The bindings between input events and commands are recorded in data structures called keymaps. Each binding in a keymap associates (or binds) an individual event type either to another keymap or to a command. When an event type is bound to a keymap, that keymap is used to look up the next input event; this continues until a command is found. The whole process is called key lookup.
A keymap is a table mapping event types to definitions (which can be any Lisp objects, though only certain types are meaningful for execution by the command loop). Given an event (or an event type) and a keymap, Emacs can get the event's definition. Events include characters, function keys, and mouse actions (see section Input Events).
A sequence of input events that form a unit is called a key sequence, or key for short. A sequence of one event is always a key sequence, and so are some multi-event sequences.
A keymap determines a binding or definition for any key sequence. If the key sequence is a single event, its binding is the definition of the event in the keymap. The binding of a key sequence of more than one event is found by an iterative process: the binding of the first event is found, and must be a keymap; then the second event's binding is found in that keymap, and so on until all the events in the key sequence are used up.
If the binding of a key sequence is a keymap, we call the key
sequence a prefix key. Otherwise, we call it a
complete key (because no more events can be added to it).
If the binding is nil, we call the key
undefined. Examples of prefix keys are C-c,
C-x, and C-x 4. Examples of defined complete
keys are X, RET, and C-x 4 C-f.
Examples of undefined complete keys are C-x C-g, and
C-c 3. See section Prefix
Keys, for more details.
The rule for finding the binding of a key sequence assumes that the intermediate bindings (found for the events before the last) are all keymaps; if this is not so, the sequence of events does not form a unit--it is not really one key sequence. In other words, removing one or more events from the end of any valid key sequence must always yield a prefix key. For example, C-f C-n is not a key sequence; C-f is not a prefix key, so a longer sequence starting with C-f cannot be a key sequence.
The set of possible multi-event key sequences depends on the bindings for prefix keys; therefore, it can be different for different keymaps, and can change when bindings are changed. However, a one-event sequence is always a key sequence, because it does not depend on any prefix keys for its well-formedness.
At any time, several primary keymaps are active---that is, in use for finding key bindings. These are the global map, which is shared by all buffers; the local keymap, which is usually associated with a specific major mode; and zero or more minor mode keymaps, which belong to currently enabled minor modes. (Not all minor modes have keymaps.) The local keymap bindings shadow (i.e., take precedence over) the corresponding global bindings. The minor mode keymaps shadow both local and global keymaps. See section Active Keymaps, for details.
A keymap is a list whose CAR is the symbol keymap.
The remaining elements of the list define the key bindings of the
keymap. Use the function keymapp (see below) to test
whether an object is a keymap.
Several kinds of elements may appear in a keymap, after the
symbol keymap that begins it:
(type . binding)(t . binding)vectornil for that character.
Such a binding of nil overrides any default key
binding in the keymap, for ASCII characters. However, default
bindings are still meaningful for events other than ASCII
characters. A binding of nil does not
override lower-precedence keymaps; thus, if the local map gives a
binding of nil, Emacs uses the binding from the global
map.
string Keymaps do not directly
record bindings for the meta characters. Instead, meta characters
are regarded for purposes of key lookup as sequences of two
characters, the first of which is ESC (or whatever is
currently the value of meta-prefix-char). Thus, the
key M-a is really represented as ESC
a, and its global binding is found at the slot for
a in esc-map (see section Prefix Keys).
Here as an example is the local keymap for Lisp mode, a sparse keymap. It defines bindings for DEL and TAB, plus C-c C-l, M-C-q, and M-C-x.
lisp-mode-map
=>
(keymap
;; TAB
(9 . lisp-indent-line)
;; DEL
(127 . backward-delete-char-untabify)
(3 keymap
;; C-c C-l
(12 . run-lisp))
(27 keymap
;; M-C-q, treated as ESC C-q
(17 . indent-sexp)
;; M-C-x, treated as ESC C-x
(24 . lisp-send-defun)))
t if object is a keymap, nil
otherwise. More precisely, this function tests for a list whose CAR
is keymap.
(keymapp '(keymap))
=> t
(keymapp (current-global-map))
=> t
Here we describe the functions for creating keymaps.
nil, and does
not bind any other kind of event.
(make-keymap)
=> (keymap [nil nil nil ... nil nil])
If you specify prompt, that becomes the overall prompt string for the keymap. The prompt string is useful for menu keymaps (see section Menu Keymaps).
make-keymap.
(make-sparse-keymap)
=> (keymap)
(setq map (copy-keymap (current-local-map)))
=> (keymap
;; (This implements meta characters.)
