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1 | @c -*-texinfo-*- |
2 | @c This is part of the GNU Emacs Lisp Reference Manual. | |
2064cc6a | 3 | @c Copyright (C) 1990-1995, 1998-1999, 2001-2012 Free Software Foundation, Inc. |
b8d4c8d0 | 4 | @c See the file elisp.texi for copying conditions. |
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5 | @node Command Loop, Keymaps, Minibuffers, Top |
6 | @chapter Command Loop | |
7 | @cindex editor command loop | |
8 | @cindex command loop | |
9 | ||
10 | When you run Emacs, it enters the @dfn{editor command loop} almost | |
11 | immediately. This loop reads key sequences, executes their definitions, | |
12 | and displays the results. In this chapter, we describe how these things | |
13 | are done, and the subroutines that allow Lisp programs to do them. | |
14 | ||
15 | @menu | |
16 | * Command Overview:: How the command loop reads commands. | |
17 | * Defining Commands:: Specifying how a function should read arguments. | |
18 | * Interactive Call:: Calling a command, so that it will read arguments. | |
77832c61 | 19 | * Distinguish Interactive:: Making a command distinguish interactive calls. |
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20 | * Command Loop Info:: Variables set by the command loop for you to examine. |
21 | * Adjusting Point:: Adjustment of point after a command. | |
d24880de | 22 | * Input Events:: What input looks like when you read it. |
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23 | * Reading Input:: How to read input events from the keyboard or mouse. |
24 | * Special Events:: Events processed immediately and individually. | |
25 | * Waiting:: Waiting for user input or elapsed time. | |
26 | * Quitting:: How @kbd{C-g} works. How to catch or defer quitting. | |
27 | * Prefix Command Arguments:: How the commands to set prefix args work. | |
28 | * Recursive Editing:: Entering a recursive edit, | |
29 | and why you usually shouldn't. | |
30 | * Disabling Commands:: How the command loop handles disabled commands. | |
31 | * Command History:: How the command history is set up, and how accessed. | |
32 | * Keyboard Macros:: How keyboard macros are implemented. | |
33 | @end menu | |
34 | ||
35 | @node Command Overview | |
36 | @section Command Loop Overview | |
37 | ||
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38 | The first thing the command loop must do is read a key sequence, |
39 | which is a sequence of input events that translates into a command. | |
40 | It does this by calling the function @code{read-key-sequence}. Lisp | |
41 | programs can also call this function (@pxref{Key Sequence Input}). | |
42 | They can also read input at a lower level with @code{read-key} or | |
43 | @code{read-event} (@pxref{Reading One Event}), or discard pending | |
44 | input with @code{discard-input} (@pxref{Event Input Misc}). | |
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45 | |
46 | The key sequence is translated into a command through the currently | |
47 | active keymaps. @xref{Key Lookup}, for information on how this is done. | |
48 | The result should be a keyboard macro or an interactively callable | |
49 | function. If the key is @kbd{M-x}, then it reads the name of another | |
50 | command, which it then calls. This is done by the command | |
51 | @code{execute-extended-command} (@pxref{Interactive Call}). | |
52 | ||
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53 | Prior to executing the command, Emacs runs @code{undo-boundary} to |
54 | create an undo boundary. @xref{Maintaining Undo}. | |
55 | ||
56 | To execute a command, Emacs first reads its arguments by calling | |
57 | @code{command-execute} (@pxref{Interactive Call}). For commands | |
58 | written in Lisp, the @code{interactive} specification says how to read | |
59 | the arguments. This may use the prefix argument (@pxref{Prefix | |
60 | Command Arguments}) or may read with prompting in the minibuffer | |
61 | (@pxref{Minibuffers}). For example, the command @code{find-file} has | |
62 | an @code{interactive} specification which says to read a file name | |
63 | using the minibuffer. The function body of @code{find-file} does not | |
64 | use the minibuffer, so if you call @code{find-file} as a function from | |
65 | Lisp code, you must supply the file name string as an ordinary Lisp | |
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66 | function argument. |
67 | ||
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68 | If the command is a keyboard macro (i.e.@: a string or vector), |
69 | Emacs executes it using @code{execute-kbd-macro} (@pxref{Keyboard | |
70 | Macros}). | |
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71 | |
72 | @defvar pre-command-hook | |
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73 | This normal hook is run by the editor command loop before it executes |
74 | each command. At that time, @code{this-command} contains the command | |
75 | that is about to run, and @code{last-command} describes the previous | |
76 | command. @xref{Command Loop Info}. | |
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77 | @end defvar |
78 | ||
79 | @defvar post-command-hook | |
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80 | This normal hook is run by the editor command loop after it executes |
81 | each command (including commands terminated prematurely by quitting or | |
82 | by errors). At that time, @code{this-command} refers to the command | |
83 | that just ran, and @code{last-command} refers to the command before | |
84 | that. | |
85 | ||
86 | This hook is also run when Emacs first enters the command loop (at | |
87 | which point @code{this-command} and @code{last-command} are both | |
88 | @code{nil}). | |
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89 | @end defvar |
90 | ||
91 | Quitting is suppressed while running @code{pre-command-hook} and | |
92 | @code{post-command-hook}. If an error happens while executing one of | |
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93 | these hooks, it does not terminate execution of the hook; instead |
94 | the error is silenced and the function in which the error occurred | |
95 | is removed from the hook. | |
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96 | |
97 | A request coming into the Emacs server (@pxref{Emacs Server,,, | |
98 | emacs, The GNU Emacs Manual}) runs these two hooks just as a keyboard | |
99 | command does. | |
100 | ||
101 | @node Defining Commands | |
102 | @section Defining Commands | |
103 | @cindex defining commands | |
104 | @cindex commands, defining | |
105 | @cindex functions, making them interactive | |
106 | @cindex interactive function | |
107 | ||
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108 | The special form @code{interactive} turns a Lisp function into a |
109 | command. The @code{interactive} form must be located at top-level in | |
110 | the function body (usually as the first form in the body), or in the | |
111 | @code{interactive-form} property of the function symbol. When the | |
112 | @code{interactive} form is located in the function body, it does | |
113 | nothing when actually executed. Its presence serves as a flag, which | |
114 | tells the Emacs command loop that the function can be called | |
115 | interactively. The argument of the @code{interactive} form controls | |
116 | the reading of arguments for an interactive call. | |
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117 | |
118 | @menu | |
119 | * Using Interactive:: General rules for @code{interactive}. | |
120 | * Interactive Codes:: The standard letter-codes for reading arguments | |
121 | in various ways. | |
122 | * Interactive Examples:: Examples of how to read interactive arguments. | |
123 | @end menu | |
124 | ||
125 | @node Using Interactive | |
126 | @subsection Using @code{interactive} | |
127 | @cindex arguments, interactive entry | |
128 | ||
129 | This section describes how to write the @code{interactive} form that | |
130 | makes a Lisp function an interactively-callable command, and how to | |
131 | examine a command's @code{interactive} form. | |
132 | ||
133 | @defspec interactive arg-descriptor | |
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134 | This special form declares that a function is a command, and that it |
135 | may therefore be called interactively (via @kbd{M-x} or by entering a | |
136 | key sequence bound to it). The argument @var{arg-descriptor} declares | |
137 | how to compute the arguments to the command when the command is called | |
138 | interactively. | |
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139 | |
140 | A command may be called from Lisp programs like any other function, but | |
141 | then the caller supplies the arguments and @var{arg-descriptor} has no | |
142 | effect. | |
143 | ||
c3aaf1d7 | 144 | @cindex @code{interactive-form}, function property |
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145 | The @code{interactive} form must be located at top-level in the |
146 | function body, or in the function symbol's @code{interactive-form} | |
147 | property (@pxref{Symbol Plists}). It has its effect because the | |
148 | command loop looks for it before calling the function | |
149 | (@pxref{Interactive Call}). Once the function is called, all its body | |
150 | forms are executed; at this time, if the @code{interactive} form | |
151 | occurs within the body, the form simply returns @code{nil} without | |
152 | even evaluating its argument. | |
153 | ||
154 | By convention, you should put the @code{interactive} form in the | |
155 | function body, as the first top-level form. If there is an | |
156 | @code{interactive} form in both the @code{interactive-form} symbol | |
157 | property and the function body, the former takes precedence. The | |
158 | @code{interactive-form} symbol property can be used to add an | |
159 | interactive form to an existing function, or change how its arguments | |
160 | are processed interactively, without redefining the function. | |
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161 | @end defspec |
162 | ||
163 | There are three possibilities for the argument @var{arg-descriptor}: | |
164 | ||
165 | @itemize @bullet | |
166 | @item | |
167 | It may be omitted or @code{nil}; then the command is called with no | |
168 | arguments. This leads quickly to an error if the command requires one | |
169 | or more arguments. | |
170 | ||
171 | @item | |
9fa6d455 | 172 | It may be a string; its contents are a sequence of elements separated |
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173 | by newlines, one for each argument@footnote{Some elements actually |
174 | supply two arguments.}. Each element consists of a code character | |
5cba88a2 | 175 | (@pxref{Interactive Codes}) optionally followed by a prompt (which |
9fa6d455 | 176 | some code characters use and some ignore). Here is an example: |
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177 | |
178 | @smallexample | |
9fa6d455 | 179 | (interactive "P\nbFrobnicate buffer: ") |
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180 | @end smallexample |
181 | ||
182 | @noindent | |
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183 | The code letter @samp{P} sets the command's first argument to the raw |
184 | command prefix (@pxref{Prefix Command Arguments}). @samp{bFrobnicate | |
185 | buffer: } prompts the user with @samp{Frobnicate buffer: } to enter | |
186 | the name of an existing buffer, which becomes the second and final | |
187 | argument. | |
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188 | |
189 | @c Emacs 19 feature | |
190 | The prompt string can use @samp{%} to include previous argument values | |
191 | (starting with the first argument) in the prompt. This is done using | |
192 | @code{format} (@pxref{Formatting Strings}). For example, here is how | |
193 | you could read the name of an existing buffer followed by a new name to | |
194 | give to that buffer: | |
195 | ||
196 | @smallexample | |
197 | @group | |
198 | (interactive "bBuffer to rename: \nsRename buffer %s to: ") | |
199 | @end group | |
200 | @end smallexample | |
201 | ||
202 | @cindex @samp{*} in @code{interactive} | |
203 | @cindex read-only buffers in interactive | |
ee6e73b8 | 204 | If @samp{*} appears at the beginning of the string, then an error is |
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205 | signaled if the buffer is read-only. |
206 | ||
207 | @cindex @samp{@@} in @code{interactive} | |
208 | @c Emacs 19 feature | |
ee6e73b8 | 209 | If @samp{@@} appears at the beginning of the string, and if the key |
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210 | sequence used to invoke the command includes any mouse events, then |
211 | the window associated with the first of those events is selected | |
212 | before the command is run. | |
213 | ||
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214 | @cindex @samp{^} in @code{interactive} |
215 | @cindex shift-selection, and @code{interactive} spec | |
216 | If @samp{^} appears at the beginning of the string, and if the command | |
217 | was invoked through @dfn{shift-translation}, set the mark and activate | |
218 | the region temporarily, or extend an already active region, before the | |
219 | command is run. If the command was invoked without shift-translation, | |
220 | and the region is temporarily active, deactivate the region before the | |
221 | command is run. Shift-translation is controlled on the user level by | |
222 | @code{shift-select-mode}; see @ref{Shift Selection,,, emacs, The GNU | |
223 | Emacs Manual}. | |
224 | ||
225 | You can use @samp{*}, @samp{@@}, and @code{^} together; the order does | |
226 | not matter. Actual reading of arguments is controlled by the rest of | |
227 | the prompt string (starting with the first character that is not | |
228 | @samp{*}, @samp{@@}, or @samp{^}). | |
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229 | |
230 | @item | |
231 | It may be a Lisp expression that is not a string; then it should be a | |
232 | form that is evaluated to get a list of arguments to pass to the | |
233 | command. Usually this form will call various functions to read input | |
234 | from the user, most often through the minibuffer (@pxref{Minibuffers}) | |
235 | or directly from the keyboard (@pxref{Reading Input}). | |
236 | ||
237 | Providing point or the mark as an argument value is also common, but | |
238 | if you do this @emph{and} read input (whether using the minibuffer or | |
239 | not), be sure to get the integer values of point or the mark after | |
240 | reading. The current buffer may be receiving subprocess output; if | |
241 | subprocess output arrives while the command is waiting for input, it | |
242 | could relocate point and the mark. | |
243 | ||
244 | Here's an example of what @emph{not} to do: | |
245 | ||
246 | @smallexample | |
247 | (interactive | |
248 | (list (region-beginning) (region-end) | |
249 | (read-string "Foo: " nil 'my-history))) | |
250 | @end smallexample | |
251 | ||
252 | @noindent | |
253 | Here's how to avoid the problem, by examining point and the mark after | |
254 | reading the keyboard input: | |
255 | ||
256 | @smallexample | |
257 | (interactive | |
258 | (let ((string (read-string "Foo: " nil 'my-history))) | |
259 | (list (region-beginning) (region-end) string))) | |
260 | @end smallexample | |
261 | ||
262 | @strong{Warning:} the argument values should not include any data | |
263 | types that can't be printed and then read. Some facilities save | |
264 | @code{command-history} in a file to be read in the subsequent | |
265 | sessions; if a command's arguments contain a data type that prints | |
266 | using @samp{#<@dots{}>} syntax, those facilities won't work. | |
267 | ||
268 | There are, however, a few exceptions: it is ok to use a limited set of | |
269 | expressions such as @code{(point)}, @code{(mark)}, | |
270 | @code{(region-beginning)}, and @code{(region-end)}, because Emacs | |
271 | recognizes them specially and puts the expression (rather than its | |
272 | value) into the command history. To see whether the expression you | |
273 | wrote is one of these exceptions, run the command, then examine | |
274 | @code{(car command-history)}. | |
275 | @end itemize | |
276 | ||
277 | @cindex examining the @code{interactive} form | |
278 | @defun interactive-form function | |
279 | This function returns the @code{interactive} form of @var{function}. | |
280 | If @var{function} is an interactively callable function | |
281 | (@pxref{Interactive Call}), the value is the command's | |
282 | @code{interactive} form @code{(interactive @var{spec})}, which | |
283 | specifies how to compute its arguments. Otherwise, the value is | |
284 | @code{nil}. If @var{function} is a symbol, its function definition is | |
285 | used. | |
286 | @end defun | |
287 | ||
288 | @node Interactive Codes | |
289 | @comment node-name, next, previous, up | |
290 | @subsection Code Characters for @code{interactive} | |
291 | @cindex interactive code description | |
292 | @cindex description for interactive codes | |
293 | @cindex codes, interactive, description of | |
294 | @cindex characters for interactive codes | |
295 | ||
296 | The code character descriptions below contain a number of key words, | |
297 | defined here as follows: | |
298 | ||
299 | @table @b | |
300 | @item Completion | |
301 | @cindex interactive completion | |
302 | Provide completion. @key{TAB}, @key{SPC}, and @key{RET} perform name | |
303 | completion because the argument is read using @code{completing-read} | |
304 | (@pxref{Completion}). @kbd{?} displays a list of possible completions. | |
305 | ||
306 | @item Existing | |
307 | Require the name of an existing object. An invalid name is not | |
308 | accepted; the commands to exit the minibuffer do not exit if the current | |
309 | input is not valid. | |
310 | ||
311 | @item Default | |
312 | @cindex default argument string | |
313 | A default value of some sort is used if the user enters no text in the | |
314 | minibuffer. The default depends on the code character. | |
315 | ||
316 | @item No I/O | |
317 | This code letter computes an argument without reading any input. | |
318 | Therefore, it does not use a prompt string, and any prompt string you | |
319 | supply is ignored. | |
320 | ||
321 | Even though the code letter doesn't use a prompt string, you must follow | |
322 | it with a newline if it is not the last code character in the string. | |
323 | ||
324 | @item Prompt | |
325 | A prompt immediately follows the code character. The prompt ends either | |
326 | with the end of the string or with a newline. | |
327 | ||
328 | @item Special | |
329 | This code character is meaningful only at the beginning of the | |
330 | interactive string, and it does not look for a prompt or a newline. | |
331 | It is a single, isolated character. | |
332 | @end table | |
333 | ||
334 | @cindex reading interactive arguments | |
335 | Here are the code character descriptions for use with @code{interactive}: | |
336 | ||
337 | @table @samp | |
338 | @item * | |
339 | Signal an error if the current buffer is read-only. Special. | |
340 | ||
341 | @item @@ | |
342 | Select the window mentioned in the first mouse event in the key | |
343 | sequence that invoked this command. Special. | |
344 | ||
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345 | @item ^ |
346 | If the command was invoked through shift-translation, set the mark and | |
347 | activate the region temporarily, or extend an already active region, | |
348 | before the command is run. If the command was invoked without | |
349 | shift-translation, and the region is temporarily active, deactivate | |
350 | the region before the command is run. Special. | |
351 | ||
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352 | @item a |
353 | A function name (i.e., a symbol satisfying @code{fboundp}). Existing, | |
354 | Completion, Prompt. | |
355 | ||
356 | @item b | |
357 | The name of an existing buffer. By default, uses the name of the | |
358 | current buffer (@pxref{Buffers}). Existing, Completion, Default, | |
359 | Prompt. | |
360 | ||
361 | @item B | |
362 | A buffer name. The buffer need not exist. By default, uses the name of | |
363 | a recently used buffer other than the current buffer. Completion, | |
364 | Default, Prompt. | |
365 | ||
366 | @item c | |
367 | A character. The cursor does not move into the echo area. Prompt. | |
368 | ||
369 | @item C | |
370 | A command name (i.e., a symbol satisfying @code{commandp}). Existing, | |
371 | Completion, Prompt. | |
372 | ||
373 | @item d | |
374 | @cindex position argument | |
375 | The position of point, as an integer (@pxref{Point}). No I/O. | |
376 | ||
377 | @item D | |
378 | A directory name. The default is the current default directory of the | |
379 | current buffer, @code{default-directory} (@pxref{File Name Expansion}). | |
380 | Existing, Completion, Default, Prompt. | |
381 | ||
382 | @item e | |
383 | The first or next mouse event in the key sequence that invoked the command. | |
384 | More precisely, @samp{e} gets events that are lists, so you can look at | |
385 | the data in the lists. @xref{Input Events}. No I/O. | |
386 | ||
387 | You can use @samp{e} more than once in a single command's interactive | |
