@c -*-texinfo-*-
@c This is part of the XEmacs Lisp Reference Manual.
@c Copyright (C) 1990, 1991, 1992, 1993 Free Software Foundation, Inc. 
@c See the file lispref.texi for copying conditions.
@setfilename ../../info/keymaps.info
@node Keymaps, Menus, Command Loop, Top
@chapter Keymaps
@cindex keymap

@c This section is largely different from the one in FSF Emacs.

  The bindings between input events and commands are recorded in data
structures called @dfn{keymaps}.  Each binding in a keymap associates
(or @dfn{binds}) an individual event type either with another keymap or
with a command.  When an event is bound to a keymap, that keymap is
used to look up the next character typed; this continues until a command
is found.  The whole process is called @dfn{key lookup}.

  NOTE: Keymap documentation has not been completely updated for XEmacs.
Some of the information below is incorrect.

@menu
* Keymap Terminology::        	Definitions of terms pertaining to keymaps.
* Format of Keymaps::		What a keymap looks like as a Lisp object.
* Creating Keymaps:: 		Functions to create and copy keymaps.
* Inheritance and Keymaps::	How one keymap can inherit the bindings
				   of another keymap.
* Prefix Keys::                 Defining a key with a keymap as its definition.
* Active Keymaps::	        Each buffer has a local keymap
                                   to override the standard (global) bindings.
				   A minor mode can also override them.
* Key Lookup::                  How extracting elements from keymaps works.
* Functions for Key Lookup::    How to request key lookup.
* Changing Key Bindings::       Redefining a key in a keymap.
* Key Binding Commands::        Interactive interfaces for redefining keys.
* Scanning Keymaps::            Looking through all keymaps, for printing help.
@end menu

@node Keymap Terminology
@section Keymap Terminology
@cindex key
@cindex keystroke
@cindex key binding
@cindex binding of a key
@cindex complete key
@cindex undefined key

  A @dfn{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, XEmacs can get the event's definition.  Events mapped in keymaps
include keypresses, button presses, and button releases
(@pxref{Events}).

  A sequence of input events that form a unit is called a
@dfn{key sequence}, or @dfn{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 @dfn{prefix key}.  Otherwise, we call it a @dfn{complete key} (because
no more characters can be added to it).  If the binding is @code{nil},
we call the key @dfn{undefined}.  Examples of prefix keys are @kbd{C-c},
@kbd{C-x}, and @kbd{C-x 4}.  Examples of defined complete keys are
@kbd{X}, @key{RET}, and @kbd{C-x 4 C-f}.  Examples of undefined complete
keys are @kbd{C-x C-g}, and @kbd{C-c 3}.  @xref{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 a key sequence.  In other words, removing one or
more events from the end of any valid key must always yield a prefix
key.  For example, @kbd{C-f C-f} is not a key; @kbd{C-f} is not a prefix
key, so a longer sequence starting with @kbd{C-f} cannot be a key.

  Note that 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 @dfn{active}---that is, in
use for finding key bindings.  These are the @dfn{global map}, which is
shared by all buffers; the @dfn{local keymap}, which is usually
associated with a specific major mode; and zero or more @dfn{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.  @xref{Active Keymaps},
for details.

@node Format of Keymaps
@section Format of Keymaps
@cindex format of keymaps
@cindex keymap format

  A keymap is a primitive type that associates events with their
bindings.  Note that this is different from Emacs 18 and FSF Emacs,
where keymaps are lists.

@defun keymapp object
This function returns @code{t} if @var{object} is a keymap, @code{nil}
otherwise.
@end defun

@node Creating Keymaps
@section Creating Keymaps
@cindex creating keymaps

  Here we describe the functions for creating keymaps.

@defun make-keymap
This function constructs and returns a new keymap object.  All entries
in it are @code{nil}, meaning ``command undefined''.
@end defun

@defun make-sparse-keymap
This function constructs and returns a new keymap object.  All entries
in it are @code{nil}, meaning ``command undefined''.  The only
difference between this function and @code{make-keymap} is that this
function returns a ``smaller'' keymap (one that is expected to contain
fewer entries).  As keymaps dynamically resize, the distinction is not
great.
@end defun

@defun copy-keymap keymap
This function returns a copy of the keymap @var{keymap}.  The copy
starts out with the same definitions of @var{keymap}, but changing
either the copy or @var{keymap} does not affect the other.  Any key
definitions that are subkeymaps are recursively copied.

