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1 | @c -*-texinfo-*- |
2 | @c This is part of the GNU Emacs Lisp Reference Manual. | |
651f374c | 3 | @c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2002, 2003, |
ceb4c4d3 | 4 | @c 2004, 2005, 2006 Free Software Foundation, Inc. |
8db970a4 RS |
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 | |
177c0ea7 | 15 | are done, and the subroutines that allow Lisp programs to do them. |
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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 | ||
f142f62a RS |
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 | |
f142f62a RS |
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. | |
ecbfc7e9 | 77 | @xref{Command Loop Info}. |
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78 | @end defvar |
79 | ||
80 | @defvar post-command-hook | |
f142f62a RS |
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, | |
ecbfc7e9 RS |
84 | @code{this-command} refers to the command that just ran, and |
85 | @code{last-command} refers to the command before that. | |
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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 | |
14bd0b09 RS |
93 | A request coming into the Emacs server (@pxref{Emacs Server,,, |
94 | emacs, The GNU Emacs Manual}) runs these two hooks just as a keyboard | |
95 | command does. | |
96 | ||
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97 | @node Defining Commands |
98 | @section Defining Commands | |
99 | @cindex defining commands | |
100 | @cindex commands, defining | |
101 | @cindex functions, making them interactive | |
102 | @cindex interactive function | |
103 | ||
104 | A Lisp function becomes a command when its body contains, at top | |
b22f3a19 | 105 | level, a form that calls the special form @code{interactive}. This |
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106 | form does nothing when actually executed, but its presence serves as a |
107 | flag to indicate that interactive calling is permitted. Its argument | |
108 | controls the reading of arguments for an interactive call. | |
109 | ||
110 | @menu | |
111 | * Using Interactive:: General rules for @code{interactive}. | |
112 | * Interactive Codes:: The standard letter-codes for reading arguments | |
113 | in various ways. | |
114 | * Interactive Examples:: Examples of how to read interactive arguments. | |
115 | @end menu | |
116 | ||
117 | @node Using Interactive | |
118 | @subsection Using @code{interactive} | |
119 | ||
120 | This section describes how to write the @code{interactive} form that | |
2842de30 | 121 | makes a Lisp function an interactively-callable command, and how to |
5504e99c | 122 | examine a command's @code{interactive} form. |
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123 | |
124 | @defspec interactive arg-descriptor | |
125 | @cindex argument descriptors | |
126 | This special form declares that the function in which it appears is a | |
127 | command, and that it may therefore be called interactively (via | |
128 | @kbd{M-x} or by entering a key sequence bound to it). The argument | |
f142f62a RS |
129 | @var{arg-descriptor} declares how to compute the arguments to the |
130 | command when the command is called interactively. | |
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131 | |
132 | A command may be called from Lisp programs like any other function, but | |
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133 | then the caller supplies the arguments and @var{arg-descriptor} has no |
134 | effect. | |
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135 | |
136 | The @code{interactive} form has its effect because the command loop | |
137 | (actually, its subroutine @code{call-interactively}) scans through the | |
138 | function definition looking for it, before calling the function. Once | |
139 | the function is called, all its body forms including the | |
140 | @code{interactive} form are executed, but at this time | |
141 | @code{interactive} simply returns @code{nil} without even evaluating its | |
142 | argument. | |
143 | @end defspec | |
144 | ||
145 | There are three possibilities for the argument @var{arg-descriptor}: | |
146 | ||
147 | @itemize @bullet | |
148 | @item | |
149 | It may be omitted or @code{nil}; then the command is called with no | |
150 | arguments. This leads quickly to an error if the command requires one | |
151 | or more arguments. | |
152 | ||
8db970a4 RS |
153 | @item |
154 | @cindex argument prompt | |
155 | It may be a string; then its contents should consist of a code character | |
156 | followed by a prompt (which some code characters use and some ignore). | |
157 | The prompt ends either with the end of the string or with a newline. | |
158 | Here is a simple example: | |
159 | ||
160 | @smallexample | |
161 | (interactive "bFrobnicate buffer: ") | |
162 | @end smallexample | |
163 | ||
164 | @noindent | |
165 | The code letter @samp{b} says to read the name of an existing buffer, | |
166 | with completion. The buffer name is the sole argument passed to the | |
167 | command. The rest of the string is a prompt. | |
168 | ||
169 | If there is a newline character in the string, it terminates the prompt. | |
170 | If the string does not end there, then the rest of the string should | |
171 | contain another code character and prompt, specifying another argument. | |
172 | You can specify any number of arguments in this way. | |
173 | ||
174 | @c Emacs 19 feature | |
175 | The prompt string can use @samp{%} to include previous argument values | |
b22f3a19 RS |
176 | (starting with the first argument) in the prompt. This is done using |
177 | @code{format} (@pxref{Formatting Strings}). For example, here is how | |
178 | you could read the name of an existing buffer followed by a new name to | |
179 | give to that buffer: | |
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180 | |
181 | @smallexample | |
182 | @group | |
183 | (interactive "bBuffer to rename: \nsRename buffer %s to: ") | |
184 | @end group | |
185 | @end smallexample | |
186 | ||
caae20c7 | 187 | @cindex @samp{*} in @code{interactive} |
f142f62a | 188 | @cindex read-only buffers in interactive |
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189 | If the first character in the string is @samp{*}, then an error is |
190 | signaled if the buffer is read-only. | |
191 | ||
caae20c7 | 192 | @cindex @samp{@@} in @code{interactive} |
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193 | @c Emacs 19 feature |
194 | If the first character in the string is @samp{@@}, and if the key | |
195 | sequence used to invoke the command includes any mouse events, then | |
196 | the window associated with the first of those events is selected | |
197 | before the command is run. | |
198 | ||
199 | You can use @samp{*} and @samp{@@} together; the order does not matter. | |
200 | Actual reading of arguments is controlled by the rest of the prompt | |
201 | string (starting with the first character that is not @samp{*} or | |
202 | @samp{@@}). | |
df36a07e RS |
203 | |
204 | @item | |
205 | It may be a Lisp expression that is not a string; then it should be a | |
206 | form that is evaluated to get a list of arguments to pass to the | |
207 | command. Usually this form will call various functions to read input | |
58f71009 | 208 | from the user, most often through the minibuffer (@pxref{Minibuffers}) |
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209 | or directly from the keyboard (@pxref{Reading Input}). |
210 | @cindex argument evaluation form | |
211 | ||
212 | Providing point or the mark as an argument value is also common, but | |
213 | if you do this @emph{and} read input (whether using the minibuffer or | |
214 | not), be sure to get the integer values of point or the mark after | |
215 | reading. The current buffer may be receiving subprocess output; if | |
216 | subprocess output arrives while the command is waiting for input, it | |
217 | could relocate point and the mark. | |
218 | ||
219 | Here's an example of what @emph{not} to do: | |
220 | ||
221 | @smallexample | |
222 | (interactive | |
223 | (list (region-beginning) (region-end) | |
224 | (read-string "Foo: " nil 'my-history))) | |
225 | @end smallexample | |
226 | ||
227 | @noindent | |
228 | Here's how to avoid the problem, by examining point and the mark after | |
229 | reading the keyboard input: | |
230 | ||
231 | @smallexample | |
232 | (interactive | |
233 | (let ((string (read-string "Foo: " nil 'my-history))) | |
234 | (list (region-beginning) (region-end) string))) | |
235 | @end smallexample | |
76f008da RS |
236 | |
237 | @strong{Warning:} the argument values should not include any data | |
238 | types that can't be printed and then read. Some facilities save | |
239 | @code{command-history} in a file to be read in the subsequent | |
240 | sessions; if a command's arguments contain a data type that prints | |
241 | using @samp{#<@dots{}>} syntax, those facilities won't work. | |
242 | ||
243 | There are, however, a few exceptions: it is ok to use a limited set of | |
244 | expressions such as @code{(point)}, @code{(mark)}, | |
245 | @code{(region-beginning)}, and @code{(region-end)}, because Emacs | |
246 | recognizes them specially and puts the expression (rather than its | |
247 | value) into the command history. To see whether the expression you | |
248 | wrote is one of these exceptions, run the command, then examine | |
249 | @code{(car command-history)}. | |
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250 | @end itemize |
251 | ||
caae20c7 | 252 | @cindex examining the @code{interactive} form |
2842de30 | 253 | @defun interactive-form function |
5504e99c LT |
254 | This function returns the @code{interactive} form of @var{function}. |
255 | If @var{function} is an interactively callable function | |
256 | (@pxref{Interactive Call}), the value is the command's | |
257 | @code{interactive} form @code{(interactive @var{spec})}, which | |
258 | specifies how to compute its arguments. Otherwise, the value is | |
259 | @code{nil}. If @var{function} is a symbol, its function definition is | |
260 | used. | |
2842de30 EZ |
261 | @end defun |
262 | ||
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263 | @node Interactive Codes |
264 | @comment node-name, next, previous, up | |
265 | @subsection Code Characters for @code{interactive} | |
266 | @cindex interactive code description | |
267 | @cindex description for interactive codes | |
268 | @cindex codes, interactive, description of | |
269 | @cindex characters for interactive codes | |
270 | ||
271 | The code character descriptions below contain a number of key words, | |
272 | defined here as follows: | |
273 | ||
274 | @table @b | |
275 | @item Completion | |
276 | @cindex interactive completion | |
277 | Provide completion. @key{TAB}, @key{SPC}, and @key{RET} perform name | |
278 | completion because the argument is read using @code{completing-read} | |
279 | (@pxref{Completion}). @kbd{?} displays a list of possible completions. | |
280 | ||
281 | @item Existing | |
282 | Require the name of an existing object. An invalid name is not | |
283 | accepted; the commands to exit the minibuffer do not exit if the current | |
284 | input is not valid. | |
285 | ||
286 | @item Default | |
287 | @cindex default argument string | |
288 | A default value of some sort is used if the user enters no text in the | |
289 | minibuffer. The default depends on the code character. | |
290 | ||
291 | @item No I/O | |
292 | This code letter computes an argument without reading any input. | |
293 | Therefore, it does not use a prompt string, and any prompt string you | |
294 | supply is ignored. | |
295 | ||
f142f62a RS |
296 | Even though the code letter doesn't use a prompt string, you must follow |
297 | it with a newline if it is not the last code character in the string. | |
298 | ||
8db970a4 RS |
299 | @item Prompt |
300 | A prompt immediately follows the code character. The prompt ends either | |
301 | with the end of the string or with a newline. | |
302 | ||
303 | @item Special | |
304 | This code character is meaningful only at the beginning of the | |
305 | interactive string, and it does not look for a prompt or a newline. | |
306 | It is a single, isolated character. | |
307 | @end table | |
308 | ||
309 | @cindex reading interactive arguments | |
310 | Here are the code character descriptions for use with @code{interactive}: | |
311 | ||
312 | @table @samp | |
313 | @item * | |
314 | Signal an error if the current buffer is read-only. Special. | |
315 | ||
316 | @item @@ | |
317 | Select the window mentioned in the first mouse event in the key | |
318 | sequence that invoked this command. Special. | |
319 | ||
320 | @item a | |
b22f3a19 | 321 | A function name (i.e., a symbol satisfying @code{fboundp}). Existing, |
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322 | Completion, Prompt. |
323 | ||
324 | @item b | |
325 | The name of an existing buffer. By default, uses the name of the | |
326 | current buffer (@pxref{Buffers}). Existing, Completion, Default, | |
327 | Prompt. | |
328 | ||
329 | @item B | |
330 | A buffer name. The buffer need not exist. By default, uses the name of | |
331 | a recently used buffer other than the current buffer. Completion, | |
b22f3a19 | 332 | Default, Prompt. |
8db970a4 RS |
333 | |
334 | @item c | |
335 | A character. The cursor does not move into the echo area. Prompt. | |
336 | ||
337 | @item C | |
338 | A command name (i.e., a symbol satisfying @code{commandp}). Existing, | |
339 | Completion, Prompt. | |
340 | ||
341 | @item d | |
342 | @cindex position argument | |
f142f62a | 343 | The position of point, as an integer (@pxref{Point}). No I/O. |
8db970a4 RS |
344 | |
345 | @item D | |
346 | A directory name. The default is the current default directory of the | |
e35e07df | 347 | current buffer, @code{default-directory} (@pxref{File Name Expansion}). |
8db970a4 RS |
348 | Existing, Completion, Default, Prompt. |
349 | ||
350 | @item e | |
351 | The first or next mouse event in the key sequence that invoked the command. | |
b22f3a19 | 352 | More precisely, @samp{e} gets events that are lists, so you can look at |
8db970a4 RS |
353 | the data in the lists. @xref{Input Events}. No I/O. |
354 | ||
355 | You can use @samp{e} more than once in a single command's interactive | |
b22f3a19 | 356 | specification. If the key sequence that invoked the command has |
f142f62a | 357 | @var{n} events that are lists, the @var{n}th @samp{e} provides the |
b22f3a19 | 358 | @var{n}th such event. Events that are not lists, such as function keys |
ad800164 | 359 | and @acronym{ASCII} characters, do not count where @samp{e} is concerned. |
8db970a4 | 360 | |
8db970a4 RS |
361 | @item f |
362 | A file name of an existing file (@pxref{File Names}). The default | |
363 | directory is @code{default-directory}. Existing, Completion, Default, | |
364 | Prompt. | |
365 | ||
366 | @item F | |
367 | A file name. The file need not exist. Completion, Default, Prompt. | |
368 | ||
9644814c RS |
369 | @item G |
370 | A file name. The file need not exist. If the user enters just a | |
371 | directory name, then the value is just that directory name, with no | |
372 | file name within the directory added. Completion, Default, Prompt. | |
373 | ||
a9f0a989 RS |
374 | @item i |
375 | An irrelevant argument. This code always supplies @code{nil} as | |
376 | the argument's value. No I/O. | |
377 | ||
8db970a4 | 378 | @item k |
08244b81 | 379 | A key sequence (@pxref{Key Sequences}). This keeps reading events |
8db970a4 RS |
380 | until a command (or undefined command) is found in the current key |
381 | maps. The key sequence argument is represented as a string or vector. | |
382 | The cursor does not move into the echo area. Prompt. | |
383 | ||
053bc8e4 RS |
384 | If @samp{k} reads a key sequence that ends with a down-event, it also |
385 | reads and discards the following up-event. You can get access to that | |
386 | up-event with the @samp{U} code character. | |
3baa952d | 387 | |
8db970a4 RS |
388 | This kind of input is used by commands such as @code{describe-key} and |
389 | @code{global-set-key}. | |
390 | ||
22697dac KH |
391 | @item K |
392 | A key sequence, whose definition you intend to change. This works like | |
393 | @samp{k}, except that it suppresses, for the last input event in the key | |
394 | sequence, the conversions that are normally used (when necessary) to | |
395 | convert an undefined key into a defined one. | |
396 | ||
8db970a4 RS |
397 | @item m |
398 | @cindex marker argument | |
f142f62a | 399 | The position of the mark, as an integer. No I/O. |
8db970a4 | 400 | |
f9f59935 RS |
401 | @item M |
402 | Arbitrary text, read in the minibuffer using the current buffer's input | |
403 | method, and returned as a string (@pxref{Input Methods,,, emacs, The GNU | |
404 | Emacs Manual}). Prompt. | |
405 | ||
8db970a4 | 406 | @item n |
dff3f9e1 RS |
407 | A number, read with the minibuffer. If the input is not a number, the |
408 | user has to try again. @samp{n} never uses the prefix argument. | |
8db970a4 RS |
409 | Prompt. |
410 | ||
411 | @item N | |
dff3f9e1 RS |
412 | The numeric prefix argument; but if there is no prefix argument, read |
413 | a number as with @kbd{n}. The value is always a number. @xref{Prefix | |
414 | Command Arguments}. Prompt. | |
8db970a4 RS |
415 | |
416 | @item p | |
417 | @cindex numeric prefix argument usage | |
418 | The numeric prefix argument. (Note that this @samp{p} is lower case.) | |
b22f3a19 | 419 | No I/O. |
8db970a4 RS |
420 | |
421 | @item P | |
dff3f9e1 | 422 | @cindex raw prefix argument usage |
b22f3a19 RS |
423 | The raw prefix argument. (Note that this @samp{P} is upper case.) No |
424 | I/O. | |
8db970a4 RS |
425 | |
426 | @item r | |
427 | @cindex region argument | |
428 | Point and the mark, as two numeric arguments, smallest first. This is | |
429 | the only code letter that specifies two successive arguments rather than | |
430 | one. No I/O. | |
431 | ||
432 | @item s | |
433 | Arbitrary text, read in the minibuffer and returned as a string | |
434 | (@pxref{Text from Minibuffer}). Terminate the input with either | |
969fe9b5 | 435 | @kbd{C-j} or @key{RET}. (@kbd{C-q} may be used to include either of |
8db970a4 RS |
436 | these characters in the input.) Prompt. |
437 | ||
438 | @item S | |
439 | An interned symbol whose name is read in the minibuffer. Any whitespace | |
440 | character terminates the input. (Use @kbd{C-q} to include whitespace in | |
441 | the string.) Other characters that normally terminate a symbol (e.g., | |
442 | parentheses and brackets) do not do so here. Prompt. | |
443 | ||
3baa952d | 444 | @item U |
053bc8e4 RS |
445 | A key sequence or @code{nil}. Can be used after a @samp{k} or |
446 | @samp{K} argument to get the up-event that was discarded (if any) | |
447 | after @samp{k} or @samp{K} read a down-event. If no up-event has been | |
448 | discarded, @samp{U} provides @code{nil} as the argument. No I/O. | |
3baa952d | 449 | |
8db970a4 | 450 | @item v |
5504e99c LT |
451 | A variable declared to be a user option (i.e., satisfying the |
452 | predicate @code{user-variable-p}). This reads the variable using | |
453 | @code{read-variable}. @xref{Definition of read-variable}. Existing, | |
8db970a4 RS |
454 | Completion, Prompt. |
455 | ||
456 | @item x | |
b22f3a19 | 457 | A Lisp object, specified with its read syntax, terminated with a |
969fe9b5 | 458 | @kbd{C-j} or @key{RET}. The object is not evaluated. @xref{Object from |
8db970a4 RS |
459 | Minibuffer}. Prompt. |
460 | ||
461 | @item X | |
462 | @cindex evaluated expression argument | |
053bc8e4 RS |
463 | A Lisp form's value. @samp{X} reads as @samp{x} does, then evaluates |
464 | the form so that its value becomes the argument for the command. | |
465 | Prompt. | |
a9f0a989 RS |
466 | |
467 | @item z | |
468 | A coding system name (a symbol). If the user enters null input, the | |
469 | argument value is @code{nil}. @xref{Coding Systems}. Completion, | |
470 | Existing, Prompt. | |
471 | ||
472 | @item Z | |
473 | A coding system name (a symbol)---but only if this command has a prefix | |
474 | argument. With no prefix argument, @samp{Z} provides @code{nil} as the | |
