22.12 Changing Key Bindings

The way to rebind a key is to change its entry in a keymap. If you change a binding in the global keymap, the change is effective in all buffers (though it has no direct effect in buffers that shadow the global binding with a local one). If you change the current buffer's local map, that usually affects all buffers using the same major mode. The global-set-key and local-set-key functions are convenient interfaces for these operations (voir la section Commands for Binding Keys). You can also use define-key, a more general function; then you must specify explicitly the map to change.

When choosing the key sequences for Lisp programs to rebind, please follow the Emacs conventions for use of various keys (voir la section Key Binding Conventions).

In writing the key sequence to rebind, it is good to use the special escape sequences for control and meta characters (voir la section String Type). The syntax ‘\C-’ means that the following character is a control character and ‘\M-’ means that the following character is a meta character. Thus, the string "\M-x" is read as containing a single M-x, "\C-f" is read as containing a single C-f, and "\M-\C-x" and "\C-\M-x" are both read as containing a single C-M-x. You can also use this escape syntax in vectors, as well as others that aren't allowed in strings; one example is ‘[?\C-\H-x home]’. Voir la section Character Type.

The key definition and lookup functions accept an alternate syntax for event types in a key sequence that is a vector: you can use a list containing modifier names plus one base event (a character or function key name). For example, (control ?a) is equivalent to ?\C-a and (hyper control left) is equivalent to C-H-left. One advantage of such lists is that the precise numeric codes for the modifier bits don't appear in compiled files.

The functions below signal an error if keymap is not a keymap, or if key is not a string or vector representing a key sequence. You can use event types (symbols) as shorthand for events that are lists. The kbd macro (voir la section Key Sequences) is a convenient way to specify the key sequence.

Function: define-key keymap key binding

This function sets the binding for key in keymap. (If key is more than one event long, the change is actually made in another keymap reached from keymap.) The argument binding can be any Lisp object, but only certain types are meaningful. (For a list of meaningful types, see Key Lookup.) The value returned by define-key is binding.

If key is [t], this sets the default binding in keymap. When an event has no binding of its own, the Emacs command loop uses the keymap's default binding, if there is one.

Every prefix of key must be a prefix key (i.e., bound to a keymap) or undefined; otherwise an error is signaled. If some prefix of key is undefined, then define-key defines it as a prefix key so that the rest of key can be defined as specified.

If there was previously no binding for key in keymap, the new binding is added at the beginning of keymap. The order of bindings in a keymap makes no difference for keyboard input, but it does matter for menu keymaps (voir la section Menu Keymaps).

This example creates a sparse keymap and makes a number of bindings in it:

(setq map (make-sparse-keymap))
    ⇒ (keymap)
(define-key map "\C-f" 'forward-char)
    ⇒ forward-char
map
    ⇒ (keymap (6 . forward-char))

;; Build sparse submap for C-x and bind f in that.
(define-key map (kbd "C-x f") 'forward-word)
    ⇒ forward-word
map
⇒ (keymap
    (24 keymap                ; C-x
        (102 . forward-word)) ;      f
    (6 . forward-char))       ; C-f

;; Bind C-p to the ctl-x-map.
(define-key map (kbd "C-p") ctl-x-map)
;; ctl-x-map
⇒ [nil … find-file … backward-kill-sentence]

;; Bind C-f to foo in the ctl-x-map.
(define-key map (kbd "C-p C-f") 'foo)
⇒ 'foo
map
⇒ (keymap     ; Note foo in ctl-x-map.
    (16 keymap [nil … foo … backward-kill-sentence])
    (24 keymap
        (102 . forward-word))
    (6 . forward-char))

Note that storing a new binding for C-p C-f actually works by changing an entry in ctl-x-map, and this has the effect of changing the bindings of both C-p C-f and C-x C-f in the default global map.

The function substitute-key-definition scans a keymap for keys that have a certain binding and rebinds them with a different binding. Another feature which is cleaner and can often produce the same results to remap one command into another (voir la section Remapping Commands).

Function: substitute-key-definition olddef newdef keymap &optional oldmap

This function replaces olddef with newdef for any keys in keymap that were bound to olddef. In other words, olddef is replaced with newdef wherever it appears. The function returns nil.

For example, this redefines C-x C-f, if you do it in an Emacs with standard bindings:

(substitute-key-definition 'find-file 'find-file-read-only (current-global-map))

If oldmap is non-nil, that changes the behavior of substitute-key-definition: the bindings in oldmap determine which keys to rebind. The rebindings still happen in keymap, not in oldmap. Thus, you can change one map under the control of the bindings in another. For example,

(substitute-key-definition 'delete-backward-char 'my-funny-delete my-map global-map)

puts the special deletion command in my-map for whichever keys are globally bound to the standard deletion command.

Here is an example showing a keymap before and after substitution:

(setq map '(keymap (?1 . olddef-1) (?2 . olddef-2) (?3 . olddef-1))) ⇒ (keymap (49 . olddef-1) (50 . olddef-2) (51 . olddef-1)) (substitute-key-definition 'olddef-1 'newdef map) ⇒ nil map ⇒ (keymap (49 . newdef) (50 . olddef-2) (51 . newdef))

Function: suppress-keymap keymap &optional nodigits

This function changes the contents of the full keymap keymap by remapping self-insert-command to the command undefined (voir la section Remapping Commands). This has the effect of undefining all printing characters, thus making ordinary insertion of text impossible. suppress-keymap returns nil.

If nodigits is nil, then suppress-keymap defines digits to run digit-argument, and - to run negative-argument. Otherwise it makes them undefined like the rest of the printing characters.

The suppress-keymap function does not make it impossible to modify a buffer, as it does not suppress commands such as yank and quoted-insert. To prevent any modification of a buffer, make it read-only (voir la section Read-Only Buffers).

Since this function modifies keymap, you would normally use it on a newly created keymap. Operating on an existing keymap that is used for some other purpose is likely to cause trouble; for example, suppressing global-map would make it impossible to use most of Emacs.

Most often, suppress-keymap is used to initialize local keymaps of modes such as Rmail and Dired where insertion of text is not desirable and the buffer is read-only. Here is an example taken from the file ‘emacs/lisp/dired.el’, showing how the local keymap for Dired mode is set up:

(setq dired-mode-map (make-keymap)) (suppress-keymap dired-mode-map) (define-key dired-mode-map "r" 'dired-rename-file) (define-key dired-mode-map "\C-d" 'dired-flag-file-deleted) (define-key dired-mode-map "d" 'dired-flag-file-deleted) (define-key dired-mode-map "v" 'dired-view-file) (define-key dired-mode-map "e" 'dired-find-file) (define-key dired-mode-map "f" 'dired-find-file) …

Ce document a été généré par Eric Reinbold le 13 Octobre 2007 en utilisant texi2html 1.78.