| 1 | @c -*-texinfo-*- |
| 2 | @c This is part of the GNU Emacs Lisp Reference Manual. |
| 3 | @c Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1998, 1999, 2000, 2001, |
| 4 | @c 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010 |
| 5 | @c Free Software Foundation, Inc. |
| 6 | @c See the file elisp.texi for copying conditions. |
| 7 | @setfilename ../../info/text |
| 8 | @node Text, Non-ASCII Characters, Markers, Top |
| 9 | @chapter Text |
| 10 | @cindex text |
| 11 | |
| 12 | This chapter describes the functions that deal with the text in a |
| 13 | buffer. Most examine, insert, or delete text in the current buffer, |
| 14 | often operating at point or on text adjacent to point. Many are |
| 15 | interactive. All the functions that change the text provide for undoing |
| 16 | the changes (@pxref{Undo}). |
| 17 | |
| 18 | Many text-related functions operate on a region of text defined by two |
| 19 | buffer positions passed in arguments named @var{start} and @var{end}. |
| 20 | These arguments should be either markers (@pxref{Markers}) or numeric |
| 21 | character positions (@pxref{Positions}). The order of these arguments |
| 22 | does not matter; it is all right for @var{start} to be the end of the |
| 23 | region and @var{end} the beginning. For example, @code{(delete-region 1 |
| 24 | 10)} and @code{(delete-region 10 1)} are equivalent. An |
| 25 | @code{args-out-of-range} error is signaled if either @var{start} or |
| 26 | @var{end} is outside the accessible portion of the buffer. In an |
| 27 | interactive call, point and the mark are used for these arguments. |
| 28 | |
| 29 | @cindex buffer contents |
| 30 | Throughout this chapter, ``text'' refers to the characters in the |
| 31 | buffer, together with their properties (when relevant). Keep in mind |
| 32 | that point is always between two characters, and the cursor appears on |
| 33 | the character after point. |
| 34 | |
| 35 | @menu |
| 36 | * Near Point:: Examining text in the vicinity of point. |
| 37 | * Buffer Contents:: Examining text in a general fashion. |
| 38 | * Comparing Text:: Comparing substrings of buffers. |
| 39 | * Insertion:: Adding new text to a buffer. |
| 40 | * Commands for Insertion:: User-level commands to insert text. |
| 41 | * Deletion:: Removing text from a buffer. |
| 42 | * User-Level Deletion:: User-level commands to delete text. |
| 43 | * The Kill Ring:: Where removed text sometimes is saved for later use. |
| 44 | * Undo:: Undoing changes to the text of a buffer. |
| 45 | * Maintaining Undo:: How to enable and disable undo information. |
| 46 | How to control how much information is kept. |
| 47 | * Filling:: Functions for explicit filling. |
| 48 | * Margins:: How to specify margins for filling commands. |
| 49 | * Adaptive Fill:: Adaptive Fill mode chooses a fill prefix from context. |
| 50 | * Auto Filling:: How auto-fill mode is implemented to break lines. |
| 51 | * Sorting:: Functions for sorting parts of the buffer. |
| 52 | * Columns:: Computing horizontal positions, and using them. |
| 53 | * Indentation:: Functions to insert or adjust indentation. |
| 54 | * Case Changes:: Case conversion of parts of the buffer. |
| 55 | * Text Properties:: Assigning Lisp property lists to text characters. |
| 56 | * Substitution:: Replacing a given character wherever it appears. |
| 57 | * Transposition:: Swapping two portions of a buffer. |
| 58 | * Registers:: How registers are implemented. Accessing the text or |
| 59 | position stored in a register. |
| 60 | * Base 64:: Conversion to or from base 64 encoding. |
| 61 | * MD5 Checksum:: Compute the MD5 "message digest"/"checksum". |
| 62 | * Atomic Changes:: Installing several buffer changes "atomically". |
| 63 | * Change Hooks:: Supplying functions to be run when text is changed. |
| 64 | @end menu |
| 65 | |
| 66 | @node Near Point |
| 67 | @section Examining Text Near Point |
| 68 | @cindex text near point |
| 69 | |
| 70 | Many functions are provided to look at the characters around point. |
| 71 | Several simple functions are described here. See also @code{looking-at} |
| 72 | in @ref{Regexp Search}. |
| 73 | |
| 74 | In the following four functions, ``beginning'' or ``end'' of buffer |
| 75 | refers to the beginning or end of the accessible portion. |
| 76 | |
| 77 | @defun char-after &optional position |
| 78 | This function returns the character in the current buffer at (i.e., |
| 79 | immediately after) position @var{position}. If @var{position} is out of |
| 80 | range for this purpose, either before the beginning of the buffer, or at |
| 81 | or beyond the end, then the value is @code{nil}. The default for |
| 82 | @var{position} is point. |
| 83 | |
| 84 | In the following example, assume that the first character in the |
| 85 | buffer is @samp{@@}: |
| 86 | |
| 87 | @example |
| 88 | @group |
| 89 | (char-to-string (char-after 1)) |
| 90 | @result{} "@@" |
| 91 | @end group |
| 92 | @end example |
| 93 | @end defun |
| 94 | |
| 95 | @defun char-before &optional position |
| 96 | This function returns the character in the current buffer immediately |
| 97 | before position @var{position}. If @var{position} is out of range for |
| 98 | this purpose, either at or before the beginning of the buffer, or beyond |
| 99 | the end, then the value is @code{nil}. The default for |
| 100 | @var{position} is point. |
| 101 | @end defun |
| 102 | |
| 103 | @defun following-char |
| 104 | This function returns the character following point in the current |
| 105 | buffer. This is similar to @code{(char-after (point))}. However, if |
| 106 | point is at the end of the buffer, then @code{following-char} returns 0. |
| 107 | |
| 108 | Remember that point is always between characters, and the cursor |
| 109 | normally appears over the character following point. Therefore, the |
| 110 | character returned by @code{following-char} is the character the |
| 111 | cursor is over. |
| 112 | |
| 113 | In this example, point is between the @samp{a} and the @samp{c}. |
| 114 | |
| 115 | @example |
| 116 | @group |
| 117 | ---------- Buffer: foo ---------- |
| 118 | Gentlemen may cry ``Pea@point{}ce! Peace!,'' |
| 119 | but there is no peace. |
| 120 | ---------- Buffer: foo ---------- |
| 121 | @end group |
| 122 | |
| 123 | @group |
| 124 | (char-to-string (preceding-char)) |
| 125 | @result{} "a" |
| 126 | (char-to-string (following-char)) |
| 127 | @result{} "c" |
| 128 | @end group |
| 129 | @end example |
| 130 | @end defun |
| 131 | |
| 132 | @defun preceding-char |
| 133 | This function returns the character preceding point in the current |
| 134 | buffer. See above, under @code{following-char}, for an example. If |
| 135 | point is at the beginning of the buffer, @code{preceding-char} returns |
| 136 | 0. |
| 137 | @end defun |
| 138 | |
| 139 | @defun bobp |
| 140 | This function returns @code{t} if point is at the beginning of the |
| 141 | buffer. If narrowing is in effect, this means the beginning of the |
| 142 | accessible portion of the text. See also @code{point-min} in |
| 143 | @ref{Point}. |
| 144 | @end defun |
| 145 | |
| 146 | @defun eobp |
| 147 | This function returns @code{t} if point is at the end of the buffer. |
| 148 | If narrowing is in effect, this means the end of accessible portion of |
| 149 | the text. See also @code{point-max} in @xref{Point}. |
| 150 | @end defun |
| 151 | |
| 152 | @defun bolp |
| 153 | This function returns @code{t} if point is at the beginning of a line. |
| 154 | @xref{Text Lines}. The beginning of the buffer (or of its accessible |
| 155 | portion) always counts as the beginning of a line. |
| 156 | @end defun |
| 157 | |
| 158 | @defun eolp |
| 159 | This function returns @code{t} if point is at the end of a line. The |
| 160 | end of the buffer (or of its accessible portion) is always considered |
| 161 | the end of a line. |
| 162 | @end defun |
| 163 | |
| 164 | @node Buffer Contents |
| 165 | @section Examining Buffer Contents |
| 166 | |
| 167 | This section describes functions that allow a Lisp program to |
| 168 | convert any portion of the text in the buffer into a string. |
| 169 | |
| 170 | @defun buffer-substring start end |
| 171 | This function returns a string containing a copy of the text of the |
| 172 | region defined by positions @var{start} and @var{end} in the current |
| 173 | buffer. If the arguments are not positions in the accessible portion of |
| 174 | the buffer, @code{buffer-substring} signals an @code{args-out-of-range} |
| 175 | error. |
| 176 | |
| 177 | It is not necessary for @var{start} to be less than @var{end}; the |
| 178 | arguments can be given in either order. But most often the smaller |
| 179 | argument is written first. |
| 180 | |
| 181 | Here's an example which assumes Font-Lock mode is not enabled: |
| 182 | |
| 183 | @example |
| 184 | @group |
