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1 | @c -*-texinfo-*- |
2 | @c This is part of the GNU Emacs Lisp Reference Manual. | |
2064cc6a | 3 | @c Copyright (C) 1990-1995, 1998-1999, 2001-2012 Free Software Foundation, Inc. |
b8d4c8d0 | 4 | @c See the file elisp.texi for copying conditions. |
ecc6530d | 5 | @node Command Loop |
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6 | @chapter Command Loop |
7 | @cindex editor command loop | |
8 | @cindex command loop | |
9 | ||
10 | When you run Emacs, it enters the @dfn{editor command loop} almost | |
11 | immediately. This loop reads key sequences, executes their definitions, | |
12 | and displays the results. In this chapter, we describe how these things | |
13 | are done, and the subroutines that allow Lisp programs to do them. | |
14 | ||
15 | @menu | |
16 | * Command Overview:: How the command loop reads commands. | |
17 | * Defining Commands:: Specifying how a function should read arguments. | |
18 | * Interactive Call:: Calling a command, so that it will read arguments. | |
77832c61 | 19 | * Distinguish Interactive:: Making a command distinguish interactive calls. |
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20 | * Command Loop Info:: Variables set by the command loop for you to examine. |
21 | * Adjusting Point:: Adjustment of point after a command. | |
d24880de | 22 | * Input Events:: What input looks like when you read it. |
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23 | * Reading Input:: How to read input events from the keyboard or mouse. |
24 | * Special Events:: Events processed immediately and individually. | |
25 | * Waiting:: Waiting for user input or elapsed time. | |
26 | * Quitting:: How @kbd{C-g} works. How to catch or defer quitting. | |
27 | * Prefix Command Arguments:: How the commands to set prefix args work. | |
28 | * Recursive Editing:: Entering a recursive edit, | |
29 | and why you usually shouldn't. | |
30 | * Disabling Commands:: How the command loop handles disabled commands. | |
31 | * Command History:: How the command history is set up, and how accessed. | |
32 | * Keyboard Macros:: How keyboard macros are implemented. | |
33 | @end menu | |
34 | ||
35 | @node Command Overview | |
36 | @section Command Loop Overview | |
37 | ||
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38 | The first thing the command loop must do is read a key sequence, |
39 | which is a sequence of input events that translates into a command. | |
40 | It does this by calling the function @code{read-key-sequence}. Lisp | |
41 | programs can also call this function (@pxref{Key Sequence Input}). | |
42 | They can also read input at a lower level with @code{read-key} or | |
43 | @code{read-event} (@pxref{Reading One Event}), or discard pending | |
44 | input with @code{discard-input} (@pxref{Event Input Misc}). | |
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45 | |
46 | The key sequence is translated into a command through the currently | |
47 | active keymaps. @xref{Key Lookup}, for information on how this is done. | |
48 | The result should be a keyboard macro or an interactively callable | |
49 | function. If the key is @kbd{M-x}, then it reads the name of another | |
50 | command, which it then calls. This is done by the command | |
51 | @code{execute-extended-command} (@pxref{Interactive Call}). | |
52 | ||
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53 | Prior to executing the command, Emacs runs @code{undo-boundary} to |
54 | create an undo boundary. @xref{Maintaining Undo}. | |
55 | ||
56 | To execute a command, Emacs first reads its arguments by calling | |
57 | @code{command-execute} (@pxref{Interactive Call}). For commands | |
58 | written in Lisp, the @code{interactive} specification says how to read | |
59 | the arguments. This may use the prefix argument (@pxref{Prefix | |
60 | Command Arguments}) or may read with prompting in the minibuffer | |
61 | (@pxref{Minibuffers}). For example, the command @code{find-file} has | |
62 | an @code{interactive} specification which says to read a file name | |
63 | using the minibuffer. The function body of @code{find-file} does not | |
64 | use the minibuffer, so if you call @code{find-file} as a function from | |
65 | Lisp code, you must supply the file name string as an ordinary Lisp | |
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66 | function argument. |
67 | ||
1df7defd | 68 | If the command is a keyboard macro (i.e., a string or vector), |
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69 | Emacs executes it using @code{execute-kbd-macro} (@pxref{Keyboard |
70 | Macros}). | |
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71 | |
72 | @defvar pre-command-hook | |
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73 | This normal hook is run by the editor command loop before it executes |
74 | each command. At that time, @code{this-command} contains the command | |
75 | that is about to run, and @code{last-command} describes the previous | |
76 | command. @xref{Command Loop Info}. | |
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77 | @end defvar |
78 | ||
79 | @defvar post-command-hook | |
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80 | This normal hook is run by the editor command loop after it executes |
81 | each command (including commands terminated prematurely by quitting or | |
82 | by errors). At that time, @code{this-command} refers to the command | |
83 | that just ran, and @code{last-command} refers to the command before | |
84 | that. | |
85 | ||
86 | This hook is also run when Emacs first enters the command loop (at | |
87 | which point @code{this-command} and @code{last-command} are both | |
88 | @code{nil}). | |
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89 | @end defvar |
90 | ||
91 | Quitting is suppressed while running @code{pre-command-hook} and | |
92 | @code{post-command-hook}. If an error happens while executing one of | |
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93 | these hooks, it does not terminate execution of the hook; instead |
94 | the error is silenced and the function in which the error occurred | |
95 | is removed from the hook. | |
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96 | |
97 | A request coming into the Emacs server (@pxref{Emacs Server,,, | |
98 | emacs, The GNU Emacs Manual}) runs these two hooks just as a keyboard | |
99 | command does. | |
100 | ||
101 | @node Defining Commands | |
102 | @section Defining Commands | |
103 | @cindex defining commands | |
104 | @cindex commands, defining | |
105 | @cindex functions, making them interactive | |
106 | @cindex interactive function | |
107 | ||
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108 | The special form @code{interactive} turns a Lisp function into a |
109 | command. The @code{interactive} form must be located at top-level in | |
110 | the function body (usually as the first form in the body), or in the | |
111 | @code{interactive-form} property of the function symbol. When the | |
112 | @code{interactive} form is located in the function body, it does | |
113 | nothing when actually executed. Its presence serves as a flag, which | |
114 | tells the Emacs command loop that the function can be called | |
115 | interactively. The argument of the @code{interactive} form controls | |
116 | the reading of arguments for an interactive call. | |
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117 | |
118 | @menu | |
119 | * Using Interactive:: General rules for @code{interactive}. | |
120 | * Interactive Codes:: The standard letter-codes for reading arguments | |
121 | in various ways. | |
122 | * Interactive Examples:: Examples of how to read interactive arguments. | |
123 | @end menu | |
124 | ||
125 | @node Using Interactive | |
126 | @subsection Using @code{interactive} | |
127 | @cindex arguments, interactive entry | |
128 | ||
129 | This section describes how to write the @code{interactive} form that | |
130 | makes a Lisp function an interactively-callable command, and how to | |
131 | examine a command's @code{interactive} form. | |
132 | ||
133 | @defspec interactive arg-descriptor | |
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134 | This special form declares that a function is a command, and that it |
135 | may therefore be called interactively (via @kbd{M-x} or by entering a | |
136 | key sequence bound to it). The argument @var{arg-descriptor} declares | |
137 | how to compute the arguments to the command when the command is called | |
138 | interactively. | |
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139 | |
140 | A command may be called from Lisp programs like any other function, but | |
141 | then the caller supplies the arguments and @var{arg-descriptor} has no | |
142 | effect. | |
143 | ||
f02f19bd | 144 | @cindex @code{interactive-form}, symbol property |
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145 | The @code{interactive} form must be located at top-level in the |
146 | function body, or in the function symbol's @code{interactive-form} | |
f02f19bd | 147 | property (@pxref{Symbol Properties}). It has its effect because the |
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148 | command loop looks for it before calling the function |
149 | (@pxref{Interactive Call}). Once the function is called, all its body | |
150 | forms are executed; at this time, if the @code{interactive} form | |
151 | occurs within the body, the form simply returns @code{nil} without | |
152 | even evaluating its argument. | |
153 | ||
154 | By convention, you should put the @code{interactive} form in the | |
155 | function body, as the first top-level form. If there is an | |
156 | @code{interactive} form in both the @code{interactive-form} symbol | |
157 | property and the function body, the former takes precedence. The | |
158 | @code{interactive-form} symbol property can be used to add an | |
159 | interactive form to an existing function, or change how its arguments | |
160 | are processed interactively, without redefining the function. | |
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161 | @end defspec |
162 | ||
163 | There are three possibilities for the argument @var{arg-descriptor}: | |
164 | ||
165 | @itemize @bullet | |
166 | @item | |
167 | It may be omitted or @code{nil}; then the command is called with no | |
168 | arguments. This leads quickly to an error if the command requires one | |
169 | or more arguments. | |
170 | ||
171 | @item | |
9fa6d455 | 172 | It may be a string; its contents are a sequence of elements separated |
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173 | by newlines, one for each argument@footnote{Some elements actually |
174 | supply two arguments.}. Each element consists of a code character | |
5cba88a2 | 175 | (@pxref{Interactive Codes}) optionally followed by a prompt (which |
9fa6d455 | 176 | some code characters use and some ignore). Here is an example: |
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177 | |
178 | @smallexample | |
9fa6d455 | 179 | (interactive "P\nbFrobnicate buffer: ") |
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180 | @end smallexample |
181 | ||
182 | @noindent | |
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183 | The code letter @samp{P} sets the command's first argument to the raw |
184 | command prefix (@pxref{Prefix Command Arguments}). @samp{bFrobnicate | |
185 | buffer: } prompts the user with @samp{Frobnicate buffer: } to enter | |
186 | the name of an existing buffer, which becomes the second and final | |
187 | argument. | |
b8d4c8d0 | 188 | |
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189 | The prompt string can use @samp{%} to include previous argument values |
190 | (starting with the first argument) in the prompt. This is done using | |
191 | @code{format} (@pxref{Formatting Strings}). For example, here is how | |
192 | you could read the name of an existing buffer followed by a new name to | |
193 | give to that buffer: | |
194 | ||
195 | @smallexample | |
196 | @group | |
197 | (interactive "bBuffer to rename: \nsRename buffer %s to: ") | |
198 | @end group | |
199 | @end smallexample | |
200 | ||
201 | @cindex @samp{*} in @code{interactive} | |
202 | @cindex read-only buffers in interactive | |
ee6e73b8 | 203 | If @samp{*} appears at the beginning of the string, then an error is |
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204 | signaled if the buffer is read-only. |
205 | ||
206 | @cindex @samp{@@} in @code{interactive} | |
ee6e73b8 | 207 | If @samp{@@} appears at the beginning of the string, and if the key |
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208 | sequence used to invoke the command includes any mouse events, then |
209 | the window associated with the first of those events is selected | |
210 | before the command is run. | |
211 | ||
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212 | @cindex @samp{^} in @code{interactive} |
213 | @cindex shift-selection, and @code{interactive} spec | |
214 | If @samp{^} appears at the beginning of the string, and if the command | |
215 | was invoked through @dfn{shift-translation}, set the mark and activate | |
216 | the region temporarily, or extend an already active region, before the | |
217 | command is run. If the command was invoked without shift-translation, | |
218 | and the region is temporarily active, deactivate the region before the | |
219 | command is run. Shift-translation is controlled on the user level by | |
220 | @code{shift-select-mode}; see @ref{Shift Selection,,, emacs, The GNU | |
221 | Emacs Manual}. | |
222 | ||
223 | You can use @samp{*}, @samp{@@}, and @code{^} together; the order does | |
224 | not matter. Actual reading of arguments is controlled by the rest of | |
225 | the prompt string (starting with the first character that is not | |
226 | @samp{*}, @samp{@@}, or @samp{^}). | |
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227 | |
228 | @item | |
229 | It may be a Lisp expression that is not a string; then it should be a | |
230 | form that is evaluated to get a list of arguments to pass to the | |
231 | command. Usually this form will call various functions to read input | |
232 | from the user, most often through the minibuffer (@pxref{Minibuffers}) | |
233 | or directly from the keyboard (@pxref{Reading Input}). | |
234 | ||
235 | Providing point or the mark as an argument value is also common, but | |
236 | if you do this @emph{and} read input (whether using the minibuffer or | |
237 | not), be sure to get the integer values of point or the mark after | |
238 | reading. The current buffer may be receiving subprocess output; if | |
239 | subprocess output arrives while the command is waiting for input, it | |
240 | could relocate point and the mark. | |
241 | ||
242 | Here's an example of what @emph{not} to do: | |
243 | ||
244 | @smallexample | |
245 | (interactive | |
246 | (list (region-beginning) (region-end) | |
247 | (read-string "Foo: " nil 'my-history))) | |
248 | @end smallexample | |
249 | ||
250 | @noindent | |
251 | Here's how to avoid the problem, by examining point and the mark after | |
252 | reading the keyboard input: | |
253 | ||
254 | @smallexample | |
255 | (interactive | |
256 | (let ((string (read-string "Foo: " nil 'my-history))) | |
257 | (list (region-beginning) (region-end) string))) | |
258 | @end smallexample | |
259 | ||
260 | @strong{Warning:} the argument values should not include any data | |
261 | types that can't be printed and then read. Some facilities save | |
262 | @code{command-history} in a file to be read in the subsequent | |
263 | sessions; if a command's arguments contain a data type that prints | |
264 | using @samp{#<@dots{}>} syntax, those facilities won't work. | |
265 | ||
266 | There are, however, a few exceptions: it is ok to use a limited set of | |
267 | expressions such as @code{(point)}, @code{(mark)}, | |
268 | @code{(region-beginning)}, and @code{(region-end)}, because Emacs | |
269 | recognizes them specially and puts the expression (rather than its | |
270 | value) into the command history. To see whether the expression you | |
271 | wrote is one of these exceptions, run the command, then examine | |
272 | @code{(car command-history)}. | |
273 | @end itemize | |
274 | ||
275 | @cindex examining the @code{interactive} form | |
276 | @defun interactive-form function | |
277 | This function returns the @code{interactive} form of @var{function}. | |
278 | If @var{function} is an interactively callable function | |
279 | (@pxref{Interactive Call}), the value is the command's | |
280 | @code{interactive} form @code{(interactive @var{spec})}, which | |
281 | specifies how to compute its arguments. Otherwise, the value is | |
282 | @code{nil}. If @var{function} is a symbol, its function definition is | |
283 | used. | |
284 | @end defun | |
285 | ||
286 | @node Interactive Codes | |
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287 | @subsection Code Characters for @code{interactive} |
288 | @cindex interactive code description | |
289 | @cindex description for interactive codes | |
290 | @cindex codes, interactive, description of | |
291 | @cindex characters for interactive codes | |
292 | ||
293 | The code character descriptions below contain a number of key words, | |
294 | defined here as follows: | |
295 | ||
296 | @table @b | |
297 | @item Completion | |
298 | @cindex interactive completion | |
299 | Provide completion. @key{TAB}, @key{SPC}, and @key{RET} perform name | |
300 | completion because the argument is read using @code{completing-read} | |
301 | (@pxref{Completion}). @kbd{?} displays a list of possible completions. | |
302 | ||
303 | @item Existing | |
304 | Require the name of an existing object. An invalid name is not | |
305 | accepted; the commands to exit the minibuffer do not exit if the current | |
306 | input is not valid. | |
307 | ||
308 | @item Default | |
309 | @cindex default argument string | |
310 | A default value of some sort is used if the user enters no text in the | |
311 | minibuffer. The default depends on the code character. | |
312 | ||
313 | @item No I/O | |
314 | This code letter computes an argument without reading any input. | |
315 | Therefore, it does not use a prompt string, and any prompt string you | |
316 | supply is ignored. | |
317 | ||
318 | Even though the code letter doesn't use a prompt string, you must follow | |
319 | it with a newline if it is not the last code character in the string. | |
320 | ||
321 | @item Prompt | |
322 | A prompt immediately follows the code character. The prompt ends either | |
323 | with the end of the string or with a newline. | |
324 | ||
325 | @item Special | |
326 | This code character is meaningful only at the beginning of the | |
327 | interactive string, and it does not look for a prompt or a newline. | |
328 | It is a single, isolated character. | |
329 | @end table | |
330 | ||
331 | @cindex reading interactive arguments | |
332 | Here are the code character descriptions for use with @code{interactive}: | |
333 | ||
334 | @table @samp | |
335 | @item * | |
336 | Signal an error if the current buffer is read-only. Special. | |
337 | ||
338 | @item @@ | |
339 | Select the window mentioned in the first mouse event in the key | |
340 | sequence that invoked this command. Special. | |
341 | ||
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342 | @item ^ |
343 | If the command was invoked through shift-translation, set the mark and | |
344 | activate the region temporarily, or extend an already active region, | |
345 | before the command is run. If the command was invoked without | |
346 | shift-translation, and the region is temporarily active, deactivate | |
347 | the region before the command is run. Special. | |
348 | ||
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349 | @item a |
350 | A function name (i.e., a symbol satisfying @code{fboundp}). Existing, | |
351 | Completion, Prompt. | |
352 | ||
353 | @item b | |
354 | The name of an existing buffer. By default, uses the name of the | |
355 | current buffer (@pxref{Buffers}). Existing, Completion, Default, | |
356 | Prompt. | |
357 | ||
358 | @item B | |
359 | A buffer name. The buffer need not exist. By default, uses the name of | |
360 | a recently used buffer other than the current buffer. Completion, | |
361 | Default, Prompt. | |
362 | ||
363 | @item c | |
364 | A character. The cursor does not move into the echo area. Prompt. | |
365 | ||
366 | @item C | |
367 | A command name (i.e., a symbol satisfying @code{commandp}). Existing, | |
368 | Completion, Prompt. | |
369 | ||
370 | @item d | |
371 | @cindex position argument | |
372 | The position of point, as an integer (@pxref{Point}). No I/O. | |
373 | ||
374 | @item D | |
375 | A directory name. The default is the current default directory of the | |
376 | current buffer, @code{default-directory} (@pxref{File Name Expansion}). | |
377 | Existing, Completion, Default, Prompt. | |
378 | ||
379 | @item e | |
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380 | The first or next non-keyboard event in the key sequence that invoked |
381 | the command. More precisely, @samp{e} gets events that are lists, so | |
382 | you can look at the data in the lists. @xref{Input Events}. No I/O. | |
383 | ||
384 | You use @samp{e} for mouse events and for special system events | |
385 | (@pxref{Misc Events}). The event list that the command receives | |
386 | depends on the event. @xref{Input Events}, which describes the forms | |
387 | of the list for each event in the corresponding subsections. | |
