2 @c This is part of the GNU Emacs Lisp Reference Manual.
3 @c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2001, 2002,
4 @c 2003, 2004, 2005, 2006, 2007 Free Software Foundation, Inc.
5 @c See the file elisp.texi for copying conditions.
6 @setfilename ../info/commands
7 @node Command Loop, Keymaps, Minibuffers, Top
9 @cindex editor command loop
12 When you run Emacs, it enters the @dfn{editor command loop} almost
13 immediately. This loop reads key sequences, executes their definitions,
14 and displays the results. In this chapter, we describe how these things
15 are done, and the subroutines that allow Lisp programs to do them.
18 * Command Overview:: How the command loop reads commands.
19 * Defining Commands:: Specifying how a function should read arguments.
20 * Interactive Call:: Calling a command, so that it will read arguments.
21 * Command Loop Info:: Variables set by the command loop for you to examine.
22 * Adjusting Point:: Adjustment of point after a command.
23 * Input Events:: What input looks like when you read it.
24 * Reading Input:: How to read input events from the keyboard or mouse.
25 * Special Events:: Events processed immediately and individually.
26 * Waiting:: Waiting for user input or elapsed time.
27 * Quitting:: How @kbd{C-g} works. How to catch or defer quitting.
28 * Prefix Command Arguments:: How the commands to set prefix args work.
29 * Recursive Editing:: Entering a recursive edit,
30 and why you usually shouldn't.
31 * Disabling Commands:: How the command loop handles disabled commands.
32 * Command History:: How the command history is set up, and how accessed.
33 * Keyboard Macros:: How keyboard macros are implemented.
36 @node Command Overview
37 @section Command Loop Overview
39 The first thing the command loop must do is read a key sequence, which
40 is a sequence of events that translates into a command. It does this by
41 calling the function @code{read-key-sequence}. Your Lisp code can also
42 call this function (@pxref{Key Sequence Input}). Lisp programs can also
43 do input at a lower level with @code{read-event} (@pxref{Reading One
44 Event}) or discard pending input with @code{discard-input}
45 (@pxref{Event Input Misc}).
47 The key sequence is translated into a command through the currently
48 active keymaps. @xref{Key Lookup}, for information on how this is done.
49 The result should be a keyboard macro or an interactively callable
50 function. If the key is @kbd{M-x}, then it reads the name of another
51 command, which it then calls. This is done by the command
52 @code{execute-extended-command} (@pxref{Interactive Call}).
54 To execute a command requires first reading the arguments for it.
55 This is done by calling @code{command-execute} (@pxref{Interactive
56 Call}). For commands written in Lisp, the @code{interactive}
57 specification says how to read the arguments. This may use the prefix
58 argument (@pxref{Prefix Command Arguments}) or may read with prompting
59 in the minibuffer (@pxref{Minibuffers}). For example, the command
60 @code{find-file} has an @code{interactive} specification which says to
61 read a file name using the minibuffer. The command's function body does
62 not use the minibuffer; if you call this command from Lisp code as a
63 function, you must supply the file name string as an ordinary Lisp
66 If the command is a string or vector (i.e., a keyboard macro) then
67 @code{execute-kbd-macro} is used to execute it. You can call this
68 function yourself (@pxref{Keyboard Macros}).
70 To terminate the execution of a running command, type @kbd{C-g}. This
71 character causes @dfn{quitting} (@pxref{Quitting}).
73 @defvar pre-command-hook
74 The editor command loop runs this normal hook before each command. At
75 that time, @code{this-command} contains the command that is about to
76 run, and @code{last-command} describes the previous command.
77 @xref{Command Loop Info}.
80 @defvar post-command-hook
81 The editor command loop runs this normal hook after each command
82 (including commands terminated prematurely by quitting or by errors),
83 and also when the command loop is first entered. At that time,
84 @code{this-command} refers to the command that just ran, and
85 @code{last-command} refers to the command before that.
88 Quitting is suppressed while running @code{pre-command-hook} and
89 @code{post-command-hook}. If an error happens while executing one of
90 these hooks, it terminates execution of the hook, and clears the hook
91 variable to @code{nil} so as to prevent an infinite loop of errors.
93 A request coming into the Emacs server (@pxref{Emacs Server,,,
94 emacs, The GNU Emacs Manual}) runs these two hooks just as a keyboard
97 @node Defining Commands
98 @section Defining Commands
99 @cindex defining commands
100 @cindex commands, defining
101 @cindex functions, making them interactive
102 @cindex interactive function
104 A Lisp function becomes a command when its body contains, at top
105 level, a form that calls the special form @code{interactive}. This
106 form does nothing when actually executed, but its presence serves as a
107 flag to indicate that interactive calling is permitted. Its argument
108 controls the reading of arguments for an interactive call.
111 * Using Interactive:: General rules for @code{interactive}.
112 * Interactive Codes:: The standard letter-codes for reading arguments
114 * Interactive Examples:: Examples of how to read interactive arguments.
117 @node Using Interactive
118 @subsection Using @code{interactive}
120 This section describes how to write the @code{interactive} form that
121 makes a Lisp function an interactively-callable command, and how to
122 examine a command's @code{interactive} form.
124 @defspec interactive arg-descriptor
125 @cindex argument descriptors
126 This special form declares that the function in which it appears is a
127 command, and that it may therefore be called interactively (via
128 @kbd{M-x} or by entering a key sequence bound to it). The argument
129 @var{arg-descriptor} declares how to compute the arguments to the
130 command when the command is called interactively.
132 A command may be called from Lisp programs like any other function, but
133 then the caller supplies the arguments and @var{arg-descriptor} has no
136 The @code{interactive} form has its effect because the command loop
137 (actually, its subroutine @code{call-interactively}) scans through the
138 function definition looking for it, before calling the function. Once
139 the function is called, all its body forms including the
140 @code{interactive} form are executed, but at this time
141 @code{interactive} simply returns @code{nil} without even evaluating its
145 There are three possibilities for the argument @var{arg-descriptor}:
149 It may be omitted or @code{nil}; then the command is called with no
150 arguments. This leads quickly to an error if the command requires one
154 @cindex argument prompt
155 It may be a string; then its contents should consist of a code character
156 followed by a prompt (which some code characters use and some ignore).
157 The prompt ends either with the end of the string or with a newline.
158 Here is a simple example:
161 (interactive "bFrobnicate buffer: ")
165 The code letter @samp{b} says to read the name of an existing buffer,
166 with completion. The buffer name is the sole argument passed to the
167 command. The rest of the string is a prompt.
169 If there is a newline character in the string, it terminates the prompt.
170 If the string does not end there, then the rest of the string should
171 contain another code character and prompt, specifying another argument.
172 You can specify any number of arguments in this way.
175 The prompt string can use @samp{%} to include previous argument values
176 (starting with the first argument) in the prompt. This is done using
177 @code{format} (@pxref{Formatting Strings}). For example, here is how
178 you could read the name of an existing buffer followed by a new name to
183 (interactive "bBuffer to rename: \nsRename buffer %s to: ")
187 @cindex @samp{*} in @code{interactive}
188 @cindex read-only buffers in interactive
189 If the first character in the string is @samp{*}, then an error is
190 signaled if the buffer is read-only.
192 @cindex @samp{@@} in @code{interactive}
194 If the first character in the string is @samp{@@}, and if the key
195 sequence used to invoke the command includes any mouse events, then
196 the window associated with the first of those events is selected
197 before the command is run.
199 You can use @samp{*} and @samp{@@} together; the order does not matter.
200 Actual reading of arguments is controlled by the rest of the prompt
201 string (starting with the first character that is not @samp{*} or
205 It may be a Lisp expression that is not a string; then it should be a
206 form that is evaluated to get a list of arguments to pass to the
207 command. Usually this form will call various functions to read input
208 from the user, most often through the minibuffer (@pxref{Minibuffers})
209 or directly from the keyboard (@pxref{Reading Input}).
210 @cindex argument evaluation form
212 Providing point or the mark as an argument value is also common, but
213 if you do this @emph{and} read input (whether using the minibuffer or
214 not), be sure to get the integer values of point or the mark after
215 reading. The current buffer may be receiving subprocess output; if
216 subprocess output arrives while the command is waiting for input, it
217 could relocate point and the mark.
219 Here's an example of what @emph{not} to do:
223 (list (region-beginning) (region-end)
224 (read-string "Foo: " nil 'my-history)))
228 Here's how to avoid the problem, by examining point and the mark after
229 reading the keyboard input:
233 (let ((string (read-string "Foo: " nil 'my-history)))
234 (list (region-beginning) (region-end) string)))
237 @strong{Warning:} the argument values should not include any data
238 types that can't be printed and then read. Some facilities save
239 @code{command-history} in a file to be read in the subsequent
240 sessions; if a command's arguments contain a data type that prints
241 using @samp{#<@dots{}>} syntax, those facilities won't work.
243 There are, however, a few exceptions: it is ok to use a limited set of
244 expressions such as @code{(point)}, @code{(mark)},
245 @code{(region-beginning)}, and @code{(region-end)}, because Emacs
246 recognizes them specially and puts the expression (rather than its
247 value) into the command history. To see whether the expression you
248 wrote is one of these exceptions, run the command, then examine
249 @code{(car command-history)}.
252 @cindex examining the @code{interactive} form
253 @defun interactive-form function
254 This function returns the @code{interactive} form of @var{function}.
255 If @var{function} is an interactively callable function
256 (@pxref{Interactive Call}), the value is the command's
257 @code{interactive} form @code{(interactive @var{spec})}, which
258 specifies how to compute its arguments. Otherwise, the value is
259 @code{nil}. If @var{function} is a symbol, its function definition is
263 @node Interactive Codes
264 @comment node-name, next, previous, up
265 @subsection Code Characters for @code{interactive}
266 @cindex interactive code description
267 @cindex description for interactive codes
268 @cindex codes, interactive, description of
269 @cindex characters for interactive codes
271 The code character descriptions below contain a number of key words,
272 defined here as follows:
276 @cindex interactive completion
277 Provide completion. @key{TAB}, @key{SPC}, and @key{RET} perform name
278 completion because the argument is read using @code{completing-read}
279 (@pxref{Completion}). @kbd{?} displays a list of possible completions.
282 Require the name of an existing object. An invalid name is not
283 accepted; the commands to exit the minibuffer do not exit if the current
287 @cindex default argument string
288 A default value of some sort is used if the user enters no text in the
289 minibuffer. The default depends on the code character.
292 This code letter computes an argument without reading any input.
293 Therefore, it does not use a prompt string, and any prompt string you
296 Even though the code letter doesn't use a prompt string, you must follow
297 it with a newline if it is not the last code character in the string.
300 A prompt immediately follows the code character. The prompt ends either
301 with the end of the string or with a newline.
304 This code character is meaningful only at the beginning of the
305 interactive string, and it does not look for a prompt or a newline.
306 It is a single, isolated character.
309 @cindex reading interactive arguments
310 Here are the code character descriptions for use with @code{interactive}:
314 Signal an error if the current buffer is read-only. Special.
317 Select the window mentioned in the first mouse event in the key
318 sequence that invoked this command. Special.
321 A function name (i.e., a symbol satisfying @code{fboundp}). Existing,
325 The name of an existing buffer. By default, uses the name of the
326 current buffer (@pxref{Buffers}). Existing, Completion, Default,
330 A buffer name. The buffer need not exist. By default, uses the name of
331 a recently used buffer other than the current buffer. Completion,
335 A character. The cursor does not move into the echo area. Prompt.
338 A command name (i.e., a symbol satisfying @code{commandp}). Existing,
342 @cindex position argument
343 The position of point, as an integer (@pxref{Point}). No I/O.
346 A directory name. The default is the current default directory of the
347 current buffer, @code{default-directory} (@pxref{File Name Expansion}).
348 Existing, Completion, Default, Prompt.
351 The first or next mouse event in the key sequence that invoked the command.
352 More precisely, @samp{e} gets events that are lists, so you can look at
353 the data in the lists. @xref{Input Events}. No I/O.
355 You can use @samp{e} more than once in a single command's interactive
356 specification. If the key sequence that invoked the command has
357 @var{n} events that are lists, the @var{n}th @samp{e} provides the
358 @var{n}th such event. Events that are not lists, such as function keys
359 and @acronym{ASCII} characters, do not count where @samp{e} is concerned.
362 A file name of an existing file (@pxref{File Names}). The default
363 directory is @code{default-directory}. Existing, Completion, Default,
367 A file name. The file need not exist. Completion, Default, Prompt.
370 A file name. The file need not exist. If the user enters just a
371 directory name, then the value is just that directory name, with no
372 file name within the directory added. Completion, Default, Prompt.
375 An irrelevant argument. This code always supplies @code{nil} as
376 the argument's value. No I/O.
379 A key sequence (@pxref{Key Sequences}). This keeps reading events
380 until a command (or undefined command) is found in the current key
381 maps. The key sequence argument is represented as a string or vector.
382 The cursor does not move into the echo area. Prompt.
384 If @samp{k} reads a key sequence that ends with a down-event, it also
385 reads and discards the following up-event. You can get access to that
386 up-event with the @samp{U} code character.
388 This kind of input is used by commands such as @code{describe-key} and
389 @code{global-set-key}.
392 A key sequence, whose definition you intend to change. This works like
393 @samp{k}, except that it suppresses, for the last input event in the key
394 sequence, the conversions that are normally used (when necessary) to
395 convert an undefined key into a defined one.
398 @cindex marker argument
399 The position of the mark, as an integer. No I/O.
402 Arbitrary text, read in the minibuffer using the current buffer's input
403 method, and returned as a string (@pxref{Input Methods,,, emacs, The GNU
404 Emacs Manual}). Prompt.
407 A number, read with the minibuffer. If the input is not a number, the
408 user has to try again. @samp{n} never uses the prefix argument.
