2 @c This is part of the GNU Emacs Lisp Reference Manual.
3 @c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998 Free Software Foundation, Inc.
4 @c See the file elisp.texi for copying conditions.
5 @setfilename ../info/commands
6 @node Command Loop, Keymaps, Minibuffers, Top
8 @cindex editor command loop
11 When you run Emacs, it enters the @dfn{editor command loop} almost
12 immediately. This loop reads key sequences, executes their definitions,
13 and displays the results. In this chapter, we describe how these things
14 are done, and the subroutines that allow Lisp programs to do them.
17 * Command Overview:: How the command loop reads commands.
18 * Defining Commands:: Specifying how a function should read arguments.
19 * Interactive Call:: Calling a command, so that it will read arguments.
20 * Command Loop Info:: Variables set by the command loop for you to examine.
21 * Input Events:: What input looks like when you read it.
22 * Reading Input:: How to read input events from the keyboard or mouse.
23 * Special Events:: Events processed immediately and individually.
24 * Waiting:: Waiting for user input or elapsed time.
25 * Quitting:: How @kbd{C-g} works. How to catch or defer quitting.
26 * Prefix Command Arguments:: How the commands to set prefix args work.
27 * Recursive Editing:: Entering a recursive edit,
28 and why you usually shouldn't.
29 * Disabling Commands:: How the command loop handles disabled commands.
30 * Command History:: How the command history is set up, and how accessed.
31 * Keyboard Macros:: How keyboard macros are implemented.
34 @node Command Overview
35 @section Command Loop Overview
37 The first thing the command loop must do is read a key sequence, which
38 is a sequence of events that translates into a command. It does this by
39 calling the function @code{read-key-sequence}. Your Lisp code can also
40 call this function (@pxref{Key Sequence Input}). Lisp programs can also
41 do input at a lower level with @code{read-event} (@pxref{Reading One
42 Event}) or discard pending input with @code{discard-input}
43 (@pxref{Event Input Misc}).
45 The key sequence is translated into a command through the currently
46 active keymaps. @xref{Key Lookup}, for information on how this is done.
47 The result should be a keyboard macro or an interactively callable
48 function. If the key is @kbd{M-x}, then it reads the name of another
49 command, which it then calls. This is done by the command
50 @code{execute-extended-command} (@pxref{Interactive Call}).
52 To execute a command requires first reading the arguments for it.
53 This is done by calling @code{command-execute} (@pxref{Interactive
54 Call}). For commands written in Lisp, the @code{interactive}
55 specification says how to read the arguments. This may use the prefix
56 argument (@pxref{Prefix Command Arguments}) or may read with prompting
57 in the minibuffer (@pxref{Minibuffers}). For example, the command
58 @code{find-file} has an @code{interactive} specification which says to
59 read a file name using the minibuffer. The command's function body does
60 not use the minibuffer; if you call this command from Lisp code as a
61 function, you must supply the file name string as an ordinary Lisp
64 If the command is a string or vector (i.e., a keyboard macro) then
65 @code{execute-kbd-macro} is used to execute it. You can call this
66 function yourself (@pxref{Keyboard Macros}).
68 To terminate the execution of a running command, type @kbd{C-g}. This
69 character causes @dfn{quitting} (@pxref{Quitting}).
71 @defvar pre-command-hook
72 The editor command loop runs this normal hook before each command. At
73 that time, @code{this-command} contains the command that is about to
74 run, and @code{last-command} describes the previous command.
78 @defvar post-command-hook
79 The editor command loop runs this normal hook after each command
80 (including commands terminated prematurely by quitting or by errors),
81 and also when the command loop is first entered. At that time,
82 @code{this-command} describes the command that just ran, and
83 @code{last-command} describes the command before that. @xref{Hooks}.
86 Quitting is suppressed while running @code{pre-command-hook} and
87 @code{post-command-hook}. If an error happens while executing one of
88 these hooks, it terminates execution of the hook, and clears the hook
89 variable to @code{nil} so as to prevent an infinite loop of errors.
91 @node Defining Commands
92 @section Defining Commands
93 @cindex defining commands
94 @cindex commands, defining
95 @cindex functions, making them interactive
96 @cindex interactive function
98 A Lisp function becomes a command when its body contains, at top
99 level, a form that calls the special form @code{interactive}. This
100 form does nothing when actually executed, but its presence serves as a
101 flag to indicate that interactive calling is permitted. Its argument
102 controls the reading of arguments for an interactive call.
105 * Using Interactive:: General rules for @code{interactive}.
106 * Interactive Codes:: The standard letter-codes for reading arguments
108 * Interactive Examples:: Examples of how to read interactive arguments.
111 @node Using Interactive
112 @subsection Using @code{interactive}
114 This section describes how to write the @code{interactive} form that
115 makes a Lisp function an interactively-callable command.
117 @defspec interactive arg-descriptor
118 @cindex argument descriptors
119 This special form declares that the function in which it appears is a
120 command, and that it may therefore be called interactively (via
121 @kbd{M-x} or by entering a key sequence bound to it). The argument
122 @var{arg-descriptor} declares how to compute the arguments to the
123 command when the command is called interactively.
125 A command may be called from Lisp programs like any other function, but
126 then the caller supplies the arguments and @var{arg-descriptor} has no
129 The @code{interactive} form has its effect because the command loop
130 (actually, its subroutine @code{call-interactively}) scans through the
131 function definition looking for it, before calling the function. Once
132 the function is called, all its body forms including the
133 @code{interactive} form are executed, but at this time
134 @code{interactive} simply returns @code{nil} without even evaluating its
138 There are three possibilities for the argument @var{arg-descriptor}:
142 It may be omitted or @code{nil}; then the command is called with no
143 arguments. This leads quickly to an error if the command requires one
147 It may be a Lisp expression that is not a string; then it should be a
148 form that is evaluated to get a list of arguments to pass to the
150 @cindex argument evaluation form
152 If this expression reads keyboard input (this includes using the
153 minibuffer), keep in mind that the integer value of point or the mark
154 before reading input may be incorrect after reading input. This is
155 because the current buffer may be receiving subprocess output;
156 if subprocess output arrives while the command is waiting for input,
157 it could relocate point and the mark.
159 Here's an example of what @emph{not} to do:
163 (list (region-beginning) (region-end)
164 (read-string "Foo: " nil 'my-history)))
168 Here's how to avoid the problem, by examining point and the mark only
169 after reading the keyboard input:
173 (let ((string (read-string "Foo: " nil 'my-history)))
174 (list (region-beginning) (region-end) string)))
178 @cindex argument prompt
179 It may be a string; then its contents should consist of a code character
180 followed by a prompt (which some code characters use and some ignore).
181 The prompt ends either with the end of the string or with a newline.
182 Here is a simple example:
185 (interactive "bFrobnicate buffer: ")
189 The code letter @samp{b} says to read the name of an existing buffer,
190 with completion. The buffer name is the sole argument passed to the
191 command. The rest of the string is a prompt.
193 If there is a newline character in the string, it terminates the prompt.
194 If the string does not end there, then the rest of the string should
195 contain another code character and prompt, specifying another argument.
196 You can specify any number of arguments in this way.
199 The prompt string can use @samp{%} to include previous argument values
200 (starting with the first argument) in the prompt. This is done using
201 @code{format} (@pxref{Formatting Strings}). For example, here is how
202 you could read the name of an existing buffer followed by a new name to
207 (interactive "bBuffer to rename: \nsRename buffer %s to: ")
211 @cindex @samp{*} in interactive
212 @cindex read-only buffers in interactive
213 If the first character in the string is @samp{*}, then an error is
214 signaled if the buffer is read-only.
216 @cindex @samp{@@} in interactive
218 If the first character in the string is @samp{@@}, and if the key
219 sequence used to invoke the command includes any mouse events, then
220 the window associated with the first of those events is selected
221 before the command is run.
223 You can use @samp{*} and @samp{@@} together; the order does not matter.
224 Actual reading of arguments is controlled by the rest of the prompt
225 string (starting with the first character that is not @samp{*} or
229 @node Interactive Codes
230 @comment node-name, next, previous, up
231 @subsection Code Characters for @code{interactive}
232 @cindex interactive code description
233 @cindex description for interactive codes
234 @cindex codes, interactive, description of
235 @cindex characters for interactive codes
237 The code character descriptions below contain a number of key words,
238 defined here as follows:
242 @cindex interactive completion
243 Provide completion. @key{TAB}, @key{SPC}, and @key{RET} perform name
244 completion because the argument is read using @code{completing-read}
245 (@pxref{Completion}). @kbd{?} displays a list of possible completions.
248 Require the name of an existing object. An invalid name is not
249 accepted; the commands to exit the minibuffer do not exit if the current
253 @cindex default argument string
254 A default value of some sort is used if the user enters no text in the
255 minibuffer. The default depends on the code character.
258 This code letter computes an argument without reading any input.
259 Therefore, it does not use a prompt string, and any prompt string you
262 Even though the code letter doesn't use a prompt string, you must follow
263 it with a newline if it is not the last code character in the string.
266 A prompt immediately follows the code character. The prompt ends either
267 with the end of the string or with a newline.
270 This code character is meaningful only at the beginning of the
271 interactive string, and it does not look for a prompt or a newline.
272 It is a single, isolated character.
275 @cindex reading interactive arguments
276 Here are the code character descriptions for use with @code{interactive}:
280 Signal an error if the current buffer is read-only. Special.
283 Select the window mentioned in the first mouse event in the key
284 sequence that invoked this command. Special.
287 A function name (i.e., a symbol satisfying @code{fboundp}). Existing,
291 The name of an existing buffer. By default, uses the name of the
292 current buffer (@pxref{Buffers}). Existing, Completion, Default,
296 A buffer name. The buffer need not exist. By default, uses the name of
297 a recently used buffer other than the current buffer. Completion,
301 A character. The cursor does not move into the echo area. Prompt.
304 A command name (i.e., a symbol satisfying @code{commandp}). Existing,
308 @cindex position argument
309 The position of point, as an integer (@pxref{Point}). No I/O.
312 A directory name. The default is the current default directory of the
313 current buffer, @code{default-directory} (@pxref{System Environment}).
314 Existing, Completion, Default, Prompt.
317 The first or next mouse event in the key sequence that invoked the command.
318 More precisely, @samp{e} gets events that are lists, so you can look at
319 the data in the lists. @xref{Input Events}. No I/O.
