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 * Distinguish Interactive:: Making a command distinguish interactive calls.
22 * Command Loop Info:: Variables set by the command loop for you to examine.
23 * Adjusting Point:: Adjustment of point after a command.
24 * Input Events:: What input looks like when you read it.
25 * Reading Input:: How to read input events from the keyboard or mouse.
26 * Special Events:: Events processed immediately and individually.
27 * Waiting:: Waiting for user input or elapsed time.
28 * Quitting:: How @kbd{C-g} works. How to catch or defer quitting.
29 * Prefix Command Arguments:: How the commands to set prefix args work.
30 * Recursive Editing:: Entering a recursive edit,
31 and why you usually shouldn't.
32 * Disabling Commands:: How the command loop handles disabled commands.
33 * Command History:: How the command history is set up, and how accessed.
34 * Keyboard Macros:: How keyboard macros are implemented.
37 @node Command Overview
38 @section Command Loop Overview
40 The first thing the command loop must do is read a key sequence, which
41 is a sequence of events that translates into a command. It does this by
42 calling the function @code{read-key-sequence}. Your Lisp code can also
43 call this function (@pxref{Key Sequence Input}). Lisp programs can also
44 do input at a lower level with @code{read-event} (@pxref{Reading One
45 Event}) or discard pending input with @code{discard-input}
46 (@pxref{Event Input Misc}).
48 The key sequence is translated into a command through the currently
49 active keymaps. @xref{Key Lookup}, for information on how this is done.
50 The result should be a keyboard macro or an interactively callable
51 function. If the key is @kbd{M-x}, then it reads the name of another
52 command, which it then calls. This is done by the command
53 @code{execute-extended-command} (@pxref{Interactive Call}).
55 To execute a command requires first reading the arguments for it.
56 This is done by calling @code{command-execute} (@pxref{Interactive
57 Call}). For commands written in Lisp, the @code{interactive}
58 specification says how to read the arguments. This may use the prefix
59 argument (@pxref{Prefix Command Arguments}) or may read with prompting
60 in the minibuffer (@pxref{Minibuffers}). For example, the command
61 @code{find-file} has an @code{interactive} specification which says to
62 read a file name using the minibuffer. The command's function body does
63 not use the minibuffer; if you call this command from Lisp code as a
64 function, you must supply the file name string as an ordinary Lisp
67 If the command is a string or vector (i.e., a keyboard macro) then
68 @code{execute-kbd-macro} is used to execute it. You can call this
69 function yourself (@pxref{Keyboard Macros}).
71 To terminate the execution of a running command, type @kbd{C-g}. This
72 character causes @dfn{quitting} (@pxref{Quitting}).
74 @defvar pre-command-hook
75 The editor command loop runs this normal hook before each command. At
76 that time, @code{this-command} contains the command that is about to
77 run, and @code{last-command} describes the previous command.
78 @xref{Command Loop Info}.
81 @defvar post-command-hook
82 The editor command loop runs this normal hook after each command
83 (including commands terminated prematurely by quitting or by errors),
84 and also when the command loop is first entered. At that time,
85 @code{this-command} refers to the command that just ran, and
86 @code{last-command} refers to the command before that.
89 Quitting is suppressed while running @code{pre-command-hook} and
90 @code{post-command-hook}. If an error happens while executing one of
91 these hooks, it terminates execution of the hook, and clears the hook
92 variable to @code{nil} so as to prevent an infinite loop of errors.
94 A request coming into the Emacs server (@pxref{Emacs Server,,,
95 emacs, The GNU Emacs Manual}) runs these two hooks just as a keyboard
98 @node Defining Commands
99 @section Defining Commands
100 @cindex defining commands
101 @cindex commands, defining
102 @cindex functions, making them interactive
103 @cindex interactive function
105 A Lisp function becomes a command when its body contains, at top
106 level, a form that calls the special form @code{interactive}. This
107 form does nothing when actually executed, but its presence serves as a
108 flag to indicate that interactive calling is permitted. Its argument
109 controls the reading of arguments for an interactive call.
112 * Using Interactive:: General rules for @code{interactive}.
113 * Interactive Codes:: The standard letter-codes for reading arguments
115 * Interactive Examples:: Examples of how to read interactive arguments.
118 @node Using Interactive
119 @subsection Using @code{interactive}
120 @cindex arguments, interactive entry
122 This section describes how to write the @code{interactive} form that
123 makes a Lisp function an interactively-callable command, and how to
124 examine a command's @code{interactive} form.
126 @defspec interactive arg-descriptor
127 This special form declares that the function in which it appears is a
128 command, and that it may therefore be called interactively (via
129 @kbd{M-x} or by entering a key sequence bound to it). The argument
130 @var{arg-descriptor} declares how to compute the arguments to the
131 command when the command is called interactively.
133 A command may be called from Lisp programs like any other function, but
134 then the caller supplies the arguments and @var{arg-descriptor} has no
137 The @code{interactive} form has its effect because the command loop
138 (actually, its subroutine @code{call-interactively}) scans through the
139 function definition looking for it, before calling the function. Once
140 the function is called, all its body forms including the
141 @code{interactive} form are executed, but at this time
142 @code{interactive} simply returns @code{nil} without even evaluating its
146 There are three possibilities for the argument @var{arg-descriptor}:
150 It may be omitted or @code{nil}; then the command is called with no
151 arguments. This leads quickly to an error if the command requires one
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}).
211 Providing point or the mark as an argument value is also common, but
212 if you do this @emph{and} read input (whether using the minibuffer or
213 not), be sure to get the integer values of point or the mark after
214 reading. The current buffer may be receiving subprocess output; if
215 subprocess output arrives while the command is waiting for input, it
216 could relocate point and the mark.
218 Here's an example of what @emph{not} to do:
222 (list (region-beginning) (region-end)
223 (read-string "Foo: " nil 'my-history)))
227 Here's how to avoid the problem, by examining point and the mark after
228 reading the keyboard input:
232 (let ((string (read-string "Foo: " nil 'my-history)))
233 (list (region-beginning) (region-end) string)))
236 @strong{Warning:} the argument values should not include any data
237 types that can't be printed and then read. Some facilities save
238 @code{command-history} in a file to be read in the subsequent
239 sessions; if a command's arguments contain a data type that prints
240 using @samp{#<@dots{}>} syntax, those facilities won't work.
242 There are, however, a few exceptions: it is ok to use a limited set of
243 expressions such as @code{(point)}, @code{(mark)},
244 @code{(region-beginning)}, and @code{(region-end)}, because Emacs
245 recognizes them specially and puts the expression (rather than its
246 value) into the command history. To see whether the expression you
247 wrote is one of these exceptions, run the command, then examine
248 @code{(car command-history)}.
251 @cindex examining the @code{interactive} form
252 @defun interactive-form function
253 This function returns the @code{interactive} form of @var{function}.
254 If @var{function} is an interactively callable function
255 (@pxref{Interactive Call}), the value is the command's
256 @code{interactive} form @code{(interactive @var{spec})}, which
257 specifies how to compute its arguments. Otherwise, the value is
258 @code{nil}. If @var{function} is a symbol, its function definition is
262 @node Interactive Codes
263 @comment node-name, next, previous, up
264 @subsection Code Characters for @code{interactive}
265 @cindex interactive code description
266 @cindex description for interactive codes
267 @cindex codes, interactive, description of
268 @cindex characters for interactive codes
270 The code character descriptions below contain a number of key words,
271 defined here as follows:
275 @cindex interactive completion
276 Provide completion. @key{TAB}, @key{SPC}, and @key{RET} perform name
277 completion because the argument is read using @code{completing-read}
278 (@pxref{Completion}). @kbd{?} displays a list of possible completions.
281 Require the name of an existing object. An invalid name is not
282 accepted; the commands to exit the minibuffer do not exit if the current
286 @cindex default argument string
287 A default value of some sort is used if the user enters no text in the
288 minibuffer. The default depends on the code character.
291 This code letter computes an argument without reading any input.
292 Therefore, it does not use a prompt string, and any prompt string you
295 Even though the code letter doesn't use a prompt string, you must follow
296 it with a newline if it is not the last code character in the string.
299 A prompt immediately follows the code character. The prompt ends either
300 with the end of the string or with a newline.
303 This code character is meaningful only at the beginning of the
304 interactive string, and it does not look for a prompt or a newline.
305 It is a single, isolated character.
308 @cindex reading interactive arguments
309 Here are the code character descriptions for use with @code{interactive}:
313 Signal an error if the current buffer is read-only. Special.
316 Select the window mentioned in the first mouse event in the key
317 sequence that invoked this command. Special.
320 A function name (i.e., a symbol satisfying @code{fboundp}). Existing,
324 The name of an existing buffer. By default, uses the name of the
325 current buffer (@pxref{Buffers}). Existing, Completion, Default,
329 A buffer name. The buffer need not exist. By default, uses the name of
330 a recently used buffer other than the current buffer. Completion,
334 A character. The cursor does not move into the echo area. Prompt.
337 A command name (i.e., a symbol satisfying @code{commandp}). Existing,
341 @cindex position argument
342 The position of point, as an integer (@pxref{Point}). No I/O.
345 A directory name. The default is the current default directory of the
346 current buffer, @code{default-directory} (@pxref{File Name Expansion}).
347 Existing, Completion, Default, Prompt.
350 The first or next mouse event in the key sequence that invoked the command.
351 More precisely, @samp{e} gets events that are lists, so you can look at
352 the data in the lists. @xref{Input Events}. No I/O.
354 You can use @samp{e} more than once in a single command's interactive
355 specification. If the key sequence that invoked the command has
356 @var{n} events that are lists, the @var{n}th @samp{e} provides the
357 @var{n}th such event. Events that are not lists, such as function keys
358 and @acronym{ASCII} characters, do not count where @samp{e} is concerned.
361 A file name of an existing file (@pxref{File Names}). The default
362 directory is @code{default-directory}. Existing, Completion, Default,
366 A file name. The file need not exist. Completion, Default, Prompt.
369 A file name. The file need not exist. If the user enters just a
370 directory name, then the value is just that directory name, with no
371 file name within the directory added. Completion, Default, Prompt.
374 An irrelevant argument. This code always supplies @code{nil} as
375 the argument's value. No I/O.
378 A key sequence (@pxref{Key Sequences}). This keeps reading events
379 until a command (or undefined command) is found in the current key
380 maps. The key sequence argument is represented as a string or vector.
381 The cursor does not move into the echo area. Prompt.
383 If @samp{k} reads a key sequence that ends with a down-event, it also
384 reads and discards the following up-event. You can get access to that
385 up-event with the @samp{U} code character.
387 This kind of input is used by commands such as @code{describe-key} and
388 @code{global-set-key}.
391 A key sequence, whose definition you intend to change. This works like
392 @samp{k}, except that it suppresses, for the last input event in the key
393 sequence, the conversions that are normally used (when necessary) to
394 convert an undefined key into a defined one.
397 @cindex marker argument
398 The position of the mark, as an integer. No I/O.
401 Arbitrary text, read in the minibuffer using the current buffer's input
402 method, and returned as a string (@pxref{Input Methods,,, emacs, The GNU
403 Emacs Manual}). Prompt.
406 A number, read with the minibuffer. If the input is not a number, the
407 user has to try again. @samp{n} never uses the prefix argument.
411 The numeric prefix argument; but if there is no prefix argument, read
412 a number as with @kbd{n}. The value is always a number. @xref{Prefix
413 Command Arguments}. Prompt.
416 @cindex numeric prefix argument usage
417 The numeric prefix argument. (Note that this @samp{p} is lower case.)
421 @cindex raw prefix argument usage
422 The raw prefix argument. (Note that this @samp{P} is upper case.) No
426 @cindex region argument
427 Point and the mark, as two numeric arguments, smallest first. This is
428 the only code letter that specifies two successive arguments rather than
432 Arbitrary text, read in the minibuffer and returned as a string
433 (@pxref{Text from Minibuffer}). Terminate the input with either
434 @kbd{C-j} or @key{RET}. (@kbd{C-q} may be used to include either of
435 these characters in the input.) Prompt.
438 An interned symbol whose name is read in the minibuffer. Any whitespace
439 character terminates the input. (Use @kbd{C-q} to include whitespace in
440 the string.) Other characters that normally terminate a symbol (e.g.,
441 parentheses and brackets) do not do so here. Prompt.
444 A key sequence or @code{nil}. Can be used after a @samp{k} or
445 @samp{K} argument to get the up-event that was discarded (if any)
446 after @samp{k} or @samp{K} read a down-event. If no up-event has been
447 discarded, @samp{U} provides @code{nil} as the argument. No I/O.
450 A variable declared to be a user option (i.e., satisfying the
451 predicate @code{user-variable-p}). This reads the variable using
452 @code{read-variable}. @xref{Definition of read-variable}. Existing,
456 A Lisp object, specified with its read syntax, terminated with a
457 @kbd{C-j} or @key{RET}. The object is not evaluated. @xref{Object from
461 @cindex evaluated expression argument
462 A Lisp form's value. @samp{X} reads as @samp{x} does, then evaluates
463 the form so that its value becomes the argument for the command.
467 A coding system name (a symbol). If the user enters null input, the
468 argument value is @code{nil}. @xref{Coding Systems}. Completion,
472 A coding system name (a symbol)---but only if this command has a prefix
473 argument. With no prefix argument, @samp{Z} provides @code{nil} as the
474 argument value. Completion, Existing, Prompt.
477 @node Interactive Examples
478 @comment node-name, next, previous, up
479 @subsection Examples of Using @code{interactive}
480 @cindex examples of using @code{interactive}
481 @cindex @code{interactive}, examples of using
483 Here are some examples of @code{interactive}:
487 (defun foo1 () ; @r{@code{foo1} takes no arguments,}
488 (interactive) ; @r{just moves forward two words.}
494 (defun foo2 (n) ; @r{@code{foo2} takes one argument,}
495 (interactive "p") ; @r{which is the numeric prefix.}
496 (forward-word (* 2 n)))
501 (defun foo3 (n) ; @r{@code{foo3} takes one argument,}
502 (interactive "nCount:") ; @r{which is read with the Minibuffer.}
503 (forward-word (* 2 n)))
508 (defun three-b (b1 b2 b3)
509 "Select three existing buffers.