| 185 | ---------- Buffer: foo ---------- |
| 186 | This is the contents of buffer foo |
| 187 | |
| 188 | ---------- Buffer: foo ---------- |
| 189 | @end group |
| 190 | |
| 191 | @group |
| 192 | (buffer-substring 1 10) |
| 193 | @result{} "This is t" |
| 194 | @end group |
| 195 | @group |
| 196 | (buffer-substring (point-max) 10) |
| 197 | @result{} "he contents of buffer foo\n" |
| 198 | @end group |
| 199 | @end example |
| 200 | |
| 201 | If the text being copied has any text properties, these are copied into |
| 202 | the string along with the characters they belong to. @xref{Text |
| 203 | Properties}. However, overlays (@pxref{Overlays}) in the buffer and |
| 204 | their properties are ignored, not copied. |
| 205 | |
| 206 | For example, if Font-Lock mode is enabled, you might get results like |
| 207 | these: |
| 208 | |
| 209 | @example |
| 210 | @group |
| 211 | (buffer-substring 1 10) |
| 212 | @result{} #("This is t" 0 1 (fontified t) 1 9 (fontified t)) |
| 213 | @end group |
| 214 | @end example |
| 215 | @end defun |
| 216 | |
| 217 | @defun buffer-substring-no-properties start end |
| 218 | This is like @code{buffer-substring}, except that it does not copy text |
| 219 | properties, just the characters themselves. @xref{Text Properties}. |
| 220 | @end defun |
| 221 | |
| 222 | @defun filter-buffer-substring start end &optional delete noprops |
| 223 | This function passes the buffer text between @var{start} and @var{end} |
| 224 | through the filter functions specified by the variable |
| 225 | @code{buffer-substring-filters}, and returns the value from the last |
| 226 | filter function. If @code{buffer-substring-filters} is @code{nil}, |
| 227 | the value is the unaltered text from the buffer, what |
| 228 | @code{buffer-substring} would return. |
| 229 | |
| 230 | If @var{delete} is non-@code{nil}, this function deletes the text |
| 231 | between @var{start} and @var{end} after copying it, like |
| 232 | @code{delete-and-extract-region}. |
| 233 | |
| 234 | If @var{noprops} is non-@code{nil}, the final string returned does not |
| 235 | include text properties, while the string passed through the filters |
| 236 | still includes text properties from the buffer text. |
| 237 | |
| 238 | Lisp code should use this function instead of @code{buffer-substring}, |
| 239 | @code{buffer-substring-no-properties}, |
| 240 | or @code{delete-and-extract-region} when copying into user-accessible |
| 241 | data structures such as the kill-ring, X clipboard, and registers. |
| 242 | Major and minor modes can add functions to |
| 243 | @code{buffer-substring-filters} to alter such text as it is copied out |
| 244 | of the buffer. |
| 245 | @end defun |
| 246 | |
| 247 | @defvar buffer-substring-filters |
| 248 | This variable should be a list of functions that accept a single |
| 249 | argument, a string, and return a string. |
| 250 | @code{filter-buffer-substring} passes the buffer substring to the |
| 251 | first function in this list, and the return value of each function is |
| 252 | passed to the next function. The return value of the last function is |
| 253 | used as the return value of @code{filter-buffer-substring}. |
| 254 | |
| 255 | As a special convention, point is set to the start of the buffer text |
| 256 | being operated on (i.e., the @var{start} argument for |
| 257 | @code{filter-buffer-substring}) before these functions are called. |
| 258 | |
| 259 | If this variable is @code{nil}, no filtering is performed. |
| 260 | @end defvar |
| 261 | |
| 262 | @defun buffer-string |
| 263 | This function returns the contents of the entire accessible portion of |
| 264 | the current buffer as a string. It is equivalent to |
| 265 | |
| 266 | @example |
| 267 | (buffer-substring (point-min) (point-max)) |
| 268 | @end example |
| 269 | |
| 270 | @example |
| 271 | @group |
| 272 | ---------- Buffer: foo ---------- |
| 273 | This is the contents of buffer foo |
| 274 | |
| 275 | ---------- Buffer: foo ---------- |
| 276 | |
| 277 | (buffer-string) |
| 278 | @result{} "This is the contents of buffer foo\n" |
| 279 | @end group |
| 280 | @end example |
| 281 | @end defun |
| 282 | |
| 283 | @defun current-word &optional strict really-word |
| 284 | This function returns the symbol (or word) at or near point, as a string. |
| 285 | The return value includes no text properties. |
| 286 | |
| 287 | If the optional argument @var{really-word} is non-@code{nil}, it finds a |
| 288 | word; otherwise, it finds a symbol (which includes both word |
| 289 | characters and symbol constituent characters). |
| 290 | |
| 291 | If the optional argument @var{strict} is non-@code{nil}, then point |
| 292 | must be in or next to the symbol or word---if no symbol or word is |
| 293 | there, the function returns @code{nil}. Otherwise, a nearby symbol or |
| 294 | word on the same line is acceptable. |
| 295 | @end defun |
| 296 | |
| 297 | @defun thing-at-point thing |
| 298 | Return the @var{thing} around or next to point, as a string. |
| 299 | |
| 300 | The argument @var{thing} is a symbol which specifies a kind of syntactic |
| 301 | entity. Possibilities include @code{symbol}, @code{list}, @code{sexp}, |
| 302 | @code{defun}, @code{filename}, @code{url}, @code{word}, @code{sentence}, |
| 303 | @code{whitespace}, @code{line}, @code{page}, and others. |
| 304 | |
| 305 | @example |
| 306 | ---------- Buffer: foo ---------- |
| 307 | Gentlemen may cry ``Pea@point{}ce! Peace!,'' |
| 308 | but there is no peace. |
| 309 | ---------- Buffer: foo ---------- |
| 310 | |
| 311 | (thing-at-point 'word) |
| 312 | @result{} "Peace" |
| 313 | (thing-at-point 'line) |
| 314 | @result{} "Gentlemen may cry ``Peace! Peace!,''\n" |
| 315 | (thing-at-point 'whitespace) |
| 316 | @result{} nil |
| 317 | @end example |
| 318 | @end defun |
| 319 | |
| 320 | @node Comparing Text |
| 321 | @section Comparing Text |
| 322 | @cindex comparing buffer text |
| 323 | |
| 324 | This function lets you compare portions of the text in a buffer, without |
| 325 | copying them into strings first. |
| 326 | |
| 327 | @defun compare-buffer-substrings buffer1 start1 end1 buffer2 start2 end2 |
| 328 | This function lets you compare two substrings of the same buffer or two |
| 329 | different buffers. The first three arguments specify one substring, |
| 330 | giving a buffer (or a buffer name) and two positions within the |
| 331 | buffer. The last three arguments specify the other substring in the |
| 332 | same way. You can use @code{nil} for @var{buffer1}, @var{buffer2}, or |
| 333 | both to stand for the current buffer. |
| 334 | |
| 335 | The value is negative if the first substring is less, positive if the |
| 336 | first is greater, and zero if they are equal. The absolute value of |
| 337 | the result is one plus the index of the first differing characters |
| 338 | within the substrings. |
| 339 | |
| 340 | This function ignores case when comparing characters |
| 341 | if @code{case-fold-search} is non-@code{nil}. It always ignores |
| 342 | text properties. |
| 343 | |
| 344 | Suppose the current buffer contains the text @samp{foobarbar |
| 345 | haha!rara!}; then in this example the two substrings are @samp{rbar } |
| 346 | and @samp{rara!}. The value is 2 because the first substring is greater |
| 347 | at the second character. |
| 348 | |
| 349 | @example |
| 350 | (compare-buffer-substrings nil 6 11 nil 16 21) |
| 351 | @result{} 2 |
| 352 | @end example |
| 353 | @end defun |
| 354 | |
| 355 | @node Insertion |
| 356 | @section Inserting Text |
| 357 | @cindex insertion of text |
| 358 | @cindex text insertion |
| 359 | |
| 360 | @cindex insertion before point |
| 361 | @cindex before point, insertion |
| 362 | @dfn{Insertion} means adding new text to a buffer. The inserted text |
| 363 | goes at point---between the character before point and the character |
| 364 | after point. Some insertion functions leave point before the inserted |
| 365 | text, while other functions leave it after. We call the former |
| 366 | insertion @dfn{after point} and the latter insertion @dfn{before point}. |
| 367 | |
| 368 | Insertion relocates markers that point at positions after the |
| 369 | insertion point, so that they stay with the surrounding text |
| 370 | (@pxref{Markers}). When a marker points at the place of insertion, |
| 371 | insertion may or may not relocate the marker, depending on the marker's |
| 372 | insertion type (@pxref{Marker Insertion Types}). Certain special |
| 373 | functions such as @code{insert-before-markers} relocate all such markers |
| 374 | to point after the inserted text, regardless of the markers' insertion |
| 375 | type. |
| 376 | |
| 377 | Insertion functions signal an error if the current buffer is |
| 378 | read-only or if they insert within read-only text. |
| 379 | |
