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1 | @c -*-texinfo-*- |
2 | @c This is part of the GNU Emacs Lisp Reference Manual. | |
fd897522 GM |
3 | @c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999 |
4 | @c Free Software Foundation, Inc. | |
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5 | @c See the file elisp.texi for copying conditions. |
6 | @setfilename ../info/commands | |
7 | @node Command Loop, Keymaps, Minibuffers, Top | |
8 | @chapter Command Loop | |
9 | @cindex editor command loop | |
10 | @cindex command loop | |
11 | ||
12 | When you run Emacs, it enters the @dfn{editor command loop} almost | |
13 | immediately. This loop reads key sequences, executes their definitions, | |
14 | and displays the results. In this chapter, we describe how these things | |
15 | are done, and the subroutines that allow Lisp programs to do them. | |
16 | ||
17 | @menu | |
18 | * Command Overview:: How the command loop reads commands. | |
19 | * Defining Commands:: Specifying how a function should read arguments. | |
20 | * Interactive Call:: Calling a command, so that it will read arguments. | |
21 | * Command Loop Info:: Variables set by the command loop for you to examine. | |
2468d0c0 | 22 | * Adjusting Point:: Adjustment of point after a command. |
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23 | * Input Events:: What input looks like when you read it. |
24 | * Reading Input:: How to read input events from the keyboard or mouse. | |
f9f59935 | 25 | * Special Events:: Events processed immediately and individually. |
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26 | * Waiting:: Waiting for user input or elapsed time. |
27 | * Quitting:: How @kbd{C-g} works. How to catch or defer quitting. | |
28 | * Prefix Command Arguments:: How the commands to set prefix args work. | |
29 | * Recursive Editing:: Entering a recursive edit, | |
30 | and why you usually shouldn't. | |
31 | * Disabling Commands:: How the command loop handles disabled commands. | |
32 | * Command History:: How the command history is set up, and how accessed. | |
33 | * Keyboard Macros:: How keyboard macros are implemented. | |
34 | @end menu | |
35 | ||
36 | @node Command Overview | |
37 | @section Command Loop Overview | |
38 | ||
39 | The first thing the command loop must do is read a key sequence, which | |
40 | is a sequence of events that translates into a command. It does this by | |
41 | calling the function @code{read-key-sequence}. Your Lisp code can also | |
42 | call this function (@pxref{Key Sequence Input}). Lisp programs can also | |
43 | do input at a lower level with @code{read-event} (@pxref{Reading One | |
44 | Event}) or discard pending input with @code{discard-input} | |
f142f62a | 45 | (@pxref{Event Input Misc}). |
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46 | |
47 | The key sequence is translated into a command through the currently | |
48 | active keymaps. @xref{Key Lookup}, for information on how this is done. | |
49 | The result should be a keyboard macro or an interactively callable | |
50 | function. If the key is @kbd{M-x}, then it reads the name of another | |
f142f62a | 51 | command, which it then calls. This is done by the command |
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52 | @code{execute-extended-command} (@pxref{Interactive Call}). |
53 | ||
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54 | To execute a command requires first reading the arguments for it. |
55 | This is done by calling @code{command-execute} (@pxref{Interactive | |
56 | Call}). For commands written in Lisp, the @code{interactive} | |
57 | specification says how to read the arguments. This may use the prefix | |
58 | argument (@pxref{Prefix Command Arguments}) or may read with prompting | |
59 | in the minibuffer (@pxref{Minibuffers}). For example, the command | |
60 | @code{find-file} has an @code{interactive} specification which says to | |
61 | read a file name using the minibuffer. The command's function body does | |
62 | not use the minibuffer; if you call this command from Lisp code as a | |
63 | function, you must supply the file name string as an ordinary Lisp | |
64 | function argument. | |
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65 | |
66 | If the command is a string or vector (i.e., a keyboard macro) then | |
67 | @code{execute-kbd-macro} is used to execute it. You can call this | |
68 | function yourself (@pxref{Keyboard Macros}). | |
69 | ||
f142f62a RS |
70 | To terminate the execution of a running command, type @kbd{C-g}. This |
71 | character causes @dfn{quitting} (@pxref{Quitting}). | |
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72 | |
73 | @defvar pre-command-hook | |
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74 | The editor command loop runs this normal hook before each command. At |
75 | that time, @code{this-command} contains the command that is about to | |
76 | run, and @code{last-command} describes the previous command. | |
b22f3a19 | 77 | @xref{Hooks}. |
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78 | @end defvar |
79 | ||
80 | @defvar post-command-hook | |
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81 | The editor command loop runs this normal hook after each command |
82 | (including commands terminated prematurely by quitting or by errors), | |
83 | and also when the command loop is first entered. At that time, | |
84 | @code{this-command} describes the command that just ran, and | |
b22f3a19 | 85 | @code{last-command} describes the command before that. @xref{Hooks}. |
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86 | @end defvar |
87 | ||
b22f3a19 | 88 | Quitting is suppressed while running @code{pre-command-hook} and |
bfe721d1 | 89 | @code{post-command-hook}. If an error happens while executing one of |
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90 | these hooks, it terminates execution of the hook, and clears the hook |
91 | variable to @code{nil} so as to prevent an infinite loop of errors. | |
b22f3a19 | 92 | |
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93 | @node Defining Commands |
94 | @section Defining Commands | |
95 | @cindex defining commands | |
96 | @cindex commands, defining | |
97 | @cindex functions, making them interactive | |
98 | @cindex interactive function | |
99 | ||
100 | A Lisp function becomes a command when its body contains, at top | |
b22f3a19 | 101 | level, a form that calls the special form @code{interactive}. This |
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102 | form does nothing when actually executed, but its presence serves as a |
103 | flag to indicate that interactive calling is permitted. Its argument | |
104 | controls the reading of arguments for an interactive call. | |
105 | ||
106 | @menu | |
107 | * Using Interactive:: General rules for @code{interactive}. | |
108 | * Interactive Codes:: The standard letter-codes for reading arguments | |
109 | in various ways. | |
110 | * Interactive Examples:: Examples of how to read interactive arguments. | |
111 | @end menu | |
112 | ||
113 | @node Using Interactive | |
114 | @subsection Using @code{interactive} | |
115 | ||
116 | This section describes how to write the @code{interactive} form that | |
2842de30 | 117 | makes a Lisp function an interactively-callable command, and how to |
caae20c7 | 118 | examine a commands's @code{interactive} form. |
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119 | |
120 | @defspec interactive arg-descriptor | |
121 | @cindex argument descriptors | |
122 | This special form declares that the function in which it appears is a | |
123 | command, and that it may therefore be called interactively (via | |
124 | @kbd{M-x} or by entering a key sequence bound to it). The argument | |
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125 | @var{arg-descriptor} declares how to compute the arguments to the |
126 | command when the command is called interactively. | |
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127 | |
128 | A command may be called from Lisp programs like any other function, but | |
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129 | then the caller supplies the arguments and @var{arg-descriptor} has no |
130 | effect. | |
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131 | |
132 | The @code{interactive} form has its effect because the command loop | |
133 | (actually, its subroutine @code{call-interactively}) scans through the | |
134 | function definition looking for it, before calling the function. Once | |
135 | the function is called, all its body forms including the | |
136 | @code{interactive} form are executed, but at this time | |
137 | @code{interactive} simply returns @code{nil} without even evaluating its | |
138 | argument. | |
139 | @end defspec | |
140 | ||
141 | There are three possibilities for the argument @var{arg-descriptor}: | |
142 | ||
143 | @itemize @bullet | |
144 | @item | |
145 | It may be omitted or @code{nil}; then the command is called with no | |
146 | arguments. This leads quickly to an error if the command requires one | |
147 | or more arguments. | |
148 | ||
149 | @item | |
150 | It may be a Lisp expression that is not a string; then it should be a | |
151 | form that is evaluated to get a list of arguments to pass to the | |
152 | command. | |
153 | @cindex argument evaluation form | |
154 | ||
3a2485be RS |
155 | If this expression reads keyboard input (this includes using the |
156 | minibuffer), keep in mind that the integer value of point or the mark | |
157 | before reading input may be incorrect after reading input. This is | |
158 | because the current buffer may be receiving subprocess output; | |
159 | if subprocess output arrives while the command is waiting for input, | |
160 | it could relocate point and the mark. | |
161 | ||
162 | Here's an example of what @emph{not} to do: | |
163 | ||
164 | @smallexample | |
165 | (interactive | |
166 | (list (region-beginning) (region-end) | |
167 | (read-string "Foo: " nil 'my-history))) | |
168 | @end smallexample | |
169 | ||
170 | @noindent | |
171 | Here's how to avoid the problem, by examining point and the mark only | |
172 | after reading the keyboard input: | |
173 | ||
174 | @smallexample | |
175 | (interactive | |
176 | (let ((string (read-string "Foo: " nil 'my-history))) | |
177 | (list (region-beginning) (region-end) string))) | |
178 | @end smallexample | |
179 | ||
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180 | @item |
181 | @cindex argument prompt | |
182 | It may be a string; then its contents should consist of a code character | |
183 | followed by a prompt (which some code characters use and some ignore). | |
184 | The prompt ends either with the end of the string or with a newline. | |
185 | Here is a simple example: | |
186 | ||
187 | @smallexample | |
188 | (interactive "bFrobnicate buffer: ") | |
189 | @end smallexample | |
190 | ||
191 | @noindent | |
192 | The code letter @samp{b} says to read the name of an existing buffer, | |
193 | with completion. The buffer name is the sole argument passed to the | |
194 | command. The rest of the string is a prompt. | |
195 | ||
196 | If there is a newline character in the string, it terminates the prompt. | |
197 | If the string does not end there, then the rest of the string should | |
198 | contain another code character and prompt, specifying another argument. | |
199 | You can specify any number of arguments in this way. | |
200 | ||
201 | @c Emacs 19 feature | |
202 | The prompt string can use @samp{%} to include previous argument values | |
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203 | (starting with the first argument) in the prompt. This is done using |
204 | @code{format} (@pxref{Formatting Strings}). For example, here is how | |
205 | you could read the name of an existing buffer followed by a new name to | |
206 | give to that buffer: | |
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207 | |
208 | @smallexample | |
209 | @group | |
210 | (interactive "bBuffer to rename: \nsRename buffer %s to: ") | |
211 | @end group | |
212 | @end smallexample | |
213 | ||
caae20c7 | 214 | @cindex @samp{*} in @code{interactive} |
f142f62a | 215 | @cindex read-only buffers in interactive |
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216 | If the first character in the string is @samp{*}, then an error is |
217 | signaled if the buffer is read-only. | |
218 | ||
caae20c7 | 219 | @cindex @samp{@@} in @code{interactive} |
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220 | @c Emacs 19 feature |
221 | If the first character in the string is @samp{@@}, and if the key | |
222 | sequence used to invoke the command includes any mouse events, then | |
223 | the window associated with the first of those events is selected | |
224 | before the command is run. | |
225 | ||
226 | You can use @samp{*} and @samp{@@} together; the order does not matter. | |
227 | Actual reading of arguments is controlled by the rest of the prompt | |
228 | string (starting with the first character that is not @samp{*} or | |
229 | @samp{@@}). | |
230 | @end itemize | |
231 | ||
caae20c7 | 232 | @cindex examining the @code{interactive} form |
2842de30 | 233 | @defun interactive-form function |
caae20c7 | 234 | This function returns the @code{interactive} form of @var{function}. If |
2842de30 EZ |
235 | @var{function} is a command (@pxref{Interactive Call}), the value is a |
236 | list of the form @code{(interactive @var{spec})}, where @var{spec} is | |
237 | the descriptor specification used by the command's @code{interactive} | |
238 | form to compute the function's arguments (@pxref{Using Interactive}). | |
239 | If @var{function} is not a command, @code{interactive-form} returns | |
240 | @code{nil}. | |
241 | @end defun | |
242 | ||
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243 | @node Interactive Codes |
244 | @comment node-name, next, previous, up | |
245 | @subsection Code Characters for @code{interactive} | |
246 | @cindex interactive code description | |
247 | @cindex description for interactive codes | |
248 | @cindex codes, interactive, description of | |
249 | @cindex characters for interactive codes | |
250 | ||
251 | The code character descriptions below contain a number of key words, | |
252 | defined here as follows: | |
253 | ||
254 | @table @b | |
255 | @item Completion | |
256 | @cindex interactive completion | |
257 | Provide completion. @key{TAB}, @key{SPC}, and @key{RET} perform name | |
258 | completion because the argument is read using @code{completing-read} | |
259 | (@pxref{Completion}). @kbd{?} displays a list of possible completions. | |
260 | ||
261 | @item Existing | |
262 | Require the name of an existing object. An invalid name is not | |
263 | accepted; the commands to exit the minibuffer do not exit if the current | |
264 | input is not valid. | |
265 | ||
266 | @item Default | |
267 | @cindex default argument string | |
268 | A default value of some sort is used if the user enters no text in the | |
269 | minibuffer. The default depends on the code character. | |
270 | ||
271 | @item No I/O | |
272 | This code letter computes an argument without reading any input. | |
273 | Therefore, it does not use a prompt string, and any prompt string you | |
274 | supply is ignored. | |
275 | ||
f142f62a RS |
276 | Even though the code letter doesn't use a prompt string, you must follow |
277 | it with a newline if it is not the last code character in the string. | |
278 | ||
8db970a4 RS |
279 | @item Prompt |
280 | A prompt immediately follows the code character. The prompt ends either | |
281 | with the end of the string or with a newline. | |
282 | ||
283 | @item Special | |
284 | This code character is meaningful only at the beginning of the | |
285 | interactive string, and it does not look for a prompt or a newline. | |
286 | It is a single, isolated character. | |
287 | @end table | |
288 | ||
289 | @cindex reading interactive arguments | |
290 | Here are the code character descriptions for use with @code{interactive}: | |
291 | ||
292 | @table @samp | |
293 | @item * | |
294 | Signal an error if the current buffer is read-only. Special. | |
295 | ||
296 | @item @@ | |
297 | Select the window mentioned in the first mouse event in the key | |
298 | sequence that invoked this command. Special. | |
299 | ||
300 | @item a | |
b22f3a19 | 301 | A function name (i.e., a symbol satisfying @code{fboundp}). Existing, |
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302 | Completion, Prompt. |
303 | ||
304 | @item b | |
305 | The name of an existing buffer. By default, uses the name of the | |
306 | current buffer (@pxref{Buffers}). Existing, Completion, Default, | |
307 | Prompt. | |
308 | ||
309 | @item B | |
310 | A buffer name. The buffer need not exist. By default, uses the name of | |
311 | a recently used buffer other than the current buffer. Completion, | |
b22f3a19 | 312 | Default, Prompt. |
8db970a4 RS |
313 | |
314 | @item c | |
315 | A character. The cursor does not move into the echo area. Prompt. | |
316 | ||
317 | @item C | |
318 | A command name (i.e., a symbol satisfying @code{commandp}). Existing, | |
319 | Completion, Prompt. | |
320 | ||
321 | @item d | |
322 | @cindex position argument | |
f142f62a | 323 | The position of point, as an integer (@pxref{Point}). No I/O. |
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324 | |
325 | @item D | |
326 | A directory name. The default is the current default directory of the | |
327 | current buffer, @code{default-directory} (@pxref{System Environment}). | |
328 | Existing, Completion, Default, Prompt. | |
329 | ||
330 | @item e | |