510 Put them into three windows, selecting the last one."
512 (interactive "bBuffer1:\nbBuffer2:\nbBuffer3:")
513 (delete-other-windows)
514 (split-window (selected-window) 8)
515 (switch-to-buffer b1)
517 (split-window (selected-window) 8)
518 (switch-to-buffer b2)
520 (switch-to-buffer b3))
523 (three-b "*scratch*" "declarations.texi" "*mail*")
528 @node Interactive Call
529 @section Interactive Call
530 @cindex interactive call
532 After the command loop has translated a key sequence into a command it
533 invokes that command using the function @code{command-execute}. If the
534 command is a function, @code{command-execute} calls
535 @code{call-interactively}, which reads the arguments and calls the
536 command. You can also call these functions yourself.
538 @defun commandp object &optional for-call-interactively
539 Returns @code{t} if @var{object} is suitable for calling interactively;
540 that is, if @var{object} is a command. Otherwise, returns @code{nil}.
542 The interactively callable objects include strings and vectors (treated
543 as keyboard macros), lambda expressions that contain a top-level call to
544 @code{interactive}, byte-code function objects made from such lambda
545 expressions, autoload objects that are declared as interactive
546 (non-@code{nil} fourth argument to @code{autoload}), and some of the
549 A symbol satisfies @code{commandp} if its function definition
550 satisfies @code{commandp}. Keys and keymaps are not commands.
551 Rather, they are used to look up commands (@pxref{Keymaps}).
553 If @var{for-call-interactively} is non-@code{nil}, then
554 @code{commandp} returns @code{t} only for objects that
555 @code{call-interactively} could call---thus, not for keyboard macros.
557 See @code{documentation} in @ref{Accessing Documentation}, for a
558 realistic example of using @code{commandp}.
561 @defun call-interactively command &optional record-flag keys
562 This function calls the interactively callable function @var{command},
563 reading arguments according to its interactive calling specifications.
564 It returns whatever @var{command} returns. An error is signaled if
565 @var{command} is not a function or if it cannot be called
566 interactively (i.e., is not a command). Note that keyboard macros
567 (strings and vectors) are not accepted, even though they are
568 considered commands, because they are not functions. If @var{command}
569 is a symbol, then @code{call-interactively} uses its function definition.
571 @cindex record command history
572 If @var{record-flag} is non-@code{nil}, then this command and its
573 arguments are unconditionally added to the list @code{command-history}.
574 Otherwise, the command is added only if it uses the minibuffer to read
575 an argument. @xref{Command History}.
577 The argument @var{keys}, if given, should be a vector which specifies
578 the sequence of events to supply if the command inquires which events
579 were used to invoke it. If @var{keys} is omitted or @code{nil}, the
580 default is the return value of @code{this-command-keys-vector}.
581 @xref{Definition of this-command-keys-vector}.
584 @defun command-execute command &optional record-flag keys special
585 @cindex keyboard macro execution
586 This function executes @var{command}. The argument @var{command} must
587 satisfy the @code{commandp} predicate; i.e., it must be an interactively
588 callable function or a keyboard macro.
590 A string or vector as @var{command} is executed with
591 @code{execute-kbd-macro}. A function is passed to
592 @code{call-interactively}, along with the optional @var{record-flag}
595 A symbol is handled by using its function definition in its place. A
596 symbol with an @code{autoload} definition counts as a command if it was
597 declared to stand for an interactively callable function. Such a
598 definition is handled by loading the specified library and then
599 rechecking the definition of the symbol.
601 The argument @var{special}, if given, means to ignore the prefix
602 argument and not clear it. This is used for executing special events
603 (@pxref{Special Events}).
606 @deffn Command execute-extended-command prefix-argument
607 @cindex read command name
608 This function reads a command name from the minibuffer using
609 @code{completing-read} (@pxref{Completion}). Then it uses
610 @code{command-execute} to call the specified command. Whatever that
611 command returns becomes the value of @code{execute-extended-command}.
613 @cindex execute with prefix argument
614 If the command asks for a prefix argument, it receives the value
615 @var{prefix-argument}. If @code{execute-extended-command} is called
616 interactively, the current raw prefix argument is used for
617 @var{prefix-argument}, and thus passed on to whatever command is run.
619 @c !!! Should this be @kindex?
621 @code{execute-extended-command} is the normal definition of @kbd{M-x},
622 so it uses the string @w{@samp{M-x }} as a prompt. (It would be better
623 to take the prompt from the events used to invoke
624 @code{execute-extended-command}, but that is painful to implement.) A
625 description of the value of the prefix argument, if any, also becomes
630 (execute-extended-command 3)
631 ---------- Buffer: Minibuffer ----------
632 3 M-x forward-word RET
633 ---------- Buffer: Minibuffer ----------
639 @node Distinguish Interactive
640 @section Distinguish Interactive Calls
642 Sometimes a command should display additional visual feedback (such
643 as an informative message in the echo area) for interactive calls
644 only. There are three ways to do this. The recommended way to test
645 whether the function was called using @code{call-interactively} is to
646 give it an optional argument @code{print-message} and use the
647 @code{interactive} spec to make it non-@code{nil} in interactive
648 calls. Here's an example:
651 (defun foo (&optional print-message)
658 We use @code{"p"} because the numeric prefix argument is never
659 @code{nil}. Defined in this way, the function does display the
660 message when called from a keyboard macro.
662 The above method with the additional argument is usually best,
663 because it allows callers to say ``treat this call as interactive.''
664 But you can also do the job in a simpler way by testing
665 @code{called-interactively-p}.
667 @defun called-interactively-p
668 This function returns @code{t} when the calling function was called
669 using @code{call-interactively}.
671 If the containing function was called by Lisp evaluation (or with
672 @code{apply} or @code{funcall}), then it was not called interactively.
675 Here's an example of using @code{called-interactively-p}:
681 (when (called-interactively-p)
688 ;; @r{Type @kbd{M-x foo}.}
698 Here is another example that contrasts direct and indirect
699 calls to @code{called-interactively-p}.
705 (setq foobar (list (foo) (called-interactively-p))))
710 ;; @r{Type @kbd{M-x bar}.}
711 ;; @r{This does not display a message.}
720 If you want to treat commands run in keyboard macros just like calls
721 from Lisp programs, test @code{interactive-p} instead of
722 @code{called-interactively-p}.
725 This function returns @code{t} if the containing function (the one
726 whose code includes the call to @code{interactive-p}) was called in
727 direct response to user input. This means that it was called with the
728 function @code{call-interactively}, and that a keyboard macro is
729 not running, and that Emacs is not running in batch mode.
732 @node Command Loop Info
733 @comment node-name, next, previous, up
734 @section Information from the Command Loop
736 The editor command loop sets several Lisp variables to keep status
737 records for itself and for commands that are run. With the exception of
738 @code{this-command} and @code{last-command} it's generally a bad idea to
739 change any of these variables in a Lisp program.
742 This variable records the name of the previous command executed by the
743 command loop (the one before the current command). Normally the value
744 is a symbol with a function definition, but this is not guaranteed.
746 The value is copied from @code{this-command} when a command returns to
747 the command loop, except when the command has specified a prefix
748 argument for the following command.
750 This variable is always local to the current terminal and cannot be
751 buffer-local. @xref{Multiple Displays}.
754 @defvar real-last-command
755 This variable is set up by Emacs just like @code{last-command},
756 but never altered by Lisp programs.
759 @defvar last-repeatable-command
760 This variable stores the most recently executed command that was not
761 part of an input event. This is the command @code{repeat} will try to
762 repeat, @xref{Repeating,,, emacs, The GNU Emacs Manual}.
766 @cindex current command
767 This variable records the name of the command now being executed by
768 the editor command loop. Like @code{last-command}, it is normally a symbol
769 with a function definition.
771 The command loop sets this variable just before running a command, and
772 copies its value into @code{last-command} when the command finishes
773 (unless the command specified a prefix argument for the following
776 @cindex kill command repetition
777 Some commands set this variable during their execution, as a flag for
778 whatever command runs next. In particular, the functions for killing text
779 set @code{this-command} to @code{kill-region} so that any kill commands
780 immediately following will know to append the killed text to the
784 If you do not want a particular command to be recognized as the previous
785 command in the case where it got an error, you must code that command to
786 prevent this. One way is to set @code{this-command} to @code{t} at the
787 beginning of the command, and set @code{this-command} back to its proper
788 value at the end, like this:
791 (defun foo (args@dots{})
792 (interactive @dots{})
793 (let ((old-this-command this-command))
794 (setq this-command t)
795 @r{@dots{}do the work@dots{}}
796 (setq this-command old-this-command)))
800 We do not bind @code{this-command} with @code{let} because that would
801 restore the old value in case of error---a feature of @code{let} which
802 in this case does precisely what we want to avoid.
804 @defvar this-original-command
805 This has the same value as @code{this-command} except when command
806 remapping occurs (@pxref{Remapping Commands}). In that case,
807 @code{this-command} gives the command actually run (the result of
808 remapping), and @code{this-original-command} gives the command that
809 was specified to run but remapped into another command.
812 @defun this-command-keys
813 This function returns a string or vector containing the key sequence
814 that invoked the present command, plus any previous commands that
815 generated the prefix argument for this command. Any events read by the
816 command using @code{read-event} without a timeout get tacked on to the end.
818 However, if the command has called @code{read-key-sequence}, it
819 returns the last read key sequence. @xref{Key Sequence Input}. The
820 value is a string if all events in the sequence were characters that
821 fit in a string. @xref{Input Events}.
826 ;; @r{Now use @kbd{C-u C-x C-e} to evaluate that.}
832 @defun this-command-keys-vector
833 @anchor{Definition of this-command-keys-vector}
834 Like @code{this-command-keys}, except that it always returns the events
835 in a vector, so you don't need to deal with the complexities of storing
836 input events in a string (@pxref{Strings of Events}).
839 @defun clear-this-command-keys &optional keep-record
840 This function empties out the table of events for
841 @code{this-command-keys} to return. Unless @var{keep-record} is
842 non-@code{nil}, it also empties the records that the function
843 @code{recent-keys} (@pxref{Recording Input}) will subsequently return.
844 This is useful after reading a password, to prevent the password from
845 echoing inadvertently as part of the next command in certain cases.
848 @defvar last-nonmenu-event
849 This variable holds the last input event read as part of a key sequence,
850 not counting events resulting from mouse menus.
852 One use of this variable is for telling @code{x-popup-menu} where to pop
853 up a menu. It is also used internally by @code{y-or-n-p}
854 (@pxref{Yes-or-No Queries}).
857 @defvar last-command-event
858 @defvarx last-command-char
859 This variable is set to the last input event that was read by the
860 command loop as part of a command. The principal use of this variable
861 is in @code{self-insert-command}, which uses it to decide which
867 ;; @r{Now use @kbd{C-u C-x C-e} to evaluate that.}
873 The value is 5 because that is the @acronym{ASCII} code for @kbd{C-e}.
875 The alias @code{last-command-char} exists for compatibility with
880 @defvar last-event-frame
881 This variable records which frame the last input event was directed to.
882 Usually this is the frame that was selected when the event was
883 generated, but if that frame has redirected input focus to another
884 frame, the value is the frame to which the event was redirected.
887 If the last event came from a keyboard macro, the value is @code{macro}.
890 @node Adjusting Point
891 @section Adjusting Point After Commands
892 @cindex adjusting point
893 @cindex invisible/intangible text, and point
894 @cindex @code{display} property, and point display
895 @cindex @code{composition} property, and point display
897 It is not easy to display a value of point in the middle of a
898 sequence of text that has the @code{display}, @code{composition} or
899 @code{intangible} property, or is invisible. Therefore, after a
900 command finishes and returns to the command loop, if point is within
901 such a sequence, the command loop normally moves point to the edge of
904 A command can inhibit this feature by setting the variable
905 @code{disable-point-adjustment}:
907 @defvar disable-point-adjustment
908 If this variable is non-@code{nil} when a command returns to the
909 command loop, then the command loop does not check for those text
910 properties, and does not move point out of sequences that have them.
912 The command loop sets this variable to @code{nil} before each command,
913 so if a command sets it, the effect applies only to that command.
916 @defvar global-disable-point-adjustment
917 If you set this variable to a non-@code{nil} value, the feature of
918 moving point out of these sequences is completely turned off.
922 @section Input Events
926 The Emacs command loop reads a sequence of @dfn{input events} that
927 represent keyboard or mouse activity. The events for keyboard activity
928 are characters or symbols; mouse events are always lists. This section
929 describes the representation and meaning of input events in detail.
932 This function returns non-@code{nil} if @var{object} is an input event
935 Note that any symbol might be used as an event or an event type.
936 @code{eventp} cannot distinguish whether a symbol is intended by Lisp
937 code to be used as an event. Instead, it distinguishes whether the
938 symbol has actually been used in an event that has been read as input in
939 the current Emacs session. If a symbol has not yet been so used,
940 @code{eventp} returns @code{nil}.
944 * Keyboard Events:: Ordinary characters--keys with symbols on them.
945 * Function Keys:: Function keys--keys with names, not symbols.
946 * Mouse Events:: Overview of mouse events.
947 * Click Events:: Pushing and releasing a mouse button.
948 * Drag Events:: Moving the mouse before releasing the button.
949 * Button-Down Events:: A button was pushed and not yet released.
950 * Repeat Events:: Double and triple click (or drag, or down).
951 * Motion Events:: Just moving the mouse, not pushing a button.
