| 1 | @c -*-texinfo-*- |
| 2 | @c This is part of the GNU Emacs Lisp Reference Manual. |
| 3 | @c Copyright (C) 1990-1995, 1998-1999, 2001-2013 Free Software |
| 4 | @c Foundation, Inc. |
| 5 | @c See the file elisp.texi for copying conditions. |
| 6 | @node Command Loop |
| 7 | @chapter Command Loop |
| 8 | @cindex editor command loop |
| 9 | @cindex command loop |
| 10 | |
| 11 | When you run Emacs, it enters the @dfn{editor command loop} almost |
| 12 | immediately. This loop reads key sequences, executes their definitions, |
| 13 | and displays the results. In this chapter, we describe how these things |
| 14 | are done, and the subroutines that allow Lisp programs to do them. |
| 15 | |
| 16 | @menu |
| 17 | * Command Overview:: How the command loop reads commands. |
| 18 | * Defining Commands:: Specifying how a function should read arguments. |
| 19 | * Interactive Call:: Calling a command, so that it will read arguments. |
| 20 | * Distinguish Interactive:: Making a command distinguish interactive calls. |
| 21 | * Command Loop Info:: Variables set by the command loop for you to examine. |
| 22 | * Adjusting Point:: Adjustment of point after a command. |
| 23 | * Input Events:: What input looks like when you read it. |
| 24 | * Reading Input:: How to read input events from the keyboard or mouse. |
| 25 | * Special Events:: Events processed immediately and individually. |
| 26 | * Waiting:: Waiting for user input or elapsed time. |
| 27 | * Quitting:: How @kbd{C-g} works. How to catch or defer quitting. |
| 28 | * Prefix Command Arguments:: How the commands to set prefix args work. |
| 29 | * Recursive Editing:: Entering a recursive edit, |
| 30 | and why you usually shouldn't. |
| 31 | * Disabling Commands:: How the command loop handles disabled commands. |
| 32 | * Command History:: How the command history is set up, and how accessed. |
| 33 | * Keyboard Macros:: How keyboard macros are implemented. |
| 34 | @end menu |
| 35 | |
| 36 | @node Command Overview |
| 37 | @section Command Loop Overview |
| 38 | |
| 39 | The first thing the command loop must do is read a key sequence, |
| 40 | which is a sequence of input events that translates into a command. |
| 41 | It does this by calling the function @code{read-key-sequence}. Lisp |
| 42 | programs can also call this function (@pxref{Key Sequence Input}). |
| 43 | They can also read input at a lower level with @code{read-key} or |
| 44 | @code{read-event} (@pxref{Reading One Event}), or discard pending |
| 45 | input with @code{discard-input} (@pxref{Event Input Misc}). |
| 46 | |
| 47 | The key sequence is translated into a command through the currently |
| 48 | active keymaps. @xref{Key Lookup}, for information on how this is done. |
| 49 | The result should be a keyboard macro or an interactively callable |
| 50 | function. If the key is @kbd{M-x}, then it reads the name of another |
| 51 | command, which it then calls. This is done by the command |
| 52 | @code{execute-extended-command} (@pxref{Interactive Call}). |
| 53 | |
| 54 | Prior to executing the command, Emacs runs @code{undo-boundary} to |
| 55 | create an undo boundary. @xref{Maintaining Undo}. |
| 56 | |
| 57 | To execute a command, Emacs first reads its arguments by calling |
| 58 | @code{command-execute} (@pxref{Interactive Call}). For commands |
| 59 | written in Lisp, the @code{interactive} specification says how to read |
| 60 | the arguments. This may use the prefix argument (@pxref{Prefix |
| 61 | Command Arguments}) or may read with prompting in the minibuffer |
| 62 | (@pxref{Minibuffers}). For example, the command @code{find-file} has |
| 63 | an @code{interactive} specification which says to read a file name |
| 64 | using the minibuffer. The function body of @code{find-file} does not |
| 65 | use the minibuffer, so if you call @code{find-file} as a function from |
| 66 | Lisp code, you must supply the file name string as an ordinary Lisp |
| 67 | function argument. |
| 68 | |
| 69 | If the command is a keyboard macro (i.e., a string or vector), |
| 70 | Emacs executes it using @code{execute-kbd-macro} (@pxref{Keyboard |
| 71 | Macros}). |
| 72 | |
| 73 | @defvar pre-command-hook |
| 74 | This normal hook is run by the editor command loop before it executes |
| 75 | each command. At that time, @code{this-command} contains the command |
| 76 | that is about to run, and @code{last-command} describes the previous |
| 77 | command. @xref{Command Loop Info}. |
| 78 | @end defvar |
| 79 | |
| 80 | @defvar post-command-hook |
| 81 | This normal hook is run by the editor command loop after it executes |
| 82 | each command (including commands terminated prematurely by quitting or |
| 83 | by errors). At that time, @code{this-command} refers to the command |
| 84 | that just ran, and @code{last-command} refers to the command before |
| 85 | that. |
| 86 | |
| 87 | This hook is also run when Emacs first enters the command loop (at |
| 88 | which point @code{this-command} and @code{last-command} are both |
| 89 | @code{nil}). |
| 90 | @end defvar |
| 91 | |
| 92 | Quitting is suppressed while running @code{pre-command-hook} and |
| 93 | @code{post-command-hook}. If an error happens while executing one of |
| 94 | these hooks, it does not terminate execution of the hook; instead |
| 95 | the error is silenced and the function in which the error occurred |
| 96 | is removed from the hook. |
| 97 | |
| 98 | A request coming into the Emacs server (@pxref{Emacs Server,,, |
| 99 | emacs, The GNU Emacs Manual}) runs these two hooks just as a keyboard |
| 100 | command does. |
| 101 | |
| 102 | @node Defining Commands |
| 103 | @section Defining Commands |
| 104 | @cindex defining commands |
| 105 | @cindex commands, defining |
| 106 | @cindex functions, making them interactive |
| 107 | @cindex interactive function |
| 108 | |
| 109 | The special form @code{interactive} turns a Lisp function into a |
| 110 | command. The @code{interactive} form must be located at top-level in |
| 111 | the function body (usually as the first form in the body), or in the |
| 112 | @code{interactive-form} property of the function symbol. When the |
| 113 | @code{interactive} form is located in the function body, it does |
| 114 | nothing when actually executed. Its presence serves as a flag, which |
| 115 | tells the Emacs command loop that the function can be called |
| 116 | interactively. The argument of the @code{interactive} form controls |
| 117 | the reading of arguments for an interactive call. |
| 118 | |
| 119 | @menu |
| 120 | * Using Interactive:: General rules for @code{interactive}. |
| 121 | * Interactive Codes:: The standard letter-codes for reading arguments |
| 122 | in various ways. |
| 123 | * Interactive Examples:: Examples of how to read interactive arguments. |
| 124 | @end menu |
| 125 | |
| 126 | @node Using Interactive |
| 127 | @subsection Using @code{interactive} |
| 128 | @cindex arguments, interactive entry |
| 129 | |
| 130 | This section describes how to write the @code{interactive} form that |
| 131 | makes a Lisp function an interactively-callable command, and how to |
| 132 | examine a command's @code{interactive} form. |
| 133 | |
| 134 | @defspec interactive arg-descriptor |
| 135 | This special form declares that a function is a command, and that it |
| 136 | may therefore be called interactively (via @kbd{M-x} or by entering a |
| 137 | key sequence bound to it). The argument @var{arg-descriptor} declares |
| 138 | how to compute the arguments to the command when the command is called |
| 139 | interactively. |
| 140 | |
| 141 | A command may be called from Lisp programs like any other function, but |
| 142 | then the caller supplies the arguments and @var{arg-descriptor} has no |
| 143 | effect. |
| 144 | |
| 145 | @cindex @code{interactive-form}, symbol property |
| 146 | The @code{interactive} form must be located at top-level in the |
| 147 | function body, or in the function symbol's @code{interactive-form} |
| 148 | property (@pxref{Symbol Properties}). It has its effect because the |
| 149 | command loop looks for it before calling the function |
| 150 | (@pxref{Interactive Call}). Once the function is called, all its body |
| 151 | forms are executed; at this time, if the @code{interactive} form |
| 152 | occurs within the body, the form simply returns @code{nil} without |
| 153 | even evaluating its argument. |
| 154 | |
| 155 | By convention, you should put the @code{interactive} form in the |
| 156 | function body, as the first top-level form. If there is an |
| 157 | @code{interactive} form in both the @code{interactive-form} symbol |
| 158 | property and the function body, the former takes precedence. The |
| 159 | @code{interactive-form} symbol property can be used to add an |
| 160 | interactive form to an existing function, or change how its arguments |
| 161 | are processed interactively, without redefining the function. |
| 162 | @end defspec |
| 163 | |
| 164 | There are three possibilities for the argument @var{arg-descriptor}: |
| 165 | |
| 166 | @itemize @bullet |
| 167 | @item |
| 168 | It may be omitted or @code{nil}; then the command is called with no |
| 169 | arguments. This leads quickly to an error if the command requires one |
| 170 | or more arguments. |
| 171 | |
| 172 | @item |
| 173 | It may be a string; its contents are a sequence of elements separated |
| 174 | by newlines, one for each argument@footnote{Some elements actually |
| 175 | supply two arguments.}. Each element consists of a code character |
| 176 | (@pxref{Interactive Codes}) optionally followed by a prompt (which |
| 177 | some code characters use and some ignore). Here is an example: |
| 178 | |
| 179 | @smallexample |
| 180 | (interactive "P\nbFrobnicate buffer: ") |
| 181 | @end smallexample |
| 182 | |
| 183 | @noindent |
| 184 | The code letter @samp{P} sets the command's first argument to the raw |
| 185 | command prefix (@pxref{Prefix Command Arguments}). @samp{bFrobnicate |
| 186 | buffer: } prompts the user with @samp{Frobnicate buffer: } to enter |
| 187 | the name of an existing buffer, which becomes the second and final |
| 188 | argument. |
| 189 | |
| 190 | The prompt string can use @samp{%} to include previous argument values |
| 191 | (starting with the first argument) in the prompt. This is done using |
| 192 | @code{format} (@pxref{Formatting Strings}). For example, here is how |
| 193 | you could read the name of an existing buffer followed by a new name to |
| 194 | give to that buffer: |
| 195 | |
| 196 | @smallexample |
| 197 | @group |
| 198 | (interactive "bBuffer to rename: \nsRename buffer %s to: ") |
| 199 | @end group |
| 200 | @end smallexample |
| 201 | |
| 202 | @cindex @samp{*} in @code{interactive} |
| 203 | @cindex read-only buffers in interactive |
| 204 | If @samp{*} appears at the beginning of the string, then an error is |
| 205 | signaled if the buffer is read-only. |
| 206 | |
| 207 | @cindex @samp{@@} in @code{interactive} |
| 208 | If @samp{@@} appears at the beginning of the string, and if the key |
| 209 | sequence used to invoke the command includes any mouse events, then |
| 210 | the window associated with the first of those events is selected |
| 211 | before the command is run. |
| 212 | |
| 213 | @cindex @samp{^} in @code{interactive} |
| 214 | @cindex shift-selection, and @code{interactive} spec |
| 215 | If @samp{^} appears at the beginning of the string, and if the command |
| 216 | was invoked through @dfn{shift-translation}, set the mark and activate |
| 217 | the region temporarily, or extend an already active region, before the |
| 218 | command is run. If the command was invoked without shift-translation, |
| 219 | and the region is temporarily active, deactivate the region before the |
| 220 | command is run. Shift-translation is controlled on the user level by |
| 221 | @code{shift-select-mode}; see @ref{Shift Selection,,, emacs, The GNU |
| 222 | Emacs Manual}. |
| 223 | |
| 224 | You can use @samp{*}, @samp{@@}, and @code{^} together; the order does |
| 225 | not matter. Actual reading of arguments is controlled by the rest of |
| 226 | the prompt string (starting with the first character that is not |
| 227 | @samp{*}, @samp{@@}, or @samp{^}). |
| 228 | |
| 229 | @item |
| 230 | It may be a Lisp expression that is not a string; then it should be a |
| 231 | form that is evaluated to get a list of arguments to pass to the |
| 232 | command. Usually this form will call various functions to read input |
| 233 | from the user, most often through the minibuffer (@pxref{Minibuffers}) |
| 234 | or directly from the keyboard (@pxref{Reading Input}). |
| 235 | |
| 236 | Providing point or the mark as an argument value is also common, but |
| 237 | if you do this @emph{and} read input (whether using the minibuffer or |
| 238 | not), be sure to get the integer values of point or the mark after |
| 239 | reading. The current buffer may be receiving subprocess output; if |
| 240 | subprocess output arrives while the command is waiting for input, it |
| 241 | could relocate point and the mark. |
| 242 | |
| 243 | Here's an example of what @emph{not} to do: |
| 244 | |
| 245 | @smallexample |
| 246 | (interactive |
| 247 | (list (region-beginning) (region-end) |
| 248 | (read-string "Foo: " nil 'my-history))) |
| 249 | @end smallexample |
| 250 | |
| 251 | @noindent |
| 252 | Here's how to avoid the problem, by examining point and the mark after |
| 253 | reading the keyboard input: |
| 254 | |
| 255 | @smallexample |
| 256 | (interactive |
| 257 | (let ((string (read-string "Foo: " nil 'my-history))) |
| 258 | (list (region-beginning) (region-end) string))) |
| 259 | @end smallexample |
| 260 | |
| 261 | @strong{Warning:} the argument values should not include any data |
| 262 | types that can't be printed and then read. Some facilities save |
| 263 | @code{command-history} in a file to be read in the subsequent |
| 264 | sessions; if a command's arguments contain a data type that prints |
| 265 | using @samp{#<@dots{}>} syntax, those facilities won't work. |
| 266 | |
| 267 | There are, however, a few exceptions: it is ok to use a limited set of |
| 268 | expressions such as @code{(point)}, @code{(mark)}, |
| 269 | @code{(region-beginning)}, and @code{(region-end)}, because Emacs |
| 270 | recognizes them specially and puts the expression (rather than its |
| 271 | value) into the command history. To see whether the expression you |
| 272 | wrote is one of these exceptions, run the command, then examine |
| 273 | @code{(car command-history)}. |
| 274 | @end itemize |
| 275 | |
| 276 | @cindex examining the @code{interactive} form |
| 277 | @defun interactive-form function |
| 278 | This function returns the @code{interactive} form of @var{function}. |
| 279 | If @var{function} is an interactively callable function |
| 280 | (@pxref{Interactive Call}), the value is the command's |
| 281 | @code{interactive} form @code{(interactive @var{spec})}, which |
| 282 | specifies how to compute its arguments. Otherwise, the value is |
| 283 | @code{nil}. If @var{function} is a symbol, its function definition is |
| 284 | used. |
| 285 | @end defun |
| 286 | |
| 287 | @node Interactive Codes |
| 288 | @subsection Code Characters for @code{interactive} |
| 289 | @cindex interactive code description |
| 290 | @cindex description for interactive codes |
| 291 | @cindex codes, interactive, description of |
| 292 | @cindex characters for interactive codes |
| 293 | |
| 294 | The code character descriptions below contain a number of key words, |
| 295 | defined here as follows: |
| 296 | |
| 297 | @table @b |
| 298 | @item Completion |
| 299 | @cindex interactive completion |
| 300 | Provide completion. @key{TAB}, @key{SPC}, and @key{RET} perform name |
| 301 | completion because the argument is read using @code{completing-read} |
| 302 | (@pxref{Completion}). @kbd{?} displays a list of possible completions. |
| 303 | |
| 304 | @item Existing |
| 305 | Require the name of an existing object. An invalid name is not |
| 306 | accepted; the commands to exit the minibuffer do not exit if the current |
| 307 | input is not valid. |
| 308 | |
| 309 | @item Default |
| 310 | @cindex default argument string |
| 311 | A default value of some sort is used if the user enters no text in the |
| 312 | minibuffer. The default depends on the code character. |
| 313 | |
| 314 | @item No I/O |
| 315 | This code letter computes an argument without reading any input. |
| 316 | Therefore, it does not use a prompt string, and any prompt string you |
| 317 | supply is ignored. |
| 318 | |
| 319 | Even though the code letter doesn't use a prompt string, you must follow |
| 320 | it with a newline if it is not the last code character in the string. |
| 321 | |
| 322 | @item Prompt |
| 323 | A prompt immediately follows the code character. The prompt ends either |
| 324 | with the end of the string or with a newline. |
| 325 | |
| 326 | @item Special |
| 327 | This code character is meaningful only at the beginning of the |
| 328 | interactive string, and it does not look for a prompt or a newline. |
| 329 | It is a single, isolated character. |
| 330 | @end table |
| 331 | |
| 332 | @cindex reading interactive arguments |
| 333 | Here are the code character descriptions for use with @code{interactive}: |
| 334 | |
| 335 | @table @samp |
| 336 | @item * |
| 337 | Signal an error if the current buffer is read-only. Special. |
| 338 | |
| 339 | @item @@ |
| 340 | Select the window mentioned in the first mouse event in the key |
| 341 | sequence that invoked this command. Special. |
| 342 | |
| 343 | @item ^ |
| 344 | If the command was invoked through shift-translation, set the mark and |
| 345 | activate the region temporarily, or extend an already active region, |
| 346 | before the command is run. If the command was invoked without |
| 347 | shift-translation, and the region is temporarily active, deactivate |
| 348 | the region before the command is run. Special. |
| 349 | |
| 350 | @item a |
| 351 | A function name (i.e., a symbol satisfying @code{fboundp}). Existing, |
| 352 | Completion, Prompt. |
| 353 | |
| 354 | @item b |
| 355 | The name of an existing buffer. By default, uses the name of the |
| 356 | current buffer (@pxref{Buffers}). Existing, Completion, Default, |
| 357 | Prompt. |
| 358 | |
| 359 | @item B |
| 360 | A buffer name. The buffer need not exist. By default, uses the name of |
| 361 | a recently used buffer other than the current buffer. Completion, |
| 362 | Default, Prompt. |
| 363 | |
| 364 | @item c |
| 365 | A character. The cursor does not move into the echo area. Prompt. |
| 366 | |
| 367 | @item C |
| 368 | A command name (i.e., a symbol satisfying @code{commandp}). Existing, |
| 369 | Completion, Prompt. |
| 370 | |
| 371 | @item d |
| 372 | @cindex position argument |
| 373 | The position of point, as an integer (@pxref{Point}). No I/O. |
| 374 | |
| 375 | @item D |
| 376 | A directory name. The default is the current default directory of the |
| 377 | current buffer, @code{default-directory} (@pxref{File Name Expansion}). |
| 378 | Existing, Completion, Default, Prompt. |
| 379 | |
| 380 | @item e |
| 381 | The first or next non-keyboard event in the key sequence that invoked |
| 382 | the command. More precisely, @samp{e} gets events that are lists, so |
| 383 | you can look at the data in the lists. @xref{Input Events}. No I/O. |
| 384 | |
| 385 | You use @samp{e} for mouse events and for special system events |
| 386 | (@pxref{Misc Events}). The event list that the command receives |
| 387 | depends on the event. @xref{Input Events}, which describes the forms |
| 388 | of the list for each event in the corresponding subsections. |
| 389 | |
| 390 | You can use @samp{e} more than once in a single command's interactive |
| 391 | specification. If the key sequence that invoked the command has |
| 392 | @var{n} events that are lists, the @var{n}th @samp{e} provides the |
| 393 | @var{n}th such event. Events that are not lists, such as function keys |
| 394 | and @acronym{ASCII} characters, do not count where @samp{e} is concerned. |
| 395 | |
| 396 | @item f |
| 397 | A file name of an existing file (@pxref{File Names}). The default |
| 398 | directory is @code{default-directory}. Existing, Completion, Default, |
| 399 | Prompt. |
| 400 | |
| 401 | @item F |
| 402 | A file name. The file need not exist. Completion, Default, Prompt. |
| 403 | |
| 404 | @item G |
| 405 | A file name. The file need not exist. If the user enters just a |
| 406 | directory name, then the value is just that directory name, with no |
| 407 | file name within the directory added. Completion, Default, Prompt. |
| 408 | |
| 409 | @item i |
| 410 | An irrelevant argument. This code always supplies @code{nil} as |
| 411 | the argument's value. No I/O. |
| 412 | |
| 413 | @item k |
| 414 | A key sequence (@pxref{Key Sequences}). This keeps reading events |
| 415 | until a command (or undefined command) is found in the current key |
| 416 | maps. The key sequence argument is represented as a string or vector. |
| 417 | The cursor does not move into the echo area. Prompt. |