475 | argument value. Completion, Existing, Prompt. | |
8db970a4 RS |
476 | @end table |
477 | ||
478 | @node Interactive Examples | |
479 | @comment node-name, next, previous, up | |
480 | @subsection Examples of Using @code{interactive} | |
481 | @cindex examples of using @code{interactive} | |
177c0ea7 | 482 | @cindex @code{interactive}, examples of using |
8db970a4 RS |
483 | |
484 | Here are some examples of @code{interactive}: | |
485 | ||
486 | @example | |
487 | @group | |
488 | (defun foo1 () ; @r{@code{foo1} takes no arguments,} | |
489 | (interactive) ; @r{just moves forward two words.} | |
490 | (forward-word 2)) | |
491 | @result{} foo1 | |
492 | @end group | |
493 | ||
494 | @group | |
495 | (defun foo2 (n) ; @r{@code{foo2} takes one argument,} | |
496 | (interactive "p") ; @r{which is the numeric prefix.} | |
497 | (forward-word (* 2 n))) | |
498 | @result{} foo2 | |
499 | @end group | |
500 | ||
501 | @group | |
502 | (defun foo3 (n) ; @r{@code{foo3} takes one argument,} | |
503 | (interactive "nCount:") ; @r{which is read with the Minibuffer.} | |
504 | (forward-word (* 2 n))) | |
505 | @result{} foo3 | |
506 | @end group | |
507 | ||
508 | @group | |
509 | (defun three-b (b1 b2 b3) | |
510 | "Select three existing buffers. | |
511 | Put them into three windows, selecting the last one." | |
512 | @end group | |
513 | (interactive "bBuffer1:\nbBuffer2:\nbBuffer3:") | |
514 | (delete-other-windows) | |
515 | (split-window (selected-window) 8) | |
516 | (switch-to-buffer b1) | |
517 | (other-window 1) | |
518 | (split-window (selected-window) 8) | |
519 | (switch-to-buffer b2) | |
520 | (other-window 1) | |
521 | (switch-to-buffer b3)) | |
522 | @result{} three-b | |
523 | @group | |
524 | (three-b "*scratch*" "declarations.texi" "*mail*") | |
525 | @result{} nil | |
526 | @end group | |
527 | @end example | |
528 | ||
529 | @node Interactive Call | |
530 | @section Interactive Call | |
531 | @cindex interactive call | |
532 | ||
f9f59935 RS |
533 | After the command loop has translated a key sequence into a command it |
534 | invokes that command using the function @code{command-execute}. If the | |
535 | command is a function, @code{command-execute} calls | |
536 | @code{call-interactively}, which reads the arguments and calls the | |
537 | command. You can also call these functions yourself. | |
8db970a4 | 538 | |
041b0e7b | 539 | @defun commandp object &optional for-call-interactively |
8db970a4 | 540 | Returns @code{t} if @var{object} is suitable for calling interactively; |
177c0ea7 | 541 | that is, if @var{object} is a command. Otherwise, returns @code{nil}. |
8db970a4 RS |
542 | |
543 | The interactively callable objects include strings and vectors (treated | |
544 | as keyboard macros), lambda expressions that contain a top-level call to | |
bfe721d1 | 545 | @code{interactive}, byte-code function objects made from such lambda |
f142f62a RS |
546 | expressions, autoload objects that are declared as interactive |
547 | (non-@code{nil} fourth argument to @code{autoload}), and some of the | |
548 | primitive functions. | |
8db970a4 | 549 | |
041b0e7b RS |
550 | A symbol satisfies @code{commandp} if its function definition |
551 | satisfies @code{commandp}. Keys and keymaps are not commands. | |
552 | Rather, they are used to look up commands (@pxref{Keymaps}). | |
8db970a4 | 553 | |
041b0e7b RS |
554 | If @var{for-call-interactively} is non-@code{nil}, then |
555 | @code{commandp} returns @code{t} only for objects that | |
556 | @code{call-interactively} could call---thus, not for keyboard macros. | |
8db970a4 RS |
557 | |
558 | See @code{documentation} in @ref{Accessing Documentation}, for a | |
559 | realistic example of using @code{commandp}. | |
560 | @end defun | |
561 | ||
f9f59935 | 562 | @defun call-interactively command &optional record-flag keys |
8db970a4 RS |
563 | This function calls the interactively callable function @var{command}, |
564 | reading arguments according to its interactive calling specifications. | |
5504e99c LT |
565 | It returns whatever @var{command} returns. An error is signaled if |
566 | @var{command} is not a function or if it cannot be called | |
567 | interactively (i.e., is not a command). Note that keyboard macros | |
568 | (strings and vectors) are not accepted, even though they are | |
569 | considered commands, because they are not functions. If @var{command} | |
570 | is a symbol, then @code{call-interactively} uses its function definition. | |
8db970a4 RS |
571 | |
572 | @cindex record command history | |
573 | If @var{record-flag} is non-@code{nil}, then this command and its | |
574 | arguments are unconditionally added to the list @code{command-history}. | |
575 | Otherwise, the command is added only if it uses the minibuffer to read | |
576 | an argument. @xref{Command History}. | |
f9f59935 RS |
577 | |
578 | The argument @var{keys}, if given, specifies the sequence of events to | |
969fe9b5 | 579 | supply if the command inquires which events were used to invoke it. |
5504e99c LT |
580 | If @var{keys} is omitted or @code{nil}, the return value of |
581 | @code{this-command-keys} is used. @xref{Definition of this-command-keys}. | |
8db970a4 RS |
582 | @end defun |
583 | ||
79ddc9c9 | 584 | @defun command-execute command &optional record-flag keys special |
8db970a4 | 585 | @cindex keyboard macro execution |
f9f59935 RS |
586 | This function executes @var{command}. The argument @var{command} must |
587 | satisfy the @code{commandp} predicate; i.e., it must be an interactively | |
588 | callable function or a keyboard macro. | |
8db970a4 RS |
589 | |
590 | A string or vector as @var{command} is executed with | |
591 | @code{execute-kbd-macro}. A function is passed to | |
5504e99c LT |
592 | @code{call-interactively}, along with the optional @var{record-flag} |
593 | and @var{keys}. | |
8db970a4 RS |
594 | |
595 | A symbol is handled by using its function definition in its place. A | |
596 | symbol with an @code{autoload} definition counts as a command if it was | |
597 | declared to stand for an interactively callable function. Such a | |
598 | definition is handled by loading the specified library and then | |
599 | rechecking the definition of the symbol. | |
f9f59935 | 600 | |
79ddc9c9 GM |
601 | The argument @var{special}, if given, means to ignore the prefix |
602 | argument and not clear it. This is used for executing special events | |
603 | (@pxref{Special Events}). | |
8db970a4 RS |
604 | @end defun |
605 | ||
606 | @deffn Command execute-extended-command prefix-argument | |
607 | @cindex read command name | |
608 | This function reads a command name from the minibuffer using | |
609 | @code{completing-read} (@pxref{Completion}). Then it uses | |
610 | @code{command-execute} to call the specified command. Whatever that | |
611 | command returns becomes the value of @code{execute-extended-command}. | |
612 | ||
613 | @cindex execute with prefix argument | |
f142f62a RS |
614 | If the command asks for a prefix argument, it receives the value |
615 | @var{prefix-argument}. If @code{execute-extended-command} is called | |
616 | interactively, the current raw prefix argument is used for | |
8db970a4 RS |
617 | @var{prefix-argument}, and thus passed on to whatever command is run. |
618 | ||
619 | @c !!! Should this be @kindex? | |
620 | @cindex @kbd{M-x} | |
621 | @code{execute-extended-command} is the normal definition of @kbd{M-x}, | |
622 | so it uses the string @w{@samp{M-x }} as a prompt. (It would be better | |
623 | to take the prompt from the events used to invoke | |
624 | @code{execute-extended-command}, but that is painful to implement.) A | |
625 | description of the value of the prefix argument, if any, also becomes | |
626 | part of the prompt. | |
627 | ||
628 | @example | |
629 | @group | |
34079653 | 630 | (execute-extended-command 3) |
8db970a4 | 631 | ---------- Buffer: Minibuffer ---------- |
34079653 | 632 | 3 M-x forward-word RET |
8db970a4 RS |
633 | ---------- Buffer: Minibuffer ---------- |
634 | @result{} t | |
635 | @end group | |
636 | @end example | |
637 | @end deffn | |
638 | ||
639 | @defun interactive-p | |
dff3f9e1 RS |
640 | This function returns @code{t} if the containing function (the one |
641 | whose code includes the call to @code{interactive-p}) was called in | |
642 | direct response to user input. This means that it was called with the | |
643 | function @code{call-interactively}, and that a keyboard macro is | |
9d0d1070 | 644 | not running, and that Emacs is not running in batch mode. |
dff3f9e1 RS |
645 | |
646 | If the containing function was called by Lisp evaluation (or with | |
647 | @code{apply} or @code{funcall}), then it was not called interactively. | |
969fe9b5 | 648 | @end defun |
8db970a4 | 649 | |
dff3f9e1 RS |
650 | The most common use of @code{interactive-p} is for deciding whether |
651 | to give the user additional visual feedback (such as by printing an | |
652 | informative message). For example: | |
8db970a4 RS |
653 | |
654 | @example | |
655 | @group | |
dff3f9e1 | 656 | ;; @r{Here's the usual way to use @code{interactive-p}.} |
8db970a4 RS |
657 | (defun foo () |
658 | (interactive) | |
969fe9b5 RS |
659 | (when (interactive-p) |
660 | (message "foo"))) | |
8db970a4 RS |
661 | @result{} foo |
662 | @end group | |
663 | ||
664 | @group | |
dff3f9e1 | 665 | ;; @r{This function is just to illustrate the behavior.} |
8db970a4 RS |
666 | (defun bar () |
667 | (interactive) | |
668 | (setq foobar (list (foo) (interactive-p)))) | |
669 | @result{} bar | |
670 | @end group | |
671 | ||
672 | @group | |
673 | ;; @r{Type @kbd{M-x foo}.} | |
674 | @print{} foo | |
675 | @end group | |
676 | ||
677 | @group | |
678 | ;; @r{Type @kbd{M-x bar}.} | |
dff3f9e1 | 679 | ;; @r{This does not display a message.} |
8db970a4 RS |
680 | @end group |
681 | ||
682 | @group | |
683 | foobar | |
684 | @result{} (nil t) | |
685 | @end group | |
686 | @end example | |
969fe9b5 | 687 | |
dff3f9e1 RS |
688 | If you want to test @emph{only} whether the function was called |
689 | using @code{call-interactively}, add an optional argument | |
690 | @code{print-message} which should be non-@code{nil} in an interactive | |
691 | call, and use the @code{interactive} spec to make sure it is | |
692 | non-@code{nil}. Here's an example: | |
969fe9b5 RS |
693 | |
694 | @example | |
695 | (defun foo (&optional print-message) | |
696 | (interactive "p") | |
697 | (when print-message | |
698 | (message "foo"))) | |
699 | @end example | |
700 | ||
8e5f9510 | 701 | @noindent |
dff3f9e1 RS |
702 | Defined in this way, the function does display the message when called |
703 | from a keyboard macro. We use @code{"p"} because the numeric prefix | |
704 | argument is never @code{nil}. | |
8db970a4 | 705 | |
9d0d1070 RS |
706 | @defun called-interactively-p |
707 | This function returns @code{t} when the calling function was called | |
708 | using @code{call-interactively}. | |
709 | ||
710 | When possible, instead of using this function, you should use the | |
711 | method in the example above; that method makes it possible for a | |
712 | caller to ``pretend'' that the function was called interactively. | |
713 | @end defun | |
714 | ||
8db970a4 RS |
715 | @node Command Loop Info |
716 | @comment node-name, next, previous, up | |
717 | @section Information from the Command Loop | |
718 | ||
719 | The editor command loop sets several Lisp variables to keep status | |
177c0ea7 | 720 | records for itself and for commands that are run. |
8db970a4 RS |
721 | |
722 | @defvar last-command | |
723 | This variable records the name of the previous command executed by the | |
724 | command loop (the one before the current command). Normally the value | |
725 | is a symbol with a function definition, but this is not guaranteed. | |
726 | ||
f142f62a | 727 | The value is copied from @code{this-command} when a command returns to |
f9f59935 RS |
728 | the command loop, except when the command has specified a prefix |
729 | argument for the following command. | |
bfe721d1 KH |
730 | |
731 | This variable is always local to the current terminal and cannot be | |
732 | buffer-local. @xref{Multiple Displays}. | |
8db970a4 RS |
733 | @end defvar |
734 | ||
03c6b7f6 RS |
735 | @defvar real-last-command |
736 | This variable is set up by Emacs just like @code{last-command}, | |
737 | but never altered by Lisp programs. | |
738 | @end defvar | |
739 | ||
8db970a4 RS |
740 | @defvar this-command |
741 | @cindex current command | |
742 | This variable records the name of the command now being executed by | |
743 | the editor command loop. Like @code{last-command}, it is normally a symbol | |
744 | with a function definition. | |
745 | ||
f142f62a RS |
746 | The command loop sets this variable just before running a command, and |
747 | copies its value into @code{last-command} when the command finishes | |
f9f59935 | 748 | (unless the command specified a prefix argument for the following |
f142f62a | 749 | command). |
8db970a4 RS |
750 | |
751 | @cindex kill command repetition | |
f142f62a | 752 | Some commands set this variable during their execution, as a flag for |
bfe721d1 | 753 | whatever command runs next. In particular, the functions for killing text |
f142f62a RS |
754 | set @code{this-command} to @code{kill-region} so that any kill commands |
755 | immediately following will know to append the killed text to the | |
756 | previous kill. | |
8db970a4 RS |
757 | @end defvar |
758 | ||
759 | If you do not want a particular command to be recognized as the previous | |
760 | command in the case where it got an error, you must code that command to | |
761 | prevent this. One way is to set @code{this-command} to @code{t} at the | |
762 | beginning of the command, and set @code{this-command} back to its proper | |
763 | value at the end, like this: | |
764 | ||
765 | @example | |
766 | (defun foo (args@dots{}) | |
767 | (interactive @dots{}) | |
768 | (let ((old-this-command this-command)) | |
769 | (setq this-command t) | |
770 | @r{@dots{}do the work@dots{}} | |
771 | (setq this-command old-this-command))) | |
772 | @end example | |
773 | ||
f9f59935 RS |
774 | @noindent |
775 | We do not bind @code{this-command} with @code{let} because that would | |
776 | restore the old value in case of error---a feature of @code{let} which | |
777 | in this case does precisely what we want to avoid. | |
778 | ||
041b0e7b RS |
779 | @defvar this-original-command |
780 | This has the same value as @code{this-command} except when command | |
781 | remapping occurs (@pxref{Remapping Commands}). In that case, | |
782 | @code{this-command} gives the command actually run (the result of | |
783 | remapping), and @code{this-original-command} gives the command that | |
784 | was specified to run but remapped into another command. | |
785 | @end defvar | |
786 | ||
8db970a4 | 787 | @defun this-command-keys |
5504e99c | 788 | @anchor{Definition of this-command-keys} |
8db970a4 RS |
789 | This function returns a string or vector containing the key sequence |
790 | that invoked the present command, plus any previous commands that | |
5504e99c LT |
791 | generated the prefix argument for this command. However, if the |
792 | command has called @code{read-key-sequence}, it returns the last read | |
de700726 LT |
793 | key sequence. @xref{Key Sequence Input}. The value is a string if |
794 | all events in the sequence were characters that fit in a string. | |
795 | @xref{Input Events}. | |
8db970a4 RS |
796 | |
797 | @example | |
798 | @group | |
799 | (this-command-keys) | |
b22f3a19 | 800 | ;; @r{Now use @kbd{C-u C-x C-e} to evaluate that.} |
8db970a4 RS |
801 | @result{} "^U^X^E" |
802 | @end group | |
803 | @end example | |
804 | @end defun | |
805 | ||
969fe9b5 | 806 | @defun this-command-keys-vector |
2468d0c0 DL |
807 | Like @code{this-command-keys}, except that it always returns the events |
808 | in a vector, so you don't need to deal with the complexities of storing | |
809 | input events in a string (@pxref{Strings of Events}). | |
969fe9b5 RS |
810 | @end defun |
811 | ||
5504e99c | 812 | @defun clear-this-command-keys &optional keep-record |
b6954afd | 813 | This function empties out the table of events for |
5504e99c LT |
814 | @code{this-command-keys} to return. Unless @var{keep-record} is |
815 | non-@code{nil}, it also empties the records that the function | |
816 | @code{recent-keys} (@pxref{Recording Input}) will subsequently return. | |
817 | This is useful after reading a password, to prevent the password from | |
818 | echoing inadvertently as part of the next command in certain cases. | |
b6954afd RS |
819 | @end defun |
820 | ||
8db970a4 | 821 | @defvar last-nonmenu-event |
969fe9b5 RS |
822 | This variable holds the last input event read as part of a key sequence, |
823 | not counting events resulting from mouse menus. | |
8db970a4 | 824 | |
f9f59935 | 825 | One use of this variable is for telling @code{x-popup-menu} where to pop |
969fe9b5 RS |
826 | up a menu. It is also used internally by @code{y-or-n-p} |
827 | (@pxref{Yes-or-No Queries}). | |
8db970a4 RS |
828 | @end defvar |
829 | ||
830 | @defvar last-command-event | |
831 | @defvarx last-command-char | |
832 | This variable is set to the last input event that was read by the | |
833 | command loop as part of a command. The principal use of this variable | |
834 | is in @code{self-insert-command}, which uses it to decide which | |
835 | character to insert. | |
836 | ||
837 | @example | |
838 | @group | |
f142f62a | 839 | last-command-event |
b22f3a19 | 840 | ;; @r{Now use @kbd{C-u C-x C-e} to evaluate that.} |
8db970a4 RS |
841 | @result{} 5 |
842 | @end group | |
843 | @end example | |
844 | ||
845 | @noindent | |
ad800164 | 846 | The value is 5 because that is the @acronym{ASCII} code for @kbd{C-e}. |
8db970a4 RS |
847 | |
848 | The alias @code{last-command-char} exists for compatibility with | |
849 | Emacs version 18. | |
850 | @end defvar | |
851 | ||
852 | @c Emacs 19 feature | |
853 | @defvar last-event-frame | |
854 | This variable records which frame the last input event was directed to. | |
855 | Usually this is the frame that was selected when the event was | |
856 | generated, but if that frame has redirected input focus to another | |
857 | frame, the value is the frame to which the event was redirected. | |
858 | @xref{Input Focus}. | |
5504e99c LT |
859 | |
860 | If the last event came from a keyboard macro, the value is @code{macro}. | |
8db970a4 RS |
861 | @end defvar |
862 | ||
2468d0c0 DL |
863 | @node Adjusting Point |
864 | @section Adjusting Point After Commands | |
865 | ||
ecbfc7e9 RS |
866 | It is not easy to display a value of point in the middle of a |
867 | sequence of text that has the @code{display}, @code{composition} or | |
868 | @code{intangible} property, or is invisible. Therefore, after a | |
869 | command finishes and returns to the command loop, if point is within | |
870 | such a sequence, the command loop normally moves point to the edge of | |
871 | the sequence. | |
2468d0c0 DL |
872 | |
873 | A command can inhibit this feature by setting the variable | |
874 | @code{disable-point-adjustment}: | |
875 | ||
876 | @defvar disable-point-adjustment | |
ecbfc7e9 RS |
877 | If this variable is non-@code{nil} when a command returns to the |
878 | command loop, then the command loop does not check for those text | |
879 | properties, and does not move point out of sequences that have them. | |
2468d0c0 DL |
880 | |
881 | The command loop sets this variable to @code{nil} before each command, | |
882 | so if a command sets it, the effect applies only to that command. | |
883 | @end defvar | |
884 | ||
885 | @defvar global-disable-point-adjustment | |
2468d0c0 DL |
886 | If you set this variable to a non-@code{nil} value, the feature of |
887 | moving point out of these sequences is completely turned off. | |
888 | @end defvar | |
889 | ||
8db970a4 RS |
890 | @node Input Events |
891 | @section Input Events | |
892 | @cindex events | |
893 | @cindex input events | |
894 | ||
895 | The Emacs command loop reads a sequence of @dfn{input events} that | |
896 | represent keyboard or mouse activity. The events for keyboard activity | |
897 | are characters or symbols; mouse events are always lists. This section | |