| 380 | These functions copy text characters from strings and buffers along |
| 381 | with their properties. The inserted characters have exactly the same |
| 382 | properties as the characters they were copied from. By contrast, |
| 383 | characters specified as separate arguments, not part of a string or |
| 384 | buffer, inherit their text properties from the neighboring text. |
| 385 | |
| 386 | The insertion functions convert text from unibyte to multibyte in |
| 387 | order to insert in a multibyte buffer, and vice versa---if the text |
| 388 | comes from a string or from a buffer. However, they do not convert |
| 389 | unibyte character codes 128 through 255 to multibyte characters, not |
| 390 | even if the current buffer is a multibyte buffer. @xref{Converting |
| 391 | Representations}. |
| 392 | |
| 393 | @defun insert &rest args |
| 394 | This function inserts the strings and/or characters @var{args} into the |
| 395 | current buffer, at point, moving point forward. In other words, it |
| 396 | inserts the text before point. An error is signaled unless all |
| 397 | @var{args} are either strings or characters. The value is @code{nil}. |
| 398 | @end defun |
| 399 | |
| 400 | @defun insert-before-markers &rest args |
| 401 | This function inserts the strings and/or characters @var{args} into the |
| 402 | current buffer, at point, moving point forward. An error is signaled |
| 403 | unless all @var{args} are either strings or characters. The value is |
| 404 | @code{nil}. |
| 405 | |
| 406 | This function is unlike the other insertion functions in that it |
| 407 | relocates markers initially pointing at the insertion point, to point |
| 408 | after the inserted text. If an overlay begins at the insertion point, |
| 409 | the inserted text falls outside the overlay; if a nonempty overlay |
| 410 | ends at the insertion point, the inserted text falls inside that |
| 411 | overlay. |
| 412 | @end defun |
| 413 | |
| 414 | @defun insert-char character count &optional inherit |
| 415 | This function inserts @var{count} instances of @var{character} into the |
| 416 | current buffer before point. The argument @var{count} should be an |
| 417 | integer, and @var{character} must be a character. The value is @code{nil}. |
| 418 | |
| 419 | This function does not convert unibyte character codes 128 through 255 |
| 420 | to multibyte characters, not even if the current buffer is a multibyte |
| 421 | buffer. @xref{Converting Representations}. |
| 422 | |
| 423 | If @var{inherit} is non-@code{nil}, then the inserted characters inherit |
| 424 | sticky text properties from the two characters before and after the |
| 425 | insertion point. @xref{Sticky Properties}. |
| 426 | @end defun |
| 427 | |
| 428 | @defun insert-buffer-substring from-buffer-or-name &optional start end |
| 429 | This function inserts a portion of buffer @var{from-buffer-or-name} |
| 430 | (which must already exist) into the current buffer before point. The |
| 431 | text inserted is the region between @var{start} and @var{end}. (These |
| 432 | arguments default to the beginning and end of the accessible portion of |
| 433 | that buffer.) This function returns @code{nil}. |
| 434 | |
| 435 | In this example, the form is executed with buffer @samp{bar} as the |
| 436 | current buffer. We assume that buffer @samp{bar} is initially empty. |
| 437 | |
| 438 | @example |
| 439 | @group |
| 440 | ---------- Buffer: foo ---------- |
| 441 | We hold these truths to be self-evident, that all |
| 442 | ---------- Buffer: foo ---------- |
| 443 | @end group |
| 444 | |
| 445 | @group |
| 446 | (insert-buffer-substring "foo" 1 20) |
| 447 | @result{} nil |
| 448 | |
| 449 | ---------- Buffer: bar ---------- |
| 450 | We hold these truth@point{} |
| 451 | ---------- Buffer: bar ---------- |
| 452 | @end group |
| 453 | @end example |
| 454 | @end defun |
| 455 | |
| 456 | @defun insert-buffer-substring-no-properties from-buffer-or-name &optional start end |
| 457 | This is like @code{insert-buffer-substring} except that it does not |
| 458 | copy any text properties. |
| 459 | @end defun |
| 460 | |
| 461 | @xref{Sticky Properties}, for other insertion functions that inherit |
| 462 | text properties from the nearby text in addition to inserting it. |
| 463 | Whitespace inserted by indentation functions also inherits text |
| 464 | properties. |
| 465 | |
| 466 | @node Commands for Insertion |
| 467 | @section User-Level Insertion Commands |
| 468 | |
| 469 | This section describes higher-level commands for inserting text, |
| 470 | commands intended primarily for the user but useful also in Lisp |
| 471 | programs. |
| 472 | |
| 473 | @deffn Command insert-buffer from-buffer-or-name |
| 474 | This command inserts the entire accessible contents of |
| 475 | @var{from-buffer-or-name} (which must exist) into the current buffer |
| 476 | after point. It leaves the mark after the inserted text. The value |
| 477 | is @code{nil}. |
| 478 | @end deffn |
| 479 | |
| 480 | @deffn Command self-insert-command count |
| 481 | @cindex character insertion |
| 482 | @cindex self-insertion |
| 483 | This command inserts the last character typed; it does so @var{count} |
| 484 | times, before point, and returns @code{nil}. Most printing characters |
| 485 | are bound to this command. In routine use, @code{self-insert-command} |
| 486 | is the most frequently called function in Emacs, but programs rarely use |
| 487 | it except to install it on a keymap. |
| 488 | |
| 489 | In an interactive call, @var{count} is the numeric prefix argument. |
| 490 | |
| 491 | Self-insertion translates the input character through |
| 492 | @code{translation-table-for-input}. @xref{Translation of Characters}. |
| 493 | |
| 494 | This command calls @code{auto-fill-function} whenever that is |
| 495 | non-@code{nil} and the character inserted is in the table |
| 496 | @code{auto-fill-chars} (@pxref{Auto Filling}). |
| 497 | |
| 498 | @c Cross refs reworded to prevent overfull hbox. --rjc 15mar92 |
| 499 | This command performs abbrev expansion if Abbrev mode is enabled and |
| 500 | the inserted character does not have word-constituent |
| 501 | syntax. (@xref{Abbrevs}, and @ref{Syntax Class Table}.) It is also |
| 502 | responsible for calling @code{blink-paren-function} when the inserted |
| 503 | character has close parenthesis syntax (@pxref{Blinking}). |
| 504 | |
| 505 | Do not try substituting your own definition of |
| 506 | @code{self-insert-command} for the standard one. The editor command |
| 507 | loop handles this function specially. |
| 508 | @end deffn |
| 509 | |
| 510 | @deffn Command newline &optional number-of-newlines |
| 511 | This command inserts newlines into the current buffer before point. |
| 512 | If @var{number-of-newlines} is supplied, that many newline characters |
| 513 | are inserted. |
| 514 | |
| 515 | @cindex newline and Auto Fill mode |
| 516 | This function calls @code{auto-fill-function} if the current column |
| 517 | number is greater than the value of @code{fill-column} and |
| 518 | @var{number-of-newlines} is @code{nil}. Typically what |
| 519 | @code{auto-fill-function} does is insert a newline; thus, the overall |
| 520 | result in this case is to insert two newlines at different places: one |
| 521 | at point, and another earlier in the line. @code{newline} does not |
| 522 | auto-fill if @var{number-of-newlines} is non-@code{nil}. |
| 523 | |
| 524 | This command indents to the left margin if that is not zero. |
| 525 | @xref{Margins}. |
| 526 | |
| 527 | The value returned is @code{nil}. In an interactive call, @var{count} |
| 528 | is the numeric prefix argument. |
| 529 | @end deffn |
| 530 | |
| 531 | @defvar overwrite-mode |
| 532 | This variable controls whether overwrite mode is in effect. The value |
| 533 | should be @code{overwrite-mode-textual}, @code{overwrite-mode-binary}, |
| 534 | or @code{nil}. @code{overwrite-mode-textual} specifies textual |
| 535 | overwrite mode (treats newlines and tabs specially), and |
| 536 | @code{overwrite-mode-binary} specifies binary overwrite mode (treats |
| 537 | newlines and tabs like any other characters). |
| 538 | @end defvar |
| 539 | |
| 540 | @node Deletion |
| 541 | @section Deleting Text |
| 542 | @cindex text deletion |
| 543 | |
| 544 | @cindex deleting text vs killing |
| 545 | Deletion means removing part of the text in a buffer, without saving |
| 546 | it in the kill ring (@pxref{The Kill Ring}). Deleted text can't be |
| 547 | yanked, but can be reinserted using the undo mechanism (@pxref{Undo}). |
| 548 | Some deletion functions do save text in the kill ring in some special |
| 549 | cases. |
| 550 | |
| 551 | All of the deletion functions operate on the current buffer. |
| 552 | |
| 553 | @deffn Command erase-buffer |
| 554 | This function deletes the entire text of the current buffer |
