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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}) |
df36a07e RS |
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 | |
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236 | @end itemize |
237 | ||
caae20c7 | 238 | @cindex examining the @code{interactive} form |
2842de30 | 239 | @defun interactive-form function |
5504e99c LT |
240 | This function returns the @code{interactive} form of @var{function}. |
241 | If @var{function} is an interactively callable function | |
242 | (@pxref{Interactive Call}), the value is the command's | |
243 | @code{interactive} form @code{(interactive @var{spec})}, which | |
244 | specifies how to compute its arguments. Otherwise, the value is | |
245 | @code{nil}. If @var{function} is a symbol, its function definition is | |
246 | used. | |
2842de30 EZ |
247 | @end defun |
248 | ||
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249 | @node Interactive Codes |
250 | @comment node-name, next, previous, up | |
251 | @subsection Code Characters for @code{interactive} | |
252 | @cindex interactive code description | |
253 | @cindex description for interactive codes | |
254 | @cindex codes, interactive, description of | |
255 | @cindex characters for interactive codes | |
256 | ||
257 | The code character descriptions below contain a number of key words, | |
258 | defined here as follows: | |
259 | ||
260 | @table @b | |
261 | @item Completion | |
262 | @cindex interactive completion | |
263 | Provide completion. @key{TAB}, @key{SPC}, and @key{RET} perform name | |
264 | completion because the argument is read using @code{completing-read} | |
265 | (@pxref{Completion}). @kbd{?} displays a list of possible completions. | |
266 | ||
267 | @item Existing | |
268 | Require the name of an existing object. An invalid name is not | |
269 | accepted; the commands to exit the minibuffer do not exit if the current | |
270 | input is not valid. | |
271 | ||
272 | @item Default | |
273 | @cindex default argument string | |
274 | A default value of some sort is used if the user enters no text in the | |
275 | minibuffer. The default depends on the code character. | |
276 | ||
277 | @item No I/O | |
278 | This code letter computes an argument without reading any input. | |
279 | Therefore, it does not use a prompt string, and any prompt string you | |
280 | supply is ignored. | |
281 | ||
f142f62a RS |
282 | Even though the code letter doesn't use a prompt string, you must follow |
283 | it with a newline if it is not the last code character in the string. | |
284 | ||
8db970a4 RS |
285 | @item Prompt |
286 | A prompt immediately follows the code character. The prompt ends either | |
287 | with the end of the string or with a newline. | |
288 | ||
289 | @item Special | |
290 | This code character is meaningful only at the beginning of the | |
291 | interactive string, and it does not look for a prompt or a newline. | |
292 | It is a single, isolated character. | |
293 | @end table | |
294 | ||
295 | @cindex reading interactive arguments | |
296 | Here are the code character descriptions for use with @code{interactive}: | |
297 | ||
298 | @table @samp | |
299 | @item * | |
300 | Signal an error if the current buffer is read-only. Special. | |
301 | ||
302 | @item @@ | |
303 | Select the window mentioned in the first mouse event in the key | |
304 | sequence that invoked this command. Special. | |
305 | ||
306 | @item a | |
b22f3a19 | 307 | A function name (i.e., a symbol satisfying @code{fboundp}). Existing, |
8db970a4 RS |
308 | Completion, Prompt. |
309 | ||
310 | @item b | |
311 | The name of an existing buffer. By default, uses the name of the | |
312 | current buffer (@pxref{Buffers}). Existing, Completion, Default, | |
313 | Prompt. | |
314 | ||
315 | @item B | |
316 | A buffer name. The buffer need not exist. By default, uses the name of | |
317 | a recently used buffer other than the current buffer. Completion, | |
b22f3a19 | 318 | Default, Prompt. |
8db970a4 RS |
319 | |
320 | @item c | |
321 | A character. The cursor does not move into the echo area. Prompt. | |
322 | ||
323 | @item C | |
324 | A command name (i.e., a symbol satisfying @code{commandp}). Existing, | |
325 | Completion, Prompt. | |
326 | ||
327 | @item d | |
328 | @cindex position argument | |
f142f62a | 329 | The position of point, as an integer (@pxref{Point}). No I/O. |
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330 | |
331 | @item D | |
332 | A directory name. The default is the current default directory of the | |
e35e07df | 333 | current buffer, @code{default-directory} (@pxref{File Name Expansion}). |
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334 | Existing, Completion, Default, Prompt. |
335 | ||
336 | @item e | |
337 | The first or next mouse event in the key sequence that invoked the command. | |
b22f3a19 | 338 | More precisely, @samp{e} gets events that are lists, so you can look at |
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339 | the data in the lists. @xref{Input Events}. No I/O. |
340 | ||
341 | You can use @samp{e} more than once in a single command's interactive | |
b22f3a19 | 342 | specification. If the key sequence that invoked the command has |
f142f62a | 343 | @var{n} events that are lists, the @var{n}th @samp{e} provides the |
b22f3a19 | 344 | @var{n}th such event. Events that are not lists, such as function keys |
ad800164 | 345 | and @acronym{ASCII} characters, do not count where @samp{e} is concerned. |
8db970a4 | 346 | |
8db970a4 RS |
347 | @item f |
348 | A file name of an existing file (@pxref{File Names}). The default | |
349 | directory is @code{default-directory}. Existing, Completion, Default, | |
350 | Prompt. | |
351 | ||
352 | @item F | |
353 | A file name. The file need not exist. Completion, Default, Prompt. | |
354 | ||
9644814c RS |
355 | @item G |
356 | A file name. The file need not exist. If the user enters just a | |
357 | directory name, then the value is just that directory name, with no | |
358 | file name within the directory added. Completion, Default, Prompt. | |
359 | ||
a9f0a989 RS |
360 | @item i |
361 | An irrelevant argument. This code always supplies @code{nil} as | |
362 | the argument's value. No I/O. | |
363 | ||
8db970a4 | 364 | @item k |
08244b81 | 365 | A key sequence (@pxref{Key Sequences}). This keeps reading events |
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366 | until a command (or undefined command) is found in the current key |
367 | maps. The key sequence argument is represented as a string or vector. | |
368 | The cursor does not move into the echo area. Prompt. | |
369 | ||
053bc8e4 RS |
370 | If @samp{k} reads a key sequence that ends with a down-event, it also |
371 | reads and discards the following up-event. You can get access to that | |
372 | up-event with the @samp{U} code character. | |
3baa952d | 373 | |
8db970a4 RS |
374 | This kind of input is used by commands such as @code{describe-key} and |
375 | @code{global-set-key}. | |
376 | ||
22697dac KH |
377 | @item K |
378 | A key sequence, whose definition you intend to change. This works like | |
379 | @samp{k}, except that it suppresses, for the last input event in the key | |
380 | sequence, the conversions that are normally used (when necessary) to | |
381 | convert an undefined key into a defined one. | |
382 | ||
8db970a4 RS |
383 | @item m |
384 | @cindex marker argument | |
f142f62a | 385 | The position of the mark, as an integer. No I/O. |
8db970a4 | 386 | |
f9f59935 RS |
387 | @item M |
388 | Arbitrary text, read in the minibuffer using the current buffer's input | |
389 | method, and returned as a string (@pxref{Input Methods,,, emacs, The GNU | |
390 | Emacs Manual}). Prompt. | |
391 | ||
8db970a4 | 392 | @item n |
dff3f9e1 RS |
393 | A number, read with the minibuffer. If the input is not a number, the |
394 | user has to try again. @samp{n} never uses the prefix argument. | |
8db970a4 RS |
395 | Prompt. |
396 | ||
397 | @item N | |
dff3f9e1 RS |
398 | The numeric prefix argument; but if there is no prefix argument, read |
399 | a number as with @kbd{n}. The value is always a number. @xref{Prefix | |
400 | Command Arguments}. Prompt. | |
8db970a4 RS |
401 | |
402 | @item p | |
403 | @cindex numeric prefix argument usage | |
404 | The numeric prefix argument. (Note that this @samp{p} is lower case.) | |
b22f3a19 | 405 | No I/O. |
8db970a4 RS |
406 | |
407 | @item P | |
dff3f9e1 | 408 | @cindex raw prefix argument usage |
b22f3a19 RS |
409 | The raw prefix argument. (Note that this @samp{P} is upper case.) No |
410 | I/O. | |
8db970a4 RS |
411 | |
412 | @item r | |
413 | @cindex region argument | |
414 | Point and the mark, as two numeric arguments, smallest first. This is | |
415 | the only code letter that specifies two successive arguments rather than | |
416 | one. No I/O. | |
417 | ||
418 | @item s | |
419 | Arbitrary text, read in the minibuffer and returned as a string | |
420 | (@pxref{Text from Minibuffer}). Terminate the input with either | |
969fe9b5 | 421 | @kbd{C-j} or @key{RET}. (@kbd{C-q} may be used to include either of |
8db970a4 RS |
422 | these characters in the input.) Prompt. |
423 | ||
424 | @item S | |
425 | An interned symbol whose name is read in the minibuffer. Any whitespace | |
426 | character terminates the input. (Use @kbd{C-q} to include whitespace in | |
427 | the string.) Other characters that normally terminate a symbol (e.g., | |
428 | parentheses and brackets) do not do so here. Prompt. | |
429 | ||
3baa952d | 430 | @item U |
053bc8e4 RS |
431 | A key sequence or @code{nil}. Can be used after a @samp{k} or |
432 | @samp{K} argument to get the up-event that was discarded (if any) | |
433 | after @samp{k} or @samp{K} read a down-event. If no up-event has been | |
434 | discarded, @samp{U} provides @code{nil} as the argument. No I/O. | |
3baa952d | 435 | |
8db970a4 | 436 | @item v |
5504e99c LT |
437 | A variable declared to be a user option (i.e., satisfying the |
438 | predicate @code{user-variable-p}). This reads the variable using | |
439 | @code{read-variable}. @xref{Definition of read-variable}. Existing, | |
8db970a4 RS |
440 | Completion, Prompt. |
441 | ||
442 | @item x | |
b22f3a19 | 443 | A Lisp object, specified with its read syntax, terminated with a |
969fe9b5 | 444 | @kbd{C-j} or @key{RET}. The object is not evaluated. @xref{Object from |
8db970a4 RS |
445 | Minibuffer}. Prompt. |
446 | ||
447 | @item X | |
448 | @cindex evaluated expression argument | |
053bc8e4 RS |
449 | A Lisp form's value. @samp{X} reads as @samp{x} does, then evaluates |
450 | the form so that its value becomes the argument for the command. | |
451 | Prompt. | |
a9f0a989 RS |
452 | |
453 | @item z | |
454 | A coding system name (a symbol). If the user enters null input, the | |
455 | argument value is @code{nil}. @xref{Coding Systems}. Completion, | |
456 | Existing, Prompt. | |
457 | ||
458 | @item Z | |
459 | A coding system name (a symbol)---but only if this command has a prefix | |
460 | argument. With no prefix argument, @samp{Z} provides @code{nil} as the | |
461 | argument value. Completion, Existing, Prompt. | |
8db970a4 RS |
462 | @end table |
463 | ||
464 | @node Interactive Examples | |
465 | @comment node-name, next, previous, up | |
466 | @subsection Examples of Using @code{interactive} | |
467 | @cindex examples of using @code{interactive} | |
177c0ea7 | 468 | @cindex @code{interactive}, examples of using |
8db970a4 RS |
469 | |
470 | Here are some examples of @code{interactive}: | |
471 | ||
472 | @example | |
473 | @group | |
474 | (defun foo1 () ; @r{@code{foo1} takes no arguments,} | |
475 | (interactive) ; @r{just moves forward two words.} | |
476 | (forward-word 2)) | |
477 | @result{} foo1 | |
478 | @end group | |
479 | ||
480 | @group | |
481 | (defun foo2 (n) ; @r{@code{foo2} takes one argument,} | |
482 | (interactive "p") ; @r{which is the numeric prefix.} | |
483 | (forward-word (* 2 n))) | |
484 | @result{} foo2 | |
485 | @end group | |
486 | ||
487 | @group | |
488 | (defun foo3 (n) ; @r{@code{foo3} takes one argument,} | |
489 | (interactive "nCount:") ; @r{which is read with the Minibuffer.} | |
490 | (forward-word (* 2 n))) | |
491 | @result{} foo3 | |
492 | @end group | |
493 | ||
494 | @group | |
495 | (defun three-b (b1 b2 b3) | |
496 | "Select three existing buffers. | |
497 | Put them into three windows, selecting the last one." | |
498 | @end group | |
499 | (interactive "bBuffer1:\nbBuffer2:\nbBuffer3:") | |
500 | (delete-other-windows) | |
501 | (split-window (selected-window) 8) | |
502 | (switch-to-buffer b1) | |
503 | (other-window 1) | |
504 | (split-window (selected-window) 8) | |
505 | (switch-to-buffer b2) | |
506 | (other-window 1) | |
507 | (switch-to-buffer b3)) | |
508 | @result{} three-b | |
509 | @group | |
510 | (three-b "*scratch*" "declarations.texi" "*mail*") | |
511 | @result{} nil | |
512 | @end group | |
513 | @end example | |
514 | ||
515 | @node Interactive Call | |
516 | @section Interactive Call | |
517 | @cindex interactive call | |
518 | ||
f9f59935 RS |
519 | After the command loop has translated a key sequence into a command it |
520 | invokes that command using the function @code{command-execute}. If the | |
521 | command is a function, @code{command-execute} calls | |
522 | @code{call-interactively}, which reads the arguments and calls the | |
523 | command. You can also call these functions yourself. | |
8db970a4 | 524 | |
041b0e7b | 525 | @defun commandp object &optional for-call-interactively |
8db970a4 | 526 | Returns @code{t} if @var{object} is suitable for calling interactively; |
177c0ea7 | 527 | that is, if @var{object} is a command. Otherwise, returns @code{nil}. |
8db970a4 RS |
528 | |
529 | The interactively callable objects include strings and vectors (treated | |
530 | as keyboard macros), lambda expressions that contain a top-level call to | |
bfe721d1 | 531 | @code{interactive}, byte-code function objects made from such lambda |
f142f62a RS |
532 | expressions, autoload objects that are declared as interactive |
533 | (non-@code{nil} fourth argument to @code{autoload}), and some of the | |
534 | primitive functions. | |
8db970a4 | 535 | |
041b0e7b RS |
536 | A symbol satisfies @code{commandp} if its function definition |
537 | satisfies @code{commandp}. Keys and keymaps are not commands. | |
538 | Rather, they are used to look up commands (@pxref{Keymaps}). | |
8db970a4 | 539 | |
041b0e7b RS |
540 | If @var{for-call-interactively} is non-@code{nil}, then |
541 | @code{commandp} returns @code{t} only for objects that | |
542 | @code{call-interactively} could call---thus, not for keyboard macros. | |
8db970a4 RS |
543 | |
544 | See @code{documentation} in @ref{Accessing Documentation}, for a | |
545 | realistic example of using @code{commandp}. | |
546 | @end defun | |
547 | ||
f9f59935 | 548 | @defun call-interactively command &optional record-flag keys |
8db970a4 RS |
549 | This function calls the interactively callable function @var{command}, |
550 | reading arguments according to its interactive calling specifications. | |
5504e99c LT |
551 | It returns whatever @var{command} returns. An error is signaled if |
552 | @var{command} is not a function or if it cannot be called | |
553 | interactively (i.e., is not a command). Note that keyboard macros | |
554 | (strings and vectors) are not accepted, even though they are | |
555 | considered commands, because they are not functions. If @var{command} | |
556 | is a symbol, then @code{call-interactively} uses its function definition. | |
8db970a4 RS |
557 | |
558 | @cindex record command history | |
559 | If @var{record-flag} is non-@code{nil}, then this command and its | |
560 | arguments are unconditionally added to the list @code{command-history}. | |
561 | Otherwise, the command is added only if it uses the minibuffer to read | |
562 | an argument. @xref{Command History}. | |
f9f59935 RS |
563 | |
564 | The argument @var{keys}, if given, specifies the sequence of events to | |
969fe9b5 | 565 | supply if the command inquires which events were used to invoke it. |
5504e99c LT |
566 | If @var{keys} is omitted or @code{nil}, the return value of |
567 | @code{this-command-keys} is used. @xref{Definition of this-command-keys}. | |
8db970a4 RS |
568 | @end defun |
569 | ||
79ddc9c9 | 570 | @defun command-execute command &optional record-flag keys special |
8db970a4 | 571 | @cindex keyboard macro execution |
f9f59935 RS |
572 | This function executes @var{command}. The argument @var{command} must |
573 | satisfy the @code{commandp} predicate; i.e., it must be an interactively | |
574 | callable function or a keyboard macro. | |
8db970a4 RS |
575 | |
576 | A string or vector as @var{command} is executed with | |
577 | @code{execute-kbd-macro}. A function is passed to | |
5504e99c LT |
578 | @code{call-interactively}, along with the optional @var{record-flag} |
579 | and @var{keys}. | |
8db970a4 RS |
580 | |
581 | A symbol is handled by using its function definition in its place. A | |
582 | symbol with an @code{autoload} definition counts as a command if it was | |
583 | declared to stand for an interactively callable function. Such a | |
584 | definition is handled by loading the specified library and then | |
585 | rechecking the definition of the symbol. | |
f9f59935 | 586 | |
79ddc9c9 GM |
587 | The argument @var{special}, if given, means to ignore the prefix |
588 | argument and not clear it. This is used for executing special events | |
589 | (@pxref{Special Events}). | |
8db970a4 RS |
590 | @end defun |
591 | ||
592 | @deffn Command execute-extended-command prefix-argument | |
593 | @cindex read command name | |
594 | This function reads a command name from the minibuffer using | |
595 | @code{completing-read} (@pxref{Completion}). Then it uses | |
596 | @code{command-execute} to call the specified command. Whatever that | |
597 | command returns becomes the value of @code{execute-extended-command}. | |
598 | ||
599 | @cindex execute with prefix argument | |
f142f62a RS |
600 | If the command asks for a prefix argument, it receives the value |
601 | @var{prefix-argument}. If @code{execute-extended-command} is called | |
602 | interactively, the current raw prefix argument is used for | |
8db970a4 RS |
603 | @var{prefix-argument}, and thus passed on to whatever command is run. |
604 | ||
605 | @c !!! Should this be @kindex? | |
606 | @cindex @kbd{M-x} | |
