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1 | @c -*-texinfo-*- |
2 | @c This is part of the GNU Emacs Lisp Reference Manual. | |
f142f62a | 3 | @c Copyright (C) 1990, 1991, 1992, 1993, 1994 Free Software Foundation, Inc. |
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4 | @c See the file elisp.texi for copying conditions. |
5 | @setfilename ../info/commands | |
6 | @node Command Loop, Keymaps, Minibuffers, Top | |
7 | @chapter Command Loop | |
8 | @cindex editor command loop | |
9 | @cindex command loop | |
10 | ||
11 | When you run Emacs, it enters the @dfn{editor command loop} almost | |
12 | immediately. This loop reads key sequences, executes their definitions, | |
13 | and displays the results. In this chapter, we describe how these things | |
14 | are done, and the subroutines that allow Lisp programs to do them. | |
15 | ||
16 | @menu | |
17 | * Command Overview:: How the command loop reads commands. | |
18 | * Defining Commands:: Specifying how a function should read arguments. | |
19 | * Interactive Call:: Calling a command, so that it will read arguments. | |
20 | * Command Loop Info:: Variables set by the command loop for you to examine. | |
21 | * Input Events:: What input looks like when you read it. | |
22 | * Reading Input:: How to read input events from the keyboard or mouse. | |
23 | * Waiting:: Waiting for user input or elapsed time. | |
24 | * Quitting:: How @kbd{C-g} works. How to catch or defer quitting. | |
25 | * Prefix Command Arguments:: How the commands to set prefix args work. | |
26 | * Recursive Editing:: Entering a recursive edit, | |
27 | and why you usually shouldn't. | |
28 | * Disabling Commands:: How the command loop handles disabled commands. | |
29 | * Command History:: How the command history is set up, and how accessed. | |
30 | * Keyboard Macros:: How keyboard macros are implemented. | |
31 | @end menu | |
32 | ||
33 | @node Command Overview | |
34 | @section Command Loop Overview | |
35 | ||
36 | The first thing the command loop must do is read a key sequence, which | |
37 | is a sequence of events that translates into a command. It does this by | |
38 | calling the function @code{read-key-sequence}. Your Lisp code can also | |
39 | call this function (@pxref{Key Sequence Input}). Lisp programs can also | |
40 | do input at a lower level with @code{read-event} (@pxref{Reading One | |
41 | Event}) or discard pending input with @code{discard-input} | |
f142f62a | 42 | (@pxref{Event Input Misc}). |
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43 | |
44 | The key sequence is translated into a command through the currently | |
45 | active keymaps. @xref{Key Lookup}, for information on how this is done. | |
46 | The result should be a keyboard macro or an interactively callable | |
47 | function. If the key is @kbd{M-x}, then it reads the name of another | |
f142f62a | 48 | command, which it then calls. This is done by the command |
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49 | @code{execute-extended-command} (@pxref{Interactive Call}). |
50 | ||
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51 | To execute a command requires first reading the arguments for it. |
52 | This is done by calling @code{command-execute} (@pxref{Interactive | |
53 | Call}). For commands written in Lisp, the @code{interactive} | |
54 | specification says how to read the arguments. This may use the prefix | |
55 | argument (@pxref{Prefix Command Arguments}) or may read with prompting | |
56 | in the minibuffer (@pxref{Minibuffers}). For example, the command | |
57 | @code{find-file} has an @code{interactive} specification which says to | |
58 | read a file name using the minibuffer. The command's function body does | |
59 | not use the minibuffer; if you call this command from Lisp code as a | |
60 | function, you must supply the file name string as an ordinary Lisp | |
61 | function argument. | |
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62 | |
63 | If the command is a string or vector (i.e., a keyboard macro) then | |
64 | @code{execute-kbd-macro} is used to execute it. You can call this | |
65 | function yourself (@pxref{Keyboard Macros}). | |
66 | ||
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67 | To terminate the execution of a running command, type @kbd{C-g}. This |
68 | character causes @dfn{quitting} (@pxref{Quitting}). | |
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69 | |
70 | @defvar pre-command-hook | |
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71 | The editor command loop runs this normal hook before each command. At |
72 | that time, @code{this-command} contains the command that is about to | |
73 | run, and @code{last-command} describes the previous command. | |
b22f3a19 | 74 | @xref{Hooks}. |
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75 | @end defvar |
76 | ||
77 | @defvar post-command-hook | |
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78 | The editor command loop runs this normal hook after each command |
79 | (including commands terminated prematurely by quitting or by errors), | |
80 | and also when the command loop is first entered. At that time, | |
81 | @code{this-command} describes the command that just ran, and | |
b22f3a19 | 82 | @code{last-command} describes the command before that. @xref{Hooks}. |
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83 | @end defvar |
84 | ||
b22f3a19 | 85 | Quitting is suppressed while running @code{pre-command-hook} and |
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86 | @code{post-command-hook}. If an error happens while executing one of |
87 | these hooks, it terminates execution of the hook, but that is all it | |
88 | does. | |
b22f3a19 | 89 | |
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90 | @node Defining Commands |
91 | @section Defining Commands | |
92 | @cindex defining commands | |
93 | @cindex commands, defining | |
94 | @cindex functions, making them interactive | |
95 | @cindex interactive function | |
96 | ||
97 | A Lisp function becomes a command when its body contains, at top | |
b22f3a19 | 98 | level, a form that calls the special form @code{interactive}. This |
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99 | form does nothing when actually executed, but its presence serves as a |
100 | flag to indicate that interactive calling is permitted. Its argument | |
101 | controls the reading of arguments for an interactive call. | |
102 | ||
103 | @menu | |
104 | * Using Interactive:: General rules for @code{interactive}. | |
105 | * Interactive Codes:: The standard letter-codes for reading arguments | |
106 | in various ways. | |
107 | * Interactive Examples:: Examples of how to read interactive arguments. | |
108 | @end menu | |
109 | ||
110 | @node Using Interactive | |
111 | @subsection Using @code{interactive} | |
112 | ||
113 | This section describes how to write the @code{interactive} form that | |
114 | makes a Lisp function an interactively-callable command. | |
115 | ||
116 | @defspec interactive arg-descriptor | |
117 | @cindex argument descriptors | |
118 | This special form declares that the function in which it appears is a | |
119 | command, and that it may therefore be called interactively (via | |
120 | @kbd{M-x} or by entering a key sequence bound to it). The argument | |
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121 | @var{arg-descriptor} declares how to compute the arguments to the |
122 | command when the command is called interactively. | |
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123 | |
124 | A command may be called from Lisp programs like any other function, but | |
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125 | then the caller supplies the arguments and @var{arg-descriptor} has no |
126 | effect. | |
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127 | |
128 | The @code{interactive} form has its effect because the command loop | |
129 | (actually, its subroutine @code{call-interactively}) scans through the | |
130 | function definition looking for it, before calling the function. Once | |
131 | the function is called, all its body forms including the | |
132 | @code{interactive} form are executed, but at this time | |
133 | @code{interactive} simply returns @code{nil} without even evaluating its | |
134 | argument. | |
135 | @end defspec | |
136 | ||
137 | There are three possibilities for the argument @var{arg-descriptor}: | |
138 | ||
139 | @itemize @bullet | |
140 | @item | |
141 | It may be omitted or @code{nil}; then the command is called with no | |
142 | arguments. This leads quickly to an error if the command requires one | |
143 | or more arguments. | |
144 | ||
145 | @item | |
146 | It may be a Lisp expression that is not a string; then it should be a | |
147 | form that is evaluated to get a list of arguments to pass to the | |
148 | command. | |
149 | @cindex argument evaluation form | |
150 | ||
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151 | If this expression reads keyboard input (this includes using the |
152 | minibuffer), keep in mind that the integer value of point or the mark | |
153 | before reading input may be incorrect after reading input. This is | |
154 | because the current buffer may be receiving subprocess output; | |
155 | if subprocess output arrives while the command is waiting for input, | |
156 | it could relocate point and the mark. | |
157 | ||
158 | Here's an example of what @emph{not} to do: | |
159 | ||
160 | @smallexample | |
161 | (interactive | |
162 | (list (region-beginning) (region-end) | |
163 | (read-string "Foo: " nil 'my-history))) | |
164 | @end smallexample | |
165 | ||
166 | @noindent | |
167 | Here's how to avoid the problem, by examining point and the mark only | |
168 | after reading the keyboard input: | |
169 | ||
170 | @smallexample | |
171 | (interactive | |
172 | (let ((string (read-string "Foo: " nil 'my-history))) | |
173 | (list (region-beginning) (region-end) string))) | |
174 | @end smallexample | |
175 | ||
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176 | @item |
177 | @cindex argument prompt | |
178 | It may be a string; then its contents should consist of a code character | |
179 | followed by a prompt (which some code characters use and some ignore). | |
180 | The prompt ends either with the end of the string or with a newline. | |
181 | Here is a simple example: | |
182 | ||
183 | @smallexample | |
184 | (interactive "bFrobnicate buffer: ") | |
185 | @end smallexample | |
186 | ||
187 | @noindent | |
188 | The code letter @samp{b} says to read the name of an existing buffer, | |
189 | with completion. The buffer name is the sole argument passed to the | |
190 | command. The rest of the string is a prompt. | |
191 | ||
192 | If there is a newline character in the string, it terminates the prompt. | |
193 | If the string does not end there, then the rest of the string should | |
194 | contain another code character and prompt, specifying another argument. | |
195 | You can specify any number of arguments in this way. | |
196 | ||
197 | @c Emacs 19 feature | |
198 | The prompt string can use @samp{%} to include previous argument values | |
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199 | (starting with the first argument) in the prompt. This is done using |
200 | @code{format} (@pxref{Formatting Strings}). For example, here is how | |
201 | you could read the name of an existing buffer followed by a new name to | |
202 | give to that buffer: | |
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203 | |
204 | @smallexample | |
205 | @group | |
206 | (interactive "bBuffer to rename: \nsRename buffer %s to: ") | |
207 | @end group | |
208 | @end smallexample | |
209 | ||
210 | @cindex @samp{*} in interactive | |
f142f62a | 211 | @cindex read-only buffers in interactive |
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212 | If the first character in the string is @samp{*}, then an error is |
213 | signaled if the buffer is read-only. | |
214 | ||
215 | @cindex @samp{@@} in interactive | |
216 | @c Emacs 19 feature | |
217 | If the first character in the string is @samp{@@}, and if the key | |
218 | sequence used to invoke the command includes any mouse events, then | |
219 | the window associated with the first of those events is selected | |
220 | before the command is run. | |
221 | ||
222 | You can use @samp{*} and @samp{@@} together; the order does not matter. | |
223 | Actual reading of arguments is controlled by the rest of the prompt | |
224 | string (starting with the first character that is not @samp{*} or | |
225 | @samp{@@}). | |
226 | @end itemize | |
227 | ||
228 | @node Interactive Codes | |
229 | @comment node-name, next, previous, up | |
230 | @subsection Code Characters for @code{interactive} | |
231 | @cindex interactive code description | |
232 | @cindex description for interactive codes | |
233 | @cindex codes, interactive, description of | |
234 | @cindex characters for interactive codes | |
235 | ||
236 | The code character descriptions below contain a number of key words, | |
237 | defined here as follows: | |
238 | ||
239 | @table @b | |
240 | @item Completion | |
241 | @cindex interactive completion | |
242 | Provide completion. @key{TAB}, @key{SPC}, and @key{RET} perform name | |
243 | completion because the argument is read using @code{completing-read} | |
244 | (@pxref{Completion}). @kbd{?} displays a list of possible completions. | |
245 | ||
246 | @item Existing | |
247 | Require the name of an existing object. An invalid name is not | |
248 | accepted; the commands to exit the minibuffer do not exit if the current | |
249 | input is not valid. | |
250 | ||
251 | @item Default | |
252 | @cindex default argument string | |
253 | A default value of some sort is used if the user enters no text in the | |
254 | minibuffer. The default depends on the code character. | |
255 | ||
256 | @item No I/O | |
257 | This code letter computes an argument without reading any input. | |
258 | Therefore, it does not use a prompt string, and any prompt string you | |
259 | supply is ignored. | |
260 | ||
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261 | Even though the code letter doesn't use a prompt string, you must follow |
262 | it with a newline if it is not the last code character in the string. | |
263 | ||
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264 | @item Prompt |
265 | A prompt immediately follows the code character. The prompt ends either | |
266 | with the end of the string or with a newline. | |
267 | ||
268 | @item Special | |
269 | This code character is meaningful only at the beginning of the | |
270 | interactive string, and it does not look for a prompt or a newline. | |
271 | It is a single, isolated character. | |
272 | @end table | |
273 | ||
274 | @cindex reading interactive arguments | |
275 | Here are the code character descriptions for use with @code{interactive}: | |
276 | ||
277 | @table @samp | |
278 | @item * | |
279 | Signal an error if the current buffer is read-only. Special. | |
280 | ||
281 | @item @@ | |
282 | Select the window mentioned in the first mouse event in the key | |
283 | sequence that invoked this command. Special. | |
284 | ||
285 | @item a | |
b22f3a19 | 286 | A function name (i.e., a symbol satisfying @code{fboundp}). Existing, |
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287 | Completion, Prompt. |