| 555 | (@emph{not} just the accessible portion), leaving it |
| 556 | empty. If the buffer is read-only, it signals a @code{buffer-read-only} |
| 557 | error; if some of the text in it is read-only, it signals a |
| 558 | @code{text-read-only} error. Otherwise, it deletes the text without |
| 559 | asking for any confirmation. It returns @code{nil}. |
| 560 | |
| 561 | Normally, deleting a large amount of text from a buffer inhibits further |
| 562 | auto-saving of that buffer ``because it has shrunk.'' However, |
| 563 | @code{erase-buffer} does not do this, the idea being that the future |
| 564 | text is not really related to the former text, and its size should not |
| 565 | be compared with that of the former text. |
| 566 | @end deffn |
| 567 | |
| 568 | @deffn Command delete-region start end |
| 569 | This command deletes the text between positions @var{start} and |
| 570 | @var{end} in the current buffer, and returns @code{nil}. If point was |
| 571 | inside the deleted region, its value afterward is @var{start}. |
| 572 | Otherwise, point relocates with the surrounding text, as markers do. |
| 573 | @end deffn |
| 574 | |
| 575 | @defun delete-and-extract-region start end |
| 576 | This function deletes the text between positions @var{start} and |
| 577 | @var{end} in the current buffer, and returns a string containing the |
| 578 | text just deleted. |
| 579 | |
| 580 | If point was inside the deleted region, its value afterward is |
| 581 | @var{start}. Otherwise, point relocates with the surrounding text, as |
| 582 | markers do. |
| 583 | @end defun |
| 584 | |
| 585 | @deffn Command delete-char count &optional killp |
| 586 | This command deletes @var{count} characters directly after point, or |
| 587 | before point if @var{count} is negative. If @var{killp} is |
| 588 | non-@code{nil}, then it saves the deleted characters in the kill ring. |
| 589 | |
| 590 | In an interactive call, @var{count} is the numeric prefix argument, and |
| 591 | @var{killp} is the unprocessed prefix argument. Therefore, if a prefix |
| 592 | argument is supplied, the text is saved in the kill ring. If no prefix |
| 593 | argument is supplied, then one character is deleted, but not saved in |
| 594 | the kill ring. |
| 595 | |
| 596 | The value returned is always @code{nil}. |
| 597 | @end deffn |
| 598 | |
| 599 | @deffn Command delete-backward-char count &optional killp |
| 600 | @cindex deleting previous char |
| 601 | This command deletes @var{count} characters directly before point, or |
| 602 | after point if @var{count} is negative. If @var{killp} is |
| 603 | non-@code{nil}, then it saves the deleted characters in the kill ring. |
| 604 | |
| 605 | In an interactive call, @var{count} is the numeric prefix argument, and |
| 606 | @var{killp} is the unprocessed prefix argument. Therefore, if a prefix |
| 607 | argument is supplied, the text is saved in the kill ring. If no prefix |
| 608 | argument is supplied, then one character is deleted, but not saved in |
| 609 | the kill ring. |
| 610 | |
| 611 | The value returned is always @code{nil}. |
| 612 | @end deffn |
| 613 | |
| 614 | @deffn Command backward-delete-char-untabify count &optional killp |
| 615 | @cindex tab deletion |
| 616 | This command deletes @var{count} characters backward, changing tabs |
| 617 | into spaces. When the next character to be deleted is a tab, it is |
| 618 | first replaced with the proper number of spaces to preserve alignment |
| 619 | and then one of those spaces is deleted instead of the tab. If |
| 620 | @var{killp} is non-@code{nil}, then the command saves the deleted |
| 621 | characters in the kill ring. |
| 622 | |
| 623 | Conversion of tabs to spaces happens only if @var{count} is positive. |
| 624 | If it is negative, exactly @minus{}@var{count} characters after point |
| 625 | are deleted. |
| 626 | |
| 627 | In an interactive call, @var{count} is the numeric prefix argument, and |
| 628 | @var{killp} is the unprocessed prefix argument. Therefore, if a prefix |
| 629 | argument is supplied, the text is saved in the kill ring. If no prefix |
| 630 | argument is supplied, then one character is deleted, but not saved in |
| 631 | the kill ring. |
| 632 | |
| 633 | The value returned is always @code{nil}. |
| 634 | @end deffn |
| 635 | |
| 636 | @defopt backward-delete-char-untabify-method |
| 637 | This option specifies how @code{backward-delete-char-untabify} should |
| 638 | deal with whitespace. Possible values include @code{untabify}, the |
| 639 | default, meaning convert a tab to many spaces and delete one; |
| 640 | @code{hungry}, meaning delete all tabs and spaces before point with |
| 641 | one command; @code{all} meaning delete all tabs, spaces and newlines |
| 642 | before point, and @code{nil}, meaning do nothing special for |
| 643 | whitespace characters. |
| 644 | @end defopt |
| 645 | |
| 646 | @node User-Level Deletion |
| 647 | @section User-Level Deletion Commands |
| 648 | |
| 649 | This section describes higher-level commands for deleting text, |
| 650 | commands intended primarily for the user but useful also in Lisp |
| 651 | programs. |
| 652 | |
| 653 | @deffn Command delete-horizontal-space &optional backward-only |
| 654 | @cindex deleting whitespace |
| 655 | This function deletes all spaces and tabs around point. It returns |
| 656 | @code{nil}. |
| 657 | |
| 658 | If @var{backward-only} is non-@code{nil}, the function deletes |
| 659 | spaces and tabs before point, but not after point. |
| 660 | |
| 661 | In the following examples, we call @code{delete-horizontal-space} four |
| 662 | times, once on each line, with point between the second and third |
| 663 | characters on the line each time. |
| 664 | |
| 665 | @example |
| 666 | @group |
| 667 | ---------- Buffer: foo ---------- |
| 668 | I @point{}thought |
| 669 | I @point{} thought |
| 670 | We@point{} thought |
| 671 | Yo@point{}u thought |
| 672 | ---------- Buffer: foo ---------- |
| 673 | @end group |
| 674 | |
| 675 | @group |
| 676 | (delete-horizontal-space) ; @r{Four times.} |
| 677 | @result{} nil |
| 678 | |
| 679 | ---------- Buffer: foo ---------- |
| 680 | Ithought |
| 681 | Ithought |
| 682 | Wethought |
| 683 | You thought |
| 684 | ---------- Buffer: foo ---------- |
| 685 | @end group |
| 686 | @end example |
| 687 | @end deffn |
| 688 | |
| 689 | @deffn Command delete-indentation &optional join-following-p |
| 690 | This function joins the line point is on to the previous line, deleting |
| 691 | any whitespace at the join and in some cases replacing it with one |
| 692 | space. If @var{join-following-p} is non-@code{nil}, |
| 693 | @code{delete-indentation} joins this line to the following line |
| 694 | instead. The function returns @code{nil}. |
| 695 | |
| 696 | If there is a fill prefix, and the second of the lines being joined |
| 697 | starts with the prefix, then @code{delete-indentation} deletes the |
| 698 | fill prefix before joining the lines. @xref{Margins}. |
| 699 | |
| 700 | In the example below, point is located on the line starting |
| 701 | @samp{events}, and it makes no difference if there are trailing spaces |
| 702 | in the preceding line. |
| 703 | |
| 704 | @smallexample |
| 705 | @group |
| 706 | ---------- Buffer: foo ---------- |
| 707 | When in the course of human |
| 708 | @point{} events, it becomes necessary |
| 709 | ---------- Buffer: foo ---------- |
| 710 | @end group |
| 711 | |
| 712 | (delete-indentation) |
| 713 | @result{} nil |
| 714 | |
| 715 | @group |
| 716 | ---------- Buffer: foo ---------- |
| 717 | When in the course of human@point{} events, it becomes necessary |
| 718 | ---------- Buffer: foo ---------- |
| 719 | @end group |
| 720 | @end smallexample |
| 721 | |
| 722 | After the lines are joined, the function @code{fixup-whitespace} is |
| 723 | responsible for deciding whether to leave a space at the junction. |
| 724 | @end deffn |
| 725 | |
| 726 | @deffn Command fixup-whitespace |
| 727 | This function replaces all the horizontal whitespace surrounding point |
| 728 | with either one space or no space, according to the context. It |
| 729 | returns @code{nil}. |
| 730 | |
| 731 | At the beginning or end of a line, the appropriate amount of space is |
| 732 | none. Before a character with close parenthesis syntax, or after a |
| 733 | character with open parenthesis or expression-prefix syntax, no space is |
| 734 | also appropriate. Otherwise, one space is appropriate. @xref{Syntax |
| 735 | Class Table}. |
| 736 | |
| 737 | In the example below, @code{fixup-whitespace} is called the first time |
| 738 | with point before the word @samp{spaces} in the first line. For the |
| 739 | second invocation, point is directly after the @samp{(}. |
| 740 | |
| 741 | @smallexample |
| 742 | @group |
| 743 | ---------- Buffer: foo ---------- |