(27 keymap
(83 . center-paragraph)
(115 . center-line))
(9 . tab-to-tab-stop))
(eq map (current-local-map))
=> nil
(equal map (current-local-map))
=> t
A keymap can inherit the bindings of another keymap, which we call the parent keymap. Such a keymap looks like this:
(keymap bindings... . parent-keymap)
The effect is that this keymap inherits all the bindings of parent-keymap, whatever they may be at the time a key is looked up, but can add to them or override them with bindings.
If you change the bindings in parent-keymap using
define-key or other key-binding functions, these
changes are visible in the inheriting keymap unless shadowed by
bindings. The converse is not true: if you use
define-key to change the inheriting keymap, that
affects bindings, but has no effect on
parent-keymap.
The proper way to construct a keymap with a parent is to use
set-keymap-parent; if you have code that directly
constructs a keymap with a parent, please convert the program to
use set-keymap-parent instead.
keymap-parent returns nil.
nil, this
function gives keymap no parent at all. If keymap has submaps (bindings for prefix keys), they too receive new parent keymaps that reflect what parent specifies for those prefix keys.
Here is an example showing how to make a keymap that inherits
from text-mode-map:
(let ((map (make-sparse-keymap))) (set-keymap-parent map text-mode-map) map)
A prefix key is a key sequence whose binding is a
keymap. The keymap defines what to do with key sequences that
extend the prefix key. For example, C-x is a prefix key,
and it uses a keymap that is also stored in the variable
ctl-x-map. This keymap defines bindings for key
sequences starting with C-x.
Some of the standard Emacs prefix keys use keymaps that are also found in Lisp variables:
esc-map is the global keymap for
the ESC prefix key. Thus, the global definitions of all
meta characters are actually found here. This map is also the
function definition of ESC-prefix.
help-map is
the global keymap for the C-h prefix key.
mode-specific-map is the global
keymap for the prefix key C-c. This map is actually
global, not mode-specific, but its name provides useful information
about C-c in the output of C-h b
(display-bindings), since the main use of this prefix
key is for mode-specific bindings.
ctl-x-map is the global keymap used for the
C-x prefix key. This map is found via the function cell
of the symbol Control-X-prefix.
mule-keymap is the global keymap
used for the C-x RET prefix key.
ctl-x-4-map is the global keymap
used for the C-x 4 prefix key.
ctl-x-5-map is the global keymap
used for the C-x 5 prefix key.
2C-mode-map is the global keymap
used for the C-x 6 prefix key.
vc-prefix-map is the global keymap
used for the C-x v prefix key.
facemenu-keymap is the global
keymap used for the M-g prefix key.
The keymap binding of a prefix key is used for looking up the
event that follows the prefix key. (It may instead be a symbol
whose function definition is a keymap. The effect is the same, but
the symbol serves as a name for the prefix key.) Thus, the binding
of C-x is the symbol Control-X-prefix,
whose function cell holds the keymap for C-x commands.
(The same keymap is also the value of ctl-x-map.)
Prefix key definitions can appear in any active keymap. The definitions of C-c, C-x, C-h and ESC as prefix keys appear in the global map, so these prefix keys are always available. Major and minor modes can redefine a key as a prefix by putting a prefix key definition for it in the local map or the minor mode's map. See section Active Keymaps.
If a key is defined as a prefix in more than one active map, then its various definitions are in effect merged: the commands defined in the minor mode keymaps come first, followed by those in the local map's prefix definition, and then by those from the global map.
In the following example, we make C-p a prefix key in
the local keymap, in such a way that C-p is identical to
C-x. Then the binding for C-p C-f is the
function find-file, just like C-x C-f. The
key sequence C-p 6 is not found in any active
keymap.
(use-local-map (make-sparse-keymap))
=> nil
(local-set-key "\C-p" ctl-x-map)
=> nil
(key-binding "\C-p\C-f")
=> find-file
(key-binding "\C-p6")
=> nil
This function also sets symbol as a variable, with the keymap as its value. It returns symbol.
Emacs normally contains many keymaps; at any given time, just a few of them are active in that they participate in the interpretation of user input. These are the global keymap, the current buffer's local keymap, and the keymaps of any enabled minor modes.
The global keymap holds the bindings of keys that are
defined regardless of the current buffer, such as C-f.
The variable global-map holds this keymap, which is
always active.
Each buffer may have another keymap, its local keymap,
which may contain new or overriding definitions for keys. The
current buffer's local keymap is always active except when
overriding-local-map overrides it. Text properties can
specify an alternative local map for certain parts of the buffer;
see section Properties with Special
Meanings.
Each minor mode can have a keymap; if it does, the keymap is active when the minor mode is enabled.
The variable overriding-local-map, if
non-nil, specifies another local keymap that overrides
the buffer's local map and all the minor mode keymaps.