288 | ||
289 | @item b | |
290 | The name of an existing buffer. By default, uses the name of the | |
291 | current buffer (@pxref{Buffers}). Existing, Completion, Default, | |
292 | Prompt. | |
293 | ||
294 | @item B | |
295 | A buffer name. The buffer need not exist. By default, uses the name of | |
296 | a recently used buffer other than the current buffer. Completion, | |
b22f3a19 | 297 | Default, Prompt. |
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298 | |
299 | @item c | |
300 | A character. The cursor does not move into the echo area. Prompt. | |
301 | ||
302 | @item C | |
303 | A command name (i.e., a symbol satisfying @code{commandp}). Existing, | |
304 | Completion, Prompt. | |
305 | ||
306 | @item d | |
307 | @cindex position argument | |
f142f62a | 308 | The position of point, as an integer (@pxref{Point}). No I/O. |
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309 | |
310 | @item D | |
311 | A directory name. The default is the current default directory of the | |
312 | current buffer, @code{default-directory} (@pxref{System Environment}). | |
313 | Existing, Completion, Default, Prompt. | |
314 | ||
315 | @item e | |
316 | The first or next mouse event in the key sequence that invoked the command. | |
b22f3a19 | 317 | More precisely, @samp{e} gets events that are lists, so you can look at |
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318 | the data in the lists. @xref{Input Events}. No I/O. |
319 | ||
320 | You can use @samp{e} more than once in a single command's interactive | |
b22f3a19 | 321 | specification. If the key sequence that invoked the command has |
f142f62a | 322 | @var{n} events that are lists, the @var{n}th @samp{e} provides the |
b22f3a19 | 323 | @var{n}th such event. Events that are not lists, such as function keys |
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324 | and @sc{ASCII} characters, do not count where @samp{e} is concerned. |
325 | ||
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326 | @item f |
327 | A file name of an existing file (@pxref{File Names}). The default | |
328 | directory is @code{default-directory}. Existing, Completion, Default, | |
329 | Prompt. | |
330 | ||
331 | @item F | |
332 | A file name. The file need not exist. Completion, Default, Prompt. | |
333 | ||
334 | @item k | |
335 | A key sequence (@pxref{Keymap Terminology}). This keeps reading events | |
336 | until a command (or undefined command) is found in the current key | |
337 | maps. The key sequence argument is represented as a string or vector. | |
338 | The cursor does not move into the echo area. Prompt. | |
339 | ||
340 | This kind of input is used by commands such as @code{describe-key} and | |
341 | @code{global-set-key}. | |
342 | ||
22697dac KH |
343 | @item K |
344 | A key sequence, whose definition you intend to change. This works like | |
345 | @samp{k}, except that it suppresses, for the last input event in the key | |
346 | sequence, the conversions that are normally used (when necessary) to | |
347 | convert an undefined key into a defined one. | |
348 | ||
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349 | @item m |
350 | @cindex marker argument | |
f142f62a | 351 | The position of the mark, as an integer. No I/O. |
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352 | |
353 | @item n | |
354 | A number read with the minibuffer. If the input is not a number, the | |
355 | user is asked to try again. The prefix argument, if any, is not used. | |
356 | Prompt. | |
357 | ||
358 | @item N | |
359 | @cindex raw prefix argument usage | |
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360 | The numeric prefix argument; but if there is no prefix argument, read a |
361 | number as with @kbd{n}. Requires a number. @xref{Prefix Command | |
b22f3a19 | 362 | Arguments}. Prompt. |
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363 | |
364 | @item p | |
365 | @cindex numeric prefix argument usage | |
366 | The numeric prefix argument. (Note that this @samp{p} is lower case.) | |
b22f3a19 | 367 | No I/O. |
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368 | |
369 | @item P | |
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370 | The raw prefix argument. (Note that this @samp{P} is upper case.) No |
371 | I/O. | |
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372 | |
373 | @item r | |
374 | @cindex region argument | |
375 | Point and the mark, as two numeric arguments, smallest first. This is | |
376 | the only code letter that specifies two successive arguments rather than | |
377 | one. No I/O. | |
378 | ||
379 | @item s | |
380 | Arbitrary text, read in the minibuffer and returned as a string | |
381 | (@pxref{Text from Minibuffer}). Terminate the input with either | |
382 | @key{LFD} or @key{RET}. (@kbd{C-q} may be used to include either of | |
383 | these characters in the input.) Prompt. | |
384 | ||
385 | @item S | |
386 | An interned symbol whose name is read in the minibuffer. Any whitespace | |
387 | character terminates the input. (Use @kbd{C-q} to include whitespace in | |
388 | the string.) Other characters that normally terminate a symbol (e.g., | |
389 | parentheses and brackets) do not do so here. Prompt. | |
390 | ||
391 | @item v | |
392 | A variable declared to be a user option (i.e., satisfying the predicate | |
393 | @code{user-variable-p}). @xref{High-Level Completion}. Existing, | |
394 | Completion, Prompt. | |
395 | ||
396 | @item x | |
b22f3a19 | 397 | A Lisp object, specified with its read syntax, terminated with a |
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398 | @key{LFD} or @key{RET}. The object is not evaluated. @xref{Object from |
399 | Minibuffer}. Prompt. | |
400 | ||
401 | @item X | |
402 | @cindex evaluated expression argument | |
403 | A Lisp form is read as with @kbd{x}, but then evaluated so that its | |
404 | value becomes the argument for the command. Prompt. | |
405 | @end table | |
406 | ||
407 | @node Interactive Examples | |
408 | @comment node-name, next, previous, up | |
409 | @subsection Examples of Using @code{interactive} | |
410 | @cindex examples of using @code{interactive} | |
411 | @cindex @code{interactive}, examples of using | |
412 | ||
413 | Here are some examples of @code{interactive}: | |
414 | ||
415 | @example | |
416 | @group | |
417 | (defun foo1 () ; @r{@code{foo1} takes no arguments,} | |
418 | (interactive) ; @r{just moves forward two words.} | |
419 | (forward-word 2)) | |
420 | @result{} foo1 | |
421 | @end group | |
422 | ||
423 | @group | |
424 | (defun foo2 (n) ; @r{@code{foo2} takes one argument,} | |
425 | (interactive "p") ; @r{which is the numeric prefix.} | |
426 | (forward-word (* 2 n))) | |
427 | @result{} foo2 | |
428 | @end group | |
429 | ||
430 | @group | |
431 | (defun foo3 (n) ; @r{@code{foo3} takes one argument,} | |
432 | (interactive "nCount:") ; @r{which is read with the Minibuffer.} | |
433 | (forward-word (* 2 n))) | |
434 | @result{} foo3 | |
435 | @end group | |
436 | ||
437 | @group | |
438 | (defun three-b (b1 b2 b3) | |
439 | "Select three existing buffers. | |
440 | Put them into three windows, selecting the last one." | |
441 | @end group | |
442 | (interactive "bBuffer1:\nbBuffer2:\nbBuffer3:") | |
443 | (delete-other-windows) | |
444 | (split-window (selected-window) 8) | |
445 | (switch-to-buffer b1) | |
446 | (other-window 1) | |
447 | (split-window (selected-window) 8) | |
448 | (switch-to-buffer b2) | |
449 | (other-window 1) | |
450 | (switch-to-buffer b3)) | |
451 | @result{} three-b | |
452 | @group | |
453 | (three-b "*scratch*" "declarations.texi" "*mail*") | |
454 | @result{} nil | |
455 | @end group | |
456 | @end example | |
457 | ||
458 | @node Interactive Call | |
459 | @section Interactive Call | |
460 | @cindex interactive call | |
461 | ||
462 | After the command loop has translated a key sequence into a | |
463 | definition, it invokes that definition using the function | |
464 | @code{command-execute}. If the definition is a function that is a | |
465 | command, @code{command-execute} calls @code{call-interactively}, which | |
466 | reads the arguments and calls the command. You can also call these | |
467 | functions yourself. | |
468 | ||
469 | @defun commandp object | |
470 | Returns @code{t} if @var{object} is suitable for calling interactively; | |
471 | that is, if @var{object} is a command. Otherwise, returns @code{nil}. | |
472 | ||
473 | The interactively callable objects include strings and vectors (treated | |
474 | as keyboard macros), lambda expressions that contain a top-level call to | |
bfe721d1 | 475 | @code{interactive}, byte-code function objects made from such lambda |
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476 | expressions, autoload objects that are declared as interactive |
477 | (non-@code{nil} fourth argument to @code{autoload}), and some of the | |
478 | primitive functions. | |
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479 | |
480 | A symbol is @code{commandp} if its function definition is | |
481 | @code{commandp}. | |
482 | ||
483 | Keys and keymaps are not commands. Rather, they are used to look up | |
484 | commands (@pxref{Keymaps}). | |
485 | ||
486 | See @code{documentation} in @ref{Accessing Documentation}, for a | |
487 | realistic example of using @code{commandp}. | |
488 | @end defun | |
489 | ||
490 | @defun call-interactively command &optional record-flag | |
491 | This function calls the interactively callable function @var{command}, | |
492 | reading arguments according to its interactive calling specifications. | |
b22f3a19 RS |
493 | An error is signaled if @var{command} is not a function or if it cannot |
494 | be called interactively (i.e., is not a command). Note that keyboard | |
495 | macros (strings and vectors) are not accepted, even though they are | |
496 | considered commands, because they are not functions. | |
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497 | |
498 | @cindex record command history | |
499 | If @var{record-flag} is non-@code{nil}, then this command and its | |
500 | arguments are unconditionally added to the list @code{command-history}. | |
501 | Otherwise, the command is added only if it uses the minibuffer to read | |
502 | an argument. @xref{Command History}. | |
503 | @end defun | |
504 | ||
505 | @defun command-execute command &optional record-flag | |
506 | @cindex keyboard macro execution | |
507 | This function executes @var{command} as an editing command. The | |
508 | argument @var{command} must satisfy the @code{commandp} predicate; i.e., | |
f142f62a | 509 | it must be an interactively callable function or a keyboard macro. |
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510 | |
511 | A string or vector as @var{command} is executed with | |
512 | @code{execute-kbd-macro}. A function is passed to | |
513 | @code{call-interactively}, along with the optional @var{record-flag}. | |
514 | ||
515 | A symbol is handled by using its function definition in its place. A | |
516 | symbol with an @code{autoload} definition counts as a command if it was | |
517 | declared to stand for an interactively callable function. Such a | |
518 | definition is handled by loading the specified library and then | |
519 | rechecking the definition of the symbol. | |
520 | @end defun | |
521 | ||
522 | @deffn Command execute-extended-command prefix-argument | |
523 | @cindex read command name | |
524 | This function reads a command name from the minibuffer using | |
525 | @code{completing-read} (@pxref{Completion}). Then it uses | |
526 | @code{command-execute} to call the specified command. Whatever that | |
527 | command returns becomes the value of @code{execute-extended-command}. | |
528 | ||
529 | @cindex execute with prefix argument | |
f142f62a RS |
530 | If the command asks for a prefix argument, it receives the value |
531 | @var{prefix-argument}. If @code{execute-extended-command} is called | |
532 | interactively, the current raw prefix argument is used for | |
8db970a4 RS |
533 | @var{prefix-argument}, and thus passed on to whatever command is run. |
534 | ||
535 | @c !!! Should this be @kindex? | |
536 | @cindex @kbd{M-x} | |
537 | @code{execute-extended-command} is the normal definition of @kbd{M-x}, | |
538 | so it uses the string @w{@samp{M-x }} as a prompt. (It would be better | |
539 | to take the prompt from the events used to invoke | |
540 | @code{execute-extended-command}, but that is painful to implement.) A | |
541 | description of the value of the prefix argument, if any, also becomes | |
542 | part of the prompt. | |
543 | ||
544 | @example | |
545 | @group | |
546 | (execute-extended-command 1) | |
547 | ---------- Buffer: Minibuffer ---------- | |
b22f3a19 | 548 | 1 M-x forward-word RET |
8db970a4 RS |
549 | ---------- Buffer: Minibuffer ---------- |
550 | @result{} t | |
551 | @end group | |
552 | @end example | |
553 | @end deffn | |
554 | ||
555 | @defun interactive-p | |
9e2b495b RS |
556 | This function returns @code{t} if the containing function (the one whose |
557 | code includes the call to @code{interactive-p}) was called | |
558 | interactively, with the function @code{call-interactively}. (It makes | |
559 | no difference whether @code{call-interactively} was called from Lisp or | |
560 | directly from the editor command loop.) If the containing function was | |
561 | called by Lisp evaluation (or with @code{apply} or @code{funcall}), then | |
562 | it was not called interactively. | |
8db970a4 | 563 | |
f142f62a | 564 | The most common use of @code{interactive-p} is for deciding whether to |
8db970a4 RS |
565 | print an informative message. As a special exception, |
566 | @code{interactive-p} returns @code{nil} whenever a keyboard macro is | |
567 | being run. This is to suppress the informative messages and speed | |
568 | execution of the macro. | |
569 | ||
570 | For example: | |
571 | ||
572 | @example | |
573 | @group | |
574 | (defun foo () | |
575 | (interactive) | |
576 | (and (interactive-p) | |
577 | (message "foo"))) | |
578 | @result{} foo | |
579 | @end group | |
580 | ||
581 | @group | |
582 | (defun bar () | |
583 | (interactive) | |
584 | (setq foobar (list (foo) (interactive-p)))) | |
585 | @result{} bar | |
586 | @end group | |
587 | ||
588 | @group | |
589 | ;; @r{Type @kbd{M-x foo}.} | |
590 | @print{} foo | |
591 | @end group | |
592 | ||
593 | @group | |
594 | ;; @r{Type @kbd{M-x bar}.} | |
595 | ;; @r{This does not print anything.} | |
596 | @end group | |
597 | ||
598 | @group | |
599 | foobar | |
600 | @result{} (nil t) | |
601 | @end group | |
602 | @end example | |
603 | @end defun | |
604 | ||
605 | @node Command Loop Info | |
606 | @comment node-name, next, previous, up | |
607 | @section Information from the Command Loop | |
608 | ||
609 | The editor command loop sets several Lisp variables to keep status | |
610 | records for itself and for commands that are run. | |
611 | ||
612 | @defvar last-command | |
613 | This variable records the name of the previous command executed by the | |
614 | command loop (the one before the current command). Normally the value | |
615 | is a symbol with a function definition, but this is not guaranteed. | |
616 | ||
f142f62a RS |
617 | The value is copied from @code{this-command} when a command returns to |
618 | the command loop, except when the command specifies a prefix argument | |