This function returns a copy of @var{keymap}.  Any keymaps which
appear directly as bindings in @var{keymap} are also copied recursively,
and so on to any number of levels.  However, recursive copying does not
take place when the definition of a character is a symbol whose function
definition is a keymap; the same symbol appears in the new copy.

@example
@group
(setq map (copy-keymap (current-local-map)))
@result{} #<keymap 3 entries 0x21f80>
@end group

@group
(eq map (current-local-map))
    @result{} nil
@end group
@ignore @c Doesn't work!
@group
(equal map (current-local-map))
    @result{} t
@end group
@end ignore
@end example
@end defun

@node Inheritance and Keymaps
@section Inheritance and Keymaps
@cindex keymap inheritance
@cindex inheriting a keymap's bindings
@cindex keymap parent
@cindex parent of a keymap

  A keymap can inherit the bindings of other keymaps.  The other
keymaps are called the keymap's @dfn{parents}, and are set with
@code{set-keymap-parents}.  When searching for a binding for a key
sequence in a particular keymap, that keymap itself will first be
searched; then, if no binding was found in the map and it has parents,
the first parent keymap will be searched; then that keymap's parent will
be searched, and so on, until either a binding for the key sequence is
found, or a keymap without a parent is encountered.  At this point,
the search will continue with the next parent of the most recently
encountered keymap that has another parent, etc.  Essentially, a
depth-first search of all the ancestors of the keymap is conducted.

@code{(current-global-map)} is the default parent of all keymaps.

@defun set-keymap-parents keymap parents
This function sets the parent keymaps of @var{keymap} to the list
@var{parents}.

If you change the bindings in one of the keymaps in @var{parents} using
@code{define-key} or other key-binding functions, these changes are
visible in @var{keymap} unless shadowed by bindings in that map or in
earlier-searched ancestors.  The converse is not true: if you use
@code{define-key} to change @var{keymap}, that affects the bindings in
that map, but has no effect on any of the keymaps in @var{parents}.
@end defun

@defun keymap-parents keymap
This function returns the list of parent keymaps of @var{keymap}, or
@code{nil} if @var{keymap} has no parents.
@end defun

@node Prefix Keys
@section Prefix Keys
@cindex prefix key

  A @dfn{prefix key} has an associated keymap which defines what to do
with key sequences that start with the prefix key.  For example,
@kbd{C-x} is a prefix key, and it uses a keymap which is also stored in
the variable @code{ctl-x-map}.  Here is a list of the standard prefix
keys of XEmacs and their keymaps:

@itemize @bullet
@item
@cindex @kbd{C-h}
@vindex help-map
@code{help-map} is used for events that follow @kbd{C-h}.

@item
@cindex @kbd{C-c}
@vindex mode-specific-map
@code{mode-specific-map} is for events that follow @kbd{C-c}.  This
map is not actually mode specific; its name was chosen to be informative
for the user in @kbd{C-h b} (@code{display-bindings}), where it
describes the main use of the @kbd{C-c} prefix key.

@item
@cindex @kbd{C-x}
@vindex ctl-x-map
@findex Control-X-prefix
@code{ctl-x-map} is the variable name for the map used for events
that follow @kbd{C-x}.  This map is also the function definition of
@code{Control-X-prefix}.

@item
@cindex @kbd{C-x 4}
@vindex ctl-x-4-map
@code{ctl-x-4-map} is used for events that follow @kbd{C-x 4}.

@c Emacs 19 feature
@item
@cindex @kbd{C-x 5}
@vindex ctl-x-5-map
@code{ctl-x-5-map} used is for events that follow @kbd{C-x 5}.

@c Emacs 19 feature
@item
@cindex @kbd{C-x n}
@cindex @kbd{C-x r}
@cindex @kbd{C-x a}
A nameless keymap is used for events that follow @kbd{C-x n}.
Others are used for events following @kbd{C-x r} and @kbd{C-x a}.

@item
@vindex esc-map
@findex ESC-prefix
@code{esc-map} is an evil hack that is present for compatibility
purposes with Emacs 18.  Defining a key in @code{esc-map} is equivalent
to defining the same key in @code{global-map} but with the @key{META}
prefix added.  You should @emph{not} use this in your code. (This map is
also the function definition of @code{ESC-prefix}.)
@end itemize

  The binding of a prefix key is the keymap to use for looking up the
events that follow 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 @kbd{C-x} is
the symbol @code{Control-X-prefix}, whose function definition is the
keymap for @kbd{C-x} commands.  (The same keymap is also the value of
@code{ctl-x-map}.)