All the active keymaps are used together to determine what command to execute when a key is entered. Emacs searches these maps one by one, in order of decreasing precedence, until it finds a binding in one of the maps. The procedure for searching a single keymap is called key lookup; see section Key Lookup.
Normally, Emacs first searches for the key in the minor mode
maps, in the order specified by minor-mode-map-alist;
if they do not supply a binding for the key, Emacs searches the
local map; if that too has no binding, Emacs then searches the
global map. However, if overriding-local-map is
non-nil, Emacs searches that map first, before the
global map.
Since every buffer that uses
the same major mode normally uses the same local keymap, you can
think of the keymap as local to the mode. A change to the local
keymap of a buffer (using local-set-key, for example)
is seen also in the other buffers that share that keymap.
The local keymaps that are used for Lisp mode and some other
major modes exist even if they have not yet been used. These local
maps are the values of variables such as
lisp-mode-map. For most major modes, which are less
frequently used, the local keymap is constructed only when the mode
is used for the first time in a session.
The minibuffer has local keymaps, too; they contain various completion and exit commands. See section Introduction to Minibuffers.
Emacs has other keymaps that are used in a different
way--translating events within read-key-sequence. See
section Translating Input
Events.
See section Standard Keymaps, for a list of standard keymaps.
self-insert-command
to all of the printing characters. It is normal practice to change the bindings in the global map, but you should not assign this variable any value other than the keymap it starts out with.
global-map unless you change one or the other.
(current-global-map)
=> (keymap [set-mark-command beginning-of-line ...
delete-backward-char])
nil if it has none.
In the following example, the keymap for the
`*scratch*' buffer (using Lisp Interaction mode) is a
sparse keymap in which the entry for ESC, ASCII code 27,
is another sparse keymap.
(current-local-map)
=> (keymap
(10 . eval-print-last-sexp)
(9 . lisp-indent-line)
(127 . backward-delete-char-untabify)
(27 keymap
(24 . eval-defun)
(17 . indent-sexp)))
nil. It is very unusual to change the global keymap.
nil, then the buffer has no local
keymap. use-local-map returns nil. Most
major mode commands use this function.
(variable . keymap)
The keymap keymap is active whenever
variable has a non-nil value. Typically
variable is the variable that enables or disables a
minor mode. See section Keymaps and
Minor Modes.
Note that elements of minor-mode-map-alist do not
have the same structure as elements of
minor-mode-alist. The map must be the CDR of the
element; a list with the map as the CADR will not do. The CADR can
be either a keymap (a list) or a symbol whose function definition
is a keymap.
When more than one minor mode keymap is active, their order of
priority is the order of minor-mode-map-alist. But you
should design minor modes so that they don't interfere with each
other. If you do this properly, the order will not matter.
See section Keymaps and Minor
Modes, for more information about minor modes. See also
minor-mode-key-binding (see section Functions for Key Lookup).
minor-mode-map-alist:
(variable . keymap). If a variable appears as an element of
minor-mode-overriding-map-alist, the map specified by
that element totally replaces any map specified for the same
variable in minor-mode-map-alist.
minor-mode-overriding-map-alist is automatically
buffer-local in all buffers.
nil,
this variable holds a keymap to use instead of the buffer's local
keymap and instead of all the minor mode keymaps. This keymap, if
any, overrides all other maps that would have been active, except
for the current global map.
nil,
this variable holds a keymap to use instead of
overriding-local-map, the buffer's local keymap and
all the minor mode keymaps. This variable is always local to the current terminal and cannot be buffer-local. See section Multiple Displays. It is used to implement incremental search mode.
nil, the value of
overriding-local-map or
overriding-terminal-local-map can affect the display
of the menu bar. The default value is nil, so those
map variables have no effect on the menu bar. Note that these two map variables do affect the execution of key sequences entered using the menu bar, even if they do not affect the menu bar display. So if a menu bar key sequence comes in, you should clear the variables before looking up and executing that key sequence. Modes that use the variables would typically do this anyway; normally they respond to events that they do not handle by "unreading" them and exiting.
read-event. See section Special Events.
Key lookup is the process of finding the binding of a key sequence from a given keymap. Actual execution of the binding is not part of key lookup.
Key lookup uses just the event type of each event in the key
sequence; the rest of the event is ignored. In fact, a key sequence
used for key lookup may designate mouse events with just their
types (symbols) instead of with entire mouse events (lists). See
section Input Events. Such a
"key-sequence" is insufficient for command-execute to
run, but it is sufficient for looking up or rebinding a key.
