This is Info file ../../info/lispref.info, produced by Makeinfo-1.63
from the input file lispref.texi.

   Edition History:

   GNU Emacs Lisp Reference Manual Second Edition (v2.01), May 1993 GNU
Emacs Lisp Reference Manual Further Revised (v2.02), August 1993 Lucid
Emacs Lisp Reference Manual (for 19.10) First Edition, March 1994
XEmacs Lisp Programmer's Manual (for 19.12) Second Edition, April 1995
GNU Emacs Lisp Reference Manual v2.4, June 1995 XEmacs Lisp
Programmer's Manual (for 19.13) Third Edition, July 1995 XEmacs Lisp
Reference Manual (for 19.14 and 20.0) v3.1, March 1996

   Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995 Free Software
Foundation, Inc.  Copyright (C) 1994, 1995 Sun Microsystems, Inc.
Copyright (C) 1995, 1996 Ben Wing.

   Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
preserved on all copies.

   Permission is granted to copy and distribute modified versions of
this manual under the conditions for verbatim copying, provided that the
entire resulting derived work is distributed under the terms of a
permission notice identical to this one.

   Permission is granted to copy and distribute translations of this
manual into another language, under the above conditions for modified
versions, except that this permission notice may be stated in a
translation approved by the Foundation.

   Permission is granted to copy and distribute modified versions of
this manual under the conditions for verbatim copying, provided also
that the section entitled "GNU General Public License" is included
exactly as in the original, and provided that the entire resulting
derived work is distributed under the terms of a permission notice
identical to this one.

   Permission is granted to copy and distribute translations of this
manual into another language, under the above conditions for modified
versions, except that the section entitled "GNU General Public License"
may be included in a translation approved by the Free Software
Foundation instead of in the original English.


File: lispref.info,  Node: Peeking and Discarding,  Prev: Quoted Character Input,  Up: Reading Input

Miscellaneous Event Input Features
----------------------------------

   This section describes how to "peek ahead" at events without using
them up, how to check for pending input, and how to discard pending
input.

   See also the variables `last-command-event' and `last-command-char'
(*Note Command Loop Info::).

 - Variable: unread-command-events
     This variable holds a list of events waiting to be read as command
     input.  The events are used in the order they appear in the list,
     and removed one by one as they are used.

     The variable is needed because in some cases a function reads a
     event and then decides not to use it.  Storing the event in this
     variable causes it to be processed normally, by the command loop
     or by the functions to read command input.

     For example, the function that implements numeric prefix arguments
     reads any number of digits.  When it finds a non-digit event, it
     must unread the event so that it can be read normally by the
     command loop.  Likewise, incremental search uses this feature to
     unread events with no special meaning in a search, because these
     events should exit the search and then execute normally.


 - Variable: unread-command-event
     This variable holds a single event to be read as command input.

     This variable is mostly obsolete now that you can use
     `unread-command-events' instead; it exists only to support programs
     written for versions of XEmacs prior to 19.12.

 - Function: input-pending-p
     This function determines whether any command input is currently
     available to be read.  It returns immediately, with value `t' if
     there is available input, `nil' otherwise.  On rare occasions it
     may return `t' when no input is available.

 - Variable: last-input-event
     This variable is set to the last keyboard or mouse button event
     received.

     This variable is off limits: you may not set its value or modify
     the event that is its value, as it is destructively modified by
     `read-key-sequence'.  If you want to keep a pointer to this value,
     you must use `copy-event'.

     Note that this variable is an alias for `last-input-char' in FSF
     Emacs.

     In the example below, a character is read (the character `1').  It
     becomes the value of `last-input-event', while `C-e' (from the
     `C-x C-e' command used to evaluate this expression) remains the
     value of `last-command-event'.

          (progn (print (next-command-event))
                 (print last-command-event)
                 last-input-event)
               -| #<keypress-event 1>
               -| #<keypress-event control-E>
               => #<keypress-event 1>

 - Variable: last-input-char
     If the value of `last-input-event' is a keyboard event, then this
     is the nearest ASCII equivalent to it.  Remember that there is
     *not* a 1:1 mapping between keyboard events and ASCII characters:
     the set of keyboard events is much larger, so writing code that
     examines this variable to determine what key has been typed is bad
     practice, unless you are certain that it will be one of a small
     set of characters.

     This function exists for compatibility with Emacs version 18.

