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This is Info file ../../info/lispref.info, produced by Makeinfo version 1.68 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 XEmacs Lisp Reference Manual (for 19.15 and 20.1, 20.2) v3.2, April, May 1997 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: Reading One Event, Next: Dispatching an Event, Prev: Key Sequence Input, Up: Reading Input Reading One Event ----------------- The lowest level functions for command input are those which read a single event. These functions often make a distinction between "command events", which are user actions (keystrokes and mouse actions), and other events, which serve as communication between XEmacs and the window system. - Function: next-event &optional EVENT PROMPT This function reads and returns the next available event from the window system or terminal driver, waiting if necessary until an event is available. Pass this object to `dispatch-event' to handle it. If an event object is supplied, it is filled in and returned; otherwise a new event object will be created. Events can come directly from the user, from a keyboard macro, or from `unread-command-events'. In most cases, the function `next-command-event' is more appropriate. - Function: next-command-event &optional EVENT This function returns the next available "user" event from the window system or terminal driver. Pass this object to `dispatch-event' to handle it. If an event object is supplied, it is filled in and returned, otherwise a new event object will be created. The event returned will be a keyboard, mouse press, or mouse release event. If there are non-command events available (mouse motion, sub-process output, etc) then these will be executed (with `dispatch-event') and discarded. This function is provided as a convenience; it is equivalent to the Lisp code (while (progn (next-event event) (not (or (key-press-event-p event) (button-press-event-p event) (button-release-event-p event) (menu-event-p event)))) (dispatch-event event)) Here is what happens if you call `next-command-event' and then press the right-arrow function key: (next-command-event) => #<keypress-event right> - Function: read-char This function reads and returns a character of command input. If a mouse click is detected, an error is signalled. The character typed is returned as an ASCII value. This function is retained for compatibility with Emacs 18, and is most likely the wrong thing for you to be using: consider using `next-command-event' instead. - Function: enqueue-eval-event FUNCTION OBJECT This function adds an eval event to the back of the queue. The eval event will be the next event read after all pending events. File: lispref.info, Node: Dispatching an Event, Next: Quoted Character Input, Prev: Reading One Event, Up: Reading Input Dispatching an Event -------------------- - Function: dispatch-event EVENT Given an event object returned by `next-event', this function executes it. This is the basic function that makes XEmacs respond to user input; it also deals with notifications from the window system (such as Expose events). File: lispref.info, Node: Quoted Character Input, Next: Peeking and Discarding, Prev: Dispatching an Event, Up: Reading Input Quoted Character Input ---------------------- You can use the function `read-quoted-char' to ask the user to specify a character, and allow the user to specify a control or meta character conveniently, either literally or as an octal character code. The command `quoted-insert' uses this function. - Function: read-quoted-char &optional PROMPT This function is like `read-char', except that if the first character read is an octal digit (0-7), it reads up to two more octal digits (but stopping if a non-octal digit is found) and returns the character represented by those digits in octal. Quitting is suppressed when the first character is read, so that the user can enter a `C-g'. *Note Quitting::. If PROMPT is supplied, it specifies a string for prompting the user. The prompt string is always displayed in the echo area, followed by a single `-'. In the following example, the user types in the octal number 177 (which is 127 in decimal). (read-quoted-char "What character") ---------- Echo Area ---------- What character-177 ---------- Echo Area ---------- => 127 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: (xemacs)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.