331 | The first or next mouse event in the key sequence that invoked the command. | |
b22f3a19 | 332 | More precisely, @samp{e} gets events that are lists, so you can look at |
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333 | the data in the lists. @xref{Input Events}. No I/O. |
334 | ||
335 | You can use @samp{e} more than once in a single command's interactive | |
b22f3a19 | 336 | specification. If the key sequence that invoked the command has |
f142f62a | 337 | @var{n} events that are lists, the @var{n}th @samp{e} provides the |
b22f3a19 | 338 | @var{n}th such event. Events that are not lists, such as function keys |
8241495d | 339 | and @sc{ascii} characters, do not count where @samp{e} is concerned. |
8db970a4 | 340 | |
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341 | @item f |
342 | A file name of an existing file (@pxref{File Names}). The default | |
343 | directory is @code{default-directory}. Existing, Completion, Default, | |
344 | Prompt. | |
345 | ||
346 | @item F | |
347 | A file name. The file need not exist. Completion, Default, Prompt. | |
348 | ||
a9f0a989 RS |
349 | @item i |
350 | An irrelevant argument. This code always supplies @code{nil} as | |
351 | the argument's value. No I/O. | |
352 | ||
8db970a4 RS |
353 | @item k |
354 | A key sequence (@pxref{Keymap Terminology}). This keeps reading events | |
355 | until a command (or undefined command) is found in the current key | |
356 | maps. The key sequence argument is represented as a string or vector. | |
357 | The cursor does not move into the echo area. Prompt. | |
358 | ||
359 | This kind of input is used by commands such as @code{describe-key} and | |
360 | @code{global-set-key}. | |
361 | ||
22697dac KH |
362 | @item K |
363 | A key sequence, whose definition you intend to change. This works like | |
364 | @samp{k}, except that it suppresses, for the last input event in the key | |
365 | sequence, the conversions that are normally used (when necessary) to | |
366 | convert an undefined key into a defined one. | |
367 | ||
8db970a4 RS |
368 | @item m |
369 | @cindex marker argument | |
f142f62a | 370 | The position of the mark, as an integer. No I/O. |
8db970a4 | 371 | |
f9f59935 RS |
372 | @item M |
373 | Arbitrary text, read in the minibuffer using the current buffer's input | |
374 | method, and returned as a string (@pxref{Input Methods,,, emacs, The GNU | |
375 | Emacs Manual}). Prompt. | |
376 | ||
8db970a4 RS |
377 | @item n |
378 | A number read with the minibuffer. If the input is not a number, the | |
379 | user is asked to try again. The prefix argument, if any, is not used. | |
380 | Prompt. | |
381 | ||
382 | @item N | |
383 | @cindex raw prefix argument usage | |
b39da8b1 RS |
384 | The numeric prefix argument; but if there is no prefix argument, read a |
385 | number as with @kbd{n}. Requires a number. @xref{Prefix Command | |
b22f3a19 | 386 | Arguments}. Prompt. |
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387 | |
388 | @item p | |
389 | @cindex numeric prefix argument usage | |
390 | The numeric prefix argument. (Note that this @samp{p} is lower case.) | |
b22f3a19 | 391 | No I/O. |
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392 | |
393 | @item P | |
b22f3a19 RS |
394 | The raw prefix argument. (Note that this @samp{P} is upper case.) No |
395 | I/O. | |
8db970a4 RS |
396 | |
397 | @item r | |
398 | @cindex region argument | |
399 | Point and the mark, as two numeric arguments, smallest first. This is | |
400 | the only code letter that specifies two successive arguments rather than | |
401 | one. No I/O. | |
402 | ||
403 | @item s | |
404 | Arbitrary text, read in the minibuffer and returned as a string | |
405 | (@pxref{Text from Minibuffer}). Terminate the input with either | |
969fe9b5 | 406 | @kbd{C-j} or @key{RET}. (@kbd{C-q} may be used to include either of |
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407 | these characters in the input.) Prompt. |
408 | ||
409 | @item S | |
410 | An interned symbol whose name is read in the minibuffer. Any whitespace | |
411 | character terminates the input. (Use @kbd{C-q} to include whitespace in | |
412 | the string.) Other characters that normally terminate a symbol (e.g., | |
413 | parentheses and brackets) do not do so here. Prompt. | |
414 | ||
415 | @item v | |
416 | A variable declared to be a user option (i.e., satisfying the predicate | |
417 | @code{user-variable-p}). @xref{High-Level Completion}. Existing, | |
418 | Completion, Prompt. | |
419 | ||
420 | @item x | |
b22f3a19 | 421 | A Lisp object, specified with its read syntax, terminated with a |
969fe9b5 | 422 | @kbd{C-j} or @key{RET}. The object is not evaluated. @xref{Object from |
8db970a4 RS |
423 | Minibuffer}. Prompt. |
424 | ||
425 | @item X | |
426 | @cindex evaluated expression argument | |
427 | A Lisp form is read as with @kbd{x}, but then evaluated so that its | |
428 | value becomes the argument for the command. Prompt. | |
a9f0a989 RS |
429 | |
430 | @item z | |
431 | A coding system name (a symbol). If the user enters null input, the | |
432 | argument value is @code{nil}. @xref{Coding Systems}. Completion, | |
433 | Existing, Prompt. | |
434 | ||
435 | @item Z | |
436 | A coding system name (a symbol)---but only if this command has a prefix | |
437 | argument. With no prefix argument, @samp{Z} provides @code{nil} as the | |
438 | argument value. Completion, Existing, Prompt. | |
8db970a4 RS |
439 | @end table |
440 | ||
441 | @node Interactive Examples | |
442 | @comment node-name, next, previous, up | |
443 | @subsection Examples of Using @code{interactive} | |
444 | @cindex examples of using @code{interactive} | |
445 | @cindex @code{interactive}, examples of using | |
446 | ||
447 | Here are some examples of @code{interactive}: | |
448 | ||
449 | @example | |
450 | @group | |
451 | (defun foo1 () ; @r{@code{foo1} takes no arguments,} | |
452 | (interactive) ; @r{just moves forward two words.} | |
453 | (forward-word 2)) | |
454 | @result{} foo1 | |
455 | @end group | |
456 | ||
457 | @group | |
458 | (defun foo2 (n) ; @r{@code{foo2} takes one argument,} | |
459 | (interactive "p") ; @r{which is the numeric prefix.} | |
460 | (forward-word (* 2 n))) | |
461 | @result{} foo2 | |
462 | @end group | |
463 | ||
464 | @group | |
465 | (defun foo3 (n) ; @r{@code{foo3} takes one argument,} | |
466 | (interactive "nCount:") ; @r{which is read with the Minibuffer.} | |
467 | (forward-word (* 2 n))) | |
468 | @result{} foo3 | |
469 | @end group | |
470 | ||
471 | @group | |
472 | (defun three-b (b1 b2 b3) | |
473 | "Select three existing buffers. | |
474 | Put them into three windows, selecting the last one." | |
475 | @end group | |
476 | (interactive "bBuffer1:\nbBuffer2:\nbBuffer3:") | |
477 | (delete-other-windows) | |
478 | (split-window (selected-window) 8) | |
479 | (switch-to-buffer b1) | |
480 | (other-window 1) | |
481 | (split-window (selected-window) 8) | |
482 | (switch-to-buffer b2) | |
483 | (other-window 1) | |
484 | (switch-to-buffer b3)) | |
485 | @result{} three-b | |
486 | @group | |
487 | (three-b "*scratch*" "declarations.texi" "*mail*") | |
488 | @result{} nil | |
489 | @end group | |
490 | @end example | |
491 | ||
492 | @node Interactive Call | |
493 | @section Interactive Call | |
494 | @cindex interactive call | |
495 | ||
f9f59935 RS |
496 | After the command loop has translated a key sequence into a command it |
497 | invokes that command using the function @code{command-execute}. If the | |
498 | command is a function, @code{command-execute} calls | |
499 | @code{call-interactively}, which reads the arguments and calls the | |
500 | command. You can also call these functions yourself. | |
8db970a4 RS |
501 | |
502 | @defun commandp object | |
503 | Returns @code{t} if @var{object} is suitable for calling interactively; | |
504 | that is, if @var{object} is a command. Otherwise, returns @code{nil}. | |
505 | ||
506 | The interactively callable objects include strings and vectors (treated | |
507 | as keyboard macros), lambda expressions that contain a top-level call to | |
bfe721d1 | 508 | @code{interactive}, byte-code function objects made from such lambda |
f142f62a RS |
509 | expressions, autoload objects that are declared as interactive |
510 | (non-@code{nil} fourth argument to @code{autoload}), and some of the | |
511 | primitive functions. | |
8db970a4 | 512 | |
969fe9b5 | 513 | A symbol satisfies @code{commandp} if its function definition satisfies |
8db970a4 RS |
514 | @code{commandp}. |
515 | ||
516 | Keys and keymaps are not commands. Rather, they are used to look up | |
517 | commands (@pxref{Keymaps}). | |
518 | ||
519 | See @code{documentation} in @ref{Accessing Documentation}, for a | |
520 | realistic example of using @code{commandp}. | |
521 | @end defun | |
522 | ||
f9f59935 | 523 | @defun call-interactively command &optional record-flag keys |
8db970a4 RS |
524 | This function calls the interactively callable function @var{command}, |
525 | reading arguments according to its interactive calling specifications. | |
b22f3a19 RS |
526 | An error is signaled if @var{command} is not a function or if it cannot |
527 | be called interactively (i.e., is not a command). Note that keyboard | |
528 | macros (strings and vectors) are not accepted, even though they are | |
529 | considered commands, because they are not functions. | |
8db970a4 RS |
530 | |
531 | @cindex record command history | |
532 | If @var{record-flag} is non-@code{nil}, then this command and its | |
533 | arguments are unconditionally added to the list @code{command-history}. | |
534 | Otherwise, the command is added only if it uses the minibuffer to read | |
535 | an argument. @xref{Command History}. | |
f9f59935 RS |
536 | |
537 | The argument @var{keys}, if given, specifies the sequence of events to | |
969fe9b5 | 538 | supply if the command inquires which events were used to invoke it. |
8db970a4 RS |
539 | @end defun |
540 | ||
79ddc9c9 | 541 | @defun command-execute command &optional record-flag keys special |
8db970a4 | 542 | @cindex keyboard macro execution |
f9f59935 RS |
543 | This function executes @var{command}. The argument @var{command} must |
544 | satisfy the @code{commandp} predicate; i.e., it must be an interactively | |
545 | callable function or a keyboard macro. | |
8db970a4 RS |
546 | |
547 | A string or vector as @var{command} is executed with | |
548 | @code{execute-kbd-macro}. A function is passed to | |
549 | @code{call-interactively}, along with the optional @var{record-flag}. | |
550 | ||
551 | A symbol is handled by using its function definition in its place. A | |
552 | symbol with an @code{autoload} definition counts as a command if it was | |
553 | declared to stand for an interactively callable function. Such a | |
554 | definition is handled by loading the specified library and then | |
555 | rechecking the definition of the symbol. | |
f9f59935 RS |
556 | |
557 | The argument @var{keys}, if given, specifies the sequence of events to | |
969fe9b5 | 558 | supply if the command inquires which events were used to invoke it. |
79ddc9c9 GM |
559 | |
560 | The argument @var{special}, if given, means to ignore the prefix | |
561 | argument and not clear it. This is used for executing special events | |
562 | (@pxref{Special Events}). | |
8db970a4 RS |
563 | @end defun |
564 | ||
565 | @deffn Command execute-extended-command prefix-argument | |
566 | @cindex read command name | |
567 | This function reads a command name from the minibuffer using | |
568 | @code{completing-read} (@pxref{Completion}). Then it uses | |
569 | @code{command-execute} to call the specified command. Whatever that | |
570 | command returns becomes the value of @code{execute-extended-command}. | |
571 | ||
572 | @cindex execute with prefix argument | |
f142f62a RS |
573 | If the command asks for a prefix argument, it receives the value |
574 | @var{prefix-argument}. If @code{execute-extended-command} is called | |
575 | interactively, the current raw prefix argument is used for | |
8db970a4 RS |
576 | @var{prefix-argument}, and thus passed on to whatever command is run. |
577 | ||
578 | @c !!! Should this be @kindex? | |
579 | @cindex @kbd{M-x} | |
580 | @code{execute-extended-command} is the normal definition of @kbd{M-x}, | |
581 | so it uses the string @w{@samp{M-x }} as a prompt. (It would be better | |
582 | to take the prompt from the events used to invoke | |
583 | @code{execute-extended-command}, but that is painful to implement.) A | |
584 | description of the value of the prefix argument, if any, also becomes | |
585 | part of the prompt. | |
586 | ||
587 | @example | |
588 | @group | |
589 | (execute-extended-command 1) | |
590 | ---------- Buffer: Minibuffer ---------- | |
b22f3a19 | 591 | 1 M-x forward-word RET |
8db970a4 RS |
592 | ---------- Buffer: Minibuffer ---------- |
593 | @result{} t | |
594 | @end group | |
595 | @end example | |
596 | @end deffn | |
597 | ||
598 | @defun interactive-p | |
9e2b495b RS |
599 | This function returns @code{t} if the containing function (the one whose |
600 | code includes the call to @code{interactive-p}) was called | |
601 | interactively, with the function @code{call-interactively}. (It makes | |
602 | no difference whether @code{call-interactively} was called from Lisp or | |
603 | directly from the editor command loop.) If the containing function was | |
604 | called by Lisp evaluation (or with @code{apply} or @code{funcall}), then | |
605 | it was not called interactively. | |
969fe9b5 | 606 | @end defun |
8db970a4 | 607 | |
969fe9b5 | 608 | The most common use of @code{interactive-p} is for deciding whether to |
8db970a4 RS |
609 | print an informative message. As a special exception, |
610 | @code{interactive-p} returns @code{nil} whenever a keyboard macro is | |
611 | being run. This is to suppress the informative messages and speed | |
612 | execution of the macro. | |
613 | ||
969fe9b5 | 614 | For example: |
8db970a4 RS |
615 | |
616 | @example | |
617 | @group | |
618 | (defun foo () | |
619 | (interactive) | |
969fe9b5 RS |
620 | (when (interactive-p) |
621 | (message "foo"))) | |
8db970a4 RS |
622 | @result{} foo |
623 | @end group | |
624 | ||
625 | @group | |
626 | (defun bar () | |
627 | (interactive) | |
628 | (setq foobar (list (foo) (interactive-p)))) | |
629 | @result{} bar | |
630 | @end group | |
631 | ||
632 | @group | |
633 | ;; @r{Type @kbd{M-x foo}.} | |
634 | @print{} foo | |
635 | @end group | |
636 | ||
637 | @group | |
638 | ;; @r{Type @kbd{M-x bar}.} | |
639 | ;; @r{This does not print anything.} | |
640 | @end group | |
641 | ||
642 | @group | |
643 | foobar | |
644 | @result{} (nil t) | |
645 | @end group | |
646 | @end example | |
969fe9b5 RS |
647 | |
648 | The other way to do this sort of job is to make the command take an | |
649 | argument @code{print-message} which should be non-@code{nil} in an | |
650 | interactive call, and use the @code{interactive} spec to make sure it is | |
651 | non-@code{nil}. Here's how: | |
652 | ||
653 | @example | |
654 | (defun foo (&optional print-message) | |
655 | (interactive "p") | |
656 | (when print-message | |
657 | (message "foo"))) | |
658 | @end example | |
659 | ||
660 | The numeric prefix argument, provided by @samp{p}, is never @code{nil}. | |
8db970a4 RS |
661 | |
662 | @node Command Loop Info | |
663 | @comment node-name, next, previous, up | |
664 | @section Information from the Command Loop | |
665 | ||
666 | The editor command loop sets several Lisp variables to keep status | |
667 | records for itself and for commands that are run. | |
668 | ||
669 | @defvar last-command | |
670 | This variable records the name of the previous command executed by the | |
671 | command loop (the one before the current command). Normally the value | |
672 | is a symbol with a function definition, but this is not guaranteed. | |
673 | ||
f142f62a | 674 | The value is copied from @code{this-command} when a command returns to |
f9f59935 RS |
675 | the command loop, except when the command has specified a prefix |
676 | argument for the following command. | |
bfe721d1 KH |
677 | |
678 | This variable is always local to the current terminal and cannot be | |
679 | buffer-local. @xref{Multiple Displays}. | |
8db970a4 RS |
680 | @end defvar |
681 | ||
03c6b7f6 RS |
682 | @defvar real-last-command |
683 | This variable is set up by Emacs just like @code{last-command}, | |
684 | but never altered by Lisp programs. | |
685 | @end defvar | |
686 | ||
8db970a4 RS |
687 | @defvar this-command |
688 | @cindex current command | |
689 | This variable records the name of the command now being executed by | |
690 | the editor command loop. Like @code{last-command}, it is normally a symbol | |
691 | with a function definition. | |
692 | ||
f142f62a RS |
693 | The command loop sets this variable just before running a command, and |
694 | copies its value into @code{last-command} when the command finishes | |
f9f59935 | 695 | (unless the command specified a prefix argument for the following |
f142f62a | 696 | command). |
8db970a4 RS |
697 | |
698 | @cindex kill command repetition | |
f142f62a | 699 | Some commands set this variable during their execution, as a flag for |
bfe721d1 | 700 | whatever command runs next. In particular, the functions for killing text |
f142f62a RS |
701 | set @code{this-command} to @code{kill-region} so that any kill commands |
702 | immediately following will know to append the killed text to the | |
703 | previous kill. | |
8db970a4 RS |
704 | @end defvar |
705 | ||
706 | If you do not want a particular command to be recognized as the previous | |
707 | command in the case where it got an error, you must code that command to | |