388 | specification. If the key sequence that invoked the command has | |
389 | @var{n} events that are lists, the @var{n}th @samp{e} provides the | |
390 | @var{n}th such event. Events that are not lists, such as function keys | |
391 | and @acronym{ASCII} characters, do not count where @samp{e} is concerned. | |
392 | ||
393 | @item f | |
394 | A file name of an existing file (@pxref{File Names}). The default | |
395 | directory is @code{default-directory}. Existing, Completion, Default, | |
396 | Prompt. | |
397 | ||
398 | @item F | |
399 | A file name. The file need not exist. Completion, Default, Prompt. | |
400 | ||
401 | @item G | |
402 | A file name. The file need not exist. If the user enters just a | |
403 | directory name, then the value is just that directory name, with no | |
404 | file name within the directory added. Completion, Default, Prompt. | |
405 | ||
406 | @item i | |
407 | An irrelevant argument. This code always supplies @code{nil} as | |
408 | the argument's value. No I/O. | |
409 | ||
410 | @item k | |
411 | A key sequence (@pxref{Key Sequences}). This keeps reading events | |
412 | until a command (or undefined command) is found in the current key | |
413 | maps. The key sequence argument is represented as a string or vector. | |
414 | The cursor does not move into the echo area. Prompt. | |
415 | ||
416 | If @samp{k} reads a key sequence that ends with a down-event, it also | |
417 | reads and discards the following up-event. You can get access to that | |
418 | up-event with the @samp{U} code character. | |
419 | ||
420 | This kind of input is used by commands such as @code{describe-key} and | |
421 | @code{global-set-key}. | |
422 | ||
423 | @item K | |
424 | A key sequence, whose definition you intend to change. This works like | |
425 | @samp{k}, except that it suppresses, for the last input event in the key | |
426 | sequence, the conversions that are normally used (when necessary) to | |
427 | convert an undefined key into a defined one. | |
428 | ||
429 | @item m | |
430 | @cindex marker argument | |
431 | The position of the mark, as an integer. No I/O. | |
432 | ||
433 | @item M | |
434 | Arbitrary text, read in the minibuffer using the current buffer's input | |
435 | method, and returned as a string (@pxref{Input Methods,,, emacs, The GNU | |
436 | Emacs Manual}). Prompt. | |
437 | ||
438 | @item n | |
439 | A number, read with the minibuffer. If the input is not a number, the | |
440 | user has to try again. @samp{n} never uses the prefix argument. | |
441 | Prompt. | |
442 | ||
443 | @item N | |
444 | The numeric prefix argument; but if there is no prefix argument, read | |
445 | a number as with @kbd{n}. The value is always a number. @xref{Prefix | |
446 | Command Arguments}. Prompt. | |
447 | ||
448 | @item p | |
449 | @cindex numeric prefix argument usage | |
450 | The numeric prefix argument. (Note that this @samp{p} is lower case.) | |
451 | No I/O. | |
452 | ||
453 | @item P | |
454 | @cindex raw prefix argument usage | |
455 | The raw prefix argument. (Note that this @samp{P} is upper case.) No | |
456 | I/O. | |
457 | ||
458 | @item r | |
459 | @cindex region argument | |
460 | Point and the mark, as two numeric arguments, smallest first. This is | |
461 | the only code letter that specifies two successive arguments rather than | |
462 | one. No I/O. | |
463 | ||
464 | @item s | |
465 | Arbitrary text, read in the minibuffer and returned as a string | |
466 | (@pxref{Text from Minibuffer}). Terminate the input with either | |
467 | @kbd{C-j} or @key{RET}. (@kbd{C-q} may be used to include either of | |
468 | these characters in the input.) Prompt. | |
469 | ||
470 | @item S | |
471 | An interned symbol whose name is read in the minibuffer. Any whitespace | |
472 | character terminates the input. (Use @kbd{C-q} to include whitespace in | |
473 | the string.) Other characters that normally terminate a symbol (e.g., | |
474 | parentheses and brackets) do not do so here. Prompt. | |
475 | ||
476 | @item U | |
477 | A key sequence or @code{nil}. Can be used after a @samp{k} or | |
478 | @samp{K} argument to get the up-event that was discarded (if any) | |
479 | after @samp{k} or @samp{K} read a down-event. If no up-event has been | |
480 | discarded, @samp{U} provides @code{nil} as the argument. No I/O. | |
481 | ||
482 | @item v | |
483 | A variable declared to be a user option (i.e., satisfying the | |
b4d3bc10 | 484 | predicate @code{custom-variable-p}). This reads the variable using |
b8d4c8d0 GM |
485 | @code{read-variable}. @xref{Definition of read-variable}. Existing, |
486 | Completion, Prompt. | |
487 | ||
488 | @item x | |
489 | A Lisp object, specified with its read syntax, terminated with a | |
490 | @kbd{C-j} or @key{RET}. The object is not evaluated. @xref{Object from | |
491 | Minibuffer}. Prompt. | |
492 | ||
493 | @item X | |
494 | @cindex evaluated expression argument | |
495 | A Lisp form's value. @samp{X} reads as @samp{x} does, then evaluates | |
496 | the form so that its value becomes the argument for the command. | |
497 | Prompt. | |
498 | ||
499 | @item z | |
500 | A coding system name (a symbol). If the user enters null input, the | |
501 | argument value is @code{nil}. @xref{Coding Systems}. Completion, | |
502 | Existing, Prompt. | |
503 | ||
504 | @item Z | |
505 | A coding system name (a symbol)---but only if this command has a prefix | |
506 | argument. With no prefix argument, @samp{Z} provides @code{nil} as the | |
507 | argument value. Completion, Existing, Prompt. | |
508 | @end table | |
509 | ||
510 | @node Interactive Examples | |
511 | @comment node-name, next, previous, up | |
512 | @subsection Examples of Using @code{interactive} | |
513 | @cindex examples of using @code{interactive} | |
514 | @cindex @code{interactive}, examples of using | |
515 | ||
516 | Here are some examples of @code{interactive}: | |
517 | ||
518 | @example | |
519 | @group | |
520 | (defun foo1 () ; @r{@code{foo1} takes no arguments,} | |
521 | (interactive) ; @r{just moves forward two words.} | |
522 | (forward-word 2)) | |
523 | @result{} foo1 | |
524 | @end group | |
525 | ||
526 | @group | |
527 | (defun foo2 (n) ; @r{@code{foo2} takes one argument,} | |
ee6e73b8 EZ |
528 | (interactive "^p") ; @r{which is the numeric prefix.} |
529 | ; @r{under @code{shift-select-mode},} | |
530 | ; @r{will activate or extend region.} | |
b8d4c8d0 GM |
531 | (forward-word (* 2 n))) |
532 | @result{} foo2 | |
533 | @end group | |
534 | ||
535 | @group | |
536 | (defun foo3 (n) ; @r{@code{foo3} takes one argument,} | |
537 | (interactive "nCount:") ; @r{which is read with the Minibuffer.} | |
538 | (forward-word (* 2 n))) | |
539 | @result{} foo3 | |
540 | @end group | |
541 | ||
542 | @group | |
543 | (defun three-b (b1 b2 b3) | |
544 | "Select three existing buffers. | |
545 | Put them into three windows, selecting the last one." | |
546 | @end group | |
547 | (interactive "bBuffer1:\nbBuffer2:\nbBuffer3:") | |
548 | (delete-other-windows) | |
549 | (split-window (selected-window) 8) | |
550 | (switch-to-buffer b1) | |
551 | (other-window 1) | |
552 | (split-window (selected-window) 8) | |
553 | (switch-to-buffer b2) | |
554 | (other-window 1) | |
555 | (switch-to-buffer b3)) | |
556 | @result{} three-b | |
557 | @group | |
558 | (three-b "*scratch*" "declarations.texi" "*mail*") | |
559 | @result{} nil | |
560 | @end group | |
561 | @end example | |
562 | ||
563 | @node Interactive Call | |
564 | @section Interactive Call | |
565 | @cindex interactive call | |
566 | ||
8421dd35 CY |
567 | After the command loop has translated a key sequence into a command, |
568 | it invokes that command using the function @code{command-execute}. If | |
569 | the command is a function, @code{command-execute} calls | |
b8d4c8d0 GM |
570 | @code{call-interactively}, which reads the arguments and calls the |
571 | command. You can also call these functions yourself. | |
572 | ||
34106abe CY |
573 | Note that the term ``command'', in this context, refers to an |
574 | interactively callable function (or function-like object), or a | |
575 | keyboard macro. It does not refer to the key sequence used to invoke | |
576 | a command (@pxref{Keymaps}). | |
b8d4c8d0 | 577 | |
34106abe CY |
578 | @defun commandp object &optional for-call-interactively |
579 | This function returns @code{t} if @var{object} is a command. | |
580 | Otherwise, it returns @code{nil}. | |
581 | ||
582 | Commands include strings and vectors (which are treated as keyboard | |
583 | macros), lambda expressions that contain a top-level | |
584 | @code{interactive} form (@pxref{Using Interactive}), byte-code | |
585 | function objects made from such lambda expressions, autoload objects | |
586 | that are declared as interactive (non-@code{nil} fourth argument to | |
587 | @code{autoload}), and some primitive functions. Also, a symbol is | |
588 | considered a command if it has a non-@code{nil} | |
8421dd35 | 589 | @code{interactive-form} property, or if its function definition |
34106abe | 590 | satisfies @code{commandp}. |
b8d4c8d0 GM |
591 | |
592 | If @var{for-call-interactively} is non-@code{nil}, then | |
593 | @code{commandp} returns @code{t} only for objects that | |
594 | @code{call-interactively} could call---thus, not for keyboard macros. | |
595 | ||
596 | See @code{documentation} in @ref{Accessing Documentation}, for a | |
597 | realistic example of using @code{commandp}. | |
598 | @end defun | |
599 | ||
600 | @defun call-interactively command &optional record-flag keys | |
601 | This function calls the interactively callable function @var{command}, | |
54e10184 LMI |
602 | providing arguments according to its interactive calling specifications. |
603 | It returns whatever @var{command} returns. | |
604 | ||
605 | If, for instance, you have a function with the following signature: | |
606 | ||
607 | @example | |
608 | (defun foo (begin end) | |
609 | (interactive "r") | |
610 | ...) | |
611 | @end example | |
612 | ||
613 | then saying | |
614 | ||
615 | @example | |
616 | (call-interactively 'foo) | |
617 | @end example | |
618 | ||
619 | will call @code{foo} with the region (@code{point} and @code{mark}) as | |
620 | the arguments. | |
621 | ||
622 | An error is signaled if @var{command} is not a function or if it | |
623 | cannot be called interactively (i.e., is not a command). Note that | |
624 | keyboard macros (strings and vectors) are not accepted, even though | |
625 | they are considered commands, because they are not functions. If | |
626 | @var{command} is a symbol, then @code{call-interactively} uses its | |
627 | function definition. | |
b8d4c8d0 GM |
628 | |
629 | @cindex record command history | |
630 | If @var{record-flag} is non-@code{nil}, then this command and its | |
631 | arguments are unconditionally added to the list @code{command-history}. | |
632 | Otherwise, the command is added only if it uses the minibuffer to read | |
633 | an argument. @xref{Command History}. | |
634 | ||
635 | The argument @var{keys}, if given, should be a vector which specifies | |
636 | the sequence of events to supply if the command inquires which events | |
637 | were used to invoke it. If @var{keys} is omitted or @code{nil}, the | |
638 | default is the return value of @code{this-command-keys-vector}. | |
639 | @xref{Definition of this-command-keys-vector}. | |
640 | @end defun | |
641 | ||
642 | @defun command-execute command &optional record-flag keys special | |
643 | @cindex keyboard macro execution | |
644 | This function executes @var{command}. The argument @var{command} must | |
645 | satisfy the @code{commandp} predicate; i.e., it must be an interactively | |
646 | callable function or a keyboard macro. | |
647 | ||
648 | A string or vector as @var{command} is executed with | |
649 | @code{execute-kbd-macro}. A function is passed to | |
34106abe CY |
650 | @code{call-interactively} (see above), along with the |
651 | @var{record-flag} and @var{keys} arguments. | |
b8d4c8d0 | 652 | |
34106abe CY |
653 | If @var{command} is a symbol, its function definition is used in its |
654 | place. A symbol with an @code{autoload} definition counts as a | |
655 | command if it was declared to stand for an interactively callable | |
656 | function. Such a definition is handled by loading the specified | |
657 | library and then rechecking the definition of the symbol. | |
b8d4c8d0 GM |
658 | |
659 | The argument @var{special}, if given, means to ignore the prefix | |
660 | argument and not clear it. This is used for executing special events | |
661 | (@pxref{Special Events}). | |
662 | @end defun | |
663 | ||
664 | @deffn Command execute-extended-command prefix-argument | |
665 | @cindex read command name | |
666 | This function reads a command name from the minibuffer using | |
667 | @code{completing-read} (@pxref{Completion}). Then it uses | |
668 | @code{command-execute} to call the specified command. Whatever that | |
669 | command returns becomes the value of @code{execute-extended-command}. | |
670 | ||
671 | @cindex execute with prefix argument | |
672 | If the command asks for a prefix argument, it receives the value | |
673 | @var{prefix-argument}. If @code{execute-extended-command} is called | |
674 | interactively, the current raw prefix argument is used for | |
675 | @var{prefix-argument}, and thus passed on to whatever command is run. | |
676 | ||
677 | @c !!! Should this be @kindex? | |
678 | @cindex @kbd{M-x} | |
679 | @code{execute-extended-command} is the normal definition of @kbd{M-x}, | |
680 | so it uses the string @w{@samp{M-x }} as a prompt. (It would be better | |
681 | to take the prompt from the events used to invoke | |
682 | @code{execute-extended-command}, but that is painful to implement.) A | |
683 | description of the value of the prefix argument, if any, also becomes | |
684 | part of the prompt. | |
685 | ||
686 | @example | |
687 | @group | |
688 | (execute-extended-command 3) | |
689 | ---------- Buffer: Minibuffer ---------- | |
690 | 3 M-x forward-word RET | |
691 | ---------- Buffer: Minibuffer ---------- | |
692 | @result{} t | |
693 | @end group | |
694 | @end example | |
695 | @end deffn | |
696 | ||
77832c61 RS |
697 | @node Distinguish Interactive |
698 | @section Distinguish Interactive Calls | |
699 | ||
700 | Sometimes a command should display additional visual feedback (such | |
701 | as an informative message in the echo area) for interactive calls | |
702 | only. There are three ways to do this. The recommended way to test | |
703 | whether the function was called using @code{call-interactively} is to | |
704 | give it an optional argument @code{print-message} and use the | |
705 | @code{interactive} spec to make it non-@code{nil} in interactive | |
706 | calls. Here's an example: | |
707 | ||
708 | @example | |
709 | (defun foo (&optional print-message) | |
710 | (interactive "p") | |
711 | (when print-message | |
712 | (message "foo"))) | |
713 | @end example | |
714 | ||
715 | @noindent | |
716 | We use @code{"p"} because the numeric prefix argument is never | |
717 | @code{nil}. Defined in this way, the function does display the | |
718 | message when called from a keyboard macro. | |
719 | ||
720 | The above method with the additional argument is usually best, | |
16152b76 | 721 | because it allows callers to say ``treat this call as interactive''. |
89a9e058 | 722 | But you can also do the job by testing @code{called-interactively-p}. |
77832c61 | 723 | |
eb5ed549 | 724 | @defun called-interactively-p kind |
77832c61 RS |
725 | This function returns @code{t} when the calling function was called |
726 | using @code{call-interactively}. | |
b8d4c8d0 | 727 | |
eb5ed549 CY |
728 | The argument @var{kind} should be either the symbol @code{interactive} |
729 | or the symbol @code{any}. If it is @code{interactive}, then | |
730 | @code{called-interactively-p} returns @code{t} only if the call was | |
731 | made directly by the user---e.g., if the user typed a key sequence | |
732 | bound to the calling function, but @emph{not} if the user ran a | |
733 | keyboard macro that called the function (@pxref{Keyboard Macros}). If | |
734 | @var{kind} is @code{any}, @code{called-interactively-p} returns | |
735 | @code{t} for any kind of interactive call, including keyboard macros. | |
736 | ||
737 | If in doubt, use @code{any}; the only known proper use of | |
738 | @code{interactive} is if you need to decide whether to display a | |
739 | helpful message while a function is running. | |
740 | ||
741 | A function is never considered to be called interactively if it was | |
742 | called via Lisp evaluation (or with @code{apply} or @code{funcall}). | |
b8d4c8d0 GM |
743 | @end defun |
744 | ||
eb5ed549 CY |
745 | @noindent |
746 | Here is an example of using @code{called-interactively-p}: | |
b8d4c8d0 GM |
747 | |
748 | @example | |
749 | @group | |
b8d4c8d0 GM |
750 | (defun foo () |
751 | (interactive) | |
eb5ed549 CY |
752 | (when (called-interactively-p 'any) |
753 | (message "Interactive!") | |
754 | 'foo-called-interactively)) | |
b8d4c8d0 GM |
755 | @end group |
756 | ||
757 | @group | |
77832c61 | 758 | ;; @r{Type @kbd{M-x foo}.} |
eb5ed549 | 759 | @print{} Interactive! |
b8d4c8d0 GM |
760 | @end group |
761 | ||
762 | @group | |
77832c61 | 763 | (foo) |
eb5ed549 | 764 | @result{} nil |
77832c61 RS |
765 | @end group |
766 | @end example | |
767 | ||
eb5ed549 CY |
768 | @noindent |
769 | Here is another example that contrasts direct and indirect calls to | |
770 | @code{called-interactively-p}. | |
77832c61 RS |
771 | |
772 | @example | |
773 | @group | |
774 | (defun bar () | |
775 | (interactive) | |
eb5ed549 | 776 | (message "%s" (list (foo) (called-interactively-p 'any)))) |
b8d4c8d0 GM |
777 | @end group |
778 | ||
779 | @group | |
780 | ;; @r{Type @kbd{M-x bar}.} | |
eb5ed549 | 781 | @print{} (nil t) |
b8d4c8d0 GM |
782 | @end group |
783 | @end example | |
784 | ||
b8d4c8d0 GM |
785 | @node Command Loop Info |
786 | @comment node-name, next, previous, up | |
787 | @section Information from the Command Loop | |
788 | ||
789 | The editor command loop sets several Lisp variables to keep status | |
1bb1f7d3 MR |
790 | records for itself and for commands that are run. With the exception of |
791 | @code{this-command} and @code{last-command} it's generally a bad idea to | |
792 | change any of these variables in a Lisp program. | |
b8d4c8d0 GM |
793 | |
794 | @defvar last-command | |
795 | This variable records the name of the previous command executed by the | |
796 | command loop (the one before the current command). Normally the value | |
797 | is a symbol with a function definition, but this is not guaranteed. | |
798 | ||
799 | The value is copied from @code{this-command} when a command returns to | |
800 | the command loop, except when the command has specified a prefix | |
801 | argument for the following command. | |
802 | ||
803 | This variable is always local to the current terminal and cannot be | |
3ec61d4e | 804 | buffer-local. @xref{Multiple Terminals}. |
b8d4c8d0 GM |
805 | @end defvar |
806 | ||
807 | @defvar real-last-command | |
808 | This variable is set up by Emacs just like @code{last-command}, | |
809 | but never altered by Lisp programs. | |
810 | @end defvar | |
811 | ||
1bb1f7d3 MR |
812 | @defvar last-repeatable-command |
813 | This variable stores the most recently executed command that was not | |
814 | part of an input event. This is the command @code{repeat} will try to | |
815 | repeat, @xref{Repeating,,, emacs, The GNU Emacs Manual}. | |
816 | @end defvar | |
817 | ||
b8d4c8d0 GM |
818 | @defvar this-command |
819 | @cindex current command | |
820 | This variable records the name of the command now being executed by | |
821 | the editor command loop. Like @code{last-command}, it is normally a symbol | |
822 | with a function definition. | |
823 | ||
824 | The command loop sets this variable just before running a command, and | |
825 | copies its value into @code{last-command} when the command finishes | |
826 | (unless the command specified a prefix argument for the following | |
827 | command). | |
828 | ||
829 | @cindex kill command repetition | |
830 | Some commands set this variable during their execution, as a flag for | |
831 | whatever command runs next. In particular, the functions for killing text | |
832 | set @code{this-command} to @code{kill-region} so that any kill commands | |
833 | immediately following will know to append the killed text to the | |
834 | previous kill. | |
835 | @end defvar | |
836 | ||
837 | If you do not want a particular command to be recognized as the previous | |
838 | command in the case where it got an error, you must code that command to | |
839 | prevent this. One way is to set @code{this-command} to @code{t} at the | |
840 | beginning of the command, and set @code{this-command} back to its proper | |
841 | value at the end, like this: | |
842 | ||
843 | @example | |
844 | (defun foo (args@dots{}) | |
845 | (interactive @dots{}) | |
846 | (let ((old-this-command this-command)) | |
847 | (setq this-command t) | |
848 | @r{@dots{}do the work@dots{}} | |
849 | (setq this-command old-this-command))) | |
850 | @end example | |
851 | ||
852 | @noindent | |
853 | We do not bind @code{this-command} with @code{let} because that would | |