 - Function: discard-input
     This function discards the contents of the terminal input buffer
     and cancels any keyboard macro that might be in the process of
     definition.  It returns `nil'.

     In the following example, the user may type a number of characters
     right after starting the evaluation of the form.  After the
     `sleep-for' finishes sleeping, `discard-input' discards any
     characters typed during the sleep.

          (progn (sleep-for 2)
                 (discard-input))
               => nil


File: lispref.info,  Node: Waiting,  Next: Quitting,  Prev: Reading Input,  Up: Command Loop

Waiting for Elapsed Time or Input
=================================

   The wait functions are designed to wait for a certain amount of time
to pass or until there is input.  For example, you may wish to pause in
the middle of a computation to allow the user time to view the display.
`sit-for' pauses and updates the screen, and returns immediately if
input comes in, while `sleep-for' pauses without updating the screen.

   Note that in FSF Emacs, the commands `sit-for' and `sleep-for' take
two arguments to specify the time (one integer and one float value),
instead of a single argument that can be either an integer or a float.

 - Function: sit-for SECONDS &optional NODISP
     This function performs redisplay (provided there is no pending
     input from the user), then waits SECONDS seconds, or until input is
     available.  The result is `t' if `sit-for' waited the full time
     with no input arriving (see `input-pending-p' in *Note Peeking and
     Discarding::).  Otherwise, the value is `nil'.

     The argument SECONDS need not be an integer.  If it is a floating
     point number, `sit-for' waits for a fractional number of seconds.

     Redisplay is normally preempted if input arrives, and does not
     happen at all if input is available before it starts. (You can
     force screen updating in such a case by using `force-redisplay'.
     *Note Refresh Screen::.) If there is no input pending, you can
     force an update with no delay by using `(sit-for 0)'.

     If NODISP is non-`nil', then `sit-for' does not redisplay, but it
     still returns as soon as input is available (or when the timeout
     elapses).

     The usual purpose of `sit-for' is to give the user time to read
     text that you display.

 - Function: sleep-for SECONDS
     This function simply pauses for SECONDS seconds without updating
     the display.  This function pays no attention to available input.
     It returns `nil'.

     The argument SECONDS need not be an integer.  If it is a floating
     point number, `sleep-for' waits for a fractional number of seconds.

     Use `sleep-for' when you wish to guarantee a delay.

   *Note Time of Day::, for functions to get the current time.


File: lispref.info,  Node: Quitting,  Next: Prefix Command Arguments,  Prev: Waiting,  Up: Command Loop

Quitting
========

   Typing `C-g' while a Lisp function is running causes XEmacs to
"quit" whatever it is doing.  This means that control returns to the
innermost active command loop.

   Typing `C-g' while the command loop is waiting for keyboard input
does not cause a quit; it acts as an ordinary input character.  In the
simplest case, you cannot tell the difference, because `C-g' normally
runs the command `keyboard-quit', whose effect is to quit.  However,
when `C-g' follows a prefix key, the result is an undefined key.  The
effect is to cancel the prefix key as well as any prefix argument.

   In the minibuffer, `C-g' has a different definition: it aborts out
of the minibuffer.  This means, in effect, that it exits the minibuffer
and then quits.  (Simply quitting would return to the command loop
*within* the minibuffer.)  The reason why `C-g' does not quit directly
when the command reader is reading input is so that its meaning can be
redefined in the minibuffer in this way.  `C-g' following a prefix key
is not redefined in the minibuffer, and it has its normal effect of
canceling the prefix key and prefix argument.  This too would not be
possible if `C-g' always quit directly.

   When `C-g' does directly quit, it does so by setting the variable
`quit-flag' to `t'.  XEmacs checks this variable at appropriate times
and quits if it is not `nil'.  Setting `quit-flag' non-`nil' in any way
thus causes a quit.

   At the level of C code, quitting cannot happen just anywhere; only
at the special places that check `quit-flag'.  The reason for this is
that quitting at other places might leave an inconsistency in XEmacs's
internal state.  Because quitting is delayed until a safe place,
quitting cannot make XEmacs crash.

   Certain functions such as `read-key-sequence' or `read-quoted-char'
prevent quitting entirely even though they wait for input.  Instead of
quitting, `C-g' serves as the requested input.  In the case of
`read-key-sequence', this serves to bring about the special behavior of
`C-g' in the command loop.  In the case of `read-quoted-char', this is
so that `C-q' can be used to quote a `C-g'.