321 You can use @samp{e} more than once in a single command's interactive
322 specification. If the key sequence that invoked the command has
323 @var{n} events that are lists, the @var{n}th @samp{e} provides the
324 @var{n}th such event. Events that are not lists, such as function keys
325 and @sc{ASCII} characters, do not count where @samp{e} is concerned.
328 A file name of an existing file (@pxref{File Names}). The default
329 directory is @code{default-directory}. Existing, Completion, Default,
333 A file name. The file need not exist. Completion, Default, Prompt.
336 A key sequence (@pxref{Keymap Terminology}). This keeps reading events
337 until a command (or undefined command) is found in the current key
338 maps. The key sequence argument is represented as a string or vector.
339 The cursor does not move into the echo area. Prompt.
341 This kind of input is used by commands such as @code{describe-key} and
342 @code{global-set-key}.
345 A key sequence, whose definition you intend to change. This works like
346 @samp{k}, except that it suppresses, for the last input event in the key
347 sequence, the conversions that are normally used (when necessary) to
348 convert an undefined key into a defined one.
351 @cindex marker argument
352 The position of the mark, as an integer. No I/O.
355 Arbitrary text, read in the minibuffer using the current buffer's input
356 method, and returned as a string (@pxref{Input Methods,,, emacs, The GNU
357 Emacs Manual}). Prompt.
360 A number read with the minibuffer. If the input is not a number, the
361 user is asked to try again. The prefix argument, if any, is not used.
365 @cindex raw prefix argument usage
366 The numeric prefix argument; but if there is no prefix argument, read a
367 number as with @kbd{n}. Requires a number. @xref{Prefix Command
371 @cindex numeric prefix argument usage
372 The numeric prefix argument. (Note that this @samp{p} is lower case.)
376 The raw prefix argument. (Note that this @samp{P} is upper case.) No
380 @cindex region argument
381 Point and the mark, as two numeric arguments, smallest first. This is
382 the only code letter that specifies two successive arguments rather than
386 Arbitrary text, read in the minibuffer and returned as a string
387 (@pxref{Text from Minibuffer}). Terminate the input with either
388 @key{LFD} or @key{RET}. (@kbd{C-q} may be used to include either of
389 these characters in the input.) Prompt.
392 An interned symbol whose name is read in the minibuffer. Any whitespace
393 character terminates the input. (Use @kbd{C-q} to include whitespace in
394 the string.) Other characters that normally terminate a symbol (e.g.,
395 parentheses and brackets) do not do so here. Prompt.
398 A variable declared to be a user option (i.e., satisfying the predicate
399 @code{user-variable-p}). @xref{High-Level Completion}. Existing,
403 A Lisp object, specified with its read syntax, terminated with a
404 @key{LFD} or @key{RET}. The object is not evaluated. @xref{Object from
408 @cindex evaluated expression argument
409 A Lisp form is read as with @kbd{x}, but then evaluated so that its
410 value becomes the argument for the command. Prompt.
413 @node Interactive Examples
414 @comment node-name, next, previous, up
415 @subsection Examples of Using @code{interactive}
416 @cindex examples of using @code{interactive}
417 @cindex @code{interactive}, examples of using
419 Here are some examples of @code{interactive}:
423 (defun foo1 () ; @r{@code{foo1} takes no arguments,}
424 (interactive) ; @r{just moves forward two words.}
430 (defun foo2 (n) ; @r{@code{foo2} takes one argument,}
431 (interactive "p") ; @r{which is the numeric prefix.}
432 (forward-word (* 2 n)))
437 (defun foo3 (n) ; @r{@code{foo3} takes one argument,}
438 (interactive "nCount:") ; @r{which is read with the Minibuffer.}
439 (forward-word (* 2 n)))
444 (defun three-b (b1 b2 b3)
445 "Select three existing buffers.
446 Put them into three windows, selecting the last one."
448 (interactive "bBuffer1:\nbBuffer2:\nbBuffer3:")
449 (delete-other-windows)
450 (split-window (selected-window) 8)
451 (switch-to-buffer b1)
453 (split-window (selected-window) 8)
454 (switch-to-buffer b2)
456 (switch-to-buffer b3))
459 (three-b "*scratch*" "declarations.texi" "*mail*")
464 @node Interactive Call
465 @section Interactive Call
466 @cindex interactive call
468 After the command loop has translated a key sequence into a command it
469 invokes that command using the function @code{command-execute}. If the
470 command is a function, @code{command-execute} calls
471 @code{call-interactively}, which reads the arguments and calls the
472 command. You can also call these functions yourself.
474 @defun commandp object
475 Returns @code{t} if @var{object} is suitable for calling interactively;
476 that is, if @var{object} is a command. Otherwise, returns @code{nil}.
478 The interactively callable objects include strings and vectors (treated
479 as keyboard macros), lambda expressions that contain a top-level call to
480 @code{interactive}, byte-code function objects made from such lambda
481 expressions, autoload objects that are declared as interactive
482 (non-@code{nil} fourth argument to @code{autoload}), and some of the
485 A symbol is @code{commandp} if its function definition is
488 Keys and keymaps are not commands. Rather, they are used to look up
489 commands (@pxref{Keymaps}).
491 See @code{documentation} in @ref{Accessing Documentation}, for a
492 realistic example of using @code{commandp}.
495 @defun call-interactively command &optional record-flag keys
496 This function calls the interactively callable function @var{command},
497 reading arguments according to its interactive calling specifications.
498 An error is signaled if @var{command} is not a function or if it cannot
499 be called interactively (i.e., is not a command). Note that keyboard
500 macros (strings and vectors) are not accepted, even though they are
501 considered commands, because they are not functions.
503 @cindex record command history
504 If @var{record-flag} is non-@code{nil}, then this command and its
505 arguments are unconditionally added to the list @code{command-history}.
506 Otherwise, the command is added only if it uses the minibuffer to read
507 an argument. @xref{Command History}.
509 The argument @var{keys}, if given, specifies the sequence of events to
510 use if the command inquires which events were used to invoke it.
513 @defun command-execute command &optional record-flag keys
514 @cindex keyboard macro execution
515 This function executes @var{command}. The argument @var{command} must
516 satisfy the @code{commandp} predicate; i.e., it must be an interactively
517 callable function or a keyboard macro.
519 A string or vector as @var{command} is executed with
520 @code{execute-kbd-macro}. A function is passed to
521 @code{call-interactively}, along with the optional @var{record-flag}.
523 A symbol is handled by using its function definition in its place. A
524 symbol with an @code{autoload} definition counts as a command if it was
525 declared to stand for an interactively callable function. Such a
526 definition is handled by loading the specified library and then
527 rechecking the definition of the symbol.
529 The argument @var{keys}, if given, specifies the sequence of events to
530 use if the command inquires which events were used to invoke it.
533 @deffn Command execute-extended-command prefix-argument
534 @cindex read command name
535 This function reads a command name from the minibuffer using
536 @code{completing-read} (@pxref{Completion}). Then it uses
537 @code{command-execute} to call the specified command. Whatever that
538 command returns becomes the value of @code{execute-extended-command}.
540 @cindex execute with prefix argument
541 If the command asks for a prefix argument, it receives the value
542 @var{prefix-argument}. If @code{execute-extended-command} is called
543 interactively, the current raw prefix argument is used for
544 @var{prefix-argument}, and thus passed on to whatever command is run.
546 @c !!! Should this be @kindex?
548 @code{execute-extended-command} is the normal definition of @kbd{M-x},
549 so it uses the string @w{@samp{M-x }} as a prompt. (It would be better
550 to take the prompt from the events used to invoke
551 @code{execute-extended-command}, but that is painful to implement.) A
552 description of the value of the prefix argument, if any, also becomes
557 (execute-extended-command 1)
558 ---------- Buffer: Minibuffer ----------
559 1 M-x forward-word RET
560 ---------- Buffer: Minibuffer ----------
567 This function returns @code{t} if the containing function (the one whose
568 code includes the call to @code{interactive-p}) was called
569 interactively, with the function @code{call-interactively}. (It makes
570 no difference whether @code{call-interactively} was called from Lisp or
571 directly from the editor command loop.) If the containing function was
572 called by Lisp evaluation (or with @code{apply} or @code{funcall}), then
573 it was not called interactively.
575 The most common use of @code{interactive-p} is for deciding whether to
576 print an informative message. As a special exception,
577 @code{interactive-p} returns @code{nil} whenever a keyboard macro is
578 being run. This is to suppress the informative messages and speed
579 execution of the macro.
595 (setq foobar (list (foo) (interactive-p))))
600 ;; @r{Type @kbd{M-x foo}.}
605 ;; @r{Type @kbd{M-x bar}.}
606 ;; @r{This does not print anything.}
616 @node Command Loop Info
617 @comment node-name, next, previous, up
618 @section Information from the Command Loop
620 The editor command loop sets several Lisp variables to keep status
621 records for itself and for commands that are run.
624 This variable records the name of the previous command executed by the
625 command loop (the one before the current command). Normally the value
626 is a symbol with a function definition, but this is not guaranteed.
628 The value is copied from @code{this-command} when a command returns to
629 the command loop, except when the command has specified a prefix
630 argument for the following command.
632 This variable is always local to the current terminal and cannot be
633 buffer-local. @xref{Multiple Displays}.
637 @cindex current command
638 This variable records the name of the command now being executed by
639 the editor command loop. Like @code{last-command}, it is normally a symbol
640 with a function definition.
642 The command loop sets this variable just before running a command, and
643 copies its value into @code{last-command} when the command finishes
644 (unless the command specified a prefix argument for the following
647 @cindex kill command repetition
648 Some commands set this variable during their execution, as a flag for
649 whatever command runs next. In particular, the functions for killing text
650 set @code{this-command} to @code{kill-region} so that any kill commands
651 immediately following will know to append the killed text to the
655 If you do not want a particular command to be recognized as the previous
656 command in the case where it got an error, you must code that command to
657 prevent this. One way is to set @code{this-command} to @code{t} at the
658 beginning of the command, and set @code{this-command} back to its proper
659 value at the end, like this:
662 (defun foo (args@dots{})
663 (interactive @dots{})
664 (let ((old-this-command this-command))
665 (setq this-command t)
666 @r{@dots{}do the work@dots{}}
667 (setq this-command old-this-command)))
671 We do not bind @code{this-command} with @code{let} because that would
672 restore the old value in case of error---a feature of @code{let} which
673 in this case does precisely what we want to avoid.