952 * Focus Events:: Moving the mouse between frames.
953 * Misc Events:: Other events the system can generate.
954 * Event Examples:: Examples of the lists for mouse events.
955 * Classifying Events:: Finding the modifier keys in an event symbol.
957 * Accessing Events:: Functions to extract info from events.
958 * Strings of Events:: Special considerations for putting
959 keyboard character events in a string.
962 @node Keyboard Events
963 @subsection Keyboard Events
964 @cindex keyboard events
966 There are two kinds of input you can get from the keyboard: ordinary
967 keys, and function keys. Ordinary keys correspond to characters; the
968 events they generate are represented in Lisp as characters. The event
969 type of a character event is the character itself (an integer); see
970 @ref{Classifying Events}.
972 @cindex modifier bits (of input character)
973 @cindex basic code (of input character)
974 An input character event consists of a @dfn{basic code} between 0 and
975 524287, plus any or all of these @dfn{modifier bits}:
986 bit in the character code indicates a character
987 typed with the meta key held down.
997 bit in the character code indicates a non-@acronym{ASCII}
1000 @sc{ascii} control characters such as @kbd{C-a} have special basic
1001 codes of their own, so Emacs needs no special bit to indicate them.
1002 Thus, the code for @kbd{C-a} is just 1.
1004 But if you type a control combination not in @acronym{ASCII}, such as
1005 @kbd{%} with the control key, the numeric value you get is the code
1013 (assuming the terminal supports non-@acronym{ASCII}
1014 control characters).
1024 bit in the character code indicates an @acronym{ASCII} control
1025 character typed with the shift key held down.
1027 For letters, the basic code itself indicates upper versus lower case;
1028 for digits and punctuation, the shift key selects an entirely different
1029 character with a different basic code. In order to keep within the
1030 @acronym{ASCII} character set whenever possible, Emacs avoids using the
1037 bit for those characters.
1039 However, @acronym{ASCII} provides no way to distinguish @kbd{C-A} from
1040 @kbd{C-a}, so Emacs uses the
1047 bit in @kbd{C-A} and not in
1058 bit in the character code indicates a character
1059 typed with the hyper key held down.
1069 bit in the character code indicates a character
1070 typed with the super key held down.
1080 bit in the character code indicates a character typed with
1081 the alt key held down. (On some terminals, the key labeled @key{ALT}
1082 is actually the meta key.)
1085 It is best to avoid mentioning specific bit numbers in your program.
1086 To test the modifier bits of a character, use the function
1087 @code{event-modifiers} (@pxref{Classifying Events}). When making key
1088 bindings, you can use the read syntax for characters with modifier bits
1089 (@samp{\C-}, @samp{\M-}, and so on). For making key bindings with
1090 @code{define-key}, you can use lists such as @code{(control hyper ?x)} to
1091 specify the characters (@pxref{Changing Key Bindings}). The function
1092 @code{event-convert-list} converts such a list into an event type
1093 (@pxref{Classifying Events}).
1096 @subsection Function Keys
1098 @cindex function keys
1099 Most keyboards also have @dfn{function keys}---keys that have names or
1100 symbols that are not characters. Function keys are represented in Emacs
1101 Lisp as symbols; the symbol's name is the function key's label, in lower
1102 case. For example, pressing a key labeled @key{F1} places the symbol
1103 @code{f1} in the input stream.
1105 The event type of a function key event is the event symbol itself.
1106 @xref{Classifying Events}.
1108 Here are a few special cases in the symbol-naming convention for
1112 @item @code{backspace}, @code{tab}, @code{newline}, @code{return}, @code{delete}
1113 These keys correspond to common @acronym{ASCII} control characters that have
1114 special keys on most keyboards.
1116 In @acronym{ASCII}, @kbd{C-i} and @key{TAB} are the same character. If the
1117 terminal can distinguish between them, Emacs conveys the distinction to
1118 Lisp programs by representing the former as the integer 9, and the
1119 latter as the symbol @code{tab}.
1121 Most of the time, it's not useful to distinguish the two. So normally
1122 @code{function-key-map} (@pxref{Translation Keymaps}) is set up to map
1123 @code{tab} into 9. Thus, a key binding for character code 9 (the
1124 character @kbd{C-i}) also applies to @code{tab}. Likewise for the other
1125 symbols in this group. The function @code{read-char} likewise converts
1126 these events into characters.
1128 In @acronym{ASCII}, @key{BS} is really @kbd{C-h}. But @code{backspace}
1129 converts into the character code 127 (@key{DEL}), not into code 8
1130 (@key{BS}). This is what most users prefer.
1132 @item @code{left}, @code{up}, @code{right}, @code{down}
1134 @item @code{kp-add}, @code{kp-decimal}, @code{kp-divide}, @dots{}
1135 Keypad keys (to the right of the regular keyboard).
1136 @item @code{kp-0}, @code{kp-1}, @dots{}
1137 Keypad keys with digits.
1138 @item @code{kp-f1}, @code{kp-f2}, @code{kp-f3}, @code{kp-f4}
1140 @item @code{kp-home}, @code{kp-left}, @code{kp-up}, @code{kp-right}, @code{kp-down}
1141 Keypad arrow keys. Emacs normally translates these into the
1142 corresponding non-keypad keys @code{home}, @code{left}, @dots{}
1143 @item @code{kp-prior}, @code{kp-next}, @code{kp-end}, @code{kp-begin}, @code{kp-insert}, @code{kp-delete}
1144 Additional keypad duplicates of keys ordinarily found elsewhere. Emacs
1145 normally translates these into the like-named non-keypad keys.
1148 You can use the modifier keys @key{ALT}, @key{CTRL}, @key{HYPER},
1149 @key{META}, @key{SHIFT}, and @key{SUPER} with function keys. The way to
1150 represent them is with prefixes in the symbol name:
1156 The control modifier.
1167 Thus, the symbol for the key @key{F3} with @key{META} held down is
1168 @code{M-f3}. When you use more than one prefix, we recommend you
1169 write them in alphabetical order; but the order does not matter in
1170 arguments to the key-binding lookup and modification functions.
1173 @subsection Mouse Events
1175 Emacs supports four kinds of mouse events: click events, drag events,
1176 button-down events, and motion events. All mouse events are represented
1177 as lists. The @sc{car} of the list is the event type; this says which
1178 mouse button was involved, and which modifier keys were used with it.
1179 The event type can also distinguish double or triple button presses
1180 (@pxref{Repeat Events}). The rest of the list elements give position
1181 and time information.
1183 For key lookup, only the event type matters: two events of the same type
1184 necessarily run the same command. The command can access the full
1185 values of these events using the @samp{e} interactive code.
1186 @xref{Interactive Codes}.
1188 A key sequence that starts with a mouse event is read using the keymaps
1189 of the buffer in the window that the mouse was in, not the current
1190 buffer. This does not imply that clicking in a window selects that
1191 window or its buffer---that is entirely under the control of the command
1192 binding of the key sequence.
1195 @subsection Click Events
1197 @cindex mouse click event
1199 When the user presses a mouse button and releases it at the same
1200 location, that generates a @dfn{click} event. All mouse click event
1201 share the same format:
1204 (@var{event-type} @var{position} @var{click-count})
1208 @item @var{event-type}
1209 This is a symbol that indicates which mouse button was used. It is
1210 one of the symbols @code{mouse-1}, @code{mouse-2}, @dots{}, where the
1211 buttons are numbered left to right.
1213 You can also use prefixes @samp{A-}, @samp{C-}, @samp{H-}, @samp{M-},
1214 @samp{S-} and @samp{s-} for modifiers alt, control, hyper, meta, shift
1215 and super, just as you would with function keys.
1217 This symbol also serves as the event type of the event. Key bindings
1218 describe events by their types; thus, if there is a key binding for
1219 @code{mouse-1}, that binding would apply to all events whose
1220 @var{event-type} is @code{mouse-1}.
1222 @item @var{position}
1223 This is the position where the mouse click occurred. The actual
1224 format of @var{position} depends on what part of a window was clicked
1227 For mouse click events in the text area, mode line, header line, or in
1228 the marginal areas, @var{position} has this form:
1231 (@var{window} @var{pos-or-area} (@var{x} . @var{y}) @var{timestamp}
1232 @var{object} @var{text-pos} (@var{col} . @var{row})
1233 @var{image} (@var{dx} . @var{dy}) (@var{width} . @var{height}))
1238 This is the window in which the click occurred.
1240 @item @var{pos-or-area}
1241 This is the buffer position of the character clicked on in the text
1242 area, or if clicked outside the text area, it is the window area in
1243 which the click occurred. It is one of the symbols @code{mode-line},
1244 @code{header-line}, @code{vertical-line}, @code{left-margin},
1245 @code{right-margin}, @code{left-fringe}, or @code{right-fringe}.
1247 In one special case, @var{pos-or-area} is a list containing a symbol (one
1248 of the symbols listed above) instead of just the symbol. This happens
1249 after the imaginary prefix keys for the event are inserted into the
1250 input stream. @xref{Key Sequence Input}.
1253 @item @var{x}, @var{y}
1254 These are the pixel coordinates of the click, relative to
1255 the top left corner of @var{window}, which is @code{(0 . 0)}.
1256 For the mode or header line, @var{y} does not have meaningful data.
1257 For the vertical line, @var{x} does not have meaningful data.
1259 @item @var{timestamp}
1260 This is the time at which the event occurred, in milliseconds.
1263 This is the object on which the click occurred. It is either
1264 @code{nil} if there is no string property, or it has the form
1265 (@var{string} . @var{string-pos}) when there is a string-type text
1266 property at the click position.
1270 This is the string on which the click occurred, including any
1273 @item @var{string-pos}
1274 This is the position in the string on which the click occurred,
1275 relevant if properties at the click need to be looked up.
1278 @item @var{text-pos}
1279 For clicks on a marginal area or on a fringe, this is the buffer
1280 position of the first visible character in the corresponding line in
1281 the window. For other events, it is the current buffer position in
1284 @item @var{col}, @var{row}
1285 These are the actual coordinates of the glyph under the @var{x},
1286 @var{y} position, possibly padded with default character width
1287 glyphs if @var{x} is beyond the last glyph on the line.
1290 This is the image object on which the click occurred. It is either
1291 @code{nil} if there is no image at the position clicked on, or it is
1292 an image object as returned by @code{find-image} if click was in an image.
1294 @item @var{dx}, @var{dy}
1295 These are the pixel coordinates of the click, relative to
1296 the top left corner of @var{object}, which is @code{(0 . 0)}. If
1297 @var{object} is @code{nil}, the coordinates are relative to the top
1298 left corner of the character glyph clicked on.
1300 @item @var{width}, @var{height}
1301 These are the pixel width and height of @var{object} or, if this is
1302 @code{nil}, those of the character glyph clicked on.
1306 For mouse clicks on a scroll-bar, @var{position} has this form:
1309 (@var{window} @var{area} (@var{portion} . @var{whole}) @var{timestamp} @var{part})
1314 This is the window whose scroll-bar was clicked on.
1317 This is the scroll bar where the click occurred. It is one of the
1318 symbols @code{vertical-scroll-bar} or @code{horizontal-scroll-bar}.
1321 This is the distance of the click from the top or left end of
1325 This is the length of the entire scroll bar.
1327 @item @var{timestamp}
1328 This is the time at which the event occurred, in milliseconds.
1331 This is the part of the scroll-bar which was clicked on. It is one
1332 of the symbols @code{above-handle}, @code{handle}, @code{below-handle},
1333 @code{up}, @code{down}, @code{top}, @code{bottom}, and @code{end-scroll}.
1336 @item @var{click-count}
1337 This is the number of rapid repeated presses so far of the same mouse
1338 button. @xref{Repeat Events}.
1342 @subsection Drag Events
1344 @cindex mouse drag event
1346 With Emacs, you can have a drag event without even changing your
1347 clothes. A @dfn{drag event} happens every time the user presses a mouse
1348 button and then moves the mouse to a different character position before
1349 releasing the button. Like all mouse events, drag events are
1350 represented in Lisp as lists. The lists record both the starting mouse
1351 position and the final position, like this:
1355 (@var{window1} START-POSITION)
1356 (@var{window2} END-POSITION))
1359 For a drag event, the name of the symbol @var{event-type} contains the
1360 prefix @samp{drag-}. For example, dragging the mouse with button 2
1361 held down generates a @code{drag-mouse-2} event. The second and third
1362 elements of the event give the starting and ending position of the
1363 drag. They have the same form as @var{position} in a click event
1364 (@pxref{Click Events}) that is not on the scroll bar part of the
1365 window. You can access the second element of any mouse event in the
1366 same way, with no need to distinguish drag events from others.
1368 The @samp{drag-} prefix follows the modifier key prefixes such as
1369 @samp{C-} and @samp{M-}.
1371 If @code{read-key-sequence} receives a drag event that has no key
1372 binding, and the corresponding click event does have a binding, it
1373 changes the drag event into a click event at the drag's starting
1374 position. This means that you don't have to distinguish between click
1375 and drag events unless you want to.
1377 @node Button-Down Events
1378 @subsection Button-Down Events
1379 @cindex button-down event
1381 Click and drag events happen when the user releases a mouse button.
1382 They cannot happen earlier, because there is no way to distinguish a
1383 click from a drag until the button is released.
1385 If you want to take action as soon as a button is pressed, you need to
1386 handle @dfn{button-down} events.@footnote{Button-down is the
1387 conservative antithesis of drag.} These occur as soon as a button is
1388 pressed. They are represented by lists that look exactly like click
1389 events (@pxref{Click Events}), except that the @var{event-type} symbol
1390 name contains the prefix @samp{down-}. The @samp{down-} prefix follows
1391 modifier key prefixes such as @samp{C-} and @samp{M-}.