619 | for the following command. | |
bfe721d1 KH |
620 | |
621 | This variable is always local to the current terminal and cannot be | |
622 | buffer-local. @xref{Multiple Displays}. | |
8db970a4 RS |
623 | @end defvar |
624 | ||
625 | @defvar this-command | |
626 | @cindex current command | |
627 | This variable records the name of the command now being executed by | |
628 | the editor command loop. Like @code{last-command}, it is normally a symbol | |
629 | with a function definition. | |
630 | ||
f142f62a RS |
631 | The command loop sets this variable just before running a command, and |
632 | copies its value into @code{last-command} when the command finishes | |
633 | (unless the command specifies a prefix argument for the following | |
634 | command). | |
8db970a4 RS |
635 | |
636 | @cindex kill command repetition | |
f142f62a | 637 | Some commands set this variable during their execution, as a flag for |
bfe721d1 | 638 | whatever command runs next. In particular, the functions for killing text |
f142f62a RS |
639 | set @code{this-command} to @code{kill-region} so that any kill commands |
640 | immediately following will know to append the killed text to the | |
641 | previous kill. | |
8db970a4 RS |
642 | @end defvar |
643 | ||
644 | If you do not want a particular command to be recognized as the previous | |
645 | command in the case where it got an error, you must code that command to | |
646 | prevent this. One way is to set @code{this-command} to @code{t} at the | |
647 | beginning of the command, and set @code{this-command} back to its proper | |
648 | value at the end, like this: | |
649 | ||
650 | @example | |
651 | (defun foo (args@dots{}) | |
652 | (interactive @dots{}) | |
653 | (let ((old-this-command this-command)) | |
654 | (setq this-command t) | |
655 | @r{@dots{}do the work@dots{}} | |
656 | (setq this-command old-this-command))) | |
657 | @end example | |
658 | ||
659 | @defun this-command-keys | |
660 | This function returns a string or vector containing the key sequence | |
661 | that invoked the present command, plus any previous commands that | |
662 | generated the prefix argument for this command. The value is a string | |
663 | if all those events were characters. @xref{Input Events}. | |
664 | ||
665 | @example | |
666 | @group | |
667 | (this-command-keys) | |
b22f3a19 | 668 | ;; @r{Now use @kbd{C-u C-x C-e} to evaluate that.} |
8db970a4 RS |
669 | @result{} "^U^X^E" |
670 | @end group | |
671 | @end example | |
672 | @end defun | |
673 | ||
674 | @defvar last-nonmenu-event | |
675 | This variable holds the last input event read as part of a key | |
f142f62a | 676 | sequence, not counting events resulting from mouse menus. |
8db970a4 RS |
677 | |
678 | One use of this variable is to figure out a good default location to | |
679 | pop up another menu. | |
680 | @end defvar | |
681 | ||
682 | @defvar last-command-event | |
683 | @defvarx last-command-char | |
684 | This variable is set to the last input event that was read by the | |
685 | command loop as part of a command. The principal use of this variable | |
686 | is in @code{self-insert-command}, which uses it to decide which | |
687 | character to insert. | |
688 | ||
689 | @example | |
690 | @group | |
f142f62a | 691 | last-command-event |
b22f3a19 | 692 | ;; @r{Now use @kbd{C-u C-x C-e} to evaluate that.} |
8db970a4 RS |
693 | @result{} 5 |
694 | @end group | |
695 | @end example | |
696 | ||
697 | @noindent | |
698 | The value is 5 because that is the @sc{ASCII} code for @kbd{C-e}. | |
699 | ||
700 | The alias @code{last-command-char} exists for compatibility with | |
701 | Emacs version 18. | |
702 | @end defvar | |
703 | ||
704 | @c Emacs 19 feature | |
705 | @defvar last-event-frame | |
706 | This variable records which frame the last input event was directed to. | |
707 | Usually this is the frame that was selected when the event was | |
708 | generated, but if that frame has redirected input focus to another | |
709 | frame, the value is the frame to which the event was redirected. | |
710 | @xref{Input Focus}. | |
711 | @end defvar | |
712 | ||
8db970a4 RS |
713 | @node Input Events |
714 | @section Input Events | |
715 | @cindex events | |
716 | @cindex input events | |
717 | ||
718 | The Emacs command loop reads a sequence of @dfn{input events} that | |
719 | represent keyboard or mouse activity. The events for keyboard activity | |
720 | are characters or symbols; mouse events are always lists. This section | |
721 | describes the representation and meaning of input events in detail. | |
722 | ||
8db970a4 | 723 | @defun eventp object |
d473987a | 724 | This function returns non-@code{nil} if @var{object} is an input event. |
8db970a4 RS |
725 | @end defun |
726 | ||
727 | @menu | |
728 | * Keyboard Events:: Ordinary characters--keys with symbols on them. | |
729 | * Function Keys:: Function keys--keys with names, not symbols. | |
f142f62a | 730 | * Mouse Events:: Overview of mouse events. |
8db970a4 RS |
731 | * Click Events:: Pushing and releasing a mouse button. |
732 | * Drag Events:: Moving the mouse before releasing the button. | |
733 | * Button-Down Events:: A button was pushed and not yet released. | |
734 | * Repeat Events:: Double and triple click (or drag, or down). | |
735 | * Motion Events:: Just moving the mouse, not pushing a button. | |
736 | * Focus Events:: Moving the mouse between frames. | |
22697dac | 737 | * Misc Events:: Other events window systems can generate. |
8db970a4 RS |
738 | * Event Examples:: Examples of the lists for mouse events. |
739 | * Classifying Events:: Finding the modifier keys in an event symbol. | |
740 | Event types. | |
741 | * Accessing Events:: Functions to extract info from events. | |
742 | * Strings of Events:: Special considerations for putting | |
743 | keyboard character events in a string. | |
744 | @end menu | |
745 | ||
746 | @node Keyboard Events | |
747 | @subsection Keyboard Events | |
748 | ||
749 | There are two kinds of input you can get from the keyboard: ordinary | |
750 | keys, and function keys. Ordinary keys correspond to characters; the | |
751 | events they generate are represented in Lisp as characters. In Emacs | |
f142f62a RS |
752 | versions 18 and earlier, characters were the only events. The event |
753 | type of a character event is the character itself (an integer); | |
754 | see @ref{Classifying Events}. | |
8db970a4 RS |
755 | |
756 | @cindex modifier bits (of input character) | |
757 | @cindex basic code (of input character) | |
758 | An input character event consists of a @dfn{basic code} between 0 and | |
759 | 255, plus any or all of these @dfn{modifier bits}: | |
760 | ||
761 | @table @asis | |
762 | @item meta | |
bfe721d1 KH |
763 | The |
764 | @iftex | |
765 | $2^{27}$ | |
766 | @end iftex | |
767 | @ifinfo | |
768 | 2**27 | |
769 | @end ifinfo | |
770 | bit in the character code indicates a character | |
8db970a4 RS |
771 | typed with the meta key held down. |
772 | ||
773 | @item control | |
bfe721d1 KH |
774 | The |
775 | @iftex | |
776 | $2^{26}$ | |
777 | @end iftex | |
778 | @ifinfo | |
779 | 2**26 | |
780 | @end ifinfo | |
781 | bit in the character code indicates a non-@sc{ASCII} | |
8db970a4 RS |
782 | control character. |
783 | ||
784 | @sc{ASCII} control characters such as @kbd{C-a} have special basic | |
785 | codes of their own, so Emacs needs no special bit to indicate them. | |
786 | Thus, the code for @kbd{C-a} is just 1. | |
787 | ||
788 | But if you type a control combination not in @sc{ASCII}, such as | |
789 | @kbd{%} with the control key, the numeric value you get is the code | |
bfe721d1 KH |
790 | for @kbd{%} plus |
791 | @iftex | |
792 | $2^{26}$ | |
793 | @end iftex | |
794 | @ifinfo | |
795 | 2**26 | |
796 | @end ifinfo | |
797 | (assuming the terminal supports non-@sc{ASCII} | |
8db970a4 RS |
798 | control characters). |
799 | ||
800 | @item shift | |
bfe721d1 KH |
801 | The |
802 | @iftex | |
803 | $2^{25}$ | |
804 | @end iftex | |
805 | @ifinfo | |
806 | 2**25 | |
807 | @end ifinfo | |
808 | bit in the character code indicates an @sc{ASCII} control | |
8db970a4 RS |
809 | character typed with the shift key held down. |
810 | ||
811 | For letters, the basic code indicates upper versus lower case; for | |
812 | digits and punctuation, the shift key selects an entirely different | |
813 | character with a different basic code. In order to keep within | |
814 | the @sc{ASCII} character set whenever possible, Emacs avoids using | |
bfe721d1 KH |
815 | the |
816 | @iftex | |
817 | $2^{25}$ | |
818 | @end iftex | |
819 | @ifinfo | |
820 | 2**25 | |
821 | @end ifinfo | |
822 | bit for those characters. | |
8db970a4 RS |
823 | |
824 | However, @sc{ASCII} provides no way to distinguish @kbd{C-A} from | |
bfe721d1 KH |
825 | @kbd{C-a}, so Emacs uses the |
826 | @iftex | |
827 | $2^{25}$ | |
828 | @end iftex | |
829 | @ifinfo | |
830 | 2**25 | |
831 | @end ifinfo | |
832 | bit in @kbd{C-A} and not in | |
8db970a4 RS |
833 | @kbd{C-a}. |
834 | ||
835 | @item hyper | |
bfe721d1 KH |
836 | The |
837 | @iftex | |
838 | $2^{24}$ | |
839 | @end iftex | |
840 | @ifinfo | |
841 | 2**24 | |
842 | @end ifinfo | |
843 | bit in the character code indicates a character | |
8db970a4 RS |
844 | typed with the hyper key held down. |
845 | ||
846 | @item super | |
bfe721d1 KH |
847 | The |
848 | @iftex | |
849 | $2^{23}$ | |
850 | @end iftex | |
851 | @ifinfo | |
852 | 2**23 | |
853 | @end ifinfo | |
854 | bit in the character code indicates a character | |
8db970a4 RS |
855 | typed with the super key held down. |
856 | ||
857 | @item alt | |
bfe721d1 KH |
858 | The |
859 | @iftex | |
860 | $2^{22}$ | |
861 | @end iftex | |
862 | @ifinfo | |
863 | 2**22 | |
864 | @end ifinfo | |
865 | bit in the character code indicates a character typed with | |
8db970a4 RS |
866 | the alt key held down. (On some terminals, the key labeled @key{ALT} |
867 | is actually the meta key.) | |
868 | @end table | |
869 | ||
bfe721d1 KH |
870 | It is best to avoid mentioning specific bit numbers in your program. |
871 | To test the modifier bits of a character, use the function | |
872 | @code{event-modifiers} (@pxref{Classifying Events}). When making key | |
873 | bindings, you can use the read syntax for characters with modifier bits | |
874 | (@samp{\C-}, @samp{\M-}, and so on). For making key bindings with | |
875 | @code{define-key}, you can use lists such as @code{(control hyper ?x)} to | |
876 | specify the characters (@pxref{Changing Key Bindings}). The function | |
877 | @code{event-convert-list} converts such a list into an event type | |
878 | (@pxref{Classifying Events}). | |
8db970a4 RS |
879 | |
880 | @node Function Keys | |
881 | @subsection Function Keys | |
882 | ||
883 | @cindex function keys | |
b22f3a19 | 884 | Most keyboards also have @dfn{function keys}---keys that have names or |
8db970a4 | 885 | symbols that are not characters. Function keys are represented in Lisp |
f142f62a RS |
886 | as symbols; the symbol's name is the function key's label, in lower |
887 | case. For example, pressing a key labeled @key{F1} places the symbol | |
888 | @code{f1} in the input stream. | |
8db970a4 | 889 | |
f142f62a RS |
890 | The event type of a function key event is the event symbol itself. |
891 | @xref{Classifying Events}. | |
8db970a4 | 892 | |
b22f3a19 | 893 | Here are a few special cases in the symbol-naming convention for |
8db970a4 RS |
894 | function keys: |
895 | ||
896 | @table @asis | |
897 | @item @code{backspace}, @code{tab}, @code{newline}, @code{return}, @code{delete} | |
898 | These keys correspond to common @sc{ASCII} control characters that have | |
899 | special keys on most keyboards. | |
900 | ||
f142f62a RS |
901 | In @sc{ASCII}, @kbd{C-i} and @key{TAB} are the same character. If the |
902 | terminal can distinguish between them, Emacs conveys the distinction to | |
903 | Lisp programs by representing the former as the integer 9, and the | |
904 | latter as the symbol @code{tab}. | |
8db970a4 RS |
905 | |
906 | Most of the time, it's not useful to distinguish the two. So normally | |
4324b7ab RS |
907 | @code{function-key-map} (@pxref{Translating Input}) is set up to map |
908 | @code{tab} into 9. Thus, a key binding for character code 9 (the | |
909 | character @kbd{C-i}) also applies to @code{tab}. Likewise for the other | |
910 | symbols in this group. The function @code{read-char} likewise converts | |
911 | these events into characters. | |
8db970a4 RS |
912 | |
913 | In @sc{ASCII}, @key{BS} is really @kbd{C-h}. But @code{backspace} | |
914 | converts into the character code 127 (@key{DEL}), not into code 8 | |
915 | (@key{BS}). This is what most users prefer. | |
916 | ||
b22f3a19 RS |
917 | @item @code{left}, @code{up}, @code{right}, @code{down} |
918 | Cursor arrow keys | |
8db970a4 RS |
919 | @item @code{kp-add}, @code{kp-decimal}, @code{kp-divide}, @dots{} |
920 | Keypad keys (to the right of the regular keyboard). | |
921 | @item @code{kp-0}, @code{kp-1}, @dots{} | |
922 | Keypad keys with digits. | |
923 | @item @code{kp-f1}, @code{kp-f2}, @code{kp-f3}, @code{kp-f4} | |
924 | Keypad PF keys. | |
b22f3a19 RS |
925 | @item @code{kp-home}, @code{kp-left}, @code{kp-up}, @code{kp-right}, @code{kp-down} |
926 | Keypad arrow keys. Emacs normally translates these | |
927 | into the non-keypad keys @code{home}, @code{left}, @dots{} | |
928 | @item @code{kp-prior}, @code{kp-next}, @code{kp-end}, @code{kp-begin}, @code{kp-insert}, @code{kp-delete} | |
929 | Additional keypad duplicates of keys ordinarily found elsewhere. Emacs | |
930 | normally translates these into the like-named non-keypad keys. | |
8db970a4 RS |
931 | @end table |
932 | ||
b22f3a19 RS |
933 | You can use the modifier keys @key{ALT}, @key{CTRL}, @key{HYPER}, |
934 | @key{META}, @key{SHIFT}, and @key{SUPER} with function keys. The way to | |
935 | represent them is with prefixes in the symbol name: | |
8db970a4 RS |
936 | |
937 | @table @samp | |
938 | @item A- | |
939 | The alt modifier. | |
940 | @item C- | |
941 | The control modifier. | |
942 | @item H- | |
943 | The hyper modifier. | |
944 | @item M- | |
945 | The meta modifier. | |
946 | @item S- | |
947 | The shift modifier. | |
948 | @item s- | |
949 | The super modifier. | |
950 | @end table | |
951 | ||
952 | Thus, the symbol for the key @key{F3} with @key{META} held down is | |
8609b2e2 | 953 | @code{M-f3}. When you use more than one prefix, we recommend you |
f142f62a RS |
954 | write them in alphabetical order; but the order does not matter in |
955 | arguments to the key-binding lookup and modification functions. | |
956 | ||
957 | @node Mouse Events | |
958 | @subsection Mouse Events | |
959 | ||
960 | Emacs supports four kinds of mouse events: click events, drag events, | |
961 | button-down events, and motion events. All mouse events are represented | |
962 | as lists. The @sc{car} of the list is the event type; this says which | |
963 | mouse button was involved, and which modifier keys were used with it. | |
964 | The event type can also distinguish double or triple button presses | |
965 | (@pxref{Repeat Events}). The rest of the list elements give position | |
966 | and time information. | |
967 | ||
968 | For key lookup, only the event type matters: two events of the same type | |
969 | necessarily run the same command. The command can access the full | |
970 | values of these events using the @samp{e} interactive code. | |