| 744 | This has too many @point{}spaces |
| 745 | This has too many spaces at the start of (@point{} this list) |
| 746 | ---------- Buffer: foo ---------- |
| 747 | @end group |
| 748 | |
| 749 | @group |
| 750 | (fixup-whitespace) |
| 751 | @result{} nil |
| 752 | (fixup-whitespace) |
| 753 | @result{} nil |
| 754 | @end group |
| 755 | |
| 756 | @group |
| 757 | ---------- Buffer: foo ---------- |
| 758 | This has too many spaces |
| 759 | This has too many spaces at the start of (this list) |
| 760 | ---------- Buffer: foo ---------- |
| 761 | @end group |
| 762 | @end smallexample |
| 763 | @end deffn |
| 764 | |
| 765 | @deffn Command just-one-space &optional n |
| 766 | @comment !!SourceFile simple.el |
| 767 | This command replaces any spaces and tabs around point with a single |
| 768 | space, or @var{n} spaces if @var{n} is specified. It returns |
| 769 | @code{nil}. |
| 770 | @end deffn |
| 771 | |
| 772 | @deffn Command delete-blank-lines |
| 773 | This function deletes blank lines surrounding point. If point is on a |
| 774 | blank line with one or more blank lines before or after it, then all but |
| 775 | one of them are deleted. If point is on an isolated blank line, then it |
| 776 | is deleted. If point is on a nonblank line, the command deletes all |
| 777 | blank lines immediately following it. |
| 778 | |
| 779 | A blank line is defined as a line containing only tabs and spaces. |
| 780 | |
| 781 | @code{delete-blank-lines} returns @code{nil}. |
| 782 | @end deffn |
| 783 | |
| 784 | @node The Kill Ring |
| 785 | @section The Kill Ring |
| 786 | @cindex kill ring |
| 787 | |
| 788 | @dfn{Kill functions} delete text like the deletion functions, but save |
| 789 | it so that the user can reinsert it by @dfn{yanking}. Most of these |
| 790 | functions have @samp{kill-} in their name. By contrast, the functions |
| 791 | whose names start with @samp{delete-} normally do not save text for |
| 792 | yanking (though they can still be undone); these are ``deletion'' |
| 793 | functions. |
| 794 | |
| 795 | Most of the kill commands are primarily for interactive use, and are |
| 796 | not described here. What we do describe are the functions provided for |
| 797 | use in writing such commands. You can use these functions to write |
| 798 | commands for killing text. When you need to delete text for internal |
| 799 | purposes within a Lisp function, you should normally use deletion |
| 800 | functions, so as not to disturb the kill ring contents. |
| 801 | @xref{Deletion}. |
| 802 | |
| 803 | Killed text is saved for later yanking in the @dfn{kill ring}. This |
| 804 | is a list that holds a number of recent kills, not just the last text |
| 805 | kill. We call this a ``ring'' because yanking treats it as having |
| 806 | elements in a cyclic order. The list is kept in the variable |
| 807 | @code{kill-ring}, and can be operated on with the usual functions for |
| 808 | lists; there are also specialized functions, described in this section, |
| 809 | that treat it as a ring. |
| 810 | |
| 811 | Some people think this use of the word ``kill'' is unfortunate, since |
| 812 | it refers to operations that specifically @emph{do not} destroy the |
| 813 | entities ``killed.'' This is in sharp contrast to ordinary life, in |
| 814 | which death is permanent and ``killed'' entities do not come back to |
| 815 | life. Therefore, other metaphors have been proposed. For example, the |
| 816 | term ``cut ring'' makes sense to people who, in pre-computer days, used |
| 817 | scissors and paste to cut up and rearrange manuscripts. However, it |
| 818 | would be difficult to change the terminology now. |
| 819 | |
| 820 | @menu |
| 821 | * Kill Ring Concepts:: What text looks like in the kill ring. |
| 822 | * Kill Functions:: Functions that kill text. |
| 823 | * Yanking:: How yanking is done. |
| 824 | * Yank Commands:: Commands that access the kill ring. |
| 825 | * Low-Level Kill Ring:: Functions and variables for kill ring access. |
| 826 | * Internals of Kill Ring:: Variables that hold kill ring data. |
| 827 | @end menu |
| 828 | |
| 829 | @node Kill Ring Concepts |
| 830 | @comment node-name, next, previous, up |
| 831 | @subsection Kill Ring Concepts |
| 832 | |
| 833 | The kill ring records killed text as strings in a list, most recent |
| 834 | first. A short kill ring, for example, might look like this: |
| 835 | |
| 836 | @example |
| 837 | ("some text" "a different piece of text" "even older text") |
| 838 | @end example |
| 839 | |
| 840 | @noindent |
| 841 | When the list reaches @code{kill-ring-max} entries in length, adding a |
| 842 | new entry automatically deletes the last entry. |
| 843 | |
| 844 | When kill commands are interwoven with other commands, each kill |
| 845 | command makes a new entry in the kill ring. Multiple kill commands in |
| 846 | succession build up a single kill ring entry, which would be yanked as a |
| 847 | unit; the second and subsequent consecutive kill commands add text to |
| 848 | the entry made by the first one. |
| 849 | |
| 850 | For yanking, one entry in the kill ring is designated the ``front'' of |
| 851 | the ring. Some yank commands ``rotate'' the ring by designating a |
| 852 | different element as the ``front.'' But this virtual rotation doesn't |
| 853 | change the list itself---the most recent entry always comes first in the |
| 854 | list. |
| 855 | |
| 856 | @node Kill Functions |
| 857 | @comment node-name, next, previous, up |
| 858 | @subsection Functions for Killing |
| 859 | |
| 860 | @code{kill-region} is the usual subroutine for killing text. Any |
| 861 | command that calls this function is a ``kill command'' (and should |
| 862 | probably have @samp{kill} in its name). @code{kill-region} puts the |
| 863 | newly killed text in a new element at the beginning of the kill ring or |
| 864 | adds it to the most recent element. It determines automatically (using |
| 865 | @code{last-command}) whether the previous command was a kill command, |
| 866 | and if so appends the killed text to the most recent entry. |
| 867 | |
| 868 | @deffn Command kill-region start end &optional yank-handler |
| 869 | This function kills the text in the region defined by @var{start} and |
| 870 | @var{end}. The text is deleted but saved in the kill ring, along with |
| 871 | its text properties. The value is always @code{nil}. |
| 872 | |
| 873 | In an interactive call, @var{start} and @var{end} are point and |
| 874 | the mark. |
| 875 | |
| 876 | @c Emacs 19 feature |
| 877 | If the buffer or text is read-only, @code{kill-region} modifies the kill |
| 878 | ring just the same, then signals an error without modifying the buffer. |
| 879 | This is convenient because it lets the user use a series of kill |
| 880 | commands to copy text from a read-only buffer into the kill ring. |
| 881 | |
| 882 | If @var{yank-handler} is non-@code{nil}, this puts that value onto |
| 883 | the string of killed text, as a @code{yank-handler} text property. |
| 884 | @xref{Yanking}. Note that if @var{yank-handler} is @code{nil}, any |
| 885 | @code{yank-handler} properties present on the killed text are copied |
| 886 | onto the kill ring, like other text properties. |
| 887 | @end deffn |
| 888 | |
| 889 | @defopt kill-read-only-ok |
| 890 | If this option is non-@code{nil}, @code{kill-region} does not signal an |
| 891 | error if the buffer or text is read-only. Instead, it simply returns, |
| 892 | updating the kill ring but not changing the buffer. |
| 893 | @end defopt |
| 894 | |
| 895 | @deffn Command copy-region-as-kill start end |
| 896 | This command saves the region defined by @var{start} and @var{end} on |
| 897 | the kill ring (including text properties), but does not delete the text |
| 898 | from the buffer. It returns @code{nil}. |
| 899 | |
| 900 | The command does not set @code{this-command} to @code{kill-region}, so a |
| 901 | subsequent kill command does not append to the same kill ring entry. |
| 902 | |
| 903 | @c FIXME Why is it better? Why isn't copy-region-as-kill obsolete then? |
| 904 | @c Why is it used in many places in Emacs? |
| 905 | In Lisp programs, it is better to use @code{kill-new} or |
| 906 | @code{kill-append} instead of this command. @xref{Low-Level Kill Ring}. |
| 907 | @end deffn |
| 908 | |
| 909 | @node Yanking |
| 910 | @subsection Yanking |
| 911 | |
| 912 | Yanking means inserting text from the kill ring, but it does |
| 913 | not insert the text blindly. Yank commands and some other commands |
| 914 | use @code{insert-for-yank} to perform special processing on the |
| 915 | text that they copy into the buffer. |
| 916 | |
| 917 | @defun insert-for-yank string |
| 918 | This function normally works like @code{insert} except that it doesn't |
| 919 | insert the text properties in the @code{yank-excluded-properties} |