607 | @code{execute-extended-command} is the normal definition of @kbd{M-x}, | |
608 | so it uses the string @w{@samp{M-x }} as a prompt. (It would be better | |
609 | to take the prompt from the events used to invoke | |
610 | @code{execute-extended-command}, but that is painful to implement.) A | |
611 | description of the value of the prefix argument, if any, also becomes | |
612 | part of the prompt. | |
613 | ||
614 | @example | |
615 | @group | |
616 | (execute-extended-command 1) | |
617 | ---------- Buffer: Minibuffer ---------- | |
b22f3a19 | 618 | 1 M-x forward-word RET |
8db970a4 RS |
619 | ---------- Buffer: Minibuffer ---------- |
620 | @result{} t | |
621 | @end group | |
622 | @end example | |
623 | @end deffn | |
624 | ||
625 | @defun interactive-p | |
dff3f9e1 RS |
626 | This function returns @code{t} if the containing function (the one |
627 | whose code includes the call to @code{interactive-p}) was called in | |
628 | direct response to user input. This means that it was called with the | |
629 | function @code{call-interactively}, and that a keyboard macro is | |
9d0d1070 | 630 | not running, and that Emacs is not running in batch mode. |
dff3f9e1 RS |
631 | |
632 | If the containing function was called by Lisp evaluation (or with | |
633 | @code{apply} or @code{funcall}), then it was not called interactively. | |
969fe9b5 | 634 | @end defun |
8db970a4 | 635 | |
dff3f9e1 RS |
636 | The most common use of @code{interactive-p} is for deciding whether |
637 | to give the user additional visual feedback (such as by printing an | |
638 | informative message). For example: | |
8db970a4 RS |
639 | |
640 | @example | |
641 | @group | |
dff3f9e1 | 642 | ;; @r{Here's the usual way to use @code{interactive-p}.} |
8db970a4 RS |
643 | (defun foo () |
644 | (interactive) | |
969fe9b5 RS |
645 | (when (interactive-p) |
646 | (message "foo"))) | |
8db970a4 RS |
647 | @result{} foo |
648 | @end group | |
649 | ||
650 | @group | |
dff3f9e1 | 651 | ;; @r{This function is just to illustrate the behavior.} |
8db970a4 RS |
652 | (defun bar () |
653 | (interactive) | |
654 | (setq foobar (list (foo) (interactive-p)))) | |
655 | @result{} bar | |
656 | @end group | |
657 | ||
658 | @group | |
659 | ;; @r{Type @kbd{M-x foo}.} | |
660 | @print{} foo | |
661 | @end group | |
662 | ||
663 | @group | |
664 | ;; @r{Type @kbd{M-x bar}.} | |
dff3f9e1 | 665 | ;; @r{This does not display a message.} |
8db970a4 RS |
666 | @end group |
667 | ||
668 | @group | |
669 | foobar | |
670 | @result{} (nil t) | |
671 | @end group | |
672 | @end example | |
969fe9b5 | 673 | |
dff3f9e1 RS |
674 | If you want to test @emph{only} whether the function was called |
675 | using @code{call-interactively}, add an optional argument | |
676 | @code{print-message} which should be non-@code{nil} in an interactive | |
677 | call, and use the @code{interactive} spec to make sure it is | |
678 | non-@code{nil}. Here's an example: | |
969fe9b5 RS |
679 | |
680 | @example | |
681 | (defun foo (&optional print-message) | |
682 | (interactive "p") | |
683 | (when print-message | |
684 | (message "foo"))) | |
685 | @end example | |
686 | ||
8e5f9510 | 687 | @noindent |
dff3f9e1 RS |
688 | Defined in this way, the function does display the message when called |
689 | from a keyboard macro. We use @code{"p"} because the numeric prefix | |
690 | argument is never @code{nil}. | |
8db970a4 | 691 | |
9d0d1070 RS |
692 | @defun called-interactively-p |
693 | This function returns @code{t} when the calling function was called | |
694 | using @code{call-interactively}. | |
695 | ||
696 | When possible, instead of using this function, you should use the | |
697 | method in the example above; that method makes it possible for a | |
698 | caller to ``pretend'' that the function was called interactively. | |
699 | @end defun | |
700 | ||
8db970a4 RS |
701 | @node Command Loop Info |
702 | @comment node-name, next, previous, up | |
703 | @section Information from the Command Loop | |
704 | ||
705 | The editor command loop sets several Lisp variables to keep status | |
177c0ea7 | 706 | records for itself and for commands that are run. |
8db970a4 RS |
707 | |
708 | @defvar last-command | |
709 | This variable records the name of the previous command executed by the | |
710 | command loop (the one before the current command). Normally the value | |
711 | is a symbol with a function definition, but this is not guaranteed. | |
712 | ||
f142f62a | 713 | The value is copied from @code{this-command} when a command returns to |
f9f59935 RS |
714 | the command loop, except when the command has specified a prefix |
715 | argument for the following command. | |
bfe721d1 KH |
716 | |
717 | This variable is always local to the current terminal and cannot be | |
718 | buffer-local. @xref{Multiple Displays}. | |
8db970a4 RS |
719 | @end defvar |
720 | ||
03c6b7f6 RS |
721 | @defvar real-last-command |
722 | This variable is set up by Emacs just like @code{last-command}, | |
723 | but never altered by Lisp programs. | |
724 | @end defvar | |
725 | ||
8db970a4 RS |
726 | @defvar this-command |
727 | @cindex current command | |
728 | This variable records the name of the command now being executed by | |
729 | the editor command loop. Like @code{last-command}, it is normally a symbol | |
730 | with a function definition. | |
731 | ||
f142f62a RS |
732 | The command loop sets this variable just before running a command, and |
733 | copies its value into @code{last-command} when the command finishes | |
f9f59935 | 734 | (unless the command specified a prefix argument for the following |
f142f62a | 735 | command). |
8db970a4 RS |
736 | |
737 | @cindex kill command repetition | |
f142f62a | 738 | Some commands set this variable during their execution, as a flag for |
bfe721d1 | 739 | whatever command runs next. In particular, the functions for killing text |
f142f62a RS |
740 | set @code{this-command} to @code{kill-region} so that any kill commands |
741 | immediately following will know to append the killed text to the | |
742 | previous kill. | |
8db970a4 RS |
743 | @end defvar |
744 | ||
745 | If you do not want a particular command to be recognized as the previous | |
746 | command in the case where it got an error, you must code that command to | |
747 | prevent this. One way is to set @code{this-command} to @code{t} at the | |
748 | beginning of the command, and set @code{this-command} back to its proper | |
749 | value at the end, like this: | |
750 | ||
751 | @example | |
752 | (defun foo (args@dots{}) | |
753 | (interactive @dots{}) | |
754 | (let ((old-this-command this-command)) | |
755 | (setq this-command t) | |
756 | @r{@dots{}do the work@dots{}} | |
757 | (setq this-command old-this-command))) | |
758 | @end example | |
759 | ||
f9f59935 RS |
760 | @noindent |
761 | We do not bind @code{this-command} with @code{let} because that would | |
762 | restore the old value in case of error---a feature of @code{let} which | |
763 | in this case does precisely what we want to avoid. | |
764 | ||
041b0e7b RS |
765 | @defvar this-original-command |
766 | This has the same value as @code{this-command} except when command | |
767 | remapping occurs (@pxref{Remapping Commands}). In that case, | |
768 | @code{this-command} gives the command actually run (the result of | |
769 | remapping), and @code{this-original-command} gives the command that | |
770 | was specified to run but remapped into another command. | |
771 | @end defvar | |
772 | ||
8db970a4 | 773 | @defun this-command-keys |
5504e99c | 774 | @anchor{Definition of this-command-keys} |
8db970a4 RS |
775 | This function returns a string or vector containing the key sequence |
776 | that invoked the present command, plus any previous commands that | |
5504e99c LT |
777 | generated the prefix argument for this command. However, if the |
778 | command has called @code{read-key-sequence}, it returns the last read | |
de700726 LT |
779 | key sequence. @xref{Key Sequence Input}. The value is a string if |
780 | all events in the sequence were characters that fit in a string. | |
781 | @xref{Input Events}. | |
8db970a4 RS |
782 | |
783 | @example | |
784 | @group | |
785 | (this-command-keys) | |
b22f3a19 | 786 | ;; @r{Now use @kbd{C-u C-x C-e} to evaluate that.} |
8db970a4 RS |
787 | @result{} "^U^X^E" |
788 | @end group | |
789 | @end example | |
790 | @end defun | |
791 | ||
969fe9b5 | 792 | @defun this-command-keys-vector |
2468d0c0 DL |
793 | Like @code{this-command-keys}, except that it always returns the events |
794 | in a vector, so you don't need to deal with the complexities of storing | |
795 | input events in a string (@pxref{Strings of Events}). | |
969fe9b5 RS |
796 | @end defun |
797 | ||
b6954afd | 798 | @tindex clear-this-command-keys |
5504e99c | 799 | @defun clear-this-command-keys &optional keep-record |
b6954afd | 800 | This function empties out the table of events for |
5504e99c LT |
801 | @code{this-command-keys} to return. Unless @var{keep-record} is |
802 | non-@code{nil}, it also empties the records that the function | |
803 | @code{recent-keys} (@pxref{Recording Input}) will subsequently return. | |
804 | This is useful after reading a password, to prevent the password from | |
805 | echoing inadvertently as part of the next command in certain cases. | |
b6954afd RS |
806 | @end defun |
807 | ||
8db970a4 | 808 | @defvar last-nonmenu-event |
969fe9b5 RS |
809 | This variable holds the last input event read as part of a key sequence, |
810 | not counting events resulting from mouse menus. | |
8db970a4 | 811 | |
f9f59935 | 812 | One use of this variable is for telling @code{x-popup-menu} where to pop |
969fe9b5 RS |
813 | up a menu. It is also used internally by @code{y-or-n-p} |
814 | (@pxref{Yes-or-No Queries}). | |
8db970a4 RS |
815 | @end defvar |
816 | ||
817 | @defvar last-command-event | |
818 | @defvarx last-command-char | |
819 | This variable is set to the last input event that was read by the | |
820 | command loop as part of a command. The principal use of this variable | |
821 | is in @code{self-insert-command}, which uses it to decide which | |
822 | character to insert. | |
823 | ||
824 | @example | |
825 | @group | |
f142f62a | 826 | last-command-event |
b22f3a19 | 827 | ;; @r{Now use @kbd{C-u C-x C-e} to evaluate that.} |
8db970a4 RS |
828 | @result{} 5 |
829 | @end group | |
830 | @end example | |
831 | ||
832 | @noindent | |
ad800164 | 833 | The value is 5 because that is the @acronym{ASCII} code for @kbd{C-e}. |
8db970a4 RS |
834 | |
835 | The alias @code{last-command-char} exists for compatibility with | |
836 | Emacs version 18. | |
837 | @end defvar | |
838 | ||
839 | @c Emacs 19 feature | |
840 | @defvar last-event-frame | |
841 | This variable records which frame the last input event was directed to. | |
842 | Usually this is the frame that was selected when the event was | |
843 | generated, but if that frame has redirected input focus to another | |
844 | frame, the value is the frame to which the event was redirected. | |
845 | @xref{Input Focus}. | |
5504e99c LT |
846 | |
847 | If the last event came from a keyboard macro, the value is @code{macro}. | |
8db970a4 RS |
848 | @end defvar |
849 | ||
2468d0c0 DL |
850 | @node Adjusting Point |
851 | @section Adjusting Point After Commands | |
852 | ||
ecbfc7e9 RS |
853 | It is not easy to display a value of point in the middle of a |
854 | sequence of text that has the @code{display}, @code{composition} or | |
855 | @code{intangible} property, or is invisible. Therefore, after a | |
856 | command finishes and returns to the command loop, if point is within | |
857 | such a sequence, the command loop normally moves point to the edge of | |
858 | the sequence. | |
2468d0c0 DL |
859 | |
860 | A command can inhibit this feature by setting the variable | |
861 | @code{disable-point-adjustment}: | |
862 | ||
863 | @defvar disable-point-adjustment | |
864 | @tindex disable-point-adjustment | |
ecbfc7e9 RS |
865 | If this variable is non-@code{nil} when a command returns to the |
866 | command loop, then the command loop does not check for those text | |
867 | properties, and does not move point out of sequences that have them. | |
2468d0c0 DL |
868 | |
869 | The command loop sets this variable to @code{nil} before each command, | |
870 | so if a command sets it, the effect applies only to that command. | |
871 | @end defvar | |
872 | ||
873 | @defvar global-disable-point-adjustment | |
874 | @tindex global-disable-point-adjustment | |
875 | If you set this variable to a non-@code{nil} value, the feature of | |
876 | moving point out of these sequences is completely turned off. | |
877 | @end defvar | |
878 | ||
8db970a4 RS |
879 | @node Input Events |
880 | @section Input Events | |
881 | @cindex events | |
882 | @cindex input events | |
883 | ||
884 | The Emacs command loop reads a sequence of @dfn{input events} that | |
885 | represent keyboard or mouse activity. The events for keyboard activity | |
886 | are characters or symbols; mouse events are always lists. This section | |
887 | describes the representation and meaning of input events in detail. | |
888 | ||
8db970a4 | 889 | @defun eventp object |
a9f0a989 RS |
890 | This function returns non-@code{nil} if @var{object} is an input event |
891 | or event type. | |
892 | ||
893 | Note that any symbol might be used as an event or an event type. | |
894 | @code{eventp} cannot distinguish whether a symbol is intended by Lisp | |
895 | code to be used as an event. Instead, it distinguishes whether the | |
896 | symbol has actually been used in an event that has been read as input in | |
897 | the current Emacs session. If a symbol has not yet been so used, | |
898 | @code{eventp} returns @code{nil}. | |
8db970a4 RS |
899 | @end defun |
900 | ||
901 | @menu | |
902 | * Keyboard Events:: Ordinary characters--keys with symbols on them. | |
903 | * Function Keys:: Function keys--keys with names, not symbols. | |
f142f62a | 904 | * Mouse Events:: Overview of mouse events. |
8db970a4 RS |
905 | * Click Events:: Pushing and releasing a mouse button. |
906 | * Drag Events:: Moving the mouse before releasing the button. | |
907 | * Button-Down Events:: A button was pushed and not yet released. | |
908 | * Repeat Events:: Double and triple click (or drag, or down). | |
909 | * Motion Events:: Just moving the mouse, not pushing a button. | |
910 | * Focus Events:: Moving the mouse between frames. | |
7790d5cd | 911 | * Misc Events:: Other events the system can generate. |
8db970a4 RS |
912 | * Event Examples:: Examples of the lists for mouse events. |
913 | * Classifying Events:: Finding the modifier keys in an event symbol. | |
914 | Event types. | |
915 | * Accessing Events:: Functions to extract info from events. | |
916 | * Strings of Events:: Special considerations for putting | |
917 | keyboard character events in a string. | |
918 | @end menu | |
919 | ||
920 | @node Keyboard Events | |
921 | @subsection Keyboard Events | |
922 | ||
923 | There are two kinds of input you can get from the keyboard: ordinary | |
924 | keys, and function keys. Ordinary keys correspond to characters; the | |
969fe9b5 RS |
925 | events they generate are represented in Lisp as characters. The event |
926 | type of a character event is the character itself (an integer); see | |
927 | @ref{Classifying Events}. | |
8db970a4 RS |
928 | |
929 | @cindex modifier bits (of input character) | |
930 | @cindex basic code (of input character) | |
931 | An input character event consists of a @dfn{basic code} between 0 and | |
f9f59935 | 932 | 524287, plus any or all of these @dfn{modifier bits}: |
8db970a4 RS |
933 | |
934 | @table @asis | |
935 | @item meta | |
bfe721d1 | 936 | The |
969fe9b5 | 937 | @tex |
8241495d | 938 | @math{2^{27}} |
969fe9b5 | 939 | @end tex |
37680279 | 940 | @ifnottex |
bfe721d1 | 941 | 2**27 |
37680279 | 942 | @end ifnottex |
bfe721d1 | 943 | bit in the character code indicates a character |
8db970a4 RS |
944 | typed with the meta key held down. |
945 | ||
946 | @item control | |
bfe721d1 | 947 | The |
969fe9b5 | 948 | @tex |
8241495d | 949 | @math{2^{26}} |
969fe9b5 | 950 | @end tex |
37680279 | 951 | @ifnottex |
bfe721d1 | 952 | 2**26 |
37680279 | 953 | @end ifnottex |
ad800164 | 954 | bit in the character code indicates a non-@acronym{ASCII} |
8db970a4 RS |
955 | control character. |
956 | ||
8241495d | 957 | @sc{ascii} control characters such as @kbd{C-a} have special basic |
8db970a4 RS |
958 | codes of their own, so Emacs needs no special bit to indicate them. |
959 | Thus, the code for @kbd{C-a} is just 1. | |
960 | ||
ad800164 | 961 | But if you type a control combination not in @acronym{ASCII}, such as |
8db970a4 | 962 | @kbd{%} with the control key, the numeric value you get is the code |
bfe721d1 | 963 | for @kbd{%} plus |
969fe9b5 | 964 | @tex |
8241495d | 965 | @math{2^{26}} |
969fe9b5 | 966 | @end tex |
37680279 | 967 | @ifnottex |
bfe721d1 | 968 | 2**26 |
37680279 | 969 | @end ifnottex |
ad800164 | 970 | (assuming the terminal supports non-@acronym{ASCII} |
8db970a4 RS |
971 | control characters). |
972 | ||
973 | @item shift | |
bfe721d1 | 974 | The |
969fe9b5 | 975 | @tex |
8241495d | 976 | @math{2^{25}} |
969fe9b5 | 977 | @end tex |
37680279 | 978 | @ifnottex |
bfe721d1 | 979 | 2**25 |
37680279 | 980 | @end ifnottex |
ad800164 | 981 | bit in the character code indicates an @acronym{ASCII} control |
8db970a4 RS |
982 | character typed with the shift key held down. |
983 | ||
f9f59935 RS |
984 | For letters, the basic code itself indicates upper versus lower case; |
985 | for digits and punctuation, the shift key selects an entirely different | |
986 | character with a different basic code. In order to keep within the | |
ad800164 | 987 | @acronym{ASCII} character set whenever possible, Emacs avoids using the |
969fe9b5 | 988 | @tex |
8241495d | 989 | @math{2^{25}} |
969fe9b5 | 990 | @end tex |
37680279 | 991 | @ifnottex |
bfe721d1 | 992 | 2**25 |
37680279 | 993 | @end ifnottex |
bfe721d1 | 994 | bit for those characters. |
8db970a4 | 995 | |
ad800164 | 996 | However, @acronym{ASCII} provides no way to distinguish @kbd{C-A} from |
bfe721d1 | 997 | @kbd{C-a}, so Emacs uses the |
969fe9b5 | 998 | @tex |
8241495d | 999 | @math{2^{25}} |
969fe9b5 | 1000 | @end tex |
37680279 | 1001 | @ifnottex |
bfe721d1 | 1002 | 2**25 |
37680279 | 1003 | @end ifnottex |
bfe721d1 | 1004 | bit in @kbd{C-A} and not in |
8db970a4 RS |
1005 | @kbd{C-a}. |
1006 | ||