412 The numeric prefix argument; but if there is no prefix argument, read
413 a number as with @kbd{n}. The value is always a number. @xref{Prefix
414 Command Arguments}. Prompt.
417 @cindex numeric prefix argument usage
418 The numeric prefix argument. (Note that this @samp{p} is lower case.)
422 @cindex raw prefix argument usage
423 The raw prefix argument. (Note that this @samp{P} is upper case.) No
427 @cindex region argument
428 Point and the mark, as two numeric arguments, smallest first. This is
429 the only code letter that specifies two successive arguments rather than
433 Arbitrary text, read in the minibuffer and returned as a string
434 (@pxref{Text from Minibuffer}). Terminate the input with either
435 @kbd{C-j} or @key{RET}. (@kbd{C-q} may be used to include either of
436 these characters in the input.) Prompt.
439 An interned symbol whose name is read in the minibuffer. Any whitespace
440 character terminates the input. (Use @kbd{C-q} to include whitespace in
441 the string.) Other characters that normally terminate a symbol (e.g.,
442 parentheses and brackets) do not do so here. Prompt.
445 A key sequence or @code{nil}. Can be used after a @samp{k} or
446 @samp{K} argument to get the up-event that was discarded (if any)
447 after @samp{k} or @samp{K} read a down-event. If no up-event has been
448 discarded, @samp{U} provides @code{nil} as the argument. No I/O.
451 A variable declared to be a user option (i.e., satisfying the
452 predicate @code{user-variable-p}). This reads the variable using
453 @code{read-variable}. @xref{Definition of read-variable}. Existing,
457 A Lisp object, specified with its read syntax, terminated with a
458 @kbd{C-j} or @key{RET}. The object is not evaluated. @xref{Object from
462 @cindex evaluated expression argument
463 A Lisp form's value. @samp{X} reads as @samp{x} does, then evaluates
464 the form so that its value becomes the argument for the command.
468 A coding system name (a symbol). If the user enters null input, the
469 argument value is @code{nil}. @xref{Coding Systems}. Completion,
473 A coding system name (a symbol)---but only if this command has a prefix
474 argument. With no prefix argument, @samp{Z} provides @code{nil} as the
475 argument value. Completion, Existing, Prompt.
478 @node Interactive Examples
479 @comment node-name, next, previous, up
480 @subsection Examples of Using @code{interactive}
481 @cindex examples of using @code{interactive}
482 @cindex @code{interactive}, examples of using
484 Here are some examples of @code{interactive}:
488 (defun foo1 () ; @r{@code{foo1} takes no arguments,}
489 (interactive) ; @r{just moves forward two words.}
495 (defun foo2 (n) ; @r{@code{foo2} takes one argument,}
496 (interactive "p") ; @r{which is the numeric prefix.}
497 (forward-word (* 2 n)))
502 (defun foo3 (n) ; @r{@code{foo3} takes one argument,}
503 (interactive "nCount:") ; @r{which is read with the Minibuffer.}
504 (forward-word (* 2 n)))
509 (defun three-b (b1 b2 b3)
510 "Select three existing buffers.
511 Put them into three windows, selecting the last one."
513 (interactive "bBuffer1:\nbBuffer2:\nbBuffer3:")
514 (delete-other-windows)
515 (split-window (selected-window) 8)
516 (switch-to-buffer b1)
518 (split-window (selected-window) 8)
519 (switch-to-buffer b2)
521 (switch-to-buffer b3))
524 (three-b "*scratch*" "declarations.texi" "*mail*")
529 @node Interactive Call
530 @section Interactive Call
531 @cindex interactive call
533 After the command loop has translated a key sequence into a command it
534 invokes that command using the function @code{command-execute}. If the
535 command is a function, @code{command-execute} calls
536 @code{call-interactively}, which reads the arguments and calls the
537 command. You can also call these functions yourself.
539 @defun commandp object &optional for-call-interactively
540 Returns @code{t} if @var{object} is suitable for calling interactively;
541 that is, if @var{object} is a command. Otherwise, returns @code{nil}.
543 The interactively callable objects include strings and vectors (treated
544 as keyboard macros), lambda expressions that contain a top-level call to
545 @code{interactive}, byte-code function objects made from such lambda
546 expressions, autoload objects that are declared as interactive
547 (non-@code{nil} fourth argument to @code{autoload}), and some of the
550 A symbol satisfies @code{commandp} if its function definition
551 satisfies @code{commandp}. Keys and keymaps are not commands.
552 Rather, they are used to look up commands (@pxref{Keymaps}).
554 If @var{for-call-interactively} is non-@code{nil}, then
555 @code{commandp} returns @code{t} only for objects that
556 @code{call-interactively} could call---thus, not for keyboard macros.
558 See @code{documentation} in @ref{Accessing Documentation}, for a
559 realistic example of using @code{commandp}.
562 @defun call-interactively command &optional record-flag keys
563 This function calls the interactively callable function @var{command},
564 reading arguments according to its interactive calling specifications.
565 It returns whatever @var{command} returns. An error is signaled if
566 @var{command} is not a function or if it cannot be called
567 interactively (i.e., is not a command). Note that keyboard macros
568 (strings and vectors) are not accepted, even though they are
569 considered commands, because they are not functions. If @var{command}
570 is a symbol, then @code{call-interactively} uses its function definition.
572 @cindex record command history
573 If @var{record-flag} is non-@code{nil}, then this command and its
574 arguments are unconditionally added to the list @code{command-history}.
575 Otherwise, the command is added only if it uses the minibuffer to read
576 an argument. @xref{Command History}.
578 The argument @var{keys}, if given, should be a vector which specifies
579 the sequence of events to supply if the command inquires which events
580 were used to invoke it. If @var{keys} is omitted or @code{nil}, the
581 default is the return value of @code{this-command-keys-vector}.
582 @xref{Definition of this-command-keys-vector}.
585 @defun command-execute command &optional record-flag keys special
586 @cindex keyboard macro execution
587 This function executes @var{command}. The argument @var{command} must
588 satisfy the @code{commandp} predicate; i.e., it must be an interactively
589 callable function or a keyboard macro.
591 A string or vector as @var{command} is executed with
592 @code{execute-kbd-macro}. A function is passed to
593 @code{call-interactively}, along with the optional @var{record-flag}
596 A symbol is handled by using its function definition in its place. A
597 symbol with an @code{autoload} definition counts as a command if it was
598 declared to stand for an interactively callable function. Such a
599 definition is handled by loading the specified library and then
600 rechecking the definition of the symbol.
602 The argument @var{special}, if given, means to ignore the prefix
603 argument and not clear it. This is used for executing special events
604 (@pxref{Special Events}).
607 @deffn Command execute-extended-command prefix-argument
608 @cindex read command name
609 This function reads a command name from the minibuffer using
610 @code{completing-read} (@pxref{Completion}). Then it uses
611 @code{command-execute} to call the specified command. Whatever that
612 command returns becomes the value of @code{execute-extended-command}.
614 @cindex execute with prefix argument
615 If the command asks for a prefix argument, it receives the value
616 @var{prefix-argument}. If @code{execute-extended-command} is called
617 interactively, the current raw prefix argument is used for
618 @var{prefix-argument}, and thus passed on to whatever command is run.
620 @c !!! Should this be @kindex?
622 @code{execute-extended-command} is the normal definition of @kbd{M-x},
623 so it uses the string @w{@samp{M-x }} as a prompt. (It would be better
624 to take the prompt from the events used to invoke
625 @code{execute-extended-command}, but that is painful to implement.) A
626 description of the value of the prefix argument, if any, also becomes
631 (execute-extended-command 3)
632 ---------- Buffer: Minibuffer ----------
633 3 M-x forward-word RET
634 ---------- Buffer: Minibuffer ----------
641 This function returns @code{t} if the containing function (the one
642 whose code includes the call to @code{interactive-p}) was called in
643 direct response to user input. This means that it was called with the
644 function @code{call-interactively}, and that a keyboard macro is
645 not running, and that Emacs is not running in batch mode.
647 If the containing function was called by Lisp evaluation (or with
648 @code{apply} or @code{funcall}), then it was not called interactively.
651 The most common use of @code{interactive-p} is for deciding whether
652 to give the user additional visual feedback (such as by printing an
653 informative message). For example:
657 ;; @r{Here's the usual way to use @code{interactive-p}.}
660 (when (interactive-p)
666 ;; @r{This function is just to illustrate the behavior.}
669 (setq foobar (list (foo) (interactive-p))))
674 ;; @r{Type @kbd{M-x foo}.}
679 ;; @r{Type @kbd{M-x bar}.}
680 ;; @r{This does not display a message.}
689 If you want to test @emph{only} whether the function was called
690 using @code{call-interactively}, add an optional argument
691 @code{print-message} which should be non-@code{nil} in an interactive
692 call, and use the @code{interactive} spec to make sure it is
693 non-@code{nil}. Here's an example:
696 (defun foo (&optional print-message)
703 Defined in this way, the function does display the message when called
704 from a keyboard macro. We use @code{"p"} because the numeric prefix
705 argument is never @code{nil}.
707 @defun called-interactively-p
708 This function returns @code{t} when the calling function was called
709 using @code{call-interactively}.
711 When possible, instead of using this function, you should use the
712 method in the example above; that method makes it possible for a
713 caller to ``pretend'' that the function was called interactively.
716 @node Command Loop Info
717 @comment node-name, next, previous, up
718 @section Information from the Command Loop
720 The editor command loop sets several Lisp variables to keep status
721 records for itself and for commands that are run.
724 This variable records the name of the previous command executed by the
725 command loop (the one before the current command). Normally the value
726 is a symbol with a function definition, but this is not guaranteed.
728 The value is copied from @code{this-command} when a command returns to
729 the command loop, except when the command has specified a prefix
730 argument for the following command.
732 This variable is always local to the current terminal and cannot be
733 buffer-local. @xref{Multiple Displays}.
736 @defvar real-last-command
737 This variable is set up by Emacs just like @code{last-command},
738 but never altered by Lisp programs.
742 @cindex current command
743 This variable records the name of the command now being executed by
744 the editor command loop. Like @code{last-command}, it is normally a symbol
745 with a function definition.
747 The command loop sets this variable just before running a command, and
748 copies its value into @code{last-command} when the command finishes
749 (unless the command specified a prefix argument for the following
752 @cindex kill command repetition
753 Some commands set this variable during their execution, as a flag for
754 whatever command runs next. In particular, the functions for killing text
755 set @code{this-command} to @code{kill-region} so that any kill commands
756 immediately following will know to append the killed text to the
760 If you do not want a particular command to be recognized as the previous
761 command in the case where it got an error, you must code that command to
762 prevent this. One way is to set @code{this-command} to @code{t} at the
763 beginning of the command, and set @code{this-command} back to its proper
764 value at the end, like this:
767 (defun foo (args@dots{})
768 (interactive @dots{})
769 (let ((old-this-command this-command))
770 (setq this-command t)
771 @r{@dots{}do the work@dots{}}
772 (setq this-command old-this-command)))
776 We do not bind @code{this-command} with @code{let} because that would
777 restore the old value in case of error---a feature of @code{let} which
778 in this case does precisely what we want to avoid.
780 @defvar this-original-command
781 This has the same value as @code{this-command} except when command
782 remapping occurs (@pxref{Remapping Commands}). In that case,
783 @code{this-command} gives the command actually run (the result of
784 remapping), and @code{this-original-command} gives the command that
785 was specified to run but remapped into another command.
788 @defun this-command-keys
789 This function returns a string or vector containing the key sequence
790 that invoked the present command, plus any previous commands that
791 generated the prefix argument for this command. Any events read by the
792 command using @code{read-event} without a timeout get tacked on to the end.
794 However, if the command has called @code{read-key-sequence}, it
795 returns the last read key sequence. @xref{Key Sequence Input}. The
796 value is a string if all events in the sequence were characters that
797 fit in a string. @xref{Input Events}.
802 ;; @r{Now use @kbd{C-u C-x C-e} to evaluate that.}
808 @defun this-command-keys-vector
809 @anchor{Definition of this-command-keys-vector}
810 Like @code{this-command-keys}, except that it always returns the events
811 in a vector, so you don't need to deal with the complexities of storing
812 input events in a string (@pxref{Strings of Events}).
815 @defun clear-this-command-keys &optional keep-record
816 This function empties out the table of events for
817 @code{this-command-keys} to return. Unless @var{keep-record} is
818 non-@code{nil}, it also empties the records that the function
819 @code{recent-keys} (@pxref{Recording Input}) will subsequently return.
820 This is useful after reading a password, to prevent the password from
821 echoing inadvertently as part of the next command in certain cases.
824 @defvar last-nonmenu-event
825 This variable holds the last input event read as part of a key sequence,
826 not counting events resulting from mouse menus.
828 One use of this variable is for telling @code{x-popup-menu} where to pop
829 up a menu. It is also used internally by @code{y-or-n-p}
830 (@pxref{Yes-or-No Queries}).
833 @defvar last-command-event
834 @defvarx last-command-char
835 This variable is set to the last input event that was read by the
836 command loop as part of a command. The principal use of this variable
837 is in @code{self-insert-command}, which uses it to decide which
843 ;; @r{Now use @kbd{C-u C-x C-e} to evaluate that.}
849 The value is 5 because that is the @acronym{ASCII} code for @kbd{C-e}.
851 The alias @code{last-command-char} exists for compatibility with
856 @defvar last-event-frame
857 This variable records which frame the last input event was directed to.
858 Usually this is the frame that was selected when the event was
859 generated, but if that frame has redirected input focus to another
860 frame, the value is the frame to which the event was redirected.
863 If the last event came from a keyboard macro, the value is @code{macro}.
866 @node Adjusting Point
867 @section Adjusting Point After Commands
869 It is not easy to display a value of point in the middle of a
870 sequence of text that has the @code{display}, @code{composition} or
871 @code{intangible} property, or is invisible. Therefore, after a
872 command finishes and returns to the command loop, if point is within
873 such a sequence, the command loop normally moves point to the edge of
876 A command can inhibit this feature by setting the variable
877 @code{disable-point-adjustment}:
879 @defvar disable-point-adjustment
880 If this variable is non-@code{nil} when a command returns to the
881 command loop, then the command loop does not check for those text
882 properties, and does not move point out of sequences that have them.
884 The command loop sets this variable to @code{nil} before each command,
885 so if a command sets it, the effect applies only to that command.