708 | prevent this. One way is to set @code{this-command} to @code{t} at the | |
709 | beginning of the command, and set @code{this-command} back to its proper | |
710 | value at the end, like this: | |
711 | ||
712 | @example | |
713 | (defun foo (args@dots{}) | |
714 | (interactive @dots{}) | |
715 | (let ((old-this-command this-command)) | |
716 | (setq this-command t) | |
717 | @r{@dots{}do the work@dots{}} | |
718 | (setq this-command old-this-command))) | |
719 | @end example | |
720 | ||
f9f59935 RS |
721 | @noindent |
722 | We do not bind @code{this-command} with @code{let} because that would | |
723 | restore the old value in case of error---a feature of @code{let} which | |
724 | in this case does precisely what we want to avoid. | |
725 | ||
8db970a4 RS |
726 | @defun this-command-keys |
727 | This function returns a string or vector containing the key sequence | |
728 | that invoked the present command, plus any previous commands that | |
729 | generated the prefix argument for this command. The value is a string | |
730 | if all those events were characters. @xref{Input Events}. | |
731 | ||
732 | @example | |
733 | @group | |
734 | (this-command-keys) | |
b22f3a19 | 735 | ;; @r{Now use @kbd{C-u C-x C-e} to evaluate that.} |
8db970a4 RS |
736 | @result{} "^U^X^E" |
737 | @end group | |
738 | @end example | |
739 | @end defun | |
740 | ||
969fe9b5 | 741 | @defun this-command-keys-vector |
2468d0c0 DL |
742 | Like @code{this-command-keys}, except that it always returns the events |
743 | in a vector, so you don't need to deal with the complexities of storing | |
744 | input events in a string (@pxref{Strings of Events}). | |
969fe9b5 RS |
745 | @end defun |
746 | ||
b6954afd RS |
747 | @tindex clear-this-command-keys |
748 | @defun clear-this-command-keys | |
749 | This function empties out the table of events for | |
caae20c7 RS |
750 | @code{this-command-keys} to return, and also empties the records that |
751 | the function @code{recent-keys} (@pxref{Recording Input}) will | |
752 | subsequently return. This is useful after reading a password, to | |
753 | prevent the password from echoing inadvertently as part of the next | |
754 | command in certain cases. | |
b6954afd RS |
755 | @end defun |
756 | ||
8db970a4 | 757 | @defvar last-nonmenu-event |
969fe9b5 RS |
758 | This variable holds the last input event read as part of a key sequence, |
759 | not counting events resulting from mouse menus. | |
8db970a4 | 760 | |
f9f59935 | 761 | One use of this variable is for telling @code{x-popup-menu} where to pop |
969fe9b5 RS |
762 | up a menu. It is also used internally by @code{y-or-n-p} |
763 | (@pxref{Yes-or-No Queries}). | |
8db970a4 RS |
764 | @end defvar |
765 | ||
766 | @defvar last-command-event | |
767 | @defvarx last-command-char | |
768 | This variable is set to the last input event that was read by the | |
769 | command loop as part of a command. The principal use of this variable | |
770 | is in @code{self-insert-command}, which uses it to decide which | |
771 | character to insert. | |
772 | ||
773 | @example | |
774 | @group | |
f142f62a | 775 | last-command-event |
b22f3a19 | 776 | ;; @r{Now use @kbd{C-u C-x C-e} to evaluate that.} |
8db970a4 RS |
777 | @result{} 5 |
778 | @end group | |
779 | @end example | |
780 | ||
781 | @noindent | |
8241495d | 782 | The value is 5 because that is the @sc{ascii} code for @kbd{C-e}. |
8db970a4 RS |
783 | |
784 | The alias @code{last-command-char} exists for compatibility with | |
785 | Emacs version 18. | |
786 | @end defvar | |
787 | ||
788 | @c Emacs 19 feature | |
789 | @defvar last-event-frame | |
790 | This variable records which frame the last input event was directed to. | |
791 | Usually this is the frame that was selected when the event was | |
792 | generated, but if that frame has redirected input focus to another | |
793 | frame, the value is the frame to which the event was redirected. | |
794 | @xref{Input Focus}. | |
795 | @end defvar | |
796 | ||
2468d0c0 DL |
797 | @node Adjusting Point |
798 | @section Adjusting Point After Commands | |
799 | ||
800 | It is not easy to display a value of point in the middle of a sequence | |
801 | of text that has the @code{display} or @code{composition} property. So | |
802 | after a command finishes and returns to the command loop, if point is | |
803 | within such a sequence, the command loop normally moves point to the | |
804 | edge of the sequence. | |
805 | ||
806 | A command can inhibit this feature by setting the variable | |
807 | @code{disable-point-adjustment}: | |
808 | ||
809 | @defvar disable-point-adjustment | |
810 | @tindex disable-point-adjustment | |
811 | If this variable is non-@code{nil} when a command returns to the command | |
812 | loop, then the command loop does not check for text properties such as | |
813 | @code{display} and @code{composition}, and does not move point out of | |
814 | sequences that have these properties. | |
815 | ||
816 | The command loop sets this variable to @code{nil} before each command, | |
817 | so if a command sets it, the effect applies only to that command. | |
818 | @end defvar | |
819 | ||
820 | @defvar global-disable-point-adjustment | |
821 | @tindex global-disable-point-adjustment | |
822 | If you set this variable to a non-@code{nil} value, the feature of | |
823 | moving point out of these sequences is completely turned off. | |
824 | @end defvar | |
825 | ||
8db970a4 RS |
826 | @node Input Events |
827 | @section Input Events | |
828 | @cindex events | |
829 | @cindex input events | |
830 | ||
831 | The Emacs command loop reads a sequence of @dfn{input events} that | |
832 | represent keyboard or mouse activity. The events for keyboard activity | |
833 | are characters or symbols; mouse events are always lists. This section | |
834 | describes the representation and meaning of input events in detail. | |
835 | ||
8db970a4 | 836 | @defun eventp object |
a9f0a989 RS |
837 | This function returns non-@code{nil} if @var{object} is an input event |
838 | or event type. | |
839 | ||
840 | Note that any symbol might be used as an event or an event type. | |
841 | @code{eventp} cannot distinguish whether a symbol is intended by Lisp | |
842 | code to be used as an event. Instead, it distinguishes whether the | |
843 | symbol has actually been used in an event that has been read as input in | |
844 | the current Emacs session. If a symbol has not yet been so used, | |
845 | @code{eventp} returns @code{nil}. | |
8db970a4 RS |
846 | @end defun |
847 | ||
848 | @menu | |
849 | * Keyboard Events:: Ordinary characters--keys with symbols on them. | |
850 | * Function Keys:: Function keys--keys with names, not symbols. | |
f142f62a | 851 | * Mouse Events:: Overview of mouse events. |
8db970a4 RS |
852 | * Click Events:: Pushing and releasing a mouse button. |
853 | * Drag Events:: Moving the mouse before releasing the button. | |
854 | * Button-Down Events:: A button was pushed and not yet released. | |
855 | * Repeat Events:: Double and triple click (or drag, or down). | |
856 | * Motion Events:: Just moving the mouse, not pushing a button. | |
857 | * Focus Events:: Moving the mouse between frames. | |
22697dac | 858 | * Misc Events:: Other events window systems can generate. |
8db970a4 RS |
859 | * Event Examples:: Examples of the lists for mouse events. |
860 | * Classifying Events:: Finding the modifier keys in an event symbol. | |
861 | Event types. | |
862 | * Accessing Events:: Functions to extract info from events. | |
863 | * Strings of Events:: Special considerations for putting | |
864 | keyboard character events in a string. | |
865 | @end menu | |
866 | ||
867 | @node Keyboard Events | |
868 | @subsection Keyboard Events | |
869 | ||
870 | There are two kinds of input you can get from the keyboard: ordinary | |
871 | keys, and function keys. Ordinary keys correspond to characters; the | |
969fe9b5 RS |
872 | events they generate are represented in Lisp as characters. The event |
873 | type of a character event is the character itself (an integer); see | |
874 | @ref{Classifying Events}. | |
8db970a4 RS |
875 | |
876 | @cindex modifier bits (of input character) | |
877 | @cindex basic code (of input character) | |
878 | An input character event consists of a @dfn{basic code} between 0 and | |
f9f59935 | 879 | 524287, plus any or all of these @dfn{modifier bits}: |
8db970a4 RS |
880 | |
881 | @table @asis | |
882 | @item meta | |
bfe721d1 | 883 | The |
969fe9b5 | 884 | @tex |
8241495d | 885 | @math{2^{27}} |
969fe9b5 | 886 | @end tex |
37680279 | 887 | @ifnottex |
bfe721d1 | 888 | 2**27 |
37680279 | 889 | @end ifnottex |
bfe721d1 | 890 | bit in the character code indicates a character |
8db970a4 RS |
891 | typed with the meta key held down. |
892 | ||
893 | @item control | |
bfe721d1 | 894 | The |
969fe9b5 | 895 | @tex |
8241495d | 896 | @math{2^{26}} |
969fe9b5 | 897 | @end tex |
37680279 | 898 | @ifnottex |
bfe721d1 | 899 | 2**26 |
37680279 | 900 | @end ifnottex |
8241495d | 901 | bit in the character code indicates a non-@sc{ascii} |
8db970a4 RS |
902 | control character. |
903 | ||
8241495d | 904 | @sc{ascii} control characters such as @kbd{C-a} have special basic |
8db970a4 RS |
905 | codes of their own, so Emacs needs no special bit to indicate them. |
906 | Thus, the code for @kbd{C-a} is just 1. | |
907 | ||
8241495d | 908 | But if you type a control combination not in @sc{ascii}, such as |
8db970a4 | 909 | @kbd{%} with the control key, the numeric value you get is the code |
bfe721d1 | 910 | for @kbd{%} plus |
969fe9b5 | 911 | @tex |
8241495d | 912 | @math{2^{26}} |
969fe9b5 | 913 | @end tex |
37680279 | 914 | @ifnottex |
bfe721d1 | 915 | 2**26 |
37680279 | 916 | @end ifnottex |
8241495d | 917 | (assuming the terminal supports non-@sc{ascii} |
8db970a4 RS |
918 | control characters). |
919 | ||
920 | @item shift | |
bfe721d1 | 921 | The |
969fe9b5 | 922 | @tex |
8241495d | 923 | @math{2^{25}} |
969fe9b5 | 924 | @end tex |
37680279 | 925 | @ifnottex |
bfe721d1 | 926 | 2**25 |
37680279 | 927 | @end ifnottex |
8241495d | 928 | bit in the character code indicates an @sc{ascii} control |
8db970a4 RS |
929 | character typed with the shift key held down. |
930 | ||
f9f59935 RS |
931 | For letters, the basic code itself indicates upper versus lower case; |
932 | for digits and punctuation, the shift key selects an entirely different | |
933 | character with a different basic code. In order to keep within the | |
8241495d | 934 | @sc{ascii} character set whenever possible, Emacs avoids using the |
969fe9b5 | 935 | @tex |
8241495d | 936 | @math{2^{25}} |
969fe9b5 | 937 | @end tex |
37680279 | 938 | @ifnottex |
bfe721d1 | 939 | 2**25 |
37680279 | 940 | @end ifnottex |
bfe721d1 | 941 | bit for those characters. |
8db970a4 | 942 | |
8241495d | 943 | However, @sc{ascii} provides no way to distinguish @kbd{C-A} from |
bfe721d1 | 944 | @kbd{C-a}, so Emacs uses the |
969fe9b5 | 945 | @tex |
8241495d | 946 | @math{2^{25}} |
969fe9b5 | 947 | @end tex |
37680279 | 948 | @ifnottex |
bfe721d1 | 949 | 2**25 |
37680279 | 950 | @end ifnottex |
bfe721d1 | 951 | bit in @kbd{C-A} and not in |
8db970a4 RS |
952 | @kbd{C-a}. |
953 | ||
954 | @item hyper | |
bfe721d1 | 955 | The |
969fe9b5 | 956 | @tex |
8241495d | 957 | @math{2^{24}} |
969fe9b5 | 958 | @end tex |
37680279 | 959 | @ifnottex |
bfe721d1 | 960 | 2**24 |
37680279 | 961 | @end ifnottex |
bfe721d1 | 962 | bit in the character code indicates a character |
8db970a4 RS |
963 | typed with the hyper key held down. |
964 | ||
965 | @item super | |
bfe721d1 | 966 | The |
969fe9b5 | 967 | @tex |
8241495d | 968 | @math{2^{23}} |
969fe9b5 | 969 | @end tex |
37680279 | 970 | @ifnottex |
bfe721d1 | 971 | 2**23 |
37680279 | 972 | @end ifnottex |
bfe721d1 | 973 | bit in the character code indicates a character |
8db970a4 RS |
974 | typed with the super key held down. |
975 | ||
976 | @item alt | |
bfe721d1 | 977 | The |
969fe9b5 | 978 | @tex |
8241495d | 979 | @math{2^{22}} |
969fe9b5 | 980 | @end tex |
37680279 | 981 | @ifnottex |
bfe721d1 | 982 | 2**22 |
37680279 | 983 | @end ifnottex |
bfe721d1 | 984 | bit in the character code indicates a character typed with |
8db970a4 RS |
985 | the alt key held down. (On some terminals, the key labeled @key{ALT} |
986 | is actually the meta key.) | |
987 | @end table | |
988 | ||
bfe721d1 KH |
989 | It is best to avoid mentioning specific bit numbers in your program. |
990 | To test the modifier bits of a character, use the function | |
991 | @code{event-modifiers} (@pxref{Classifying Events}). When making key | |
992 | bindings, you can use the read syntax for characters with modifier bits | |
993 | (@samp{\C-}, @samp{\M-}, and so on). For making key bindings with | |
994 | @code{define-key}, you can use lists such as @code{(control hyper ?x)} to | |
995 | specify the characters (@pxref{Changing Key Bindings}). The function | |
996 | @code{event-convert-list} converts such a list into an event type | |
997 | (@pxref{Classifying Events}). | |
8db970a4 RS |
998 | |
999 | @node Function Keys | |
1000 | @subsection Function Keys | |
1001 | ||
1002 | @cindex function keys | |
b22f3a19 | 1003 | Most keyboards also have @dfn{function keys}---keys that have names or |
f9f59935 RS |
1004 | symbols that are not characters. Function keys are represented in Emacs |
1005 | Lisp as symbols; the symbol's name is the function key's label, in lower | |
f142f62a RS |
1006 | case. For example, pressing a key labeled @key{F1} places the symbol |
1007 | @code{f1} in the input stream. | |
8db970a4 | 1008 | |
f142f62a RS |
1009 | The event type of a function key event is the event symbol itself. |
1010 | @xref{Classifying Events}. | |
8db970a4 | 1011 | |
b22f3a19 | 1012 | Here are a few special cases in the symbol-naming convention for |
8db970a4 RS |
1013 | function keys: |
1014 | ||
1015 | @table @asis | |
1016 | @item @code{backspace}, @code{tab}, @code{newline}, @code{return}, @code{delete} | |
8241495d | 1017 | These keys correspond to common @sc{ascii} control characters that have |
8db970a4 RS |
1018 | special keys on most keyboards. |
1019 | ||
8241495d | 1020 | In @sc{ascii}, @kbd{C-i} and @key{TAB} are the same character. If the |
f142f62a RS |
1021 | terminal can distinguish between them, Emacs conveys the distinction to |
1022 | Lisp programs by representing the former as the integer 9, and the | |
1023 | latter as the symbol @code{tab}. | |
8db970a4 RS |
1024 | |
1025 | Most of the time, it's not useful to distinguish the two. So normally | |
4324b7ab RS |
1026 | @code{function-key-map} (@pxref{Translating Input}) is set up to map |
1027 | @code{tab} into 9. Thus, a key binding for character code 9 (the | |
1028 | character @kbd{C-i}) also applies to @code{tab}. Likewise for the other | |
1029 | symbols in this group. The function @code{read-char} likewise converts | |
1030 | these events into characters. | |
8db970a4 | 1031 | |
8241495d | 1032 | In @sc{ascii}, @key{BS} is really @kbd{C-h}. But @code{backspace} |
8db970a4 RS |
1033 | converts into the character code 127 (@key{DEL}), not into code 8 |
1034 | (@key{BS}). This is what most users prefer. | |
1035 | ||
b22f3a19 RS |
1036 | @item @code{left}, @code{up}, @code{right}, @code{down} |
1037 | Cursor arrow keys | |
8db970a4 RS |
1038 | @item @code{kp-add}, @code{kp-decimal}, @code{kp-divide}, @dots{} |
1039 | Keypad keys (to the right of the regular keyboard). | |
1040 | @item @code{kp-0}, @code{kp-1}, @dots{} | |
1041 | Keypad keys with digits. | |
1042 | @item @code{kp-f1}, @code{kp-f2}, @code{kp-f3}, @code{kp-f4} | |
1043 | Keypad PF keys. | |
b22f3a19 | 1044 | @item @code{kp-home}, @code{kp-left}, @code{kp-up}, @code{kp-right}, @code{kp-down} |
f9f59935 RS |
1045 | Keypad arrow keys. Emacs normally translates these into the |
1046 | corresponding non-keypad keys @code{home}, @code{left}, @dots{} | |
b22f3a19 RS |
1047 | @item @code{kp-prior}, @code{kp-next}, @code{kp-end}, @code{kp-begin}, @code{kp-insert}, @code{kp-delete} |
1048 | Additional keypad duplicates of keys ordinarily found elsewhere. Emacs | |
1049 | normally translates these into the like-named non-keypad keys. | |
8db970a4 RS |
1050 | @end table |
1051 | ||
b22f3a19 RS |
1052 | You can use the modifier keys @key{ALT}, @key{CTRL}, @key{HYPER}, |
1053 | @key{META}, @key{SHIFT}, and @key{SUPER} with function keys. The way to | |
1054 | represent them is with prefixes in the symbol name: | |
8db970a4 RS |
1055 | |
1056 | @table @samp | |
1057 | @item A- | |
1058 | The alt modifier. | |
1059 | @item C- | |
1060 | The control modifier. | |
1061 | @item H- | |
1062 | The hyper modifier. | |
1063 | @item M- | |
1064 | The meta modifier. | |
1065 | @item S- | |
1066 | The shift modifier. | |
1067 | @item s- | |
1068 | The super modifier. | |
1069 | @end table | |
1070 | ||
1071 | Thus, the symbol for the key @key{F3} with @key{META} held down is | |
8609b2e2 | 1072 | @code{M-f3}. When you use more than one prefix, we recommend you |
f142f62a RS |
1073 | write them in alphabetical order; but the order does not matter in |
1074 | arguments to the key-binding lookup and modification functions. | |
1075 | ||
1076 | @node Mouse Events | |
1077 | @subsection Mouse Events | |
1078 | ||
1079 | Emacs supports four kinds of mouse events: click events, drag events, | |
1080 | button-down events, and motion events. All mouse events are represented | |
1081 | as lists. The @sc{car} of the list is the event type; this says which | |
1082 | mouse button was involved, and which modifier keys were used with it. | |
1083 | The event type can also distinguish double or triple button presses | |
1084 | (@pxref{Repeat Events}). The rest of the list elements give position | |
1085 | and time information. | |
1086 | ||