898 | describes the representation and meaning of input events in detail. | |
899 | ||
8db970a4 | 900 | @defun eventp object |
a9f0a989 RS |
901 | This function returns non-@code{nil} if @var{object} is an input event |
902 | or event type. | |
903 | ||
904 | Note that any symbol might be used as an event or an event type. | |
905 | @code{eventp} cannot distinguish whether a symbol is intended by Lisp | |
906 | code to be used as an event. Instead, it distinguishes whether the | |
907 | symbol has actually been used in an event that has been read as input in | |
908 | the current Emacs session. If a symbol has not yet been so used, | |
909 | @code{eventp} returns @code{nil}. | |
8db970a4 RS |
910 | @end defun |
911 | ||
912 | @menu | |
913 | * Keyboard Events:: Ordinary characters--keys with symbols on them. | |
914 | * Function Keys:: Function keys--keys with names, not symbols. | |
f142f62a | 915 | * Mouse Events:: Overview of mouse events. |
8db970a4 RS |
916 | * Click Events:: Pushing and releasing a mouse button. |
917 | * Drag Events:: Moving the mouse before releasing the button. | |
918 | * Button-Down Events:: A button was pushed and not yet released. | |
919 | * Repeat Events:: Double and triple click (or drag, or down). | |
920 | * Motion Events:: Just moving the mouse, not pushing a button. | |
921 | * Focus Events:: Moving the mouse between frames. | |
7790d5cd | 922 | * Misc Events:: Other events the system can generate. |
8db970a4 RS |
923 | * Event Examples:: Examples of the lists for mouse events. |
924 | * Classifying Events:: Finding the modifier keys in an event symbol. | |
925 | Event types. | |
926 | * Accessing Events:: Functions to extract info from events. | |
927 | * Strings of Events:: Special considerations for putting | |
928 | keyboard character events in a string. | |
929 | @end menu | |
930 | ||
931 | @node Keyboard Events | |
932 | @subsection Keyboard Events | |
933 | ||
934 | There are two kinds of input you can get from the keyboard: ordinary | |
935 | keys, and function keys. Ordinary keys correspond to characters; the | |
969fe9b5 RS |
936 | events they generate are represented in Lisp as characters. The event |
937 | type of a character event is the character itself (an integer); see | |
938 | @ref{Classifying Events}. | |
8db970a4 RS |
939 | |
940 | @cindex modifier bits (of input character) | |
941 | @cindex basic code (of input character) | |
942 | An input character event consists of a @dfn{basic code} between 0 and | |
f9f59935 | 943 | 524287, plus any or all of these @dfn{modifier bits}: |
8db970a4 RS |
944 | |
945 | @table @asis | |
946 | @item meta | |
bfe721d1 | 947 | The |
969fe9b5 | 948 | @tex |
8241495d | 949 | @math{2^{27}} |
969fe9b5 | 950 | @end tex |
37680279 | 951 | @ifnottex |
bfe721d1 | 952 | 2**27 |
37680279 | 953 | @end ifnottex |
bfe721d1 | 954 | bit in the character code indicates a character |
8db970a4 RS |
955 | typed with the meta key held down. |
956 | ||
957 | @item control | |
bfe721d1 | 958 | The |
969fe9b5 | 959 | @tex |
8241495d | 960 | @math{2^{26}} |
969fe9b5 | 961 | @end tex |
37680279 | 962 | @ifnottex |
bfe721d1 | 963 | 2**26 |
37680279 | 964 | @end ifnottex |
ad800164 | 965 | bit in the character code indicates a non-@acronym{ASCII} |
8db970a4 RS |
966 | control character. |
967 | ||
8241495d | 968 | @sc{ascii} control characters such as @kbd{C-a} have special basic |
8db970a4 RS |
969 | codes of their own, so Emacs needs no special bit to indicate them. |
970 | Thus, the code for @kbd{C-a} is just 1. | |
971 | ||
ad800164 | 972 | But if you type a control combination not in @acronym{ASCII}, such as |
8db970a4 | 973 | @kbd{%} with the control key, the numeric value you get is the code |
bfe721d1 | 974 | for @kbd{%} plus |
969fe9b5 | 975 | @tex |
8241495d | 976 | @math{2^{26}} |
969fe9b5 | 977 | @end tex |
37680279 | 978 | @ifnottex |
bfe721d1 | 979 | 2**26 |
37680279 | 980 | @end ifnottex |
ad800164 | 981 | (assuming the terminal supports non-@acronym{ASCII} |
8db970a4 RS |
982 | control characters). |
983 | ||
984 | @item shift | |
bfe721d1 | 985 | The |
969fe9b5 | 986 | @tex |
8241495d | 987 | @math{2^{25}} |
969fe9b5 | 988 | @end tex |
37680279 | 989 | @ifnottex |
bfe721d1 | 990 | 2**25 |
37680279 | 991 | @end ifnottex |
ad800164 | 992 | bit in the character code indicates an @acronym{ASCII} control |
8db970a4 RS |
993 | character typed with the shift key held down. |
994 | ||
f9f59935 RS |
995 | For letters, the basic code itself indicates upper versus lower case; |
996 | for digits and punctuation, the shift key selects an entirely different | |
997 | character with a different basic code. In order to keep within the | |
ad800164 | 998 | @acronym{ASCII} character set whenever possible, Emacs avoids using the |
969fe9b5 | 999 | @tex |
8241495d | 1000 | @math{2^{25}} |
969fe9b5 | 1001 | @end tex |
37680279 | 1002 | @ifnottex |
bfe721d1 | 1003 | 2**25 |
37680279 | 1004 | @end ifnottex |
bfe721d1 | 1005 | bit for those characters. |
8db970a4 | 1006 | |
ad800164 | 1007 | However, @acronym{ASCII} provides no way to distinguish @kbd{C-A} from |
bfe721d1 | 1008 | @kbd{C-a}, so Emacs uses the |
969fe9b5 | 1009 | @tex |
8241495d | 1010 | @math{2^{25}} |
969fe9b5 | 1011 | @end tex |
37680279 | 1012 | @ifnottex |
bfe721d1 | 1013 | 2**25 |
37680279 | 1014 | @end ifnottex |
bfe721d1 | 1015 | bit in @kbd{C-A} and not in |
8db970a4 RS |
1016 | @kbd{C-a}. |
1017 | ||
1018 | @item hyper | |
bfe721d1 | 1019 | The |
969fe9b5 | 1020 | @tex |
8241495d | 1021 | @math{2^{24}} |
969fe9b5 | 1022 | @end tex |
37680279 | 1023 | @ifnottex |
bfe721d1 | 1024 | 2**24 |
37680279 | 1025 | @end ifnottex |
bfe721d1 | 1026 | bit in the character code indicates a character |
8db970a4 RS |
1027 | typed with the hyper key held down. |
1028 | ||
1029 | @item super | |
bfe721d1 | 1030 | The |
969fe9b5 | 1031 | @tex |
8241495d | 1032 | @math{2^{23}} |
969fe9b5 | 1033 | @end tex |
37680279 | 1034 | @ifnottex |
bfe721d1 | 1035 | 2**23 |
37680279 | 1036 | @end ifnottex |
bfe721d1 | 1037 | bit in the character code indicates a character |
8db970a4 RS |
1038 | typed with the super key held down. |
1039 | ||
1040 | @item alt | |
bfe721d1 | 1041 | The |
969fe9b5 | 1042 | @tex |
8241495d | 1043 | @math{2^{22}} |
969fe9b5 | 1044 | @end tex |
37680279 | 1045 | @ifnottex |
bfe721d1 | 1046 | 2**22 |
37680279 | 1047 | @end ifnottex |
bfe721d1 | 1048 | bit in the character code indicates a character typed with |
8db970a4 RS |
1049 | the alt key held down. (On some terminals, the key labeled @key{ALT} |
1050 | is actually the meta key.) | |
1051 | @end table | |
1052 | ||
bfe721d1 KH |
1053 | It is best to avoid mentioning specific bit numbers in your program. |
1054 | To test the modifier bits of a character, use the function | |
1055 | @code{event-modifiers} (@pxref{Classifying Events}). When making key | |
1056 | bindings, you can use the read syntax for characters with modifier bits | |
1057 | (@samp{\C-}, @samp{\M-}, and so on). For making key bindings with | |
1058 | @code{define-key}, you can use lists such as @code{(control hyper ?x)} to | |
1059 | specify the characters (@pxref{Changing Key Bindings}). The function | |
1060 | @code{event-convert-list} converts such a list into an event type | |
1061 | (@pxref{Classifying Events}). | |
8db970a4 RS |
1062 | |
1063 | @node Function Keys | |
1064 | @subsection Function Keys | |
1065 | ||
1066 | @cindex function keys | |
b22f3a19 | 1067 | Most keyboards also have @dfn{function keys}---keys that have names or |
f9f59935 RS |
1068 | symbols that are not characters. Function keys are represented in Emacs |
1069 | Lisp as symbols; the symbol's name is the function key's label, in lower | |
f142f62a RS |
1070 | case. For example, pressing a key labeled @key{F1} places the symbol |
1071 | @code{f1} in the input stream. | |
8db970a4 | 1072 | |
f142f62a RS |
1073 | The event type of a function key event is the event symbol itself. |
1074 | @xref{Classifying Events}. | |
8db970a4 | 1075 | |
b22f3a19 | 1076 | Here are a few special cases in the symbol-naming convention for |
8db970a4 RS |
1077 | function keys: |
1078 | ||
1079 | @table @asis | |
1080 | @item @code{backspace}, @code{tab}, @code{newline}, @code{return}, @code{delete} | |
ad800164 | 1081 | These keys correspond to common @acronym{ASCII} control characters that have |
8db970a4 RS |
1082 | special keys on most keyboards. |
1083 | ||
ad800164 | 1084 | In @acronym{ASCII}, @kbd{C-i} and @key{TAB} are the same character. If the |
f142f62a RS |
1085 | terminal can distinguish between them, Emacs conveys the distinction to |
1086 | Lisp programs by representing the former as the integer 9, and the | |
1087 | latter as the symbol @code{tab}. | |
8db970a4 RS |
1088 | |
1089 | Most of the time, it's not useful to distinguish the two. So normally | |
160ab7f9 | 1090 | @code{function-key-map} (@pxref{Translation Keymaps}) is set up to map |
4324b7ab RS |
1091 | @code{tab} into 9. Thus, a key binding for character code 9 (the |
1092 | character @kbd{C-i}) also applies to @code{tab}. Likewise for the other | |
1093 | symbols in this group. The function @code{read-char} likewise converts | |
1094 | these events into characters. | |
8db970a4 | 1095 | |
ad800164 | 1096 | In @acronym{ASCII}, @key{BS} is really @kbd{C-h}. But @code{backspace} |
8db970a4 RS |
1097 | converts into the character code 127 (@key{DEL}), not into code 8 |
1098 | (@key{BS}). This is what most users prefer. | |
1099 | ||
b22f3a19 RS |
1100 | @item @code{left}, @code{up}, @code{right}, @code{down} |
1101 | Cursor arrow keys | |
8db970a4 RS |
1102 | @item @code{kp-add}, @code{kp-decimal}, @code{kp-divide}, @dots{} |
1103 | Keypad keys (to the right of the regular keyboard). | |
1104 | @item @code{kp-0}, @code{kp-1}, @dots{} | |
1105 | Keypad keys with digits. | |
1106 | @item @code{kp-f1}, @code{kp-f2}, @code{kp-f3}, @code{kp-f4} | |
1107 | Keypad PF keys. | |
b22f3a19 | 1108 | @item @code{kp-home}, @code{kp-left}, @code{kp-up}, @code{kp-right}, @code{kp-down} |
f9f59935 RS |
1109 | Keypad arrow keys. Emacs normally translates these into the |
1110 | corresponding non-keypad keys @code{home}, @code{left}, @dots{} | |
b22f3a19 RS |
1111 | @item @code{kp-prior}, @code{kp-next}, @code{kp-end}, @code{kp-begin}, @code{kp-insert}, @code{kp-delete} |
1112 | Additional keypad duplicates of keys ordinarily found elsewhere. Emacs | |
1113 | normally translates these into the like-named non-keypad keys. | |
8db970a4 RS |
1114 | @end table |
1115 | ||
b22f3a19 RS |
1116 | You can use the modifier keys @key{ALT}, @key{CTRL}, @key{HYPER}, |
1117 | @key{META}, @key{SHIFT}, and @key{SUPER} with function keys. The way to | |
1118 | represent them is with prefixes in the symbol name: | |
8db970a4 RS |
1119 | |
1120 | @table @samp | |
1121 | @item A- | |
1122 | The alt modifier. | |
1123 | @item C- | |
1124 | The control modifier. | |
1125 | @item H- | |
1126 | The hyper modifier. | |
1127 | @item M- | |
1128 | The meta modifier. | |
1129 | @item S- | |
1130 | The shift modifier. | |
1131 | @item s- | |
1132 | The super modifier. | |
1133 | @end table | |
1134 | ||
1135 | Thus, the symbol for the key @key{F3} with @key{META} held down is | |
8609b2e2 | 1136 | @code{M-f3}. When you use more than one prefix, we recommend you |
f142f62a RS |
1137 | write them in alphabetical order; but the order does not matter in |
1138 | arguments to the key-binding lookup and modification functions. | |
1139 | ||
1140 | @node Mouse Events | |
1141 | @subsection Mouse Events | |
1142 | ||
1143 | Emacs supports four kinds of mouse events: click events, drag events, | |
1144 | button-down events, and motion events. All mouse events are represented | |
4bdcd3ef | 1145 | as lists. The @sc{car} of the list is the event type; this says which |
f142f62a RS |
1146 | mouse button was involved, and which modifier keys were used with it. |
1147 | The event type can also distinguish double or triple button presses | |
1148 | (@pxref{Repeat Events}). The rest of the list elements give position | |
1149 | and time information. | |
1150 | ||
1151 | For key lookup, only the event type matters: two events of the same type | |
1152 | necessarily run the same command. The command can access the full | |
1153 | values of these events using the @samp{e} interactive code. | |
1154 | @xref{Interactive Codes}. | |
1155 | ||
1156 | A key sequence that starts with a mouse event is read using the keymaps | |
1157 | of the buffer in the window that the mouse was in, not the current | |
1158 | buffer. This does not imply that clicking in a window selects that | |
1159 | window or its buffer---that is entirely under the control of the command | |
1160 | binding of the key sequence. | |
8db970a4 RS |
1161 | |
1162 | @node Click Events | |
1163 | @subsection Click Events | |
1164 | @cindex click event | |
1165 | @cindex mouse click event | |
1166 | ||
1167 | When the user presses a mouse button and releases it at the same | |
c5cb5297 KS |
1168 | location, that generates a @dfn{click} event. All mouse click event |
1169 | share the same format: | |
8db970a4 RS |
1170 | |
1171 | @example | |
c5cb5297 | 1172 | (@var{event-type} @var{position} @var{click-count}) |
b19f34c7 GM |
1173 | @end example |
1174 | ||
f142f62a RS |
1175 | @table @asis |
1176 | @item @var{event-type} | |
8db970a4 RS |
1177 | This is a symbol that indicates which mouse button was used. It is |
1178 | one of the symbols @code{mouse-1}, @code{mouse-2}, @dots{}, where the | |
f142f62a | 1179 | buttons are numbered left to right. |
8db970a4 RS |
1180 | |
1181 | You can also use prefixes @samp{A-}, @samp{C-}, @samp{H-}, @samp{M-}, | |
1182 | @samp{S-} and @samp{s-} for modifiers alt, control, hyper, meta, shift | |
1183 | and super, just as you would with function keys. | |
1184 | ||
1185 | This symbol also serves as the event type of the event. Key bindings | |
1186 | describe events by their types; thus, if there is a key binding for | |
1187 | @code{mouse-1}, that binding would apply to all events whose | |
1188 | @var{event-type} is @code{mouse-1}. | |
1189 | ||
c5cb5297 KS |
1190 | @item @var{position} |
1191 | This is the position where the mouse click occurred. The actual | |
1192 | format of @var{position} depends on what part of a window was clicked | |
1193 | on. The various formats are described below. | |
1194 | ||
1195 | @item @var{click-count} | |
1196 | This is the number of rapid repeated presses so far of the same mouse | |
1197 | button. @xref{Repeat Events}. | |
1198 | @end table | |
1199 | ||
1200 | For mouse click events in the text area, mode line, header line, or in | |
1201 | the marginal areas, @var{position} has this form: | |
1202 | ||
1203 | @example | |
f51f93f6 | 1204 | (@var{window} @var{pos-or-area} (@var{x} . @var{y}) @var{timestamp} |
5504e99c | 1205 | @var{object} @var{text-pos} (@var{col} . @var{row}) |
08988329 | 1206 | @var{image} (@var{dx} . @var{dy}) (@var{width} . @var{height})) |
c5cb5297 KS |
1207 | @end example |
1208 | ||
1209 | @table @asis | |
f142f62a | 1210 | @item @var{window} |
8db970a4 RS |
1211 | This is the window in which the click occurred. |
1212 | ||
c5cb5297 KS |
1213 | @item @var{pos-or-area} |
1214 | This is the buffer position of the character clicked on in the text | |
1215 | area, or if clicked outside the text area, it is the window area in | |
1216 | which the click occurred. It is one of the symbols @code{mode-line}, | |
1217 | @code{header-line}, @code{vertical-line}, @code{left-margin}, | |
1218 | @code{right-margin}, @code{left-fringe}, or @code{right-fringe}. | |
1219 | ||
f142f62a | 1220 | @item @var{x}, @var{y} |
b22f3a19 | 1221 | These are the pixel-denominated coordinates of the click, relative to |
07734718 | 1222 | the top left corner of @var{window}, which is @code{(0 . 0)}. |
c5cb5297 KS |
1223 | For the mode or header line, @var{y} does not have meaningful data. |
1224 | For the vertical line, @var{x} does not have meaningful data. | |
8db970a4 | 1225 | |
f142f62a | 1226 | @item @var{timestamp} |
c5cb5297 KS |
1227 | This is the time at which the event occurred, in milliseconds. |
1228 | ||
1229 | @item @var{object} | |
f51f93f6 | 1230 | This is the object on which the click occurred. It is either |
08988329 KS |
1231 | @code{nil} if there is no string property, or it has the form |
1232 | (@var{string} . @var{string-pos}) when there is a string-type text | |
1233 | property at the click position. | |
b19f34c7 GM |
1234 | |
1235 | @item @var{string} | |
1236 | This is the string on which the click occurred, including any | |
07734718 | 1237 | properties. |
b19f34c7 GM |
1238 | |
1239 | @item @var{string-pos} | |
1240 | This is the position in the string on which the click occurred, | |
1241 | relevant if properties at the click need to be looked up. | |
8db970a4 | 1242 | |
c5cb5297 KS |
1243 | @item @var{text-pos} |
1244 | For clicks on a marginal area or on a fringe, this is the buffer | |
1245 | position of the first visible character in the corresponding line in | |
1246 | the window. For other events, it is the current buffer position in | |
1247 | the window. | |
1248 | ||
1249 | @item @var{col}, @var{row} | |
1250 | These are the actual coordinates of the glyph under the @var{x}, | |
1251 | @var{y} position, possibly padded with default character width | |
1252 | glyphs if @var{x} is beyond the last glyph on the line. | |
f51f93f6 | 1253 | |
08988329 KS |
1254 | @item @var{image} |
1255 | This is the image object on which the click occurred. It is either | |
1256 | @code{nil} if there is no image at the position clicked on, or it is | |
1257 | an image object as returned by @code{find-image} if click was in an image. | |
1258 | ||
f51f93f6 KS |
1259 | @item @var{dx}, @var{dy} |
1260 | These are the pixel-denominated coordinates of the click, relative to | |
1261 | the top left corner of @var{object}, which is @code{(0 . 0)}. If | |
1262 | @var{object} is @code{nil}, the coordinates are relative to the top | |
1263 | left corner of the character glyph clicked on. | |
8db970a4 RS |
1264 | @end table |
1265 | ||
c5cb5297 KS |
1266 | For mouse clicks on a scroll-bar, @var{position} has this form: |
1267 | ||
1268 | @example | |
1269 | (@var{window} @var{area} (@var{portion} . @var{whole}) @var{timestamp} @var{part}) | |
1270 | @end example | |
1271 | ||
1272 | @table @asis | |
1273 | @item @var{window} | |
1274 | This is the window whose scroll-bar was clicked on. | |
1275 | ||
1276 | @item @var{area} | |
1277 | This is the scroll bar where the click occurred. It is one of the | |
1278 | symbols @code{vertical-scroll-bar} or @code{horizontal-scroll-bar}. | |
1279 | ||
1280 | @item @var{portion} | |
1281 | This is the distance of the click from the top or left end of | |
1282 | the scroll bar. | |
1283 | ||
1284 | @item @var{whole} | |
1285 | This is the length of the entire scroll bar. | |
1286 | ||
1287 | @item @var{timestamp} | |
1288 | This is the time at which the event occurred, in milliseconds. | |
1289 | ||
1290 | @item @var{part} | |
1291 | This is the part of the scroll-bar which was clicked on. It is one | |
1292 | of the symbols @code{above-handle}, @code{handle}, @code{below-handle}, | |
1293 | @code{up}, @code{down}, @code{top}, @code{bottom}, and @code{end-scroll}. | |
1294 | @end table | |
8db970a4 | 1295 | |
b22f3a19 RS |
1296 | In one special case, @var{buffer-pos} is a list containing a symbol (one |
1297 | of the symbols listed above) instead of just the symbol. This happens | |
1298 | after the imaginary prefix keys for the event are inserted into the | |
1299 | input stream. @xref{Key Sequence Input}. | |
8db970a4 RS |
1300 | |
1301 | @node Drag Events | |
1302 | @subsection Drag Events | |
1303 | @cindex drag event | |
1304 | @cindex mouse drag event | |
1305 | ||
1306 | With Emacs, you can have a drag event without even changing your | |
1307 | clothes. A @dfn{drag event} happens every time the user presses a mouse | |
1308 | button and then moves the mouse to a different character position before | |
1309 | releasing the button. Like all mouse events, drag events are | |
1310 | represented in Lisp as lists. The lists record both the starting mouse | |
1311 | position and the final position, like this: | |
1312 | ||
1313 | @example | |
1314 | (@var{event-type} | |
f142f62a RS |
1315 | (@var{window1} @var{buffer-pos1} (@var{x1} . @var{y1}) @var{timestamp1}) |