| 418 | |
| 419 | If @samp{k} reads a key sequence that ends with a down-event, it also |
| 420 | reads and discards the following up-event. You can get access to that |
| 421 | up-event with the @samp{U} code character. |
| 422 | |
| 423 | This kind of input is used by commands such as @code{describe-key} and |
| 424 | @code{global-set-key}. |
| 425 | |
| 426 | @item K |
| 427 | A key sequence, whose definition you intend to change. This works like |
| 428 | @samp{k}, except that it suppresses, for the last input event in the key |
| 429 | sequence, the conversions that are normally used (when necessary) to |
| 430 | convert an undefined key into a defined one. |
| 431 | |
| 432 | @item m |
| 433 | @cindex marker argument |
| 434 | The position of the mark, as an integer. No I/O. |
| 435 | |
| 436 | @item M |
| 437 | Arbitrary text, read in the minibuffer using the current buffer's input |
| 438 | method, and returned as a string (@pxref{Input Methods,,, emacs, The GNU |
| 439 | Emacs Manual}). Prompt. |
| 440 | |
| 441 | @item n |
| 442 | A number, read with the minibuffer. If the input is not a number, the |
| 443 | user has to try again. @samp{n} never uses the prefix argument. |
| 444 | Prompt. |
| 445 | |
| 446 | @item N |
| 447 | The numeric prefix argument; but if there is no prefix argument, read |
| 448 | a number as with @kbd{n}. The value is always a number. @xref{Prefix |
| 449 | Command Arguments}. Prompt. |
| 450 | |
| 451 | @item p |
| 452 | @cindex numeric prefix argument usage |
| 453 | The numeric prefix argument. (Note that this @samp{p} is lower case.) |
| 454 | No I/O. |
| 455 | |
| 456 | @item P |
| 457 | @cindex raw prefix argument usage |
| 458 | The raw prefix argument. (Note that this @samp{P} is upper case.) No |
| 459 | I/O. |
| 460 | |
| 461 | @item r |
| 462 | @cindex region argument |
| 463 | Point and the mark, as two numeric arguments, smallest first. This is |
| 464 | the only code letter that specifies two successive arguments rather than |
| 465 | one. No I/O. |
| 466 | |
| 467 | @item s |
| 468 | Arbitrary text, read in the minibuffer and returned as a string |
| 469 | (@pxref{Text from Minibuffer}). Terminate the input with either |
| 470 | @kbd{C-j} or @key{RET}. (@kbd{C-q} may be used to include either of |
| 471 | these characters in the input.) Prompt. |
| 472 | |
| 473 | @item S |
| 474 | An interned symbol whose name is read in the minibuffer. Terminate |
| 475 | the input with either @kbd{C-j} or @key{RET}. Other characters that |
| 476 | normally terminate a symbol (e.g., whitespace, parentheses and |
| 477 | brackets) do not do so here. Prompt. |
| 478 | |
| 479 | @item U |
| 480 | A key sequence or @code{nil}. Can be used after a @samp{k} or |
| 481 | @samp{K} argument to get the up-event that was discarded (if any) |
| 482 | after @samp{k} or @samp{K} read a down-event. If no up-event has been |
| 483 | discarded, @samp{U} provides @code{nil} as the argument. No I/O. |
| 484 | |
| 485 | @item v |
| 486 | A variable declared to be a user option (i.e., satisfying the |
| 487 | predicate @code{custom-variable-p}). This reads the variable using |
| 488 | @code{read-variable}. @xref{Definition of read-variable}. Existing, |
| 489 | Completion, Prompt. |
| 490 | |
| 491 | @item x |
| 492 | A Lisp object, specified with its read syntax, terminated with a |
| 493 | @kbd{C-j} or @key{RET}. The object is not evaluated. @xref{Object from |
| 494 | Minibuffer}. Prompt. |
| 495 | |
| 496 | @item X |
| 497 | @cindex evaluated expression argument |
| 498 | A Lisp form's value. @samp{X} reads as @samp{x} does, then evaluates |
| 499 | the form so that its value becomes the argument for the command. |
| 500 | Prompt. |
| 501 | |
| 502 | @item z |
| 503 | A coding system name (a symbol). If the user enters null input, the |
| 504 | argument value is @code{nil}. @xref{Coding Systems}. Completion, |
| 505 | Existing, Prompt. |
| 506 | |
| 507 | @item Z |
| 508 | A coding system name (a symbol)---but only if this command has a prefix |
| 509 | argument. With no prefix argument, @samp{Z} provides @code{nil} as the |
| 510 | argument value. Completion, Existing, Prompt. |
| 511 | @end table |
| 512 | |
| 513 | @node Interactive Examples |
| 514 | @subsection Examples of Using @code{interactive} |
| 515 | @cindex examples of using @code{interactive} |
| 516 | @cindex @code{interactive}, examples of using |
| 517 | |
| 518 | Here are some examples of @code{interactive}: |
| 519 | |
| 520 | @example |
| 521 | @group |
| 522 | (defun foo1 () ; @r{@code{foo1} takes no arguments,} |
| 523 | (interactive) ; @r{just moves forward two words.} |
| 524 | (forward-word 2)) |
| 525 | @result{} foo1 |
| 526 | @end group |
| 527 | |
| 528 | @group |
| 529 | (defun foo2 (n) ; @r{@code{foo2} takes one argument,} |
| 530 | (interactive "^p") ; @r{which is the numeric prefix.} |
| 531 | ; @r{under @code{shift-select-mode},} |
| 532 | ; @r{will activate or extend region.} |
| 533 | (forward-word (* 2 n))) |
| 534 | @result{} foo2 |
| 535 | @end group |
| 536 | |
| 537 | @group |
| 538 | (defun foo3 (n) ; @r{@code{foo3} takes one argument,} |
| 539 | (interactive "nCount:") ; @r{which is read with the Minibuffer.} |
| 540 | (forward-word (* 2 n))) |
| 541 | @result{} foo3 |
| 542 | @end group |
| 543 | |
| 544 | @group |
| 545 | (defun three-b (b1 b2 b3) |
| 546 | "Select three existing buffers. |
| 547 | Put them into three windows, selecting the last one." |
| 548 | @end group |
| 549 | (interactive "bBuffer1:\nbBuffer2:\nbBuffer3:") |
| 550 | (delete-other-windows) |
| 551 | (split-window (selected-window) 8) |
| 552 | (switch-to-buffer b1) |
| 553 | (other-window 1) |
| 554 | (split-window (selected-window) 8) |
| 555 | (switch-to-buffer b2) |
| 556 | (other-window 1) |
| 557 | (switch-to-buffer b3)) |
| 558 | @result{} three-b |
| 559 | @group |
| 560 | (three-b "*scratch*" "declarations.texi" "*mail*") |
| 561 | @result{} nil |
| 562 | @end group |
| 563 | @end example |
| 564 | |
| 565 | @node Interactive Call |
| 566 | @section Interactive Call |
| 567 | @cindex interactive call |
| 568 | |
| 569 | After the command loop has translated a key sequence into a command, |
| 570 | it invokes that command using the function @code{command-execute}. If |
| 571 | the command is a function, @code{command-execute} calls |
| 572 | @code{call-interactively}, which reads the arguments and calls the |
| 573 | command. You can also call these functions yourself. |
| 574 | |
| 575 | Note that the term ``command'', in this context, refers to an |
| 576 | interactively callable function (or function-like object), or a |
| 577 | keyboard macro. It does not refer to the key sequence used to invoke |
| 578 | a command (@pxref{Keymaps}). |
| 579 | |
| 580 | @defun commandp object &optional for-call-interactively |
| 581 | This function returns @code{t} if @var{object} is a command. |
| 582 | Otherwise, it returns @code{nil}. |
| 583 | |
| 584 | Commands include strings and vectors (which are treated as keyboard |
| 585 | macros), lambda expressions that contain a top-level |
| 586 | @code{interactive} form (@pxref{Using Interactive}), byte-code |
| 587 | function objects made from such lambda expressions, autoload objects |
| 588 | that are declared as interactive (non-@code{nil} fourth argument to |
| 589 | @code{autoload}), and some primitive functions. Also, a symbol is |
| 590 | considered a command if it has a non-@code{nil} |
| 591 | @code{interactive-form} property, or if its function definition |
| 592 | satisfies @code{commandp}. |
| 593 | |
| 594 | If @var{for-call-interactively} is non-@code{nil}, then |
| 595 | @code{commandp} returns @code{t} only for objects that |
| 596 | @code{call-interactively} could call---thus, not for keyboard macros. |
| 597 | |
| 598 | See @code{documentation} in @ref{Accessing Documentation}, for a |
| 599 | realistic example of using @code{commandp}. |
| 600 | @end defun |
| 601 | |
| 602 | @defun call-interactively command &optional record-flag keys |
| 603 | This function calls the interactively callable function @var{command}, |
| 604 | providing arguments according to its interactive calling specifications. |
| 605 | It returns whatever @var{command} returns. |
| 606 | |
| 607 | If, for instance, you have a function with the following signature: |
| 608 | |
| 609 | @example |
| 610 | (defun foo (begin end) |
| 611 | (interactive "r") |
| 612 | ...) |
| 613 | @end example |
| 614 | |
| 615 | then saying |
| 616 | |
| 617 | @example |
| 618 | (call-interactively 'foo) |
| 619 | @end example |
| 620 | |
| 621 | will call @code{foo} with the region (@code{point} and @code{mark}) as |
| 622 | the arguments. |
| 623 | |
| 624 | An error is signaled if @var{command} is not a function or if it |
| 625 | cannot be called interactively (i.e., is not a command). Note that |
| 626 | keyboard macros (strings and vectors) are not accepted, even though |
| 627 | they are considered commands, because they are not functions. If |
| 628 | @var{command} is a symbol, then @code{call-interactively} uses its |
| 629 | function definition. |
| 630 | |
| 631 | @cindex record command history |
| 632 | If @var{record-flag} is non-@code{nil}, then this command and its |
| 633 | arguments are unconditionally added to the list @code{command-history}. |
| 634 | Otherwise, the command is added only if it uses the minibuffer to read |
| 635 | an argument. @xref{Command History}. |
| 636 | |
| 637 | The argument @var{keys}, if given, should be a vector which specifies |
| 638 | the sequence of events to supply if the command inquires which events |
| 639 | were used to invoke it. If @var{keys} is omitted or @code{nil}, the |
| 640 | default is the return value of @code{this-command-keys-vector}. |
| 641 | @xref{Definition of this-command-keys-vector}. |
| 642 | @end defun |
| 643 | |
| 644 | @defun command-execute command &optional record-flag keys special |
| 645 | @cindex keyboard macro execution |
| 646 | This function executes @var{command}. The argument @var{command} must |
| 647 | satisfy the @code{commandp} predicate; i.e., it must be an interactively |
| 648 | callable function or a keyboard macro. |
| 649 | |
| 650 | A string or vector as @var{command} is executed with |
| 651 | @code{execute-kbd-macro}. A function is passed to |
| 652 | @code{call-interactively} (see above), along with the |
| 653 | @var{record-flag} and @var{keys} arguments. |
| 654 | |
| 655 | If @var{command} is a symbol, its function definition is used in its |
| 656 | place. A symbol with an @code{autoload} definition counts as a |
| 657 | command if it was declared to stand for an interactively callable |
| 658 | function. Such a definition is handled by loading the specified |
| 659 | library and then rechecking the definition of the symbol. |
| 660 | |
| 661 | The argument @var{special}, if given, means to ignore the prefix |
| 662 | argument and not clear it. This is used for executing special events |
| 663 | (@pxref{Special Events}). |
| 664 | @end defun |
| 665 | |
| 666 | @deffn Command execute-extended-command prefix-argument |
| 667 | @cindex read command name |
| 668 | This function reads a command name from the minibuffer using |
| 669 | @code{completing-read} (@pxref{Completion}). Then it uses |
| 670 | @code{command-execute} to call the specified command. Whatever that |
| 671 | command returns becomes the value of @code{execute-extended-command}. |
| 672 | |
| 673 | @cindex execute with prefix argument |
| 674 | If the command asks for a prefix argument, it receives the value |
| 675 | @var{prefix-argument}. If @code{execute-extended-command} is called |
| 676 | interactively, the current raw prefix argument is used for |
| 677 | @var{prefix-argument}, and thus passed on to whatever command is run. |
| 678 | |
| 679 | @c !!! Should this be @kindex? |
| 680 | @cindex @kbd{M-x} |
| 681 | @code{execute-extended-command} is the normal definition of @kbd{M-x}, |
| 682 | so it uses the string @w{@samp{M-x }} as a prompt. (It would be better |
| 683 | to take the prompt from the events used to invoke |
| 684 | @code{execute-extended-command}, but that is painful to implement.) A |
| 685 | description of the value of the prefix argument, if any, also becomes |
| 686 | part of the prompt. |
| 687 | |
| 688 | @example |
| 689 | @group |
| 690 | (execute-extended-command 3) |
| 691 | ---------- Buffer: Minibuffer ---------- |
| 692 | 3 M-x forward-word RET |
| 693 | ---------- Buffer: Minibuffer ---------- |
| 694 | @result{} t |
| 695 | @end group |
| 696 | @end example |
| 697 | @end deffn |
| 698 | |
| 699 | @node Distinguish Interactive |
| 700 | @section Distinguish Interactive Calls |
| 701 | |
| 702 | Sometimes a command should display additional visual feedback (such |
| 703 | as an informative message in the echo area) for interactive calls |
| 704 | only. There are three ways to do this. The recommended way to test |
| 705 | whether the function was called using @code{call-interactively} is to |
| 706 | give it an optional argument @code{print-message} and use the |
| 707 | @code{interactive} spec to make it non-@code{nil} in interactive |
| 708 | calls. Here's an example: |
| 709 | |
| 710 | @example |
| 711 | (defun foo (&optional print-message) |
| 712 | (interactive "p") |
| 713 | (when print-message |
| 714 | (message "foo"))) |
| 715 | @end example |
| 716 | |
| 717 | @noindent |
| 718 | We use @code{"p"} because the numeric prefix argument is never |
| 719 | @code{nil}. Defined in this way, the function does display the |
| 720 | message when called from a keyboard macro. |
| 721 | |
| 722 | The above method with the additional argument is usually best, |
| 723 | because it allows callers to say ``treat this call as interactive''. |
| 724 | But you can also do the job by testing @code{called-interactively-p}. |
| 725 | |
| 726 | @defun called-interactively-p kind |
| 727 | This function returns @code{t} when the calling function was called |
| 728 | using @code{call-interactively}. |
| 729 | |
| 730 | The argument @var{kind} should be either the symbol @code{interactive} |
| 731 | or the symbol @code{any}. If it is @code{interactive}, then |
| 732 | @code{called-interactively-p} returns @code{t} only if the call was |
| 733 | made directly by the user---e.g., if the user typed a key sequence |
| 734 | bound to the calling function, but @emph{not} if the user ran a |
| 735 | keyboard macro that called the function (@pxref{Keyboard Macros}). If |
| 736 | @var{kind} is @code{any}, @code{called-interactively-p} returns |
| 737 | @code{t} for any kind of interactive call, including keyboard macros. |
| 738 | |
| 739 | If in doubt, use @code{any}; the only known proper use of |
| 740 | @code{interactive} is if you need to decide whether to display a |
| 741 | helpful message while a function is running. |
| 742 | |
| 743 | A function is never considered to be called interactively if it was |
| 744 | called via Lisp evaluation (or with @code{apply} or @code{funcall}). |
| 745 | @end defun |
| 746 | |
| 747 | @noindent |
| 748 | Here is an example of using @code{called-interactively-p}: |
| 749 | |
| 750 | @example |
| 751 | @group |
| 752 | (defun foo () |
| 753 | (interactive) |
| 754 | (when (called-interactively-p 'any) |
| 755 | (message "Interactive!") |
| 756 | 'foo-called-interactively)) |
| 757 | @end group |
| 758 | |
| 759 | @group |
| 760 | ;; @r{Type @kbd{M-x foo}.} |
| 761 | @print{} Interactive! |
| 762 | @end group |
| 763 | |
| 764 | @group |
| 765 | (foo) |
| 766 | @result{} nil |
| 767 | @end group |
| 768 | @end example |
| 769 | |
| 770 | @noindent |
| 771 | Here is another example that contrasts direct and indirect calls to |
| 772 | @code{called-interactively-p}. |
| 773 | |
| 774 | @example |
| 775 | @group |
| 776 | (defun bar () |
| 777 | (interactive) |
| 778 | (message "%s" (list (foo) (called-interactively-p 'any)))) |
| 779 | @end group |
| 780 | |
| 781 | @group |
| 782 | ;; @r{Type @kbd{M-x bar}.} |
| 783 | @print{} (nil t) |
| 784 | @end group |
| 785 | @end example |
| 786 | |
| 787 | @node Command Loop Info |
| 788 | @section Information from the Command Loop |
| 789 | |
| 790 | The editor command loop sets several Lisp variables to keep status |
| 791 | records for itself and for commands that are run. With the exception of |
| 792 | @code{this-command} and @code{last-command} it's generally a bad idea to |
| 793 | change any of these variables in a Lisp program. |
| 794 | |
| 795 | @defvar last-command |
| 796 | This variable records the name of the previous command executed by the |
| 797 | command loop (the one before the current command). Normally the value |
| 798 | is a symbol with a function definition, but this is not guaranteed. |
| 799 | |
| 800 | The value is copied from @code{this-command} when a command returns to |
| 801 | the command loop, except when the command has specified a prefix |
| 802 | argument for the following command. |
| 803 | |
| 804 | This variable is always local to the current terminal and cannot be |
| 805 | buffer-local. @xref{Multiple Terminals}. |
| 806 | @end defvar |
| 807 | |
| 808 | @defvar real-last-command |
| 809 | This variable is set up by Emacs just like @code{last-command}, |
| 810 | but never altered by Lisp programs. |
| 811 | @end defvar |
| 812 | |
| 813 | @defvar last-repeatable-command |
| 814 | This variable stores the most recently executed command that was not |
| 815 | part of an input event. This is the command @code{repeat} will try to |
| 816 | repeat, @xref{Repeating,,, emacs, The GNU Emacs Manual}. |
| 817 | @end defvar |
| 818 | |
| 819 | @defvar this-command |
| 820 | @cindex current command |
| 821 | This variable records the name of the command now being executed by |
| 822 | the editor command loop. Like @code{last-command}, it is normally a symbol |
| 823 | with a function definition. |
| 824 | |
| 825 | The command loop sets this variable just before running a command, and |
| 826 | copies its value into @code{last-command} when the command finishes |
| 827 | (unless the command specified a prefix argument for the following |
| 828 | command). |
| 829 | |
| 830 | @cindex kill command repetition |
| 831 | Some commands set this variable during their execution, as a flag for |
| 832 | whatever command runs next. In particular, the functions for killing text |
| 833 | set @code{this-command} to @code{kill-region} so that any kill commands |
| 834 | immediately following will know to append the killed text to the |
| 835 | previous kill. |
| 836 | @end defvar |
| 837 | |
| 838 | If you do not want a particular command to be recognized as the previous |
| 839 | command in the case where it got an error, you must code that command to |
| 840 | prevent this. One way is to set @code{this-command} to @code{t} at the |
| 841 | beginning of the command, and set @code{this-command} back to its proper |
| 842 | value at the end, like this: |
| 843 | |
| 844 | @example |
| 845 | (defun foo (args@dots{}) |
| 846 | (interactive @dots{}) |
| 847 | (let ((old-this-command this-command)) |
| 848 | (setq this-command t) |
| 849 | @r{@dots{}do the work@dots{}} |
| 850 | (setq this-command old-this-command))) |
| 851 | @end example |
| 852 | |
| 853 | @noindent |
| 854 | We do not bind @code{this-command} with @code{let} because that would |
| 855 | restore the old value in case of error---a feature of @code{let} which |
| 856 | in this case does precisely what we want to avoid. |
| 857 | |
| 858 | @defvar this-original-command |
| 859 | This has the same value as @code{this-command} except when command |
| 860 | remapping occurs (@pxref{Remapping Commands}). In that case, |
| 861 | @code{this-command} gives the command actually run (the result of |
| 862 | remapping), and @code{this-original-command} gives the command that |
| 863 | was specified to run but remapped into another command. |
| 864 | @end defvar |
| 865 | |
| 866 | @defun this-command-keys |
| 867 | This function returns a string or vector containing the key sequence |
| 868 | that invoked the present command, plus any previous commands that |
| 869 | generated the prefix argument for this command. Any events read by the |
| 870 | command using @code{read-event} without a timeout get tacked on to the end. |
| 871 | |
| 872 | However, if the command has called @code{read-key-sequence}, it |
| 873 | returns the last read key sequence. @xref{Key Sequence Input}. The |
| 874 | value is a string if all events in the sequence were characters that |
| 875 | fit in a string. @xref{Input Events}. |
| 876 | |
| 877 | @example |
| 878 | @group |
| 879 | (this-command-keys) |
| 880 | ;; @r{Now use @kbd{C-u C-x C-e} to evaluate that.} |
| 881 | @result{} "^U^X^E" |
| 882 | @end group |
| 883 | @end example |
| 884 | @end defun |
| 885 | |
| 886 | @defun this-command-keys-vector |
| 887 | @anchor{Definition of this-command-keys-vector} |
| 888 | Like @code{this-command-keys}, except that it always returns the events |
| 889 | in a vector, so you don't need to deal with the complexities of storing |
| 890 | input events in a string (@pxref{Strings of Events}). |