675 @defun this-command-keys
676 This function returns a string or vector containing the key sequence
677 that invoked the present command, plus any previous commands that
678 generated the prefix argument for this command. The value is a string
679 if all those events were characters. @xref{Input Events}.
684 ;; @r{Now use @kbd{C-u C-x C-e} to evaluate that.}
690 @defvar last-nonmenu-event
691 This variable holds the last input event read as part of a key
692 sequence, not counting events resulting from mouse menus.
694 One use of this variable is for telling @code{x-popup-menu} where to pop
698 @defvar last-command-event
699 @defvarx last-command-char
700 This variable is set to the last input event that was read by the
701 command loop as part of a command. The principal use of this variable
702 is in @code{self-insert-command}, which uses it to decide which
708 ;; @r{Now use @kbd{C-u C-x C-e} to evaluate that.}
714 The value is 5 because that is the @sc{ASCII} code for @kbd{C-e}.
716 The alias @code{last-command-char} exists for compatibility with
721 @defvar last-event-frame
722 This variable records which frame the last input event was directed to.
723 Usually this is the frame that was selected when the event was
724 generated, but if that frame has redirected input focus to another
725 frame, the value is the frame to which the event was redirected.
730 @section Input Events
734 The Emacs command loop reads a sequence of @dfn{input events} that
735 represent keyboard or mouse activity. The events for keyboard activity
736 are characters or symbols; mouse events are always lists. This section
737 describes the representation and meaning of input events in detail.
740 This function returns non-@code{nil} if @var{object} is an input event.
745 * Keyboard Events:: Ordinary characters--keys with symbols on them.
746 * Function Keys:: Function keys--keys with names, not symbols.
747 * Mouse Events:: Overview of mouse events.
748 * Click Events:: Pushing and releasing a mouse button.
749 * Drag Events:: Moving the mouse before releasing the button.
750 * Button-Down Events:: A button was pushed and not yet released.
751 * Repeat Events:: Double and triple click (or drag, or down).
752 * Motion Events:: Just moving the mouse, not pushing a button.
753 * Focus Events:: Moving the mouse between frames.
754 * Misc Events:: Other events window systems can generate.
755 * Event Examples:: Examples of the lists for mouse events.
756 * Classifying Events:: Finding the modifier keys in an event symbol.
758 * Accessing Events:: Functions to extract info from events.
759 * Strings of Events:: Special considerations for putting
760 keyboard character events in a string.
763 @node Keyboard Events
764 @subsection Keyboard Events
766 There are two kinds of input you can get from the keyboard: ordinary
767 keys, and function keys. Ordinary keys correspond to characters; the
768 events they generate are represented in Lisp as characters. In Emacs
769 versions 18 and earlier, characters were the only events. The event
770 type of a character event is the character itself (an integer);
771 see @ref{Classifying Events}.
773 @cindex modifier bits (of input character)
774 @cindex basic code (of input character)
775 An input character event consists of a @dfn{basic code} between 0 and
776 524287, plus any or all of these @dfn{modifier bits}:
787 bit in the character code indicates a character
788 typed with the meta key held down.
798 bit in the character code indicates a non-@sc{ASCII}
801 @sc{ASCII} control characters such as @kbd{C-a} have special basic
802 codes of their own, so Emacs needs no special bit to indicate them.
803 Thus, the code for @kbd{C-a} is just 1.
805 But if you type a control combination not in @sc{ASCII}, such as
806 @kbd{%} with the control key, the numeric value you get is the code
814 (assuming the terminal supports non-@sc{ASCII}
825 bit in the character code indicates an @sc{ASCII} control
826 character typed with the shift key held down.
828 For letters, the basic code itself indicates upper versus lower case;
829 for digits and punctuation, the shift key selects an entirely different
830 character with a different basic code. In order to keep within the
831 @sc{ASCII} character set whenever possible, Emacs avoids using the
838 bit for those characters.
840 However, @sc{ASCII} provides no way to distinguish @kbd{C-A} from
841 @kbd{C-a}, so Emacs uses the
848 bit in @kbd{C-A} and not in
859 bit in the character code indicates a character
860 typed with the hyper key held down.
870 bit in the character code indicates a character
871 typed with the super key held down.
881 bit in the character code indicates a character typed with
882 the alt key held down. (On some terminals, the key labeled @key{ALT}
883 is actually the meta key.)
886 It is best to avoid mentioning specific bit numbers in your program.
887 To test the modifier bits of a character, use the function
888 @code{event-modifiers} (@pxref{Classifying Events}). When making key
889 bindings, you can use the read syntax for characters with modifier bits
890 (@samp{\C-}, @samp{\M-}, and so on). For making key bindings with
891 @code{define-key}, you can use lists such as @code{(control hyper ?x)} to
892 specify the characters (@pxref{Changing Key Bindings}). The function
893 @code{event-convert-list} converts such a list into an event type
894 (@pxref{Classifying Events}).
897 @subsection Function Keys
899 @cindex function keys
900 Most keyboards also have @dfn{function keys}---keys that have names or
901 symbols that are not characters. Function keys are represented in Emacs
902 Lisp as symbols; the symbol's name is the function key's label, in lower
903 case. For example, pressing a key labeled @key{F1} places the symbol
904 @code{f1} in the input stream.
906 The event type of a function key event is the event symbol itself.
907 @xref{Classifying Events}.
909 Here are a few special cases in the symbol-naming convention for
913 @item @code{backspace}, @code{tab}, @code{newline}, @code{return}, @code{delete}
914 These keys correspond to common @sc{ASCII} control characters that have
915 special keys on most keyboards.
917 In @sc{ASCII}, @kbd{C-i} and @key{TAB} are the same character. If the
918 terminal can distinguish between them, Emacs conveys the distinction to
919 Lisp programs by representing the former as the integer 9, and the
920 latter as the symbol @code{tab}.
922 Most of the time, it's not useful to distinguish the two. So normally
923 @code{function-key-map} (@pxref{Translating Input}) is set up to map
924 @code{tab} into 9. Thus, a key binding for character code 9 (the
925 character @kbd{C-i}) also applies to @code{tab}. Likewise for the other
926 symbols in this group. The function @code{read-char} likewise converts
927 these events into characters.
929 In @sc{ASCII}, @key{BS} is really @kbd{C-h}. But @code{backspace}
930 converts into the character code 127 (@key{DEL}), not into code 8
931 (@key{BS}). This is what most users prefer.
933 @item @code{left}, @code{up}, @code{right}, @code{down}
935 @item @code{kp-add}, @code{kp-decimal}, @code{kp-divide}, @dots{}
936 Keypad keys (to the right of the regular keyboard).
937 @item @code{kp-0}, @code{kp-1}, @dots{}
938 Keypad keys with digits.
939 @item @code{kp-f1}, @code{kp-f2}, @code{kp-f3}, @code{kp-f4}
941 @item @code{kp-home}, @code{kp-left}, @code{kp-up}, @code{kp-right}, @code{kp-down}
942 Keypad arrow keys. Emacs normally translates these into the
943 corresponding non-keypad keys @code{home}, @code{left}, @dots{}
944 @item @code{kp-prior}, @code{kp-next}, @code{kp-end}, @code{kp-begin}, @code{kp-insert}, @code{kp-delete}
945 Additional keypad duplicates of keys ordinarily found elsewhere. Emacs
946 normally translates these into the like-named non-keypad keys.
949 You can use the modifier keys @key{ALT}, @key{CTRL}, @key{HYPER},
950 @key{META}, @key{SHIFT}, and @key{SUPER} with function keys. The way to
951 represent them is with prefixes in the symbol name:
957 The control modifier.
968 Thus, the symbol for the key @key{F3} with @key{META} held down is
969 @code{M-f3}. When you use more than one prefix, we recommend you
970 write them in alphabetical order; but the order does not matter in
971 arguments to the key-binding lookup and modification functions.
974 @subsection Mouse Events
976 Emacs supports four kinds of mouse events: click events, drag events,
977 button-down events, and motion events. All mouse events are represented
978 as lists. The @sc{car} of the list is the event type; this says which
979 mouse button was involved, and which modifier keys were used with it.
980 The event type can also distinguish double or triple button presses
981 (@pxref{Repeat Events}). The rest of the list elements give position
982 and time information.
984 For key lookup, only the event type matters: two events of the same type
985 necessarily run the same command. The command can access the full
986 values of these events using the @samp{e} interactive code.
987 @xref{Interactive Codes}.
989 A key sequence that starts with a mouse event is read using the keymaps
990 of the buffer in the window that the mouse was in, not the current
991 buffer. This does not imply that clicking in a window selects that
992 window or its buffer---that is entirely under the control of the command
993 binding of the key sequence.
996 @subsection Click Events
998 @cindex mouse click event
1000 When the user presses a mouse button and releases it at the same
1001 location, that generates a @dfn{click} event. Mouse click events have
1006 (@var{window} @var{buffer-pos} (@var{x} . @var{y}) @var{timestamp})
1010 Here is what the elements normally mean:
1013 @item @var{event-type}
1014 This is a symbol that indicates which mouse button was used. It is
1015 one of the symbols @code{mouse-1}, @code{mouse-2}, @dots{}, where the
1016 buttons are numbered left to right.
1018 You can also use prefixes @samp{A-}, @samp{C-}, @samp{H-}, @samp{M-},
1019 @samp{S-} and @samp{s-} for modifiers alt, control, hyper, meta, shift
1020 and super, just as you would with function keys.
1022 This symbol also serves as the event type of the event. Key bindings
1023 describe events by their types; thus, if there is a key binding for
1024 @code{mouse-1}, that binding would apply to all events whose
1025 @var{event-type} is @code{mouse-1}.
1028 This is the window in which the click occurred.
1030 @item @var{x}, @var{y}
1031 These are the pixel-denominated coordinates of the click, relative to
1032 the top left corner of @var{window}, which is @code{(0 . 0)}.
1034 @item @var{buffer-pos}
1035 This is the buffer position of the character clicked on.
1037 @item @var{timestamp}
1038 This is the time at which the event occurred, in milliseconds. (Since
1039 this value wraps around the entire range of Emacs Lisp integers in about
1040 five hours, it is useful only for relating the times of nearby events.)
1042 @item @var{click-count}
1043 This is the number of rapid repeated presses so far of the same mouse
1044 button. @xref{Repeat Events}.
1047 The meanings of @var{buffer-pos}, @var{x} and @var{y} are somewhat
1048 different when the event location is in a special part of the screen,
1049 such as the mode line or a scroll bar.