971 | @xref{Interactive Codes}. | |
972 | ||
973 | A key sequence that starts with a mouse event is read using the keymaps | |
974 | of the buffer in the window that the mouse was in, not the current | |
975 | buffer. This does not imply that clicking in a window selects that | |
976 | window or its buffer---that is entirely under the control of the command | |
977 | binding of the key sequence. | |
8db970a4 RS |
978 | |
979 | @node Click Events | |
980 | @subsection Click Events | |
981 | @cindex click event | |
982 | @cindex mouse click event | |
983 | ||
984 | When the user presses a mouse button and releases it at the same | |
985 | location, that generates a @dfn{click} event. Mouse click events have | |
986 | this form: | |
987 | ||
988 | @example | |
989 | (@var{event-type} | |
f142f62a | 990 | (@var{window} @var{buffer-pos} (@var{x} . @var{y}) @var{timestamp}) |
8db970a4 RS |
991 | @var{click-count}) |
992 | @end example | |
993 | ||
994 | Here is what the elements normally mean: | |
995 | ||
f142f62a RS |
996 | @table @asis |
997 | @item @var{event-type} | |
8db970a4 RS |
998 | This is a symbol that indicates which mouse button was used. It is |
999 | one of the symbols @code{mouse-1}, @code{mouse-2}, @dots{}, where the | |
f142f62a | 1000 | buttons are numbered left to right. |
8db970a4 RS |
1001 | |
1002 | You can also use prefixes @samp{A-}, @samp{C-}, @samp{H-}, @samp{M-}, | |
1003 | @samp{S-} and @samp{s-} for modifiers alt, control, hyper, meta, shift | |
1004 | and super, just as you would with function keys. | |
1005 | ||
1006 | This symbol also serves as the event type of the event. Key bindings | |
1007 | describe events by their types; thus, if there is a key binding for | |
1008 | @code{mouse-1}, that binding would apply to all events whose | |
1009 | @var{event-type} is @code{mouse-1}. | |
1010 | ||
f142f62a | 1011 | @item @var{window} |
8db970a4 RS |
1012 | This is the window in which the click occurred. |
1013 | ||
f142f62a | 1014 | @item @var{x}, @var{y} |
b22f3a19 RS |
1015 | These are the pixel-denominated coordinates of the click, relative to |
1016 | the top left corner of @var{window}, which is @code{(0 . 0)}. | |
8db970a4 | 1017 | |
f142f62a | 1018 | @item @var{buffer-pos} |
8db970a4 RS |
1019 | This is the buffer position of the character clicked on. |
1020 | ||
f142f62a | 1021 | @item @var{timestamp} |
8db970a4 RS |
1022 | This is the time at which the event occurred, in milliseconds. (Since |
1023 | this value wraps around the entire range of Emacs Lisp integers in about | |
1024 | five hours, it is useful only for relating the times of nearby events.) | |
1025 | ||
f142f62a | 1026 | @item @var{click-count} |
8db970a4 RS |
1027 | This is the number of rapid repeated presses so far of the same mouse |
1028 | button. @xref{Repeat Events}. | |
1029 | @end table | |
1030 | ||
f142f62a RS |
1031 | The meanings of @var{buffer-pos}, @var{x} and @var{y} are somewhat |
1032 | different when the event location is in a special part of the screen, | |
1033 | such as the mode line or a scroll bar. | |
8db970a4 RS |
1034 | |
1035 | If the location is in a scroll bar, then @var{buffer-pos} is the symbol | |
1036 | @code{vertical-scroll-bar} or @code{horizontal-scroll-bar}, and the pair | |
1037 | @code{(@var{x} . @var{y})} is replaced with a pair @code{(@var{portion} | |
1038 | . @var{whole})}, where @var{portion} is the distance of the click from | |
1039 | the top or left end of the scroll bar, and @var{whole} is the length of | |
1040 | the entire scroll bar. | |
1041 | ||
1042 | If the position is on a mode line or the vertical line separating | |
1043 | @var{window} from its neighbor to the right, then @var{buffer-pos} is | |
1044 | the symbol @code{mode-line} or @code{vertical-line}. For the mode line, | |
f142f62a RS |
1045 | @var{y} does not have meaningful data. For the vertical line, @var{x} |
1046 | does not have meaningful data. | |
8db970a4 | 1047 | |
b22f3a19 RS |
1048 | In one special case, @var{buffer-pos} is a list containing a symbol (one |
1049 | of the symbols listed above) instead of just the symbol. This happens | |
1050 | after the imaginary prefix keys for the event are inserted into the | |
1051 | input stream. @xref{Key Sequence Input}. | |
8db970a4 RS |
1052 | |
1053 | @node Drag Events | |
1054 | @subsection Drag Events | |
1055 | @cindex drag event | |
1056 | @cindex mouse drag event | |
1057 | ||
1058 | With Emacs, you can have a drag event without even changing your | |
1059 | clothes. A @dfn{drag event} happens every time the user presses a mouse | |
1060 | button and then moves the mouse to a different character position before | |
1061 | releasing the button. Like all mouse events, drag events are | |
1062 | represented in Lisp as lists. The lists record both the starting mouse | |
1063 | position and the final position, like this: | |
1064 | ||
1065 | @example | |
1066 | (@var{event-type} | |
f142f62a RS |
1067 | (@var{window1} @var{buffer-pos1} (@var{x1} . @var{y1}) @var{timestamp1}) |
1068 | (@var{window2} @var{buffer-pos2} (@var{x2} . @var{y2}) @var{timestamp2}) | |
8db970a4 RS |
1069 | @var{click-count}) |
1070 | @end example | |
1071 | ||
1072 | For a drag event, the name of the symbol @var{event-type} contains the | |
1073 | prefix @samp{drag-}. The second and third elements of the event give | |
1074 | the starting and ending position of the drag. Aside from that, the data | |
1075 | have the same meanings as in a click event (@pxref{Click Events}). You | |
1076 | can access the second element of any mouse event in the same way, with | |
1077 | no need to distinguish drag events from others. | |
1078 | ||
1079 | The @samp{drag-} prefix follows the modifier key prefixes such as | |
1080 | @samp{C-} and @samp{M-}. | |
1081 | ||
b22f3a19 | 1082 | If @code{read-key-sequence} receives a drag event that has no key |
8db970a4 RS |
1083 | binding, and the corresponding click event does have a binding, it |
1084 | changes the drag event into a click event at the drag's starting | |
1085 | position. This means that you don't have to distinguish between click | |
1086 | and drag events unless you want to. | |
1087 | ||
1088 | @node Button-Down Events | |
1089 | @subsection Button-Down Events | |
1090 | @cindex button-down event | |
1091 | ||
1092 | Click and drag events happen when the user releases a mouse button. | |
1093 | They cannot happen earlier, because there is no way to distinguish a | |
1094 | click from a drag until the button is released. | |
1095 | ||
1096 | If you want to take action as soon as a button is pressed, you need to | |
1097 | handle @dfn{button-down} events.@footnote{Button-down is the | |
f142f62a | 1098 | conservative antithesis of drag.} These occur as soon as a button is |
b22f3a19 | 1099 | pressed. They are represented by lists that look exactly like click |
f142f62a RS |
1100 | events (@pxref{Click Events}), except that the @var{event-type} symbol |
1101 | name contains the prefix @samp{down-}. The @samp{down-} prefix follows | |
8db970a4 RS |
1102 | modifier key prefixes such as @samp{C-} and @samp{M-}. |
1103 | ||
b22f3a19 RS |
1104 | The function @code{read-key-sequence}, and therefore the Emacs command |
1105 | loop as well, ignore any button-down events that don't have command | |
1106 | bindings. This means that you need not worry about defining button-down | |
1107 | events unless you want them to do something. The usual reason to define | |
1108 | a button-down event is so that you can track mouse motion (by reading | |
1109 | motion events) until the button is released. @xref{Motion Events}. | |
8db970a4 RS |
1110 | |
1111 | @node Repeat Events | |
1112 | @subsection Repeat Events | |
1113 | @cindex repeat events | |
1114 | @cindex double-click events | |
1115 | @cindex triple-click events | |
1116 | ||
1117 | If you press the same mouse button more than once in quick succession | |
f142f62a RS |
1118 | without moving the mouse, Emacs generates special @dfn{repeat} mouse |
1119 | events for the second and subsequent presses. | |
8db970a4 RS |
1120 | |
1121 | The most common repeat events are @dfn{double-click} events. Emacs | |
1122 | generates a double-click event when you click a button twice; the event | |
1123 | happens when you release the button (as is normal for all click | |
1124 | events). | |
1125 | ||
1126 | The event type of a double-click event contains the prefix | |
f142f62a | 1127 | @samp{double-}. Thus, a double click on the second mouse button with |
8db970a4 RS |
1128 | @key{meta} held down comes to the Lisp program as |
1129 | @code{M-double-mouse-2}. If a double-click event has no binding, the | |
1130 | binding of the corresponding ordinary click event is used to execute | |
1131 | it. Thus, you need not pay attention to the double click feature | |
1132 | unless you really want to. | |
1133 | ||
1134 | When the user performs a double click, Emacs generates first an ordinary | |
f142f62a RS |
1135 | click event, and then a double-click event. Therefore, you must design |
1136 | the command binding of the double click event to assume that the | |
8db970a4 RS |
1137 | single-click command has already run. It must produce the desired |
1138 | results of a double click, starting from the results of a single click. | |
1139 | ||
f142f62a RS |
1140 | This is convenient, if the meaning of a double click somehow ``builds |
1141 | on'' the meaning of a single click---which is recommended user interface | |
1142 | design practice for double clicks. | |
8db970a4 RS |
1143 | |
1144 | If you click a button, then press it down again and start moving the | |
1145 | mouse with the button held down, then you get a @dfn{double-drag} event | |
1146 | when you ultimately release the button. Its event type contains | |
1147 | @samp{double-drag} instead of just @samp{drag}. If a double-drag event | |
1148 | has no binding, Emacs looks for an alternate binding as if the event | |
b22f3a19 | 1149 | were an ordinary drag. |
8db970a4 RS |
1150 | |
1151 | Before the double-click or double-drag event, Emacs generates a | |
f142f62a RS |
1152 | @dfn{double-down} event when the user presses the button down for the |
1153 | second time. Its event type contains @samp{double-down} instead of just | |
8db970a4 RS |
1154 | @samp{down}. If a double-down event has no binding, Emacs looks for an |
1155 | alternate binding as if the event were an ordinary button-down event. | |
f142f62a RS |
1156 | If it finds no binding that way either, the double-down event is |
1157 | ignored. | |
8db970a4 RS |
1158 | |
1159 | To summarize, when you click a button and then press it again right | |
b22f3a19 RS |
1160 | away, Emacs generates a down event and a click event for the first |
1161 | click, a double-down event when you press the button again, and finally | |
1162 | either a double-click or a double-drag event. | |
8db970a4 RS |
1163 | |
1164 | If you click a button twice and then press it again, all in quick | |
1165 | succession, Emacs generates a @dfn{triple-down} event, followed by | |
1166 | either a @dfn{triple-click} or a @dfn{triple-drag}. The event types of | |
1167 | these events contain @samp{triple} instead of @samp{double}. If any | |
1168 | triple event has no binding, Emacs uses the binding that it would use | |
1169 | for the corresponding double event. | |
1170 | ||
f142f62a RS |
1171 | If you click a button three or more times and then press it again, the |
1172 | events for the presses beyond the third are all triple events. Emacs | |
1173 | does not have separate event types for quadruple, quintuple, etc.@: | |
1174 | events. However, you can look at the event list to find out precisely | |
1175 | how many times the button was pressed. | |
8db970a4 RS |
1176 | |
1177 | @defun event-click-count event | |
1178 | This function returns the number of consecutive button presses that led | |
1179 | up to @var{event}. If @var{event} is a double-down, double-click or | |
1180 | double-drag event, the value is 2. If @var{event} is a triple event, | |
1181 | the value is 3 or greater. If @var{event} is an ordinary mouse event | |
1182 | (not a repeat event), the value is 1. | |
1183 | @end defun | |
1184 | ||
1185 | @defvar double-click-time | |
f142f62a RS |
1186 | To generate repeat events, successive mouse button presses must be at |
1187 | the same screen position, and the number of milliseconds between | |
1188 | successive button presses must be less than the value of | |
8db970a4 RS |
1189 | @code{double-click-time}. Setting @code{double-click-time} to |
1190 | @code{nil} disables multi-click detection entirely. Setting it to | |
1191 | @code{t} removes the time limit; Emacs then detects multi-clicks by | |
1192 | position only. | |
1193 | @end defvar | |
1194 | ||
1195 | @node Motion Events | |
1196 | @subsection Motion Events | |
1197 | @cindex motion event | |
1198 | @cindex mouse motion events | |
1199 | ||
1200 | Emacs sometimes generates @dfn{mouse motion} events to describe motion | |
1201 | of the mouse without any button activity. Mouse motion events are | |
1202 | represented by lists that look like this: | |
1203 | ||
1204 | @example | |
1205 | (mouse-movement | |
f142f62a | 1206 | (@var{window} @var{buffer-pos} (@var{x} . @var{y}) @var{timestamp})) |
8db970a4 RS |
1207 | @end example |
1208 | ||
1209 | The second element of the list describes the current position of the | |
1210 | mouse, just as in a click event (@pxref{Click Events}). | |
1211 | ||
1212 | The special form @code{track-mouse} enables generation of motion events | |
1213 | within its body. Outside of @code{track-mouse} forms, Emacs does not | |
1214 | generate events for mere motion of the mouse, and these events do not | |
1215 | appear. | |
1216 | ||
1217 | @defspec track-mouse body@dots{} | |
1218 | This special form executes @var{body}, with generation of mouse motion | |
1219 | events enabled. Typically @var{body} would use @code{read-event} | |
1220 | to read the motion events and modify the display accordingly. | |
1221 | ||
1222 | When the user releases the button, that generates a click event. | |
f142f62a RS |
1223 | Typically, @var{body} should return when it sees the click event, and |
1224 | discard that event. | |
8db970a4 RS |
1225 | @end defspec |
1226 | ||
1227 | @node Focus Events | |
1228 | @subsection Focus Events | |
1229 | @cindex focus event | |
1230 | ||
1231 | Window systems provide general ways for the user to control which window | |
1232 | gets keyboard input. This choice of window is called the @dfn{focus}. | |
1233 | When the user does something to switch between Emacs frames, that | |
1234 | generates a @dfn{focus event}. The normal definition of a focus event, | |
1235 | in the global keymap, is to select a new frame within Emacs, as the user | |
1236 | would expect. @xref{Input Focus}. | |
1237 | ||
1238 | Focus events are represented in Lisp as lists that look like this: | |
1239 | ||
1240 | @example | |
1241 | (switch-frame @var{new-frame}) | |
1242 | @end example | |
1243 | ||
1244 | @noindent | |
1245 | where @var{new-frame} is the frame switched to. | |
1246 | ||
b22f3a19 RS |
1247 | Most X window managers are set up so that just moving the mouse into a |
1248 | window is enough to set the focus there. Emacs appears to do this, | |
1249 | because it changes the cursor to solid in the new frame. However, there | |