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388 | |
389 | You can use @samp{e} more than once in a single command's interactive | |
390 | specification. If the key sequence that invoked the command has | |
391 | @var{n} events that are lists, the @var{n}th @samp{e} provides the | |
392 | @var{n}th such event. Events that are not lists, such as function keys | |
393 | and @acronym{ASCII} characters, do not count where @samp{e} is concerned. | |
394 | ||
395 | @item f | |
396 | A file name of an existing file (@pxref{File Names}). The default | |
397 | directory is @code{default-directory}. Existing, Completion, Default, | |
398 | Prompt. | |
399 | ||
400 | @item F | |
401 | A file name. The file need not exist. Completion, Default, Prompt. | |
402 | ||
403 | @item G | |
404 | A file name. The file need not exist. If the user enters just a | |
405 | directory name, then the value is just that directory name, with no | |
406 | file name within the directory added. Completion, Default, Prompt. | |
407 | ||
408 | @item i | |
409 | An irrelevant argument. This code always supplies @code{nil} as | |
410 | the argument's value. No I/O. | |
411 | ||
412 | @item k | |
413 | A key sequence (@pxref{Key Sequences}). This keeps reading events | |
414 | until a command (or undefined command) is found in the current key | |
415 | maps. The key sequence argument is represented as a string or vector. | |
416 | The cursor does not move into the echo area. Prompt. | |
417 | ||
418 | If @samp{k} reads a key sequence that ends with a down-event, it also | |
419 | reads and discards the following up-event. You can get access to that | |
420 | up-event with the @samp{U} code character. | |
421 | ||
422 | This kind of input is used by commands such as @code{describe-key} and | |
423 | @code{global-set-key}. | |
424 | ||
425 | @item K | |
426 | A key sequence, whose definition you intend to change. This works like | |
427 | @samp{k}, except that it suppresses, for the last input event in the key | |
428 | sequence, the conversions that are normally used (when necessary) to | |
429 | convert an undefined key into a defined one. | |
430 | ||
431 | @item m | |
432 | @cindex marker argument | |
433 | The position of the mark, as an integer. No I/O. | |
434 | ||
435 | @item M | |
436 | Arbitrary text, read in the minibuffer using the current buffer's input | |
437 | method, and returned as a string (@pxref{Input Methods,,, emacs, The GNU | |
438 | Emacs Manual}). Prompt. | |
439 | ||
440 | @item n | |
441 | A number, read with the minibuffer. If the input is not a number, the | |
442 | user has to try again. @samp{n} never uses the prefix argument. | |
443 | Prompt. | |
444 | ||
445 | @item N | |
446 | The numeric prefix argument; but if there is no prefix argument, read | |
447 | a number as with @kbd{n}. The value is always a number. @xref{Prefix | |
448 | Command Arguments}. Prompt. | |
449 | ||
450 | @item p | |
451 | @cindex numeric prefix argument usage | |
452 | The numeric prefix argument. (Note that this @samp{p} is lower case.) | |
453 | No I/O. | |
454 | ||
455 | @item P | |
456 | @cindex raw prefix argument usage | |
457 | The raw prefix argument. (Note that this @samp{P} is upper case.) No | |
458 | I/O. | |
459 | ||
460 | @item r | |
461 | @cindex region argument | |
462 | Point and the mark, as two numeric arguments, smallest first. This is | |
463 | the only code letter that specifies two successive arguments rather than | |
464 | one. No I/O. | |
465 | ||
466 | @item s | |
467 | Arbitrary text, read in the minibuffer and returned as a string | |
468 | (@pxref{Text from Minibuffer}). Terminate the input with either | |
469 | @kbd{C-j} or @key{RET}. (@kbd{C-q} may be used to include either of | |
470 | these characters in the input.) Prompt. | |
471 | ||
472 | @item S | |
473 | An interned symbol whose name is read in the minibuffer. Any whitespace | |
474 | character terminates the input. (Use @kbd{C-q} to include whitespace in | |
475 | the string.) Other characters that normally terminate a symbol (e.g., | |
476 | parentheses and brackets) do not do so here. Prompt. | |
477 | ||
478 | @item U | |
479 | A key sequence or @code{nil}. Can be used after a @samp{k} or | |
480 | @samp{K} argument to get the up-event that was discarded (if any) | |
481 | after @samp{k} or @samp{K} read a down-event. If no up-event has been | |
482 | discarded, @samp{U} provides @code{nil} as the argument. No I/O. | |
483 | ||
484 | @item v | |
485 | A variable declared to be a user option (i.e., satisfying the | |
b4d3bc10 | 486 | predicate @code{custom-variable-p}). This reads the variable using |
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487 | @code{read-variable}. @xref{Definition of read-variable}. Existing, |
488 | Completion, Prompt. | |
489 | ||
490 | @item x | |
491 | A Lisp object, specified with its read syntax, terminated with a | |
492 | @kbd{C-j} or @key{RET}. The object is not evaluated. @xref{Object from | |
493 | Minibuffer}. Prompt. | |
494 | ||
495 | @item X | |
496 | @cindex evaluated expression argument | |
497 | A Lisp form's value. @samp{X} reads as @samp{x} does, then evaluates | |
498 | the form so that its value becomes the argument for the command. | |
499 | Prompt. | |
500 | ||
501 | @item z | |
502 | A coding system name (a symbol). If the user enters null input, the | |
503 | argument value is @code{nil}. @xref{Coding Systems}. Completion, | |
504 | Existing, Prompt. | |
505 | ||
506 | @item Z | |
507 | A coding system name (a symbol)---but only if this command has a prefix | |
508 | argument. With no prefix argument, @samp{Z} provides @code{nil} as the | |
509 | argument value. Completion, Existing, Prompt. | |
510 | @end table | |
511 | ||
512 | @node Interactive Examples | |
b8d4c8d0 GM |
513 | @subsection Examples of Using @code{interactive} |
514 | @cindex examples of using @code{interactive} | |
515 | @cindex @code{interactive}, examples of using | |
516 | ||
517 | Here are some examples of @code{interactive}: | |
518 | ||
519 | @example | |
520 | @group | |
521 | (defun foo1 () ; @r{@code{foo1} takes no arguments,} | |
522 | (interactive) ; @r{just moves forward two words.} | |
523 | (forward-word 2)) | |
524 | @result{} foo1 | |
525 | @end group | |
526 | ||
527 | @group | |
528 | (defun foo2 (n) ; @r{@code{foo2} takes one argument,} | |
ee6e73b8 EZ |
529 | (interactive "^p") ; @r{which is the numeric prefix.} |
530 | ; @r{under @code{shift-select-mode},} | |
531 | ; @r{will activate or extend region.} | |
b8d4c8d0 GM |
532 | (forward-word (* 2 n))) |
533 | @result{} foo2 | |
534 | @end group | |
535 | ||
536 | @group | |
537 | (defun foo3 (n) ; @r{@code{foo3} takes one argument,} | |
538 | (interactive "nCount:") ; @r{which is read with the Minibuffer.} | |
539 | (forward-word (* 2 n))) | |
540 | @result{} foo3 | |
541 | @end group | |
542 | ||
543 | @group | |
544 | (defun three-b (b1 b2 b3) | |
545 | "Select three existing buffers. | |
546 | Put them into three windows, selecting the last one." | |
547 | @end group | |
548 | (interactive "bBuffer1:\nbBuffer2:\nbBuffer3:") | |
549 | (delete-other-windows) | |
550 | (split-window (selected-window) 8) | |
551 | (switch-to-buffer b1) | |
552 | (other-window 1) | |
553 | (split-window (selected-window) 8) | |
554 | (switch-to-buffer b2) | |
555 | (other-window 1) | |
556 | (switch-to-buffer b3)) | |
557 | @result{} three-b | |
558 | @group | |
559 | (three-b "*scratch*" "declarations.texi" "*mail*") | |
560 | @result{} nil | |
561 | @end group | |
562 | @end example | |
563 | ||
564 | @node Interactive Call | |
565 | @section Interactive Call | |
566 | @cindex interactive call | |
567 | ||
8421dd35 CY |
568 | After the command loop has translated a key sequence into a command, |
569 | it invokes that command using the function @code{command-execute}. If | |
570 | the command is a function, @code{command-execute} calls | |
b8d4c8d0 GM |
571 | @code{call-interactively}, which reads the arguments and calls the |
572 | command. You can also call these functions yourself. | |
573 | ||
34106abe CY |
574 | Note that the term ``command'', in this context, refers to an |
575 | interactively callable function (or function-like object), or a | |
576 | keyboard macro. It does not refer to the key sequence used to invoke | |
577 | a command (@pxref{Keymaps}). | |
b8d4c8d0 | 578 | |
34106abe CY |
579 | @defun commandp object &optional for-call-interactively |
580 | This function returns @code{t} if @var{object} is a command. | |
581 | Otherwise, it returns @code{nil}. | |
582 | ||
583 | Commands include strings and vectors (which are treated as keyboard | |
584 | macros), lambda expressions that contain a top-level | |
585 | @code{interactive} form (@pxref{Using Interactive}), byte-code | |
586 | function objects made from such lambda expressions, autoload objects | |
587 | that are declared as interactive (non-@code{nil} fourth argument to | |
588 | @code{autoload}), and some primitive functions. Also, a symbol is | |
589 | considered a command if it has a non-@code{nil} | |
8421dd35 | 590 | @code{interactive-form} property, or if its function definition |
34106abe | 591 | satisfies @code{commandp}. |
b8d4c8d0 GM |
592 | |
593 | If @var{for-call-interactively} is non-@code{nil}, then | |
594 | @code{commandp} returns @code{t} only for objects that | |
595 | @code{call-interactively} could call---thus, not for keyboard macros. | |
596 | ||
597 | See @code{documentation} in @ref{Accessing Documentation}, for a | |
598 | realistic example of using @code{commandp}. | |
599 | @end defun | |
600 | ||
601 | @defun call-interactively command &optional record-flag keys | |
602 | This function calls the interactively callable function @var{command}, | |
54e10184 LMI |
603 | providing arguments according to its interactive calling specifications. |
604 | It returns whatever @var{command} returns. | |
605 | ||
606 | If, for instance, you have a function with the following signature: | |
607 | ||
608 | @example | |
609 | (defun foo (begin end) | |
610 | (interactive "r") | |
611 | ...) | |
612 | @end example | |
613 | ||
614 | then saying | |
615 | ||
616 | @example | |
617 | (call-interactively 'foo) | |
618 | @end example | |
619 | ||
620 | will call @code{foo} with the region (@code{point} and @code{mark}) as | |
621 | the arguments. | |
622 | ||
623 | An error is signaled if @var{command} is not a function or if it | |
624 | cannot be called interactively (i.e., is not a command). Note that | |
625 | keyboard macros (strings and vectors) are not accepted, even though | |
626 | they are considered commands, because they are not functions. If | |
627 | @var{command} is a symbol, then @code{call-interactively} uses its | |
628 | function definition. | |
b8d4c8d0 GM |
629 | |
630 | @cindex record command history | |
631 | If @var{record-flag} is non-@code{nil}, then this command and its | |
632 | arguments are unconditionally added to the list @code{command-history}. | |
633 | Otherwise, the command is added only if it uses the minibuffer to read | |
634 | an argument. @xref{Command History}. | |
635 | ||
636 | The argument @var{keys}, if given, should be a vector which specifies | |
637 | the sequence of events to supply if the command inquires which events | |
638 | were used to invoke it. If @var{keys} is omitted or @code{nil}, the | |
639 | default is the return value of @code{this-command-keys-vector}. | |
640 | @xref{Definition of this-command-keys-vector}. | |
641 | @end defun | |
642 | ||
643 | @defun command-execute command &optional record-flag keys special | |
644 | @cindex keyboard macro execution | |
645 | This function executes @var{command}. The argument @var{command} must | |
646 | satisfy the @code{commandp} predicate; i.e., it must be an interactively | |
647 | callable function or a keyboard macro. | |
648 | ||
649 | A string or vector as @var{command} is executed with | |
650 | @code{execute-kbd-macro}. A function is passed to | |
34106abe CY |
651 | @code{call-interactively} (see above), along with the |
652 | @var{record-flag} and @var{keys} arguments. | |
b8d4c8d0 | 653 | |
34106abe CY |
654 | If @var{command} is a symbol, its function definition is used in its |
655 | place. A symbol with an @code{autoload} definition counts as a | |
656 | command if it was declared to stand for an interactively callable | |
657 | function. Such a definition is handled by loading the specified | |
658 | library and then rechecking the definition of the symbol. | |
b8d4c8d0 GM |
659 | |
660 | The argument @var{special}, if given, means to ignore the prefix | |
661 | argument and not clear it. This is used for executing special events | |
662 | (@pxref{Special Events}). | |
663 | @end defun | |
664 | ||
665 | @deffn Command execute-extended-command prefix-argument | |
666 | @cindex read command name | |
667 | This function reads a command name from the minibuffer using | |
668 | @code{completing-read} (@pxref{Completion}). Then it uses | |
669 | @code{command-execute} to call the specified command. Whatever that | |
670 | command returns becomes the value of @code{execute-extended-command}. | |
671 | ||
672 | @cindex execute with prefix argument | |
673 | If the command asks for a prefix argument, it receives the value | |
674 | @var{prefix-argument}. If @code{execute-extended-command} is called | |
675 | interactively, the current raw prefix argument is used for | |
676 | @var{prefix-argument}, and thus passed on to whatever command is run. | |
677 | ||
678 | @c !!! Should this be @kindex? | |
679 | @cindex @kbd{M-x} | |
680 | @code{execute-extended-command} is the normal definition of @kbd{M-x}, | |
681 | so it uses the string @w{@samp{M-x }} as a prompt. (It would be better | |
682 | to take the prompt from the events used to invoke | |
683 | @code{execute-extended-command}, but that is painful to implement.) A | |
684 | description of the value of the prefix argument, if any, also becomes | |
685 | part of the prompt. | |
686 | ||
687 | @example | |
688 | @group | |
689 | (execute-extended-command 3) | |
690 | ---------- Buffer: Minibuffer ---------- | |
691 | 3 M-x forward-word RET | |
692 | ---------- Buffer: Minibuffer ---------- | |
693 | @result{} t | |
694 | @end group | |
695 | @end example | |
696 | @end deffn | |
697 | ||
77832c61 RS |
698 | @node Distinguish Interactive |
699 | @section Distinguish Interactive Calls | |
700 | ||
701 | Sometimes a command should display additional visual feedback (such | |
702 | as an informative message in the echo area) for interactive calls | |
703 | only. There are three ways to do this. The recommended way to test | |
704 | whether the function was called using @code{call-interactively} is to | |
705 | give it an optional argument @code{print-message} and use the | |
706 | @code{interactive} spec to make it non-@code{nil} in interactive | |
707 | calls. Here's an example: | |
708 | ||
709 | @example | |
710 | (defun foo (&optional print-message) | |
711 | (interactive "p") | |
712 | (when print-message | |
713 | (message "foo"))) | |
714 | @end example | |
715 | ||
716 | @noindent | |
717 | We use @code{"p"} because the numeric prefix argument is never | |
718 | @code{nil}. Defined in this way, the function does display the | |
719 | message when called from a keyboard macro. | |
720 | ||
721 | The above method with the additional argument is usually best, | |
16152b76 | 722 | because it allows callers to say ``treat this call as interactive''. |
89a9e058 | 723 | But you can also do the job by testing @code{called-interactively-p}. |
77832c61 | 724 | |
eb5ed549 | 725 | @defun called-interactively-p kind |
77832c61 RS |
726 | This function returns @code{t} when the calling function was called |
727 | using @code{call-interactively}. | |
b8d4c8d0 | 728 | |
eb5ed549 CY |
729 | The argument @var{kind} should be either the symbol @code{interactive} |
730 | or the symbol @code{any}. If it is @code{interactive}, then | |
731 | @code{called-interactively-p} returns @code{t} only if the call was | |
732 | made directly by the user---e.g., if the user typed a key sequence | |
733 | bound to the calling function, but @emph{not} if the user ran a | |
734 | keyboard macro that called the function (@pxref{Keyboard Macros}). If | |
735 | @var{kind} is @code{any}, @code{called-interactively-p} returns | |
736 | @code{t} for any kind of interactive call, including keyboard macros. | |
737 | ||
738 | If in doubt, use @code{any}; the only known proper use of | |
739 | @code{interactive} is if you need to decide whether to display a | |
740 | helpful message while a function is running. | |
741 | ||
742 | A function is never considered to be called interactively if it was | |
743 | called via Lisp evaluation (or with @code{apply} or @code{funcall}). | |
b8d4c8d0 GM |
744 | @end defun |
745 | ||
eb5ed549 CY |
746 | @noindent |
747 | Here is an example of using @code{called-interactively-p}: | |
b8d4c8d0 GM |
748 | |
749 | @example | |
750 | @group | |
b8d4c8d0 GM |
751 | (defun foo () |
752 | (interactive) | |
eb5ed549 CY |
753 | (when (called-interactively-p 'any) |
754 | (message "Interactive!") | |
755 | 'foo-called-interactively)) | |
b8d4c8d0 GM |
756 | @end group |
757 | ||
758 | @group | |
77832c61 | 759 | ;; @r{Type @kbd{M-x foo}.} |
eb5ed549 | 760 | @print{} Interactive! |
b8d4c8d0 GM |
761 | @end group |
762 | ||
763 | @group | |
77832c61 | 764 | (foo) |
eb5ed549 | 765 | @result{} nil |
77832c61 RS |
766 | @end group |
767 | @end example | |
768 | ||
eb5ed549 CY |
769 | @noindent |
770 | Here is another example that contrasts direct and indirect calls to | |
771 | @code{called-interactively-p}. | |
77832c61 RS |
772 | |
773 | @example | |
774 | @group | |
775 | (defun bar () | |
776 | (interactive) | |
eb5ed549 | 777 | (message "%s" (list (foo) (called-interactively-p 'any)))) |
b8d4c8d0 GM |
778 | @end group |
779 | ||
780 | @group | |
781 | ;; @r{Type @kbd{M-x bar}.} | |
eb5ed549 | 782 | @print{} (nil t) |
b8d4c8d0 GM |
783 | @end group |
784 | @end example | |
785 | ||
b8d4c8d0 | 786 | @node Command Loop Info |
b8d4c8d0 GM |
787 | @section Information from the Command Loop |
788 | ||
789 | The editor command loop sets several Lisp variables to keep status | |
1bb1f7d3 MR |
790 | records for itself and for commands that are run. With the exception of |
791 | @code{this-command} and @code{last-command} it's generally a bad idea to | |
792 | change any of these variables in a Lisp program. | |
b8d4c8d0 GM |
793 | |
794 | @defvar last-command | |
795 | This variable records the name of the previous command executed by the | |
796 | command loop (the one before the current command). Normally the value | |
797 | is a symbol with a function definition, but this is not guaranteed. | |
798 | ||
799 | The value is copied from @code{this-command} when a command returns to | |
800 | the command loop, except when the command has specified a prefix | |
801 | argument for the following command. | |
802 | ||
803 | This variable is always local to the current terminal and cannot be | |
3ec61d4e | 804 | buffer-local. @xref{Multiple Terminals}. |
b8d4c8d0 GM |
805 | @end defvar |
806 | ||
807 | @defvar real-last-command | |
808 | This variable is set up by Emacs just like @code{last-command}, | |
809 | but never altered by Lisp programs. | |
810 | @end defvar | |
811 | ||
1bb1f7d3 MR |
812 | @defvar last-repeatable-command |
813 | This variable stores the most recently executed command that was not | |
814 | part of an input event. This is the command @code{repeat} will try to | |
815 | repeat, @xref{Repeating,,, emacs, The GNU Emacs Manual}. | |
816 | @end defvar | |
817 | ||
b8d4c8d0 GM |
818 | @defvar this-command |
819 | @cindex current command | |
820 | This variable records the name of the command now being executed by | |
821 | the editor command loop. Like @code{last-command}, it is normally a symbol | |
822 | with a function definition. | |
823 | ||
824 | The command loop sets this variable just before running a command, and | |
825 | copies its value into @code{last-command} when the command finishes | |
826 | (unless the command specified a prefix argument for the following | |
827 | command). | |
828 | ||
829 | @cindex kill command repetition | |
830 | Some commands set this variable during their execution, as a flag for | |
831 | whatever command runs next. In particular, the functions for killing text | |
832 | set @code{this-command} to @code{kill-region} so that any kill commands | |
833 | immediately following will know to append the killed text to the | |
834 | previous kill. | |
835 | @end defvar | |
836 | ||
837 | If you do not want a particular command to be recognized as the previous | |
838 | command in the case where it got an error, you must code that command to | |
839 | prevent this. One way is to set @code{this-command} to @code{t} at the | |
840 | beginning of the command, and set @code{this-command} back to its proper | |
841 | value at the end, like this: | |
842 | ||
843 | @example | |
844 | (defun foo (args@dots{}) | |
845 | (interactive @dots{}) | |
846 | (let ((old-this-command this-command)) | |
847 | (setq this-command t) | |
848 | @r{@dots{}do the work@dots{}} | |
849 | (setq this-command old-this-command))) | |
850 | @end example | |
851 | ||
852 | @noindent | |
853 | We do not bind @code{this-command} with @code{let} because that would | |
854 | restore the old value in case of error---a feature of @code{let} which | |
855 | in this case does precisely what we want to avoid. | |
856 | ||
857 | @defvar this-original-command | |