1051 If the location is in a scroll bar, then @var{buffer-pos} is the symbol
1052 @code{vertical-scroll-bar} or @code{horizontal-scroll-bar}, and the pair
1053 @code{(@var{x} . @var{y})} is replaced with a pair @code{(@var{portion}
1054 . @var{whole})}, where @var{portion} is the distance of the click from
1055 the top or left end of the scroll bar, and @var{whole} is the length of
1056 the entire scroll bar.
1058 If the position is on a mode line or the vertical line separating
1059 @var{window} from its neighbor to the right, then @var{buffer-pos} is
1060 the symbol @code{mode-line} or @code{vertical-line}. For the mode line,
1061 @var{y} does not have meaningful data. For the vertical line, @var{x}
1062 does not have meaningful data.
1064 In one special case, @var{buffer-pos} is a list containing a symbol (one
1065 of the symbols listed above) instead of just the symbol. This happens
1066 after the imaginary prefix keys for the event are inserted into the
1067 input stream. @xref{Key Sequence Input}.
1070 @subsection Drag Events
1072 @cindex mouse drag event
1074 With Emacs, you can have a drag event without even changing your
1075 clothes. A @dfn{drag event} happens every time the user presses a mouse
1076 button and then moves the mouse to a different character position before
1077 releasing the button. Like all mouse events, drag events are
1078 represented in Lisp as lists. The lists record both the starting mouse
1079 position and the final position, like this:
1083 (@var{window1} @var{buffer-pos1} (@var{x1} . @var{y1}) @var{timestamp1})
1084 (@var{window2} @var{buffer-pos2} (@var{x2} . @var{y2}) @var{timestamp2})
1088 For a drag event, the name of the symbol @var{event-type} contains the
1089 prefix @samp{drag-}. For example, dragging the mouse with button 2 held
1090 down generates a @code{drag-mouse-2} event. The second and third
1091 elements of the event give the starting and ending position of the drag.
1092 Aside from that, the data have the same meanings as in a click event
1093 (@pxref{Click Events}). You can access the second element of any mouse
1094 event in the same way, with no need to distinguish drag events from
1097 The @samp{drag-} prefix follows the modifier key prefixes such as
1098 @samp{C-} and @samp{M-}.
1100 If @code{read-key-sequence} receives a drag event that has no key
1101 binding, and the corresponding click event does have a binding, it
1102 changes the drag event into a click event at the drag's starting
1103 position. This means that you don't have to distinguish between click
1104 and drag events unless you want to.
1106 @node Button-Down Events
1107 @subsection Button-Down Events
1108 @cindex button-down event
1110 Click and drag events happen when the user releases a mouse button.
1111 They cannot happen earlier, because there is no way to distinguish a
1112 click from a drag until the button is released.
1114 If you want to take action as soon as a button is pressed, you need to
1115 handle @dfn{button-down} events.@footnote{Button-down is the
1116 conservative antithesis of drag.} These occur as soon as a button is
1117 pressed. They are represented by lists that look exactly like click
1118 events (@pxref{Click Events}), except that the @var{event-type} symbol
1119 name contains the prefix @samp{down-}. The @samp{down-} prefix follows
1120 modifier key prefixes such as @samp{C-} and @samp{M-}.
1122 The function @code{read-key-sequence}, and therefore the Emacs command
1123 loop as well, ignore any button-down events that don't have command
1124 bindings. This means that you need not worry about defining button-down
1125 events unless you want them to do something. The usual reason to define
1126 a button-down event is so that you can track mouse motion (by reading
1127 motion events) until the button is released. @xref{Motion Events}.
1130 @subsection Repeat Events
1131 @cindex repeat events
1132 @cindex double-click events
1133 @cindex triple-click events
1135 If you press the same mouse button more than once in quick succession
1136 without moving the mouse, Emacs generates special @dfn{repeat} mouse
1137 events for the second and subsequent presses.
1139 The most common repeat events are @dfn{double-click} events. Emacs
1140 generates a double-click event when you click a button twice; the event
1141 happens when you release the button (as is normal for all click
1144 The event type of a double-click event contains the prefix
1145 @samp{double-}. Thus, a double click on the second mouse button with
1146 @key{meta} held down comes to the Lisp program as
1147 @code{M-double-mouse-2}. If a double-click event has no binding, the
1148 binding of the corresponding ordinary click event is used to execute
1149 it. Thus, you need not pay attention to the double click feature
1150 unless you really want to.
1152 When the user performs a double click, Emacs generates first an ordinary
1153 click event, and then a double-click event. Therefore, you must design
1154 the command binding of the double click event to assume that the
1155 single-click command has already run. It must produce the desired
1156 results of a double click, starting from the results of a single click.
1158 This is convenient, if the meaning of a double click somehow ``builds
1159 on'' the meaning of a single click---which is recommended user interface
1160 design practice for double clicks.
1162 If you click a button, then press it down again and start moving the
1163 mouse with the button held down, then you get a @dfn{double-drag} event
1164 when you ultimately release the button. Its event type contains
1165 @samp{double-drag} instead of just @samp{drag}. If a double-drag event
1166 has no binding, Emacs looks for an alternate binding as if the event
1167 were an ordinary drag.
1169 Before the double-click or double-drag event, Emacs generates a
1170 @dfn{double-down} event when the user presses the button down for the
1171 second time. Its event type contains @samp{double-down} instead of just
1172 @samp{down}. If a double-down event has no binding, Emacs looks for an
1173 alternate binding as if the event were an ordinary button-down event.
1174 If it finds no binding that way either, the double-down event is
1177 To summarize, when you click a button and then press it again right
1178 away, Emacs generates a down event and a click event for the first
1179 click, a double-down event when you press the button again, and finally
1180 either a double-click or a double-drag event.
1182 If you click a button twice and then press it again, all in quick
1183 succession, Emacs generates a @dfn{triple-down} event, followed by
1184 either a @dfn{triple-click} or a @dfn{triple-drag}. The event types of
1185 these events contain @samp{triple} instead of @samp{double}. If any
1186 triple event has no binding, Emacs uses the binding that it would use
1187 for the corresponding double event.
1189 If you click a button three or more times and then press it again, the
1190 events for the presses beyond the third are all triple events. Emacs
1191 does not have separate event types for quadruple, quintuple, etc.@:
1192 events. However, you can look at the event list to find out precisely
1193 how many times the button was pressed.
1195 @defun event-click-count event
1196 This function returns the number of consecutive button presses that led
1197 up to @var{event}. If @var{event} is a double-down, double-click or
1198 double-drag event, the value is 2. If @var{event} is a triple event,
1199 the value is 3 or greater. If @var{event} is an ordinary mouse event
1200 (not a repeat event), the value is 1.
1203 @defvar double-click-time
1204 To generate repeat events, successive mouse button presses must be at
1205 the same screen position, and the number of milliseconds between
1206 successive button presses must be less than the value of
1207 @code{double-click-time}. Setting @code{double-click-time} to
1208 @code{nil} disables multi-click detection entirely. Setting it to
1209 @code{t} removes the time limit; Emacs then detects multi-clicks by
1214 @subsection Motion Events
1215 @cindex motion event
1216 @cindex mouse motion events
1218 Emacs sometimes generates @dfn{mouse motion} events to describe motion
1219 of the mouse without any button activity. Mouse motion events are
1220 represented by lists that look like this:
1224 (@var{window} @var{buffer-pos} (@var{x} . @var{y}) @var{timestamp}))
1227 The second element of the list describes the current position of the
1228 mouse, just as in a click event (@pxref{Click Events}).
1230 The special form @code{track-mouse} enables generation of motion events
1231 within its body. Outside of @code{track-mouse} forms, Emacs does not
1232 generate events for mere motion of the mouse, and these events do not
1235 @defspec track-mouse body@dots{}
1236 This special form executes @var{body}, with generation of mouse motion
1237 events enabled. Typically @var{body} would use @code{read-event}
1238 to read the motion events and modify the display accordingly.
1240 When the user releases the button, that generates a click event.
1241 Typically, @var{body} should return when it sees the click event, and
1246 @subsection Focus Events
1249 Window systems provide general ways for the user to control which window
1250 gets keyboard input. This choice of window is called the @dfn{focus}.
1251 When the user does something to switch between Emacs frames, that
1252 generates a @dfn{focus event}. The normal definition of a focus event,
1253 in the global keymap, is to select a new frame within Emacs, as the user
1254 would expect. @xref{Input Focus}.
1256 Focus events are represented in Lisp as lists that look like this:
1259 (switch-frame @var{new-frame})
1263 where @var{new-frame} is the frame switched to.
1265 Most X window managers are set up so that just moving the mouse into a
1266 window is enough to set the focus there. Emacs appears to do this,
1267 because it changes the cursor to solid in the new frame. However, there
1268 is no need for the Lisp program to know about the focus change until
1269 some other kind of input arrives. So Emacs generates a focus event only
1270 when the user actually types a keyboard key or presses a mouse button in
1271 the new frame; just moving the mouse between frames does not generate a
1274 A focus event in the middle of a key sequence would garble the
1275 sequence. So Emacs never generates a focus event in the middle of a key
1276 sequence. If the user changes focus in the middle of a key
1277 sequence---that is, after a prefix key---then Emacs reorders the events
1278 so that the focus event comes either before or after the multi-event key
1279 sequence, and not within it.
1282 @subsection Miscellaneous Window System Events
1284 A few other event types represent occurrences within the window system.
1287 @cindex @code{delete-frame} event
1288 @item (delete-frame (@var{frame}))
1289 This kind of event indicates that the user gave the window manager
1290 a command to delete a particular window, which happens to be an Emacs frame.
1292 The standard definition of the @code{delete-frame} event is to delete @var{frame}.
1294 @cindex @code{iconify-frame} event
1295 @item (iconify-frame (@var{frame}))
1296 This kind of event indicates that the user iconified @var{frame} using
1297 the window manager. Its standard definition is @code{ignore}; since the
1298 frame has already been iconified, Emacs has no work to do. The purpose
1299 of this event type is so that you can keep track of such events if you
1302 @cindex @code{make-frame-visible} event
1303 @item (make-frame-visible (@var{frame}))
1304 This kind of event indicates that the user deiconified @var{frame} using
1305 the window manager. Its standard definition is @code{ignore}; since the
1306 frame has already been made visible, Emacs has no work to do.