1007 | @item hyper | |
bfe721d1 | 1008 | The |
969fe9b5 | 1009 | @tex |
8241495d | 1010 | @math{2^{24}} |
969fe9b5 | 1011 | @end tex |
37680279 | 1012 | @ifnottex |
bfe721d1 | 1013 | 2**24 |
37680279 | 1014 | @end ifnottex |
bfe721d1 | 1015 | bit in the character code indicates a character |
8db970a4 RS |
1016 | typed with the hyper key held down. |
1017 | ||
1018 | @item super | |
bfe721d1 | 1019 | The |
969fe9b5 | 1020 | @tex |
8241495d | 1021 | @math{2^{23}} |
969fe9b5 | 1022 | @end tex |
37680279 | 1023 | @ifnottex |
bfe721d1 | 1024 | 2**23 |
37680279 | 1025 | @end ifnottex |
bfe721d1 | 1026 | bit in the character code indicates a character |
8db970a4 RS |
1027 | typed with the super key held down. |
1028 | ||
1029 | @item alt | |
bfe721d1 | 1030 | The |
969fe9b5 | 1031 | @tex |
8241495d | 1032 | @math{2^{22}} |
969fe9b5 | 1033 | @end tex |
37680279 | 1034 | @ifnottex |
bfe721d1 | 1035 | 2**22 |
37680279 | 1036 | @end ifnottex |
bfe721d1 | 1037 | bit in the character code indicates a character typed with |
8db970a4 RS |
1038 | the alt key held down. (On some terminals, the key labeled @key{ALT} |
1039 | is actually the meta key.) | |
1040 | @end table | |
1041 | ||
bfe721d1 KH |
1042 | It is best to avoid mentioning specific bit numbers in your program. |
1043 | To test the modifier bits of a character, use the function | |
1044 | @code{event-modifiers} (@pxref{Classifying Events}). When making key | |
1045 | bindings, you can use the read syntax for characters with modifier bits | |
1046 | (@samp{\C-}, @samp{\M-}, and so on). For making key bindings with | |
1047 | @code{define-key}, you can use lists such as @code{(control hyper ?x)} to | |
1048 | specify the characters (@pxref{Changing Key Bindings}). The function | |
1049 | @code{event-convert-list} converts such a list into an event type | |
1050 | (@pxref{Classifying Events}). | |
8db970a4 RS |
1051 | |
1052 | @node Function Keys | |
1053 | @subsection Function Keys | |
1054 | ||
1055 | @cindex function keys | |
b22f3a19 | 1056 | Most keyboards also have @dfn{function keys}---keys that have names or |
f9f59935 RS |
1057 | symbols that are not characters. Function keys are represented in Emacs |
1058 | Lisp as symbols; the symbol's name is the function key's label, in lower | |
f142f62a RS |
1059 | case. For example, pressing a key labeled @key{F1} places the symbol |
1060 | @code{f1} in the input stream. | |
8db970a4 | 1061 | |
f142f62a RS |
1062 | The event type of a function key event is the event symbol itself. |
1063 | @xref{Classifying Events}. | |
8db970a4 | 1064 | |
b22f3a19 | 1065 | Here are a few special cases in the symbol-naming convention for |
8db970a4 RS |
1066 | function keys: |
1067 | ||
1068 | @table @asis | |
1069 | @item @code{backspace}, @code{tab}, @code{newline}, @code{return}, @code{delete} | |
ad800164 | 1070 | These keys correspond to common @acronym{ASCII} control characters that have |
8db970a4 RS |
1071 | special keys on most keyboards. |
1072 | ||
ad800164 | 1073 | In @acronym{ASCII}, @kbd{C-i} and @key{TAB} are the same character. If the |
f142f62a RS |
1074 | terminal can distinguish between them, Emacs conveys the distinction to |
1075 | Lisp programs by representing the former as the integer 9, and the | |
1076 | latter as the symbol @code{tab}. | |
8db970a4 RS |
1077 | |
1078 | Most of the time, it's not useful to distinguish the two. So normally | |
4324b7ab RS |
1079 | @code{function-key-map} (@pxref{Translating Input}) is set up to map |
1080 | @code{tab} into 9. Thus, a key binding for character code 9 (the | |
1081 | character @kbd{C-i}) also applies to @code{tab}. Likewise for the other | |
1082 | symbols in this group. The function @code{read-char} likewise converts | |
1083 | these events into characters. | |
8db970a4 | 1084 | |
ad800164 | 1085 | In @acronym{ASCII}, @key{BS} is really @kbd{C-h}. But @code{backspace} |
8db970a4 RS |
1086 | converts into the character code 127 (@key{DEL}), not into code 8 |
1087 | (@key{BS}). This is what most users prefer. | |
1088 | ||
b22f3a19 RS |
1089 | @item @code{left}, @code{up}, @code{right}, @code{down} |
1090 | Cursor arrow keys | |
8db970a4 RS |
1091 | @item @code{kp-add}, @code{kp-decimal}, @code{kp-divide}, @dots{} |
1092 | Keypad keys (to the right of the regular keyboard). | |
1093 | @item @code{kp-0}, @code{kp-1}, @dots{} | |
1094 | Keypad keys with digits. | |
1095 | @item @code{kp-f1}, @code{kp-f2}, @code{kp-f3}, @code{kp-f4} | |
1096 | Keypad PF keys. | |
b22f3a19 | 1097 | @item @code{kp-home}, @code{kp-left}, @code{kp-up}, @code{kp-right}, @code{kp-down} |
f9f59935 RS |
1098 | Keypad arrow keys. Emacs normally translates these into the |
1099 | corresponding non-keypad keys @code{home}, @code{left}, @dots{} | |
b22f3a19 RS |
1100 | @item @code{kp-prior}, @code{kp-next}, @code{kp-end}, @code{kp-begin}, @code{kp-insert}, @code{kp-delete} |
1101 | Additional keypad duplicates of keys ordinarily found elsewhere. Emacs | |
1102 | normally translates these into the like-named non-keypad keys. | |
8db970a4 RS |
1103 | @end table |
1104 | ||
b22f3a19 RS |
1105 | You can use the modifier keys @key{ALT}, @key{CTRL}, @key{HYPER}, |
1106 | @key{META}, @key{SHIFT}, and @key{SUPER} with function keys. The way to | |
1107 | represent them is with prefixes in the symbol name: | |
8db970a4 RS |
1108 | |
1109 | @table @samp | |
1110 | @item A- | |
1111 | The alt modifier. | |
1112 | @item C- | |
1113 | The control modifier. | |
1114 | @item H- | |
1115 | The hyper modifier. | |
1116 | @item M- | |
1117 | The meta modifier. | |
1118 | @item S- | |
1119 | The shift modifier. | |
1120 | @item s- | |
1121 | The super modifier. | |
1122 | @end table | |
1123 | ||
1124 | Thus, the symbol for the key @key{F3} with @key{META} held down is | |
8609b2e2 | 1125 | @code{M-f3}. When you use more than one prefix, we recommend you |
f142f62a RS |
1126 | write them in alphabetical order; but the order does not matter in |
1127 | arguments to the key-binding lookup and modification functions. | |
1128 | ||
1129 | @node Mouse Events | |
1130 | @subsection Mouse Events | |
1131 | ||
1132 | Emacs supports four kinds of mouse events: click events, drag events, | |
1133 | button-down events, and motion events. All mouse events are represented | |
4bdcd3ef | 1134 | as lists. The @sc{car} of the list is the event type; this says which |
f142f62a RS |
1135 | mouse button was involved, and which modifier keys were used with it. |
1136 | The event type can also distinguish double or triple button presses | |
1137 | (@pxref{Repeat Events}). The rest of the list elements give position | |
1138 | and time information. | |
1139 | ||
1140 | For key lookup, only the event type matters: two events of the same type | |
1141 | necessarily run the same command. The command can access the full | |
1142 | values of these events using the @samp{e} interactive code. | |
1143 | @xref{Interactive Codes}. | |
1144 | ||
1145 | A key sequence that starts with a mouse event is read using the keymaps | |
1146 | of the buffer in the window that the mouse was in, not the current | |
1147 | buffer. This does not imply that clicking in a window selects that | |
1148 | window or its buffer---that is entirely under the control of the command | |
1149 | binding of the key sequence. | |
8db970a4 RS |
1150 | |
1151 | @node Click Events | |
1152 | @subsection Click Events | |
1153 | @cindex click event | |
1154 | @cindex mouse click event | |
1155 | ||
1156 | When the user presses a mouse button and releases it at the same | |
c5cb5297 KS |
1157 | location, that generates a @dfn{click} event. All mouse click event |
1158 | share the same format: | |
8db970a4 RS |
1159 | |
1160 | @example | |
c5cb5297 | 1161 | (@var{event-type} @var{position} @var{click-count}) |
b19f34c7 GM |
1162 | @end example |
1163 | ||
f142f62a RS |
1164 | @table @asis |
1165 | @item @var{event-type} | |
8db970a4 RS |
1166 | This is a symbol that indicates which mouse button was used. It is |
1167 | one of the symbols @code{mouse-1}, @code{mouse-2}, @dots{}, where the | |
f142f62a | 1168 | buttons are numbered left to right. |
8db970a4 RS |
1169 | |
1170 | You can also use prefixes @samp{A-}, @samp{C-}, @samp{H-}, @samp{M-}, | |
1171 | @samp{S-} and @samp{s-} for modifiers alt, control, hyper, meta, shift | |
1172 | and super, just as you would with function keys. | |
1173 | ||
1174 | This symbol also serves as the event type of the event. Key bindings | |
1175 | describe events by their types; thus, if there is a key binding for | |
1176 | @code{mouse-1}, that binding would apply to all events whose | |
1177 | @var{event-type} is @code{mouse-1}. | |
1178 | ||
c5cb5297 KS |
1179 | @item @var{position} |
1180 | This is the position where the mouse click occurred. The actual | |
1181 | format of @var{position} depends on what part of a window was clicked | |
1182 | on. The various formats are described below. | |
1183 | ||
1184 | @item @var{click-count} | |
1185 | This is the number of rapid repeated presses so far of the same mouse | |
1186 | button. @xref{Repeat Events}. | |
1187 | @end table | |
1188 | ||
1189 | For mouse click events in the text area, mode line, header line, or in | |
1190 | the marginal areas, @var{position} has this form: | |
1191 | ||
1192 | @example | |
f51f93f6 | 1193 | (@var{window} @var{pos-or-area} (@var{x} . @var{y}) @var{timestamp} |
5504e99c | 1194 | @var{object} @var{text-pos} (@var{col} . @var{row}) |
08988329 | 1195 | @var{image} (@var{dx} . @var{dy}) (@var{width} . @var{height})) |
c5cb5297 KS |
1196 | @end example |
1197 | ||
1198 | @table @asis | |
f142f62a | 1199 | @item @var{window} |
8db970a4 RS |
1200 | This is the window in which the click occurred. |
1201 | ||
c5cb5297 KS |
1202 | @item @var{pos-or-area} |
1203 | This is the buffer position of the character clicked on in the text | |
1204 | area, or if clicked outside the text area, it is the window area in | |
1205 | which the click occurred. It is one of the symbols @code{mode-line}, | |
1206 | @code{header-line}, @code{vertical-line}, @code{left-margin}, | |
1207 | @code{right-margin}, @code{left-fringe}, or @code{right-fringe}. | |
1208 | ||
f142f62a | 1209 | @item @var{x}, @var{y} |
b22f3a19 | 1210 | These are the pixel-denominated coordinates of the click, relative to |
07734718 | 1211 | the top left corner of @var{window}, which is @code{(0 . 0)}. |
c5cb5297 KS |
1212 | For the mode or header line, @var{y} does not have meaningful data. |
1213 | For the vertical line, @var{x} does not have meaningful data. | |
8db970a4 | 1214 | |
f142f62a | 1215 | @item @var{timestamp} |
c5cb5297 KS |
1216 | This is the time at which the event occurred, in milliseconds. |
1217 | ||
1218 | @item @var{object} | |
f51f93f6 | 1219 | This is the object on which the click occurred. It is either |
08988329 KS |
1220 | @code{nil} if there is no string property, or it has the form |
1221 | (@var{string} . @var{string-pos}) when there is a string-type text | |
1222 | property at the click position. | |
b19f34c7 GM |
1223 | |
1224 | @item @var{string} | |
1225 | This is the string on which the click occurred, including any | |
07734718 | 1226 | properties. |
b19f34c7 GM |
1227 | |
1228 | @item @var{string-pos} | |
1229 | This is the position in the string on which the click occurred, | |
1230 | relevant if properties at the click need to be looked up. | |
8db970a4 | 1231 | |
c5cb5297 KS |
1232 | @item @var{text-pos} |
1233 | For clicks on a marginal area or on a fringe, this is the buffer | |
1234 | position of the first visible character in the corresponding line in | |
1235 | the window. For other events, it is the current buffer position in | |
1236 | the window. | |
1237 | ||
1238 | @item @var{col}, @var{row} | |
1239 | These are the actual coordinates of the glyph under the @var{x}, | |
1240 | @var{y} position, possibly padded with default character width | |
1241 | glyphs if @var{x} is beyond the last glyph on the line. | |
f51f93f6 | 1242 | |
08988329 KS |
1243 | @item @var{image} |
1244 | This is the image object on which the click occurred. It is either | |
1245 | @code{nil} if there is no image at the position clicked on, or it is | |
1246 | an image object as returned by @code{find-image} if click was in an image. | |
1247 | ||
f51f93f6 KS |
1248 | @item @var{dx}, @var{dy} |
1249 | These are the pixel-denominated coordinates of the click, relative to | |
1250 | the top left corner of @var{object}, which is @code{(0 . 0)}. If | |
1251 | @var{object} is @code{nil}, the coordinates are relative to the top | |
1252 | left corner of the character glyph clicked on. | |
8db970a4 RS |
1253 | @end table |
1254 | ||
c5cb5297 KS |
1255 | For mouse clicks on a scroll-bar, @var{position} has this form: |
1256 | ||
1257 | @example | |
1258 | (@var{window} @var{area} (@var{portion} . @var{whole}) @var{timestamp} @var{part}) | |
1259 | @end example | |
1260 | ||
1261 | @table @asis | |
1262 | @item @var{window} | |
1263 | This is the window whose scroll-bar was clicked on. | |
1264 | ||
1265 | @item @var{area} | |
1266 | This is the scroll bar where the click occurred. It is one of the | |
1267 | symbols @code{vertical-scroll-bar} or @code{horizontal-scroll-bar}. | |
1268 | ||
1269 | @item @var{portion} | |
1270 | This is the distance of the click from the top or left end of | |
1271 | the scroll bar. | |
1272 | ||
1273 | @item @var{whole} | |
1274 | This is the length of the entire scroll bar. | |
1275 | ||
1276 | @item @var{timestamp} | |
1277 | This is the time at which the event occurred, in milliseconds. | |
1278 | ||
1279 | @item @var{part} | |
1280 | This is the part of the scroll-bar which was clicked on. It is one | |
1281 | of the symbols @code{above-handle}, @code{handle}, @code{below-handle}, | |
1282 | @code{up}, @code{down}, @code{top}, @code{bottom}, and @code{end-scroll}. | |
1283 | @end table | |
8db970a4 | 1284 | |
b22f3a19 RS |
1285 | In one special case, @var{buffer-pos} is a list containing a symbol (one |
1286 | of the symbols listed above) instead of just the symbol. This happens | |
1287 | after the imaginary prefix keys for the event are inserted into the | |
1288 | input stream. @xref{Key Sequence Input}. | |
8db970a4 RS |
1289 | |
1290 | @node Drag Events | |
1291 | @subsection Drag Events | |
1292 | @cindex drag event | |
1293 | @cindex mouse drag event | |
1294 | ||
1295 | With Emacs, you can have a drag event without even changing your | |
1296 | clothes. A @dfn{drag event} happens every time the user presses a mouse | |
1297 | button and then moves the mouse to a different character position before | |
1298 | releasing the button. Like all mouse events, drag events are | |
1299 | represented in Lisp as lists. The lists record both the starting mouse | |
1300 | position and the final position, like this: | |
1301 | ||
1302 | @example | |
1303 | (@var{event-type} | |
f142f62a RS |
1304 | (@var{window1} @var{buffer-pos1} (@var{x1} . @var{y1}) @var{timestamp1}) |
1305 | (@var{window2} @var{buffer-pos2} (@var{x2} . @var{y2}) @var{timestamp2}) | |
8db970a4 RS |
1306 | @var{click-count}) |
1307 | @end example | |
1308 | ||
1309 | For a drag event, the name of the symbol @var{event-type} contains the | |
f9f59935 RS |
1310 | prefix @samp{drag-}. For example, dragging the mouse with button 2 held |
1311 | down generates a @code{drag-mouse-2} event. The second and third | |
1312 | elements of the event give the starting and ending position of the drag. | |
1313 | Aside from that, the data have the same meanings as in a click event | |
1314 | (@pxref{Click Events}). You can access the second element of any mouse | |
1315 | event in the same way, with no need to distinguish drag events from | |
1316 | others. | |
8db970a4 RS |
1317 | |
1318 | The @samp{drag-} prefix follows the modifier key prefixes such as | |
1319 | @samp{C-} and @samp{M-}. | |
1320 | ||
b22f3a19 | 1321 | If @code{read-key-sequence} receives a drag event that has no key |
8db970a4 RS |
1322 | binding, and the corresponding click event does have a binding, it |
1323 | changes the drag event into a click event at the drag's starting | |
1324 | position. This means that you don't have to distinguish between click | |
1325 | and drag events unless you want to. | |
1326 | ||
1327 | @node Button-Down Events | |
1328 | @subsection Button-Down Events | |
1329 | @cindex button-down event | |
1330 | ||
1331 | Click and drag events happen when the user releases a mouse button. | |
1332 | They cannot happen earlier, because there is no way to distinguish a | |
1333 | click from a drag until the button is released. | |
1334 | ||
1335 | If you want to take action as soon as a button is pressed, you need to | |
1336 | handle @dfn{button-down} events.@footnote{Button-down is the | |
f142f62a | 1337 | conservative antithesis of drag.} These occur as soon as a button is |
b22f3a19 | 1338 | pressed. They are represented by lists that look exactly like click |
f142f62a RS |
1339 | events (@pxref{Click Events}), except that the @var{event-type} symbol |
1340 | name contains the prefix @samp{down-}. The @samp{down-} prefix follows | |
8db970a4 RS |
1341 | modifier key prefixes such as @samp{C-} and @samp{M-}. |
1342 | ||
969fe9b5 RS |
1343 | The function @code{read-key-sequence} ignores any button-down events |
1344 | that don't have command bindings; therefore, the Emacs command loop | |
1345 | ignores them too. This means that you need not worry about defining | |
1346 | button-down events unless you want them to do something. The usual | |
1347 | reason to define a button-down event is so that you can track mouse | |
1348 | motion (by reading motion events) until the button is released. | |
1349 | @xref{Motion Events}. | |
8db970a4 RS |
1350 | |
1351 | @node Repeat Events | |
1352 | @subsection Repeat Events | |
1353 | @cindex repeat events | |
1354 | @cindex double-click events | |
1355 | @cindex triple-click events | |
2468d0c0 | 1356 | @cindex mouse events, repeated |
8db970a4 RS |
1357 | |
1358 | If you press the same mouse button more than once in quick succession | |
f142f62a RS |
1359 | without moving the mouse, Emacs generates special @dfn{repeat} mouse |
1360 | events for the second and subsequent presses. | |
8db970a4 RS |
1361 | |
1362 | The most common repeat events are @dfn{double-click} events. Emacs | |
1363 | generates a double-click event when you click a button twice; the event | |
1364 | happens when you release the button (as is normal for all click | |