854 | restore the old value in case of error---a feature of @code{let} which | |
855 | in this case does precisely what we want to avoid. | |
856 | ||
857 | @defvar this-original-command | |
858 | This has the same value as @code{this-command} except when command | |
859 | remapping occurs (@pxref{Remapping Commands}). In that case, | |
860 | @code{this-command} gives the command actually run (the result of | |
861 | remapping), and @code{this-original-command} gives the command that | |
862 | was specified to run but remapped into another command. | |
863 | @end defvar | |
864 | ||
865 | @defun this-command-keys | |
866 | This function returns a string or vector containing the key sequence | |
867 | that invoked the present command, plus any previous commands that | |
868 | generated the prefix argument for this command. Any events read by the | |
869 | command using @code{read-event} without a timeout get tacked on to the end. | |
870 | ||
871 | However, if the command has called @code{read-key-sequence}, it | |
872 | returns the last read key sequence. @xref{Key Sequence Input}. The | |
873 | value is a string if all events in the sequence were characters that | |
874 | fit in a string. @xref{Input Events}. | |
875 | ||
876 | @example | |
877 | @group | |
878 | (this-command-keys) | |
879 | ;; @r{Now use @kbd{C-u C-x C-e} to evaluate that.} | |
880 | @result{} "^U^X^E" | |
881 | @end group | |
882 | @end example | |
883 | @end defun | |
884 | ||
885 | @defun this-command-keys-vector | |
886 | @anchor{Definition of this-command-keys-vector} | |
887 | Like @code{this-command-keys}, except that it always returns the events | |
888 | in a vector, so you don't need to deal with the complexities of storing | |
889 | input events in a string (@pxref{Strings of Events}). | |
890 | @end defun | |
891 | ||
892 | @defun clear-this-command-keys &optional keep-record | |
893 | This function empties out the table of events for | |
894 | @code{this-command-keys} to return. Unless @var{keep-record} is | |
895 | non-@code{nil}, it also empties the records that the function | |
896 | @code{recent-keys} (@pxref{Recording Input}) will subsequently return. | |
897 | This is useful after reading a password, to prevent the password from | |
898 | echoing inadvertently as part of the next command in certain cases. | |
899 | @end defun | |
900 | ||
901 | @defvar last-nonmenu-event | |
902 | This variable holds the last input event read as part of a key sequence, | |
903 | not counting events resulting from mouse menus. | |
904 | ||
905 | One use of this variable is for telling @code{x-popup-menu} where to pop | |
906 | up a menu. It is also used internally by @code{y-or-n-p} | |
907 | (@pxref{Yes-or-No Queries}). | |
908 | @end defvar | |
909 | ||
910 | @defvar last-command-event | |
911 | @defvarx last-command-char | |
912 | This variable is set to the last input event that was read by the | |
913 | command loop as part of a command. The principal use of this variable | |
914 | is in @code{self-insert-command}, which uses it to decide which | |
915 | character to insert. | |
916 | ||
917 | @example | |
918 | @group | |
919 | last-command-event | |
920 | ;; @r{Now use @kbd{C-u C-x C-e} to evaluate that.} | |
921 | @result{} 5 | |
922 | @end group | |
923 | @end example | |
924 | ||
925 | @noindent | |
926 | The value is 5 because that is the @acronym{ASCII} code for @kbd{C-e}. | |
927 | ||
ab756fb3 | 928 | The alias @code{last-command-char} is obsolete. |
b8d4c8d0 GM |
929 | @end defvar |
930 | ||
931 | @c Emacs 19 feature | |
932 | @defvar last-event-frame | |
933 | This variable records which frame the last input event was directed to. | |
934 | Usually this is the frame that was selected when the event was | |
935 | generated, but if that frame has redirected input focus to another | |
936 | frame, the value is the frame to which the event was redirected. | |
937 | @xref{Input Focus}. | |
938 | ||
939 | If the last event came from a keyboard macro, the value is @code{macro}. | |
940 | @end defvar | |
941 | ||
942 | @node Adjusting Point | |
943 | @section Adjusting Point After Commands | |
944 | @cindex adjusting point | |
945 | @cindex invisible/intangible text, and point | |
946 | @cindex @code{display} property, and point display | |
947 | @cindex @code{composition} property, and point display | |
948 | ||
949 | It is not easy to display a value of point in the middle of a | |
950 | sequence of text that has the @code{display}, @code{composition} or | |
a7cdbfce SM |
951 | is invisible. Therefore, after a command finishes and returns to the |
952 | command loop, if point is within such a sequence, the command loop | |
953 | normally moves point to the edge of the sequence. | |
b8d4c8d0 GM |
954 | |
955 | A command can inhibit this feature by setting the variable | |
956 | @code{disable-point-adjustment}: | |
957 | ||
958 | @defvar disable-point-adjustment | |
959 | If this variable is non-@code{nil} when a command returns to the | |
960 | command loop, then the command loop does not check for those text | |
961 | properties, and does not move point out of sequences that have them. | |
962 | ||
963 | The command loop sets this variable to @code{nil} before each command, | |
964 | so if a command sets it, the effect applies only to that command. | |
965 | @end defvar | |
966 | ||
967 | @defvar global-disable-point-adjustment | |
968 | If you set this variable to a non-@code{nil} value, the feature of | |
969 | moving point out of these sequences is completely turned off. | |
970 | @end defvar | |
971 | ||
972 | @node Input Events | |
973 | @section Input Events | |
974 | @cindex events | |
975 | @cindex input events | |
976 | ||
977 | The Emacs command loop reads a sequence of @dfn{input events} that | |
978 | represent keyboard or mouse activity. The events for keyboard activity | |
979 | are characters or symbols; mouse events are always lists. This section | |
980 | describes the representation and meaning of input events in detail. | |
981 | ||
982 | @defun eventp object | |
983 | This function returns non-@code{nil} if @var{object} is an input event | |
984 | or event type. | |
985 | ||
986 | Note that any symbol might be used as an event or an event type. | |
987 | @code{eventp} cannot distinguish whether a symbol is intended by Lisp | |
988 | code to be used as an event. Instead, it distinguishes whether the | |
989 | symbol has actually been used in an event that has been read as input in | |
990 | the current Emacs session. If a symbol has not yet been so used, | |
991 | @code{eventp} returns @code{nil}. | |
992 | @end defun | |
993 | ||
994 | @menu | |
d24880de GM |
995 | * Keyboard Events:: Ordinary characters--keys with symbols on them. |
996 | * Function Keys:: Function keys--keys with names, not symbols. | |
b8d4c8d0 | 997 | * Mouse Events:: Overview of mouse events. |
d24880de GM |
998 | * Click Events:: Pushing and releasing a mouse button. |
999 | * Drag Events:: Moving the mouse before releasing the button. | |
1000 | * Button-Down Events:: A button was pushed and not yet released. | |
b8d4c8d0 | 1001 | * Repeat Events:: Double and triple click (or drag, or down). |
d24880de GM |
1002 | * Motion Events:: Just moving the mouse, not pushing a button. |
1003 | * Focus Events:: Moving the mouse between frames. | |
b8d4c8d0 | 1004 | * Misc Events:: Other events the system can generate. |
d24880de GM |
1005 | * Event Examples:: Examples of the lists for mouse events. |
1006 | * Classifying Events:: Finding the modifier keys in an event symbol. | |
1007 | Event types. | |
1008 | * Accessing Mouse:: Functions to extract info from mouse events. | |
1009 | * Accessing Scroll:: Functions to get info from scroll bar events. | |
b8d4c8d0 | 1010 | * Strings of Events:: Special considerations for putting |
d24880de | 1011 | keyboard character events in a string. |
b8d4c8d0 GM |
1012 | @end menu |
1013 | ||
1014 | @node Keyboard Events | |
1015 | @subsection Keyboard Events | |
1016 | @cindex keyboard events | |
1017 | ||
1018 | There are two kinds of input you can get from the keyboard: ordinary | |
1019 | keys, and function keys. Ordinary keys correspond to characters; the | |
1020 | events they generate are represented in Lisp as characters. The event | |
1021 | type of a character event is the character itself (an integer); see | |
1022 | @ref{Classifying Events}. | |
1023 | ||
1024 | @cindex modifier bits (of input character) | |
1025 | @cindex basic code (of input character) | |
1026 | An input character event consists of a @dfn{basic code} between 0 and | |
1027 | 524287, plus any or all of these @dfn{modifier bits}: | |
1028 | ||
1029 | @table @asis | |
1030 | @item meta | |
1031 | The | |
1032 | @tex | |
1033 | @math{2^{27}} | |
1034 | @end tex | |
1035 | @ifnottex | |
1036 | 2**27 | |
1037 | @end ifnottex | |
1038 | bit in the character code indicates a character | |
1039 | typed with the meta key held down. | |
1040 | ||
1041 | @item control | |
1042 | The | |
1043 | @tex | |
1044 | @math{2^{26}} | |
1045 | @end tex | |
1046 | @ifnottex | |
1047 | 2**26 | |
1048 | @end ifnottex | |
1049 | bit in the character code indicates a non-@acronym{ASCII} | |
1050 | control character. | |
1051 | ||
1052 | @sc{ascii} control characters such as @kbd{C-a} have special basic | |
1053 | codes of their own, so Emacs needs no special bit to indicate them. | |
1054 | Thus, the code for @kbd{C-a} is just 1. | |
1055 | ||
1056 | But if you type a control combination not in @acronym{ASCII}, such as | |
1057 | @kbd{%} with the control key, the numeric value you get is the code | |
1058 | for @kbd{%} plus | |
1059 | @tex | |
1060 | @math{2^{26}} | |
1061 | @end tex | |
1062 | @ifnottex | |
1063 | 2**26 | |
1064 | @end ifnottex | |
1065 | (assuming the terminal supports non-@acronym{ASCII} | |
1066 | control characters). | |
1067 | ||
1068 | @item shift | |
1069 | The | |
1070 | @tex | |
1071 | @math{2^{25}} | |
1072 | @end tex | |
1073 | @ifnottex | |
1074 | 2**25 | |
1075 | @end ifnottex | |
1076 | bit in the character code indicates an @acronym{ASCII} control | |
1077 | character typed with the shift key held down. | |
1078 | ||
1079 | For letters, the basic code itself indicates upper versus lower case; | |
1080 | for digits and punctuation, the shift key selects an entirely different | |
1081 | character with a different basic code. In order to keep within the | |
1082 | @acronym{ASCII} character set whenever possible, Emacs avoids using the | |
1083 | @tex | |
1084 | @math{2^{25}} | |
1085 | @end tex | |
1086 | @ifnottex | |
1087 | 2**25 | |
1088 | @end ifnottex | |
1089 | bit for those characters. | |
1090 | ||
1091 | However, @acronym{ASCII} provides no way to distinguish @kbd{C-A} from | |
1092 | @kbd{C-a}, so Emacs uses the | |
1093 | @tex | |
1094 | @math{2^{25}} | |
1095 | @end tex | |
1096 | @ifnottex | |
1097 | 2**25 | |
1098 | @end ifnottex | |
1099 | bit in @kbd{C-A} and not in | |
1100 | @kbd{C-a}. | |
1101 | ||
1102 | @item hyper | |
1103 | The | |
1104 | @tex | |
1105 | @math{2^{24}} | |
1106 | @end tex | |
1107 | @ifnottex | |
1108 | 2**24 | |
1109 | @end ifnottex | |
1110 | bit in the character code indicates a character | |
1111 | typed with the hyper key held down. | |
1112 | ||
1113 | @item super | |
1114 | The | |
1115 | @tex | |
1116 | @math{2^{23}} | |
1117 | @end tex | |
1118 | @ifnottex | |
1119 | 2**23 | |
1120 | @end ifnottex | |
1121 | bit in the character code indicates a character | |
1122 | typed with the super key held down. | |
1123 | ||
1124 | @item alt | |
1125 | The | |
1126 | @tex | |
1127 | @math{2^{22}} | |
1128 | @end tex | |
1129 | @ifnottex | |
1130 | 2**22 | |
1131 | @end ifnottex | |
34106abe CY |
1132 | bit in the character code indicates a character typed with the alt key |
1133 | held down. (The key labeled @key{Alt} on most keyboards is actually | |
1134 | treated as the meta key, not this.) | |
b8d4c8d0 GM |
1135 | @end table |
1136 | ||
1137 | It is best to avoid mentioning specific bit numbers in your program. | |
1138 | To test the modifier bits of a character, use the function | |
1139 | @code{event-modifiers} (@pxref{Classifying Events}). When making key | |
1140 | bindings, you can use the read syntax for characters with modifier bits | |
1141 | (@samp{\C-}, @samp{\M-}, and so on). For making key bindings with | |
1142 | @code{define-key}, you can use lists such as @code{(control hyper ?x)} to | |
1143 | specify the characters (@pxref{Changing Key Bindings}). The function | |
1144 | @code{event-convert-list} converts such a list into an event type | |
1145 | (@pxref{Classifying Events}). | |
1146 | ||
1147 | @node Function Keys | |
1148 | @subsection Function Keys | |
1149 | ||
1150 | @cindex function keys | |
1151 | Most keyboards also have @dfn{function keys}---keys that have names or | |
34106abe CY |
1152 | symbols that are not characters. Function keys are represented in |
1153 | Emacs Lisp as symbols; the symbol's name is the function key's label, | |
1154 | in lower case. For example, pressing a key labeled @key{F1} generates | |
1155 | an input event represented by the symbol @code{f1}. | |
b8d4c8d0 GM |
1156 | |
1157 | The event type of a function key event is the event symbol itself. | |
1158 | @xref{Classifying Events}. | |
1159 | ||
1160 | Here are a few special cases in the symbol-naming convention for | |
1161 | function keys: | |
1162 | ||
1163 | @table @asis | |
1164 | @item @code{backspace}, @code{tab}, @code{newline}, @code{return}, @code{delete} | |
1165 | These keys correspond to common @acronym{ASCII} control characters that have | |
1166 | special keys on most keyboards. | |
1167 | ||
1168 | In @acronym{ASCII}, @kbd{C-i} and @key{TAB} are the same character. If the | |
1169 | terminal can distinguish between them, Emacs conveys the distinction to | |
1170 | Lisp programs by representing the former as the integer 9, and the | |
1171 | latter as the symbol @code{tab}. | |
1172 | ||
1173 | Most of the time, it's not useful to distinguish the two. So normally | |
d3ae77bc EZ |
1174 | @code{local-function-key-map} (@pxref{Translation Keymaps}) is set up |
1175 | to map @code{tab} into 9. Thus, a key binding for character code 9 | |
1176 | (the character @kbd{C-i}) also applies to @code{tab}. Likewise for | |
1177 | the other symbols in this group. The function @code{read-char} | |
1178 | likewise converts these events into characters. | |
b8d4c8d0 GM |
1179 | |
1180 | In @acronym{ASCII}, @key{BS} is really @kbd{C-h}. But @code{backspace} | |
1181 | converts into the character code 127 (@key{DEL}), not into code 8 | |
1182 | (@key{BS}). This is what most users prefer. | |
1183 | ||
1184 | @item @code{left}, @code{up}, @code{right}, @code{down} | |
1185 | Cursor arrow keys | |
1186 | @item @code{kp-add}, @code{kp-decimal}, @code{kp-divide}, @dots{} | |
1187 | Keypad keys (to the right of the regular keyboard). | |
1188 | @item @code{kp-0}, @code{kp-1}, @dots{} | |
1189 | Keypad keys with digits. | |
1190 | @item @code{kp-f1}, @code{kp-f2}, @code{kp-f3}, @code{kp-f4} | |
1191 | Keypad PF keys. | |
1192 | @item @code{kp-home}, @code{kp-left}, @code{kp-up}, @code{kp-right}, @code{kp-down} | |
1193 | Keypad arrow keys. Emacs normally translates these into the | |
1194 | corresponding non-keypad keys @code{home}, @code{left}, @dots{} | |
1195 | @item @code{kp-prior}, @code{kp-next}, @code{kp-end}, @code{kp-begin}, @code{kp-insert}, @code{kp-delete} | |
1196 | Additional keypad duplicates of keys ordinarily found elsewhere. Emacs | |
1197 | normally translates these into the like-named non-keypad keys. | |
1198 | @end table | |
1199 | ||
1200 | You can use the modifier keys @key{ALT}, @key{CTRL}, @key{HYPER}, | |
1201 | @key{META}, @key{SHIFT}, and @key{SUPER} with function keys. The way to | |
1202 | represent them is with prefixes in the symbol name: | |
1203 | ||
1204 | @table @samp | |
1205 | @item A- | |
1206 | The alt modifier. | |
1207 | @item C- | |
1208 | The control modifier. | |
1209 | @item H- | |
1210 | The hyper modifier. | |
1211 | @item M- | |
1212 | The meta modifier. | |
1213 | @item S- | |
1214 | The shift modifier. | |
1215 | @item s- | |
1216 | The super modifier. | |
1217 | @end table | |
1218 | ||
1219 | Thus, the symbol for the key @key{F3} with @key{META} held down is | |
1220 | @code{M-f3}. When you use more than one prefix, we recommend you | |
1221 | write them in alphabetical order; but the order does not matter in | |
1222 | arguments to the key-binding lookup and modification functions. | |
1223 | ||
1224 | @node Mouse Events | |
1225 | @subsection Mouse Events | |
1226 | ||
1227 | Emacs supports four kinds of mouse events: click events, drag events, | |
1228 | button-down events, and motion events. All mouse events are represented | |
1229 | as lists. The @sc{car} of the list is the event type; this says which | |
1230 | mouse button was involved, and which modifier keys were used with it. | |
1231 | The event type can also distinguish double or triple button presses | |
1232 | (@pxref{Repeat Events}). The rest of the list elements give position | |
1233 | and time information. | |
1234 | ||
1235 | For key lookup, only the event type matters: two events of the same type | |
1236 | necessarily run the same command. The command can access the full | |
1237 | values of these events using the @samp{e} interactive code. | |
1238 | @xref{Interactive Codes}. | |
1239 | ||
1240 | A key sequence that starts with a mouse event is read using the keymaps | |
1241 | of the buffer in the window that the mouse was in, not the current | |
1242 | buffer. This does not imply that clicking in a window selects that | |
1243 | window or its buffer---that is entirely under the control of the command | |
1244 | binding of the key sequence. | |
1245 | ||
1246 | @node Click Events | |
1247 | @subsection Click Events | |
1248 | @cindex click event | |
1249 | @cindex mouse click event | |
1250 | ||
1251 | When the user presses a mouse button and releases it at the same | |
1252 | location, that generates a @dfn{click} event. All mouse click event | |
1253 | share the same format: | |
1254 | ||
1255 | @example | |
1256 | (@var{event-type} @var{position} @var{click-count}) | |
1257 | @end example | |
1258 | ||
1259 | @table @asis | |
1260 | @item @var{event-type} | |
1261 | This is a symbol that indicates which mouse button was used. It is | |
1262 | one of the symbols @code{mouse-1}, @code{mouse-2}, @dots{}, where the | |
1263 | buttons are numbered left to right. | |
1264 | ||
1265 | You can also use prefixes @samp{A-}, @samp{C-}, @samp{H-}, @samp{M-}, | |
1266 | @samp{S-} and @samp{s-} for modifiers alt, control, hyper, meta, shift | |
1267 | and super, just as you would with function keys. | |
1268 | ||
1269 | This symbol also serves as the event type of the event. Key bindings | |
1270 | describe events by their types; thus, if there is a key binding for | |
1271 | @code{mouse-1}, that binding would apply to all events whose | |
1272 | @var{event-type} is @code{mouse-1}. | |
1273 | ||
1274 | @item @var{position} | |
1275 | This is the position where the mouse click occurred. The actual | |
1276 | format of @var{position} depends on what part of a window was clicked | |
1277 | on. | |
1278 | ||
1279 | For mouse click events in the text area, mode line, header line, or in | |
1280 | the marginal areas, @var{position} has this form: | |
1281 | ||
1282 | @example | |
1283 | (@var{window} @var{pos-or-area} (@var{x} . @var{y}) @var{timestamp} | |
1284 | @var{object} @var{text-pos} (@var{col} . @var{row}) | |
1285 | @var{image} (@var{dx} . @var{dy}) (@var{width} . @var{height})) | |
1286 | @end example | |
1287 | ||
34106abe CY |
1288 | @noindent |
1289 | The meanings of these list elements are documented below. | |
1290 | @xref{Accessing Mouse}, for functions that let you easily access these | |
1291 | elements. | |
1292 | ||
b8d4c8d0 GM |
1293 | @table @asis |
1294 | @item @var{window} | |
1295 | This is the window in which the click occurred. | |
1296 | ||
1297 | @item @var{pos-or-area} | |
1298 | This is the buffer position of the character clicked on in the text | |
1299 | area, or if clicked outside the text area, it is the window area in | |
1300 | which the click occurred. It is one of the symbols @code{mode-line}, | |
1301 | @code{header-line}, @code{vertical-line}, @code{left-margin}, | |
1302 | @code{right-margin}, @code{left-fringe}, or @code{right-fringe}. | |
1303 | ||
34106abe CY |
1304 | In one special case, @var{pos-or-area} is a list containing a symbol |
1305 | (one of the symbols listed above) instead of just the symbol. This | |
1306 | happens after the imaginary prefix keys for the event are registered | |
1307 | by Emacs. @xref{Key Sequence Input}. | |
b8d4c8d0 GM |
1308 | |
1309 | @item @var{x}, @var{y} | |
34106abe CY |
1310 | These are the relative pixel coordinates of the click. For clicks in |
1311 | the text area of a window, the coordinate origin @code{(0 . 0)} is | |
1312 | taken to be the top left corner of the text area. @xref{Window | |
1313 | Sizes}. For clicks in a mode line or header line, the coordinate | |
1314 | origin is the top left corner of the window itself. For fringes, | |
1315 | margins, and the vertical border, @var{x} does not have meaningful | |
1316 | data. For fringes and margins, @var{y} is relative to the bottom edge | |