1087 | For key lookup, only the event type matters: two events of the same type | |
1088 | necessarily run the same command. The command can access the full | |
1089 | values of these events using the @samp{e} interactive code. | |
1090 | @xref{Interactive Codes}. | |
1091 | ||
1092 | A key sequence that starts with a mouse event is read using the keymaps | |
1093 | of the buffer in the window that the mouse was in, not the current | |
1094 | buffer. This does not imply that clicking in a window selects that | |
1095 | window or its buffer---that is entirely under the control of the command | |
1096 | binding of the key sequence. | |
8db970a4 RS |
1097 | |
1098 | @node Click Events | |
1099 | @subsection Click Events | |
1100 | @cindex click event | |
1101 | @cindex mouse click event | |
1102 | ||
1103 | When the user presses a mouse button and releases it at the same | |
1104 | location, that generates a @dfn{click} event. Mouse click events have | |
1105 | this form: | |
1106 | ||
1107 | @example | |
1108 | (@var{event-type} | |
f142f62a | 1109 | (@var{window} @var{buffer-pos} (@var{x} . @var{y}) @var{timestamp}) |
8db970a4 RS |
1110 | @var{click-count}) |
1111 | @end example | |
1112 | ||
1113 | Here is what the elements normally mean: | |
1114 | ||
f142f62a RS |
1115 | @table @asis |
1116 | @item @var{event-type} | |
8db970a4 RS |
1117 | This is a symbol that indicates which mouse button was used. It is |
1118 | one of the symbols @code{mouse-1}, @code{mouse-2}, @dots{}, where the | |
f142f62a | 1119 | buttons are numbered left to right. |
8db970a4 RS |
1120 | |
1121 | You can also use prefixes @samp{A-}, @samp{C-}, @samp{H-}, @samp{M-}, | |
1122 | @samp{S-} and @samp{s-} for modifiers alt, control, hyper, meta, shift | |
1123 | and super, just as you would with function keys. | |
1124 | ||
1125 | This symbol also serves as the event type of the event. Key bindings | |
1126 | describe events by their types; thus, if there is a key binding for | |
1127 | @code{mouse-1}, that binding would apply to all events whose | |
1128 | @var{event-type} is @code{mouse-1}. | |
1129 | ||
f142f62a | 1130 | @item @var{window} |
8db970a4 RS |
1131 | This is the window in which the click occurred. |
1132 | ||
f142f62a | 1133 | @item @var{x}, @var{y} |
b22f3a19 RS |
1134 | These are the pixel-denominated coordinates of the click, relative to |
1135 | the top left corner of @var{window}, which is @code{(0 . 0)}. | |
8db970a4 | 1136 | |
f142f62a | 1137 | @item @var{buffer-pos} |
8db970a4 RS |
1138 | This is the buffer position of the character clicked on. |
1139 | ||
f142f62a | 1140 | @item @var{timestamp} |
8db970a4 RS |
1141 | This is the time at which the event occurred, in milliseconds. (Since |
1142 | this value wraps around the entire range of Emacs Lisp integers in about | |
1143 | five hours, it is useful only for relating the times of nearby events.) | |
1144 | ||
f142f62a | 1145 | @item @var{click-count} |
8db970a4 RS |
1146 | This is the number of rapid repeated presses so far of the same mouse |
1147 | button. @xref{Repeat Events}. | |
1148 | @end table | |
1149 | ||
f142f62a RS |
1150 | The meanings of @var{buffer-pos}, @var{x} and @var{y} are somewhat |
1151 | different when the event location is in a special part of the screen, | |
1152 | such as the mode line or a scroll bar. | |
8db970a4 RS |
1153 | |
1154 | If the location is in a scroll bar, then @var{buffer-pos} is the symbol | |
1155 | @code{vertical-scroll-bar} or @code{horizontal-scroll-bar}, and the pair | |
1156 | @code{(@var{x} . @var{y})} is replaced with a pair @code{(@var{portion} | |
1157 | . @var{whole})}, where @var{portion} is the distance of the click from | |
1158 | the top or left end of the scroll bar, and @var{whole} is the length of | |
1159 | the entire scroll bar. | |
1160 | ||
1161 | If the position is on a mode line or the vertical line separating | |
1162 | @var{window} from its neighbor to the right, then @var{buffer-pos} is | |
79ddc9c9 GM |
1163 | the symbol @code{mode-line}, @code{header-line}, or |
1164 | @code{vertical-line}. For the mode line, @var{y} does not have | |
1165 | meaningful data. For the vertical line, @var{x} does not have | |
1166 | meaningful data. | |
8db970a4 | 1167 | |
b22f3a19 RS |
1168 | In one special case, @var{buffer-pos} is a list containing a symbol (one |
1169 | of the symbols listed above) instead of just the symbol. This happens | |
1170 | after the imaginary prefix keys for the event are inserted into the | |
1171 | input stream. @xref{Key Sequence Input}. | |
8db970a4 RS |
1172 | |
1173 | @node Drag Events | |
1174 | @subsection Drag Events | |
1175 | @cindex drag event | |
1176 | @cindex mouse drag event | |
1177 | ||
1178 | With Emacs, you can have a drag event without even changing your | |
1179 | clothes. A @dfn{drag event} happens every time the user presses a mouse | |
1180 | button and then moves the mouse to a different character position before | |
1181 | releasing the button. Like all mouse events, drag events are | |
1182 | represented in Lisp as lists. The lists record both the starting mouse | |
1183 | position and the final position, like this: | |
1184 | ||
1185 | @example | |
1186 | (@var{event-type} | |
f142f62a RS |
1187 | (@var{window1} @var{buffer-pos1} (@var{x1} . @var{y1}) @var{timestamp1}) |
1188 | (@var{window2} @var{buffer-pos2} (@var{x2} . @var{y2}) @var{timestamp2}) | |
8db970a4 RS |
1189 | @var{click-count}) |
1190 | @end example | |
1191 | ||
1192 | For a drag event, the name of the symbol @var{event-type} contains the | |
f9f59935 RS |
1193 | prefix @samp{drag-}. For example, dragging the mouse with button 2 held |
1194 | down generates a @code{drag-mouse-2} event. The second and third | |
1195 | elements of the event give the starting and ending position of the drag. | |
1196 | Aside from that, the data have the same meanings as in a click event | |
1197 | (@pxref{Click Events}). You can access the second element of any mouse | |
1198 | event in the same way, with no need to distinguish drag events from | |
1199 | others. | |
8db970a4 RS |
1200 | |
1201 | The @samp{drag-} prefix follows the modifier key prefixes such as | |
1202 | @samp{C-} and @samp{M-}. | |
1203 | ||
b22f3a19 | 1204 | If @code{read-key-sequence} receives a drag event that has no key |
8db970a4 RS |
1205 | binding, and the corresponding click event does have a binding, it |
1206 | changes the drag event into a click event at the drag's starting | |
1207 | position. This means that you don't have to distinguish between click | |
1208 | and drag events unless you want to. | |
1209 | ||
1210 | @node Button-Down Events | |
1211 | @subsection Button-Down Events | |
1212 | @cindex button-down event | |
1213 | ||
1214 | Click and drag events happen when the user releases a mouse button. | |
1215 | They cannot happen earlier, because there is no way to distinguish a | |
1216 | click from a drag until the button is released. | |
1217 | ||
1218 | If you want to take action as soon as a button is pressed, you need to | |
1219 | handle @dfn{button-down} events.@footnote{Button-down is the | |
f142f62a | 1220 | conservative antithesis of drag.} These occur as soon as a button is |
b22f3a19 | 1221 | pressed. They are represented by lists that look exactly like click |
f142f62a RS |
1222 | events (@pxref{Click Events}), except that the @var{event-type} symbol |
1223 | name contains the prefix @samp{down-}. The @samp{down-} prefix follows | |
8db970a4 RS |
1224 | modifier key prefixes such as @samp{C-} and @samp{M-}. |
1225 | ||
969fe9b5 RS |
1226 | The function @code{read-key-sequence} ignores any button-down events |
1227 | that don't have command bindings; therefore, the Emacs command loop | |
1228 | ignores them too. This means that you need not worry about defining | |
1229 | button-down events unless you want them to do something. The usual | |
1230 | reason to define a button-down event is so that you can track mouse | |
1231 | motion (by reading motion events) until the button is released. | |
1232 | @xref{Motion Events}. | |
8db970a4 RS |
1233 | |
1234 | @node Repeat Events | |
1235 | @subsection Repeat Events | |
1236 | @cindex repeat events | |
1237 | @cindex double-click events | |
1238 | @cindex triple-click events | |
2468d0c0 | 1239 | @cindex mouse events, repeated |
8db970a4 RS |
1240 | |
1241 | If you press the same mouse button more than once in quick succession | |
f142f62a RS |
1242 | without moving the mouse, Emacs generates special @dfn{repeat} mouse |
1243 | events for the second and subsequent presses. | |
8db970a4 RS |
1244 | |
1245 | The most common repeat events are @dfn{double-click} events. Emacs | |
1246 | generates a double-click event when you click a button twice; the event | |
1247 | happens when you release the button (as is normal for all click | |
1248 | events). | |
1249 | ||
1250 | The event type of a double-click event contains the prefix | |
f142f62a | 1251 | @samp{double-}. Thus, a double click on the second mouse button with |
8db970a4 RS |
1252 | @key{meta} held down comes to the Lisp program as |
1253 | @code{M-double-mouse-2}. If a double-click event has no binding, the | |
1254 | binding of the corresponding ordinary click event is used to execute | |
1255 | it. Thus, you need not pay attention to the double click feature | |
1256 | unless you really want to. | |
1257 | ||
1258 | When the user performs a double click, Emacs generates first an ordinary | |
f142f62a RS |
1259 | click event, and then a double-click event. Therefore, you must design |
1260 | the command binding of the double click event to assume that the | |
8db970a4 RS |
1261 | single-click command has already run. It must produce the desired |
1262 | results of a double click, starting from the results of a single click. | |
1263 | ||
f142f62a RS |
1264 | This is convenient, if the meaning of a double click somehow ``builds |
1265 | on'' the meaning of a single click---which is recommended user interface | |
1266 | design practice for double clicks. | |
8db970a4 RS |
1267 | |
1268 | If you click a button, then press it down again and start moving the | |
1269 | mouse with the button held down, then you get a @dfn{double-drag} event | |
1270 | when you ultimately release the button. Its event type contains | |
1271 | @samp{double-drag} instead of just @samp{drag}. If a double-drag event | |
1272 | has no binding, Emacs looks for an alternate binding as if the event | |
b22f3a19 | 1273 | were an ordinary drag. |
8db970a4 RS |
1274 | |
1275 | Before the double-click or double-drag event, Emacs generates a | |
f142f62a RS |
1276 | @dfn{double-down} event when the user presses the button down for the |
1277 | second time. Its event type contains @samp{double-down} instead of just | |
8db970a4 RS |
1278 | @samp{down}. If a double-down event has no binding, Emacs looks for an |
1279 | alternate binding as if the event were an ordinary button-down event. | |
f142f62a RS |
1280 | If it finds no binding that way either, the double-down event is |
1281 | ignored. | |
8db970a4 RS |
1282 | |
1283 | To summarize, when you click a button and then press it again right | |
b22f3a19 RS |
1284 | away, Emacs generates a down event and a click event for the first |
1285 | click, a double-down event when you press the button again, and finally | |
1286 | either a double-click or a double-drag event. | |
8db970a4 RS |
1287 | |
1288 | If you click a button twice and then press it again, all in quick | |
1289 | succession, Emacs generates a @dfn{triple-down} event, followed by | |
1290 | either a @dfn{triple-click} or a @dfn{triple-drag}. The event types of | |
1291 | these events contain @samp{triple} instead of @samp{double}. If any | |
1292 | triple event has no binding, Emacs uses the binding that it would use | |
1293 | for the corresponding double event. | |
1294 | ||
f142f62a RS |
1295 | If you click a button three or more times and then press it again, the |
1296 | events for the presses beyond the third are all triple events. Emacs | |
1297 | does not have separate event types for quadruple, quintuple, etc.@: | |
1298 | events. However, you can look at the event list to find out precisely | |
1299 | how many times the button was pressed. | |
8db970a4 RS |
1300 | |
1301 | @defun event-click-count event | |
1302 | This function returns the number of consecutive button presses that led | |
1303 | up to @var{event}. If @var{event} is a double-down, double-click or | |
1304 | double-drag event, the value is 2. If @var{event} is a triple event, | |
1305 | the value is 3 or greater. If @var{event} is an ordinary mouse event | |
1306 | (not a repeat event), the value is 1. | |
1307 | @end defun | |
1308 | ||
99af9d83 | 1309 | @defvar double-click-fuzz |
f142f62a | 1310 | To generate repeat events, successive mouse button presses must be at |
99af9d83 GM |
1311 | approximately the same screen position. The value of |
1312 | @code{double-click-fuzz} specifies the maximum number of pixels the | |
1313 | mouse may be moved between two successive clicks to make a | |
1314 | double-click. | |
1315 | @end defvar | |
1316 | ||
1317 | @defvar double-click-time | |
1318 | To generate repeat events, the number of milliseconds between | |
f142f62a | 1319 | successive button presses must be less than the value of |
8db970a4 RS |
1320 | @code{double-click-time}. Setting @code{double-click-time} to |
1321 | @code{nil} disables multi-click detection entirely. Setting it to | |
1322 | @code{t} removes the time limit; Emacs then detects multi-clicks by | |
1323 | position only. | |
1324 | @end defvar | |
1325 | ||
1326 | @node Motion Events | |
1327 | @subsection Motion Events | |
1328 | @cindex motion event | |
1329 | @cindex mouse motion events | |
1330 | ||
1331 | Emacs sometimes generates @dfn{mouse motion} events to describe motion | |
1332 | of the mouse without any button activity. Mouse motion events are | |
1333 | represented by lists that look like this: | |
1334 | ||
1335 | @example | |
969fe9b5 | 1336 | (mouse-movement (@var{window} @var{buffer-pos} (@var{x} . @var{y}) @var{timestamp})) |
8db970a4 RS |
1337 | @end example |
1338 | ||
1339 | The second element of the list describes the current position of the | |
1340 | mouse, just as in a click event (@pxref{Click Events}). | |
1341 | ||
1342 | The special form @code{track-mouse} enables generation of motion events | |
1343 | within its body. Outside of @code{track-mouse} forms, Emacs does not | |
1344 | generate events for mere motion of the mouse, and these events do not | |
969fe9b5 | 1345 | appear. @xref{Mouse Tracking}. |
8db970a4 RS |
1346 | |
1347 | @node Focus Events | |
1348 | @subsection Focus Events | |
1349 | @cindex focus event | |
1350 | ||
1351 | Window systems provide general ways for the user to control which window | |
1352 | gets keyboard input. This choice of window is called the @dfn{focus}. | |
1353 | When the user does something to switch between Emacs frames, that | |
1354 | generates a @dfn{focus event}. The normal definition of a focus event, | |
1355 | in the global keymap, is to select a new frame within Emacs, as the user | |
1356 | would expect. @xref{Input Focus}. | |
1357 | ||
1358 | Focus events are represented in Lisp as lists that look like this: | |
1359 | ||
1360 | @example | |
1361 | (switch-frame @var{new-frame}) | |
1362 | @end example | |
1363 | ||
1364 | @noindent | |
1365 | where @var{new-frame} is the frame switched to. | |
1366 | ||
b22f3a19 RS |
1367 | Most X window managers are set up so that just moving the mouse into a |
1368 | window is enough to set the focus there. Emacs appears to do this, | |
1369 | because it changes the cursor to solid in the new frame. However, there | |
1370 | is no need for the Lisp program to know about the focus change until | |
1371 | some other kind of input arrives. So Emacs generates a focus event only | |
1372 | when the user actually types a keyboard key or presses a mouse button in | |
1373 | the new frame; just moving the mouse between frames does not generate a | |
1374 | focus event. | |
8db970a4 RS |
1375 | |
1376 | A focus event in the middle of a key sequence would garble the | |
1377 | sequence. So Emacs never generates a focus event in the middle of a key | |
1378 | sequence. If the user changes focus in the middle of a key | |
1379 | sequence---that is, after a prefix key---then Emacs reorders the events | |
1380 | so that the focus event comes either before or after the multi-event key | |
1381 | sequence, and not within it. | |
1382 | ||
22697dac KH |
1383 | @node Misc Events |
1384 | @subsection Miscellaneous Window System Events | |
1385 | ||
1386 | A few other event types represent occurrences within the window system. | |
1387 | ||
1388 | @table @code | |
1389 | @cindex @code{delete-frame} event | |
1390 | @item (delete-frame (@var{frame})) | |
1391 | This kind of event indicates that the user gave the window manager | |
1392 | a command to delete a particular window, which happens to be an Emacs frame. | |
1393 | ||
1394 | The standard definition of the @code{delete-frame} event is to delete @var{frame}. | |
1395 | ||
1396 | @cindex @code{iconify-frame} event | |
1397 | @item (iconify-frame (@var{frame})) | |
1398 | This kind of event indicates that the user iconified @var{frame} using | |
d473987a RS |
1399 | the window manager. Its standard definition is @code{ignore}; since the |
1400 | frame has already been iconified, Emacs has no work to do. The purpose | |
1401 | of this event type is so that you can keep track of such events if you | |
1402 | want to. | |
22697dac | 1403 | |
1774d17e RS |
1404 | @cindex @code{make-frame-visible} event |
1405 | @item (make-frame-visible (@var{frame})) | |