1316 | (@var{window2} @var{buffer-pos2} (@var{x2} . @var{y2}) @var{timestamp2}) | |
8db970a4 RS |
1317 | @var{click-count}) |
1318 | @end example | |
1319 | ||
1320 | For a drag event, the name of the symbol @var{event-type} contains the | |
f9f59935 RS |
1321 | prefix @samp{drag-}. For example, dragging the mouse with button 2 held |
1322 | down generates a @code{drag-mouse-2} event. The second and third | |
1323 | elements of the event give the starting and ending position of the drag. | |
1324 | Aside from that, the data have the same meanings as in a click event | |
1325 | (@pxref{Click Events}). You can access the second element of any mouse | |
1326 | event in the same way, with no need to distinguish drag events from | |
1327 | others. | |
8db970a4 RS |
1328 | |
1329 | The @samp{drag-} prefix follows the modifier key prefixes such as | |
1330 | @samp{C-} and @samp{M-}. | |
1331 | ||
b22f3a19 | 1332 | If @code{read-key-sequence} receives a drag event that has no key |
8db970a4 RS |
1333 | binding, and the corresponding click event does have a binding, it |
1334 | changes the drag event into a click event at the drag's starting | |
1335 | position. This means that you don't have to distinguish between click | |
1336 | and drag events unless you want to. | |
1337 | ||
1338 | @node Button-Down Events | |
1339 | @subsection Button-Down Events | |
1340 | @cindex button-down event | |
1341 | ||
1342 | Click and drag events happen when the user releases a mouse button. | |
1343 | They cannot happen earlier, because there is no way to distinguish a | |
1344 | click from a drag until the button is released. | |
1345 | ||
1346 | If you want to take action as soon as a button is pressed, you need to | |
1347 | handle @dfn{button-down} events.@footnote{Button-down is the | |
f142f62a | 1348 | conservative antithesis of drag.} These occur as soon as a button is |
b22f3a19 | 1349 | pressed. They are represented by lists that look exactly like click |
f142f62a RS |
1350 | events (@pxref{Click Events}), except that the @var{event-type} symbol |
1351 | name contains the prefix @samp{down-}. The @samp{down-} prefix follows | |
8db970a4 RS |
1352 | modifier key prefixes such as @samp{C-} and @samp{M-}. |
1353 | ||
969fe9b5 RS |
1354 | The function @code{read-key-sequence} ignores any button-down events |
1355 | that don't have command bindings; therefore, the Emacs command loop | |
1356 | ignores them too. This means that you need not worry about defining | |
1357 | button-down events unless you want them to do something. The usual | |
1358 | reason to define a button-down event is so that you can track mouse | |
1359 | motion (by reading motion events) until the button is released. | |
1360 | @xref{Motion Events}. | |
8db970a4 RS |
1361 | |
1362 | @node Repeat Events | |
1363 | @subsection Repeat Events | |
1364 | @cindex repeat events | |
1365 | @cindex double-click events | |
1366 | @cindex triple-click events | |
2468d0c0 | 1367 | @cindex mouse events, repeated |
8db970a4 RS |
1368 | |
1369 | If you press the same mouse button more than once in quick succession | |
f142f62a RS |
1370 | without moving the mouse, Emacs generates special @dfn{repeat} mouse |
1371 | events for the second and subsequent presses. | |
8db970a4 RS |
1372 | |
1373 | The most common repeat events are @dfn{double-click} events. Emacs | |
1374 | generates a double-click event when you click a button twice; the event | |
1375 | happens when you release the button (as is normal for all click | |
1376 | events). | |
1377 | ||
1378 | The event type of a double-click event contains the prefix | |
f142f62a | 1379 | @samp{double-}. Thus, a double click on the second mouse button with |
8db970a4 RS |
1380 | @key{meta} held down comes to the Lisp program as |
1381 | @code{M-double-mouse-2}. If a double-click event has no binding, the | |
1382 | binding of the corresponding ordinary click event is used to execute | |
177c0ea7 | 1383 | it. Thus, you need not pay attention to the double click feature |
8db970a4 RS |
1384 | unless you really want to. |
1385 | ||
1386 | When the user performs a double click, Emacs generates first an ordinary | |
f142f62a RS |
1387 | click event, and then a double-click event. Therefore, you must design |
1388 | the command binding of the double click event to assume that the | |
8db970a4 RS |
1389 | single-click command has already run. It must produce the desired |
1390 | results of a double click, starting from the results of a single click. | |
1391 | ||
f142f62a RS |
1392 | This is convenient, if the meaning of a double click somehow ``builds |
1393 | on'' the meaning of a single click---which is recommended user interface | |
1394 | design practice for double clicks. | |
8db970a4 RS |
1395 | |
1396 | If you click a button, then press it down again and start moving the | |
1397 | mouse with the button held down, then you get a @dfn{double-drag} event | |
1398 | when you ultimately release the button. Its event type contains | |
1399 | @samp{double-drag} instead of just @samp{drag}. If a double-drag event | |
1400 | has no binding, Emacs looks for an alternate binding as if the event | |
b22f3a19 | 1401 | were an ordinary drag. |
8db970a4 RS |
1402 | |
1403 | Before the double-click or double-drag event, Emacs generates a | |
f142f62a RS |
1404 | @dfn{double-down} event when the user presses the button down for the |
1405 | second time. Its event type contains @samp{double-down} instead of just | |
8db970a4 RS |
1406 | @samp{down}. If a double-down event has no binding, Emacs looks for an |
1407 | alternate binding as if the event were an ordinary button-down event. | |
f142f62a RS |
1408 | If it finds no binding that way either, the double-down event is |
1409 | ignored. | |
8db970a4 RS |
1410 | |
1411 | To summarize, when you click a button and then press it again right | |
b22f3a19 RS |
1412 | away, Emacs generates a down event and a click event for the first |
1413 | click, a double-down event when you press the button again, and finally | |
1414 | either a double-click or a double-drag event. | |
8db970a4 RS |
1415 | |
1416 | If you click a button twice and then press it again, all in quick | |
1417 | succession, Emacs generates a @dfn{triple-down} event, followed by | |
1418 | either a @dfn{triple-click} or a @dfn{triple-drag}. The event types of | |
1419 | these events contain @samp{triple} instead of @samp{double}. If any | |
1420 | triple event has no binding, Emacs uses the binding that it would use | |
1421 | for the corresponding double event. | |
1422 | ||
f142f62a RS |
1423 | If you click a button three or more times and then press it again, the |
1424 | events for the presses beyond the third are all triple events. Emacs | |
1425 | does not have separate event types for quadruple, quintuple, etc.@: | |
1426 | events. However, you can look at the event list to find out precisely | |
1427 | how many times the button was pressed. | |
8db970a4 RS |
1428 | |
1429 | @defun event-click-count event | |
1430 | This function returns the number of consecutive button presses that led | |
1431 | up to @var{event}. If @var{event} is a double-down, double-click or | |
1432 | double-drag event, the value is 2. If @var{event} is a triple event, | |
1433 | the value is 3 or greater. If @var{event} is an ordinary mouse event | |
1434 | (not a repeat event), the value is 1. | |
1435 | @end defun | |
1436 | ||
5504e99c | 1437 | @defopt double-click-fuzz |
f142f62a | 1438 | To generate repeat events, successive mouse button presses must be at |
99af9d83 GM |
1439 | approximately the same screen position. The value of |
1440 | @code{double-click-fuzz} specifies the maximum number of pixels the | |
5504e99c LT |
1441 | mouse may be moved (horizontally or vertically) between two successive |
1442 | clicks to make a double-click. | |
99af9d83 | 1443 | |
5504e99c LT |
1444 | This variable is also the threshold for motion of the mouse to count |
1445 | as a drag. | |
1446 | @end defopt | |
1447 | ||
1448 | @defopt double-click-time | |
99af9d83 | 1449 | To generate repeat events, the number of milliseconds between |
f142f62a | 1450 | successive button presses must be less than the value of |
8db970a4 RS |
1451 | @code{double-click-time}. Setting @code{double-click-time} to |
1452 | @code{nil} disables multi-click detection entirely. Setting it to | |
1453 | @code{t} removes the time limit; Emacs then detects multi-clicks by | |
1454 | position only. | |
5504e99c | 1455 | @end defopt |
8db970a4 RS |
1456 | |
1457 | @node Motion Events | |
1458 | @subsection Motion Events | |
1459 | @cindex motion event | |
1460 | @cindex mouse motion events | |
1461 | ||
1462 | Emacs sometimes generates @dfn{mouse motion} events to describe motion | |
1463 | of the mouse without any button activity. Mouse motion events are | |
1464 | represented by lists that look like this: | |
1465 | ||
1466 | @example | |
969fe9b5 | 1467 | (mouse-movement (@var{window} @var{buffer-pos} (@var{x} . @var{y}) @var{timestamp})) |
8db970a4 RS |
1468 | @end example |
1469 | ||
1470 | The second element of the list describes the current position of the | |
1471 | mouse, just as in a click event (@pxref{Click Events}). | |
1472 | ||
1473 | The special form @code{track-mouse} enables generation of motion events | |
1474 | within its body. Outside of @code{track-mouse} forms, Emacs does not | |
1475 | generate events for mere motion of the mouse, and these events do not | |
969fe9b5 | 1476 | appear. @xref{Mouse Tracking}. |
8db970a4 RS |
1477 | |
1478 | @node Focus Events | |
1479 | @subsection Focus Events | |
1480 | @cindex focus event | |
1481 | ||
1482 | Window systems provide general ways for the user to control which window | |
1483 | gets keyboard input. This choice of window is called the @dfn{focus}. | |
1484 | When the user does something to switch between Emacs frames, that | |
1485 | generates a @dfn{focus event}. The normal definition of a focus event, | |
1486 | in the global keymap, is to select a new frame within Emacs, as the user | |
1487 | would expect. @xref{Input Focus}. | |
1488 | ||
1489 | Focus events are represented in Lisp as lists that look like this: | |
1490 | ||
1491 | @example | |
1492 | (switch-frame @var{new-frame}) | |
1493 | @end example | |
1494 | ||
1495 | @noindent | |
1496 | where @var{new-frame} is the frame switched to. | |
1497 | ||
b22f3a19 RS |
1498 | Most X window managers are set up so that just moving the mouse into a |
1499 | window is enough to set the focus there. Emacs appears to do this, | |
1500 | because it changes the cursor to solid in the new frame. However, there | |
1501 | is no need for the Lisp program to know about the focus change until | |
1502 | some other kind of input arrives. So Emacs generates a focus event only | |
1503 | when the user actually types a keyboard key or presses a mouse button in | |
1504 | the new frame; just moving the mouse between frames does not generate a | |
1505 | focus event. | |
8db970a4 RS |
1506 | |
1507 | A focus event in the middle of a key sequence would garble the | |
1508 | sequence. So Emacs never generates a focus event in the middle of a key | |
1509 | sequence. If the user changes focus in the middle of a key | |
1510 | sequence---that is, after a prefix key---then Emacs reorders the events | |
1511 | so that the focus event comes either before or after the multi-event key | |
1512 | sequence, and not within it. | |
1513 | ||
22697dac | 1514 | @node Misc Events |
7790d5cd | 1515 | @subsection Miscellaneous System Events |
22697dac | 1516 | |
7790d5cd | 1517 | A few other event types represent occurrences within the system. |
22697dac KH |
1518 | |
1519 | @table @code | |
1520 | @cindex @code{delete-frame} event | |
1521 | @item (delete-frame (@var{frame})) | |
1522 | This kind of event indicates that the user gave the window manager | |
1523 | a command to delete a particular window, which happens to be an Emacs frame. | |
1524 | ||
1525 | The standard definition of the @code{delete-frame} event is to delete @var{frame}. | |
1526 | ||
1527 | @cindex @code{iconify-frame} event | |
1528 | @item (iconify-frame (@var{frame})) | |
1529 | This kind of event indicates that the user iconified @var{frame} using | |
d473987a RS |
1530 | the window manager. Its standard definition is @code{ignore}; since the |
1531 | frame has already been iconified, Emacs has no work to do. The purpose | |
1532 | of this event type is so that you can keep track of such events if you | |
1533 | want to. | |
22697dac | 1534 | |
1774d17e RS |
1535 | @cindex @code{make-frame-visible} event |
1536 | @item (make-frame-visible (@var{frame})) | |
22697dac KH |
1537 | This kind of event indicates that the user deiconified @var{frame} using |
1538 | the window manager. Its standard definition is @code{ignore}; since the | |
d473987a | 1539 | frame has already been made visible, Emacs has no work to do. |
a9f0a989 | 1540 | |
d2fab890 JR |
1541 | @cindex @code{wheel-up} event |
1542 | @cindex @code{wheel-down} event | |
1543 | @item (wheel-up @var{position}) | |
1544 | @item (wheel-down @var{position}) | |
dff3f9e1 RS |
1545 | These kinds of event are generated by moving a mouse wheel. Their |
1546 | usual meaning is a kind of scroll or zoom. | |
a9f0a989 RS |
1547 | |
1548 | The element @var{position} is a list describing the position of the | |
1549 | event, in the same format as used in a mouse-click event. | |
1550 | ||
dff3f9e1 RS |
1551 | This kind of event is generated only on some kinds of systems. On some |
1552 | systems, @code{mouse-4} and @code{mouse-5} are used instead. For | |
1553 | portable code, use the variables @code{mouse-wheel-up-event} and | |
1554 | @code{mouse-wheel-down-event} defined in @file{mwheel.el} to determine | |
1555 | what event types to expect for the mouse wheel. | |
a9f0a989 RS |
1556 | |
1557 | @cindex @code{drag-n-drop} event | |
1558 | @item (drag-n-drop @var{position} @var{files}) | |
1559 | This kind of event is generated when a group of files is | |
1560 | selected in an application outside of Emacs, and then dragged and | |
1561 | dropped onto an Emacs frame. | |
1562 | ||
1563 | The element @var{position} is a list describing the position of the | |
1564 | event, in the same format as used in a mouse-click event, and | |
1565 | @var{files} is the list of file names that were dragged and dropped. | |
1566 | The usual way to handle this event is by visiting these files. | |
1567 | ||
1568 | This kind of event is generated, at present, only on some kinds of | |
1569 | systems. | |
7790d5cd | 1570 | |
16bbbfd8 EZ |
1571 | @cindex @code{help-echo} event |
1572 | @item help-echo | |
1573 | This kind of event is generated when a mouse pointer moves onto a | |
1574 | portion of buffer text which has a @code{help-echo} text property. | |
1575 | The generated event has this form: | |
1576 | ||
1577 | @example | |
f75fbf43 | 1578 | (help-echo @var{frame} @var{help} @var{window} @var{object} @var{pos}) |
16bbbfd8 EZ |
1579 | @end example |
1580 | ||
1581 | @noindent | |
1582 | The precise meaning of the event parameters and the way these | |
1583 | parameters are used to display the help-echo text are described in | |
1584 | @ref{Text help-echo}. | |
1585 | ||
7790d5cd RS |
1586 | @cindex @code{usr1-signal} event |
1587 | @cindex @code{usr2-signal} event | |
1588 | @item usr1-signal | |
1589 | @itemx usr2-signal | |
1590 | These events are generated when the Emacs process receives the signals | |
1591 | @code{SIGUSR1} and @code{SIGUSR2}. They contain no additional data | |
1592 | because signals do not carry additional information. | |
22697dac KH |
1593 | @end table |
1594 | ||
bfe721d1 KH |
1595 | If one of these events arrives in the middle of a key sequence---that |
1596 | is, after a prefix key---then Emacs reorders the events so that this | |
1597 | event comes either before or after the multi-event key sequence, not | |
1598 | within it. | |
1599 | ||
8db970a4 RS |
1600 | @node Event Examples |
1601 | @subsection Event Examples | |
1602 | ||
1603 | If the user presses and releases the left mouse button over the same | |
1604 | location, that generates a sequence of events like this: | |
1605 | ||
1606 | @smallexample | |
1607 | (down-mouse-1 (#<window 18 on NEWS> 2613 (0 . 38) -864320)) | |
1608 | (mouse-1 (#<window 18 on NEWS> 2613 (0 . 38) -864180)) | |
1609 | @end smallexample | |
1610 | ||
f142f62a | 1611 | While holding the control key down, the user might hold down the |
8db970a4 RS |
1612 | second mouse button, and drag the mouse from one line to the next. |
1613 | That produces two events, as shown here: | |
1614 | ||
1615 | @smallexample | |
1616 | (C-down-mouse-2 (#<window 18 on NEWS> 3440 (0 . 27) -731219)) | |
1617 | (C-drag-mouse-2 (#<window 18 on NEWS> 3440 (0 . 27) -731219) | |
1618 | (#<window 18 on NEWS> 3510 (0 . 28) -729648)) | |
1619 | @end smallexample | |
1620 | ||
f142f62a | 1621 | While holding down the meta and shift keys, the user might press the |
8db970a4 | 1622 | second mouse button on the window's mode line, and then drag the mouse |
f142f62a | 1623 | into another window. That produces a pair of events like these: |
8db970a4 RS |
1624 | |
1625 | @smallexample | |
1626 | (M-S-down-mouse-2 (#<window 18 on NEWS> mode-line (33 . 31) -457844)) | |
1627 | (M-S-drag-mouse-2 (#<window 18 on NEWS> mode-line (33 . 31) -457844) | |
1628 | (#<window 20 on carlton-sanskrit.tex> 161 (33 . 3) | |
1629 | -453816)) | |
1630 | @end smallexample | |
1631 | ||
1632 | @node Classifying Events | |
1633 | @subsection Classifying Events | |
1634 | @cindex event type | |
1635 | ||
b22f3a19 RS |
1636 | Every event has an @dfn{event type}, which classifies the event for |
1637 | key binding purposes. For a keyboard event, the event type equals the | |
1638 | event value; thus, the event type for a character is the character, and | |
1639 | the event type for a function key symbol is the symbol itself. For | |
4bdcd3ef | 1640 | events that are lists, the event type is the symbol in the @sc{car} of |
b22f3a19 | 1641 | the list. Thus, the event type is always a symbol or a character. |
8db970a4 RS |
1642 | |
1643 | Two events of the same type are equivalent where key bindings are | |
1644 | concerned; thus, they always run the same command. That does not | |
1645 | necessarily mean they do the same things, however, as some commands look | |
1646 | at the whole event to decide what to do. For example, some commands use | |
f142f62a | 1647 | the location of a mouse event to decide where in the buffer to act. |
8db970a4 RS |
1648 | |
1649 | Sometimes broader classifications of events are useful. For example, | |
1650 | you might want to ask whether an event involved the @key{META} key, | |
1651 | regardless of which other key or mouse button was used. | |
1652 | ||
1653 | The functions @code{event-modifiers} and @code{event-basic-type} are | |
1654 | provided to get such information conveniently. | |
1655 | ||
1656 | @defun event-modifiers event | |
f142f62a RS |
1657 | This function returns a list of the modifiers that @var{event} has. The |
1658 | modifiers are symbols; they include @code{shift}, @code{control}, | |
8db970a4 | 1659 | @code{meta}, @code{alt}, @code{hyper} and @code{super}. In addition, |
f142f62a | 1660 | the modifiers list of a mouse event symbol always contains one of |
5504e99c LT |
1661 | @code{click}, @code{drag}, and @code{down}. For double or triple |
1662 | events, it also contains @code{double} or @code{triple}. | |
f142f62a | 1663 | |
5504e99c LT |
1664 | The argument @var{event} may be an entire event object, or just an |
1665 | event type. If @var{event} is a symbol that has never been used in an | |
1666 | event that has been read as input in the current Emacs session, then | |
1667 | @code{event-modifiers} can return @code{nil}, even when @var{event} | |
1668 | actually has modifiers. | |
f142f62a RS |
1669 | |
1670 | Here are some examples: | |
8db970a4 RS |
1671 | |
1672 | @example | |
1673 | (event-modifiers ?a) | |
1674 | @result{} nil | |
5504e99c LT |
1675 | (event-modifiers ?A) |
1676 | @result{} (shift) | |
8db970a4 RS |
1677 | (event-modifiers ?\C-a) |
1678 | @result{} (control) | |
1679 | (event-modifiers ?\C-%) | |
1680 | @result{} (control) | |
1681 | (event-modifiers ?\C-\S-a) | |