1317 | of the header line. In all cases, the @var{x} and @var{y} coordinates | |
1318 | increase rightward and downward respectively. | |
b8d4c8d0 GM |
1319 | |
1320 | @item @var{timestamp} | |
1321 | This is the time at which the event occurred, in milliseconds. | |
1322 | ||
1323 | @item @var{object} | |
34106abe CY |
1324 | This is either @code{nil} if there is no string-type text property at |
1325 | the click position, or a cons cell of the form (@var{string} | |
1326 | . @var{string-pos}) if there is one: | |
b8d4c8d0 GM |
1327 | |
1328 | @table @asis | |
1329 | @item @var{string} | |
34106abe | 1330 | The string which was clicked on, including any properties. |
b8d4c8d0 GM |
1331 | |
1332 | @item @var{string-pos} | |
34106abe | 1333 | The position in the string where the click occurred. |
b8d4c8d0 GM |
1334 | @end table |
1335 | ||
1336 | @item @var{text-pos} | |
1337 | For clicks on a marginal area or on a fringe, this is the buffer | |
1338 | position of the first visible character in the corresponding line in | |
1339 | the window. For other events, it is the current buffer position in | |
1340 | the window. | |
1341 | ||
1342 | @item @var{col}, @var{row} | |
34106abe CY |
1343 | These are the actual column and row coordinate numbers of the glyph |
1344 | under the @var{x}, @var{y} position. If @var{x} lies beyond the last | |
1345 | column of actual text on its line, @var{col} is reported by adding | |
1346 | fictional extra columns that have the default character width. Row 0 | |
1347 | is taken to be the header line if the window has one, or the topmost | |
1348 | row of the text area otherwise. Column 0 is taken to be the leftmost | |
1349 | column of the text area for clicks on a window text area, or the | |
1350 | leftmost mode line or header line column for clicks there. For clicks | |
1351 | on fringes or vertical borders, these have no meaningful data. For | |
1352 | clicks on margins, @var{col} is measured from the left edge of the | |
1353 | margin area and @var{row} is measured from the top of the margin area. | |
b8d4c8d0 GM |
1354 | |
1355 | @item @var{image} | |
1356 | This is the image object on which the click occurred. It is either | |
1357 | @code{nil} if there is no image at the position clicked on, or it is | |
1358 | an image object as returned by @code{find-image} if click was in an image. | |
1359 | ||
1360 | @item @var{dx}, @var{dy} | |
1361 | These are the pixel coordinates of the click, relative to | |
1362 | the top left corner of @var{object}, which is @code{(0 . 0)}. If | |
1363 | @var{object} is @code{nil}, the coordinates are relative to the top | |
1364 | left corner of the character glyph clicked on. | |
1365 | ||
1366 | @item @var{width}, @var{height} | |
1367 | These are the pixel width and height of @var{object} or, if this is | |
1368 | @code{nil}, those of the character glyph clicked on. | |
1369 | @end table | |
8547874a | 1370 | |
b8d4c8d0 GM |
1371 | @sp 1 |
1372 | For mouse clicks on a scroll-bar, @var{position} has this form: | |
1373 | ||
1374 | @example | |
1375 | (@var{window} @var{area} (@var{portion} . @var{whole}) @var{timestamp} @var{part}) | |
1376 | @end example | |
1377 | ||
1378 | @table @asis | |
1379 | @item @var{window} | |
1380 | This is the window whose scroll-bar was clicked on. | |
1381 | ||
1382 | @item @var{area} | |
1383 | This is the scroll bar where the click occurred. It is one of the | |
1384 | symbols @code{vertical-scroll-bar} or @code{horizontal-scroll-bar}. | |
1385 | ||
1386 | @item @var{portion} | |
1387 | This is the distance of the click from the top or left end of | |
1388 | the scroll bar. | |
1389 | ||
1390 | @item @var{whole} | |
1391 | This is the length of the entire scroll bar. | |
1392 | ||
1393 | @item @var{timestamp} | |
1394 | This is the time at which the event occurred, in milliseconds. | |
1395 | ||
1396 | @item @var{part} | |
1397 | This is the part of the scroll-bar which was clicked on. It is one | |
1398 | of the symbols @code{above-handle}, @code{handle}, @code{below-handle}, | |
1399 | @code{up}, @code{down}, @code{top}, @code{bottom}, and @code{end-scroll}. | |
1400 | @end table | |
1401 | ||
1402 | @item @var{click-count} | |
1403 | This is the number of rapid repeated presses so far of the same mouse | |
1404 | button. @xref{Repeat Events}. | |
1405 | @end table | |
1406 | ||
1407 | @node Drag Events | |
1408 | @subsection Drag Events | |
1409 | @cindex drag event | |
1410 | @cindex mouse drag event | |
1411 | ||
1412 | With Emacs, you can have a drag event without even changing your | |
1413 | clothes. A @dfn{drag event} happens every time the user presses a mouse | |
1414 | button and then moves the mouse to a different character position before | |
1415 | releasing the button. Like all mouse events, drag events are | |
1416 | represented in Lisp as lists. The lists record both the starting mouse | |
1417 | position and the final position, like this: | |
1418 | ||
1419 | @example | |
1420 | (@var{event-type} | |
1421 | (@var{window1} START-POSITION) | |
1422 | (@var{window2} END-POSITION)) | |
1423 | @end example | |
1424 | ||
1425 | For a drag event, the name of the symbol @var{event-type} contains the | |
1426 | prefix @samp{drag-}. For example, dragging the mouse with button 2 | |
1427 | held down generates a @code{drag-mouse-2} event. The second and third | |
1428 | elements of the event give the starting and ending position of the | |
1429 | drag. They have the same form as @var{position} in a click event | |
1430 | (@pxref{Click Events}) that is not on the scroll bar part of the | |
1431 | window. You can access the second element of any mouse event in the | |
1432 | same way, with no need to distinguish drag events from others. | |
1433 | ||
1434 | The @samp{drag-} prefix follows the modifier key prefixes such as | |
1435 | @samp{C-} and @samp{M-}. | |
1436 | ||
1437 | If @code{read-key-sequence} receives a drag event that has no key | |
1438 | binding, and the corresponding click event does have a binding, it | |
1439 | changes the drag event into a click event at the drag's starting | |
1440 | position. This means that you don't have to distinguish between click | |
1441 | and drag events unless you want to. | |
1442 | ||
1443 | @node Button-Down Events | |
1444 | @subsection Button-Down Events | |
1445 | @cindex button-down event | |
1446 | ||
1447 | Click and drag events happen when the user releases a mouse button. | |
1448 | They cannot happen earlier, because there is no way to distinguish a | |
1449 | click from a drag until the button is released. | |
1450 | ||
1451 | If you want to take action as soon as a button is pressed, you need to | |
1452 | handle @dfn{button-down} events.@footnote{Button-down is the | |
1453 | conservative antithesis of drag.} These occur as soon as a button is | |
1454 | pressed. They are represented by lists that look exactly like click | |
1455 | events (@pxref{Click Events}), except that the @var{event-type} symbol | |
1456 | name contains the prefix @samp{down-}. The @samp{down-} prefix follows | |
1457 | modifier key prefixes such as @samp{C-} and @samp{M-}. | |
1458 | ||
1459 | The function @code{read-key-sequence} ignores any button-down events | |
1460 | that don't have command bindings; therefore, the Emacs command loop | |
1461 | ignores them too. This means that you need not worry about defining | |
1462 | button-down events unless you want them to do something. The usual | |
1463 | reason to define a button-down event is so that you can track mouse | |
1464 | motion (by reading motion events) until the button is released. | |
1465 | @xref{Motion Events}. | |
1466 | ||
1467 | @node Repeat Events | |
1468 | @subsection Repeat Events | |
1469 | @cindex repeat events | |
1470 | @cindex double-click events | |
1471 | @cindex triple-click events | |
1472 | @cindex mouse events, repeated | |
1473 | ||
1474 | If you press the same mouse button more than once in quick succession | |
1475 | without moving the mouse, Emacs generates special @dfn{repeat} mouse | |
1476 | events for the second and subsequent presses. | |
1477 | ||
1478 | The most common repeat events are @dfn{double-click} events. Emacs | |
1479 | generates a double-click event when you click a button twice; the event | |
1480 | happens when you release the button (as is normal for all click | |
1481 | events). | |
1482 | ||
1483 | The event type of a double-click event contains the prefix | |
1484 | @samp{double-}. Thus, a double click on the second mouse button with | |
1485 | @key{meta} held down comes to the Lisp program as | |
1486 | @code{M-double-mouse-2}. If a double-click event has no binding, the | |
1487 | binding of the corresponding ordinary click event is used to execute | |
1488 | it. Thus, you need not pay attention to the double click feature | |
1489 | unless you really want to. | |
1490 | ||
1491 | When the user performs a double click, Emacs generates first an ordinary | |
1492 | click event, and then a double-click event. Therefore, you must design | |
1493 | the command binding of the double click event to assume that the | |
1494 | single-click command has already run. It must produce the desired | |
1495 | results of a double click, starting from the results of a single click. | |
1496 | ||
1497 | This is convenient, if the meaning of a double click somehow ``builds | |
1498 | on'' the meaning of a single click---which is recommended user interface | |
1499 | design practice for double clicks. | |
1500 | ||
1501 | If you click a button, then press it down again and start moving the | |
1502 | mouse with the button held down, then you get a @dfn{double-drag} event | |
1503 | when you ultimately release the button. Its event type contains | |
1504 | @samp{double-drag} instead of just @samp{drag}. If a double-drag event | |
1505 | has no binding, Emacs looks for an alternate binding as if the event | |
1506 | were an ordinary drag. | |
1507 | ||
1508 | Before the double-click or double-drag event, Emacs generates a | |
1509 | @dfn{double-down} event when the user presses the button down for the | |
1510 | second time. Its event type contains @samp{double-down} instead of just | |
1511 | @samp{down}. If a double-down event has no binding, Emacs looks for an | |
1512 | alternate binding as if the event were an ordinary button-down event. | |
1513 | If it finds no binding that way either, the double-down event is | |
1514 | ignored. | |
1515 | ||
1516 | To summarize, when you click a button and then press it again right | |
1517 | away, Emacs generates a down event and a click event for the first | |
1518 | click, a double-down event when you press the button again, and finally | |
1519 | either a double-click or a double-drag event. | |
1520 | ||
1521 | If you click a button twice and then press it again, all in quick | |
1522 | succession, Emacs generates a @dfn{triple-down} event, followed by | |
1523 | either a @dfn{triple-click} or a @dfn{triple-drag}. The event types of | |
1524 | these events contain @samp{triple} instead of @samp{double}. If any | |
1525 | triple event has no binding, Emacs uses the binding that it would use | |
1526 | for the corresponding double event. | |
1527 | ||
1528 | If you click a button three or more times and then press it again, the | |
1529 | events for the presses beyond the third are all triple events. Emacs | |
1530 | does not have separate event types for quadruple, quintuple, etc.@: | |
1531 | events. However, you can look at the event list to find out precisely | |
1532 | how many times the button was pressed. | |
1533 | ||
1534 | @defun event-click-count event | |
1535 | This function returns the number of consecutive button presses that led | |
1536 | up to @var{event}. If @var{event} is a double-down, double-click or | |
1537 | double-drag event, the value is 2. If @var{event} is a triple event, | |
1538 | the value is 3 or greater. If @var{event} is an ordinary mouse event | |
1539 | (not a repeat event), the value is 1. | |
1540 | @end defun | |
1541 | ||
1542 | @defopt double-click-fuzz | |
1543 | To generate repeat events, successive mouse button presses must be at | |
1544 | approximately the same screen position. The value of | |
1545 | @code{double-click-fuzz} specifies the maximum number of pixels the | |
1546 | mouse may be moved (horizontally or vertically) between two successive | |
1547 | clicks to make a double-click. | |
1548 | ||
1549 | This variable is also the threshold for motion of the mouse to count | |
1550 | as a drag. | |
1551 | @end defopt | |
1552 | ||
1553 | @defopt double-click-time | |
1554 | To generate repeat events, the number of milliseconds between | |
1555 | successive button presses must be less than the value of | |
1556 | @code{double-click-time}. Setting @code{double-click-time} to | |
1557 | @code{nil} disables multi-click detection entirely. Setting it to | |
1558 | @code{t} removes the time limit; Emacs then detects multi-clicks by | |
1559 | position only. | |
1560 | @end defopt | |
1561 | ||
1562 | @node Motion Events | |
1563 | @subsection Motion Events | |
1564 | @cindex motion event | |
1565 | @cindex mouse motion events | |
1566 | ||
1567 | Emacs sometimes generates @dfn{mouse motion} events to describe motion | |
1568 | of the mouse without any button activity. Mouse motion events are | |
1569 | represented by lists that look like this: | |
1570 | ||
1571 | @example | |
603f5979 | 1572 | (mouse-movement POSITION) |
b8d4c8d0 GM |
1573 | @end example |
1574 | ||
1575 | The second element of the list describes the current position of the | |
1576 | mouse, just as in a click event (@pxref{Click Events}). | |
1577 | ||
1578 | The special form @code{track-mouse} enables generation of motion events | |
1579 | within its body. Outside of @code{track-mouse} forms, Emacs does not | |
1580 | generate events for mere motion of the mouse, and these events do not | |
1581 | appear. @xref{Mouse Tracking}. | |
1582 | ||
1583 | @node Focus Events | |
1584 | @subsection Focus Events | |
1585 | @cindex focus event | |
1586 | ||
1587 | Window systems provide general ways for the user to control which window | |
1588 | gets keyboard input. This choice of window is called the @dfn{focus}. | |
1589 | When the user does something to switch between Emacs frames, that | |
1590 | generates a @dfn{focus event}. The normal definition of a focus event, | |
1591 | in the global keymap, is to select a new frame within Emacs, as the user | |
1592 | would expect. @xref{Input Focus}. | |
1593 | ||
1594 | Focus events are represented in Lisp as lists that look like this: | |
1595 | ||
1596 | @example | |
1597 | (switch-frame @var{new-frame}) | |
1598 | @end example | |
1599 | ||
1600 | @noindent | |
1601 | where @var{new-frame} is the frame switched to. | |
1602 | ||
4b0f7178 CY |
1603 | Some X window managers are set up so that just moving the mouse into a |
1604 | window is enough to set the focus there. Usually, there is no need | |
1605 | for a Lisp program to know about the focus change until some other | |
1606 | kind of input arrives. Emacs generates a focus event only when the | |
1607 | user actually types a keyboard key or presses a mouse button in the | |
1608 | new frame; just moving the mouse between frames does not generate a | |
b8d4c8d0 GM |
1609 | focus event. |
1610 | ||
1611 | A focus event in the middle of a key sequence would garble the | |
1612 | sequence. So Emacs never generates a focus event in the middle of a key | |
1613 | sequence. If the user changes focus in the middle of a key | |
1614 | sequence---that is, after a prefix key---then Emacs reorders the events | |
1615 | so that the focus event comes either before or after the multi-event key | |
1616 | sequence, and not within it. | |
1617 | ||
1618 | @node Misc Events | |
1619 | @subsection Miscellaneous System Events | |
1620 | ||
1621 | A few other event types represent occurrences within the system. | |
1622 | ||
1623 | @table @code | |
1624 | @cindex @code{delete-frame} event | |
1625 | @item (delete-frame (@var{frame})) | |
1626 | This kind of event indicates that the user gave the window manager | |
1627 | a command to delete a particular window, which happens to be an Emacs frame. | |
1628 | ||
1629 | The standard definition of the @code{delete-frame} event is to delete @var{frame}. | |
1630 | ||
1631 | @cindex @code{iconify-frame} event | |
1632 | @item (iconify-frame (@var{frame})) | |
1633 | This kind of event indicates that the user iconified @var{frame} using | |
1634 | the window manager. Its standard definition is @code{ignore}; since the | |
1635 | frame has already been iconified, Emacs has no work to do. The purpose | |
1636 | of this event type is so that you can keep track of such events if you | |
1637 | want to. | |
1638 | ||
1639 | @cindex @code{make-frame-visible} event | |
1640 | @item (make-frame-visible (@var{frame})) | |
1641 | This kind of event indicates that the user deiconified @var{frame} using | |
1642 | the window manager. Its standard definition is @code{ignore}; since the | |
1643 | frame has already been made visible, Emacs has no work to do. | |
1644 | ||
1645 | @cindex @code{wheel-up} event | |
1646 | @cindex @code{wheel-down} event | |
1647 | @item (wheel-up @var{position}) | |
1648 | @item (wheel-down @var{position}) | |
1649 | These kinds of event are generated by moving a mouse wheel. Their | |
1650 | usual meaning is a kind of scroll or zoom. | |
1651 | ||
1652 | The element @var{position} is a list describing the position of the | |
e8a6cc19 EZ |
1653 | event, in the same format as used in a mouse-click event (@pxref{Click |
1654 | Events}). | |
b8d4c8d0 | 1655 | |
be0a5fb7 KR |
1656 | @vindex mouse-wheel-up-event |
1657 | @vindex mouse-wheel-down-event | |
b8d4c8d0 GM |
1658 | This kind of event is generated only on some kinds of systems. On some |
1659 | systems, @code{mouse-4} and @code{mouse-5} are used instead. For | |
1660 | portable code, use the variables @code{mouse-wheel-up-event} and | |
1661 | @code{mouse-wheel-down-event} defined in @file{mwheel.el} to determine | |
1662 | what event types to expect for the mouse wheel. | |
1663 | ||
1664 | @cindex @code{drag-n-drop} event | |
1665 | @item (drag-n-drop @var{position} @var{files}) | |
1666 | This kind of event is generated when a group of files is | |
1667 | selected in an application outside of Emacs, and then dragged and | |
1668 | dropped onto an Emacs frame. | |
1669 | ||
1670 | The element @var{position} is a list describing the position of the | |
e8a6cc19 EZ |
1671 | event, in the same format as used in a mouse-click event (@pxref{Click |
1672 | Events}), and @var{files} is the list of file names that were dragged | |
1673 | and dropped. The usual way to handle this event is by visiting these | |
1674 | files. | |
b8d4c8d0 GM |
1675 | |
1676 | This kind of event is generated, at present, only on some kinds of | |
1677 | systems. | |
1678 | ||
1679 | @cindex @code{help-echo} event | |
1680 | @item help-echo | |
1681 | This kind of event is generated when a mouse pointer moves onto a | |
1682 | portion of buffer text which has a @code{help-echo} text property. | |
1683 | The generated event has this form: | |
1684 | ||
1685 | @example | |
1686 | (help-echo @var{frame} @var{help} @var{window} @var{object} @var{pos}) | |
1687 | @end example | |
1688 | ||
1689 | @noindent | |
1690 | The precise meaning of the event parameters and the way these | |
1691 | parameters are used to display the help-echo text are described in | |
1692 | @ref{Text help-echo}. | |
1693 | ||
1694 | @cindex @code{sigusr1} event | |
1695 | @cindex @code{sigusr2} event | |
1696 | @cindex user signals | |
1697 | @item sigusr1 | |
1698 | @itemx sigusr2 | |
1699 | These events are generated when the Emacs process receives | |
1700 | the signals @code{SIGUSR1} and @code{SIGUSR2}. They contain no | |
1701 | additional data because signals do not carry additional information. | |
7aa5aad8 | 1702 | They can be useful for debugging (@pxref{Error Debugging}). |
b8d4c8d0 GM |
1703 | |
1704 | To catch a user signal, bind the corresponding event to an interactive | |
1705 | command in the @code{special-event-map} (@pxref{Active Keymaps}). | |
1706 | The command is called with no arguments, and the specific signal event is | |
1707 | available in @code{last-input-event}. For example: | |
1708 | ||
1709 | @smallexample | |
1710 | (defun sigusr-handler () | |
1711 | (interactive) | |
1712 | (message "Caught signal %S" last-input-event)) | |
1713 | ||
1714 | (define-key special-event-map [sigusr1] 'sigusr-handler) | |
1715 | @end smallexample | |
1716 | ||
1717 | To test the signal handler, you can make Emacs send a signal to itself: | |
1718 | ||
1719 | @smallexample | |
1720 | (signal-process (emacs-pid) 'sigusr1) | |
1721 | @end smallexample | |
1722 | @end table | |
1723 | ||
1724 | If one of these events arrives in the middle of a key sequence---that | |
1725 | is, after a prefix key---then Emacs reorders the events so that this | |
1726 | event comes either before or after the multi-event key sequence, not | |
1727 | within it. | |
1728 | ||
1729 | @node Event Examples | |
1730 | @subsection Event Examples | |
1731 | ||
1732 | If the user presses and releases the left mouse button over the same | |
