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