888 @defvar global-disable-point-adjustment
889 If you set this variable to a non-@code{nil} value, the feature of
890 moving point out of these sequences is completely turned off.
894 @section Input Events
898 The Emacs command loop reads a sequence of @dfn{input events} that
899 represent keyboard or mouse activity. The events for keyboard activity
900 are characters or symbols; mouse events are always lists. This section
901 describes the representation and meaning of input events in detail.
904 This function returns non-@code{nil} if @var{object} is an input event
907 Note that any symbol might be used as an event or an event type.
908 @code{eventp} cannot distinguish whether a symbol is intended by Lisp
909 code to be used as an event. Instead, it distinguishes whether the
910 symbol has actually been used in an event that has been read as input in
911 the current Emacs session. If a symbol has not yet been so used,
912 @code{eventp} returns @code{nil}.
916 * Keyboard Events:: Ordinary characters--keys with symbols on them.
917 * Function Keys:: Function keys--keys with names, not symbols.
918 * Mouse Events:: Overview of mouse events.
919 * Click Events:: Pushing and releasing a mouse button.
920 * Drag Events:: Moving the mouse before releasing the button.
921 * Button-Down Events:: A button was pushed and not yet released.
922 * Repeat Events:: Double and triple click (or drag, or down).
923 * Motion Events:: Just moving the mouse, not pushing a button.
924 * Focus Events:: Moving the mouse between frames.
925 * Misc Events:: Other events the system can generate.
926 * Event Examples:: Examples of the lists for mouse events.
927 * Classifying Events:: Finding the modifier keys in an event symbol.
929 * Accessing Events:: Functions to extract info from events.
930 * Strings of Events:: Special considerations for putting
931 keyboard character events in a string.
934 @node Keyboard Events
935 @subsection Keyboard Events
936 @cindex keyboard events
938 There are two kinds of input you can get from the keyboard: ordinary
939 keys, and function keys. Ordinary keys correspond to characters; the
940 events they generate are represented in Lisp as characters. The event
941 type of a character event is the character itself (an integer); see
942 @ref{Classifying Events}.
944 @cindex modifier bits (of input character)
945 @cindex basic code (of input character)
946 An input character event consists of a @dfn{basic code} between 0 and
947 524287, plus any or all of these @dfn{modifier bits}:
958 bit in the character code indicates a character
959 typed with the meta key held down.
969 bit in the character code indicates a non-@acronym{ASCII}
972 @sc{ascii} control characters such as @kbd{C-a} have special basic
973 codes of their own, so Emacs needs no special bit to indicate them.
974 Thus, the code for @kbd{C-a} is just 1.
976 But if you type a control combination not in @acronym{ASCII}, such as
977 @kbd{%} with the control key, the numeric value you get is the code
985 (assuming the terminal supports non-@acronym{ASCII}
996 bit in the character code indicates an @acronym{ASCII} control
997 character typed with the shift key held down.
999 For letters, the basic code itself indicates upper versus lower case;
1000 for digits and punctuation, the shift key selects an entirely different
1001 character with a different basic code. In order to keep within the
1002 @acronym{ASCII} character set whenever possible, Emacs avoids using the
1009 bit for those characters.
1011 However, @acronym{ASCII} provides no way to distinguish @kbd{C-A} from
1012 @kbd{C-a}, so Emacs uses the
1019 bit in @kbd{C-A} and not in
1030 bit in the character code indicates a character
1031 typed with the hyper key held down.
1041 bit in the character code indicates a character
1042 typed with the super key held down.
1052 bit in the character code indicates a character typed with
1053 the alt key held down. (On some terminals, the key labeled @key{ALT}
1054 is actually the meta key.)
1057 It is best to avoid mentioning specific bit numbers in your program.
1058 To test the modifier bits of a character, use the function
1059 @code{event-modifiers} (@pxref{Classifying Events}). When making key
1060 bindings, you can use the read syntax for characters with modifier bits
1061 (@samp{\C-}, @samp{\M-}, and so on). For making key bindings with
1062 @code{define-key}, you can use lists such as @code{(control hyper ?x)} to
1063 specify the characters (@pxref{Changing Key Bindings}). The function
1064 @code{event-convert-list} converts such a list into an event type
1065 (@pxref{Classifying Events}).
1068 @subsection Function Keys
1070 @cindex function keys
1071 Most keyboards also have @dfn{function keys}---keys that have names or
1072 symbols that are not characters. Function keys are represented in Emacs
1073 Lisp as symbols; the symbol's name is the function key's label, in lower
1074 case. For example, pressing a key labeled @key{F1} places the symbol
1075 @code{f1} in the input stream.
1077 The event type of a function key event is the event symbol itself.
1078 @xref{Classifying Events}.
1080 Here are a few special cases in the symbol-naming convention for
1084 @item @code{backspace}, @code{tab}, @code{newline}, @code{return}, @code{delete}
1085 These keys correspond to common @acronym{ASCII} control characters that have
1086 special keys on most keyboards.
1088 In @acronym{ASCII}, @kbd{C-i} and @key{TAB} are the same character. If the
1089 terminal can distinguish between them, Emacs conveys the distinction to
1090 Lisp programs by representing the former as the integer 9, and the
1091 latter as the symbol @code{tab}.
1093 Most of the time, it's not useful to distinguish the two. So normally
1094 @code{function-key-map} (@pxref{Translation Keymaps}) is set up to map
1095 @code{tab} into 9. Thus, a key binding for character code 9 (the
1096 character @kbd{C-i}) also applies to @code{tab}. Likewise for the other
1097 symbols in this group. The function @code{read-char} likewise converts
1098 these events into characters.
1100 In @acronym{ASCII}, @key{BS} is really @kbd{C-h}. But @code{backspace}
1101 converts into the character code 127 (@key{DEL}), not into code 8
1102 (@key{BS}). This is what most users prefer.
1104 @item @code{left}, @code{up}, @code{right}, @code{down}
1106 @item @code{kp-add}, @code{kp-decimal}, @code{kp-divide}, @dots{}
1107 Keypad keys (to the right of the regular keyboard).
1108 @item @code{kp-0}, @code{kp-1}, @dots{}
1109 Keypad keys with digits.
1110 @item @code{kp-f1}, @code{kp-f2}, @code{kp-f3}, @code{kp-f4}
1112 @item @code{kp-home}, @code{kp-left}, @code{kp-up}, @code{kp-right}, @code{kp-down}
1113 Keypad arrow keys. Emacs normally translates these into the
1114 corresponding non-keypad keys @code{home}, @code{left}, @dots{}
1115 @item @code{kp-prior}, @code{kp-next}, @code{kp-end}, @code{kp-begin}, @code{kp-insert}, @code{kp-delete}
1116 Additional keypad duplicates of keys ordinarily found elsewhere. Emacs
1117 normally translates these into the like-named non-keypad keys.
1120 You can use the modifier keys @key{ALT}, @key{CTRL}, @key{HYPER},
1121 @key{META}, @key{SHIFT}, and @key{SUPER} with function keys. The way to
1122 represent them is with prefixes in the symbol name:
1128 The control modifier.
1139 Thus, the symbol for the key @key{F3} with @key{META} held down is
1140 @code{M-f3}. When you use more than one prefix, we recommend you
1141 write them in alphabetical order; but the order does not matter in
1142 arguments to the key-binding lookup and modification functions.
1145 @subsection Mouse Events
1147 Emacs supports four kinds of mouse events: click events, drag events,
1148 button-down events, and motion events. All mouse events are represented
1149 as lists. The @sc{car} of the list is the event type; this says which
1150 mouse button was involved, and which modifier keys were used with it.
1151 The event type can also distinguish double or triple button presses
1152 (@pxref{Repeat Events}). The rest of the list elements give position
1153 and time information.
1155 For key lookup, only the event type matters: two events of the same type
1156 necessarily run the same command. The command can access the full
1157 values of these events using the @samp{e} interactive code.
1158 @xref{Interactive Codes}.
1160 A key sequence that starts with a mouse event is read using the keymaps
1161 of the buffer in the window that the mouse was in, not the current
1162 buffer. This does not imply that clicking in a window selects that
1163 window or its buffer---that is entirely under the control of the command
1164 binding of the key sequence.
1167 @subsection Click Events
1169 @cindex mouse click event
1171 When the user presses a mouse button and releases it at the same
1172 location, that generates a @dfn{click} event. All mouse click event
1173 share the same format:
1176 (@var{event-type} @var{position} @var{click-count})
1180 @item @var{event-type}
1181 This is a symbol that indicates which mouse button was used. It is
1182 one of the symbols @code{mouse-1}, @code{mouse-2}, @dots{}, where the
1183 buttons are numbered left to right.
1185 You can also use prefixes @samp{A-}, @samp{C-}, @samp{H-}, @samp{M-},
1186 @samp{S-} and @samp{s-} for modifiers alt, control, hyper, meta, shift
1187 and super, just as you would with function keys.
1189 This symbol also serves as the event type of the event. Key bindings
1190 describe events by their types; thus, if there is a key binding for
1191 @code{mouse-1}, that binding would apply to all events whose
1192 @var{event-type} is @code{mouse-1}.
1194 @item @var{position}
1195 This is the position where the mouse click occurred. The actual
1196 format of @var{position} depends on what part of a window was clicked
1197 on. The various formats are described below.
1199 @item @var{click-count}
1200 This is the number of rapid repeated presses so far of the same mouse
1201 button. @xref{Repeat Events}.
1204 For mouse click events in the text area, mode line, header line, or in
1205 the marginal areas, @var{position} has this form:
1208 (@var{window} @var{pos-or-area} (@var{x} . @var{y}) @var{timestamp}
1209 @var{object} @var{text-pos} (@var{col} . @var{row})
1210 @var{image} (@var{dx} . @var{dy}) (@var{width} . @var{height}))
1215 This is the window in which the click occurred.
1217 @item @var{pos-or-area}
1218 This is the buffer position of the character clicked on in the text
1219 area, or if clicked outside the text area, it is the window area in
1220 which the click occurred. It is one of the symbols @code{mode-line},
1221 @code{header-line}, @code{vertical-line}, @code{left-margin},
1222 @code{right-margin}, @code{left-fringe}, or @code{right-fringe}.
1224 @item @var{x}, @var{y}
1225 These are the pixel-denominated coordinates of the click, relative to
1226 the top left corner of @var{window}, which is @code{(0 . 0)}.
1227 For the mode or header line, @var{y} does not have meaningful data.
1228 For the vertical line, @var{x} does not have meaningful data.
1230 @item @var{timestamp}
1231 This is the time at which the event occurred, in milliseconds.
1234 This is the object on which the click occurred. It is either
1235 @code{nil} if there is no string property, or it has the form
1236 (@var{string} . @var{string-pos}) when there is a string-type text
1237 property at the click position.
1240 This is the string on which the click occurred, including any
1243 @item @var{string-pos}
1244 This is the position in the string on which the click occurred,
1245 relevant if properties at the click need to be looked up.
1247 @item @var{text-pos}
1248 For clicks on a marginal area or on a fringe, this is the buffer
1249 position of the first visible character in the corresponding line in
1250 the window. For other events, it is the current buffer position in
1253 @item @var{col}, @var{row}
1254 These are the actual coordinates of the glyph under the @var{x},
1255 @var{y} position, possibly padded with default character width
1256 glyphs if @var{x} is beyond the last glyph on the line.
1259 This is the image object on which the click occurred. It is either
1260 @code{nil} if there is no image at the position clicked on, or it is
1261 an image object as returned by @code{find-image} if click was in an image.
1263 @item @var{dx}, @var{dy}
1264 These are the pixel-denominated coordinates of the click, relative to
1265 the top left corner of @var{object}, which is @code{(0 . 0)}. If
1266 @var{object} is @code{nil}, the coordinates are relative to the top
1267 left corner of the character glyph clicked on.
1270 For mouse clicks on a scroll-bar, @var{position} has this form:
1273 (@var{window} @var{area} (@var{portion} . @var{whole}) @var{timestamp} @var{part})
1278 This is the window whose scroll-bar was clicked on.
1281 This is the scroll bar where the click occurred. It is one of the
1282 symbols @code{vertical-scroll-bar} or @code{horizontal-scroll-bar}.
1285 This is the distance of the click from the top or left end of
1289 This is the length of the entire scroll bar.
1291 @item @var{timestamp}
1292 This is the time at which the event occurred, in milliseconds.
1295 This is the part of the scroll-bar which was clicked on. It is one
1296 of the symbols @code{above-handle}, @code{handle}, @code{below-handle},
1297 @code{up}, @code{down}, @code{top}, @code{bottom}, and @code{end-scroll}.
1300 In one special case, @var{buffer-pos} is a list containing a symbol (one
1301 of the symbols listed above) instead of just the symbol. This happens
1302 after the imaginary prefix keys for the event are inserted into the
1303 input stream. @xref{Key Sequence Input}.
1306 @subsection Drag Events
1308 @cindex mouse drag event
1310 With Emacs, you can have a drag event without even changing your
1311 clothes. A @dfn{drag event} happens every time the user presses a mouse
1312 button and then moves the mouse to a different character position before
1313 releasing the button. Like all mouse events, drag events are
1314 represented in Lisp as lists. The lists record both the starting mouse
1315 position and the final position, like this:
1319 (@var{window1} @var{buffer-pos1} (@var{x1} . @var{y1}) @var{timestamp1})
1320 (@var{window2} @var{buffer-pos2} (@var{x2} . @var{y2}) @var{timestamp2})
1324 For a drag event, the name of the symbol @var{event-type} contains the
1325 prefix @samp{drag-}. For example, dragging the mouse with button 2 held
1326 down generates a @code{drag-mouse-2} event. The second and third
1327 elements of the event give the starting and ending position of the drag.
1328 Aside from that, the data have the same meanings as in a click event
1329 (@pxref{Click Events}). You can access the second element of any mouse
1330 event in the same way, with no need to distinguish drag events from
1333 The @samp{drag-} prefix follows the modifier key prefixes such as
1334 @samp{C-} and @samp{M-}.