1733 | location, that generates a sequence of events like this: | |
1734 | ||
1735 | @smallexample | |
1736 | (down-mouse-1 (#<window 18 on NEWS> 2613 (0 . 38) -864320)) | |
1737 | (mouse-1 (#<window 18 on NEWS> 2613 (0 . 38) -864180)) | |
1738 | @end smallexample | |
1739 | ||
1740 | While holding the control key down, the user might hold down the | |
1741 | second mouse button, and drag the mouse from one line to the next. | |
1742 | That produces two events, as shown here: | |
1743 | ||
1744 | @smallexample | |
1745 | (C-down-mouse-2 (#<window 18 on NEWS> 3440 (0 . 27) -731219)) | |
1746 | (C-drag-mouse-2 (#<window 18 on NEWS> 3440 (0 . 27) -731219) | |
1747 | (#<window 18 on NEWS> 3510 (0 . 28) -729648)) | |
1748 | @end smallexample | |
1749 | ||
1750 | While holding down the meta and shift keys, the user might press the | |
1751 | second mouse button on the window's mode line, and then drag the mouse | |
1752 | into another window. That produces a pair of events like these: | |
1753 | ||
1754 | @smallexample | |
1755 | (M-S-down-mouse-2 (#<window 18 on NEWS> mode-line (33 . 31) -457844)) | |
1756 | (M-S-drag-mouse-2 (#<window 18 on NEWS> mode-line (33 . 31) -457844) | |
1757 | (#<window 20 on carlton-sanskrit.tex> 161 (33 . 3) | |
1758 | -453816)) | |
1759 | @end smallexample | |
1760 | ||
1761 | To handle a SIGUSR1 signal, define an interactive function, and | |
1762 | bind it to the @code{signal usr1} event sequence: | |
1763 | ||
1764 | @smallexample | |
1765 | (defun usr1-handler () | |
1766 | (interactive) | |
1767 | (message "Got USR1 signal")) | |
1768 | (global-set-key [signal usr1] 'usr1-handler) | |
1769 | @end smallexample | |
1770 | ||
1771 | @node Classifying Events | |
1772 | @subsection Classifying Events | |
1773 | @cindex event type | |
1774 | ||
1775 | Every event has an @dfn{event type}, which classifies the event for | |
1776 | key binding purposes. For a keyboard event, the event type equals the | |
1777 | event value; thus, the event type for a character is the character, and | |
1778 | the event type for a function key symbol is the symbol itself. For | |
1779 | events that are lists, the event type is the symbol in the @sc{car} of | |
1780 | the list. Thus, the event type is always a symbol or a character. | |
1781 | ||
1782 | Two events of the same type are equivalent where key bindings are | |
1783 | concerned; thus, they always run the same command. That does not | |
1784 | necessarily mean they do the same things, however, as some commands look | |
1785 | at the whole event to decide what to do. For example, some commands use | |
1786 | the location of a mouse event to decide where in the buffer to act. | |
1787 | ||
1788 | Sometimes broader classifications of events are useful. For example, | |
1789 | you might want to ask whether an event involved the @key{META} key, | |
1790 | regardless of which other key or mouse button was used. | |
1791 | ||
1792 | The functions @code{event-modifiers} and @code{event-basic-type} are | |
1793 | provided to get such information conveniently. | |
1794 | ||
1795 | @defun event-modifiers event | |
1796 | This function returns a list of the modifiers that @var{event} has. The | |
1797 | modifiers are symbols; they include @code{shift}, @code{control}, | |
1798 | @code{meta}, @code{alt}, @code{hyper} and @code{super}. In addition, | |
1799 | the modifiers list of a mouse event symbol always contains one of | |
1800 | @code{click}, @code{drag}, and @code{down}. For double or triple | |
1801 | events, it also contains @code{double} or @code{triple}. | |
1802 | ||
1803 | The argument @var{event} may be an entire event object, or just an | |
1804 | event type. If @var{event} is a symbol that has never been used in an | |
1805 | event that has been read as input in the current Emacs session, then | |
1806 | @code{event-modifiers} can return @code{nil}, even when @var{event} | |
1807 | actually has modifiers. | |
1808 | ||
1809 | Here are some examples: | |
1810 | ||
1811 | @example | |
1812 | (event-modifiers ?a) | |
1813 | @result{} nil | |
1814 | (event-modifiers ?A) | |
1815 | @result{} (shift) | |
1816 | (event-modifiers ?\C-a) | |
1817 | @result{} (control) | |
1818 | (event-modifiers ?\C-%) | |
1819 | @result{} (control) | |
1820 | (event-modifiers ?\C-\S-a) | |
1821 | @result{} (control shift) | |
1822 | (event-modifiers 'f5) | |
1823 | @result{} nil | |
1824 | (event-modifiers 's-f5) | |
1825 | @result{} (super) | |
1826 | (event-modifiers 'M-S-f5) | |
1827 | @result{} (meta shift) | |
1828 | (event-modifiers 'mouse-1) | |
1829 | @result{} (click) | |
1830 | (event-modifiers 'down-mouse-1) | |
1831 | @result{} (down) | |
1832 | @end example | |
1833 | ||
1834 | The modifiers list for a click event explicitly contains @code{click}, | |
1835 | but the event symbol name itself does not contain @samp{click}. | |
1836 | @end defun | |
1837 | ||
1838 | @defun event-basic-type event | |
1839 | This function returns the key or mouse button that @var{event} | |
1840 | describes, with all modifiers removed. The @var{event} argument is as | |
1841 | in @code{event-modifiers}. For example: | |
1842 | ||
1843 | @example | |
1844 | (event-basic-type ?a) | |
1845 | @result{} 97 | |
1846 | (event-basic-type ?A) | |
1847 | @result{} 97 | |
1848 | (event-basic-type ?\C-a) | |
1849 | @result{} 97 | |
1850 | (event-basic-type ?\C-\S-a) | |
1851 | @result{} 97 | |
1852 | (event-basic-type 'f5) | |
1853 | @result{} f5 | |
1854 | (event-basic-type 's-f5) | |
1855 | @result{} f5 | |
1856 | (event-basic-type 'M-S-f5) | |
1857 | @result{} f5 | |
1858 | (event-basic-type 'down-mouse-1) | |
1859 | @result{} mouse-1 | |
1860 | @end example | |
1861 | @end defun | |
1862 | ||
1863 | @defun mouse-movement-p object | |
1864 | This function returns non-@code{nil} if @var{object} is a mouse movement | |
1865 | event. | |
1866 | @end defun | |
1867 | ||
1868 | @defun event-convert-list list | |
1869 | This function converts a list of modifier names and a basic event type | |
1870 | to an event type which specifies all of them. The basic event type | |
1871 | must be the last element of the list. For example, | |
1872 | ||
1873 | @example | |
1874 | (event-convert-list '(control ?a)) | |
1875 | @result{} 1 | |
1876 | (event-convert-list '(control meta ?a)) | |
1877 | @result{} -134217727 | |
1878 | (event-convert-list '(control super f1)) | |
1879 | @result{} C-s-f1 | |
1880 | @end example | |
1881 | @end defun | |
1882 | ||
ec7d5b1e RS |
1883 | @node Accessing Mouse |
1884 | @subsection Accessing Mouse Events | |
b8d4c8d0 GM |
1885 | @cindex mouse events, data in |
1886 | ||
1887 | This section describes convenient functions for accessing the data in | |
1888 | a mouse button or motion event. | |
1889 | ||
1890 | These two functions return the starting or ending position of a | |
34106abe | 1891 | mouse-button event, as a list of this form (@pxref{Click Events}): |
b8d4c8d0 GM |
1892 | |
1893 | @example | |
1894 | (@var{window} @var{pos-or-area} (@var{x} . @var{y}) @var{timestamp} | |
1895 | @var{object} @var{text-pos} (@var{col} . @var{row}) | |
1896 | @var{image} (@var{dx} . @var{dy}) (@var{width} . @var{height})) | |
1897 | @end example | |
1898 | ||
1899 | @defun event-start event | |
1900 | This returns the starting position of @var{event}. | |
1901 | ||
1902 | If @var{event} is a click or button-down event, this returns the | |
1903 | location of the event. If @var{event} is a drag event, this returns the | |
1904 | drag's starting position. | |
1905 | @end defun | |
1906 | ||
1907 | @defun event-end event | |
1908 | This returns the ending position of @var{event}. | |
1909 | ||
1910 | If @var{event} is a drag event, this returns the position where the user | |
1911 | released the mouse button. If @var{event} is a click or button-down | |
1912 | event, the value is actually the starting position, which is the only | |
1913 | position such events have. | |
1914 | @end defun | |
1915 | ||
1916 | @cindex mouse position list, accessing | |
1917 | These functions take a position list as described above, and | |
1918 | return various parts of it. | |
1919 | ||
1920 | @defun posn-window position | |
1921 | Return the window that @var{position} is in. | |
1922 | @end defun | |
1923 | ||
1924 | @defun posn-area position | |
1925 | Return the window area recorded in @var{position}. It returns @code{nil} | |
1926 | when the event occurred in the text area of the window; otherwise, it | |
1927 | is a symbol identifying the area in which the event occurred. | |
1928 | @end defun | |
1929 | ||
1930 | @defun posn-point position | |
1931 | Return the buffer position in @var{position}. When the event occurred | |
1932 | in the text area of the window, in a marginal area, or on a fringe, | |
1933 | this is an integer specifying a buffer position. Otherwise, the value | |
1934 | is undefined. | |
1935 | @end defun | |
1936 | ||
1937 | @defun posn-x-y position | |
1938 | Return the pixel-based x and y coordinates in @var{position}, as a | |
1939 | cons cell @code{(@var{x} . @var{y})}. These coordinates are relative | |
1940 | to the window given by @code{posn-window}. | |
1941 | ||
34106abe CY |
1942 | This example shows how to convert the window-relative coordinates in |
1943 | the text area of a window into frame-relative coordinates: | |
b8d4c8d0 GM |
1944 | |
1945 | @example | |
1946 | (defun frame-relative-coordinates (position) | |
34106abe CY |
1947 | "Return frame-relative coordinates from POSITION. |
1948 | POSITION is assumed to lie in a window text area." | |
b8d4c8d0 GM |
1949 | (let* ((x-y (posn-x-y position)) |
1950 | (window (posn-window position)) | |
1951 | (edges (window-inside-pixel-edges window))) | |
1952 | (cons (+ (car x-y) (car edges)) | |
1953 | (+ (cdr x-y) (cadr edges))))) | |
1954 | @end example | |
1955 | @end defun | |
1956 | ||
1957 | @defun posn-col-row position | |
a41c8660 CY |
1958 | This function returns a cons cell @code{(@var{col} . @var{row})}, |
1959 | containing the estimated column and row corresponding to buffer | |
1960 | position @var{position}. The return value is given in units of the | |
1961 | frame's default character width and height, as computed from the | |
1962 | @var{x} and @var{y} values corresponding to @var{position}. (So, if | |
1963 | the actual characters have non-default sizes, the actual row and | |
1964 | column may differ from these computed values.) | |
1965 | ||
1966 | Note that @var{row} is counted from the top of the text area. If the | |
1967 | window possesses a header line (@pxref{Header Lines}), it is | |
1968 | @emph{not} counted as the first line. | |
b8d4c8d0 GM |
1969 | @end defun |
1970 | ||
1971 | @defun posn-actual-col-row position | |
1972 | Return the actual row and column in @var{position}, as a cons cell | |
34106abe CY |
1973 | @code{(@var{col} . @var{row})}. The values are the actual row and |
1974 | column numbers in the window. @xref{Click Events}, for details. It | |
1975 | returns @code{nil} if @var{position} does not include actual positions | |
1976 | values. | |
b8d4c8d0 GM |
1977 | @end defun |
1978 | ||
1979 | @defun posn-string position | |
1980 | Return the string object in @var{position}, either @code{nil}, or a | |
1981 | cons cell @code{(@var{string} . @var{string-pos})}. | |
1982 | @end defun | |
1983 | ||
1984 | @defun posn-image position | |
1985 | Return the image object in @var{position}, either @code{nil}, or an | |
1986 | image @code{(image ...)}. | |
1987 | @end defun | |
1988 | ||
1989 | @defun posn-object position | |
1990 | Return the image or string object in @var{position}, either | |
1991 | @code{nil}, an image @code{(image ...)}, or a cons cell | |
1992 | @code{(@var{string} . @var{string-pos})}. | |
1993 | @end defun | |
1994 | ||
1995 | @defun posn-object-x-y position | |
1996 | Return the pixel-based x and y coordinates relative to the upper left | |
1997 | corner of the object in @var{position} as a cons cell @code{(@var{dx} | |
1998 | . @var{dy})}. If the @var{position} is a buffer position, return the | |
1999 | relative position in the character at that position. | |
2000 | @end defun | |
2001 | ||
2002 | @defun posn-object-width-height position | |
2003 | Return the pixel width and height of the object in @var{position} as a | |
2004 | cons cell @code{(@var{width} . @var{height})}. If the @var{position} | |
2005 | is a buffer position, return the size of the character at that position. | |
2006 | @end defun | |
2007 | ||
2008 | @cindex timestamp of a mouse event | |
2009 | @defun posn-timestamp position | |
2010 | Return the timestamp in @var{position}. This is the time at which the | |
2011 | event occurred, in milliseconds. | |
2012 | @end defun | |
2013 | ||
2014 | These functions compute a position list given particular buffer | |
2015 | position or screen position. You can access the data in this position | |
2016 | list with the functions described above. | |
2017 | ||
2018 | @defun posn-at-point &optional pos window | |
2019 | This function returns a position list for position @var{pos} in | |
2020 | @var{window}. @var{pos} defaults to point in @var{window}; | |
2021 | @var{window} defaults to the selected window. | |
2022 | ||
2023 | @code{posn-at-point} returns @code{nil} if @var{pos} is not visible in | |
2024 | @var{window}. | |
2025 | @end defun | |
2026 | ||
2027 | @defun posn-at-x-y x y &optional frame-or-window whole | |
2028 | This function returns position information corresponding to pixel | |
2029 | coordinates @var{x} and @var{y} in a specified frame or window, | |
2030 | @var{frame-or-window}, which defaults to the selected window. | |
2031 | The coordinates @var{x} and @var{y} are relative to the | |
2032 | frame or window used. | |
2033 | If @var{whole} is @code{nil}, the coordinates are relative | |
2034 | to the window text area, otherwise they are relative to | |
2035 | the entire window area including scroll bars, margins and fringes. | |
2036 | @end defun | |
2037 | ||
ec7d5b1e RS |
2038 | @node Accessing Scroll |
2039 | @subsection Accessing Scroll Bar Events | |
2040 | @cindex scroll bar events, data in | |
2041 | ||
b8d4c8d0 GM |
2042 | These functions are useful for decoding scroll bar events. |
2043 | ||
2044 | @defun scroll-bar-event-ratio event | |
2045 | This function returns the fractional vertical position of a scroll bar | |
2046 | event within the scroll bar. The value is a cons cell | |
2047 | @code{(@var{portion} . @var{whole})} containing two integers whose ratio | |
2048 | is the fractional position. | |
2049 | @end defun | |
2050 | ||
2051 | @defun scroll-bar-scale ratio total | |
2052 | This function multiplies (in effect) @var{ratio} by @var{total}, | |
2053 | rounding the result to an integer. The argument @var{ratio} is not a | |
2054 | number, but rather a pair @code{(@var{num} . @var{denom})}---typically a | |
2055 | value returned by @code{scroll-bar-event-ratio}. | |
2056 | ||
2057 | This function is handy for scaling a position on a scroll bar into a | |
2058 | buffer position. Here's how to do that: | |
2059 | ||
2060 | @example | |
2061 | (+ (point-min) | |
2062 | (scroll-bar-scale | |
2063 | (posn-x-y (event-start event)) | |
2064 | (- (point-max) (point-min)))) | |
2065 | @end example | |
2066 | ||
2067 | Recall that scroll bar events have two integers forming a ratio, in place | |
2068 | of a pair of x and y coordinates. | |
2069 | @end defun | |
2070 | ||
2071 | @node Strings of Events | |
2072 | @subsection Putting Keyboard Events in Strings | |
2073 | @cindex keyboard events in strings | |
2074 | @cindex strings with keyboard events | |
2075 | ||
2076 | In most of the places where strings are used, we conceptualize the | |
2077 | string as containing text characters---the same kind of characters found | |
2078 | in buffers or files. Occasionally Lisp programs use strings that | |
2079 | conceptually contain keyboard characters; for example, they may be key | |
2080 | sequences or keyboard macro definitions. However, storing keyboard | |
2081 | characters in a string is a complex matter, for reasons of historical | |
2082 | compatibility, and it is not always possible. | |
2083 | ||
2084 | We recommend that new programs avoid dealing with these complexities | |
2085 | by not storing keyboard events in strings. Here is how to do that: | |
2086 | ||
2087 | @itemize @bullet | |
2088 | @item | |
2089 | Use vectors instead of strings for key sequences, when you plan to use | |
2090 | them for anything other than as arguments to @code{lookup-key} and | |
2091 | @code{define-key}. For example, you can use | |
2092 | @code{read-key-sequence-vector} instead of @code{read-key-sequence}, and | |
2093 | @code{this-command-keys-vector} instead of @code{this-command-keys}. | |
2094 | ||
2095 | @item | |
2096 | Use vectors to write key sequence constants containing meta characters, | |
2097 | even when passing them directly to @code{define-key}. | |
2098 | ||
2099 | @item | |
2100 | When you have to look at the contents of a key sequence that might be a | |
2101 | string, use @code{listify-key-sequence} (@pxref{Event Input Misc}) | |
2102 | first, to convert it to a list. | |
2103 | @end itemize | |
2104 | ||
2105 | The complexities stem from the modifier bits that keyboard input | |
2106 | characters can include. Aside from the Meta modifier, none of these | |
2107 | modifier bits can be included in a string, and the Meta modifier is | |
2108 | allowed only in special cases. | |
2109 | ||
2110 | The earliest GNU Emacs versions represented meta characters as codes | |
2111 | in the range of 128 to 255. At that time, the basic character codes | |
2112 | ranged from 0 to 127, so all keyboard character codes did fit in a | |
2113 | string. Many Lisp programs used @samp{\M-} in string constants to stand | |
2114 | for meta characters, especially in arguments to @code{define-key} and | |
2115 | similar functions, and key sequences and sequences of events were always | |
2116 | represented as strings. | |
2117 | ||
2118 | When we added support for larger basic character codes beyond 127, and | |
2119 | additional modifier bits, we had to change the representation of meta | |
2120 | characters. Now the flag that represents the Meta modifier in a | |
2121 | character is | |
2122 | @tex | |
2123 | @math{2^{27}} | |
2124 | @end tex | |
2125 | @ifnottex | |
2126 | 2**27 | |
2127 | @end ifnottex | |
2128 | and such numbers cannot be included in a string. | |
2129 | ||
2130 | To support programs with @samp{\M-} in string constants, there are | |
2131 | special rules for including certain meta characters in a string. | |
2132 | Here are the rules for interpreting a string as a sequence of input | |
2133 | characters: | |
2134 | ||
2135 | @itemize @bullet | |
2136 | @item | |
2137 | If the keyboard character value is in the range of 0 to 127, it can go | |
2138 | in the string unchanged. | |
2139 | ||
2140 | @item | |
2141 | The meta variants of those characters, with codes in the range of | |
2142 | @tex | |
2143 | @math{2^{27}} | |
2144 | @end tex | |
2145 | @ifnottex | |
2146 | 2**27 | |
2147 | @end ifnottex | |
2148 | to | |
2149 | @tex | |
2150 | @math{2^{27} + 127}, | |
2151 | @end tex | |
2152 | @ifnottex | |
2153 | 2**27+127, | |
2154 | @end ifnottex | |
2155 | can also go in the string, but you must change their | |
2156 | numeric values. You must set the | |
2157 | @tex | |
2158 | @math{2^{7}} | |
2159 | @end tex | |
2160 | @ifnottex | |
2161 | 2**7 | |
2162 | @end ifnottex | |
2163 | bit instead of the | |
2164 | @tex | |
2165 | @math{2^{27}} | |
2166 | @end tex | |
2167 | @ifnottex | |
2168 | 2**27 | |
2169 | @end ifnottex | |
2170 | bit, resulting in a value between 128 and 255. Only a unibyte string | |
2171 | can include these codes. | |
2172 | ||
2173 | @item | |
2174 | Non-@acronym{ASCII} characters above 256 can be included in a multibyte string. | |
2175 | ||
2176 | @item | |
2177 | Other keyboard character events cannot fit in a string. This includes | |
2178 | keyboard events in the range of 128 to 255. | |
2179 | @end itemize | |
2180 | ||
2181 | Functions such as @code{read-key-sequence} that construct strings of | |
2182 | keyboard input characters follow these rules: they construct vectors | |
2183 | instead of strings, when the events won't fit in a string. | |
2184 | ||
2185 | When you use the read syntax @samp{\M-} in a string, it produces a | |
2186 | code in the range of 128 to 255---the same code that you get if you | |
2187 | modify the corresponding keyboard event to put it in the string. Thus, | |
2188 | meta events in strings work consistently regardless of how they get into | |
2189 | the strings. | |
2190 | ||
2191 | However, most programs would do well to avoid these issues by | |
2192 | following the recommendations at the beginning of this section. | |
2193 | ||
2194 | @node Reading Input | |
2195 | @section Reading Input | |
2196 | @cindex read input | |
2197 | @cindex keyboard input | |
2198 | ||
2199 | The editor command loop reads key sequences using the function | |
2200 | @code{read-key-sequence}, which uses @code{read-event}. These and other | |
2201 | functions for event input are also available for use in Lisp programs. | |
2202 | See also @code{momentary-string-display} in @ref{Temporary Displays}, | |
2203 | and @code{sit-for} in @ref{Waiting}. @xref{Terminal Input}, for | |