1393 The function @code{read-key-sequence} ignores any button-down events
1394 that don't have command bindings; therefore, the Emacs command loop
1395 ignores them too. This means that you need not worry about defining
1396 button-down events unless you want them to do something. The usual
1397 reason to define a button-down event is so that you can track mouse
1398 motion (by reading motion events) until the button is released.
1399 @xref{Motion Events}.
1402 @subsection Repeat Events
1403 @cindex repeat events
1404 @cindex double-click events
1405 @cindex triple-click events
1406 @cindex mouse events, repeated
1408 If you press the same mouse button more than once in quick succession
1409 without moving the mouse, Emacs generates special @dfn{repeat} mouse
1410 events for the second and subsequent presses.
1412 The most common repeat events are @dfn{double-click} events. Emacs
1413 generates a double-click event when you click a button twice; the event
1414 happens when you release the button (as is normal for all click
1417 The event type of a double-click event contains the prefix
1418 @samp{double-}. Thus, a double click on the second mouse button with
1419 @key{meta} held down comes to the Lisp program as
1420 @code{M-double-mouse-2}. If a double-click event has no binding, the
1421 binding of the corresponding ordinary click event is used to execute
1422 it. Thus, you need not pay attention to the double click feature
1423 unless you really want to.
1425 When the user performs a double click, Emacs generates first an ordinary
1426 click event, and then a double-click event. Therefore, you must design
1427 the command binding of the double click event to assume that the
1428 single-click command has already run. It must produce the desired
1429 results of a double click, starting from the results of a single click.
1431 This is convenient, if the meaning of a double click somehow ``builds
1432 on'' the meaning of a single click---which is recommended user interface
1433 design practice for double clicks.
1435 If you click a button, then press it down again and start moving the
1436 mouse with the button held down, then you get a @dfn{double-drag} event
1437 when you ultimately release the button. Its event type contains
1438 @samp{double-drag} instead of just @samp{drag}. If a double-drag event
1439 has no binding, Emacs looks for an alternate binding as if the event
1440 were an ordinary drag.
1442 Before the double-click or double-drag event, Emacs generates a
1443 @dfn{double-down} event when the user presses the button down for the
1444 second time. Its event type contains @samp{double-down} instead of just
1445 @samp{down}. If a double-down event has no binding, Emacs looks for an
1446 alternate binding as if the event were an ordinary button-down event.
1447 If it finds no binding that way either, the double-down event is
1450 To summarize, when you click a button and then press it again right
1451 away, Emacs generates a down event and a click event for the first
1452 click, a double-down event when you press the button again, and finally
1453 either a double-click or a double-drag event.
1455 If you click a button twice and then press it again, all in quick
1456 succession, Emacs generates a @dfn{triple-down} event, followed by
1457 either a @dfn{triple-click} or a @dfn{triple-drag}. The event types of
1458 these events contain @samp{triple} instead of @samp{double}. If any
1459 triple event has no binding, Emacs uses the binding that it would use
1460 for the corresponding double event.
1462 If you click a button three or more times and then press it again, the
1463 events for the presses beyond the third are all triple events. Emacs
1464 does not have separate event types for quadruple, quintuple, etc.@:
1465 events. However, you can look at the event list to find out precisely
1466 how many times the button was pressed.
1468 @defun event-click-count event
1469 This function returns the number of consecutive button presses that led
1470 up to @var{event}. If @var{event} is a double-down, double-click or
1471 double-drag event, the value is 2. If @var{event} is a triple event,
1472 the value is 3 or greater. If @var{event} is an ordinary mouse event
1473 (not a repeat event), the value is 1.
1476 @defopt double-click-fuzz
1477 To generate repeat events, successive mouse button presses must be at
1478 approximately the same screen position. The value of
1479 @code{double-click-fuzz} specifies the maximum number of pixels the
1480 mouse may be moved (horizontally or vertically) between two successive
1481 clicks to make a double-click.
1483 This variable is also the threshold for motion of the mouse to count
1487 @defopt double-click-time
1488 To generate repeat events, the number of milliseconds between
1489 successive button presses must be less than the value of
1490 @code{double-click-time}. Setting @code{double-click-time} to
1491 @code{nil} disables multi-click detection entirely. Setting it to
1492 @code{t} removes the time limit; Emacs then detects multi-clicks by
1497 @subsection Motion Events
1498 @cindex motion event
1499 @cindex mouse motion events
1501 Emacs sometimes generates @dfn{mouse motion} events to describe motion
1502 of the mouse without any button activity. Mouse motion events are
1503 represented by lists that look like this:
1506 (mouse-movement (POSITION))
1509 The second element of the list describes the current position of the
1510 mouse, just as in a click event (@pxref{Click Events}).
1512 The special form @code{track-mouse} enables generation of motion events
1513 within its body. Outside of @code{track-mouse} forms, Emacs does not
1514 generate events for mere motion of the mouse, and these events do not
1515 appear. @xref{Mouse Tracking}.
1518 @subsection Focus Events
1521 Window systems provide general ways for the user to control which window
1522 gets keyboard input. This choice of window is called the @dfn{focus}.
1523 When the user does something to switch between Emacs frames, that
1524 generates a @dfn{focus event}. The normal definition of a focus event,
1525 in the global keymap, is to select a new frame within Emacs, as the user
1526 would expect. @xref{Input Focus}.
1528 Focus events are represented in Lisp as lists that look like this:
1531 (switch-frame @var{new-frame})
1535 where @var{new-frame} is the frame switched to.
1537 Most X window managers are set up so that just moving the mouse into a
1538 window is enough to set the focus there. Emacs appears to do this,
1539 because it changes the cursor to solid in the new frame. However, there
1540 is no need for the Lisp program to know about the focus change until
1541 some other kind of input arrives. So Emacs generates a focus event only
1542 when the user actually types a keyboard key or presses a mouse button in
1543 the new frame; just moving the mouse between frames does not generate a
1546 A focus event in the middle of a key sequence would garble the
1547 sequence. So Emacs never generates a focus event in the middle of a key
1548 sequence. If the user changes focus in the middle of a key
1549 sequence---that is, after a prefix key---then Emacs reorders the events
1550 so that the focus event comes either before or after the multi-event key
1551 sequence, and not within it.
1554 @subsection Miscellaneous System Events
1556 A few other event types represent occurrences within the system.
1559 @cindex @code{delete-frame} event
1560 @item (delete-frame (@var{frame}))
1561 This kind of event indicates that the user gave the window manager
1562 a command to delete a particular window, which happens to be an Emacs frame.
1564 The standard definition of the @code{delete-frame} event is to delete @var{frame}.
1566 @cindex @code{iconify-frame} event
1567 @item (iconify-frame (@var{frame}))
1568 This kind of event indicates that the user iconified @var{frame} using
1569 the window manager. Its standard definition is @code{ignore}; since the
1570 frame has already been iconified, Emacs has no work to do. The purpose
1571 of this event type is so that you can keep track of such events if you
1574 @cindex @code{make-frame-visible} event
1575 @item (make-frame-visible (@var{frame}))
1576 This kind of event indicates that the user deiconified @var{frame} using
1577 the window manager. Its standard definition is @code{ignore}; since the
1578 frame has already been made visible, Emacs has no work to do.
1580 @cindex @code{wheel-up} event
1581 @cindex @code{wheel-down} event
1582 @item (wheel-up @var{position})
1583 @item (wheel-down @var{position})
1584 These kinds of event are generated by moving a mouse wheel. Their
1585 usual meaning is a kind of scroll or zoom.
1587 The element @var{position} is a list describing the position of the
1588 event, in the same format as used in a mouse-click event.
1590 This kind of event is generated only on some kinds of systems. On some
1591 systems, @code{mouse-4} and @code{mouse-5} are used instead. For
1592 portable code, use the variables @code{mouse-wheel-up-event} and
1593 @code{mouse-wheel-down-event} defined in @file{mwheel.el} to determine
1594 what event types to expect for the mouse wheel.
1596 @cindex @code{drag-n-drop} event
1597 @item (drag-n-drop @var{position} @var{files})
1598 This kind of event is generated when a group of files is
1599 selected in an application outside of Emacs, and then dragged and
1600 dropped onto an Emacs frame.
1602 The element @var{position} is a list describing the position of the
1603 event, in the same format as used in a mouse-click event, and
1604 @var{files} is the list of file names that were dragged and dropped.
1605 The usual way to handle this event is by visiting these files.
1607 This kind of event is generated, at present, only on some kinds of
1610 @cindex @code{help-echo} event
1612 This kind of event is generated when a mouse pointer moves onto a
1613 portion of buffer text which has a @code{help-echo} text property.
1614 The generated event has this form:
1617 (help-echo @var{frame} @var{help} @var{window} @var{object} @var{pos})
1621 The precise meaning of the event parameters and the way these
1622 parameters are used to display the help-echo text are described in
1623 @ref{Text help-echo}.
1625 @cindex @code{sigusr1} event
1626 @cindex @code{sigusr2} event
1627 @cindex user signals
1630 These events are generated when the Emacs process receives
1631 the signals @code{SIGUSR1} and @code{SIGUSR2}. They contain no
1632 additional data because signals do not carry additional information.
1634 To catch a user signal, bind the corresponding event to an interactive
1635 command in the @code{special-event-map} (@pxref{Active Keymaps}).
1636 The command is called with no arguments, and the specific signal event is
1637 available in @code{last-input-event}. For example:
1640 (defun sigusr-handler ()
1642 (message "Caught signal %S" last-input-event))
1644 (define-key special-event-map [sigusr1] 'sigusr-handler)
1647 To test the signal handler, you can make Emacs send a signal to itself:
1650 (signal-process (emacs-pid) 'sigusr1)
1654 If one of these events arrives in the middle of a key sequence---that
1655 is, after a prefix key---then Emacs reorders the events so that this
1656 event comes either before or after the multi-event key sequence, not
1659 @node Event Examples
1660 @subsection Event Examples
1662 If the user presses and releases the left mouse button over the same
1663 location, that generates a sequence of events like this:
1666 (down-mouse-1 (#<window 18 on NEWS> 2613 (0 . 38) -864320))
1667 (mouse-1 (#<window 18 on NEWS> 2613 (0 . 38) -864180))
1670 While holding the control key down, the user might hold down the
1671 second mouse button, and drag the mouse from one line to the next.
1672 That produces two events, as shown here:
1675 (C-down-mouse-2 (#<window 18 on NEWS> 3440 (0 . 27) -731219))
1676 (C-drag-mouse-2 (#<window 18 on NEWS> 3440 (0 . 27) -731219)
1677 (#<window 18 on NEWS> 3510 (0 . 28) -729648))
1680 While holding down the meta and shift keys, the user might press the
1681 second mouse button on the window's mode line, and then drag the mouse
1682 into another window. That produces a pair of events like these:
1685 (M-S-down-mouse-2 (#<window 18 on NEWS> mode-line (33 . 31) -457844))
1686 (M-S-drag-mouse-2 (#<window 18 on NEWS> mode-line (33 . 31) -457844)
1687 (#<window 20 on carlton-sanskrit.tex> 161 (33 . 3)
1691 To handle a SIGUSR1 signal, define an interactive function, and
1692 bind it to the @code{signal usr1} event sequence:
1695 (defun usr1-handler ()
1697 (message "Got USR1 signal"))
1698 (global-set-key [signal usr1] 'usr1-handler)
1701 @node Classifying Events
1702 @subsection Classifying Events
1705 Every event has an @dfn{event type}, which classifies the event for
1706 key binding purposes. For a keyboard event, the event type equals the
1707 event value; thus, the event type for a character is the character, and
1708 the event type for a function key symbol is the symbol itself. For
1709 events that are lists, the event type is the symbol in the @sc{car} of
1710 the list. Thus, the event type is always a symbol or a character.
1712 Two events of the same type are equivalent where key bindings are
1713 concerned; thus, they always run the same command. That does not
1714 necessarily mean they do the same things, however, as some commands look
1715 at the whole event to decide what to do. For example, some commands use
1716 the location of a mouse event to decide where in the buffer to act.
1718 Sometimes broader classifications of events are useful. For example,
1719 you might want to ask whether an event involved the @key{META} key,
1720 regardless of which other key or mouse button was used.
1722 The functions @code{event-modifiers} and @code{event-basic-type} are
1723 provided to get such information conveniently.
1725 @defun event-modifiers event
1726 This function returns a list of the modifiers that @var{event} has. The
1727 modifiers are symbols; they include @code{shift}, @code{control},
1728 @code{meta}, @code{alt}, @code{hyper} and @code{super}. In addition,
1729 the modifiers list of a mouse event symbol always contains one of
1730 @code{click}, @code{drag}, and @code{down}. For double or triple
1731 events, it also contains @code{double} or @code{triple}.
1733 The argument @var{event} may be an entire event object, or just an
1734 event type. If @var{event} is a symbol that has never been used in an
1735 event that has been read as input in the current Emacs session, then
1736 @code{event-modifiers} can return @code{nil}, even when @var{event}
1737 actually has modifiers.
1739 Here are some examples:
1742 (event-modifiers ?a)
1744 (event-modifiers ?A)
1746 (event-modifiers ?\C-a)
1748 (event-modifiers ?\C-%)
1750 (event-modifiers ?\C-\S-a)
1751 @result{} (control shift)
1752 (event-modifiers 'f5)
1754 (event-modifiers 's-f5)
1756 (event-modifiers 'M-S-f5)
1757 @result{} (meta shift)
1758 (event-modifiers 'mouse-1)
1760 (event-modifiers 'down-mouse-1)
1764 The modifiers list for a click event explicitly contains @code{click},
1765 but the event symbol name itself does not contain @samp{click}.