858 | This has the same value as @code{this-command} except when command | |
859 | remapping occurs (@pxref{Remapping Commands}). In that case, | |
860 | @code{this-command} gives the command actually run (the result of | |
861 | remapping), and @code{this-original-command} gives the command that | |
862 | was specified to run but remapped into another command. | |
863 | @end defvar | |
864 | ||
865 | @defun this-command-keys | |
866 | This function returns a string or vector containing the key sequence | |
867 | that invoked the present command, plus any previous commands that | |
868 | generated the prefix argument for this command. Any events read by the | |
869 | command using @code{read-event} without a timeout get tacked on to the end. | |
870 | ||
871 | However, if the command has called @code{read-key-sequence}, it | |
872 | returns the last read key sequence. @xref{Key Sequence Input}. The | |
873 | value is a string if all events in the sequence were characters that | |
874 | fit in a string. @xref{Input Events}. | |
875 | ||
876 | @example | |
877 | @group | |
878 | (this-command-keys) | |
879 | ;; @r{Now use @kbd{C-u C-x C-e} to evaluate that.} | |
880 | @result{} "^U^X^E" | |
881 | @end group | |
882 | @end example | |
883 | @end defun | |
884 | ||
885 | @defun this-command-keys-vector | |
886 | @anchor{Definition of this-command-keys-vector} | |
887 | Like @code{this-command-keys}, except that it always returns the events | |
888 | in a vector, so you don't need to deal with the complexities of storing | |
889 | input events in a string (@pxref{Strings of Events}). | |
890 | @end defun | |
891 | ||
892 | @defun clear-this-command-keys &optional keep-record | |
893 | This function empties out the table of events for | |
894 | @code{this-command-keys} to return. Unless @var{keep-record} is | |
895 | non-@code{nil}, it also empties the records that the function | |
896 | @code{recent-keys} (@pxref{Recording Input}) will subsequently return. | |
897 | This is useful after reading a password, to prevent the password from | |
898 | echoing inadvertently as part of the next command in certain cases. | |
899 | @end defun | |
900 | ||
901 | @defvar last-nonmenu-event | |
902 | This variable holds the last input event read as part of a key sequence, | |
903 | not counting events resulting from mouse menus. | |
904 | ||
905 | One use of this variable is for telling @code{x-popup-menu} where to pop | |
906 | up a menu. It is also used internally by @code{y-or-n-p} | |
907 | (@pxref{Yes-or-No Queries}). | |
908 | @end defvar | |
909 | ||
910 | @defvar last-command-event | |
b8d4c8d0 GM |
911 | This variable is set to the last input event that was read by the |
912 | command loop as part of a command. The principal use of this variable | |
913 | is in @code{self-insert-command}, which uses it to decide which | |
914 | character to insert. | |
915 | ||
916 | @example | |
917 | @group | |
918 | last-command-event | |
919 | ;; @r{Now use @kbd{C-u C-x C-e} to evaluate that.} | |
920 | @result{} 5 | |
921 | @end group | |
922 | @end example | |
923 | ||
924 | @noindent | |
925 | The value is 5 because that is the @acronym{ASCII} code for @kbd{C-e}. | |
b8d4c8d0 GM |
926 | @end defvar |
927 | ||
b8d4c8d0 GM |
928 | @defvar last-event-frame |
929 | This variable records which frame the last input event was directed to. | |
930 | Usually this is the frame that was selected when the event was | |
931 | generated, but if that frame has redirected input focus to another | |
932 | frame, the value is the frame to which the event was redirected. | |
933 | @xref{Input Focus}. | |
934 | ||
935 | If the last event came from a keyboard macro, the value is @code{macro}. | |
936 | @end defvar | |
937 | ||
938 | @node Adjusting Point | |
939 | @section Adjusting Point After Commands | |
940 | @cindex adjusting point | |
941 | @cindex invisible/intangible text, and point | |
942 | @cindex @code{display} property, and point display | |
943 | @cindex @code{composition} property, and point display | |
944 | ||
945 | It is not easy to display a value of point in the middle of a | |
946 | sequence of text that has the @code{display}, @code{composition} or | |
a7cdbfce SM |
947 | is invisible. Therefore, after a command finishes and returns to the |
948 | command loop, if point is within such a sequence, the command loop | |
949 | normally moves point to the edge of the sequence. | |
b8d4c8d0 GM |
950 | |
951 | A command can inhibit this feature by setting the variable | |
952 | @code{disable-point-adjustment}: | |
953 | ||
954 | @defvar disable-point-adjustment | |
955 | If this variable is non-@code{nil} when a command returns to the | |
956 | command loop, then the command loop does not check for those text | |
957 | properties, and does not move point out of sequences that have them. | |
958 | ||
959 | The command loop sets this variable to @code{nil} before each command, | |
960 | so if a command sets it, the effect applies only to that command. | |
961 | @end defvar | |
962 | ||
963 | @defvar global-disable-point-adjustment | |
964 | If you set this variable to a non-@code{nil} value, the feature of | |
965 | moving point out of these sequences is completely turned off. | |
966 | @end defvar | |
967 | ||
968 | @node Input Events | |
969 | @section Input Events | |
970 | @cindex events | |
971 | @cindex input events | |
972 | ||
973 | The Emacs command loop reads a sequence of @dfn{input events} that | |
1ada2e55 EZ |
974 | represent keyboard or mouse activity, or system events sent to Emacs. |
975 | The events for keyboard activity are characters or symbols; other | |
976 | events are always lists. This section describes the representation | |
977 | and meaning of input events in detail. | |
b8d4c8d0 GM |
978 | |
979 | @defun eventp object | |
980 | This function returns non-@code{nil} if @var{object} is an input event | |
981 | or event type. | |
982 | ||
983 | Note that any symbol might be used as an event or an event type. | |
984 | @code{eventp} cannot distinguish whether a symbol is intended by Lisp | |
985 | code to be used as an event. Instead, it distinguishes whether the | |
986 | symbol has actually been used in an event that has been read as input in | |
987 | the current Emacs session. If a symbol has not yet been so used, | |
988 | @code{eventp} returns @code{nil}. | |
989 | @end defun | |
990 | ||
991 | @menu | |
d24880de GM |
992 | * Keyboard Events:: Ordinary characters--keys with symbols on them. |
993 | * Function Keys:: Function keys--keys with names, not symbols. | |
b8d4c8d0 | 994 | * Mouse Events:: Overview of mouse events. |
d24880de GM |
995 | * Click Events:: Pushing and releasing a mouse button. |
996 | * Drag Events:: Moving the mouse before releasing the button. | |
997 | * Button-Down Events:: A button was pushed and not yet released. | |
b8d4c8d0 | 998 | * Repeat Events:: Double and triple click (or drag, or down). |
d24880de GM |
999 | * Motion Events:: Just moving the mouse, not pushing a button. |
1000 | * Focus Events:: Moving the mouse between frames. | |
b8d4c8d0 | 1001 | * Misc Events:: Other events the system can generate. |
d24880de GM |
1002 | * Event Examples:: Examples of the lists for mouse events. |
1003 | * Classifying Events:: Finding the modifier keys in an event symbol. | |
1004 | Event types. | |
1005 | * Accessing Mouse:: Functions to extract info from mouse events. | |
1006 | * Accessing Scroll:: Functions to get info from scroll bar events. | |
b8d4c8d0 | 1007 | * Strings of Events:: Special considerations for putting |
d24880de | 1008 | keyboard character events in a string. |
b8d4c8d0 GM |
1009 | @end menu |
1010 | ||
1011 | @node Keyboard Events | |
1012 | @subsection Keyboard Events | |
1013 | @cindex keyboard events | |
1014 | ||
1015 | There are two kinds of input you can get from the keyboard: ordinary | |
1016 | keys, and function keys. Ordinary keys correspond to characters; the | |
1017 | events they generate are represented in Lisp as characters. The event | |
1018 | type of a character event is the character itself (an integer); see | |
1019 | @ref{Classifying Events}. | |
1020 | ||
1021 | @cindex modifier bits (of input character) | |
1022 | @cindex basic code (of input character) | |
1023 | An input character event consists of a @dfn{basic code} between 0 and | |
1024 | 524287, plus any or all of these @dfn{modifier bits}: | |
1025 | ||
1026 | @table @asis | |
1027 | @item meta | |
1028 | The | |
1029 | @tex | |
1030 | @math{2^{27}} | |
1031 | @end tex | |
1032 | @ifnottex | |
1033 | 2**27 | |
1034 | @end ifnottex | |
1035 | bit in the character code indicates a character | |
1036 | typed with the meta key held down. | |
1037 | ||
1038 | @item control | |
1039 | The | |
1040 | @tex | |
1041 | @math{2^{26}} | |
1042 | @end tex | |
1043 | @ifnottex | |
1044 | 2**26 | |
1045 | @end ifnottex | |
1046 | bit in the character code indicates a non-@acronym{ASCII} | |
1047 | control character. | |
1048 | ||
1049 | @sc{ascii} control characters such as @kbd{C-a} have special basic | |
1050 | codes of their own, so Emacs needs no special bit to indicate them. | |
1051 | Thus, the code for @kbd{C-a} is just 1. | |
1052 | ||
1053 | But if you type a control combination not in @acronym{ASCII}, such as | |
1054 | @kbd{%} with the control key, the numeric value you get is the code | |
1055 | for @kbd{%} plus | |
1056 | @tex | |
1057 | @math{2^{26}} | |
1058 | @end tex | |
1059 | @ifnottex | |
1060 | 2**26 | |
1061 | @end ifnottex | |
1062 | (assuming the terminal supports non-@acronym{ASCII} | |
1063 | control characters). | |
1064 | ||
1065 | @item shift | |
1066 | The | |
1067 | @tex | |
1068 | @math{2^{25}} | |
1069 | @end tex | |
1070 | @ifnottex | |
1071 | 2**25 | |
1072 | @end ifnottex | |
1073 | bit in the character code indicates an @acronym{ASCII} control | |
1074 | character typed with the shift key held down. | |
1075 | ||
1076 | For letters, the basic code itself indicates upper versus lower case; | |
1077 | for digits and punctuation, the shift key selects an entirely different | |
1078 | character with a different basic code. In order to keep within the | |
1079 | @acronym{ASCII} character set whenever possible, Emacs avoids using the | |
1080 | @tex | |
1081 | @math{2^{25}} | |
1082 | @end tex | |
1083 | @ifnottex | |
1084 | 2**25 | |
1085 | @end ifnottex | |
1086 | bit for those characters. | |
1087 | ||
1088 | However, @acronym{ASCII} provides no way to distinguish @kbd{C-A} from | |
1089 | @kbd{C-a}, so Emacs uses the | |
1090 | @tex | |
1091 | @math{2^{25}} | |
1092 | @end tex | |
1093 | @ifnottex | |
1094 | 2**25 | |
1095 | @end ifnottex | |
1096 | bit in @kbd{C-A} and not in | |
1097 | @kbd{C-a}. | |
1098 | ||
1099 | @item hyper | |
1100 | The | |
1101 | @tex | |
1102 | @math{2^{24}} | |
1103 | @end tex | |
1104 | @ifnottex | |
1105 | 2**24 | |
1106 | @end ifnottex | |
1107 | bit in the character code indicates a character | |
1108 | typed with the hyper key held down. | |
1109 | ||
1110 | @item super | |
1111 | The | |
1112 | @tex | |
1113 | @math{2^{23}} | |
1114 | @end tex | |
1115 | @ifnottex | |
1116 | 2**23 | |
1117 | @end ifnottex | |
1118 | bit in the character code indicates a character | |
1119 | typed with the super key held down. | |
1120 | ||
1121 | @item alt | |
1122 | The | |
1123 | @tex | |
1124 | @math{2^{22}} | |
1125 | @end tex | |
1126 | @ifnottex | |
1127 | 2**22 | |
1128 | @end ifnottex | |
34106abe CY |
1129 | bit in the character code indicates a character typed with the alt key |
1130 | held down. (The key labeled @key{Alt} on most keyboards is actually | |
1131 | treated as the meta key, not this.) | |
b8d4c8d0 GM |
1132 | @end table |
1133 | ||
1134 | It is best to avoid mentioning specific bit numbers in your program. | |
1135 | To test the modifier bits of a character, use the function | |
1136 | @code{event-modifiers} (@pxref{Classifying Events}). When making key | |
1137 | bindings, you can use the read syntax for characters with modifier bits | |
1138 | (@samp{\C-}, @samp{\M-}, and so on). For making key bindings with | |
1139 | @code{define-key}, you can use lists such as @code{(control hyper ?x)} to | |
1140 | specify the characters (@pxref{Changing Key Bindings}). The function | |
1141 | @code{event-convert-list} converts such a list into an event type | |
1142 | (@pxref{Classifying Events}). | |
1143 | ||
1144 | @node Function Keys | |
1145 | @subsection Function Keys | |
1146 | ||
1147 | @cindex function keys | |
1148 | Most keyboards also have @dfn{function keys}---keys that have names or | |
34106abe CY |
1149 | symbols that are not characters. Function keys are represented in |
1150 | Emacs Lisp as symbols; the symbol's name is the function key's label, | |
1151 | in lower case. For example, pressing a key labeled @key{F1} generates | |
1152 | an input event represented by the symbol @code{f1}. | |
b8d4c8d0 GM |
1153 | |
1154 | The event type of a function key event is the event symbol itself. | |
1155 | @xref{Classifying Events}. | |
1156 | ||
1157 | Here are a few special cases in the symbol-naming convention for | |
1158 | function keys: | |
1159 | ||
1160 | @table @asis | |
1161 | @item @code{backspace}, @code{tab}, @code{newline}, @code{return}, @code{delete} | |
1162 | These keys correspond to common @acronym{ASCII} control characters that have | |
1163 | special keys on most keyboards. | |
1164 | ||
1165 | In @acronym{ASCII}, @kbd{C-i} and @key{TAB} are the same character. If the | |
1166 | terminal can distinguish between them, Emacs conveys the distinction to | |
1167 | Lisp programs by representing the former as the integer 9, and the | |
1168 | latter as the symbol @code{tab}. | |
1169 | ||
1170 | Most of the time, it's not useful to distinguish the two. So normally | |
d3ae77bc EZ |
1171 | @code{local-function-key-map} (@pxref{Translation Keymaps}) is set up |
1172 | to map @code{tab} into 9. Thus, a key binding for character code 9 | |
1173 | (the character @kbd{C-i}) also applies to @code{tab}. Likewise for | |
1174 | the other symbols in this group. The function @code{read-char} | |
1175 | likewise converts these events into characters. | |
b8d4c8d0 GM |
1176 | |
1177 | In @acronym{ASCII}, @key{BS} is really @kbd{C-h}. But @code{backspace} | |
1178 | converts into the character code 127 (@key{DEL}), not into code 8 | |
1179 | (@key{BS}). This is what most users prefer. | |
1180 | ||
1181 | @item @code{left}, @code{up}, @code{right}, @code{down} | |
1182 | Cursor arrow keys | |
1183 | @item @code{kp-add}, @code{kp-decimal}, @code{kp-divide}, @dots{} | |
1184 | Keypad keys (to the right of the regular keyboard). | |
1185 | @item @code{kp-0}, @code{kp-1}, @dots{} | |
1186 | Keypad keys with digits. | |
1187 | @item @code{kp-f1}, @code{kp-f2}, @code{kp-f3}, @code{kp-f4} | |
1188 | Keypad PF keys. | |
1189 | @item @code{kp-home}, @code{kp-left}, @code{kp-up}, @code{kp-right}, @code{kp-down} | |
1190 | Keypad arrow keys. Emacs normally translates these into the | |
1191 | corresponding non-keypad keys @code{home}, @code{left}, @dots{} | |
1192 | @item @code{kp-prior}, @code{kp-next}, @code{kp-end}, @code{kp-begin}, @code{kp-insert}, @code{kp-delete} | |
1193 | Additional keypad duplicates of keys ordinarily found elsewhere. Emacs | |
1194 | normally translates these into the like-named non-keypad keys. | |
1195 | @end table | |
1196 | ||
1197 | You can use the modifier keys @key{ALT}, @key{CTRL}, @key{HYPER}, | |
1198 | @key{META}, @key{SHIFT}, and @key{SUPER} with function keys. The way to | |
1199 | represent them is with prefixes in the symbol name: | |
1200 | ||
1201 | @table @samp | |
1202 | @item A- | |
1203 | The alt modifier. | |
1204 | @item C- | |
1205 | The control modifier. | |
1206 | @item H- | |
1207 | The hyper modifier. | |
1208 | @item M- | |
1209 | The meta modifier. | |
1210 | @item S- | |
1211 | The shift modifier. | |
1212 | @item s- | |
1213 | The super modifier. | |
1214 | @end table | |
1215 | ||
1216 | Thus, the symbol for the key @key{F3} with @key{META} held down is | |
1217 | @code{M-f3}. When you use more than one prefix, we recommend you | |
1218 | write them in alphabetical order; but the order does not matter in | |
1219 | arguments to the key-binding lookup and modification functions. | |
1220 | ||
1221 | @node Mouse Events | |
1222 | @subsection Mouse Events | |
1223 | ||
1224 | Emacs supports four kinds of mouse events: click events, drag events, | |
1225 | button-down events, and motion events. All mouse events are represented | |
1226 | as lists. The @sc{car} of the list is the event type; this says which | |
1227 | mouse button was involved, and which modifier keys were used with it. | |
1228 | The event type can also distinguish double or triple button presses | |
1229 | (@pxref{Repeat Events}). The rest of the list elements give position | |
1230 | and time information. | |
1231 | ||
1232 | For key lookup, only the event type matters: two events of the same type | |
1233 | necessarily run the same command. The command can access the full | |
1234 | values of these events using the @samp{e} interactive code. | |
1235 | @xref{Interactive Codes}. | |
1236 | ||
1237 | A key sequence that starts with a mouse event is read using the keymaps | |
1238 | of the buffer in the window that the mouse was in, not the current | |
1239 | buffer. This does not imply that clicking in a window selects that | |
1240 | window or its buffer---that is entirely under the control of the command | |
1241 | binding of the key sequence. | |
1242 | ||
1243 | @node Click Events | |
1244 | @subsection Click Events | |
1245 | @cindex click event | |
1246 | @cindex mouse click event | |
1247 | ||
1248 | When the user presses a mouse button and releases it at the same | |
1249 | location, that generates a @dfn{click} event. All mouse click event | |
1250 | share the same format: | |
1251 | ||
1252 | @example | |
1253 | (@var{event-type} @var{position} @var{click-count}) | |
1254 | @end example | |
1255 | ||
1256 | @table @asis | |
1257 | @item @var{event-type} | |
1258 | This is a symbol that indicates which mouse button was used. It is | |
1259 | one of the symbols @code{mouse-1}, @code{mouse-2}, @dots{}, where the | |
1260 | buttons are numbered left to right. | |
1261 | ||
1262 | You can also use prefixes @samp{A-}, @samp{C-}, @samp{H-}, @samp{M-}, | |
1263 | @samp{S-} and @samp{s-} for modifiers alt, control, hyper, meta, shift | |
1264 | and super, just as you would with function keys. | |
1265 | ||
1266 | This symbol also serves as the event type of the event. Key bindings | |
1267 | describe events by their types; thus, if there is a key binding for | |
1268 | @code{mouse-1}, that binding would apply to all events whose | |
1269 | @var{event-type} is @code{mouse-1}. | |
1270 | ||
1271 | @item @var{position} | |
48de8b12 CY |
1272 | @cindex mouse position list |
1273 | This is a @dfn{mouse position list} specifying where the mouse click | |
1274 | occurred; see below for details. | |
b8d4c8d0 | 1275 | |
48de8b12 CY |
1276 | @item @var{click-count} |
1277 | This is the number of rapid repeated presses so far of the same mouse | |
1278 | button. @xref{Repeat Events}. | |
1279 | @end table | |
1280 | ||
1281 | To access the contents of a mouse position list in the | |
1282 | @var{position} slot of a click event, you should typically use the | |
1283 | functions documented in @ref{Accessing Mouse}. The explicit format of | |
1284 | the list depends on where the click occurred. For clicks in the text | |
1285 | area, mode line, header line, or in the fringe or marginal areas, the | |
1286 | mouse position list has the form | |
b8d4c8d0 GM |
1287 | |
1288 | @example | |
1289 | (@var{window} @var{pos-or-area} (@var{x} . @var{y}) @var{timestamp} | |
1290 | @var{object} @var{text-pos} (@var{col} . @var{row}) | |
1291 | @var{image} (@var{dx} . @var{dy}) (@var{width} . @var{height})) | |
1292 | @end example | |
1293 | ||
34106abe | 1294 | @noindent |
48de8b12 | 1295 | The meanings of these list elements are as follows: |
34106abe | 1296 | |
b8d4c8d0 GM |
1297 | @table @asis |
1298 | @item @var{window} | |
48de8b12 | 1299 | The window in which the click occurred. |
b8d4c8d0 GM |
1300 | |
1301 | @item @var{pos-or-area} | |
48de8b12 CY |
1302 | The buffer position of the character clicked on in the text area; or, |
1303 | if the click was outside the text area, the window area where it | |
1304 | occurred. It is one of the symbols @code{mode-line}, | |
b8d4c8d0 GM |
1305 | @code{header-line}, @code{vertical-line}, @code{left-margin}, |
1306 | @code{right-margin}, @code{left-fringe}, or @code{right-fringe}. | |
1307 | ||
34106abe CY |
1308 | In one special case, @var{pos-or-area} is a list containing a symbol |
1309 | (one of the symbols listed above) instead of just the symbol. This | |
1310 | happens after the imaginary prefix keys for the event are registered | |
1311 | by Emacs. @xref{Key Sequence Input}. | |
b8d4c8d0 GM |
1312 | |
1313 | @item @var{x}, @var{y} | |
48de8b12 CY |
1314 | The relative pixel coordinates of the click. For clicks in the text |
1315 | area of a window, the coordinate origin @code{(0 . 0)} is taken to be | |
1316 | the top left corner of the text area. @xref{Window Sizes}. For | |
1317 | clicks in a mode line or header line, the coordinate origin is the top | |
1318 | left corner of the window itself. For fringes, margins, and the | |
1319 | vertical border, @var{x} does not have meaningful data. For fringes | |
1320 | and margins, @var{y} is relative to the bottom edge of the header | |
1321 | line. In all cases, the @var{x} and @var{y} coordinates increase | |