1309 If one of these events arrives in the middle of a key sequence---that
1310 is, after a prefix key---then Emacs reorders the events so that this
1311 event comes either before or after the multi-event key sequence, not
1314 @node Event Examples
1315 @subsection Event Examples
1317 If the user presses and releases the left mouse button over the same
1318 location, that generates a sequence of events like this:
1321 (down-mouse-1 (#<window 18 on NEWS> 2613 (0 . 38) -864320))
1322 (mouse-1 (#<window 18 on NEWS> 2613 (0 . 38) -864180))
1325 While holding the control key down, the user might hold down the
1326 second mouse button, and drag the mouse from one line to the next.
1327 That produces two events, as shown here:
1330 (C-down-mouse-2 (#<window 18 on NEWS> 3440 (0 . 27) -731219))
1331 (C-drag-mouse-2 (#<window 18 on NEWS> 3440 (0 . 27) -731219)
1332 (#<window 18 on NEWS> 3510 (0 . 28) -729648))
1335 While holding down the meta and shift keys, the user might press the
1336 second mouse button on the window's mode line, and then drag the mouse
1337 into another window. That produces a pair of events like these:
1340 (M-S-down-mouse-2 (#<window 18 on NEWS> mode-line (33 . 31) -457844))
1341 (M-S-drag-mouse-2 (#<window 18 on NEWS> mode-line (33 . 31) -457844)
1342 (#<window 20 on carlton-sanskrit.tex> 161 (33 . 3)
1346 @node Classifying Events
1347 @subsection Classifying Events
1350 Every event has an @dfn{event type}, which classifies the event for
1351 key binding purposes. For a keyboard event, the event type equals the
1352 event value; thus, the event type for a character is the character, and
1353 the event type for a function key symbol is the symbol itself. For
1354 events that are lists, the event type is the symbol in the @sc{car} of
1355 the list. Thus, the event type is always a symbol or a character.
1357 Two events of the same type are equivalent where key bindings are
1358 concerned; thus, they always run the same command. That does not
1359 necessarily mean they do the same things, however, as some commands look
1360 at the whole event to decide what to do. For example, some commands use
1361 the location of a mouse event to decide where in the buffer to act.
1363 Sometimes broader classifications of events are useful. For example,
1364 you might want to ask whether an event involved the @key{META} key,
1365 regardless of which other key or mouse button was used.
1367 The functions @code{event-modifiers} and @code{event-basic-type} are
1368 provided to get such information conveniently.
1370 @defun event-modifiers event
1371 This function returns a list of the modifiers that @var{event} has. The
1372 modifiers are symbols; they include @code{shift}, @code{control},
1373 @code{meta}, @code{alt}, @code{hyper} and @code{super}. In addition,
1374 the modifiers list of a mouse event symbol always contains one of
1375 @code{click}, @code{drag}, and @code{down}.
1377 The argument @var{event} may be an entire event object, or just an event
1380 Here are some examples:
1383 (event-modifiers ?a)
1385 (event-modifiers ?\C-a)
1387 (event-modifiers ?\C-%)
1389 (event-modifiers ?\C-\S-a)
1390 @result{} (control shift)
1391 (event-modifiers 'f5)
1393 (event-modifiers 's-f5)
1395 (event-modifiers 'M-S-f5)
1396 @result{} (meta shift)
1397 (event-modifiers 'mouse-1)
1399 (event-modifiers 'down-mouse-1)
1403 The modifiers list for a click event explicitly contains @code{click},
1404 but the event symbol name itself does not contain @samp{click}.
1407 @defun event-basic-type event
1408 This function returns the key or mouse button that @var{event}
1409 describes, with all modifiers removed. For example:
1412 (event-basic-type ?a)
1414 (event-basic-type ?A)
1416 (event-basic-type ?\C-a)
1418 (event-basic-type ?\C-\S-a)
1420 (event-basic-type 'f5)
1422 (event-basic-type 's-f5)
1424 (event-basic-type 'M-S-f5)
1426 (event-basic-type 'down-mouse-1)
1431 @defun mouse-movement-p object
1432 This function returns non-@code{nil} if @var{object} is a mouse movement
1436 @defun event-convert-list list
1437 This function converts a list of modifier names and a basic event type
1438 to an event type which specifies all of them. For example,
1441 (event-convert-list '(control ?a))
1443 (event-convert-list '(control meta ?a))
1444 @result{} -134217727
1445 (event-convert-list '(control super f1))
1450 @node Accessing Events
1451 @subsection Accessing Events
1453 This section describes convenient functions for accessing the data in
1454 a mouse button or motion event.
1456 These two functions return the starting or ending position of a
1457 mouse-button event. The position is a list of this form:
1460 (@var{window} @var{buffer-position} (@var{x} . @var{y}) @var{timestamp})
1463 @defun event-start event
1464 This returns the starting position of @var{event}.
1466 If @var{event} is a click or button-down event, this returns the
1467 location of the event. If @var{event} is a drag event, this returns the
1468 drag's starting position.
1471 @defun event-end event
1472 This returns the ending position of @var{event}.
1474 If @var{event} is a drag event, this returns the position where the user
1475 released the mouse button. If @var{event} is a click or button-down
1476 event, the value is actually the starting position, which is the only
1477 position such events have.
1480 These five functions take a position as described above, and return
1481 various parts of it.
1483 @defun posn-window position
1484 Return the window that @var{position} is in.
1487 @defun posn-point position
1488 Return the buffer position in @var{position}. This is an integer.
1491 @defun posn-x-y position
1492 Return the pixel-based x and y coordinates in @var{position}, as a cons
1493 cell @code{(@var{x} . @var{y})}.
1496 @defun posn-col-row position
1497 Return the row and column (in units of characters) of @var{position}, as
1498 a cons cell @code{(@var{col} . @var{row})}. These are computed from the
1499 @var{x} and @var{y} values actually found in @var{position}.
1502 @defun posn-timestamp position
1503 Return the timestamp in @var{position}.
1506 @defun scroll-bar-event-ratio event
1507 This function returns the fractional vertical position of a scroll bar
1508 event within the scroll bar. The value is a cons cell
1509 @code{(@var{portion} . @var{whole})} containing two integers whose ratio
1510 is the fractional position.
1513 @defun scroll-bar-scale ratio total
1514 This function multiplies (in effect) @var{ratio} by @var{total},
1515 rounding the result to an integer. The argument @var{ratio} is not a
1516 number, but rather a pair @code{(@var{num} . @var{denom})}---typically a
1517 value returned by @code{scroll-bar-event-ratio}.
1519 This function is handy for scaling a position on a scroll bar into a
1520 buffer position. Here's how to do that:
1525 (posn-x-y (event-start event))
1526 (- (point-max) (point-min))))
1529 Recall that scroll bar events have two integers forming ratio in place
1530 of a pair of x and y coordinates.
1533 @node Strings of Events
1534 @subsection Putting Keyboard Events in Strings
1536 In most of the places where strings are used, we conceptualize the
1537 string as containing text characters---the same kind of characters found
1538 in buffers or files. Occasionally Lisp programs use strings that
1539 conceptually contain keyboard characters; for example, they may be key
1540 sequences or keyboard macro definitions. There are special rules for
1541 how to put keyboard characters into a string, because they are not
1542 limited to the range of 0 to 255 as text characters are.
1544 A keyboard character typed using the @key{META} key is called a
1545 @dfn{meta character}. The numeric code for such an event includes the
1552 bit; it does not even come close to fitting in a string. However,
1553 earlier Emacs versions used a different representation for these
1554 characters, which gave them codes in the range of 128 to 255. That did
1555 fit in a string, and many Lisp programs contain string constants that
1556 use @samp{\M-} to express meta characters, especially as the argument to
1557 @code{define-key} and similar functions.
1559 We provide backward compatibility to run those programs using special
1560 rules for how to put a keyboard character event in a string. Here are
1565 If the keyboard character value is in the range of 0 to 127, it can go
1566 in the string unchanged.
1569 The meta variants of those characters, with codes in the range of
1583 can also go in the string, but you must change their
1584 numeric values. You must set the
1599 resulting in a value between 128 and 255.
1602 Other keyboard character events cannot fit in a string. This includes
1603 keyboard events in the range of 128 to 255.
1606 Functions such as @code{read-key-sequence} that construct strings of
1607 keyboard input characters follow these rules: they construct vectors
1608 instead of strings, when the events won't fit in a string.
1610 When you use the read syntax @samp{\M-} in a string, it produces a
1611 code in the range of 128 to 255---the same code that you get if you
1612 modify the corresponding keyboard event to put it in the string. Thus,
1613 meta events in strings work consistently regardless of how they get into
1616 The reason we changed the representation of meta characters as
1617 keyboard events is to make room for basic character codes beyond 127,
1618 and support meta variants of such larger character codes.
1620 New programs can avoid dealing with these special compatibility rules
1621 by using vectors instead of strings for key sequences when there is any
1622 possibility that they might contain meta characters, and by using
1623 @code{listify-key-sequence} to access a string of events.
1625 @defun listify-key-sequence key
1626 This function converts the string or vector @var{key} to a list of
1627 events, which you can put in @code{unread-command-events}. Converting a
1628 vector is simple, but converting a string is tricky because of the
1629 special representation used for meta characters in a string.
1633 @section Reading Input
1635 The editor command loop reads keyboard input using the function
1636 @code{read-key-sequence}, which uses @code{read-event}. These and other
1637 functions for keyboard input are also available for use in Lisp
1638 programs. See also @code{momentary-string-display} in @ref{Temporary
1639 Displays}, and @code{sit-for} in @ref{Waiting}. @xref{Terminal Input},
1640 for functions and variables for controlling terminal input modes and
1641 debugging terminal input. @xref{Translating Input}, for features you
1642 can use for translating or modifying input events while reading them.
1644 For higher-level input facilities, see @ref{Minibuffers}.
1647 * Key Sequence Input:: How to read one key sequence.
1648 * Reading One Event:: How to read just one event.
1649 * Quoted Character Input:: Asking the user to specify a character.
1650 * Event Input Misc:: How to reread or throw away input events.
1653 @node Key Sequence Input
1654 @subsection Key Sequence Input
1655 @cindex key sequence input
1657 The command loop reads input a key sequence at a time, by calling
1658 @code{read-key-sequence}. Lisp programs can also call this function;
1659 for example, @code{describe-key} uses it to read the key to describe.
1661 @defun read-key-sequence prompt
1662 @cindex key sequence
1663 This function reads a key sequence and returns it as a string or
1664 vector. It keeps reading events until it has accumulated a complete key
1665 sequence; that is, enough to specify a non-prefix command using the
1666 currently active keymaps.