1768 @defun event-basic-type event
1769 This function returns the key or mouse button that @var{event}
1770 describes, with all modifiers removed. The @var{event} argument is as
1771 in @code{event-modifiers}. For example:
1774 (event-basic-type ?a)
1776 (event-basic-type ?A)
1778 (event-basic-type ?\C-a)
1780 (event-basic-type ?\C-\S-a)
1782 (event-basic-type 'f5)
1784 (event-basic-type 's-f5)
1786 (event-basic-type 'M-S-f5)
1788 (event-basic-type 'down-mouse-1)
1793 @defun mouse-movement-p object
1794 This function returns non-@code{nil} if @var{object} is a mouse movement
1798 @defun event-convert-list list
1799 This function converts a list of modifier names and a basic event type
1800 to an event type which specifies all of them. The basic event type
1801 must be the last element of the list. For example,
1804 (event-convert-list '(control ?a))
1806 (event-convert-list '(control meta ?a))
1807 @result{} -134217727
1808 (event-convert-list '(control super f1))
1813 @node Accessing Events
1814 @subsection Accessing Events
1815 @cindex mouse events, data in
1817 This section describes convenient functions for accessing the data in
1818 a mouse button or motion event.
1820 These two functions return the starting or ending position of a
1821 mouse-button event, as a list of this form:
1824 (@var{window} @var{pos-or-area} (@var{x} . @var{y}) @var{timestamp}
1825 @var{object} @var{text-pos} (@var{col} . @var{row})
1826 @var{image} (@var{dx} . @var{dy}) (@var{width} . @var{height}))
1829 @defun event-start event
1830 This returns the starting position of @var{event}.
1832 If @var{event} is a click or button-down event, this returns the
1833 location of the event. If @var{event} is a drag event, this returns the
1834 drag's starting position.
1837 @defun event-end event
1838 This returns the ending position of @var{event}.
1840 If @var{event} is a drag event, this returns the position where the user
1841 released the mouse button. If @var{event} is a click or button-down
1842 event, the value is actually the starting position, which is the only
1843 position such events have.
1846 @cindex mouse position list, accessing
1847 These functions take a position list as described above, and
1848 return various parts of it.
1850 @defun posn-window position
1851 Return the window that @var{position} is in.
1854 @defun posn-area position
1855 Return the window area recorded in @var{position}. It returns @code{nil}
1856 when the event occurred in the text area of the window; otherwise, it
1857 is a symbol identifying the area in which the event occurred.
1860 @defun posn-point position
1861 Return the buffer position in @var{position}. When the event occurred
1862 in the text area of the window, in a marginal area, or on a fringe,
1863 this is an integer specifying a buffer position. Otherwise, the value
1867 @defun posn-x-y position
1868 Return the pixel-based x and y coordinates in @var{position}, as a
1869 cons cell @code{(@var{x} . @var{y})}. These coordinates are relative
1870 to the window given by @code{posn-window}.
1872 This example shows how to convert these window-relative coordinates
1873 into frame-relative coordinates:
1876 (defun frame-relative-coordinates (position)
1877 "Return frame-relative coordinates from POSITION."
1878 (let* ((x-y (posn-x-y position))
1879 (window (posn-window position))
1880 (edges (window-inside-pixel-edges window)))
1881 (cons (+ (car x-y) (car edges))
1882 (+ (cdr x-y) (cadr edges)))))
1886 @defun posn-col-row position
1887 Return the row and column (in units of the frame's default character
1888 height and width) of @var{position}, as a cons cell @code{(@var{col} .
1889 @var{row})}. These are computed from the @var{x} and @var{y} values
1890 actually found in @var{position}.
1893 @defun posn-actual-col-row position
1894 Return the actual row and column in @var{position}, as a cons cell
1895 @code{(@var{col} . @var{row})}. The values are the actual row number
1896 in the window, and the actual character number in that row. It returns
1897 @code{nil} if @var{position} does not include actual positions values.
1898 You can use @code{posn-col-row} to get approximate values.
1901 @defun posn-string position
1902 Return the string object in @var{position}, either @code{nil}, or a
1903 cons cell @code{(@var{string} . @var{string-pos})}.
1906 @defun posn-image position
1907 Return the image object in @var{position}, either @code{nil}, or an
1908 image @code{(image ...)}.
1911 @defun posn-object position
1912 Return the image or string object in @var{position}, either
1913 @code{nil}, an image @code{(image ...)}, or a cons cell
1914 @code{(@var{string} . @var{string-pos})}.
1917 @defun posn-object-x-y position
1918 Return the pixel-based x and y coordinates relative to the upper left
1919 corner of the object in @var{position} as a cons cell @code{(@var{dx}
1920 . @var{dy})}. If the @var{position} is a buffer position, return the
1921 relative position in the character at that position.
1924 @defun posn-object-width-height position
1925 Return the pixel width and height of the object in @var{position} as a
1926 cons cell @code{(@var{width} . @var{height})}. If the @var{position}
1927 is a buffer position, return the size of the character at that position.
1930 @cindex timestamp of a mouse event
1931 @defun posn-timestamp position
1932 Return the timestamp in @var{position}. This is the time at which the
1933 event occurred, in milliseconds.
1936 These functions compute a position list given particular buffer
1937 position or screen position. You can access the data in this position
1938 list with the functions described above.
1940 @defun posn-at-point &optional pos window
1941 This function returns a position list for position @var{pos} in
1942 @var{window}. @var{pos} defaults to point in @var{window};
1943 @var{window} defaults to the selected window.
1945 @code{posn-at-point} returns @code{nil} if @var{pos} is not visible in
1949 @defun posn-at-x-y x y &optional frame-or-window whole
1950 This function returns position information corresponding to pixel
1951 coordinates @var{x} and @var{y} in a specified frame or window,
1952 @var{frame-or-window}, which defaults to the selected window.
1953 The coordinates @var{x} and @var{y} are relative to the
1954 frame or window used.
1955 If @var{whole} is @code{nil}, the coordinates are relative
1956 to the window text area, otherwise they are relative to
1957 the entire window area including scroll bars, margins and fringes.
1960 These functions are useful for decoding scroll bar events.
1962 @defun scroll-bar-event-ratio event
1963 This function returns the fractional vertical position of a scroll bar
1964 event within the scroll bar. The value is a cons cell
1965 @code{(@var{portion} . @var{whole})} containing two integers whose ratio
1966 is the fractional position.
1969 @defun scroll-bar-scale ratio total
1970 This function multiplies (in effect) @var{ratio} by @var{total},
1971 rounding the result to an integer. The argument @var{ratio} is not a
1972 number, but rather a pair @code{(@var{num} . @var{denom})}---typically a
1973 value returned by @code{scroll-bar-event-ratio}.
1975 This function is handy for scaling a position on a scroll bar into a
1976 buffer position. Here's how to do that:
1981 (posn-x-y (event-start event))
1982 (- (point-max) (point-min))))
1985 Recall that scroll bar events have two integers forming a ratio, in place
1986 of a pair of x and y coordinates.
1989 @node Strings of Events
1990 @subsection Putting Keyboard Events in Strings
1991 @cindex keyboard events in strings
1992 @cindex strings with keyboard events
1994 In most of the places where strings are used, we conceptualize the
1995 string as containing text characters---the same kind of characters found
1996 in buffers or files. Occasionally Lisp programs use strings that
1997 conceptually contain keyboard characters; for example, they may be key
1998 sequences or keyboard macro definitions. However, storing keyboard
1999 characters in a string is a complex matter, for reasons of historical
2000 compatibility, and it is not always possible.
2002 We recommend that new programs avoid dealing with these complexities
2003 by not storing keyboard events in strings. Here is how to do that:
2007 Use vectors instead of strings for key sequences, when you plan to use
2008 them for anything other than as arguments to @code{lookup-key} and
2009 @code{define-key}. For example, you can use
2010 @code{read-key-sequence-vector} instead of @code{read-key-sequence}, and
2011 @code{this-command-keys-vector} instead of @code{this-command-keys}.
2014 Use vectors to write key sequence constants containing meta characters,
2015 even when passing them directly to @code{define-key}.
2018 When you have to look at the contents of a key sequence that might be a
2019 string, use @code{listify-key-sequence} (@pxref{Event Input Misc})
2020 first, to convert it to a list.
2023 The complexities stem from the modifier bits that keyboard input
2024 characters can include. Aside from the Meta modifier, none of these
2025 modifier bits can be included in a string, and the Meta modifier is
2026 allowed only in special cases.
2028 The earliest GNU Emacs versions represented meta characters as codes
2029 in the range of 128 to 255. At that time, the basic character codes
2030 ranged from 0 to 127, so all keyboard character codes did fit in a
2031 string. Many Lisp programs used @samp{\M-} in string constants to stand
2032 for meta characters, especially in arguments to @code{define-key} and
2033 similar functions, and key sequences and sequences of events were always
2034 represented as strings.
2036 When we added support for larger basic character codes beyond 127, and
2037 additional modifier bits, we had to change the representation of meta
2038 characters. Now the flag that represents the Meta modifier in a
2046 and such numbers cannot be included in a string.
2048 To support programs with @samp{\M-} in string constants, there are
2049 special rules for including certain meta characters in a string.
2050 Here are the rules for interpreting a string as a sequence of input
2055 If the keyboard character value is in the range of 0 to 127, it can go
2056 in the string unchanged.
2059 The meta variants of those characters, with codes in the range of
2068 @math{2^{27} + 127},
2073 can also go in the string, but you must change their
2074 numeric values. You must set the
2088 bit, resulting in a value between 128 and 255. Only a unibyte string
2089 can include these codes.
2092 Non-@acronym{ASCII} characters above 256 can be included in a multibyte string.
2095 Other keyboard character events cannot fit in a string. This includes
2096 keyboard events in the range of 128 to 255.
2099 Functions such as @code{read-key-sequence} that construct strings of
2100 keyboard input characters follow these rules: they construct vectors
2101 instead of strings, when the events won't fit in a string.
2103 When you use the read syntax @samp{\M-} in a string, it produces a
2104 code in the range of 128 to 255---the same code that you get if you
2105 modify the corresponding keyboard event to put it in the string. Thus,
2106 meta events in strings work consistently regardless of how they get into
2109 However, most programs would do well to avoid these issues by
2110 following the recommendations at the beginning of this section.
2113 @section Reading Input
2115 @cindex keyboard input
2117 The editor command loop reads key sequences using the function
2118 @code{read-key-sequence}, which uses @code{read-event}. These and other
2119 functions for event input are also available for use in Lisp programs.
2120 See also @code{momentary-string-display} in @ref{Temporary Displays},
2121 and @code{sit-for} in @ref{Waiting}. @xref{Terminal Input}, for
2122 functions and variables for controlling terminal input modes and
2123 debugging terminal input.
2125 For higher-level input facilities, see @ref{Minibuffers}.
2128 * Key Sequence Input:: How to read one key sequence.
2129 * Reading One Event:: How to read just one event.
2130 * Event Mod:: How Emacs modifies events as they are read.
2131 * Invoking the Input Method:: How reading an event uses the input method.
2132 * Quoted Character Input:: Asking the user to specify a character.
2133 * Event Input Misc:: How to reread or throw away input events.
2136 @node Key Sequence Input
2137 @subsection Key Sequence Input
2138 @cindex key sequence input
2140 The command loop reads input a key sequence at a time, by calling
2141 @code{read-key-sequence}. Lisp programs can also call this function;
2142 for example, @code{describe-key} uses it to read the key to describe.
2144 @defun read-key-sequence prompt &optional continue-echo dont-downcase-last switch-frame-ok command-loop
2145 This function reads a key sequence and returns it as a string or
2146 vector. It keeps reading events until it has accumulated a complete key
2147 sequence; that is, enough to specify a non-prefix command using the
2148 currently active keymaps. (Remember that a key sequence that starts
2149 with a mouse event is read using the keymaps of the buffer in the
2150 window that the mouse was in, not the current buffer.)
2152 If the events are all characters and all can fit in a string, then
2153 @code{read-key-sequence} returns a string (@pxref{Strings of Events}).
2154 Otherwise, it returns a vector, since a vector can hold all kinds of
2155 events---characters, symbols, and lists. The elements of the string or
2156 vector are the events in the key sequence.
2158 Reading a key sequence includes translating the events in various
2159 ways. @xref{Translation Keymaps}.
2161 The argument @var{prompt} is either a string to be displayed in the
2162 echo area as a prompt, or @code{nil}, meaning not to display a prompt.
2163 The argument @var{continue-echo}, if non-@code{nil}, means to echo
2164 this key as a continuation of the previous key.
2166 Normally any upper case event is converted to lower case if the
2167 original event is undefined and the lower case equivalent is defined.
2168 The argument @var{dont-downcase-last}, if non-@code{nil}, means do not
2169 convert the last event to lower case. This is appropriate for reading
2170 a key sequence to be defined.
2172 The argument @var{switch-frame-ok}, if non-@code{nil}, means that this
2173 function should process a @code{switch-frame} event if the user
2174 switches frames before typing anything. If the user switches frames
2175 in the middle of a key sequence, or at the start of the sequence but
2176 @var{switch-frame-ok} is @code{nil}, then the event will be put off
2177 until after the current key sequence.
2179 The argument @var{command-loop}, if non-@code{nil}, means that this
2180 key sequence is being read by something that will read commands one
2181 after another. It should be @code{nil} if the caller will read just
2184 In the following example, Emacs displays the prompt @samp{?} in the
2185 echo area, and then the user types @kbd{C-x C-f}.
2188 (read-key-sequence "?")
2191 ---------- Echo Area ----------
2193 ---------- Echo Area ----------
2199 The function @code{read-key-sequence} suppresses quitting: @kbd{C-g}
2200 typed while reading with this function works like any other character,
2201 and does not set @code{quit-flag}. @xref{Quitting}.
2204 @defun read-key-sequence-vector prompt &optional continue-echo dont-downcase-last switch-frame-ok command-loop
2205 This is like @code{read-key-sequence} except that it always
2206 returns the key sequence as a vector, never as a string.
2207 @xref{Strings of Events}.