| 891 | @end defun |
| 892 | |
| 893 | @defun clear-this-command-keys &optional keep-record |
| 894 | This function empties out the table of events for |
| 895 | @code{this-command-keys} to return. Unless @var{keep-record} is |
| 896 | non-@code{nil}, it also empties the records that the function |
| 897 | @code{recent-keys} (@pxref{Recording Input}) will subsequently return. |
| 898 | This is useful after reading a password, to prevent the password from |
| 899 | echoing inadvertently as part of the next command in certain cases. |
| 900 | @end defun |
| 901 | |
| 902 | @defvar last-nonmenu-event |
| 903 | This variable holds the last input event read as part of a key sequence, |
| 904 | not counting events resulting from mouse menus. |
| 905 | |
| 906 | One use of this variable is for telling @code{x-popup-menu} where to pop |
| 907 | up a menu. It is also used internally by @code{y-or-n-p} |
| 908 | (@pxref{Yes-or-No Queries}). |
| 909 | @end defvar |
| 910 | |
| 911 | @defvar last-command-event |
| 912 | This variable is set to the last input event that was read by the |
| 913 | command loop as part of a command. The principal use of this variable |
| 914 | is in @code{self-insert-command}, which uses it to decide which |
| 915 | character to insert. |
| 916 | |
| 917 | @example |
| 918 | @group |
| 919 | last-command-event |
| 920 | ;; @r{Now use @kbd{C-u C-x C-e} to evaluate that.} |
| 921 | @result{} 5 |
| 922 | @end group |
| 923 | @end example |
| 924 | |
| 925 | @noindent |
| 926 | The value is 5 because that is the @acronym{ASCII} code for @kbd{C-e}. |
| 927 | @end defvar |
| 928 | |
| 929 | @defvar last-event-frame |
| 930 | This variable records which frame the last input event was directed to. |
| 931 | Usually this is the frame that was selected when the event was |
| 932 | generated, but if that frame has redirected input focus to another |
| 933 | frame, the value is the frame to which the event was redirected. |
| 934 | @xref{Input Focus}. |
| 935 | |
| 936 | If the last event came from a keyboard macro, the value is @code{macro}. |
| 937 | @end defvar |
| 938 | |
| 939 | @node Adjusting Point |
| 940 | @section Adjusting Point After Commands |
| 941 | @cindex adjusting point |
| 942 | @cindex invisible/intangible text, and point |
| 943 | @cindex @code{display} property, and point display |
| 944 | @cindex @code{composition} property, and point display |
| 945 | |
| 946 | It is not easy to display a value of point in the middle of a |
| 947 | sequence of text that has the @code{display}, @code{composition} or |
| 948 | is invisible. Therefore, after a command finishes and returns to the |
| 949 | command loop, if point is within such a sequence, the command loop |
| 950 | normally moves point to the edge of the sequence. |
| 951 | |
| 952 | A command can inhibit this feature by setting the variable |
| 953 | @code{disable-point-adjustment}: |
| 954 | |
| 955 | @defvar disable-point-adjustment |
| 956 | If this variable is non-@code{nil} when a command returns to the |
| 957 | command loop, then the command loop does not check for those text |
| 958 | properties, and does not move point out of sequences that have them. |
| 959 | |
| 960 | The command loop sets this variable to @code{nil} before each command, |
| 961 | so if a command sets it, the effect applies only to that command. |
| 962 | @end defvar |
| 963 | |
| 964 | @defvar global-disable-point-adjustment |
| 965 | If you set this variable to a non-@code{nil} value, the feature of |
| 966 | moving point out of these sequences is completely turned off. |
| 967 | @end defvar |
| 968 | |
| 969 | @node Input Events |
| 970 | @section Input Events |
| 971 | @cindex events |
| 972 | @cindex input events |
| 973 | |
| 974 | The Emacs command loop reads a sequence of @dfn{input events} that |
| 975 | represent keyboard or mouse activity, or system events sent to Emacs. |
| 976 | The events for keyboard activity are characters or symbols; other |
| 977 | events are always lists. This section describes the representation |
| 978 | and meaning of input events in detail. |
| 979 | |
| 980 | @defun eventp object |
| 981 | This function returns non-@code{nil} if @var{object} is an input event |
| 982 | or event type. |
| 983 | |
| 984 | Note that any symbol might be used as an event or an event type. |
| 985 | @code{eventp} cannot distinguish whether a symbol is intended by Lisp |
| 986 | code to be used as an event. Instead, it distinguishes whether the |
| 987 | symbol has actually been used in an event that has been read as input in |
| 988 | the current Emacs session. If a symbol has not yet been so used, |
| 989 | @code{eventp} returns @code{nil}. |
| 990 | @end defun |
| 991 | |
| 992 | @menu |
| 993 | * Keyboard Events:: Ordinary characters--keys with symbols on them. |
| 994 | * Function Keys:: Function keys--keys with names, not symbols. |
| 995 | * Mouse Events:: Overview of mouse events. |
| 996 | * Click Events:: Pushing and releasing a mouse button. |
| 997 | * Drag Events:: Moving the mouse before releasing the button. |
| 998 | * Button-Down Events:: A button was pushed and not yet released. |
| 999 | * Repeat Events:: Double and triple click (or drag, or down). |
| 1000 | * Motion Events:: Just moving the mouse, not pushing a button. |
| 1001 | * Focus Events:: Moving the mouse between frames. |
| 1002 | * Misc Events:: Other events the system can generate. |
| 1003 | * Event Examples:: Examples of the lists for mouse events. |
| 1004 | * Classifying Events:: Finding the modifier keys in an event symbol. |
| 1005 | Event types. |
| 1006 | * Accessing Mouse:: Functions to extract info from mouse events. |
| 1007 | * Accessing Scroll:: Functions to get info from scroll bar events. |
| 1008 | * Strings of Events:: Special considerations for putting |
| 1009 | keyboard character events in a string. |
| 1010 | @end menu |
| 1011 | |
| 1012 | @node Keyboard Events |
| 1013 | @subsection Keyboard Events |
| 1014 | @cindex keyboard events |
| 1015 | |
| 1016 | There are two kinds of input you can get from the keyboard: ordinary |
| 1017 | keys, and function keys. Ordinary keys correspond to characters; the |
| 1018 | events they generate are represented in Lisp as characters. The event |
| 1019 | type of a character event is the character itself (an integer); see |
| 1020 | @ref{Classifying Events}. |
| 1021 | |
| 1022 | @cindex modifier bits (of input character) |
| 1023 | @cindex basic code (of input character) |
| 1024 | An input character event consists of a @dfn{basic code} between 0 and |
| 1025 | 524287, plus any or all of these @dfn{modifier bits}: |
| 1026 | |
| 1027 | @table @asis |
| 1028 | @item meta |
| 1029 | The |
| 1030 | @tex |
| 1031 | @math{2^{27}} |
| 1032 | @end tex |
| 1033 | @ifnottex |
| 1034 | 2**27 |
| 1035 | @end ifnottex |
| 1036 | bit in the character code indicates a character |
| 1037 | typed with the meta key held down. |
| 1038 | |
| 1039 | @item control |
| 1040 | The |
| 1041 | @tex |
| 1042 | @math{2^{26}} |
| 1043 | @end tex |
| 1044 | @ifnottex |
| 1045 | 2**26 |
| 1046 | @end ifnottex |
| 1047 | bit in the character code indicates a non-@acronym{ASCII} |
| 1048 | control character. |
| 1049 | |
| 1050 | @sc{ascii} control characters such as @kbd{C-a} have special basic |
| 1051 | codes of their own, so Emacs needs no special bit to indicate them. |
| 1052 | Thus, the code for @kbd{C-a} is just 1. |
| 1053 | |
| 1054 | But if you type a control combination not in @acronym{ASCII}, such as |
| 1055 | @kbd{%} with the control key, the numeric value you get is the code |
| 1056 | for @kbd{%} plus |
| 1057 | @tex |
| 1058 | @math{2^{26}} |
| 1059 | @end tex |
| 1060 | @ifnottex |
| 1061 | 2**26 |
| 1062 | @end ifnottex |
| 1063 | (assuming the terminal supports non-@acronym{ASCII} |
| 1064 | control characters). |
| 1065 | |
| 1066 | @item shift |
| 1067 | The |
| 1068 | @tex |
| 1069 | @math{2^{25}} |
| 1070 | @end tex |
| 1071 | @ifnottex |
| 1072 | 2**25 |
| 1073 | @end ifnottex |
| 1074 | bit in the character code indicates an @acronym{ASCII} control |
| 1075 | character typed with the shift key held down. |
| 1076 | |
| 1077 | For letters, the basic code itself indicates upper versus lower case; |
| 1078 | for digits and punctuation, the shift key selects an entirely different |
| 1079 | character with a different basic code. In order to keep within the |
| 1080 | @acronym{ASCII} character set whenever possible, Emacs avoids using the |
| 1081 | @tex |
| 1082 | @math{2^{25}} |
| 1083 | @end tex |
| 1084 | @ifnottex |
| 1085 | 2**25 |
| 1086 | @end ifnottex |
| 1087 | bit for those characters. |
| 1088 | |
| 1089 | However, @acronym{ASCII} provides no way to distinguish @kbd{C-A} from |
| 1090 | @kbd{C-a}, so Emacs uses the |
| 1091 | @tex |
| 1092 | @math{2^{25}} |
| 1093 | @end tex |
| 1094 | @ifnottex |
| 1095 | 2**25 |
| 1096 | @end ifnottex |
| 1097 | bit in @kbd{C-A} and not in |
| 1098 | @kbd{C-a}. |
| 1099 | |
| 1100 | @item hyper |
| 1101 | The |
| 1102 | @tex |
| 1103 | @math{2^{24}} |
| 1104 | @end tex |
| 1105 | @ifnottex |
| 1106 | 2**24 |
| 1107 | @end ifnottex |
| 1108 | bit in the character code indicates a character |
| 1109 | typed with the hyper key held down. |
| 1110 | |
| 1111 | @item super |
| 1112 | The |
| 1113 | @tex |
| 1114 | @math{2^{23}} |
| 1115 | @end tex |
| 1116 | @ifnottex |
| 1117 | 2**23 |
| 1118 | @end ifnottex |
| 1119 | bit in the character code indicates a character |
| 1120 | typed with the super key held down. |
| 1121 | |
| 1122 | @item alt |
| 1123 | The |
| 1124 | @tex |
| 1125 | @math{2^{22}} |
| 1126 | @end tex |
| 1127 | @ifnottex |
| 1128 | 2**22 |
| 1129 | @end ifnottex |
| 1130 | bit in the character code indicates a character typed with the alt key |
| 1131 | held down. (The key labeled @key{Alt} on most keyboards is actually |
| 1132 | treated as the meta key, not this.) |
| 1133 | @end table |
| 1134 | |
| 1135 | It is best to avoid mentioning specific bit numbers in your program. |
| 1136 | To test the modifier bits of a character, use the function |
| 1137 | @code{event-modifiers} (@pxref{Classifying Events}). When making key |
| 1138 | bindings, you can use the read syntax for characters with modifier bits |
| 1139 | (@samp{\C-}, @samp{\M-}, and so on). For making key bindings with |
| 1140 | @code{define-key}, you can use lists such as @code{(control hyper ?x)} to |
| 1141 | specify the characters (@pxref{Changing Key Bindings}). The function |
| 1142 | @code{event-convert-list} converts such a list into an event type |
| 1143 | (@pxref{Classifying Events}). |
| 1144 | |
| 1145 | @node Function Keys |
| 1146 | @subsection Function Keys |
| 1147 | |
| 1148 | @cindex function keys |
| 1149 | Most keyboards also have @dfn{function keys}---keys that have names or |
| 1150 | symbols that are not characters. Function keys are represented in |
| 1151 | Emacs Lisp as symbols; the symbol's name is the function key's label, |
| 1152 | in lower case. For example, pressing a key labeled @key{F1} generates |
| 1153 | an input event represented by the symbol @code{f1}. |
| 1154 | |
| 1155 | The event type of a function key event is the event symbol itself. |
| 1156 | @xref{Classifying Events}. |
| 1157 | |
| 1158 | Here are a few special cases in the symbol-naming convention for |
| 1159 | function keys: |
| 1160 | |
| 1161 | @table @asis |
| 1162 | @item @code{backspace}, @code{tab}, @code{newline}, @code{return}, @code{delete} |
| 1163 | These keys correspond to common @acronym{ASCII} control characters that have |
| 1164 | special keys on most keyboards. |
| 1165 | |
| 1166 | In @acronym{ASCII}, @kbd{C-i} and @key{TAB} are the same character. If the |
| 1167 | terminal can distinguish between them, Emacs conveys the distinction to |
| 1168 | Lisp programs by representing the former as the integer 9, and the |
| 1169 | latter as the symbol @code{tab}. |
| 1170 | |
| 1171 | Most of the time, it's not useful to distinguish the two. So normally |
| 1172 | @code{local-function-key-map} (@pxref{Translation Keymaps}) is set up |
| 1173 | to map @code{tab} into 9. Thus, a key binding for character code 9 |
| 1174 | (the character @kbd{C-i}) also applies to @code{tab}. Likewise for |
| 1175 | the other symbols in this group. The function @code{read-char} |
| 1176 | likewise converts these events into characters. |
| 1177 | |
| 1178 | In @acronym{ASCII}, @key{BS} is really @kbd{C-h}. But @code{backspace} |
| 1179 | converts into the character code 127 (@key{DEL}), not into code 8 |
| 1180 | (@key{BS}). This is what most users prefer. |
| 1181 | |
| 1182 | @item @code{left}, @code{up}, @code{right}, @code{down} |
| 1183 | Cursor arrow keys |
| 1184 | @item @code{kp-add}, @code{kp-decimal}, @code{kp-divide}, @dots{} |
| 1185 | Keypad keys (to the right of the regular keyboard). |
| 1186 | @item @code{kp-0}, @code{kp-1}, @dots{} |
| 1187 | Keypad keys with digits. |
| 1188 | @item @code{kp-f1}, @code{kp-f2}, @code{kp-f3}, @code{kp-f4} |
| 1189 | Keypad PF keys. |
| 1190 | @item @code{kp-home}, @code{kp-left}, @code{kp-up}, @code{kp-right}, @code{kp-down} |
| 1191 | Keypad arrow keys. Emacs normally translates these into the |
| 1192 | corresponding non-keypad keys @code{home}, @code{left}, @dots{} |
| 1193 | @item @code{kp-prior}, @code{kp-next}, @code{kp-end}, @code{kp-begin}, @code{kp-insert}, @code{kp-delete} |
| 1194 | Additional keypad duplicates of keys ordinarily found elsewhere. Emacs |
| 1195 | normally translates these into the like-named non-keypad keys. |
| 1196 | @end table |
| 1197 | |
| 1198 | You can use the modifier keys @key{ALT}, @key{CTRL}, @key{HYPER}, |
| 1199 | @key{META}, @key{SHIFT}, and @key{SUPER} with function keys. The way to |
| 1200 | represent them is with prefixes in the symbol name: |
| 1201 | |
| 1202 | @table @samp |
| 1203 | @item A- |
| 1204 | The alt modifier. |
| 1205 | @item C- |
| 1206 | The control modifier. |
| 1207 | @item H- |
| 1208 | The hyper modifier. |
| 1209 | @item M- |
| 1210 | The meta modifier. |
| 1211 | @item S- |
| 1212 | The shift modifier. |
| 1213 | @item s- |
| 1214 | The super modifier. |
| 1215 | @end table |
| 1216 | |
| 1217 | Thus, the symbol for the key @key{F3} with @key{META} held down is |
| 1218 | @code{M-f3}. When you use more than one prefix, we recommend you |
| 1219 | write them in alphabetical order; but the order does not matter in |
| 1220 | arguments to the key-binding lookup and modification functions. |
| 1221 | |
| 1222 | @node Mouse Events |
| 1223 | @subsection Mouse Events |
| 1224 | |
| 1225 | Emacs supports four kinds of mouse events: click events, drag events, |
| 1226 | button-down events, and motion events. All mouse events are represented |
| 1227 | as lists. The @sc{car} of the list is the event type; this says which |
| 1228 | mouse button was involved, and which modifier keys were used with it. |
| 1229 | The event type can also distinguish double or triple button presses |
| 1230 | (@pxref{Repeat Events}). The rest of the list elements give position |
| 1231 | and time information. |
| 1232 | |
| 1233 | For key lookup, only the event type matters: two events of the same type |
| 1234 | necessarily run the same command. The command can access the full |
| 1235 | values of these events using the @samp{e} interactive code. |
| 1236 | @xref{Interactive Codes}. |
| 1237 | |
| 1238 | A key sequence that starts with a mouse event is read using the keymaps |
| 1239 | of the buffer in the window that the mouse was in, not the current |
| 1240 | buffer. This does not imply that clicking in a window selects that |
| 1241 | window or its buffer---that is entirely under the control of the command |
| 1242 | binding of the key sequence. |
| 1243 | |
| 1244 | @node Click Events |
| 1245 | @subsection Click Events |
| 1246 | @cindex click event |
| 1247 | @cindex mouse click event |
| 1248 | |
| 1249 | When the user presses a mouse button and releases it at the same |
| 1250 | location, that generates a @dfn{click} event. All mouse click event |
| 1251 | share the same format: |
| 1252 | |
| 1253 | @example |
| 1254 | (@var{event-type} @var{position} @var{click-count}) |
| 1255 | @end example |
| 1256 | |
| 1257 | @table @asis |
| 1258 | @item @var{event-type} |
| 1259 | This is a symbol that indicates which mouse button was used. It is |
| 1260 | one of the symbols @code{mouse-1}, @code{mouse-2}, @dots{}, where the |
| 1261 | buttons are numbered left to right. |
| 1262 | |
| 1263 | You can also use prefixes @samp{A-}, @samp{C-}, @samp{H-}, @samp{M-}, |
| 1264 | @samp{S-} and @samp{s-} for modifiers alt, control, hyper, meta, shift |
| 1265 | and super, just as you would with function keys. |
| 1266 | |
| 1267 | This symbol also serves as the event type of the event. Key bindings |
| 1268 | describe events by their types; thus, if there is a key binding for |
| 1269 | @code{mouse-1}, that binding would apply to all events whose |
| 1270 | @var{event-type} is @code{mouse-1}. |
| 1271 | |
| 1272 | @item @var{position} |
| 1273 | @cindex mouse position list |
| 1274 | This is a @dfn{mouse position list} specifying where the mouse click |
| 1275 | occurred; see below for details. |
| 1276 | |
| 1277 | @item @var{click-count} |
| 1278 | This is the number of rapid repeated presses so far of the same mouse |
| 1279 | button. @xref{Repeat Events}. |
| 1280 | @end table |
| 1281 | |
| 1282 | To access the contents of a mouse position list in the |
| 1283 | @var{position} slot of a click event, you should typically use the |
| 1284 | functions documented in @ref{Accessing Mouse}. The explicit format of |
| 1285 | the list depends on where the click occurred. For clicks in the text |
| 1286 | area, mode line, header line, or in the fringe or marginal areas, the |
| 1287 | mouse position list has the form |
| 1288 | |
| 1289 | @example |
| 1290 | (@var{window} @var{pos-or-area} (@var{x} . @var{y}) @var{timestamp} |
| 1291 | @var{object} @var{text-pos} (@var{col} . @var{row}) |
| 1292 | @var{image} (@var{dx} . @var{dy}) (@var{width} . @var{height})) |
| 1293 | @end example |
| 1294 | |
| 1295 | @noindent |
| 1296 | The meanings of these list elements are as follows: |
| 1297 | |
| 1298 | @table @asis |
| 1299 | @item @var{window} |
| 1300 | The window in which the click occurred. |
| 1301 | |
| 1302 | @item @var{pos-or-area} |
| 1303 | The buffer position of the character clicked on in the text area; or, |
| 1304 | if the click was outside the text area, the window area where it |
| 1305 | occurred. It is one of the symbols @code{mode-line}, |
| 1306 | @code{header-line}, @code{vertical-line}, @code{left-margin}, |
| 1307 | @code{right-margin}, @code{left-fringe}, or @code{right-fringe}. |
| 1308 | |
| 1309 | In one special case, @var{pos-or-area} is a list containing a symbol |
| 1310 | (one of the symbols listed above) instead of just the symbol. This |
| 1311 | happens after the imaginary prefix keys for the event are registered |
| 1312 | by Emacs. @xref{Key Sequence Input}. |
| 1313 | |
| 1314 | @item @var{x}, @var{y} |
| 1315 | The relative pixel coordinates of the click. For clicks in the text |
| 1316 | area of a window, the coordinate origin @code{(0 . 0)} is taken to be |
| 1317 | the top left corner of the text area. @xref{Window Sizes}. For |
| 1318 | clicks in a mode line or header line, the coordinate origin is the top |
| 1319 | left corner of the window itself. For fringes, margins, and the |
| 1320 | vertical border, @var{x} does not have meaningful data. For fringes |
| 1321 | and margins, @var{y} is relative to the bottom edge of the header |
| 1322 | line. In all cases, the @var{x} and @var{y} coordinates increase |
| 1323 | rightward and downward respectively. |
| 1324 | |
| 1325 | @item @var{timestamp} |
| 1326 | The time at which the event occurred, as an integer number of |
| 1327 | milliseconds since a system-dependent initial time. |
| 1328 | |
| 1329 | @item @var{object} |
| 1330 | Either @code{nil} if there is no string-type text property at the |
| 1331 | click position, or a cons cell of the form (@var{string} |
| 1332 | . @var{string-pos}) if there is one: |
| 1333 | |
| 1334 | @table @asis |
| 1335 | @item @var{string} |
| 1336 | The string which was clicked on, including any properties. |
| 1337 | |
| 1338 | @item @var{string-pos} |
| 1339 | The position in the string where the click occurred. |
| 1340 | @end table |
| 1341 | |
| 1342 | @item @var{text-pos} |
| 1343 | For clicks on a marginal area or on a fringe, this is the buffer |
| 1344 | position of the first visible character in the corresponding line in |
| 1345 | the window. For other events, it is the current buffer position in |
| 1346 | the window. |
| 1347 | |
| 1348 | @item @var{col}, @var{row} |
| 1349 | These are the actual column and row coordinate numbers of the glyph |
| 1350 | under the @var{x}, @var{y} position. If @var{x} lies beyond the last |
| 1351 | column of actual text on its line, @var{col} is reported by adding |
| 1352 | fictional extra columns that have the default character width. Row 0 |
| 1353 | is taken to be the header line if the window has one, or the topmost |