   You can prevent quitting for a portion of a Lisp function by binding
the variable `inhibit-quit' to a non-`nil' value.  Then, although `C-g'
still sets `quit-flag' to `t' as usual, the usual result of this--a
quit--is prevented.  Eventually, `inhibit-quit' will become `nil'
again, such as when its binding is unwound at the end of a `let' form.
At that time, if `quit-flag' is still non-`nil', the requested quit
happens immediately.  This behavior is ideal when you wish to make sure
that quitting does not happen within a "critical section" of the
program.

   In some functions (such as `read-quoted-char'), `C-g' is handled in
a special way that does not involve quitting.  This is done by reading
the input with `inhibit-quit' bound to `t', and setting `quit-flag' to
`nil' before `inhibit-quit' becomes `nil' again.  This excerpt from the
definition of `read-quoted-char' shows how this is done; it also shows
that normal quitting is permitted after the first character of input.

     (defun read-quoted-char (&optional prompt)
       "...DOCUMENTATION..."
       (let ((count 0) (code 0) char)
         (while (< count 3)
           (let ((inhibit-quit (zerop count))
                 (help-form nil))
             (and prompt (message "%s-" prompt))
             (setq char (read-char))
             (if inhibit-quit (setq quit-flag nil)))
           ...)
         (logand 255 code)))

 - Variable: quit-flag
     If this variable is non-`nil', then XEmacs quits immediately,
     unless `inhibit-quit' is non-`nil'.  Typing `C-g' ordinarily sets
     `quit-flag' non-`nil', regardless of `inhibit-quit'.

 - Variable: inhibit-quit
     This variable determines whether XEmacs should quit when
     `quit-flag' is set to a value other than `nil'.  If `inhibit-quit'
     is non-`nil', then `quit-flag' has no special effect.

 - Command: keyboard-quit
     This function signals the `quit' condition with `(signal 'quit
     nil)'.  This is the same thing that quitting does.  (See `signal'
     in *Note Errors::.)

   You can specify a character other than `C-g' to use for quitting.
See the function `set-input-mode' in *Note Terminal Input::.


File: lispref.info,  Node: Prefix Command Arguments,  Next: Recursive Editing,  Prev: Quitting,  Up: Command Loop

Prefix Command Arguments
========================

   Most XEmacs commands can use a "prefix argument", a number specified
before the command itself.  (Don't confuse prefix arguments with prefix
keys.)  The prefix argument is at all times represented by a value,
which may be `nil', meaning there is currently no prefix argument.
Each command may use the prefix argument or ignore it.

   There are two representations of the prefix argument: "raw" and
"numeric".  The editor command loop uses the raw representation
internally, and so do the Lisp variables that store the information, but
commands can request either representation.

   Here are the possible values of a raw prefix argument:

   * `nil', meaning there is no prefix argument.  Its numeric value is
     1, but numerous commands make a distinction between `nil' and the
     integer 1.

   * An integer, which stands for itself.

   * A list of one element, which is an integer.  This form of prefix
     argument results from one or a succession of `C-u''s with no
     digits.  The numeric value is the integer in the list, but some
     commands make a distinction between such a list and an integer
     alone.

   * The symbol `-'.  This indicates that `M--' or `C-u -' was typed,
     without following digits.  The equivalent numeric value is -1, but
     some commands make a distinction between the integer -1 and the
     symbol `-'.

   We illustrate these possibilities by calling the following function
with various prefixes:

     (defun display-prefix (arg)
       "Display the value of the raw prefix arg."
       (interactive "P")
       (message "%s" arg))

Here are the results of calling `display-prefix' with various raw
prefix arguments:

             M-x display-prefix  -| nil
     
     C-u     M-x display-prefix  -| (4)
     
     C-u C-u M-x display-prefix  -| (16)
     
     C-u 3   M-x display-prefix  -| 3
     
     M-3     M-x display-prefix  -| 3      ; (Same as `C-u 3'.)
     
     C-3     M-x display-prefix  -| 3      ; (Same as `C-u 3'.)
     
     C-u -   M-x display-prefix  -| -
     
     M--     M-x display-prefix  -| -      ; (Same as `C-u -'.)
     
     C--     M-x display-prefix  -| -      ; (Same as `C-u -'.)
     