2210 @cindex upper case key sequence
2211 @cindex downcasing in @code{lookup-key}
2212 If an input character is upper-case (or has the shift modifier) and
2213 has no key binding, but its lower-case equivalent has one, then
2214 @code{read-key-sequence} converts the character to lower case. Note
2215 that @code{lookup-key} does not perform case conversion in this way.
2217 The function @code{read-key-sequence} also transforms some mouse events.
2218 It converts unbound drag events into click events, and discards unbound
2219 button-down events entirely. It also reshuffles focus events and
2220 miscellaneous window events so that they never appear in a key sequence
2221 with any other events.
2223 @cindex @code{header-line} prefix key
2224 @cindex @code{mode-line} prefix key
2225 @cindex @code{vertical-line} prefix key
2226 @cindex @code{horizontal-scroll-bar} prefix key
2227 @cindex @code{vertical-scroll-bar} prefix key
2228 @cindex @code{menu-bar} prefix key
2229 @cindex mouse events, in special parts of frame
2230 When mouse events occur in special parts of a window, such as a mode
2231 line or a scroll bar, the event type shows nothing special---it is the
2232 same symbol that would normally represent that combination of mouse
2233 button and modifier keys. The information about the window part is kept
2234 elsewhere in the event---in the coordinates. But
2235 @code{read-key-sequence} translates this information into imaginary
2236 ``prefix keys,'' all of which are symbols: @code{header-line},
2237 @code{horizontal-scroll-bar}, @code{menu-bar}, @code{mode-line},
2238 @code{vertical-line}, and @code{vertical-scroll-bar}. You can define
2239 meanings for mouse clicks in special window parts by defining key
2240 sequences using these imaginary prefix keys.
2242 For example, if you call @code{read-key-sequence} and then click the
2243 mouse on the window's mode line, you get two events, like this:
2246 (read-key-sequence "Click on the mode line: ")
2247 @result{} [mode-line
2249 (#<window 6 on NEWS> mode-line
2250 (40 . 63) 5959987))]
2253 @defvar num-input-keys
2255 This variable's value is the number of key sequences processed so far in
2256 this Emacs session. This includes key sequences read from the terminal
2257 and key sequences read from keyboard macros being executed.
2260 @node Reading One Event
2261 @subsection Reading One Event
2262 @cindex reading a single event
2263 @cindex event, reading only one
2265 The lowest level functions for command input are those that read a
2268 None of the three functions below suppresses quitting.
2270 @defun read-event &optional prompt inherit-input-method seconds
2271 This function reads and returns the next event of command input, waiting
2272 if necessary until an event is available. Events can come directly from
2273 the user or from a keyboard macro.
2275 If the optional argument @var{prompt} is non-@code{nil}, it should be a
2276 string to display in the echo area as a prompt. Otherwise,
2277 @code{read-event} does not display any message to indicate it is waiting
2278 for input; instead, it prompts by echoing: it displays descriptions of
2279 the events that led to or were read by the current command. @xref{The
2282 If @var{inherit-input-method} is non-@code{nil}, then the current input
2283 method (if any) is employed to make it possible to enter a
2284 non-@acronym{ASCII} character. Otherwise, input method handling is disabled
2285 for reading this event.
2287 If @code{cursor-in-echo-area} is non-@code{nil}, then @code{read-event}
2288 moves the cursor temporarily to the echo area, to the end of any message
2289 displayed there. Otherwise @code{read-event} does not move the cursor.
2291 If @var{seconds} is non-@code{nil}, it should be a number specifying
2292 the maximum time to wait for input, in seconds. If no input arrives
2293 within that time, @code{read-event} stops waiting and returns
2294 @code{nil}. A floating-point value for @var{seconds} means to wait
2295 for a fractional number of seconds. Some systems support only a whole
2296 number of seconds; on these systems, @var{seconds} is rounded down.
2297 If @var{seconds} is @code{nil}, @code{read-event} waits as long as
2298 necessary for input to arrive.
2300 If @var{seconds} is @code{nil}, Emacs is considered idle while waiting
2301 for user input to arrive. Idle timers---those created with
2302 @code{run-with-idle-timer} (@pxref{Idle Timers})---can run during this
2303 period. However, if @var{seconds} is non-@code{nil}, the state of
2304 idleness remains unchanged. If Emacs is non-idle when
2305 @code{read-event} is called, it remains non-idle throughout the
2306 operation of @code{read-event}; if Emacs is idle (which can happen if
2307 the call happens inside an idle timer), it remains idle.
2309 If @code{read-event} gets an event that is defined as a help character,
2310 then in some cases @code{read-event} processes the event directly without
2311 returning. @xref{Help Functions}. Certain other events, called
2312 @dfn{special events}, are also processed directly within
2313 @code{read-event} (@pxref{Special Events}).
2315 Here is what happens if you call @code{read-event} and then press the
2316 right-arrow function key:
2326 @defun read-char &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 (i.e. a mouse click or
2329 function key event), @code{read-char} signals an error. The arguments
2330 work as in @code{read-event}.
2332 In the first example, the user types the character @kbd{1} (@acronym{ASCII}
2333 code 49). The second example shows a keyboard macro definition that
2334 calls @code{read-char} from the minibuffer using @code{eval-expression}.
2335 @code{read-char} reads the keyboard macro's very next character, which
2336 is @kbd{1}. Then @code{eval-expression} displays its return value in
2346 ;; @r{We assume here you use @kbd{M-:} to evaluate this.}
2347 (symbol-function 'foo)
2348 @result{} "^[:(read-char)^M1"
2351 (execute-kbd-macro 'foo)
2358 @defun read-char-exclusive &optional prompt inherit-input-method seconds
2359 This function reads and returns a character of command input. If the
2360 user generates an event which is not a character,
2361 @code{read-char-exclusive} ignores it and reads another event, until it
2362 gets a character. The arguments work as in @code{read-event}.
2365 @defvar num-nonmacro-input-events
2366 This variable holds the total number of input events received so far
2367 from the terminal---not counting those generated by keyboard macros.
2371 @subsection Modifying and Translating Input Events
2373 Emacs modifies every event it reads according to
2374 @code{extra-keyboard-modifiers}, then translates it through
2375 @code{keyboard-translate-table} (if applicable), before returning it
2376 from @code{read-event}.
2379 @defvar extra-keyboard-modifiers
2380 This variable lets Lisp programs ``press'' the modifier keys on the
2381 keyboard. The value is a character. Only the modifiers of the
2382 character matter. Each time the user types a keyboard key, it is
2383 altered as if those modifier keys were held down. For instance, if
2384 you bind @code{extra-keyboard-modifiers} to @code{?\C-\M-a}, then all
2385 keyboard input characters typed during the scope of the binding will
2386 have the control and meta modifiers applied to them. The character
2387 @code{?\C-@@}, equivalent to the integer 0, does not count as a control
2388 character for this purpose, but as a character with no modifiers.
2389 Thus, setting @code{extra-keyboard-modifiers} to zero cancels any
2392 When using a window system, the program can ``press'' any of the
2393 modifier keys in this way. Otherwise, only the @key{CTL} and @key{META}
2394 keys can be virtually pressed.
2396 Note that this variable applies only to events that really come from
2397 the keyboard, and has no effect on mouse events or any other events.
2400 @defvar keyboard-translate-table
2401 This variable is the translate table for keyboard characters. It lets
2402 you reshuffle the keys on the keyboard without changing any command
2403 bindings. Its value is normally a char-table, or else @code{nil}.
2404 (It can also be a string or vector, but this is considered obsolete.)
2406 If @code{keyboard-translate-table} is a char-table
2407 (@pxref{Char-Tables}), then each character read from the keyboard is
2408 looked up in this char-table. If the value found there is
2409 non-@code{nil}, then it is used instead of the actual input character.
2411 Note that this translation is the first thing that happens to a
2412 character after it is read from the terminal. Record-keeping features
2413 such as @code{recent-keys} and dribble files record the characters after
2416 Note also that this translation is done before the characters are
2417 supplied to input methods (@pxref{Input Methods}). Use
2418 @code{translation-table-for-input} (@pxref{Translation of Characters}),
2419 if you want to translate characters after input methods operate.
2422 @defun keyboard-translate from to
2423 This function modifies @code{keyboard-translate-table} to translate
2424 character code @var{from} into character code @var{to}. It creates
2425 the keyboard translate table if necessary.
2428 Here's an example of using the @code{keyboard-translate-table} to
2429 make @kbd{C-x}, @kbd{C-c} and @kbd{C-v} perform the cut, copy and paste
2433 (keyboard-translate ?\C-x 'control-x)
2434 (keyboard-translate ?\C-c 'control-c)
2435 (keyboard-translate ?\C-v 'control-v)
2436 (global-set-key [control-x] 'kill-region)
2437 (global-set-key [control-c] 'kill-ring-save)
2438 (global-set-key [control-v] 'yank)
2442 On a graphical terminal that supports extended @acronym{ASCII} input,
2443 you can still get the standard Emacs meanings of one of those
2444 characters by typing it with the shift key. That makes it a different
2445 character as far as keyboard translation is concerned, but it has the
2448 @xref{Translation Keymaps}, for mechanisms that translate event sequences
2449 at the level of @code{read-key-sequence}.
2451 @node Invoking the Input Method
2452 @subsection Invoking the Input Method
2454 The event-reading functions invoke the current input method, if any
2455 (@pxref{Input Methods}). If the value of @code{input-method-function}
2456 is non-@code{nil}, it should be a function; when @code{read-event} reads
2457 a printing character (including @key{SPC}) with no modifier bits, it
2458 calls that function, passing the character as an argument.
2460 @defvar input-method-function
2461 If this is non-@code{nil}, its value specifies the current input method
2464 @strong{Warning:} don't bind this variable with @code{let}. It is often
2465 buffer-local, and if you bind it around reading input (which is exactly
2466 when you @emph{would} bind it), switching buffers asynchronously while
2467 Emacs is waiting will cause the value to be restored in the wrong
2471 The input method function should return a list of events which should
2472 be used as input. (If the list is @code{nil}, that means there is no
2473 input, so @code{read-event} waits for another event.) These events are
2474 processed before the events in @code{unread-command-events}
2475 (@pxref{Event Input Misc}). Events
2476 returned by the input method function are not passed to the input method
2477 function again, even if they are printing characters with no modifier
2480 If the input method function calls @code{read-event} or
2481 @code{read-key-sequence}, it should bind @code{input-method-function} to
2482 @code{nil} first, to prevent recursion.
2484 The input method function is not called when reading the second and
2485 subsequent events of a key sequence. Thus, these characters are not
2486 subject to input method processing. The input method function should
2487 test the values of @code{overriding-local-map} and
2488 @code{overriding-terminal-local-map}; if either of these variables is
2489 non-@code{nil}, the input method should put its argument into a list and
2490 return that list with no further processing.
2492 @node Quoted Character Input
2493 @subsection Quoted Character Input
2494 @cindex quoted character input
2496 You can use the function @code{read-quoted-char} to ask the user to
2497 specify a character, and allow the user to specify a control or meta
2498 character conveniently, either literally or as an octal character code.
2499 The command @code{quoted-insert} uses this function.
2501 @defun read-quoted-char &optional prompt
2502 @cindex octal character input
2503 @cindex control characters, reading
2504 @cindex nonprinting characters, reading
2505 This function is like @code{read-char}, except that if the first
2506 character read is an octal digit (0-7), it reads any number of octal
2507 digits (but stopping if a non-octal digit is found), and returns the
2508 character represented by that numeric character code. If the
2509 character that terminates the sequence of octal digits is @key{RET},
2510 it is discarded. Any other terminating character is used as input
2511 after this function returns.
2513 Quitting is suppressed when the first character is read, so that the
2514 user can enter a @kbd{C-g}. @xref{Quitting}.
2516 If @var{prompt} is supplied, it specifies a string for prompting the
2517 user. The prompt string is always displayed in the echo area, followed
2518 by a single @samp{-}.
2520 In the following example, the user types in the octal number 177 (which
2524 (read-quoted-char "What character")
2527 ---------- Echo Area ----------
2528 What character @kbd{1 7 7}-
2529 ---------- Echo Area ----------
2537 @node Event Input Misc
2538 @subsection Miscellaneous Event Input Features
2540 This section describes how to ``peek ahead'' at events without using
2541 them up, how to check for pending input, and how to discard pending
2542 input. See also the function @code{read-passwd} (@pxref{Reading a
2545 @defvar unread-command-events
2547 @cindex peeking at input
2548 This variable holds a list of events waiting to be read as command
2549 input. The events are used in the order they appear in the list, and
2550 removed one by one as they are used.
2552 The variable is needed because in some cases a function reads an event
2553 and then decides not to use it. Storing the event in this variable
2554 causes it to be processed normally, by the command loop or by the
2555 functions to read command input.
2557 @cindex prefix argument unreading
2558 For example, the function that implements numeric prefix arguments reads
2559 any number of digits. When it finds a non-digit event, it must unread
2560 the event so that it can be read normally by the command loop.
2561 Likewise, incremental search uses this feature to unread events with no
2562 special meaning in a search, because these events should exit the search
2563 and then execute normally.
2565 The reliable and easy way to extract events from a key sequence so as to
2566 put them in @code{unread-command-events} is to use
2567 @code{listify-key-sequence} (@pxref{Strings of Events}).
2569 Normally you add events to the front of this list, so that the events
2570 most recently unread will be reread first.
2572 Events read from this list are not normally added to the current
2573 command's key sequence (as returned by e.g. @code{this-command-keys}),
2574 as the events will already have been added once as they were read for
2575 the first time. An element of the form @code{(@code{t} . @var{event})}
2576 forces @var{event} to be added to the current command's key sequence.
2579 @defun listify-key-sequence key
2580 This function converts the string or vector @var{key} to a list of
2581 individual events, which you can put in @code{unread-command-events}.