2204 | functions and variables for controlling terminal input modes and | |
2205 | debugging terminal input. | |
2206 | ||
2207 | For higher-level input facilities, see @ref{Minibuffers}. | |
2208 | ||
2209 | @menu | |
d24880de GM |
2210 | * Key Sequence Input:: How to read one key sequence. |
2211 | * Reading One Event:: How to read just one event. | |
b8d4c8d0 GM |
2212 | * Event Mod:: How Emacs modifies events as they are read. |
2213 | * Invoking the Input Method:: How reading an event uses the input method. | |
d24880de GM |
2214 | * Quoted Character Input:: Asking the user to specify a character. |
2215 | * Event Input Misc:: How to reread or throw away input events. | |
b8d4c8d0 GM |
2216 | @end menu |
2217 | ||
2218 | @node Key Sequence Input | |
2219 | @subsection Key Sequence Input | |
2220 | @cindex key sequence input | |
2221 | ||
2222 | The command loop reads input a key sequence at a time, by calling | |
2223 | @code{read-key-sequence}. Lisp programs can also call this function; | |
2224 | for example, @code{describe-key} uses it to read the key to describe. | |
2225 | ||
2226 | @defun read-key-sequence prompt &optional continue-echo dont-downcase-last switch-frame-ok command-loop | |
2227 | This function reads a key sequence and returns it as a string or | |
2228 | vector. It keeps reading events until it has accumulated a complete key | |
2229 | sequence; that is, enough to specify a non-prefix command using the | |
2230 | currently active keymaps. (Remember that a key sequence that starts | |
2231 | with a mouse event is read using the keymaps of the buffer in the | |
2232 | window that the mouse was in, not the current buffer.) | |
2233 | ||
2234 | If the events are all characters and all can fit in a string, then | |
2235 | @code{read-key-sequence} returns a string (@pxref{Strings of Events}). | |
2236 | Otherwise, it returns a vector, since a vector can hold all kinds of | |
2237 | events---characters, symbols, and lists. The elements of the string or | |
2238 | vector are the events in the key sequence. | |
2239 | ||
2240 | Reading a key sequence includes translating the events in various | |
2241 | ways. @xref{Translation Keymaps}. | |
2242 | ||
2243 | The argument @var{prompt} is either a string to be displayed in the | |
2244 | echo area as a prompt, or @code{nil}, meaning not to display a prompt. | |
2245 | The argument @var{continue-echo}, if non-@code{nil}, means to echo | |
2246 | this key as a continuation of the previous key. | |
2247 | ||
2248 | Normally any upper case event is converted to lower case if the | |
2249 | original event is undefined and the lower case equivalent is defined. | |
2250 | The argument @var{dont-downcase-last}, if non-@code{nil}, means do not | |
2251 | convert the last event to lower case. This is appropriate for reading | |
2252 | a key sequence to be defined. | |
2253 | ||
2254 | The argument @var{switch-frame-ok}, if non-@code{nil}, means that this | |
2255 | function should process a @code{switch-frame} event if the user | |
2256 | switches frames before typing anything. If the user switches frames | |
2257 | in the middle of a key sequence, or at the start of the sequence but | |
2258 | @var{switch-frame-ok} is @code{nil}, then the event will be put off | |
2259 | until after the current key sequence. | |
2260 | ||
2261 | The argument @var{command-loop}, if non-@code{nil}, means that this | |
2262 | key sequence is being read by something that will read commands one | |
2263 | after another. It should be @code{nil} if the caller will read just | |
2264 | one key sequence. | |
2265 | ||
2266 | In the following example, Emacs displays the prompt @samp{?} in the | |
2267 | echo area, and then the user types @kbd{C-x C-f}. | |
2268 | ||
2269 | @example | |
2270 | (read-key-sequence "?") | |
2271 | ||
2272 | @group | |
2273 | ---------- Echo Area ---------- | |
2274 | ?@kbd{C-x C-f} | |
2275 | ---------- Echo Area ---------- | |
2276 | ||
2277 | @result{} "^X^F" | |
2278 | @end group | |
2279 | @end example | |
2280 | ||
2281 | The function @code{read-key-sequence} suppresses quitting: @kbd{C-g} | |
2282 | typed while reading with this function works like any other character, | |
2283 | and does not set @code{quit-flag}. @xref{Quitting}. | |
2284 | @end defun | |
2285 | ||
2286 | @defun read-key-sequence-vector prompt &optional continue-echo dont-downcase-last switch-frame-ok command-loop | |
2287 | This is like @code{read-key-sequence} except that it always | |
2288 | returns the key sequence as a vector, never as a string. | |
2289 | @xref{Strings of Events}. | |
2290 | @end defun | |
2291 | ||
2292 | @cindex upper case key sequence | |
2293 | @cindex downcasing in @code{lookup-key} | |
ee6e73b8 | 2294 | @cindex shift-translation |
b8d4c8d0 GM |
2295 | If an input character is upper-case (or has the shift modifier) and |
2296 | has no key binding, but its lower-case equivalent has one, then | |
2297 | @code{read-key-sequence} converts the character to lower case. Note | |
2298 | that @code{lookup-key} does not perform case conversion in this way. | |
2299 | ||
ee6e73b8 EZ |
2300 | @vindex this-command-keys-shift-translated |
2301 | When reading input results in such a @dfn{shift-translation}, Emacs | |
2302 | sets the variable @code{this-command-keys-shift-translated} to a | |
77111ca6 CY |
2303 | non-@code{nil} value. Lisp programs can examine this variable if they |
2304 | need to modify their behavior when invoked by shift-translated keys. | |
2305 | For example, the function @code{handle-shift-selection} examines the | |
2306 | value of this variable to determine how to activate or deactivate the | |
2307 | region (@pxref{The Mark, handle-shift-selection}). | |
ee6e73b8 | 2308 | |
b8d4c8d0 GM |
2309 | The function @code{read-key-sequence} also transforms some mouse events. |
2310 | It converts unbound drag events into click events, and discards unbound | |
2311 | button-down events entirely. It also reshuffles focus events and | |
2312 | miscellaneous window events so that they never appear in a key sequence | |
2313 | with any other events. | |
2314 | ||
2315 | @cindex @code{header-line} prefix key | |
2316 | @cindex @code{mode-line} prefix key | |
2317 | @cindex @code{vertical-line} prefix key | |
2318 | @cindex @code{horizontal-scroll-bar} prefix key | |
2319 | @cindex @code{vertical-scroll-bar} prefix key | |
2320 | @cindex @code{menu-bar} prefix key | |
2321 | @cindex mouse events, in special parts of frame | |
2322 | When mouse events occur in special parts of a window, such as a mode | |
2323 | line or a scroll bar, the event type shows nothing special---it is the | |
2324 | same symbol that would normally represent that combination of mouse | |
2325 | button and modifier keys. The information about the window part is kept | |
2326 | elsewhere in the event---in the coordinates. But | |
2327 | @code{read-key-sequence} translates this information into imaginary | |
16152b76 | 2328 | ``prefix keys'', all of which are symbols: @code{header-line}, |
b8d4c8d0 GM |
2329 | @code{horizontal-scroll-bar}, @code{menu-bar}, @code{mode-line}, |
2330 | @code{vertical-line}, and @code{vertical-scroll-bar}. You can define | |
2331 | meanings for mouse clicks in special window parts by defining key | |
2332 | sequences using these imaginary prefix keys. | |
2333 | ||
2334 | For example, if you call @code{read-key-sequence} and then click the | |
2335 | mouse on the window's mode line, you get two events, like this: | |
2336 | ||
2337 | @example | |
2338 | (read-key-sequence "Click on the mode line: ") | |
2339 | @result{} [mode-line | |
2340 | (mouse-1 | |
2341 | (#<window 6 on NEWS> mode-line | |
2342 | (40 . 63) 5959987))] | |
2343 | @end example | |
2344 | ||
2345 | @defvar num-input-keys | |
2346 | @c Emacs 19 feature | |
2347 | This variable's value is the number of key sequences processed so far in | |
2348 | this Emacs session. This includes key sequences read from the terminal | |
2349 | and key sequences read from keyboard macros being executed. | |
2350 | @end defvar | |
2351 | ||
2352 | @node Reading One Event | |
2353 | @subsection Reading One Event | |
2354 | @cindex reading a single event | |
2355 | @cindex event, reading only one | |
2356 | ||
eb5ed549 CY |
2357 | The lowest level functions for command input are @code{read-event}, |
2358 | @code{read-char}, and @code{read-char-exclusive}. | |
b8d4c8d0 GM |
2359 | |
2360 | @defun read-event &optional prompt inherit-input-method seconds | |
2361 | This function reads and returns the next event of command input, waiting | |
2362 | if necessary until an event is available. Events can come directly from | |
2363 | the user or from a keyboard macro. | |
2364 | ||
2365 | If the optional argument @var{prompt} is non-@code{nil}, it should be a | |
2366 | string to display in the echo area as a prompt. Otherwise, | |
2367 | @code{read-event} does not display any message to indicate it is waiting | |
2368 | for input; instead, it prompts by echoing: it displays descriptions of | |
2369 | the events that led to or were read by the current command. @xref{The | |
2370 | Echo Area}. | |
2371 | ||
2372 | If @var{inherit-input-method} is non-@code{nil}, then the current input | |
2373 | method (if any) is employed to make it possible to enter a | |
2374 | non-@acronym{ASCII} character. Otherwise, input method handling is disabled | |
2375 | for reading this event. | |
2376 | ||
2377 | If @code{cursor-in-echo-area} is non-@code{nil}, then @code{read-event} | |
2378 | moves the cursor temporarily to the echo area, to the end of any message | |
2379 | displayed there. Otherwise @code{read-event} does not move the cursor. | |
2380 | ||
2381 | If @var{seconds} is non-@code{nil}, it should be a number specifying | |
2382 | the maximum time to wait for input, in seconds. If no input arrives | |
2383 | within that time, @code{read-event} stops waiting and returns | |
2384 | @code{nil}. A floating-point value for @var{seconds} means to wait | |
2385 | for a fractional number of seconds. Some systems support only a whole | |
2386 | number of seconds; on these systems, @var{seconds} is rounded down. | |
2387 | If @var{seconds} is @code{nil}, @code{read-event} waits as long as | |
2388 | necessary for input to arrive. | |
2389 | ||
2390 | If @var{seconds} is @code{nil}, Emacs is considered idle while waiting | |
2391 | for user input to arrive. Idle timers---those created with | |
2392 | @code{run-with-idle-timer} (@pxref{Idle Timers})---can run during this | |
2393 | period. However, if @var{seconds} is non-@code{nil}, the state of | |
2394 | idleness remains unchanged. If Emacs is non-idle when | |
2395 | @code{read-event} is called, it remains non-idle throughout the | |
2396 | operation of @code{read-event}; if Emacs is idle (which can happen if | |
2397 | the call happens inside an idle timer), it remains idle. | |
2398 | ||
2399 | If @code{read-event} gets an event that is defined as a help character, | |
2400 | then in some cases @code{read-event} processes the event directly without | |
2401 | returning. @xref{Help Functions}. Certain other events, called | |
2402 | @dfn{special events}, are also processed directly within | |
2403 | @code{read-event} (@pxref{Special Events}). | |
2404 | ||
2405 | Here is what happens if you call @code{read-event} and then press the | |
2406 | right-arrow function key: | |
2407 | ||
2408 | @example | |
2409 | @group | |
2410 | (read-event) | |
2411 | @result{} right | |
2412 | @end group | |
2413 | @end example | |
2414 | @end defun | |
2415 | ||
2416 | @defun read-char &optional prompt inherit-input-method seconds | |
2417 | This function reads and returns a character of command input. If the | |
2418 | user generates an event which is not a character (i.e. a mouse click or | |
2419 | function key event), @code{read-char} signals an error. The arguments | |
2420 | work as in @code{read-event}. | |
2421 | ||
2422 | In the first example, the user types the character @kbd{1} (@acronym{ASCII} | |
2423 | code 49). The second example shows a keyboard macro definition that | |
2424 | calls @code{read-char} from the minibuffer using @code{eval-expression}. | |
2425 | @code{read-char} reads the keyboard macro's very next character, which | |
2426 | is @kbd{1}. Then @code{eval-expression} displays its return value in | |
2427 | the echo area. | |
2428 | ||
2429 | @example | |
2430 | @group | |
2431 | (read-char) | |
2432 | @result{} 49 | |
2433 | @end group | |
2434 | ||
2435 | @group | |
2436 | ;; @r{We assume here you use @kbd{M-:} to evaluate this.} | |
2437 | (symbol-function 'foo) | |
2438 | @result{} "^[:(read-char)^M1" | |
2439 | @end group | |
2440 | @group | |
2441 | (execute-kbd-macro 'foo) | |
2442 | @print{} 49 | |
2443 | @result{} nil | |
2444 | @end group | |
2445 | @end example | |
2446 | @end defun | |
2447 | ||
2448 | @defun read-char-exclusive &optional prompt inherit-input-method seconds | |
2449 | This function reads and returns a character of command input. If the | |
2450 | user generates an event which is not a character, | |
2451 | @code{read-char-exclusive} ignores it and reads another event, until it | |
2452 | gets a character. The arguments work as in @code{read-event}. | |
2453 | @end defun | |
2454 | ||
eb5ed549 CY |
2455 | None of the above functions suppress quitting. |
2456 | ||
b8d4c8d0 GM |
2457 | @defvar num-nonmacro-input-events |
2458 | This variable holds the total number of input events received so far | |
2459 | from the terminal---not counting those generated by keyboard macros. | |
2460 | @end defvar | |
2461 | ||
eb5ed549 CY |
2462 | We emphasize that, unlike @code{read-key-sequence}, the functions |
2463 | @code{read-event}, @code{read-char}, and @code{read-char-exclusive} do | |
2464 | not perform the translations described in @ref{Translation Keymaps}. | |
2465 | If you wish to read a single key taking these translations into | |
2466 | account, use the function @code{read-key}: | |
2467 | ||
2468 | @defun read-key &optional prompt | |
2469 | This function reads a single key. It is ``intermediate'' between | |
2470 | @code{read-key-sequence} and @code{read-event}. Unlike the former, it | |
2471 | reads a single key, not a key sequence. Unlike the latter, it does | |
2472 | not return a raw event, but decodes and translates the user input | |
2473 | according to @code{input-decode-map}, @code{local-function-key-map}, | |
2474 | and @code{key-translation-map} (@pxref{Translation Keymaps}). | |
2475 | ||
2476 | The argument @var{prompt} is either a string to be displayed in the | |
2477 | echo area as a prompt, or @code{nil}, meaning not to display a prompt. | |
2478 | @end defun | |
2479 | ||
7e2734bc GM |
2480 | @defun read-char-choice prompt chars &optional inhibit-quit |
2481 | This function uses @code{read-key} to read and return a single | |
2482 | character. It ignores any input that is not a member of @var{chars}, | |
2483 | a list of accepted characters. Optionally, it will also ignore | |
2484 | keyboard-quit events while it is waiting for valid input. If you bind | |
2485 | @code{help-form} (@pxref{Help Functions}) to a non-@code{nil} value | |
2486 | while calling @code{read-char-choice}, then pressing @code{help-char} | |
2487 | causes it to evaluate @code{help-form} and display the result. It | |
2488 | then continues to wait for a valid input character, or keyboard-quit. | |
2489 | @end defun | |
2490 | ||
b8d4c8d0 GM |
2491 | @node Event Mod |
2492 | @subsection Modifying and Translating Input Events | |
2493 | ||
2494 | Emacs modifies every event it reads according to | |
2495 | @code{extra-keyboard-modifiers}, then translates it through | |
2496 | @code{keyboard-translate-table} (if applicable), before returning it | |
2497 | from @code{read-event}. | |
2498 | ||
2499 | @c Emacs 19 feature | |
2500 | @defvar extra-keyboard-modifiers | |
2501 | This variable lets Lisp programs ``press'' the modifier keys on the | |
2502 | keyboard. The value is a character. Only the modifiers of the | |
2503 | character matter. Each time the user types a keyboard key, it is | |
2504 | altered as if those modifier keys were held down. For instance, if | |
2505 | you bind @code{extra-keyboard-modifiers} to @code{?\C-\M-a}, then all | |
2506 | keyboard input characters typed during the scope of the binding will | |
2507 | have the control and meta modifiers applied to them. The character | |
2508 | @code{?\C-@@}, equivalent to the integer 0, does not count as a control | |
2509 | character for this purpose, but as a character with no modifiers. | |
2510 | Thus, setting @code{extra-keyboard-modifiers} to zero cancels any | |
2511 | modification. | |
2512 | ||
2513 | When using a window system, the program can ``press'' any of the | |
2514 | modifier keys in this way. Otherwise, only the @key{CTL} and @key{META} | |
2515 | keys can be virtually pressed. | |
2516 | ||
2517 | Note that this variable applies only to events that really come from | |
2518 | the keyboard, and has no effect on mouse events or any other events. | |
2519 | @end defvar | |
2520 | ||
2521 | @defvar keyboard-translate-table | |
d3ae77bc EZ |
2522 | This terminal-local variable is the translate table for keyboard |
2523 | characters. It lets you reshuffle the keys on the keyboard without | |
2524 | changing any command bindings. Its value is normally a char-table, or | |
2525 | else @code{nil}. (It can also be a string or vector, but this is | |
2526 | considered obsolete.) | |
b8d4c8d0 GM |
2527 | |
2528 | If @code{keyboard-translate-table} is a char-table | |
2529 | (@pxref{Char-Tables}), then each character read from the keyboard is | |
2530 | looked up in this char-table. If the value found there is | |
2531 | non-@code{nil}, then it is used instead of the actual input character. | |
2532 | ||
2533 | Note that this translation is the first thing that happens to a | |
2534 | character after it is read from the terminal. Record-keeping features | |
2535 | such as @code{recent-keys} and dribble files record the characters after | |
2536 | translation. | |
2537 | ||
2538 | Note also that this translation is done before the characters are | |
a894169f EZ |
2539 | supplied to input methods (@pxref{Input Methods}). Use |
2540 | @code{translation-table-for-input} (@pxref{Translation of Characters}), | |
2541 | if you want to translate characters after input methods operate. | |
b8d4c8d0 GM |
2542 | @end defvar |
2543 | ||
2544 | @defun keyboard-translate from to | |
2545 | This function modifies @code{keyboard-translate-table} to translate | |
2546 | character code @var{from} into character code @var{to}. It creates | |
2547 | the keyboard translate table if necessary. | |
2548 | @end defun | |
2549 | ||
2550 | Here's an example of using the @code{keyboard-translate-table} to | |
2551 | make @kbd{C-x}, @kbd{C-c} and @kbd{C-v} perform the cut, copy and paste | |
2552 | operations: | |
2553 | ||
2554 | @example | |
2555 | (keyboard-translate ?\C-x 'control-x) | |
2556 | (keyboard-translate ?\C-c 'control-c) | |
2557 | (keyboard-translate ?\C-v 'control-v) | |
2558 | (global-set-key [control-x] 'kill-region) | |
2559 | (global-set-key [control-c] 'kill-ring-save) | |
2560 | (global-set-key [control-v] 'yank) | |
2561 | @end example | |
2562 | ||
2563 | @noindent | |
2564 | On a graphical terminal that supports extended @acronym{ASCII} input, | |
2565 | you can still get the standard Emacs meanings of one of those | |
2566 | characters by typing it with the shift key. That makes it a different | |
2567 | character as far as keyboard translation is concerned, but it has the | |
2568 | same usual meaning. | |
2569 | ||
2570 | @xref{Translation Keymaps}, for mechanisms that translate event sequences | |
2571 | at the level of @code{read-key-sequence}. | |
2572 | ||
2573 | @node Invoking the Input Method | |
2574 | @subsection Invoking the Input Method | |
2575 | ||
2576 | The event-reading functions invoke the current input method, if any | |
2577 | (@pxref{Input Methods}). If the value of @code{input-method-function} | |
2578 | is non-@code{nil}, it should be a function; when @code{read-event} reads | |
2579 | a printing character (including @key{SPC}) with no modifier bits, it | |
2580 | calls that function, passing the character as an argument. | |
2581 | ||
2582 | @defvar input-method-function | |
2583 | If this is non-@code{nil}, its value specifies the current input method | |
2584 | function. | |
2585 | ||
2586 | @strong{Warning:} don't bind this variable with @code{let}. It is often | |
2587 | buffer-local, and if you bind it around reading input (which is exactly | |
2588 | when you @emph{would} bind it), switching buffers asynchronously while | |
2589 | Emacs is waiting will cause the value to be restored in the wrong | |
2590 | buffer. | |
2591 | @end defvar | |
2592 | ||
2593 | The input method function should return a list of events which should | |
2594 | be used as input. (If the list is @code{nil}, that means there is no | |
2595 | input, so @code{read-event} waits for another event.) These events are | |
2596 | processed before the events in @code{unread-command-events} | |
2597 | (@pxref{Event Input Misc}). Events | |
2598 | returned by the input method function are not passed to the input method | |