22697dac KH |
1406 | This kind of event indicates that the user deiconified @var{frame} using |
1407 | the window manager. Its standard definition is @code{ignore}; since the | |
d473987a | 1408 | frame has already been made visible, Emacs has no work to do. |
a9f0a989 RS |
1409 | |
1410 | @cindex @code{mouse-wheel} event | |
1411 | @item (mouse-wheel @var{position} @var{delta}) | |
1412 | This kind of event is generated by moving a wheel on a mouse (such as | |
1413 | the MS Intellimouse). Its effect is typically a kind of scroll or zoom. | |
1414 | ||
1415 | The element @var{delta} describes the amount and direction of the wheel | |
1416 | rotation. Its absolute value is the number of increments by which the | |
1417 | wheel was rotated. A negative @var{delta} indicates that the wheel was | |
1418 | rotated backwards, towards the user, and a positive @var{delta} | |
1419 | indicates that the wheel was rotated forward, away from the user. | |
1420 | ||
1421 | The element @var{position} is a list describing the position of the | |
1422 | event, in the same format as used in a mouse-click event. | |
1423 | ||
1424 | This kind of event is generated only on some kinds of systems. | |
1425 | ||
1426 | @cindex @code{drag-n-drop} event | |
1427 | @item (drag-n-drop @var{position} @var{files}) | |
1428 | This kind of event is generated when a group of files is | |
1429 | selected in an application outside of Emacs, and then dragged and | |
1430 | dropped onto an Emacs frame. | |
1431 | ||
1432 | The element @var{position} is a list describing the position of the | |
1433 | event, in the same format as used in a mouse-click event, and | |
1434 | @var{files} is the list of file names that were dragged and dropped. | |
1435 | The usual way to handle this event is by visiting these files. | |
1436 | ||
1437 | This kind of event is generated, at present, only on some kinds of | |
1438 | systems. | |
22697dac KH |
1439 | @end table |
1440 | ||
bfe721d1 KH |
1441 | If one of these events arrives in the middle of a key sequence---that |
1442 | is, after a prefix key---then Emacs reorders the events so that this | |
1443 | event comes either before or after the multi-event key sequence, not | |
1444 | within it. | |
1445 | ||
8db970a4 RS |
1446 | @node Event Examples |
1447 | @subsection Event Examples | |
1448 | ||
1449 | If the user presses and releases the left mouse button over the same | |
1450 | location, that generates a sequence of events like this: | |
1451 | ||
1452 | @smallexample | |
1453 | (down-mouse-1 (#<window 18 on NEWS> 2613 (0 . 38) -864320)) | |
1454 | (mouse-1 (#<window 18 on NEWS> 2613 (0 . 38) -864180)) | |
1455 | @end smallexample | |
1456 | ||
f142f62a | 1457 | While holding the control key down, the user might hold down the |
8db970a4 RS |
1458 | second mouse button, and drag the mouse from one line to the next. |
1459 | That produces two events, as shown here: | |
1460 | ||
1461 | @smallexample | |
1462 | (C-down-mouse-2 (#<window 18 on NEWS> 3440 (0 . 27) -731219)) | |
1463 | (C-drag-mouse-2 (#<window 18 on NEWS> 3440 (0 . 27) -731219) | |
1464 | (#<window 18 on NEWS> 3510 (0 . 28) -729648)) | |
1465 | @end smallexample | |
1466 | ||
f142f62a | 1467 | While holding down the meta and shift keys, the user might press the |
8db970a4 | 1468 | second mouse button on the window's mode line, and then drag the mouse |
f142f62a | 1469 | into another window. That produces a pair of events like these: |
8db970a4 RS |
1470 | |
1471 | @smallexample | |
1472 | (M-S-down-mouse-2 (#<window 18 on NEWS> mode-line (33 . 31) -457844)) | |
1473 | (M-S-drag-mouse-2 (#<window 18 on NEWS> mode-line (33 . 31) -457844) | |
1474 | (#<window 20 on carlton-sanskrit.tex> 161 (33 . 3) | |
1475 | -453816)) | |
1476 | @end smallexample | |
1477 | ||
1478 | @node Classifying Events | |
1479 | @subsection Classifying Events | |
1480 | @cindex event type | |
1481 | ||
b22f3a19 RS |
1482 | Every event has an @dfn{event type}, which classifies the event for |
1483 | key binding purposes. For a keyboard event, the event type equals the | |
1484 | event value; thus, the event type for a character is the character, and | |
1485 | the event type for a function key symbol is the symbol itself. For | |
1486 | events that are lists, the event type is the symbol in the @sc{car} of | |
1487 | the list. Thus, the event type is always a symbol or a character. | |
8db970a4 RS |
1488 | |
1489 | Two events of the same type are equivalent where key bindings are | |
1490 | concerned; thus, they always run the same command. That does not | |
1491 | necessarily mean they do the same things, however, as some commands look | |
1492 | at the whole event to decide what to do. For example, some commands use | |
f142f62a | 1493 | the location of a mouse event to decide where in the buffer to act. |
8db970a4 RS |
1494 | |
1495 | Sometimes broader classifications of events are useful. For example, | |
1496 | you might want to ask whether an event involved the @key{META} key, | |
1497 | regardless of which other key or mouse button was used. | |
1498 | ||
1499 | The functions @code{event-modifiers} and @code{event-basic-type} are | |
1500 | provided to get such information conveniently. | |
1501 | ||
1502 | @defun event-modifiers event | |
f142f62a RS |
1503 | This function returns a list of the modifiers that @var{event} has. The |
1504 | modifiers are symbols; they include @code{shift}, @code{control}, | |
8db970a4 | 1505 | @code{meta}, @code{alt}, @code{hyper} and @code{super}. In addition, |
f142f62a RS |
1506 | the modifiers list of a mouse event symbol always contains one of |
1507 | @code{click}, @code{drag}, and @code{down}. | |
1508 | ||
1509 | The argument @var{event} may be an entire event object, or just an event | |
1510 | type. | |
1511 | ||
1512 | Here are some examples: | |
8db970a4 RS |
1513 | |
1514 | @example | |
1515 | (event-modifiers ?a) | |
1516 | @result{} nil | |
1517 | (event-modifiers ?\C-a) | |
1518 | @result{} (control) | |
1519 | (event-modifiers ?\C-%) | |
1520 | @result{} (control) | |
1521 | (event-modifiers ?\C-\S-a) | |
1522 | @result{} (control shift) | |
1523 | (event-modifiers 'f5) | |
1524 | @result{} nil | |
1525 | (event-modifiers 's-f5) | |
1526 | @result{} (super) | |
1527 | (event-modifiers 'M-S-f5) | |
1528 | @result{} (meta shift) | |
1529 | (event-modifiers 'mouse-1) | |
1530 | @result{} (click) | |
1531 | (event-modifiers 'down-mouse-1) | |
1532 | @result{} (down) | |
1533 | @end example | |
1534 | ||
1535 | The modifiers list for a click event explicitly contains @code{click}, | |
1536 | but the event symbol name itself does not contain @samp{click}. | |
1537 | @end defun | |
1538 | ||
1539 | @defun event-basic-type event | |
1540 | This function returns the key or mouse button that @var{event} | |
1541 | describes, with all modifiers removed. For example: | |
1542 | ||
1543 | @example | |
1544 | (event-basic-type ?a) | |
1545 | @result{} 97 | |
1546 | (event-basic-type ?A) | |
1547 | @result{} 97 | |
1548 | (event-basic-type ?\C-a) | |
1549 | @result{} 97 | |
1550 | (event-basic-type ?\C-\S-a) | |
1551 | @result{} 97 | |
1552 | (event-basic-type 'f5) | |
1553 | @result{} f5 | |
1554 | (event-basic-type 's-f5) | |
1555 | @result{} f5 | |
1556 | (event-basic-type 'M-S-f5) | |
1557 | @result{} f5 | |
1558 | (event-basic-type 'down-mouse-1) | |
1559 | @result{} mouse-1 | |
1560 | @end example | |
1561 | @end defun | |
1562 | ||
1563 | @defun mouse-movement-p object | |
1564 | This function returns non-@code{nil} if @var{object} is a mouse movement | |
1565 | event. | |
1566 | @end defun | |
1567 | ||
bfe721d1 KH |
1568 | @defun event-convert-list list |
1569 | This function converts a list of modifier names and a basic event type | |
1570 | to an event type which specifies all of them. For example, | |
1571 | ||
1572 | @example | |
1573 | (event-convert-list '(control ?a)) | |
1574 | @result{} 1 | |
1575 | (event-convert-list '(control meta ?a)) | |
1576 | @result{} -134217727 | |
1577 | (event-convert-list '(control super f1)) | |
1578 | @result{} C-s-f1 | |
1579 | @end example | |
1580 | @end defun | |
1581 | ||
8db970a4 RS |
1582 | @node Accessing Events |
1583 | @subsection Accessing Events | |
2468d0c0 DL |
1584 | @cindex mouse events, accessing the data |
1585 | @cindex accessing data of mouse events | |
8db970a4 RS |
1586 | |
1587 | This section describes convenient functions for accessing the data in | |
f142f62a | 1588 | a mouse button or motion event. |
8db970a4 | 1589 | |
f142f62a | 1590 | These two functions return the starting or ending position of a |
969fe9b5 | 1591 | mouse-button event, as a list of this form: |
8db970a4 | 1592 | |
f142f62a | 1593 | @example |
b22f3a19 | 1594 | (@var{window} @var{buffer-position} (@var{x} . @var{y}) @var{timestamp}) |
f142f62a | 1595 | @end example |
8db970a4 RS |
1596 | |
1597 | @defun event-start event | |
1598 | This returns the starting position of @var{event}. | |
1599 | ||
1600 | If @var{event} is a click or button-down event, this returns the | |
1601 | location of the event. If @var{event} is a drag event, this returns the | |
1602 | drag's starting position. | |
1603 | @end defun | |
1604 | ||
1605 | @defun event-end event | |
1606 | This returns the ending position of @var{event}. | |
1607 | ||
1608 | If @var{event} is a drag event, this returns the position where the user | |
1609 | released the mouse button. If @var{event} is a click or button-down | |
1610 | event, the value is actually the starting position, which is the only | |
1611 | position such events have. | |
1612 | @end defun | |
1613 | ||
2468d0c0 | 1614 | @cindex mouse position list, accessing |
969fe9b5 RS |
1615 | These five functions take a position list as described above, and |
1616 | return various parts of it. | |
8db970a4 RS |
1617 | |
1618 | @defun posn-window position | |
1619 | Return the window that @var{position} is in. | |
1620 | @end defun | |
1621 | ||
1622 | @defun posn-point position | |
f142f62a | 1623 | Return the buffer position in @var{position}. This is an integer. |
8db970a4 RS |
1624 | @end defun |
1625 | ||
1626 | @defun posn-x-y position | |
b22f3a19 RS |
1627 | Return the pixel-based x and y coordinates in @var{position}, as a cons |
1628 | cell @code{(@var{x} . @var{y})}. | |
8db970a4 RS |
1629 | @end defun |
1630 | ||
1631 | @defun posn-col-row position | |
f142f62a | 1632 | Return the row and column (in units of characters) of @var{position}, as |
8db970a4 RS |
1633 | a cons cell @code{(@var{col} . @var{row})}. These are computed from the |
1634 | @var{x} and @var{y} values actually found in @var{position}. | |
1635 | @end defun | |
1636 | ||
2468d0c0 DL |
1637 | @cindex mouse event, timestamp |
1638 | @cindex timestamp of a mouse event | |
8db970a4 | 1639 | @defun posn-timestamp position |
f142f62a | 1640 | Return the timestamp in @var{position}. |
8db970a4 RS |
1641 | @end defun |
1642 | ||
969fe9b5 RS |
1643 | These functions are useful for decoding scroll bar events. |
1644 | ||
b22f3a19 RS |
1645 | @defun scroll-bar-event-ratio event |
1646 | This function returns the fractional vertical position of a scroll bar | |
1647 | event within the scroll bar. The value is a cons cell | |
1648 | @code{(@var{portion} . @var{whole})} containing two integers whose ratio | |
1649 | is the fractional position. | |
1650 | @end defun | |
1651 | ||
8db970a4 | 1652 | @defun scroll-bar-scale ratio total |
b22f3a19 RS |
1653 | This function multiplies (in effect) @var{ratio} by @var{total}, |
1654 | rounding the result to an integer. The argument @var{ratio} is not a | |
1655 | number, but rather a pair @code{(@var{num} . @var{denom})}---typically a | |
1656 | value returned by @code{scroll-bar-event-ratio}. | |
8db970a4 | 1657 | |
f142f62a RS |
1658 | This function is handy for scaling a position on a scroll bar into a |
1659 | buffer position. Here's how to do that: | |
8db970a4 RS |
1660 | |
1661 | @example | |
1662 | (+ (point-min) | |
1663 | (scroll-bar-scale | |
b22f3a19 | 1664 | (posn-x-y (event-start event)) |
8db970a4 RS |
1665 | (- (point-max) (point-min)))) |
1666 | @end example | |
b22f3a19 | 1667 | |
1911e6e5 | 1668 | Recall that scroll bar events have two integers forming a ratio, in place |
b22f3a19 | 1669 | of a pair of x and y coordinates. |
8db970a4 RS |
1670 | @end defun |
1671 | ||
1672 | @node Strings of Events | |
1673 | @subsection Putting Keyboard Events in Strings | |
2468d0c0 DL |
1674 | @cindex keyboard events in strings |
1675 | @cindex strings with keyboard events | |
8db970a4 RS |
1676 | |
1677 | In most of the places where strings are used, we conceptualize the | |
1678 | string as containing text characters---the same kind of characters found | |
b22f3a19 | 1679 | in buffers or files. Occasionally Lisp programs use strings that |
8db970a4 | 1680 | conceptually contain keyboard characters; for example, they may be key |
969fe9b5 RS |
1681 | sequences or keyboard macro definitions. However, storing keyboard |
1682 | characters in a string is a complex matter, for reasons of historical | |
1683 | compatibility, and it is not always possible. | |
1684 | ||
1685 | We recommend that new programs avoid dealing with these complexities | |
1686 | by not storing keyboard events in strings. Here is how to do that: | |
1687 | ||
1688 | @itemize @bullet | |
1689 | @item | |
1690 | Use vectors instead of strings for key sequences, when you plan to use | |
a9f0a989 | 1691 | them for anything other than as arguments to @code{lookup-key} and |
969fe9b5 RS |
1692 | @code{define-key}. For example, you can use |
1693 | @code{read-key-sequence-vector} instead of @code{read-key-sequence}, and | |
1694 | @code{this-command-keys-vector} instead of @code{this-command-keys}. | |
1695 | ||
1696 | @item | |
1697 | Use vectors to write key sequence constants containing meta characters, | |
1698 | even when passing them directly to @code{define-key}. | |
1699 | ||
1700 | @item | |
1701 | When you have to look at the contents of a key sequence that might be a | |
1702 | string, use @code{listify-key-sequence} (@pxref{Event Input Misc}) | |
1703 | first, to convert it to a list. | |
1704 | @end itemize | |
8db970a4 | 1705 | |
969fe9b5 RS |
1706 | The complexities stem from the modifier bits that keyboard input |
1707 | characters can include. Aside from the Meta modifier, none of these | |
1708 | modifier bits can be included in a string, and the Meta modifier is | |
1709 | allowed only in special cases. | |
1710 | ||
1711 | The earliest GNU Emacs versions represented meta characters as codes | |
1712 | in the range of 128 to 255. At that time, the basic character codes | |
1713 | ranged from 0 to 127, so all keyboard character codes did fit in a | |
1714 | string. Many Lisp programs used @samp{\M-} in string constants to stand | |
1715 | for meta characters, especially in arguments to @code{define-key} and | |
1716 | similar functions, and key sequences and sequences of events were always | |
1717 | represented as strings. | |
1718 | ||
1719 | When we added support for larger basic character codes beyond 127, and | |
1720 | additional modifier bits, we had to change the representation of meta | |
1721 | characters. Now the flag that represents the Meta modifier in a | |
1722 | character is | |
1723 | @tex | |
8241495d | 1724 | @math{2^{27}} |
969fe9b5 | 1725 | @end tex |
37680279 | 1726 | @ifnottex |
bfe721d1 | 1727 | 2**27 |
37680279 | 1728 | @end ifnottex |
969fe9b5 | 1729 | and such numbers cannot be included in a string. |
8db970a4 | 1730 | |
969fe9b5 RS |
1731 | To support programs with @samp{\M-} in string constants, there are |
1732 | special rules for including certain meta characters in a string. | |
1911e6e5 RS |
1733 | Here are the rules for interpreting a string as a sequence of input |
1734 | characters: | |
8db970a4 RS |
1735 | |
1736 | @itemize @bullet | |
1737 | @item | |
f142f62a RS |
1738 | If the keyboard character value is in the range of 0 to 127, it can go |
1739 | in the string unchanged. | |
8db970a4 RS |
1740 | |
1741 | @item | |
bfe721d1 | 1742 | The meta variants of those characters, with codes in the range of |
969fe9b5 | 1743 | @tex |
8241495d | 1744 | @math{2^{27}} |
969fe9b5 | 1745 | @end tex |
37680279 | 1746 | @ifnottex |
bfe721d1 | 1747 | 2**27 |
37680279 | 1748 | @end ifnottex |
bfe721d1 | 1749 | to |
969fe9b5 | 1750 | @tex |
8241495d | 1751 | @math{2^{27} + 127}, |
969fe9b5 | 1752 | @end tex |
37680279 | 1753 | @ifnottex |
bfe721d1 | 1754 | 2**27+127, |
37680279 | 1755 | @end ifnottex |
bfe721d1 KH |
1756 | can also go in the string, but you must change their |
1757 | numeric values. You must set the | |
969fe9b5 | 1758 | @tex |
8241495d | 1759 | @math{2^{7}} |
969fe9b5 | 1760 | @end tex |
37680279 | 1761 | @ifnottex |
bfe721d1 | 1762 | 2**7 |
37680279 | 1763 | @end ifnottex |
bfe721d1 | 1764 | bit instead of the |
969fe9b5 | 1765 | @tex |
8241495d | 1766 | @math{2^{27}} |
969fe9b5 | 1767 | @end tex |
37680279 | 1768 | @ifnottex |
bfe721d1 | 1769 | 2**27 |
37680279 | 1770 | @end ifnottex |
969fe9b5 RS |
1771 | bit, resulting in a value between 128 and 255. Only a unibyte string |
1772 | can include these codes. | |
1773 | ||
1774 | @item | |
8241495d | 1775 | Non-@sc{ascii} characters above 256 can be included in a multibyte string. |
8db970a4 RS |
1776 | |
1777 | @item | |
1778 | Other keyboard character events cannot fit in a string. This includes | |
1779 | keyboard events in the range of 128 to 255. | |
1780 | @end itemize | |
1781 | ||
f9f59935 RS |
1782 | Functions such as @code{read-key-sequence} that construct strings of |
1783 | keyboard input characters follow these rules: they construct vectors | |
f142f62a | 1784 | instead of strings, when the events won't fit in a string. |