1336 If @code{read-key-sequence} receives a drag event that has no key
1337 binding, and the corresponding click event does have a binding, it
1338 changes the drag event into a click event at the drag's starting
1339 position. This means that you don't have to distinguish between click
1340 and drag events unless you want to.
1342 @node Button-Down Events
1343 @subsection Button-Down Events
1344 @cindex button-down event
1346 Click and drag events happen when the user releases a mouse button.
1347 They cannot happen earlier, because there is no way to distinguish a
1348 click from a drag until the button is released.
1350 If you want to take action as soon as a button is pressed, you need to
1351 handle @dfn{button-down} events.@footnote{Button-down is the
1352 conservative antithesis of drag.} These occur as soon as a button is
1353 pressed. They are represented by lists that look exactly like click
1354 events (@pxref{Click Events}), except that the @var{event-type} symbol
1355 name contains the prefix @samp{down-}. The @samp{down-} prefix follows
1356 modifier key prefixes such as @samp{C-} and @samp{M-}.
1358 The function @code{read-key-sequence} ignores any button-down events
1359 that don't have command bindings; therefore, the Emacs command loop
1360 ignores them too. This means that you need not worry about defining
1361 button-down events unless you want them to do something. The usual
1362 reason to define a button-down event is so that you can track mouse
1363 motion (by reading motion events) until the button is released.
1364 @xref{Motion Events}.
1367 @subsection Repeat Events
1368 @cindex repeat events
1369 @cindex double-click events
1370 @cindex triple-click events
1371 @cindex mouse events, repeated
1373 If you press the same mouse button more than once in quick succession
1374 without moving the mouse, Emacs generates special @dfn{repeat} mouse
1375 events for the second and subsequent presses.
1377 The most common repeat events are @dfn{double-click} events. Emacs
1378 generates a double-click event when you click a button twice; the event
1379 happens when you release the button (as is normal for all click
1382 The event type of a double-click event contains the prefix
1383 @samp{double-}. Thus, a double click on the second mouse button with
1384 @key{meta} held down comes to the Lisp program as
1385 @code{M-double-mouse-2}. If a double-click event has no binding, the
1386 binding of the corresponding ordinary click event is used to execute
1387 it. Thus, you need not pay attention to the double click feature
1388 unless you really want to.
1390 When the user performs a double click, Emacs generates first an ordinary
1391 click event, and then a double-click event. Therefore, you must design
1392 the command binding of the double click event to assume that the
1393 single-click command has already run. It must produce the desired
1394 results of a double click, starting from the results of a single click.
1396 This is convenient, if the meaning of a double click somehow ``builds
1397 on'' the meaning of a single click---which is recommended user interface
1398 design practice for double clicks.
1400 If you click a button, then press it down again and start moving the
1401 mouse with the button held down, then you get a @dfn{double-drag} event
1402 when you ultimately release the button. Its event type contains
1403 @samp{double-drag} instead of just @samp{drag}. If a double-drag event
1404 has no binding, Emacs looks for an alternate binding as if the event
1405 were an ordinary drag.
1407 Before the double-click or double-drag event, Emacs generates a
1408 @dfn{double-down} event when the user presses the button down for the
1409 second time. Its event type contains @samp{double-down} instead of just
1410 @samp{down}. If a double-down event has no binding, Emacs looks for an
1411 alternate binding as if the event were an ordinary button-down event.
1412 If it finds no binding that way either, the double-down event is
1415 To summarize, when you click a button and then press it again right
1416 away, Emacs generates a down event and a click event for the first
1417 click, a double-down event when you press the button again, and finally
1418 either a double-click or a double-drag event.
1420 If you click a button twice and then press it again, all in quick
1421 succession, Emacs generates a @dfn{triple-down} event, followed by
1422 either a @dfn{triple-click} or a @dfn{triple-drag}. The event types of
1423 these events contain @samp{triple} instead of @samp{double}. If any
1424 triple event has no binding, Emacs uses the binding that it would use
1425 for the corresponding double event.
1427 If you click a button three or more times and then press it again, the
1428 events for the presses beyond the third are all triple events. Emacs
1429 does not have separate event types for quadruple, quintuple, etc.@:
1430 events. However, you can look at the event list to find out precisely
1431 how many times the button was pressed.
1433 @defun event-click-count event
1434 This function returns the number of consecutive button presses that led
1435 up to @var{event}. If @var{event} is a double-down, double-click or
1436 double-drag event, the value is 2. If @var{event} is a triple event,
1437 the value is 3 or greater. If @var{event} is an ordinary mouse event
1438 (not a repeat event), the value is 1.
1441 @defopt double-click-fuzz
1442 To generate repeat events, successive mouse button presses must be at
1443 approximately the same screen position. The value of
1444 @code{double-click-fuzz} specifies the maximum number of pixels the
1445 mouse may be moved (horizontally or vertically) between two successive
1446 clicks to make a double-click.
1448 This variable is also the threshold for motion of the mouse to count
1452 @defopt double-click-time
1453 To generate repeat events, the number of milliseconds between
1454 successive button presses must be less than the value of
1455 @code{double-click-time}. Setting @code{double-click-time} to
1456 @code{nil} disables multi-click detection entirely. Setting it to
1457 @code{t} removes the time limit; Emacs then detects multi-clicks by
1462 @subsection Motion Events
1463 @cindex motion event
1464 @cindex mouse motion events
1466 Emacs sometimes generates @dfn{mouse motion} events to describe motion
1467 of the mouse without any button activity. Mouse motion events are
1468 represented by lists that look like this:
1471 (mouse-movement (@var{window} @var{buffer-pos} (@var{x} . @var{y}) @var{timestamp}))
1474 The second element of the list describes the current position of the
1475 mouse, just as in a click event (@pxref{Click Events}).
1477 The special form @code{track-mouse} enables generation of motion events
1478 within its body. Outside of @code{track-mouse} forms, Emacs does not
1479 generate events for mere motion of the mouse, and these events do not
1480 appear. @xref{Mouse Tracking}.
1483 @subsection Focus Events
1486 Window systems provide general ways for the user to control which window
1487 gets keyboard input. This choice of window is called the @dfn{focus}.
1488 When the user does something to switch between Emacs frames, that
1489 generates a @dfn{focus event}. The normal definition of a focus event,
1490 in the global keymap, is to select a new frame within Emacs, as the user
1491 would expect. @xref{Input Focus}.
1493 Focus events are represented in Lisp as lists that look like this:
1496 (switch-frame @var{new-frame})
1500 where @var{new-frame} is the frame switched to.
1502 Most X window managers are set up so that just moving the mouse into a
1503 window is enough to set the focus there. Emacs appears to do this,
1504 because it changes the cursor to solid in the new frame. However, there
1505 is no need for the Lisp program to know about the focus change until
1506 some other kind of input arrives. So Emacs generates a focus event only
1507 when the user actually types a keyboard key or presses a mouse button in
1508 the new frame; just moving the mouse between frames does not generate a
1511 A focus event in the middle of a key sequence would garble the
1512 sequence. So Emacs never generates a focus event in the middle of a key
1513 sequence. If the user changes focus in the middle of a key
1514 sequence---that is, after a prefix key---then Emacs reorders the events
1515 so that the focus event comes either before or after the multi-event key
1516 sequence, and not within it.
1519 @subsection Miscellaneous System Events
1521 A few other event types represent occurrences within the system.
1524 @cindex @code{delete-frame} event
1525 @item (delete-frame (@var{frame}))
1526 This kind of event indicates that the user gave the window manager
1527 a command to delete a particular window, which happens to be an Emacs frame.
1529 The standard definition of the @code{delete-frame} event is to delete @var{frame}.
1531 @cindex @code{iconify-frame} event
1532 @item (iconify-frame (@var{frame}))
1533 This kind of event indicates that the user iconified @var{frame} using
1534 the window manager. Its standard definition is @code{ignore}; since the
1535 frame has already been iconified, Emacs has no work to do. The purpose
1536 of this event type is so that you can keep track of such events if you
1539 @cindex @code{make-frame-visible} event
1540 @item (make-frame-visible (@var{frame}))
1541 This kind of event indicates that the user deiconified @var{frame} using
1542 the window manager. Its standard definition is @code{ignore}; since the
1543 frame has already been made visible, Emacs has no work to do.
1545 @cindex @code{wheel-up} event
1546 @cindex @code{wheel-down} event
1547 @item (wheel-up @var{position})
1548 @item (wheel-down @var{position})
1549 These kinds of event are generated by moving a mouse wheel. Their
1550 usual meaning is a kind of scroll or zoom.
1552 The element @var{position} is a list describing the position of the
1553 event, in the same format as used in a mouse-click event.
1555 This kind of event is generated only on some kinds of systems. On some
1556 systems, @code{mouse-4} and @code{mouse-5} are used instead. For
1557 portable code, use the variables @code{mouse-wheel-up-event} and
1558 @code{mouse-wheel-down-event} defined in @file{mwheel.el} to determine
1559 what event types to expect for the mouse wheel.
1561 @cindex @code{drag-n-drop} event
1562 @item (drag-n-drop @var{position} @var{files})
1563 This kind of event is generated when a group of files is
1564 selected in an application outside of Emacs, and then dragged and
1565 dropped onto an Emacs frame.
1567 The element @var{position} is a list describing the position of the
1568 event, in the same format as used in a mouse-click event, and
1569 @var{files} is the list of file names that were dragged and dropped.
1570 The usual way to handle this event is by visiting these files.
1572 This kind of event is generated, at present, only on some kinds of
1575 @cindex @code{help-echo} event
1577 This kind of event is generated when a mouse pointer moves onto a
1578 portion of buffer text which has a @code{help-echo} text property.
1579 The generated event has this form:
1582 (help-echo @var{frame} @var{help} @var{window} @var{object} @var{pos})
1586 The precise meaning of the event parameters and the way these
1587 parameters are used to display the help-echo text are described in
1588 @ref{Text help-echo}.
1590 @cindex @code{sigusr1} event
1591 @cindex @code{sigusr2} event
1592 @cindex user signals
1595 These events are generated when the Emacs process receives
1596 the signals @code{SIGUSR1} and @code{SIGUSR2}. They contain no
1597 additional data because signals do not carry additional information.
1599 To catch a user signal, bind the corresponding event to an interactive
1600 command in the @code{special-event-map} (@pxref{Active Keymaps}).
1601 The command is called with no arguments, and the specific signal event is
1602 available in @code{last-input-event}. For example:
1605 (defun sigusr-handler ()
1607 (message "Caught signal %S" last-input-event))
1609 (define-key special-event-map [sigusr1] 'sigusr-handler)
1612 To test the signal handler, you can make Emacs send a signal to itself:
1615 (signal-process (emacs-pid) 'sigusr1)
1619 If one of these events arrives in the middle of a key sequence---that
1620 is, after a prefix key---then Emacs reorders the events so that this
1621 event comes either before or after the multi-event key sequence, not
1624 @node Event Examples
1625 @subsection Event Examples
1627 If the user presses and releases the left mouse button over the same
1628 location, that generates a sequence of events like this:
1631 (down-mouse-1 (#<window 18 on NEWS> 2613 (0 . 38) -864320))
1632 (mouse-1 (#<window 18 on NEWS> 2613 (0 . 38) -864180))
1635 While holding the control key down, the user might hold down the
1636 second mouse button, and drag the mouse from one line to the next.
1637 That produces two events, as shown here:
1640 (C-down-mouse-2 (#<window 18 on NEWS> 3440 (0 . 27) -731219))
1641 (C-drag-mouse-2 (#<window 18 on NEWS> 3440 (0 . 27) -731219)
1642 (#<window 18 on NEWS> 3510 (0 . 28) -729648))
1645 While holding down the meta and shift keys, the user might press the
1646 second mouse button on the window's mode line, and then drag the mouse
1647 into another window. That produces a pair of events like these:
1650 (M-S-down-mouse-2 (#<window 18 on NEWS> mode-line (33 . 31) -457844))
1651 (M-S-drag-mouse-2 (#<window 18 on NEWS> mode-line (33 . 31) -457844)
1652 (#<window 20 on carlton-sanskrit.tex> 161 (33 . 3)
1656 To handle a SIGUSR1 signal, define an interactive function, and
1657 bind it to the @code{signal usr1} event sequence:
1660 (defun usr1-handler ()
1662 (message "Got USR1 signal"))
1663 (global-set-key [signal usr1] 'usr1-handler)
1666 @node Classifying Events
1667 @subsection Classifying Events
1670 Every event has an @dfn{event type}, which classifies the event for
1671 key binding purposes. For a keyboard event, the event type equals the
1672 event value; thus, the event type for a character is the character, and
1673 the event type for a function key symbol is the symbol itself. For
1674 events that are lists, the event type is the symbol in the @sc{car} of
1675 the list. Thus, the event type is always a symbol or a character.
1677 Two events of the same type are equivalent where key bindings are
1678 concerned; thus, they always run the same command. That does not
1679 necessarily mean they do the same things, however, as some commands look
1680 at the whole event to decide what to do. For example, some commands use
1681 the location of a mouse event to decide where in the buffer to act.
1683 Sometimes broader classifications of events are useful. For example,
1684 you might want to ask whether an event involved the @key{META} key,
1685 regardless of which other key or mouse button was used.
1687 The functions @code{event-modifiers} and @code{event-basic-type} are
1688 provided to get such information conveniently.
1690 @defun event-modifiers event
1691 This function returns a list of the modifiers that @var{event} has. The
1692 modifiers are symbols; they include @code{shift}, @code{control},
1693 @code{meta}, @code{alt}, @code{hyper} and @code{super}. In addition,
1694 the modifiers list of a mouse event symbol always contains one of
1695 @code{click}, @code{drag}, and @code{down}. For double or triple
1696 events, it also contains @code{double} or @code{triple}.
1698 The argument @var{event} may be an entire event object, or just an
1699 event type. If @var{event} is a symbol that has never been used in an
1700 event that has been read as input in the current Emacs session, then
1701 @code{event-modifiers} can return @code{nil}, even when @var{event}
1702 actually has modifiers.