2599 | function again, even if they are printing characters with no modifier | |
2600 | bits. | |
2601 | ||
2602 | If the input method function calls @code{read-event} or | |
2603 | @code{read-key-sequence}, it should bind @code{input-method-function} to | |
2604 | @code{nil} first, to prevent recursion. | |
2605 | ||
2606 | The input method function is not called when reading the second and | |
2607 | subsequent events of a key sequence. Thus, these characters are not | |
2608 | subject to input method processing. The input method function should | |
2609 | test the values of @code{overriding-local-map} and | |
2610 | @code{overriding-terminal-local-map}; if either of these variables is | |
2611 | non-@code{nil}, the input method should put its argument into a list and | |
2612 | return that list with no further processing. | |
2613 | ||
2614 | @node Quoted Character Input | |
2615 | @subsection Quoted Character Input | |
2616 | @cindex quoted character input | |
2617 | ||
2618 | You can use the function @code{read-quoted-char} to ask the user to | |
2619 | specify a character, and allow the user to specify a control or meta | |
2620 | character conveniently, either literally or as an octal character code. | |
2621 | The command @code{quoted-insert} uses this function. | |
2622 | ||
2623 | @defun read-quoted-char &optional prompt | |
2624 | @cindex octal character input | |
2625 | @cindex control characters, reading | |
2626 | @cindex nonprinting characters, reading | |
2627 | This function is like @code{read-char}, except that if the first | |
2628 | character read is an octal digit (0-7), it reads any number of octal | |
2629 | digits (but stopping if a non-octal digit is found), and returns the | |
2630 | character represented by that numeric character code. If the | |
2631 | character that terminates the sequence of octal digits is @key{RET}, | |
2632 | it is discarded. Any other terminating character is used as input | |
2633 | after this function returns. | |
2634 | ||
2635 | Quitting is suppressed when the first character is read, so that the | |
2636 | user can enter a @kbd{C-g}. @xref{Quitting}. | |
2637 | ||
2638 | If @var{prompt} is supplied, it specifies a string for prompting the | |
2639 | user. The prompt string is always displayed in the echo area, followed | |
2640 | by a single @samp{-}. | |
2641 | ||
2642 | In the following example, the user types in the octal number 177 (which | |
2643 | is 127 in decimal). | |
2644 | ||
2645 | @example | |
2646 | (read-quoted-char "What character") | |
2647 | ||
2648 | @group | |
2649 | ---------- Echo Area ---------- | |
2650 | What character @kbd{1 7 7}- | |
2651 | ---------- Echo Area ---------- | |
2652 | ||
2653 | @result{} 127 | |
2654 | @end group | |
2655 | @end example | |
2656 | @end defun | |
2657 | ||
2658 | @need 2000 | |
2659 | @node Event Input Misc | |
2660 | @subsection Miscellaneous Event Input Features | |
2661 | ||
2662 | This section describes how to ``peek ahead'' at events without using | |
2663 | them up, how to check for pending input, and how to discard pending | |
2664 | input. See also the function @code{read-passwd} (@pxref{Reading a | |
2665 | Password}). | |
2666 | ||
2667 | @defvar unread-command-events | |
2668 | @cindex next input | |
2669 | @cindex peeking at input | |
2670 | This variable holds a list of events waiting to be read as command | |
2671 | input. The events are used in the order they appear in the list, and | |
2672 | removed one by one as they are used. | |
2673 | ||
2674 | The variable is needed because in some cases a function reads an event | |
2675 | and then decides not to use it. Storing the event in this variable | |
2676 | causes it to be processed normally, by the command loop or by the | |
2677 | functions to read command input. | |
2678 | ||
2679 | @cindex prefix argument unreading | |
2680 | For example, the function that implements numeric prefix arguments reads | |
2681 | any number of digits. When it finds a non-digit event, it must unread | |
2682 | the event so that it can be read normally by the command loop. | |
2683 | Likewise, incremental search uses this feature to unread events with no | |
2684 | special meaning in a search, because these events should exit the search | |
2685 | and then execute normally. | |
2686 | ||
34106abe CY |
2687 | The reliable and easy way to extract events from a key sequence so as |
2688 | to put them in @code{unread-command-events} is to use | |
2689 | @code{listify-key-sequence} (see below). | |
b8d4c8d0 GM |
2690 | |
2691 | Normally you add events to the front of this list, so that the events | |
2692 | most recently unread will be reread first. | |
2693 | ||
2694 | Events read from this list are not normally added to the current | |
2695 | command's key sequence (as returned by e.g. @code{this-command-keys}), | |
2696 | as the events will already have been added once as they were read for | |
2697 | the first time. An element of the form @code{(@code{t} . @var{event})} | |
2698 | forces @var{event} to be added to the current command's key sequence. | |
2699 | @end defvar | |
2700 | ||
2701 | @defun listify-key-sequence key | |
2702 | This function converts the string or vector @var{key} to a list of | |
2703 | individual events, which you can put in @code{unread-command-events}. | |
2704 | @end defun | |
2705 | ||
eceeb5fc | 2706 | @ignore |
b8d4c8d0 GM |
2707 | @defvar unread-command-char |
2708 | This variable holds a character to be read as command input. | |
16152b76 | 2709 | A value of -1 means ``empty''. |
b8d4c8d0 GM |
2710 | |
2711 | This variable is mostly obsolete now that you can use | |
2712 | @code{unread-command-events} instead; it exists only to support programs | |
2713 | written for Emacs versions 18 and earlier. | |
2714 | @end defvar | |
eceeb5fc | 2715 | @end ignore |
b8d4c8d0 GM |
2716 | |
2717 | @defun input-pending-p | |
2718 | @cindex waiting for command key input | |
2719 | This function determines whether any command input is currently | |
2720 | available to be read. It returns immediately, with value @code{t} if | |
2721 | there is available input, @code{nil} otherwise. On rare occasions it | |
2722 | may return @code{t} when no input is available. | |
2723 | @end defun | |
2724 | ||
2725 | @defvar last-input-event | |
2726 | @defvarx last-input-char | |
2727 | This variable records the last terminal input event read, whether | |
2728 | as part of a command or explicitly by a Lisp program. | |
2729 | ||
2730 | In the example below, the Lisp program reads the character @kbd{1}, | |
2731 | @acronym{ASCII} code 49. It becomes the value of @code{last-input-event}, | |
2732 | while @kbd{C-e} (we assume @kbd{C-x C-e} command is used to evaluate | |
2733 | this expression) remains the value of @code{last-command-event}. | |
2734 | ||
2735 | @example | |
2736 | @group | |
2737 | (progn (print (read-char)) | |
2738 | (print last-command-event) | |
2739 | last-input-event) | |
2740 | @print{} 49 | |
2741 | @print{} 5 | |
2742 | @result{} 49 | |
2743 | @end group | |
2744 | @end example | |
2745 | ||
ab756fb3 | 2746 | The alias @code{last-input-char} is obsolete. |
b8d4c8d0 GM |
2747 | @end defvar |
2748 | ||
2749 | @defmac while-no-input body@dots{} | |
2750 | This construct runs the @var{body} forms and returns the value of the | |
2751 | last one---but only if no input arrives. If any input arrives during | |
2752 | the execution of the @var{body} forms, it aborts them (working much | |
2753 | like a quit). The @code{while-no-input} form returns @code{nil} if | |
2754 | aborted by a real quit, and returns @code{t} if aborted by arrival of | |
2755 | other input. | |
2756 | ||
2757 | If a part of @var{body} binds @code{inhibit-quit} to non-@code{nil}, | |
2758 | arrival of input during those parts won't cause an abort until | |
2759 | the end of that part. | |
2760 | ||
2761 | If you want to be able to distinguish all possible values computed | |
2762 | by @var{body} from both kinds of abort conditions, write the code | |
2763 | like this: | |
2764 | ||
2765 | @example | |
2766 | (while-no-input | |
2767 | (list | |
2768 | (progn . @var{body}))) | |
2769 | @end example | |
2770 | @end defmac | |
2771 | ||
2772 | @defun discard-input | |
2773 | @cindex flushing input | |
2774 | @cindex discarding input | |
2775 | @cindex keyboard macro, terminating | |
2776 | This function discards the contents of the terminal input buffer and | |
2777 | cancels any keyboard macro that might be in the process of definition. | |
2778 | It returns @code{nil}. | |
2779 | ||
2780 | In the following example, the user may type a number of characters right | |
2781 | after starting the evaluation of the form. After the @code{sleep-for} | |
2782 | finishes sleeping, @code{discard-input} discards any characters typed | |
2783 | during the sleep. | |
2784 | ||
2785 | @example | |
2786 | (progn (sleep-for 2) | |
2787 | (discard-input)) | |
2788 | @result{} nil | |
2789 | @end example | |
2790 | @end defun | |
2791 | ||
2792 | @node Special Events | |
2793 | @section Special Events | |
2794 | ||
2795 | @cindex special events | |
34106abe CY |
2796 | Certain @dfn{special events} are handled at a very low level---as soon |
2797 | as they are read. The @code{read-event} function processes these | |
2798 | events itself, and never returns them. Instead, it keeps waiting for | |
2799 | the first event that is not special and returns that one. | |
b8d4c8d0 | 2800 | |
34106abe CY |
2801 | Special events do not echo, they are never grouped into key |
2802 | sequences, and they never appear in the value of | |
b8d4c8d0 GM |
2803 | @code{last-command-event} or @code{(this-command-keys)}. They do not |
2804 | discard a numeric argument, they cannot be unread with | |
2805 | @code{unread-command-events}, they may not appear in a keyboard macro, | |
2806 | and they are not recorded in a keyboard macro while you are defining | |
2807 | one. | |
2808 | ||
34106abe CY |
2809 | Special events do, however, appear in @code{last-input-event} |
2810 | immediately after they are read, and this is the way for the event's | |
2811 | definition to find the actual event. | |
b8d4c8d0 | 2812 | |
34106abe | 2813 | The events types @code{iconify-frame}, @code{make-frame-visible}, |
b8d4c8d0 GM |
2814 | @code{delete-frame}, @code{drag-n-drop}, and user signals like |
2815 | @code{sigusr1} are normally handled in this way. The keymap which | |
34106abe CY |
2816 | defines how to handle special events---and which events are |
2817 | special---is in the variable @code{special-event-map} (@pxref{Active | |
2818 | Keymaps}). | |
b8d4c8d0 GM |
2819 | |
2820 | @node Waiting | |
2821 | @section Waiting for Elapsed Time or Input | |
2822 | @cindex waiting | |
2823 | ||
2824 | The wait functions are designed to wait for a certain amount of time | |
2825 | to pass or until there is input. For example, you may wish to pause in | |
2826 | the middle of a computation to allow the user time to view the display. | |
2827 | @code{sit-for} pauses and updates the screen, and returns immediately if | |
2828 | input comes in, while @code{sleep-for} pauses without updating the | |
2829 | screen. | |
2830 | ||
2831 | @defun sit-for seconds &optional nodisp | |
2832 | This function performs redisplay (provided there is no pending input | |
2833 | from the user), then waits @var{seconds} seconds, or until input is | |
2834 | available. The usual purpose of @code{sit-for} is to give the user | |
2835 | time to read text that you display. The value is @code{t} if | |
2836 | @code{sit-for} waited the full time with no input arriving | |
2837 | (@pxref{Event Input Misc}). Otherwise, the value is @code{nil}. | |
2838 | ||
2839 | The argument @var{seconds} need not be an integer. If it is a floating | |
2840 | point number, @code{sit-for} waits for a fractional number of seconds. | |
2841 | Some systems support only a whole number of seconds; on these systems, | |
2842 | @var{seconds} is rounded down. | |
2843 | ||
2844 | The expression @code{(sit-for 0)} is equivalent to @code{(redisplay)}, | |
2845 | i.e. it requests a redisplay, without any delay, if there is no pending input. | |
2846 | @xref{Forcing Redisplay}. | |
2847 | ||
2848 | If @var{nodisp} is non-@code{nil}, then @code{sit-for} does not | |
2849 | redisplay, but it still returns as soon as input is available (or when | |
2850 | the timeout elapses). | |
2851 | ||
2852 | In batch mode (@pxref{Batch Mode}), @code{sit-for} cannot be | |
2853 | interrupted, even by input from the standard input descriptor. It is | |
2854 | thus equivalent to @code{sleep-for}, which is described below. | |
2855 | ||
2856 | It is also possible to call @code{sit-for} with three arguments, | |
2857 | as @code{(sit-for @var{seconds} @var{millisec} @var{nodisp})}, | |
2858 | but that is considered obsolete. | |
2859 | @end defun | |
2860 | ||
2861 | @defun sleep-for seconds &optional millisec | |
2862 | This function simply pauses for @var{seconds} seconds without updating | |
2863 | the display. It pays no attention to available input. It returns | |
2864 | @code{nil}. | |
2865 | ||
2866 | The argument @var{seconds} need not be an integer. If it is a floating | |
2867 | point number, @code{sleep-for} waits for a fractional number of seconds. | |
2868 | Some systems support only a whole number of seconds; on these systems, | |
2869 | @var{seconds} is rounded down. | |
2870 | ||
2871 | The optional argument @var{millisec} specifies an additional waiting | |
2872 | period measured in milliseconds. This adds to the period specified by | |
2873 | @var{seconds}. If the system doesn't support waiting fractions of a | |
2874 | second, you get an error if you specify nonzero @var{millisec}. | |
2875 | ||
2876 | Use @code{sleep-for} when you wish to guarantee a delay. | |
2877 | @end defun | |
2878 | ||
2879 | @xref{Time of Day}, for functions to get the current time. | |
2880 | ||
2881 | @node Quitting | |
2882 | @section Quitting | |
2883 | @cindex @kbd{C-g} | |
2884 | @cindex quitting | |
2885 | @cindex interrupt Lisp functions | |
2886 | ||
2887 | Typing @kbd{C-g} while a Lisp function is running causes Emacs to | |
2888 | @dfn{quit} whatever it is doing. This means that control returns to the | |
2889 | innermost active command loop. | |
2890 | ||
2891 | Typing @kbd{C-g} while the command loop is waiting for keyboard input | |
2892 | does not cause a quit; it acts as an ordinary input character. In the | |
2893 | simplest case, you cannot tell the difference, because @kbd{C-g} | |
2894 | normally runs the command @code{keyboard-quit}, whose effect is to quit. | |
2895 | However, when @kbd{C-g} follows a prefix key, they combine to form an | |
2896 | undefined key. The effect is to cancel the prefix key as well as any | |
2897 | prefix argument. | |
2898 | ||
2899 | In the minibuffer, @kbd{C-g} has a different definition: it aborts out | |
2900 | of the minibuffer. This means, in effect, that it exits the minibuffer | |
2901 | and then quits. (Simply quitting would return to the command loop | |
2902 | @emph{within} the minibuffer.) The reason why @kbd{C-g} does not quit | |
2903 | directly when the command reader is reading input is so that its meaning | |
2904 | can be redefined in the minibuffer in this way. @kbd{C-g} following a | |
2905 | prefix key is not redefined in the minibuffer, and it has its normal | |
2906 | effect of canceling the prefix key and prefix argument. This too | |
2907 | would not be possible if @kbd{C-g} always quit directly. | |
2908 | ||
2909 | When @kbd{C-g} does directly quit, it does so by setting the variable | |
2910 | @code{quit-flag} to @code{t}. Emacs checks this variable at appropriate | |
2911 | times and quits if it is not @code{nil}. Setting @code{quit-flag} | |
2912 | non-@code{nil} in any way thus causes a quit. | |
2913 | ||
2914 | At the level of C code, quitting cannot happen just anywhere; only at the | |
2915 | special places that check @code{quit-flag}. The reason for this is | |
2916 | that quitting at other places might leave an inconsistency in Emacs's | |
2917 | internal state. Because quitting is delayed until a safe place, quitting | |
2918 | cannot make Emacs crash. | |
2919 | ||
2920 | Certain functions such as @code{read-key-sequence} or | |
2921 | @code{read-quoted-char} prevent quitting entirely even though they wait | |
2922 | for input. Instead of quitting, @kbd{C-g} serves as the requested | |
2923 | input. In the case of @code{read-key-sequence}, this serves to bring | |
2924 | about the special behavior of @kbd{C-g} in the command loop. In the | |
2925 | case of @code{read-quoted-char}, this is so that @kbd{C-q} can be used | |
2926 | to quote a @kbd{C-g}. | |
2927 | ||
2928 | @cindex preventing quitting | |
2929 | You can prevent quitting for a portion of a Lisp function by binding | |
2930 | the variable @code{inhibit-quit} to a non-@code{nil} value. Then, | |
2931 | although @kbd{C-g} still sets @code{quit-flag} to @code{t} as usual, the | |
2932 | usual result of this---a quit---is prevented. Eventually, | |
2933 | @code{inhibit-quit} will become @code{nil} again, such as when its | |
2934 | binding is unwound at the end of a @code{let} form. At that time, if | |
2935 | @code{quit-flag} is still non-@code{nil}, the requested quit happens | |
2936 | immediately. This behavior is ideal when you wish to make sure that | |
2937 | quitting does not happen within a ``critical section'' of the program. | |
2938 | ||
2939 | @cindex @code{read-quoted-char} quitting | |
2940 | In some functions (such as @code{read-quoted-char}), @kbd{C-g} is | |
2941 | handled in a special way that does not involve quitting. This is done | |
2942 | by reading the input with @code{inhibit-quit} bound to @code{t}, and | |
2943 | setting @code{quit-flag} to @code{nil} before @code{inhibit-quit} | |
2944 | becomes @code{nil} again. This excerpt from the definition of | |
2945 | @code{read-quoted-char} shows how this is done; it also shows that | |
2946 | normal quitting is permitted after the first character of input. | |
2947 | ||
2948 | @example | |
2949 | (defun read-quoted-char (&optional prompt) | |
2950 | "@dots{}@var{documentation}@dots{}" | |
2951 | (let ((message-log-max nil) done (first t) (code 0) char) | |
2952 | (while (not done) | |
2953 | (let ((inhibit-quit first) | |
2954 | @dots{}) | |
d24880de GM |
2955 | (and prompt (message "%s-" prompt)) |
2956 | (setq char (read-event)) | |
2957 | (if inhibit-quit (setq quit-flag nil))) | |
b8d4c8d0 GM |
2958 | @r{@dots{}set the variable @code{code}@dots{}}) |
2959 | code)) | |
2960 | @end example | |
2961 | ||
2962 | @defvar quit-flag | |
2963 | If this variable is non-@code{nil}, then Emacs quits immediately, unless | |
2964 | @code{inhibit-quit} is non-@code{nil}. Typing @kbd{C-g} ordinarily sets | |
2965 | @code{quit-flag} non-@code{nil}, regardless of @code{inhibit-quit}. | |
2966 | @end defvar | |
2967 | ||
2968 | @defvar inhibit-quit | |
2969 | This variable determines whether Emacs should quit when @code{quit-flag} | |
2970 | is set to a value other than @code{nil}. If @code{inhibit-quit} is | |
2971 | non-@code{nil}, then @code{quit-flag} has no special effect. | |
2972 | @end defvar | |
2973 | ||
2974 | @defmac with-local-quit body@dots{} | |
2975 | This macro executes @var{body} forms in sequence, but allows quitting, at | |
2976 | least locally, within @var{body} even if @code{inhibit-quit} was | |
2977 | non-@code{nil} outside this construct. It returns the value of the | |
2978 | last form in @var{body}, unless exited by quitting, in which case | |
2979 | it returns @code{nil}. | |
2980 | ||
2981 | If @code{inhibit-quit} is @code{nil} on entry to @code{with-local-quit}, | |
2982 | it only executes the @var{body}, and setting @code{quit-flag} causes | |
2983 | a normal quit. However, if @code{inhibit-quit} is non-@code{nil} so | |
2984 | that ordinary quitting is delayed, a non-@code{nil} @code{quit-flag} | |
2985 | triggers a special kind of local quit. This ends the execution of | |
2986 | @var{body} and exits the @code{with-local-quit} body with | |
2987 | @code{quit-flag} still non-@code{nil}, so that another (ordinary) quit | |
2988 | will happen as soon as that is allowed. If @code{quit-flag} is | |
2989 | already non-@code{nil} at the beginning of @var{body}, the local quit | |
2990 | happens immediately and the body doesn't execute at all. | |
2991 | ||
2992 | This macro is mainly useful in functions that can be called from | |
2993 | timers, process filters, process sentinels, @code{pre-command-hook}, | |
2994 | @code{post-command-hook}, and other places where @code{inhibit-quit} is | |
2995 | normally bound to @code{t}. | |
2996 | @end defmac | |
2997 | ||
2998 | @deffn Command keyboard-quit | |
2999 | This function signals the @code{quit} condition with @code{(signal 'quit | |
3000 | nil)}. This is the same thing that quitting does. (See @code{signal} | |
3001 | in @ref{Errors}.) | |
3002 | @end deffn | |
3003 | ||
3004 | You can specify a character other than @kbd{C-g} to use for quitting. | |
3005 | See the function @code{set-input-mode} in @ref{Terminal Input}. | |
3006 | ||
3007 | @node Prefix Command Arguments | |
3008 | @section Prefix Command Arguments | |
3009 | @cindex prefix argument | |
3010 | @cindex raw prefix argument | |
3011 | @cindex numeric prefix argument | |