1322 | rightward and downward respectively. | |
b8d4c8d0 GM |
1323 | |
1324 | @item @var{timestamp} | |
48de8b12 CY |
1325 | The time at which the event occurred, as an integer number of |
1326 | milliseconds since a system-dependent initial time. | |
b8d4c8d0 GM |
1327 | |
1328 | @item @var{object} | |
48de8b12 CY |
1329 | Either @code{nil} if there is no string-type text property at the |
1330 | click position, or a cons cell of the form (@var{string} | |
34106abe | 1331 | . @var{string-pos}) if there is one: |
b8d4c8d0 GM |
1332 | |
1333 | @table @asis | |
1334 | @item @var{string} | |
34106abe | 1335 | The string which was clicked on, including any properties. |
b8d4c8d0 GM |
1336 | |
1337 | @item @var{string-pos} | |
34106abe | 1338 | The position in the string where the click occurred. |
b8d4c8d0 GM |
1339 | @end table |
1340 | ||
1341 | @item @var{text-pos} | |
1342 | For clicks on a marginal area or on a fringe, this is the buffer | |
1343 | position of the first visible character in the corresponding line in | |
1344 | the window. For other events, it is the current buffer position in | |
1345 | the window. | |
1346 | ||
1347 | @item @var{col}, @var{row} | |
34106abe CY |
1348 | These are the actual column and row coordinate numbers of the glyph |
1349 | under the @var{x}, @var{y} position. If @var{x} lies beyond the last | |
1350 | column of actual text on its line, @var{col} is reported by adding | |
1351 | fictional extra columns that have the default character width. Row 0 | |
1352 | is taken to be the header line if the window has one, or the topmost | |
1353 | row of the text area otherwise. Column 0 is taken to be the leftmost | |
1354 | column of the text area for clicks on a window text area, or the | |
1355 | leftmost mode line or header line column for clicks there. For clicks | |
1356 | on fringes or vertical borders, these have no meaningful data. For | |
1357 | clicks on margins, @var{col} is measured from the left edge of the | |
1358 | margin area and @var{row} is measured from the top of the margin area. | |
b8d4c8d0 GM |
1359 | |
1360 | @item @var{image} | |
1361 | This is the image object on which the click occurred. It is either | |
1362 | @code{nil} if there is no image at the position clicked on, or it is | |
1363 | an image object as returned by @code{find-image} if click was in an image. | |
1364 | ||
1365 | @item @var{dx}, @var{dy} | |
1366 | These are the pixel coordinates of the click, relative to | |
1367 | the top left corner of @var{object}, which is @code{(0 . 0)}. If | |
1368 | @var{object} is @code{nil}, the coordinates are relative to the top | |
1369 | left corner of the character glyph clicked on. | |
1370 | ||
1371 | @item @var{width}, @var{height} | |
1372 | These are the pixel width and height of @var{object} or, if this is | |
1373 | @code{nil}, those of the character glyph clicked on. | |
1374 | @end table | |
8547874a | 1375 | |
48de8b12 | 1376 | For clicks on a scroll bar, @var{position} has this form: |
b8d4c8d0 GM |
1377 | |
1378 | @example | |
1379 | (@var{window} @var{area} (@var{portion} . @var{whole}) @var{timestamp} @var{part}) | |
1380 | @end example | |
1381 | ||
1382 | @table @asis | |
1383 | @item @var{window} | |
48de8b12 | 1384 | The window whose scroll bar was clicked on. |
b8d4c8d0 GM |
1385 | |
1386 | @item @var{area} | |
48de8b12 | 1387 | This is the symbol @code{vertical-scroll-bar}. |
b8d4c8d0 GM |
1388 | |
1389 | @item @var{portion} | |
48de8b12 CY |
1390 | The number of pixels from the top of the scroll bar to the click |
1391 | position. On some toolkits, including GTK+, Emacs cannot extract this | |
1392 | data, so the value is always @code{0}. | |
b8d4c8d0 GM |
1393 | |
1394 | @item @var{whole} | |
48de8b12 CY |
1395 | The total length, in pixels, of the scroll bar. On some toolkits, |
1396 | including GTK+, Emacs cannot extract this data, so the value is always | |
1397 | @code{0}. | |
b8d4c8d0 GM |
1398 | |
1399 | @item @var{timestamp} | |
48de8b12 CY |
1400 | The time at which the event occurred, in milliseconds. On some |
1401 | toolkits, including GTK+, Emacs cannot extract this data, so the value | |
1402 | is always @code{0}. | |
b8d4c8d0 GM |
1403 | |
1404 | @item @var{part} | |
48de8b12 CY |
1405 | The part of the scroll bar on which the click occurred. It is one of |
1406 | the symbols @code{handle} (the scroll bar handle), @code{above-handle} | |
1407 | (the area above the handle), @code{below-handle} (the area below the | |
1408 | handle), @code{up} (the up arrow at one end of the scroll bar), or | |
1409 | @code{down} (the down arrow at one end of the scroll bar). | |
1410 | @c The `top', `bottom', and `end-scroll' codes don't seem to be used. | |
b8d4c8d0 GM |
1411 | @end table |
1412 | ||
b8d4c8d0 GM |
1413 | |
1414 | @node Drag Events | |
1415 | @subsection Drag Events | |
1416 | @cindex drag event | |
1417 | @cindex mouse drag event | |
1418 | ||
1419 | With Emacs, you can have a drag event without even changing your | |
1420 | clothes. A @dfn{drag event} happens every time the user presses a mouse | |
1421 | button and then moves the mouse to a different character position before | |
1422 | releasing the button. Like all mouse events, drag events are | |
1423 | represented in Lisp as lists. The lists record both the starting mouse | |
1424 | position and the final position, like this: | |
1425 | ||
1426 | @example | |
1427 | (@var{event-type} | |
1428 | (@var{window1} START-POSITION) | |
1429 | (@var{window2} END-POSITION)) | |
1430 | @end example | |
1431 | ||
1432 | For a drag event, the name of the symbol @var{event-type} contains the | |
1433 | prefix @samp{drag-}. For example, dragging the mouse with button 2 | |
1434 | held down generates a @code{drag-mouse-2} event. The second and third | |
1435 | elements of the event give the starting and ending position of the | |
48de8b12 CY |
1436 | drag, as mouse position lists (@pxref{Click Events}). You can access |
1437 | the second element of any mouse event in the same way, with no need to | |
1438 | distinguish drag events from others. | |
b8d4c8d0 GM |
1439 | |
1440 | The @samp{drag-} prefix follows the modifier key prefixes such as | |
1441 | @samp{C-} and @samp{M-}. | |
1442 | ||
1443 | If @code{read-key-sequence} receives a drag event that has no key | |
1444 | binding, and the corresponding click event does have a binding, it | |
1445 | changes the drag event into a click event at the drag's starting | |
1446 | position. This means that you don't have to distinguish between click | |
1447 | and drag events unless you want to. | |
1448 | ||
1449 | @node Button-Down Events | |
1450 | @subsection Button-Down Events | |
1451 | @cindex button-down event | |
1452 | ||
1453 | Click and drag events happen when the user releases a mouse button. | |
1454 | They cannot happen earlier, because there is no way to distinguish a | |
1455 | click from a drag until the button is released. | |
1456 | ||
1457 | If you want to take action as soon as a button is pressed, you need to | |
1458 | handle @dfn{button-down} events.@footnote{Button-down is the | |
1459 | conservative antithesis of drag.} These occur as soon as a button is | |
1460 | pressed. They are represented by lists that look exactly like click | |
1461 | events (@pxref{Click Events}), except that the @var{event-type} symbol | |
1462 | name contains the prefix @samp{down-}. The @samp{down-} prefix follows | |
1463 | modifier key prefixes such as @samp{C-} and @samp{M-}. | |
1464 | ||
1465 | The function @code{read-key-sequence} ignores any button-down events | |
1466 | that don't have command bindings; therefore, the Emacs command loop | |
1467 | ignores them too. This means that you need not worry about defining | |
1468 | button-down events unless you want them to do something. The usual | |
1469 | reason to define a button-down event is so that you can track mouse | |
1470 | motion (by reading motion events) until the button is released. | |
1471 | @xref{Motion Events}. | |
1472 | ||
1473 | @node Repeat Events | |
1474 | @subsection Repeat Events | |
1475 | @cindex repeat events | |
1476 | @cindex double-click events | |
1477 | @cindex triple-click events | |
1478 | @cindex mouse events, repeated | |
1479 | ||
1480 | If you press the same mouse button more than once in quick succession | |
1481 | without moving the mouse, Emacs generates special @dfn{repeat} mouse | |
1482 | events for the second and subsequent presses. | |
1483 | ||
1484 | The most common repeat events are @dfn{double-click} events. Emacs | |
1485 | generates a double-click event when you click a button twice; the event | |
1486 | happens when you release the button (as is normal for all click | |
1487 | events). | |
1488 | ||
1489 | The event type of a double-click event contains the prefix | |
1490 | @samp{double-}. Thus, a double click on the second mouse button with | |
1491 | @key{meta} held down comes to the Lisp program as | |
1492 | @code{M-double-mouse-2}. If a double-click event has no binding, the | |
1493 | binding of the corresponding ordinary click event is used to execute | |
1494 | it. Thus, you need not pay attention to the double click feature | |
1495 | unless you really want to. | |
1496 | ||
1497 | When the user performs a double click, Emacs generates first an ordinary | |
1498 | click event, and then a double-click event. Therefore, you must design | |
1499 | the command binding of the double click event to assume that the | |
1500 | single-click command has already run. It must produce the desired | |
1501 | results of a double click, starting from the results of a single click. | |
1502 | ||
1503 | This is convenient, if the meaning of a double click somehow ``builds | |
1504 | on'' the meaning of a single click---which is recommended user interface | |
1505 | design practice for double clicks. | |
1506 | ||
1507 | If you click a button, then press it down again and start moving the | |
1508 | mouse with the button held down, then you get a @dfn{double-drag} event | |
1509 | when you ultimately release the button. Its event type contains | |
1510 | @samp{double-drag} instead of just @samp{drag}. If a double-drag event | |
1511 | has no binding, Emacs looks for an alternate binding as if the event | |
1512 | were an ordinary drag. | |
1513 | ||
1514 | Before the double-click or double-drag event, Emacs generates a | |
1515 | @dfn{double-down} event when the user presses the button down for the | |
1516 | second time. Its event type contains @samp{double-down} instead of just | |
1517 | @samp{down}. If a double-down event has no binding, Emacs looks for an | |
1518 | alternate binding as if the event were an ordinary button-down event. | |
1519 | If it finds no binding that way either, the double-down event is | |
1520 | ignored. | |
1521 | ||
1522 | To summarize, when you click a button and then press it again right | |
1523 | away, Emacs generates a down event and a click event for the first | |
1524 | click, a double-down event when you press the button again, and finally | |
1525 | either a double-click or a double-drag event. | |
1526 | ||
1527 | If you click a button twice and then press it again, all in quick | |
1528 | succession, Emacs generates a @dfn{triple-down} event, followed by | |
1529 | either a @dfn{triple-click} or a @dfn{triple-drag}. The event types of | |
1530 | these events contain @samp{triple} instead of @samp{double}. If any | |
1531 | triple event has no binding, Emacs uses the binding that it would use | |
1532 | for the corresponding double event. | |
1533 | ||
1534 | If you click a button three or more times and then press it again, the | |
1535 | events for the presses beyond the third are all triple events. Emacs | |
1536 | does not have separate event types for quadruple, quintuple, etc.@: | |
1537 | events. However, you can look at the event list to find out precisely | |
1538 | how many times the button was pressed. | |
1539 | ||
1540 | @defun event-click-count event | |
1541 | This function returns the number of consecutive button presses that led | |
1542 | up to @var{event}. If @var{event} is a double-down, double-click or | |
1543 | double-drag event, the value is 2. If @var{event} is a triple event, | |
1544 | the value is 3 or greater. If @var{event} is an ordinary mouse event | |
1545 | (not a repeat event), the value is 1. | |
1546 | @end defun | |
1547 | ||
1548 | @defopt double-click-fuzz | |
1549 | To generate repeat events, successive mouse button presses must be at | |
1550 | approximately the same screen position. The value of | |
1551 | @code{double-click-fuzz} specifies the maximum number of pixels the | |
1552 | mouse may be moved (horizontally or vertically) between two successive | |
1553 | clicks to make a double-click. | |
1554 | ||
1555 | This variable is also the threshold for motion of the mouse to count | |
1556 | as a drag. | |
1557 | @end defopt | |
1558 | ||
1559 | @defopt double-click-time | |
1560 | To generate repeat events, the number of milliseconds between | |
1561 | successive button presses must be less than the value of | |
1562 | @code{double-click-time}. Setting @code{double-click-time} to | |
1563 | @code{nil} disables multi-click detection entirely. Setting it to | |
1564 | @code{t} removes the time limit; Emacs then detects multi-clicks by | |
1565 | position only. | |
1566 | @end defopt | |
1567 | ||
1568 | @node Motion Events | |
1569 | @subsection Motion Events | |
1570 | @cindex motion event | |
1571 | @cindex mouse motion events | |
1572 | ||
1573 | Emacs sometimes generates @dfn{mouse motion} events to describe motion | |
1574 | of the mouse without any button activity. Mouse motion events are | |
1575 | represented by lists that look like this: | |
1576 | ||
1577 | @example | |
603f5979 | 1578 | (mouse-movement POSITION) |
b8d4c8d0 GM |
1579 | @end example |
1580 | ||
48de8b12 CY |
1581 | @noindent |
1582 | @var{position} is a mouse position list (@pxref{Click Events}), | |
1583 | specifying the current position of the mouse cursor. | |
b8d4c8d0 | 1584 | |
48de8b12 CY |
1585 | The special form @code{track-mouse} enables generation of motion |
1586 | events within its body. Outside of @code{track-mouse} forms, Emacs | |
1587 | does not generate events for mere motion of the mouse, and these | |
1588 | events do not appear. @xref{Mouse Tracking}. | |
b8d4c8d0 GM |
1589 | |
1590 | @node Focus Events | |
1591 | @subsection Focus Events | |
1592 | @cindex focus event | |
1593 | ||
1594 | Window systems provide general ways for the user to control which window | |
1595 | gets keyboard input. This choice of window is called the @dfn{focus}. | |
1596 | When the user does something to switch between Emacs frames, that | |
1597 | generates a @dfn{focus event}. The normal definition of a focus event, | |
1598 | in the global keymap, is to select a new frame within Emacs, as the user | |
1599 | would expect. @xref{Input Focus}. | |
1600 | ||
1601 | Focus events are represented in Lisp as lists that look like this: | |
1602 | ||
1603 | @example | |
1604 | (switch-frame @var{new-frame}) | |
1605 | @end example | |
1606 | ||
1607 | @noindent | |
1608 | where @var{new-frame} is the frame switched to. | |
1609 | ||
4b0f7178 CY |
1610 | Some X window managers are set up so that just moving the mouse into a |
1611 | window is enough to set the focus there. Usually, there is no need | |
1612 | for a Lisp program to know about the focus change until some other | |
1613 | kind of input arrives. Emacs generates a focus event only when the | |
1614 | user actually types a keyboard key or presses a mouse button in the | |
1615 | new frame; just moving the mouse between frames does not generate a | |
b8d4c8d0 GM |
1616 | focus event. |
1617 | ||
1618 | A focus event in the middle of a key sequence would garble the | |
1619 | sequence. So Emacs never generates a focus event in the middle of a key | |
1620 | sequence. If the user changes focus in the middle of a key | |
1621 | sequence---that is, after a prefix key---then Emacs reorders the events | |
1622 | so that the focus event comes either before or after the multi-event key | |
1623 | sequence, and not within it. | |
1624 | ||
1625 | @node Misc Events | |
1626 | @subsection Miscellaneous System Events | |
1627 | ||
1628 | A few other event types represent occurrences within the system. | |
1629 | ||
1630 | @table @code | |
1631 | @cindex @code{delete-frame} event | |
1632 | @item (delete-frame (@var{frame})) | |
1633 | This kind of event indicates that the user gave the window manager | |
1634 | a command to delete a particular window, which happens to be an Emacs frame. | |
1635 | ||
1636 | The standard definition of the @code{delete-frame} event is to delete @var{frame}. | |
1637 | ||
1638 | @cindex @code{iconify-frame} event | |
1639 | @item (iconify-frame (@var{frame})) | |
1640 | This kind of event indicates that the user iconified @var{frame} using | |
1641 | the window manager. Its standard definition is @code{ignore}; since the | |
1642 | frame has already been iconified, Emacs has no work to do. The purpose | |
1643 | of this event type is so that you can keep track of such events if you | |
1644 | want to. | |
1645 | ||
1646 | @cindex @code{make-frame-visible} event | |
1647 | @item (make-frame-visible (@var{frame})) | |
1648 | This kind of event indicates that the user deiconified @var{frame} using | |
1649 | the window manager. Its standard definition is @code{ignore}; since the | |
1650 | frame has already been made visible, Emacs has no work to do. | |
1651 | ||
1652 | @cindex @code{wheel-up} event | |
1653 | @cindex @code{wheel-down} event | |
1654 | @item (wheel-up @var{position}) | |
48de8b12 CY |
1655 | @itemx (wheel-down @var{position}) |
1656 | These kinds of event are generated by moving a mouse wheel. The | |
1657 | @var{position} element is a mouse position list (@pxref{Click | |
1658 | Events}), specifying the position of the mouse cursor when the event | |
1659 | occurred. | |
b8d4c8d0 | 1660 | |
be0a5fb7 KR |
1661 | @vindex mouse-wheel-up-event |
1662 | @vindex mouse-wheel-down-event | |
b8d4c8d0 GM |
1663 | This kind of event is generated only on some kinds of systems. On some |
1664 | systems, @code{mouse-4} and @code{mouse-5} are used instead. For | |
1665 | portable code, use the variables @code{mouse-wheel-up-event} and | |
1666 | @code{mouse-wheel-down-event} defined in @file{mwheel.el} to determine | |
1667 | what event types to expect for the mouse wheel. | |
1668 | ||
1669 | @cindex @code{drag-n-drop} event | |
1670 | @item (drag-n-drop @var{position} @var{files}) | |
1671 | This kind of event is generated when a group of files is | |
1672 | selected in an application outside of Emacs, and then dragged and | |
1673 | dropped onto an Emacs frame. | |
1674 | ||
1675 | The element @var{position} is a list describing the position of the | |
e8a6cc19 EZ |
1676 | event, in the same format as used in a mouse-click event (@pxref{Click |
1677 | Events}), and @var{files} is the list of file names that were dragged | |
1678 | and dropped. The usual way to handle this event is by visiting these | |
1679 | files. | |
b8d4c8d0 GM |
1680 | |
1681 | This kind of event is generated, at present, only on some kinds of | |
1682 | systems. | |
1683 | ||
1684 | @cindex @code{help-echo} event | |
1685 | @item help-echo | |
1686 | This kind of event is generated when a mouse pointer moves onto a | |
1687 | portion of buffer text which has a @code{help-echo} text property. | |
1688 | The generated event has this form: | |
1689 | ||
1690 | @example | |
1691 | (help-echo @var{frame} @var{help} @var{window} @var{object} @var{pos}) | |
1692 | @end example | |
1693 | ||
1694 | @noindent | |
1695 | The precise meaning of the event parameters and the way these | |
1696 | parameters are used to display the help-echo text are described in | |
1697 | @ref{Text help-echo}. | |
1698 | ||
1699 | @cindex @code{sigusr1} event | |
1700 | @cindex @code{sigusr2} event | |
1701 | @cindex user signals | |
1702 | @item sigusr1 | |
1703 | @itemx sigusr2 | |
1704 | These events are generated when the Emacs process receives | |
1705 | the signals @code{SIGUSR1} and @code{SIGUSR2}. They contain no | |
1706 | additional data because signals do not carry additional information. | |
7aa5aad8 | 1707 | They can be useful for debugging (@pxref{Error Debugging}). |
b8d4c8d0 GM |
1708 | |
1709 | To catch a user signal, bind the corresponding event to an interactive | |
1710 | command in the @code{special-event-map} (@pxref{Active Keymaps}). | |
1711 | The command is called with no arguments, and the specific signal event is | |
1712 | available in @code{last-input-event}. For example: | |
1713 | ||
1714 | @smallexample | |
1715 | (defun sigusr-handler () | |
1716 | (interactive) | |
1717 | (message "Caught signal %S" last-input-event)) | |
1718 | ||
1719 | (define-key special-event-map [sigusr1] 'sigusr-handler) | |
1720 | @end smallexample | |
1721 | ||
1722 | To test the signal handler, you can make Emacs send a signal to itself: | |
1723 | ||
1724 | @smallexample | |
1725 | (signal-process (emacs-pid) 'sigusr1) | |
1726 | @end smallexample | |
0bd8297f EZ |
1727 | |
1728 | @cindex @code{language-change} event | |
1729 | @item language-change | |
1730 | This kind of event is generated on MS-Windows when the input language | |
1731 | has changed. This typically means that the keyboard keys will send to | |
1732 | Emacs characters from a different language. The generated event has | |
1733 | this form: | |
1734 | ||
1735 | @smallexample | |