1682 | @result{} (control shift) | |
1683 | (event-modifiers 'f5) | |
1684 | @result{} nil | |
1685 | (event-modifiers 's-f5) | |
1686 | @result{} (super) | |
1687 | (event-modifiers 'M-S-f5) | |
1688 | @result{} (meta shift) | |
1689 | (event-modifiers 'mouse-1) | |
1690 | @result{} (click) | |
1691 | (event-modifiers 'down-mouse-1) | |
1692 | @result{} (down) | |
1693 | @end example | |
1694 | ||
1695 | The modifiers list for a click event explicitly contains @code{click}, | |
1696 | but the event symbol name itself does not contain @samp{click}. | |
1697 | @end defun | |
1698 | ||
1699 | @defun event-basic-type event | |
1700 | This function returns the key or mouse button that @var{event} | |
5504e99c LT |
1701 | describes, with all modifiers removed. The @var{event} argument is as |
1702 | in @code{event-modifiers}. For example: | |
8db970a4 RS |
1703 | |
1704 | @example | |
1705 | (event-basic-type ?a) | |
1706 | @result{} 97 | |
1707 | (event-basic-type ?A) | |
1708 | @result{} 97 | |
1709 | (event-basic-type ?\C-a) | |
1710 | @result{} 97 | |
1711 | (event-basic-type ?\C-\S-a) | |
1712 | @result{} 97 | |
1713 | (event-basic-type 'f5) | |
1714 | @result{} f5 | |
1715 | (event-basic-type 's-f5) | |
1716 | @result{} f5 | |
1717 | (event-basic-type 'M-S-f5) | |
1718 | @result{} f5 | |
1719 | (event-basic-type 'down-mouse-1) | |
1720 | @result{} mouse-1 | |
1721 | @end example | |
1722 | @end defun | |
1723 | ||
1724 | @defun mouse-movement-p object | |
1725 | This function returns non-@code{nil} if @var{object} is a mouse movement | |
1726 | event. | |
1727 | @end defun | |
1728 | ||
bfe721d1 KH |
1729 | @defun event-convert-list list |
1730 | This function converts a list of modifier names and a basic event type | |
5504e99c LT |
1731 | to an event type which specifies all of them. The basic event type |
1732 | must be the last element of the list. For example, | |
bfe721d1 KH |
1733 | |
1734 | @example | |
1735 | (event-convert-list '(control ?a)) | |
1736 | @result{} 1 | |
1737 | (event-convert-list '(control meta ?a)) | |
1738 | @result{} -134217727 | |
1739 | (event-convert-list '(control super f1)) | |
1740 | @result{} C-s-f1 | |
1741 | @end example | |
1742 | @end defun | |
1743 | ||
8db970a4 RS |
1744 | @node Accessing Events |
1745 | @subsection Accessing Events | |
2468d0c0 DL |
1746 | @cindex mouse events, accessing the data |
1747 | @cindex accessing data of mouse events | |
8db970a4 RS |
1748 | |
1749 | This section describes convenient functions for accessing the data in | |
f142f62a | 1750 | a mouse button or motion event. |
8db970a4 | 1751 | |
f142f62a | 1752 | These two functions return the starting or ending position of a |
969fe9b5 | 1753 | mouse-button event, as a list of this form: |
8db970a4 | 1754 | |
f142f62a | 1755 | @example |
f51f93f6 | 1756 | (@var{window} @var{pos-or-area} (@var{x} . @var{y}) @var{timestamp} |
08988329 KS |
1757 | @var{object} @var{text-pos} (@var{col} . @var{row}) |
1758 | @var{image} (@var{dx} . @var{dy}) (@var{width} . @var{height})) | |
f142f62a | 1759 | @end example |
8db970a4 RS |
1760 | |
1761 | @defun event-start event | |
1762 | This returns the starting position of @var{event}. | |
1763 | ||
1764 | If @var{event} is a click or button-down event, this returns the | |
1765 | location of the event. If @var{event} is a drag event, this returns the | |
1766 | drag's starting position. | |
1767 | @end defun | |
1768 | ||
1769 | @defun event-end event | |
1770 | This returns the ending position of @var{event}. | |
1771 | ||
1772 | If @var{event} is a drag event, this returns the position where the user | |
1773 | released the mouse button. If @var{event} is a click or button-down | |
1774 | event, the value is actually the starting position, which is the only | |
1775 | position such events have. | |
1776 | @end defun | |
1777 | ||
2468d0c0 | 1778 | @cindex mouse position list, accessing |
6e41ce9c | 1779 | These functions take a position list as described above, and |
969fe9b5 | 1780 | return various parts of it. |
8db970a4 RS |
1781 | |
1782 | @defun posn-window position | |
1783 | Return the window that @var{position} is in. | |
1784 | @end defun | |
1785 | ||
c5cb5297 | 1786 | @defun posn-area position |
f51f93f6 | 1787 | Return the window area recorded in @var{position}. It returns @code{nil} |
c5cb5297 | 1788 | when the event occurred in the text area of the window; otherwise, it |
4a182c75 | 1789 | is a symbol identifying the area in which the event occurred. |
c5cb5297 KS |
1790 | @end defun |
1791 | ||
8db970a4 | 1792 | @defun posn-point position |
c5cb5297 KS |
1793 | Return the buffer position in @var{position}. When the event occurred |
1794 | in the text area of the window, in a marginal area, or on a fringe, | |
1795 | this is an integer specifying a buffer position. Otherwise, the value | |
1796 | is undefined. | |
1797 | @end defun | |
1798 | ||
8db970a4 | 1799 | @defun posn-x-y position |
6e41ce9c RS |
1800 | Return the pixel-based x and y coordinates in @var{position}, as a |
1801 | cons cell @code{(@var{x} . @var{y})}. These coordinates are relative | |
1802 | to the window given by @code{posn-window}. | |
1803 | ||
1804 | This example shows how to convert these window-relative coordinates | |
1805 | into frame-relative coordinates: | |
1806 | ||
1807 | @example | |
1808 | (defun frame-relative-coordinates (position) | |
1809 | "Return frame-relative coordinates from POSITION." | |
1810 | (let* ((x-y (posn-x-y position)) | |
1811 | (window (posn-window position)) | |
1812 | (edges (window-inside-pixel-edges window))) | |
1813 | (cons (+ (car x-y) (car edges)) | |
1814 | (+ (cdr x-y) (cadr edges))))) | |
1815 | @end example | |
8db970a4 RS |
1816 | @end defun |
1817 | ||
1818 | @defun posn-col-row position | |
6e41ce9c RS |
1819 | Return the row and column (in units of the frame's default character |
1820 | height and width) of @var{position}, as a cons cell @code{(@var{col} . | |
1821 | @var{row})}. These are computed from the @var{x} and @var{y} values | |
1822 | actually found in @var{position}. | |
c5cb5297 KS |
1823 | @end defun |
1824 | ||
1825 | @defun posn-actual-col-row position | |
1826 | Return the actual row and column in @var{position}, as a cons cell | |
1827 | @code{(@var{col} . @var{row})}. The values are the actual row number | |
6e41ce9c RS |
1828 | in the window, and the actual character number in that row. It returns |
1829 | @code{nil} if @var{position} does not include actual positions values. | |
1830 | You can use @code{posn-col-row} to get approximate values. | |
8db970a4 RS |
1831 | @end defun |
1832 | ||
08988329 KS |
1833 | @defun posn-string position |
1834 | Return the string object in @var{position}, either @code{nil}, or a | |
1835 | cons cell @code{(@var{string} . @var{string-pos})}. | |
1836 | @end defun | |
1837 | ||
1838 | @defun posn-image position | |
1839 | Return the image object in @var{position}, either @code{nil}, or an | |
1840 | image @code{(image ...)}. | |
1841 | @end defun | |
1842 | ||
f51f93f6 | 1843 | @defun posn-object position |
08988329 KS |
1844 | Return the image or string object in @var{position}, either |
1845 | @code{nil}, an image @code{(image ...)}, or a cons cell | |
1846 | @code{(@var{string} . @var{string-pos})}. | |
f51f93f6 KS |
1847 | @end defun |
1848 | ||
1849 | @defun posn-object-x-y position | |
1850 | Return the pixel-based x and y coordinates relative to the upper left | |
08988329 KS |
1851 | corner of the object in @var{position} as a cons cell @code{(@var{dx} |
1852 | . @var{dy})}. If the @var{position} is a buffer position, return the | |
1853 | relative position in the character at that position. | |
1854 | @end defun | |
1855 | ||
1856 | @defun posn-object-width-height position | |
1857 | Return the pixel width and height of the object in @var{position} as a | |
1858 | cons cell @code{(@var{width} . @var{height})}. If the @var{position} | |
1859 | is a buffer position, return the size of the character at that position. | |
f51f93f6 KS |
1860 | @end defun |
1861 | ||
2468d0c0 DL |
1862 | @cindex mouse event, timestamp |
1863 | @cindex timestamp of a mouse event | |
5504e99c | 1864 | @defun posn-timestamp position |
f51f93f6 KS |
1865 | Return the timestamp in @var{position}. This is the time at which the |
1866 | event occurred, in milliseconds. | |
6e41ce9c RS |
1867 | @end defun |
1868 | ||
1869 | These functions compute a position list given particular buffer | |
1870 | position or screen position. You can access the data in this position | |
1871 | list with the functions described above. | |
1872 | ||
1873 | @defun posn-at-point &optional pos window | |
1874 | This function returns a position list for position @var{pos} in | |
1875 | @var{window}. @var{pos} defaults to point in @var{window}; | |
1876 | @var{window} defaults to the selected window. | |
1877 | ||
1878 | @code{posn-at-point} returns @code{nil} if @var{pos} is not visible in | |
1879 | @var{window}. | |
1880 | @end defun | |
1881 | ||
cfa284c4 | 1882 | @defun posn-at-x-y x y &optional frame-or-window whole |
6e41ce9c RS |
1883 | This function returns position information corresponding to pixel |
1884 | coordinates @var{x} and @var{y} in a specified frame or window, | |
1885 | @var{frame-or-window}, which defaults to the selected window. | |
1886 | The coordinates @var{x} and @var{y} are relative to the | |
1887 | frame or window used. | |
cfa284c4 KS |
1888 | If @var{whole} is @code{nil}, the coordinates are relative |
1889 | to the window text area, otherwise they are relative to | |
1890 | the entire window area including scroll bars, margins and fringes. | |
8db970a4 RS |
1891 | @end defun |
1892 | ||
969fe9b5 RS |
1893 | These functions are useful for decoding scroll bar events. |
1894 | ||
b22f3a19 RS |
1895 | @defun scroll-bar-event-ratio event |
1896 | This function returns the fractional vertical position of a scroll bar | |
1897 | event within the scroll bar. The value is a cons cell | |
1898 | @code{(@var{portion} . @var{whole})} containing two integers whose ratio | |
1899 | is the fractional position. | |
1900 | @end defun | |
1901 | ||
8db970a4 | 1902 | @defun scroll-bar-scale ratio total |
b22f3a19 RS |
1903 | This function multiplies (in effect) @var{ratio} by @var{total}, |
1904 | rounding the result to an integer. The argument @var{ratio} is not a | |
1905 | number, but rather a pair @code{(@var{num} . @var{denom})}---typically a | |
1906 | value returned by @code{scroll-bar-event-ratio}. | |
8db970a4 | 1907 | |
f142f62a RS |
1908 | This function is handy for scaling a position on a scroll bar into a |
1909 | buffer position. Here's how to do that: | |
8db970a4 RS |
1910 | |
1911 | @example | |
1912 | (+ (point-min) | |
1913 | (scroll-bar-scale | |
b22f3a19 | 1914 | (posn-x-y (event-start event)) |
8db970a4 RS |
1915 | (- (point-max) (point-min)))) |
1916 | @end example | |
b22f3a19 | 1917 | |
1911e6e5 | 1918 | Recall that scroll bar events have two integers forming a ratio, in place |
b22f3a19 | 1919 | of a pair of x and y coordinates. |
8db970a4 RS |
1920 | @end defun |
1921 | ||
1922 | @node Strings of Events | |
1923 | @subsection Putting Keyboard Events in Strings | |
2468d0c0 DL |
1924 | @cindex keyboard events in strings |
1925 | @cindex strings with keyboard events | |
8db970a4 RS |
1926 | |
1927 | In most of the places where strings are used, we conceptualize the | |
1928 | string as containing text characters---the same kind of characters found | |
b22f3a19 | 1929 | in buffers or files. Occasionally Lisp programs use strings that |
8db970a4 | 1930 | conceptually contain keyboard characters; for example, they may be key |
969fe9b5 RS |
1931 | sequences or keyboard macro definitions. However, storing keyboard |
1932 | characters in a string is a complex matter, for reasons of historical | |
1933 | compatibility, and it is not always possible. | |
1934 | ||
1935 | We recommend that new programs avoid dealing with these complexities | |
1936 | by not storing keyboard events in strings. Here is how to do that: | |
1937 | ||
1938 | @itemize @bullet | |
1939 | @item | |
1940 | Use vectors instead of strings for key sequences, when you plan to use | |
a9f0a989 | 1941 | them for anything other than as arguments to @code{lookup-key} and |
969fe9b5 RS |
1942 | @code{define-key}. For example, you can use |
1943 | @code{read-key-sequence-vector} instead of @code{read-key-sequence}, and | |
1944 | @code{this-command-keys-vector} instead of @code{this-command-keys}. | |
1945 | ||
1946 | @item | |
1947 | Use vectors to write key sequence constants containing meta characters, | |
1948 | even when passing them directly to @code{define-key}. | |
1949 | ||
1950 | @item | |
1951 | When you have to look at the contents of a key sequence that might be a | |
1952 | string, use @code{listify-key-sequence} (@pxref{Event Input Misc}) | |
1953 | first, to convert it to a list. | |
1954 | @end itemize | |
8db970a4 | 1955 | |
969fe9b5 RS |
1956 | The complexities stem from the modifier bits that keyboard input |
1957 | characters can include. Aside from the Meta modifier, none of these | |
1958 | modifier bits can be included in a string, and the Meta modifier is | |
1959 | allowed only in special cases. | |
1960 | ||
1961 | The earliest GNU Emacs versions represented meta characters as codes | |
1962 | in the range of 128 to 255. At that time, the basic character codes | |
1963 | ranged from 0 to 127, so all keyboard character codes did fit in a | |
1964 | string. Many Lisp programs used @samp{\M-} in string constants to stand | |
1965 | for meta characters, especially in arguments to @code{define-key} and | |
1966 | similar functions, and key sequences and sequences of events were always | |
1967 | represented as strings. | |
1968 | ||
1969 | When we added support for larger basic character codes beyond 127, and | |
1970 | additional modifier bits, we had to change the representation of meta | |
1971 | characters. Now the flag that represents the Meta modifier in a | |
1972 | character is | |
1973 | @tex | |
8241495d | 1974 | @math{2^{27}} |
969fe9b5 | 1975 | @end tex |
37680279 | 1976 | @ifnottex |
bfe721d1 | 1977 | 2**27 |
37680279 | 1978 | @end ifnottex |
969fe9b5 | 1979 | and such numbers cannot be included in a string. |
8db970a4 | 1980 | |
969fe9b5 RS |
1981 | To support programs with @samp{\M-} in string constants, there are |
1982 | special rules for including certain meta characters in a string. | |
1911e6e5 RS |
1983 | Here are the rules for interpreting a string as a sequence of input |
1984 | characters: | |
8db970a4 RS |
1985 | |
1986 | @itemize @bullet | |
1987 | @item | |
f142f62a RS |
1988 | If the keyboard character value is in the range of 0 to 127, it can go |
1989 | in the string unchanged. | |
8db970a4 RS |
1990 | |
1991 | @item | |
bfe721d1 | 1992 | The meta variants of those characters, with codes in the range of |
969fe9b5 | 1993 | @tex |
8241495d | 1994 | @math{2^{27}} |
969fe9b5 | 1995 | @end tex |
37680279 | 1996 | @ifnottex |
bfe721d1 | 1997 | 2**27 |
37680279 | 1998 | @end ifnottex |
bfe721d1 | 1999 | to |
969fe9b5 | 2000 | @tex |
8241495d | 2001 | @math{2^{27} + 127}, |
969fe9b5 | 2002 | @end tex |
37680279 | 2003 | @ifnottex |
bfe721d1 | 2004 | 2**27+127, |
37680279 | 2005 | @end ifnottex |
bfe721d1 KH |
2006 | can also go in the string, but you must change their |
2007 | numeric values. You must set the | |
969fe9b5 | 2008 | @tex |
8241495d | 2009 | @math{2^{7}} |
969fe9b5 | 2010 | @end tex |
37680279 | 2011 | @ifnottex |
bfe721d1 | 2012 | 2**7 |
37680279 | 2013 | @end ifnottex |
bfe721d1 | 2014 | bit instead of the |
969fe9b5 | 2015 | @tex |
8241495d | 2016 | @math{2^{27}} |
969fe9b5 | 2017 | @end tex |
37680279 | 2018 | @ifnottex |
bfe721d1 | 2019 | 2**27 |
37680279 | 2020 | @end ifnottex |
969fe9b5 RS |
2021 | bit, resulting in a value between 128 and 255. Only a unibyte string |
2022 | can include these codes. | |
2023 | ||
2024 | @item | |
ad800164 | 2025 | Non-@acronym{ASCII} characters above 256 can be included in a multibyte string. |
8db970a4 RS |
2026 | |
2027 | @item | |
2028 | Other keyboard character events cannot fit in a string. This includes | |
2029 | keyboard events in the range of 128 to 255. | |
2030 | @end itemize | |
2031 | ||
f9f59935 RS |
2032 | Functions such as @code{read-key-sequence} that construct strings of |
2033 | keyboard input characters follow these rules: they construct vectors | |
f142f62a | 2034 | instead of strings, when the events won't fit in a string. |
8db970a4 RS |
2035 | |
2036 | When you use the read syntax @samp{\M-} in a string, it produces a | |
2037 | code in the range of 128 to 255---the same code that you get if you | |
2038 | modify the corresponding keyboard event to put it in the string. Thus, | |
2039 | meta events in strings work consistently regardless of how they get into | |
2040 | the strings. | |
2041 | ||
969fe9b5 RS |
2042 | However, most programs would do well to avoid these issues by |
2043 | following the recommendations at the beginning of this section. | |
f142f62a | 2044 | |
8db970a4 RS |
2045 | @node Reading Input |
2046 | @section Reading Input | |
2047 | ||
969fe9b5 | 2048 | The editor command loop reads key sequences using the function |
8db970a4 | 2049 | @code{read-key-sequence}, which uses @code{read-event}. These and other |
969fe9b5 RS |
2050 | functions for event input are also available for use in Lisp programs. |
2051 | See also @code{momentary-string-display} in @ref{Temporary Displays}, | |
2052 | and @code{sit-for} in @ref{Waiting}. @xref{Terminal Input}, for | |
2053 | functions and variables for controlling terminal input modes and | |
160ab7f9 | 2054 | debugging terminal input. |
8db970a4 RS |
2055 | |
2056 | For higher-level input facilities, see @ref{Minibuffers}. | |
2057 | ||
2058 | @menu | |
2059 | * Key Sequence Input:: How to read one key sequence. | |
2060 | * Reading One Event:: How to read just one event. | |
160ab7f9 | 2061 | * Event Mod:: How Emacs modifies events as they are read. |
b6954afd | 2062 | * Invoking the Input Method:: How reading an event uses the input method. |
8db970a4 | 2063 | * Quoted Character Input:: Asking the user to specify a character. |
f142f62a | 2064 | * Event Input Misc:: How to reread or throw away input events. |
8db970a4 RS |
2065 | @end menu |
2066 | ||
2067 | @node Key Sequence Input | |
2068 | @subsection Key Sequence Input | |
2069 | @cindex key sequence input | |
2070 | ||
2071 | The command loop reads input a key sequence at a time, by calling | |
2072 | @code{read-key-sequence}. Lisp programs can also call this function; | |
2073 | for example, @code{describe-key} uses it to read the key to describe. | |
2074 | ||
ecbfc7e9 | 2075 | @defun read-key-sequence prompt &optional continue-echo dont-downcase-last switch-frame-ok command-loop |
8db970a4 RS |
2076 | @cindex key sequence |
2077 | This function reads a key sequence and returns it as a string or | |
f9f59935 | 2078 | vector. It keeps reading events until it has accumulated a complete key |
8db970a4 | 2079 | sequence; that is, enough to specify a non-prefix command using the |
5504e99c LT |
2080 | currently active keymaps. (Remember that a key sequence that starts |
2081 | with a mouse event is read using the keymaps of the buffer in the | |
2082 | window that the mouse was in, not the current buffer.) | |
8db970a4 RS |
2083 | |
2084 | If the events are all characters and all can fit in a string, then | |
2085 | @code{read-key-sequence} returns a string (@pxref{Strings of Events}). | |
2086 | Otherwise, it returns a vector, since a vector can hold all kinds of | |
2087 | events---characters, symbols, and lists. The elements of the string or | |
2088 | vector are the events in the key sequence. | |
2089 | ||
2b83bc43 | 2090 | Reading a key sequence includes translating the events in various |
160ab7f9 | 2091 | ways. @xref{Translation Keymaps}. |
2b83bc43 | 2092 | |
ecbfc7e9 RS |
2093 | The argument @var{prompt} is either a string to be displayed in the |
2094 | echo area as a prompt, or @code{nil}, meaning not to display a prompt. | |
2095 | The argument @var{continue-echo}, if non-@code{nil}, means to echo | |
2096 | this key as a continuation of the previous key. | |
2097 | ||
2098 | Normally any upper case event is converted to lower case if the | |