| 1354 | row of the text area otherwise. Column 0 is taken to be the leftmost |
| 1355 | column of the text area for clicks on a window text area, or the |
| 1356 | leftmost mode line or header line column for clicks there. For clicks |
| 1357 | on fringes or vertical borders, these have no meaningful data. For |
| 1358 | clicks on margins, @var{col} is measured from the left edge of the |
| 1359 | margin area and @var{row} is measured from the top of the margin area. |
| 1360 | |
| 1361 | @item @var{image} |
| 1362 | This is the image object on which the click occurred. It is either |
| 1363 | @code{nil} if there is no image at the position clicked on, or it is |
| 1364 | an image object as returned by @code{find-image} if click was in an image. |
| 1365 | |
| 1366 | @item @var{dx}, @var{dy} |
| 1367 | These are the pixel coordinates of the click, relative to |
| 1368 | the top left corner of @var{object}, which is @code{(0 . 0)}. If |
| 1369 | @var{object} is @code{nil}, the coordinates are relative to the top |
| 1370 | left corner of the character glyph clicked on. |
| 1371 | |
| 1372 | @item @var{width}, @var{height} |
| 1373 | These are the pixel width and height of @var{object} or, if this is |
| 1374 | @code{nil}, those of the character glyph clicked on. |
| 1375 | @end table |
| 1376 | |
| 1377 | For clicks on a scroll bar, @var{position} has this form: |
| 1378 | |
| 1379 | @example |
| 1380 | (@var{window} @var{area} (@var{portion} . @var{whole}) @var{timestamp} @var{part}) |
| 1381 | @end example |
| 1382 | |
| 1383 | @table @asis |
| 1384 | @item @var{window} |
| 1385 | The window whose scroll bar was clicked on. |
| 1386 | |
| 1387 | @item @var{area} |
| 1388 | This is the symbol @code{vertical-scroll-bar}. |
| 1389 | |
| 1390 | @item @var{portion} |
| 1391 | The number of pixels from the top of the scroll bar to the click |
| 1392 | position. On some toolkits, including GTK+, Emacs cannot extract this |
| 1393 | data, so the value is always @code{0}. |
| 1394 | |
| 1395 | @item @var{whole} |
| 1396 | The total length, in pixels, of the scroll bar. On some toolkits, |
| 1397 | including GTK+, Emacs cannot extract this data, so the value is always |
| 1398 | @code{0}. |
| 1399 | |
| 1400 | @item @var{timestamp} |
| 1401 | The time at which the event occurred, in milliseconds. On some |
| 1402 | toolkits, including GTK+, Emacs cannot extract this data, so the value |
| 1403 | is always @code{0}. |
| 1404 | |
| 1405 | @item @var{part} |
| 1406 | The part of the scroll bar on which the click occurred. It is one of |
| 1407 | the symbols @code{handle} (the scroll bar handle), @code{above-handle} |
| 1408 | (the area above the handle), @code{below-handle} (the area below the |
| 1409 | handle), @code{up} (the up arrow at one end of the scroll bar), or |
| 1410 | @code{down} (the down arrow at one end of the scroll bar). |
| 1411 | @c The `top', `bottom', and `end-scroll' codes don't seem to be used. |
| 1412 | @end table |
| 1413 | |
| 1414 | |
| 1415 | @node Drag Events |
| 1416 | @subsection Drag Events |
| 1417 | @cindex drag event |
| 1418 | @cindex mouse drag event |
| 1419 | |
| 1420 | With Emacs, you can have a drag event without even changing your |
| 1421 | clothes. A @dfn{drag event} happens every time the user presses a mouse |
| 1422 | button and then moves the mouse to a different character position before |
| 1423 | releasing the button. Like all mouse events, drag events are |
| 1424 | represented in Lisp as lists. The lists record both the starting mouse |
| 1425 | position and the final position, like this: |
| 1426 | |
| 1427 | @example |
| 1428 | (@var{event-type} |
| 1429 | (@var{window1} START-POSITION) |
| 1430 | (@var{window2} END-POSITION)) |
| 1431 | @end example |
| 1432 | |
| 1433 | For a drag event, the name of the symbol @var{event-type} contains the |
| 1434 | prefix @samp{drag-}. For example, dragging the mouse with button 2 |
| 1435 | held down generates a @code{drag-mouse-2} event. The second and third |
| 1436 | elements of the event give the starting and ending position of the |
| 1437 | drag, as mouse position lists (@pxref{Click Events}). You can access |
| 1438 | the second element of any mouse event in the same way, with no need to |
| 1439 | distinguish drag events from others. |
| 1440 | |
| 1441 | The @samp{drag-} prefix follows the modifier key prefixes such as |
| 1442 | @samp{C-} and @samp{M-}. |
| 1443 | |
| 1444 | If @code{read-key-sequence} receives a drag event that has no key |
| 1445 | binding, and the corresponding click event does have a binding, it |
| 1446 | changes the drag event into a click event at the drag's starting |
| 1447 | position. This means that you don't have to distinguish between click |
| 1448 | and drag events unless you want to. |
| 1449 | |
| 1450 | @node Button-Down Events |
| 1451 | @subsection Button-Down Events |
| 1452 | @cindex button-down event |
| 1453 | |
| 1454 | Click and drag events happen when the user releases a mouse button. |
| 1455 | They cannot happen earlier, because there is no way to distinguish a |
| 1456 | click from a drag until the button is released. |
| 1457 | |
| 1458 | If you want to take action as soon as a button is pressed, you need to |
| 1459 | handle @dfn{button-down} events.@footnote{Button-down is the |
| 1460 | conservative antithesis of drag.} These occur as soon as a button is |
| 1461 | pressed. They are represented by lists that look exactly like click |
| 1462 | events (@pxref{Click Events}), except that the @var{event-type} symbol |
| 1463 | name contains the prefix @samp{down-}. The @samp{down-} prefix follows |
| 1464 | modifier key prefixes such as @samp{C-} and @samp{M-}. |
| 1465 | |
| 1466 | The function @code{read-key-sequence} ignores any button-down events |
| 1467 | that don't have command bindings; therefore, the Emacs command loop |
| 1468 | ignores them too. This means that you need not worry about defining |
| 1469 | button-down events unless you want them to do something. The usual |
| 1470 | reason to define a button-down event is so that you can track mouse |
| 1471 | motion (by reading motion events) until the button is released. |
| 1472 | @xref{Motion Events}. |
| 1473 | |
| 1474 | @node Repeat Events |
| 1475 | @subsection Repeat Events |
| 1476 | @cindex repeat events |
| 1477 | @cindex double-click events |
| 1478 | @cindex triple-click events |
| 1479 | @cindex mouse events, repeated |
| 1480 | |
| 1481 | If you press the same mouse button more than once in quick succession |
| 1482 | without moving the mouse, Emacs generates special @dfn{repeat} mouse |
| 1483 | events for the second and subsequent presses. |
| 1484 | |
| 1485 | The most common repeat events are @dfn{double-click} events. Emacs |
| 1486 | generates a double-click event when you click a button twice; the event |
| 1487 | happens when you release the button (as is normal for all click |
| 1488 | events). |
| 1489 | |
| 1490 | The event type of a double-click event contains the prefix |
| 1491 | @samp{double-}. Thus, a double click on the second mouse button with |
| 1492 | @key{meta} held down comes to the Lisp program as |
| 1493 | @code{M-double-mouse-2}. If a double-click event has no binding, the |
| 1494 | binding of the corresponding ordinary click event is used to execute |
| 1495 | it. Thus, you need not pay attention to the double click feature |
| 1496 | unless you really want to. |
| 1497 | |
| 1498 | When the user performs a double click, Emacs generates first an ordinary |
| 1499 | click event, and then a double-click event. Therefore, you must design |
| 1500 | the command binding of the double click event to assume that the |
| 1501 | single-click command has already run. It must produce the desired |
| 1502 | results of a double click, starting from the results of a single click. |
| 1503 | |
| 1504 | This is convenient, if the meaning of a double click somehow ``builds |
| 1505 | on'' the meaning of a single click---which is recommended user interface |
| 1506 | design practice for double clicks. |
| 1507 | |
| 1508 | If you click a button, then press it down again and start moving the |
| 1509 | mouse with the button held down, then you get a @dfn{double-drag} event |
| 1510 | when you ultimately release the button. Its event type contains |
| 1511 | @samp{double-drag} instead of just @samp{drag}. If a double-drag event |
| 1512 | has no binding, Emacs looks for an alternate binding as if the event |
| 1513 | were an ordinary drag. |
| 1514 | |
| 1515 | Before the double-click or double-drag event, Emacs generates a |
| 1516 | @dfn{double-down} event when the user presses the button down for the |
| 1517 | second time. Its event type contains @samp{double-down} instead of just |
| 1518 | @samp{down}. If a double-down event has no binding, Emacs looks for an |
| 1519 | alternate binding as if the event were an ordinary button-down event. |
| 1520 | If it finds no binding that way either, the double-down event is |
| 1521 | ignored. |
| 1522 | |
| 1523 | To summarize, when you click a button and then press it again right |
| 1524 | away, Emacs generates a down event and a click event for the first |
| 1525 | click, a double-down event when you press the button again, and finally |
| 1526 | either a double-click or a double-drag event. |
| 1527 | |
| 1528 | If you click a button twice and then press it again, all in quick |
| 1529 | succession, Emacs generates a @dfn{triple-down} event, followed by |
| 1530 | either a @dfn{triple-click} or a @dfn{triple-drag}. The event types of |
| 1531 | these events contain @samp{triple} instead of @samp{double}. If any |
| 1532 | triple event has no binding, Emacs uses the binding that it would use |
| 1533 | for the corresponding double event. |
| 1534 | |
| 1535 | If you click a button three or more times and then press it again, the |
| 1536 | events for the presses beyond the third are all triple events. Emacs |
| 1537 | does not have separate event types for quadruple, quintuple, etc.@: |
| 1538 | events. However, you can look at the event list to find out precisely |
| 1539 | how many times the button was pressed. |
| 1540 | |
| 1541 | @defun event-click-count event |
| 1542 | This function returns the number of consecutive button presses that led |
| 1543 | up to @var{event}. If @var{event} is a double-down, double-click or |
| 1544 | double-drag event, the value is 2. If @var{event} is a triple event, |
| 1545 | the value is 3 or greater. If @var{event} is an ordinary mouse event |
| 1546 | (not a repeat event), the value is 1. |
| 1547 | @end defun |
| 1548 | |
| 1549 | @defopt double-click-fuzz |
| 1550 | To generate repeat events, successive mouse button presses must be at |
| 1551 | approximately the same screen position. The value of |
| 1552 | @code{double-click-fuzz} specifies the maximum number of pixels the |
| 1553 | mouse may be moved (horizontally or vertically) between two successive |
| 1554 | clicks to make a double-click. |
| 1555 | |
| 1556 | This variable is also the threshold for motion of the mouse to count |
| 1557 | as a drag. |
| 1558 | @end defopt |
| 1559 | |
| 1560 | @defopt double-click-time |
| 1561 | To generate repeat events, the number of milliseconds between |
| 1562 | successive button presses must be less than the value of |
| 1563 | @code{double-click-time}. Setting @code{double-click-time} to |
| 1564 | @code{nil} disables multi-click detection entirely. Setting it to |
| 1565 | @code{t} removes the time limit; Emacs then detects multi-clicks by |
| 1566 | position only. |
| 1567 | @end defopt |
| 1568 | |
| 1569 | @node Motion Events |
| 1570 | @subsection Motion Events |
| 1571 | @cindex motion event |
| 1572 | @cindex mouse motion events |
| 1573 | |
| 1574 | Emacs sometimes generates @dfn{mouse motion} events to describe motion |
| 1575 | of the mouse without any button activity. Mouse motion events are |
| 1576 | represented by lists that look like this: |
| 1577 | |
| 1578 | @example |
| 1579 | (mouse-movement POSITION) |
| 1580 | @end example |
| 1581 | |
| 1582 | @noindent |
| 1583 | @var{position} is a mouse position list (@pxref{Click Events}), |
| 1584 | specifying the current position of the mouse cursor. |
| 1585 | |
| 1586 | The special form @code{track-mouse} enables generation of motion |
| 1587 | events within its body. Outside of @code{track-mouse} forms, Emacs |
| 1588 | does not generate events for mere motion of the mouse, and these |
| 1589 | events do not appear. @xref{Mouse Tracking}. |
| 1590 | |
| 1591 | @node Focus Events |
| 1592 | @subsection Focus Events |
| 1593 | @cindex focus event |
| 1594 | |
| 1595 | Window systems provide general ways for the user to control which window |
| 1596 | gets keyboard input. This choice of window is called the @dfn{focus}. |
| 1597 | When the user does something to switch between Emacs frames, that |
| 1598 | generates a @dfn{focus event}. The normal definition of a focus event, |
| 1599 | in the global keymap, is to select a new frame within Emacs, as the user |
| 1600 | would expect. @xref{Input Focus}. |
| 1601 | |
| 1602 | Focus events are represented in Lisp as lists that look like this: |
| 1603 | |
| 1604 | @example |
| 1605 | (switch-frame @var{new-frame}) |
| 1606 | @end example |
| 1607 | |
| 1608 | @noindent |
| 1609 | where @var{new-frame} is the frame switched to. |
| 1610 | |
| 1611 | Some X window managers are set up so that just moving the mouse into a |
| 1612 | window is enough to set the focus there. Usually, there is no need |
| 1613 | for a Lisp program to know about the focus change until some other |
| 1614 | kind of input arrives. Emacs generates a focus event only when the |
| 1615 | user actually types a keyboard key or presses a mouse button in the |
| 1616 | new frame; just moving the mouse between frames does not generate a |
| 1617 | focus event. |
| 1618 | |
| 1619 | A focus event in the middle of a key sequence would garble the |
| 1620 | sequence. So Emacs never generates a focus event in the middle of a key |
| 1621 | sequence. If the user changes focus in the middle of a key |
| 1622 | sequence---that is, after a prefix key---then Emacs reorders the events |
| 1623 | so that the focus event comes either before or after the multi-event key |
| 1624 | sequence, and not within it. |
| 1625 | |
| 1626 | @node Misc Events |
| 1627 | @subsection Miscellaneous System Events |
| 1628 | |
| 1629 | A few other event types represent occurrences within the system. |
| 1630 | |
| 1631 | @table @code |
| 1632 | @cindex @code{delete-frame} event |
| 1633 | @item (delete-frame (@var{frame})) |
| 1634 | This kind of event indicates that the user gave the window manager |
| 1635 | a command to delete a particular window, which happens to be an Emacs frame. |
| 1636 | |
| 1637 | The standard definition of the @code{delete-frame} event is to delete @var{frame}. |
| 1638 | |
| 1639 | @cindex @code{iconify-frame} event |
| 1640 | @item (iconify-frame (@var{frame})) |
| 1641 | This kind of event indicates that the user iconified @var{frame} using |
| 1642 | the window manager. Its standard definition is @code{ignore}; since the |
| 1643 | frame has already been iconified, Emacs has no work to do. The purpose |
| 1644 | of this event type is so that you can keep track of such events if you |
| 1645 | want to. |
| 1646 | |
| 1647 | @cindex @code{make-frame-visible} event |
| 1648 | @item (make-frame-visible (@var{frame})) |
| 1649 | This kind of event indicates that the user deiconified @var{frame} using |
| 1650 | the window manager. Its standard definition is @code{ignore}; since the |
| 1651 | frame has already been made visible, Emacs has no work to do. |
| 1652 | |
| 1653 | @cindex @code{wheel-up} event |
| 1654 | @cindex @code{wheel-down} event |
| 1655 | @item (wheel-up @var{position}) |
| 1656 | @itemx (wheel-down @var{position}) |
| 1657 | These kinds of event are generated by moving a mouse wheel. The |
| 1658 | @var{position} element is a mouse position list (@pxref{Click |
| 1659 | Events}), specifying the position of the mouse cursor when the event |
| 1660 | occurred. |
| 1661 | |
| 1662 | @vindex mouse-wheel-up-event |
| 1663 | @vindex mouse-wheel-down-event |
| 1664 | This kind of event is generated only on some kinds of systems. On some |
| 1665 | systems, @code{mouse-4} and @code{mouse-5} are used instead. For |
| 1666 | portable code, use the variables @code{mouse-wheel-up-event} and |
| 1667 | @code{mouse-wheel-down-event} defined in @file{mwheel.el} to determine |
| 1668 | what event types to expect for the mouse wheel. |
| 1669 | |
| 1670 | @cindex @code{drag-n-drop} event |
| 1671 | @item (drag-n-drop @var{position} @var{files}) |
| 1672 | This kind of event is generated when a group of files is |
| 1673 | selected in an application outside of Emacs, and then dragged and |
| 1674 | dropped onto an Emacs frame. |
| 1675 | |
| 1676 | The element @var{position} is a list describing the position of the |
| 1677 | event, in the same format as used in a mouse-click event (@pxref{Click |
| 1678 | Events}), and @var{files} is the list of file names that were dragged |
| 1679 | and dropped. The usual way to handle this event is by visiting these |
| 1680 | files. |
| 1681 | |
| 1682 | This kind of event is generated, at present, only on some kinds of |
| 1683 | systems. |
| 1684 | |
| 1685 | @cindex @code{help-echo} event |
| 1686 | @item help-echo |
| 1687 | This kind of event is generated when a mouse pointer moves onto a |
| 1688 | portion of buffer text which has a @code{help-echo} text property. |
| 1689 | The generated event has this form: |
| 1690 | |
| 1691 | @example |
| 1692 | (help-echo @var{frame} @var{help} @var{window} @var{object} @var{pos}) |
| 1693 | @end example |
| 1694 | |
| 1695 | @noindent |
| 1696 | The precise meaning of the event parameters and the way these |
| 1697 | parameters are used to display the help-echo text are described in |
| 1698 | @ref{Text help-echo}. |
| 1699 | |
| 1700 | @cindex @code{sigusr1} event |
| 1701 | @cindex @code{sigusr2} event |
| 1702 | @cindex user signals |
| 1703 | @item sigusr1 |
| 1704 | @itemx sigusr2 |
| 1705 | These events are generated when the Emacs process receives |
| 1706 | the signals @code{SIGUSR1} and @code{SIGUSR2}. They contain no |
| 1707 | additional data because signals do not carry additional information. |
| 1708 | They can be useful for debugging (@pxref{Error Debugging}). |
| 1709 | |
| 1710 | To catch a user signal, bind the corresponding event to an interactive |
| 1711 | command in the @code{special-event-map} (@pxref{Active Keymaps}). |
| 1712 | The command is called with no arguments, and the specific signal event is |
| 1713 | available in @code{last-input-event}. For example: |
| 1714 | |
| 1715 | @smallexample |
| 1716 | (defun sigusr-handler () |
| 1717 | (interactive) |
| 1718 | (message "Caught signal %S" last-input-event)) |
| 1719 | |
| 1720 | (define-key special-event-map [sigusr1] 'sigusr-handler) |
| 1721 | @end smallexample |
| 1722 | |
| 1723 | To test the signal handler, you can make Emacs send a signal to itself: |
| 1724 | |
| 1725 | @smallexample |
| 1726 | (signal-process (emacs-pid) 'sigusr1) |
| 1727 | @end smallexample |
| 1728 | |
| 1729 | @cindex @code{language-change} event |
| 1730 | @item language-change |
| 1731 | This kind of event is generated on MS-Windows when the input language |
| 1732 | has changed. This typically means that the keyboard keys will send to |
| 1733 | Emacs characters from a different language. The generated event has |
| 1734 | this form: |
| 1735 | |
| 1736 | @smallexample |
| 1737 | (language-change @var{frame} @var{codepage} @var{language-id}) |
| 1738 | @end smallexample |
| 1739 | |
| 1740 | @noindent |
| 1741 | Here @var{frame} is the frame which was current when the input |
| 1742 | language changed; @var{codepage} is the new codepage number; and |
| 1743 | @var{language-id} is the numerical ID of the new input language. The |
| 1744 | coding-system (@pxref{Coding Systems}) that corresponds to |
| 1745 | @var{codepage} is @code{cp@var{codepage}} or |
| 1746 | @code{windows-@var{codepage}}. To convert @var{language-id} to a |
| 1747 | string (e.g., to use it for various language-dependent features, such |
| 1748 | as @code{set-language-environment}), use the |
| 1749 | @code{w32-get-locale-info} function, like this: |
| 1750 | |
| 1751 | @smallexample |
| 1752 | ;; Get the abbreviated language name, such as "ENU" for English |
| 1753 | (w32-get-locale-info language-id) |
| 1754 | ;; Get the full English name of the language, |
| 1755 | ;; such as "English (United States)" |
| 1756 | (w32-get-locale-info language-id 4097) |
| 1757 | ;; Get the full localized name of the language |
| 1758 | (w32-get-locale-info language-id t) |
| 1759 | @end smallexample |
| 1760 | @end table |
| 1761 | |
| 1762 | If one of these events arrives in the middle of a key sequence---that |
| 1763 | is, after a prefix key---then Emacs reorders the events so that this |
| 1764 | event comes either before or after the multi-event key sequence, not |
| 1765 | within it. |