  Prefix key definitions of this sort can appear in any active keymap.
The definitions of @kbd{C-c}, @kbd{C-x}, @kbd{C-h} and @key{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.  @xref{Active Keymaps}.

  If a key is defined as a prefix in more than one active map, then the
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 @kbd{C-p} a prefix key in the local
keymap, in such a way that @kbd{C-p} is identical to @kbd{C-x}.  Then
the binding for @kbd{C-p C-f} is the function @code{find-file}, just
like @kbd{C-x C-f}.  The key sequence @kbd{C-p 6} is not found in any
active keymap.

@example
@group
(use-local-map (make-sparse-keymap))
    @result{} nil
@end group
@group
(local-set-key "\C-p" ctl-x-map)
    @result{} nil
@end group
@group
(key-binding "\C-p\C-f")
    @result{} find-file
@end group

@group
(key-binding "\C-p6")
    @result{} nil
@end group
@end example

@defun define-prefix-command symbol &optional mapvar
@cindex prefix command
  This function defines @var{symbol} as a prefix command: it creates a
sparse keymap and stores it as @var{symbol}'s function definition.
Storing the symbol as the binding of a key makes the key a prefix key
which has a name.  If optional argument @var{mapvar} is not specified,
it also sets @var{symbol} as a variable, to have the keymap as its
value. (If @var{mapvar} is given and is not @code{t}, its value is
stored as the value of @var{symbol}.) The function returns @var{symbol}.

  In Emacs version 18, only the function definition of @var{symbol} was
set, not the value as a variable.
@end defun

@node Active Keymaps
@section Active Keymaps
@cindex active keymap
@cindex global keymap
@cindex local keymap

  XEmacs normally contains many keymaps; at any given time, just a few of
them are @dfn{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 @dfn{global keymap} holds the bindings of keys that are defined
regardless of the current buffer, such as @kbd{C-f}.  The variable
@code{global-map} holds this keymap, which is always active.

  Each buffer may have another keymap, its @dfn{local keymap}, which may
contain new or overriding definitions for keys.  At all times, the
current buffer's local keymap is active.  Text properties can specify an
alternative local map for certain parts of the buffer; see @ref{Special
Properties}.

  Each minor mode may have a keymap; if it does, the keymap is active
whenever the minor mode is enabled.

  All the active keymaps are used together to determine what command to
execute when a key is entered.  The key lookup proceeds as described
earlier (@pxref{Key Lookup}), but XEmacs @emph{first} searches for the
key in the minor mode maps (one map at a time); if they do not supply a
binding for the key, XEmacs searches the local map; if that too has no
binding, XEmacs then searches the global map.

@cindex major mode keymap
  Since every buffer that uses the same major mode normally uses the
very same local keymap, it may appear as if the keymap is local to the
mode.  A change to the local keymap of a buffer (using
@code{local-set-key}, for example) will be seen also in the other
buffers that share that keymap.

  The local keymaps that are used for Lisp mode, C mode, and several
other major modes exist even if they have not yet been used.  These
local maps are the values of the variables @code{lisp-mode-map},
@code{c-mode-map}, and so on.  For most other 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.  @xref{Minibuffers}.

  @xref{Standard Keymaps}, for a list of standard keymaps.

@defvar global-map
  This variable contains the default global keymap that maps XEmacs
keyboard input to commands.  Normally this keymap is the global keymap.
The default global keymap is a full keymap that binds
@code{self-insert-command} to all of the printing characters.
@end defvar

@defun current-global-map
  This function returns the current global keymap.  This is always the
same as the value of @code{global-map} unless you change one or the
other.

@example
@group
(current-global-map)
@result{} (keymap [set-mark-command beginning-of-line @dots{} 
            delete-backward-char])
@end group
@end example
@end defun

@defun current-local-map
  This function returns the current buffer's local keymap, or @code{nil}
if it has none.  In the following example, the keymap for the
@samp{*scratch*} buffer (using Lisp Interaction mode) is a sparse keymap
in which the entry for @key{ESC}, @sc{ASCII} code 27, is another sparse
keymap.

@example
@group
(current-local-map)
@result{} (keymap 
    (10 . eval-print-last-sexp) 
    (9 . lisp-indent-line) 
    (127 . backward-delete-char-untabify) 
@end group
@group
    (27 keymap 
        (24 . eval-defun) 
        (17 . indent-sexp)))
@end group
@end example
@end defun

@defun current-minor-mode-maps
This function returns a list of the keymaps of currently enabled minor modes.
@end defun

@defun use-global-map keymap
  This function makes @var{keymap} the new current global keymap.  It
returns @code{nil}.