1736 | (language-change @var{frame} @var{codepage} @var{language-id}) | |
1737 | @end smallexample | |
1738 | ||
1739 | @noindent | |
1740 | Here @var{frame} is the frame which was current when the input | |
1741 | language changed; @var{codepage} is the new codepage number; and | |
1742 | @var{language-id} is the numerical ID of the new input language. The | |
1743 | coding-system (@pxref{Coding Systems}) that corresponds to | |
1744 | @var{codepage} is @code{cp@var{codepage}} or | |
1745 | @code{windows-@var{codepage}}. To convert @var{language-id} to a | |
1746 | string (e.g., to use it for various language-dependent features, such | |
1747 | as @code{set-language-environment}), use the | |
1748 | @code{w32-get-locale-info} function, like this: | |
1749 | ||
1750 | @smallexample | |
1751 | ;; Get the abbreviated language name, such as "ENU" for English | |
1752 | (w32-get-locale-info language-id) | |
1753 | ;; Get the full English name of the language, | |
1754 | ;; such as "English (United States)" | |
1755 | (w32-get-locale-info language-id 4097) | |
1756 | ;; Get the full localized name of the language | |
1757 | (w32-get-locale-info language-id t) | |
1758 | @end smallexample | |
b8d4c8d0 GM |
1759 | @end table |
1760 | ||
1761 | If one of these events arrives in the middle of a key sequence---that | |
1762 | is, after a prefix key---then Emacs reorders the events so that this | |
1763 | event comes either before or after the multi-event key sequence, not | |
1764 | within it. | |
1765 | ||
1766 | @node Event Examples | |
1767 | @subsection Event Examples | |
1768 | ||
1769 | If the user presses and releases the left mouse button over the same | |
1770 | location, that generates a sequence of events like this: | |
1771 | ||
1772 | @smallexample | |
1773 | (down-mouse-1 (#<window 18 on NEWS> 2613 (0 . 38) -864320)) | |
1774 | (mouse-1 (#<window 18 on NEWS> 2613 (0 . 38) -864180)) | |
1775 | @end smallexample | |
1776 | ||
1777 | While holding the control key down, the user might hold down the | |
1778 | second mouse button, and drag the mouse from one line to the next. | |
1779 | That produces two events, as shown here: | |
1780 | ||
1781 | @smallexample | |
1782 | (C-down-mouse-2 (#<window 18 on NEWS> 3440 (0 . 27) -731219)) | |
1783 | (C-drag-mouse-2 (#<window 18 on NEWS> 3440 (0 . 27) -731219) | |
1784 | (#<window 18 on NEWS> 3510 (0 . 28) -729648)) | |
1785 | @end smallexample | |
1786 | ||
1787 | While holding down the meta and shift keys, the user might press the | |
1788 | second mouse button on the window's mode line, and then drag the mouse | |
1789 | into another window. That produces a pair of events like these: | |
1790 | ||
1791 | @smallexample | |
1792 | (M-S-down-mouse-2 (#<window 18 on NEWS> mode-line (33 . 31) -457844)) | |
1793 | (M-S-drag-mouse-2 (#<window 18 on NEWS> mode-line (33 . 31) -457844) | |
1794 | (#<window 20 on carlton-sanskrit.tex> 161 (33 . 3) | |
1795 | -453816)) | |
1796 | @end smallexample | |
1797 | ||
1798 | To handle a SIGUSR1 signal, define an interactive function, and | |
1799 | bind it to the @code{signal usr1} event sequence: | |
1800 | ||
1801 | @smallexample | |
1802 | (defun usr1-handler () | |
1803 | (interactive) | |
1804 | (message "Got USR1 signal")) | |
1805 | (global-set-key [signal usr1] 'usr1-handler) | |
1806 | @end smallexample | |
1807 | ||
1808 | @node Classifying Events | |
1809 | @subsection Classifying Events | |
1810 | @cindex event type | |
1811 | ||
1812 | Every event has an @dfn{event type}, which classifies the event for | |
1813 | key binding purposes. For a keyboard event, the event type equals the | |
1814 | event value; thus, the event type for a character is the character, and | |
1815 | the event type for a function key symbol is the symbol itself. For | |
1816 | events that are lists, the event type is the symbol in the @sc{car} of | |
1817 | the list. Thus, the event type is always a symbol or a character. | |
1818 | ||
1819 | Two events of the same type are equivalent where key bindings are | |
1820 | concerned; thus, they always run the same command. That does not | |
1821 | necessarily mean they do the same things, however, as some commands look | |
1822 | at the whole event to decide what to do. For example, some commands use | |
1823 | the location of a mouse event to decide where in the buffer to act. | |
1824 | ||
1825 | Sometimes broader classifications of events are useful. For example, | |
1826 | you might want to ask whether an event involved the @key{META} key, | |
1827 | regardless of which other key or mouse button was used. | |
1828 | ||
1829 | The functions @code{event-modifiers} and @code{event-basic-type} are | |
1830 | provided to get such information conveniently. | |
1831 | ||
1832 | @defun event-modifiers event | |
1833 | This function returns a list of the modifiers that @var{event} has. The | |
1834 | modifiers are symbols; they include @code{shift}, @code{control}, | |
1835 | @code{meta}, @code{alt}, @code{hyper} and @code{super}. In addition, | |
1836 | the modifiers list of a mouse event symbol always contains one of | |
1837 | @code{click}, @code{drag}, and @code{down}. For double or triple | |
1838 | events, it also contains @code{double} or @code{triple}. | |
1839 | ||
1840 | The argument @var{event} may be an entire event object, or just an | |
1841 | event type. If @var{event} is a symbol that has never been used in an | |
1842 | event that has been read as input in the current Emacs session, then | |
1843 | @code{event-modifiers} can return @code{nil}, even when @var{event} | |
1844 | actually has modifiers. | |
1845 | ||
1846 | Here are some examples: | |
1847 | ||
1848 | @example | |
1849 | (event-modifiers ?a) | |
1850 | @result{} nil | |
1851 | (event-modifiers ?A) | |
1852 | @result{} (shift) | |
1853 | (event-modifiers ?\C-a) | |
1854 | @result{} (control) | |
1855 | (event-modifiers ?\C-%) | |
1856 | @result{} (control) | |
1857 | (event-modifiers ?\C-\S-a) | |
1858 | @result{} (control shift) | |
1859 | (event-modifiers 'f5) | |
1860 | @result{} nil | |
1861 | (event-modifiers 's-f5) | |
1862 | @result{} (super) | |
1863 | (event-modifiers 'M-S-f5) | |
1864 | @result{} (meta shift) | |
1865 | (event-modifiers 'mouse-1) | |
1866 | @result{} (click) | |
1867 | (event-modifiers 'down-mouse-1) | |
1868 | @result{} (down) | |
1869 | @end example | |
1870 | ||
1871 | The modifiers list for a click event explicitly contains @code{click}, | |
1872 | but the event symbol name itself does not contain @samp{click}. | |
1873 | @end defun | |
1874 | ||
1875 | @defun event-basic-type event | |
1876 | This function returns the key or mouse button that @var{event} | |
1877 | describes, with all modifiers removed. The @var{event} argument is as | |
1878 | in @code{event-modifiers}. For example: | |
1879 | ||
1880 | @example | |
1881 | (event-basic-type ?a) | |
1882 | @result{} 97 | |
1883 | (event-basic-type ?A) | |
1884 | @result{} 97 | |
1885 | (event-basic-type ?\C-a) | |
1886 | @result{} 97 | |
1887 | (event-basic-type ?\C-\S-a) | |
1888 | @result{} 97 | |
1889 | (event-basic-type 'f5) | |
1890 | @result{} f5 | |
1891 | (event-basic-type 's-f5) | |
1892 | @result{} f5 | |
1893 | (event-basic-type 'M-S-f5) | |
1894 | @result{} f5 | |
1895 | (event-basic-type 'down-mouse-1) | |
1896 | @result{} mouse-1 | |
1897 | @end example | |
1898 | @end defun | |
1899 | ||
1900 | @defun mouse-movement-p object | |
1901 | This function returns non-@code{nil} if @var{object} is a mouse movement | |
1902 | event. | |
1903 | @end defun | |
1904 | ||
1905 | @defun event-convert-list list | |
1906 | This function converts a list of modifier names and a basic event type | |
1907 | to an event type which specifies all of them. The basic event type | |
1908 | must be the last element of the list. For example, | |
1909 | ||
1910 | @example | |
1911 | (event-convert-list '(control ?a)) | |
1912 | @result{} 1 | |
1913 | (event-convert-list '(control meta ?a)) | |
1914 | @result{} -134217727 | |
1915 | (event-convert-list '(control super f1)) | |
1916 | @result{} C-s-f1 | |
1917 | @end example | |
1918 | @end defun | |
1919 | ||
ec7d5b1e RS |
1920 | @node Accessing Mouse |
1921 | @subsection Accessing Mouse Events | |
b8d4c8d0 GM |
1922 | @cindex mouse events, data in |
1923 | ||
1924 | This section describes convenient functions for accessing the data in | |
1925 | a mouse button or motion event. | |
1926 | ||
48de8b12 CY |
1927 | The following two functions return a mouse position list |
1928 | (@pxref{Click Events}), specifying the position of a mouse event. | |
b8d4c8d0 GM |
1929 | |
1930 | @defun event-start event | |
1931 | This returns the starting position of @var{event}. | |
1932 | ||
1933 | If @var{event} is a click or button-down event, this returns the | |
1934 | location of the event. If @var{event} is a drag event, this returns the | |
1935 | drag's starting position. | |
1936 | @end defun | |
1937 | ||
1938 | @defun event-end event | |
1939 | This returns the ending position of @var{event}. | |
1940 | ||
1941 | If @var{event} is a drag event, this returns the position where the user | |
1942 | released the mouse button. If @var{event} is a click or button-down | |
1943 | event, the value is actually the starting position, which is the only | |
1944 | position such events have. | |
1945 | @end defun | |
1946 | ||
48de8b12 CY |
1947 | @defun posnp object |
1948 | This function returns non-@code{nil} if @var{object} is a mouse | |
735135f9 | 1949 | position list, in either of the formats documented in @ref{Click |
48de8b12 CY |
1950 | Events}); and @code{nil} otherwise. |
1951 | @end defun | |
1952 | ||
b8d4c8d0 | 1953 | @cindex mouse position list, accessing |
48de8b12 CY |
1954 | These functions take a mouse position list as argument, and return |
1955 | various parts of it: | |
b8d4c8d0 GM |
1956 | |
1957 | @defun posn-window position | |
1958 | Return the window that @var{position} is in. | |
1959 | @end defun | |
1960 | ||
1961 | @defun posn-area position | |
1962 | Return the window area recorded in @var{position}. It returns @code{nil} | |
1963 | when the event occurred in the text area of the window; otherwise, it | |
1964 | is a symbol identifying the area in which the event occurred. | |
1965 | @end defun | |
1966 | ||
1967 | @defun posn-point position | |
1968 | Return the buffer position in @var{position}. When the event occurred | |
1969 | in the text area of the window, in a marginal area, or on a fringe, | |
1970 | this is an integer specifying a buffer position. Otherwise, the value | |
1971 | is undefined. | |
1972 | @end defun | |
1973 | ||
1974 | @defun posn-x-y position | |
1975 | Return the pixel-based x and y coordinates in @var{position}, as a | |
1976 | cons cell @code{(@var{x} . @var{y})}. These coordinates are relative | |
1977 | to the window given by @code{posn-window}. | |
1978 | ||
34106abe CY |
1979 | This example shows how to convert the window-relative coordinates in |
1980 | the text area of a window into frame-relative coordinates: | |
b8d4c8d0 GM |
1981 | |
1982 | @example | |
1983 | (defun frame-relative-coordinates (position) | |
34106abe CY |
1984 | "Return frame-relative coordinates from POSITION. |
1985 | POSITION is assumed to lie in a window text area." | |
b8d4c8d0 GM |
1986 | (let* ((x-y (posn-x-y position)) |
1987 | (window (posn-window position)) | |
1988 | (edges (window-inside-pixel-edges window))) | |
1989 | (cons (+ (car x-y) (car edges)) | |
1990 | (+ (cdr x-y) (cadr edges))))) | |
1991 | @end example | |
1992 | @end defun | |
1993 | ||
1994 | @defun posn-col-row position | |
a41c8660 CY |
1995 | This function returns a cons cell @code{(@var{col} . @var{row})}, |
1996 | containing the estimated column and row corresponding to buffer | |
1997 | position @var{position}. The return value is given in units of the | |
1998 | frame's default character width and height, as computed from the | |
1999 | @var{x} and @var{y} values corresponding to @var{position}. (So, if | |
2000 | the actual characters have non-default sizes, the actual row and | |
2001 | column may differ from these computed values.) | |
2002 | ||
2003 | Note that @var{row} is counted from the top of the text area. If the | |
2004 | window possesses a header line (@pxref{Header Lines}), it is | |
2005 | @emph{not} counted as the first line. | |
b8d4c8d0 GM |
2006 | @end defun |
2007 | ||
2008 | @defun posn-actual-col-row position | |
2009 | Return the actual row and column in @var{position}, as a cons cell | |
34106abe CY |
2010 | @code{(@var{col} . @var{row})}. The values are the actual row and |
2011 | column numbers in the window. @xref{Click Events}, for details. It | |
2012 | returns @code{nil} if @var{position} does not include actual positions | |
2013 | values. | |
b8d4c8d0 GM |
2014 | @end defun |
2015 | ||
2016 | @defun posn-string position | |
2017 | Return the string object in @var{position}, either @code{nil}, or a | |
2018 | cons cell @code{(@var{string} . @var{string-pos})}. | |
2019 | @end defun | |
2020 | ||
2021 | @defun posn-image position | |
2022 | Return the image object in @var{position}, either @code{nil}, or an | |
2023 | image @code{(image ...)}. | |
2024 | @end defun | |
2025 | ||
2026 | @defun posn-object position | |
2027 | Return the image or string object in @var{position}, either | |
2028 | @code{nil}, an image @code{(image ...)}, or a cons cell | |
2029 | @code{(@var{string} . @var{string-pos})}. | |
2030 | @end defun | |
2031 | ||
2032 | @defun posn-object-x-y position | |
2033 | Return the pixel-based x and y coordinates relative to the upper left | |
2034 | corner of the object in @var{position} as a cons cell @code{(@var{dx} | |
2035 | . @var{dy})}. If the @var{position} is a buffer position, return the | |
2036 | relative position in the character at that position. | |
2037 | @end defun | |
2038 | ||
2039 | @defun posn-object-width-height position | |
2040 | Return the pixel width and height of the object in @var{position} as a | |
2041 | cons cell @code{(@var{width} . @var{height})}. If the @var{position} | |
2042 | is a buffer position, return the size of the character at that position. | |
2043 | @end defun | |
2044 | ||
2045 | @cindex timestamp of a mouse event | |
2046 | @defun posn-timestamp position | |
2047 | Return the timestamp in @var{position}. This is the time at which the | |
2048 | event occurred, in milliseconds. | |
2049 | @end defun | |
2050 | ||
2051 | These functions compute a position list given particular buffer | |
2052 | position or screen position. You can access the data in this position | |
2053 | list with the functions described above. | |
2054 | ||
2055 | @defun posn-at-point &optional pos window | |
2056 | This function returns a position list for position @var{pos} in | |
2057 | @var{window}. @var{pos} defaults to point in @var{window}; | |
2058 | @var{window} defaults to the selected window. | |
2059 | ||
2060 | @code{posn-at-point} returns @code{nil} if @var{pos} is not visible in | |
2061 | @var{window}. | |
2062 | @end defun | |
2063 | ||
2064 | @defun posn-at-x-y x y &optional frame-or-window whole | |
2065 | This function returns position information corresponding to pixel | |
2066 | coordinates @var{x} and @var{y} in a specified frame or window, | |
2067 | @var{frame-or-window}, which defaults to the selected window. | |
2068 | The coordinates @var{x} and @var{y} are relative to the | |
2069 | frame or window used. | |
2070 | If @var{whole} is @code{nil}, the coordinates are relative | |
2071 | to the window text area, otherwise they are relative to | |
2072 | the entire window area including scroll bars, margins and fringes. | |
2073 | @end defun | |
2074 | ||
ec7d5b1e RS |
2075 | @node Accessing Scroll |
2076 | @subsection Accessing Scroll Bar Events | |
2077 | @cindex scroll bar events, data in | |
2078 | ||
b8d4c8d0 GM |
2079 | These functions are useful for decoding scroll bar events. |
2080 | ||
2081 | @defun scroll-bar-event-ratio event | |
2082 | This function returns the fractional vertical position of a scroll bar | |
2083 | event within the scroll bar. The value is a cons cell | |
2084 | @code{(@var{portion} . @var{whole})} containing two integers whose ratio | |
2085 | is the fractional position. | |
2086 | @end defun | |
2087 | ||
2088 | @defun scroll-bar-scale ratio total | |
2089 | This function multiplies (in effect) @var{ratio} by @var{total}, | |
2090 | rounding the result to an integer. The argument @var{ratio} is not a | |
2091 | number, but rather a pair @code{(@var{num} . @var{denom})}---typically a | |
2092 | value returned by @code{scroll-bar-event-ratio}. | |
2093 | ||
2094 | This function is handy for scaling a position on a scroll bar into a | |
2095 | buffer position. Here's how to do that: | |
2096 | ||
2097 | @example | |
2098 | (+ (point-min) | |
2099 | (scroll-bar-scale | |
2100 | (posn-x-y (event-start event)) | |
2101 | (- (point-max) (point-min)))) | |
2102 | @end example | |
2103 | ||
2104 | Recall that scroll bar events have two integers forming a ratio, in place | |
2105 | of a pair of x and y coordinates. | |
2106 | @end defun | |
2107 | ||
2108 | @node Strings of Events | |
2109 | @subsection Putting Keyboard Events in Strings | |
2110 | @cindex keyboard events in strings | |
2111 | @cindex strings with keyboard events | |
2112 | ||
2113 | In most of the places where strings are used, we conceptualize the | |
2114 | string as containing text characters---the same kind of characters found | |
2115 | in buffers or files. Occasionally Lisp programs use strings that | |
2116 | conceptually contain keyboard characters; for example, they may be key | |
2117 | sequences or keyboard macro definitions. However, storing keyboard | |
2118 | characters in a string is a complex matter, for reasons of historical | |
2119 | compatibility, and it is not always possible. | |
2120 | ||
2121 | We recommend that new programs avoid dealing with these complexities | |
2122 | by not storing keyboard events in strings. Here is how to do that: | |
2123 | ||
2124 | @itemize @bullet | |
2125 | @item | |
2126 | Use vectors instead of strings for key sequences, when you plan to use | |
2127 | them for anything other than as arguments to @code{lookup-key} and | |
2128 | @code{define-key}. For example, you can use | |
2129 | @code{read-key-sequence-vector} instead of @code{read-key-sequence}, and | |
2130 | @code{this-command-keys-vector} instead of @code{this-command-keys}. | |
2131 | ||
2132 | @item | |
2133 | Use vectors to write key sequence constants containing meta characters, | |
2134 | even when passing them directly to @code{define-key}. | |
2135 | ||
2136 | @item | |
2137 | When you have to look at the contents of a key sequence that might be a | |
2138 | string, use @code{listify-key-sequence} (@pxref{Event Input Misc}) | |
2139 | first, to convert it to a list. | |
2140 | @end itemize | |
2141 | ||
2142 | The complexities stem from the modifier bits that keyboard input | |
2143 | characters can include. Aside from the Meta modifier, none of these | |
2144 | modifier bits can be included in a string, and the Meta modifier is | |
2145 | allowed only in special cases. | |
2146 | ||
2147 | The earliest GNU Emacs versions represented meta characters as codes | |
2148 | in the range of 128 to 255. At that time, the basic character codes | |
2149 | ranged from 0 to 127, so all keyboard character codes did fit in a | |
2150 | string. Many Lisp programs used @samp{\M-} in string constants to stand | |
2151 | for meta characters, especially in arguments to @code{define-key} and | |
2152 | similar functions, and key sequences and sequences of events were always | |
2153 | represented as strings. | |
2154 | ||
2155 | When we added support for larger basic character codes beyond 127, and | |
2156 | additional modifier bits, we had to change the representation of meta | |
2157 | characters. Now the flag that represents the Meta modifier in a | |
2158 | character is | |
2159 | @tex | |
2160 | @math{2^{27}} | |
2161 | @end tex | |
2162 | @ifnottex | |
2163 | 2**27 | |
2164 | @end ifnottex | |
2165 | and such numbers cannot be included in a string. | |
2166 | ||
2167 | To support programs with @samp{\M-} in string constants, there are | |
2168 | special rules for including certain meta characters in a string. | |
2169 | Here are the rules for interpreting a string as a sequence of input | |
2170 | characters: | |
2171 | ||
2172 | @itemize @bullet | |
2173 | @item | |
2174 | If the keyboard character value is in the range of 0 to 127, it can go | |
2175 | in the string unchanged. | |
2176 | ||
2177 | @item | |
2178 | The meta variants of those characters, with codes in the range of | |
2179 | @tex | |
2180 | @math{2^{27}} | |
2181 | @end tex | |
2182 | @ifnottex | |
2183 | 2**27 | |
2184 | @end ifnottex | |
2185 | to | |
2186 | @tex | |
2187 | @math{2^{27} + 127}, | |
2188 | @end tex | |
2189 | @ifnottex | |
2190 | 2**27+127, | |
2191 | @end ifnottex | |
2192 | can also go in the string, but you must change their | |
2193 | numeric values. You must set the | |
2194 | @tex | |
2195 | @math{2^{7}} | |
2196 | @end tex | |
2197 | @ifnottex | |
2198 | 2**7 | |
2199 | @end ifnottex | |
2200 | bit instead of the | |
2201 | @tex | |
2202 | @math{2^{27}} | |
2203 | @end tex | |
2204 | @ifnottex | |
2205 | 2**27 | |
2206 | @end ifnottex | |
2207 | bit, resulting in a value between 128 and 255. Only a unibyte string | |
2208 | can include these codes. | |
2209 | ||
2210 | @item | |
2211 | Non-@acronym{ASCII} characters above 256 can be included in a multibyte string. | |
2212 | ||
2213 | @item | |