1704 Here are some examples:
1707 (event-modifiers ?a)
1709 (event-modifiers ?A)
1711 (event-modifiers ?\C-a)
1713 (event-modifiers ?\C-%)
1715 (event-modifiers ?\C-\S-a)
1716 @result{} (control shift)
1717 (event-modifiers 'f5)
1719 (event-modifiers 's-f5)
1721 (event-modifiers 'M-S-f5)
1722 @result{} (meta shift)
1723 (event-modifiers 'mouse-1)
1725 (event-modifiers 'down-mouse-1)
1729 The modifiers list for a click event explicitly contains @code{click},
1730 but the event symbol name itself does not contain @samp{click}.
1733 @defun event-basic-type event
1734 This function returns the key or mouse button that @var{event}
1735 describes, with all modifiers removed. The @var{event} argument is as
1736 in @code{event-modifiers}. For example:
1739 (event-basic-type ?a)
1741 (event-basic-type ?A)
1743 (event-basic-type ?\C-a)
1745 (event-basic-type ?\C-\S-a)
1747 (event-basic-type 'f5)
1749 (event-basic-type 's-f5)
1751 (event-basic-type 'M-S-f5)
1753 (event-basic-type 'down-mouse-1)
1758 @defun mouse-movement-p object
1759 This function returns non-@code{nil} if @var{object} is a mouse movement
1763 @defun event-convert-list list
1764 This function converts a list of modifier names and a basic event type
1765 to an event type which specifies all of them. The basic event type
1766 must be the last element of the list. For example,
1769 (event-convert-list '(control ?a))
1771 (event-convert-list '(control meta ?a))
1772 @result{} -134217727
1773 (event-convert-list '(control super f1))
1778 @node Accessing Events
1779 @subsection Accessing Events
1780 @cindex mouse events, accessing the data
1781 @cindex accessing data of mouse events
1783 This section describes convenient functions for accessing the data in
1784 a mouse button or motion event.
1786 These two functions return the starting or ending position of a
1787 mouse-button event, as a list of this form:
1790 (@var{window} @var{pos-or-area} (@var{x} . @var{y}) @var{timestamp}
1791 @var{object} @var{text-pos} (@var{col} . @var{row})
1792 @var{image} (@var{dx} . @var{dy}) (@var{width} . @var{height}))
1795 @defun event-start event
1796 This returns the starting position of @var{event}.
1798 If @var{event} is a click or button-down event, this returns the
1799 location of the event. If @var{event} is a drag event, this returns the
1800 drag's starting position.
1803 @defun event-end event
1804 This returns the ending position of @var{event}.
1806 If @var{event} is a drag event, this returns the position where the user
1807 released the mouse button. If @var{event} is a click or button-down
1808 event, the value is actually the starting position, which is the only
1809 position such events have.
1812 @cindex mouse position list, accessing
1813 These functions take a position list as described above, and
1814 return various parts of it.
1816 @defun posn-window position
1817 Return the window that @var{position} is in.
1820 @defun posn-area position
1821 Return the window area recorded in @var{position}. It returns @code{nil}
1822 when the event occurred in the text area of the window; otherwise, it
1823 is a symbol identifying the area in which the event occurred.
1826 @defun posn-point position
1827 Return the buffer position in @var{position}. When the event occurred
1828 in the text area of the window, in a marginal area, or on a fringe,
1829 this is an integer specifying a buffer position. Otherwise, the value
1833 @defun posn-x-y position
1834 Return the pixel-based x and y coordinates in @var{position}, as a
1835 cons cell @code{(@var{x} . @var{y})}. These coordinates are relative
1836 to the window given by @code{posn-window}.
1838 This example shows how to convert these window-relative coordinates
1839 into frame-relative coordinates:
1842 (defun frame-relative-coordinates (position)
1843 "Return frame-relative coordinates from POSITION."
1844 (let* ((x-y (posn-x-y position))
1845 (window (posn-window position))
1846 (edges (window-inside-pixel-edges window)))
1847 (cons (+ (car x-y) (car edges))
1848 (+ (cdr x-y) (cadr edges)))))
1852 @defun posn-col-row position
1853 Return the row and column (in units of the frame's default character
1854 height and width) of @var{position}, as a cons cell @code{(@var{col} .
1855 @var{row})}. These are computed from the @var{x} and @var{y} values
1856 actually found in @var{position}.
1859 @defun posn-actual-col-row position
1860 Return the actual row and column in @var{position}, as a cons cell
1861 @code{(@var{col} . @var{row})}. The values are the actual row number
1862 in the window, and the actual character number in that row. It returns
1863 @code{nil} if @var{position} does not include actual positions values.
1864 You can use @code{posn-col-row} to get approximate values.
1867 @defun posn-string position
1868 Return the string object in @var{position}, either @code{nil}, or a
1869 cons cell @code{(@var{string} . @var{string-pos})}.
1872 @defun posn-image position
1873 Return the image object in @var{position}, either @code{nil}, or an
1874 image @code{(image ...)}.
1877 @defun posn-object position
1878 Return the image or string object in @var{position}, either
1879 @code{nil}, an image @code{(image ...)}, or a cons cell
1880 @code{(@var{string} . @var{string-pos})}.
1883 @defun posn-object-x-y position
1884 Return the pixel-based x and y coordinates relative to the upper left
1885 corner of the object in @var{position} as a cons cell @code{(@var{dx}
1886 . @var{dy})}. If the @var{position} is a buffer position, return the
1887 relative position in the character at that position.
1890 @defun posn-object-width-height position
1891 Return the pixel width and height of the object in @var{position} as a
1892 cons cell @code{(@var{width} . @var{height})}. If the @var{position}
1893 is a buffer position, return the size of the character at that position.
1896 @cindex mouse event, timestamp
1897 @cindex timestamp of a mouse event
1898 @defun posn-timestamp position
1899 Return the timestamp in @var{position}. This is the time at which the
1900 event occurred, in milliseconds.
1903 These functions compute a position list given particular buffer
1904 position or screen position. You can access the data in this position
1905 list with the functions described above.
1907 @defun posn-at-point &optional pos window
1908 This function returns a position list for position @var{pos} in
1909 @var{window}. @var{pos} defaults to point in @var{window};
1910 @var{window} defaults to the selected window.
1912 @code{posn-at-point} returns @code{nil} if @var{pos} is not visible in
1916 @defun posn-at-x-y x y &optional frame-or-window whole
1917 This function returns position information corresponding to pixel
1918 coordinates @var{x} and @var{y} in a specified frame or window,
1919 @var{frame-or-window}, which defaults to the selected window.
1920 The coordinates @var{x} and @var{y} are relative to the
1921 frame or window used.
1922 If @var{whole} is @code{nil}, the coordinates are relative
1923 to the window text area, otherwise they are relative to
1924 the entire window area including scroll bars, margins and fringes.
1927 These functions are useful for decoding scroll bar events.
1929 @defun scroll-bar-event-ratio event
1930 This function returns the fractional vertical position of a scroll bar
1931 event within the scroll bar. The value is a cons cell
1932 @code{(@var{portion} . @var{whole})} containing two integers whose ratio
1933 is the fractional position.
1936 @defun scroll-bar-scale ratio total
1937 This function multiplies (in effect) @var{ratio} by @var{total},
1938 rounding the result to an integer. The argument @var{ratio} is not a
1939 number, but rather a pair @code{(@var{num} . @var{denom})}---typically a
1940 value returned by @code{scroll-bar-event-ratio}.
1942 This function is handy for scaling a position on a scroll bar into a
1943 buffer position. Here's how to do that:
1948 (posn-x-y (event-start event))
1949 (- (point-max) (point-min))))
1952 Recall that scroll bar events have two integers forming a ratio, in place
1953 of a pair of x and y coordinates.
1956 @node Strings of Events
1957 @subsection Putting Keyboard Events in Strings
1958 @cindex keyboard events in strings
1959 @cindex strings with keyboard events
1961 In most of the places where strings are used, we conceptualize the
1962 string as containing text characters---the same kind of characters found
1963 in buffers or files. Occasionally Lisp programs use strings that
1964 conceptually contain keyboard characters; for example, they may be key
1965 sequences or keyboard macro definitions. However, storing keyboard
1966 characters in a string is a complex matter, for reasons of historical
1967 compatibility, and it is not always possible.
1969 We recommend that new programs avoid dealing with these complexities
1970 by not storing keyboard events in strings. Here is how to do that:
1974 Use vectors instead of strings for key sequences, when you plan to use
1975 them for anything other than as arguments to @code{lookup-key} and
1976 @code{define-key}. For example, you can use
1977 @code{read-key-sequence-vector} instead of @code{read-key-sequence}, and
1978 @code{this-command-keys-vector} instead of @code{this-command-keys}.
1981 Use vectors to write key sequence constants containing meta characters,
1982 even when passing them directly to @code{define-key}.
1985 When you have to look at the contents of a key sequence that might be a
1986 string, use @code{listify-key-sequence} (@pxref{Event Input Misc})
1987 first, to convert it to a list.
1990 The complexities stem from the modifier bits that keyboard input
1991 characters can include. Aside from the Meta modifier, none of these
1992 modifier bits can be included in a string, and the Meta modifier is
1993 allowed only in special cases.
1995 The earliest GNU Emacs versions represented meta characters as codes
1996 in the range of 128 to 255. At that time, the basic character codes
1997 ranged from 0 to 127, so all keyboard character codes did fit in a
1998 string. Many Lisp programs used @samp{\M-} in string constants to stand
1999 for meta characters, especially in arguments to @code{define-key} and
2000 similar functions, and key sequences and sequences of events were always
2001 represented as strings.
2003 When we added support for larger basic character codes beyond 127, and
2004 additional modifier bits, we had to change the representation of meta
2005 characters. Now the flag that represents the Meta modifier in a
2013 and such numbers cannot be included in a string.
2015 To support programs with @samp{\M-} in string constants, there are
2016 special rules for including certain meta characters in a string.
2017 Here are the rules for interpreting a string as a sequence of input
2022 If the keyboard character value is in the range of 0 to 127, it can go
2023 in the string unchanged.
2026 The meta variants of those characters, with codes in the range of
2035 @math{2^{27} + 127},
2040 can also go in the string, but you must change their
2041 numeric values. You must set the
2055 bit, resulting in a value between 128 and 255. Only a unibyte string
2056 can include these codes.
2059 Non-@acronym{ASCII} characters above 256 can be included in a multibyte string.
2062 Other keyboard character events cannot fit in a string. This includes
2063 keyboard events in the range of 128 to 255.
2066 Functions such as @code{read-key-sequence} that construct strings of
2067 keyboard input characters follow these rules: they construct vectors
2068 instead of strings, when the events won't fit in a string.
2070 When you use the read syntax @samp{\M-} in a string, it produces a
2071 code in the range of 128 to 255---the same code that you get if you
2072 modify the corresponding keyboard event to put it in the string. Thus,
2073 meta events in strings work consistently regardless of how they get into
2076 However, most programs would do well to avoid these issues by
2077 following the recommendations at the beginning of this section.
2080 @section Reading Input
2082 @cindex keyboard input
2084 The editor command loop reads key sequences using the function
2085 @code{read-key-sequence}, which uses @code{read-event}. These and other
2086 functions for event input are also available for use in Lisp programs.
2087 See also @code{momentary-string-display} in @ref{Temporary Displays},
2088 and @code{sit-for} in @ref{Waiting}. @xref{Terminal Input}, for
2089 functions and variables for controlling terminal input modes and
2090 debugging terminal input.
2092 For higher-level input facilities, see @ref{Minibuffers}.
2095 * Key Sequence Input:: How to read one key sequence.
2096 * Reading One Event:: How to read just one event.
2097 * Event Mod:: How Emacs modifies events as they are read.
2098 * Invoking the Input Method:: How reading an event uses the input method.
2099 * Quoted Character Input:: Asking the user to specify a character.
2100 * Event Input Misc:: How to reread or throw away input events.
2103 @node Key Sequence Input
2104 @subsection Key Sequence Input
2105 @cindex key sequence input
2107 The command loop reads input a key sequence at a time, by calling
2108 @code{read-key-sequence}. Lisp programs can also call this function;
2109 for example, @code{describe-key} uses it to read the key to describe.
2111 @defun read-key-sequence prompt &optional continue-echo dont-downcase-last switch-frame-ok command-loop
2112 @cindex key sequence
2113 This function reads a key sequence and returns it as a string or
2114 vector. It keeps reading events until it has accumulated a complete key
2115 sequence; that is, enough to specify a non-prefix command using the
2116 currently active keymaps. (Remember that a key sequence that starts
2117 with a mouse event is read using the keymaps of the buffer in the
2118 window that the mouse was in, not the current buffer.)
2120 If the events are all characters and all can fit in a string, then
2121 @code{read-key-sequence} returns a string (@pxref{Strings of Events}).
2122 Otherwise, it returns a vector, since a vector can hold all kinds of
2123 events---characters, symbols, and lists. The elements of the string or
2124 vector are the events in the key sequence.
2126 Reading a key sequence includes translating the events in various
2127 ways. @xref{Translation Keymaps}.
2129 The argument @var{prompt} is either a string to be displayed in the
2130 echo area as a prompt, or @code{nil}, meaning not to display a prompt.
2131 The argument @var{continue-echo}, if non-@code{nil}, means to echo
2132 this key as a continuation of the previous key.
2134 Normally any upper case event is converted to lower case if the
2135 original event is undefined and the lower case equivalent is defined.
2136 The argument @var{dont-downcase-last}, if non-@code{nil}, means do not
2137 convert the last event to lower case. This is appropriate for reading
2138 a key sequence to be defined.
2140 The argument @var{switch-frame-ok}, if non-@code{nil}, means that this
2141 function should process a @code{switch-frame} event if the user
2142 switches frames before typing anything. If the user switches frames
2143 in the middle of a key sequence, or at the start of the sequence but
2144 @var{switch-frame-ok} is @code{nil}, then the event will be put off
2145 until after the current key sequence.
2147 The argument @var{command-loop}, if non-@code{nil}, means that this
2148 key sequence is being read by something that will read commands one
2149 after another. It should be @code{nil} if the caller will read just
2152 In the following example, Emacs displays the prompt @samp{?} in the
2153 echo area, and then the user types @kbd{C-x C-f}.