  It is very unusual to change the global keymap.
@end defun

@defun use-local-map keymap
  This function makes @var{keymap} the new current local keymap of the
current buffer.  If @var{keymap} is @code{nil}, then there will be no
local keymap.  It returns @code{nil}.  Most major modes use this
function.
@end defun

@c Emacs 19 feature
@defvar minor-mode-map-alist
This variable is an alist describing keymaps that may or may not be
active according to the values of certain variables.  Its elements look
like this:

@example
(@var{variable} . @var{keymap})
@end example

The keymap @var{keymap} is active whenever @var{variable} has a
non-@code{nil} value.  Typically @var{variable} is the variable which
enables or disables a minor mode.  @xref{Keymaps and Minor Modes}.

When more than one minor mode keymap is active, their order of priority
is the order of @code{minor-mode-map-alist}.

See also @code{minor-mode-key-binding} in @ref{Functions for Key
Lookup}.
@end defvar

@node Key Lookup
@section Key Lookup
@cindex key lookup
@cindex keymap entry

  @dfn{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 types 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).  @xref{Events}.
Such a pseudo-key-sequence is insufficient for @code{command-execute},
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 @dfn{keymap entry} to describe the value directly
associated with an event type in a keymap.  While any Lisp object may be
stored as a keymap entry, not all make sense for key lookup.  Here is a
list of the meaningful kinds of keymap entries:

@table @asis
@item @code{nil}
@cindex @code{nil} in keymap
@code{nil} 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,
that is equivalent to an entry of @code{nil} for that type.

@item @var{keymap}
@cindex keymap in keymap
The events used so far in the lookup form a prefix key.  The next
event of the key sequence is looked up in @var{keymap}.

@item @var{command}
@cindex command in keymap
The events used so far in the lookup form a complete key,
and @var{command} is its binding.

@item @var{string}
@itemx @var{vector}
@cindex string in keymap
The events used so far in the lookup form a complete key, whose
binding is a keyboard macro.  See @ref{Keyboard Macros}, for more
information.

@item @var{list}
@cindex list in keymap
The meaning of a list depends on the types of the elements of the list.

@itemize @bullet
@item
If the @sc{car} of @var{list} is the symbol @code{keymap}, then the list
is a keymap, and is treated as a keymap (see above).

@item
@cindex @code{lambda} in keymap
If the @sc{car} of @var{list} is @code{lambda}, then the list is a
lambda expression.  This is presumed to be a command, and is treated as
such (see above).

@item
If the @sc{car} of @var{list} is a keymap and the @sc{cdr} is an event
type, then this is an @dfn{indirect entry}:

@example
(@var{othermap} . @var{othertype})
@end example

When key lookup encounters an indirect entry, it looks up instead the
binding of @var{othertype} in @var{othermap} and uses that.

This feature permits you to define one key as an alias for another key.
For example, an entry whose @sc{car} is the keymap called @code{esc-map}
and whose @sc{cdr} is 32 (the code for space) means, ``Use the global
binding of @kbd{Meta-@key{SPC}}, whatever that may be.''
@end itemize

@item @var{symbol}
@cindex symbol in keymap
The function definition of @var{symbol} is used in place of
@var{symbol}.  If that too is a symbol, then this process is repeated,
any number of times.  Ultimately this should lead to an object which is
a keymap, a command or a keyboard macro.  A list is allowed if it is a
keymap or a command, but indirect entries are not understood when found
via symbols.

Note that keymaps and keyboard macros (strings and vectors) are not
valid functions, so a symbol with a keymap, string or vector as its
function definition is also invalid as a function.  It is, however,
valid as a key binding.  If the definition is a keyboard macro, then the
symbol is also valid as an argument to @code{command-execute}
(@pxref{Interactive Call}).

@cindex @code{undefined} in keymap
@kindex invalid-function
The symbol @code{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 @code{undefined}; but that command does the same
thing that is done automatically for an undefined key: it rings the bell
(by calling @code{ding}) but does not signal an error.

@cindex preventing prefix key
@code{undefined} is used in local keymaps to override a global key
binding and make the key ``undefined'' locally.  A local binding of
@code{nil} would fail to do this because it would not override the
global binding.

