
    Commented Sep 18, 2019 at 23:13
  • As you become more proficient in Emacs, you can find examples that do things similar to what you want, and then you can modify them to suit your needs. I realize you are just starting out and this might seem daunting, but seeing what makes it tick and trying out new things is often a helpful learning experience. Sometimes you will get lucky and find something exactly on-point, but more often than not, you may need to create a custom solution that best suits your needs for a given project.
    – lawlist
    Commented Sep 19, 2019 at 3:24

1 Answer 1


The following minor-mode wo-ctrl-c-mode frees all active keybindings from the control modifier insofar there are no other modifiers such as meta or shift and the resulting key-binding is not already occupied.

That minor mode is activated along with read-only-mode and when opening files without write-permission with find-file.

At least in Emacs 26.2 one needs to treat find-file separately since that function (more exactly find-file-noselect) sets the buffer-read-only flag directly and not through the function read-only-mode.

(defun wo-ctrl-c-map ()
  "Return a keymap freeing keys from control-modifier."
  (let ((newmap (make-sparse-keymap)))
     (lambda (map)
        (lambda (event binding)
          (let ((basic-event (vector (event-basic-type event))))
            (when (and (equal (event-modifiers event) '(control))
                       (equal (key-binding basic-event) #'self-insert-command)
                       (null (lookup-key newmap basic-event)))
              (define-key newmap basic-event binding))))

(defvar-local wo-ctrl-c-mode-active nil
  "If `wo-ctrl-c-mode' is active it sets this variable to a non-nil value.
This is a protection against consecutive calls of (wo-ctrl-c-mode 1).
The value is actually a list containing the original local map as element.")

(define-minor-mode wo-ctrl-c-mode
  "Bind all keys with control modifier also directly."
  :lighter " α"
  (if wo-ctrl-c-mode
      (unless wo-ctrl-c-mode-active ;;< protection against two consecutive calls of (wo-ctrl-c-mode 1)
    (setq wo-ctrl-c-mode-active (list (current-local-map)))
    (let ((map (wo-ctrl-c-map)))
      (set-keymap-parent map (car wo-ctrl-c-mode-active))
      (use-local-map map)))
    (when wo-ctrl-c-mode-active
      (use-local-map (car wo-ctrl-c-mode-active))
      (setq wo-ctrl-c-mode-active nil))))

(defun wo-ctrl-c-when-read-only ()
  "Activate `wo-ctrl-c-mode' when buffer is read-only."
  (if buffer-read-only
    (wo-ctrl-c-mode -1)))

(add-hook 'read-only-mode-hook #'wo-ctrl-c-when-read-only)

;; `find-file-noselect' sets `buffer-read-only' directly:
(add-hook 'find-file-hook #'wo-ctrl-c-when-read-only)

Tested with
emacs-version: GNU Emacs 26.2 (build 2, i686-pc-linux-gnu, GTK+ Version 3.22.30) of 2019-04-12

  • eval your lisp , result is "Wrong type argument: listp, wo-ctrl-c-map"
    – dongli si
    Commented Sep 21, 2019 at 8:54
  • @donglisi Sorry about that. I added the quote at '(wo-ctrl-c-mode) afterwards. When I tested it again wo-ctrl-c-mode-map was already defined, the :keymap expression was not evaluated, and this caused the test to be wrongly positive. (I should have tested with a newly started emacs -Q instance). I've re-worked the solution such that it does not use the minor mode map but the local keymap. That improves using the minor mode for multiple buffers in read-only-mode. If one switches off wo-ctrl-c-mode the original local mode map is restored.
    – Tobias
    Commented Sep 21, 2019 at 22:45

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