When the key sequence consists of multiple events, key lookup processes the events sequentially: the binding of the first event is found, and must be a keymap; then the second event's binding is found in that keymap, and so on until all the events in the key sequence are used up. (The binding thus found for the last event may or may not be a keymap.) Thus, the process of key lookup is defined in terms of a simpler process for looking up a single event in a keymap. How that is done depends on the type of object associated with the event in that keymap.
Let's use the term keymap entry to describe the value
found by looking up an event type in a keymap. (This doesn't
include the item string and other extra elements in menu key
bindings, because lookup-key and other key lookup
functions don't include them in the returned value.) While any Lisp
object may be stored in a keymap as a keymap entry, not all make
sense for key lookup. Here is a table of the meaningful kinds of
keymap entries:
nilnil means that
the events used so far in the lookup form an undefined key. When a
keymap fails to mention an event type at all, and has no default
binding, that is equivalent to a binding of nil for
that event type.
keymap, then the list is a keymap, and is treated as a
keymap (see above).
lambda, then the list is a lambda
expression. This is presumed to be a command, and is treated as
such (see above).
(othermap . othertype)When key lookup encounters an indirect entry, it looks up instead the binding of othertype in othermap and uses that. This feature permits you to define one key as an alias for another key. For example, an entry whose CAR is the keymap called
esc-map and whose CDR is 32 (the code for
SPC) means, "Use the global binding of
Meta-SPC, whatever that may be."
command-execute (see section Interactive Call). The symbol undefined is worth
special mention: it means to treat the key as undefined. Strictly
speaking, the key is defined, and its binding is the command
undefined; but that command does the same thing that
is done automatically for an undefined key: it rings the bell (by
calling ding) but does not signal an error. undefined is used in
local keymaps to override a global key binding and make the key
"undefined" locally. A local binding of nil would fail
to do this because it would not override the global binding.
In short, a keymap entry may be a keymap, a command, a keyboard
macro, a symbol that leads to one of them, or an indirection or
nil. Here is an example of a sparse keymap with two
characters bound to commands and one bound to another keymap. This
map is the normal value of emacs-lisp-mode-map. Note
that 9 is the code for TAB, 127 for DEL, 27
for ESC, 17 for C-q and 24 for
C-x.
(keymap (9 . lisp-indent-line)
(127 . backward-delete-char-untabify)
(27 keymap (17 . indent-sexp) (24 . eval-defun)))
Here are the functions and variables pertaining to key lookup.
lookup-key. Here are examples:
(lookup-key (current-global-map) "\C-x\C-f")
=> find-file
(lookup-key (current-global-map) "\C-x\C-f12345")
=> 2
If the string or vector key is not a valid key sequence according to the prefix keys specified in keymap, it must be "too long" and have extra events at the end that do not fit into a single key sequence. Then the value is a number, the number of events at the front of key that compose a complete key.
If accept-defaults is non-nil, then
lookup-key considers default bindings as well as
bindings for the specific events in key. Otherwise,
lookup-key reports only bindings for the specific
sequence key, ignoring default bindings except when you
explicitly ask about them. (To do this, supply t as an
element of key; see section Format of Keymaps.)
If key contains a meta character, that character is
implicitly replaced by a two-character sequence: the value of
meta-prefix-char, followed by the corresponding
non-meta character. Thus, the first example below is handled by
conversion into the second example.
(lookup-key (current-global-map) "\M-f")
=> forward-word
(lookup-key (current-global-map) "\ef")
=> forward-word
Unlike read-key-sequence, this function does not
modify the specified events in ways that discard information (see
section Key Sequence Input). In
particular, it does not convert letters to lower case and it does
not change drag events to clicks.
ding, but does not cause an error.
nil if key is
undefined in the keymaps. The argument accept-defaults controls checking for
default bindings, as in lookup-key (above).
An error is signaled if key is not a string or a vector.
(key-binding "\C-x\C-f")
=> find-file
nil if it is undefined there. The argument accept-defaults controls checking for
default bindings, as in lookup-key (above).
nil if it is undefined there. The argument accept-defaults controls checking for
default bindings, as in lookup-key (above).
(modename
. binding), where modename is the
variable that enables the minor mode, and binding is
key's binding in that mode. If key has no
minor-mode bindings, the value is nil. If the first binding found is not a prefix definition (a keymap or a symbol defined as a keymap), all subsequent bindings from other minor modes are omitted, since they would be completely shadowed. Similarly, the list omits non-prefix bindings that follow prefix bindings.
The argument accept-defaults controls checking for
default bindings, as in lookup-key (above).
As long as the value of meta-prefix-char remains
27, key lookup translates M-b into ESC
b, which is normally defined as the
backward-word command. However, if you set
meta-prefix-char to 24, the code for C-x,
then Emacs will translate M-b into C-x b,
whose standard binding is the switch-to-buffer
command. Here is an illustration:
meta-prefix-char ; The default value.