| 1766 | |
| 1767 | @node Event Examples |
| 1768 | @subsection Event Examples |
| 1769 | |
| 1770 | If the user presses and releases the left mouse button over the same |
| 1771 | location, that generates a sequence of events like this: |
| 1772 | |
| 1773 | @smallexample |
| 1774 | (down-mouse-1 (#<window 18 on NEWS> 2613 (0 . 38) -864320)) |
| 1775 | (mouse-1 (#<window 18 on NEWS> 2613 (0 . 38) -864180)) |
| 1776 | @end smallexample |
| 1777 | |
| 1778 | While holding the control key down, the user might hold down the |
| 1779 | second mouse button, and drag the mouse from one line to the next. |
| 1780 | That produces two events, as shown here: |
| 1781 | |
| 1782 | @smallexample |
| 1783 | (C-down-mouse-2 (#<window 18 on NEWS> 3440 (0 . 27) -731219)) |
| 1784 | (C-drag-mouse-2 (#<window 18 on NEWS> 3440 (0 . 27) -731219) |
| 1785 | (#<window 18 on NEWS> 3510 (0 . 28) -729648)) |
| 1786 | @end smallexample |
| 1787 | |
| 1788 | While holding down the meta and shift keys, the user might press the |
| 1789 | second mouse button on the window's mode line, and then drag the mouse |
| 1790 | into another window. That produces a pair of events like these: |
| 1791 | |
| 1792 | @smallexample |
| 1793 | (M-S-down-mouse-2 (#<window 18 on NEWS> mode-line (33 . 31) -457844)) |
| 1794 | (M-S-drag-mouse-2 (#<window 18 on NEWS> mode-line (33 . 31) -457844) |
| 1795 | (#<window 20 on carlton-sanskrit.tex> 161 (33 . 3) |
| 1796 | -453816)) |
| 1797 | @end smallexample |
| 1798 | |
| 1799 | To handle a SIGUSR1 signal, define an interactive function, and |
| 1800 | bind it to the @code{signal usr1} event sequence: |
| 1801 | |
| 1802 | @smallexample |
| 1803 | (defun usr1-handler () |
| 1804 | (interactive) |
| 1805 | (message "Got USR1 signal")) |
| 1806 | (global-set-key [signal usr1] 'usr1-handler) |
| 1807 | @end smallexample |
| 1808 | |
| 1809 | @node Classifying Events |
| 1810 | @subsection Classifying Events |
| 1811 | @cindex event type |
| 1812 | |
| 1813 | Every event has an @dfn{event type}, which classifies the event for |
| 1814 | key binding purposes. For a keyboard event, the event type equals the |
| 1815 | event value; thus, the event type for a character is the character, and |
| 1816 | the event type for a function key symbol is the symbol itself. For |
| 1817 | events that are lists, the event type is the symbol in the @sc{car} of |
| 1818 | the list. Thus, the event type is always a symbol or a character. |
| 1819 | |
| 1820 | Two events of the same type are equivalent where key bindings are |
| 1821 | concerned; thus, they always run the same command. That does not |
| 1822 | necessarily mean they do the same things, however, as some commands look |
| 1823 | at the whole event to decide what to do. For example, some commands use |
| 1824 | the location of a mouse event to decide where in the buffer to act. |
| 1825 | |
| 1826 | Sometimes broader classifications of events are useful. For example, |
| 1827 | you might want to ask whether an event involved the @key{META} key, |
| 1828 | regardless of which other key or mouse button was used. |
| 1829 | |
| 1830 | The functions @code{event-modifiers} and @code{event-basic-type} are |
| 1831 | provided to get such information conveniently. |
| 1832 | |
| 1833 | @defun event-modifiers event |
| 1834 | This function returns a list of the modifiers that @var{event} has. The |
| 1835 | modifiers are symbols; they include @code{shift}, @code{control}, |
| 1836 | @code{meta}, @code{alt}, @code{hyper} and @code{super}. In addition, |
| 1837 | the modifiers list of a mouse event symbol always contains one of |
| 1838 | @code{click}, @code{drag}, and @code{down}. For double or triple |
| 1839 | events, it also contains @code{double} or @code{triple}. |
| 1840 | |
| 1841 | The argument @var{event} may be an entire event object, or just an |
| 1842 | event type. If @var{event} is a symbol that has never been used in an |
| 1843 | event that has been read as input in the current Emacs session, then |
| 1844 | @code{event-modifiers} can return @code{nil}, even when @var{event} |
| 1845 | actually has modifiers. |
| 1846 | |
| 1847 | Here are some examples: |
| 1848 | |
| 1849 | @example |
| 1850 | (event-modifiers ?a) |
| 1851 | @result{} nil |
| 1852 | (event-modifiers ?A) |
| 1853 | @result{} (shift) |
| 1854 | (event-modifiers ?\C-a) |
| 1855 | @result{} (control) |
| 1856 | (event-modifiers ?\C-%) |
| 1857 | @result{} (control) |
| 1858 | (event-modifiers ?\C-\S-a) |
| 1859 | @result{} (control shift) |
| 1860 | (event-modifiers 'f5) |
| 1861 | @result{} nil |
| 1862 | (event-modifiers 's-f5) |
| 1863 | @result{} (super) |
| 1864 | (event-modifiers 'M-S-f5) |
| 1865 | @result{} (meta shift) |
| 1866 | (event-modifiers 'mouse-1) |
| 1867 | @result{} (click) |
| 1868 | (event-modifiers 'down-mouse-1) |
| 1869 | @result{} (down) |
| 1870 | @end example |
| 1871 | |
| 1872 | The modifiers list for a click event explicitly contains @code{click}, |
| 1873 | but the event symbol name itself does not contain @samp{click}. |
| 1874 | @end defun |
| 1875 | |
| 1876 | @defun event-basic-type event |
| 1877 | This function returns the key or mouse button that @var{event} |
| 1878 | describes, with all modifiers removed. The @var{event} argument is as |
| 1879 | in @code{event-modifiers}. For example: |
| 1880 | |
| 1881 | @example |
| 1882 | (event-basic-type ?a) |
| 1883 | @result{} 97 |
| 1884 | (event-basic-type ?A) |
| 1885 | @result{} 97 |
| 1886 | (event-basic-type ?\C-a) |
| 1887 | @result{} 97 |
| 1888 | (event-basic-type ?\C-\S-a) |
| 1889 | @result{} 97 |
| 1890 | (event-basic-type 'f5) |
| 1891 | @result{} f5 |
| 1892 | (event-basic-type 's-f5) |
| 1893 | @result{} f5 |
| 1894 | (event-basic-type 'M-S-f5) |
| 1895 | @result{} f5 |
| 1896 | (event-basic-type 'down-mouse-1) |
| 1897 | @result{} mouse-1 |
| 1898 | @end example |
| 1899 | @end defun |
| 1900 | |
| 1901 | @defun mouse-movement-p object |
| 1902 | This function returns non-@code{nil} if @var{object} is a mouse movement |
| 1903 | event. |
| 1904 | @end defun |
| 1905 | |
| 1906 | @defun event-convert-list list |
| 1907 | This function converts a list of modifier names and a basic event type |
| 1908 | to an event type which specifies all of them. The basic event type |
| 1909 | must be the last element of the list. For example, |
| 1910 | |
| 1911 | @example |
| 1912 | (event-convert-list '(control ?a)) |
| 1913 | @result{} 1 |
| 1914 | (event-convert-list '(control meta ?a)) |
| 1915 | @result{} -134217727 |
| 1916 | (event-convert-list '(control super f1)) |
| 1917 | @result{} C-s-f1 |
| 1918 | @end example |
| 1919 | @end defun |
| 1920 | |
| 1921 | @node Accessing Mouse |
| 1922 | @subsection Accessing Mouse Events |
| 1923 | @cindex mouse events, data in |
| 1924 | |
| 1925 | This section describes convenient functions for accessing the data in |
| 1926 | a mouse button or motion event. |
| 1927 | |
| 1928 | The following two functions return a mouse position list |
| 1929 | (@pxref{Click Events}), specifying the position of a mouse event. |
| 1930 | |
| 1931 | @defun event-start event |
| 1932 | This returns the starting position of @var{event}. |
| 1933 | |
| 1934 | If @var{event} is a click or button-down event, this returns the |
| 1935 | location of the event. If @var{event} is a drag event, this returns the |
| 1936 | drag's starting position. |
| 1937 | @end defun |
| 1938 | |
| 1939 | @defun event-end event |
| 1940 | This returns the ending position of @var{event}. |
| 1941 | |
| 1942 | If @var{event} is a drag event, this returns the position where the user |
| 1943 | released the mouse button. If @var{event} is a click or button-down |
| 1944 | event, the value is actually the starting position, which is the only |
| 1945 | position such events have. |
| 1946 | @end defun |
| 1947 | |
| 1948 | @defun posnp object |
| 1949 | This function returns non-@code{nil} if @var{object} is a mouse |
| 1950 | position list, in either of the formats documented in @ref{Click |
| 1951 | Events}); and @code{nil} otherwise. |
| 1952 | @end defun |
| 1953 | |
| 1954 | @cindex mouse position list, accessing |
| 1955 | These functions take a mouse position list as argument, and return |
| 1956 | various parts of it: |
| 1957 | |
| 1958 | @defun posn-window position |
| 1959 | Return the window that @var{position} is in. |
| 1960 | @end defun |
| 1961 | |
| 1962 | @defun posn-area position |
| 1963 | Return the window area recorded in @var{position}. It returns @code{nil} |
| 1964 | when the event occurred in the text area of the window; otherwise, it |
| 1965 | is a symbol identifying the area in which the event occurred. |
| 1966 | @end defun |
| 1967 | |
| 1968 | @defun posn-point position |
| 1969 | Return the buffer position in @var{position}. When the event occurred |
| 1970 | in the text area of the window, in a marginal area, or on a fringe, |
| 1971 | this is an integer specifying a buffer position. Otherwise, the value |
| 1972 | is undefined. |
| 1973 | @end defun |
| 1974 | |
| 1975 | @defun posn-x-y position |
| 1976 | Return the pixel-based x and y coordinates in @var{position}, as a |
| 1977 | cons cell @code{(@var{x} . @var{y})}. These coordinates are relative |
| 1978 | to the window given by @code{posn-window}. |
| 1979 | |
| 1980 | This example shows how to convert the window-relative coordinates in |
| 1981 | the text area of a window into frame-relative coordinates: |
| 1982 | |
| 1983 | @example |
| 1984 | (defun frame-relative-coordinates (position) |
| 1985 | "Return frame-relative coordinates from POSITION. |
| 1986 | POSITION is assumed to lie in a window text area." |
| 1987 | (let* ((x-y (posn-x-y position)) |
| 1988 | (window (posn-window position)) |
| 1989 | (edges (window-inside-pixel-edges window))) |
| 1990 | (cons (+ (car x-y) (car edges)) |
| 1991 | (+ (cdr x-y) (cadr edges))))) |
| 1992 | @end example |
| 1993 | @end defun |
| 1994 | |
| 1995 | @defun posn-col-row position |
| 1996 | This function returns a cons cell @code{(@var{col} . @var{row})}, |
| 1997 | containing the estimated column and row corresponding to buffer |
| 1998 | position @var{position}. The return value is given in units of the |
| 1999 | frame's default character width and height, as computed from the |
| 2000 | @var{x} and @var{y} values corresponding to @var{position}. (So, if |
| 2001 | the actual characters have non-default sizes, the actual row and |
| 2002 | column may differ from these computed values.) |
| 2003 | |
| 2004 | Note that @var{row} is counted from the top of the text area. If the |
| 2005 | window possesses a header line (@pxref{Header Lines}), it is |
| 2006 | @emph{not} counted as the first line. |
| 2007 | @end defun |
| 2008 | |
| 2009 | @defun posn-actual-col-row position |
| 2010 | Return the actual row and column in @var{position}, as a cons cell |
| 2011 | @code{(@var{col} . @var{row})}. The values are the actual row and |
| 2012 | column numbers in the window. @xref{Click Events}, for details. It |
| 2013 | returns @code{nil} if @var{position} does not include actual positions |
| 2014 | values. |
| 2015 | @end defun |
| 2016 | |
| 2017 | @defun posn-string position |
| 2018 | Return the string object in @var{position}, either @code{nil}, or a |
| 2019 | cons cell @code{(@var{string} . @var{string-pos})}. |
| 2020 | @end defun |
| 2021 | |
| 2022 | @defun posn-image position |
| 2023 | Return the image object in @var{position}, either @code{nil}, or an |
| 2024 | image @code{(image ...)}. |
| 2025 | @end defun |
| 2026 | |
| 2027 | @defun posn-object position |
| 2028 | Return the image or string object in @var{position}, either |
| 2029 | @code{nil}, an image @code{(image ...)}, or a cons cell |
| 2030 | @code{(@var{string} . @var{string-pos})}. |
| 2031 | @end defun |
| 2032 | |
| 2033 | @defun posn-object-x-y position |
| 2034 | Return the pixel-based x and y coordinates relative to the upper left |
| 2035 | corner of the object in @var{position} as a cons cell @code{(@var{dx} |
| 2036 | . @var{dy})}. If the @var{position} is a buffer position, return the |
| 2037 | relative position in the character at that position. |
| 2038 | @end defun |
| 2039 | |
| 2040 | @defun posn-object-width-height position |
| 2041 | Return the pixel width and height of the object in @var{position} as a |
| 2042 | cons cell @code{(@var{width} . @var{height})}. If the @var{position} |
| 2043 | is a buffer position, return the size of the character at that position. |
| 2044 | @end defun |
| 2045 | |
| 2046 | @cindex timestamp of a mouse event |
| 2047 | @defun posn-timestamp position |
| 2048 | Return the timestamp in @var{position}. This is the time at which the |
| 2049 | event occurred, in milliseconds. |
| 2050 | @end defun |
| 2051 | |
| 2052 | These functions compute a position list given particular buffer |
| 2053 | position or screen position. You can access the data in this position |
| 2054 | list with the functions described above. |
| 2055 | |
| 2056 | @defun posn-at-point &optional pos window |
| 2057 | This function returns a position list for position @var{pos} in |
| 2058 | @var{window}. @var{pos} defaults to point in @var{window}; |
| 2059 | @var{window} defaults to the selected window. |
| 2060 | |
| 2061 | @code{posn-at-point} returns @code{nil} if @var{pos} is not visible in |
| 2062 | @var{window}. |
| 2063 | @end defun |
| 2064 | |
| 2065 | @defun posn-at-x-y x y &optional frame-or-window whole |
| 2066 | This function returns position information corresponding to pixel |
| 2067 | coordinates @var{x} and @var{y} in a specified frame or window, |
| 2068 | @var{frame-or-window}, which defaults to the selected window. |
| 2069 | The coordinates @var{x} and @var{y} are relative to the |
| 2070 | frame or window used. |
| 2071 | If @var{whole} is @code{nil}, the coordinates are relative |
| 2072 | to the window text area, otherwise they are relative to |
| 2073 | the entire window area including scroll bars, margins and fringes. |
| 2074 | @end defun |
| 2075 | |
| 2076 | @node Accessing Scroll |
| 2077 | @subsection Accessing Scroll Bar Events |
| 2078 | @cindex scroll bar events, data in |
| 2079 | |
| 2080 | These functions are useful for decoding scroll bar events. |
| 2081 | |
| 2082 | @defun scroll-bar-event-ratio event |
| 2083 | This function returns the fractional vertical position of a scroll bar |
| 2084 | event within the scroll bar. The value is a cons cell |
| 2085 | @code{(@var{portion} . @var{whole})} containing two integers whose ratio |
| 2086 | is the fractional position. |
| 2087 | @end defun |
| 2088 | |
| 2089 | @defun scroll-bar-scale ratio total |
| 2090 | This function multiplies (in effect) @var{ratio} by @var{total}, |
| 2091 | rounding the result to an integer. The argument @var{ratio} is not a |
| 2092 | number, but rather a pair @code{(@var{num} . @var{denom})}---typically a |
| 2093 | value returned by @code{scroll-bar-event-ratio}. |
| 2094 | |
| 2095 | This function is handy for scaling a position on a scroll bar into a |
| 2096 | buffer position. Here's how to do that: |
| 2097 | |
| 2098 | @example |
| 2099 | (+ (point-min) |
| 2100 | (scroll-bar-scale |
| 2101 | (posn-x-y (event-start event)) |
| 2102 | (- (point-max) (point-min)))) |
| 2103 | @end example |
| 2104 | |
| 2105 | Recall that scroll bar events have two integers forming a ratio, in place |
| 2106 | of a pair of x and y coordinates. |
| 2107 | @end defun |
| 2108 | |
| 2109 | @node Strings of Events |
| 2110 | @subsection Putting Keyboard Events in Strings |
| 2111 | @cindex keyboard events in strings |
| 2112 | @cindex strings with keyboard events |
| 2113 | |
| 2114 | In most of the places where strings are used, we conceptualize the |
| 2115 | string as containing text characters---the same kind of characters found |
| 2116 | in buffers or files. Occasionally Lisp programs use strings that |
| 2117 | conceptually contain keyboard characters; for example, they may be key |
| 2118 | sequences or keyboard macro definitions. However, storing keyboard |
| 2119 | characters in a string is a complex matter, for reasons of historical |
| 2120 | compatibility, and it is not always possible. |
| 2121 | |
| 2122 | We recommend that new programs avoid dealing with these complexities |
| 2123 | by not storing keyboard events in strings. Here is how to do that: |
| 2124 | |
| 2125 | @itemize @bullet |
| 2126 | @item |
| 2127 | Use vectors instead of strings for key sequences, when you plan to use |
| 2128 | them for anything other than as arguments to @code{lookup-key} and |
| 2129 | @code{define-key}. For example, you can use |
| 2130 | @code{read-key-sequence-vector} instead of @code{read-key-sequence}, and |
| 2131 | @code{this-command-keys-vector} instead of @code{this-command-keys}. |
| 2132 | |
| 2133 | @item |
| 2134 | Use vectors to write key sequence constants containing meta characters, |
| 2135 | even when passing them directly to @code{define-key}. |
| 2136 | |
| 2137 | @item |
| 2138 | When you have to look at the contents of a key sequence that might be a |
| 2139 | string, use @code{listify-key-sequence} (@pxref{Event Input Misc}) |
| 2140 | first, to convert it to a list. |
| 2141 | @end itemize |
| 2142 | |
| 2143 | The complexities stem from the modifier bits that keyboard input |
| 2144 | characters can include. Aside from the Meta modifier, none of these |
| 2145 | modifier bits can be included in a string, and the Meta modifier is |
| 2146 | allowed only in special cases. |
| 2147 | |
| 2148 | The earliest GNU Emacs versions represented meta characters as codes |
| 2149 | in the range of 128 to 255. At that time, the basic character codes |
| 2150 | ranged from 0 to 127, so all keyboard character codes did fit in a |
| 2151 | string. Many Lisp programs used @samp{\M-} in string constants to stand |
| 2152 | for meta characters, especially in arguments to @code{define-key} and |
| 2153 | similar functions, and key sequences and sequences of events were always |
| 2154 | represented as strings. |
| 2155 | |
| 2156 | When we added support for larger basic character codes beyond 127, and |
| 2157 | additional modifier bits, we had to change the representation of meta |
| 2158 | characters. Now the flag that represents the Meta modifier in a |
| 2159 | character is |
| 2160 | @tex |
| 2161 | @math{2^{27}} |
| 2162 | @end tex |
| 2163 | @ifnottex |
| 2164 | 2**27 |
| 2165 | @end ifnottex |
| 2166 | and such numbers cannot be included in a string. |
| 2167 | |
| 2168 | To support programs with @samp{\M-} in string constants, there are |
| 2169 | special rules for including certain meta characters in a string. |
| 2170 | Here are the rules for interpreting a string as a sequence of input |
| 2171 | characters: |
| 2172 | |
| 2173 | @itemize @bullet |
| 2174 | @item |
| 2175 | If the keyboard character value is in the range of 0 to 127, it can go |
| 2176 | in the string unchanged. |
| 2177 | |
| 2178 | @item |
| 2179 | The meta variants of those characters, with codes in the range of |
| 2180 | @tex |
| 2181 | @math{2^{27}} |
| 2182 | @end tex |
| 2183 | @ifnottex |
| 2184 | 2**27 |
| 2185 | @end ifnottex |
| 2186 | to |
| 2187 | @tex |
| 2188 | @math{2^{27} + 127}, |
| 2189 | @end tex |
| 2190 | @ifnottex |
| 2191 | 2**27+127, |
| 2192 | @end ifnottex |
| 2193 | can also go in the string, but you must change their |
| 2194 | numeric values. You must set the |
| 2195 | @tex |
| 2196 | @math{2^{7}} |
| 2197 | @end tex |
| 2198 | @ifnottex |
| 2199 | 2**7 |
| 2200 | @end ifnottex |
| 2201 | bit instead of the |
| 2202 | @tex |
| 2203 | @math{2^{27}} |
| 2204 | @end tex |
| 2205 | @ifnottex |
| 2206 | 2**27 |
| 2207 | @end ifnottex |
| 2208 | bit, resulting in a value between 128 and 255. Only a unibyte string |
| 2209 | can include these codes. |
| 2210 | |
| 2211 | @item |
| 2212 | Non-@acronym{ASCII} characters above 256 can be included in a multibyte string. |
| 2213 | |
| 2214 | @item |
| 2215 | Other keyboard character events cannot fit in a string. This includes |
| 2216 | keyboard events in the range of 128 to 255. |
| 2217 | @end itemize |
| 2218 | |
| 2219 | Functions such as @code{read-key-sequence} that construct strings of |
| 2220 | keyboard input characters follow these rules: they construct vectors |
| 2221 | instead of strings, when the events won't fit in a string. |
| 2222 | |
| 2223 | When you use the read syntax @samp{\M-} in a string, it produces a |
| 2224 | code in the range of 128 to 255---the same code that you get if you |
| 2225 | modify the corresponding keyboard event to put it in the string. Thus, |
| 2226 | meta events in strings work consistently regardless of how they get into |
| 2227 | the strings. |
| 2228 | |
| 2229 | However, most programs would do well to avoid these issues by |
| 2230 | following the recommendations at the beginning of this section. |
| 2231 | |
| 2232 | @node Reading Input |
| 2233 | @section Reading Input |
| 2234 | @cindex read input |
| 2235 | @cindex keyboard input |
| 2236 | |
| 2237 | The editor command loop reads key sequences using the function |
| 2238 | @code{read-key-sequence}, which uses @code{read-event}. These and other |