8db970a4 RS |
1785 | |
1786 | When you use the read syntax @samp{\M-} in a string, it produces a | |
1787 | code in the range of 128 to 255---the same code that you get if you | |
1788 | modify the corresponding keyboard event to put it in the string. Thus, | |
1789 | meta events in strings work consistently regardless of how they get into | |
1790 | the strings. | |
1791 | ||
969fe9b5 RS |
1792 | However, most programs would do well to avoid these issues by |
1793 | following the recommendations at the beginning of this section. | |
f142f62a | 1794 | |
8db970a4 RS |
1795 | @node Reading Input |
1796 | @section Reading Input | |
1797 | ||
969fe9b5 | 1798 | The editor command loop reads key sequences using the function |
8db970a4 | 1799 | @code{read-key-sequence}, which uses @code{read-event}. These and other |
969fe9b5 RS |
1800 | functions for event input are also available for use in Lisp programs. |
1801 | See also @code{momentary-string-display} in @ref{Temporary Displays}, | |
1802 | and @code{sit-for} in @ref{Waiting}. @xref{Terminal Input}, for | |
1803 | functions and variables for controlling terminal input modes and | |
4324b7ab RS |
1804 | debugging terminal input. @xref{Translating Input}, for features you |
1805 | can use for translating or modifying input events while reading them. | |
8db970a4 RS |
1806 | |
1807 | For higher-level input facilities, see @ref{Minibuffers}. | |
1808 | ||
1809 | @menu | |
1810 | * Key Sequence Input:: How to read one key sequence. | |
1811 | * Reading One Event:: How to read just one event. | |
b6954afd | 1812 | * Invoking the Input Method:: How reading an event uses the input method. |
8db970a4 | 1813 | * Quoted Character Input:: Asking the user to specify a character. |
f142f62a | 1814 | * Event Input Misc:: How to reread or throw away input events. |
8db970a4 RS |
1815 | @end menu |
1816 | ||
1817 | @node Key Sequence Input | |
1818 | @subsection Key Sequence Input | |
1819 | @cindex key sequence input | |
1820 | ||
1821 | The command loop reads input a key sequence at a time, by calling | |
1822 | @code{read-key-sequence}. Lisp programs can also call this function; | |
1823 | for example, @code{describe-key} uses it to read the key to describe. | |
1824 | ||
1825 | @defun read-key-sequence prompt | |
1826 | @cindex key sequence | |
1827 | This function reads a key sequence and returns it as a string or | |
f9f59935 | 1828 | vector. It keeps reading events until it has accumulated a complete key |
8db970a4 RS |
1829 | sequence; that is, enough to specify a non-prefix command using the |
1830 | currently active keymaps. | |
1831 | ||
1832 | If the events are all characters and all can fit in a string, then | |
1833 | @code{read-key-sequence} returns a string (@pxref{Strings of Events}). | |
1834 | Otherwise, it returns a vector, since a vector can hold all kinds of | |
1835 | events---characters, symbols, and lists. The elements of the string or | |
1836 | vector are the events in the key sequence. | |
1837 | ||
8db970a4 RS |
1838 | The argument @var{prompt} is either a string to be displayed in the echo |
1839 | area as a prompt, or @code{nil}, meaning not to display a prompt. | |
1840 | ||
1841 | In the example below, the prompt @samp{?} is displayed in the echo area, | |
1842 | and the user types @kbd{C-x C-f}. | |
1843 | ||
1844 | @example | |
1845 | (read-key-sequence "?") | |
1846 | ||
1847 | @group | |
1848 | ---------- Echo Area ---------- | |
1849 | ?@kbd{C-x C-f} | |
1850 | ---------- Echo Area ---------- | |
1851 | ||
1852 | @result{} "^X^F" | |
1853 | @end group | |
1854 | @end example | |
969fe9b5 RS |
1855 | |
1856 | The function @code{read-key-sequence} suppresses quitting: @kbd{C-g} | |
1857 | typed while reading with this function works like any other character, | |
1858 | and does not set @code{quit-flag}. @xref{Quitting}. | |
1859 | @end defun | |
1860 | ||
1861 | @defun read-key-sequence-vector prompt | |
1862 | This is like @code{read-key-sequence} except that it always | |
1863 | returns the key sequence as a vector, never as a string. | |
1864 | @xref{Strings of Events}. | |
8db970a4 RS |
1865 | @end defun |
1866 | ||
8db970a4 RS |
1867 | @cindex upper case key sequence |
1868 | @cindex downcasing in @code{lookup-key} | |
b22f3a19 RS |
1869 | If an input character is an upper-case letter and has no key binding, |
1870 | but its lower-case equivalent has one, then @code{read-key-sequence} | |
8db970a4 RS |
1871 | converts the character to lower case. Note that @code{lookup-key} does |
1872 | not perform case conversion in this way. | |
1873 | ||
1874 | The function @code{read-key-sequence} also transforms some mouse events. | |
1875 | It converts unbound drag events into click events, and discards unbound | |
bfe721d1 KH |
1876 | button-down events entirely. It also reshuffles focus events and |
1877 | miscellaneous window events so that they never appear in a key sequence | |
1878 | with any other events. | |
8db970a4 | 1879 | |
2468d0c0 DL |
1880 | @cindex @code{header-line} prefix key |
1881 | @cindex @code{mode-line} prefix key | |
1882 | @cindex @code{vertical-line} prefix key | |
1883 | @cindex @code{horizontal-scroll-bar} prefix key | |
1884 | @cindex @code{vertical-scroll-bar} prefix key | |
1885 | @cindex @code{menu-bar} prefix key | |
1886 | @cindex mouse events, in special parts of frame | |
8db970a4 | 1887 | When mouse events occur in special parts of a window, such as a mode |
f142f62a RS |
1888 | line or a scroll bar, the event type shows nothing special---it is the |
1889 | same symbol that would normally represent that combination of mouse | |
f9f59935 RS |
1890 | button and modifier keys. The information about the window part is kept |
1891 | elsewhere in the event---in the coordinates. But | |
f142f62a | 1892 | @code{read-key-sequence} translates this information into imaginary |
080a57ba | 1893 | ``prefix keys'', all of which are symbols: @code{header-line}, |
2468d0c0 DL |
1894 | @code{horizontal-scroll-bar}, @code{menu-bar}, @code{mode-line}, |
1895 | @code{vertical-line}, and @code{vertical-scroll-bar}. You can define | |
1896 | meanings for mouse clicks in special window parts by defining key | |
1897 | sequences using these imaginary prefix keys. | |
f142f62a | 1898 | |
8db970a4 | 1899 | For example, if you call @code{read-key-sequence} and then click the |
bfe721d1 | 1900 | mouse on the window's mode line, you get two events, like this: |
8db970a4 | 1901 | |
f142f62a | 1902 | @example |
8db970a4 RS |
1903 | (read-key-sequence "Click on the mode line: ") |
1904 | @result{} [mode-line | |
f142f62a RS |
1905 | (mouse-1 |
1906 | (#<window 6 on NEWS> mode-line | |
1907 | (40 . 63) 5959987))] | |
1908 | @end example | |
8db970a4 | 1909 | |
f9f59935 RS |
1910 | @defvar num-input-keys |
1911 | @c Emacs 19 feature | |
1912 | This variable's value is the number of key sequences processed so far in | |
1913 | this Emacs session. This includes key sequences read from the terminal | |
1914 | and key sequences read from keyboard macros being executed. | |
1915 | @end defvar | |
1916 | ||
f9f59935 RS |
1917 | @defvar num-nonmacro-input-events |
1918 | This variable holds the total number of input events received so far | |
1919 | from the terminal---not counting those generated by keyboard macros. | |
1920 | @end defvar | |
1921 | ||
8db970a4 RS |
1922 | @node Reading One Event |
1923 | @subsection Reading One Event | |
2468d0c0 DL |
1924 | @cindex reading a single event |
1925 | @cindex event, reading only one | |
8db970a4 | 1926 | |
b22f3a19 | 1927 | The lowest level functions for command input are those that read a |
8db970a4 RS |
1928 | single event. |
1929 | ||
b6954afd | 1930 | @defun read-event &optional prompt inherit-input-method |
8db970a4 RS |
1931 | This function reads and returns the next event of command input, waiting |
1932 | if necessary until an event is available. Events can come directly from | |
1933 | the user or from a keyboard macro. | |
1934 | ||
b6954afd RS |
1935 | If the optional argument @var{prompt} is non-@code{nil}, it should be a |
1936 | string to display in the echo area as a prompt. Otherwise, | |
1937 | @code{read-event} does not display any message to indicate it is waiting | |
1938 | for input; instead, it prompts by echoing: it displays descriptions of | |
1939 | the events that led to or were read by the current command. @xref{The | |
1940 | Echo Area}. | |
8db970a4 | 1941 | |
b6954afd RS |
1942 | If @var{inherit-input-method} is non-@code{nil}, then the current input |
1943 | method (if any) is employed to make it possible to enter a | |
8241495d | 1944 | non-@sc{ascii} character. Otherwise, input method handling is disabled |
b6954afd | 1945 | for reading this event. |
2eb4136f | 1946 | |
8db970a4 RS |
1947 | If @code{cursor-in-echo-area} is non-@code{nil}, then @code{read-event} |
1948 | moves the cursor temporarily to the echo area, to the end of any message | |
1949 | displayed there. Otherwise @code{read-event} does not move the cursor. | |
8db970a4 | 1950 | |
1911e6e5 | 1951 | If @code{read-event} gets an event that is defined as a help character, in |
a9f0a989 RS |
1952 | some cases @code{read-event} processes the event directly without |
1953 | returning. @xref{Help Functions}. Certain other events, called | |
1954 | @dfn{special events}, are also processed directly within | |
1955 | @code{read-event} (@pxref{Special Events}). | |
1956 | ||
8db970a4 RS |
1957 | Here is what happens if you call @code{read-event} and then press the |
1958 | right-arrow function key: | |
1959 | ||
1960 | @example | |
1961 | @group | |
1962 | (read-event) | |
1963 | @result{} right | |
1964 | @end group | |
1965 | @end example | |
f142f62a | 1966 | @end defun |
8db970a4 | 1967 | |
b6954afd RS |
1968 | @defun read-char &optional prompt inherit-input-method |
1969 | This function reads and returns a character of command input. If the | |
1970 | user generates an event which is not a character (i.e. a mouse click or | |
1971 | function key event), @code{read-char} signals an error. The arguments | |
1972 | work as in @code{read-event}. | |
8db970a4 | 1973 | |
8241495d | 1974 | In the first example, the user types the character @kbd{1} (@sc{ascii} |
f142f62a RS |
1975 | code 49). The second example shows a keyboard macro definition that |
1976 | calls @code{read-char} from the minibuffer using @code{eval-expression}. | |
1977 | @code{read-char} reads the keyboard macro's very next character, which | |
1978 | is @kbd{1}. Then @code{eval-expression} displays its return value in | |
1979 | the echo area. | |
8db970a4 RS |
1980 | |
1981 | @example | |
1982 | @group | |
1983 | (read-char) | |
1984 | @result{} 49 | |
1985 | @end group | |
1986 | ||
1987 | @group | |
bfe721d1 | 1988 | ;; @r{We assume here you use @kbd{M-:} to evaluate this.} |
8db970a4 | 1989 | (symbol-function 'foo) |
bfe721d1 | 1990 | @result{} "^[:(read-char)^M1" |
8db970a4 RS |
1991 | @end group |
1992 | @group | |
f142f62a | 1993 | (execute-kbd-macro 'foo) |
8db970a4 RS |
1994 | @print{} 49 |
1995 | @result{} nil | |
1996 | @end group | |
1997 | @end example | |
1998 | @end defun | |
1999 | ||
b6954afd RS |
2000 | @defun read-char-exclusive &optional prompt inherit-input-method |
2001 | This function reads and returns a character of command input. If the | |
2002 | user generates an event which is not a character, | |
2003 | @code{read-char-exclusive} ignores it and reads another event, until it | |
2004 | gets a character. The arguments work as in @code{read-event}. | |
2005 | @end defun | |
2006 | ||
2007 | @node Invoking the Input Method | |
2008 | @subsection Invoking the Input Method | |
2009 | ||
2010 | The event-reading functions invoke the current input method, if any | |
2011 | (@pxref{Input Methods}). If the value of @code{input-method-function} | |
2012 | is non-@code{nil}, it should be a function; when @code{read-event} reads | |
2013 | a printing character (including @key{SPC}) with no modifier bits, it | |
2014 | calls that function, passing the character as an argument. | |
39d6d9bd RS |
2015 | |
2016 | @defvar input-method-function | |
2017 | If this is non-@code{nil}, its value specifies the current input method | |
2018 | function. | |
2eb4136f RS |
2019 | |
2020 | @strong{Note:} Don't bind this variable with @code{let}. It is often | |
2021 | buffer-local, and if you bind it around reading input (which is exactly | |
2022 | when you @emph{would} bind it), switching buffers asynchronously while | |
2023 | Emacs is waiting will cause the value to be restored in the wrong | |
2024 | buffer. | |
39d6d9bd RS |
2025 | @end defvar |
2026 | ||
2027 | The input method function should return a list of events which should | |
2028 | be used as input. (If the list is @code{nil}, that means there is no | |
2029 | input, so @code{read-event} waits for another event.) These events are | |
2468d0c0 DL |
2030 | processed before the events in @code{unread-command-events} |
2031 | (@pxref{Event Input Misc}). Events | |
39d6d9bd RS |
2032 | returned by the input method function are not passed to the input method |
2033 | function again, even if they are printing characters with no modifier | |
2034 | bits. | |
2035 | ||
2036 | If the input method function calls @code{read-event} or | |
2037 | @code{read-key-sequence}, it should bind @code{input-method-function} to | |
2038 | @code{nil} first, to prevent recursion. | |
2039 | ||
2040 | The input method function is not called when reading the second and | |
b6954afd RS |
2041 | subsequent events of a key sequence. Thus, these characters are not |
2042 | subject to input method processing. The input method function should | |
2043 | test the values of @code{overriding-local-map} and | |
2044 | @code{overriding-terminal-local-map}; if either of these variables is | |
2045 | non-@code{nil}, the input method should put its argument into a list and | |
2046 | return that list with no further processing. | |
39d6d9bd | 2047 | |
8db970a4 RS |
2048 | @node Quoted Character Input |
2049 | @subsection Quoted Character Input | |
2050 | @cindex quoted character input | |
2051 | ||
b22f3a19 RS |
2052 | You can use the function @code{read-quoted-char} to ask the user to |
2053 | specify a character, and allow the user to specify a control or meta | |
2054 | character conveniently, either literally or as an octal character code. | |
2055 | The command @code{quoted-insert} uses this function. | |
8db970a4 RS |
2056 | |
2057 | @defun read-quoted-char &optional prompt | |
2058 | @cindex octal character input | |
2059 | @cindex control characters, reading | |
2060 | @cindex nonprinting characters, reading | |
2061 | This function is like @code{read-char}, except that if the first | |
969fe9b5 RS |
2062 | character read is an octal digit (0-7), it reads any number of octal |
2063 | digits (but stopping if a non-octal digit is found), and returns the | |
2064 | character represented by that numeric character code. | |
8db970a4 RS |
2065 | |
2066 | Quitting is suppressed when the first character is read, so that the | |
2067 | user can enter a @kbd{C-g}. @xref{Quitting}. | |
2068 | ||
2069 | If @var{prompt} is supplied, it specifies a string for prompting the | |
f142f62a | 2070 | user. The prompt string is always displayed in the echo area, followed |
8db970a4 RS |
2071 | by a single @samp{-}. |
2072 | ||
2073 | In the following example, the user types in the octal number 177 (which | |
2074 | is 127 in decimal). | |
2075 | ||
2076 | @example | |
2077 | (read-quoted-char "What character") | |
2078 | ||
2079 | @group | |
2080 | ---------- Echo Area ---------- | |
2081 | What character-@kbd{177} | |
2082 | ---------- Echo Area ---------- | |
2083 | ||
2084 | @result{} 127 | |
2085 | @end group | |
2086 | @end example | |
2087 | @end defun | |
2088 | ||
b22f3a19 | 2089 | @need 2000 |
f142f62a RS |
2090 | @node Event Input Misc |
2091 | @subsection Miscellaneous Event Input Features | |
2092 | ||
2093 | This section describes how to ``peek ahead'' at events without using | |
2094 | them up, how to check for pending input, and how to discard pending | |
1911e6e5 RS |
2095 | input. See also the function @code{read-passwd} (@pxref{Reading a |
2096 | Password}). | |
8db970a4 RS |
2097 | |
2098 | @defvar unread-command-events | |
2099 | @cindex next input | |
2100 | @cindex peeking at input | |
2101 | This variable holds a list of events waiting to be read as command | |
f142f62a RS |
2102 | input. The events are used in the order they appear in the list, and |
2103 | removed one by one as they are used. | |
8db970a4 | 2104 | |
f9f59935 | 2105 | The variable is needed because in some cases a function reads an event |
f142f62a RS |
2106 | and then decides not to use it. Storing the event in this variable |
2107 | causes it to be processed normally, by the command loop or by the | |
2108 | functions to read command input. | |
8db970a4 RS |
2109 | |
2110 | @cindex prefix argument unreading | |
2111 | For example, the function that implements numeric prefix arguments reads | |
2112 | any number of digits. When it finds a non-digit event, it must unread | |
2113 | the event so that it can be read normally by the command loop. | |
f142f62a RS |
2114 | Likewise, incremental search uses this feature to unread events with no |
2115 | special meaning in a search, because these events should exit the search | |
2116 | and then execute normally. | |
2117 | ||
b22f3a19 RS |
2118 | The reliable and easy way to extract events from a key sequence so as to |
2119 | put them in @code{unread-command-events} is to use | |
f142f62a | 2120 | @code{listify-key-sequence} (@pxref{Strings of Events}). |
f9f59935 RS |
2121 | |