1250 | is no need for the Lisp program to know about the focus change until | |
1251 | some other kind of input arrives. So Emacs generates a focus event only | |
1252 | when the user actually types a keyboard key or presses a mouse button in | |
1253 | the new frame; just moving the mouse between frames does not generate a | |
1254 | focus event. | |
8db970a4 RS |
1255 | |
1256 | A focus event in the middle of a key sequence would garble the | |
1257 | sequence. So Emacs never generates a focus event in the middle of a key | |
1258 | sequence. If the user changes focus in the middle of a key | |
1259 | sequence---that is, after a prefix key---then Emacs reorders the events | |
1260 | so that the focus event comes either before or after the multi-event key | |
1261 | sequence, and not within it. | |
1262 | ||
22697dac KH |
1263 | @node Misc Events |
1264 | @subsection Miscellaneous Window System Events | |
1265 | ||
1266 | A few other event types represent occurrences within the window system. | |
1267 | ||
1268 | @table @code | |
1269 | @cindex @code{delete-frame} event | |
1270 | @item (delete-frame (@var{frame})) | |
1271 | This kind of event indicates that the user gave the window manager | |
1272 | a command to delete a particular window, which happens to be an Emacs frame. | |
1273 | ||
1274 | The standard definition of the @code{delete-frame} event is to delete @var{frame}. | |
1275 | ||
1276 | @cindex @code{iconify-frame} event | |
1277 | @item (iconify-frame (@var{frame})) | |
1278 | This kind of event indicates that the user iconified @var{frame} using | |
d473987a RS |
1279 | the window manager. Its standard definition is @code{ignore}; since the |
1280 | frame has already been iconified, Emacs has no work to do. The purpose | |
1281 | of this event type is so that you can keep track of such events if you | |
1282 | want to. | |
22697dac | 1283 | |
1774d17e RS |
1284 | @cindex @code{make-frame-visible} event |
1285 | @item (make-frame-visible (@var{frame})) | |
22697dac KH |
1286 | This kind of event indicates that the user deiconified @var{frame} using |
1287 | the window manager. Its standard definition is @code{ignore}; since the | |
d473987a | 1288 | frame has already been made visible, Emacs has no work to do. |
22697dac KH |
1289 | @end table |
1290 | ||
bfe721d1 KH |
1291 | If one of these events arrives in the middle of a key sequence---that |
1292 | is, after a prefix key---then Emacs reorders the events so that this | |
1293 | event comes either before or after the multi-event key sequence, not | |
1294 | within it. | |
1295 | ||
8db970a4 RS |
1296 | @node Event Examples |
1297 | @subsection Event Examples | |
1298 | ||
1299 | If the user presses and releases the left mouse button over the same | |
1300 | location, that generates a sequence of events like this: | |
1301 | ||
1302 | @smallexample | |
1303 | (down-mouse-1 (#<window 18 on NEWS> 2613 (0 . 38) -864320)) | |
1304 | (mouse-1 (#<window 18 on NEWS> 2613 (0 . 38) -864180)) | |
1305 | @end smallexample | |
1306 | ||
f142f62a | 1307 | While holding the control key down, the user might hold down the |
8db970a4 RS |
1308 | second mouse button, and drag the mouse from one line to the next. |
1309 | That produces two events, as shown here: | |
1310 | ||
1311 | @smallexample | |
1312 | (C-down-mouse-2 (#<window 18 on NEWS> 3440 (0 . 27) -731219)) | |
1313 | (C-drag-mouse-2 (#<window 18 on NEWS> 3440 (0 . 27) -731219) | |
1314 | (#<window 18 on NEWS> 3510 (0 . 28) -729648)) | |
1315 | @end smallexample | |
1316 | ||
f142f62a | 1317 | While holding down the meta and shift keys, the user might press the |
8db970a4 | 1318 | second mouse button on the window's mode line, and then drag the mouse |
f142f62a | 1319 | into another window. That produces a pair of events like these: |
8db970a4 RS |
1320 | |
1321 | @smallexample | |
1322 | (M-S-down-mouse-2 (#<window 18 on NEWS> mode-line (33 . 31) -457844)) | |
1323 | (M-S-drag-mouse-2 (#<window 18 on NEWS> mode-line (33 . 31) -457844) | |
1324 | (#<window 20 on carlton-sanskrit.tex> 161 (33 . 3) | |
1325 | -453816)) | |
1326 | @end smallexample | |
1327 | ||
1328 | @node Classifying Events | |
1329 | @subsection Classifying Events | |
1330 | @cindex event type | |
1331 | ||
b22f3a19 RS |
1332 | Every event has an @dfn{event type}, which classifies the event for |
1333 | key binding purposes. For a keyboard event, the event type equals the | |
1334 | event value; thus, the event type for a character is the character, and | |
1335 | the event type for a function key symbol is the symbol itself. For | |
1336 | events that are lists, the event type is the symbol in the @sc{car} of | |
1337 | the list. Thus, the event type is always a symbol or a character. | |
8db970a4 RS |
1338 | |
1339 | Two events of the same type are equivalent where key bindings are | |
1340 | concerned; thus, they always run the same command. That does not | |
1341 | necessarily mean they do the same things, however, as some commands look | |
1342 | at the whole event to decide what to do. For example, some commands use | |
f142f62a | 1343 | the location of a mouse event to decide where in the buffer to act. |
8db970a4 RS |
1344 | |
1345 | Sometimes broader classifications of events are useful. For example, | |
1346 | you might want to ask whether an event involved the @key{META} key, | |
1347 | regardless of which other key or mouse button was used. | |
1348 | ||
1349 | The functions @code{event-modifiers} and @code{event-basic-type} are | |
1350 | provided to get such information conveniently. | |
1351 | ||
1352 | @defun event-modifiers event | |
f142f62a RS |
1353 | This function returns a list of the modifiers that @var{event} has. The |
1354 | modifiers are symbols; they include @code{shift}, @code{control}, | |
8db970a4 | 1355 | @code{meta}, @code{alt}, @code{hyper} and @code{super}. In addition, |
f142f62a RS |
1356 | the modifiers list of a mouse event symbol always contains one of |
1357 | @code{click}, @code{drag}, and @code{down}. | |
1358 | ||
1359 | The argument @var{event} may be an entire event object, or just an event | |
1360 | type. | |
1361 | ||
1362 | Here are some examples: | |
8db970a4 RS |
1363 | |
1364 | @example | |
1365 | (event-modifiers ?a) | |
1366 | @result{} nil | |
1367 | (event-modifiers ?\C-a) | |
1368 | @result{} (control) | |
1369 | (event-modifiers ?\C-%) | |
1370 | @result{} (control) | |
1371 | (event-modifiers ?\C-\S-a) | |
1372 | @result{} (control shift) | |
1373 | (event-modifiers 'f5) | |
1374 | @result{} nil | |
1375 | (event-modifiers 's-f5) | |
1376 | @result{} (super) | |
1377 | (event-modifiers 'M-S-f5) | |
1378 | @result{} (meta shift) | |
1379 | (event-modifiers 'mouse-1) | |
1380 | @result{} (click) | |
1381 | (event-modifiers 'down-mouse-1) | |
1382 | @result{} (down) | |
1383 | @end example | |
1384 | ||
1385 | The modifiers list for a click event explicitly contains @code{click}, | |
1386 | but the event symbol name itself does not contain @samp{click}. | |
1387 | @end defun | |
1388 | ||
1389 | @defun event-basic-type event | |
1390 | This function returns the key or mouse button that @var{event} | |
1391 | describes, with all modifiers removed. For example: | |
1392 | ||
1393 | @example | |
1394 | (event-basic-type ?a) | |
1395 | @result{} 97 | |
1396 | (event-basic-type ?A) | |
1397 | @result{} 97 | |
1398 | (event-basic-type ?\C-a) | |
1399 | @result{} 97 | |
1400 | (event-basic-type ?\C-\S-a) | |
1401 | @result{} 97 | |
1402 | (event-basic-type 'f5) | |
1403 | @result{} f5 | |
1404 | (event-basic-type 's-f5) | |
1405 | @result{} f5 | |
1406 | (event-basic-type 'M-S-f5) | |
1407 | @result{} f5 | |
1408 | (event-basic-type 'down-mouse-1) | |
1409 | @result{} mouse-1 | |
1410 | @end example | |
1411 | @end defun | |
1412 | ||
1413 | @defun mouse-movement-p object | |
1414 | This function returns non-@code{nil} if @var{object} is a mouse movement | |
1415 | event. | |
1416 | @end defun | |
1417 | ||
bfe721d1 KH |
1418 | @defun event-convert-list list |
1419 | This function converts a list of modifier names and a basic event type | |
1420 | to an event type which specifies all of them. For example, | |
1421 | ||
1422 | @example | |
1423 | (event-convert-list '(control ?a)) | |
1424 | @result{} 1 | |
1425 | (event-convert-list '(control meta ?a)) | |
1426 | @result{} -134217727 | |
1427 | (event-convert-list '(control super f1)) | |
1428 | @result{} C-s-f1 | |
1429 | @end example | |
1430 | @end defun | |
1431 | ||
8db970a4 RS |
1432 | @node Accessing Events |
1433 | @subsection Accessing Events | |
1434 | ||
1435 | This section describes convenient functions for accessing the data in | |
f142f62a | 1436 | a mouse button or motion event. |
8db970a4 | 1437 | |
f142f62a | 1438 | These two functions return the starting or ending position of a |
8db970a4 RS |
1439 | mouse-button event. The position is a list of this form: |
1440 | ||
f142f62a | 1441 | @example |
b22f3a19 | 1442 | (@var{window} @var{buffer-position} (@var{x} . @var{y}) @var{timestamp}) |
f142f62a | 1443 | @end example |
8db970a4 RS |
1444 | |
1445 | @defun event-start event | |
1446 | This returns the starting position of @var{event}. | |
1447 | ||
1448 | If @var{event} is a click or button-down event, this returns the | |
1449 | location of the event. If @var{event} is a drag event, this returns the | |
1450 | drag's starting position. | |
1451 | @end defun | |
1452 | ||
1453 | @defun event-end event | |
1454 | This returns the ending position of @var{event}. | |
1455 | ||
1456 | If @var{event} is a drag event, this returns the position where the user | |
1457 | released the mouse button. If @var{event} is a click or button-down | |
1458 | event, the value is actually the starting position, which is the only | |
1459 | position such events have. | |
1460 | @end defun | |
1461 | ||
e414b03f | 1462 | These five functions take a position as described above, and return |
b22f3a19 | 1463 | various parts of it. |
8db970a4 RS |
1464 | |
1465 | @defun posn-window position | |
1466 | Return the window that @var{position} is in. | |
1467 | @end defun | |
1468 | ||
1469 | @defun posn-point position | |
f142f62a | 1470 | Return the buffer position in @var{position}. This is an integer. |
8db970a4 RS |
1471 | @end defun |
1472 | ||
1473 | @defun posn-x-y position | |
b22f3a19 RS |
1474 | Return the pixel-based x and y coordinates in @var{position}, as a cons |
1475 | cell @code{(@var{x} . @var{y})}. | |
8db970a4 RS |
1476 | @end defun |
1477 | ||
1478 | @defun posn-col-row position | |
f142f62a | 1479 | Return the row and column (in units of characters) of @var{position}, as |
8db970a4 RS |
1480 | a cons cell @code{(@var{col} . @var{row})}. These are computed from the |
1481 | @var{x} and @var{y} values actually found in @var{position}. | |
1482 | @end defun | |
1483 | ||
1484 | @defun posn-timestamp position | |
f142f62a | 1485 | Return the timestamp in @var{position}. |
8db970a4 RS |
1486 | @end defun |
1487 | ||
b22f3a19 RS |
1488 | @defun scroll-bar-event-ratio event |
1489 | This function returns the fractional vertical position of a scroll bar | |
1490 | event within the scroll bar. The value is a cons cell | |
1491 | @code{(@var{portion} . @var{whole})} containing two integers whose ratio | |
1492 | is the fractional position. | |
1493 | @end defun | |
1494 | ||
8db970a4 | 1495 | @defun scroll-bar-scale ratio total |
b22f3a19 RS |
1496 | This function multiplies (in effect) @var{ratio} by @var{total}, |
1497 | rounding the result to an integer. The argument @var{ratio} is not a | |
1498 | number, but rather a pair @code{(@var{num} . @var{denom})}---typically a | |
1499 | value returned by @code{scroll-bar-event-ratio}. | |
8db970a4 | 1500 | |
f142f62a RS |
1501 | This function is handy for scaling a position on a scroll bar into a |
1502 | buffer position. Here's how to do that: | |
8db970a4 RS |
1503 | |
1504 | @example | |
1505 | (+ (point-min) | |
1506 | (scroll-bar-scale | |
b22f3a19 | 1507 | (posn-x-y (event-start event)) |
8db970a4 RS |
1508 | (- (point-max) (point-min)))) |
1509 | @end example | |
b22f3a19 RS |
1510 | |
1511 | Recall that scroll bar events have two integers forming ratio in place | |
1512 | of a pair of x and y coordinates. | |
8db970a4 RS |
1513 | @end defun |
1514 | ||
1515 | @node Strings of Events | |
1516 | @subsection Putting Keyboard Events in Strings | |
1517 | ||
1518 | In most of the places where strings are used, we conceptualize the | |
1519 | string as containing text characters---the same kind of characters found | |
b22f3a19 | 1520 | in buffers or files. Occasionally Lisp programs use strings that |
8db970a4 RS |
1521 | conceptually contain keyboard characters; for example, they may be key |
1522 | sequences or keyboard macro definitions. There are special rules for | |
1523 | how to put keyboard characters into a string, because they are not | |
1524 | limited to the range of 0 to 255 as text characters are. | |
1525 | ||
1526 | A keyboard character typed using the @key{META} key is called a | |
1527 | @dfn{meta character}. The numeric code for such an event includes the | |
bfe721d1 KH |
1528 | @iftex |
1529 | $2^{27}$ | |
1530 | @end iftex | |
1531 | @ifinfo | |
1532 | 2**27 | |
1533 | @end ifinfo | |
1534 | bit; it does not even come close to fitting in a string. However, | |
8db970a4 RS |
1535 | earlier Emacs versions used a different representation for these |
1536 | characters, which gave them codes in the range of 128 to 255. That did | |
1537 | fit in a string, and many Lisp programs contain string constants that | |
1538 | use @samp{\M-} to express meta characters, especially as the argument to | |
1539 | @code{define-key} and similar functions. | |
1540 | ||
f142f62a | 1541 | We provide backward compatibility to run those programs using special |
8db970a4 RS |
1542 | rules for how to put a keyboard character event in a string. Here are |
1543 | the rules: | |
1544 | ||
1545 | @itemize @bullet | |
1546 | @item | |
f142f62a RS |
1547 | If the keyboard character value is in the range of 0 to 127, it can go |
1548 | in the string unchanged. | |
8db970a4 RS |
1549 | |
1550 | @item | |
bfe721d1 KH |
1551 | The meta variants of those characters, with codes in the range of |
1552 | @iftex | |
1553 | $2^{27}$ | |
1554 | @end iftex | |
1555 | @ifinfo | |
1556 | 2**27 | |
1557 | @end ifinfo | |
1558 | to | |
1559 | @iftex | |
1560 | $2^{27} + 127$, | |
1561 | @end iftex | |
1562 | @ifinfo | |
1563 | 2**27+127, | |
1564 | @end ifinfo | |
1565 | can also go in the string, but you must change their | |
1566 | numeric values. You must set the | |
1567 | @iftex | |
1568 | $2^{7}$ | |
1569 | @end iftex | |
1570 | @ifinfo | |
1571 | 2**7 | |
1572 | @end ifinfo | |
1573 | bit instead of the | |
1574 | @iftex | |
1575 | $2^{27}$ | |
1576 | @end iftex | |
1577 | @ifinfo | |
1578 | 2**27 | |
1579 | @end ifinfo | |
1580 | bit, | |
f142f62a | 1581 | resulting in a value between 128 and 255. |
8db970a4 RS |
1582 | |
1583 | @item | |
1584 | Other keyboard character events cannot fit in a string. This includes | |
1585 | keyboard events in the range of 128 to 255. | |
1586 | @end itemize | |
1587 | ||
1588 | Functions such as @code{read-key-sequence} that can construct strings | |
f142f62a RS |
1589 | of keyboard input characters follow these rules. They construct vectors |
1590 | instead of strings, when the events won't fit in a string. | |
8db970a4 RS |
1591 | |