2214 | Other keyboard character events cannot fit in a string. This includes | |
2215 | keyboard events in the range of 128 to 255. | |
2216 | @end itemize | |
2217 | ||
2218 | Functions such as @code{read-key-sequence} that construct strings of | |
2219 | keyboard input characters follow these rules: they construct vectors | |
2220 | instead of strings, when the events won't fit in a string. | |
2221 | ||
2222 | When you use the read syntax @samp{\M-} in a string, it produces a | |
2223 | code in the range of 128 to 255---the same code that you get if you | |
2224 | modify the corresponding keyboard event to put it in the string. Thus, | |
2225 | meta events in strings work consistently regardless of how they get into | |
2226 | the strings. | |
2227 | ||
2228 | However, most programs would do well to avoid these issues by | |
2229 | following the recommendations at the beginning of this section. | |
2230 | ||
2231 | @node Reading Input | |
2232 | @section Reading Input | |
2233 | @cindex read input | |
2234 | @cindex keyboard input | |
2235 | ||
2236 | The editor command loop reads key sequences using the function | |
2237 | @code{read-key-sequence}, which uses @code{read-event}. These and other | |
2238 | functions for event input are also available for use in Lisp programs. | |
2239 | See also @code{momentary-string-display} in @ref{Temporary Displays}, | |
2240 | and @code{sit-for} in @ref{Waiting}. @xref{Terminal Input}, for | |
2241 | functions and variables for controlling terminal input modes and | |
2242 | debugging terminal input. | |
2243 | ||
2244 | For higher-level input facilities, see @ref{Minibuffers}. | |
2245 | ||
2246 | @menu | |
d24880de GM |
2247 | * Key Sequence Input:: How to read one key sequence. |
2248 | * Reading One Event:: How to read just one event. | |
b8d4c8d0 GM |
2249 | * Event Mod:: How Emacs modifies events as they are read. |
2250 | * Invoking the Input Method:: How reading an event uses the input method. | |
d24880de GM |
2251 | * Quoted Character Input:: Asking the user to specify a character. |
2252 | * Event Input Misc:: How to reread or throw away input events. | |
b8d4c8d0 GM |
2253 | @end menu |
2254 | ||
2255 | @node Key Sequence Input | |
2256 | @subsection Key Sequence Input | |
2257 | @cindex key sequence input | |
2258 | ||
2259 | The command loop reads input a key sequence at a time, by calling | |
2260 | @code{read-key-sequence}. Lisp programs can also call this function; | |
2261 | for example, @code{describe-key} uses it to read the key to describe. | |
2262 | ||
2263 | @defun read-key-sequence prompt &optional continue-echo dont-downcase-last switch-frame-ok command-loop | |
2264 | This function reads a key sequence and returns it as a string or | |
2265 | vector. It keeps reading events until it has accumulated a complete key | |
2266 | sequence; that is, enough to specify a non-prefix command using the | |
2267 | currently active keymaps. (Remember that a key sequence that starts | |
2268 | with a mouse event is read using the keymaps of the buffer in the | |
2269 | window that the mouse was in, not the current buffer.) | |
2270 | ||
2271 | If the events are all characters and all can fit in a string, then | |
2272 | @code{read-key-sequence} returns a string (@pxref{Strings of Events}). | |
2273 | Otherwise, it returns a vector, since a vector can hold all kinds of | |
2274 | events---characters, symbols, and lists. The elements of the string or | |
2275 | vector are the events in the key sequence. | |
2276 | ||
2277 | Reading a key sequence includes translating the events in various | |
2278 | ways. @xref{Translation Keymaps}. | |
2279 | ||
2280 | The argument @var{prompt} is either a string to be displayed in the | |
2281 | echo area as a prompt, or @code{nil}, meaning not to display a prompt. | |
2282 | The argument @var{continue-echo}, if non-@code{nil}, means to echo | |
2283 | this key as a continuation of the previous key. | |
2284 | ||
2285 | Normally any upper case event is converted to lower case if the | |
2286 | original event is undefined and the lower case equivalent is defined. | |
2287 | The argument @var{dont-downcase-last}, if non-@code{nil}, means do not | |
2288 | convert the last event to lower case. This is appropriate for reading | |
2289 | a key sequence to be defined. | |
2290 | ||
2291 | The argument @var{switch-frame-ok}, if non-@code{nil}, means that this | |
2292 | function should process a @code{switch-frame} event if the user | |
2293 | switches frames before typing anything. If the user switches frames | |
2294 | in the middle of a key sequence, or at the start of the sequence but | |
2295 | @var{switch-frame-ok} is @code{nil}, then the event will be put off | |
2296 | until after the current key sequence. | |
2297 | ||
2298 | The argument @var{command-loop}, if non-@code{nil}, means that this | |
2299 | key sequence is being read by something that will read commands one | |
2300 | after another. It should be @code{nil} if the caller will read just | |
2301 | one key sequence. | |
2302 | ||
2303 | In the following example, Emacs displays the prompt @samp{?} in the | |
2304 | echo area, and then the user types @kbd{C-x C-f}. | |
2305 | ||
2306 | @example | |
2307 | (read-key-sequence "?") | |
2308 | ||
2309 | @group | |
2310 | ---------- Echo Area ---------- | |
2311 | ?@kbd{C-x C-f} | |
2312 | ---------- Echo Area ---------- | |
2313 | ||
2314 | @result{} "^X^F" | |
2315 | @end group | |
2316 | @end example | |
2317 | ||
2318 | The function @code{read-key-sequence} suppresses quitting: @kbd{C-g} | |
2319 | typed while reading with this function works like any other character, | |
2320 | and does not set @code{quit-flag}. @xref{Quitting}. | |
2321 | @end defun | |
2322 | ||
2323 | @defun read-key-sequence-vector prompt &optional continue-echo dont-downcase-last switch-frame-ok command-loop | |
2324 | This is like @code{read-key-sequence} except that it always | |
2325 | returns the key sequence as a vector, never as a string. | |
2326 | @xref{Strings of Events}. | |
2327 | @end defun | |
2328 | ||
2329 | @cindex upper case key sequence | |
2330 | @cindex downcasing in @code{lookup-key} | |
ee6e73b8 | 2331 | @cindex shift-translation |
b8d4c8d0 GM |
2332 | If an input character is upper-case (or has the shift modifier) and |
2333 | has no key binding, but its lower-case equivalent has one, then | |
2334 | @code{read-key-sequence} converts the character to lower case. Note | |
2335 | that @code{lookup-key} does not perform case conversion in this way. | |
2336 | ||
ee6e73b8 EZ |
2337 | @vindex this-command-keys-shift-translated |
2338 | When reading input results in such a @dfn{shift-translation}, Emacs | |
2339 | sets the variable @code{this-command-keys-shift-translated} to a | |
77111ca6 CY |
2340 | non-@code{nil} value. Lisp programs can examine this variable if they |
2341 | need to modify their behavior when invoked by shift-translated keys. | |
2342 | For example, the function @code{handle-shift-selection} examines the | |
2343 | value of this variable to determine how to activate or deactivate the | |
2344 | region (@pxref{The Mark, handle-shift-selection}). | |
ee6e73b8 | 2345 | |
b8d4c8d0 GM |
2346 | The function @code{read-key-sequence} also transforms some mouse events. |
2347 | It converts unbound drag events into click events, and discards unbound | |
2348 | button-down events entirely. It also reshuffles focus events and | |
2349 | miscellaneous window events so that they never appear in a key sequence | |
2350 | with any other events. | |
2351 | ||
2352 | @cindex @code{header-line} prefix key | |
2353 | @cindex @code{mode-line} prefix key | |
2354 | @cindex @code{vertical-line} prefix key | |
2355 | @cindex @code{horizontal-scroll-bar} prefix key | |
2356 | @cindex @code{vertical-scroll-bar} prefix key | |
2357 | @cindex @code{menu-bar} prefix key | |
2358 | @cindex mouse events, in special parts of frame | |
2359 | When mouse events occur in special parts of a window, such as a mode | |
2360 | line or a scroll bar, the event type shows nothing special---it is the | |
2361 | same symbol that would normally represent that combination of mouse | |
2362 | button and modifier keys. The information about the window part is kept | |
2363 | elsewhere in the event---in the coordinates. But | |
2364 | @code{read-key-sequence} translates this information into imaginary | |
16152b76 | 2365 | ``prefix keys'', all of which are symbols: @code{header-line}, |
b8d4c8d0 GM |
2366 | @code{horizontal-scroll-bar}, @code{menu-bar}, @code{mode-line}, |
2367 | @code{vertical-line}, and @code{vertical-scroll-bar}. You can define | |
2368 | meanings for mouse clicks in special window parts by defining key | |
2369 | sequences using these imaginary prefix keys. | |
2370 | ||
2371 | For example, if you call @code{read-key-sequence} and then click the | |
2372 | mouse on the window's mode line, you get two events, like this: | |
2373 | ||
2374 | @example | |
2375 | (read-key-sequence "Click on the mode line: ") | |
2376 | @result{} [mode-line | |
2377 | (mouse-1 | |
2378 | (#<window 6 on NEWS> mode-line | |
2379 | (40 . 63) 5959987))] | |
2380 | @end example | |
2381 | ||
2382 | @defvar num-input-keys | |
b8d4c8d0 GM |
2383 | This variable's value is the number of key sequences processed so far in |
2384 | this Emacs session. This includes key sequences read from the terminal | |
2385 | and key sequences read from keyboard macros being executed. | |
2386 | @end defvar | |
2387 | ||
2388 | @node Reading One Event | |
2389 | @subsection Reading One Event | |
2390 | @cindex reading a single event | |
2391 | @cindex event, reading only one | |
2392 | ||
eb5ed549 CY |
2393 | The lowest level functions for command input are @code{read-event}, |
2394 | @code{read-char}, and @code{read-char-exclusive}. | |
b8d4c8d0 GM |
2395 | |
2396 | @defun read-event &optional prompt inherit-input-method seconds | |
2397 | This function reads and returns the next event of command input, waiting | |
2398 | if necessary until an event is available. Events can come directly from | |
2399 | the user or from a keyboard macro. | |
2400 | ||
2401 | If the optional argument @var{prompt} is non-@code{nil}, it should be a | |
2402 | string to display in the echo area as a prompt. Otherwise, | |
2403 | @code{read-event} does not display any message to indicate it is waiting | |
2404 | for input; instead, it prompts by echoing: it displays descriptions of | |
2405 | the events that led to or were read by the current command. @xref{The | |
2406 | Echo Area}. | |
2407 | ||
2408 | If @var{inherit-input-method} is non-@code{nil}, then the current input | |
2409 | method (if any) is employed to make it possible to enter a | |
2410 | non-@acronym{ASCII} character. Otherwise, input method handling is disabled | |
2411 | for reading this event. | |
2412 | ||
2413 | If @code{cursor-in-echo-area} is non-@code{nil}, then @code{read-event} | |
2414 | moves the cursor temporarily to the echo area, to the end of any message | |
2415 | displayed there. Otherwise @code{read-event} does not move the cursor. | |
2416 | ||
2417 | If @var{seconds} is non-@code{nil}, it should be a number specifying | |
2418 | the maximum time to wait for input, in seconds. If no input arrives | |
2419 | within that time, @code{read-event} stops waiting and returns | |
2420 | @code{nil}. A floating-point value for @var{seconds} means to wait | |
2421 | for a fractional number of seconds. Some systems support only a whole | |
2422 | number of seconds; on these systems, @var{seconds} is rounded down. | |
2423 | If @var{seconds} is @code{nil}, @code{read-event} waits as long as | |
2424 | necessary for input to arrive. | |
2425 | ||
2426 | If @var{seconds} is @code{nil}, Emacs is considered idle while waiting | |
2427 | for user input to arrive. Idle timers---those created with | |
2428 | @code{run-with-idle-timer} (@pxref{Idle Timers})---can run during this | |
2429 | period. However, if @var{seconds} is non-@code{nil}, the state of | |
2430 | idleness remains unchanged. If Emacs is non-idle when | |
2431 | @code{read-event} is called, it remains non-idle throughout the | |
2432 | operation of @code{read-event}; if Emacs is idle (which can happen if | |
2433 | the call happens inside an idle timer), it remains idle. | |
2434 | ||
2435 | If @code{read-event} gets an event that is defined as a help character, | |
2436 | then in some cases @code{read-event} processes the event directly without | |
2437 | returning. @xref{Help Functions}. Certain other events, called | |
2438 | @dfn{special events}, are also processed directly within | |
2439 | @code{read-event} (@pxref{Special Events}). | |
2440 | ||
2441 | Here is what happens if you call @code{read-event} and then press the | |
2442 | right-arrow function key: | |
2443 | ||
2444 | @example | |
2445 | @group | |
2446 | (read-event) | |
2447 | @result{} right | |
2448 | @end group | |
2449 | @end example | |
2450 | @end defun | |
2451 | ||
2452 | @defun read-char &optional prompt inherit-input-method seconds | |
2453 | This function reads and returns a character of command input. If the | |
1df7defd | 2454 | user generates an event which is not a character (i.e., a mouse click or |
b8d4c8d0 GM |
2455 | function key event), @code{read-char} signals an error. The arguments |
2456 | work as in @code{read-event}. | |
2457 | ||
2458 | In the first example, the user types the character @kbd{1} (@acronym{ASCII} | |
2459 | code 49). The second example shows a keyboard macro definition that | |
2460 | calls @code{read-char} from the minibuffer using @code{eval-expression}. | |
2461 | @code{read-char} reads the keyboard macro's very next character, which | |
2462 | is @kbd{1}. Then @code{eval-expression} displays its return value in | |
2463 | the echo area. | |
2464 | ||
2465 | @example | |
2466 | @group | |
2467 | (read-char) | |
2468 | @result{} 49 | |
2469 | @end group | |
2470 | ||
2471 | @group | |
2472 | ;; @r{We assume here you use @kbd{M-:} to evaluate this.} | |
2473 | (symbol-function 'foo) | |
2474 | @result{} "^[:(read-char)^M1" | |
2475 | @end group | |
2476 | @group | |
2477 | (execute-kbd-macro 'foo) | |
2478 | @print{} 49 | |
2479 | @result{} nil | |
2480 | @end group | |
2481 | @end example | |
2482 | @end defun | |
2483 | ||
2484 | @defun read-char-exclusive &optional prompt inherit-input-method seconds | |
2485 | This function reads and returns a character of command input. If the | |
2486 | user generates an event which is not a character, | |
2487 | @code{read-char-exclusive} ignores it and reads another event, until it | |
2488 | gets a character. The arguments work as in @code{read-event}. | |
2489 | @end defun | |
2490 | ||
eb5ed549 CY |
2491 | None of the above functions suppress quitting. |
2492 | ||
b8d4c8d0 GM |
2493 | @defvar num-nonmacro-input-events |
2494 | This variable holds the total number of input events received so far | |
2495 | from the terminal---not counting those generated by keyboard macros. | |
2496 | @end defvar | |
2497 | ||
eb5ed549 CY |
2498 | We emphasize that, unlike @code{read-key-sequence}, the functions |
2499 | @code{read-event}, @code{read-char}, and @code{read-char-exclusive} do | |
2500 | not perform the translations described in @ref{Translation Keymaps}. | |
2501 | If you wish to read a single key taking these translations into | |
2502 | account, use the function @code{read-key}: | |
2503 | ||
2504 | @defun read-key &optional prompt | |
2505 | This function reads a single key. It is ``intermediate'' between | |
2506 | @code{read-key-sequence} and @code{read-event}. Unlike the former, it | |
2507 | reads a single key, not a key sequence. Unlike the latter, it does | |
2508 | not return a raw event, but decodes and translates the user input | |
2509 | according to @code{input-decode-map}, @code{local-function-key-map}, | |
2510 | and @code{key-translation-map} (@pxref{Translation Keymaps}). | |
2511 | ||
2512 | The argument @var{prompt} is either a string to be displayed in the | |
2513 | echo area as a prompt, or @code{nil}, meaning not to display a prompt. | |
2514 | @end defun | |
2515 | ||
7e2734bc GM |
2516 | @defun read-char-choice prompt chars &optional inhibit-quit |
2517 | This function uses @code{read-key} to read and return a single | |
2518 | character. It ignores any input that is not a member of @var{chars}, | |
2519 | a list of accepted characters. Optionally, it will also ignore | |
2520 | keyboard-quit events while it is waiting for valid input. If you bind | |
2521 | @code{help-form} (@pxref{Help Functions}) to a non-@code{nil} value | |
2522 | while calling @code{read-char-choice}, then pressing @code{help-char} | |
2523 | causes it to evaluate @code{help-form} and display the result. It | |
2524 | then continues to wait for a valid input character, or keyboard-quit. | |
2525 | @end defun | |
2526 | ||
b8d4c8d0 GM |
2527 | @node Event Mod |
2528 | @subsection Modifying and Translating Input Events | |
2529 | ||
2530 | Emacs modifies every event it reads according to | |
2531 | @code{extra-keyboard-modifiers}, then translates it through | |
2532 | @code{keyboard-translate-table} (if applicable), before returning it | |
2533 | from @code{read-event}. | |
2534 | ||
b8d4c8d0 GM |
2535 | @defvar extra-keyboard-modifiers |
2536 | This variable lets Lisp programs ``press'' the modifier keys on the | |
2537 | keyboard. The value is a character. Only the modifiers of the | |
2538 | character matter. Each time the user types a keyboard key, it is | |
2539 | altered as if those modifier keys were held down. For instance, if | |
2540 | you bind @code{extra-keyboard-modifiers} to @code{?\C-\M-a}, then all | |
2541 | keyboard input characters typed during the scope of the binding will | |
2542 | have the control and meta modifiers applied to them. The character | |
2543 | @code{?\C-@@}, equivalent to the integer 0, does not count as a control | |
2544 | character for this purpose, but as a character with no modifiers. | |
2545 | Thus, setting @code{extra-keyboard-modifiers} to zero cancels any | |
2546 | modification. | |
2547 | ||
2548 | When using a window system, the program can ``press'' any of the | |
2549 | modifier keys in this way. Otherwise, only the @key{CTL} and @key{META} | |
2550 | keys can be virtually pressed. | |
2551 | ||
2552 | Note that this variable applies only to events that really come from | |
2553 | the keyboard, and has no effect on mouse events or any other events. | |
2554 | @end defvar | |
2555 | ||
2556 | @defvar keyboard-translate-table | |
d3ae77bc EZ |
2557 | This terminal-local variable is the translate table for keyboard |
2558 | characters. It lets you reshuffle the keys on the keyboard without | |
2559 | changing any command bindings. Its value is normally a char-table, or | |
2560 | else @code{nil}. (It can also be a string or vector, but this is | |
2561 | considered obsolete.) | |
b8d4c8d0 GM |
2562 | |
2563 | If @code{keyboard-translate-table} is a char-table | |
2564 | (@pxref{Char-Tables}), then each character read from the keyboard is | |
2565 | looked up in this char-table. If the value found there is | |
2566 | non-@code{nil}, then it is used instead of the actual input character. | |
2567 | ||
2568 | Note that this translation is the first thing that happens to a | |
2569 | character after it is read from the terminal. Record-keeping features | |
2570 | such as @code{recent-keys} and dribble files record the characters after | |
2571 | translation. | |
2572 | ||
2573 | Note also that this translation is done before the characters are | |
a894169f EZ |
2574 | supplied to input methods (@pxref{Input Methods}). Use |
2575 | @code{translation-table-for-input} (@pxref{Translation of Characters}), | |
2576 | if you want to translate characters after input methods operate. | |
b8d4c8d0 GM |
2577 | @end defvar |
2578 | ||
2579 | @defun keyboard-translate from to | |
2580 | This function modifies @code{keyboard-translate-table} to translate | |
2581 | character code @var{from} into character code @var{to}. It creates | |
2582 | the keyboard translate table if necessary. | |
2583 | @end defun | |
2584 | ||
2585 | Here's an example of using the @code{keyboard-translate-table} to | |
2586 | make @kbd{C-x}, @kbd{C-c} and @kbd{C-v} perform the cut, copy and paste | |
2587 | operations: | |
2588 | ||
2589 | @example | |
2590 | (keyboard-translate ?\C-x 'control-x) | |
2591 | (keyboard-translate ?\C-c 'control-c) | |
2592 | (keyboard-translate ?\C-v 'control-v) | |
2593 | (global-set-key [control-x] 'kill-region) | |
2594 | (global-set-key [control-c] 'kill-ring-save) | |
2595 | (global-set-key [control-v] 'yank) | |
2596 | @end example | |
2597 | ||
2598 | @noindent | |
2599 | On a graphical terminal that supports extended @acronym{ASCII} input, | |
2600 | you can still get the standard Emacs meanings of one of those | |
2601 | characters by typing it with the shift key. That makes it a different | |
2602 | character as far as keyboard translation is concerned, but it has the | |
2603 | same usual meaning. | |
2604 | ||
2605 | @xref{Translation Keymaps}, for mechanisms that translate event sequences | |
2606 | at the level of @code{read-key-sequence}. | |
2607 | ||
2608 | @node Invoking the Input Method | |
2609 | @subsection Invoking the Input Method | |
2610 | ||
2611 | The event-reading functions invoke the current input method, if any | |
2612 | (@pxref{Input Methods}). If the value of @code{input-method-function} | |
2613 | is non-@code{nil}, it should be a function; when @code{read-event} reads | |
2614 | a printing character (including @key{SPC}) with no modifier bits, it | |