     C-u - 7 M-x display-prefix  -| -7
     
     M-- 7   M-x display-prefix  -| -7     ; (Same as `C-u -7'.)
     
     C-- 7   M-x display-prefix  -| -7     ; (Same as `C-u -7'.)

   XEmacs uses two variables to store the prefix argument: `prefix-arg'
and `current-prefix-arg'.  Commands such as `universal-argument' that
set up prefix arguments for other commands store them in `prefix-arg'.
In contrast, `current-prefix-arg' conveys the prefix argument to the
current command, so setting it has no effect on the prefix arguments
for future commands.

   Normally, commands specify which representation to use for the prefix
argument, either numeric or raw, in the `interactive' declaration.
(*Note Using Interactive::.)  Alternatively, functions may look at the
value of the prefix argument directly in the variable
`current-prefix-arg', but this is less clean.

 - Function: prefix-numeric-value ARG
     This function returns the numeric meaning of a valid raw prefix
     argument value, ARG.  The argument may be a symbol, a number, or a
     list.  If it is `nil', the value 1 is returned; if it is `-', the
     value -1 is returned; if it is a number, that number is returned;
     if it is a list, the CAR of that list (which should be a number) is
     returned.

 - Variable: current-prefix-arg
     This variable holds the raw prefix argument for the *current*
     command.  Commands may examine it directly, but the usual way to
     access it is with `(interactive "P")'.

 - Variable: prefix-arg
     The value of this variable is the raw prefix argument for the
     *next* editing command.  Commands that specify prefix arguments for
     the following command work by setting this variable.

   Do not call the functions `universal-argument', `digit-argument', or
`negative-argument' unless you intend to let the user enter the prefix
argument for the *next* command.

 - Command: universal-argument
     This command reads input and specifies a prefix argument for the
     following command.  Don't call this command yourself unless you
     know what you are doing.

 - Command: digit-argument ARG
     This command adds to the prefix argument for the following
     command.  The argument ARG is the raw prefix argument as it was
     before this command; it is used to compute the updated prefix
     argument.  Don't call this command yourself unless you know what
     you are doing.

 - Command: negative-argument ARG
     This command adds to the numeric argument for the next command.
     The argument ARG is the raw prefix argument as it was before this
     command; its value is negated to form the new prefix argument.
     Don't call this command yourself unless you know what you are
     doing.


File: lispref.info,  Node: Recursive Editing,  Next: Disabling Commands,  Prev: Prefix Command Arguments,  Up: Command Loop

Recursive Editing
=================

   The XEmacs command loop is entered automatically when XEmacs starts
up.  This top-level invocation of the command loop never exits; it keeps
running as long as XEmacs does.  Lisp programs can also invoke the
command loop.  Since this makes more than one activation of the command
loop, we call it "recursive editing".  A recursive editing level has
the effect of suspending whatever command invoked it and permitting the
user to do arbitrary editing before resuming that command.

   The commands available during recursive editing are the same ones
available in the top-level editing loop and defined in the keymaps.
Only a few special commands exit the recursive editing level; the others
return to the recursive editing level when they finish.  (The special
commands for exiting are always available, but they do nothing when
recursive editing is not in progress.)

   All command loops, including recursive ones, set up all-purpose error
handlers so that an error in a command run from the command loop will
not exit the loop.

   Minibuffer input is a special kind of recursive editing.  It has a
few special wrinkles, such as enabling display of the minibuffer and the
minibuffer window, but fewer than you might suppose.  Certain keys
behave differently in the minibuffer, but that is only because of the
minibuffer's local map; if you switch windows, you get the usual XEmacs
commands.

   To invoke a recursive editing level, call the function
`recursive-edit'.  This function contains the command loop; it also
contains a call to `catch' with tag `exit', which makes it possible to
exit the recursive editing level by throwing to `exit' (*note Catch and
Throw::.).  If you throw a value other than `t', then `recursive-edit'
returns normally to the function that called it.  The command `C-M-c'
(`exit-recursive-edit') does this.  Throwing a `t' value causes
`recursive-edit' to quit, so that control returns to the command loop
one level up.  This is called "aborting", and is done by `C-]'
(`abort-recursive-edit').