2099 | original event is undefined and the lower case equivalent is defined. | |
2100 | The argument @var{dont-downcase-last}, if non-@code{nil}, means do not | |
2101 | convert the last event to lower case. This is appropriate for reading | |
2102 | a key sequence to be defined. | |
2103 | ||
2104 | The argument @var{switch-frame-ok}, if non-@code{nil}, means that this | |
2105 | function should process a @code{switch-frame} event if the user | |
2106 | switches frames before typing anything. If the user switches frames | |
2107 | in the middle of a key sequence, or at the start of the sequence but | |
2108 | @var{switch-frame-ok} is @code{nil}, then the event will be put off | |
2109 | until after the current key sequence. | |
2110 | ||
2111 | The argument @var{command-loop}, if non-@code{nil}, means that this | |
2112 | key sequence is being read by something that will read commands one | |
2113 | after another. It should be @code{nil} if the caller will read just | |
2114 | one key sequence. | |
8db970a4 | 2115 | |
2b83bc43 RS |
2116 | In the following example, Emacs displays the prompt @samp{?} in the |
2117 | echo area, and then the user types @kbd{C-x C-f}. | |
8db970a4 RS |
2118 | |
2119 | @example | |
2120 | (read-key-sequence "?") | |
2121 | ||
2122 | @group | |
2123 | ---------- Echo Area ---------- | |
2124 | ?@kbd{C-x C-f} | |
2125 | ---------- Echo Area ---------- | |
2126 | ||
2127 | @result{} "^X^F" | |
2128 | @end group | |
2129 | @end example | |
969fe9b5 RS |
2130 | |
2131 | The function @code{read-key-sequence} suppresses quitting: @kbd{C-g} | |
2132 | typed while reading with this function works like any other character, | |
2133 | and does not set @code{quit-flag}. @xref{Quitting}. | |
2134 | @end defun | |
2135 | ||
ecbfc7e9 | 2136 | @defun read-key-sequence-vector prompt &optional continue-echo dont-downcase-last switch-frame-ok command-loop |
969fe9b5 RS |
2137 | This is like @code{read-key-sequence} except that it always |
2138 | returns the key sequence as a vector, never as a string. | |
2139 | @xref{Strings of Events}. | |
8db970a4 RS |
2140 | @end defun |
2141 | ||
8db970a4 RS |
2142 | @cindex upper case key sequence |
2143 | @cindex downcasing in @code{lookup-key} | |
b071e512 RS |
2144 | If an input character is upper-case (or has the shift modifier) and |
2145 | has no key binding, but its lower-case equivalent has one, then | |
2146 | @code{read-key-sequence} converts the character to lower case. Note | |
2147 | that @code{lookup-key} does not perform case conversion in this way. | |
8db970a4 RS |
2148 | |
2149 | The function @code{read-key-sequence} also transforms some mouse events. | |
2150 | It converts unbound drag events into click events, and discards unbound | |
bfe721d1 KH |
2151 | button-down events entirely. It also reshuffles focus events and |
2152 | miscellaneous window events so that they never appear in a key sequence | |
2153 | with any other events. | |
8db970a4 | 2154 | |
2468d0c0 DL |
2155 | @cindex @code{header-line} prefix key |
2156 | @cindex @code{mode-line} prefix key | |
2157 | @cindex @code{vertical-line} prefix key | |
2158 | @cindex @code{horizontal-scroll-bar} prefix key | |
2159 | @cindex @code{vertical-scroll-bar} prefix key | |
2160 | @cindex @code{menu-bar} prefix key | |
2161 | @cindex mouse events, in special parts of frame | |
8db970a4 | 2162 | When mouse events occur in special parts of a window, such as a mode |
f142f62a RS |
2163 | line or a scroll bar, the event type shows nothing special---it is the |
2164 | same symbol that would normally represent that combination of mouse | |
f9f59935 RS |
2165 | button and modifier keys. The information about the window part is kept |
2166 | elsewhere in the event---in the coordinates. But | |
f142f62a | 2167 | @code{read-key-sequence} translates this information into imaginary |
827b7ee7 | 2168 | ``prefix keys,'' all of which are symbols: @code{header-line}, |
2468d0c0 DL |
2169 | @code{horizontal-scroll-bar}, @code{menu-bar}, @code{mode-line}, |
2170 | @code{vertical-line}, and @code{vertical-scroll-bar}. You can define | |
2171 | meanings for mouse clicks in special window parts by defining key | |
2172 | sequences using these imaginary prefix keys. | |
f142f62a | 2173 | |
8db970a4 | 2174 | For example, if you call @code{read-key-sequence} and then click the |
bfe721d1 | 2175 | mouse on the window's mode line, you get two events, like this: |
8db970a4 | 2176 | |
f142f62a | 2177 | @example |
8db970a4 RS |
2178 | (read-key-sequence "Click on the mode line: ") |
2179 | @result{} [mode-line | |
f142f62a RS |
2180 | (mouse-1 |
2181 | (#<window 6 on NEWS> mode-line | |
2182 | (40 . 63) 5959987))] | |
2183 | @end example | |
8db970a4 | 2184 | |
f9f59935 RS |
2185 | @defvar num-input-keys |
2186 | @c Emacs 19 feature | |
2187 | This variable's value is the number of key sequences processed so far in | |
2188 | this Emacs session. This includes key sequences read from the terminal | |
2189 | and key sequences read from keyboard macros being executed. | |
2190 | @end defvar | |
2191 | ||
8db970a4 RS |
2192 | @node Reading One Event |
2193 | @subsection Reading One Event | |
2468d0c0 DL |
2194 | @cindex reading a single event |
2195 | @cindex event, reading only one | |
8db970a4 | 2196 | |
b22f3a19 | 2197 | The lowest level functions for command input are those that read a |
8db970a4 RS |
2198 | single event. |
2199 | ||
5504e99c LT |
2200 | None of the three functions below suppresses quitting. |
2201 | ||
c1c3d4f7 | 2202 | @defun read-event &optional prompt inherit-input-method seconds |
8db970a4 RS |
2203 | This function reads and returns the next event of command input, waiting |
2204 | if necessary until an event is available. Events can come directly from | |
2205 | the user or from a keyboard macro. | |
2206 | ||
b6954afd RS |
2207 | If the optional argument @var{prompt} is non-@code{nil}, it should be a |
2208 | string to display in the echo area as a prompt. Otherwise, | |
2209 | @code{read-event} does not display any message to indicate it is waiting | |
2210 | for input; instead, it prompts by echoing: it displays descriptions of | |
2211 | the events that led to or were read by the current command. @xref{The | |
2212 | Echo Area}. | |
8db970a4 | 2213 | |
b6954afd RS |
2214 | If @var{inherit-input-method} is non-@code{nil}, then the current input |
2215 | method (if any) is employed to make it possible to enter a | |
ad800164 | 2216 | non-@acronym{ASCII} character. Otherwise, input method handling is disabled |
b6954afd | 2217 | for reading this event. |
2eb4136f | 2218 | |
8db970a4 RS |
2219 | If @code{cursor-in-echo-area} is non-@code{nil}, then @code{read-event} |
2220 | moves the cursor temporarily to the echo area, to the end of any message | |
2221 | displayed there. Otherwise @code{read-event} does not move the cursor. | |
8db970a4 | 2222 | |
ae4bce67 | 2223 | If @var{seconds} is non-@code{nil}, it should be a number specifying |
c1c3d4f7 CY |
2224 | the maximum time to wait for input, in seconds. If no input arrives |
2225 | within that time, @code{read-event} stops waiting and returns | |
ae4bce67 | 2226 | @code{nil}. A floating-point value for @var{seconds} means to wait |
c1c3d4f7 | 2227 | for a fractional number of seconds. Some systems support only a whole |
ae4bce67 KS |
2228 | number of seconds; on these systems, @var{seconds} is rounded down. |
2229 | If @var{seconds} is @code{nil}, @code{read-event} waits as long as | |
c1c3d4f7 CY |
2230 | necessary for input to arrive. |
2231 | ||
9411b080 CY |
2232 | If @var{seconds} is @code{nil}, Emacs is considered idle while waiting |
2233 | for user input to arrive. Idle timers---those created with | |
4721317c | 2234 | @code{run-with-idle-timer} (@pxref{Idle Timers})---can run during this |
9411b080 CY |
2235 | period. However, if @var{seconds} is non-@code{nil}, the state of |
2236 | idleness remains unchanged. If Emacs is non-idle when | |
2237 | @code{read-event} is called, it remains non-idle throughout the | |
2238 | operation of @code{read-event}; if Emacs is idle (which can happen if | |
2239 | the call happens inside an idle timer), it remains idle. | |
2240 | ||
5504e99c LT |
2241 | If @code{read-event} gets an event that is defined as a help character, |
2242 | then in some cases @code{read-event} processes the event directly without | |
a9f0a989 RS |
2243 | returning. @xref{Help Functions}. Certain other events, called |
2244 | @dfn{special events}, are also processed directly within | |
2245 | @code{read-event} (@pxref{Special Events}). | |
2246 | ||
8db970a4 RS |
2247 | Here is what happens if you call @code{read-event} and then press the |
2248 | right-arrow function key: | |
2249 | ||
2250 | @example | |
2251 | @group | |
2252 | (read-event) | |
2253 | @result{} right | |
2254 | @end group | |
2255 | @end example | |
f142f62a | 2256 | @end defun |
8db970a4 | 2257 | |
c1c3d4f7 | 2258 | @defun read-char &optional prompt inherit-input-method seconds |
b6954afd RS |
2259 | This function reads and returns a character of command input. If the |
2260 | user generates an event which is not a character (i.e. a mouse click or | |
2261 | function key event), @code{read-char} signals an error. The arguments | |
2262 | work as in @code{read-event}. | |
8db970a4 | 2263 | |
ad800164 | 2264 | In the first example, the user types the character @kbd{1} (@acronym{ASCII} |
f142f62a RS |
2265 | code 49). The second example shows a keyboard macro definition that |
2266 | calls @code{read-char} from the minibuffer using @code{eval-expression}. | |
2267 | @code{read-char} reads the keyboard macro's very next character, which | |
2268 | is @kbd{1}. Then @code{eval-expression} displays its return value in | |
2269 | the echo area. | |
8db970a4 RS |
2270 | |
2271 | @example | |
2272 | @group | |
2273 | (read-char) | |
2274 | @result{} 49 | |
2275 | @end group | |
2276 | ||
2277 | @group | |
bfe721d1 | 2278 | ;; @r{We assume here you use @kbd{M-:} to evaluate this.} |
8db970a4 | 2279 | (symbol-function 'foo) |
bfe721d1 | 2280 | @result{} "^[:(read-char)^M1" |
8db970a4 RS |
2281 | @end group |
2282 | @group | |
f142f62a | 2283 | (execute-kbd-macro 'foo) |
8db970a4 RS |
2284 | @print{} 49 |
2285 | @result{} nil | |
2286 | @end group | |
2287 | @end example | |
2288 | @end defun | |
2289 | ||
c1c3d4f7 | 2290 | @defun read-char-exclusive &optional prompt inherit-input-method seconds |
b6954afd RS |
2291 | This function reads and returns a character of command input. If the |
2292 | user generates an event which is not a character, | |
2293 | @code{read-char-exclusive} ignores it and reads another event, until it | |
2294 | gets a character. The arguments work as in @code{read-event}. | |
2295 | @end defun | |
2296 | ||
2b83bc43 RS |
2297 | @defvar num-nonmacro-input-events |
2298 | This variable holds the total number of input events received so far | |
2299 | from the terminal---not counting those generated by keyboard macros. | |
2300 | @end defvar | |
2301 | ||
160ab7f9 RS |
2302 | @node Event Mod |
2303 | @subsection Modifying and Translating Input Events | |
2304 | ||
2305 | Emacs modifies every event it reads according to | |
2306 | @code{extra-keyboard-modifiers}, then translates it through | |
2307 | @code{keyboard-translate-table} (if applicable), before returning it | |
2308 | from @code{read-event}. | |
2309 | ||
2310 | @c Emacs 19 feature | |
2311 | @defvar extra-keyboard-modifiers | |
2312 | This variable lets Lisp programs ``press'' the modifier keys on the | |
2313 | keyboard. The value is a character. Only the modifiers of the | |
2314 | character matter. Each time the user types a keyboard key, it is | |
2315 | altered as if those modifier keys were held down. For instance, if | |
2316 | you bind @code{extra-keyboard-modifiers} to @code{?\C-\M-a}, then all | |
2317 | keyboard input characters typed during the scope of the binding will | |
2318 | have the control and meta modifiers applied to them. The character | |
2319 | @code{?\C-@@}, equivalent to the integer 0, does not count as a control | |
2320 | character for this purpose, but as a character with no modifiers. | |
2321 | Thus, setting @code{extra-keyboard-modifiers} to zero cancels any | |
2322 | modification. | |
2323 | ||
2324 | When using a window system, the program can ``press'' any of the | |
2325 | modifier keys in this way. Otherwise, only the @key{CTL} and @key{META} | |
2326 | keys can be virtually pressed. | |
2327 | ||
2328 | Note that this variable applies only to events that really come from | |
2329 | the keyboard, and has no effect on mouse events or any other events. | |
2330 | @end defvar | |
2331 | ||
2332 | @defvar keyboard-translate-table | |
2333 | This variable is the translate table for keyboard characters. It lets | |
2334 | you reshuffle the keys on the keyboard without changing any command | |
2335 | bindings. Its value is normally a char-table, or else @code{nil}. | |
2336 | (It can also be a string or vector, but this is considered obsolete.) | |
2337 | ||
2338 | If @code{keyboard-translate-table} is a char-table | |
2339 | (@pxref{Char-Tables}), then each character read from the keyboard is | |
2340 | looked up in this char-table. If the value found there is | |
2341 | non-@code{nil}, then it is used instead of the actual input character. | |
2342 | ||
2343 | Note that this translation is the first thing that happens to a | |
2344 | character after it is read from the terminal. Record-keeping features | |
2345 | such as @code{recent-keys} and dribble files record the characters after | |
2346 | translation. | |
2347 | ||
2348 | Note also that this translation is done before the characters are | |
2349 | supplied to input methods (@pxref{Input Methods}). Use | |
2350 | @code{translation-table-for-input} (@pxref{Translation of Characters}), | |
2351 | if you want to translate characters after input methods operate. | |
2352 | @end defvar | |
2353 | ||
2354 | @defun keyboard-translate from to | |
2355 | This function modifies @code{keyboard-translate-table} to translate | |
2356 | character code @var{from} into character code @var{to}. It creates | |
2357 | the keyboard translate table if necessary. | |
2358 | @end defun | |
2359 | ||
2360 | Here's an example of using the @code{keyboard-translate-table} to | |
2361 | make @kbd{C-x}, @kbd{C-c} and @kbd{C-v} perform the cut, copy and paste | |
2362 | operations: | |
2363 | ||
2364 | @example | |
2365 | (keyboard-translate ?\C-x 'control-x) | |
2366 | (keyboard-translate ?\C-c 'control-c) | |
2367 | (keyboard-translate ?\C-v 'control-v) | |
2368 | (global-set-key [control-x] 'kill-region) | |
2369 | (global-set-key [control-c] 'kill-ring-save) | |
2370 | (global-set-key [control-v] 'yank) | |
2371 | @end example | |
2372 | ||
2373 | @noindent | |
2374 | On a graphical terminal that supports extended @acronym{ASCII} input, | |
2375 | you can still get the standard Emacs meanings of one of those | |
2376 | characters by typing it with the shift key. That makes it a different | |
2377 | character as far as keyboard translation is concerned, but it has the | |
2378 | same usual meaning. | |
2379 | ||
2380 | @xref{Translation Keymaps}, for mechanisms that translate event sequences | |
2381 | at the level of @code{read-key-sequence}. | |
2382 | ||
b6954afd RS |
2383 | @node Invoking the Input Method |
2384 | @subsection Invoking the Input Method | |
2385 | ||
2386 | The event-reading functions invoke the current input method, if any | |
2387 | (@pxref{Input Methods}). If the value of @code{input-method-function} | |
2388 | is non-@code{nil}, it should be a function; when @code{read-event} reads | |
2389 | a printing character (including @key{SPC}) with no modifier bits, it | |
2390 | calls that function, passing the character as an argument. | |
39d6d9bd RS |
2391 | |
2392 | @defvar input-method-function | |
2393 | If this is non-@code{nil}, its value specifies the current input method | |
2394 | function. | |
2eb4136f | 2395 | |
6142d1d0 | 2396 | @strong{Warning:} don't bind this variable with @code{let}. It is often |
2eb4136f RS |
2397 | buffer-local, and if you bind it around reading input (which is exactly |
2398 | when you @emph{would} bind it), switching buffers asynchronously while | |
2399 | Emacs is waiting will cause the value to be restored in the wrong | |
2400 | buffer. | |
39d6d9bd RS |
2401 | @end defvar |
2402 | ||
2403 | The input method function should return a list of events which should | |
2404 | be used as input. (If the list is @code{nil}, that means there is no | |
2405 | input, so @code{read-event} waits for another event.) These events are | |
2468d0c0 DL |
2406 | processed before the events in @code{unread-command-events} |
2407 | (@pxref{Event Input Misc}). Events | |
39d6d9bd RS |
2408 | returned by the input method function are not passed to the input method |
2409 | function again, even if they are printing characters with no modifier | |
2410 | bits. | |
2411 | ||
2412 | If the input method function calls @code{read-event} or | |
2413 | @code{read-key-sequence}, it should bind @code{input-method-function} to | |
2414 | @code{nil} first, to prevent recursion. | |
2415 | ||
2416 | The input method function is not called when reading the second and | |
b6954afd RS |
2417 | subsequent events of a key sequence. Thus, these characters are not |
2418 | subject to input method processing. The input method function should | |
2419 | test the values of @code{overriding-local-map} and | |
2420 | @code{overriding-terminal-local-map}; if either of these variables is | |
2421 | non-@code{nil}, the input method should put its argument into a list and | |
2422 | return that list with no further processing. | |
39d6d9bd | 2423 | |
8db970a4 RS |
2424 | @node Quoted Character Input |
2425 | @subsection Quoted Character Input | |
2426 | @cindex quoted character input | |
2427 | ||
b22f3a19 RS |
2428 | You can use the function @code{read-quoted-char} to ask the user to |
2429 | specify a character, and allow the user to specify a control or meta | |
2430 | character conveniently, either literally or as an octal character code. | |
2431 | The command @code{quoted-insert} uses this function. | |
8db970a4 RS |
2432 | |
2433 | @defun read-quoted-char &optional prompt | |
2434 | @cindex octal character input | |
2435 | @cindex control characters, reading | |
2436 | @cindex nonprinting characters, reading | |
2437 | This function is like @code{read-char}, except that if the first | |
969fe9b5 RS |
2438 | character read is an octal digit (0-7), it reads any number of octal |
2439 | digits (but stopping if a non-octal digit is found), and returns the | |
5504e99c LT |
2440 | character represented by that numeric character code. If the |
2441 | character that terminates the sequence of octal digits is @key{RET}, | |
2442 | it is discarded. Any other terminating character is used as input | |
2443 | after this function returns. | |
8db970a4 RS |
2444 | |
2445 | Quitting is suppressed when the first character is read, so that the | |
2446 | user can enter a @kbd{C-g}. @xref{Quitting}. | |
2447 | ||
2448 | If @var{prompt} is supplied, it specifies a string for prompting the | |
f142f62a | 2449 | user. The prompt string is always displayed in the echo area, followed |
8db970a4 RS |
2450 | by a single @samp{-}. |
2451 | ||
2452 | In the following example, the user types in the octal number 177 (which | |
2453 | is 127 in decimal). | |
2454 | ||
2455 | @example | |
2456 | (read-quoted-char "What character") | |
2457 | ||
2458 | @group | |
2459 | ---------- Echo Area ---------- | |
5504e99c | 2460 | What character @kbd{1 7 7}- |
8db970a4 RS |
2461 | ---------- Echo Area ---------- |
2462 | ||
2463 | @result{} 127 | |
2464 | @end group | |
2465 | @end example | |
2466 | @end defun | |
2467 | ||
b22f3a19 | 2468 | @need 2000 |
f142f62a RS |
2469 | @node Event Input Misc |
2470 | @subsection Miscellaneous Event Input Features | |
2471 | ||
2472 | This section describes how to ``peek ahead'' at events without using | |
2473 | them up, how to check for pending input, and how to discard pending | |
1911e6e5 RS |
2474 | input. See also the function @code{read-passwd} (@pxref{Reading a |
2475 | Password}). | |
8db970a4 RS |
2476 | |
2477 | @defvar unread-command-events | |