| 920 | list. However, if any part of @var{string} has a non-@code{nil} |
| 921 | @code{yank-handler} text property, that property can do various |
| 922 | special processing on that part of the text being inserted. |
| 923 | @end defun |
| 924 | |
| 925 | @defun insert-buffer-substring-as-yank buf &optional start end |
| 926 | This function resembles @code{insert-buffer-substring} except that it |
| 927 | doesn't insert the text properties in the |
| 928 | @code{yank-excluded-properties} list. |
| 929 | @end defun |
| 930 | |
| 931 | You can put a @code{yank-handler} text property on all or part of |
| 932 | the text to control how it will be inserted if it is yanked. The |
| 933 | @code{insert-for-yank} function looks for that property. The property |
| 934 | value must be a list of one to four elements, with the following |
| 935 | format (where elements after the first may be omitted): |
| 936 | |
| 937 | @example |
| 938 | (@var{function} @var{param} @var{noexclude} @var{undo}) |
| 939 | @end example |
| 940 | |
| 941 | Here is what the elements do: |
| 942 | |
| 943 | @table @var |
| 944 | @item function |
| 945 | When @var{function} is present and non-@code{nil}, it is called instead of |
| 946 | @code{insert} to insert the string. @var{function} takes one |
| 947 | argument---the string to insert. |
| 948 | |
| 949 | @item param |
| 950 | If @var{param} is present and non-@code{nil}, it replaces @var{string} |
| 951 | (or the part of @var{string} being processed) as the object passed to |
| 952 | @var{function} (or @code{insert}); for example, if @var{function} is |
| 953 | @code{yank-rectangle}, @var{param} should be a list of strings to |
| 954 | insert as a rectangle. |
| 955 | |
| 956 | @item noexclude |
| 957 | If @var{noexclude} is present and non-@code{nil}, the normal removal of the |
| 958 | yank-excluded-properties is not performed; instead @var{function} is |
| 959 | responsible for removing those properties. This may be necessary |
| 960 | if @var{function} adjusts point before or after inserting the object. |
| 961 | |
| 962 | @item undo |
| 963 | If @var{undo} is present and non-@code{nil}, it is a function that will be |
| 964 | called by @code{yank-pop} to undo the insertion of the current object. |
| 965 | It is called with two arguments, the start and end of the current |
| 966 | region. @var{function} can set @code{yank-undo-function} to override |
| 967 | the @var{undo} value. |
| 968 | @end table |
| 969 | |
| 970 | @node Yank Commands |
| 971 | @comment node-name, next, previous, up |
| 972 | @subsection Functions for Yanking |
| 973 | |
| 974 | This section describes higher-level commands for yanking, which are |
| 975 | intended primarily for the user but useful also in Lisp programs. |
| 976 | Both @code{yank} and @code{yank-pop} honor the |
| 977 | @code{yank-excluded-properties} variable and @code{yank-handler} text |
| 978 | property (@pxref{Yanking}). |
| 979 | |
| 980 | @deffn Command yank &optional arg |
| 981 | @cindex inserting killed text |
| 982 | This command inserts before point the text at the front of the kill |
| 983 | ring. It sets the mark at the beginning of that text, using |
| 984 | @code{push-mark} (@pxref{The Mark}), and puts point at the end. |
| 985 | |
| 986 | If @var{arg} is a non-@code{nil} list (which occurs interactively when |
| 987 | the user types @kbd{C-u} with no digits), then @code{yank} inserts the |
| 988 | text as described above, but puts point before the yanked text and |
| 989 | sets the mark after it. |
| 990 | |
| 991 | If @var{arg} is a number, then @code{yank} inserts the @var{arg}th |
| 992 | most recently killed text---the @var{arg}th element of the kill ring |
| 993 | list, counted cyclically from the front, which is considered the |
| 994 | first element for this purpose. |
| 995 | |
| 996 | @code{yank} does not alter the contents of the kill ring, unless it |
| 997 | used text provided by another program, in which case it pushes that text |
| 998 | onto the kill ring. However if @var{arg} is an integer different from |
| 999 | one, it rotates the kill ring to place the yanked string at the front. |
| 1000 | |
| 1001 | @code{yank} returns @code{nil}. |
| 1002 | @end deffn |
| 1003 | |
| 1004 | @deffn Command yank-pop &optional arg |
| 1005 | This command replaces the just-yanked entry from the kill ring with a |
| 1006 | different entry from the kill ring. |
| 1007 | |
| 1008 | This is allowed only immediately after a @code{yank} or another |
| 1009 | @code{yank-pop}. At such a time, the region contains text that was just |
| 1010 | inserted by yanking. @code{yank-pop} deletes that text and inserts in |
| 1011 | its place a different piece of killed text. It does not add the deleted |
| 1012 | text to the kill ring, since it is already in the kill ring somewhere. |
| 1013 | It does however rotate the kill ring to place the newly yanked string at |
| 1014 | the front. |
| 1015 | |
| 1016 | If @var{arg} is @code{nil}, then the replacement text is the previous |
| 1017 | element of the kill ring. If @var{arg} is numeric, the replacement is |
| 1018 | the @var{arg}th previous kill. If @var{arg} is negative, a more recent |
| 1019 | kill is the replacement. |
| 1020 | |
| 1021 | The sequence of kills in the kill ring wraps around, so that after the |
| 1022 | oldest one comes the newest one, and before the newest one goes the |
| 1023 | oldest. |
| 1024 | |
| 1025 | The return value is always @code{nil}. |
| 1026 | @end deffn |
| 1027 | |
| 1028 | @defvar yank-undo-function |
| 1029 | If this variable is non-@code{nil}, the function @code{yank-pop} uses |
| 1030 | its value instead of @code{delete-region} to delete the text |
| 1031 | inserted by the previous @code{yank} or |
| 1032 | @code{yank-pop} command. The value must be a function of two |
| 1033 | arguments, the start and end of the current region. |
| 1034 | |
| 1035 | The function @code{insert-for-yank} automatically sets this variable |
| 1036 | according to the @var{undo} element of the @code{yank-handler} |
| 1037 | text property, if there is one. |
| 1038 | @end defvar |
| 1039 | |
| 1040 | @node Low-Level Kill Ring |
| 1041 | @subsection Low-Level Kill Ring |
| 1042 | |
| 1043 | These functions and variables provide access to the kill ring at a |
| 1044 | lower level, but are still convenient for use in Lisp programs, |
| 1045 | because they take care of interaction with window system selections |
| 1046 | (@pxref{Window System Selections}). |
| 1047 | |
| 1048 | @defun current-kill n &optional do-not-move |
| 1049 | The function @code{current-kill} rotates the yanking pointer, which |
| 1050 | designates the ``front'' of the kill ring, by @var{n} places (from newer |
| 1051 | kills to older ones), and returns the text at that place in the ring. |
| 1052 | |
| 1053 | If the optional second argument @var{do-not-move} is non-@code{nil}, |
| 1054 | then @code{current-kill} doesn't alter the yanking pointer; it just |
| 1055 | returns the @var{n}th kill, counting from the current yanking pointer. |
| 1056 | |
| 1057 | If @var{n} is zero, indicating a request for the latest kill, |
| 1058 | @code{current-kill} calls the value of |
| 1059 | @code{interprogram-paste-function} (documented below) before |
| 1060 | consulting the kill ring. If that value is a function and calling it |
| 1061 | returns a string or a list of several string, @code{current-kill} |
| 1062 | pushes the strings onto the kill ring and returns the first string. |
| 1063 | It also sets the yanking pointer to point to the kill-ring entry of |
| 1064 | the first string returned by @code{interprogram-paste-function}, |
| 1065 | regardless of the value of @var{do-not-move}. Otherwise, |
| 1066 | @code{current-kill} does not treat a zero value for @var{n} specially: |
| 1067 | it returns the entry pointed at by the yanking pointer and does not |
| 1068 | move the yanking pointer. |
| 1069 | @end defun |
| 1070 | |
| 1071 | @defun kill-new string &optional replace yank-handler |
| 1072 | This function pushes the text @var{string} onto the kill ring and |
| 1073 | makes the yanking pointer point to it. It discards the oldest entry |
| 1074 | if appropriate. It also invokes the value of |
| 1075 | @code{interprogram-cut-function} (see below). |
| 1076 | |
| 1077 | If @var{replace} is non-@code{nil}, then @code{kill-new} replaces the |
| 1078 | first element of the kill ring with @var{string}, rather than pushing |
| 1079 | @var{string} onto the kill ring. |
| 1080 | |
| 1081 | If @var{yank-handler} is non-@code{nil}, this puts that value onto |
| 1082 | the string of killed text, as a @code{yank-handler} property. |
| 1083 | @xref{Yanking}. Note that if @var{yank-handler} is @code{nil}, then |
| 1084 | @code{kill-new} copies any @code{yank-handler} properties present on |
| 1085 | @var{string} onto the kill ring, as it does with other text properties. |
