Emacs: How to Override Minor Mode Keybinding

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This page shows you how to override minor mode keys. You should be familiar with the basics of setting keys. 〔☛ Emacs: How to Define Keys

To define minor mode keys, you need to modify the key of that mode's keymap, and this needs to happen after that mode finished loading, because otherwise when the mode is activated, its keymap definition may overrides yours.

Well written major modes will run hook at the end. So, you can use a hook to define your keybinding. Minor modes usually do not have hooks. In that case, you can call (require 'minor mode feature symbol) first, then define your keybinding.

The exact steps may not be the same for every mode, but the principle is the same. The following shows several examples.

General Steps

⓪ Start with this template in your init file:

(defun xah-isearch-mode-keys ()
  "xah keybindings for `isearch-mode'.
For `isearch-mode-hook'."
  (define-key isearch-mode-map (kbd "<next>") 'isearch-repeat-forward) ; page down key
  (define-key isearch-mode-map (kbd "<prior>") 'isearch-repeat-backward) ; page up key

(add-hook 'isearch-mode-hook 'xah-isearch-mode-keys )

① Call describe-function, then type the mode activation command name, then click on the link to open its elisp source code file.

② In the elisp source code, search for run-mode-hooks or “-hook”. You'll find the right hook name to add. (most major mode shoud have a hook)

③ in the mode's source code, search for “-mode-map” or “-map” to look at the keys it defines.

Note that not all modes defines a keymap in its source file. Some inherit from other modes, some uses keymaps from other elisp file that are not modes, some doesn't have a keymap.

Rebind Displaced Commands

When you redefine some keys in a mode's keymap, be sure to make bindings for the displaced commands if those commands are important to you. For example, in shell-mode, i wanted “M-p” to do something. The “M-p” is previous-history-element. I think that command is useful enough to have a hotkey. So, i defined some other key for that. (You can call describe-key command to find out a key's binding while in that mode.)


Modify Isearch Keys

By default, 【Ctrl+s】 will do a interactive search. Pressing that again will find the next match. Suppose you prefer to have 【Alt+s】 instead, so in your emacs init file you defined:

(global-set-key (kbd "M-s") 'isearch-forward)
(global-set-key (kbd "M-S") 'isearch-backward)

You want to use “M-s” to repeat the search. However, once you are in the isearch prompt, technically it is a minor mode called isearch-mode. In isearch-mode, “C-s” is defined to run isearch-repeat-forward. You want “M-s” to run isearch-repeat-forward. Here's the code to reclaim it:

(add-hook 'isearch-mode-hook
 (lambda ()
 (define-key isearch-mode-map (kbd "M-s") 'isearch-repeat-forward)
 (define-key isearch-mode-map (kbd "M-S") 'isearch-repeat-backward)

Modify Shell Keys

shell and shell-commandAlt+!】 have many special keys. Suppose you want to change them. They both use a keymap named comint-mode-map. The following is a example of redefining some of its keys.

(defun xah-shell-modes-hook ()
  "xah keybindings for shell related modes."
   (define-key comint-mode-map (kbd "M-p") 'recenter) ; was comint-previous-input
   (define-key comint-mode-map (kbd "M-n") 'nil) ; was comint-next-input
   (define-key comint-mode-map (kbd "M-r") 'kill-word) ; was comint-previous-matching-input
   (define-key comint-mode-map (kbd "M-s") 'other-window) ; was comint-next-matching-input

   ;; rebind displaced commands that i still want a key
   (define-key comint-mode-map (kbd "<f11>") 'comint-previous-input)
   (define-key comint-mode-map (kbd "<f12>") 'comint-next-input)
   (define-key comint-mode-map (kbd "S-<f11>") 'comint-previous-matching-input)
   (define-key comint-mode-map (kbd "S-<f12>") 'comint-next-matching-input)

;; reclaim some keybinding used by `shell' and `shell-command' . they use keys in `comint-mode-map'.
(add-hook 'comint-mode-hook 'xah-shell-modes-hook)

Modify Minibuffer Keys

The minibuffer is where emacs does prompts. It defines the following keybinding:

Minibuffer's Keybinding

Here's a example of how to redefine its keybinding:

;; reclaim some bindings used in minibuffer for ergoemacs bindings for QWERTY
(define-key minibuffer-local-map (kbd "M-p") 'recenter) ; was previous-history-element. Use ↑ key or f11.
(define-key minibuffer-local-map (kbd "M-n") 'nil) ; was next-history-element. Use ↓ key or f12.

(define-key minibuffer-local-map (kbd "M-r") 'kill-word) ; was previous-matching-history-element.
(define-key minibuffer-local-map (kbd "M-s") 'other-window) ; was nest-matching-history-element

;; add back some bindings for commands whose binding we displaced
(define-key minibuffer-local-map (kbd "<f11>") 'previous-history-element)
(define-key minibuffer-local-map (kbd "<f12>") 'next-history-element)
(define-key minibuffer-local-map (kbd "S-<f11>") 'previous-matching-history-element)
(define-key minibuffer-local-map (kbd "S-<f12>") 'next-matching-history-element)

(info "(elisp) Text from Minibuffer")

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