1365 | events). | |
1366 | ||
1367 | The event type of a double-click event contains the prefix | |
f142f62a | 1368 | @samp{double-}. Thus, a double click on the second mouse button with |
8db970a4 RS |
1369 | @key{meta} held down comes to the Lisp program as |
1370 | @code{M-double-mouse-2}. If a double-click event has no binding, the | |
1371 | binding of the corresponding ordinary click event is used to execute | |
177c0ea7 | 1372 | it. Thus, you need not pay attention to the double click feature |
8db970a4 RS |
1373 | unless you really want to. |
1374 | ||
1375 | When the user performs a double click, Emacs generates first an ordinary | |
f142f62a RS |
1376 | click event, and then a double-click event. Therefore, you must design |
1377 | the command binding of the double click event to assume that the | |
8db970a4 RS |
1378 | single-click command has already run. It must produce the desired |
1379 | results of a double click, starting from the results of a single click. | |
1380 | ||
f142f62a RS |
1381 | This is convenient, if the meaning of a double click somehow ``builds |
1382 | on'' the meaning of a single click---which is recommended user interface | |
1383 | design practice for double clicks. | |
8db970a4 RS |
1384 | |
1385 | If you click a button, then press it down again and start moving the | |
1386 | mouse with the button held down, then you get a @dfn{double-drag} event | |
1387 | when you ultimately release the button. Its event type contains | |
1388 | @samp{double-drag} instead of just @samp{drag}. If a double-drag event | |
1389 | has no binding, Emacs looks for an alternate binding as if the event | |
b22f3a19 | 1390 | were an ordinary drag. |
8db970a4 RS |
1391 | |
1392 | Before the double-click or double-drag event, Emacs generates a | |
f142f62a RS |
1393 | @dfn{double-down} event when the user presses the button down for the |
1394 | second time. Its event type contains @samp{double-down} instead of just | |
8db970a4 RS |
1395 | @samp{down}. If a double-down event has no binding, Emacs looks for an |
1396 | alternate binding as if the event were an ordinary button-down event. | |
f142f62a RS |
1397 | If it finds no binding that way either, the double-down event is |
1398 | ignored. | |
8db970a4 RS |
1399 | |
1400 | To summarize, when you click a button and then press it again right | |
b22f3a19 RS |
1401 | away, Emacs generates a down event and a click event for the first |
1402 | click, a double-down event when you press the button again, and finally | |
1403 | either a double-click or a double-drag event. | |
8db970a4 RS |
1404 | |
1405 | If you click a button twice and then press it again, all in quick | |
1406 | succession, Emacs generates a @dfn{triple-down} event, followed by | |
1407 | either a @dfn{triple-click} or a @dfn{triple-drag}. The event types of | |
1408 | these events contain @samp{triple} instead of @samp{double}. If any | |
1409 | triple event has no binding, Emacs uses the binding that it would use | |
1410 | for the corresponding double event. | |
1411 | ||
f142f62a RS |
1412 | If you click a button three or more times and then press it again, the |
1413 | events for the presses beyond the third are all triple events. Emacs | |
1414 | does not have separate event types for quadruple, quintuple, etc.@: | |
1415 | events. However, you can look at the event list to find out precisely | |
1416 | how many times the button was pressed. | |
8db970a4 RS |
1417 | |
1418 | @defun event-click-count event | |
1419 | This function returns the number of consecutive button presses that led | |
1420 | up to @var{event}. If @var{event} is a double-down, double-click or | |
1421 | double-drag event, the value is 2. If @var{event} is a triple event, | |
1422 | the value is 3 or greater. If @var{event} is an ordinary mouse event | |
1423 | (not a repeat event), the value is 1. | |
1424 | @end defun | |
1425 | ||
5504e99c | 1426 | @defopt double-click-fuzz |
f142f62a | 1427 | To generate repeat events, successive mouse button presses must be at |
99af9d83 GM |
1428 | approximately the same screen position. The value of |
1429 | @code{double-click-fuzz} specifies the maximum number of pixels the | |
5504e99c LT |
1430 | mouse may be moved (horizontally or vertically) between two successive |
1431 | clicks to make a double-click. | |
99af9d83 | 1432 | |
5504e99c LT |
1433 | This variable is also the threshold for motion of the mouse to count |
1434 | as a drag. | |
1435 | @end defopt | |
1436 | ||
1437 | @defopt double-click-time | |
99af9d83 | 1438 | To generate repeat events, the number of milliseconds between |
f142f62a | 1439 | successive button presses must be less than the value of |
8db970a4 RS |
1440 | @code{double-click-time}. Setting @code{double-click-time} to |
1441 | @code{nil} disables multi-click detection entirely. Setting it to | |
1442 | @code{t} removes the time limit; Emacs then detects multi-clicks by | |
1443 | position only. | |
5504e99c | 1444 | @end defopt |
8db970a4 RS |
1445 | |
1446 | @node Motion Events | |
1447 | @subsection Motion Events | |
1448 | @cindex motion event | |
1449 | @cindex mouse motion events | |
1450 | ||
1451 | Emacs sometimes generates @dfn{mouse motion} events to describe motion | |
1452 | of the mouse without any button activity. Mouse motion events are | |
1453 | represented by lists that look like this: | |
1454 | ||
1455 | @example | |
969fe9b5 | 1456 | (mouse-movement (@var{window} @var{buffer-pos} (@var{x} . @var{y}) @var{timestamp})) |
8db970a4 RS |
1457 | @end example |
1458 | ||
1459 | The second element of the list describes the current position of the | |
1460 | mouse, just as in a click event (@pxref{Click Events}). | |
1461 | ||
1462 | The special form @code{track-mouse} enables generation of motion events | |
1463 | within its body. Outside of @code{track-mouse} forms, Emacs does not | |
1464 | generate events for mere motion of the mouse, and these events do not | |
969fe9b5 | 1465 | appear. @xref{Mouse Tracking}. |
8db970a4 RS |
1466 | |
1467 | @node Focus Events | |
1468 | @subsection Focus Events | |
1469 | @cindex focus event | |
1470 | ||
1471 | Window systems provide general ways for the user to control which window | |
1472 | gets keyboard input. This choice of window is called the @dfn{focus}. | |
1473 | When the user does something to switch between Emacs frames, that | |
1474 | generates a @dfn{focus event}. The normal definition of a focus event, | |
1475 | in the global keymap, is to select a new frame within Emacs, as the user | |
1476 | would expect. @xref{Input Focus}. | |
1477 | ||
1478 | Focus events are represented in Lisp as lists that look like this: | |
1479 | ||
1480 | @example | |
1481 | (switch-frame @var{new-frame}) | |
1482 | @end example | |
1483 | ||
1484 | @noindent | |
1485 | where @var{new-frame} is the frame switched to. | |
1486 | ||
b22f3a19 RS |
1487 | Most X window managers are set up so that just moving the mouse into a |
1488 | window is enough to set the focus there. Emacs appears to do this, | |
1489 | because it changes the cursor to solid in the new frame. However, there | |
1490 | is no need for the Lisp program to know about the focus change until | |
1491 | some other kind of input arrives. So Emacs generates a focus event only | |
1492 | when the user actually types a keyboard key or presses a mouse button in | |
1493 | the new frame; just moving the mouse between frames does not generate a | |
1494 | focus event. | |
8db970a4 RS |
1495 | |
1496 | A focus event in the middle of a key sequence would garble the | |
1497 | sequence. So Emacs never generates a focus event in the middle of a key | |
1498 | sequence. If the user changes focus in the middle of a key | |
1499 | sequence---that is, after a prefix key---then Emacs reorders the events | |
1500 | so that the focus event comes either before or after the multi-event key | |
1501 | sequence, and not within it. | |
1502 | ||
22697dac | 1503 | @node Misc Events |
7790d5cd | 1504 | @subsection Miscellaneous System Events |
22697dac | 1505 | |
7790d5cd | 1506 | A few other event types represent occurrences within the system. |
22697dac KH |
1507 | |
1508 | @table @code | |
1509 | @cindex @code{delete-frame} event | |
1510 | @item (delete-frame (@var{frame})) | |
1511 | This kind of event indicates that the user gave the window manager | |
1512 | a command to delete a particular window, which happens to be an Emacs frame. | |
1513 | ||
1514 | The standard definition of the @code{delete-frame} event is to delete @var{frame}. | |
1515 | ||
1516 | @cindex @code{iconify-frame} event | |
1517 | @item (iconify-frame (@var{frame})) | |
1518 | This kind of event indicates that the user iconified @var{frame} using | |
d473987a RS |
1519 | the window manager. Its standard definition is @code{ignore}; since the |
1520 | frame has already been iconified, Emacs has no work to do. The purpose | |
1521 | of this event type is so that you can keep track of such events if you | |
1522 | want to. | |
22697dac | 1523 | |
1774d17e RS |
1524 | @cindex @code{make-frame-visible} event |
1525 | @item (make-frame-visible (@var{frame})) | |
22697dac KH |
1526 | This kind of event indicates that the user deiconified @var{frame} using |
1527 | the window manager. Its standard definition is @code{ignore}; since the | |
d473987a | 1528 | frame has already been made visible, Emacs has no work to do. |
a9f0a989 | 1529 | |
d2fab890 JR |
1530 | @cindex @code{wheel-up} event |
1531 | @cindex @code{wheel-down} event | |
1532 | @item (wheel-up @var{position}) | |
1533 | @item (wheel-down @var{position}) | |
dff3f9e1 RS |
1534 | These kinds of event are generated by moving a mouse wheel. Their |
1535 | usual meaning is a kind of scroll or zoom. | |
a9f0a989 RS |
1536 | |
1537 | The element @var{position} is a list describing the position of the | |
1538 | event, in the same format as used in a mouse-click event. | |
1539 | ||
dff3f9e1 RS |
1540 | This kind of event is generated only on some kinds of systems. On some |
1541 | systems, @code{mouse-4} and @code{mouse-5} are used instead. For | |
1542 | portable code, use the variables @code{mouse-wheel-up-event} and | |
1543 | @code{mouse-wheel-down-event} defined in @file{mwheel.el} to determine | |
1544 | what event types to expect for the mouse wheel. | |
a9f0a989 RS |
1545 | |
1546 | @cindex @code{drag-n-drop} event | |
1547 | @item (drag-n-drop @var{position} @var{files}) | |
1548 | This kind of event is generated when a group of files is | |
1549 | selected in an application outside of Emacs, and then dragged and | |
1550 | dropped onto an Emacs frame. | |
1551 | ||
1552 | The element @var{position} is a list describing the position of the | |
1553 | event, in the same format as used in a mouse-click event, and | |
1554 | @var{files} is the list of file names that were dragged and dropped. | |
1555 | The usual way to handle this event is by visiting these files. | |
1556 | ||
1557 | This kind of event is generated, at present, only on some kinds of | |
1558 | systems. | |
7790d5cd | 1559 | |
16bbbfd8 EZ |
1560 | @cindex @code{help-echo} event |
1561 | @item help-echo | |
1562 | This kind of event is generated when a mouse pointer moves onto a | |
1563 | portion of buffer text which has a @code{help-echo} text property. | |
1564 | The generated event has this form: | |
1565 | ||
1566 | @example | |
f75fbf43 | 1567 | (help-echo @var{frame} @var{help} @var{window} @var{object} @var{pos}) |
16bbbfd8 EZ |
1568 | @end example |
1569 | ||
1570 | @noindent | |
1571 | The precise meaning of the event parameters and the way these | |
1572 | parameters are used to display the help-echo text are described in | |
1573 | @ref{Text help-echo}. | |
1574 | ||
7790d5cd RS |
1575 | @cindex @code{usr1-signal} event |
1576 | @cindex @code{usr2-signal} event | |
1577 | @item usr1-signal | |
1578 | @itemx usr2-signal | |
1579 | These events are generated when the Emacs process receives the signals | |
1580 | @code{SIGUSR1} and @code{SIGUSR2}. They contain no additional data | |
1581 | because signals do not carry additional information. | |
22697dac KH |
1582 | @end table |
1583 | ||
bfe721d1 KH |
1584 | If one of these events arrives in the middle of a key sequence---that |
1585 | is, after a prefix key---then Emacs reorders the events so that this | |
1586 | event comes either before or after the multi-event key sequence, not | |
1587 | within it. | |
1588 | ||
8db970a4 RS |
1589 | @node Event Examples |
1590 | @subsection Event Examples | |
1591 | ||
1592 | If the user presses and releases the left mouse button over the same | |
1593 | location, that generates a sequence of events like this: | |
1594 | ||
1595 | @smallexample | |
1596 | (down-mouse-1 (#<window 18 on NEWS> 2613 (0 . 38) -864320)) | |
1597 | (mouse-1 (#<window 18 on NEWS> 2613 (0 . 38) -864180)) | |
1598 | @end smallexample | |
1599 | ||
f142f62a | 1600 | While holding the control key down, the user might hold down the |
8db970a4 RS |
1601 | second mouse button, and drag the mouse from one line to the next. |
1602 | That produces two events, as shown here: | |
1603 | ||
1604 | @smallexample | |
1605 | (C-down-mouse-2 (#<window 18 on NEWS> 3440 (0 . 27) -731219)) | |
1606 | (C-drag-mouse-2 (#<window 18 on NEWS> 3440 (0 . 27) -731219) | |
1607 | (#<window 18 on NEWS> 3510 (0 . 28) -729648)) | |
1608 | @end smallexample | |
1609 | ||
f142f62a | 1610 | While holding down the meta and shift keys, the user might press the |
8db970a4 | 1611 | second mouse button on the window's mode line, and then drag the mouse |
f142f62a | 1612 | into another window. That produces a pair of events like these: |
8db970a4 RS |
1613 | |
1614 | @smallexample | |
1615 | (M-S-down-mouse-2 (#<window 18 on NEWS> mode-line (33 . 31) -457844)) | |
1616 | (M-S-drag-mouse-2 (#<window 18 on NEWS> mode-line (33 . 31) -457844) | |
1617 | (#<window 20 on carlton-sanskrit.tex> 161 (33 . 3) | |
1618 | -453816)) | |
1619 | @end smallexample | |
1620 | ||
1621 | @node Classifying Events | |
1622 | @subsection Classifying Events | |
1623 | @cindex event type | |
1624 | ||
b22f3a19 RS |
1625 | Every event has an @dfn{event type}, which classifies the event for |
1626 | key binding purposes. For a keyboard event, the event type equals the | |
1627 | event value; thus, the event type for a character is the character, and | |
1628 | the event type for a function key symbol is the symbol itself. For | |
4bdcd3ef | 1629 | events that are lists, the event type is the symbol in the @sc{car} of |
b22f3a19 | 1630 | the list. Thus, the event type is always a symbol or a character. |
8db970a4 RS |
1631 | |
1632 | Two events of the same type are equivalent where key bindings are | |
1633 | concerned; thus, they always run the same command. That does not | |
1634 | necessarily mean they do the same things, however, as some commands look | |
1635 | at the whole event to decide what to do. For example, some commands use | |
f142f62a | 1636 | the location of a mouse event to decide where in the buffer to act. |
8db970a4 RS |
1637 | |
1638 | Sometimes broader classifications of events are useful. For example, | |
1639 | you might want to ask whether an event involved the @key{META} key, | |
1640 | regardless of which other key or mouse button was used. | |
1641 | ||
1642 | The functions @code{event-modifiers} and @code{event-basic-type} are | |
1643 | provided to get such information conveniently. | |
1644 | ||
1645 | @defun event-modifiers event | |
f142f62a RS |
1646 | This function returns a list of the modifiers that @var{event} has. The |
1647 | modifiers are symbols; they include @code{shift}, @code{control}, | |
8db970a4 | 1648 | @code{meta}, @code{alt}, @code{hyper} and @code{super}. In addition, |
f142f62a | 1649 | the modifiers list of a mouse event symbol always contains one of |
5504e99c LT |
1650 | @code{click}, @code{drag}, and @code{down}. For double or triple |
1651 | events, it also contains @code{double} or @code{triple}. | |
f142f62a | 1652 | |
5504e99c LT |
1653 | The argument @var{event} may be an entire event object, or just an |
1654 | event type. If @var{event} is a symbol that has never been used in an | |
1655 | event that has been read as input in the current Emacs session, then | |
1656 | @code{event-modifiers} can return @code{nil}, even when @var{event} | |
1657 | actually has modifiers. | |
f142f62a RS |
1658 | |
1659 | Here are some examples: | |
8db970a4 RS |
1660 | |
1661 | @example | |
1662 | (event-modifiers ?a) | |
1663 | @result{} nil | |
5504e99c LT |
1664 | (event-modifiers ?A) |
1665 | @result{} (shift) | |
8db970a4 RS |
1666 | (event-modifiers ?\C-a) |
1667 | @result{} (control) | |
1668 | (event-modifiers ?\C-%) | |
1669 | @result{} (control) | |
1670 | (event-modifiers ?\C-\S-a) | |
1671 | @result{} (control shift) | |
1672 | (event-modifiers 'f5) | |
1673 | @result{} nil | |
1674 | (event-modifiers 's-f5) | |
1675 | @result{} (super) | |
1676 | (event-modifiers 'M-S-f5) | |
1677 | @result{} (meta shift) | |
1678 | (event-modifiers 'mouse-1) | |
1679 | @result{} (click) | |
1680 | (event-modifiers 'down-mouse-1) | |
1681 | @result{} (down) | |
1682 | @end example | |
1683 | ||
1684 | The modifiers list for a click event explicitly contains @code{click}, | |
1685 | but the event symbol name itself does not contain @samp{click}. | |
1686 | @end defun | |
1687 | ||
1688 | @defun event-basic-type event | |
1689 | This function returns the key or mouse button that @var{event} | |
5504e99c LT |
1690 | describes, with all modifiers removed. The @var{event} argument is as |
1691 | in @code{event-modifiers}. For example: | |
8db970a4 RS |
1692 | |
1693 | @example | |
1694 | (event-basic-type ?a) | |
1695 | @result{} 97 | |
1696 | (event-basic-type ?A) | |
1697 | @result{} 97 | |
1698 | (event-basic-type ?\C-a) | |
1699 | @result{} 97 | |
1700 | (event-basic-type ?\C-\S-a) | |
1701 | @result{} 97 | |
1702 | (event-basic-type 'f5) | |
1703 | @result{} f5 | |
1704 | (event-basic-type 's-f5) | |
1705 | @result{} f5 | |
1706 | (event-basic-type 'M-S-f5) | |
1707 | @result{} f5 | |
1708 | (event-basic-type 'down-mouse-1) | |
1709 | @result{} mouse-1 | |
1710 | @end example | |
1711 | @end defun | |
1712 | ||
1713 | @defun mouse-movement-p object | |
1714 | This function returns non-@code{nil} if @var{object} is a mouse movement | |
1715 | event. | |
1716 | @end defun | |
1717 | ||
bfe721d1 KH |
1718 | @defun event-convert-list list |