=> 27
(key-binding "\M-b")
=> backward-word
?\C-x ; The print representation
=> 24 ; of a character.
(setq meta-prefix-char 24)
=> 24
(key-binding "\M-b")
=> switch-to-buffer ; Now, typing M-b is
; like typing C-x b.
(setq meta-prefix-char 27) ; Avoid confusion!
=> 27 ; Restore the default value!
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 (see section Commands
for Binding Keys). You can also use define-key, a
more general function; then you must specify explicitly the map to
change.
In writing the key sequence to rebind, it is
good to use the special escape sequences for control and meta
characters (see 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]'. See 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.
For the functions below, an error is signaled 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.
define-key is binding. 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 in most cases, but it does matter for menu keymaps (see section Menu Keymaps).
Here is an example that 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 "\C-xf" '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 "\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 "\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.
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, then its bindings
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))
undefined. This makes 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 (see
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) ...
This section describes some convenient interactive interfaces
for changing key bindings. They work by calling
define-key.
People often use global-set-key in their
`.emacs' file for simple customization. For example,
(global-set-key "\C-x\C-\\" 'next-line)
or
(global-set-key [?\C-x ?\C-\\] 'next-line)
or
(global-set-key [(control ?x) (control ?\\)] 'next-line)
redefines C-x C-\ to move down a line.
(global-set-key [M-mouse-1] 'mouse-set-point)
redefines the first (leftmost) mouse button, typed with the Meta key, to set point where you click.
(global-set-key key definition) == (define-key (current-global-map) key definition)
One use of this function is in preparation for defining a longer key that uses key as a prefix--which would not be allowed if key has a non-prefix binding. For example:
(global-unset-key "\C-l")
=> nil
(global-set-key "\C-l\C-l" 'redraw-display)
=> nil
This function is implemented simply using
define-key:
(global-unset-key key) == (define-key (current-global-map) key nil)
(local-set-key key definition) == (define-key (current-local-map) key definition)
(local-unset-key key) == (define-key (current-local-map) key nil)
This section describes functions used to scan all the current keymaps for the sake of printing help information.
(key .
map), where key is a prefix key whose
definition in keymap is map. The elements of the alist are ordered so that the key
increases in length. The first element is always ("" .
keymap), because the specified keymap is
accessible from itself with a prefix of no events.
If prefix is given, it should be a prefix key
sequence; then accessible-keymaps includes only the
submaps whose prefixes start with prefix. These elements
look just as they do in the value of
(accessible-keymaps); the only difference is that some
elements are omitted.
In the example below, the returned alist indicates that the key
ESC, which is displayed as `^[', is a
prefix key whose definition is the sparse keymap (keymap (83
. center-paragraph) (115 . foo)).
(accessible-keymaps (current-local-map))
=>(("" keymap
(27 keymap ; Note this keymap for ESC is repeated below.
(83 . center-paragraph)
(115 . center-line))
(9 . tab-to-tab-stop))
("^[" keymap
(83 . center-paragraph)
(115 . foo)))
In the following example, C-h is a prefix key that
uses a sparse keymap starting with (keymap (118 .
describe-variable)...). Another prefix, C-x 4,
uses a keymap which is also the value of the variable
ctl-x-4-map. The event mode-line is one
of several dummy events used as prefixes for mouse actions in
special parts of a window.
(accessible-keymaps (current-global-map))
=> (("" keymap [set-mark-command beginning-of-line ...
delete-backward-char])
("^H" keymap (118 . describe-variable) ...
(8 . help-for-help))
("^X" keymap [x-flush-mouse-queue ...
backward-kill-sentence])
("^[" keymap [mark-sexp backward-sexp ...
backward-kill-word])
("^X4" keymap (15 . display-buffer) ...)
([mode-line] keymap
(S-mouse-2 . mouse-split-window-horizontally) ...))
These are not all the keymaps you would see in actuality.
where-is command (see section
`Help' in The GNU Emacs Manual). It returns a list of
key sequences (of any length) that are bound to command
in a set of keymaps. The argument command can be any object; it is
compared with all keymap entries using eq.
If keymap is nil, then the maps used are
the current active keymaps, disregarding
overriding-local-map (that is, pretending its value is
nil). If keymap is non-nil,
then the maps searched are keymap and the global
keymap.
Usually it's best to use overriding-local-map as
the expression for keymap. Then
where-is-internal searches precisely the keymaps that
are active. To search only the global map, pass
(keymap) (an empty keymap) as keymap.
If firstonly is non-ascii, then the
value is a single string representing the first key sequence found,
rather than a list of all possible key sequences. If
firstonly is t, then the value is the first
key sequence, except that key sequences consisting entirely of
ASCII characters (or meta variants of ASCII characters) are
preferred to all other key sequences.