| 2239 | functions for event input are also available for use in Lisp programs. |
| 2240 | See also @code{momentary-string-display} in @ref{Temporary Displays}, |
| 2241 | and @code{sit-for} in @ref{Waiting}. @xref{Terminal Input}, for |
| 2242 | functions and variables for controlling terminal input modes and |
| 2243 | debugging terminal input. |
| 2244 | |
| 2245 | For higher-level input facilities, see @ref{Minibuffers}. |
| 2246 | |
| 2247 | @menu |
| 2248 | * Key Sequence Input:: How to read one key sequence. |
| 2249 | * Reading One Event:: How to read just one event. |
| 2250 | * Event Mod:: How Emacs modifies events as they are read. |
| 2251 | * Invoking the Input Method:: How reading an event uses the input method. |
| 2252 | * Quoted Character Input:: Asking the user to specify a character. |
| 2253 | * Event Input Misc:: How to reread or throw away input events. |
| 2254 | @end menu |
| 2255 | |
| 2256 | @node Key Sequence Input |
| 2257 | @subsection Key Sequence Input |
| 2258 | @cindex key sequence input |
| 2259 | |
| 2260 | The command loop reads input a key sequence at a time, by calling |
| 2261 | @code{read-key-sequence}. Lisp programs can also call this function; |
| 2262 | for example, @code{describe-key} uses it to read the key to describe. |
| 2263 | |
| 2264 | @defun read-key-sequence prompt &optional continue-echo dont-downcase-last switch-frame-ok command-loop |
| 2265 | This function reads a key sequence and returns it as a string or |
| 2266 | vector. It keeps reading events until it has accumulated a complete key |
| 2267 | sequence; that is, enough to specify a non-prefix command using the |
| 2268 | currently active keymaps. (Remember that a key sequence that starts |
| 2269 | with a mouse event is read using the keymaps of the buffer in the |
| 2270 | window that the mouse was in, not the current buffer.) |
| 2271 | |
| 2272 | If the events are all characters and all can fit in a string, then |
| 2273 | @code{read-key-sequence} returns a string (@pxref{Strings of Events}). |
| 2274 | Otherwise, it returns a vector, since a vector can hold all kinds of |
| 2275 | events---characters, symbols, and lists. The elements of the string or |
| 2276 | vector are the events in the key sequence. |
| 2277 | |
| 2278 | Reading a key sequence includes translating the events in various |
| 2279 | ways. @xref{Translation Keymaps}. |
| 2280 | |
| 2281 | The argument @var{prompt} is either a string to be displayed in the |
| 2282 | echo area as a prompt, or @code{nil}, meaning not to display a prompt. |
| 2283 | The argument @var{continue-echo}, if non-@code{nil}, means to echo |
| 2284 | this key as a continuation of the previous key. |
| 2285 | |
| 2286 | Normally any upper case event is converted to lower case if the |
| 2287 | original event is undefined and the lower case equivalent is defined. |
| 2288 | The argument @var{dont-downcase-last}, if non-@code{nil}, means do not |
| 2289 | convert the last event to lower case. This is appropriate for reading |
| 2290 | a key sequence to be defined. |
| 2291 | |
| 2292 | The argument @var{switch-frame-ok}, if non-@code{nil}, means that this |
| 2293 | function should process a @code{switch-frame} event if the user |
| 2294 | switches frames before typing anything. If the user switches frames |
| 2295 | in the middle of a key sequence, or at the start of the sequence but |
| 2296 | @var{switch-frame-ok} is @code{nil}, then the event will be put off |
| 2297 | until after the current key sequence. |
| 2298 | |
| 2299 | The argument @var{command-loop}, if non-@code{nil}, means that this |
| 2300 | key sequence is being read by something that will read commands one |
| 2301 | after another. It should be @code{nil} if the caller will read just |
| 2302 | one key sequence. |
| 2303 | |
| 2304 | In the following example, Emacs displays the prompt @samp{?} in the |
| 2305 | echo area, and then the user types @kbd{C-x C-f}. |
| 2306 | |
| 2307 | @example |
| 2308 | (read-key-sequence "?") |
| 2309 | |
| 2310 | @group |
| 2311 | ---------- Echo Area ---------- |
| 2312 | ?@kbd{C-x C-f} |
| 2313 | ---------- Echo Area ---------- |
| 2314 | |
| 2315 | @result{} "^X^F" |
| 2316 | @end group |
| 2317 | @end example |
| 2318 | |
| 2319 | The function @code{read-key-sequence} suppresses quitting: @kbd{C-g} |
| 2320 | typed while reading with this function works like any other character, |
| 2321 | and does not set @code{quit-flag}. @xref{Quitting}. |
| 2322 | @end defun |
| 2323 | |
| 2324 | @defun read-key-sequence-vector prompt &optional continue-echo dont-downcase-last switch-frame-ok command-loop |
| 2325 | This is like @code{read-key-sequence} except that it always |
| 2326 | returns the key sequence as a vector, never as a string. |
| 2327 | @xref{Strings of Events}. |
| 2328 | @end defun |
| 2329 | |
| 2330 | @cindex upper case key sequence |
| 2331 | @cindex downcasing in @code{lookup-key} |
| 2332 | @cindex shift-translation |
| 2333 | If an input character is upper-case (or has the shift modifier) and |
| 2334 | has no key binding, but its lower-case equivalent has one, then |
| 2335 | @code{read-key-sequence} converts the character to lower case. Note |
| 2336 | that @code{lookup-key} does not perform case conversion in this way. |
| 2337 | |
| 2338 | @vindex this-command-keys-shift-translated |
| 2339 | When reading input results in such a @dfn{shift-translation}, Emacs |
| 2340 | sets the variable @code{this-command-keys-shift-translated} to a |
| 2341 | non-@code{nil} value. Lisp programs can examine this variable if they |
| 2342 | need to modify their behavior when invoked by shift-translated keys. |
| 2343 | For example, the function @code{handle-shift-selection} examines the |
| 2344 | value of this variable to determine how to activate or deactivate the |
| 2345 | region (@pxref{The Mark, handle-shift-selection}). |
| 2346 | |
| 2347 | The function @code{read-key-sequence} also transforms some mouse events. |
| 2348 | It converts unbound drag events into click events, and discards unbound |
| 2349 | button-down events entirely. It also reshuffles focus events and |
| 2350 | miscellaneous window events so that they never appear in a key sequence |
| 2351 | with any other events. |
| 2352 | |
| 2353 | @cindex @code{header-line} prefix key |
| 2354 | @cindex @code{mode-line} prefix key |
| 2355 | @cindex @code{vertical-line} prefix key |
| 2356 | @cindex @code{horizontal-scroll-bar} prefix key |
| 2357 | @cindex @code{vertical-scroll-bar} prefix key |
| 2358 | @cindex @code{menu-bar} prefix key |
| 2359 | @cindex mouse events, in special parts of frame |
| 2360 | When mouse events occur in special parts of a window, such as a mode |
| 2361 | line or a scroll bar, the event type shows nothing special---it is the |
| 2362 | same symbol that would normally represent that combination of mouse |
| 2363 | button and modifier keys. The information about the window part is kept |
| 2364 | elsewhere in the event---in the coordinates. But |
| 2365 | @code{read-key-sequence} translates this information into imaginary |
| 2366 | ``prefix keys'', all of which are symbols: @code{header-line}, |
| 2367 | @code{horizontal-scroll-bar}, @code{menu-bar}, @code{mode-line}, |
| 2368 | @code{vertical-line}, and @code{vertical-scroll-bar}. You can define |
| 2369 | meanings for mouse clicks in special window parts by defining key |
| 2370 | sequences using these imaginary prefix keys. |
| 2371 | |
| 2372 | For example, if you call @code{read-key-sequence} and then click the |
| 2373 | mouse on the window's mode line, you get two events, like this: |
| 2374 | |
| 2375 | @example |
| 2376 | (read-key-sequence "Click on the mode line: ") |
| 2377 | @result{} [mode-line |
| 2378 | (mouse-1 |
| 2379 | (#<window 6 on NEWS> mode-line |
| 2380 | (40 . 63) 5959987))] |
| 2381 | @end example |
| 2382 | |
| 2383 | @defvar num-input-keys |
| 2384 | This variable's value is the number of key sequences processed so far in |
| 2385 | this Emacs session. This includes key sequences read from the terminal |
| 2386 | and key sequences read from keyboard macros being executed. |
| 2387 | @end defvar |
| 2388 | |
| 2389 | @node Reading One Event |
| 2390 | @subsection Reading One Event |
| 2391 | @cindex reading a single event |
| 2392 | @cindex event, reading only one |
| 2393 | |
| 2394 | The lowest level functions for command input are @code{read-event}, |
| 2395 | @code{read-char}, and @code{read-char-exclusive}. |
| 2396 | |
| 2397 | @defun read-event &optional prompt inherit-input-method seconds |
| 2398 | This function reads and returns the next event of command input, waiting |
| 2399 | if necessary until an event is available. Events can come directly from |
| 2400 | the user or from a keyboard macro. |
| 2401 | |
| 2402 | If the optional argument @var{prompt} is non-@code{nil}, it should be a |
| 2403 | string to display in the echo area as a prompt. Otherwise, |
| 2404 | @code{read-event} does not display any message to indicate it is waiting |
| 2405 | for input; instead, it prompts by echoing: it displays descriptions of |
| 2406 | the events that led to or were read by the current command. @xref{The |
| 2407 | Echo Area}. |
| 2408 | |
| 2409 | If @var{inherit-input-method} is non-@code{nil}, then the current input |
| 2410 | method (if any) is employed to make it possible to enter a |
| 2411 | non-@acronym{ASCII} character. Otherwise, input method handling is disabled |
| 2412 | for reading this event. |
| 2413 | |
| 2414 | If @code{cursor-in-echo-area} is non-@code{nil}, then @code{read-event} |
| 2415 | moves the cursor temporarily to the echo area, to the end of any message |
| 2416 | displayed there. Otherwise @code{read-event} does not move the cursor. |
| 2417 | |
| 2418 | If @var{seconds} is non-@code{nil}, it should be a number specifying |
| 2419 | the maximum time to wait for input, in seconds. If no input arrives |
| 2420 | within that time, @code{read-event} stops waiting and returns |
| 2421 | @code{nil}. A floating-point value for @var{seconds} means to wait |
| 2422 | for a fractional number of seconds. Some systems support only a whole |
| 2423 | number of seconds; on these systems, @var{seconds} is rounded down. |
| 2424 | If @var{seconds} is @code{nil}, @code{read-event} waits as long as |
| 2425 | necessary for input to arrive. |
| 2426 | |
| 2427 | If @var{seconds} is @code{nil}, Emacs is considered idle while waiting |
| 2428 | for user input to arrive. Idle timers---those created with |
| 2429 | @code{run-with-idle-timer} (@pxref{Idle Timers})---can run during this |
| 2430 | period. However, if @var{seconds} is non-@code{nil}, the state of |
| 2431 | idleness remains unchanged. If Emacs is non-idle when |
| 2432 | @code{read-event} is called, it remains non-idle throughout the |
| 2433 | operation of @code{read-event}; if Emacs is idle (which can happen if |
| 2434 | the call happens inside an idle timer), it remains idle. |
| 2435 | |
| 2436 | If @code{read-event} gets an event that is defined as a help character, |
| 2437 | then in some cases @code{read-event} processes the event directly without |
| 2438 | returning. @xref{Help Functions}. Certain other events, called |
| 2439 | @dfn{special events}, are also processed directly within |
| 2440 | @code{read-event} (@pxref{Special Events}). |
| 2441 | |
| 2442 | Here is what happens if you call @code{read-event} and then press the |
| 2443 | right-arrow function key: |
| 2444 | |
| 2445 | @example |
| 2446 | @group |
| 2447 | (read-event) |
| 2448 | @result{} right |
| 2449 | @end group |
| 2450 | @end example |
| 2451 | @end defun |
| 2452 | |
| 2453 | @defun read-char &optional prompt inherit-input-method seconds |
| 2454 | This function reads and returns a character of command input. If the |
| 2455 | user generates an event which is not a character (i.e., a mouse click or |
| 2456 | function key event), @code{read-char} signals an error. The arguments |
| 2457 | work as in @code{read-event}. |
| 2458 | |
| 2459 | In the first example, the user types the character @kbd{1} (@acronym{ASCII} |
| 2460 | code 49). The second example shows a keyboard macro definition that |
| 2461 | calls @code{read-char} from the minibuffer using @code{eval-expression}. |
| 2462 | @code{read-char} reads the keyboard macro's very next character, which |
| 2463 | is @kbd{1}. Then @code{eval-expression} displays its return value in |
| 2464 | the echo area. |
| 2465 | |
| 2466 | @example |
| 2467 | @group |
| 2468 | (read-char) |
| 2469 | @result{} 49 |
| 2470 | @end group |
| 2471 | |
| 2472 | @group |
| 2473 | ;; @r{We assume here you use @kbd{M-:} to evaluate this.} |
| 2474 | (symbol-function 'foo) |
| 2475 | @result{} "^[:(read-char)^M1" |
| 2476 | @end group |
| 2477 | @group |
| 2478 | (execute-kbd-macro 'foo) |
| 2479 | @print{} 49 |
| 2480 | @result{} nil |
| 2481 | @end group |
| 2482 | @end example |
| 2483 | @end defun |
| 2484 | |
| 2485 | @defun read-char-exclusive &optional prompt inherit-input-method seconds |
| 2486 | This function reads and returns a character of command input. If the |
| 2487 | user generates an event which is not a character, |
| 2488 | @code{read-char-exclusive} ignores it and reads another event, until it |
| 2489 | gets a character. The arguments work as in @code{read-event}. |
| 2490 | @end defun |
| 2491 | |
| 2492 | None of the above functions suppress quitting. |
| 2493 | |
| 2494 | @defvar num-nonmacro-input-events |
| 2495 | This variable holds the total number of input events received so far |
| 2496 | from the terminal---not counting those generated by keyboard macros. |
| 2497 | @end defvar |
| 2498 | |
| 2499 | We emphasize that, unlike @code{read-key-sequence}, the functions |
| 2500 | @code{read-event}, @code{read-char}, and @code{read-char-exclusive} do |
| 2501 | not perform the translations described in @ref{Translation Keymaps}. |
| 2502 | If you wish to read a single key taking these translations into |
| 2503 | account, use the function @code{read-key}: |
| 2504 | |
| 2505 | @defun read-key &optional prompt |
| 2506 | This function reads a single key. It is ``intermediate'' between |
| 2507 | @code{read-key-sequence} and @code{read-event}. Unlike the former, it |
| 2508 | reads a single key, not a key sequence. Unlike the latter, it does |
| 2509 | not return a raw event, but decodes and translates the user input |
| 2510 | according to @code{input-decode-map}, @code{local-function-key-map}, |
| 2511 | and @code{key-translation-map} (@pxref{Translation Keymaps}). |
| 2512 | |
| 2513 | The argument @var{prompt} is either a string to be displayed in the |
| 2514 | echo area as a prompt, or @code{nil}, meaning not to display a prompt. |
| 2515 | @end defun |
| 2516 | |
| 2517 | @defun read-char-choice prompt chars &optional inhibit-quit |
| 2518 | This function uses @code{read-key} to read and return a single |
| 2519 | character. It ignores any input that is not a member of @var{chars}, |
| 2520 | a list of accepted characters. Optionally, it will also ignore |
| 2521 | keyboard-quit events while it is waiting for valid input. If you bind |
| 2522 | @code{help-form} (@pxref{Help Functions}) to a non-@code{nil} value |
| 2523 | while calling @code{read-char-choice}, then pressing @code{help-char} |
| 2524 | causes it to evaluate @code{help-form} and display the result. It |
| 2525 | then continues to wait for a valid input character, or keyboard-quit. |
| 2526 | @end defun |
| 2527 | |
| 2528 | @node Event Mod |
| 2529 | @subsection Modifying and Translating Input Events |
| 2530 | |
| 2531 | Emacs modifies every event it reads according to |
| 2532 | @code{extra-keyboard-modifiers}, then translates it through |
| 2533 | @code{keyboard-translate-table} (if applicable), before returning it |
| 2534 | from @code{read-event}. |
| 2535 | |
| 2536 | @defvar extra-keyboard-modifiers |
| 2537 | This variable lets Lisp programs ``press'' the modifier keys on the |
| 2538 | keyboard. The value is a character. Only the modifiers of the |
| 2539 | character matter. Each time the user types a keyboard key, it is |
| 2540 | altered as if those modifier keys were held down. For instance, if |
| 2541 | you bind @code{extra-keyboard-modifiers} to @code{?\C-\M-a}, then all |
| 2542 | keyboard input characters typed during the scope of the binding will |
| 2543 | have the control and meta modifiers applied to them. The character |
| 2544 | @code{?\C-@@}, equivalent to the integer 0, does not count as a control |
| 2545 | character for this purpose, but as a character with no modifiers. |
| 2546 | Thus, setting @code{extra-keyboard-modifiers} to zero cancels any |
| 2547 | modification. |
| 2548 | |
| 2549 | When using a window system, the program can ``press'' any of the |
| 2550 | modifier keys in this way. Otherwise, only the @key{CTL} and @key{META} |
| 2551 | keys can be virtually pressed. |
| 2552 | |
| 2553 | Note that this variable applies only to events that really come from |
| 2554 | the keyboard, and has no effect on mouse events or any other events. |
| 2555 | @end defvar |
| 2556 | |
| 2557 | @defvar keyboard-translate-table |
| 2558 | This terminal-local variable is the translate table for keyboard |
| 2559 | characters. It lets you reshuffle the keys on the keyboard without |
| 2560 | changing any command bindings. Its value is normally a char-table, or |
| 2561 | else @code{nil}. (It can also be a string or vector, but this is |
| 2562 | considered obsolete.) |
| 2563 | |
| 2564 | If @code{keyboard-translate-table} is a char-table |
| 2565 | (@pxref{Char-Tables}), then each character read from the keyboard is |
| 2566 | looked up in this char-table. If the value found there is |
| 2567 | non-@code{nil}, then it is used instead of the actual input character. |
| 2568 | |
| 2569 | Note that this translation is the first thing that happens to a |
| 2570 | character after it is read from the terminal. Record-keeping features |
| 2571 | such as @code{recent-keys} and dribble files record the characters after |
| 2572 | translation. |
| 2573 | |
| 2574 | Note also that this translation is done before the characters are |
| 2575 | supplied to input methods (@pxref{Input Methods}). Use |
| 2576 | @code{translation-table-for-input} (@pxref{Translation of Characters}), |
| 2577 | if you want to translate characters after input methods operate. |
| 2578 | @end defvar |
| 2579 | |
| 2580 | @defun keyboard-translate from to |
| 2581 | This function modifies @code{keyboard-translate-table} to translate |
| 2582 | character code @var{from} into character code @var{to}. It creates |
| 2583 | the keyboard translate table if necessary. |
| 2584 | @end defun |
| 2585 | |
| 2586 | Here's an example of using the @code{keyboard-translate-table} to |
| 2587 | make @kbd{C-x}, @kbd{C-c} and @kbd{C-v} perform the cut, copy and paste |
| 2588 | operations: |
| 2589 | |
| 2590 | @example |
| 2591 | (keyboard-translate ?\C-x 'control-x) |
| 2592 | (keyboard-translate ?\C-c 'control-c) |
| 2593 | (keyboard-translate ?\C-v 'control-v) |
| 2594 | (global-set-key [control-x] 'kill-region) |
| 2595 | (global-set-key [control-c] 'kill-ring-save) |
| 2596 | (global-set-key [control-v] 'yank) |
| 2597 | @end example |
| 2598 | |
| 2599 | @noindent |
| 2600 | On a graphical terminal that supports extended @acronym{ASCII} input, |
| 2601 | you can still get the standard Emacs meanings of one of those |
| 2602 | characters by typing it with the shift key. That makes it a different |
| 2603 | character as far as keyboard translation is concerned, but it has the |
| 2604 | same usual meaning. |
| 2605 | |
| 2606 | @xref{Translation Keymaps}, for mechanisms that translate event sequences |
| 2607 | at the level of @code{read-key-sequence}. |
| 2608 | |
| 2609 | @node Invoking the Input Method |
| 2610 | @subsection Invoking the Input Method |
| 2611 | |
| 2612 | The event-reading functions invoke the current input method, if any |
| 2613 | (@pxref{Input Methods}). If the value of @code{input-method-function} |
| 2614 | is non-@code{nil}, it should be a function; when @code{read-event} reads |
| 2615 | a printing character (including @key{SPC}) with no modifier bits, it |
| 2616 | calls that function, passing the character as an argument. |
| 2617 | |
| 2618 | @defvar input-method-function |
| 2619 | If this is non-@code{nil}, its value specifies the current input method |
| 2620 | function. |
| 2621 | |
| 2622 | @strong{Warning:} don't bind this variable with @code{let}. It is often |
| 2623 | buffer-local, and if you bind it around reading input (which is exactly |
| 2624 | when you @emph{would} bind it), switching buffers asynchronously while |
| 2625 | Emacs is waiting will cause the value to be restored in the wrong |
| 2626 | buffer. |
| 2627 | @end defvar |
| 2628 | |
| 2629 | The input method function should return a list of events which should |
| 2630 | be used as input. (If the list is @code{nil}, that means there is no |
| 2631 | input, so @code{read-event} waits for another event.) These events are |
| 2632 | processed before the events in @code{unread-command-events} |