1719 | This function converts a list of modifier names and a basic event type | |
5504e99c LT |
1720 | to an event type which specifies all of them. The basic event type |
1721 | must be the last element of the list. For example, | |
bfe721d1 KH |
1722 | |
1723 | @example | |
1724 | (event-convert-list '(control ?a)) | |
1725 | @result{} 1 | |
1726 | (event-convert-list '(control meta ?a)) | |
1727 | @result{} -134217727 | |
1728 | (event-convert-list '(control super f1)) | |
1729 | @result{} C-s-f1 | |
1730 | @end example | |
1731 | @end defun | |
1732 | ||
8db970a4 RS |
1733 | @node Accessing Events |
1734 | @subsection Accessing Events | |
2468d0c0 DL |
1735 | @cindex mouse events, accessing the data |
1736 | @cindex accessing data of mouse events | |
8db970a4 RS |
1737 | |
1738 | This section describes convenient functions for accessing the data in | |
f142f62a | 1739 | a mouse button or motion event. |
8db970a4 | 1740 | |
f142f62a | 1741 | These two functions return the starting or ending position of a |
969fe9b5 | 1742 | mouse-button event, as a list of this form: |
8db970a4 | 1743 | |
f142f62a | 1744 | @example |
f51f93f6 | 1745 | (@var{window} @var{pos-or-area} (@var{x} . @var{y}) @var{timestamp} |
08988329 KS |
1746 | @var{object} @var{text-pos} (@var{col} . @var{row}) |
1747 | @var{image} (@var{dx} . @var{dy}) (@var{width} . @var{height})) | |
f142f62a | 1748 | @end example |
8db970a4 RS |
1749 | |
1750 | @defun event-start event | |
1751 | This returns the starting position of @var{event}. | |
1752 | ||
1753 | If @var{event} is a click or button-down event, this returns the | |
1754 | location of the event. If @var{event} is a drag event, this returns the | |
1755 | drag's starting position. | |
1756 | @end defun | |
1757 | ||
1758 | @defun event-end event | |
1759 | This returns the ending position of @var{event}. | |
1760 | ||
1761 | If @var{event} is a drag event, this returns the position where the user | |
1762 | released the mouse button. If @var{event} is a click or button-down | |
1763 | event, the value is actually the starting position, which is the only | |
1764 | position such events have. | |
1765 | @end defun | |
1766 | ||
2468d0c0 | 1767 | @cindex mouse position list, accessing |
6e41ce9c | 1768 | These functions take a position list as described above, and |
969fe9b5 | 1769 | return various parts of it. |
8db970a4 RS |
1770 | |
1771 | @defun posn-window position | |
1772 | Return the window that @var{position} is in. | |
1773 | @end defun | |
1774 | ||
c5cb5297 | 1775 | @defun posn-area position |
f51f93f6 | 1776 | Return the window area recorded in @var{position}. It returns @code{nil} |
c5cb5297 | 1777 | when the event occurred in the text area of the window; otherwise, it |
4a182c75 | 1778 | is a symbol identifying the area in which the event occurred. |
c5cb5297 KS |
1779 | @end defun |
1780 | ||
8db970a4 | 1781 | @defun posn-point position |
c5cb5297 KS |
1782 | Return the buffer position in @var{position}. When the event occurred |
1783 | in the text area of the window, in a marginal area, or on a fringe, | |
1784 | this is an integer specifying a buffer position. Otherwise, the value | |
1785 | is undefined. | |
1786 | @end defun | |
1787 | ||
8db970a4 | 1788 | @defun posn-x-y position |
6e41ce9c RS |
1789 | Return the pixel-based x and y coordinates in @var{position}, as a |
1790 | cons cell @code{(@var{x} . @var{y})}. These coordinates are relative | |
1791 | to the window given by @code{posn-window}. | |
1792 | ||
1793 | This example shows how to convert these window-relative coordinates | |
1794 | into frame-relative coordinates: | |
1795 | ||
1796 | @example | |
1797 | (defun frame-relative-coordinates (position) | |
1798 | "Return frame-relative coordinates from POSITION." | |
1799 | (let* ((x-y (posn-x-y position)) | |
1800 | (window (posn-window position)) | |
1801 | (edges (window-inside-pixel-edges window))) | |
1802 | (cons (+ (car x-y) (car edges)) | |
1803 | (+ (cdr x-y) (cadr edges))))) | |
1804 | @end example | |
8db970a4 RS |
1805 | @end defun |
1806 | ||
1807 | @defun posn-col-row position | |
6e41ce9c RS |
1808 | Return the row and column (in units of the frame's default character |
1809 | height and width) of @var{position}, as a cons cell @code{(@var{col} . | |
1810 | @var{row})}. These are computed from the @var{x} and @var{y} values | |
1811 | actually found in @var{position}. | |
c5cb5297 KS |
1812 | @end defun |
1813 | ||
1814 | @defun posn-actual-col-row position | |
1815 | Return the actual row and column in @var{position}, as a cons cell | |
1816 | @code{(@var{col} . @var{row})}. The values are the actual row number | |
6e41ce9c RS |
1817 | in the window, and the actual character number in that row. It returns |
1818 | @code{nil} if @var{position} does not include actual positions values. | |
1819 | You can use @code{posn-col-row} to get approximate values. | |
8db970a4 RS |
1820 | @end defun |
1821 | ||
08988329 KS |
1822 | @defun posn-string position |
1823 | Return the string object in @var{position}, either @code{nil}, or a | |
1824 | cons cell @code{(@var{string} . @var{string-pos})}. | |
1825 | @end defun | |
1826 | ||
1827 | @defun posn-image position | |
1828 | Return the image object in @var{position}, either @code{nil}, or an | |
1829 | image @code{(image ...)}. | |
1830 | @end defun | |
1831 | ||
f51f93f6 | 1832 | @defun posn-object position |
08988329 KS |
1833 | Return the image or string object in @var{position}, either |
1834 | @code{nil}, an image @code{(image ...)}, or a cons cell | |
1835 | @code{(@var{string} . @var{string-pos})}. | |
f51f93f6 KS |
1836 | @end defun |
1837 | ||
1838 | @defun posn-object-x-y position | |
1839 | Return the pixel-based x and y coordinates relative to the upper left | |
08988329 KS |
1840 | corner of the object in @var{position} as a cons cell @code{(@var{dx} |
1841 | . @var{dy})}. If the @var{position} is a buffer position, return the | |
1842 | relative position in the character at that position. | |
1843 | @end defun | |
1844 | ||
1845 | @defun posn-object-width-height position | |
1846 | Return the pixel width and height of the object in @var{position} as a | |
1847 | cons cell @code{(@var{width} . @var{height})}. If the @var{position} | |
1848 | is a buffer position, return the size of the character at that position. | |
f51f93f6 KS |
1849 | @end defun |
1850 | ||
2468d0c0 DL |
1851 | @cindex mouse event, timestamp |
1852 | @cindex timestamp of a mouse event | |
5504e99c | 1853 | @defun posn-timestamp position |
f51f93f6 KS |
1854 | Return the timestamp in @var{position}. This is the time at which the |
1855 | event occurred, in milliseconds. | |
6e41ce9c RS |
1856 | @end defun |
1857 | ||
1858 | These functions compute a position list given particular buffer | |
1859 | position or screen position. You can access the data in this position | |
1860 | list with the functions described above. | |
1861 | ||
1862 | @defun posn-at-point &optional pos window | |
1863 | This function returns a position list for position @var{pos} in | |
1864 | @var{window}. @var{pos} defaults to point in @var{window}; | |
1865 | @var{window} defaults to the selected window. | |
1866 | ||
1867 | @code{posn-at-point} returns @code{nil} if @var{pos} is not visible in | |
1868 | @var{window}. | |
1869 | @end defun | |
1870 | ||
cfa284c4 | 1871 | @defun posn-at-x-y x y &optional frame-or-window whole |
6e41ce9c RS |
1872 | This function returns position information corresponding to pixel |
1873 | coordinates @var{x} and @var{y} in a specified frame or window, | |
1874 | @var{frame-or-window}, which defaults to the selected window. | |
1875 | The coordinates @var{x} and @var{y} are relative to the | |
1876 | frame or window used. | |
cfa284c4 KS |
1877 | If @var{whole} is @code{nil}, the coordinates are relative |
1878 | to the window text area, otherwise they are relative to | |
1879 | the entire window area including scroll bars, margins and fringes. | |
8db970a4 RS |
1880 | @end defun |
1881 | ||
969fe9b5 RS |
1882 | These functions are useful for decoding scroll bar events. |
1883 | ||
b22f3a19 RS |
1884 | @defun scroll-bar-event-ratio event |
1885 | This function returns the fractional vertical position of a scroll bar | |
1886 | event within the scroll bar. The value is a cons cell | |
1887 | @code{(@var{portion} . @var{whole})} containing two integers whose ratio | |
1888 | is the fractional position. | |
1889 | @end defun | |
1890 | ||
8db970a4 | 1891 | @defun scroll-bar-scale ratio total |
b22f3a19 RS |
1892 | This function multiplies (in effect) @var{ratio} by @var{total}, |
1893 | rounding the result to an integer. The argument @var{ratio} is not a | |
1894 | number, but rather a pair @code{(@var{num} . @var{denom})}---typically a | |
1895 | value returned by @code{scroll-bar-event-ratio}. | |
8db970a4 | 1896 | |
f142f62a RS |
1897 | This function is handy for scaling a position on a scroll bar into a |
1898 | buffer position. Here's how to do that: | |
8db970a4 RS |
1899 | |
1900 | @example | |
1901 | (+ (point-min) | |
1902 | (scroll-bar-scale | |
b22f3a19 | 1903 | (posn-x-y (event-start event)) |
8db970a4 RS |
1904 | (- (point-max) (point-min)))) |
1905 | @end example | |
b22f3a19 | 1906 | |
1911e6e5 | 1907 | Recall that scroll bar events have two integers forming a ratio, in place |
b22f3a19 | 1908 | of a pair of x and y coordinates. |
8db970a4 RS |
1909 | @end defun |
1910 | ||
1911 | @node Strings of Events | |
1912 | @subsection Putting Keyboard Events in Strings | |
2468d0c0 DL |
1913 | @cindex keyboard events in strings |
1914 | @cindex strings with keyboard events | |
8db970a4 RS |
1915 | |
1916 | In most of the places where strings are used, we conceptualize the | |
1917 | string as containing text characters---the same kind of characters found | |
b22f3a19 | 1918 | in buffers or files. Occasionally Lisp programs use strings that |
8db970a4 | 1919 | conceptually contain keyboard characters; for example, they may be key |
969fe9b5 RS |
1920 | sequences or keyboard macro definitions. However, storing keyboard |
1921 | characters in a string is a complex matter, for reasons of historical | |
1922 | compatibility, and it is not always possible. | |
1923 | ||
1924 | We recommend that new programs avoid dealing with these complexities | |
1925 | by not storing keyboard events in strings. Here is how to do that: | |
1926 | ||
1927 | @itemize @bullet | |
1928 | @item | |
1929 | Use vectors instead of strings for key sequences, when you plan to use | |
a9f0a989 | 1930 | them for anything other than as arguments to @code{lookup-key} and |
969fe9b5 RS |
1931 | @code{define-key}. For example, you can use |
1932 | @code{read-key-sequence-vector} instead of @code{read-key-sequence}, and | |
1933 | @code{this-command-keys-vector} instead of @code{this-command-keys}. | |
1934 | ||
1935 | @item | |
1936 | Use vectors to write key sequence constants containing meta characters, | |
1937 | even when passing them directly to @code{define-key}. | |
1938 | ||
1939 | @item | |
1940 | When you have to look at the contents of a key sequence that might be a | |
1941 | string, use @code{listify-key-sequence} (@pxref{Event Input Misc}) | |
1942 | first, to convert it to a list. | |
1943 | @end itemize | |
8db970a4 | 1944 | |
969fe9b5 RS |
1945 | The complexities stem from the modifier bits that keyboard input |
1946 | characters can include. Aside from the Meta modifier, none of these | |
1947 | modifier bits can be included in a string, and the Meta modifier is | |
1948 | allowed only in special cases. | |
1949 | ||
1950 | The earliest GNU Emacs versions represented meta characters as codes | |
1951 | in the range of 128 to 255. At that time, the basic character codes | |
1952 | ranged from 0 to 127, so all keyboard character codes did fit in a | |
1953 | string. Many Lisp programs used @samp{\M-} in string constants to stand | |
1954 | for meta characters, especially in arguments to @code{define-key} and | |
1955 | similar functions, and key sequences and sequences of events were always | |
1956 | represented as strings. | |
1957 | ||
1958 | When we added support for larger basic character codes beyond 127, and | |
1959 | additional modifier bits, we had to change the representation of meta | |
1960 | characters. Now the flag that represents the Meta modifier in a | |
1961 | character is | |
1962 | @tex | |
8241495d | 1963 | @math{2^{27}} |
969fe9b5 | 1964 | @end tex |
37680279 | 1965 | @ifnottex |
bfe721d1 | 1966 | 2**27 |
37680279 | 1967 | @end ifnottex |
969fe9b5 | 1968 | and such numbers cannot be included in a string. |
8db970a4 | 1969 | |
969fe9b5 RS |
1970 | To support programs with @samp{\M-} in string constants, there are |
1971 | special rules for including certain meta characters in a string. | |
1911e6e5 RS |
1972 | Here are the rules for interpreting a string as a sequence of input |
1973 | characters: | |
8db970a4 RS |
1974 | |
1975 | @itemize @bullet | |
1976 | @item | |
f142f62a RS |
1977 | If the keyboard character value is in the range of 0 to 127, it can go |
1978 | in the string unchanged. | |
8db970a4 RS |
1979 | |
1980 | @item | |
bfe721d1 | 1981 | The meta variants of those characters, with codes in the range of |
969fe9b5 | 1982 | @tex |
8241495d | 1983 | @math{2^{27}} |
969fe9b5 | 1984 | @end tex |
37680279 | 1985 | @ifnottex |
bfe721d1 | 1986 | 2**27 |
37680279 | 1987 | @end ifnottex |
bfe721d1 | 1988 | to |
969fe9b5 | 1989 | @tex |
8241495d | 1990 | @math{2^{27} + 127}, |
969fe9b5 | 1991 | @end tex |
37680279 | 1992 | @ifnottex |
bfe721d1 | 1993 | 2**27+127, |
37680279 | 1994 | @end ifnottex |
bfe721d1 KH |
1995 | can also go in the string, but you must change their |
1996 | numeric values. You must set the | |
969fe9b5 | 1997 | @tex |
8241495d | 1998 | @math{2^{7}} |
969fe9b5 | 1999 | @end tex |
37680279 | 2000 | @ifnottex |
bfe721d1 | 2001 | 2**7 |
37680279 | 2002 | @end ifnottex |
bfe721d1 | 2003 | bit instead of the |
969fe9b5 | 2004 | @tex |
8241495d | 2005 | @math{2^{27}} |
969fe9b5 | 2006 | @end tex |
37680279 | 2007 | @ifnottex |
bfe721d1 | 2008 | 2**27 |
37680279 | 2009 | @end ifnottex |
969fe9b5 RS |
2010 | bit, resulting in a value between 128 and 255. Only a unibyte string |
2011 | can include these codes. | |
2012 | ||
2013 | @item | |
ad800164 | 2014 | Non-@acronym{ASCII} characters above 256 can be included in a multibyte string. |
8db970a4 RS |
2015 | |
2016 | @item | |
2017 | Other keyboard character events cannot fit in a string. This includes | |
2018 | keyboard events in the range of 128 to 255. | |
2019 | @end itemize | |
2020 | ||
f9f59935 RS |
2021 | Functions such as @code{read-key-sequence} that construct strings of |
2022 | keyboard input characters follow these rules: they construct vectors | |
f142f62a | 2023 | instead of strings, when the events won't fit in a string. |
8db970a4 RS |
2024 | |
2025 | When you use the read syntax @samp{\M-} in a string, it produces a | |
2026 | code in the range of 128 to 255---the same code that you get if you | |
2027 | modify the corresponding keyboard event to put it in the string. Thus, | |
2028 | meta events in strings work consistently regardless of how they get into | |
2029 | the strings. | |
2030 | ||
969fe9b5 RS |
2031 | However, most programs would do well to avoid these issues by |
2032 | following the recommendations at the beginning of this section. | |
f142f62a | 2033 | |
8db970a4 RS |
2034 | @node Reading Input |
2035 | @section Reading Input | |
2036 | ||
969fe9b5 | 2037 | The editor command loop reads key sequences using the function |
8db970a4 | 2038 | @code{read-key-sequence}, which uses @code{read-event}. These and other |
969fe9b5 RS |
2039 | functions for event input are also available for use in Lisp programs. |
2040 | See also @code{momentary-string-display} in @ref{Temporary Displays}, | |
2041 | and @code{sit-for} in @ref{Waiting}. @xref{Terminal Input}, for | |
2042 | functions and variables for controlling terminal input modes and | |
4324b7ab RS |
2043 | debugging terminal input. @xref{Translating Input}, for features you |
2044 | can use for translating or modifying input events while reading them. | |
8db970a4 RS |
2045 | |
2046 | For higher-level input facilities, see @ref{Minibuffers}. | |
2047 | ||
2048 | @menu | |
2049 | * Key Sequence Input:: How to read one key sequence. | |
2050 | * Reading One Event:: How to read just one event. | |
b6954afd | 2051 | * Invoking the Input Method:: How reading an event uses the input method. |
8db970a4 | 2052 | * Quoted Character Input:: Asking the user to specify a character. |
f142f62a | 2053 | * Event Input Misc:: How to reread or throw away input events. |
8db970a4 RS |
2054 | @end menu |
2055 | ||
2056 | @node Key Sequence Input | |
2057 | @subsection Key Sequence Input | |
2058 | @cindex key sequence input | |
2059 | ||
2060 | The command loop reads input a key sequence at a time, by calling | |
2061 | @code{read-key-sequence}. Lisp programs can also call this function; | |
2062 | for example, @code{describe-key} uses it to read the key to describe. | |
2063 | ||
ecbfc7e9 | 2064 | @defun read-key-sequence prompt &optional continue-echo dont-downcase-last switch-frame-ok command-loop |
8db970a4 RS |
2065 | @cindex key sequence |
2066 | This function reads a key sequence and returns it as a string or | |
f9f59935 | 2067 | vector. It keeps reading events until it has accumulated a complete key |
8db970a4 | 2068 | sequence; that is, enough to specify a non-prefix command using the |
5504e99c LT |
2069 | currently active keymaps. (Remember that a key sequence that starts |
2070 | with a mouse event is read using the keymaps of the buffer in the | |
2071 | window that the mouse was in, not the current buffer.) | |
8db970a4 RS |
2072 | |
2073 | If the events are all characters and all can fit in a string, then | |
2074 | @code{read-key-sequence} returns a string (@pxref{Strings of Events}). | |
2075 | Otherwise, it returns a vector, since a vector can hold all kinds of | |
2076 | events---characters, symbols, and lists. The elements of the string or | |
2077 | vector are the events in the key sequence. | |
2078 | ||
2b83bc43 RS |
2079 | Reading a key sequence includes translating the events in various |
2080 | ways. @xref{Translating Input}. | |
2081 | ||
ecbfc7e9 RS |
2082 | The argument @var{prompt} is either a string to be displayed in the |
2083 | echo area as a prompt, or @code{nil}, meaning not to display a prompt. | |