2584 @defvar unread-command-char
2585 This variable holds a character to be read as command input.
2586 A value of -1 means ``empty.''
2588 This variable is mostly obsolete now that you can use
2589 @code{unread-command-events} instead; it exists only to support programs
2590 written for Emacs versions 18 and earlier.
2593 @defun input-pending-p
2594 @cindex waiting for command key input
2595 This function determines whether any command input is currently
2596 available to be read. It returns immediately, with value @code{t} if
2597 there is available input, @code{nil} otherwise. On rare occasions it
2598 may return @code{t} when no input is available.
2601 @defvar last-input-event
2602 @defvarx last-input-char
2603 This variable records the last terminal input event read, whether
2604 as part of a command or explicitly by a Lisp program.
2606 In the example below, the Lisp program reads the character @kbd{1},
2607 @acronym{ASCII} code 49. It becomes the value of @code{last-input-event},
2608 while @kbd{C-e} (we assume @kbd{C-x C-e} command is used to evaluate
2609 this expression) remains the value of @code{last-command-event}.
2613 (progn (print (read-char))
2614 (print last-command-event)
2622 The alias @code{last-input-char} exists for compatibility with
2626 @defmac while-no-input body@dots{}
2627 This construct runs the @var{body} forms and returns the value of the
2628 last one---but only if no input arrives. If any input arrives during
2629 the execution of the @var{body} forms, it aborts them (working much
2630 like a quit). The @code{while-no-input} form returns @code{nil} if
2631 aborted by a real quit, and returns @code{t} if aborted by arrival of
2634 If a part of @var{body} binds @code{inhibit-quit} to non-@code{nil},
2635 arrival of input during those parts won't cause an abort until
2636 the end of that part.
2638 If you want to be able to distinguish all possible values computed
2639 by @var{body} from both kinds of abort conditions, write the code
2645 (progn . @var{body})))
2649 @defun discard-input
2650 @cindex flushing input
2651 @cindex discarding input
2652 @cindex keyboard macro, terminating
2653 This function discards the contents of the terminal input buffer and
2654 cancels any keyboard macro that might be in the process of definition.
2655 It returns @code{nil}.
2657 In the following example, the user may type a number of characters right
2658 after starting the evaluation of the form. After the @code{sleep-for}
2659 finishes sleeping, @code{discard-input} discards any characters typed
2663 (progn (sleep-for 2)
2669 @node Special Events
2670 @section Special Events
2672 @cindex special events
2673 Special events are handled at a very low level---as soon as they are
2674 read. The @code{read-event} function processes these events itself, and
2675 never returns them. Instead, it keeps waiting for the first event
2676 that is not special and returns that one.
2678 Events that are handled in this way do not echo, they are never grouped
2679 into key sequences, and they never appear in the value of
2680 @code{last-command-event} or @code{(this-command-keys)}. They do not
2681 discard a numeric argument, they cannot be unread with
2682 @code{unread-command-events}, they may not appear in a keyboard macro,
2683 and they are not recorded in a keyboard macro while you are defining
2686 These events do, however, appear in @code{last-input-event} immediately
2687 after they are read, and this is the way for the event's definition to
2688 find the actual event.
2690 The events types @code{iconify-frame}, @code{make-frame-visible},
2691 @code{delete-frame}, @code{drag-n-drop}, and user signals like
2692 @code{sigusr1} are normally handled in this way. The keymap which
2693 defines how to handle special events---and which events are special---is
2694 in the variable @code{special-event-map} (@pxref{Active Keymaps}).
2697 @section Waiting for Elapsed Time or Input
2700 The wait functions are designed to wait for a certain amount of time
2701 to pass or until there is input. For example, you may wish to pause in
2702 the middle of a computation to allow the user time to view the display.
2703 @code{sit-for} pauses and updates the screen, and returns immediately if
2704 input comes in, while @code{sleep-for} pauses without updating the
2707 @defun sit-for seconds &optional nodisp
2708 This function performs redisplay (provided there is no pending input
2709 from the user), then waits @var{seconds} seconds, or until input is
2710 available. The usual purpose of @code{sit-for} is to give the user
2711 time to read text that you display. The value is @code{t} if
2712 @code{sit-for} waited the full time with no input arriving
2713 (@pxref{Event Input Misc}). Otherwise, the value is @code{nil}.
2715 The argument @var{seconds} need not be an integer. If it is a floating
2716 point number, @code{sit-for} waits for a fractional number of seconds.
2717 Some systems support only a whole number of seconds; on these systems,
2718 @var{seconds} is rounded down.
2720 The expression @code{(sit-for 0)} is equivalent to @code{(redisplay)},
2721 i.e. it requests a redisplay, without any delay, if there is no pending input.
2722 @xref{Forcing Redisplay}.
2724 If @var{nodisp} is non-@code{nil}, then @code{sit-for} does not
2725 redisplay, but it still returns as soon as input is available (or when
2726 the timeout elapses).
2728 In batch mode (@pxref{Batch Mode}), @code{sit-for} cannot be
2729 interrupted, even by input from the standard input descriptor. It is
2730 thus equivalent to @code{sleep-for}, which is described below.
2732 It is also possible to call @code{sit-for} with three arguments,
2733 as @code{(sit-for @var{seconds} @var{millisec} @var{nodisp})},
2734 but that is considered obsolete.
2737 @defun sleep-for seconds &optional millisec
2738 This function simply pauses for @var{seconds} seconds without updating
2739 the display. It pays no attention to available input. It returns
2742 The argument @var{seconds} need not be an integer. If it is a floating
2743 point number, @code{sleep-for} waits for a fractional number of seconds.
2744 Some systems support only a whole number of seconds; on these systems,
2745 @var{seconds} is rounded down.
2747 The optional argument @var{millisec} specifies an additional waiting
2748 period measured in milliseconds. This adds to the period specified by
2749 @var{seconds}. If the system doesn't support waiting fractions of a
2750 second, you get an error if you specify nonzero @var{millisec}.
2752 Use @code{sleep-for} when you wish to guarantee a delay.
2755 @xref{Time of Day}, for functions to get the current time.
2761 @cindex interrupt Lisp functions
2763 Typing @kbd{C-g} while a Lisp function is running causes Emacs to
2764 @dfn{quit} whatever it is doing. This means that control returns to the
2765 innermost active command loop.
2767 Typing @kbd{C-g} while the command loop is waiting for keyboard input
2768 does not cause a quit; it acts as an ordinary input character. In the
2769 simplest case, you cannot tell the difference, because @kbd{C-g}
2770 normally runs the command @code{keyboard-quit}, whose effect is to quit.
2771 However, when @kbd{C-g} follows a prefix key, they combine to form an
2772 undefined key. The effect is to cancel the prefix key as well as any
2775 In the minibuffer, @kbd{C-g} has a different definition: it aborts out
2776 of the minibuffer. This means, in effect, that it exits the minibuffer
2777 and then quits. (Simply quitting would return to the command loop
2778 @emph{within} the minibuffer.) The reason why @kbd{C-g} does not quit
2779 directly when the command reader is reading input is so that its meaning
2780 can be redefined in the minibuffer in this way. @kbd{C-g} following a
2781 prefix key is not redefined in the minibuffer, and it has its normal
2782 effect of canceling the prefix key and prefix argument. This too
2783 would not be possible if @kbd{C-g} always quit directly.
2785 When @kbd{C-g} does directly quit, it does so by setting the variable
2786 @code{quit-flag} to @code{t}. Emacs checks this variable at appropriate
2787 times and quits if it is not @code{nil}. Setting @code{quit-flag}
2788 non-@code{nil} in any way thus causes a quit.
2790 At the level of C code, quitting cannot happen just anywhere; only at the
2791 special places that check @code{quit-flag}. The reason for this is
2792 that quitting at other places might leave an inconsistency in Emacs's
2793 internal state. Because quitting is delayed until a safe place, quitting
2794 cannot make Emacs crash.
2796 Certain functions such as @code{read-key-sequence} or
2797 @code{read-quoted-char} prevent quitting entirely even though they wait
2798 for input. Instead of quitting, @kbd{C-g} serves as the requested
2799 input. In the case of @code{read-key-sequence}, this serves to bring
2800 about the special behavior of @kbd{C-g} in the command loop. In the
2801 case of @code{read-quoted-char}, this is so that @kbd{C-q} can be used
2802 to quote a @kbd{C-g}.
2804 @cindex preventing quitting
2805 You can prevent quitting for a portion of a Lisp function by binding
2806 the variable @code{inhibit-quit} to a non-@code{nil} value. Then,
2807 although @kbd{C-g} still sets @code{quit-flag} to @code{t} as usual, the
2808 usual result of this---a quit---is prevented. Eventually,
2809 @code{inhibit-quit} will become @code{nil} again, such as when its
2810 binding is unwound at the end of a @code{let} form. At that time, if
2811 @code{quit-flag} is still non-@code{nil}, the requested quit happens
2812 immediately. This behavior is ideal when you wish to make sure that
2813 quitting does not happen within a ``critical section'' of the program.
2815 @cindex @code{read-quoted-char} quitting
2816 In some functions (such as @code{read-quoted-char}), @kbd{C-g} is
2817 handled in a special way that does not involve quitting. This is done
2818 by reading the input with @code{inhibit-quit} bound to @code{t}, and
2819 setting @code{quit-flag} to @code{nil} before @code{inhibit-quit}
2820 becomes @code{nil} again. This excerpt from the definition of
2821 @code{read-quoted-char} shows how this is done; it also shows that
2822 normal quitting is permitted after the first character of input.
2825 (defun read-quoted-char (&optional prompt)
2826 "@dots{}@var{documentation}@dots{}"
2827 (let ((message-log-max nil) done (first t) (code 0) char)
2829 (let ((inhibit-quit first)
2831 (and prompt (message "%s-" prompt))
2832 (setq char (read-event))
2833 (if inhibit-quit (setq quit-flag nil)))
2834 @r{@dots{}set the variable @code{code}@dots{}})
2839 If this variable is non-@code{nil}, then Emacs quits immediately, unless
2840 @code{inhibit-quit} is non-@code{nil}. Typing @kbd{C-g} ordinarily sets
2841 @code{quit-flag} non-@code{nil}, regardless of @code{inhibit-quit}.
2844 @defvar inhibit-quit
2845 This variable determines whether Emacs should quit when @code{quit-flag}
2846 is set to a value other than @code{nil}. If @code{inhibit-quit} is
2847 non-@code{nil}, then @code{quit-flag} has no special effect.
2850 @defmac with-local-quit body@dots{}
2851 This macro executes @var{body} forms in sequence, but allows quitting, at
2852 least locally, within @var{body} even if @code{inhibit-quit} was
2853 non-@code{nil} outside this construct. It returns the value of the
2854 last form in @var{body}, unless exited by quitting, in which case
2855 it returns @code{nil}.
2857 If @code{inhibit-quit} is @code{nil} on entry to @code{with-local-quit},
2858 it only executes the @var{body}, and setting @code{quit-flag} causes
2859 a normal quit. However, if @code{inhibit-quit} is non-@code{nil} so
2860 that ordinary quitting is delayed, a non-@code{nil} @code{quit-flag}
2861 triggers a special kind of local quit. This ends the execution of
2862 @var{body} and exits the @code{with-local-quit} body with
2863 @code{quit-flag} still non-@code{nil}, so that another (ordinary) quit
2864 will happen as soon as that is allowed. If @code{quit-flag} is
2865 already non-@code{nil} at the beginning of @var{body}, the local quit
2866 happens immediately and the body doesn't execute at all.
2868 This macro is mainly useful in functions that can be called from
2869 timers, process filters, process sentinels, @code{pre-command-hook},
2870 @code{post-command-hook}, and other places where @code{inhibit-quit} is
2871 normally bound to @code{t}.
2874 @deffn Command keyboard-quit
2875 This function signals the @code{quit} condition with @code{(signal 'quit
2876 nil)}. This is the same thing that quitting does. (See @code{signal}
2880 You can specify a character other than @kbd{C-g} to use for quitting.
2881 See the function @code{set-input-mode} in @ref{Terminal Input}.
2883 @node Prefix Command Arguments
2884 @section Prefix Command Arguments
2885 @cindex prefix argument
2886 @cindex raw prefix argument
2887 @cindex numeric prefix argument
2889 Most Emacs commands can use a @dfn{prefix argument}, a number
2890 specified before the command itself. (Don't confuse prefix arguments
2891 with prefix keys.) The prefix argument is at all times represented by a
2892 value, which may be @code{nil}, meaning there is currently no prefix
2893 argument. Each command may use the prefix argument or ignore it.
2895 There are two representations of the prefix argument: @dfn{raw} and
2896 @dfn{numeric}. The editor command loop uses the raw representation
2897 internally, and so do the Lisp variables that store the information, but
2898 commands can request either representation.
2900 Here are the possible values of a raw prefix argument:
2904 @code{nil}, meaning there is no prefix argument. Its numeric value is
2905 1, but numerous commands make a distinction between @code{nil} and the
2909 An integer, which stands for itself.
2912 A list of one element, which is an integer. This form of prefix
2913 argument results from one or a succession of @kbd{C-u}'s with no
2914 digits. The numeric value is the integer in the list, but some
2915 commands make a distinction between such a list and an integer alone.
2918 The symbol @code{-}. This indicates that @kbd{M--} or @kbd{C-u -} was
2919 typed, without following digits. The equivalent numeric value is
2920 @minus{}1, but some commands make a distinction between the integer
2921 @minus{}1 and the symbol @code{-}.
2924 We illustrate these possibilities by calling the following function with
2929 (defun display-prefix (arg)
2930 "Display the value of the raw prefix arg."