1668 If the events are all characters and all can fit in a string, then
1669 @code{read-key-sequence} returns a string (@pxref{Strings of Events}).
1670 Otherwise, it returns a vector, since a vector can hold all kinds of
1671 events---characters, symbols, and lists. The elements of the string or
1672 vector are the events in the key sequence.
1674 The function @code{read-key-sequence} suppresses quitting: @kbd{C-g}
1675 typed while reading with this function works like any other character,
1676 and does not set @code{quit-flag}. @xref{Quitting}.
1678 The argument @var{prompt} is either a string to be displayed in the echo
1679 area as a prompt, or @code{nil}, meaning not to display a prompt.
1681 In the example below, the prompt @samp{?} is displayed in the echo area,
1682 and the user types @kbd{C-x C-f}.
1685 (read-key-sequence "?")
1688 ---------- Echo Area ----------
1690 ---------- Echo Area ----------
1697 @cindex upper case key sequence
1698 @cindex downcasing in @code{lookup-key}
1699 If an input character is an upper-case letter and has no key binding,
1700 but its lower-case equivalent has one, then @code{read-key-sequence}
1701 converts the character to lower case. Note that @code{lookup-key} does
1702 not perform case conversion in this way.
1704 The function @code{read-key-sequence} also transforms some mouse events.
1705 It converts unbound drag events into click events, and discards unbound
1706 button-down events entirely. It also reshuffles focus events and
1707 miscellaneous window events so that they never appear in a key sequence
1708 with any other events.
1710 When mouse events occur in special parts of a window, such as a mode
1711 line or a scroll bar, the event type shows nothing special---it is the
1712 same symbol that would normally represent that combination of mouse
1713 button and modifier keys. The information about the window part is kept
1714 elsewhere in the event---in the coordinates. But
1715 @code{read-key-sequence} translates this information into imaginary
1716 ``prefix keys'', all of which are symbols: @code{mode-line},
1717 @code{vertical-line}, @code{horizontal-scroll-bar} and
1718 @code{vertical-scroll-bar}. You can define meanings for mouse clicks in
1719 special window parts by defining key sequences using these imaginary
1722 For example, if you call @code{read-key-sequence} and then click the
1723 mouse on the window's mode line, you get two events, like this:
1726 (read-key-sequence "Click on the mode line: ")
1727 @result{} [mode-line
1729 (#<window 6 on NEWS> mode-line
1730 (40 . 63) 5959987))]
1733 @defvar num-input-keys
1735 This variable's value is the number of key sequences processed so far in
1736 this Emacs session. This includes key sequences read from the terminal
1737 and key sequences read from keyboard macros being executed.
1740 @tindex num-nonmacro-input-events
1741 @defvar num-nonmacro-input-events
1742 This variable holds the total number of input events received so far
1743 from the terminal---not counting those generated by keyboard macros.
1746 @node Reading One Event
1747 @subsection Reading One Event
1749 The lowest level functions for command input are those that read a
1753 This function reads and returns the next event of command input, waiting
1754 if necessary until an event is available. Events can come directly from
1755 the user or from a keyboard macro.
1757 The function @code{read-event} does not display any message to indicate
1758 it is waiting for input; use @code{message} first, if you wish to
1759 display one. If you have not displayed a message, @code{read-event}
1760 prompts by echoing: it displays descriptions of the events that led to
1761 or were read by the current command. @xref{The Echo Area}.
1763 If @code{cursor-in-echo-area} is non-@code{nil}, then @code{read-event}
1764 moves the cursor temporarily to the echo area, to the end of any message
1765 displayed there. Otherwise @code{read-event} does not move the cursor.
1767 Here is what happens if you call @code{read-event} and then press the
1768 right-arrow function key:
1779 This function reads and returns a character of command input. It
1780 discards any events that are not characters, until it gets a character.
1782 In the first example, the user types the character @kbd{1} (@sc{ASCII}
1783 code 49). The second example shows a keyboard macro definition that
1784 calls @code{read-char} from the minibuffer using @code{eval-expression}.
1785 @code{read-char} reads the keyboard macro's very next character, which
1786 is @kbd{1}. Then @code{eval-expression} displays its return value in
1796 ;; @r{We assume here you use @kbd{M-:} to evaluate this.}
1797 (symbol-function 'foo)
1798 @result{} "^[:(read-char)^M1"
1801 (execute-kbd-macro 'foo)
1808 @node Quoted Character Input
1809 @subsection Quoted Character Input
1810 @cindex quoted character input
1812 You can use the function @code{read-quoted-char} to ask the user to
1813 specify a character, and allow the user to specify a control or meta
1814 character conveniently, either literally or as an octal character code.
1815 The command @code{quoted-insert} uses this function.
1817 @defun read-quoted-char &optional prompt
1818 @cindex octal character input
1819 @cindex control characters, reading
1820 @cindex nonprinting characters, reading
1821 This function is like @code{read-char}, except that if the first
1822 character read is an octal digit (0-7), it reads up to two more octal digits
1823 (but stopping if a non-octal digit is found) and returns the
1824 character represented by those digits in octal.
1826 Quitting is suppressed when the first character is read, so that the
1827 user can enter a @kbd{C-g}. @xref{Quitting}.
1829 If @var{prompt} is supplied, it specifies a string for prompting the
1830 user. The prompt string is always displayed in the echo area, followed
1831 by a single @samp{-}.
1833 In the following example, the user types in the octal number 177 (which
1837 (read-quoted-char "What character")
1840 ---------- Echo Area ----------
1841 What character-@kbd{177}
1842 ---------- Echo Area ----------
1850 @node Event Input Misc
1851 @subsection Miscellaneous Event Input Features
1853 This section describes how to ``peek ahead'' at events without using
1854 them up, how to check for pending input, and how to discard pending
1857 @defvar unread-command-events
1859 @cindex peeking at input
1860 This variable holds a list of events waiting to be read as command
1861 input. The events are used in the order they appear in the list, and
1862 removed one by one as they are used.
1864 The variable is needed because in some cases a function reads an event
1865 and then decides not to use it. Storing the event in this variable
1866 causes it to be processed normally, by the command loop or by the
1867 functions to read command input.
1869 @cindex prefix argument unreading
1870 For example, the function that implements numeric prefix arguments reads
1871 any number of digits. When it finds a non-digit event, it must unread
1872 the event so that it can be read normally by the command loop.
1873 Likewise, incremental search uses this feature to unread events with no
1874 special meaning in a search, because these events should exit the search
1875 and then execute normally.
1877 The reliable and easy way to extract events from a key sequence so as to
1878 put them in @code{unread-command-events} is to use
1879 @code{listify-key-sequence} (@pxref{Strings of Events}).
1881 Normally you add events to the front of this list, so that the events
1882 most recently unread will be reread first.
1885 @defvar unread-command-char
1886 This variable holds a character to be read as command input.
1887 A value of -1 means ``empty''.
1889 This variable is mostly obsolete now that you can use
1890 @code{unread-command-events} instead; it exists only to support programs
1891 written for Emacs versions 18 and earlier.
1894 @defun input-pending-p
1895 @cindex waiting for command key input
1896 This function determines whether any command input is currently
1897 available to be read. It returns immediately, with value @code{t} if
1898 there is available input, @code{nil} otherwise. On rare occasions it
1899 may return @code{t} when no input is available.
1902 @defvar last-input-event
1903 This variable records the last terminal input event read, whether
1904 as part of a command or explicitly by a Lisp program.
1906 In the example below, the Lisp program reads the character @kbd{1},
1907 @sc{ASCII} code 49. It becomes the value of @code{last-input-event},
1908 while @kbd{C-e} (we assume @kbd{C-x C-e} command is used to evaluate
1909 this expression) remains the value of @code{last-command-event}.
1913 (progn (print (read-char))
1914 (print last-command-event)
1922 @vindex last-input-char
1923 The alias @code{last-input-char} exists for compatibility with
1927 @defun discard-input
1929 @cindex discard input
1930 @cindex terminate keyboard macro
1931 This function discards the contents of the terminal input buffer and
1932 cancels any keyboard macro that might be in the process of definition.
1933 It returns @code{nil}.
1935 In the following example, the user may type a number of characters right
1936 after starting the evaluation of the form. After the @code{sleep-for}
1937 finishes sleeping, @code{discard-input} discards any characters typed
1941 (progn (sleep-for 2)
1947 @node Special Events
1948 @section Special Events
1950 @cindex special events
1951 Special events are handled at a very low level---as soon as they are
1952 read. The @code{read-event} function processes these events itself, and
1955 Events that are handled in this way do not echo, they are never grouped
1956 into key sequences, and they never appear in the value of
1957 @code{last-command-event} or @code{(this-command-keys)}. They do not
1958 discard a numeric argument, they cannot be unread with
1959 @code{unread-command-events}, they may not appear in a keyboard macro,
1960 and they are not recorded in a keyboard macro while you are defining
1963 These events do, however, appear in @code{last-input-event} immediately
1964 after they are read, and this is the way for the event's definition to
1965 find the actual event.
1967 The events types @code{iconify-frame}, @code{make-frame-visible} and
1968 @code{delete-frame} are normally handled in this way. The keymap which
1969 defines how to handle special events---and which events are special---is
1970 in the variable @code{special-event-map} (@pxref{Active Keymaps}).
1973 @section Waiting for Elapsed Time or Input
1977 The wait functions are designed to wait for a certain amount of time
1978 to pass or until there is input. For example, you may wish to pause in
1979 the middle of a computation to allow the user time to view the display.
1980 @code{sit-for} pauses and updates the screen, and returns immediately if
1981 input comes in, while @code{sleep-for} pauses without updating the
1984 @defun sit-for seconds &optional millisec nodisp
1985 This function performs redisplay (provided there is no pending input
1986 from the user), then waits @var{seconds} seconds, or until input is
1987 available. The value is @code{t} if @code{sit-for} waited the full
1988 time with no input arriving (see @code{input-pending-p} in @ref{Event
1989 Input Misc}). Otherwise, the value is @code{nil}.
1991 The argument @var{seconds} need not be an integer. If it is a floating
1992 point number, @code{sit-for} waits for a fractional number of seconds.
1993 Some systems support only a whole number of seconds; on these systems,
1994 @var{seconds} is rounded down.
1996 The optional argument @var{millisec} specifies an additional waiting
1997 period measured in milliseconds. This adds to the period specified by
1998 @var{seconds}. If the system doesn't support waiting fractions of a
1999 second, you get an error if you specify nonzero @var{millisec}.