2084 | The argument @var{continue-echo}, if non-@code{nil}, means to echo | |
2085 | this key as a continuation of the previous key. | |
2086 | ||
2087 | Normally any upper case event is converted to lower case if the | |
2088 | original event is undefined and the lower case equivalent is defined. | |
2089 | The argument @var{dont-downcase-last}, if non-@code{nil}, means do not | |
2090 | convert the last event to lower case. This is appropriate for reading | |
2091 | a key sequence to be defined. | |
2092 | ||
2093 | The argument @var{switch-frame-ok}, if non-@code{nil}, means that this | |
2094 | function should process a @code{switch-frame} event if the user | |
2095 | switches frames before typing anything. If the user switches frames | |
2096 | in the middle of a key sequence, or at the start of the sequence but | |
2097 | @var{switch-frame-ok} is @code{nil}, then the event will be put off | |
2098 | until after the current key sequence. | |
2099 | ||
2100 | The argument @var{command-loop}, if non-@code{nil}, means that this | |
2101 | key sequence is being read by something that will read commands one | |
2102 | after another. It should be @code{nil} if the caller will read just | |
2103 | one key sequence. | |
8db970a4 | 2104 | |
2b83bc43 RS |
2105 | In the following example, Emacs displays the prompt @samp{?} in the |
2106 | echo area, and then the user types @kbd{C-x C-f}. | |
8db970a4 RS |
2107 | |
2108 | @example | |
2109 | (read-key-sequence "?") | |
2110 | ||
2111 | @group | |
2112 | ---------- Echo Area ---------- | |
2113 | ?@kbd{C-x C-f} | |
2114 | ---------- Echo Area ---------- | |
2115 | ||
2116 | @result{} "^X^F" | |
2117 | @end group | |
2118 | @end example | |
969fe9b5 RS |
2119 | |
2120 | The function @code{read-key-sequence} suppresses quitting: @kbd{C-g} | |
2121 | typed while reading with this function works like any other character, | |
2122 | and does not set @code{quit-flag}. @xref{Quitting}. | |
2123 | @end defun | |
2124 | ||
ecbfc7e9 | 2125 | @defun read-key-sequence-vector prompt &optional continue-echo dont-downcase-last switch-frame-ok command-loop |
969fe9b5 RS |
2126 | This is like @code{read-key-sequence} except that it always |
2127 | returns the key sequence as a vector, never as a string. | |
2128 | @xref{Strings of Events}. | |
8db970a4 RS |
2129 | @end defun |
2130 | ||
8db970a4 RS |
2131 | @cindex upper case key sequence |
2132 | @cindex downcasing in @code{lookup-key} | |
b071e512 RS |
2133 | If an input character is upper-case (or has the shift modifier) and |
2134 | has no key binding, but its lower-case equivalent has one, then | |
2135 | @code{read-key-sequence} converts the character to lower case. Note | |
2136 | that @code{lookup-key} does not perform case conversion in this way. | |
8db970a4 RS |
2137 | |
2138 | The function @code{read-key-sequence} also transforms some mouse events. | |
2139 | It converts unbound drag events into click events, and discards unbound | |
bfe721d1 KH |
2140 | button-down events entirely. It also reshuffles focus events and |
2141 | miscellaneous window events so that they never appear in a key sequence | |
2142 | with any other events. | |
8db970a4 | 2143 | |
2468d0c0 DL |
2144 | @cindex @code{header-line} prefix key |
2145 | @cindex @code{mode-line} prefix key | |
2146 | @cindex @code{vertical-line} prefix key | |
2147 | @cindex @code{horizontal-scroll-bar} prefix key | |
2148 | @cindex @code{vertical-scroll-bar} prefix key | |
2149 | @cindex @code{menu-bar} prefix key | |
2150 | @cindex mouse events, in special parts of frame | |
8db970a4 | 2151 | When mouse events occur in special parts of a window, such as a mode |
f142f62a RS |
2152 | line or a scroll bar, the event type shows nothing special---it is the |
2153 | same symbol that would normally represent that combination of mouse | |
f9f59935 RS |
2154 | button and modifier keys. The information about the window part is kept |
2155 | elsewhere in the event---in the coordinates. But | |
f142f62a | 2156 | @code{read-key-sequence} translates this information into imaginary |
080a57ba | 2157 | ``prefix keys'', all of which are symbols: @code{header-line}, |
2468d0c0 DL |
2158 | @code{horizontal-scroll-bar}, @code{menu-bar}, @code{mode-line}, |
2159 | @code{vertical-line}, and @code{vertical-scroll-bar}. You can define | |
2160 | meanings for mouse clicks in special window parts by defining key | |
2161 | sequences using these imaginary prefix keys. | |
f142f62a | 2162 | |
8db970a4 | 2163 | For example, if you call @code{read-key-sequence} and then click the |
bfe721d1 | 2164 | mouse on the window's mode line, you get two events, like this: |
8db970a4 | 2165 | |
f142f62a | 2166 | @example |
8db970a4 RS |
2167 | (read-key-sequence "Click on the mode line: ") |
2168 | @result{} [mode-line | |
f142f62a RS |
2169 | (mouse-1 |
2170 | (#<window 6 on NEWS> mode-line | |
2171 | (40 . 63) 5959987))] | |
2172 | @end example | |
8db970a4 | 2173 | |
f9f59935 RS |
2174 | @defvar num-input-keys |
2175 | @c Emacs 19 feature | |
2176 | This variable's value is the number of key sequences processed so far in | |
2177 | this Emacs session. This includes key sequences read from the terminal | |
2178 | and key sequences read from keyboard macros being executed. | |
2179 | @end defvar | |
2180 | ||
8db970a4 RS |
2181 | @node Reading One Event |
2182 | @subsection Reading One Event | |
2468d0c0 DL |
2183 | @cindex reading a single event |
2184 | @cindex event, reading only one | |
8db970a4 | 2185 | |
b22f3a19 | 2186 | The lowest level functions for command input are those that read a |
8db970a4 RS |
2187 | single event. |
2188 | ||
5504e99c LT |
2189 | None of the three functions below suppresses quitting. |
2190 | ||
b6954afd | 2191 | @defun read-event &optional prompt inherit-input-method |
8db970a4 RS |
2192 | This function reads and returns the next event of command input, waiting |
2193 | if necessary until an event is available. Events can come directly from | |
2194 | the user or from a keyboard macro. | |
2195 | ||
b6954afd RS |
2196 | If the optional argument @var{prompt} is non-@code{nil}, it should be a |
2197 | string to display in the echo area as a prompt. Otherwise, | |
2198 | @code{read-event} does not display any message to indicate it is waiting | |
2199 | for input; instead, it prompts by echoing: it displays descriptions of | |
2200 | the events that led to or were read by the current command. @xref{The | |
2201 | Echo Area}. | |
8db970a4 | 2202 | |
b6954afd RS |
2203 | If @var{inherit-input-method} is non-@code{nil}, then the current input |
2204 | method (if any) is employed to make it possible to enter a | |
ad800164 | 2205 | non-@acronym{ASCII} character. Otherwise, input method handling is disabled |
b6954afd | 2206 | for reading this event. |
2eb4136f | 2207 | |
8db970a4 RS |
2208 | If @code{cursor-in-echo-area} is non-@code{nil}, then @code{read-event} |
2209 | moves the cursor temporarily to the echo area, to the end of any message | |
2210 | displayed there. Otherwise @code{read-event} does not move the cursor. | |
8db970a4 | 2211 | |
5504e99c LT |
2212 | If @code{read-event} gets an event that is defined as a help character, |
2213 | then in some cases @code{read-event} processes the event directly without | |
a9f0a989 RS |
2214 | returning. @xref{Help Functions}. Certain other events, called |
2215 | @dfn{special events}, are also processed directly within | |
2216 | @code{read-event} (@pxref{Special Events}). | |
2217 | ||
8db970a4 RS |
2218 | Here is what happens if you call @code{read-event} and then press the |
2219 | right-arrow function key: | |
2220 | ||
2221 | @example | |
2222 | @group | |
2223 | (read-event) | |
2224 | @result{} right | |
2225 | @end group | |
2226 | @end example | |
f142f62a | 2227 | @end defun |
8db970a4 | 2228 | |
b6954afd RS |
2229 | @defun read-char &optional prompt inherit-input-method |
2230 | This function reads and returns a character of command input. If the | |
2231 | user generates an event which is not a character (i.e. a mouse click or | |
2232 | function key event), @code{read-char} signals an error. The arguments | |
2233 | work as in @code{read-event}. | |
8db970a4 | 2234 | |
ad800164 | 2235 | In the first example, the user types the character @kbd{1} (@acronym{ASCII} |
f142f62a RS |
2236 | code 49). The second example shows a keyboard macro definition that |
2237 | calls @code{read-char} from the minibuffer using @code{eval-expression}. | |
2238 | @code{read-char} reads the keyboard macro's very next character, which | |
2239 | is @kbd{1}. Then @code{eval-expression} displays its return value in | |
2240 | the echo area. | |
8db970a4 RS |
2241 | |
2242 | @example | |
2243 | @group | |
2244 | (read-char) | |
2245 | @result{} 49 | |
2246 | @end group | |
2247 | ||
2248 | @group | |
bfe721d1 | 2249 | ;; @r{We assume here you use @kbd{M-:} to evaluate this.} |
8db970a4 | 2250 | (symbol-function 'foo) |
bfe721d1 | 2251 | @result{} "^[:(read-char)^M1" |
8db970a4 RS |
2252 | @end group |
2253 | @group | |
f142f62a | 2254 | (execute-kbd-macro 'foo) |
8db970a4 RS |
2255 | @print{} 49 |
2256 | @result{} nil | |
2257 | @end group | |
2258 | @end example | |
2259 | @end defun | |
2260 | ||
b6954afd RS |
2261 | @defun read-char-exclusive &optional prompt inherit-input-method |
2262 | This function reads and returns a character of command input. If the | |
2263 | user generates an event which is not a character, | |
2264 | @code{read-char-exclusive} ignores it and reads another event, until it | |
2265 | gets a character. The arguments work as in @code{read-event}. | |
2266 | @end defun | |
2267 | ||
2b83bc43 RS |
2268 | @defvar num-nonmacro-input-events |
2269 | This variable holds the total number of input events received so far | |
2270 | from the terminal---not counting those generated by keyboard macros. | |
2271 | @end defvar | |
2272 | ||
b6954afd RS |
2273 | @node Invoking the Input Method |
2274 | @subsection Invoking the Input Method | |
2275 | ||
2276 | The event-reading functions invoke the current input method, if any | |
2277 | (@pxref{Input Methods}). If the value of @code{input-method-function} | |
2278 | is non-@code{nil}, it should be a function; when @code{read-event} reads | |
2279 | a printing character (including @key{SPC}) with no modifier bits, it | |
2280 | calls that function, passing the character as an argument. | |
39d6d9bd RS |
2281 | |
2282 | @defvar input-method-function | |
2283 | If this is non-@code{nil}, its value specifies the current input method | |
2284 | function. | |
2eb4136f | 2285 | |
6142d1d0 | 2286 | @strong{Warning:} don't bind this variable with @code{let}. It is often |
2eb4136f RS |
2287 | buffer-local, and if you bind it around reading input (which is exactly |
2288 | when you @emph{would} bind it), switching buffers asynchronously while | |
2289 | Emacs is waiting will cause the value to be restored in the wrong | |
2290 | buffer. | |
39d6d9bd RS |
2291 | @end defvar |
2292 | ||
2293 | The input method function should return a list of events which should | |
2294 | be used as input. (If the list is @code{nil}, that means there is no | |
2295 | input, so @code{read-event} waits for another event.) These events are | |
2468d0c0 DL |
2296 | processed before the events in @code{unread-command-events} |
2297 | (@pxref{Event Input Misc}). Events | |
39d6d9bd RS |
2298 | returned by the input method function are not passed to the input method |
2299 | function again, even if they are printing characters with no modifier | |
2300 | bits. | |
2301 | ||
2302 | If the input method function calls @code{read-event} or | |
2303 | @code{read-key-sequence}, it should bind @code{input-method-function} to | |
2304 | @code{nil} first, to prevent recursion. | |
2305 | ||
2306 | The input method function is not called when reading the second and | |
b6954afd RS |
2307 | subsequent events of a key sequence. Thus, these characters are not |
2308 | subject to input method processing. The input method function should | |
2309 | test the values of @code{overriding-local-map} and | |
2310 | @code{overriding-terminal-local-map}; if either of these variables is | |
2311 | non-@code{nil}, the input method should put its argument into a list and | |
2312 | return that list with no further processing. | |
39d6d9bd | 2313 | |
8db970a4 RS |
2314 | @node Quoted Character Input |
2315 | @subsection Quoted Character Input | |
2316 | @cindex quoted character input | |
2317 | ||
b22f3a19 RS |
2318 | You can use the function @code{read-quoted-char} to ask the user to |
2319 | specify a character, and allow the user to specify a control or meta | |
2320 | character conveniently, either literally or as an octal character code. | |
2321 | The command @code{quoted-insert} uses this function. | |
8db970a4 RS |
2322 | |
2323 | @defun read-quoted-char &optional prompt | |
2324 | @cindex octal character input | |
2325 | @cindex control characters, reading | |
2326 | @cindex nonprinting characters, reading | |
2327 | This function is like @code{read-char}, except that if the first | |
969fe9b5 RS |
2328 | character read is an octal digit (0-7), it reads any number of octal |
2329 | digits (but stopping if a non-octal digit is found), and returns the | |
5504e99c LT |
2330 | character represented by that numeric character code. If the |
2331 | character that terminates the sequence of octal digits is @key{RET}, | |
2332 | it is discarded. Any other terminating character is used as input | |
2333 | after this function returns. | |
8db970a4 RS |
2334 | |
2335 | Quitting is suppressed when the first character is read, so that the | |
2336 | user can enter a @kbd{C-g}. @xref{Quitting}. | |
2337 | ||
2338 | If @var{prompt} is supplied, it specifies a string for prompting the | |
f142f62a | 2339 | user. The prompt string is always displayed in the echo area, followed |
8db970a4 RS |
2340 | by a single @samp{-}. |
2341 | ||
2342 | In the following example, the user types in the octal number 177 (which | |
2343 | is 127 in decimal). | |
2344 | ||
2345 | @example | |
2346 | (read-quoted-char "What character") | |
2347 | ||
2348 | @group | |
2349 | ---------- Echo Area ---------- | |
5504e99c | 2350 | What character @kbd{1 7 7}- |
8db970a4 RS |
2351 | ---------- Echo Area ---------- |
2352 | ||
2353 | @result{} 127 | |
2354 | @end group | |
2355 | @end example | |
2356 | @end defun | |
2357 | ||
b22f3a19 | 2358 | @need 2000 |
f142f62a RS |
2359 | @node Event Input Misc |
2360 | @subsection Miscellaneous Event Input Features | |
2361 | ||
2362 | This section describes how to ``peek ahead'' at events without using | |
2363 | them up, how to check for pending input, and how to discard pending | |
1911e6e5 RS |
2364 | input. See also the function @code{read-passwd} (@pxref{Reading a |
2365 | Password}). | |
8db970a4 RS |
2366 | |
2367 | @defvar unread-command-events | |
2368 | @cindex next input | |
2369 | @cindex peeking at input | |
2370 | This variable holds a list of events waiting to be read as command | |
f142f62a RS |
2371 | input. The events are used in the order they appear in the list, and |
2372 | removed one by one as they are used. | |
8db970a4 | 2373 | |
f9f59935 | 2374 | The variable is needed because in some cases a function reads an event |
f142f62a RS |
2375 | and then decides not to use it. Storing the event in this variable |
2376 | causes it to be processed normally, by the command loop or by the | |
2377 | functions to read command input. | |
8db970a4 RS |
2378 | |
2379 | @cindex prefix argument unreading | |
2380 | For example, the function that implements numeric prefix arguments reads | |
2381 | any number of digits. When it finds a non-digit event, it must unread | |
2382 | the event so that it can be read normally by the command loop. | |
177c0ea7 | 2383 | Likewise, incremental search uses this feature to unread events with no |
f142f62a RS |
2384 | special meaning in a search, because these events should exit the search |
2385 | and then execute normally. | |
2386 | ||
b22f3a19 RS |
2387 | The reliable and easy way to extract events from a key sequence so as to |
2388 | put them in @code{unread-command-events} is to use | |
f142f62a | 2389 | @code{listify-key-sequence} (@pxref{Strings of Events}). |
f9f59935 RS |
2390 | |
2391 | Normally you add events to the front of this list, so that the events | |
2392 | most recently unread will be reread first. | |
8db970a4 RS |
2393 | @end defvar |
2394 | ||
969fe9b5 RS |
2395 | @defun listify-key-sequence key |
2396 | This function converts the string or vector @var{key} to a list of | |
2397 | individual events, which you can put in @code{unread-command-events}. | |
2398 | @end defun | |
2399 | ||
8db970a4 RS |
2400 | @defvar unread-command-char |
2401 | This variable holds a character to be read as command input. | |
2402 | A value of -1 means ``empty''. | |
2403 | ||
f142f62a | 2404 | This variable is mostly obsolete now that you can use |
8db970a4 RS |
2405 | @code{unread-command-events} instead; it exists only to support programs |
2406 | written for Emacs versions 18 and earlier. | |
2407 | @end defvar | |
2408 | ||
8db970a4 RS |
2409 | @defun input-pending-p |
2410 | @cindex waiting for command key input | |
2411 | This function determines whether any command input is currently | |
2412 | available to be read. It returns immediately, with value @code{t} if | |
f142f62a RS |
2413 | there is available input, @code{nil} otherwise. On rare occasions it |
2414 | may return @code{t} when no input is available. | |
8db970a4 RS |
2415 | @end defun |
2416 | ||
2417 | @defvar last-input-event | |
969fe9b5 | 2418 | @defvarx last-input-char |
f142f62a | 2419 | This variable records the last terminal input event read, whether |
8db970a4 RS |
2420 | as part of a command or explicitly by a Lisp program. |
2421 | ||
f142f62a | 2422 | In the example below, the Lisp program reads the character @kbd{1}, |
ad800164 | 2423 | @acronym{ASCII} code 49. It becomes the value of @code{last-input-event}, |
bfe721d1 KH |
2424 | while @kbd{C-e} (we assume @kbd{C-x C-e} command is used to evaluate |
2425 | this expression) remains the value of @code{last-command-event}. | |
8db970a4 RS |
2426 | |
2427 | @example | |
2428 | @group | |
2429 | (progn (print (read-char)) | |
f142f62a RS |
2430 | (print last-command-event) |
2431 | last-input-event) | |
8db970a4 RS |
2432 | @print{} 49 |
2433 | @print{} 5 | |
2434 | @result{} 49 | |
2435 | @end group | |
2436 | @end example | |