2937 Here are the results of calling @code{display-prefix} with various
2938 raw prefix arguments:
2941 M-x display-prefix @print{} nil
2943 C-u M-x display-prefix @print{} (4)
2945 C-u C-u M-x display-prefix @print{} (16)
2947 C-u 3 M-x display-prefix @print{} 3
2949 M-3 M-x display-prefix @print{} 3 ; @r{(Same as @code{C-u 3}.)}
2951 C-u - M-x display-prefix @print{} -
2953 M-- M-x display-prefix @print{} - ; @r{(Same as @code{C-u -}.)}
2955 C-u - 7 M-x display-prefix @print{} -7
2957 M-- 7 M-x display-prefix @print{} -7 ; @r{(Same as @code{C-u -7}.)}
2960 Emacs uses two variables to store the prefix argument:
2961 @code{prefix-arg} and @code{current-prefix-arg}. Commands such as
2962 @code{universal-argument} that set up prefix arguments for other
2963 commands store them in @code{prefix-arg}. In contrast,
2964 @code{current-prefix-arg} conveys the prefix argument to the current
2965 command, so setting it has no effect on the prefix arguments for future
2968 Normally, commands specify which representation to use for the prefix
2969 argument, either numeric or raw, in the @code{interactive} specification.
2970 (@xref{Using Interactive}.) Alternatively, functions may look at the
2971 value of the prefix argument directly in the variable
2972 @code{current-prefix-arg}, but this is less clean.
2974 @defun prefix-numeric-value arg
2975 This function returns the numeric meaning of a valid raw prefix argument
2976 value, @var{arg}. The argument may be a symbol, a number, or a list.
2977 If it is @code{nil}, the value 1 is returned; if it is @code{-}, the
2978 value @minus{}1 is returned; if it is a number, that number is returned;
2979 if it is a list, the @sc{car} of that list (which should be a number) is
2983 @defvar current-prefix-arg
2984 This variable holds the raw prefix argument for the @emph{current}
2985 command. Commands may examine it directly, but the usual method for
2986 accessing it is with @code{(interactive "P")}.
2990 The value of this variable is the raw prefix argument for the
2991 @emph{next} editing command. Commands such as @code{universal-argument}
2992 that specify prefix arguments for the following command work by setting
2996 @defvar last-prefix-arg
2997 The raw prefix argument value used by the previous command.
3000 The following commands exist to set up prefix arguments for the
3001 following command. Do not call them for any other reason.
3003 @deffn Command universal-argument
3004 This command reads input and specifies a prefix argument for the
3005 following command. Don't call this command yourself unless you know
3009 @deffn Command digit-argument arg
3010 This command adds to the prefix argument for the following command. The
3011 argument @var{arg} is the raw prefix argument as it was before this
3012 command; it is used to compute the updated prefix argument. Don't call
3013 this command yourself unless you know what you are doing.
3016 @deffn Command negative-argument arg
3017 This command adds to the numeric argument for the next command. The
3018 argument @var{arg} is the raw prefix argument as it was before this
3019 command; its value is negated to form the new prefix argument. Don't
3020 call this command yourself unless you know what you are doing.
3023 @node Recursive Editing
3024 @section Recursive Editing
3025 @cindex recursive command loop
3026 @cindex recursive editing level
3027 @cindex command loop, recursive
3029 The Emacs command loop is entered automatically when Emacs starts up.
3030 This top-level invocation of the command loop never exits; it keeps
3031 running as long as Emacs does. Lisp programs can also invoke the
3032 command loop. Since this makes more than one activation of the command
3033 loop, we call it @dfn{recursive editing}. A recursive editing level has
3034 the effect of suspending whatever command invoked it and permitting the
3035 user to do arbitrary editing before resuming that command.
3037 The commands available during recursive editing are the same ones
3038 available in the top-level editing loop and defined in the keymaps.
3039 Only a few special commands exit the recursive editing level; the others
3040 return to the recursive editing level when they finish. (The special
3041 commands for exiting are always available, but they do nothing when
3042 recursive editing is not in progress.)
3044 All command loops, including recursive ones, set up all-purpose error
3045 handlers so that an error in a command run from the command loop will
3048 @cindex minibuffer input
3049 Minibuffer input is a special kind of recursive editing. It has a few
3050 special wrinkles, such as enabling display of the minibuffer and the
3051 minibuffer window, but fewer than you might suppose. Certain keys
3052 behave differently in the minibuffer, but that is only because of the
3053 minibuffer's local map; if you switch windows, you get the usual Emacs
3056 @cindex @code{throw} example
3058 @cindex exit recursive editing
3060 To invoke a recursive editing level, call the function
3061 @code{recursive-edit}. This function contains the command loop; it also
3062 contains a call to @code{catch} with tag @code{exit}, which makes it
3063 possible to exit the recursive editing level by throwing to @code{exit}
3064 (@pxref{Catch and Throw}). If you throw a value other than @code{t},
3065 then @code{recursive-edit} returns normally to the function that called
3066 it. The command @kbd{C-M-c} (@code{exit-recursive-edit}) does this.
3067 Throwing a @code{t} value causes @code{recursive-edit} to quit, so that
3068 control returns to the command loop one level up. This is called
3069 @dfn{aborting}, and is done by @kbd{C-]} (@code{abort-recursive-edit}).
3071 Most applications should not use recursive editing, except as part of
3072 using the minibuffer. Usually it is more convenient for the user if you
3073 change the major mode of the current buffer temporarily to a special
3074 major mode, which should have a command to go back to the previous mode.
3075 (The @kbd{e} command in Rmail uses this technique.) Or, if you wish to
3076 give the user different text to edit ``recursively,'' create and select
3077 a new buffer in a special mode. In this mode, define a command to
3078 complete the processing and go back to the previous buffer. (The
3079 @kbd{m} command in Rmail does this.)
3081 Recursive edits are useful in debugging. You can insert a call to
3082 @code{debug} into a function definition as a sort of breakpoint, so that
3083 you can look around when the function gets there. @code{debug} invokes
3084 a recursive edit but also provides the other features of the debugger.
3086 Recursive editing levels are also used when you type @kbd{C-r} in
3087 @code{query-replace} or use @kbd{C-x q} (@code{kbd-macro-query}).
3089 @defun recursive-edit
3090 @cindex suspend evaluation
3091 This function invokes the editor command loop. It is called
3092 automatically by the initialization of Emacs, to let the user begin
3093 editing. When called from a Lisp program, it enters a recursive editing
3096 If the current buffer is not the same as the selected window's buffer,
3097 @code{recursive-edit} saves and restores the current buffer. Otherwise,
3098 if you switch buffers, the buffer you switched to is current after
3099 @code{recursive-edit} returns.
3101 In the following example, the function @code{simple-rec} first
3102 advances point one word, then enters a recursive edit, printing out a
3103 message in the echo area. The user can then do any editing desired, and
3104 then type @kbd{C-M-c} to exit and continue executing @code{simple-rec}.
3107 (defun simple-rec ()
3109 (message "Recursive edit in progress")
3112 @result{} simple-rec
3118 @deffn Command exit-recursive-edit
3119 This function exits from the innermost recursive edit (including
3120 minibuffer input). Its definition is effectively @code{(throw 'exit
3124 @deffn Command abort-recursive-edit
3125 This function aborts the command that requested the innermost recursive
3126 edit (including minibuffer input), by signaling @code{quit}
3127 after exiting the recursive edit. Its definition is effectively
3128 @code{(throw 'exit t)}. @xref{Quitting}.
3131 @deffn Command top-level
3132 This function exits all recursive editing levels; it does not return a
3133 value, as it jumps completely out of any computation directly back to
3134 the main command loop.
3137 @defun recursion-depth
3138 This function returns the current depth of recursive edits. When no
3139 recursive edit is active, it returns 0.
3142 @node Disabling Commands
3143 @section Disabling Commands
3144 @cindex disabled command
3146 @dfn{Disabling a command} marks the command as requiring user
3147 confirmation before it can be executed. Disabling is used for commands
3148 which might be confusing to beginning users, to prevent them from using
3149 the commands by accident.
3152 The low-level mechanism for disabling a command is to put a
3153 non-@code{nil} @code{disabled} property on the Lisp symbol for the
3154 command. These properties are normally set up by the user's
3155 init file (@pxref{Init File}) with Lisp expressions such as this:
3158 (put 'upcase-region 'disabled t)
3162 For a few commands, these properties are present by default (you can
3163 remove them in your init file if you wish).
3165 If the value of the @code{disabled} property is a string, the message
3166 saying the command is disabled includes that string. For example:
3169 (put 'delete-region 'disabled
3170 "Text deleted this way cannot be yanked back!\n")
3173 @xref{Disabling,,, emacs, The GNU Emacs Manual}, for the details on
3174 what happens when a disabled command is invoked interactively.
3175 Disabling a command has no effect on calling it as a function from Lisp
3178 @deffn Command enable-command command
3179 Allow @var{command} (a symbol) to be executed without special
3180 confirmation from now on, and alter the user's init file (@pxref{Init
3181 File}) so that this will apply to future sessions.
3184 @deffn Command disable-command command
3185 Require special confirmation to execute @var{command} from now on, and
3186 alter the user's init file so that this will apply to future sessions.
3189 @defvar disabled-command-function
3190 The value of this variable should be a function. When the user
3191 invokes a disabled command interactively, this function is called
3192 instead of the disabled command. It can use @code{this-command-keys}
3193 to determine what the user typed to run the command, and thus find the
3196 The value may also be @code{nil}. Then all commands work normally,
3199 By default, the value is a function that asks the user whether to
3203 @node Command History
3204 @section Command History
3205 @cindex command history
3206 @cindex complex command
3207 @cindex history of commands
3209 The command loop keeps a history of the complex commands that have
3210 been executed, to make it convenient to repeat these commands. A
3211 @dfn{complex command} is one for which the interactive argument reading
3212 uses the minibuffer. This includes any @kbd{M-x} command, any
3213 @kbd{M-:} command, and any command whose @code{interactive}
3214 specification reads an argument from the minibuffer. Explicit use of
3215 the minibuffer during the execution of the command itself does not cause
3216 the command to be considered complex.
3218 @defvar command-history
3219 This variable's value is a list of recent complex commands, each
3220 represented as a form to evaluate. It continues to accumulate all
3221 complex commands for the duration of the editing session, but when it
3222 reaches the maximum size (@pxref{Minibuffer History}), the oldest
3223 elements are deleted as new ones are added.
3228 @result{} ((switch-to-buffer "chistory.texi")
3229 (describe-key "^X^[")
3230 (visit-tags-table "~/emacs/src/")
3231 (find-tag "repeat-complex-command"))
3236 This history list is actually a special case of minibuffer history
3237 (@pxref{Minibuffer History}), with one special twist: the elements are
3238 expressions rather than strings.
3240 There are a number of commands devoted to the editing and recall of
3241 previous commands. The commands @code{repeat-complex-command}, and
3242 @code{list-command-history} are described in the user manual
3243 (@pxref{Repetition,,, emacs, The GNU Emacs Manual}). Within the
3244 minibuffer, the usual minibuffer history commands are available.
3246 @node Keyboard Macros
3247 @section Keyboard Macros
3248 @cindex keyboard macros
3250 A @dfn{keyboard macro} is a canned sequence of input events that can
3251 be considered a command and made the definition of a key. The Lisp
3252 representation of a keyboard macro is a string or vector containing the
3253 events. Don't confuse keyboard macros with Lisp macros
3256 @defun execute-kbd-macro kbdmacro &optional count loopfunc
3257 This function executes @var{kbdmacro} as a sequence of events. If
3258 @var{kbdmacro} is a string or vector, then the events in it are executed
3259 exactly as if they had been input by the user. The sequence is
3260 @emph{not} expected to be a single key sequence; normally a keyboard
3261 macro definition consists of several key sequences concatenated.
3263 If @var{kbdmacro} is a symbol, then its function definition is used in
3264 place of @var{kbdmacro}. If that is another symbol, this process repeats.
3265 Eventually the result should be a string or vector. If the result is
3266 not a symbol, string, or vector, an error is signaled.
3268 The argument @var{count} is a repeat count; @var{kbdmacro} is executed that
3269 many times. If @var{count} is omitted or @code{nil}, @var{kbdmacro} is
3270 executed once. If it is 0, @var{kbdmacro} is executed over and over until it
3271 encounters an error or a failing search.
3273 If @var{loopfunc} is non-@code{nil}, it is a function that is called,
3274 without arguments, prior to each iteration of the macro. If
3275 @var{loopfunc} returns @code{nil}, then this stops execution of the macro.
3277 @xref{Reading One Event}, for an example of using @code{execute-kbd-macro}.
3280 @defvar executing-kbd-macro
3281 This variable contains the string or vector that defines the keyboard
3282 macro that is currently executing. It is @code{nil} if no macro is
3283 currently executing. A command can test this variable so as to behave
3284 differently when run from an executing macro. Do not set this variable
3288 @defvar defining-kbd-macro
3289 This variable is non-@code{nil} if and only if a keyboard macro is
3290 being defined. A command can test this variable so as to behave
3291 differently while a macro is being defined. The value is
3292 @code{append} while appending to the definition of an existing macro.
3293 The commands @code{start-kbd-macro}, @code{kmacro-start-macro} and
3294 @code{end-kbd-macro} set this variable---do not set it yourself.
3296 The variable is always local to the current terminal and cannot be
3297 buffer-local. @xref{Multiple Displays}.
3300 @defvar last-kbd-macro
3301 This variable is the definition of the most recently defined keyboard
3302 macro. Its value is a string or vector, or @code{nil}.
3304 The variable is always local to the current terminal and cannot be
3305 buffer-local. @xref{Multiple Displays}.
3308 @defvar kbd-macro-termination-hook
3309 This normal hook (@pxref{Standard Hooks}) is run when a keyboard
3310 macro terminates, regardless of what caused it to terminate (reaching
3311 the macro end or an error which ended the macro prematurely).
3315 arch-tag: e34944ad-7d5c-4980-be00-36a5fe54d4b1