2122 | Normally you add events to the front of this list, so that the events | |
2123 | most recently unread will be reread first. | |
8db970a4 RS |
2124 | @end defvar |
2125 | ||
969fe9b5 RS |
2126 | @defun listify-key-sequence key |
2127 | This function converts the string or vector @var{key} to a list of | |
2128 | individual events, which you can put in @code{unread-command-events}. | |
2129 | @end defun | |
2130 | ||
8db970a4 RS |
2131 | @defvar unread-command-char |
2132 | This variable holds a character to be read as command input. | |
2133 | A value of -1 means ``empty''. | |
2134 | ||
f142f62a | 2135 | This variable is mostly obsolete now that you can use |
8db970a4 RS |
2136 | @code{unread-command-events} instead; it exists only to support programs |
2137 | written for Emacs versions 18 and earlier. | |
2138 | @end defvar | |
2139 | ||
8db970a4 RS |
2140 | @defun input-pending-p |
2141 | @cindex waiting for command key input | |
2142 | This function determines whether any command input is currently | |
2143 | available to be read. It returns immediately, with value @code{t} if | |
f142f62a RS |
2144 | there is available input, @code{nil} otherwise. On rare occasions it |
2145 | may return @code{t} when no input is available. | |
8db970a4 RS |
2146 | @end defun |
2147 | ||
2148 | @defvar last-input-event | |
969fe9b5 | 2149 | @defvarx last-input-char |
f142f62a | 2150 | This variable records the last terminal input event read, whether |
8db970a4 RS |
2151 | as part of a command or explicitly by a Lisp program. |
2152 | ||
f142f62a | 2153 | In the example below, the Lisp program reads the character @kbd{1}, |
8241495d | 2154 | @sc{ascii} code 49. It becomes the value of @code{last-input-event}, |
bfe721d1 KH |
2155 | while @kbd{C-e} (we assume @kbd{C-x C-e} command is used to evaluate |
2156 | this expression) remains the value of @code{last-command-event}. | |
8db970a4 RS |
2157 | |
2158 | @example | |
2159 | @group | |
2160 | (progn (print (read-char)) | |
f142f62a RS |
2161 | (print last-command-event) |
2162 | last-input-event) | |
8db970a4 RS |
2163 | @print{} 49 |
2164 | @print{} 5 | |
2165 | @result{} 49 | |
2166 | @end group | |
2167 | @end example | |
2168 | ||
2169 | The alias @code{last-input-char} exists for compatibility with | |
2170 | Emacs version 18. | |
2171 | @end defvar | |
2172 | ||
2173 | @defun discard-input | |
2174 | @cindex flush input | |
2175 | @cindex discard input | |
2176 | @cindex terminate keyboard macro | |
2177 | This function discards the contents of the terminal input buffer and | |
2178 | cancels any keyboard macro that might be in the process of definition. | |
2179 | It returns @code{nil}. | |
2180 | ||
2181 | In the following example, the user may type a number of characters right | |
2182 | after starting the evaluation of the form. After the @code{sleep-for} | |
f142f62a RS |
2183 | finishes sleeping, @code{discard-input} discards any characters typed |
2184 | during the sleep. | |
8db970a4 RS |
2185 | |
2186 | @example | |
2187 | (progn (sleep-for 2) | |
f142f62a | 2188 | (discard-input)) |
8db970a4 RS |
2189 | @result{} nil |
2190 | @end example | |
2191 | @end defun | |
2192 | ||
f9f59935 RS |
2193 | @node Special Events |
2194 | @section Special Events | |
2195 | ||
2196 | @cindex special events | |
2197 | Special events are handled at a very low level---as soon as they are | |
2198 | read. The @code{read-event} function processes these events itself, and | |
2199 | never returns them. | |
2200 | ||
2201 | Events that are handled in this way do not echo, they are never grouped | |
2202 | into key sequences, and they never appear in the value of | |
2203 | @code{last-command-event} or @code{(this-command-keys)}. They do not | |
2204 | discard a numeric argument, they cannot be unread with | |
2205 | @code{unread-command-events}, they may not appear in a keyboard macro, | |
2206 | and they are not recorded in a keyboard macro while you are defining | |
2207 | one. | |
2208 | ||
2209 | These events do, however, appear in @code{last-input-event} immediately | |
2210 | after they are read, and this is the way for the event's definition to | |
2211 | find the actual event. | |
2212 | ||
2213 | The events types @code{iconify-frame}, @code{make-frame-visible} and | |
2214 | @code{delete-frame} are normally handled in this way. The keymap which | |
2215 | defines how to handle special events---and which events are special---is | |
2216 | in the variable @code{special-event-map} (@pxref{Active Keymaps}). | |
2217 | ||
8db970a4 RS |
2218 | @node Waiting |
2219 | @section Waiting for Elapsed Time or Input | |
2220 | @cindex pausing | |
2221 | @cindex waiting | |
2222 | ||
f142f62a RS |
2223 | The wait functions are designed to wait for a certain amount of time |
2224 | to pass or until there is input. For example, you may wish to pause in | |
2225 | the middle of a computation to allow the user time to view the display. | |
2226 | @code{sit-for} pauses and updates the screen, and returns immediately if | |
2227 | input comes in, while @code{sleep-for} pauses without updating the | |
2228 | screen. | |
8db970a4 RS |
2229 | |
2230 | @defun sit-for seconds &optional millisec nodisp | |
2231 | This function performs redisplay (provided there is no pending input | |
2232 | from the user), then waits @var{seconds} seconds, or until input is | |
f142f62a RS |
2233 | available. The value is @code{t} if @code{sit-for} waited the full |
2234 | time with no input arriving (see @code{input-pending-p} in @ref{Event | |
2235 | Input Misc}). Otherwise, the value is @code{nil}. | |
8db970a4 | 2236 | |
bfe721d1 KH |
2237 | The argument @var{seconds} need not be an integer. If it is a floating |
2238 | point number, @code{sit-for} waits for a fractional number of seconds. | |
2239 | Some systems support only a whole number of seconds; on these systems, | |
2240 | @var{seconds} is rounded down. | |
2241 | ||
8db970a4 RS |
2242 | The optional argument @var{millisec} specifies an additional waiting |
2243 | period measured in milliseconds. This adds to the period specified by | |
bfe721d1 KH |
2244 | @var{seconds}. If the system doesn't support waiting fractions of a |
2245 | second, you get an error if you specify nonzero @var{millisec}. | |
8db970a4 | 2246 | |
8241495d RS |
2247 | The expression @code{(sit-for 0)} is a convenient way to request a |
2248 | redisplay, without any delay. @xref{Forcing Redisplay}. | |
8db970a4 RS |
2249 | |
2250 | If @var{nodisp} is non-@code{nil}, then @code{sit-for} does not | |
2251 | redisplay, but it still returns as soon as input is available (or when | |
2252 | the timeout elapses). | |
2253 | ||
22697dac KH |
2254 | Iconifying or deiconifying a frame makes @code{sit-for} return, because |
2255 | that generates an event. @xref{Misc Events}. | |
2256 | ||
8db970a4 RS |
2257 | The usual purpose of @code{sit-for} is to give the user time to read |
2258 | text that you display. | |
2259 | @end defun | |
2260 | ||
2261 | @defun sleep-for seconds &optional millisec | |
2262 | This function simply pauses for @var{seconds} seconds without updating | |
2263 | the display. It pays no attention to available input. It returns | |
2264 | @code{nil}. | |
2265 | ||
bfe721d1 KH |
2266 | The argument @var{seconds} need not be an integer. If it is a floating |
2267 | point number, @code{sleep-for} waits for a fractional number of seconds. | |
2268 | Some systems support only a whole number of seconds; on these systems, | |
2269 | @var{seconds} is rounded down. | |
2270 | ||
8db970a4 RS |
2271 | The optional argument @var{millisec} specifies an additional waiting |
2272 | period measured in milliseconds. This adds to the period specified by | |
bfe721d1 KH |
2273 | @var{seconds}. If the system doesn't support waiting fractions of a |
2274 | second, you get an error if you specify nonzero @var{millisec}. | |
8db970a4 RS |
2275 | |
2276 | Use @code{sleep-for} when you wish to guarantee a delay. | |
2277 | @end defun | |
2278 | ||
2279 | @xref{Time of Day}, for functions to get the current time. | |
2280 | ||
2281 | @node Quitting | |
2282 | @section Quitting | |
2283 | @cindex @kbd{C-g} | |
2284 | @cindex quitting | |
2285 | ||
b22f3a19 RS |
2286 | Typing @kbd{C-g} while a Lisp function is running causes Emacs to |
2287 | @dfn{quit} whatever it is doing. This means that control returns to the | |
2288 | innermost active command loop. | |
8db970a4 RS |
2289 | |
2290 | Typing @kbd{C-g} while the command loop is waiting for keyboard input | |
2291 | does not cause a quit; it acts as an ordinary input character. In the | |
2292 | simplest case, you cannot tell the difference, because @kbd{C-g} | |
2293 | normally runs the command @code{keyboard-quit}, whose effect is to quit. | |
969fe9b5 RS |
2294 | However, when @kbd{C-g} follows a prefix key, they combine to form an |
2295 | undefined key. The effect is to cancel the prefix key as well as any | |
2296 | prefix argument. | |
8db970a4 RS |
2297 | |
2298 | In the minibuffer, @kbd{C-g} has a different definition: it aborts out | |
2299 | of the minibuffer. This means, in effect, that it exits the minibuffer | |
2300 | and then quits. (Simply quitting would return to the command loop | |
2301 | @emph{within} the minibuffer.) The reason why @kbd{C-g} does not quit | |
2302 | directly when the command reader is reading input is so that its meaning | |
2303 | can be redefined in the minibuffer in this way. @kbd{C-g} following a | |
2304 | prefix key is not redefined in the minibuffer, and it has its normal | |
2305 | effect of canceling the prefix key and prefix argument. This too | |
f142f62a | 2306 | would not be possible if @kbd{C-g} always quit directly. |
8db970a4 | 2307 | |
b22f3a19 | 2308 | When @kbd{C-g} does directly quit, it does so by setting the variable |
f142f62a RS |
2309 | @code{quit-flag} to @code{t}. Emacs checks this variable at appropriate |
2310 | times and quits if it is not @code{nil}. Setting @code{quit-flag} | |
8db970a4 RS |
2311 | non-@code{nil} in any way thus causes a quit. |
2312 | ||
f142f62a | 2313 | At the level of C code, quitting cannot happen just anywhere; only at the |
b22f3a19 | 2314 | special places that check @code{quit-flag}. The reason for this is |
8db970a4 RS |
2315 | that quitting at other places might leave an inconsistency in Emacs's |
2316 | internal state. Because quitting is delayed until a safe place, quitting | |
2317 | cannot make Emacs crash. | |
2318 | ||
2319 | Certain functions such as @code{read-key-sequence} or | |
2320 | @code{read-quoted-char} prevent quitting entirely even though they wait | |
2321 | for input. Instead of quitting, @kbd{C-g} serves as the requested | |
2322 | input. In the case of @code{read-key-sequence}, this serves to bring | |
2323 | about the special behavior of @kbd{C-g} in the command loop. In the | |
2324 | case of @code{read-quoted-char}, this is so that @kbd{C-q} can be used | |
2325 | to quote a @kbd{C-g}. | |
2326 | ||
2327 | You can prevent quitting for a portion of a Lisp function by binding | |
2328 | the variable @code{inhibit-quit} to a non-@code{nil} value. Then, | |
2329 | although @kbd{C-g} still sets @code{quit-flag} to @code{t} as usual, the | |
2330 | usual result of this---a quit---is prevented. Eventually, | |
2331 | @code{inhibit-quit} will become @code{nil} again, such as when its | |
2332 | binding is unwound at the end of a @code{let} form. At that time, if | |
2333 | @code{quit-flag} is still non-@code{nil}, the requested quit happens | |
b22f3a19 RS |
2334 | immediately. This behavior is ideal when you wish to make sure that |
2335 | quitting does not happen within a ``critical section'' of the program. | |
8db970a4 RS |
2336 | |
2337 | @cindex @code{read-quoted-char} quitting | |
2338 | In some functions (such as @code{read-quoted-char}), @kbd{C-g} is | |
b22f3a19 | 2339 | handled in a special way that does not involve quitting. This is done |
f142f62a | 2340 | by reading the input with @code{inhibit-quit} bound to @code{t}, and |
8db970a4 RS |
2341 | setting @code{quit-flag} to @code{nil} before @code{inhibit-quit} |
2342 | becomes @code{nil} again. This excerpt from the definition of | |
2343 | @code{read-quoted-char} shows how this is done; it also shows that | |
2344 | normal quitting is permitted after the first character of input. | |
2345 | ||
2346 | @example | |
2347 | (defun read-quoted-char (&optional prompt) | |
2348 | "@dots{}@var{documentation}@dots{}" | |
969fe9b5 RS |
2349 | (let ((message-log-max nil) done (first t) (code 0) char) |
2350 | (while (not done) | |
2351 | (let ((inhibit-quit first) | |
2352 | @dots{}) | |
2353 | (and prompt (message "%s-" prompt)) | |
2354 | (setq char (read-event)) | |
2355 | (if inhibit-quit (setq quit-flag nil))) | |
2356 | @r{@dots{}set the variable @code{code}@dots{}}) | |
2357 | code)) | |
8db970a4 RS |
2358 | @end example |
2359 | ||
2360 | @defvar quit-flag | |
f142f62a RS |
2361 | If this variable is non-@code{nil}, then Emacs quits immediately, unless |
2362 | @code{inhibit-quit} is non-@code{nil}. Typing @kbd{C-g} ordinarily sets | |
8db970a4 RS |
2363 | @code{quit-flag} non-@code{nil}, regardless of @code{inhibit-quit}. |
2364 | @end defvar | |
2365 | ||
2366 | @defvar inhibit-quit | |
2367 | This variable determines whether Emacs should quit when @code{quit-flag} | |
2368 | is set to a value other than @code{nil}. If @code{inhibit-quit} is | |
2369 | non-@code{nil}, then @code{quit-flag} has no special effect. | |
2370 | @end defvar | |
2371 | ||
2372 | @deffn Command keyboard-quit | |
2373 | This function signals the @code{quit} condition with @code{(signal 'quit | |
2374 | nil)}. This is the same thing that quitting does. (See @code{signal} | |
2375 | in @ref{Errors}.) | |
2376 | @end deffn | |
2377 | ||
2378 | You can specify a character other than @kbd{C-g} to use for quitting. | |
2379 | See the function @code{set-input-mode} in @ref{Terminal Input}. | |
2380 | ||
2381 | @node Prefix Command Arguments | |
2382 | @section Prefix Command Arguments | |
2383 | @cindex prefix argument | |
2384 | @cindex raw prefix argument | |
2385 | @cindex numeric prefix argument | |
2386 | ||
2387 | Most Emacs commands can use a @dfn{prefix argument}, a number | |
2388 | specified before the command itself. (Don't confuse prefix arguments | |
b22f3a19 RS |
2389 | with prefix keys.) The prefix argument is at all times represented by a |
2390 | value, which may be @code{nil}, meaning there is currently no prefix | |
2391 | argument. Each command may use the prefix argument or ignore it. | |
8db970a4 RS |
2392 | |
2393 | There are two representations of the prefix argument: @dfn{raw} and | |
2394 | @dfn{numeric}. The editor command loop uses the raw representation | |
2395 | internally, and so do the Lisp variables that store the information, but | |
2396 | commands can request either representation. | |
2397 | ||
2398 | Here are the possible values of a raw prefix argument: | |
2399 | ||
2400 | @itemize @bullet | |
2401 | @item | |
2402 | @code{nil}, meaning there is no prefix argument. Its numeric value is | |
2403 | 1, but numerous commands make a distinction between @code{nil} and the | |
2404 | integer 1. | |
2405 | ||
2406 | @item | |
2407 | An integer, which stands for itself. | |
2408 | ||
2409 | @item | |
2410 | A list of one element, which is an integer. This form of prefix | |
2411 | argument results from one or a succession of @kbd{C-u}'s with no | |
2412 | digits. The numeric value is the integer in the list, but some | |
2413 | commands make a distinction between such a list and an integer alone. | |
2414 | ||
2415 | @item | |
2416 | The symbol @code{-}. This indicates that @kbd{M--} or @kbd{C-u -} was | |
2417 | typed, without following digits. The equivalent numeric value is | |
2418 | @minus{}1, but some commands make a distinction between the integer | |
2419 | @minus{}1 and the symbol @code{-}. | |
2420 | @end itemize | |
2421 | ||
f142f62a RS |
2422 | We illustrate these possibilities by calling the following function with |
2423 | various prefixes: | |
8db970a4 RS |
2424 | |
2425 | @example | |
2426 | @group | |
2427 | (defun display-prefix (arg) | |
2428 | "Display the value of the raw prefix arg." | |
2429 | (interactive "P") | |
2430 | (message "%s" arg)) | |
2431 | @end group | |
2432 | @end example | |
2433 | ||
2434 | @noindent | |
2435 | Here are the results of calling @code{display-prefix} with various | |
2436 | raw prefix arguments: | |
2437 | ||
2438 | @example | |
2439 | M-x display-prefix @print{} nil | |
2440 | ||
2441 | C-u M-x display-prefix @print{} (4) | |
2442 | ||
2443 | C-u C-u M-x display-prefix @print{} (16) | |
2444 | ||
2445 | C-u 3 M-x display-prefix @print{} 3 | |
2446 | ||
2447 | M-3 M-x display-prefix @print{} 3 ; @r{(Same as @code{C-u 3}.)} | |
2448 | ||
2449 | C-u - M-x display-prefix @print{} - | |
2450 | ||
f142f62a | 2451 | M-- M-x display-prefix @print{} - ; @r{(Same as @code{C-u -}.)} |
8db970a4 | 2452 | |
f142f62a | 2453 | C-u - 7 M-x display-prefix @print{} -7 |
8db970a4 | 2454 | |
f142f62a | 2455 | M-- 7 M-x display-prefix @print{} -7 ; @r{(Same as @code{C-u -7}.)} |
8db970a4 RS |
2456 | @end example |
2457 | ||
2458 | Emacs uses two variables to store the prefix argument: | |
2459 | @code{prefix-arg} and @code{current-prefix-arg}. Commands such as | |
2460 | @code{universal-argument} that set up prefix arguments for other | |
2461 | commands store them in @code{prefix-arg}. In contrast, | |
2462 | @code{current-prefix-arg} conveys the prefix argument to the current | |
2463 | command, so setting it has no effect on the prefix arguments for future | |
2464 | commands. | |
2465 | ||
2466 | Normally, commands specify which representation to use for the prefix | |