2437 | ||
2438 | The alias @code{last-input-char} exists for compatibility with | |
2439 | Emacs version 18. | |
2440 | @end defvar | |
2441 | ||
4049cdfa | 2442 | @defmac while-no-input body@dots{} |
7d9f1aed RS |
2443 | This construct runs the @var{body} forms and returns the value of the |
2444 | last one---but only if no input arrives. If any input arrives during | |
2445 | the execution of the @var{body} forms, it aborts them (working much | |
2446 | like a quit). The @code{while-no-input} form returns @code{nil} if | |
2447 | aborted by a real quit, and returns @code{t} if aborted by arrival of | |
2448 | other input. | |
a5034239 RS |
2449 | |
2450 | If a part of @var{body} binds @code{inhibit-quit} to non-@code{nil}, | |
2451 | arrival of input during those parts won't cause an abort until | |
2452 | the end of that part. | |
7d9f1aed | 2453 | |
5a36d834 | 2454 | If you want to be able to distinguish all possible values computed |
7d9f1aed RS |
2455 | by @var{body} from both kinds of abort conditions, write the code |
2456 | like this: | |
2457 | ||
2458 | @example | |
2459 | (while-no-input | |
2460 | (list | |
2461 | (progn . @var{body}))) | |
2462 | @end example | |
a5034239 RS |
2463 | @end defmac |
2464 | ||
8db970a4 RS |
2465 | @defun discard-input |
2466 | @cindex flush input | |
2467 | @cindex discard input | |
2468 | @cindex terminate keyboard macro | |
2469 | This function discards the contents of the terminal input buffer and | |
2470 | cancels any keyboard macro that might be in the process of definition. | |
2471 | It returns @code{nil}. | |
2472 | ||
2473 | In the following example, the user may type a number of characters right | |
2474 | after starting the evaluation of the form. After the @code{sleep-for} | |
177c0ea7 | 2475 | finishes sleeping, @code{discard-input} discards any characters typed |
f142f62a | 2476 | during the sleep. |
8db970a4 RS |
2477 | |
2478 | @example | |
2479 | (progn (sleep-for 2) | |
f142f62a | 2480 | (discard-input)) |
8db970a4 RS |
2481 | @result{} nil |
2482 | @end example | |
2483 | @end defun | |
2484 | ||
f9f59935 RS |
2485 | @node Special Events |
2486 | @section Special Events | |
2487 | ||
2488 | @cindex special events | |
2489 | Special events are handled at a very low level---as soon as they are | |
2490 | read. The @code{read-event} function processes these events itself, and | |
5504e99c LT |
2491 | never returns them. Instead, it keeps waiting for the first event |
2492 | that is not special and returns that one. | |
f9f59935 RS |
2493 | |
2494 | Events that are handled in this way do not echo, they are never grouped | |
2495 | into key sequences, and they never appear in the value of | |
2496 | @code{last-command-event} or @code{(this-command-keys)}. They do not | |
2497 | discard a numeric argument, they cannot be unread with | |
2498 | @code{unread-command-events}, they may not appear in a keyboard macro, | |
2499 | and they are not recorded in a keyboard macro while you are defining | |
2500 | one. | |
2501 | ||
2502 | These events do, however, appear in @code{last-input-event} immediately | |
2503 | after they are read, and this is the way for the event's definition to | |
2504 | find the actual event. | |
2505 | ||
2506 | The events types @code{iconify-frame}, @code{make-frame-visible} and | |
2507 | @code{delete-frame} are normally handled in this way. The keymap which | |
2508 | defines how to handle special events---and which events are special---is | |
2509 | in the variable @code{special-event-map} (@pxref{Active Keymaps}). | |
2510 | ||
8db970a4 RS |
2511 | @node Waiting |
2512 | @section Waiting for Elapsed Time or Input | |
2513 | @cindex pausing | |
2514 | @cindex waiting | |
2515 | ||
f142f62a RS |
2516 | The wait functions are designed to wait for a certain amount of time |
2517 | to pass or until there is input. For example, you may wish to pause in | |
2518 | the middle of a computation to allow the user time to view the display. | |
2519 | @code{sit-for} pauses and updates the screen, and returns immediately if | |
2520 | input comes in, while @code{sleep-for} pauses without updating the | |
2521 | screen. | |
8db970a4 | 2522 | |
14bd0b09 | 2523 | @defun sit-for seconds &optional nodisp |
8db970a4 RS |
2524 | This function performs redisplay (provided there is no pending input |
2525 | from the user), then waits @var{seconds} seconds, or until input is | |
f142f62a | 2526 | available. The value is @code{t} if @code{sit-for} waited the full |
177c0ea7 | 2527 | time with no input arriving (see @code{input-pending-p} in @ref{Event |
f142f62a | 2528 | Input Misc}). Otherwise, the value is @code{nil}. |
8db970a4 | 2529 | |
bfe721d1 KH |
2530 | The argument @var{seconds} need not be an integer. If it is a floating |
2531 | point number, @code{sit-for} waits for a fractional number of seconds. | |
2532 | Some systems support only a whole number of seconds; on these systems, | |
2533 | @var{seconds} is rounded down. | |
2534 | ||
8241495d RS |
2535 | The expression @code{(sit-for 0)} is a convenient way to request a |
2536 | redisplay, without any delay. @xref{Forcing Redisplay}. | |
8db970a4 RS |
2537 | |
2538 | If @var{nodisp} is non-@code{nil}, then @code{sit-for} does not | |
2539 | redisplay, but it still returns as soon as input is available (or when | |
2540 | the timeout elapses). | |
2541 | ||
22697dac KH |
2542 | Iconifying or deiconifying a frame makes @code{sit-for} return, because |
2543 | that generates an event. @xref{Misc Events}. | |
2544 | ||
8db970a4 RS |
2545 | The usual purpose of @code{sit-for} is to give the user time to read |
2546 | text that you display. | |
14bd0b09 RS |
2547 | |
2548 | It is also possible to call @code{sit-for} with three arguments, | |
2549 | as @code{(sit-for @var{seconds} @var{millisec} @var{nodisp})}, | |
2550 | but that is considered obsolete. | |
8db970a4 RS |
2551 | @end defun |
2552 | ||
2553 | @defun sleep-for seconds &optional millisec | |
2554 | This function simply pauses for @var{seconds} seconds without updating | |
2555 | the display. It pays no attention to available input. It returns | |
2556 | @code{nil}. | |
2557 | ||
bfe721d1 KH |
2558 | The argument @var{seconds} need not be an integer. If it is a floating |
2559 | point number, @code{sleep-for} waits for a fractional number of seconds. | |
2560 | Some systems support only a whole number of seconds; on these systems, | |
2561 | @var{seconds} is rounded down. | |
2562 | ||
8db970a4 RS |
2563 | The optional argument @var{millisec} specifies an additional waiting |
2564 | period measured in milliseconds. This adds to the period specified by | |
bfe721d1 KH |
2565 | @var{seconds}. If the system doesn't support waiting fractions of a |
2566 | second, you get an error if you specify nonzero @var{millisec}. | |
8db970a4 RS |
2567 | |
2568 | Use @code{sleep-for} when you wish to guarantee a delay. | |
2569 | @end defun | |
2570 | ||
2571 | @xref{Time of Day}, for functions to get the current time. | |
2572 | ||
2573 | @node Quitting | |
2574 | @section Quitting | |
2575 | @cindex @kbd{C-g} | |
2576 | @cindex quitting | |
34c0b12e | 2577 | @cindex interrupt Lisp functions |
8db970a4 | 2578 | |
b22f3a19 RS |
2579 | Typing @kbd{C-g} while a Lisp function is running causes Emacs to |
2580 | @dfn{quit} whatever it is doing. This means that control returns to the | |
2581 | innermost active command loop. | |
8db970a4 RS |
2582 | |
2583 | Typing @kbd{C-g} while the command loop is waiting for keyboard input | |
2584 | does not cause a quit; it acts as an ordinary input character. In the | |
2585 | simplest case, you cannot tell the difference, because @kbd{C-g} | |
2586 | normally runs the command @code{keyboard-quit}, whose effect is to quit. | |
969fe9b5 RS |
2587 | However, when @kbd{C-g} follows a prefix key, they combine to form an |
2588 | undefined key. The effect is to cancel the prefix key as well as any | |
2589 | prefix argument. | |
8db970a4 RS |
2590 | |
2591 | In the minibuffer, @kbd{C-g} has a different definition: it aborts out | |
2592 | of the minibuffer. This means, in effect, that it exits the minibuffer | |
2593 | and then quits. (Simply quitting would return to the command loop | |
2594 | @emph{within} the minibuffer.) The reason why @kbd{C-g} does not quit | |
2595 | directly when the command reader is reading input is so that its meaning | |
2596 | can be redefined in the minibuffer in this way. @kbd{C-g} following a | |
2597 | prefix key is not redefined in the minibuffer, and it has its normal | |
2598 | effect of canceling the prefix key and prefix argument. This too | |
f142f62a | 2599 | would not be possible if @kbd{C-g} always quit directly. |
8db970a4 | 2600 | |
b22f3a19 | 2601 | When @kbd{C-g} does directly quit, it does so by setting the variable |
f142f62a RS |
2602 | @code{quit-flag} to @code{t}. Emacs checks this variable at appropriate |
2603 | times and quits if it is not @code{nil}. Setting @code{quit-flag} | |
8db970a4 RS |
2604 | non-@code{nil} in any way thus causes a quit. |
2605 | ||
f142f62a | 2606 | At the level of C code, quitting cannot happen just anywhere; only at the |
b22f3a19 | 2607 | special places that check @code{quit-flag}. The reason for this is |
8db970a4 | 2608 | that quitting at other places might leave an inconsistency in Emacs's |
177c0ea7 | 2609 | internal state. Because quitting is delayed until a safe place, quitting |
8db970a4 RS |
2610 | cannot make Emacs crash. |
2611 | ||
2612 | Certain functions such as @code{read-key-sequence} or | |
2613 | @code{read-quoted-char} prevent quitting entirely even though they wait | |
2614 | for input. Instead of quitting, @kbd{C-g} serves as the requested | |
2615 | input. In the case of @code{read-key-sequence}, this serves to bring | |
2616 | about the special behavior of @kbd{C-g} in the command loop. In the | |
2617 | case of @code{read-quoted-char}, this is so that @kbd{C-q} can be used | |
177c0ea7 | 2618 | to quote a @kbd{C-g}. |
8db970a4 | 2619 | |
34c0b12e | 2620 | @cindex prevent quitting |
8db970a4 RS |
2621 | You can prevent quitting for a portion of a Lisp function by binding |
2622 | the variable @code{inhibit-quit} to a non-@code{nil} value. Then, | |
2623 | although @kbd{C-g} still sets @code{quit-flag} to @code{t} as usual, the | |
2624 | usual result of this---a quit---is prevented. Eventually, | |
2625 | @code{inhibit-quit} will become @code{nil} again, such as when its | |
2626 | binding is unwound at the end of a @code{let} form. At that time, if | |
2627 | @code{quit-flag} is still non-@code{nil}, the requested quit happens | |
b22f3a19 RS |
2628 | immediately. This behavior is ideal when you wish to make sure that |
2629 | quitting does not happen within a ``critical section'' of the program. | |
8db970a4 RS |
2630 | |
2631 | @cindex @code{read-quoted-char} quitting | |
2632 | In some functions (such as @code{read-quoted-char}), @kbd{C-g} is | |
b22f3a19 | 2633 | handled in a special way that does not involve quitting. This is done |
f142f62a | 2634 | by reading the input with @code{inhibit-quit} bound to @code{t}, and |
8db970a4 RS |
2635 | setting @code{quit-flag} to @code{nil} before @code{inhibit-quit} |
2636 | becomes @code{nil} again. This excerpt from the definition of | |
2637 | @code{read-quoted-char} shows how this is done; it also shows that | |
2638 | normal quitting is permitted after the first character of input. | |
2639 | ||
2640 | @example | |
2641 | (defun read-quoted-char (&optional prompt) | |
2642 | "@dots{}@var{documentation}@dots{}" | |
969fe9b5 RS |
2643 | (let ((message-log-max nil) done (first t) (code 0) char) |
2644 | (while (not done) | |
2645 | (let ((inhibit-quit first) | |
2646 | @dots{}) | |
2647 | (and prompt (message "%s-" prompt)) | |
2648 | (setq char (read-event)) | |
2649 | (if inhibit-quit (setq quit-flag nil))) | |
2650 | @r{@dots{}set the variable @code{code}@dots{}}) | |
2651 | code)) | |
8db970a4 RS |
2652 | @end example |
2653 | ||
2654 | @defvar quit-flag | |
f142f62a RS |
2655 | If this variable is non-@code{nil}, then Emacs quits immediately, unless |
2656 | @code{inhibit-quit} is non-@code{nil}. Typing @kbd{C-g} ordinarily sets | |
8db970a4 RS |
2657 | @code{quit-flag} non-@code{nil}, regardless of @code{inhibit-quit}. |
2658 | @end defvar | |
2659 | ||
2660 | @defvar inhibit-quit | |
2661 | This variable determines whether Emacs should quit when @code{quit-flag} | |
2662 | is set to a value other than @code{nil}. If @code{inhibit-quit} is | |
2663 | non-@code{nil}, then @code{quit-flag} has no special effect. | |
2664 | @end defvar | |
2665 | ||
4049cdfa JL |
2666 | @defmac with-local-quit body@dots{} |
2667 | This macro executes @var{body} forms in sequence, but allows quitting, at | |
5504e99c LT |
2668 | least locally, within @var{body} even if @code{inhibit-quit} was |
2669 | non-@code{nil} outside this construct. It returns the value of the | |
4049cdfa | 2670 | last form in @var{body}, unless exited by quitting, in which case |
eab463f6 | 2671 | it returns @code{nil}. |
5504e99c LT |
2672 | |
2673 | If @code{inhibit-quit} is @code{nil} on entry to @code{with-local-quit}, | |
4049cdfa | 2674 | it only executes the @var{body}, and setting @code{quit-flag} causes |
5504e99c LT |
2675 | a normal quit. However, if @code{inhibit-quit} is non-@code{nil} so |
2676 | that ordinary quitting is delayed, a non-@code{nil} @code{quit-flag} | |
2677 | triggers a special kind of local quit. This ends the execution of | |
4049cdfa | 2678 | @var{body} and exits the @code{with-local-quit} body with |
5504e99c LT |
2679 | @code{quit-flag} still non-@code{nil}, so that another (ordinary) quit |
2680 | will happen as soon as that is allowed. If @code{quit-flag} is | |
4049cdfa JL |
2681 | already non-@code{nil} at the beginning of @var{body}, the local quit |
2682 | happens immediately and the body doesn't execute at all. | |
5504e99c LT |
2683 | |
2684 | This macro is mainly useful in functions that can be called from | |
617e58e7 RS |
2685 | timers, process filters, process sentinels, @code{pre-command-hook}, |
2686 | @code{post-command-hook}, and other places where @code{inhibit-quit} is | |
2687 | normally bound to @code{t}. | |
5504e99c LT |
2688 | @end defmac |
2689 | ||
8db970a4 RS |
2690 | @deffn Command keyboard-quit |
2691 | This function signals the @code{quit} condition with @code{(signal 'quit | |
2692 | nil)}. This is the same thing that quitting does. (See @code{signal} | |
2693 | in @ref{Errors}.) | |
2694 | @end deffn | |
2695 | ||
2696 | You can specify a character other than @kbd{C-g} to use for quitting. | |
2697 | See the function @code{set-input-mode} in @ref{Terminal Input}. | |
177c0ea7 | 2698 | |
8db970a4 RS |
2699 | @node Prefix Command Arguments |
2700 | @section Prefix Command Arguments | |
2701 | @cindex prefix argument | |
2702 | @cindex raw prefix argument | |
2703 | @cindex numeric prefix argument | |
2704 | ||
2705 | Most Emacs commands can use a @dfn{prefix argument}, a number | |
2706 | specified before the command itself. (Don't confuse prefix arguments | |
b22f3a19 RS |
2707 | with prefix keys.) The prefix argument is at all times represented by a |
2708 | value, which may be @code{nil}, meaning there is currently no prefix | |
2709 | argument. Each command may use the prefix argument or ignore it. | |
8db970a4 RS |
2710 | |
2711 | There are two representations of the prefix argument: @dfn{raw} and | |
2712 | @dfn{numeric}. The editor command loop uses the raw representation | |
2713 | internally, and so do the Lisp variables that store the information, but | |
2714 | commands can request either representation. | |
2715 | ||
2716 | Here are the possible values of a raw prefix argument: | |
2717 | ||
2718 | @itemize @bullet | |
2719 | @item | |
2720 | @code{nil}, meaning there is no prefix argument. Its numeric value is | |
2721 | 1, but numerous commands make a distinction between @code{nil} and the | |
2722 | integer 1. | |
2723 | ||
2724 | @item | |
2725 | An integer, which stands for itself. | |
2726 | ||
2727 | @item | |
2728 | A list of one element, which is an integer. This form of prefix | |
2729 | argument results from one or a succession of @kbd{C-u}'s with no | |
2730 | digits. The numeric value is the integer in the list, but some | |
2731 | commands make a distinction between such a list and an integer alone. | |
2732 | ||
2733 | @item | |
2734 | The symbol @code{-}. This indicates that @kbd{M--} or @kbd{C-u -} was | |
2735 | typed, without following digits. The equivalent numeric value is | |
2736 | @minus{}1, but some commands make a distinction between the integer | |
2737 | @minus{}1 and the symbol @code{-}. | |
2738 | @end itemize | |
2739 | ||
f142f62a RS |
2740 | We illustrate these possibilities by calling the following function with |
2741 | various prefixes: | |
8db970a4 RS |
2742 | |
2743 | @example | |
2744 | @group | |
2745 | (defun display-prefix (arg) | |
2746 | "Display the value of the raw prefix arg." | |
2747 | (interactive "P") | |
2748 | (message "%s" arg)) | |
2749 | @end group | |
2750 | @end example | |
2751 | ||
2752 | @noindent | |
2753 | Here are the results of calling @code{display-prefix} with various | |
2754 | raw prefix arguments: | |
2755 | ||
2756 | @example | |
2757 | M-x display-prefix @print{} nil | |
2758 | ||
2759 | C-u M-x display-prefix @print{} (4) | |
2760 | ||
2761 | C-u C-u M-x display-prefix @print{} (16) | |
2762 | ||
2763 | C-u 3 M-x display-prefix @print{} 3 | |
2764 | ||
2765 | M-3 M-x display-prefix @print{} 3 ; @r{(Same as @code{C-u 3}.)} | |
2766 | ||
177c0ea7 | 2767 | C-u - M-x display-prefix @print{} - |
8db970a4 | 2768 | |
f142f62a | 2769 | M-- M-x display-prefix @print{} - ; @r{(Same as @code{C-u -}.)} |
8db970a4 | 2770 | |
177c0ea7 | 2771 | C-u - 7 M-x display-prefix @print{} -7 |
8db970a4 | 2772 | |
f142f62a | 2773 | M-- 7 M-x display-prefix @print{} -7 ; @r{(Same as @code{C-u -7}.)} |
8db970a4 RS |
2774 | @end example |
2775 | ||
2776 | Emacs uses two variables to store the prefix argument: | |
2777 | @code{prefix-arg} and @code{current-prefix-arg}. Commands such as | |
2778 | @code{universal-argument} that set up prefix arguments for other | |
2779 | commands store them in @code{prefix-arg}. In contrast, | |
2780 | @code{current-prefix-arg} conveys the prefix argument to the current | |
2781 | command, so setting it has no effect on the prefix arguments for future | |
2782 | commands. | |
2783 | ||