| 2633 | (@pxref{Event Input Misc}). Events |
| 2634 | returned by the input method function are not passed to the input method |
| 2635 | function again, even if they are printing characters with no modifier |
| 2636 | bits. |
| 2637 | |
| 2638 | If the input method function calls @code{read-event} or |
| 2639 | @code{read-key-sequence}, it should bind @code{input-method-function} to |
| 2640 | @code{nil} first, to prevent recursion. |
| 2641 | |
| 2642 | The input method function is not called when reading the second and |
| 2643 | subsequent events of a key sequence. Thus, these characters are not |
| 2644 | subject to input method processing. The input method function should |
| 2645 | test the values of @code{overriding-local-map} and |
| 2646 | @code{overriding-terminal-local-map}; if either of these variables is |
| 2647 | non-@code{nil}, the input method should put its argument into a list and |
| 2648 | return that list with no further processing. |
| 2649 | |
| 2650 | @node Quoted Character Input |
| 2651 | @subsection Quoted Character Input |
| 2652 | @cindex quoted character input |
| 2653 | |
| 2654 | You can use the function @code{read-quoted-char} to ask the user to |
| 2655 | specify a character, and allow the user to specify a control or meta |
| 2656 | character conveniently, either literally or as an octal character code. |
| 2657 | The command @code{quoted-insert} uses this function. |
| 2658 | |
| 2659 | @defun read-quoted-char &optional prompt |
| 2660 | @cindex octal character input |
| 2661 | @cindex control characters, reading |
| 2662 | @cindex nonprinting characters, reading |
| 2663 | This function is like @code{read-char}, except that if the first |
| 2664 | character read is an octal digit (0--7), it reads any number of octal |
| 2665 | digits (but stopping if a non-octal digit is found), and returns the |
| 2666 | character represented by that numeric character code. If the |
| 2667 | character that terminates the sequence of octal digits is @key{RET}, |
| 2668 | it is discarded. Any other terminating character is used as input |
| 2669 | after this function returns. |
| 2670 | |
| 2671 | Quitting is suppressed when the first character is read, so that the |
| 2672 | user can enter a @kbd{C-g}. @xref{Quitting}. |
| 2673 | |
| 2674 | If @var{prompt} is supplied, it specifies a string for prompting the |
| 2675 | user. The prompt string is always displayed in the echo area, followed |
| 2676 | by a single @samp{-}. |
| 2677 | |
| 2678 | In the following example, the user types in the octal number 177 (which |
| 2679 | is 127 in decimal). |
| 2680 | |
| 2681 | @example |
| 2682 | (read-quoted-char "What character") |
| 2683 | |
| 2684 | @group |
| 2685 | ---------- Echo Area ---------- |
| 2686 | What character @kbd{1 7 7}- |
| 2687 | ---------- Echo Area ---------- |
| 2688 | |
| 2689 | @result{} 127 |
| 2690 | @end group |
| 2691 | @end example |
| 2692 | @end defun |
| 2693 | |
| 2694 | @need 2000 |
| 2695 | @node Event Input Misc |
| 2696 | @subsection Miscellaneous Event Input Features |
| 2697 | |
| 2698 | This section describes how to ``peek ahead'' at events without using |
| 2699 | them up, how to check for pending input, and how to discard pending |
| 2700 | input. See also the function @code{read-passwd} (@pxref{Reading a |
| 2701 | Password}). |
| 2702 | |
| 2703 | @defvar unread-command-events |
| 2704 | @cindex next input |
| 2705 | @cindex peeking at input |
| 2706 | This variable holds a list of events waiting to be read as command |
| 2707 | input. The events are used in the order they appear in the list, and |
| 2708 | removed one by one as they are used. |
| 2709 | |
| 2710 | The variable is needed because in some cases a function reads an event |
| 2711 | and then decides not to use it. Storing the event in this variable |
| 2712 | causes it to be processed normally, by the command loop or by the |
| 2713 | functions to read command input. |
| 2714 | |
| 2715 | @cindex prefix argument unreading |
| 2716 | For example, the function that implements numeric prefix arguments reads |
| 2717 | any number of digits. When it finds a non-digit event, it must unread |
| 2718 | the event so that it can be read normally by the command loop. |
| 2719 | Likewise, incremental search uses this feature to unread events with no |
| 2720 | special meaning in a search, because these events should exit the search |
| 2721 | and then execute normally. |
| 2722 | |
| 2723 | The reliable and easy way to extract events from a key sequence so as |
| 2724 | to put them in @code{unread-command-events} is to use |
| 2725 | @code{listify-key-sequence} (see below). |
| 2726 | |
| 2727 | Normally you add events to the front of this list, so that the events |
| 2728 | most recently unread will be reread first. |
| 2729 | |
| 2730 | Events read from this list are not normally added to the current |
| 2731 | command's key sequence (as returned by, e.g., @code{this-command-keys}), |
| 2732 | as the events will already have been added once as they were read for |
| 2733 | the first time. An element of the form @code{(@code{t} . @var{event})} |
| 2734 | forces @var{event} to be added to the current command's key sequence. |
| 2735 | @end defvar |
| 2736 | |
| 2737 | @defun listify-key-sequence key |
| 2738 | This function converts the string or vector @var{key} to a list of |
| 2739 | individual events, which you can put in @code{unread-command-events}. |
| 2740 | @end defun |
| 2741 | |
| 2742 | @defun input-pending-p &optional check-timers |
| 2743 | @cindex waiting for command key input |
| 2744 | This function determines whether any command input is currently |
| 2745 | available to be read. It returns immediately, with value @code{t} if |
| 2746 | there is available input, @code{nil} otherwise. On rare occasions it |
| 2747 | may return @code{t} when no input is available. |
| 2748 | |
| 2749 | If the optional argument @var{check-timers} is non-@code{nil}, then if |
| 2750 | no input is available, Emacs runs any timers which are ready. |
| 2751 | @xref{Timers}. |
| 2752 | @end defun |
| 2753 | |
| 2754 | @defvar last-input-event |
| 2755 | This variable records the last terminal input event read, whether |
| 2756 | as part of a command or explicitly by a Lisp program. |
| 2757 | |
| 2758 | In the example below, the Lisp program reads the character @kbd{1}, |
| 2759 | @acronym{ASCII} code 49. It becomes the value of @code{last-input-event}, |
| 2760 | while @kbd{C-e} (we assume @kbd{C-x C-e} command is used to evaluate |
| 2761 | this expression) remains the value of @code{last-command-event}. |
| 2762 | |
| 2763 | @example |
| 2764 | @group |
| 2765 | (progn (print (read-char)) |
| 2766 | (print last-command-event) |
| 2767 | last-input-event) |
| 2768 | @print{} 49 |
| 2769 | @print{} 5 |
| 2770 | @result{} 49 |
| 2771 | @end group |
| 2772 | @end example |
| 2773 | @end defvar |
| 2774 | |
| 2775 | @defmac while-no-input body@dots{} |
| 2776 | This construct runs the @var{body} forms and returns the value of the |
| 2777 | last one---but only if no input arrives. If any input arrives during |
| 2778 | the execution of the @var{body} forms, it aborts them (working much |
| 2779 | like a quit). The @code{while-no-input} form returns @code{nil} if |
| 2780 | aborted by a real quit, and returns @code{t} if aborted by arrival of |
| 2781 | other input. |
| 2782 | |
| 2783 | If a part of @var{body} binds @code{inhibit-quit} to non-@code{nil}, |
| 2784 | arrival of input during those parts won't cause an abort until |
| 2785 | the end of that part. |
| 2786 | |
| 2787 | If you want to be able to distinguish all possible values computed |
| 2788 | by @var{body} from both kinds of abort conditions, write the code |
| 2789 | like this: |
| 2790 | |
| 2791 | @example |
| 2792 | (while-no-input |
| 2793 | (list |
| 2794 | (progn . @var{body}))) |
| 2795 | @end example |
| 2796 | @end defmac |
| 2797 | |
| 2798 | @defun discard-input |
| 2799 | @cindex flushing input |
| 2800 | @cindex discarding input |
| 2801 | @cindex keyboard macro, terminating |
| 2802 | This function discards the contents of the terminal input buffer and |
| 2803 | cancels any keyboard macro that might be in the process of definition. |
| 2804 | It returns @code{nil}. |
| 2805 | |
| 2806 | In the following example, the user may type a number of characters right |
| 2807 | after starting the evaluation of the form. After the @code{sleep-for} |
| 2808 | finishes sleeping, @code{discard-input} discards any characters typed |
| 2809 | during the sleep. |
| 2810 | |
| 2811 | @example |
| 2812 | (progn (sleep-for 2) |
| 2813 | (discard-input)) |
| 2814 | @result{} nil |
| 2815 | @end example |
| 2816 | @end defun |
| 2817 | |
| 2818 | @node Special Events |
| 2819 | @section Special Events |
| 2820 | |
| 2821 | @cindex special events |
| 2822 | Certain @dfn{special events} are handled at a very low level---as soon |
| 2823 | as they are read. The @code{read-event} function processes these |
| 2824 | events itself, and never returns them. Instead, it keeps waiting for |
| 2825 | the first event that is not special and returns that one. |
| 2826 | |
| 2827 | Special events do not echo, they are never grouped into key |
| 2828 | sequences, and they never appear in the value of |
| 2829 | @code{last-command-event} or @code{(this-command-keys)}. They do not |
| 2830 | discard a numeric argument, they cannot be unread with |
| 2831 | @code{unread-command-events}, they may not appear in a keyboard macro, |
| 2832 | and they are not recorded in a keyboard macro while you are defining |
| 2833 | one. |
| 2834 | |
| 2835 | Special events do, however, appear in @code{last-input-event} |
| 2836 | immediately after they are read, and this is the way for the event's |
| 2837 | definition to find the actual event. |
| 2838 | |
| 2839 | The events types @code{iconify-frame}, @code{make-frame-visible}, |
| 2840 | @code{delete-frame}, @code{drag-n-drop}, @code{language-change}, and |
| 2841 | user signals like @code{sigusr1} are normally handled in this way. |
| 2842 | The keymap which defines how to handle special events---and which |
| 2843 | events are special---is in the variable @code{special-event-map} |
| 2844 | (@pxref{Active Keymaps}). |
| 2845 | |
| 2846 | @node Waiting |
| 2847 | @section Waiting for Elapsed Time or Input |
| 2848 | @cindex waiting |
| 2849 | |
| 2850 | The wait functions are designed to wait for a certain amount of time |
| 2851 | to pass or until there is input. For example, you may wish to pause in |
| 2852 | the middle of a computation to allow the user time to view the display. |
| 2853 | @code{sit-for} pauses and updates the screen, and returns immediately if |
| 2854 | input comes in, while @code{sleep-for} pauses without updating the |
| 2855 | screen. |
| 2856 | |
| 2857 | @defun sit-for seconds &optional nodisp |
| 2858 | This function performs redisplay (provided there is no pending input |
| 2859 | from the user), then waits @var{seconds} seconds, or until input is |
| 2860 | available. The usual purpose of @code{sit-for} is to give the user |
| 2861 | time to read text that you display. The value is @code{t} if |
| 2862 | @code{sit-for} waited the full time with no input arriving |
| 2863 | (@pxref{Event Input Misc}). Otherwise, the value is @code{nil}. |
| 2864 | |
| 2865 | The argument @var{seconds} need not be an integer. If it is a floating |
| 2866 | point number, @code{sit-for} waits for a fractional number of seconds. |
| 2867 | Some systems support only a whole number of seconds; on these systems, |
| 2868 | @var{seconds} is rounded down. |
| 2869 | |
| 2870 | The expression @code{(sit-for 0)} is equivalent to @code{(redisplay)}, |
| 2871 | i.e., it requests a redisplay, without any delay, if there is no pending input. |
| 2872 | @xref{Forcing Redisplay}. |
| 2873 | |
| 2874 | If @var{nodisp} is non-@code{nil}, then @code{sit-for} does not |
| 2875 | redisplay, but it still returns as soon as input is available (or when |
| 2876 | the timeout elapses). |
| 2877 | |
| 2878 | In batch mode (@pxref{Batch Mode}), @code{sit-for} cannot be |
| 2879 | interrupted, even by input from the standard input descriptor. It is |
| 2880 | thus equivalent to @code{sleep-for}, which is described below. |
| 2881 | |
| 2882 | It is also possible to call @code{sit-for} with three arguments, |
| 2883 | as @code{(sit-for @var{seconds} @var{millisec} @var{nodisp})}, |
| 2884 | but that is considered obsolete. |
| 2885 | @end defun |
| 2886 | |
| 2887 | @defun sleep-for seconds &optional millisec |
| 2888 | This function simply pauses for @var{seconds} seconds without updating |
| 2889 | the display. It pays no attention to available input. It returns |
| 2890 | @code{nil}. |
| 2891 | |
| 2892 | The argument @var{seconds} need not be an integer. If it is a floating |
| 2893 | point number, @code{sleep-for} waits for a fractional number of seconds. |
| 2894 | Some systems support only a whole number of seconds; on these systems, |
| 2895 | @var{seconds} is rounded down. |
| 2896 | |
| 2897 | The optional argument @var{millisec} specifies an additional waiting |
| 2898 | period measured in milliseconds. This adds to the period specified by |
| 2899 | @var{seconds}. If the system doesn't support waiting fractions of a |
| 2900 | second, you get an error if you specify nonzero @var{millisec}. |
| 2901 | |
| 2902 | Use @code{sleep-for} when you wish to guarantee a delay. |
| 2903 | @end defun |
| 2904 | |
| 2905 | @xref{Time of Day}, for functions to get the current time. |
| 2906 | |
| 2907 | @node Quitting |
| 2908 | @section Quitting |
| 2909 | @cindex @kbd{C-g} |
| 2910 | @cindex quitting |
| 2911 | @cindex interrupt Lisp functions |
| 2912 | |
| 2913 | Typing @kbd{C-g} while a Lisp function is running causes Emacs to |
| 2914 | @dfn{quit} whatever it is doing. This means that control returns to the |
| 2915 | innermost active command loop. |
| 2916 | |
| 2917 | Typing @kbd{C-g} while the command loop is waiting for keyboard input |
| 2918 | does not cause a quit; it acts as an ordinary input character. In the |
| 2919 | simplest case, you cannot tell the difference, because @kbd{C-g} |
| 2920 | normally runs the command @code{keyboard-quit}, whose effect is to quit. |
| 2921 | However, when @kbd{C-g} follows a prefix key, they combine to form an |
| 2922 | undefined key. The effect is to cancel the prefix key as well as any |
| 2923 | prefix argument. |
| 2924 | |
| 2925 | In the minibuffer, @kbd{C-g} has a different definition: it aborts out |
| 2926 | of the minibuffer. This means, in effect, that it exits the minibuffer |
| 2927 | and then quits. (Simply quitting would return to the command loop |
| 2928 | @emph{within} the minibuffer.) The reason why @kbd{C-g} does not quit |
| 2929 | directly when the command reader is reading input is so that its meaning |
| 2930 | can be redefined in the minibuffer in this way. @kbd{C-g} following a |
| 2931 | prefix key is not redefined in the minibuffer, and it has its normal |
| 2932 | effect of canceling the prefix key and prefix argument. This too |
| 2933 | would not be possible if @kbd{C-g} always quit directly. |
| 2934 | |
| 2935 | When @kbd{C-g} does directly quit, it does so by setting the variable |
| 2936 | @code{quit-flag} to @code{t}. Emacs checks this variable at appropriate |
| 2937 | times and quits if it is not @code{nil}. Setting @code{quit-flag} |
| 2938 | non-@code{nil} in any way thus causes a quit. |
| 2939 | |
| 2940 | At the level of C code, quitting cannot happen just anywhere; only at the |
| 2941 | special places that check @code{quit-flag}. The reason for this is |
| 2942 | that quitting at other places might leave an inconsistency in Emacs's |
| 2943 | internal state. Because quitting is delayed until a safe place, quitting |
| 2944 | cannot make Emacs crash. |
| 2945 | |
| 2946 | Certain functions such as @code{read-key-sequence} or |
| 2947 | @code{read-quoted-char} prevent quitting entirely even though they wait |
| 2948 | for input. Instead of quitting, @kbd{C-g} serves as the requested |
| 2949 | input. In the case of @code{read-key-sequence}, this serves to bring |
| 2950 | about the special behavior of @kbd{C-g} in the command loop. In the |
| 2951 | case of @code{read-quoted-char}, this is so that @kbd{C-q} can be used |
| 2952 | to quote a @kbd{C-g}. |
| 2953 | |
| 2954 | @cindex preventing quitting |
| 2955 | You can prevent quitting for a portion of a Lisp function by binding |
| 2956 | the variable @code{inhibit-quit} to a non-@code{nil} value. Then, |
| 2957 | although @kbd{C-g} still sets @code{quit-flag} to @code{t} as usual, the |
| 2958 | usual result of this---a quit---is prevented. Eventually, |
| 2959 | @code{inhibit-quit} will become @code{nil} again, such as when its |
| 2960 | binding is unwound at the end of a @code{let} form. At that time, if |
| 2961 | @code{quit-flag} is still non-@code{nil}, the requested quit happens |
| 2962 | immediately. This behavior is ideal when you wish to make sure that |
| 2963 | quitting does not happen within a ``critical section'' of the program. |
| 2964 | |
| 2965 | @cindex @code{read-quoted-char} quitting |
| 2966 | In some functions (such as @code{read-quoted-char}), @kbd{C-g} is |
| 2967 | handled in a special way that does not involve quitting. This is done |
| 2968 | by reading the input with @code{inhibit-quit} bound to @code{t}, and |
| 2969 | setting @code{quit-flag} to @code{nil} before @code{inhibit-quit} |
| 2970 | becomes @code{nil} again. This excerpt from the definition of |
| 2971 | @code{read-quoted-char} shows how this is done; it also shows that |
| 2972 | normal quitting is permitted after the first character of input. |
| 2973 | |
| 2974 | @example |
| 2975 | (defun read-quoted-char (&optional prompt) |
| 2976 | "@dots{}@var{documentation}@dots{}" |
| 2977 | (let ((message-log-max nil) done (first t) (code 0) char) |
| 2978 | (while (not done) |
| 2979 | (let ((inhibit-quit first) |
| 2980 | @dots{}) |
| 2981 | (and prompt (message "%s-" prompt)) |
| 2982 | (setq char (read-event)) |
| 2983 | (if inhibit-quit (setq quit-flag nil))) |
| 2984 | @r{@dots{}set the variable @code{code}@dots{}}) |
| 2985 | code)) |
| 2986 | @end example |
| 2987 | |
| 2988 | @defvar quit-flag |
| 2989 | If this variable is non-@code{nil}, then Emacs quits immediately, unless |
| 2990 | @code{inhibit-quit} is non-@code{nil}. Typing @kbd{C-g} ordinarily sets |
| 2991 | @code{quit-flag} non-@code{nil}, regardless of @code{inhibit-quit}. |
| 2992 | @end defvar |
| 2993 | |
| 2994 | @defvar inhibit-quit |
| 2995 | This variable determines whether Emacs should quit when @code{quit-flag} |
| 2996 | is set to a value other than @code{nil}. If @code{inhibit-quit} is |
| 2997 | non-@code{nil}, then @code{quit-flag} has no special effect. |
| 2998 | @end defvar |
| 2999 | |
| 3000 | @defmac with-local-quit body@dots{} |
| 3001 | This macro executes @var{body} forms in sequence, but allows quitting, at |
| 3002 | least locally, within @var{body} even if @code{inhibit-quit} was |
| 3003 | non-@code{nil} outside this construct. It returns the value of the |
| 3004 | last form in @var{body}, unless exited by quitting, in which case |
| 3005 | it returns @code{nil}. |
| 3006 | |
| 3007 | If @code{inhibit-quit} is @code{nil} on entry to @code{with-local-quit}, |
| 3008 | it only executes the @var{body}, and setting @code{quit-flag} causes |
| 3009 | a normal quit. However, if @code{inhibit-quit} is non-@code{nil} so |
| 3010 | that ordinary quitting is delayed, a non-@code{nil} @code{quit-flag} |
| 3011 | triggers a special kind of local quit. This ends the execution of |
| 3012 | @var{body} and exits the @code{with-local-quit} body with |
| 3013 | @code{quit-flag} still non-@code{nil}, so that another (ordinary) quit |
| 3014 | will happen as soon as that is allowed. If @code{quit-flag} is |
| 3015 | already non-@code{nil} at the beginning of @var{body}, the local quit |
| 3016 | happens immediately and the body doesn't execute at all. |
| 3017 | |
| 3018 | This macro is mainly useful in functions that can be called from |
| 3019 | timers, process filters, process sentinels, @code{pre-command-hook}, |
| 3020 | @code{post-command-hook}, and other places where @code{inhibit-quit} is |
| 3021 | normally bound to @code{t}. |
| 3022 | @end defmac |
| 3023 | |
| 3024 | @deffn Command keyboard-quit |
| 3025 | This function signals the @code{quit} condition with @code{(signal 'quit |
| 3026 | nil)}. This is the same thing that quitting does. (See @code{signal} |
| 3027 | in @ref{Errors}.) |
| 3028 | @end deffn |
| 3029 | |
| 3030 | You can specify a character other than @kbd{C-g} to use for quitting. |
| 3031 | See the function @code{set-input-mode} in @ref{Terminal Input}. |
| 3032 | |
| 3033 | @node Prefix Command Arguments |
| 3034 | @section Prefix Command Arguments |
| 3035 | @cindex prefix argument |
| 3036 | @cindex raw prefix argument |
| 3037 | @cindex numeric prefix argument |
| 3038 | |
| 3039 | Most Emacs commands can use a @dfn{prefix argument}, a number |