@item @var{anything else}
If any other type of object is found, the events used so far in the
lookup form a complete key, and the object is its binding, but the
binding is not executable as a command.
@end table

  In short, a keymap entry may be a keymap, a command, a keyboard macro,
a symbol which leads to one of them, or an indirection or @code{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 @code{emacs-lisp-mode-map}.  Note that 9 is the code for @key{TAB},
127 for @key{DEL}, 27 for @key{ESC}, 17 for @kbd{C-q} and 24 for
@kbd{C-x}.

@example
@group
(keymap (9 . lisp-indent-line)
        (127 . backward-delete-char-untabify)
        (27 keymap (17 . indent-sexp) (24 . eval-defun)))
@end group
@end example

@node Functions for Key Lookup
@section Functions for Key Lookup

  Here are the functions and variables pertaining to key lookup.

@defun lookup-key keymap key &optional accept-defaults
This function returns the definition of @var{key} in @var{keymap}.  If
the string or vector @var{key} is not a valid key sequence according to
the prefix keys specified in @var{keymap} (which means it is ``too
long'' and has extra events at the end), then the value is a number, the
number of events at the front of @var{key} that compose a complete key.

@c Emacs 19 feature
If @var{accept-defaults} is non-@code{nil}, then @code{lookup-key}
considers default bindings as well as bindings for the specific events
in @var{key}.  Otherwise, @code{lookup-key} reports only bindings for
the specific sequence @var{key}, ignoring default bindings except when
an element of @var{key} is @code{t}.

All the other functions described in this chapter that look up keys use
@code{lookup-key}.

@example
@group
(lookup-key (current-global-map) "\C-x\C-f")
    @result{} find-file
@end group
@group
(lookup-key (current-global-map) "\C-x\C-f12345")
    @result{} 2
@end group
@end example

  If @var{key} contains a meta character, that character is implicitly
replaced by a two-character sequence: the value of
@code{meta-prefix-char}, followed by the corresponding non-meta
character.  Thus, the first example below is handled by conversion into
the second example.

@example
@group
(lookup-key (current-global-map) "\M-f")
    @result{} forward-word
@end group
@group
(lookup-key (current-global-map) "\ef")
    @result{} forward-word
@end group
@end example

  This function does not modify the specified events in ways that
discard information as @code{read-key-sequence} does (@pxref{Key
Sequence Input}).  In particular, it does not convert letters to lower
case and it does not change drag events to clicks.
@end defun

@deffn Command undefined
Used in keymaps to undefine keys.  It calls @code{ding}, but does
not cause an error.
@end deffn

@defun key-binding key &optional accept-defaults
This function returns the binding for @var{key} in the current
keymaps, trying all the active keymaps.  The result is @code{nil} if
@var{key} is undefined in the keymaps.

@c Emacs 19 feature
The argument @var{accept-defaults} controls checking for default
bindings, as in @code{lookup-key}.

An error is signaled if @var{key} is not a string or a vector.

@example
@group
(key-binding "\C-x\C-f")
    @result{} find-file
@end group
@end example
@end defun

@defun local-key-binding key &optional accept-defaults
This function returns the binding for @var{key} in the current
local keymap, or @code{nil} if it is undefined there.

@c Emacs 19 feature
The argument @var{accept-defaults} controls checking for default bindings,
as in @code{lookup-key} (above).
@end defun

@defun global-key-binding key &optional accept-defaults
This function returns the binding for command @var{key} in the
current global keymap, or @code{nil} if it is undefined there.

@c Emacs 19 feature
The argument @var{accept-defaults} controls checking for default bindings,
as in @code{lookup-key} (above).
@end defun

@c Emacs 19 feature
@defun minor-mode-key-binding key &optional accept-defaults
This function returns a list of all the active minor mode bindings of
@var{key}.  More precisely, it returns an alist of pairs
@code{(@var{modename} . @var{binding})}, where @var{modename} is the the
variable which enables the minor mode, and @var{binding} is @var{key}'s
binding in that mode.  If @var{key} has no minor-mode bindings, the
value is @code{nil}.

If the first binding is a non-prefix, 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 @var{accept-defaults} controls checking for default
bindings, as in @code{lookup-key} (above).
@end defun

@defvar meta-prefix-char
@cindex @key{ESC}
This variable is the meta-prefix character code.  It is used when
translating a meta character to a two-character sequence so it can be
looked up in a keymap.  For useful results, the value should be a prefix
event (@pxref{Prefix Keys}).  The default value is 27, which is the
@sc{ASCII} code for @key{ESC}.