2467 | argument, either numeric or raw, in the @code{interactive} declaration. | |
b22f3a19 | 2468 | (@xref{Using Interactive}.) Alternatively, functions may look at the |
8db970a4 RS |
2469 | value of the prefix argument directly in the variable |
2470 | @code{current-prefix-arg}, but this is less clean. | |
2471 | ||
f142f62a RS |
2472 | @defun prefix-numeric-value arg |
2473 | This function returns the numeric meaning of a valid raw prefix argument | |
2474 | value, @var{arg}. The argument may be a symbol, a number, or a list. | |
b22f3a19 RS |
2475 | If it is @code{nil}, the value 1 is returned; if it is @code{-}, the |
2476 | value @minus{}1 is returned; if it is a number, that number is returned; | |
2477 | if it is a list, the @sc{car} of that list (which should be a number) is | |
2478 | returned. | |
f142f62a RS |
2479 | @end defun |
2480 | ||
2481 | @defvar current-prefix-arg | |
2482 | This variable holds the raw prefix argument for the @emph{current} | |
9e2b495b RS |
2483 | command. Commands may examine it directly, but the usual method for |
2484 | accessing it is with @code{(interactive "P")}. | |
f142f62a RS |
2485 | @end defvar |
2486 | ||
2487 | @defvar prefix-arg | |
2488 | The value of this variable is the raw prefix argument for the | |
f9f59935 RS |
2489 | @emph{next} editing command. Commands such as @code{universal-argument} |
2490 | that specify prefix arguments for the following command work by setting | |
2491 | this variable. | |
03c6b7f6 RS |
2492 | @end defvar |
2493 | ||
03c6b7f6 RS |
2494 | @defvar last-prefix-arg |
2495 | The raw prefix argument value used by the previous command. | |
f142f62a RS |
2496 | @end defvar |
2497 | ||
f9f59935 RS |
2498 | The following commands exist to set up prefix arguments for the |
2499 | following command. Do not call them for any other reason. | |
8db970a4 RS |
2500 | |
2501 | @deffn Command universal-argument | |
2502 | This command reads input and specifies a prefix argument for the | |
2503 | following command. Don't call this command yourself unless you know | |
2504 | what you are doing. | |
2505 | @end deffn | |
2506 | ||
2507 | @deffn Command digit-argument arg | |
2508 | This command adds to the prefix argument for the following command. The | |
2509 | argument @var{arg} is the raw prefix argument as it was before this | |
2510 | command; it is used to compute the updated prefix argument. Don't call | |
2511 | this command yourself unless you know what you are doing. | |
2512 | @end deffn | |
2513 | ||
2514 | @deffn Command negative-argument arg | |
2515 | This command adds to the numeric argument for the next command. The | |
2516 | argument @var{arg} is the raw prefix argument as it was before this | |
2517 | command; its value is negated to form the new prefix argument. Don't | |
2518 | call this command yourself unless you know what you are doing. | |
2519 | @end deffn | |
2520 | ||
8db970a4 RS |
2521 | @node Recursive Editing |
2522 | @section Recursive Editing | |
2523 | @cindex recursive command loop | |
2524 | @cindex recursive editing level | |
2525 | @cindex command loop, recursive | |
2526 | ||
f142f62a RS |
2527 | The Emacs command loop is entered automatically when Emacs starts up. |
2528 | This top-level invocation of the command loop never exits; it keeps | |
2529 | running as long as Emacs does. Lisp programs can also invoke the | |
2530 | command loop. Since this makes more than one activation of the command | |
2531 | loop, we call it @dfn{recursive editing}. A recursive editing level has | |
2532 | the effect of suspending whatever command invoked it and permitting the | |
2533 | user to do arbitrary editing before resuming that command. | |
8db970a4 RS |
2534 | |
2535 | The commands available during recursive editing are the same ones | |
2536 | available in the top-level editing loop and defined in the keymaps. | |
2537 | Only a few special commands exit the recursive editing level; the others | |
f142f62a RS |
2538 | return to the recursive editing level when they finish. (The special |
2539 | commands for exiting are always available, but they do nothing when | |
2540 | recursive editing is not in progress.) | |
8db970a4 RS |
2541 | |
2542 | All command loops, including recursive ones, set up all-purpose error | |
2543 | handlers so that an error in a command run from the command loop will | |
2544 | not exit the loop. | |
2545 | ||
2546 | @cindex minibuffer input | |
2547 | Minibuffer input is a special kind of recursive editing. It has a few | |
2548 | special wrinkles, such as enabling display of the minibuffer and the | |
2549 | minibuffer window, but fewer than you might suppose. Certain keys | |
2550 | behave differently in the minibuffer, but that is only because of the | |
2551 | minibuffer's local map; if you switch windows, you get the usual Emacs | |
2552 | commands. | |
2553 | ||
2554 | @cindex @code{throw} example | |
2555 | @kindex exit | |
2556 | @cindex exit recursive editing | |
2557 | @cindex aborting | |
2558 | To invoke a recursive editing level, call the function | |
2559 | @code{recursive-edit}. This function contains the command loop; it also | |
2560 | contains a call to @code{catch} with tag @code{exit}, which makes it | |
2561 | possible to exit the recursive editing level by throwing to @code{exit} | |
2562 | (@pxref{Catch and Throw}). If you throw a value other than @code{t}, | |
2563 | then @code{recursive-edit} returns normally to the function that called | |
2564 | it. The command @kbd{C-M-c} (@code{exit-recursive-edit}) does this. | |
2565 | Throwing a @code{t} value causes @code{recursive-edit} to quit, so that | |
2566 | control returns to the command loop one level up. This is called | |
2567 | @dfn{aborting}, and is done by @kbd{C-]} (@code{abort-recursive-edit}). | |
2568 | ||
2569 | Most applications should not use recursive editing, except as part of | |
2570 | using the minibuffer. Usually it is more convenient for the user if you | |
2571 | change the major mode of the current buffer temporarily to a special | |
b22f3a19 RS |
2572 | major mode, which should have a command to go back to the previous mode. |
2573 | (The @kbd{e} command in Rmail uses this technique.) Or, if you wish to | |
2574 | give the user different text to edit ``recursively'', create and select | |
2575 | a new buffer in a special mode. In this mode, define a command to | |
2576 | complete the processing and go back to the previous buffer. (The | |
2577 | @kbd{m} command in Rmail does this.) | |
8db970a4 RS |
2578 | |
2579 | Recursive edits are useful in debugging. You can insert a call to | |
2580 | @code{debug} into a function definition as a sort of breakpoint, so that | |
2581 | you can look around when the function gets there. @code{debug} invokes | |
2582 | a recursive edit but also provides the other features of the debugger. | |
2583 | ||
2584 | Recursive editing levels are also used when you type @kbd{C-r} in | |
2585 | @code{query-replace} or use @kbd{C-x q} (@code{kbd-macro-query}). | |
2586 | ||
2587 | @defun recursive-edit | |
2588 | @cindex suspend evaluation | |
2589 | This function invokes the editor command loop. It is called | |
2590 | automatically by the initialization of Emacs, to let the user begin | |
2591 | editing. When called from a Lisp program, it enters a recursive editing | |
2592 | level. | |
2593 | ||
2594 | In the following example, the function @code{simple-rec} first | |
2595 | advances point one word, then enters a recursive edit, printing out a | |
2596 | message in the echo area. The user can then do any editing desired, and | |
2597 | then type @kbd{C-M-c} to exit and continue executing @code{simple-rec}. | |
2598 | ||
2599 | @example | |
2600 | (defun simple-rec () | |
2601 | (forward-word 1) | |
f142f62a | 2602 | (message "Recursive edit in progress") |
8db970a4 RS |
2603 | (recursive-edit) |
2604 | (forward-word 1)) | |
2605 | @result{} simple-rec | |
2606 | (simple-rec) | |
2607 | @result{} nil | |
2608 | @end example | |
2609 | @end defun | |
2610 | ||
2611 | @deffn Command exit-recursive-edit | |
2612 | This function exits from the innermost recursive edit (including | |
2613 | minibuffer input). Its definition is effectively @code{(throw 'exit | |
2614 | nil)}. | |
2615 | @end deffn | |
2616 | ||
2617 | @deffn Command abort-recursive-edit | |
2618 | This function aborts the command that requested the innermost recursive | |
2619 | edit (including minibuffer input), by signaling @code{quit} | |
2620 | after exiting the recursive edit. Its definition is effectively | |
2621 | @code{(throw 'exit t)}. @xref{Quitting}. | |
2622 | @end deffn | |
2623 | ||
2624 | @deffn Command top-level | |
2625 | This function exits all recursive editing levels; it does not return a | |
2626 | value, as it jumps completely out of any computation directly back to | |
2627 | the main command loop. | |
2628 | @end deffn | |
2629 | ||
2630 | @defun recursion-depth | |
2631 | This function returns the current depth of recursive edits. When no | |
2632 | recursive edit is active, it returns 0. | |
2633 | @end defun | |
2634 | ||
2635 | @node Disabling Commands | |
2636 | @section Disabling Commands | |
2637 | @cindex disabled command | |
2638 | ||
2639 | @dfn{Disabling a command} marks the command as requiring user | |
2640 | confirmation before it can be executed. Disabling is used for commands | |
2641 | which might be confusing to beginning users, to prevent them from using | |
2642 | the commands by accident. | |
2643 | ||
2644 | @kindex disabled | |
2645 | The low-level mechanism for disabling a command is to put a | |
2646 | non-@code{nil} @code{disabled} property on the Lisp symbol for the | |
2647 | command. These properties are normally set up by the user's | |
a40d4712 | 2648 | init file (@pxref{Init File}) with Lisp expressions such as this: |
8db970a4 RS |
2649 | |
2650 | @example | |
2651 | (put 'upcase-region 'disabled t) | |
2652 | @end example | |
2653 | ||
2654 | @noindent | |
a40d4712 PR |
2655 | For a few commands, these properties are present by default (you can |
2656 | remove them in your init file if you wish). | |
8db970a4 | 2657 | |
f142f62a RS |
2658 | If the value of the @code{disabled} property is a string, the message |
2659 | saying the command is disabled includes that string. For example: | |
8db970a4 RS |
2660 | |
2661 | @example | |
2662 | (put 'delete-region 'disabled | |
2663 | "Text deleted this way cannot be yanked back!\n") | |
2664 | @end example | |
2665 | ||
2666 | @xref{Disabling,,, emacs, The GNU Emacs Manual}, for the details on | |
2667 | what happens when a disabled command is invoked interactively. | |
2668 | Disabling a command has no effect on calling it as a function from Lisp | |
2669 | programs. | |
2670 | ||
2671 | @deffn Command enable-command command | |
2672 | Allow @var{command} to be executed without special confirmation from now | |
a40d4712 PR |
2673 | on, and (if the user confirms) alter the user's init file (@pxref{Init |
2674 | File}) so that this will apply to future sessions. | |
8db970a4 RS |
2675 | @end deffn |
2676 | ||
2677 | @deffn Command disable-command command | |
f142f62a | 2678 | Require special confirmation to execute @var{command} from now on, and |
a40d4712 | 2679 | (if the user confirms) alter the user's init file so that this |
b22f3a19 | 2680 | will apply to future sessions. |
8db970a4 RS |
2681 | @end deffn |
2682 | ||
2683 | @defvar disabled-command-hook | |
f9f59935 RS |
2684 | When the user invokes a disabled command interactively, this normal hook |
2685 | is run instead of the disabled command. The hook functions can use | |
f142f62a | 2686 | @code{this-command-keys} to determine what the user typed to run the |
b22f3a19 | 2687 | command, and thus find the command itself. @xref{Hooks}. |
8db970a4 RS |
2688 | |
2689 | By default, @code{disabled-command-hook} contains a function that asks | |
2690 | the user whether to proceed. | |
2691 | @end defvar | |
2692 | ||
2693 | @node Command History | |
2694 | @section Command History | |
2695 | @cindex command history | |
2696 | @cindex complex command | |
2697 | @cindex history of commands | |
2698 | ||
2699 | The command loop keeps a history of the complex commands that have | |
2700 | been executed, to make it convenient to repeat these commands. A | |
2701 | @dfn{complex command} is one for which the interactive argument reading | |
2702 | uses the minibuffer. This includes any @kbd{M-x} command, any | |
bfe721d1 | 2703 | @kbd{M-:} command, and any command whose @code{interactive} |
8db970a4 RS |
2704 | specification reads an argument from the minibuffer. Explicit use of |
2705 | the minibuffer during the execution of the command itself does not cause | |
2706 | the command to be considered complex. | |
2707 | ||
2708 | @defvar command-history | |
2709 | This variable's value is a list of recent complex commands, each | |
2710 | represented as a form to evaluate. It continues to accumulate all | |
a9f0a989 RS |
2711 | complex commands for the duration of the editing session, but when it |
2712 | reaches the maximum size (specified by the variable | |
2713 | @code{history-length}), the oldest elements are deleted as new ones are | |
2714 | added. | |
8db970a4 RS |
2715 | |
2716 | @example | |
2717 | @group | |
2718 | command-history | |
2719 | @result{} ((switch-to-buffer "chistory.texi") | |
2720 | (describe-key "^X^[") | |
2721 | (visit-tags-table "~/emacs/src/") | |
2722 | (find-tag "repeat-complex-command")) | |
2723 | @end group | |
2724 | @end example | |
2725 | @end defvar | |
2726 | ||
2727 | This history list is actually a special case of minibuffer history | |
2728 | (@pxref{Minibuffer History}), with one special twist: the elements are | |
2729 | expressions rather than strings. | |
2730 | ||
2731 | There are a number of commands devoted to the editing and recall of | |
2732 | previous commands. The commands @code{repeat-complex-command}, and | |
2733 | @code{list-command-history} are described in the user manual | |
2734 | (@pxref{Repetition,,, emacs, The GNU Emacs Manual}). Within the | |
f9f59935 | 2735 | minibuffer, the usual minibuffer history commands are available. |
8db970a4 RS |
2736 | |
2737 | @node Keyboard Macros | |
2738 | @section Keyboard Macros | |
2739 | @cindex keyboard macros | |
2740 | ||
2741 | A @dfn{keyboard macro} is a canned sequence of input events that can | |
f142f62a RS |
2742 | be considered a command and made the definition of a key. The Lisp |
2743 | representation of a keyboard macro is a string or vector containing the | |
2744 | events. Don't confuse keyboard macros with Lisp macros | |
2745 | (@pxref{Macros}). | |
8db970a4 | 2746 | |
f9f59935 RS |
2747 | @defun execute-kbd-macro kbdmacro &optional count |
2748 | This function executes @var{kbdmacro} as a sequence of events. If | |
2749 | @var{kbdmacro} is a string or vector, then the events in it are executed | |
8db970a4 RS |
2750 | exactly as if they had been input by the user. The sequence is |
2751 | @emph{not} expected to be a single key sequence; normally a keyboard | |
2752 | macro definition consists of several key sequences concatenated. | |
2753 | ||
f9f59935 RS |
2754 | If @var{kbdmacro} is a symbol, then its function definition is used in |
2755 | place of @var{kbdmacro}. If that is another symbol, this process repeats. | |
8db970a4 RS |
2756 | Eventually the result should be a string or vector. If the result is |
2757 | not a symbol, string, or vector, an error is signaled. | |
2758 | ||
f9f59935 RS |
2759 | The argument @var{count} is a repeat count; @var{kbdmacro} is executed that |
2760 | many times. If @var{count} is omitted or @code{nil}, @var{kbdmacro} is | |
2761 | executed once. If it is 0, @var{kbdmacro} is executed over and over until it | |
8db970a4 | 2762 | encounters an error or a failing search. |
f9f59935 RS |
2763 | |
2764 | @xref{Reading One Event}, for an example of using @code{execute-kbd-macro}. | |
8db970a4 RS |
2765 | @end defun |
2766 | ||
8db970a4 RS |
2767 | @defvar executing-macro |
2768 | This variable contains the string or vector that defines the keyboard | |
2769 | macro that is currently executing. It is @code{nil} if no macro is | |
f9f59935 | 2770 | currently executing. A command can test this variable so as to behave |
f142f62a RS |
2771 | differently when run from an executing macro. Do not set this variable |
2772 | yourself. | |
8db970a4 RS |
2773 | @end defvar |
2774 | ||
2775 | @defvar defining-kbd-macro | |
f142f62a | 2776 | This variable indicates whether a keyboard macro is being defined. A |
f9f59935 RS |
2777 | command can test this variable so as to behave differently while a macro |
2778 | is being defined. The commands @code{start-kbd-macro} and | |
f142f62a | 2779 | @code{end-kbd-macro} set this variable---do not set it yourself. |
22697dac | 2780 | |
bfe721d1 KH |
2781 | The variable is always local to the current terminal and cannot be |
2782 | buffer-local. @xref{Multiple Displays}. | |
2783 | @end defvar | |
2784 | ||
2785 | @defvar last-kbd-macro | |
2786 | This variable is the definition of the most recently defined keyboard | |
2787 | macro. Its value is a string or vector, or @code{nil}. | |
2788 | ||
2789 | The variable is always local to the current terminal and cannot be | |
22697dac | 2790 | buffer-local. @xref{Multiple Displays}. |
8db970a4 RS |
2791 | @end defvar |
2792 | ||
2842de30 EZ |
2793 | @defvar kbd-macro-termination-hook |
2794 | This normal hook (@pxref{Standard Hooks}) is run when a keyboard | |
2795 | macro terminates, regardless of what caused it to terminate (reaching | |
2796 | the macro end or an error which ended the macro prematurely). | |
2797 | @end defvar |