2615 | calls that function, passing the character as an argument. | |
2616 | ||
2617 | @defvar input-method-function | |
2618 | If this is non-@code{nil}, its value specifies the current input method | |
2619 | function. | |
2620 | ||
2621 | @strong{Warning:} don't bind this variable with @code{let}. It is often | |
2622 | buffer-local, and if you bind it around reading input (which is exactly | |
2623 | when you @emph{would} bind it), switching buffers asynchronously while | |
2624 | Emacs is waiting will cause the value to be restored in the wrong | |
2625 | buffer. | |
2626 | @end defvar | |
2627 | ||
2628 | The input method function should return a list of events which should | |
2629 | be used as input. (If the list is @code{nil}, that means there is no | |
2630 | input, so @code{read-event} waits for another event.) These events are | |
2631 | processed before the events in @code{unread-command-events} | |
2632 | (@pxref{Event Input Misc}). Events | |
2633 | returned by the input method function are not passed to the input method | |
2634 | function again, even if they are printing characters with no modifier | |
2635 | bits. | |
2636 | ||
2637 | If the input method function calls @code{read-event} or | |
2638 | @code{read-key-sequence}, it should bind @code{input-method-function} to | |
2639 | @code{nil} first, to prevent recursion. | |
2640 | ||
2641 | The input method function is not called when reading the second and | |
2642 | subsequent events of a key sequence. Thus, these characters are not | |
2643 | subject to input method processing. The input method function should | |
2644 | test the values of @code{overriding-local-map} and | |
2645 | @code{overriding-terminal-local-map}; if either of these variables is | |
2646 | non-@code{nil}, the input method should put its argument into a list and | |
2647 | return that list with no further processing. | |
2648 | ||
2649 | @node Quoted Character Input | |
2650 | @subsection Quoted Character Input | |
2651 | @cindex quoted character input | |
2652 | ||
2653 | You can use the function @code{read-quoted-char} to ask the user to | |
2654 | specify a character, and allow the user to specify a control or meta | |
2655 | character conveniently, either literally or as an octal character code. | |
2656 | The command @code{quoted-insert} uses this function. | |
2657 | ||
2658 | @defun read-quoted-char &optional prompt | |
2659 | @cindex octal character input | |
2660 | @cindex control characters, reading | |
2661 | @cindex nonprinting characters, reading | |
2662 | This function is like @code{read-char}, except that if the first | |
2663 | character read is an octal digit (0-7), it reads any number of octal | |
2664 | digits (but stopping if a non-octal digit is found), and returns the | |
2665 | character represented by that numeric character code. If the | |
2666 | character that terminates the sequence of octal digits is @key{RET}, | |
2667 | it is discarded. Any other terminating character is used as input | |
2668 | after this function returns. | |
2669 | ||
2670 | Quitting is suppressed when the first character is read, so that the | |
2671 | user can enter a @kbd{C-g}. @xref{Quitting}. | |
2672 | ||
2673 | If @var{prompt} is supplied, it specifies a string for prompting the | |
2674 | user. The prompt string is always displayed in the echo area, followed | |
2675 | by a single @samp{-}. | |
2676 | ||
2677 | In the following example, the user types in the octal number 177 (which | |
2678 | is 127 in decimal). | |
2679 | ||
2680 | @example | |
2681 | (read-quoted-char "What character") | |
2682 | ||
2683 | @group | |
2684 | ---------- Echo Area ---------- | |
2685 | What character @kbd{1 7 7}- | |
2686 | ---------- Echo Area ---------- | |
2687 | ||
2688 | @result{} 127 | |
2689 | @end group | |
2690 | @end example | |
2691 | @end defun | |
2692 | ||
2693 | @need 2000 | |
2694 | @node Event Input Misc | |
2695 | @subsection Miscellaneous Event Input Features | |
2696 | ||
2697 | This section describes how to ``peek ahead'' at events without using | |
2698 | them up, how to check for pending input, and how to discard pending | |
2699 | input. See also the function @code{read-passwd} (@pxref{Reading a | |
2700 | Password}). | |
2701 | ||
2702 | @defvar unread-command-events | |
2703 | @cindex next input | |
2704 | @cindex peeking at input | |
2705 | This variable holds a list of events waiting to be read as command | |
2706 | input. The events are used in the order they appear in the list, and | |
2707 | removed one by one as they are used. | |
2708 | ||
2709 | The variable is needed because in some cases a function reads an event | |
2710 | and then decides not to use it. Storing the event in this variable | |
2711 | causes it to be processed normally, by the command loop or by the | |
2712 | functions to read command input. | |
2713 | ||
2714 | @cindex prefix argument unreading | |
2715 | For example, the function that implements numeric prefix arguments reads | |
2716 | any number of digits. When it finds a non-digit event, it must unread | |
2717 | the event so that it can be read normally by the command loop. | |
2718 | Likewise, incremental search uses this feature to unread events with no | |
2719 | special meaning in a search, because these events should exit the search | |
2720 | and then execute normally. | |
2721 | ||
34106abe CY |
2722 | The reliable and easy way to extract events from a key sequence so as |
2723 | to put them in @code{unread-command-events} is to use | |
2724 | @code{listify-key-sequence} (see below). | |
b8d4c8d0 GM |
2725 | |
2726 | Normally you add events to the front of this list, so that the events | |
2727 | most recently unread will be reread first. | |
2728 | ||
2729 | Events read from this list are not normally added to the current | |
1df7defd | 2730 | command's key sequence (as returned by, e.g., @code{this-command-keys}), |
b8d4c8d0 GM |
2731 | as the events will already have been added once as they were read for |
2732 | the first time. An element of the form @code{(@code{t} . @var{event})} | |
2733 | forces @var{event} to be added to the current command's key sequence. | |
2734 | @end defvar | |
2735 | ||
2736 | @defun listify-key-sequence key | |
2737 | This function converts the string or vector @var{key} to a list of | |
2738 | individual events, which you can put in @code{unread-command-events}. | |
2739 | @end defun | |
2740 | ||
b8d4c8d0 GM |
2741 | @defun input-pending-p |
2742 | @cindex waiting for command key input | |
2743 | This function determines whether any command input is currently | |
2744 | available to be read. It returns immediately, with value @code{t} if | |
2745 | there is available input, @code{nil} otherwise. On rare occasions it | |
2746 | may return @code{t} when no input is available. | |
2747 | @end defun | |
2748 | ||
2749 | @defvar last-input-event | |
b8d4c8d0 GM |
2750 | This variable records the last terminal input event read, whether |
2751 | as part of a command or explicitly by a Lisp program. | |
2752 | ||
2753 | In the example below, the Lisp program reads the character @kbd{1}, | |
2754 | @acronym{ASCII} code 49. It becomes the value of @code{last-input-event}, | |
2755 | while @kbd{C-e} (we assume @kbd{C-x C-e} command is used to evaluate | |
2756 | this expression) remains the value of @code{last-command-event}. | |
2757 | ||
2758 | @example | |
2759 | @group | |
2760 | (progn (print (read-char)) | |
2761 | (print last-command-event) | |
2762 | last-input-event) | |
2763 | @print{} 49 | |
2764 | @print{} 5 | |
2765 | @result{} 49 | |
2766 | @end group | |
2767 | @end example | |
b8d4c8d0 GM |
2768 | @end defvar |
2769 | ||
2770 | @defmac while-no-input body@dots{} | |
2771 | This construct runs the @var{body} forms and returns the value of the | |
2772 | last one---but only if no input arrives. If any input arrives during | |
2773 | the execution of the @var{body} forms, it aborts them (working much | |
2774 | like a quit). The @code{while-no-input} form returns @code{nil} if | |
2775 | aborted by a real quit, and returns @code{t} if aborted by arrival of | |
2776 | other input. | |
2777 | ||
2778 | If a part of @var{body} binds @code{inhibit-quit} to non-@code{nil}, | |
2779 | arrival of input during those parts won't cause an abort until | |
2780 | the end of that part. | |
2781 | ||
2782 | If you want to be able to distinguish all possible values computed | |
2783 | by @var{body} from both kinds of abort conditions, write the code | |
2784 | like this: | |
2785 | ||
2786 | @example | |
2787 | (while-no-input | |
2788 | (list | |
2789 | (progn . @var{body}))) | |
2790 | @end example | |
2791 | @end defmac | |
2792 | ||
2793 | @defun discard-input | |
2794 | @cindex flushing input | |
2795 | @cindex discarding input | |
2796 | @cindex keyboard macro, terminating | |
2797 | This function discards the contents of the terminal input buffer and | |
2798 | cancels any keyboard macro that might be in the process of definition. | |
2799 | It returns @code{nil}. | |
2800 | ||
2801 | In the following example, the user may type a number of characters right | |
2802 | after starting the evaluation of the form. After the @code{sleep-for} | |
2803 | finishes sleeping, @code{discard-input} discards any characters typed | |
2804 | during the sleep. | |
2805 | ||
2806 | @example | |
2807 | (progn (sleep-for 2) | |
2808 | (discard-input)) | |
2809 | @result{} nil | |
2810 | @end example | |
2811 | @end defun | |
2812 | ||
2813 | @node Special Events | |
2814 | @section Special Events | |
2815 | ||
2816 | @cindex special events | |
34106abe CY |
2817 | Certain @dfn{special events} are handled at a very low level---as soon |
2818 | as they are read. The @code{read-event} function processes these | |
2819 | events itself, and never returns them. Instead, it keeps waiting for | |
2820 | the first event that is not special and returns that one. | |
b8d4c8d0 | 2821 | |
34106abe CY |
2822 | Special events do not echo, they are never grouped into key |
2823 | sequences, and they never appear in the value of | |
b8d4c8d0 GM |
2824 | @code{last-command-event} or @code{(this-command-keys)}. They do not |
2825 | discard a numeric argument, they cannot be unread with | |
2826 | @code{unread-command-events}, they may not appear in a keyboard macro, | |
2827 | and they are not recorded in a keyboard macro while you are defining | |
2828 | one. | |
2829 | ||
34106abe CY |
2830 | Special events do, however, appear in @code{last-input-event} |
2831 | immediately after they are read, and this is the way for the event's | |
2832 | definition to find the actual event. | |
b8d4c8d0 | 2833 | |
34106abe | 2834 | The events types @code{iconify-frame}, @code{make-frame-visible}, |
1ada2e55 EZ |
2835 | @code{delete-frame}, @code{drag-n-drop}, @code{language-change}, and |
2836 | user signals like @code{sigusr1} are normally handled in this way. | |
2837 | The keymap which defines how to handle special events---and which | |
2838 | events are special---is in the variable @code{special-event-map} | |
2839 | (@pxref{Active Keymaps}). | |
b8d4c8d0 GM |
2840 | |
2841 | @node Waiting | |
2842 | @section Waiting for Elapsed Time or Input | |
2843 | @cindex waiting | |
2844 | ||
2845 | The wait functions are designed to wait for a certain amount of time | |
2846 | to pass or until there is input. For example, you may wish to pause in | |
2847 | the middle of a computation to allow the user time to view the display. | |
2848 | @code{sit-for} pauses and updates the screen, and returns immediately if | |
2849 | input comes in, while @code{sleep-for} pauses without updating the | |
2850 | screen. | |
2851 | ||
2852 | @defun sit-for seconds &optional nodisp | |
2853 | This function performs redisplay (provided there is no pending input | |
2854 | from the user), then waits @var{seconds} seconds, or until input is | |
2855 | available. The usual purpose of @code{sit-for} is to give the user | |
2856 | time to read text that you display. The value is @code{t} if | |
2857 | @code{sit-for} waited the full time with no input arriving | |
2858 | (@pxref{Event Input Misc}). Otherwise, the value is @code{nil}. | |
2859 | ||
2860 | The argument @var{seconds} need not be an integer. If it is a floating | |
2861 | point number, @code{sit-for} waits for a fractional number of seconds. | |
2862 | Some systems support only a whole number of seconds; on these systems, | |
2863 | @var{seconds} is rounded down. | |
2864 | ||
2865 | The expression @code{(sit-for 0)} is equivalent to @code{(redisplay)}, | |
1df7defd | 2866 | i.e., it requests a redisplay, without any delay, if there is no pending input. |
b8d4c8d0 GM |
2867 | @xref{Forcing Redisplay}. |
2868 | ||
2869 | If @var{nodisp} is non-@code{nil}, then @code{sit-for} does not | |
2870 | redisplay, but it still returns as soon as input is available (or when | |
2871 | the timeout elapses). | |
2872 | ||
2873 | In batch mode (@pxref{Batch Mode}), @code{sit-for} cannot be | |
2874 | interrupted, even by input from the standard input descriptor. It is | |
2875 | thus equivalent to @code{sleep-for}, which is described below. | |
2876 | ||
2877 | It is also possible to call @code{sit-for} with three arguments, | |
2878 | as @code{(sit-for @var{seconds} @var{millisec} @var{nodisp})}, | |
2879 | but that is considered obsolete. | |
2880 | @end defun | |
2881 | ||
2882 | @defun sleep-for seconds &optional millisec | |
2883 | This function simply pauses for @var{seconds} seconds without updating | |
2884 | the display. It pays no attention to available input. It returns | |
2885 | @code{nil}. | |
2886 | ||
2887 | The argument @var{seconds} need not be an integer. If it is a floating | |
2888 | point number, @code{sleep-for} waits for a fractional number of seconds. | |
2889 | Some systems support only a whole number of seconds; on these systems, | |
2890 | @var{seconds} is rounded down. | |
2891 | ||
2892 | The optional argument @var{millisec} specifies an additional waiting | |
2893 | period measured in milliseconds. This adds to the period specified by | |
2894 | @var{seconds}. If the system doesn't support waiting fractions of a | |
2895 | second, you get an error if you specify nonzero @var{millisec}. | |
2896 | ||
2897 | Use @code{sleep-for} when you wish to guarantee a delay. | |
2898 | @end defun | |
2899 | ||
2900 | @xref{Time of Day}, for functions to get the current time. | |
2901 | ||
2902 | @node Quitting | |
2903 | @section Quitting | |
2904 | @cindex @kbd{C-g} | |
2905 | @cindex quitting | |
2906 | @cindex interrupt Lisp functions | |
2907 | ||
2908 | Typing @kbd{C-g} while a Lisp function is running causes Emacs to | |
2909 | @dfn{quit} whatever it is doing. This means that control returns to the | |
2910 | innermost active command loop. | |
2911 | ||
2912 | Typing @kbd{C-g} while the command loop is waiting for keyboard input | |
2913 | does not cause a quit; it acts as an ordinary input character. In the | |
2914 | simplest case, you cannot tell the difference, because @kbd{C-g} | |
2915 | normally runs the command @code{keyboard-quit}, whose effect is to quit. | |
2916 | However, when @kbd{C-g} follows a prefix key, they combine to form an | |
2917 | undefined key. The effect is to cancel the prefix key as well as any | |
2918 | prefix argument. | |
2919 | ||
2920 | In the minibuffer, @kbd{C-g} has a different definition: it aborts out | |
2921 | of the minibuffer. This means, in effect, that it exits the minibuffer | |
2922 | and then quits. (Simply quitting would return to the command loop | |
2923 | @emph{within} the minibuffer.) The reason why @kbd{C-g} does not quit | |
2924 | directly when the command reader is reading input is so that its meaning | |
2925 | can be redefined in the minibuffer in this way. @kbd{C-g} following a | |
2926 | prefix key is not redefined in the minibuffer, and it has its normal | |
2927 | effect of canceling the prefix key and prefix argument. This too | |
2928 | would not be possible if @kbd{C-g} always quit directly. | |
2929 | ||
2930 | When @kbd{C-g} does directly quit, it does so by setting the variable | |
2931 | @code{quit-flag} to @code{t}. Emacs checks this variable at appropriate | |
2932 | times and quits if it is not @code{nil}. Setting @code{quit-flag} | |
2933 | non-@code{nil} in any way thus causes a quit. | |
2934 | ||
2935 | At the level of C code, quitting cannot happen just anywhere; only at the | |
2936 | special places that check @code{quit-flag}. The reason for this is | |
2937 | that quitting at other places might leave an inconsistency in Emacs's | |
2938 | internal state. Because quitting is delayed until a safe place, quitting | |
2939 | cannot make Emacs crash. | |
2940 | ||
2941 | Certain functions such as @code{read-key-sequence} or | |
2942 | @code{read-quoted-char} prevent quitting entirely even though they wait | |
2943 | for input. Instead of quitting, @kbd{C-g} serves as the requested | |
2944 | input. In the case of @code{read-key-sequence}, this serves to bring | |
2945 | about the special behavior of @kbd{C-g} in the command loop. In the | |
2946 | case of @code{read-quoted-char}, this is so that @kbd{C-q} can be used | |
2947 | to quote a @kbd{C-g}. | |
2948 | ||
2949 | @cindex preventing quitting | |
2950 | You can prevent quitting for a portion of a Lisp function by binding | |
2951 | the variable @code{inhibit-quit} to a non-@code{nil} value. Then, | |
2952 | although @kbd{C-g} still sets @code{quit-flag} to @code{t} as usual, the | |
2953 | usual result of this---a quit---is prevented. Eventually, | |
2954 | @code{inhibit-quit} will become @code{nil} again, such as when its | |
2955 | binding is unwound at the end of a @code{let} form. At that time, if | |
2956 | @code{quit-flag} is still non-@code{nil}, the requested quit happens | |
2957 | immediately. This behavior is ideal when you wish to make sure that | |
2958 | quitting does not happen within a ``critical section'' of the program. | |
2959 | ||
2960 | @cindex @code{read-quoted-char} quitting | |
2961 | In some functions (such as @code{read-quoted-char}), @kbd{C-g} is | |
2962 | handled in a special way that does not involve quitting. This is done | |
2963 | by reading the input with @code{inhibit-quit} bound to @code{t}, and | |
2964 | setting @code{quit-flag} to @code{nil} before @code{inhibit-quit} | |
2965 | becomes @code{nil} again. This excerpt from the definition of | |
2966 | @code{read-quoted-char} shows how this is done; it also shows that | |
2967 | normal quitting is permitted after the first character of input. | |
2968 | ||
2969 | @example | |
2970 | (defun read-quoted-char (&optional prompt) | |
2971 | "@dots{}@var{documentation}@dots{}" | |
2972 | (let ((message-log-max nil) done (first t) (code 0) char) | |
2973 | (while (not done) | |
2974 | (let ((inhibit-quit first) | |
2975 | @dots{}) | |
d24880de GM |
2976 | (and prompt (message "%s-" prompt)) |
2977 | (setq char (read-event)) | |
2978 | (if inhibit-quit (setq quit-flag nil))) | |
b8d4c8d0 GM |
2979 | @r{@dots{}set the variable @code{code}@dots{}}) |
2980 | code)) | |
2981 | @end example | |
2982 | ||
2983 | @defvar quit-flag | |
2984 | If this variable is non-@code{nil}, then Emacs quits immediately, unless | |
2985 | @code{inhibit-quit} is non-@code{nil}. Typing @kbd{C-g} ordinarily sets | |
2986 | @code{quit-flag} non-@code{nil}, regardless of @code{inhibit-quit}. | |
2987 | @end defvar | |
2988 | ||
2989 | @defvar inhibit-quit | |
2990 | This variable determines whether Emacs should quit when @code{quit-flag} | |
2991 | is set to a value other than @code{nil}. If @code{inhibit-quit} is | |
2992 | non-@code{nil}, then @code{quit-flag} has no special effect. | |
2993 | @end defvar | |
2994 | ||
2995 | @defmac with-local-quit body@dots{} | |
2996 | This macro executes @var{body} forms in sequence, but allows quitting, at | |
2997 | least locally, within @var{body} even if @code{inhibit-quit} was | |
2998 | non-@code{nil} outside this construct. It returns the value of the | |
2999 | last form in @var{body}, unless exited by quitting, in which case | |
3000 | it returns @code{nil}. | |
3001 | ||
3002 | If @code{inhibit-quit} is @code{nil} on entry to @code{with-local-quit}, | |
3003 | it only executes the @var{body}, and setting @code{quit-flag} causes | |
3004 | a normal quit. However, if @code{inhibit-quit} is non-@code{nil} so | |
3005 | that ordinary quitting is delayed, a non-@code{nil} @code{quit-flag} | |
3006 | triggers a special kind of local quit. This ends the execution of | |
3007 | @var{body} and exits the @code{with-local-quit} body with | |
3008 | @code{quit-flag} still non-@code{nil}, so that another (ordinary) quit | |
3009 | will happen as soon as that is allowed. If @code{quit-flag} is | |
3010 | already non-@code{nil} at the beginning of @var{body}, the local quit | |
3011 | happens immediately and the body doesn't execute at all. | |
3012 | ||
3013 | This macro is mainly useful in functions that can be called from | |
3014 | timers, process filters, process sentinels, @code{pre-command-hook}, | |
3015 | @code{post-command-hook}, and other places where @code{inhibit-quit} is | |
3016 | normally bound to @code{t}. | |
3017 | @end defmac | |
3018 | ||
3019 | @deffn Command keyboard-quit | |
3020 | This function signals the @code{quit} condition with @code{(signal 'quit | |
3021 | nil)}. This is the same thing that quitting does. (See @code{signal} | |
3022 | in @ref{Errors}.) | |
3023 | @end deffn | |
3024 | ||
3025 | You can specify a character other than @kbd{C-g} to use for quitting. | |