2156 (read-key-sequence "?")
2159 ---------- Echo Area ----------
2161 ---------- Echo Area ----------
2167 The function @code{read-key-sequence} suppresses quitting: @kbd{C-g}
2168 typed while reading with this function works like any other character,
2169 and does not set @code{quit-flag}. @xref{Quitting}.
2172 @defun read-key-sequence-vector prompt &optional continue-echo dont-downcase-last switch-frame-ok command-loop
2173 This is like @code{read-key-sequence} except that it always
2174 returns the key sequence as a vector, never as a string.
2175 @xref{Strings of Events}.
2178 @cindex upper case key sequence
2179 @cindex downcasing in @code{lookup-key}
2180 If an input character is upper-case (or has the shift modifier) and
2181 has no key binding, but its lower-case equivalent has one, then
2182 @code{read-key-sequence} converts the character to lower case. Note
2183 that @code{lookup-key} does not perform case conversion in this way.
2185 The function @code{read-key-sequence} also transforms some mouse events.
2186 It converts unbound drag events into click events, and discards unbound
2187 button-down events entirely. It also reshuffles focus events and
2188 miscellaneous window events so that they never appear in a key sequence
2189 with any other events.
2191 @cindex @code{header-line} prefix key
2192 @cindex @code{mode-line} prefix key
2193 @cindex @code{vertical-line} prefix key
2194 @cindex @code{horizontal-scroll-bar} prefix key
2195 @cindex @code{vertical-scroll-bar} prefix key
2196 @cindex @code{menu-bar} prefix key
2197 @cindex mouse events, in special parts of frame
2198 When mouse events occur in special parts of a window, such as a mode
2199 line or a scroll bar, the event type shows nothing special---it is the
2200 same symbol that would normally represent that combination of mouse
2201 button and modifier keys. The information about the window part is kept
2202 elsewhere in the event---in the coordinates. But
2203 @code{read-key-sequence} translates this information into imaginary
2204 ``prefix keys,'' all of which are symbols: @code{header-line},
2205 @code{horizontal-scroll-bar}, @code{menu-bar}, @code{mode-line},
2206 @code{vertical-line}, and @code{vertical-scroll-bar}. You can define
2207 meanings for mouse clicks in special window parts by defining key
2208 sequences using these imaginary prefix keys.
2210 For example, if you call @code{read-key-sequence} and then click the
2211 mouse on the window's mode line, you get two events, like this:
2214 (read-key-sequence "Click on the mode line: ")
2215 @result{} [mode-line
2217 (#<window 6 on NEWS> mode-line
2218 (40 . 63) 5959987))]
2221 @defvar num-input-keys
2223 This variable's value is the number of key sequences processed so far in
2224 this Emacs session. This includes key sequences read from the terminal
2225 and key sequences read from keyboard macros being executed.
2228 @node Reading One Event
2229 @subsection Reading One Event
2230 @cindex reading a single event
2231 @cindex event, reading only one
2233 The lowest level functions for command input are those that read a
2236 None of the three functions below suppresses quitting.
2238 @defun read-event &optional prompt inherit-input-method seconds
2239 This function reads and returns the next event of command input, waiting
2240 if necessary until an event is available. Events can come directly from
2241 the user or from a keyboard macro.
2243 If the optional argument @var{prompt} is non-@code{nil}, it should be a
2244 string to display in the echo area as a prompt. Otherwise,
2245 @code{read-event} does not display any message to indicate it is waiting
2246 for input; instead, it prompts by echoing: it displays descriptions of
2247 the events that led to or were read by the current command. @xref{The
2250 If @var{inherit-input-method} is non-@code{nil}, then the current input
2251 method (if any) is employed to make it possible to enter a
2252 non-@acronym{ASCII} character. Otherwise, input method handling is disabled
2253 for reading this event.
2255 If @code{cursor-in-echo-area} is non-@code{nil}, then @code{read-event}
2256 moves the cursor temporarily to the echo area, to the end of any message
2257 displayed there. Otherwise @code{read-event} does not move the cursor.
2259 If @var{seconds} is non-@code{nil}, it should be a number specifying
2260 the maximum time to wait for input, in seconds. If no input arrives
2261 within that time, @code{read-event} stops waiting and returns
2262 @code{nil}. A floating-point value for @var{seconds} means to wait
2263 for a fractional number of seconds. Some systems support only a whole
2264 number of seconds; on these systems, @var{seconds} is rounded down.
2265 If @var{seconds} is @code{nil}, @code{read-event} waits as long as
2266 necessary for input to arrive.
2268 If @var{seconds} is @code{nil}, Emacs is considered idle while waiting
2269 for user input to arrive. Idle timers---those created with
2270 @code{run-with-idle-timer} (@pxref{Idle Timers})---can run during this
2271 period. However, if @var{seconds} is non-@code{nil}, the state of
2272 idleness remains unchanged. If Emacs is non-idle when
2273 @code{read-event} is called, it remains non-idle throughout the
2274 operation of @code{read-event}; if Emacs is idle (which can happen if
2275 the call happens inside an idle timer), it remains idle.
2277 If @code{read-event} gets an event that is defined as a help character,
2278 then in some cases @code{read-event} processes the event directly without
2279 returning. @xref{Help Functions}. Certain other events, called
2280 @dfn{special events}, are also processed directly within
2281 @code{read-event} (@pxref{Special Events}).
2283 Here is what happens if you call @code{read-event} and then press the
2284 right-arrow function key:
2294 @defun read-char &optional prompt inherit-input-method seconds
2295 This function reads and returns a character of command input. If the
2296 user generates an event which is not a character (i.e. a mouse click or
2297 function key event), @code{read-char} signals an error. The arguments
2298 work as in @code{read-event}.
2300 In the first example, the user types the character @kbd{1} (@acronym{ASCII}
2301 code 49). The second example shows a keyboard macro definition that
2302 calls @code{read-char} from the minibuffer using @code{eval-expression}.
2303 @code{read-char} reads the keyboard macro's very next character, which
2304 is @kbd{1}. Then @code{eval-expression} displays its return value in
2314 ;; @r{We assume here you use @kbd{M-:} to evaluate this.}
2315 (symbol-function 'foo)
2316 @result{} "^[:(read-char)^M1"
2319 (execute-kbd-macro 'foo)
2326 @defun read-char-exclusive &optional prompt inherit-input-method seconds
2327 This function reads and returns a character of command input. If the
2328 user generates an event which is not a character,
2329 @code{read-char-exclusive} ignores it and reads another event, until it
2330 gets a character. The arguments work as in @code{read-event}.
2333 @defvar num-nonmacro-input-events
2334 This variable holds the total number of input events received so far
2335 from the terminal---not counting those generated by keyboard macros.
2339 @subsection Modifying and Translating Input Events
2341 Emacs modifies every event it reads according to
2342 @code{extra-keyboard-modifiers}, then translates it through
2343 @code{keyboard-translate-table} (if applicable), before returning it
2344 from @code{read-event}.
2347 @defvar extra-keyboard-modifiers
2348 This variable lets Lisp programs ``press'' the modifier keys on the
2349 keyboard. The value is a character. Only the modifiers of the
2350 character matter. Each time the user types a keyboard key, it is
2351 altered as if those modifier keys were held down. For instance, if
2352 you bind @code{extra-keyboard-modifiers} to @code{?\C-\M-a}, then all
2353 keyboard input characters typed during the scope of the binding will
2354 have the control and meta modifiers applied to them. The character
2355 @code{?\C-@@}, equivalent to the integer 0, does not count as a control
2356 character for this purpose, but as a character with no modifiers.
2357 Thus, setting @code{extra-keyboard-modifiers} to zero cancels any
2360 When using a window system, the program can ``press'' any of the
2361 modifier keys in this way. Otherwise, only the @key{CTL} and @key{META}
2362 keys can be virtually pressed.
2364 Note that this variable applies only to events that really come from
2365 the keyboard, and has no effect on mouse events or any other events.
2368 @defvar keyboard-translate-table
2369 This variable is the translate table for keyboard characters. It lets
2370 you reshuffle the keys on the keyboard without changing any command
2371 bindings. Its value is normally a char-table, or else @code{nil}.
2372 (It can also be a string or vector, but this is considered obsolete.)
2374 If @code{keyboard-translate-table} is a char-table
2375 (@pxref{Char-Tables}), then each character read from the keyboard is
2376 looked up in this char-table. If the value found there is
2377 non-@code{nil}, then it is used instead of the actual input character.
2379 Note that this translation is the first thing that happens to a
2380 character after it is read from the terminal. Record-keeping features
2381 such as @code{recent-keys} and dribble files record the characters after
2384 Note also that this translation is done before the characters are
2385 supplied to input methods (@pxref{Input Methods}). Use
2386 @code{translation-table-for-input} (@pxref{Translation of Characters}),
2387 if you want to translate characters after input methods operate.
2390 @defun keyboard-translate from to
2391 This function modifies @code{keyboard-translate-table} to translate
2392 character code @var{from} into character code @var{to}. It creates
2393 the keyboard translate table if necessary.
2396 Here's an example of using the @code{keyboard-translate-table} to
2397 make @kbd{C-x}, @kbd{C-c} and @kbd{C-v} perform the cut, copy and paste
2401 (keyboard-translate ?\C-x 'control-x)
2402 (keyboard-translate ?\C-c 'control-c)
2403 (keyboard-translate ?\C-v 'control-v)
2404 (global-set-key [control-x] 'kill-region)
2405 (global-set-key [control-c] 'kill-ring-save)
2406 (global-set-key [control-v] 'yank)
2410 On a graphical terminal that supports extended @acronym{ASCII} input,
2411 you can still get the standard Emacs meanings of one of those
2412 characters by typing it with the shift key. That makes it a different
2413 character as far as keyboard translation is concerned, but it has the
2416 @xref{Translation Keymaps}, for mechanisms that translate event sequences
2417 at the level of @code{read-key-sequence}.
2419 @node Invoking the Input Method
2420 @subsection Invoking the Input Method
2422 The event-reading functions invoke the current input method, if any
2423 (@pxref{Input Methods}). If the value of @code{input-method-function}
2424 is non-@code{nil}, it should be a function; when @code{read-event} reads
2425 a printing character (including @key{SPC}) with no modifier bits, it
2426 calls that function, passing the character as an argument.
2428 @defvar input-method-function
2429 If this is non-@code{nil}, its value specifies the current input method
2432 @strong{Warning:} don't bind this variable with @code{let}. It is often
2433 buffer-local, and if you bind it around reading input (which is exactly
2434 when you @emph{would} bind it), switching buffers asynchronously while
2435 Emacs is waiting will cause the value to be restored in the wrong
2439 The input method function should return a list of events which should
2440 be used as input. (If the list is @code{nil}, that means there is no
2441 input, so @code{read-event} waits for another event.) These events are
2442 processed before the events in @code{unread-command-events}
2443 (@pxref{Event Input Misc}). Events
2444 returned by the input method function are not passed to the input method
2445 function again, even if they are printing characters with no modifier
2448 If the input method function calls @code{read-event} or
2449 @code{read-key-sequence}, it should bind @code{input-method-function} to
2450 @code{nil} first, to prevent recursion.
2452 The input method function is not called when reading the second and
2453 subsequent events of a key sequence. Thus, these characters are not
2454 subject to input method processing. The input method function should
2455 test the values of @code{overriding-local-map} and
2456 @code{overriding-terminal-local-map}; if either of these variables is
2457 non-@code{nil}, the input method should put its argument into a list and
2458 return that list with no further processing.
2460 @node Quoted Character Input
2461 @subsection Quoted Character Input
2462 @cindex quoted character input
2464 You can use the function @code{read-quoted-char} to ask the user to
2465 specify a character, and allow the user to specify a control or meta
2466 character conveniently, either literally or as an octal character code.
2467 The command @code{quoted-insert} uses this function.
2469 @defun read-quoted-char &optional prompt
2470 @cindex octal character input
2471 @cindex control characters, reading
2472 @cindex nonprinting characters, reading
2473 This function is like @code{read-char}, except that if the first
2474 character read is an octal digit (0-7), it reads any number of octal
2475 digits (but stopping if a non-octal digit is found), and returns the
2476 character represented by that numeric character code. If the
2477 character that terminates the sequence of octal digits is @key{RET},
2478 it is discarded. Any other terminating character is used as input
2479 after this function returns.
2481 Quitting is suppressed when the first character is read, so that the
2482 user can enter a @kbd{C-g}. @xref{Quitting}.
2484 If @var{prompt} is supplied, it specifies a string for prompting the
2485 user. The prompt string is always displayed in the echo area, followed
2486 by a single @samp{-}.
2488 In the following example, the user types in the octal number 177 (which
2492 (read-quoted-char "What character")
2495 ---------- Echo Area ----------
2496 What character @kbd{1 7 7}-
2497 ---------- Echo Area ----------
2505 @node Event Input Misc
2506 @subsection Miscellaneous Event Input Features
2508 This section describes how to ``peek ahead'' at events without using
2509 them up, how to check for pending input, and how to discard pending
2510 input. See also the function @code{read-passwd} (@pxref{Reading a
2513 @defvar unread-command-events
2515 @cindex peeking at input
2516 This variable holds a list of events waiting to be read as command
2517 input. The events are used in the order they appear in the list, and
2518 removed one by one as they are used.
2520 The variable is needed because in some cases a function reads an event
2521 and then decides not to use it. Storing the event in this variable
2522 causes it to be processed normally, by the command loop or by the
2523 functions to read command input.
2525 @cindex prefix argument unreading
2526 For example, the function that implements numeric prefix arguments reads
2527 any number of digits. When it finds a non-digit event, it must unread
2528 the event so that it can be read normally by the command loop.
2529 Likewise, incremental search uses this feature to unread events with no
2530 special meaning in a search, because these events should exit the search
2531 and then execute normally.
2533 The reliable and easy way to extract events from a key sequence so as to
2534 put them in @code{unread-command-events} is to use
2535 @code{listify-key-sequence} (@pxref{Strings of Events}).