As long as the value of @code{meta-prefix-char} remains 27, key
lookup translates @kbd{M-b} into @kbd{@key{ESC} b}, which is normally
defined as the @code{backward-word} command.  However, if you set
@code{meta-prefix-char} to 24, the code for @kbd{C-x}, then XEmacs will
translate @kbd{M-b} into @kbd{C-x b}, whose standard binding is the
@code{switch-to-buffer} command.

@smallexample
@group
meta-prefix-char                    ; @r{The default value.}
     @result{} 27
@end group
@group
(key-binding "\M-b")
     @result{} backward-word
@end group
@group
?\C-x                               ; @r{The print representation}
     @result{} 24                          ;   @r{of a character.}
@end group
@group
(setq meta-prefix-char 24)
     @result{} 24      
@end group
@group
(key-binding "\M-b")
     @result{} switch-to-buffer            ; @r{Now, typing @kbd{M-b} is}
                                    ;   @r{like typing @kbd{C-x b}.}

(setq meta-prefix-char 27)          ; @r{Avoid confusion!}
     @result{} 27                          ; @r{Restore the default value!}
@end group
@end smallexample
@end defvar

@node Changing Key Bindings
@section Changing Key Bindings
@cindex changing key bindings
@cindex rebinding

  The way to rebind a key is to change its entry in a keymap.  You can
change the global keymap, so that the change is effective in all buffers
(except those that override the global binding with a local one).  Or
you can change the current buffer's local map, which usually affects all
buffers using the same major mode.  The @code{global-set-key} and
@code{local-set-key} functions are convenient interfaces for these
operations.  Or you can use @code{define-key} and specify explicitly
which map to change.

  People often use @code{global-set-key} in their @file{.emacs} file for
simple customization.  For example,

@smallexample
(global-set-key "\C-x\C-\\" 'next-line)
@end smallexample

@noindent
or

@smallexample
(global-set-key [?\C-x ?\C-\\] 'next-line)
@end smallexample

@noindent
redefines @kbd{C-x C-\} to move down a line.

@smallexample
(global-set-key [M-mouse-1] 'mouse-set-point)
@end smallexample

@noindent
redefines the first (leftmost) mouse button, typed with the Meta key, to
set point where you click.

@cindex meta character key constants
@cindex control character key constants
  In writing the key sequence to rebind, it is useful to use the special
escape sequences for control and meta characters (@pxref{String Type}).
The syntax @samp{\C-} means that the following character is a control
character and @samp{\M-} means that the following character is a meta
character.  Thus, the string @code{"\M-x"} is read as containing a
single @kbd{M-x}, @code{"\C-f"} is read as containing a single
@kbd{C-f}, and @code{"\M-\C-x"} and @code{"\C-\M-x"} are both read as
containing a single @kbd{C-M-x}.

  For the functions below, an error is signaled if @var{keymap} is not a
keymap or if @var{key} is not a string or vector representing a key
sequence.  However, you can use event types (symbols) as shorthand for
events that are lists.

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

@cindex invalid prefix key error
@cindex key sequence error
  Every prefix of @var{key} must be a prefix key (i.e., bound to a
keymap) or undefined; otherwise an error is signaled.

If some prefix of @var{key} is undefined, then @code{define-key} defines
it as a prefix key so that the rest of @var{key} may be defined as
specified.

   The following example creates a sparse keymap and makes a number of
bindings:

@smallexample
@group
(setq map (make-sparse-keymap))
    @result{} (keymap)
@end group
@group
(define-key map "\C-f" 'forward-char)
    @result{} forward-char
@end group
@group
map
    @result{} (keymap (6 . forward-char))
@end group

@group
;; @r{Build sparse submap for @kbd{C-x} and bind @kbd{f} in that.}
(define-key map "\C-xf" 'forward-word)
    @result{} forward-word
@end group
@group
map
@result{} (keymap 
    (24 keymap                ; @kbd{C-x}
        (102 . forward-word)) ;      @kbd{f}
    (6 . forward-char))       ; @kbd{C-f}
@end group

@group
;; @r{Bind @kbd{C-p} to the @code{ctl-x-map}.}
(define-key map "\C-p" ctl-x-map)
;; @code{ctl-x-map}
@result{} [nil @dots{} find-file @dots{} backward-kill-sentence] 
@end group

@group
;; @r{Bind @kbd{C-f} to @code{foo} in the @code{ctl-x-map}.}
(define-key map "\C-p\C-f" 'foo)
@result{} 'foo
@end group
@group
map
@result{} (keymap     ; @r{Note @code{foo} in @code{ctl-x-map}.}
    (16 keymap [nil @dots{} foo @dots{} backward-kill-sentence])
    (24 keymap 
        (102 . forward-word))
    (6 . forward-char))
@end group
@end smallexample

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

@defun substitute-key-definition olddef newdef keymap &optional oldmap
@cindex replace bindings
This function replaces @var{olddef} with @var{newdef} for any keys in
@var{keymap} that were bound to @var{olddef}.  In other words,
@var{olddef} is replaced with @var{newdef} wherever it appears.  The
function returns @code{nil}.