If noindirect is non-nil,
where-is-internal doesn't follow indirect keymap
bindings. This makes it possible to search for an indirect
definition itself.
(where-is-internal 'describe-function)
=> ("\^hf" "\^hd")
If prefix is non-nil, it should be a
prefix key; then the listing includes only keys that start with
prefix.
The listing describes meta characters as ESC followed by the corresponding non-meta character.
When several characters with consecutive ASCII codes have the
same definition, they are shown together, as
`firstchar..lastchar'. In this
instance, you need to know the ASCII codes to understand which
characters this means. For example, in the default global map, the
characters `SPC .. ~' are described by a
single line. SPC is ASCII 32, ~ is ASCII 126,
and the characters between them include all the normal printing
characters, (e.g., letters, digits, punctuation, etc.); all these
characters are bound to self-insert-command.
A keymap can define a menu as well as bindings for keyboard keys and mouse button. Menus are usually actuated with the mouse, but they can work with the keyboard also.
A keymap is suitable for menu use if it has an overall
prompt string, which is a string that appears as an element of
the keymap. (See section Format of
Keymaps.) The string should describe the purpose of the menu.
The easiest way to construct a keymap with a prompt string is to
specify the string as an argument when you call
make-keymap or make-sparse-keymap (see
section Creating Keymaps).
The order of items in the menu is the same as the order of
bindings in the keymap. Since define-key puts new
bindings at the front, you should define the menu items starting at
the bottom of the menu and moving to the top, if you care about the
order. When you add an item to an existing menu, you can specify
its position in the menu using define-key-after (see
section Modifying Menus).
The simpler and older way to define a menu keymap binding looks like this:
(item-string . real-binding)
The CAR, item-string, is the string to be displayed in the menu. It should be short--preferably one to three words. It should describe the action of the command it corresponds to.
You can also supply a second string, called the help string, as follows:
(item-string help-string . real-binding)
Currently Emacs does not actually use help-string; it knows only how to ignore help-string in order to extract real-binding. In the future we may use help-string as extended documentation for the menu item, available on request.
As far as define-key is concerned,
item-string and help-string are part of the
event's binding. However, lookup-key returns just
real-binding, and only real-binding is used
for executing the key.
If real-binding is nil, then
item-string appears in the menu but cannot be
selected.
If real-binding is a symbol and has a
non-nil menu-enable property, that
property is an expression that controls whether the menu item is
enabled. Every time the keymap is used to display a menu, Emacs
evaluates the expression, and it enables the menu item only if the
expression's value is non-nil. When a menu item is
disabled, it is displayed in a "fuzzy" fashion, and cannot be
selected.
The menu bar does not recalculate which items are enabled every
time you look at a menu. This is because the X toolkit requires the
whole tree of menus in advance. To force recalculation of the menu
bar, call force-mode-line-update (see section Mode Line Format).
You've probably noticed that menu items show the equivalent keyboard key sequence (if any) to invoke the same command. To save time on recalculation, menu display caches this information in a sublist in the binding, like this:
(item-string [help-string] (key-binding-data) . real-binding)
Don't put these sublists in the menu item yourself; menu display calculates them automatically. Don't mention keyboard equivalents in the item strings themselves, since that is redundant.
An extended-format menu item is a more flexible and also cleaner
alternative to the simple format. It consists of a list that starts
with the symbol menu-item. To define a non-selectable
string, the item looks like this:
(menu-item item-name)
where a string consisting of two or more dashes specifies a separator line.
To define a real menu item which can be selected, the extended format item looks like this:
(menu-item item-name real-binding
. item-property-list)
Here, item-name is an expression which evaluates to the menu item string. Thus, the string need not be a constant. The third element, real-binding, is the command to execute. The tail of the list, item-property-list, has the form of a property list which contains other information. Here is a table of the properties that are supported:
:enable FORMnil means yes).
:visible FORMnil means
yes). If the item does not appear, then the menu is displayed as if
this item were not defined at all.
:help help:button (type .
selected):toggle or :radio. The CDR,
selected, should be a form; the result of evaluating it
says whether this button is currently selected. A toggle
is a menu item which is labeled as either "on" or "off" according
to the value of selected. The command itself should
toggle selected, setting it to t if it is
nil, and to nil if it is t.
Here is how the menu item to toggle the debug-on-error
flag is defined:
(menu-item "Debug on Error" toggle-debug-on-error
:button (:toggle
. (and (boundp 'debug-on-error)
debug-on-error))
This works because toggle-debug-on-error is defined as
a command which toggles the variable debug-on-error.