2537 Normally you add events to the front of this list, so that the events
2538 most recently unread will be reread first.
2540 Events read from this list are not normally added to the current
2541 command's key sequence (as returned by e.g. @code{this-command-keys}),
2542 as the events will already have been added once as they were read for
2543 the first time. An element of the form @code{(@code{t} . @var{event})}
2544 forces @var{event} to be added to the current command's key sequence.
2548 @defun listify-key-sequence key
2549 This function converts the string or vector @var{key} to a list of
2550 individual events, which you can put in @code{unread-command-events}.
2553 @defvar unread-command-char
2554 This variable holds a character to be read as command input.
2555 A value of -1 means ``empty.''
2557 This variable is mostly obsolete now that you can use
2558 @code{unread-command-events} instead; it exists only to support programs
2559 written for Emacs versions 18 and earlier.
2562 @defun input-pending-p
2563 @cindex waiting for command key input
2564 This function determines whether any command input is currently
2565 available to be read. It returns immediately, with value @code{t} if
2566 there is available input, @code{nil} otherwise. On rare occasions it
2567 may return @code{t} when no input is available.
2570 @defvar last-input-event
2571 @defvarx last-input-char
2572 This variable records the last terminal input event read, whether
2573 as part of a command or explicitly by a Lisp program.
2575 In the example below, the Lisp program reads the character @kbd{1},
2576 @acronym{ASCII} code 49. It becomes the value of @code{last-input-event},
2577 while @kbd{C-e} (we assume @kbd{C-x C-e} command is used to evaluate
2578 this expression) remains the value of @code{last-command-event}.
2582 (progn (print (read-char))
2583 (print last-command-event)
2591 The alias @code{last-input-char} exists for compatibility with
2595 @defmac while-no-input body@dots{}
2596 This construct runs the @var{body} forms and returns the value of the
2597 last one---but only if no input arrives. If any input arrives during
2598 the execution of the @var{body} forms, it aborts them (working much
2599 like a quit). The @code{while-no-input} form returns @code{nil} if
2600 aborted by a real quit, and returns @code{t} if aborted by arrival of
2603 If a part of @var{body} binds @code{inhibit-quit} to non-@code{nil},
2604 arrival of input during those parts won't cause an abort until
2605 the end of that part.
2607 If you want to be able to distinguish all possible values computed
2608 by @var{body} from both kinds of abort conditions, write the code
2614 (progn . @var{body})))
2618 @defun discard-input
2620 @cindex discard input
2621 @cindex terminate keyboard macro
2622 This function discards the contents of the terminal input buffer and
2623 cancels any keyboard macro that might be in the process of definition.
2624 It returns @code{nil}.
2626 In the following example, the user may type a number of characters right
2627 after starting the evaluation of the form. After the @code{sleep-for}
2628 finishes sleeping, @code{discard-input} discards any characters typed
2632 (progn (sleep-for 2)
2638 @node Special Events
2639 @section Special Events
2641 @cindex special events
2642 Special events are handled at a very low level---as soon as they are
2643 read. The @code{read-event} function processes these events itself, and
2644 never returns them. Instead, it keeps waiting for the first event
2645 that is not special and returns that one.
2647 Events that are handled in this way do not echo, they are never grouped
2648 into key sequences, and they never appear in the value of
2649 @code{last-command-event} or @code{(this-command-keys)}. They do not
2650 discard a numeric argument, they cannot be unread with
2651 @code{unread-command-events}, they may not appear in a keyboard macro,
2652 and they are not recorded in a keyboard macro while you are defining
2655 These events do, however, appear in @code{last-input-event} immediately
2656 after they are read, and this is the way for the event's definition to
2657 find the actual event.
2659 The events types @code{iconify-frame}, @code{make-frame-visible},
2660 @code{delete-frame}, @code{drag-n-drop}, and user signals like
2661 @code{sigusr1} are normally handled in this way. The keymap which
2662 defines how to handle special events---and which events are special---is
2663 in the variable @code{special-event-map} (@pxref{Active Keymaps}).
2666 @section Waiting for Elapsed Time or Input
2670 The wait functions are designed to wait for a certain amount of time
2671 to pass or until there is input. For example, you may wish to pause in
2672 the middle of a computation to allow the user time to view the display.
2673 @code{sit-for} pauses and updates the screen, and returns immediately if
2674 input comes in, while @code{sleep-for} pauses without updating the
2677 @defun sit-for seconds &optional nodisp
2678 This function performs redisplay (provided there is no pending input
2679 from the user), then waits @var{seconds} seconds, or until input is
2680 available. The usual purpose of @code{sit-for} is to give the user
2681 time to read text that you display. The value is @code{t} if
2682 @code{sit-for} waited the full time with no input arriving
2683 (@pxref{Event Input Misc}). Otherwise, the value is @code{nil}.
2685 The argument @var{seconds} need not be an integer. If it is a floating
2686 point number, @code{sit-for} waits for a fractional number of seconds.
2687 Some systems support only a whole number of seconds; on these systems,
2688 @var{seconds} is rounded down.
2690 The expression @code{(sit-for 0)} is equivalent to @code{(redisplay)},
2691 i.e. it requests a redisplay, without any delay, if there is no pending input.
2692 @xref{Forcing Redisplay}.
2694 If @var{nodisp} is non-@code{nil}, then @code{sit-for} does not
2695 redisplay, but it still returns as soon as input is available (or when
2696 the timeout elapses).
2698 In batch mode (@pxref{Batch Mode}), @code{sit-for} cannot be
2699 interrupted, even by input from the standard input descriptor. It is
2700 thus equivalent to @code{sleep-for}, which is described below.
2702 It is also possible to call @code{sit-for} with three arguments,
2703 as @code{(sit-for @var{seconds} @var{millisec} @var{nodisp})},
2704 but that is considered obsolete.
2707 @defun sleep-for seconds &optional millisec
2708 This function simply pauses for @var{seconds} seconds without updating
2709 the display. It pays no attention to available input. It returns
2712 The argument @var{seconds} need not be an integer. If it is a floating
2713 point number, @code{sleep-for} waits for a fractional number of seconds.
2714 Some systems support only a whole number of seconds; on these systems,
2715 @var{seconds} is rounded down.
2717 The optional argument @var{millisec} specifies an additional waiting
2718 period measured in milliseconds. This adds to the period specified by
2719 @var{seconds}. If the system doesn't support waiting fractions of a
2720 second, you get an error if you specify nonzero @var{millisec}.
2722 Use @code{sleep-for} when you wish to guarantee a delay.
2725 @xref{Time of Day}, for functions to get the current time.
2731 @cindex interrupt Lisp functions
2733 Typing @kbd{C-g} while a Lisp function is running causes Emacs to
2734 @dfn{quit} whatever it is doing. This means that control returns to the
2735 innermost active command loop.
2737 Typing @kbd{C-g} while the command loop is waiting for keyboard input
2738 does not cause a quit; it acts as an ordinary input character. In the
2739 simplest case, you cannot tell the difference, because @kbd{C-g}
2740 normally runs the command @code{keyboard-quit}, whose effect is to quit.
2741 However, when @kbd{C-g} follows a prefix key, they combine to form an
2742 undefined key. The effect is to cancel the prefix key as well as any
2745 In the minibuffer, @kbd{C-g} has a different definition: it aborts out
2746 of the minibuffer. This means, in effect, that it exits the minibuffer
2747 and then quits. (Simply quitting would return to the command loop
2748 @emph{within} the minibuffer.) The reason why @kbd{C-g} does not quit
2749 directly when the command reader is reading input is so that its meaning
2750 can be redefined in the minibuffer in this way. @kbd{C-g} following a
2751 prefix key is not redefined in the minibuffer, and it has its normal
2752 effect of canceling the prefix key and prefix argument. This too
2753 would not be possible if @kbd{C-g} always quit directly.
2755 When @kbd{C-g} does directly quit, it does so by setting the variable
2756 @code{quit-flag} to @code{t}. Emacs checks this variable at appropriate
2757 times and quits if it is not @code{nil}. Setting @code{quit-flag}
2758 non-@code{nil} in any way thus causes a quit.
2760 At the level of C code, quitting cannot happen just anywhere; only at the
2761 special places that check @code{quit-flag}. The reason for this is
2762 that quitting at other places might leave an inconsistency in Emacs's
2763 internal state. Because quitting is delayed until a safe place, quitting
2764 cannot make Emacs crash.
2766 Certain functions such as @code{read-key-sequence} or
2767 @code{read-quoted-char} prevent quitting entirely even though they wait
2768 for input. Instead of quitting, @kbd{C-g} serves as the requested
2769 input. In the case of @code{read-key-sequence}, this serves to bring
2770 about the special behavior of @kbd{C-g} in the command loop. In the
2771 case of @code{read-quoted-char}, this is so that @kbd{C-q} can be used
2772 to quote a @kbd{C-g}.
2774 @cindex prevent quitting
2775 You can prevent quitting for a portion of a Lisp function by binding
2776 the variable @code{inhibit-quit} to a non-@code{nil} value. Then,
2777 although @kbd{C-g} still sets @code{quit-flag} to @code{t} as usual, the
2778 usual result of this---a quit---is prevented. Eventually,
2779 @code{inhibit-quit} will become @code{nil} again, such as when its
2780 binding is unwound at the end of a @code{let} form. At that time, if
2781 @code{quit-flag} is still non-@code{nil}, the requested quit happens
2782 immediately. This behavior is ideal when you wish to make sure that
2783 quitting does not happen within a ``critical section'' of the program.
2785 @cindex @code{read-quoted-char} quitting
2786 In some functions (such as @code{read-quoted-char}), @kbd{C-g} is
2787 handled in a special way that does not involve quitting. This is done
2788 by reading the input with @code{inhibit-quit} bound to @code{t}, and
2789 setting @code{quit-flag} to @code{nil} before @code{inhibit-quit}
2790 becomes @code{nil} again. This excerpt from the definition of
2791 @code{read-quoted-char} shows how this is done; it also shows that
2792 normal quitting is permitted after the first character of input.
2795 (defun read-quoted-char (&optional prompt)
2796 "@dots{}@var{documentation}@dots{}"
2797 (let ((message-log-max nil) done (first t) (code 0) char)
2799 (let ((inhibit-quit first)
2801 (and prompt (message "%s-" prompt))
2802 (setq char (read-event))
2803 (if inhibit-quit (setq quit-flag nil)))
2804 @r{@dots{}set the variable @code{code}@dots{}})
2809 If this variable is non-@code{nil}, then Emacs quits immediately, unless
2810 @code{inhibit-quit} is non-@code{nil}. Typing @kbd{C-g} ordinarily sets
2811 @code{quit-flag} non-@code{nil}, regardless of @code{inhibit-quit}.
2814 @defvar inhibit-quit
2815 This variable determines whether Emacs should quit when @code{quit-flag}
2816 is set to a value other than @code{nil}. If @code{inhibit-quit} is
2817 non-@code{nil}, then @code{quit-flag} has no special effect.
2820 @defmac with-local-quit body@dots{}
2821 This macro executes @var{body} forms in sequence, but allows quitting, at
2822 least locally, within @var{body} even if @code{inhibit-quit} was
2823 non-@code{nil} outside this construct. It returns the value of the
2824 last form in @var{body}, unless exited by quitting, in which case
2825 it returns @code{nil}.
2827 If @code{inhibit-quit} is @code{nil} on entry to @code{with-local-quit},
2828 it only executes the @var{body}, and setting @code{quit-flag} causes
2829 a normal quit. However, if @code{inhibit-quit} is non-@code{nil} so
2830 that ordinary quitting is delayed, a non-@code{nil} @code{quit-flag}
2831 triggers a special kind of local quit. This ends the execution of
2832 @var{body} and exits the @code{with-local-quit} body with
2833 @code{quit-flag} still non-@code{nil}, so that another (ordinary) quit
2834 will happen as soon as that is allowed. If @code{quit-flag} is
2835 already non-@code{nil} at the beginning of @var{body}, the local quit
2836 happens immediately and the body doesn't execute at all.
2838 This macro is mainly useful in functions that can be called from
2839 timers, process filters, process sentinels, @code{pre-command-hook},
2840 @code{post-command-hook}, and other places where @code{inhibit-quit} is
2841 normally bound to @code{t}.
2844 @deffn Command keyboard-quit
2845 This function signals the @code{quit} condition with @code{(signal 'quit
2846 nil)}. This is the same thing that quitting does. (See @code{signal}
2850 You can specify a character other than @kbd{C-g} to use for quitting.
2851 See the function @code{set-input-mode} in @ref{Terminal Input}.
2853 @node Prefix Command Arguments
2854 @section Prefix Command Arguments
2855 @cindex prefix argument
2856 @cindex raw prefix argument
2857 @cindex numeric prefix argument
2859 Most Emacs commands can use a @dfn{prefix argument}, a number
2860 specified before the command itself. (Don't confuse prefix arguments
2861 with prefix keys.) The prefix argument is at all times represented by a
2862 value, which may be @code{nil}, meaning there is currently no prefix
2863 argument. Each command may use the prefix argument or ignore it.
2865 There are two representations of the prefix argument: @dfn{raw} and
2866 @dfn{numeric}. The editor command loop uses the raw representation
2867 internally, and so do the Lisp variables that store the information, but
2868 commands can request either representation.
2870 Here are the possible values of a raw prefix argument:
2874 @code{nil}, meaning there is no prefix argument. Its numeric value is
2875 1, but numerous commands make a distinction between @code{nil} and the
2879 An integer, which stands for itself.
2882 A list of one element, which is an integer. This form of prefix
2883 argument results from one or a succession of @kbd{C-u}'s with no
2884 digits. The numeric value is the integer in the list, but some
2885 commands make a distinction between such a list and an integer alone.
2888 The symbol @code{-}. This indicates that @kbd{M--} or @kbd{C-u -} was
2889 typed, without following digits. The equivalent numeric value is
2890 @minus{}1, but some commands make a distinction between the integer
2891 @minus{}1 and the symbol @code{-}.
2894 We illustrate these possibilities by calling the following function with
2899 (defun display-prefix (arg)
2900 "Display the value of the raw prefix arg."