For example, this redefines @kbd{C-x C-f}, if you do it in an XEmacs with
standard bindings:

@smallexample
@group
(substitute-key-definition 
 'find-file 'find-file-read-only (current-global-map))
@end group
@end smallexample

@c Emacs 19 feature
If @var{oldmap} is non-@code{nil}, then its bindings determine which
keys to rebind.  The rebindings still happen in @var{newmap}, not in
@var{oldmap}.  Thus, you can change one map under the control of the
bindings in another.  For example,

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

@noindent
puts the special deletion command in @code{my-map} for whichever keys
are globally bound to the standard deletion command.

@ignore
@c Emacs 18 only
Prefix keymaps that appear within @var{keymap} are not checked
recursively for keys bound to @var{olddef}; they are not changed at all.
Perhaps it would be better to check nested keymaps recursively.
@end ignore

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

@smallexample
@group
(setq map '(keymap 
            (?1 . olddef-1) 
            (?2 . olddef-2) 
            (?3 . olddef-1)))
@result{} (keymap (49 . olddef-1) (50 . olddef-2) (51 . olddef-1))
@end group

@group
(substitute-key-definition 'olddef-1 'newdef map)
@result{} nil
@end group
@group
map
@result{} (keymap (49 . newdef) (50 . olddef-2) (51 . newdef))
@end group
@end smallexample
@end defun

@defun suppress-keymap keymap &optional nodigits
@cindex @code{self-insert-command} override
  This function changes the contents of the full keymap @var{keymap} by
replacing the self-insertion commands for numbers with the
@code{digit-argument} function, unless @var{nodigits} is non-@code{nil},
and by replacing the functions for the rest of the printing characters
with @code{undefined}.  This means that ordinary insertion of text is
impossible in a buffer with a local keymap on which
@code{suppress-keymap} has been called.

  @code{suppress-keymap} returns @code{nil}.

@cindex yank suppression 
@cindex @code{quoted-insert} suppression 
The @code{suppress-keymap} function does not make it impossible to
modify a buffer, as it does not suppress commands such as @code{yank}
and @code{quoted-insert}.  To prevent any modification of a buffer, make
it read-only (@pxref{Read Only Buffers}).

  Since this function modifies @var{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 @code{global-map} would make it impossible to use
most of XEmacs.

  Most often, @code{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 @file{emacs/lisp/dired.el}, showing how the local keymap for
Dired mode is set up:

@smallexample
@group
  @dots{}
  (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)
  @dots{}
@end group
@end smallexample
@end defun

@node Key Binding Commands
@section Commands for Binding Keys

  This section describes some convenient interactive interfaces for
changing key bindings.  They work by calling @code{define-key}.

@deffn Command global-set-key key definition
  This function sets the binding of @var{key} in the current global map
to @var{definition}.

@smallexample
@group
(global-set-key @var{key} @var{definition})
@equiv{}
(define-key (current-global-map) @var{key} @var{definition})
@end group
@end smallexample
@end deffn

@deffn Command global-unset-key key
@cindex unbinding keys
  This function removes the binding of @var{key} from the current
global map.

One use of this function is in preparation for defining a longer key
which uses it implicitly as a prefix---which would not be allowed if
@var{key} has a non-prefix binding.  For example:

@smallexample
@group
(global-unset-key "\C-l")
    @result{} nil
@end group
@group
(global-set-key "\C-l\C-l" 'redraw-display)
    @result{} nil
@end group
@end smallexample

This function is implemented simply using @code{define-key}:

@smallexample
@group
(global-unset-key @var{key})
@equiv{}
(define-key (current-global-map) @var{key} nil)
@end group
@end smallexample
@end deffn

@deffn Command local-set-key key definition
  This function sets the binding of @var{key} in the current local
keymap to @var{definition}.

@smallexample
@group
(local-set-key @var{key} @var{definition})
@equiv{}
(define-key (current-local-map) @var{key} @var{definition})
@end group
@end smallexample
@end deffn

@deffn Command local-unset-key key
  This function removes the binding of @var{key} from the current
local map.