Radio buttons are a group of menu items, in which at any
time one and only one is "selected." There should be a variable
whose value says which one is selected at any time. The
selected form for each radio button in the group should
check whether the variable has the right value for selecting that
button. Clicking on the button should set the variable so that the
button you clicked on becomes selected.
:key-sequence key-sequence:key-sequence nil:keys property and finds
the keyboard equivalent anyway.
:keys string:filter filter-fnSometimes it is useful to make menu items that use the "same"
command but with different enable conditions. The best way to do
this in Emacs now is with extended menu items; before that feature
existed, it could be done by defining alias commands and using them
in menu items. Here's an example that makes two aliases for
toggle-read-only and gives them different enable
conditions:
(defalias 'make-read-only 'toggle-read-only) (put 'make-read-only 'menu-enable '(not buffer-read-only)) (defalias 'make-writable 'toggle-read-only) (put 'make-writable 'menu-enable 'buffer-read-only)
When using aliases in menus, often it is useful to display the
equivalent key bindings for the "real" command name, not the
aliases (which typically don't have any key bindings except for the
menu itself). To request this, give the alias symbol a
non-nil menu-alias property. Thus,
(put 'make-read-only 'menu-alias t) (put 'make-writable 'menu-alias t)
causes menu items for make-read-only and
make-writable to show the keyboard bindings for
toggle-read-only.
The usual way to make a menu keymap produce a menu is to make it the definition of a prefix key. (A Lisp program can explicitly pop up a menu and receive the user's choice--see section Pop-Up Menus.)
If the prefix key ends with a mouse event, Emacs handles the menu keymap by popping up a visible menu, so that the user can select a choice with the mouse. When the user clicks on a menu item, the event generated is whatever character or symbol has the binding that brought about that menu item. (A menu item may generate a series of events if the menu has multiple levels or comes from the menu bar.)
It's often best to use a button-down event to trigger the menu. Then the user can select a menu item by releasing the button.
A single keymap can appear as multiple menu panes, if you explicitly arrange for this. The way to do this is to make a keymap for each pane, then create a binding for each of those maps in the main keymap of the menu. Give each of these bindings an item string that starts with `@'. The rest of the item string becomes the name of the pane. See the file `lisp/mouse.el' for an example of this. Any ordinary bindings with `@'-less item strings are grouped into one pane, which appears along with the other panes explicitly created for the submaps.
X toolkit menus don't have panes; instead, they can have submenus. Every nested keymap becomes a submenu, whether the item string starts with `@' or not. In a toolkit version of Emacs, the only thing special about `@' at the beginning of an item string is that the `@' doesn't appear in the menu item.
You can also produce multiple panes or submenus from separate keymaps. The full definition of a prefix key always comes from merging the definitions supplied by the various active keymaps (minor mode, local, and global). When more than one of these keymaps is a menu, each of them makes a separate pane or panes (when Emacs does not use an X-toolkit) or a separate submenu (when using an X-toolkit). See section Active Keymaps.
When a prefix key ending with a keyboard event (a character or function key) has a definition that is a menu keymap, the user can use the keyboard to choose a menu item.
Emacs displays the menu alternatives (the item strings of the
bindings) in the echo area. If they don't all fit at once, the user
can type SPC to see the next line of alternatives.
Successive uses of SPC eventually get to the end of the
menu and then cycle around to the beginning. (The variable
menu-prompt-more-char specifies which character is
used for this; SPC is the default.)
When the user has found the desired alternative from the menu, he or she should type the corresponding character--the one whose binding is that alternative.
This way of using menus in an Emacs-like editor was inspired by the Hierarkey system.
Here is a complete example of defining a menu keymap. It is the definition of the `Print' submenu in the `Tools' menu in the menu bar, and it uses the simple menu item format (see section Simple Menu Items). First we create the keymap, and give it a name:
(defvar menu-bar-print-menu (make-sparse-keymap "Print"))
Next we define the menu items:
(define-key menu-bar-print-menu [ps-print-region]
'("Postscript Print Region" . ps-print-region-with-faces))
(define-key menu-bar-print-menu [ps-print-buffer]
'("Postscript Print Buffer" . ps-print-buffer-with-faces))
(define-key menu-bar-print-menu [separator-ps-print]
'("--"))
(define-key menu-bar-print-menu [print-region]
'("Print Region" . print-region))
(define-key menu-bar-print-menu [print-buffer]
'("Print Buffer" . print-buffer))
Note the symbols which the bindings are "made for"; these appear
inside square brackets, in the key sequence being defined. In some
cases, this symbol is the same as the command name; sometimes it is
different. These symbols are treated as "function keys", but they
are not real function keys on the keyboard. They do not affect the
functioning of the menu itself, but they are "echoed" in the echo
area when the user selects from the menu, and they appear in the
output of where-is and apropos.