   Most applications should not use recursive editing, except as part of
using the minibuffer.  Usually it is more convenient for the user if you
change the major mode of the current buffer temporarily to a special
major mode, which should have a command to go back to the previous mode.
(The `e' command in Rmail uses this technique.)  Or, if you wish to
give the user different text to edit "recursively", create and select a
new buffer in a special mode.  In this mode, define a command to
complete the processing and go back to the previous buffer.  (The `m'
command in Rmail does this.)

   Recursive edits are useful in debugging.  You can insert a call to
`debug' into a function definition as a sort of breakpoint, so that you
can look around when the function gets there.  `debug' invokes a
recursive edit but also provides the other features of the debugger.

   Recursive editing levels are also used when you type `C-r' in
`query-replace' or use `C-x q' (`kbd-macro-query').

 - Function: recursive-edit
     This function invokes the editor command loop.  It is called
     automatically by the initialization of XEmacs, to let the user
     begin editing.  When called from a Lisp program, it enters a
     recursive editing level.

     In the following example, the function `simple-rec' first advances
     point one word, then enters a recursive edit, printing out a
     message in the echo area.  The user can then do any editing
     desired, and then type `C-M-c' to exit and continue executing
     `simple-rec'.

          (defun simple-rec ()
            (forward-word 1)
            (message "Recursive edit in progress")
            (recursive-edit)
            (forward-word 1))
               => simple-rec
          (simple-rec)
               => nil

 - Command: exit-recursive-edit
     This function exits from the innermost recursive edit (including
     minibuffer input).  Its definition is effectively `(throw 'exit
     nil)'.

 - Command: abort-recursive-edit
     This function aborts the command that requested the innermost
     recursive edit (including minibuffer input), by signaling `quit'
     after exiting the recursive edit.  Its definition is effectively
     `(throw 'exit t)'.  *Note Quitting::.

 - Command: top-level
     This function exits all recursive editing levels; it does not
     return a value, as it jumps completely out of any computation
     directly back to the main command loop.

 - Function: recursion-depth
     This function returns the current depth of recursive edits.  When
     no recursive edit is active, it returns 0.


File: lispref.info,  Node: Disabling Commands,  Next: Command History,  Prev: Recursive Editing,  Up: Command Loop

Disabling Commands
==================

   "Disabling a command" marks the command as requiring user
confirmation before it can be executed.  Disabling is used for commands
which might be confusing to beginning users, to prevent them from using
the commands by accident.

   The low-level mechanism for disabling a command is to put a
non-`nil' `disabled' property on the Lisp symbol for the command.
These properties are normally set up by the user's `.emacs' file with
Lisp expressions such as this:

     (put 'upcase-region 'disabled t)

For a few commands, these properties are present by default and may be
removed by the `.emacs' file.

   If the value of the `disabled' property is a string, the message
saying the command is disabled includes that string.  For example:

     (put 'delete-region 'disabled
          "Text deleted this way cannot be yanked back!\n")

   *Note Disabling: (emacs)Disabling, for the details on what happens
when a disabled command is invoked interactively.  Disabling a command
has no effect on calling it as a function from Lisp programs.

 - Command: enable-command COMMAND
     Allow COMMAND to be executed without special confirmation from now
     on, and (if the user confirms) alter the user's `.emacs' file so
     that this will apply to future sessions.

 - Command: disable-command COMMAND
     Require special confirmation to execute COMMAND from now on, and
     (if the user confirms) alter the user's `.emacs' file so that this
     will apply to future sessions.

 - Variable: disabled-command-hook
     This normal hook is run instead of a disabled command, when the
     user invokes the disabled command interactively.  The hook
     functions can use `this-command-keys' to determine what the user
     typed to run the command, and thus find the command itself.  *Note
     Hooks::.

     By default, `disabled-command-hook' contains a function that asks
     the user whether to proceed.


File: lispref.info,  Node: Command History,  Next: Keyboard Macros,  Prev: Disabling Commands,  Up: Command Loop

Command History
===============

   The command loop keeps a history of the complex commands that have
been executed, to make it convenient to repeat these commands.  A
"complex command" is one for which the interactive argument reading
uses the minibuffer.  This includes any `M-x' command, any `M-:'
command, and any command whose `interactive' specification reads an
argument from the minibuffer.  Explicit use of the minibuffer during
the execution of the command itself does not cause the command to be
considered complex.