2478 | @cindex next input | |
2479 | @cindex peeking at input | |
2480 | This variable holds a list of events waiting to be read as command | |
f142f62a RS |
2481 | input. The events are used in the order they appear in the list, and |
2482 | removed one by one as they are used. | |
8db970a4 | 2483 | |
f9f59935 | 2484 | The variable is needed because in some cases a function reads an event |
f142f62a RS |
2485 | and then decides not to use it. Storing the event in this variable |
2486 | causes it to be processed normally, by the command loop or by the | |
2487 | functions to read command input. | |
8db970a4 RS |
2488 | |
2489 | @cindex prefix argument unreading | |
2490 | For example, the function that implements numeric prefix arguments reads | |
2491 | any number of digits. When it finds a non-digit event, it must unread | |
2492 | the event so that it can be read normally by the command loop. | |
177c0ea7 | 2493 | Likewise, incremental search uses this feature to unread events with no |
f142f62a RS |
2494 | special meaning in a search, because these events should exit the search |
2495 | and then execute normally. | |
2496 | ||
b22f3a19 RS |
2497 | The reliable and easy way to extract events from a key sequence so as to |
2498 | put them in @code{unread-command-events} is to use | |
f142f62a | 2499 | @code{listify-key-sequence} (@pxref{Strings of Events}). |
f9f59935 RS |
2500 | |
2501 | Normally you add events to the front of this list, so that the events | |
2502 | most recently unread will be reread first. | |
8db970a4 RS |
2503 | @end defvar |
2504 | ||
969fe9b5 RS |
2505 | @defun listify-key-sequence key |
2506 | This function converts the string or vector @var{key} to a list of | |
2507 | individual events, which you can put in @code{unread-command-events}. | |
2508 | @end defun | |
2509 | ||
8db970a4 RS |
2510 | @defvar unread-command-char |
2511 | This variable holds a character to be read as command input. | |
827b7ee7 | 2512 | A value of -1 means ``empty.'' |
8db970a4 | 2513 | |
f142f62a | 2514 | This variable is mostly obsolete now that you can use |
8db970a4 RS |
2515 | @code{unread-command-events} instead; it exists only to support programs |
2516 | written for Emacs versions 18 and earlier. | |
2517 | @end defvar | |
2518 | ||
8db970a4 RS |
2519 | @defun input-pending-p |
2520 | @cindex waiting for command key input | |
2521 | This function determines whether any command input is currently | |
2522 | available to be read. It returns immediately, with value @code{t} if | |
f142f62a RS |
2523 | there is available input, @code{nil} otherwise. On rare occasions it |
2524 | may return @code{t} when no input is available. | |
8db970a4 RS |
2525 | @end defun |
2526 | ||
2527 | @defvar last-input-event | |
969fe9b5 | 2528 | @defvarx last-input-char |
f142f62a | 2529 | This variable records the last terminal input event read, whether |
8db970a4 RS |
2530 | as part of a command or explicitly by a Lisp program. |
2531 | ||
f142f62a | 2532 | In the example below, the Lisp program reads the character @kbd{1}, |
ad800164 | 2533 | @acronym{ASCII} code 49. It becomes the value of @code{last-input-event}, |
bfe721d1 KH |
2534 | while @kbd{C-e} (we assume @kbd{C-x C-e} command is used to evaluate |
2535 | this expression) remains the value of @code{last-command-event}. | |
8db970a4 RS |
2536 | |
2537 | @example | |
2538 | @group | |
2539 | (progn (print (read-char)) | |
f142f62a RS |
2540 | (print last-command-event) |
2541 | last-input-event) | |
8db970a4 RS |
2542 | @print{} 49 |
2543 | @print{} 5 | |
2544 | @result{} 49 | |
2545 | @end group | |
2546 | @end example | |
2547 | ||
2548 | The alias @code{last-input-char} exists for compatibility with | |
2549 | Emacs version 18. | |
2550 | @end defvar | |
2551 | ||
4049cdfa | 2552 | @defmac while-no-input body@dots{} |
7d9f1aed RS |
2553 | This construct runs the @var{body} forms and returns the value of the |
2554 | last one---but only if no input arrives. If any input arrives during | |
2555 | the execution of the @var{body} forms, it aborts them (working much | |
2556 | like a quit). The @code{while-no-input} form returns @code{nil} if | |
2557 | aborted by a real quit, and returns @code{t} if aborted by arrival of | |
2558 | other input. | |
a5034239 RS |
2559 | |
2560 | If a part of @var{body} binds @code{inhibit-quit} to non-@code{nil}, | |
2561 | arrival of input during those parts won't cause an abort until | |
2562 | the end of that part. | |
7d9f1aed | 2563 | |
5a36d834 | 2564 | If you want to be able to distinguish all possible values computed |
7d9f1aed RS |
2565 | by @var{body} from both kinds of abort conditions, write the code |
2566 | like this: | |
2567 | ||
2568 | @example | |
2569 | (while-no-input | |
2570 | (list | |
2571 | (progn . @var{body}))) | |
2572 | @end example | |
a5034239 RS |
2573 | @end defmac |
2574 | ||
8db970a4 RS |
2575 | @defun discard-input |
2576 | @cindex flush input | |
2577 | @cindex discard input | |
2578 | @cindex terminate keyboard macro | |
2579 | This function discards the contents of the terminal input buffer and | |
2580 | cancels any keyboard macro that might be in the process of definition. | |
2581 | It returns @code{nil}. | |
2582 | ||
2583 | In the following example, the user may type a number of characters right | |
2584 | after starting the evaluation of the form. After the @code{sleep-for} | |
177c0ea7 | 2585 | finishes sleeping, @code{discard-input} discards any characters typed |
f142f62a | 2586 | during the sleep. |
8db970a4 RS |
2587 | |
2588 | @example | |
2589 | (progn (sleep-for 2) | |
f142f62a | 2590 | (discard-input)) |
8db970a4 RS |
2591 | @result{} nil |
2592 | @end example | |
2593 | @end defun | |
2594 | ||
f9f59935 RS |
2595 | @node Special Events |
2596 | @section Special Events | |
2597 | ||
2598 | @cindex special events | |
2599 | Special events are handled at a very low level---as soon as they are | |
2600 | read. The @code{read-event} function processes these events itself, and | |
5504e99c LT |
2601 | never returns them. Instead, it keeps waiting for the first event |
2602 | that is not special and returns that one. | |
f9f59935 RS |
2603 | |
2604 | Events that are handled in this way do not echo, they are never grouped | |
2605 | into key sequences, and they never appear in the value of | |
2606 | @code{last-command-event} or @code{(this-command-keys)}. They do not | |
2607 | discard a numeric argument, they cannot be unread with | |
2608 | @code{unread-command-events}, they may not appear in a keyboard macro, | |
2609 | and they are not recorded in a keyboard macro while you are defining | |
2610 | one. | |
2611 | ||
2612 | These events do, however, appear in @code{last-input-event} immediately | |
2613 | after they are read, and this is the way for the event's definition to | |
2614 | find the actual event. | |
2615 | ||
2616 | The events types @code{iconify-frame}, @code{make-frame-visible} and | |
2617 | @code{delete-frame} are normally handled in this way. The keymap which | |
2618 | defines how to handle special events---and which events are special---is | |
2619 | in the variable @code{special-event-map} (@pxref{Active Keymaps}). | |
2620 | ||
8db970a4 RS |
2621 | @node Waiting |
2622 | @section Waiting for Elapsed Time or Input | |
2623 | @cindex pausing | |
2624 | @cindex waiting | |
2625 | ||
f142f62a RS |
2626 | The wait functions are designed to wait for a certain amount of time |
2627 | to pass or until there is input. For example, you may wish to pause in | |
2628 | the middle of a computation to allow the user time to view the display. | |
2629 | @code{sit-for} pauses and updates the screen, and returns immediately if | |
2630 | input comes in, while @code{sleep-for} pauses without updating the | |
2631 | screen. | |
8db970a4 | 2632 | |
14bd0b09 | 2633 | @defun sit-for seconds &optional nodisp |
8db970a4 RS |
2634 | This function performs redisplay (provided there is no pending input |
2635 | from the user), then waits @var{seconds} seconds, or until input is | |
e1842332 CY |
2636 | available. The usual purpose of @code{sit-for} is to give the user |
2637 | time to read text that you display. The value is @code{t} if | |
2638 | @code{sit-for} waited the full time with no input arriving | |
2639 | (@pxref{Event Input Misc}). Otherwise, the value is @code{nil}. | |
8db970a4 | 2640 | |
bfe721d1 KH |
2641 | The argument @var{seconds} need not be an integer. If it is a floating |
2642 | point number, @code{sit-for} waits for a fractional number of seconds. | |
2643 | Some systems support only a whole number of seconds; on these systems, | |
2644 | @var{seconds} is rounded down. | |
2645 | ||
9ae011ae KS |
2646 | The expression @code{(sit-for 0)} is equivalent to @code{(redisplay)}, |
2647 | i.e. it requests a redisplay, without any delay, if there is no pending input. | |
2648 | @xref{Forcing Redisplay}. | |
8db970a4 RS |
2649 | |
2650 | If @var{nodisp} is non-@code{nil}, then @code{sit-for} does not | |
2651 | redisplay, but it still returns as soon as input is available (or when | |
2652 | the timeout elapses). | |
2653 | ||
e1842332 CY |
2654 | In batch mode (@pxref{Batch Mode}), @code{sit-for} cannot be |
2655 | interrupted, even by input from the standard input descriptor. It is | |
2656 | thus equivalent to @code{sleep-for}, which is described below. | |
14bd0b09 RS |
2657 | |
2658 | It is also possible to call @code{sit-for} with three arguments, | |
2659 | as @code{(sit-for @var{seconds} @var{millisec} @var{nodisp})}, | |
2660 | but that is considered obsolete. | |
8db970a4 RS |
2661 | @end defun |
2662 | ||
2663 | @defun sleep-for seconds &optional millisec | |
2664 | This function simply pauses for @var{seconds} seconds without updating | |
2665 | the display. It pays no attention to available input. It returns | |
2666 | @code{nil}. | |
2667 | ||
bfe721d1 KH |
2668 | The argument @var{seconds} need not be an integer. If it is a floating |
2669 | point number, @code{sleep-for} waits for a fractional number of seconds. | |
2670 | Some systems support only a whole number of seconds; on these systems, | |
2671 | @var{seconds} is rounded down. | |
2672 | ||
8db970a4 RS |
2673 | The optional argument @var{millisec} specifies an additional waiting |
2674 | period measured in milliseconds. This adds to the period specified by | |
bfe721d1 KH |
2675 | @var{seconds}. If the system doesn't support waiting fractions of a |
2676 | second, you get an error if you specify nonzero @var{millisec}. | |
8db970a4 RS |
2677 | |
2678 | Use @code{sleep-for} when you wish to guarantee a delay. | |
2679 | @end defun | |
2680 | ||
2681 | @xref{Time of Day}, for functions to get the current time. | |
2682 | ||
2683 | @node Quitting | |
2684 | @section Quitting | |
2685 | @cindex @kbd{C-g} | |
2686 | @cindex quitting | |
34c0b12e | 2687 | @cindex interrupt Lisp functions |
8db970a4 | 2688 | |
b22f3a19 RS |
2689 | Typing @kbd{C-g} while a Lisp function is running causes Emacs to |
2690 | @dfn{quit} whatever it is doing. This means that control returns to the | |
2691 | innermost active command loop. | |
8db970a4 RS |
2692 | |
2693 | Typing @kbd{C-g} while the command loop is waiting for keyboard input | |
2694 | does not cause a quit; it acts as an ordinary input character. In the | |
2695 | simplest case, you cannot tell the difference, because @kbd{C-g} | |
2696 | normally runs the command @code{keyboard-quit}, whose effect is to quit. | |
969fe9b5 RS |
2697 | However, when @kbd{C-g} follows a prefix key, they combine to form an |
2698 | undefined key. The effect is to cancel the prefix key as well as any | |
2699 | prefix argument. | |
8db970a4 RS |
2700 | |
2701 | In the minibuffer, @kbd{C-g} has a different definition: it aborts out | |
2702 | of the minibuffer. This means, in effect, that it exits the minibuffer | |
2703 | and then quits. (Simply quitting would return to the command loop | |
2704 | @emph{within} the minibuffer.) The reason why @kbd{C-g} does not quit | |
2705 | directly when the command reader is reading input is so that its meaning | |
2706 | can be redefined in the minibuffer in this way. @kbd{C-g} following a | |
2707 | prefix key is not redefined in the minibuffer, and it has its normal | |
2708 | effect of canceling the prefix key and prefix argument. This too | |
f142f62a | 2709 | would not be possible if @kbd{C-g} always quit directly. |
8db970a4 | 2710 | |
b22f3a19 | 2711 | When @kbd{C-g} does directly quit, it does so by setting the variable |
f142f62a RS |
2712 | @code{quit-flag} to @code{t}. Emacs checks this variable at appropriate |
2713 | times and quits if it is not @code{nil}. Setting @code{quit-flag} | |
8db970a4 RS |
2714 | non-@code{nil} in any way thus causes a quit. |
2715 | ||
f142f62a | 2716 | At the level of C code, quitting cannot happen just anywhere; only at the |
b22f3a19 | 2717 | special places that check @code{quit-flag}. The reason for this is |
8db970a4 | 2718 | that quitting at other places might leave an inconsistency in Emacs's |
177c0ea7 | 2719 | internal state. Because quitting is delayed until a safe place, quitting |
8db970a4 RS |
2720 | cannot make Emacs crash. |
2721 | ||
2722 | Certain functions such as @code{read-key-sequence} or | |
2723 | @code{read-quoted-char} prevent quitting entirely even though they wait | |
2724 | for input. Instead of quitting, @kbd{C-g} serves as the requested | |
2725 | input. In the case of @code{read-key-sequence}, this serves to bring | |
2726 | about the special behavior of @kbd{C-g} in the command loop. In the | |
2727 | case of @code{read-quoted-char}, this is so that @kbd{C-q} can be used | |
177c0ea7 | 2728 | to quote a @kbd{C-g}. |
8db970a4 | 2729 | |
34c0b12e | 2730 | @cindex prevent quitting |
8db970a4 RS |
2731 | You can prevent quitting for a portion of a Lisp function by binding |
2732 | the variable @code{inhibit-quit} to a non-@code{nil} value. Then, | |
2733 | although @kbd{C-g} still sets @code{quit-flag} to @code{t} as usual, the | |
2734 | usual result of this---a quit---is prevented. Eventually, | |
2735 | @code{inhibit-quit} will become @code{nil} again, such as when its | |
2736 | binding is unwound at the end of a @code{let} form. At that time, if | |
2737 | @code{quit-flag} is still non-@code{nil}, the requested quit happens | |
b22f3a19 RS |
2738 | immediately. This behavior is ideal when you wish to make sure that |
2739 | quitting does not happen within a ``critical section'' of the program. | |
8db970a4 RS |
2740 | |
2741 | @cindex @code{read-quoted-char} quitting | |
2742 | In some functions (such as @code{read-quoted-char}), @kbd{C-g} is | |
b22f3a19 | 2743 | handled in a special way that does not involve quitting. This is done |
f142f62a | 2744 | by reading the input with @code{inhibit-quit} bound to @code{t}, and |
8db970a4 RS |
2745 | setting @code{quit-flag} to @code{nil} before @code{inhibit-quit} |
2746 | becomes @code{nil} again. This excerpt from the definition of | |
2747 | @code{read-quoted-char} shows how this is done; it also shows that | |
2748 | normal quitting is permitted after the first character of input. | |
2749 | ||
2750 | @example | |
2751 | (defun read-quoted-char (&optional prompt) | |
2752 | "@dots{}@var{documentation}@dots{}" | |
969fe9b5 RS |
2753 | (let ((message-log-max nil) done (first t) (code 0) char) |
2754 | (while (not done) | |
2755 | (let ((inhibit-quit first) | |
2756 | @dots{}) | |
2757 | (and prompt (message "%s-" prompt)) | |
2758 | (setq char (read-event)) | |
2759 | (if inhibit-quit (setq quit-flag nil))) | |
2760 | @r{@dots{}set the variable @code{code}@dots{}}) | |
2761 | code)) | |
8db970a4 RS |
2762 | @end example |
2763 | ||
2764 | @defvar quit-flag | |
f142f62a RS |
2765 | If this variable is non-@code{nil}, then Emacs quits immediately, unless |
2766 | @code{inhibit-quit} is non-@code{nil}. Typing @kbd{C-g} ordinarily sets | |
8db970a4 RS |
2767 | @code{quit-flag} non-@code{nil}, regardless of @code{inhibit-quit}. |
2768 | @end defvar | |
2769 | ||
2770 | @defvar inhibit-quit | |
2771 | This variable determines whether Emacs should quit when @code{quit-flag} | |
2772 | is set to a value other than @code{nil}. If @code{inhibit-quit} is | |
2773 | non-@code{nil}, then @code{quit-flag} has no special effect. | |
2774 | @end defvar | |
2775 | ||
4049cdfa JL |
2776 | @defmac with-local-quit body@dots{} |
2777 | This macro executes @var{body} forms in sequence, but allows quitting, at | |
5504e99c LT |
2778 | least locally, within @var{body} even if @code{inhibit-quit} was |
2779 | non-@code{nil} outside this construct. It returns the value of the | |
4049cdfa | 2780 | last form in @var{body}, unless exited by quitting, in which case |
eab463f6 | 2781 | it returns @code{nil}. |
5504e99c LT |
2782 | |
2783 | If @code{inhibit-quit} is @code{nil} on entry to @code{with-local-quit}, | |
4049cdfa | 2784 | it only executes the @var{body}, and setting @code{quit-flag} causes |
5504e99c LT |
2785 | a normal quit. However, if @code{inhibit-quit} is non-@code{nil} so |
2786 | that ordinary quitting is delayed, a non-@code{nil} @code{quit-flag} | |
2787 | triggers a special kind of local quit. This ends the execution of | |
4049cdfa | 2788 | @var{body} and exits the @code{with-local-quit} body with |
5504e99c LT |
2789 | @code{quit-flag} still non-@code{nil}, so that another (ordinary) quit |
2790 | will happen as soon as that is allowed. If @code{quit-flag} is | |
4049cdfa JL |
2791 | already non-@code{nil} at the beginning of @var{body}, the local quit |
2792 | happens immediately and the body doesn't execute at all. | |
5504e99c LT |
2793 | |
2794 | This macro is mainly useful in functions that can be called from | |
617e58e7 RS |
2795 | timers, process filters, process sentinels, @code{pre-command-hook}, |
2796 | @code{post-command-hook}, and other places where @code{inhibit-quit} is | |
2797 | normally bound to @code{t}. | |
5504e99c LT |
2798 | @end defmac |
2799 | ||
8db970a4 RS |
2800 | @deffn Command keyboard-quit |
2801 | This function signals the @code{quit} condition with @code{(signal 'quit | |
2802 | nil)}. This is the same thing that quitting does. (See @code{signal} | |
2803 | in @ref{Errors}.) | |
2804 | @end deffn | |
2805 | ||
2806 | You can specify a character other than @kbd{C-g} to use for quitting. | |
2807 | See the function @code{set-input-mode} in @ref{Terminal Input}. | |
177c0ea7 | 2808 | |
8db970a4 RS |
2809 | @node Prefix Command Arguments |
2810 | @section Prefix Command Arguments | |
2811 | @cindex prefix argument | |
2812 | @cindex raw prefix argument | |
2813 | @cindex numeric prefix argument | |
2814 | ||
2815 | Most Emacs commands can use a @dfn{prefix argument}, a number | |
2816 | specified before the command itself. (Don't confuse prefix arguments | |
b22f3a19 RS |
2817 | with prefix keys.) The prefix argument is at all times represented by a |
2818 | value, which may be @code{nil}, meaning there is currently no prefix | |
2819 | argument. Each command may use the prefix argument or ignore it. | |
8db970a4 RS |
2820 | |
2821 | There are two representations of the prefix argument: @dfn{raw} and | |
2822 | @dfn{numeric}. The editor command loop uses the raw representation | |
2823 | internally, and so do the Lisp variables that store the information, but | |
2824 | commands can request either representation. | |
2825 | ||
2826 | Here are the possible values of a raw prefix argument: | |
2827 | ||
2828 | @itemize @bullet | |
2829 | @item | |
2830 | @code{nil}, meaning there is no prefix argument. Its numeric value is | |
2831 | 1, but numerous commands make a distinction between @code{nil} and the | |
2832 | integer 1. | |
2833 | ||
2834 | @item | |
2835 | An integer, which stands for itself. | |
2836 | ||
2837 | @item | |
2838 | A list of one element, which is an integer. This form of prefix | |
2839 | argument results from one or a succession of @kbd{C-u}'s with no | |
2840 | digits. The numeric value is the integer in the list, but some | |
2841 | commands make a distinction between such a list and an integer alone. | |
2842 | ||
2843 | @item | |
2844 | The symbol @code{-}. This indicates that @kbd{M--} or @kbd{C-u -} was | |
2845 | typed, without following digits. The equivalent numeric value is | |
2846 | @minus{}1, but some commands make a distinction between the integer | |