@smallexample
@group
(local-unset-key @var{key})
@equiv{}
(define-key (current-local-map) @var{key} nil)
@end group
@end smallexample
@end deffn

@node Scanning Keymaps
@section Scanning Keymaps

  This section describes functions used to scan all the current keymaps
for the sake of printing help information.

@defun accessible-keymaps keymap &optional prefix
This function returns a list of all the keymaps that can be accessed
(via prefix keys) from @var{keymap}.  The value is an association list
with elements of the form @code{(@var{key} .@: @var{map})}, where
@var{key} is a prefix key whose definition in @var{keymap} is
@var{map}.

The elements of the alist are ordered so that the @var{key} increases
in length.  The first element is always @code{("" .@: @var{keymap})},
because the specified keymap is accessible from itself with a prefix of
no events.

If @var{prefix} is given, it should be a prefix key sequence; then
@code{accessible-keymaps} includes only the submaps whose prefixes start
with @var{prefix}.  These elements look just as they do in the value of
@code{(accessible-keymaps)}; the only difference is that some elements
are omitted.

In the example below, the returned alist indicates that the key
@key{ESC}, which is displayed as @samp{^[}, is a prefix key whose
definition is the sparse keymap @code{(keymap (83 .@: center-paragraph)
(115 .@: foo))}.

@smallexample
@group
(accessible-keymaps (current-local-map))
@result{}(("" keymap 
      (27 keymap   ; @r{Note this keymap for @key{ESC} is repeated below.}
          (83 . center-paragraph)
          (115 . center-line))
      (9 . tab-to-tab-stop))
@end group

@group
   ("^[" keymap 
    (83 . center-paragraph) 
    (115 . foo)))
@end group
@end smallexample

@ignore
In the following example, @kbd{C-h} is a prefix key that uses a sparse
keymap starting with @code{(keymap (118 . describe-variable)@dots{})}.
Another prefix, @kbd{C-x 4}, uses a keymap which happens to be
@code{ctl-x-4-map}.  The event @code{mode-line} is one of several dummy
events used as prefixes for mouse actions in special parts of a window.

@smallexample
@group
(accessible-keymaps (current-global-map))
@result{} (("" keymap [set-mark-command beginning-of-line @dots{} 
                   delete-backward-char])
@end group
@group
    ("^H" keymap (118 . describe-variable) @dots{}
     (8 . help-for-help))
@end group
@group
    ("^X" keymap [x-flush-mouse-queue @dots{}
     backward-kill-sentence])
@end group
@group
    ("^[" keymap [mark-sexp backward-sexp @dots{}
     backward-kill-word])
@end group
    ("^X4" keymap (15 . display-buffer) @dots{})
@group
    ([mode-line] keymap
     (S-mouse-2 . mouse-split-window-horizontally) @dots{}))
@end group
@end smallexample
@end ignore

@noindent
These are not all the keymaps you would see in an actual case.
@end defun

@defun where-is-internal command &optional keymap firstonly
  This function returns a list of key sequences (of any length) that are
bound to @var{command} in @var{keymap} and the global keymap.  The
argument @var{command} can be any object; it is compared with all keymap
entries using @code{eq}.  If @var{keymap} is not supplied, then the
global map alone is used.

  If @var{firstonly} is non-@code{nil}, then the value is a single
string representing the first key sequence found, rather than a list of
all possible key sequences.

  This function is used by @code{where-is} (@pxref{Help, , Help, emacs,
The XEmacs Reference Manual}).

@smallexample
@group
(where-is-internal 'describe-function)
    @result{} ("\^hf" "\^hd")
@end group
@end smallexample
@end defun

@deffn Command describe-bindings prefix
This function creates a listing of all defined keys, and their
definitions.  The listing is put in a buffer named @samp{*Help*}, which
is then displayed in a window.

A meta character is shown as @key{ESC} followed by the corresponding
non-meta character.  Control characters are indicated with @kbd{C-}.

When several characters with consecutive @sc{ASCII} codes have the
same definition, they are shown together, as
@samp{@var{firstchar}..@var{lastchar}}.  In this instance, you need to
know the @sc{ASCII} codes to understand which characters this means.
For example, in the default global map, the characters @samp{@key{SPC}
..@: ~} are described by a single line.  @key{SPC} is @sc{ASCII} 32,
@kbd{~} is @sc{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 @code{self-insert-command}.

If @var{prefix} is non-@code{nil}, it should be a prefix key; then only
keys that start with @var{prefix} are described.
@end deffn