 - Variable: command-history
     This variable's value is a list of recent complex commands, each
     represented as a form to evaluate.  It continues to accumulate all
     complex commands for the duration of the editing session, but all
     but the first (most recent) thirty elements are deleted when a
     garbage collection takes place (*note Garbage Collection::.).

          command-history
          => ((switch-to-buffer "chistory.texi")
              (describe-key "^X^[")
              (visit-tags-table "~/emacs/src/")
              (find-tag "repeat-complex-command"))

   This history list is actually a special case of minibuffer history
(*note Minibuffer History::.), with one special twist: the elements are
expressions rather than strings.

   There are a number of commands devoted to the editing and recall of
previous commands.  The commands `repeat-complex-command', and
`list-command-history' are described in the user manual (*note
Repetition: (emacs)Repetition.).  Within the minibuffer, the history
commands used are the same ones available in any minibuffer.


File: lispref.info,  Node: Keyboard Macros,  Prev: Command History,  Up: Command Loop

Keyboard Macros
===============

   A "keyboard macro" is a canned sequence of input events that can be
considered a command and made the definition of a key.  The Lisp
representation of a keyboard macro is a string or vector containing the
events.  Don't confuse keyboard macros with Lisp macros (*note
Macros::.).

 - Function: execute-kbd-macro MACRO &optional COUNT
     This function executes MACRO as a sequence of events.  If MACRO is
     a string or vector, then the events in it are executed exactly as
     if they had been input by the user.  The sequence is *not*
     expected to be a single key sequence; normally a keyboard macro
     definition consists of several key sequences concatenated.

     If MACRO is a symbol, then its function definition is used in
     place of MACRO.  If that is another symbol, this process repeats.
     Eventually the result should be a string or vector.  If the result
     is not a symbol, string, or vector, an error is signaled.

     The argument COUNT is a repeat count; MACRO is executed that many
     times.  If COUNT is omitted or `nil', MACRO is executed once.  If
     it is 0, MACRO is executed over and over until it encounters an
     error or a failing search.

 - Variable: executing-macro
     This variable contains the string or vector that defines the
     keyboard macro that is currently executing.  It is `nil' if no
     macro is currently executing.  A command can test this variable to
     behave differently when run from an executing macro.  Do not set
     this variable yourself.

 - Variable: defining-kbd-macro
     This variable indicates whether a keyboard macro is being defined.
     A command can test this variable to behave differently while a
     macro is being defined.  The commands `start-kbd-macro' and
     `end-kbd-macro' set this variable--do not set it yourself.

 - Variable: last-kbd-macro
     This variable is the definition of the most recently defined
     keyboard macro.  Its value is a string or vector, or `nil'.

   The commands are described in the user's manual (*note Keyboard
Macros: (emacs)Keyboard Macros.).


File: lispref.info,  Node: Keymaps,  Next: Menus,  Prev: Command Loop,  Up: Top

Keymaps
*******

   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 with another keymap or with a
command.  When an event 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".

* 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.
* Key Sequences::               How to specify key sequences.
* 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.
* Other Keymap Functions::      Miscellaneous keymap functions.


File: lispref.info,  Node: Keymap Terminology,  Next: Format of Keymaps,  Up: Keymaps

Keymap Terminology
==================

   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, XEmacs can get the event's definition.  Events mapped in keymaps
include keypresses, button presses, and button releases (*note
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'.  *Note 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, `C-f C-n' is not a key; `C-f' is not a prefix key,
so a longer sequence starting with `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 "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.  *Note Active Keymaps::, for details.


File: lispref.info,  Node: Format of Keymaps,  Next: Creating Keymaps,  Prev: Keymap Terminology,  Up: Keymaps

Format of Keymaps
=================

   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.

 - Function: keymapp OBJECT
     This function returns `t' if OBJECT is a keymap, `nil' otherwise.


File: lispref.info,  Node: Creating Keymaps,  Next: Inheritance and Keymaps,  Prev: Format of Keymaps,  Up: Keymaps

Creating Keymaps
================

   Here we describe the functions for creating keymaps.

 - Function: make-keymap &optional NAME
     This function constructs and returns a new keymap object.  All
     entries in it are `nil', meaning "command undefined".

     Optional argument NAME specifies a name to assign to the keymap,
     as in `set-keymap-name'.  This name is only a debugging
     convenience; it is not used except when printing the keymap.

 - Function: make-sparse-keymap &optional NAME
     This function constructs and returns a new keymap object.  All
     entries in it are `nil', meaning "command undefined".  The only
     difference between this function and `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.