2847 | @minus{}1 and the symbol @code{-}. | |
2848 | @end itemize | |
2849 | ||
f142f62a RS |
2850 | We illustrate these possibilities by calling the following function with |
2851 | various prefixes: | |
8db970a4 RS |
2852 | |
2853 | @example | |
2854 | @group | |
2855 | (defun display-prefix (arg) | |
2856 | "Display the value of the raw prefix arg." | |
2857 | (interactive "P") | |
2858 | (message "%s" arg)) | |
2859 | @end group | |
2860 | @end example | |
2861 | ||
2862 | @noindent | |
2863 | Here are the results of calling @code{display-prefix} with various | |
2864 | raw prefix arguments: | |
2865 | ||
2866 | @example | |
2867 | M-x display-prefix @print{} nil | |
2868 | ||
2869 | C-u M-x display-prefix @print{} (4) | |
2870 | ||
2871 | C-u C-u M-x display-prefix @print{} (16) | |
2872 | ||
2873 | C-u 3 M-x display-prefix @print{} 3 | |
2874 | ||
2875 | M-3 M-x display-prefix @print{} 3 ; @r{(Same as @code{C-u 3}.)} | |
2876 | ||
177c0ea7 | 2877 | C-u - M-x display-prefix @print{} - |
8db970a4 | 2878 | |
f142f62a | 2879 | M-- M-x display-prefix @print{} - ; @r{(Same as @code{C-u -}.)} |
8db970a4 | 2880 | |
177c0ea7 | 2881 | C-u - 7 M-x display-prefix @print{} -7 |
8db970a4 | 2882 | |
f142f62a | 2883 | M-- 7 M-x display-prefix @print{} -7 ; @r{(Same as @code{C-u -7}.)} |
8db970a4 RS |
2884 | @end example |
2885 | ||
2886 | Emacs uses two variables to store the prefix argument: | |
2887 | @code{prefix-arg} and @code{current-prefix-arg}. Commands such as | |
2888 | @code{universal-argument} that set up prefix arguments for other | |
2889 | commands store them in @code{prefix-arg}. In contrast, | |
2890 | @code{current-prefix-arg} conveys the prefix argument to the current | |
2891 | command, so setting it has no effect on the prefix arguments for future | |
2892 | commands. | |
2893 | ||
2894 | Normally, commands specify which representation to use for the prefix | |
b3a1cf11 | 2895 | argument, either numeric or raw, in the @code{interactive} specification. |
b22f3a19 | 2896 | (@xref{Using Interactive}.) Alternatively, functions may look at the |
8db970a4 RS |
2897 | value of the prefix argument directly in the variable |
2898 | @code{current-prefix-arg}, but this is less clean. | |
2899 | ||
f142f62a RS |
2900 | @defun prefix-numeric-value arg |
2901 | This function returns the numeric meaning of a valid raw prefix argument | |
2902 | value, @var{arg}. The argument may be a symbol, a number, or a list. | |
b22f3a19 RS |
2903 | If it is @code{nil}, the value 1 is returned; if it is @code{-}, the |
2904 | value @minus{}1 is returned; if it is a number, that number is returned; | |
4bdcd3ef | 2905 | if it is a list, the @sc{car} of that list (which should be a number) is |
b22f3a19 | 2906 | returned. |
f142f62a RS |
2907 | @end defun |
2908 | ||
2909 | @defvar current-prefix-arg | |
2910 | This variable holds the raw prefix argument for the @emph{current} | |
9e2b495b RS |
2911 | command. Commands may examine it directly, but the usual method for |
2912 | accessing it is with @code{(interactive "P")}. | |
f142f62a RS |
2913 | @end defvar |
2914 | ||
2915 | @defvar prefix-arg | |
2916 | The value of this variable is the raw prefix argument for the | |
f9f59935 RS |
2917 | @emph{next} editing command. Commands such as @code{universal-argument} |
2918 | that specify prefix arguments for the following command work by setting | |
2919 | this variable. | |
03c6b7f6 RS |
2920 | @end defvar |
2921 | ||
03c6b7f6 RS |
2922 | @defvar last-prefix-arg |
2923 | The raw prefix argument value used by the previous command. | |
f142f62a RS |
2924 | @end defvar |
2925 | ||
f9f59935 RS |
2926 | The following commands exist to set up prefix arguments for the |
2927 | following command. Do not call them for any other reason. | |
8db970a4 RS |
2928 | |
2929 | @deffn Command universal-argument | |
2930 | This command reads input and specifies a prefix argument for the | |
2931 | following command. Don't call this command yourself unless you know | |
2932 | what you are doing. | |
2933 | @end deffn | |
2934 | ||
2935 | @deffn Command digit-argument arg | |
2936 | This command adds to the prefix argument for the following command. The | |
2937 | argument @var{arg} is the raw prefix argument as it was before this | |
2938 | command; it is used to compute the updated prefix argument. Don't call | |
2939 | this command yourself unless you know what you are doing. | |
2940 | @end deffn | |
2941 | ||
2942 | @deffn Command negative-argument arg | |
2943 | This command adds to the numeric argument for the next command. The | |
2944 | argument @var{arg} is the raw prefix argument as it was before this | |
2945 | command; its value is negated to form the new prefix argument. Don't | |
2946 | call this command yourself unless you know what you are doing. | |
2947 | @end deffn | |
2948 | ||
8db970a4 RS |
2949 | @node Recursive Editing |
2950 | @section Recursive Editing | |
2951 | @cindex recursive command loop | |
2952 | @cindex recursive editing level | |
2953 | @cindex command loop, recursive | |
2954 | ||
f142f62a RS |
2955 | The Emacs command loop is entered automatically when Emacs starts up. |
2956 | This top-level invocation of the command loop never exits; it keeps | |
2957 | running as long as Emacs does. Lisp programs can also invoke the | |
2958 | command loop. Since this makes more than one activation of the command | |
2959 | loop, we call it @dfn{recursive editing}. A recursive editing level has | |
2960 | the effect of suspending whatever command invoked it and permitting the | |
2961 | user to do arbitrary editing before resuming that command. | |
8db970a4 RS |
2962 | |
2963 | The commands available during recursive editing are the same ones | |
2964 | available in the top-level editing loop and defined in the keymaps. | |
2965 | Only a few special commands exit the recursive editing level; the others | |
f142f62a RS |
2966 | return to the recursive editing level when they finish. (The special |
2967 | commands for exiting are always available, but they do nothing when | |
2968 | recursive editing is not in progress.) | |
8db970a4 RS |
2969 | |
2970 | All command loops, including recursive ones, set up all-purpose error | |
2971 | handlers so that an error in a command run from the command loop will | |
2972 | not exit the loop. | |
2973 | ||
2974 | @cindex minibuffer input | |
2975 | Minibuffer input is a special kind of recursive editing. It has a few | |
2976 | special wrinkles, such as enabling display of the minibuffer and the | |
2977 | minibuffer window, but fewer than you might suppose. Certain keys | |
2978 | behave differently in the minibuffer, but that is only because of the | |
2979 | minibuffer's local map; if you switch windows, you get the usual Emacs | |
2980 | commands. | |
2981 | ||
2982 | @cindex @code{throw} example | |
2983 | @kindex exit | |
2984 | @cindex exit recursive editing | |
2985 | @cindex aborting | |
2986 | To invoke a recursive editing level, call the function | |
2987 | @code{recursive-edit}. This function contains the command loop; it also | |
2988 | contains a call to @code{catch} with tag @code{exit}, which makes it | |
2989 | possible to exit the recursive editing level by throwing to @code{exit} | |
2990 | (@pxref{Catch and Throw}). If you throw a value other than @code{t}, | |
2991 | then @code{recursive-edit} returns normally to the function that called | |
2992 | it. The command @kbd{C-M-c} (@code{exit-recursive-edit}) does this. | |
2993 | Throwing a @code{t} value causes @code{recursive-edit} to quit, so that | |
2994 | control returns to the command loop one level up. This is called | |
2995 | @dfn{aborting}, and is done by @kbd{C-]} (@code{abort-recursive-edit}). | |
2996 | ||
2997 | Most applications should not use recursive editing, except as part of | |
2998 | using the minibuffer. Usually it is more convenient for the user if you | |
2999 | change the major mode of the current buffer temporarily to a special | |
b22f3a19 RS |
3000 | major mode, which should have a command to go back to the previous mode. |
3001 | (The @kbd{e} command in Rmail uses this technique.) Or, if you wish to | |
827b7ee7 | 3002 | give the user different text to edit ``recursively,'' create and select |
b22f3a19 RS |
3003 | a new buffer in a special mode. In this mode, define a command to |
3004 | complete the processing and go back to the previous buffer. (The | |
3005 | @kbd{m} command in Rmail does this.) | |
8db970a4 RS |
3006 | |
3007 | Recursive edits are useful in debugging. You can insert a call to | |
3008 | @code{debug} into a function definition as a sort of breakpoint, so that | |
3009 | you can look around when the function gets there. @code{debug} invokes | |
3010 | a recursive edit but also provides the other features of the debugger. | |
3011 | ||
3012 | Recursive editing levels are also used when you type @kbd{C-r} in | |
3013 | @code{query-replace} or use @kbd{C-x q} (@code{kbd-macro-query}). | |
3014 | ||
3015 | @defun recursive-edit | |
3016 | @cindex suspend evaluation | |
3017 | This function invokes the editor command loop. It is called | |
3018 | automatically by the initialization of Emacs, to let the user begin | |
3019 | editing. When called from a Lisp program, it enters a recursive editing | |
3020 | level. | |
3021 | ||
3022 | In the following example, the function @code{simple-rec} first | |
3023 | advances point one word, then enters a recursive edit, printing out a | |
3024 | message in the echo area. The user can then do any editing desired, and | |
3025 | then type @kbd{C-M-c} to exit and continue executing @code{simple-rec}. | |
3026 | ||
3027 | @example | |
3028 | (defun simple-rec () | |
3029 | (forward-word 1) | |
f142f62a | 3030 | (message "Recursive edit in progress") |
8db970a4 RS |
3031 | (recursive-edit) |
3032 | (forward-word 1)) | |
3033 | @result{} simple-rec | |
3034 | (simple-rec) | |
3035 | @result{} nil | |
3036 | @end example | |
3037 | @end defun | |
3038 | ||
3039 | @deffn Command exit-recursive-edit | |
3040 | This function exits from the innermost recursive edit (including | |
3041 | minibuffer input). Its definition is effectively @code{(throw 'exit | |
177c0ea7 | 3042 | nil)}. |
8db970a4 RS |
3043 | @end deffn |
3044 | ||
3045 | @deffn Command abort-recursive-edit | |
3046 | This function aborts the command that requested the innermost recursive | |
177c0ea7 | 3047 | edit (including minibuffer input), by signaling @code{quit} |
8db970a4 RS |
3048 | after exiting the recursive edit. Its definition is effectively |
3049 | @code{(throw 'exit t)}. @xref{Quitting}. | |
3050 | @end deffn | |
3051 | ||
3052 | @deffn Command top-level | |
3053 | This function exits all recursive editing levels; it does not return a | |
3054 | value, as it jumps completely out of any computation directly back to | |
3055 | the main command loop. | |
3056 | @end deffn | |
3057 | ||
3058 | @defun recursion-depth | |
3059 | This function returns the current depth of recursive edits. When no | |
3060 | recursive edit is active, it returns 0. | |
3061 | @end defun | |
3062 | ||
3063 | @node Disabling Commands | |
3064 | @section Disabling Commands | |
3065 | @cindex disabled command | |
3066 | ||
3067 | @dfn{Disabling a command} marks the command as requiring user | |
3068 | confirmation before it can be executed. Disabling is used for commands | |
3069 | which might be confusing to beginning users, to prevent them from using | |
3070 | the commands by accident. | |
3071 | ||
3072 | @kindex disabled | |
3073 | The low-level mechanism for disabling a command is to put a | |
3074 | non-@code{nil} @code{disabled} property on the Lisp symbol for the | |
3075 | command. These properties are normally set up by the user's | |
a40d4712 | 3076 | init file (@pxref{Init File}) with Lisp expressions such as this: |
8db970a4 RS |
3077 | |
3078 | @example | |
3079 | (put 'upcase-region 'disabled t) | |
3080 | @end example | |
3081 | ||
3082 | @noindent | |
a40d4712 PR |
3083 | For a few commands, these properties are present by default (you can |
3084 | remove them in your init file if you wish). | |
8db970a4 | 3085 | |
f142f62a RS |
3086 | If the value of the @code{disabled} property is a string, the message |
3087 | saying the command is disabled includes that string. For example: | |
8db970a4 RS |
3088 | |
3089 | @example | |
3090 | (put 'delete-region 'disabled | |
3091 | "Text deleted this way cannot be yanked back!\n") | |
3092 | @end example | |
3093 | ||
3094 | @xref{Disabling,,, emacs, The GNU Emacs Manual}, for the details on | |
3095 | what happens when a disabled command is invoked interactively. | |
3096 | Disabling a command has no effect on calling it as a function from Lisp | |
3097 | programs. | |
3098 | ||
3099 | @deffn Command enable-command command | |
5504e99c LT |
3100 | Allow @var{command} (a symbol) to be executed without special |
3101 | confirmation from now on, and alter the user's init file (@pxref{Init | |
a40d4712 | 3102 | File}) so that this will apply to future sessions. |
8db970a4 RS |
3103 | @end deffn |
3104 | ||
3105 | @deffn Command disable-command command | |
f142f62a | 3106 | Require special confirmation to execute @var{command} from now on, and |
5504e99c | 3107 | alter the user's init file so that this will apply to future sessions. |
8db970a4 RS |
3108 | @end deffn |
3109 | ||
de700726 LT |
3110 | @defvar disabled-command-function |
3111 | The value of this variable should be a function. When the user | |
3112 | invokes a disabled command interactively, this function is called | |
3113 | instead of the disabled command. It can use @code{this-command-keys} | |
3114 | to determine what the user typed to run the command, and thus find the | |
3115 | command itself. | |
8db970a4 | 3116 | |
de700726 LT |
3117 | The value may also be @code{nil}. Then all commands work normally, |
3118 | even disabled ones. | |
3119 | ||
3120 | By default, the value is a function that asks the user whether to | |
3121 | proceed. | |
8db970a4 RS |
3122 | @end defvar |
3123 | ||
3124 | @node Command History | |
3125 | @section Command History | |
3126 | @cindex command history | |
3127 | @cindex complex command | |
3128 | @cindex history of commands | |
3129 | ||
3130 | The command loop keeps a history of the complex commands that have | |
3131 | been executed, to make it convenient to repeat these commands. A | |
3132 | @dfn{complex command} is one for which the interactive argument reading | |
3133 | uses the minibuffer. This includes any @kbd{M-x} command, any | |
bfe721d1 | 3134 | @kbd{M-:} command, and any command whose @code{interactive} |
8db970a4 RS |
3135 | specification reads an argument from the minibuffer. Explicit use of |
3136 | the minibuffer during the execution of the command itself does not cause | |
3137 | the command to be considered complex. | |
3138 | ||
3139 | @defvar command-history | |
3140 | This variable's value is a list of recent complex commands, each | |
3141 | represented as a form to evaluate. It continues to accumulate all | |
a9f0a989 | 3142 | complex commands for the duration of the editing session, but when it |
b18531e5 RS |
3143 | reaches the maximum size (@pxref{Minibuffer History}), the oldest |
3144 | elements are deleted as new ones are added. | |
8db970a4 RS |
3145 | |
3146 | @example | |
3147 | @group | |
3148 | command-history | |
3149 | @result{} ((switch-to-buffer "chistory.texi") | |
3150 | (describe-key "^X^[") | |
3151 | (visit-tags-table "~/emacs/src/") | |
3152 | (find-tag "repeat-complex-command")) | |
3153 | @end group | |
3154 | @end example | |
3155 | @end defvar | |
3156 | ||
3157 | This history list is actually a special case of minibuffer history | |
3158 | (@pxref{Minibuffer History}), with one special twist: the elements are | |
3159 | expressions rather than strings. | |
3160 | ||
3161 | There are a number of commands devoted to the editing and recall of | |
3162 | previous commands. The commands @code{repeat-complex-command}, and | |
3163 | @code{list-command-history} are described in the user manual | |
3164 | (@pxref{Repetition,,, emacs, The GNU Emacs Manual}). Within the | |
f9f59935 | 3165 | minibuffer, the usual minibuffer history commands are available. |
8db970a4 RS |
3166 | |
3167 | @node Keyboard Macros | |
3168 | @section Keyboard Macros | |
3169 | @cindex keyboard macros | |
3170 | ||
3171 | A @dfn{keyboard macro} is a canned sequence of input events that can | |
f142f62a RS |
3172 | be considered a command and made the definition of a key. The Lisp |
3173 | representation of a keyboard macro is a string or vector containing the | |
3174 | events. Don't confuse keyboard macros with Lisp macros | |
3175 | (@pxref{Macros}). | |
8db970a4 | 3176 | |
5504e99c | 3177 | @defun execute-kbd-macro kbdmacro &optional count loopfunc |
f9f59935 RS |
3178 | This function executes @var{kbdmacro} as a sequence of events. If |
3179 | @var{kbdmacro} is a string or vector, then the events in it are executed | |
8db970a4 RS |
3180 | exactly as if they had been input by the user. The sequence is |
3181 | @emph{not} expected to be a single key sequence; normally a keyboard | |
3182 | macro definition consists of several key sequences concatenated. | |
3183 | ||
f9f59935 RS |
3184 | If @var{kbdmacro} is a symbol, then its function definition is used in |
3185 | place of @var{kbdmacro}. If that is another symbol, this process repeats. | |
8db970a4 RS |
3186 | Eventually the result should be a string or vector. If the result is |
3187 | not a symbol, string, or vector, an error is signaled. | |
3188 | ||
f9f59935 RS |
3189 | The argument @var{count} is a repeat count; @var{kbdmacro} is executed that |
3190 | many times. If @var{count} is omitted or @code{nil}, @var{kbdmacro} is | |
3191 | executed once. If it is 0, @var{kbdmacro} is executed over and over until it | |
177c0ea7 | 3192 | encounters an error or a failing search. |
f9f59935 | 3193 | |
5504e99c LT |
3194 | If @var{loopfunc} is non-@code{nil}, it is a function that is called, |
3195 | without arguments, prior to each iteration of the macro. If | |
3196 | @var{loopfunc} returns @code{nil}, then this stops execution of the macro. | |
3197 | ||
f9f59935 | 3198 | @xref{Reading One Event}, for an example of using @code{execute-kbd-macro}. |
8db970a4 RS |
3199 | @end defun |
3200 | ||
5504e99c | 3201 | @defvar executing-kbd-macro |
8db970a4 RS |
3202 | This variable contains the string or vector that defines the keyboard |
3203 | macro that is currently executing. It is @code{nil} if no macro is | |
f9f59935 | 3204 | currently executing. A command can test this variable so as to behave |
f142f62a RS |
3205 | differently when run from an executing macro. Do not set this variable |
3206 | yourself. | |
8db970a4 RS |
3207 | @end defvar |
3208 | ||
3209 | @defvar defining-kbd-macro | |
5504e99c LT |
3210 | This variable is non-@code{nil} if and only if a keyboard macro is |
3211 | being defined. A command can test this variable so as to behave | |
f9597b5b LT |
3212 | differently while a macro is being defined. The value is |
3213 | @code{append} while appending to the definition of an existing macro. | |
3214 | The commands @code{start-kbd-macro}, @code{kmacro-start-macro} and | |
3215 | @code{end-kbd-macro} set this variable---do not set it yourself. | |
22697dac | 3216 | |
bfe721d1 KH |
3217 | The variable is always local to the current terminal and cannot be |
3218 | buffer-local. @xref{Multiple Displays}. | |
3219 | @end defvar | |
3220 | ||
3221 | @defvar last-kbd-macro | |
3222 | This variable is the definition of the most recently defined keyboard | |
3223 | macro. Its value is a string or vector, or @code{nil}. | |
3224 | ||
3225 | The variable is always local to the current terminal and cannot be | |
22697dac | 3226 | buffer-local. @xref{Multiple Displays}. |
8db970a4 RS |
3227 | @end defvar |
3228 | ||
2842de30 EZ |
3229 | @defvar kbd-macro-termination-hook |
3230 | This normal hook (@pxref{Standard Hooks}) is run when a keyboard | |
3231 | macro terminates, regardless of what caused it to terminate (reaching | |
3232 | the macro end or an error which ended the macro prematurely). | |
3233 | @end defvar | |
ab5796a9 MB |
3234 | |
3235 | @ignore | |
3236 | arch-tag: e34944ad-7d5c-4980-be00-36a5fe54d4b1 | |
3237 | @end ignore |