2784 | Normally, commands specify which representation to use for the prefix | |
b3a1cf11 | 2785 | argument, either numeric or raw, in the @code{interactive} specification. |
b22f3a19 | 2786 | (@xref{Using Interactive}.) Alternatively, functions may look at the |
8db970a4 RS |
2787 | value of the prefix argument directly in the variable |
2788 | @code{current-prefix-arg}, but this is less clean. | |
2789 | ||
f142f62a RS |
2790 | @defun prefix-numeric-value arg |
2791 | This function returns the numeric meaning of a valid raw prefix argument | |
2792 | value, @var{arg}. The argument may be a symbol, a number, or a list. | |
b22f3a19 RS |
2793 | If it is @code{nil}, the value 1 is returned; if it is @code{-}, the |
2794 | value @minus{}1 is returned; if it is a number, that number is returned; | |
4bdcd3ef | 2795 | if it is a list, the @sc{car} of that list (which should be a number) is |
b22f3a19 | 2796 | returned. |
f142f62a RS |
2797 | @end defun |
2798 | ||
2799 | @defvar current-prefix-arg | |
2800 | This variable holds the raw prefix argument for the @emph{current} | |
9e2b495b RS |
2801 | command. Commands may examine it directly, but the usual method for |
2802 | accessing it is with @code{(interactive "P")}. | |
f142f62a RS |
2803 | @end defvar |
2804 | ||
2805 | @defvar prefix-arg | |
2806 | The value of this variable is the raw prefix argument for the | |
f9f59935 RS |
2807 | @emph{next} editing command. Commands such as @code{universal-argument} |
2808 | that specify prefix arguments for the following command work by setting | |
2809 | this variable. | |
03c6b7f6 RS |
2810 | @end defvar |
2811 | ||
03c6b7f6 RS |
2812 | @defvar last-prefix-arg |
2813 | The raw prefix argument value used by the previous command. | |
f142f62a RS |
2814 | @end defvar |
2815 | ||
f9f59935 RS |
2816 | The following commands exist to set up prefix arguments for the |
2817 | following command. Do not call them for any other reason. | |
8db970a4 RS |
2818 | |
2819 | @deffn Command universal-argument | |
2820 | This command reads input and specifies a prefix argument for the | |
2821 | following command. Don't call this command yourself unless you know | |
2822 | what you are doing. | |
2823 | @end deffn | |
2824 | ||
2825 | @deffn Command digit-argument arg | |
2826 | This command adds to the prefix argument for the following command. The | |
2827 | argument @var{arg} is the raw prefix argument as it was before this | |
2828 | command; it is used to compute the updated prefix argument. Don't call | |
2829 | this command yourself unless you know what you are doing. | |
2830 | @end deffn | |
2831 | ||
2832 | @deffn Command negative-argument arg | |
2833 | This command adds to the numeric argument for the next command. The | |
2834 | argument @var{arg} is the raw prefix argument as it was before this | |
2835 | command; its value is negated to form the new prefix argument. Don't | |
2836 | call this command yourself unless you know what you are doing. | |
2837 | @end deffn | |
2838 | ||
8db970a4 RS |
2839 | @node Recursive Editing |
2840 | @section Recursive Editing | |
2841 | @cindex recursive command loop | |
2842 | @cindex recursive editing level | |
2843 | @cindex command loop, recursive | |
2844 | ||
f142f62a RS |
2845 | The Emacs command loop is entered automatically when Emacs starts up. |
2846 | This top-level invocation of the command loop never exits; it keeps | |
2847 | running as long as Emacs does. Lisp programs can also invoke the | |
2848 | command loop. Since this makes more than one activation of the command | |
2849 | loop, we call it @dfn{recursive editing}. A recursive editing level has | |
2850 | the effect of suspending whatever command invoked it and permitting the | |
2851 | user to do arbitrary editing before resuming that command. | |
8db970a4 RS |
2852 | |
2853 | The commands available during recursive editing are the same ones | |
2854 | available in the top-level editing loop and defined in the keymaps. | |
2855 | Only a few special commands exit the recursive editing level; the others | |
f142f62a RS |
2856 | return to the recursive editing level when they finish. (The special |
2857 | commands for exiting are always available, but they do nothing when | |
2858 | recursive editing is not in progress.) | |
8db970a4 RS |
2859 | |
2860 | All command loops, including recursive ones, set up all-purpose error | |
2861 | handlers so that an error in a command run from the command loop will | |
2862 | not exit the loop. | |
2863 | ||
2864 | @cindex minibuffer input | |
2865 | Minibuffer input is a special kind of recursive editing. It has a few | |
2866 | special wrinkles, such as enabling display of the minibuffer and the | |
2867 | minibuffer window, but fewer than you might suppose. Certain keys | |
2868 | behave differently in the minibuffer, but that is only because of the | |
2869 | minibuffer's local map; if you switch windows, you get the usual Emacs | |
2870 | commands. | |
2871 | ||
2872 | @cindex @code{throw} example | |
2873 | @kindex exit | |
2874 | @cindex exit recursive editing | |
2875 | @cindex aborting | |
2876 | To invoke a recursive editing level, call the function | |
2877 | @code{recursive-edit}. This function contains the command loop; it also | |
2878 | contains a call to @code{catch} with tag @code{exit}, which makes it | |
2879 | possible to exit the recursive editing level by throwing to @code{exit} | |
2880 | (@pxref{Catch and Throw}). If you throw a value other than @code{t}, | |
2881 | then @code{recursive-edit} returns normally to the function that called | |
2882 | it. The command @kbd{C-M-c} (@code{exit-recursive-edit}) does this. | |
2883 | Throwing a @code{t} value causes @code{recursive-edit} to quit, so that | |
2884 | control returns to the command loop one level up. This is called | |
2885 | @dfn{aborting}, and is done by @kbd{C-]} (@code{abort-recursive-edit}). | |
2886 | ||
2887 | Most applications should not use recursive editing, except as part of | |
2888 | using the minibuffer. Usually it is more convenient for the user if you | |
2889 | change the major mode of the current buffer temporarily to a special | |
b22f3a19 RS |
2890 | major mode, which should have a command to go back to the previous mode. |
2891 | (The @kbd{e} command in Rmail uses this technique.) Or, if you wish to | |
2892 | give the user different text to edit ``recursively'', create and select | |
2893 | a new buffer in a special mode. In this mode, define a command to | |
2894 | complete the processing and go back to the previous buffer. (The | |
2895 | @kbd{m} command in Rmail does this.) | |
8db970a4 RS |
2896 | |
2897 | Recursive edits are useful in debugging. You can insert a call to | |
2898 | @code{debug} into a function definition as a sort of breakpoint, so that | |
2899 | you can look around when the function gets there. @code{debug} invokes | |
2900 | a recursive edit but also provides the other features of the debugger. | |
2901 | ||
2902 | Recursive editing levels are also used when you type @kbd{C-r} in | |
2903 | @code{query-replace} or use @kbd{C-x q} (@code{kbd-macro-query}). | |
2904 | ||
2905 | @defun recursive-edit | |
2906 | @cindex suspend evaluation | |
2907 | This function invokes the editor command loop. It is called | |
2908 | automatically by the initialization of Emacs, to let the user begin | |
2909 | editing. When called from a Lisp program, it enters a recursive editing | |
2910 | level. | |
2911 | ||
2912 | In the following example, the function @code{simple-rec} first | |
2913 | advances point one word, then enters a recursive edit, printing out a | |
2914 | message in the echo area. The user can then do any editing desired, and | |
2915 | then type @kbd{C-M-c} to exit and continue executing @code{simple-rec}. | |
2916 | ||
2917 | @example | |
2918 | (defun simple-rec () | |
2919 | (forward-word 1) | |
f142f62a | 2920 | (message "Recursive edit in progress") |
8db970a4 RS |
2921 | (recursive-edit) |
2922 | (forward-word 1)) | |
2923 | @result{} simple-rec | |
2924 | (simple-rec) | |
2925 | @result{} nil | |
2926 | @end example | |
2927 | @end defun | |
2928 | ||
2929 | @deffn Command exit-recursive-edit | |
2930 | This function exits from the innermost recursive edit (including | |
2931 | minibuffer input). Its definition is effectively @code{(throw 'exit | |
177c0ea7 | 2932 | nil)}. |
8db970a4 RS |
2933 | @end deffn |
2934 | ||
2935 | @deffn Command abort-recursive-edit | |
2936 | This function aborts the command that requested the innermost recursive | |
177c0ea7 | 2937 | edit (including minibuffer input), by signaling @code{quit} |
8db970a4 RS |
2938 | after exiting the recursive edit. Its definition is effectively |
2939 | @code{(throw 'exit t)}. @xref{Quitting}. | |
2940 | @end deffn | |
2941 | ||
2942 | @deffn Command top-level | |
2943 | This function exits all recursive editing levels; it does not return a | |
2944 | value, as it jumps completely out of any computation directly back to | |
2945 | the main command loop. | |
2946 | @end deffn | |
2947 | ||
2948 | @defun recursion-depth | |
2949 | This function returns the current depth of recursive edits. When no | |
2950 | recursive edit is active, it returns 0. | |
2951 | @end defun | |
2952 | ||
2953 | @node Disabling Commands | |
2954 | @section Disabling Commands | |
2955 | @cindex disabled command | |
2956 | ||
2957 | @dfn{Disabling a command} marks the command as requiring user | |
2958 | confirmation before it can be executed. Disabling is used for commands | |
2959 | which might be confusing to beginning users, to prevent them from using | |
2960 | the commands by accident. | |
2961 | ||
2962 | @kindex disabled | |
2963 | The low-level mechanism for disabling a command is to put a | |
2964 | non-@code{nil} @code{disabled} property on the Lisp symbol for the | |
2965 | command. These properties are normally set up by the user's | |
a40d4712 | 2966 | init file (@pxref{Init File}) with Lisp expressions such as this: |
8db970a4 RS |
2967 | |
2968 | @example | |
2969 | (put 'upcase-region 'disabled t) | |
2970 | @end example | |
2971 | ||
2972 | @noindent | |
a40d4712 PR |
2973 | For a few commands, these properties are present by default (you can |
2974 | remove them in your init file if you wish). | |
8db970a4 | 2975 | |
f142f62a RS |
2976 | If the value of the @code{disabled} property is a string, the message |
2977 | saying the command is disabled includes that string. For example: | |
8db970a4 RS |
2978 | |
2979 | @example | |
2980 | (put 'delete-region 'disabled | |
2981 | "Text deleted this way cannot be yanked back!\n") | |
2982 | @end example | |
2983 | ||
2984 | @xref{Disabling,,, emacs, The GNU Emacs Manual}, for the details on | |
2985 | what happens when a disabled command is invoked interactively. | |
2986 | Disabling a command has no effect on calling it as a function from Lisp | |
2987 | programs. | |
2988 | ||
2989 | @deffn Command enable-command command | |
5504e99c LT |
2990 | Allow @var{command} (a symbol) to be executed without special |
2991 | confirmation from now on, and alter the user's init file (@pxref{Init | |
a40d4712 | 2992 | File}) so that this will apply to future sessions. |
8db970a4 RS |
2993 | @end deffn |
2994 | ||
2995 | @deffn Command disable-command command | |
f142f62a | 2996 | Require special confirmation to execute @var{command} from now on, and |
5504e99c | 2997 | alter the user's init file so that this will apply to future sessions. |
8db970a4 RS |
2998 | @end deffn |
2999 | ||
de700726 LT |
3000 | @defvar disabled-command-function |
3001 | The value of this variable should be a function. When the user | |
3002 | invokes a disabled command interactively, this function is called | |
3003 | instead of the disabled command. It can use @code{this-command-keys} | |
3004 | to determine what the user typed to run the command, and thus find the | |
3005 | command itself. | |
8db970a4 | 3006 | |
de700726 LT |
3007 | The value may also be @code{nil}. Then all commands work normally, |
3008 | even disabled ones. | |
3009 | ||
3010 | By default, the value is a function that asks the user whether to | |
3011 | proceed. | |
8db970a4 RS |
3012 | @end defvar |
3013 | ||
3014 | @node Command History | |
3015 | @section Command History | |
3016 | @cindex command history | |
3017 | @cindex complex command | |
3018 | @cindex history of commands | |
3019 | ||
3020 | The command loop keeps a history of the complex commands that have | |
3021 | been executed, to make it convenient to repeat these commands. A | |
3022 | @dfn{complex command} is one for which the interactive argument reading | |
3023 | uses the minibuffer. This includes any @kbd{M-x} command, any | |
bfe721d1 | 3024 | @kbd{M-:} command, and any command whose @code{interactive} |
8db970a4 RS |
3025 | specification reads an argument from the minibuffer. Explicit use of |
3026 | the minibuffer during the execution of the command itself does not cause | |
3027 | the command to be considered complex. | |
3028 | ||
3029 | @defvar command-history | |
3030 | This variable's value is a list of recent complex commands, each | |
3031 | represented as a form to evaluate. It continues to accumulate all | |
a9f0a989 | 3032 | complex commands for the duration of the editing session, but when it |
b18531e5 RS |
3033 | reaches the maximum size (@pxref{Minibuffer History}), the oldest |
3034 | elements are deleted as new ones are added. | |
8db970a4 RS |
3035 | |
3036 | @example | |
3037 | @group | |
3038 | command-history | |
3039 | @result{} ((switch-to-buffer "chistory.texi") | |
3040 | (describe-key "^X^[") | |
3041 | (visit-tags-table "~/emacs/src/") | |
3042 | (find-tag "repeat-complex-command")) | |
3043 | @end group | |
3044 | @end example | |
3045 | @end defvar | |
3046 | ||
3047 | This history list is actually a special case of minibuffer history | |
3048 | (@pxref{Minibuffer History}), with one special twist: the elements are | |
3049 | expressions rather than strings. | |
3050 | ||
3051 | There are a number of commands devoted to the editing and recall of | |
3052 | previous commands. The commands @code{repeat-complex-command}, and | |
3053 | @code{list-command-history} are described in the user manual | |
3054 | (@pxref{Repetition,,, emacs, The GNU Emacs Manual}). Within the | |
f9f59935 | 3055 | minibuffer, the usual minibuffer history commands are available. |
8db970a4 RS |
3056 | |
3057 | @node Keyboard Macros | |
3058 | @section Keyboard Macros | |
3059 | @cindex keyboard macros | |
3060 | ||
3061 | A @dfn{keyboard macro} is a canned sequence of input events that can | |
f142f62a RS |
3062 | be considered a command and made the definition of a key. The Lisp |
3063 | representation of a keyboard macro is a string or vector containing the | |
3064 | events. Don't confuse keyboard macros with Lisp macros | |
3065 | (@pxref{Macros}). | |
8db970a4 | 3066 | |
5504e99c | 3067 | @defun execute-kbd-macro kbdmacro &optional count loopfunc |
f9f59935 RS |
3068 | This function executes @var{kbdmacro} as a sequence of events. If |
3069 | @var{kbdmacro} is a string or vector, then the events in it are executed | |
8db970a4 RS |
3070 | exactly as if they had been input by the user. The sequence is |
3071 | @emph{not} expected to be a single key sequence; normally a keyboard | |
3072 | macro definition consists of several key sequences concatenated. | |
3073 | ||
f9f59935 RS |
3074 | If @var{kbdmacro} is a symbol, then its function definition is used in |
3075 | place of @var{kbdmacro}. If that is another symbol, this process repeats. | |
8db970a4 RS |
3076 | Eventually the result should be a string or vector. If the result is |
3077 | not a symbol, string, or vector, an error is signaled. | |
3078 | ||
f9f59935 RS |
3079 | The argument @var{count} is a repeat count; @var{kbdmacro} is executed that |
3080 | many times. If @var{count} is omitted or @code{nil}, @var{kbdmacro} is | |
3081 | executed once. If it is 0, @var{kbdmacro} is executed over and over until it | |
177c0ea7 | 3082 | encounters an error or a failing search. |
f9f59935 | 3083 | |
5504e99c LT |
3084 | If @var{loopfunc} is non-@code{nil}, it is a function that is called, |
3085 | without arguments, prior to each iteration of the macro. If | |
3086 | @var{loopfunc} returns @code{nil}, then this stops execution of the macro. | |
3087 | ||
f9f59935 | 3088 | @xref{Reading One Event}, for an example of using @code{execute-kbd-macro}. |
8db970a4 RS |
3089 | @end defun |
3090 | ||
5504e99c | 3091 | @defvar executing-kbd-macro |
8db970a4 RS |
3092 | This variable contains the string or vector that defines the keyboard |
3093 | macro that is currently executing. It is @code{nil} if no macro is | |
f9f59935 | 3094 | currently executing. A command can test this variable so as to behave |
f142f62a RS |
3095 | differently when run from an executing macro. Do not set this variable |
3096 | yourself. | |
8db970a4 RS |
3097 | @end defvar |
3098 | ||
3099 | @defvar defining-kbd-macro | |
5504e99c LT |
3100 | This variable is non-@code{nil} if and only if a keyboard macro is |
3101 | being defined. A command can test this variable so as to behave | |
f9597b5b LT |
3102 | differently while a macro is being defined. The value is |
3103 | @code{append} while appending to the definition of an existing macro. | |
3104 | The commands @code{start-kbd-macro}, @code{kmacro-start-macro} and | |
3105 | @code{end-kbd-macro} set this variable---do not set it yourself. | |
22697dac | 3106 | |
bfe721d1 KH |
3107 | The variable is always local to the current terminal and cannot be |
3108 | buffer-local. @xref{Multiple Displays}. | |
3109 | @end defvar | |
3110 | ||
3111 | @defvar last-kbd-macro | |
3112 | This variable is the definition of the most recently defined keyboard | |
3113 | macro. Its value is a string or vector, or @code{nil}. | |
3114 | ||
3115 | The variable is always local to the current terminal and cannot be | |
22697dac | 3116 | buffer-local. @xref{Multiple Displays}. |
8db970a4 RS |
3117 | @end defvar |
3118 | ||
2842de30 EZ |
3119 | @defvar kbd-macro-termination-hook |
3120 | This normal hook (@pxref{Standard Hooks}) is run when a keyboard | |
3121 | macro terminates, regardless of what caused it to terminate (reaching | |
3122 | the macro end or an error which ended the macro prematurely). | |
3123 | @end defvar | |
ab5796a9 MB |
3124 | |
3125 | @ignore | |
3126 | arch-tag: e34944ad-7d5c-4980-be00-36a5fe54d4b1 | |
3127 | @end ignore |