     Optional argument NAME specifies a name to assign to the keymap,
     as in `set-keymap-name'.  This name is only a debugging
     convenience; it is not used except when printing the keymap.

 - Function: set-keymap-name KEYMAP NEW-NAME
     This function assigns a "name" to a keymap.  The name is only a
     debugging convenience; it is not used except when printing the
     keymap.

 - Function: keymap-name KEYMAP
     This function returns the "name" of a keymap, as assigned using
     `set-keymap-name'.

 - Function: copy-keymap KEYMAP
     This function returns a copy of KEYMAP.  Any keymaps that appear
     directly as bindings in 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.

          (setq map (copy-keymap (current-local-map)))
          => #<keymap 3 entries 0x21f80>
          
          (eq map (current-local-map))
              => nil


File: lispref.info,  Node: Inheritance and Keymaps,  Next: Key Sequences,  Prev: Creating Keymaps,  Up: Keymaps

Inheritance and Keymaps
=======================

   A keymap can inherit the bindings of other keymaps.  The other
keymaps are called the keymap's "parents", and are set with
`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.

   `(current-global-map)' is the default parent of all keymaps.

 - Function: set-keymap-parents KEYMAP PARENTS
     This function sets the parent keymaps of KEYMAP to the list
     PARENTS.

     If you change the bindings in one of the keymaps in PARENTS using
     `define-key' or other key-binding functions, these changes are
     visible in KEYMAP unless shadowed by bindings in that map or in
     earlier-searched ancestors.  The converse is not true: if you use
     `define-key' to change KEYMAP, that affects the bindings in that
     map, but has no effect on any of the keymaps in PARENTS.

 - Function: keymap-parents KEYMAP
     This function returns the list of parent keymaps of KEYMAP, or
     `nil' if KEYMAP has no parents.

   As an alternative to specifying a parent, you can also specify a
"default binding" that is used whenever a key is not otherwise bound in
the keymap.  This is useful for terminal emulators, for example, which
may want to trap all keystrokes and pass them on in some modified
format.  Note that if you specify a default binding for a keymap,
neither the keymap's parents nor the current global map are searched for
key bindings.

 - Function: set-keymap-default-binding KEYMAP COMMAND
     This function sets the default binding of KEYMAP to COMMAND, or
     `nil' if no default is desired.

 - Function: keymap-default-binding KEYMAP
     This function returns the default binding of KEYMAP, or `nil' if
     it has none.


File: lispref.info,  Node: Key Sequences,  Next: Prefix Keys,  Prev: Inheritance and Keymaps,  Up: Keymaps

Key Sequences
=============

   Contrary to popular belief, the world is not ASCII.  When running
under a window manager, XEmacs can tell the difference between, for
example, the keystrokes `control-h', `control-shift-h', and
`backspace'.  You can, in fact, bind different commands to each of
these.

   A "key sequence" is a set of keystrokes.  A "keystroke" is a keysym
and some set of modifiers (such as CONTROL and META).  A "keysym" is
what is printed on the keys on your keyboard.

   A keysym may be represented by a symbol, or (if and only if it is
equivalent to an ASCII character in the range 32 - 255) by a character
or its equivalent ASCII code.  The `A' key may be represented by the
symbol `A', the character `?A', or by the number 65.  The `break' key
may be represented only by the symbol `break'.

   A keystroke may be represented by a list: the last element of the
list is the key (a symbol, character, or number, as above) and the
preceding elements are the symbolic names of modifier keys (CONTROL,
META, SUPER, HYPER, ALT, and SHIFT).  Thus, the sequence `control-b' is
represented by the forms `(control b)', `(control ?b)', and `(control
98)'.  A keystroke may also be represented by an event object, as
returned by the `next-command-event' and `read-key-sequence' functions.

   Note that in this context, the keystroke `control-b' is *not*
represented by the number 2 (the ASCII code for `^B') or the character
`?\^B'.  See below.

   The SHIFT modifier is somewhat of a special case.  You should not
(and cannot) use `(meta shift a)' to mean `(meta A)', since for
characters that have ASCII equivalents, the state of the shift key is
implicit in the keysym (`a' vs. `A').  You also cannot say `(shift =)'
to mean `+', as that sort of thing varies from keyboard to keyboard.
The SHIFT modifier is for use only with characters that do not have a
second keysym on the same key, such as `backspace' and `tab'.