1592 | When you use the read syntax @samp{\M-} in a string, it produces a | |
1593 | code in the range of 128 to 255---the same code that you get if you | |
1594 | modify the corresponding keyboard event to put it in the string. Thus, | |
1595 | meta events in strings work consistently regardless of how they get into | |
1596 | the strings. | |
1597 | ||
8db970a4 RS |
1598 | The reason we changed the representation of meta characters as |
1599 | keyboard events is to make room for basic character codes beyond 127, | |
1600 | and support meta variants of such larger character codes. | |
1601 | ||
f142f62a RS |
1602 | New programs can avoid dealing with these special compatibility rules |
1603 | by using vectors instead of strings for key sequences when there is any | |
1604 | possibility that they might contain meta characters, and by using | |
1605 | @code{listify-key-sequence} to access a string of events. | |
1606 | ||
1607 | @defun listify-key-sequence key | |
1608 | This function converts the string or vector @var{key} to a list of | |
b22f3a19 | 1609 | events, which you can put in @code{unread-command-events}. Converting a |
f142f62a RS |
1610 | vector is simple, but converting a string is tricky because of the |
1611 | special representation used for meta characters in a string. | |
1612 | @end defun | |
1613 | ||
8db970a4 RS |
1614 | @node Reading Input |
1615 | @section Reading Input | |
1616 | ||
1617 | The editor command loop reads keyboard input using the function | |
1618 | @code{read-key-sequence}, which uses @code{read-event}. These and other | |
1619 | functions for keyboard input are also available for use in Lisp | |
1620 | programs. See also @code{momentary-string-display} in @ref{Temporary | |
1621 | Displays}, and @code{sit-for} in @ref{Waiting}. @xref{Terminal Input}, | |
1622 | for functions and variables for controlling terminal input modes and | |
4324b7ab RS |
1623 | debugging terminal input. @xref{Translating Input}, for features you |
1624 | can use for translating or modifying input events while reading them. | |
8db970a4 RS |
1625 | |
1626 | For higher-level input facilities, see @ref{Minibuffers}. | |
1627 | ||
1628 | @menu | |
1629 | * Key Sequence Input:: How to read one key sequence. | |
1630 | * Reading One Event:: How to read just one event. | |
1631 | * Quoted Character Input:: Asking the user to specify a character. | |
f142f62a | 1632 | * Event Input Misc:: How to reread or throw away input events. |
8db970a4 RS |
1633 | @end menu |
1634 | ||
1635 | @node Key Sequence Input | |
1636 | @subsection Key Sequence Input | |
1637 | @cindex key sequence input | |
1638 | ||
1639 | The command loop reads input a key sequence at a time, by calling | |
1640 | @code{read-key-sequence}. Lisp programs can also call this function; | |
1641 | for example, @code{describe-key} uses it to read the key to describe. | |
1642 | ||
1643 | @defun read-key-sequence prompt | |
1644 | @cindex key sequence | |
1645 | This function reads a key sequence and returns it as a string or | |
1646 | vector. It keeps reading events until it has accumulated a full key | |
1647 | sequence; that is, enough to specify a non-prefix command using the | |
1648 | currently active keymaps. | |
1649 | ||
1650 | If the events are all characters and all can fit in a string, then | |
1651 | @code{read-key-sequence} returns a string (@pxref{Strings of Events}). | |
1652 | Otherwise, it returns a vector, since a vector can hold all kinds of | |
1653 | events---characters, symbols, and lists. The elements of the string or | |
1654 | vector are the events in the key sequence. | |
1655 | ||
f142f62a RS |
1656 | The function @code{read-key-sequence} suppresses quitting: @kbd{C-g} |
1657 | typed while reading with this function works like any other character, | |
1658 | and does not set @code{quit-flag}. @xref{Quitting}. | |
8db970a4 RS |
1659 | |
1660 | The argument @var{prompt} is either a string to be displayed in the echo | |
1661 | area as a prompt, or @code{nil}, meaning not to display a prompt. | |
1662 | ||
1663 | In the example below, the prompt @samp{?} is displayed in the echo area, | |
1664 | and the user types @kbd{C-x C-f}. | |
1665 | ||
1666 | @example | |
1667 | (read-key-sequence "?") | |
1668 | ||
1669 | @group | |
1670 | ---------- Echo Area ---------- | |
1671 | ?@kbd{C-x C-f} | |
1672 | ---------- Echo Area ---------- | |
1673 | ||
1674 | @result{} "^X^F" | |
1675 | @end group | |
1676 | @end example | |
1677 | @end defun | |
1678 | ||
1679 | @defvar num-input-keys | |
1680 | @c Emacs 19 feature | |
1681 | This variable's value is the number of key sequences processed so far in | |
1682 | this Emacs session. This includes key sequences read from the terminal | |
1683 | and key sequences read from keyboard macros being executed. | |
1684 | @end defvar | |
1685 | ||
1686 | @cindex upper case key sequence | |
1687 | @cindex downcasing in @code{lookup-key} | |
b22f3a19 RS |
1688 | If an input character is an upper-case letter and has no key binding, |
1689 | but its lower-case equivalent has one, then @code{read-key-sequence} | |
8db970a4 RS |
1690 | converts the character to lower case. Note that @code{lookup-key} does |
1691 | not perform case conversion in this way. | |
1692 | ||
1693 | The function @code{read-key-sequence} also transforms some mouse events. | |
1694 | It converts unbound drag events into click events, and discards unbound | |
bfe721d1 KH |
1695 | button-down events entirely. It also reshuffles focus events and |
1696 | miscellaneous window events so that they never appear in a key sequence | |
1697 | with any other events. | |
8db970a4 RS |
1698 | |
1699 | When mouse events occur in special parts of a window, such as a mode | |
f142f62a RS |
1700 | line or a scroll bar, the event type shows nothing special---it is the |
1701 | same symbol that would normally represent that combination of mouse | |
1702 | button and modifier keys. The information about the window part is | |
1703 | kept elsewhere in the event---in the coordinates. But | |
1704 | @code{read-key-sequence} translates this information into imaginary | |
1705 | prefix keys, all of which are symbols: @code{mode-line}, | |
1706 | @code{vertical-line}, @code{horizontal-scroll-bar} and | |
8db970a4 RS |
1707 | @code{vertical-scroll-bar}. |
1708 | ||
f142f62a RS |
1709 | You can define meanings for mouse clicks in special window parts by |
1710 | defining key sequences using these imaginary prefix keys. | |
1711 | ||
8db970a4 | 1712 | For example, if you call @code{read-key-sequence} and then click the |
bfe721d1 | 1713 | mouse on the window's mode line, you get two events, like this: |
8db970a4 | 1714 | |
f142f62a | 1715 | @example |
8db970a4 RS |
1716 | (read-key-sequence "Click on the mode line: ") |
1717 | @result{} [mode-line | |
f142f62a RS |
1718 | (mouse-1 |
1719 | (#<window 6 on NEWS> mode-line | |
1720 | (40 . 63) 5959987))] | |
1721 | @end example | |
8db970a4 RS |
1722 | |
1723 | @node Reading One Event | |
1724 | @subsection Reading One Event | |
1725 | ||
b22f3a19 | 1726 | The lowest level functions for command input are those that read a |
8db970a4 RS |
1727 | single event. |
1728 | ||
1729 | @defun read-event | |
1730 | This function reads and returns the next event of command input, waiting | |
1731 | if necessary until an event is available. Events can come directly from | |
1732 | the user or from a keyboard macro. | |
1733 | ||
1734 | The function @code{read-event} does not display any message to indicate | |
1735 | it is waiting for input; use @code{message} first, if you wish to | |
1736 | display one. If you have not displayed a message, @code{read-event} | |
f142f62a | 1737 | prompts by echoing: it displays descriptions of the events that led to |
8db970a4 RS |
1738 | or were read by the current command. @xref{The Echo Area}. |
1739 | ||
1740 | If @code{cursor-in-echo-area} is non-@code{nil}, then @code{read-event} | |
1741 | moves the cursor temporarily to the echo area, to the end of any message | |
1742 | displayed there. Otherwise @code{read-event} does not move the cursor. | |
8db970a4 RS |
1743 | |
1744 | Here is what happens if you call @code{read-event} and then press the | |
1745 | right-arrow function key: | |
1746 | ||
1747 | @example | |
1748 | @group | |
1749 | (read-event) | |
1750 | @result{} right | |
1751 | @end group | |
1752 | @end example | |
f142f62a | 1753 | @end defun |
8db970a4 RS |
1754 | |
1755 | @defun read-char | |
1756 | This function reads and returns a character of command input. It | |
f142f62a | 1757 | discards any events that are not characters, until it gets a character. |
8db970a4 | 1758 | |
f142f62a RS |
1759 | In the first example, the user types the character @kbd{1} (@sc{ASCII} |
1760 | code 49). The second example shows a keyboard macro definition that | |
1761 | calls @code{read-char} from the minibuffer using @code{eval-expression}. | |
1762 | @code{read-char} reads the keyboard macro's very next character, which | |
1763 | is @kbd{1}. Then @code{eval-expression} displays its return value in | |
1764 | the echo area. | |
8db970a4 RS |
1765 | |
1766 | @example | |
1767 | @group | |
1768 | (read-char) | |
1769 | @result{} 49 | |
1770 | @end group | |
1771 | ||
1772 | @group | |
bfe721d1 | 1773 | ;; @r{We assume here you use @kbd{M-:} to evaluate this.} |
8db970a4 | 1774 | (symbol-function 'foo) |
bfe721d1 | 1775 | @result{} "^[:(read-char)^M1" |
8db970a4 RS |
1776 | @end group |
1777 | @group | |
f142f62a | 1778 | (execute-kbd-macro 'foo) |
8db970a4 RS |
1779 | @print{} 49 |
1780 | @result{} nil | |
1781 | @end group | |
1782 | @end example | |
1783 | @end defun | |
1784 | ||
1785 | @node Quoted Character Input | |
1786 | @subsection Quoted Character Input | |
1787 | @cindex quoted character input | |
1788 | ||
b22f3a19 RS |
1789 | You can use the function @code{read-quoted-char} to ask the user to |
1790 | specify a character, and allow the user to specify a control or meta | |
1791 | character conveniently, either literally or as an octal character code. | |
1792 | The command @code{quoted-insert} uses this function. | |
8db970a4 RS |
1793 | |
1794 | @defun read-quoted-char &optional prompt | |
1795 | @cindex octal character input | |
1796 | @cindex control characters, reading | |
1797 | @cindex nonprinting characters, reading | |
1798 | This function is like @code{read-char}, except that if the first | |
1799 | character read is an octal digit (0-7), it reads up to two more octal digits | |
1800 | (but stopping if a non-octal digit is found) and returns the | |
f142f62a | 1801 | character represented by those digits in octal. |
8db970a4 RS |
1802 | |
1803 | Quitting is suppressed when the first character is read, so that the | |
1804 | user can enter a @kbd{C-g}. @xref{Quitting}. | |
1805 | ||
1806 | If @var{prompt} is supplied, it specifies a string for prompting the | |
f142f62a | 1807 | user. The prompt string is always displayed in the echo area, followed |
8db970a4 RS |
1808 | by a single @samp{-}. |
1809 | ||
1810 | In the following example, the user types in the octal number 177 (which | |
1811 | is 127 in decimal). | |
1812 | ||
1813 | @example | |
1814 | (read-quoted-char "What character") | |
1815 | ||
1816 | @group | |
1817 | ---------- Echo Area ---------- | |
1818 | What character-@kbd{177} | |
1819 | ---------- Echo Area ---------- | |
1820 | ||
1821 | @result{} 127 | |
1822 | @end group | |
1823 | @end example | |
1824 | @end defun | |
1825 | ||
b22f3a19 | 1826 | @need 2000 |
f142f62a RS |
1827 | @node Event Input Misc |
1828 | @subsection Miscellaneous Event Input Features | |
1829 | ||
1830 | This section describes how to ``peek ahead'' at events without using | |
1831 | them up, how to check for pending input, and how to discard pending | |
1832 | input. | |
8db970a4 RS |
1833 | |
1834 | @defvar unread-command-events | |
1835 | @cindex next input | |
1836 | @cindex peeking at input | |
1837 | This variable holds a list of events waiting to be read as command | |
f142f62a RS |
1838 | input. The events are used in the order they appear in the list, and |
1839 | removed one by one as they are used. | |
8db970a4 | 1840 | |
f142f62a RS |
1841 | The variable is needed because in some cases a function reads a event |
1842 | and then decides not to use it. Storing the event in this variable | |
1843 | causes it to be processed normally, by the command loop or by the | |
1844 | functions to read command input. | |
8db970a4 RS |
1845 | |
1846 | @cindex prefix argument unreading | |
1847 | For example, the function that implements numeric prefix arguments reads | |
1848 | any number of digits. When it finds a non-digit event, it must unread | |
1849 | the event so that it can be read normally by the command loop. | |
f142f62a RS |
1850 | Likewise, incremental search uses this feature to unread events with no |
1851 | special meaning in a search, because these events should exit the search | |
1852 | and then execute normally. | |
1853 | ||
b22f3a19 RS |
1854 | The reliable and easy way to extract events from a key sequence so as to |
1855 | put them in @code{unread-command-events} is to use | |
f142f62a | 1856 | @code{listify-key-sequence} (@pxref{Strings of Events}). |
8db970a4 RS |
1857 | @end defvar |
1858 | ||
1859 | @defvar unread-command-char | |
1860 | This variable holds a character to be read as command input. | |
1861 | A value of -1 means ``empty''. | |
1862 | ||
f142f62a | 1863 | This variable is mostly obsolete now that you can use |
8db970a4 RS |
1864 | @code{unread-command-events} instead; it exists only to support programs |
1865 | written for Emacs versions 18 and earlier. | |
1866 | @end defvar | |
1867 | ||
8db970a4 RS |
1868 | @defun input-pending-p |
1869 | @cindex waiting for command key input | |
1870 | This function determines whether any command input is currently | |
1871 | available to be read. It returns immediately, with value @code{t} if | |
f142f62a RS |
1872 | there is available input, @code{nil} otherwise. On rare occasions it |
1873 | may return @code{t} when no input is available. | |
8db970a4 RS |
1874 | @end defun |
1875 | ||
1876 | @defvar last-input-event | |
f142f62a | 1877 | This variable records the last terminal input event read, whether |
8db970a4 RS |
1878 | as part of a command or explicitly by a Lisp program. |
1879 | ||
f142f62a RS |
1880 | In the example below, the Lisp program reads the character @kbd{1}, |
1881 | @sc{ASCII} code 49. It becomes the value of @code{last-input-event}, | |
bfe721d1 KH |
1882 | while @kbd{C-e} (we assume @kbd{C-x C-e} command is used to evaluate |
1883 | this expression) remains the value of @code{last-command-event}. | |
8db970a4 RS |
1884 | |
1885 | @example | |
1886 | @group | |
1887 | (progn (print (read-char)) | |
f142f62a RS |
1888 | (print last-command-event) |
1889 | last-input-event) | |
8db970a4 RS |
1890 | @print{} 49 |
1891 | @print{} 5 | |
1892 | @result{} 49 | |
1893 | @end group | |
1894 | @end example | |
1895 | ||
f142f62a | 1896 | @vindex last-input-char |
8db970a4 RS |
1897 | The alias @code{last-input-char} exists for compatibility with |
1898 | Emacs version 18. | |
1899 | @end defvar | |
1900 | ||
1901 | @defun discard-input | |
1902 | @cindex flush input | |
1903 | @cindex discard input | |
1904 | @cindex terminate keyboard macro | |
1905 | This function discards the contents of the terminal input buffer and | |