3026 | See the function @code{set-input-mode} in @ref{Terminal Input}. | |
3027 | ||
3028 | @node Prefix Command Arguments | |
3029 | @section Prefix Command Arguments | |
3030 | @cindex prefix argument | |
3031 | @cindex raw prefix argument | |
3032 | @cindex numeric prefix argument | |
3033 | ||
3034 | Most Emacs commands can use a @dfn{prefix argument}, a number | |
3035 | specified before the command itself. (Don't confuse prefix arguments | |
3036 | with prefix keys.) The prefix argument is at all times represented by a | |
3037 | value, which may be @code{nil}, meaning there is currently no prefix | |
3038 | argument. Each command may use the prefix argument or ignore it. | |
3039 | ||
3040 | There are two representations of the prefix argument: @dfn{raw} and | |
3041 | @dfn{numeric}. The editor command loop uses the raw representation | |
3042 | internally, and so do the Lisp variables that store the information, but | |
3043 | commands can request either representation. | |
3044 | ||
3045 | Here are the possible values of a raw prefix argument: | |
3046 | ||
3047 | @itemize @bullet | |
3048 | @item | |
3049 | @code{nil}, meaning there is no prefix argument. Its numeric value is | |
3050 | 1, but numerous commands make a distinction between @code{nil} and the | |
3051 | integer 1. | |
3052 | ||
3053 | @item | |
3054 | An integer, which stands for itself. | |
3055 | ||
3056 | @item | |
3057 | A list of one element, which is an integer. This form of prefix | |
07151e49 | 3058 | argument results from one or a succession of @kbd{C-u}s with no |
b8d4c8d0 GM |
3059 | digits. The numeric value is the integer in the list, but some |
3060 | commands make a distinction between such a list and an integer alone. | |
3061 | ||
3062 | @item | |
3063 | The symbol @code{-}. This indicates that @kbd{M--} or @kbd{C-u -} was | |
3064 | typed, without following digits. The equivalent numeric value is | |
3065 | @minus{}1, but some commands make a distinction between the integer | |
3066 | @minus{}1 and the symbol @code{-}. | |
3067 | @end itemize | |
3068 | ||
3069 | We illustrate these possibilities by calling the following function with | |
3070 | various prefixes: | |
3071 | ||
3072 | @example | |
3073 | @group | |
3074 | (defun display-prefix (arg) | |
3075 | "Display the value of the raw prefix arg." | |
3076 | (interactive "P") | |
3077 | (message "%s" arg)) | |
3078 | @end group | |
3079 | @end example | |
3080 | ||
3081 | @noindent | |
3082 | Here are the results of calling @code{display-prefix} with various | |
3083 | raw prefix arguments: | |
3084 | ||
3085 | @example | |
3086 | M-x display-prefix @print{} nil | |
3087 | ||
3088 | C-u M-x display-prefix @print{} (4) | |
3089 | ||
3090 | C-u C-u M-x display-prefix @print{} (16) | |
3091 | ||
3092 | C-u 3 M-x display-prefix @print{} 3 | |
3093 | ||
3094 | M-3 M-x display-prefix @print{} 3 ; @r{(Same as @code{C-u 3}.)} | |
3095 | ||
3096 | C-u - M-x display-prefix @print{} - | |
3097 | ||
3098 | M-- M-x display-prefix @print{} - ; @r{(Same as @code{C-u -}.)} | |
3099 | ||
3100 | C-u - 7 M-x display-prefix @print{} -7 | |
3101 | ||
3102 | M-- 7 M-x display-prefix @print{} -7 ; @r{(Same as @code{C-u -7}.)} | |
3103 | @end example | |
3104 | ||
3105 | Emacs uses two variables to store the prefix argument: | |
3106 | @code{prefix-arg} and @code{current-prefix-arg}. Commands such as | |
3107 | @code{universal-argument} that set up prefix arguments for other | |
3108 | commands store them in @code{prefix-arg}. In contrast, | |
3109 | @code{current-prefix-arg} conveys the prefix argument to the current | |
3110 | command, so setting it has no effect on the prefix arguments for future | |
3111 | commands. | |
3112 | ||
3113 | Normally, commands specify which representation to use for the prefix | |
3114 | argument, either numeric or raw, in the @code{interactive} specification. | |
3115 | (@xref{Using Interactive}.) Alternatively, functions may look at the | |
3116 | value of the prefix argument directly in the variable | |
3117 | @code{current-prefix-arg}, but this is less clean. | |
3118 | ||
3119 | @defun prefix-numeric-value arg | |
3120 | This function returns the numeric meaning of a valid raw prefix argument | |
3121 | value, @var{arg}. The argument may be a symbol, a number, or a list. | |
3122 | If it is @code{nil}, the value 1 is returned; if it is @code{-}, the | |
3123 | value @minus{}1 is returned; if it is a number, that number is returned; | |
3124 | if it is a list, the @sc{car} of that list (which should be a number) is | |
3125 | returned. | |
3126 | @end defun | |
3127 | ||
3128 | @defvar current-prefix-arg | |
3129 | This variable holds the raw prefix argument for the @emph{current} | |
3130 | command. Commands may examine it directly, but the usual method for | |
3131 | accessing it is with @code{(interactive "P")}. | |
3132 | @end defvar | |
3133 | ||
3134 | @defvar prefix-arg | |
3135 | The value of this variable is the raw prefix argument for the | |
3136 | @emph{next} editing command. Commands such as @code{universal-argument} | |
3137 | that specify prefix arguments for the following command work by setting | |
3138 | this variable. | |
3139 | @end defvar | |
3140 | ||
3141 | @defvar last-prefix-arg | |
3142 | The raw prefix argument value used by the previous command. | |
3143 | @end defvar | |
3144 | ||
3145 | The following commands exist to set up prefix arguments for the | |
3146 | following command. Do not call them for any other reason. | |
3147 | ||
3148 | @deffn Command universal-argument | |
3149 | This command reads input and specifies a prefix argument for the | |
3150 | following command. Don't call this command yourself unless you know | |
3151 | what you are doing. | |
3152 | @end deffn | |
3153 | ||
3154 | @deffn Command digit-argument arg | |
3155 | This command adds to the prefix argument for the following command. The | |
3156 | argument @var{arg} is the raw prefix argument as it was before this | |
3157 | command; it is used to compute the updated prefix argument. Don't call | |
3158 | this command yourself unless you know what you are doing. | |
3159 | @end deffn | |
3160 | ||
3161 | @deffn Command negative-argument arg | |
3162 | This command adds to the numeric argument for the next command. The | |
3163 | argument @var{arg} is the raw prefix argument as it was before this | |
3164 | command; its value is negated to form the new prefix argument. Don't | |
3165 | call this command yourself unless you know what you are doing. | |
3166 | @end deffn | |
3167 | ||
3168 | @node Recursive Editing | |
3169 | @section Recursive Editing | |
3170 | @cindex recursive command loop | |
3171 | @cindex recursive editing level | |
3172 | @cindex command loop, recursive | |
3173 | ||
3174 | The Emacs command loop is entered automatically when Emacs starts up. | |
3175 | This top-level invocation of the command loop never exits; it keeps | |
3176 | running as long as Emacs does. Lisp programs can also invoke the | |
3177 | command loop. Since this makes more than one activation of the command | |
3178 | loop, we call it @dfn{recursive editing}. A recursive editing level has | |
3179 | the effect of suspending whatever command invoked it and permitting the | |
3180 | user to do arbitrary editing before resuming that command. | |
3181 | ||
3182 | The commands available during recursive editing are the same ones | |
3183 | available in the top-level editing loop and defined in the keymaps. | |
3184 | Only a few special commands exit the recursive editing level; the others | |
3185 | return to the recursive editing level when they finish. (The special | |
3186 | commands for exiting are always available, but they do nothing when | |
3187 | recursive editing is not in progress.) | |
3188 | ||
3189 | All command loops, including recursive ones, set up all-purpose error | |
3190 | handlers so that an error in a command run from the command loop will | |
3191 | not exit the loop. | |
3192 | ||
3193 | @cindex minibuffer input | |
3194 | Minibuffer input is a special kind of recursive editing. It has a few | |
3195 | special wrinkles, such as enabling display of the minibuffer and the | |
3196 | minibuffer window, but fewer than you might suppose. Certain keys | |
3197 | behave differently in the minibuffer, but that is only because of the | |
3198 | minibuffer's local map; if you switch windows, you get the usual Emacs | |
3199 | commands. | |
3200 | ||
3201 | @cindex @code{throw} example | |
3202 | @kindex exit | |
3203 | @cindex exit recursive editing | |
3204 | @cindex aborting | |
3205 | To invoke a recursive editing level, call the function | |
3206 | @code{recursive-edit}. This function contains the command loop; it also | |
3207 | contains a call to @code{catch} with tag @code{exit}, which makes it | |
3208 | possible to exit the recursive editing level by throwing to @code{exit} | |
3209 | (@pxref{Catch and Throw}). If you throw a value other than @code{t}, | |
3210 | then @code{recursive-edit} returns normally to the function that called | |
3211 | it. The command @kbd{C-M-c} (@code{exit-recursive-edit}) does this. | |
3212 | Throwing a @code{t} value causes @code{recursive-edit} to quit, so that | |
3213 | control returns to the command loop one level up. This is called | |
3214 | @dfn{aborting}, and is done by @kbd{C-]} (@code{abort-recursive-edit}). | |
3215 | ||
3216 | Most applications should not use recursive editing, except as part of | |
3217 | using the minibuffer. Usually it is more convenient for the user if you | |
3218 | change the major mode of the current buffer temporarily to a special | |
3219 | major mode, which should have a command to go back to the previous mode. | |
3220 | (The @kbd{e} command in Rmail uses this technique.) Or, if you wish to | |
16152b76 | 3221 | give the user different text to edit ``recursively'', create and select |
b8d4c8d0 GM |
3222 | a new buffer in a special mode. In this mode, define a command to |
3223 | complete the processing and go back to the previous buffer. (The | |
3224 | @kbd{m} command in Rmail does this.) | |
3225 | ||
3226 | Recursive edits are useful in debugging. You can insert a call to | |
3227 | @code{debug} into a function definition as a sort of breakpoint, so that | |
3228 | you can look around when the function gets there. @code{debug} invokes | |
3229 | a recursive edit but also provides the other features of the debugger. | |
3230 | ||
3231 | Recursive editing levels are also used when you type @kbd{C-r} in | |
3232 | @code{query-replace} or use @kbd{C-x q} (@code{kbd-macro-query}). | |
3233 | ||
0b128ac4 | 3234 | @deffn Command recursive-edit |
b8d4c8d0 GM |
3235 | @cindex suspend evaluation |
3236 | This function invokes the editor command loop. It is called | |
3237 | automatically by the initialization of Emacs, to let the user begin | |
3238 | editing. When called from a Lisp program, it enters a recursive editing | |
3239 | level. | |
3240 | ||
3241 | If the current buffer is not the same as the selected window's buffer, | |
3242 | @code{recursive-edit} saves and restores the current buffer. Otherwise, | |
3243 | if you switch buffers, the buffer you switched to is current after | |
3244 | @code{recursive-edit} returns. | |
3245 | ||
3246 | In the following example, the function @code{simple-rec} first | |
3247 | advances point one word, then enters a recursive edit, printing out a | |
3248 | message in the echo area. The user can then do any editing desired, and | |
3249 | then type @kbd{C-M-c} to exit and continue executing @code{simple-rec}. | |
3250 | ||
3251 | @example | |
3252 | (defun simple-rec () | |
3253 | (forward-word 1) | |
3254 | (message "Recursive edit in progress") | |
3255 | (recursive-edit) | |
3256 | (forward-word 1)) | |
3257 | @result{} simple-rec | |
3258 | (simple-rec) | |
3259 | @result{} nil | |
3260 | @end example | |
0b128ac4 | 3261 | @end deffn |
b8d4c8d0 GM |
3262 | |
3263 | @deffn Command exit-recursive-edit | |
3264 | This function exits from the innermost recursive edit (including | |
3265 | minibuffer input). Its definition is effectively @code{(throw 'exit | |
3266 | nil)}. | |
3267 | @end deffn | |
3268 | ||
3269 | @deffn Command abort-recursive-edit | |
3270 | This function aborts the command that requested the innermost recursive | |
3271 | edit (including minibuffer input), by signaling @code{quit} | |
3272 | after exiting the recursive edit. Its definition is effectively | |
3273 | @code{(throw 'exit t)}. @xref{Quitting}. | |
3274 | @end deffn | |
3275 | ||
3276 | @deffn Command top-level | |
3277 | This function exits all recursive editing levels; it does not return a | |
3278 | value, as it jumps completely out of any computation directly back to | |
3279 | the main command loop. | |
3280 | @end deffn | |
3281 | ||
3282 | @defun recursion-depth | |
3283 | This function returns the current depth of recursive edits. When no | |
3284 | recursive edit is active, it returns 0. | |
3285 | @end defun | |
3286 | ||
3287 | @node Disabling Commands | |
3288 | @section Disabling Commands | |
3289 | @cindex disabled command | |
3290 | ||
3291 | @dfn{Disabling a command} marks the command as requiring user | |
3292 | confirmation before it can be executed. Disabling is used for commands | |
3293 | which might be confusing to beginning users, to prevent them from using | |
3294 | the commands by accident. | |
3295 | ||
3296 | @kindex disabled | |
3297 | The low-level mechanism for disabling a command is to put a | |
3298 | non-@code{nil} @code{disabled} property on the Lisp symbol for the | |
3299 | command. These properties are normally set up by the user's | |
3300 | init file (@pxref{Init File}) with Lisp expressions such as this: | |
3301 | ||
3302 | @example | |
3303 | (put 'upcase-region 'disabled t) | |
3304 | @end example | |
3305 | ||
3306 | @noindent | |
3307 | For a few commands, these properties are present by default (you can | |
3308 | remove them in your init file if you wish). | |
3309 | ||
3310 | If the value of the @code{disabled} property is a string, the message | |
3311 | saying the command is disabled includes that string. For example: | |
3312 | ||
3313 | @example | |
3314 | (put 'delete-region 'disabled | |
3315 | "Text deleted this way cannot be yanked back!\n") | |
3316 | @end example | |
3317 | ||
3318 | @xref{Disabling,,, emacs, The GNU Emacs Manual}, for the details on | |
3319 | what happens when a disabled command is invoked interactively. | |
3320 | Disabling a command has no effect on calling it as a function from Lisp | |
3321 | programs. | |
3322 | ||
3323 | @deffn Command enable-command command | |
3324 | Allow @var{command} (a symbol) to be executed without special | |
3325 | confirmation from now on, and alter the user's init file (@pxref{Init | |
3326 | File}) so that this will apply to future sessions. | |
3327 | @end deffn | |
3328 | ||
3329 | @deffn Command disable-command command | |
3330 | Require special confirmation to execute @var{command} from now on, and | |
3331 | alter the user's init file so that this will apply to future sessions. | |
3332 | @end deffn | |
3333 | ||
3334 | @defvar disabled-command-function | |
3335 | The value of this variable should be a function. When the user | |
3336 | invokes a disabled command interactively, this function is called | |
3337 | instead of the disabled command. It can use @code{this-command-keys} | |
3338 | to determine what the user typed to run the command, and thus find the | |
3339 | command itself. | |
3340 | ||
3341 | The value may also be @code{nil}. Then all commands work normally, | |
3342 | even disabled ones. | |
3343 | ||
3344 | By default, the value is a function that asks the user whether to | |
3345 | proceed. | |
3346 | @end defvar | |
3347 | ||
3348 | @node Command History | |
3349 | @section Command History | |
3350 | @cindex command history | |
3351 | @cindex complex command | |
3352 | @cindex history of commands | |
3353 | ||
3354 | The command loop keeps a history of the complex commands that have | |
3355 | been executed, to make it convenient to repeat these commands. A | |
3356 | @dfn{complex command} is one for which the interactive argument reading | |
3357 | uses the minibuffer. This includes any @kbd{M-x} command, any | |
3358 | @kbd{M-:} command, and any command whose @code{interactive} | |
3359 | specification reads an argument from the minibuffer. Explicit use of | |
3360 | the minibuffer during the execution of the command itself does not cause | |
3361 | the command to be considered complex. | |
3362 | ||
3363 | @defvar command-history | |
3364 | This variable's value is a list of recent complex commands, each | |
3365 | represented as a form to evaluate. It continues to accumulate all | |
3366 | complex commands for the duration of the editing session, but when it | |
3367 | reaches the maximum size (@pxref{Minibuffer History}), the oldest | |
3368 | elements are deleted as new ones are added. | |
3369 | ||
3370 | @example | |
3371 | @group | |
3372 | command-history | |
3373 | @result{} ((switch-to-buffer "chistory.texi") | |
3374 | (describe-key "^X^[") | |
3375 | (visit-tags-table "~/emacs/src/") | |
3376 | (find-tag "repeat-complex-command")) | |
3377 | @end group | |
3378 | @end example | |
3379 | @end defvar | |
3380 | ||
3381 | This history list is actually a special case of minibuffer history | |
3382 | (@pxref{Minibuffer History}), with one special twist: the elements are | |
3383 | expressions rather than strings. | |
3384 | ||
3385 | There are a number of commands devoted to the editing and recall of | |
3386 | previous commands. The commands @code{repeat-complex-command}, and | |
3387 | @code{list-command-history} are described in the user manual | |
3388 | (@pxref{Repetition,,, emacs, The GNU Emacs Manual}). Within the | |
3389 | minibuffer, the usual minibuffer history commands are available. | |
3390 | ||
3391 | @node Keyboard Macros | |
3392 | @section Keyboard Macros | |
3393 | @cindex keyboard macros | |
3394 | ||
3395 | A @dfn{keyboard macro} is a canned sequence of input events that can | |
3396 | be considered a command and made the definition of a key. The Lisp | |
3397 | representation of a keyboard macro is a string or vector containing the | |
3398 | events. Don't confuse keyboard macros with Lisp macros | |
3399 | (@pxref{Macros}). | |
3400 | ||
3401 | @defun execute-kbd-macro kbdmacro &optional count loopfunc | |
3402 | This function executes @var{kbdmacro} as a sequence of events. If | |
3403 | @var{kbdmacro} is a string or vector, then the events in it are executed | |
3404 | exactly as if they had been input by the user. The sequence is | |
3405 | @emph{not} expected to be a single key sequence; normally a keyboard | |
3406 | macro definition consists of several key sequences concatenated. | |
3407 | ||
3408 | If @var{kbdmacro} is a symbol, then its function definition is used in | |
3409 | place of @var{kbdmacro}. If that is another symbol, this process repeats. | |
3410 | Eventually the result should be a string or vector. If the result is | |
3411 | not a symbol, string, or vector, an error is signaled. | |
3412 | ||
3413 | The argument @var{count} is a repeat count; @var{kbdmacro} is executed that | |
3414 | many times. If @var{count} is omitted or @code{nil}, @var{kbdmacro} is | |
3415 | executed once. If it is 0, @var{kbdmacro} is executed over and over until it | |
3416 | encounters an error or a failing search. | |
3417 | ||
3418 | If @var{loopfunc} is non-@code{nil}, it is a function that is called, | |
3419 | without arguments, prior to each iteration of the macro. If | |
3420 | @var{loopfunc} returns @code{nil}, then this stops execution of the macro. | |
3421 | ||
3422 | @xref{Reading One Event}, for an example of using @code{execute-kbd-macro}. | |
3423 | @end defun | |
3424 | ||
3425 | @defvar executing-kbd-macro | |
3426 | This variable contains the string or vector that defines the keyboard | |
3427 | macro that is currently executing. It is @code{nil} if no macro is | |
3428 | currently executing. A command can test this variable so as to behave | |
3429 | differently when run from an executing macro. Do not set this variable | |
3430 | yourself. | |
3431 | @end defvar | |
3432 | ||
3433 | @defvar defining-kbd-macro | |
3434 | This variable is non-@code{nil} if and only if a keyboard macro is | |
3435 | being defined. A command can test this variable so as to behave | |
3436 | differently while a macro is being defined. The value is | |
3437 | @code{append} while appending to the definition of an existing macro. | |
3438 | The commands @code{start-kbd-macro}, @code{kmacro-start-macro} and | |
3439 | @code{end-kbd-macro} set this variable---do not set it yourself. | |
3440 | ||
3441 | The variable is always local to the current terminal and cannot be | |
3ec61d4e | 3442 | buffer-local. @xref{Multiple Terminals}. |
b8d4c8d0 GM |
3443 | @end defvar |
3444 | ||
3445 | @defvar last-kbd-macro | |
3446 | This variable is the definition of the most recently defined keyboard | |
3447 | macro. Its value is a string or vector, or @code{nil}. | |
3448 | ||
3449 | The variable is always local to the current terminal and cannot be | |
3ec61d4e | 3450 | buffer-local. @xref{Multiple Terminals}. |
b8d4c8d0 GM |
3451 | @end defvar |
3452 | ||
3453 | @defvar kbd-macro-termination-hook | |
2064cc6a GM |
3454 | This normal hook is run when a keyboard macro terminates, regardless |
3455 | of what caused it to terminate (reaching the macro end or an error | |
3456 | which ended the macro prematurely). | |
b8d4c8d0 | 3457 | @end defvar |