2001 @cindex forcing redisplay
2002 Redisplay is always preempted if input arrives, and does not happen at
2003 all if input is available before it starts. Thus, there is no way to
2004 force screen updating if there is pending input; however, if there is no
2005 input pending, you can force an update with no delay by using
2008 If @var{nodisp} is non-@code{nil}, then @code{sit-for} does not
2009 redisplay, but it still returns as soon as input is available (or when
2010 the timeout elapses).
2012 Iconifying or deiconifying a frame makes @code{sit-for} return, because
2013 that generates an event. @xref{Misc Events}.
2015 The usual purpose of @code{sit-for} is to give the user time to read
2016 text that you display.
2019 @defun sleep-for seconds &optional millisec
2020 This function simply pauses for @var{seconds} seconds without updating
2021 the display. It pays no attention to available input. It returns
2024 The argument @var{seconds} need not be an integer. If it is a floating
2025 point number, @code{sleep-for} waits for a fractional number of seconds.
2026 Some systems support only a whole number of seconds; on these systems,
2027 @var{seconds} is rounded down.
2029 The optional argument @var{millisec} specifies an additional waiting
2030 period measured in milliseconds. This adds to the period specified by
2031 @var{seconds}. If the system doesn't support waiting fractions of a
2032 second, you get an error if you specify nonzero @var{millisec}.
2034 Use @code{sleep-for} when you wish to guarantee a delay.
2037 @xref{Time of Day}, for functions to get the current time.
2044 Typing @kbd{C-g} while a Lisp function is running causes Emacs to
2045 @dfn{quit} whatever it is doing. This means that control returns to the
2046 innermost active command loop.
2048 Typing @kbd{C-g} while the command loop is waiting for keyboard input
2049 does not cause a quit; it acts as an ordinary input character. In the
2050 simplest case, you cannot tell the difference, because @kbd{C-g}
2051 normally runs the command @code{keyboard-quit}, whose effect is to quit.
2052 However, when @kbd{C-g} follows a prefix key, the result is an undefined
2053 key. The effect is to cancel the prefix key as well as any prefix
2056 In the minibuffer, @kbd{C-g} has a different definition: it aborts out
2057 of the minibuffer. This means, in effect, that it exits the minibuffer
2058 and then quits. (Simply quitting would return to the command loop
2059 @emph{within} the minibuffer.) The reason why @kbd{C-g} does not quit
2060 directly when the command reader is reading input is so that its meaning
2061 can be redefined in the minibuffer in this way. @kbd{C-g} following a
2062 prefix key is not redefined in the minibuffer, and it has its normal
2063 effect of canceling the prefix key and prefix argument. This too
2064 would not be possible if @kbd{C-g} always quit directly.
2066 When @kbd{C-g} does directly quit, it does so by setting the variable
2067 @code{quit-flag} to @code{t}. Emacs checks this variable at appropriate
2068 times and quits if it is not @code{nil}. Setting @code{quit-flag}
2069 non-@code{nil} in any way thus causes a quit.
2071 At the level of C code, quitting cannot happen just anywhere; only at the
2072 special places that check @code{quit-flag}. The reason for this is
2073 that quitting at other places might leave an inconsistency in Emacs's
2074 internal state. Because quitting is delayed until a safe place, quitting
2075 cannot make Emacs crash.
2077 Certain functions such as @code{read-key-sequence} or
2078 @code{read-quoted-char} prevent quitting entirely even though they wait
2079 for input. Instead of quitting, @kbd{C-g} serves as the requested
2080 input. In the case of @code{read-key-sequence}, this serves to bring
2081 about the special behavior of @kbd{C-g} in the command loop. In the
2082 case of @code{read-quoted-char}, this is so that @kbd{C-q} can be used
2083 to quote a @kbd{C-g}.
2085 You can prevent quitting for a portion of a Lisp function by binding
2086 the variable @code{inhibit-quit} to a non-@code{nil} value. Then,
2087 although @kbd{C-g} still sets @code{quit-flag} to @code{t} as usual, the
2088 usual result of this---a quit---is prevented. Eventually,
2089 @code{inhibit-quit} will become @code{nil} again, such as when its
2090 binding is unwound at the end of a @code{let} form. At that time, if
2091 @code{quit-flag} is still non-@code{nil}, the requested quit happens
2092 immediately. This behavior is ideal when you wish to make sure that
2093 quitting does not happen within a ``critical section'' of the program.
2095 @cindex @code{read-quoted-char} quitting
2096 In some functions (such as @code{read-quoted-char}), @kbd{C-g} is
2097 handled in a special way that does not involve quitting. This is done
2098 by reading the input with @code{inhibit-quit} bound to @code{t}, and
2099 setting @code{quit-flag} to @code{nil} before @code{inhibit-quit}
2100 becomes @code{nil} again. This excerpt from the definition of
2101 @code{read-quoted-char} shows how this is done; it also shows that
2102 normal quitting is permitted after the first character of input.
2105 (defun read-quoted-char (&optional prompt)
2106 "@dots{}@var{documentation}@dots{}"
2107 (let ((count 0) (code 0) char)
2109 (let ((inhibit-quit (zerop count))
2111 (and prompt (message "%s-" prompt))
2112 (setq char (read-char))
2113 (if inhibit-quit (setq quit-flag nil)))
2119 If this variable is non-@code{nil}, then Emacs quits immediately, unless
2120 @code{inhibit-quit} is non-@code{nil}. Typing @kbd{C-g} ordinarily sets
2121 @code{quit-flag} non-@code{nil}, regardless of @code{inhibit-quit}.
2124 @defvar inhibit-quit
2125 This variable determines whether Emacs should quit when @code{quit-flag}
2126 is set to a value other than @code{nil}. If @code{inhibit-quit} is
2127 non-@code{nil}, then @code{quit-flag} has no special effect.
2130 @deffn Command keyboard-quit
2131 This function signals the @code{quit} condition with @code{(signal 'quit
2132 nil)}. This is the same thing that quitting does. (See @code{signal}
2136 You can specify a character other than @kbd{C-g} to use for quitting.
2137 See the function @code{set-input-mode} in @ref{Terminal Input}.
2139 @node Prefix Command Arguments
2140 @section Prefix Command Arguments
2141 @cindex prefix argument
2142 @cindex raw prefix argument
2143 @cindex numeric prefix argument
2145 Most Emacs commands can use a @dfn{prefix argument}, a number
2146 specified before the command itself. (Don't confuse prefix arguments
2147 with prefix keys.) The prefix argument is at all times represented by a
2148 value, which may be @code{nil}, meaning there is currently no prefix
2149 argument. Each command may use the prefix argument or ignore it.
2151 There are two representations of the prefix argument: @dfn{raw} and
2152 @dfn{numeric}. The editor command loop uses the raw representation
2153 internally, and so do the Lisp variables that store the information, but
2154 commands can request either representation.
2156 Here are the possible values of a raw prefix argument:
2160 @code{nil}, meaning there is no prefix argument. Its numeric value is
2161 1, but numerous commands make a distinction between @code{nil} and the
2165 An integer, which stands for itself.
2168 A list of one element, which is an integer. This form of prefix
2169 argument results from one or a succession of @kbd{C-u}'s with no
2170 digits. The numeric value is the integer in the list, but some
2171 commands make a distinction between such a list and an integer alone.
2174 The symbol @code{-}. This indicates that @kbd{M--} or @kbd{C-u -} was
2175 typed, without following digits. The equivalent numeric value is
2176 @minus{}1, but some commands make a distinction between the integer
2177 @minus{}1 and the symbol @code{-}.
2180 We illustrate these possibilities by calling the following function with
2185 (defun display-prefix (arg)
2186 "Display the value of the raw prefix arg."
2193 Here are the results of calling @code{display-prefix} with various
2194 raw prefix arguments:
2197 M-x display-prefix @print{} nil
2199 C-u M-x display-prefix @print{} (4)
2201 C-u C-u M-x display-prefix @print{} (16)
2203 C-u 3 M-x display-prefix @print{} 3
2205 M-3 M-x display-prefix @print{} 3 ; @r{(Same as @code{C-u 3}.)}
2207 C-u - M-x display-prefix @print{} -
2209 M-- M-x display-prefix @print{} - ; @r{(Same as @code{C-u -}.)}
2211 C-u - 7 M-x display-prefix @print{} -7
2213 M-- 7 M-x display-prefix @print{} -7 ; @r{(Same as @code{C-u -7}.)}
2216 Emacs uses two variables to store the prefix argument:
2217 @code{prefix-arg} and @code{current-prefix-arg}. Commands such as
2218 @code{universal-argument} that set up prefix arguments for other
2219 commands store them in @code{prefix-arg}. In contrast,
2220 @code{current-prefix-arg} conveys the prefix argument to the current
2221 command, so setting it has no effect on the prefix arguments for future
2224 Normally, commands specify which representation to use for the prefix
2225 argument, either numeric or raw, in the @code{interactive} declaration.
2226 (@xref{Using Interactive}.) Alternatively, functions may look at the
2227 value of the prefix argument directly in the variable
2228 @code{current-prefix-arg}, but this is less clean.
2230 @defun prefix-numeric-value arg
2231 This function returns the numeric meaning of a valid raw prefix argument
2232 value, @var{arg}. The argument may be a symbol, a number, or a list.
2233 If it is @code{nil}, the value 1 is returned; if it is @code{-}, the
2234 value @minus{}1 is returned; if it is a number, that number is returned;
2235 if it is a list, the @sc{car} of that list (which should be a number) is
2239 @defvar current-prefix-arg
2240 This variable holds the raw prefix argument for the @emph{current}
2241 command. Commands may examine it directly, but the usual method for
2242 accessing it is with @code{(interactive "P")}.
2246 The value of this variable is the raw prefix argument for the
2247 @emph{next} editing command. Commands such as @code{universal-argument}
2248 that specify prefix arguments for the following command work by setting
2252 The following commands exist to set up prefix arguments for the
2253 following command. Do not call them for any other reason.
2255 @deffn Command universal-argument
2256 This command reads input and specifies a prefix argument for the
2257 following command. Don't call this command yourself unless you know
2261 @deffn Command digit-argument arg
2262 This command adds to the prefix argument for the following command. The
2263 argument @var{arg} is the raw prefix argument as it was before this
2264 command; it is used to compute the updated prefix argument. Don't call
2265 this command yourself unless you know what you are doing.