   A key sequence is a vector of keystrokes.  As a degenerate case,
elements of this vector may also be keysyms if they have no modifiers.
That is, the `A' keystroke is represented by all of these forms:

     	A	?A	65	(A)	(?A)	(65)
     	[A]	[?A]	[65]	[(A)]	[(?A)]	[(65)]

   the `control-a' keystroke is represented by these forms:

     	(control A)	(control ?A)	(control 65)
     	[(control A)]	[(control ?A)]	[(control 65)]

   the key sequence `control-c control-a' is represented by these forms:

     	[(control c) (control a)]	[(control ?c) (control ?a)]
     	[(control 99) (control 65)]	etc.

   Mouse button clicks work just like keypresses: `(control button1)'
means pressing the left mouse button while holding down the control
key.  `[(control c) (shift button3)]' means `control-c', hold SHIFT,
click right.

   Commands may be bound to the mouse-button up-stroke rather than the
down-stroke as well.  `button1' means the down-stroke, and `button1up'
means the up-stroke.  Different commands may be bound to the up and
down strokes, though that is probably not what you want, so be careful.

   For backward compatibility, a key sequence may also be represented by
a string.  In this case, it represents the key sequence(s) that would
produce that sequence of ASCII characters in a purely ASCII world.  For
example, a string containing the ASCII backspace character, `"\^H"',
would represent two key sequences: `(control h)' and `backspace'.
Binding a command to this will actually bind both of those key
sequences.  Likewise for the following pairs:

     		control h	backspace
     		control i   	tab
     		control m   	return
     		control j   	linefeed
     		control [   	escape
     		control @	control space

   After binding a command to two key sequences with a form like

     	(define-key global-map "\^X\^I" 'command-1)

it is possible to redefine only one of those sequences like so:

     	(define-key global-map [(control x) (control i)] 'command-2)
     	(define-key global-map [(control x) tab] 'command-3)

   Of course, all of this applies only when running under a window
system.  If you're talking to XEmacs through a TTY connection, you
don't get any of these features.

 - Function: event-matches-key-specifier-p EVENT KEY-SPECIFIER
     This function returns non-`nil' if EVENT matches KEY-SPECIFIER,
     which can be any valid form representing a key sequence.  This can
     be useful, e.g., to determine if the user pressed `help-char' or
     `quit-char'.


File: lispref.info,  Node: Prefix Keys,  Next: Active Keymaps,  Prev: Key Sequences,  Up: Keymaps

Prefix Keys
===========

   A "prefix key" has an associated keymap that defines what to do with
key sequences that start with 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'.  Here is a list of the standard prefix keys of XEmacs and
their keymaps:

   * `help-map' is used for events that follow `C-h'.

   * `mode-specific-map' is for events that follow `C-c'.  This map is
     not actually mode specific; its name was chosen to be informative
     for the user in `C-h b' (`display-bindings'), where it describes
     the main use of the `C-c' prefix key.

   * `ctl-x-map' is the map used for events that follow `C-x'.  This
     map is also the function definition of `Control-X-prefix'.

   * `ctl-x-4-map' is used for events that follow `C-x 4'.

   * `ctl-x-5-map' is used for events that follow `C-x 5'.

   * The prefix keys `C-x n', `C-x r' and `C-x a' use keymaps that have
     no special name.

   * `esc-map' is an evil hack that is present for compatibility
     purposes with Emacs 18.  Defining a key in `esc-map' is equivalent
     to defining the same key in `global-map' but with the META prefix
     added.  You should *not* use this in your code. (This map is also
     the function definition of `ESC-prefix'.)

   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 `C-x' is
the symbol `Control-X-prefix', whose function definition is 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.  *Note 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

 - Function: define-prefix-command SYMBOL &optional MAPVAR
     This function defines SYMBOL as a prefix command: it creates a
     keymap and stores it as SYMBOL's function definition.  Storing the
     symbol as the binding of a key makes the key a prefix key that has
     a name.  If optional argument MAPVAR is not specified, it also
     sets SYMBOL as a variable, to have the keymap as its value. (If
     MAPVAR is given and is not `t', its value is stored as the value
     of SYMBOL.) The function returns SYMBOL.

     In Emacs version 18, only the function definition of SYMBOL was
     set, not the value as a variable.