1906 | cancels any keyboard macro that might be in the process of definition. | |
1907 | It returns @code{nil}. | |
1908 | ||
1909 | In the following example, the user may type a number of characters right | |
1910 | after starting the evaluation of the form. After the @code{sleep-for} | |
f142f62a RS |
1911 | finishes sleeping, @code{discard-input} discards any characters typed |
1912 | during the sleep. | |
8db970a4 RS |
1913 | |
1914 | @example | |
1915 | (progn (sleep-for 2) | |
f142f62a | 1916 | (discard-input)) |
8db970a4 RS |
1917 | @result{} nil |
1918 | @end example | |
1919 | @end defun | |
1920 | ||
1921 | @node Waiting | |
1922 | @section Waiting for Elapsed Time or Input | |
1923 | @cindex pausing | |
1924 | @cindex waiting | |
1925 | ||
f142f62a RS |
1926 | The wait functions are designed to wait for a certain amount of time |
1927 | to pass or until there is input. For example, you may wish to pause in | |
1928 | the middle of a computation to allow the user time to view the display. | |
1929 | @code{sit-for} pauses and updates the screen, and returns immediately if | |
1930 | input comes in, while @code{sleep-for} pauses without updating the | |
1931 | screen. | |
8db970a4 RS |
1932 | |
1933 | @defun sit-for seconds &optional millisec nodisp | |
1934 | This function performs redisplay (provided there is no pending input | |
1935 | from the user), then waits @var{seconds} seconds, or until input is | |
f142f62a RS |
1936 | available. The value is @code{t} if @code{sit-for} waited the full |
1937 | time with no input arriving (see @code{input-pending-p} in @ref{Event | |
1938 | Input Misc}). Otherwise, the value is @code{nil}. | |
8db970a4 | 1939 | |
bfe721d1 KH |
1940 | The argument @var{seconds} need not be an integer. If it is a floating |
1941 | point number, @code{sit-for} waits for a fractional number of seconds. | |
1942 | Some systems support only a whole number of seconds; on these systems, | |
1943 | @var{seconds} is rounded down. | |
1944 | ||
8db970a4 RS |
1945 | The optional argument @var{millisec} specifies an additional waiting |
1946 | period measured in milliseconds. This adds to the period specified by | |
bfe721d1 KH |
1947 | @var{seconds}. If the system doesn't support waiting fractions of a |
1948 | second, you get an error if you specify nonzero @var{millisec}. | |
8db970a4 RS |
1949 | |
1950 | @cindex forcing redisplay | |
1951 | Redisplay is always preempted if input arrives, and does not happen at | |
1952 | all if input is available before it starts. Thus, there is no way to | |
1953 | force screen updating if there is pending input; however, if there is no | |
1954 | input pending, you can force an update with no delay by using | |
1955 | @code{(sit-for 0)}. | |
1956 | ||
1957 | If @var{nodisp} is non-@code{nil}, then @code{sit-for} does not | |
1958 | redisplay, but it still returns as soon as input is available (or when | |
1959 | the timeout elapses). | |
1960 | ||
22697dac KH |
1961 | Iconifying or deiconifying a frame makes @code{sit-for} return, because |
1962 | that generates an event. @xref{Misc Events}. | |
1963 | ||
8db970a4 RS |
1964 | The usual purpose of @code{sit-for} is to give the user time to read |
1965 | text that you display. | |
1966 | @end defun | |
1967 | ||
1968 | @defun sleep-for seconds &optional millisec | |
1969 | This function simply pauses for @var{seconds} seconds without updating | |
1970 | the display. It pays no attention to available input. It returns | |
1971 | @code{nil}. | |
1972 | ||
bfe721d1 KH |
1973 | The argument @var{seconds} need not be an integer. If it is a floating |
1974 | point number, @code{sleep-for} waits for a fractional number of seconds. | |
1975 | Some systems support only a whole number of seconds; on these systems, | |
1976 | @var{seconds} is rounded down. | |
1977 | ||
8db970a4 RS |
1978 | The optional argument @var{millisec} specifies an additional waiting |
1979 | period measured in milliseconds. This adds to the period specified by | |
bfe721d1 KH |
1980 | @var{seconds}. If the system doesn't support waiting fractions of a |
1981 | second, you get an error if you specify nonzero @var{millisec}. | |
8db970a4 RS |
1982 | |
1983 | Use @code{sleep-for} when you wish to guarantee a delay. | |
1984 | @end defun | |
1985 | ||
1986 | @xref{Time of Day}, for functions to get the current time. | |
1987 | ||
1988 | @node Quitting | |
1989 | @section Quitting | |
1990 | @cindex @kbd{C-g} | |
1991 | @cindex quitting | |
1992 | ||
b22f3a19 RS |
1993 | Typing @kbd{C-g} while a Lisp function is running causes Emacs to |
1994 | @dfn{quit} whatever it is doing. This means that control returns to the | |
1995 | innermost active command loop. | |
8db970a4 RS |
1996 | |
1997 | Typing @kbd{C-g} while the command loop is waiting for keyboard input | |
1998 | does not cause a quit; it acts as an ordinary input character. In the | |
1999 | simplest case, you cannot tell the difference, because @kbd{C-g} | |
2000 | normally runs the command @code{keyboard-quit}, whose effect is to quit. | |
2001 | However, when @kbd{C-g} follows a prefix key, the result is an undefined | |
2002 | key. The effect is to cancel the prefix key as well as any prefix | |
2003 | argument. | |
2004 | ||
2005 | In the minibuffer, @kbd{C-g} has a different definition: it aborts out | |
2006 | of the minibuffer. This means, in effect, that it exits the minibuffer | |
2007 | and then quits. (Simply quitting would return to the command loop | |
2008 | @emph{within} the minibuffer.) The reason why @kbd{C-g} does not quit | |
2009 | directly when the command reader is reading input is so that its meaning | |
2010 | can be redefined in the minibuffer in this way. @kbd{C-g} following a | |
2011 | prefix key is not redefined in the minibuffer, and it has its normal | |
2012 | effect of canceling the prefix key and prefix argument. This too | |
f142f62a | 2013 | would not be possible if @kbd{C-g} always quit directly. |
8db970a4 | 2014 | |
b22f3a19 | 2015 | When @kbd{C-g} does directly quit, it does so by setting the variable |
f142f62a RS |
2016 | @code{quit-flag} to @code{t}. Emacs checks this variable at appropriate |
2017 | times and quits if it is not @code{nil}. Setting @code{quit-flag} | |
8db970a4 RS |
2018 | non-@code{nil} in any way thus causes a quit. |
2019 | ||
f142f62a | 2020 | At the level of C code, quitting cannot happen just anywhere; only at the |
b22f3a19 | 2021 | special places that check @code{quit-flag}. The reason for this is |
8db970a4 RS |
2022 | that quitting at other places might leave an inconsistency in Emacs's |
2023 | internal state. Because quitting is delayed until a safe place, quitting | |
2024 | cannot make Emacs crash. | |
2025 | ||
2026 | Certain functions such as @code{read-key-sequence} or | |
2027 | @code{read-quoted-char} prevent quitting entirely even though they wait | |
2028 | for input. Instead of quitting, @kbd{C-g} serves as the requested | |
2029 | input. In the case of @code{read-key-sequence}, this serves to bring | |
2030 | about the special behavior of @kbd{C-g} in the command loop. In the | |
2031 | case of @code{read-quoted-char}, this is so that @kbd{C-q} can be used | |
2032 | to quote a @kbd{C-g}. | |
2033 | ||
2034 | You can prevent quitting for a portion of a Lisp function by binding | |
2035 | the variable @code{inhibit-quit} to a non-@code{nil} value. Then, | |
2036 | although @kbd{C-g} still sets @code{quit-flag} to @code{t} as usual, the | |
2037 | usual result of this---a quit---is prevented. Eventually, | |
2038 | @code{inhibit-quit} will become @code{nil} again, such as when its | |
2039 | binding is unwound at the end of a @code{let} form. At that time, if | |
2040 | @code{quit-flag} is still non-@code{nil}, the requested quit happens | |
b22f3a19 RS |
2041 | immediately. This behavior is ideal when you wish to make sure that |
2042 | quitting does not happen within a ``critical section'' of the program. | |
8db970a4 RS |
2043 | |
2044 | @cindex @code{read-quoted-char} quitting | |
2045 | In some functions (such as @code{read-quoted-char}), @kbd{C-g} is | |
b22f3a19 | 2046 | handled in a special way that does not involve quitting. This is done |
f142f62a | 2047 | by reading the input with @code{inhibit-quit} bound to @code{t}, and |
8db970a4 RS |
2048 | setting @code{quit-flag} to @code{nil} before @code{inhibit-quit} |
2049 | becomes @code{nil} again. This excerpt from the definition of | |
2050 | @code{read-quoted-char} shows how this is done; it also shows that | |
2051 | normal quitting is permitted after the first character of input. | |
2052 | ||
2053 | @example | |
2054 | (defun read-quoted-char (&optional prompt) | |
2055 | "@dots{}@var{documentation}@dots{}" | |
2056 | (let ((count 0) (code 0) char) | |
2057 | (while (< count 3) | |
2058 | (let ((inhibit-quit (zerop count)) | |
2059 | (help-form nil)) | |
2060 | (and prompt (message "%s-" prompt)) | |
2061 | (setq char (read-char)) | |
2062 | (if inhibit-quit (setq quit-flag nil))) | |
2063 | @dots{}) | |
2064 | (logand 255 code))) | |
2065 | @end example | |
2066 | ||
2067 | @defvar quit-flag | |
f142f62a RS |
2068 | If this variable is non-@code{nil}, then Emacs quits immediately, unless |
2069 | @code{inhibit-quit} is non-@code{nil}. Typing @kbd{C-g} ordinarily sets | |
8db970a4 RS |
2070 | @code{quit-flag} non-@code{nil}, regardless of @code{inhibit-quit}. |
2071 | @end defvar | |
2072 | ||
2073 | @defvar inhibit-quit | |
2074 | This variable determines whether Emacs should quit when @code{quit-flag} | |
2075 | is set to a value other than @code{nil}. If @code{inhibit-quit} is | |
2076 | non-@code{nil}, then @code{quit-flag} has no special effect. | |
2077 | @end defvar | |
2078 | ||
2079 | @deffn Command keyboard-quit | |
2080 | This function signals the @code{quit} condition with @code{(signal 'quit | |
2081 | nil)}. This is the same thing that quitting does. (See @code{signal} | |
2082 | in @ref{Errors}.) | |
2083 | @end deffn | |
2084 | ||
2085 | You can specify a character other than @kbd{C-g} to use for quitting. | |
2086 | See the function @code{set-input-mode} in @ref{Terminal Input}. | |
2087 | ||
2088 | @node Prefix Command Arguments | |
2089 | @section Prefix Command Arguments | |
2090 | @cindex prefix argument | |
2091 | @cindex raw prefix argument | |
2092 | @cindex numeric prefix argument | |
2093 | ||
2094 | Most Emacs commands can use a @dfn{prefix argument}, a number | |
2095 | specified before the command itself. (Don't confuse prefix arguments | |
b22f3a19 RS |
2096 | with prefix keys.) The prefix argument is at all times represented by a |
2097 | value, which may be @code{nil}, meaning there is currently no prefix | |
2098 | argument. Each command may use the prefix argument or ignore it. | |
8db970a4 RS |
2099 | |
2100 | There are two representations of the prefix argument: @dfn{raw} and | |
2101 | @dfn{numeric}. The editor command loop uses the raw representation | |
2102 | internally, and so do the Lisp variables that store the information, but | |
2103 | commands can request either representation. | |
2104 | ||
2105 | Here are the possible values of a raw prefix argument: | |
2106 | ||
2107 | @itemize @bullet | |
2108 | @item | |
2109 | @code{nil}, meaning there is no prefix argument. Its numeric value is | |
2110 | 1, but numerous commands make a distinction between @code{nil} and the | |
2111 | integer 1. | |
2112 | ||
2113 | @item | |
2114 | An integer, which stands for itself. | |
2115 | ||
2116 | @item | |
2117 | A list of one element, which is an integer. This form of prefix | |
2118 | argument results from one or a succession of @kbd{C-u}'s with no | |
2119 | digits. The numeric value is the integer in the list, but some | |
2120 | commands make a distinction between such a list and an integer alone. | |
2121 | ||
2122 | @item | |
2123 | The symbol @code{-}. This indicates that @kbd{M--} or @kbd{C-u -} was | |
2124 | typed, without following digits. The equivalent numeric value is | |
2125 | @minus{}1, but some commands make a distinction between the integer | |
2126 | @minus{}1 and the symbol @code{-}. | |
2127 | @end itemize | |
2128 | ||
f142f62a RS |
2129 | We illustrate these possibilities by calling the following function with |
2130 | various prefixes: | |
8db970a4 RS |
2131 | |
2132 | @example | |
2133 | @group | |
2134 | (defun display-prefix (arg) | |
2135 | "Display the value of the raw prefix arg." | |
2136 | (interactive "P") | |
2137 | (message "%s" arg)) | |
2138 | @end group | |
2139 | @end example | |
2140 | ||
2141 | @noindent | |
2142 | Here are the results of calling @code{display-prefix} with various | |
2143 | raw prefix arguments: | |
2144 | ||
2145 | @example | |
2146 | M-x display-prefix @print{} nil | |
2147 | ||
2148 | C-u M-x display-prefix @print{} (4) | |
2149 | ||
2150 | C-u C-u M-x display-prefix @print{} (16) | |
2151 | ||
2152 | C-u 3 M-x display-prefix @print{} 3 | |
2153 | ||
2154 | M-3 M-x display-prefix @print{} 3 ; @r{(Same as @code{C-u 3}.)} | |
2155 | ||
2156 | C-u - M-x display-prefix @print{} - | |
2157 | ||
f142f62a | 2158 | M-- M-x display-prefix @print{} - ; @r{(Same as @code{C-u -}.)} |
8db970a4 | 2159 | |
f142f62a | 2160 | C-u - 7 M-x display-prefix @print{} -7 |
8db970a4 | 2161 | |
f142f62a | 2162 | M-- 7 M-x display-prefix @print{} -7 ; @r{(Same as @code{C-u -7}.)} |
8db970a4 RS |
2163 | @end example |
2164 | ||
2165 | Emacs uses two variables to store the prefix argument: | |
2166 | @code{prefix-arg} and @code{current-prefix-arg}. Commands such as | |
2167 | @code{universal-argument} that set up prefix arguments for other | |
2168 | commands store them in @code{prefix-arg}. In contrast, | |
2169 | @code{current-prefix-arg} conveys the prefix argument to the current | |
2170 | command, so setting it has no effect on the prefix arguments for future | |
2171 | commands. | |
2172 | ||
2173 | Normally, commands specify which representation to use for the prefix | |
2174 | argument, either numeric or raw, in the @code{interactive} declaration. | |
b22f3a19 | 2175 | (@xref{Using Interactive}.) Alternatively, functions may look at the |
8db970a4 RS |
2176 | value of the prefix argument directly in the variable |
2177 | @code{current-prefix-arg}, but this is less clean. | |
2178 | ||
f142f62a RS |
2179 | @defun prefix-numeric-value arg |
2180 | This function returns the numeric meaning of a valid raw prefix argument | |
2181 | value, @var{arg}. The argument may be a symbol, a number, or a list. | |
b22f3a19 RS |
2182 | If it is @code{nil}, the value 1 is returned; if it is @code{-}, the |
2183 | value @minus{}1 is returned; if it is a number, that number is returned; | |
2184 | if it is a list, the @sc{car} of that list (which should be a number) is | |
2185 | returned. | |
f142f62a RS |
2186 | @end defun |
2187 | ||
2188 | @defvar current-prefix-arg | |
2189 | This variable holds the raw prefix argument for the @emph{current} | |
9e2b495b RS |
2190 | command. Commands may examine it directly, but the usual method for |
2191 | accessing it is with @code{(interactive "P")}. | |
f142f62a RS |
2192 | @end defvar |
2193 | ||
2194 | @defvar prefix-arg | |
2195 | The value of this variable is the raw prefix argument for the | |
2196 | @emph{next} editing command. Commands that specify prefix arguments for | |
2197 | the following command work by setting this variable. | |
2198 | @end defvar | |
2199 | ||