| 1086 | @end defun |
| 1087 | |
| 1088 | @defun kill-append string before-p &optional yank-handler |
| 1089 | This function appends the text @var{string} to the first entry in the |
| 1090 | kill ring and makes the yanking pointer point to the combined entry. |
| 1091 | Normally @var{string} goes at the end of the entry, but if |
| 1092 | @var{before-p} is non-@code{nil}, it goes at the beginning. This |
| 1093 | function also invokes the value of @code{interprogram-cut-function} |
| 1094 | (see below). This handles @var{yank-handler} just like |
| 1095 | @code{kill-new}, except that if @var{yank-handler} is different from |
| 1096 | the @code{yank-handler} property of the first entry of the kill ring, |
| 1097 | @code{kill-append} pushes the concatenated string onto the kill ring, |
| 1098 | instead of replacing the original first entry with it. |
| 1099 | @end defun |
| 1100 | |
| 1101 | @defvar interprogram-paste-function |
| 1102 | This variable provides a way of transferring killed text from other |
| 1103 | programs, when you are using a window system. Its value should be |
| 1104 | @code{nil} or a function of no arguments. |
| 1105 | |
| 1106 | If the value is a function, @code{current-kill} calls it to get the |
| 1107 | ``most recent kill.'' If the function returns a non-@code{nil} value, |
| 1108 | then that value is used as the ``most recent kill.'' If it returns |
| 1109 | @code{nil}, then the front of the kill ring is used. |
| 1110 | |
| 1111 | To facilitate support for window systems that support multiple |
| 1112 | selections, this function may also return a list of strings. In that |
| 1113 | case, the first string is used as the ``most recent kill'', and all |
| 1114 | the other strings are pushed onto the kill ring, for easy access by |
| 1115 | @code{yank-pop}. |
| 1116 | |
| 1117 | The normal use of this function is to get the window system's primary |
| 1118 | selection as the most recent kill, even if the selection belongs to |
| 1119 | another application. @xref{Window System Selections}. However, if |
| 1120 | the selection was provided by the current Emacs session, this function |
| 1121 | should return @code{nil}. (If it is hard to tell whether Emacs or |
| 1122 | some other program provided the selection, it should be good enough to |
| 1123 | use @code{string=} to compare it with the last text Emacs provided.) |
| 1124 | @end defvar |
| 1125 | |
| 1126 | @defvar interprogram-cut-function |
| 1127 | This variable provides a way of communicating killed text to other |
| 1128 | programs, when you are using a window system. Its value should be |
| 1129 | @code{nil} or a function of one required and one optional argument. |
| 1130 | |
| 1131 | If the value is a function, @code{kill-new} and @code{kill-append} call |
| 1132 | it with the new first element of the kill ring as the first argument. |
| 1133 | The second, optional, argument has the same meaning as the @var{push} |
| 1134 | argument to @code{x-set-cut-buffer} (@pxref{Definition of |
| 1135 | x-set-cut-buffer}) and only affects the second and later cut buffers. |
| 1136 | |
| 1137 | The normal use of this function is to set the window system's primary |
| 1138 | selection (and first cut buffer) from the newly killed text. |
| 1139 | @xref{Window System Selections}. |
| 1140 | @end defvar |
| 1141 | |
| 1142 | @node Internals of Kill Ring |
| 1143 | @comment node-name, next, previous, up |
| 1144 | @subsection Internals of the Kill Ring |
| 1145 | |
| 1146 | The variable @code{kill-ring} holds the kill ring contents, in the |
| 1147 | form of a list of strings. The most recent kill is always at the front |
| 1148 | of the list. |
| 1149 | |
| 1150 | The @code{kill-ring-yank-pointer} variable points to a link in the |
| 1151 | kill ring list, whose @sc{car} is the text to yank next. We say it |
| 1152 | identifies the ``front'' of the ring. Moving |
| 1153 | @code{kill-ring-yank-pointer} to a different link is called |
| 1154 | @dfn{rotating the kill ring}. We call the kill ring a ``ring'' because |
| 1155 | the functions that move the yank pointer wrap around from the end of the |
| 1156 | list to the beginning, or vice-versa. Rotation of the kill ring is |
| 1157 | virtual; it does not change the value of @code{kill-ring}. |
| 1158 | |
| 1159 | Both @code{kill-ring} and @code{kill-ring-yank-pointer} are Lisp |
| 1160 | variables whose values are normally lists. The word ``pointer'' in the |
| 1161 | name of the @code{kill-ring-yank-pointer} indicates that the variable's |
| 1162 | purpose is to identify one element of the list for use by the next yank |
| 1163 | command. |
| 1164 | |
| 1165 | The value of @code{kill-ring-yank-pointer} is always @code{eq} to one |
| 1166 | of the links in the kill ring list. The element it identifies is the |
| 1167 | @sc{car} of that link. Kill commands, which change the kill ring, also |
| 1168 | set this variable to the value of @code{kill-ring}. The effect is to |
| 1169 | rotate the ring so that the newly killed text is at the front. |
| 1170 | |
| 1171 | Here is a diagram that shows the variable @code{kill-ring-yank-pointer} |
| 1172 | pointing to the second entry in the kill ring @code{("some text" "a |
| 1173 | different piece of text" "yet older text")}. |
| 1174 | |
| 1175 | @example |
| 1176 | @group |
| 1177 | kill-ring ---- kill-ring-yank-pointer |
| 1178 | | | |
| 1179 | | v |
| 1180 | | --- --- --- --- --- --- |
| 1181 | --> | | |------> | | |--> | | |--> nil |
| 1182 | --- --- --- --- --- --- |
| 1183 | | | | |
| 1184 | | | | |
| 1185 | | | -->"yet older text" |
| 1186 | | | |
| 1187 | | --> "a different piece of text" |
| 1188 | | |
| 1189 | --> "some text" |
| 1190 | @end group |
| 1191 | @end example |
| 1192 | |
| 1193 | @noindent |
| 1194 | This state of affairs might occur after @kbd{C-y} (@code{yank}) |
| 1195 | immediately followed by @kbd{M-y} (@code{yank-pop}). |
| 1196 | |
| 1197 | @defvar kill-ring |
| 1198 | This variable holds the list of killed text sequences, most recently |
| 1199 | killed first. |
| 1200 | @end defvar |
| 1201 | |
| 1202 | @defvar kill-ring-yank-pointer |
| 1203 | This variable's value indicates which element of the kill ring is at the |
| 1204 | ``front'' of the ring for yanking. More precisely, the value is a tail |
| 1205 | of the value of @code{kill-ring}, and its @sc{car} is the kill string |
| 1206 | that @kbd{C-y} should yank. |
| 1207 | @end defvar |
| 1208 | |
| 1209 | @defopt kill-ring-max |
| 1210 | The value of this variable is the maximum length to which the kill |
| 1211 | ring can grow, before elements are thrown away at the end. The default |
| 1212 | value for @code{kill-ring-max} is 60. |
| 1213 | @end defopt |
| 1214 | |
| 1215 | @node Undo |
| 1216 | @comment node-name, next, previous, up |
| 1217 | @section Undo |
| 1218 | @cindex redo |
| 1219 | |
| 1220 | Most buffers have an @dfn{undo list}, which records all changes made |
| 1221 | to the buffer's text so that they can be undone. (The buffers that |
| 1222 | don't have one are usually special-purpose buffers for which Emacs |
| 1223 | assumes that undoing is not useful. In particular, any buffer whose |
| 1224 | name begins with a space has its undo recording off by default; |
| 1225 | see @ref{Buffer Names}.) All the primitives that modify the |
| 1226 | text in the buffer automatically add elements to the front of the undo |
| 1227 | list, which is in the variable @code{buffer-undo-list}. |
| 1228 | |
| 1229 | @defvar buffer-undo-list |
| 1230 | This buffer-local variable's value is the undo list of the current |
| 1231 | buffer. A value of @code{t} disables the recording of undo information. |
| 1232 | @end defvar |
| 1233 | |
| 1234 | Here are the kinds of elements an undo list can have: |
| 1235 | |
| 1236 | @table @code |
| 1237 | @item @var{position} |
| 1238 | This kind of element records a previous value of point; undoing this |
| 1239 | element moves point to @var{position}. Ordinary cursor motion does not |
| 1240 | make any sort of undo record, but deletion operations use these entries |
| 1241 | to record where point was before the command. |
| 1242 | |
| 1243 | @item (@var{beg} . @var{end}) |
| 1244 | This kind of element indicates how to delete text that was inserted. |
| 1245 | Upon insertion, the text occupied the range @var{beg}--@var{end} in the |
| 1246 | buffer. |
| 1247 | |
| 1248 | @item (@var{text} . @var{position}) |
| 1249 | This kind of element indicates how to reinsert text that was deleted. |
| 1250 | The deleted text itself is the string @var{text}. The place to |
| 1251 | reinsert it is @code{(abs @var{position})}. If @var{position} is |
| 1252 | positive, point was at the beginning of the deleted text, otherwise it |
| 1253 | was at the end. |
| 1254 | |
| 1255 | @item (t @var{high} . @var{low}) |