2907 Here are the results of calling @code{display-prefix} with various
2908 raw prefix arguments:
2911 M-x display-prefix @print{} nil
2913 C-u M-x display-prefix @print{} (4)
2915 C-u C-u M-x display-prefix @print{} (16)
2917 C-u 3 M-x display-prefix @print{} 3
2919 M-3 M-x display-prefix @print{} 3 ; @r{(Same as @code{C-u 3}.)}
2921 C-u - M-x display-prefix @print{} -
2923 M-- M-x display-prefix @print{} - ; @r{(Same as @code{C-u -}.)}
2925 C-u - 7 M-x display-prefix @print{} -7
2927 M-- 7 M-x display-prefix @print{} -7 ; @r{(Same as @code{C-u -7}.)}
2930 Emacs uses two variables to store the prefix argument:
2931 @code{prefix-arg} and @code{current-prefix-arg}. Commands such as
2932 @code{universal-argument} that set up prefix arguments for other
2933 commands store them in @code{prefix-arg}. In contrast,
2934 @code{current-prefix-arg} conveys the prefix argument to the current
2935 command, so setting it has no effect on the prefix arguments for future
2938 Normally, commands specify which representation to use for the prefix
2939 argument, either numeric or raw, in the @code{interactive} specification.
2940 (@xref{Using Interactive}.) Alternatively, functions may look at the
2941 value of the prefix argument directly in the variable
2942 @code{current-prefix-arg}, but this is less clean.
2944 @defun prefix-numeric-value arg
2945 This function returns the numeric meaning of a valid raw prefix argument
2946 value, @var{arg}. The argument may be a symbol, a number, or a list.
2947 If it is @code{nil}, the value 1 is returned; if it is @code{-}, the
2948 value @minus{}1 is returned; if it is a number, that number is returned;
2949 if it is a list, the @sc{car} of that list (which should be a number) is
2953 @defvar current-prefix-arg
2954 This variable holds the raw prefix argument for the @emph{current}
2955 command. Commands may examine it directly, but the usual method for
2956 accessing it is with @code{(interactive "P")}.
2960 The value of this variable is the raw prefix argument for the
2961 @emph{next} editing command. Commands such as @code{universal-argument}
2962 that specify prefix arguments for the following command work by setting
2966 @defvar last-prefix-arg
2967 The raw prefix argument value used by the previous command.
2970 The following commands exist to set up prefix arguments for the
2971 following command. Do not call them for any other reason.
2973 @deffn Command universal-argument
2974 This command reads input and specifies a prefix argument for the
2975 following command. Don't call this command yourself unless you know
2979 @deffn Command digit-argument arg
2980 This command adds to the prefix argument for the following command. The
2981 argument @var{arg} is the raw prefix argument as it was before this
2982 command; it is used to compute the updated prefix argument. Don't call
2983 this command yourself unless you know what you are doing.
2986 @deffn Command negative-argument arg
2987 This command adds to the numeric argument for the next command. The
2988 argument @var{arg} is the raw prefix argument as it was before this
2989 command; its value is negated to form the new prefix argument. Don't
2990 call this command yourself unless you know what you are doing.
2993 @node Recursive Editing
2994 @section Recursive Editing
2995 @cindex recursive command loop
2996 @cindex recursive editing level
2997 @cindex command loop, recursive
2999 The Emacs command loop is entered automatically when Emacs starts up.
3000 This top-level invocation of the command loop never exits; it keeps
3001 running as long as Emacs does. Lisp programs can also invoke the
3002 command loop. Since this makes more than one activation of the command
3003 loop, we call it @dfn{recursive editing}. A recursive editing level has
3004 the effect of suspending whatever command invoked it and permitting the
3005 user to do arbitrary editing before resuming that command.
3007 The commands available during recursive editing are the same ones
3008 available in the top-level editing loop and defined in the keymaps.
3009 Only a few special commands exit the recursive editing level; the others
3010 return to the recursive editing level when they finish. (The special
3011 commands for exiting are always available, but they do nothing when
3012 recursive editing is not in progress.)
3014 All command loops, including recursive ones, set up all-purpose error
3015 handlers so that an error in a command run from the command loop will
3018 @cindex minibuffer input
3019 Minibuffer input is a special kind of recursive editing. It has a few
3020 special wrinkles, such as enabling display of the minibuffer and the
3021 minibuffer window, but fewer than you might suppose. Certain keys
3022 behave differently in the minibuffer, but that is only because of the
3023 minibuffer's local map; if you switch windows, you get the usual Emacs
3026 @cindex @code{throw} example
3028 @cindex exit recursive editing
3030 To invoke a recursive editing level, call the function
3031 @code{recursive-edit}. This function contains the command loop; it also
3032 contains a call to @code{catch} with tag @code{exit}, which makes it
3033 possible to exit the recursive editing level by throwing to @code{exit}
3034 (@pxref{Catch and Throw}). If you throw a value other than @code{t},
3035 then @code{recursive-edit} returns normally to the function that called
3036 it. The command @kbd{C-M-c} (@code{exit-recursive-edit}) does this.
3037 Throwing a @code{t} value causes @code{recursive-edit} to quit, so that
3038 control returns to the command loop one level up. This is called
3039 @dfn{aborting}, and is done by @kbd{C-]} (@code{abort-recursive-edit}).
3041 Most applications should not use recursive editing, except as part of
3042 using the minibuffer. Usually it is more convenient for the user if you
3043 change the major mode of the current buffer temporarily to a special
3044 major mode, which should have a command to go back to the previous mode.
3045 (The @kbd{e} command in Rmail uses this technique.) Or, if you wish to
3046 give the user different text to edit ``recursively,'' create and select
3047 a new buffer in a special mode. In this mode, define a command to
3048 complete the processing and go back to the previous buffer. (The
3049 @kbd{m} command in Rmail does this.)
3051 Recursive edits are useful in debugging. You can insert a call to
3052 @code{debug} into a function definition as a sort of breakpoint, so that
3053 you can look around when the function gets there. @code{debug} invokes
3054 a recursive edit but also provides the other features of the debugger.
3056 Recursive editing levels are also used when you type @kbd{C-r} in
3057 @code{query-replace} or use @kbd{C-x q} (@code{kbd-macro-query}).
3059 @defun recursive-edit
3060 @cindex suspend evaluation
3061 This function invokes the editor command loop. It is called
3062 automatically by the initialization of Emacs, to let the user begin
3063 editing. When called from a Lisp program, it enters a recursive editing
3066 If the current buffer is not the same as the selected window's buffer,
3067 @code{recursive-edit} saves and restores the current buffer. Otherwise,
3068 if you switch buffers, the buffer you switched to is current after
3069 @code{recursive-edit} returns.
3071 In the following example, the function @code{simple-rec} first
3072 advances point one word, then enters a recursive edit, printing out a
3073 message in the echo area. The user can then do any editing desired, and
3074 then type @kbd{C-M-c} to exit and continue executing @code{simple-rec}.
3077 (defun simple-rec ()
3079 (message "Recursive edit in progress")
3082 @result{} simple-rec
3088 @deffn Command exit-recursive-edit
3089 This function exits from the innermost recursive edit (including
3090 minibuffer input). Its definition is effectively @code{(throw 'exit
3094 @deffn Command abort-recursive-edit
3095 This function aborts the command that requested the innermost recursive
3096 edit (including minibuffer input), by signaling @code{quit}
3097 after exiting the recursive edit. Its definition is effectively
3098 @code{(throw 'exit t)}. @xref{Quitting}.
3101 @deffn Command top-level
3102 This function exits all recursive editing levels; it does not return a
3103 value, as it jumps completely out of any computation directly back to
3104 the main command loop.
3107 @defun recursion-depth
3108 This function returns the current depth of recursive edits. When no
3109 recursive edit is active, it returns 0.
3112 @node Disabling Commands
3113 @section Disabling Commands
3114 @cindex disabled command
3116 @dfn{Disabling a command} marks the command as requiring user
3117 confirmation before it can be executed. Disabling is used for commands
3118 which might be confusing to beginning users, to prevent them from using
3119 the commands by accident.
3122 The low-level mechanism for disabling a command is to put a
3123 non-@code{nil} @code{disabled} property on the Lisp symbol for the
3124 command. These properties are normally set up by the user's
3125 init file (@pxref{Init File}) with Lisp expressions such as this:
3128 (put 'upcase-region 'disabled t)
3132 For a few commands, these properties are present by default (you can
3133 remove them in your init file if you wish).
3135 If the value of the @code{disabled} property is a string, the message
3136 saying the command is disabled includes that string. For example:
3139 (put 'delete-region 'disabled
3140 "Text deleted this way cannot be yanked back!\n")
3143 @xref{Disabling,,, emacs, The GNU Emacs Manual}, for the details on
3144 what happens when a disabled command is invoked interactively.
3145 Disabling a command has no effect on calling it as a function from Lisp
3148 @deffn Command enable-command command
3149 Allow @var{command} (a symbol) to be executed without special
3150 confirmation from now on, and alter the user's init file (@pxref{Init
3151 File}) so that this will apply to future sessions.
3154 @deffn Command disable-command command
3155 Require special confirmation to execute @var{command} from now on, and
3156 alter the user's init file so that this will apply to future sessions.
3159 @defvar disabled-command-function
3160 The value of this variable should be a function. When the user
3161 invokes a disabled command interactively, this function is called
3162 instead of the disabled command. It can use @code{this-command-keys}
3163 to determine what the user typed to run the command, and thus find the
3166 The value may also be @code{nil}. Then all commands work normally,
3169 By default, the value is a function that asks the user whether to
3173 @node Command History
3174 @section Command History
3175 @cindex command history
3176 @cindex complex command
3177 @cindex history of commands
3179 The command loop keeps a history of the complex commands that have
3180 been executed, to make it convenient to repeat these commands. A
3181 @dfn{complex command} is one for which the interactive argument reading
3182 uses the minibuffer. This includes any @kbd{M-x} command, any
3183 @kbd{M-:} command, and any command whose @code{interactive}
3184 specification reads an argument from the minibuffer. Explicit use of
3185 the minibuffer during the execution of the command itself does not cause
3186 the command to be considered complex.
3188 @defvar command-history
3189 This variable's value is a list of recent complex commands, each
3190 represented as a form to evaluate. It continues to accumulate all
3191 complex commands for the duration of the editing session, but when it
3192 reaches the maximum size (@pxref{Minibuffer History}), the oldest
3193 elements are deleted as new ones are added.
3198 @result{} ((switch-to-buffer "chistory.texi")
3199 (describe-key "^X^[")
3200 (visit-tags-table "~/emacs/src/")
3201 (find-tag "repeat-complex-command"))
3206 This history list is actually a special case of minibuffer history
3207 (@pxref{Minibuffer History}), with one special twist: the elements are
3208 expressions rather than strings.
3210 There are a number of commands devoted to the editing and recall of
3211 previous commands. The commands @code{repeat-complex-command}, and
3212 @code{list-command-history} are described in the user manual
3213 (@pxref{Repetition,,, emacs, The GNU Emacs Manual}). Within the
3214 minibuffer, the usual minibuffer history commands are available.
3216 @node Keyboard Macros
3217 @section Keyboard Macros
3218 @cindex keyboard macros
3220 A @dfn{keyboard macro} is a canned sequence of input events that can
3221 be considered a command and made the definition of a key. The Lisp
3222 representation of a keyboard macro is a string or vector containing the
3223 events. Don't confuse keyboard macros with Lisp macros
3226 @defun execute-kbd-macro kbdmacro &optional count loopfunc
3227 This function executes @var{kbdmacro} as a sequence of events. If
3228 @var{kbdmacro} is a string or vector, then the events in it are executed
3229 exactly as if they had been input by the user. The sequence is
3230 @emph{not} expected to be a single key sequence; normally a keyboard
3231 macro definition consists of several key sequences concatenated.
3233 If @var{kbdmacro} is a symbol, then its function definition is used in
3234 place of @var{kbdmacro}. If that is another symbol, this process repeats.
3235 Eventually the result should be a string or vector. If the result is
3236 not a symbol, string, or vector, an error is signaled.
3238 The argument @var{count} is a repeat count; @var{kbdmacro} is executed that
3239 many times. If @var{count} is omitted or @code{nil}, @var{kbdmacro} is
3240 executed once. If it is 0, @var{kbdmacro} is executed over and over until it
3241 encounters an error or a failing search.
3243 If @var{loopfunc} is non-@code{nil}, it is a function that is called,
3244 without arguments, prior to each iteration of the macro. If
3245 @var{loopfunc} returns @code{nil}, then this stops execution of the macro.
3247 @xref{Reading One Event}, for an example of using @code{execute-kbd-macro}.
3250 @defvar executing-kbd-macro
3251 This variable contains the string or vector that defines the keyboard
3252 macro that is currently executing. It is @code{nil} if no macro is
3253 currently executing. A command can test this variable so as to behave
3254 differently when run from an executing macro. Do not set this variable
3258 @defvar defining-kbd-macro
3259 This variable is non-@code{nil} if and only if a keyboard macro is
3260 being defined. A command can test this variable so as to behave
3261 differently while a macro is being defined. The value is
3262 @code{append} while appending to the definition of an existing macro.
3263 The commands @code{start-kbd-macro}, @code{kmacro-start-macro} and
3264 @code{end-kbd-macro} set this variable---do not set it yourself.
3266 The variable is always local to the current terminal and cannot be
3267 buffer-local. @xref{Multiple Displays}.
3270 @defvar last-kbd-macro
3271 This variable is the definition of the most recently defined keyboard
3272 macro. Its value is a string or vector, or @code{nil}.
3274 The variable is always local to the current terminal and cannot be
3275 buffer-local. @xref{Multiple Displays}.
3278 @defvar kbd-macro-termination-hook
3279 This normal hook (@pxref{Standard Hooks}) is run when a keyboard
3280 macro terminates, regardless of what caused it to terminate (reaching
3281 the macro end or an error which ended the macro prematurely).
3285 arch-tag: e34944ad-7d5c-4980-be00-36a5fe54d4b1