9e2b495b RS |
2200 | Do not call @code{universal-argument}, @code{digit-argument}, or |
2201 | @code{negative-argument} unless you intend to let the user enter the | |
2202 | prefix argument for the @emph{next} command. | |
8db970a4 RS |
2203 | |
2204 | @deffn Command universal-argument | |
2205 | This command reads input and specifies a prefix argument for the | |
2206 | following command. Don't call this command yourself unless you know | |
2207 | what you are doing. | |
2208 | @end deffn | |
2209 | ||
2210 | @deffn Command digit-argument arg | |
2211 | This command adds to the prefix argument for the following command. The | |
2212 | argument @var{arg} is the raw prefix argument as it was before this | |
2213 | command; it is used to compute the updated prefix argument. Don't call | |
2214 | this command yourself unless you know what you are doing. | |
2215 | @end deffn | |
2216 | ||
2217 | @deffn Command negative-argument arg | |
2218 | This command adds to the numeric argument for the next command. The | |
2219 | argument @var{arg} is the raw prefix argument as it was before this | |
2220 | command; its value is negated to form the new prefix argument. Don't | |
2221 | call this command yourself unless you know what you are doing. | |
2222 | @end deffn | |
2223 | ||
8db970a4 RS |
2224 | @node Recursive Editing |
2225 | @section Recursive Editing | |
2226 | @cindex recursive command loop | |
2227 | @cindex recursive editing level | |
2228 | @cindex command loop, recursive | |
2229 | ||
f142f62a RS |
2230 | The Emacs command loop is entered automatically when Emacs starts up. |
2231 | This top-level invocation of the command loop never exits; it keeps | |
2232 | running as long as Emacs does. Lisp programs can also invoke the | |
2233 | command loop. Since this makes more than one activation of the command | |
2234 | loop, we call it @dfn{recursive editing}. A recursive editing level has | |
2235 | the effect of suspending whatever command invoked it and permitting the | |
2236 | user to do arbitrary editing before resuming that command. | |
8db970a4 RS |
2237 | |
2238 | The commands available during recursive editing are the same ones | |
2239 | available in the top-level editing loop and defined in the keymaps. | |
2240 | Only a few special commands exit the recursive editing level; the others | |
f142f62a RS |
2241 | return to the recursive editing level when they finish. (The special |
2242 | commands for exiting are always available, but they do nothing when | |
2243 | recursive editing is not in progress.) | |
8db970a4 RS |
2244 | |
2245 | All command loops, including recursive ones, set up all-purpose error | |
2246 | handlers so that an error in a command run from the command loop will | |
2247 | not exit the loop. | |
2248 | ||
2249 | @cindex minibuffer input | |
2250 | Minibuffer input is a special kind of recursive editing. It has a few | |
2251 | special wrinkles, such as enabling display of the minibuffer and the | |
2252 | minibuffer window, but fewer than you might suppose. Certain keys | |
2253 | behave differently in the minibuffer, but that is only because of the | |
2254 | minibuffer's local map; if you switch windows, you get the usual Emacs | |
2255 | commands. | |
2256 | ||
2257 | @cindex @code{throw} example | |
2258 | @kindex exit | |
2259 | @cindex exit recursive editing | |
2260 | @cindex aborting | |
2261 | To invoke a recursive editing level, call the function | |
2262 | @code{recursive-edit}. This function contains the command loop; it also | |
2263 | contains a call to @code{catch} with tag @code{exit}, which makes it | |
2264 | possible to exit the recursive editing level by throwing to @code{exit} | |
2265 | (@pxref{Catch and Throw}). If you throw a value other than @code{t}, | |
2266 | then @code{recursive-edit} returns normally to the function that called | |
2267 | it. The command @kbd{C-M-c} (@code{exit-recursive-edit}) does this. | |
2268 | Throwing a @code{t} value causes @code{recursive-edit} to quit, so that | |
2269 | control returns to the command loop one level up. This is called | |
2270 | @dfn{aborting}, and is done by @kbd{C-]} (@code{abort-recursive-edit}). | |
2271 | ||
2272 | Most applications should not use recursive editing, except as part of | |
2273 | using the minibuffer. Usually it is more convenient for the user if you | |
2274 | change the major mode of the current buffer temporarily to a special | |
b22f3a19 RS |
2275 | major mode, which should have a command to go back to the previous mode. |
2276 | (The @kbd{e} command in Rmail uses this technique.) Or, if you wish to | |
2277 | give the user different text to edit ``recursively'', create and select | |
2278 | a new buffer in a special mode. In this mode, define a command to | |
2279 | complete the processing and go back to the previous buffer. (The | |
2280 | @kbd{m} command in Rmail does this.) | |
8db970a4 RS |
2281 | |
2282 | Recursive edits are useful in debugging. You can insert a call to | |
2283 | @code{debug} into a function definition as a sort of breakpoint, so that | |
2284 | you can look around when the function gets there. @code{debug} invokes | |
2285 | a recursive edit but also provides the other features of the debugger. | |
2286 | ||
2287 | Recursive editing levels are also used when you type @kbd{C-r} in | |
2288 | @code{query-replace} or use @kbd{C-x q} (@code{kbd-macro-query}). | |
2289 | ||
2290 | @defun recursive-edit | |
2291 | @cindex suspend evaluation | |
2292 | This function invokes the editor command loop. It is called | |
2293 | automatically by the initialization of Emacs, to let the user begin | |
2294 | editing. When called from a Lisp program, it enters a recursive editing | |
2295 | level. | |
2296 | ||
2297 | In the following example, the function @code{simple-rec} first | |
2298 | advances point one word, then enters a recursive edit, printing out a | |
2299 | message in the echo area. The user can then do any editing desired, and | |
2300 | then type @kbd{C-M-c} to exit and continue executing @code{simple-rec}. | |
2301 | ||
2302 | @example | |
2303 | (defun simple-rec () | |
2304 | (forward-word 1) | |
f142f62a | 2305 | (message "Recursive edit in progress") |
8db970a4 RS |
2306 | (recursive-edit) |
2307 | (forward-word 1)) | |
2308 | @result{} simple-rec | |
2309 | (simple-rec) | |
2310 | @result{} nil | |
2311 | @end example | |
2312 | @end defun | |
2313 | ||
2314 | @deffn Command exit-recursive-edit | |
2315 | This function exits from the innermost recursive edit (including | |
2316 | minibuffer input). Its definition is effectively @code{(throw 'exit | |
2317 | nil)}. | |
2318 | @end deffn | |
2319 | ||
2320 | @deffn Command abort-recursive-edit | |
2321 | This function aborts the command that requested the innermost recursive | |
2322 | edit (including minibuffer input), by signaling @code{quit} | |
2323 | after exiting the recursive edit. Its definition is effectively | |
2324 | @code{(throw 'exit t)}. @xref{Quitting}. | |
2325 | @end deffn | |
2326 | ||
2327 | @deffn Command top-level | |
2328 | This function exits all recursive editing levels; it does not return a | |
2329 | value, as it jumps completely out of any computation directly back to | |
2330 | the main command loop. | |
2331 | @end deffn | |
2332 | ||
2333 | @defun recursion-depth | |
2334 | This function returns the current depth of recursive edits. When no | |
2335 | recursive edit is active, it returns 0. | |
2336 | @end defun | |
2337 | ||
2338 | @node Disabling Commands | |
2339 | @section Disabling Commands | |
2340 | @cindex disabled command | |
2341 | ||
2342 | @dfn{Disabling a command} marks the command as requiring user | |
2343 | confirmation before it can be executed. Disabling is used for commands | |
2344 | which might be confusing to beginning users, to prevent them from using | |
2345 | the commands by accident. | |
2346 | ||
2347 | @kindex disabled | |
2348 | The low-level mechanism for disabling a command is to put a | |
2349 | non-@code{nil} @code{disabled} property on the Lisp symbol for the | |
2350 | command. These properties are normally set up by the user's | |
2351 | @file{.emacs} file with Lisp expressions such as this: | |
2352 | ||
2353 | @example | |
2354 | (put 'upcase-region 'disabled t) | |
2355 | @end example | |
2356 | ||
2357 | @noindent | |
2358 | For a few commands, these properties are present by default and may be | |
2359 | removed by the @file{.emacs} file. | |
2360 | ||
f142f62a RS |
2361 | If the value of the @code{disabled} property is a string, the message |
2362 | saying the command is disabled includes that string. For example: | |
8db970a4 RS |
2363 | |
2364 | @example | |
2365 | (put 'delete-region 'disabled | |
2366 | "Text deleted this way cannot be yanked back!\n") | |
2367 | @end example | |
2368 | ||
2369 | @xref{Disabling,,, emacs, The GNU Emacs Manual}, for the details on | |
2370 | what happens when a disabled command is invoked interactively. | |
2371 | Disabling a command has no effect on calling it as a function from Lisp | |
2372 | programs. | |
2373 | ||
2374 | @deffn Command enable-command command | |
2375 | Allow @var{command} to be executed without special confirmation from now | |
b22f3a19 RS |
2376 | on, and (if the user confirms) alter the user's @file{.emacs} file so |
2377 | that this will apply to future sessions. | |
8db970a4 RS |
2378 | @end deffn |
2379 | ||
2380 | @deffn Command disable-command command | |
f142f62a | 2381 | Require special confirmation to execute @var{command} from now on, and |
b22f3a19 RS |
2382 | (if the user confirms) alter the user's @file{.emacs} file so that this |
2383 | will apply to future sessions. | |
8db970a4 RS |
2384 | @end deffn |
2385 | ||
2386 | @defvar disabled-command-hook | |
f142f62a RS |
2387 | This normal hook is run instead of a disabled command, when the user |
2388 | invokes the disabled command interactively. The hook functions can use | |
2389 | @code{this-command-keys} to determine what the user typed to run the | |
b22f3a19 | 2390 | command, and thus find the command itself. @xref{Hooks}. |
8db970a4 RS |
2391 | |
2392 | By default, @code{disabled-command-hook} contains a function that asks | |
2393 | the user whether to proceed. | |
2394 | @end defvar | |
2395 | ||
2396 | @node Command History | |
2397 | @section Command History | |
2398 | @cindex command history | |
2399 | @cindex complex command | |
2400 | @cindex history of commands | |
2401 | ||
2402 | The command loop keeps a history of the complex commands that have | |
2403 | been executed, to make it convenient to repeat these commands. A | |
2404 | @dfn{complex command} is one for which the interactive argument reading | |
2405 | uses the minibuffer. This includes any @kbd{M-x} command, any | |
bfe721d1 | 2406 | @kbd{M-:} command, and any command whose @code{interactive} |
8db970a4 RS |
2407 | specification reads an argument from the minibuffer. Explicit use of |
2408 | the minibuffer during the execution of the command itself does not cause | |
2409 | the command to be considered complex. | |
2410 | ||
2411 | @defvar command-history | |
2412 | This variable's value is a list of recent complex commands, each | |
2413 | represented as a form to evaluate. It continues to accumulate all | |
2414 | complex commands for the duration of the editing session, but all but | |
2415 | the first (most recent) thirty elements are deleted when a garbage | |
2416 | collection takes place (@pxref{Garbage Collection}). | |
2417 | ||
2418 | @example | |
2419 | @group | |
2420 | command-history | |
2421 | @result{} ((switch-to-buffer "chistory.texi") | |
2422 | (describe-key "^X^[") | |
2423 | (visit-tags-table "~/emacs/src/") | |
2424 | (find-tag "repeat-complex-command")) | |
2425 | @end group | |
2426 | @end example | |
2427 | @end defvar | |
2428 | ||
2429 | This history list is actually a special case of minibuffer history | |
2430 | (@pxref{Minibuffer History}), with one special twist: the elements are | |
2431 | expressions rather than strings. | |
2432 | ||
2433 | There are a number of commands devoted to the editing and recall of | |
2434 | previous commands. The commands @code{repeat-complex-command}, and | |
2435 | @code{list-command-history} are described in the user manual | |
2436 | (@pxref{Repetition,,, emacs, The GNU Emacs Manual}). Within the | |
2437 | minibuffer, the history commands used are the same ones available in any | |
2438 | minibuffer. | |
2439 | ||
2440 | @node Keyboard Macros | |
2441 | @section Keyboard Macros | |
2442 | @cindex keyboard macros | |
2443 | ||
2444 | A @dfn{keyboard macro} is a canned sequence of input events that can | |
f142f62a RS |
2445 | be considered a command and made the definition of a key. The Lisp |
2446 | representation of a keyboard macro is a string or vector containing the | |
2447 | events. Don't confuse keyboard macros with Lisp macros | |
2448 | (@pxref{Macros}). | |
8db970a4 RS |
2449 | |
2450 | @defun execute-kbd-macro macro &optional count | |
2451 | This function executes @var{macro} as a sequence of events. If | |
2452 | @var{macro} is a string or vector, then the events in it are executed | |
2453 | exactly as if they had been input by the user. The sequence is | |
2454 | @emph{not} expected to be a single key sequence; normally a keyboard | |
2455 | macro definition consists of several key sequences concatenated. | |
2456 | ||
2457 | If @var{macro} is a symbol, then its function definition is used in | |
2458 | place of @var{macro}. If that is another symbol, this process repeats. | |
2459 | Eventually the result should be a string or vector. If the result is | |
2460 | not a symbol, string, or vector, an error is signaled. | |
2461 | ||
2462 | The argument @var{count} is a repeat count; @var{macro} is executed that | |
2463 | many times. If @var{count} is omitted or @code{nil}, @var{macro} is | |
2464 | executed once. If it is 0, @var{macro} is executed over and over until it | |
2465 | encounters an error or a failing search. | |
2466 | @end defun | |
2467 | ||
8db970a4 RS |
2468 | @defvar executing-macro |
2469 | This variable contains the string or vector that defines the keyboard | |
2470 | macro that is currently executing. It is @code{nil} if no macro is | |
f142f62a RS |
2471 | currently executing. A command can test this variable to behave |
2472 | differently when run from an executing macro. Do not set this variable | |
2473 | yourself. | |
8db970a4 RS |
2474 | @end defvar |
2475 | ||
2476 | @defvar defining-kbd-macro | |
f142f62a RS |
2477 | This variable indicates whether a keyboard macro is being defined. A |
2478 | command can test this variable to behave differently while a macro is | |
2479 | being defined. The commands @code{start-kbd-macro} and | |
2480 | @code{end-kbd-macro} set this variable---do not set it yourself. | |
22697dac | 2481 | |
bfe721d1 KH |
2482 | The variable is always local to the current terminal and cannot be |
2483 | buffer-local. @xref{Multiple Displays}. | |
2484 | @end defvar | |
2485 | ||
2486 | @defvar last-kbd-macro | |
2487 | This variable is the definition of the most recently defined keyboard | |
2488 | macro. Its value is a string or vector, or @code{nil}. | |
2489 | ||
2490 | The variable is always local to the current terminal and cannot be | |
22697dac | 2491 | buffer-local. @xref{Multiple Displays}. |
8db970a4 RS |
2492 | @end defvar |
2493 |