The binding whose definition is ("--") is a
separator line. Like a real menu item, the separator has a key
symbol, in this case separator-ps-print. If one menu
has two separators, they must have two different key symbols.
Here is code to define enable conditions for two of the commands in the menu:
(put 'print-region 'menu-enable 'mark-active) (put 'ps-print-region-with-faces 'menu-enable 'mark-active)
Here is how we make this menu appear as an item in the parent menu:
(define-key menu-bar-tools-menu [print] (cons "Print" menu-bar-print-menu))
Note that this incorporates the submenu keymap, which is the
value of the variable menu-bar-print-menu, rather than
the symbol menu-bar-print-menu itself. Using that
symbol in the parent menu item would be meaningless because
menu-bar-print-menu is not a command.
If you wanted to attach the same print menu to a mouse click, you can do it this way:
(define-key global-map [C-S-down-mouse-1] menu-bar-print-menu)
We could equally well use an extended menu item (see section Extended Menu Items) for
print-region, like this:
(define-key menu-bar-print-menu [print-region]
'(menu-item "Print Region" print-region
:enable (mark-active)))
With the extended menu item, the enable condition is specified inside the menu item itself. If we wanted to make this item disappear from the menu entirely when the mark is inactive, we could do it this way:
(define-key menu-bar-print-menu [print-region]
'(menu-item "Print Region" print-region
:visible (mark-active)))
Most window systems allow each frame to have a menu
bar---a permanently displayed menu stretching horizontally
across the top of the frame. The items of the menu bar are the
subcommands of the fake "function key" menu-bar, as
defined by all the active keymaps.
To add an item to the menu bar, invent a fake "function key" of
your own (let's call it key), and make a binding for the
key sequence [menu-bar key]. Most often,
the binding is a menu keymap, so that pressing a button on the menu
bar item leads to another menu.
When more than one active keymap defines the same fake function key for the menu bar, the item appears just once. If the user clicks on that menu bar item, it brings up a single, combined menu containing all the subcommands of that item--the global subcommands, the local subcommands, and the minor mode subcommands.
The variable overriding-local-map is normally
ignored when determining the menu bar contents. That is, the menu
bar is computed from the keymaps that would be active if
overriding-local-map were nil. See
section Active Keymaps.
In order for a frame to display a menu bar, its
menu-bar-lines parameter must be greater than zero.
Emacs uses just one line for the menu bar itself; if you specify
more than one line, the other lines serve to separate the menu bar
from the windows in the frame. We recommend 1 or 2 as the value of
menu-bar-lines. See section Window Frame Parameters.
Here's an example of setting up a menu bar item:
(modify-frame-parameters (selected-frame)
'((menu-bar-lines . 2)))
;; Make a menu keymap (with a prompt string)
;; and make it the menu bar item's definition.
(define-key global-map [menu-bar words]
(cons "Words" (make-sparse-keymap "Words")))
;; Define specific subcommands in this menu.
(define-key global-map
[menu-bar words forward]
'("Forward word" . forward-word))
(define-key global-map
[menu-bar words backward]
'("Backward word" . backward-word))
A local keymap can cancel a menu bar item made by the global
keymap by rebinding the same fake function key with
undefined as the binding. For example, this is how
Dired suppresses the `Edit' menu bar item:
(define-key dired-mode-map [menu-bar edit] 'undefined)
edit is the fake function key used by the global
map for the `Edit' menu bar item. The main reason to
suppress a global menu bar item is to regain space for
mode-specific items.
This variable holds a list of fake function keys for items to
display at the end of the menu bar rather than in normal sequence.
The default value is (help-menu); thus, the
`Help' menu item normally appears at the end of the
menu bar, following local menu items.
When you insert a new item in an existing menu, you probably
want to put it in a particular place among the menu's existing
items. If you use define-key to add the item, it
normally goes at the front of the menu. To put it elsewhere in the
menu, use define-key-after:
define-key, but position the binding in
map after the binding for the event after.
The argument key should be of length one--a vector or
string with just one element. But after should be a
single event type--a symbol or a character, not a sequence. The new
binding goes after the binding for after. If
after is t, then the new binding goes last,
at the end of the keymap. Here is an example:
(define-key-after my-menu [drink]
'("Drink" . drink-command) 'eat)
makes a binding for the fake function key DRINK and puts it right after the binding for EAT.
Here is how to insert an item called `Work' in the
`Signals' menu of Shell mode, after the item
break:
(define-key-after
(lookup-key shell-mode-map [menu-bar signals])
[work] '("Work" . work-command) 'break)