2268 @deffn Command negative-argument arg
2269 This command adds to the numeric argument for the next command. The
2270 argument @var{arg} is the raw prefix argument as it was before this
2271 command; its value is negated to form the new prefix argument. Don't
2272 call this command yourself unless you know what you are doing.
2275 @node Recursive Editing
2276 @section Recursive Editing
2277 @cindex recursive command loop
2278 @cindex recursive editing level
2279 @cindex command loop, recursive
2281 The Emacs command loop is entered automatically when Emacs starts up.
2282 This top-level invocation of the command loop never exits; it keeps
2283 running as long as Emacs does. Lisp programs can also invoke the
2284 command loop. Since this makes more than one activation of the command
2285 loop, we call it @dfn{recursive editing}. A recursive editing level has
2286 the effect of suspending whatever command invoked it and permitting the
2287 user to do arbitrary editing before resuming that command.
2289 The commands available during recursive editing are the same ones
2290 available in the top-level editing loop and defined in the keymaps.
2291 Only a few special commands exit the recursive editing level; the others
2292 return to the recursive editing level when they finish. (The special
2293 commands for exiting are always available, but they do nothing when
2294 recursive editing is not in progress.)
2296 All command loops, including recursive ones, set up all-purpose error
2297 handlers so that an error in a command run from the command loop will
2300 @cindex minibuffer input
2301 Minibuffer input is a special kind of recursive editing. It has a few
2302 special wrinkles, such as enabling display of the minibuffer and the
2303 minibuffer window, but fewer than you might suppose. Certain keys
2304 behave differently in the minibuffer, but that is only because of the
2305 minibuffer's local map; if you switch windows, you get the usual Emacs
2308 @cindex @code{throw} example
2310 @cindex exit recursive editing
2312 To invoke a recursive editing level, call the function
2313 @code{recursive-edit}. This function contains the command loop; it also
2314 contains a call to @code{catch} with tag @code{exit}, which makes it
2315 possible to exit the recursive editing level by throwing to @code{exit}
2316 (@pxref{Catch and Throw}). If you throw a value other than @code{t},
2317 then @code{recursive-edit} returns normally to the function that called
2318 it. The command @kbd{C-M-c} (@code{exit-recursive-edit}) does this.
2319 Throwing a @code{t} value causes @code{recursive-edit} to quit, so that
2320 control returns to the command loop one level up. This is called
2321 @dfn{aborting}, and is done by @kbd{C-]} (@code{abort-recursive-edit}).
2323 Most applications should not use recursive editing, except as part of
2324 using the minibuffer. Usually it is more convenient for the user if you
2325 change the major mode of the current buffer temporarily to a special
2326 major mode, which should have a command to go back to the previous mode.
2327 (The @kbd{e} command in Rmail uses this technique.) Or, if you wish to
2328 give the user different text to edit ``recursively'', create and select
2329 a new buffer in a special mode. In this mode, define a command to
2330 complete the processing and go back to the previous buffer. (The
2331 @kbd{m} command in Rmail does this.)
2333 Recursive edits are useful in debugging. You can insert a call to
2334 @code{debug} into a function definition as a sort of breakpoint, so that
2335 you can look around when the function gets there. @code{debug} invokes
2336 a recursive edit but also provides the other features of the debugger.
2338 Recursive editing levels are also used when you type @kbd{C-r} in
2339 @code{query-replace} or use @kbd{C-x q} (@code{kbd-macro-query}).
2341 @defun recursive-edit
2342 @cindex suspend evaluation
2343 This function invokes the editor command loop. It is called
2344 automatically by the initialization of Emacs, to let the user begin
2345 editing. When called from a Lisp program, it enters a recursive editing
2348 In the following example, the function @code{simple-rec} first
2349 advances point one word, then enters a recursive edit, printing out a
2350 message in the echo area. The user can then do any editing desired, and
2351 then type @kbd{C-M-c} to exit and continue executing @code{simple-rec}.
2354 (defun simple-rec ()
2356 (message "Recursive edit in progress")
2359 @result{} simple-rec
2365 @deffn Command exit-recursive-edit
2366 This function exits from the innermost recursive edit (including
2367 minibuffer input). Its definition is effectively @code{(throw 'exit
2371 @deffn Command abort-recursive-edit
2372 This function aborts the command that requested the innermost recursive
2373 edit (including minibuffer input), by signaling @code{quit}
2374 after exiting the recursive edit. Its definition is effectively
2375 @code{(throw 'exit t)}. @xref{Quitting}.
2378 @deffn Command top-level
2379 This function exits all recursive editing levels; it does not return a
2380 value, as it jumps completely out of any computation directly back to
2381 the main command loop.
2384 @defun recursion-depth
2385 This function returns the current depth of recursive edits. When no
2386 recursive edit is active, it returns 0.
2389 @node Disabling Commands
2390 @section Disabling Commands
2391 @cindex disabled command
2393 @dfn{Disabling a command} marks the command as requiring user
2394 confirmation before it can be executed. Disabling is used for commands
2395 which might be confusing to beginning users, to prevent them from using
2396 the commands by accident.
2399 The low-level mechanism for disabling a command is to put a
2400 non-@code{nil} @code{disabled} property on the Lisp symbol for the
2401 command. These properties are normally set up by the user's
2402 @file{.emacs} file with Lisp expressions such as this:
2405 (put 'upcase-region 'disabled t)
2409 For a few commands, these properties are present by default and may be
2410 removed by the @file{.emacs} file.
2412 If the value of the @code{disabled} property is a string, the message
2413 saying the command is disabled includes that string. For example:
2416 (put 'delete-region 'disabled
2417 "Text deleted this way cannot be yanked back!\n")
2420 @xref{Disabling,,, emacs, The GNU Emacs Manual}, for the details on
2421 what happens when a disabled command is invoked interactively.
2422 Disabling a command has no effect on calling it as a function from Lisp
2425 @deffn Command enable-command command
2426 Allow @var{command} to be executed without special confirmation from now
2427 on, and (if the user confirms) alter the user's @file{.emacs} file so
2428 that this will apply to future sessions.
2431 @deffn Command disable-command command
2432 Require special confirmation to execute @var{command} from now on, and
2433 (if the user confirms) alter the user's @file{.emacs} file so that this
2434 will apply to future sessions.
2437 @defvar disabled-command-hook
2438 When the user invokes a disabled command interactively, this normal hook
2439 is run instead of the disabled command. The hook functions can use
2440 @code{this-command-keys} to determine what the user typed to run the
2441 command, and thus find the command itself. @xref{Hooks}.
2443 By default, @code{disabled-command-hook} contains a function that asks
2444 the user whether to proceed.
2447 @node Command History
2448 @section Command History
2449 @cindex command history
2450 @cindex complex command
2451 @cindex history of commands
2453 The command loop keeps a history of the complex commands that have
2454 been executed, to make it convenient to repeat these commands. A
2455 @dfn{complex command} is one for which the interactive argument reading
2456 uses the minibuffer. This includes any @kbd{M-x} command, any
2457 @kbd{M-:} command, and any command whose @code{interactive}
2458 specification reads an argument from the minibuffer. Explicit use of
2459 the minibuffer during the execution of the command itself does not cause
2460 the command to be considered complex.
2462 @defvar command-history
2463 This variable's value is a list of recent complex commands, each
2464 represented as a form to evaluate. It continues to accumulate all
2465 complex commands for the duration of the editing session, but all but
2466 the first (most recent) thirty elements are deleted when a garbage
2467 collection takes place (@pxref{Garbage Collection}).
2472 @result{} ((switch-to-buffer "chistory.texi")
2473 (describe-key "^X^[")
2474 (visit-tags-table "~/emacs/src/")
2475 (find-tag "repeat-complex-command"))
2480 This history list is actually a special case of minibuffer history
2481 (@pxref{Minibuffer History}), with one special twist: the elements are
2482 expressions rather than strings.
2484 There are a number of commands devoted to the editing and recall of
2485 previous commands. The commands @code{repeat-complex-command}, and
2486 @code{list-command-history} are described in the user manual
2487 (@pxref{Repetition,,, emacs, The GNU Emacs Manual}). Within the
2488 minibuffer, the usual minibuffer history commands are available.
2490 @node Keyboard Macros
2491 @section Keyboard Macros
2492 @cindex keyboard macros
2494 A @dfn{keyboard macro} is a canned sequence of input events that can
2495 be considered a command and made the definition of a key. The Lisp
2496 representation of a keyboard macro is a string or vector containing the
2497 events. Don't confuse keyboard macros with Lisp macros
2500 @defun execute-kbd-macro kbdmacro &optional count
2501 This function executes @var{kbdmacro} as a sequence of events. If
2502 @var{kbdmacro} is a string or vector, then the events in it are executed
2503 exactly as if they had been input by the user. The sequence is
2504 @emph{not} expected to be a single key sequence; normally a keyboard
2505 macro definition consists of several key sequences concatenated.
2507 If @var{kbdmacro} is a symbol, then its function definition is used in
2508 place of @var{kbdmacro}. If that is another symbol, this process repeats.
2509 Eventually the result should be a string or vector. If the result is
2510 not a symbol, string, or vector, an error is signaled.
2512 The argument @var{count} is a repeat count; @var{kbdmacro} is executed that
2513 many times. If @var{count} is omitted or @code{nil}, @var{kbdmacro} is
2514 executed once. If it is 0, @var{kbdmacro} is executed over and over until it
2515 encounters an error or a failing search.
2517 @xref{Reading One Event}, for an example of using @code{execute-kbd-macro}.
2520 @defvar executing-macro
2521 This variable contains the string or vector that defines the keyboard
2522 macro that is currently executing. It is @code{nil} if no macro is
2523 currently executing. A command can test this variable so as to behave
2524 differently when run from an executing macro. Do not set this variable
2528 @defvar defining-kbd-macro
2529 This variable indicates whether a keyboard macro is being defined. A
2530 command can test this variable so as to behave differently while a macro
2531 is being defined. The commands @code{start-kbd-macro} and
2532 @code{end-kbd-macro} set this variable---do not set it yourself.
2534 The variable is always local to the current terminal and cannot be
2535 buffer-local. @xref{Multiple Displays}.
2538 @defvar last-kbd-macro
2539 This variable is the definition of the most recently defined keyboard
2540 macro. Its value is a string or vector, or @code{nil}.
2542 The variable is always local to the current terminal and cannot be
2543 buffer-local. @xref{Multiple Displays}.