| 3040 | specified before the command itself. (Don't confuse prefix arguments |
| 3041 | with prefix keys.) The prefix argument is at all times represented by a |
| 3042 | value, which may be @code{nil}, meaning there is currently no prefix |
| 3043 | argument. Each command may use the prefix argument or ignore it. |
| 3044 | |
| 3045 | There are two representations of the prefix argument: @dfn{raw} and |
| 3046 | @dfn{numeric}. The editor command loop uses the raw representation |
| 3047 | internally, and so do the Lisp variables that store the information, but |
| 3048 | commands can request either representation. |
| 3049 | |
| 3050 | Here are the possible values of a raw prefix argument: |
| 3051 | |
| 3052 | @itemize @bullet |
| 3053 | @item |
| 3054 | @code{nil}, meaning there is no prefix argument. Its numeric value is |
| 3055 | 1, but numerous commands make a distinction between @code{nil} and the |
| 3056 | integer 1. |
| 3057 | |
| 3058 | @item |
| 3059 | An integer, which stands for itself. |
| 3060 | |
| 3061 | @item |
| 3062 | A list of one element, which is an integer. This form of prefix |
| 3063 | argument results from one or a succession of @kbd{C-u}s with no |
| 3064 | digits. The numeric value is the integer in the list, but some |
| 3065 | commands make a distinction between such a list and an integer alone. |
| 3066 | |
| 3067 | @item |
| 3068 | The symbol @code{-}. This indicates that @kbd{M--} or @kbd{C-u -} was |
| 3069 | typed, without following digits. The equivalent numeric value is |
| 3070 | @minus{}1, but some commands make a distinction between the integer |
| 3071 | @minus{}1 and the symbol @code{-}. |
| 3072 | @end itemize |
| 3073 | |
| 3074 | We illustrate these possibilities by calling the following function with |
| 3075 | various prefixes: |
| 3076 | |
| 3077 | @example |
| 3078 | @group |
| 3079 | (defun display-prefix (arg) |
| 3080 | "Display the value of the raw prefix arg." |
| 3081 | (interactive "P") |
| 3082 | (message "%s" arg)) |
| 3083 | @end group |
| 3084 | @end example |
| 3085 | |
| 3086 | @noindent |
| 3087 | Here are the results of calling @code{display-prefix} with various |
| 3088 | raw prefix arguments: |
| 3089 | |
| 3090 | @example |
| 3091 | M-x display-prefix @print{} nil |
| 3092 | |
| 3093 | C-u M-x display-prefix @print{} (4) |
| 3094 | |
| 3095 | C-u C-u M-x display-prefix @print{} (16) |
| 3096 | |
| 3097 | C-u 3 M-x display-prefix @print{} 3 |
| 3098 | |
| 3099 | M-3 M-x display-prefix @print{} 3 ; @r{(Same as @code{C-u 3}.)} |
| 3100 | |
| 3101 | C-u - M-x display-prefix @print{} - |
| 3102 | |
| 3103 | M-- M-x display-prefix @print{} - ; @r{(Same as @code{C-u -}.)} |
| 3104 | |
| 3105 | C-u - 7 M-x display-prefix @print{} -7 |
| 3106 | |
| 3107 | M-- 7 M-x display-prefix @print{} -7 ; @r{(Same as @code{C-u -7}.)} |
| 3108 | @end example |
| 3109 | |
| 3110 | Emacs uses two variables to store the prefix argument: |
| 3111 | @code{prefix-arg} and @code{current-prefix-arg}. Commands such as |
| 3112 | @code{universal-argument} that set up prefix arguments for other |
| 3113 | commands store them in @code{prefix-arg}. In contrast, |
| 3114 | @code{current-prefix-arg} conveys the prefix argument to the current |
| 3115 | command, so setting it has no effect on the prefix arguments for future |
| 3116 | commands. |
| 3117 | |
| 3118 | Normally, commands specify which representation to use for the prefix |
| 3119 | argument, either numeric or raw, in the @code{interactive} specification. |
| 3120 | (@xref{Using Interactive}.) Alternatively, functions may look at the |
| 3121 | value of the prefix argument directly in the variable |
| 3122 | @code{current-prefix-arg}, but this is less clean. |
| 3123 | |
| 3124 | @defun prefix-numeric-value arg |
| 3125 | This function returns the numeric meaning of a valid raw prefix argument |
| 3126 | value, @var{arg}. The argument may be a symbol, a number, or a list. |
| 3127 | If it is @code{nil}, the value 1 is returned; if it is @code{-}, the |
| 3128 | value @minus{}1 is returned; if it is a number, that number is returned; |
| 3129 | if it is a list, the @sc{car} of that list (which should be a number) is |
| 3130 | returned. |
| 3131 | @end defun |
| 3132 | |
| 3133 | @defvar current-prefix-arg |
| 3134 | This variable holds the raw prefix argument for the @emph{current} |
| 3135 | command. Commands may examine it directly, but the usual method for |
| 3136 | accessing it is with @code{(interactive "P")}. |
| 3137 | @end defvar |
| 3138 | |
| 3139 | @defvar prefix-arg |
| 3140 | The value of this variable is the raw prefix argument for the |
| 3141 | @emph{next} editing command. Commands such as @code{universal-argument} |
| 3142 | that specify prefix arguments for the following command work by setting |
| 3143 | this variable. |
| 3144 | @end defvar |
| 3145 | |
| 3146 | @defvar last-prefix-arg |
| 3147 | The raw prefix argument value used by the previous command. |
| 3148 | @end defvar |
| 3149 | |
| 3150 | The following commands exist to set up prefix arguments for the |
| 3151 | following command. Do not call them for any other reason. |
| 3152 | |
| 3153 | @deffn Command universal-argument |
| 3154 | This command reads input and specifies a prefix argument for the |
| 3155 | following command. Don't call this command yourself unless you know |
| 3156 | what you are doing. |
| 3157 | @end deffn |
| 3158 | |
| 3159 | @deffn Command digit-argument arg |
| 3160 | This command adds to the prefix argument for the following command. The |
| 3161 | argument @var{arg} is the raw prefix argument as it was before this |
| 3162 | command; it is used to compute the updated prefix argument. Don't call |
| 3163 | this command yourself unless you know what you are doing. |
| 3164 | @end deffn |
| 3165 | |
| 3166 | @deffn Command negative-argument arg |
| 3167 | This command adds to the numeric argument for the next command. The |
| 3168 | argument @var{arg} is the raw prefix argument as it was before this |
| 3169 | command; its value is negated to form the new prefix argument. Don't |
| 3170 | call this command yourself unless you know what you are doing. |
| 3171 | @end deffn |
| 3172 | |
| 3173 | @node Recursive Editing |
| 3174 | @section Recursive Editing |
| 3175 | @cindex recursive command loop |
| 3176 | @cindex recursive editing level |
| 3177 | @cindex command loop, recursive |
| 3178 | |
| 3179 | The Emacs command loop is entered automatically when Emacs starts up. |
| 3180 | This top-level invocation of the command loop never exits; it keeps |
| 3181 | running as long as Emacs does. Lisp programs can also invoke the |
| 3182 | command loop. Since this makes more than one activation of the command |
| 3183 | loop, we call it @dfn{recursive editing}. A recursive editing level has |
| 3184 | the effect of suspending whatever command invoked it and permitting the |
| 3185 | user to do arbitrary editing before resuming that command. |
| 3186 | |
| 3187 | The commands available during recursive editing are the same ones |
| 3188 | available in the top-level editing loop and defined in the keymaps. |
| 3189 | Only a few special commands exit the recursive editing level; the others |
| 3190 | return to the recursive editing level when they finish. (The special |
| 3191 | commands for exiting are always available, but they do nothing when |
| 3192 | recursive editing is not in progress.) |
| 3193 | |
| 3194 | All command loops, including recursive ones, set up all-purpose error |
| 3195 | handlers so that an error in a command run from the command loop will |
| 3196 | not exit the loop. |
| 3197 | |
| 3198 | @cindex minibuffer input |
| 3199 | Minibuffer input is a special kind of recursive editing. It has a few |
| 3200 | special wrinkles, such as enabling display of the minibuffer and the |
| 3201 | minibuffer window, but fewer than you might suppose. Certain keys |
| 3202 | behave differently in the minibuffer, but that is only because of the |
| 3203 | minibuffer's local map; if you switch windows, you get the usual Emacs |
| 3204 | commands. |
| 3205 | |
| 3206 | @cindex @code{throw} example |
| 3207 | @kindex exit |
| 3208 | @cindex exit recursive editing |
| 3209 | @cindex aborting |
| 3210 | To invoke a recursive editing level, call the function |
| 3211 | @code{recursive-edit}. This function contains the command loop; it also |
| 3212 | contains a call to @code{catch} with tag @code{exit}, which makes it |
| 3213 | possible to exit the recursive editing level by throwing to @code{exit} |
| 3214 | (@pxref{Catch and Throw}). If you throw a value other than @code{t}, |
| 3215 | then @code{recursive-edit} returns normally to the function that called |
| 3216 | it. The command @kbd{C-M-c} (@code{exit-recursive-edit}) does this. |
| 3217 | Throwing a @code{t} value causes @code{recursive-edit} to quit, so that |
| 3218 | control returns to the command loop one level up. This is called |
| 3219 | @dfn{aborting}, and is done by @kbd{C-]} (@code{abort-recursive-edit}). |
| 3220 | |
| 3221 | Most applications should not use recursive editing, except as part of |
| 3222 | using the minibuffer. Usually it is more convenient for the user if you |
| 3223 | change the major mode of the current buffer temporarily to a special |
| 3224 | major mode, which should have a command to go back to the previous mode. |
| 3225 | (The @kbd{e} command in Rmail uses this technique.) Or, if you wish to |
| 3226 | give the user different text to edit ``recursively'', create and select |
| 3227 | a new buffer in a special mode. In this mode, define a command to |
| 3228 | complete the processing and go back to the previous buffer. (The |
| 3229 | @kbd{m} command in Rmail does this.) |
| 3230 | |
| 3231 | Recursive edits are useful in debugging. You can insert a call to |
| 3232 | @code{debug} into a function definition as a sort of breakpoint, so that |
| 3233 | you can look around when the function gets there. @code{debug} invokes |
| 3234 | a recursive edit but also provides the other features of the debugger. |
| 3235 | |
| 3236 | Recursive editing levels are also used when you type @kbd{C-r} in |
| 3237 | @code{query-replace} or use @kbd{C-x q} (@code{kbd-macro-query}). |
| 3238 | |
| 3239 | @deffn Command recursive-edit |
| 3240 | @cindex suspend evaluation |
| 3241 | This function invokes the editor command loop. It is called |
| 3242 | automatically by the initialization of Emacs, to let the user begin |
| 3243 | editing. When called from a Lisp program, it enters a recursive editing |
| 3244 | level. |
| 3245 | |
| 3246 | If the current buffer is not the same as the selected window's buffer, |
| 3247 | @code{recursive-edit} saves and restores the current buffer. Otherwise, |
| 3248 | if you switch buffers, the buffer you switched to is current after |
| 3249 | @code{recursive-edit} returns. |
| 3250 | |
| 3251 | In the following example, the function @code{simple-rec} first |
| 3252 | advances point one word, then enters a recursive edit, printing out a |
| 3253 | message in the echo area. The user can then do any editing desired, and |
| 3254 | then type @kbd{C-M-c} to exit and continue executing @code{simple-rec}. |
| 3255 | |
| 3256 | @example |
| 3257 | (defun simple-rec () |
| 3258 | (forward-word 1) |
| 3259 | (message "Recursive edit in progress") |
| 3260 | (recursive-edit) |
| 3261 | (forward-word 1)) |
| 3262 | @result{} simple-rec |
| 3263 | (simple-rec) |
| 3264 | @result{} nil |
| 3265 | @end example |
| 3266 | @end deffn |
| 3267 | |
| 3268 | @deffn Command exit-recursive-edit |
| 3269 | This function exits from the innermost recursive edit (including |
| 3270 | minibuffer input). Its definition is effectively @code{(throw 'exit |
| 3271 | nil)}. |
| 3272 | @end deffn |
| 3273 | |
| 3274 | @deffn Command abort-recursive-edit |
| 3275 | This function aborts the command that requested the innermost recursive |
| 3276 | edit (including minibuffer input), by signaling @code{quit} |
| 3277 | after exiting the recursive edit. Its definition is effectively |
| 3278 | @code{(throw 'exit t)}. @xref{Quitting}. |
| 3279 | @end deffn |
| 3280 | |
| 3281 | @deffn Command top-level |
| 3282 | This function exits all recursive editing levels; it does not return a |
| 3283 | value, as it jumps completely out of any computation directly back to |
| 3284 | the main command loop. |
| 3285 | @end deffn |
| 3286 | |
| 3287 | @defun recursion-depth |
| 3288 | This function returns the current depth of recursive edits. When no |
| 3289 | recursive edit is active, it returns 0. |
| 3290 | @end defun |
| 3291 | |
| 3292 | @node Disabling Commands |
| 3293 | @section Disabling Commands |
| 3294 | @cindex disabled command |
| 3295 | |
| 3296 | @dfn{Disabling a command} marks the command as requiring user |
| 3297 | confirmation before it can be executed. Disabling is used for commands |
| 3298 | which might be confusing to beginning users, to prevent them from using |
| 3299 | the commands by accident. |
| 3300 | |
| 3301 | @kindex disabled |
| 3302 | The low-level mechanism for disabling a command is to put a |
| 3303 | non-@code{nil} @code{disabled} property on the Lisp symbol for the |
| 3304 | command. These properties are normally set up by the user's |
| 3305 | init file (@pxref{Init File}) with Lisp expressions such as this: |
| 3306 | |
| 3307 | @example |
| 3308 | (put 'upcase-region 'disabled t) |
| 3309 | @end example |
| 3310 | |
| 3311 | @noindent |
| 3312 | For a few commands, these properties are present by default (you can |
| 3313 | remove them in your init file if you wish). |
| 3314 | |
| 3315 | If the value of the @code{disabled} property is a string, the message |
| 3316 | saying the command is disabled includes that string. For example: |
| 3317 | |
| 3318 | @example |
| 3319 | (put 'delete-region 'disabled |
| 3320 | "Text deleted this way cannot be yanked back!\n") |
| 3321 | @end example |
| 3322 | |
| 3323 | @xref{Disabling,,, emacs, The GNU Emacs Manual}, for the details on |
| 3324 | what happens when a disabled command is invoked interactively. |
| 3325 | Disabling a command has no effect on calling it as a function from Lisp |
| 3326 | programs. |
| 3327 | |
| 3328 | @deffn Command enable-command command |
| 3329 | Allow @var{command} (a symbol) to be executed without special |
| 3330 | confirmation from now on, and alter the user's init file (@pxref{Init |
| 3331 | File}) so that this will apply to future sessions. |
| 3332 | @end deffn |
| 3333 | |
| 3334 | @deffn Command disable-command command |
| 3335 | Require special confirmation to execute @var{command} from now on, and |
| 3336 | alter the user's init file so that this will apply to future sessions. |
| 3337 | @end deffn |
| 3338 | |
| 3339 | @defvar disabled-command-function |
| 3340 | The value of this variable should be a function. When the user |
| 3341 | invokes a disabled command interactively, this function is called |
| 3342 | instead of the disabled command. It can use @code{this-command-keys} |
| 3343 | to determine what the user typed to run the command, and thus find the |
| 3344 | command itself. |
| 3345 | |
| 3346 | The value may also be @code{nil}. Then all commands work normally, |
| 3347 | even disabled ones. |
| 3348 | |
| 3349 | By default, the value is a function that asks the user whether to |
| 3350 | proceed. |
| 3351 | @end defvar |
| 3352 | |
| 3353 | @node Command History |
| 3354 | @section Command History |
| 3355 | @cindex command history |
| 3356 | @cindex complex command |
| 3357 | @cindex history of commands |
| 3358 | |
| 3359 | The command loop keeps a history of the complex commands that have |
| 3360 | been executed, to make it convenient to repeat these commands. A |
| 3361 | @dfn{complex command} is one for which the interactive argument reading |
| 3362 | uses the minibuffer. This includes any @kbd{M-x} command, any |
| 3363 | @kbd{M-:} command, and any command whose @code{interactive} |
| 3364 | specification reads an argument from the minibuffer. Explicit use of |
| 3365 | the minibuffer during the execution of the command itself does not cause |
| 3366 | the command to be considered complex. |
| 3367 | |
| 3368 | @defvar command-history |
| 3369 | This variable's value is a list of recent complex commands, each |
| 3370 | represented as a form to evaluate. It continues to accumulate all |
| 3371 | complex commands for the duration of the editing session, but when it |
| 3372 | reaches the maximum size (@pxref{Minibuffer History}), the oldest |
| 3373 | elements are deleted as new ones are added. |
| 3374 | |
| 3375 | @example |
| 3376 | @group |
| 3377 | command-history |
| 3378 | @result{} ((switch-to-buffer "chistory.texi") |
| 3379 | (describe-key "^X^[") |
| 3380 | (visit-tags-table "~/emacs/src/") |
| 3381 | (find-tag "repeat-complex-command")) |
| 3382 | @end group |
| 3383 | @end example |
| 3384 | @end defvar |
| 3385 | |
| 3386 | This history list is actually a special case of minibuffer history |
| 3387 | (@pxref{Minibuffer History}), with one special twist: the elements are |
| 3388 | expressions rather than strings. |
| 3389 | |
| 3390 | There are a number of commands devoted to the editing and recall of |
| 3391 | previous commands. The commands @code{repeat-complex-command}, and |
| 3392 | @code{list-command-history} are described in the user manual |
| 3393 | (@pxref{Repetition,,, emacs, The GNU Emacs Manual}). Within the |
| 3394 | minibuffer, the usual minibuffer history commands are available. |
| 3395 | |
| 3396 | @node Keyboard Macros |
| 3397 | @section Keyboard Macros |
| 3398 | @cindex keyboard macros |
| 3399 | |
| 3400 | A @dfn{keyboard macro} is a canned sequence of input events that can |
| 3401 | be considered a command and made the definition of a key. The Lisp |
| 3402 | representation of a keyboard macro is a string or vector containing the |
| 3403 | events. Don't confuse keyboard macros with Lisp macros |
| 3404 | (@pxref{Macros}). |
| 3405 | |
| 3406 | @defun execute-kbd-macro kbdmacro &optional count loopfunc |
| 3407 | This function executes @var{kbdmacro} as a sequence of events. If |
| 3408 | @var{kbdmacro} is a string or vector, then the events in it are executed |
| 3409 | exactly as if they had been input by the user. The sequence is |
| 3410 | @emph{not} expected to be a single key sequence; normally a keyboard |
| 3411 | macro definition consists of several key sequences concatenated. |
| 3412 | |
| 3413 | If @var{kbdmacro} is a symbol, then its function definition is used in |
| 3414 | place of @var{kbdmacro}. If that is another symbol, this process repeats. |
| 3415 | Eventually the result should be a string or vector. If the result is |
| 3416 | not a symbol, string, or vector, an error is signaled. |
| 3417 | |
| 3418 | The argument @var{count} is a repeat count; @var{kbdmacro} is executed that |
| 3419 | many times. If @var{count} is omitted or @code{nil}, @var{kbdmacro} is |
| 3420 | executed once. If it is 0, @var{kbdmacro} is executed over and over until it |
| 3421 | encounters an error or a failing search. |
| 3422 | |
| 3423 | If @var{loopfunc} is non-@code{nil}, it is a function that is called, |
| 3424 | without arguments, prior to each iteration of the macro. If |
| 3425 | @var{loopfunc} returns @code{nil}, then this stops execution of the macro. |
| 3426 | |
| 3427 | @xref{Reading One Event}, for an example of using @code{execute-kbd-macro}. |
| 3428 | @end defun |
| 3429 | |
| 3430 | @defvar executing-kbd-macro |
| 3431 | This variable contains the string or vector that defines the keyboard |
| 3432 | macro that is currently executing. It is @code{nil} if no macro is |
| 3433 | currently executing. A command can test this variable so as to behave |
| 3434 | differently when run from an executing macro. Do not set this variable |
| 3435 | yourself. |
| 3436 | @end defvar |
| 3437 | |
| 3438 | @defvar defining-kbd-macro |
| 3439 | This variable is non-@code{nil} if and only if a keyboard macro is |
| 3440 | being defined. A command can test this variable so as to behave |
| 3441 | differently while a macro is being defined. The value is |
| 3442 | @code{append} while appending to the definition of an existing macro. |
| 3443 | The commands @code{start-kbd-macro}, @code{kmacro-start-macro} and |
| 3444 | @code{end-kbd-macro} set this variable---do not set it yourself. |
| 3445 | |
| 3446 | The variable is always local to the current terminal and cannot be |
| 3447 | buffer-local. @xref{Multiple Terminals}. |
| 3448 | @end defvar |
| 3449 | |
| 3450 | @defvar last-kbd-macro |
| 3451 | This variable is the definition of the most recently defined keyboard |
| 3452 | macro. Its value is a string or vector, or @code{nil}. |
| 3453 | |
| 3454 | The variable is always local to the current terminal and cannot be |
| 3455 | buffer-local. @xref{Multiple Terminals}. |
| 3456 | @end defvar |
| 3457 | |
| 3458 | @defvar kbd-macro-termination-hook |
| 3459 | This normal hook is run when a keyboard macro terminates, regardless |
| 3460 | of what caused it to terminate (reaching the macro end or an error |
| 3461 | which ended the macro prematurely). |
| 3462 | @end defvar |