3012 | ||
3013 | Most Emacs commands can use a @dfn{prefix argument}, a number | |
3014 | specified before the command itself. (Don't confuse prefix arguments | |
3015 | with prefix keys.) The prefix argument is at all times represented by a | |
3016 | value, which may be @code{nil}, meaning there is currently no prefix | |
3017 | argument. Each command may use the prefix argument or ignore it. | |
3018 | ||
3019 | There are two representations of the prefix argument: @dfn{raw} and | |
3020 | @dfn{numeric}. The editor command loop uses the raw representation | |
3021 | internally, and so do the Lisp variables that store the information, but | |
3022 | commands can request either representation. | |
3023 | ||
3024 | Here are the possible values of a raw prefix argument: | |
3025 | ||
3026 | @itemize @bullet | |
3027 | @item | |
3028 | @code{nil}, meaning there is no prefix argument. Its numeric value is | |
3029 | 1, but numerous commands make a distinction between @code{nil} and the | |
3030 | integer 1. | |
3031 | ||
3032 | @item | |
3033 | An integer, which stands for itself. | |
3034 | ||
3035 | @item | |
3036 | A list of one element, which is an integer. This form of prefix | |
07151e49 | 3037 | argument results from one or a succession of @kbd{C-u}s with no |
b8d4c8d0 GM |
3038 | digits. The numeric value is the integer in the list, but some |
3039 | commands make a distinction between such a list and an integer alone. | |
3040 | ||
3041 | @item | |
3042 | The symbol @code{-}. This indicates that @kbd{M--} or @kbd{C-u -} was | |
3043 | typed, without following digits. The equivalent numeric value is | |
3044 | @minus{}1, but some commands make a distinction between the integer | |
3045 | @minus{}1 and the symbol @code{-}. | |
3046 | @end itemize | |
3047 | ||
3048 | We illustrate these possibilities by calling the following function with | |
3049 | various prefixes: | |
3050 | ||
3051 | @example | |
3052 | @group | |
3053 | (defun display-prefix (arg) | |
3054 | "Display the value of the raw prefix arg." | |
3055 | (interactive "P") | |
3056 | (message "%s" arg)) | |
3057 | @end group | |
3058 | @end example | |
3059 | ||
3060 | @noindent | |
3061 | Here are the results of calling @code{display-prefix} with various | |
3062 | raw prefix arguments: | |
3063 | ||
3064 | @example | |
3065 | M-x display-prefix @print{} nil | |
3066 | ||
3067 | C-u M-x display-prefix @print{} (4) | |
3068 | ||
3069 | C-u C-u M-x display-prefix @print{} (16) | |
3070 | ||
3071 | C-u 3 M-x display-prefix @print{} 3 | |
3072 | ||
3073 | M-3 M-x display-prefix @print{} 3 ; @r{(Same as @code{C-u 3}.)} | |
3074 | ||
3075 | C-u - M-x display-prefix @print{} - | |
3076 | ||
3077 | M-- M-x display-prefix @print{} - ; @r{(Same as @code{C-u -}.)} | |
3078 | ||
3079 | C-u - 7 M-x display-prefix @print{} -7 | |
3080 | ||
3081 | M-- 7 M-x display-prefix @print{} -7 ; @r{(Same as @code{C-u -7}.)} | |
3082 | @end example | |
3083 | ||
3084 | Emacs uses two variables to store the prefix argument: | |
3085 | @code{prefix-arg} and @code{current-prefix-arg}. Commands such as | |
3086 | @code{universal-argument} that set up prefix arguments for other | |
3087 | commands store them in @code{prefix-arg}. In contrast, | |
3088 | @code{current-prefix-arg} conveys the prefix argument to the current | |
3089 | command, so setting it has no effect on the prefix arguments for future | |
3090 | commands. | |
3091 | ||
3092 | Normally, commands specify which representation to use for the prefix | |
3093 | argument, either numeric or raw, in the @code{interactive} specification. | |
3094 | (@xref{Using Interactive}.) Alternatively, functions may look at the | |
3095 | value of the prefix argument directly in the variable | |
3096 | @code{current-prefix-arg}, but this is less clean. | |
3097 | ||
3098 | @defun prefix-numeric-value arg | |
3099 | This function returns the numeric meaning of a valid raw prefix argument | |
3100 | value, @var{arg}. The argument may be a symbol, a number, or a list. | |
3101 | If it is @code{nil}, the value 1 is returned; if it is @code{-}, the | |
3102 | value @minus{}1 is returned; if it is a number, that number is returned; | |
3103 | if it is a list, the @sc{car} of that list (which should be a number) is | |
3104 | returned. | |
3105 | @end defun | |
3106 | ||
3107 | @defvar current-prefix-arg | |
3108 | This variable holds the raw prefix argument for the @emph{current} | |
3109 | command. Commands may examine it directly, but the usual method for | |
3110 | accessing it is with @code{(interactive "P")}. | |
3111 | @end defvar | |
3112 | ||
3113 | @defvar prefix-arg | |
3114 | The value of this variable is the raw prefix argument for the | |
3115 | @emph{next} editing command. Commands such as @code{universal-argument} | |
3116 | that specify prefix arguments for the following command work by setting | |
3117 | this variable. | |
3118 | @end defvar | |
3119 | ||
3120 | @defvar last-prefix-arg | |
3121 | The raw prefix argument value used by the previous command. | |
3122 | @end defvar | |
3123 | ||
3124 | The following commands exist to set up prefix arguments for the | |
3125 | following command. Do not call them for any other reason. | |
3126 | ||
3127 | @deffn Command universal-argument | |
3128 | This command reads input and specifies a prefix argument for the | |
3129 | following command. Don't call this command yourself unless you know | |
3130 | what you are doing. | |
3131 | @end deffn | |
3132 | ||
3133 | @deffn Command digit-argument arg | |
3134 | This command adds to the prefix argument for the following command. The | |
3135 | argument @var{arg} is the raw prefix argument as it was before this | |
3136 | command; it is used to compute the updated prefix argument. Don't call | |
3137 | this command yourself unless you know what you are doing. | |
3138 | @end deffn | |
3139 | ||
3140 | @deffn Command negative-argument arg | |
3141 | This command adds to the numeric argument for the next command. The | |
3142 | argument @var{arg} is the raw prefix argument as it was before this | |
3143 | command; its value is negated to form the new prefix argument. Don't | |
3144 | call this command yourself unless you know what you are doing. | |
3145 | @end deffn | |
3146 | ||
3147 | @node Recursive Editing | |
3148 | @section Recursive Editing | |
3149 | @cindex recursive command loop | |
3150 | @cindex recursive editing level | |
3151 | @cindex command loop, recursive | |
3152 | ||
3153 | The Emacs command loop is entered automatically when Emacs starts up. | |
3154 | This top-level invocation of the command loop never exits; it keeps | |
3155 | running as long as Emacs does. Lisp programs can also invoke the | |
3156 | command loop. Since this makes more than one activation of the command | |
3157 | loop, we call it @dfn{recursive editing}. A recursive editing level has | |
3158 | the effect of suspending whatever command invoked it and permitting the | |
3159 | user to do arbitrary editing before resuming that command. | |
3160 | ||
3161 | The commands available during recursive editing are the same ones | |
3162 | available in the top-level editing loop and defined in the keymaps. | |
3163 | Only a few special commands exit the recursive editing level; the others | |
3164 | return to the recursive editing level when they finish. (The special | |
3165 | commands for exiting are always available, but they do nothing when | |
3166 | recursive editing is not in progress.) | |
3167 | ||
3168 | All command loops, including recursive ones, set up all-purpose error | |
3169 | handlers so that an error in a command run from the command loop will | |
3170 | not exit the loop. | |
3171 | ||
3172 | @cindex minibuffer input | |
3173 | Minibuffer input is a special kind of recursive editing. It has a few | |
3174 | special wrinkles, such as enabling display of the minibuffer and the | |
3175 | minibuffer window, but fewer than you might suppose. Certain keys | |
3176 | behave differently in the minibuffer, but that is only because of the | |
3177 | minibuffer's local map; if you switch windows, you get the usual Emacs | |
3178 | commands. | |
3179 | ||
3180 | @cindex @code{throw} example | |
3181 | @kindex exit | |
3182 | @cindex exit recursive editing | |
3183 | @cindex aborting | |
3184 | To invoke a recursive editing level, call the function | |
3185 | @code{recursive-edit}. This function contains the command loop; it also | |
3186 | contains a call to @code{catch} with tag @code{exit}, which makes it | |
3187 | possible to exit the recursive editing level by throwing to @code{exit} | |
3188 | (@pxref{Catch and Throw}). If you throw a value other than @code{t}, | |
3189 | then @code{recursive-edit} returns normally to the function that called | |
3190 | it. The command @kbd{C-M-c} (@code{exit-recursive-edit}) does this. | |
3191 | Throwing a @code{t} value causes @code{recursive-edit} to quit, so that | |
3192 | control returns to the command loop one level up. This is called | |
3193 | @dfn{aborting}, and is done by @kbd{C-]} (@code{abort-recursive-edit}). | |
3194 | ||
3195 | Most applications should not use recursive editing, except as part of | |
3196 | using the minibuffer. Usually it is more convenient for the user if you | |
3197 | change the major mode of the current buffer temporarily to a special | |
3198 | major mode, which should have a command to go back to the previous mode. | |
3199 | (The @kbd{e} command in Rmail uses this technique.) Or, if you wish to | |
16152b76 | 3200 | give the user different text to edit ``recursively'', create and select |
b8d4c8d0 GM |
3201 | a new buffer in a special mode. In this mode, define a command to |
3202 | complete the processing and go back to the previous buffer. (The | |
3203 | @kbd{m} command in Rmail does this.) | |
3204 | ||
3205 | Recursive edits are useful in debugging. You can insert a call to | |
3206 | @code{debug} into a function definition as a sort of breakpoint, so that | |
3207 | you can look around when the function gets there. @code{debug} invokes | |
3208 | a recursive edit but also provides the other features of the debugger. | |
3209 | ||
3210 | Recursive editing levels are also used when you type @kbd{C-r} in | |
3211 | @code{query-replace} or use @kbd{C-x q} (@code{kbd-macro-query}). | |
3212 | ||
0b128ac4 | 3213 | @deffn Command recursive-edit |
b8d4c8d0 GM |
3214 | @cindex suspend evaluation |
3215 | This function invokes the editor command loop. It is called | |
3216 | automatically by the initialization of Emacs, to let the user begin | |
3217 | editing. When called from a Lisp program, it enters a recursive editing | |
3218 | level. | |
3219 | ||
3220 | If the current buffer is not the same as the selected window's buffer, | |
3221 | @code{recursive-edit} saves and restores the current buffer. Otherwise, | |
3222 | if you switch buffers, the buffer you switched to is current after | |
3223 | @code{recursive-edit} returns. | |
3224 | ||
3225 | In the following example, the function @code{simple-rec} first | |
3226 | advances point one word, then enters a recursive edit, printing out a | |
3227 | message in the echo area. The user can then do any editing desired, and | |
3228 | then type @kbd{C-M-c} to exit and continue executing @code{simple-rec}. | |
3229 | ||
3230 | @example | |
3231 | (defun simple-rec () | |
3232 | (forward-word 1) | |
3233 | (message "Recursive edit in progress") | |
3234 | (recursive-edit) | |
3235 | (forward-word 1)) | |
3236 | @result{} simple-rec | |
3237 | (simple-rec) | |
3238 | @result{} nil | |
3239 | @end example | |
0b128ac4 | 3240 | @end deffn |
b8d4c8d0 GM |
3241 | |
3242 | @deffn Command exit-recursive-edit | |
3243 | This function exits from the innermost recursive edit (including | |
3244 | minibuffer input). Its definition is effectively @code{(throw 'exit | |
3245 | nil)}. | |
3246 | @end deffn | |
3247 | ||
3248 | @deffn Command abort-recursive-edit | |
3249 | This function aborts the command that requested the innermost recursive | |
3250 | edit (including minibuffer input), by signaling @code{quit} | |
3251 | after exiting the recursive edit. Its definition is effectively | |
3252 | @code{(throw 'exit t)}. @xref{Quitting}. | |
3253 | @end deffn | |
3254 | ||
3255 | @deffn Command top-level | |
3256 | This function exits all recursive editing levels; it does not return a | |
3257 | value, as it jumps completely out of any computation directly back to | |
3258 | the main command loop. | |
3259 | @end deffn | |
3260 | ||
3261 | @defun recursion-depth | |
3262 | This function returns the current depth of recursive edits. When no | |
3263 | recursive edit is active, it returns 0. | |
3264 | @end defun | |
3265 | ||
3266 | @node Disabling Commands | |
3267 | @section Disabling Commands | |
3268 | @cindex disabled command | |
3269 | ||
3270 | @dfn{Disabling a command} marks the command as requiring user | |
3271 | confirmation before it can be executed. Disabling is used for commands | |
3272 | which might be confusing to beginning users, to prevent them from using | |
3273 | the commands by accident. | |
3274 | ||
3275 | @kindex disabled | |
3276 | The low-level mechanism for disabling a command is to put a | |
3277 | non-@code{nil} @code{disabled} property on the Lisp symbol for the | |
3278 | command. These properties are normally set up by the user's | |
3279 | init file (@pxref{Init File}) with Lisp expressions such as this: | |
3280 | ||
3281 | @example | |
3282 | (put 'upcase-region 'disabled t) | |
3283 | @end example | |
3284 | ||
3285 | @noindent | |
3286 | For a few commands, these properties are present by default (you can | |
3287 | remove them in your init file if you wish). | |
3288 | ||
3289 | If the value of the @code{disabled} property is a string, the message | |
3290 | saying the command is disabled includes that string. For example: | |
3291 | ||
3292 | @example | |
3293 | (put 'delete-region 'disabled | |
3294 | "Text deleted this way cannot be yanked back!\n") | |
3295 | @end example | |
3296 | ||
3297 | @xref{Disabling,,, emacs, The GNU Emacs Manual}, for the details on | |
3298 | what happens when a disabled command is invoked interactively. | |
3299 | Disabling a command has no effect on calling it as a function from Lisp | |
3300 | programs. | |
3301 | ||
3302 | @deffn Command enable-command command | |
3303 | Allow @var{command} (a symbol) to be executed without special | |
3304 | confirmation from now on, and alter the user's init file (@pxref{Init | |
3305 | File}) so that this will apply to future sessions. | |
3306 | @end deffn | |
3307 | ||
3308 | @deffn Command disable-command command | |
3309 | Require special confirmation to execute @var{command} from now on, and | |
3310 | alter the user's init file so that this will apply to future sessions. | |
3311 | @end deffn | |
3312 | ||
3313 | @defvar disabled-command-function | |
3314 | The value of this variable should be a function. When the user | |
3315 | invokes a disabled command interactively, this function is called | |
3316 | instead of the disabled command. It can use @code{this-command-keys} | |
3317 | to determine what the user typed to run the command, and thus find the | |
3318 | command itself. | |
3319 | ||
3320 | The value may also be @code{nil}. Then all commands work normally, | |
3321 | even disabled ones. | |
3322 | ||
3323 | By default, the value is a function that asks the user whether to | |
3324 | proceed. | |
3325 | @end defvar | |
3326 | ||
3327 | @node Command History | |
3328 | @section Command History | |
3329 | @cindex command history | |
3330 | @cindex complex command | |
3331 | @cindex history of commands | |
3332 | ||
3333 | The command loop keeps a history of the complex commands that have | |
3334 | been executed, to make it convenient to repeat these commands. A | |
3335 | @dfn{complex command} is one for which the interactive argument reading | |
3336 | uses the minibuffer. This includes any @kbd{M-x} command, any | |
3337 | @kbd{M-:} command, and any command whose @code{interactive} | |
3338 | specification reads an argument from the minibuffer. Explicit use of | |
3339 | the minibuffer during the execution of the command itself does not cause | |
3340 | the command to be considered complex. | |
3341 | ||
3342 | @defvar command-history | |
3343 | This variable's value is a list of recent complex commands, each | |
3344 | represented as a form to evaluate. It continues to accumulate all | |
3345 | complex commands for the duration of the editing session, but when it | |
3346 | reaches the maximum size (@pxref{Minibuffer History}), the oldest | |
3347 | elements are deleted as new ones are added. | |
3348 | ||
3349 | @example | |
3350 | @group | |
3351 | command-history | |
3352 | @result{} ((switch-to-buffer "chistory.texi") | |
3353 | (describe-key "^X^[") | |
3354 | (visit-tags-table "~/emacs/src/") | |
3355 | (find-tag "repeat-complex-command")) | |
3356 | @end group | |
3357 | @end example | |
3358 | @end defvar | |
3359 | ||
3360 | This history list is actually a special case of minibuffer history | |
3361 | (@pxref{Minibuffer History}), with one special twist: the elements are | |
3362 | expressions rather than strings. | |
3363 | ||
3364 | There are a number of commands devoted to the editing and recall of | |
3365 | previous commands. The commands @code{repeat-complex-command}, and | |
3366 | @code{list-command-history} are described in the user manual | |
3367 | (@pxref{Repetition,,, emacs, The GNU Emacs Manual}). Within the | |
3368 | minibuffer, the usual minibuffer history commands are available. | |
3369 | ||
3370 | @node Keyboard Macros | |
3371 | @section Keyboard Macros | |
3372 | @cindex keyboard macros | |
3373 | ||
3374 | A @dfn{keyboard macro} is a canned sequence of input events that can | |
3375 | be considered a command and made the definition of a key. The Lisp | |
3376 | representation of a keyboard macro is a string or vector containing the | |
3377 | events. Don't confuse keyboard macros with Lisp macros | |
3378 | (@pxref{Macros}). | |
3379 | ||
3380 | @defun execute-kbd-macro kbdmacro &optional count loopfunc | |
3381 | This function executes @var{kbdmacro} as a sequence of events. If | |
3382 | @var{kbdmacro} is a string or vector, then the events in it are executed | |
3383 | exactly as if they had been input by the user. The sequence is | |
3384 | @emph{not} expected to be a single key sequence; normally a keyboard | |
3385 | macro definition consists of several key sequences concatenated. | |
3386 | ||
3387 | If @var{kbdmacro} is a symbol, then its function definition is used in | |
3388 | place of @var{kbdmacro}. If that is another symbol, this process repeats. | |
3389 | Eventually the result should be a string or vector. If the result is | |
3390 | not a symbol, string, or vector, an error is signaled. | |
3391 | ||
3392 | The argument @var{count} is a repeat count; @var{kbdmacro} is executed that | |
3393 | many times. If @var{count} is omitted or @code{nil}, @var{kbdmacro} is | |
3394 | executed once. If it is 0, @var{kbdmacro} is executed over and over until it | |
3395 | encounters an error or a failing search. | |
3396 | ||
3397 | If @var{loopfunc} is non-@code{nil}, it is a function that is called, | |
3398 | without arguments, prior to each iteration of the macro. If | |
3399 | @var{loopfunc} returns @code{nil}, then this stops execution of the macro. | |
3400 | ||
3401 | @xref{Reading One Event}, for an example of using @code{execute-kbd-macro}. | |
3402 | @end defun | |
3403 | ||
3404 | @defvar executing-kbd-macro | |
3405 | This variable contains the string or vector that defines the keyboard | |
3406 | macro that is currently executing. It is @code{nil} if no macro is | |
3407 | currently executing. A command can test this variable so as to behave | |
3408 | differently when run from an executing macro. Do not set this variable | |
3409 | yourself. | |
3410 | @end defvar | |
3411 | ||
3412 | @defvar defining-kbd-macro | |
3413 | This variable is non-@code{nil} if and only if a keyboard macro is | |
3414 | being defined. A command can test this variable so as to behave | |
3415 | differently while a macro is being defined. The value is | |
3416 | @code{append} while appending to the definition of an existing macro. | |
3417 | The commands @code{start-kbd-macro}, @code{kmacro-start-macro} and | |
3418 | @code{end-kbd-macro} set this variable---do not set it yourself. | |
3419 | ||
3420 | The variable is always local to the current terminal and cannot be | |
3ec61d4e | 3421 | buffer-local. @xref{Multiple Terminals}. |
b8d4c8d0 GM |
3422 | @end defvar |
3423 | ||
3424 | @defvar last-kbd-macro | |
3425 | This variable is the definition of the most recently defined keyboard | |
3426 | macro. Its value is a string or vector, or @code{nil}. | |
3427 | ||
3428 | The variable is always local to the current terminal and cannot be | |
3ec61d4e | 3429 | buffer-local. @xref{Multiple Terminals}. |
b8d4c8d0 GM |
3430 | @end defvar |
3431 | ||
3432 | @defvar kbd-macro-termination-hook | |
2064cc6a GM |
3433 | This normal hook is run when a keyboard macro terminates, regardless |
3434 | of what caused it to terminate (reaching the macro end or an error | |
3435 | which ended the macro prematurely). | |
b8d4c8d0 | 3436 | @end defvar |