| 1256 | This kind of element indicates that an unmodified buffer became |
| 1257 | modified. The elements @var{high} and @var{low} are two integers, each |
| 1258 | recording 16 bits of the visited file's modification time as of when it |
| 1259 | was previously visited or saved. @code{primitive-undo} uses those |
| 1260 | values to determine whether to mark the buffer as unmodified once again; |
| 1261 | it does so only if the file's modification time matches those numbers. |
| 1262 | |
| 1263 | @item (nil @var{property} @var{value} @var{beg} . @var{end}) |
| 1264 | This kind of element records a change in a text property. |
| 1265 | Here's how you might undo the change: |
| 1266 | |
| 1267 | @example |
| 1268 | (put-text-property @var{beg} @var{end} @var{property} @var{value}) |
| 1269 | @end example |
| 1270 | |
| 1271 | @item (@var{marker} . @var{adjustment}) |
| 1272 | This kind of element records the fact that the marker @var{marker} was |
| 1273 | relocated due to deletion of surrounding text, and that it moved |
| 1274 | @var{adjustment} character positions. Undoing this element moves |
| 1275 | @var{marker} @minus{} @var{adjustment} characters. |
| 1276 | |
| 1277 | @item (apply @var{funname} . @var{args}) |
| 1278 | This is an extensible undo item, which is undone by calling |
| 1279 | @var{funname} with arguments @var{args}. |
| 1280 | |
| 1281 | @item (apply @var{delta} @var{beg} @var{end} @var{funname} . @var{args}) |
| 1282 | This is an extensible undo item, which records a change limited to the |
| 1283 | range @var{beg} to @var{end}, which increased the size of the buffer |
| 1284 | by @var{delta}. It is undone by calling @var{funname} with arguments |
| 1285 | @var{args}. |
| 1286 | |
| 1287 | This kind of element enables undo limited to a region to determine |
| 1288 | whether the element pertains to that region. |
| 1289 | |
| 1290 | @item nil |
| 1291 | This element is a boundary. The elements between two boundaries are |
| 1292 | called a @dfn{change group}; normally, each change group corresponds to |
| 1293 | one keyboard command, and undo commands normally undo an entire group as |
| 1294 | a unit. |
| 1295 | @end table |
| 1296 | |
| 1297 | @defun undo-boundary |
| 1298 | This function places a boundary element in the undo list. The undo |
| 1299 | command stops at such a boundary, and successive undo commands undo |
| 1300 | to earlier and earlier boundaries. This function returns @code{nil}. |
| 1301 | |
| 1302 | The editor command loop automatically calls @code{undo-boundary} just |
| 1303 | before executing each key sequence, so that each undo normally undoes |
| 1304 | the effects of one command. As an exception, the command |
| 1305 | @code{self-insert-command}, which produces self-inserting input |
| 1306 | characters (@pxref{Commands for Insertion}), may remove the boundary |
| 1307 | inserted by the command loop: a boundary is accepted for the first |
| 1308 | such character, the next 19 consecutive self-inserting input |
| 1309 | characters do not have boundaries, and then the 20th does; and so on |
| 1310 | as long as the self-inserting characters continue. Hence, sequences |
| 1311 | of consecutive character insertions can be undone as a group. |
| 1312 | |
| 1313 | All buffer modifications add a boundary whenever the previous undoable |
| 1314 | change was made in some other buffer. This is to ensure that |
| 1315 | each command makes a boundary in each buffer where it makes changes. |
| 1316 | |
| 1317 | Calling this function explicitly is useful for splitting the effects of |
| 1318 | a command into more than one unit. For example, @code{query-replace} |
| 1319 | calls @code{undo-boundary} after each replacement, so that the user can |
| 1320 | undo individual replacements one by one. |
| 1321 | @end defun |
| 1322 | |
| 1323 | @defvar undo-in-progress |
| 1324 | This variable is normally @code{nil}, but the undo commands bind it to |
| 1325 | @code{t}. This is so that various kinds of change hooks can tell when |
| 1326 | they're being called for the sake of undoing. |
| 1327 | @end defvar |
| 1328 | |
| 1329 | @defun primitive-undo count list |
| 1330 | This is the basic function for undoing elements of an undo list. |
| 1331 | It undoes the first @var{count} elements of @var{list}, returning |
| 1332 | the rest of @var{list}. |
| 1333 | |
| 1334 | @code{primitive-undo} adds elements to the buffer's undo list when it |
| 1335 | changes the buffer. Undo commands avoid confusion by saving the undo |
| 1336 | list value at the beginning of a sequence of undo operations. Then the |
| 1337 | undo operations use and update the saved value. The new elements added |
| 1338 | by undoing are not part of this saved value, so they don't interfere with |
| 1339 | continuing to undo. |
| 1340 | |
| 1341 | This function does not bind @code{undo-in-progress}. |
| 1342 | @end defun |
| 1343 | |
| 1344 | @node Maintaining Undo |
| 1345 | @section Maintaining Undo Lists |
| 1346 | |
| 1347 | This section describes how to enable and disable undo information for |
| 1348 | a given buffer. It also explains how the undo list is truncated |
| 1349 | automatically so it doesn't get too big. |
| 1350 | |
| 1351 | Recording of undo information in a newly created buffer is normally |
| 1352 | enabled to start with; but if the buffer name starts with a space, the |
| 1353 | undo recording is initially disabled. You can explicitly enable or |
| 1354 | disable undo recording with the following two functions, or by setting |
| 1355 | @code{buffer-undo-list} yourself. |
| 1356 | |
| 1357 | @deffn Command buffer-enable-undo &optional buffer-or-name |
| 1358 | This command enables recording undo information for buffer |
| 1359 | @var{buffer-or-name}, so that subsequent changes can be undone. If no |
| 1360 | argument is supplied, then the current buffer is used. This function |
| 1361 | does nothing if undo recording is already enabled in the buffer. It |
| 1362 | returns @code{nil}. |
| 1363 | |
| 1364 | In an interactive call, @var{buffer-or-name} is the current buffer. |
| 1365 | You cannot specify any other buffer. |
| 1366 | @end deffn |
| 1367 | |
| 1368 | @deffn Command buffer-disable-undo &optional buffer-or-name |
| 1369 | @cindex disabling undo |
| 1370 | This function discards the undo list of @var{buffer-or-name}, and disables |
| 1371 | further recording of undo information. As a result, it is no longer |
| 1372 | possible to undo either previous changes or any subsequent changes. If |
| 1373 | the undo list of @var{buffer-or-name} is already disabled, this function |
| 1374 | has no effect. |
| 1375 | |
| 1376 | This function returns @code{nil}. |
| 1377 | @end deffn |
| 1378 | |
| 1379 | As editing continues, undo lists get longer and longer. To prevent |
| 1380 | them from using up all available memory space, garbage collection trims |
| 1381 | them back to size limits you can set. (For this purpose, the ``size'' |
| 1382 | of an undo list measures the cons cells that make up the list, plus the |
| 1383 | strings of deleted text.) Three variables control the range of acceptable |
| 1384 | sizes: @code{undo-limit}, @code{undo-strong-limit} and |
| 1385 | @code{undo-outer-limit}. In these variables, size is counted as the |
| 1386 | number of bytes occupied, which includes both saved text and other |
| 1387 | data. |
| 1388 | |
| 1389 | @defopt undo-limit |
| 1390 | This is the soft limit for the acceptable size of an undo list. The |
| 1391 | change group at which this size is exceeded is the last one kept. |
| 1392 | @end defopt |
| 1393 | |
| 1394 | @defopt undo-strong-limit |
| 1395 | This is the upper limit for the acceptable size of an undo list. The |
| 1396 | change group at which this size is exceeded is discarded itself (along |
| 1397 | with all older change groups). There is one exception: the very latest |
| 1398 | change group is only discarded if it exceeds @code{undo-outer-limit}. |
| 1399 | @end defopt |
| 1400 | |
| 1401 | @defopt undo-outer-limit |
| 1402 | If at garbage collection time the undo info for the current command |
| 1403 | exceeds this limit, Emacs discards the info and displays a warning. |
| 1404 | This is a last ditch limit to prevent memory overflow. |
| 1405 | @end defopt |
| 1406 | |
| 1407 | @defopt undo-ask-before-discard |
| 1408 | If this variable is non-@code{nil}, when the undo info exceeds |
| 1409 | @code{undo-outer-limit}, Emacs asks in the echo area whether to |
| 1410 | discard the info. The default value is @code{nil}, which means to |
| 1411 | discard it automatically. |
| 1412 | |
| 1413 | This option is mainly intended for debugging. Garbage collection is |
| 1414 | inhibited while the question is asked, which means that Emacs might |
| 1415 | leak memory if the user waits too long before answering the question. |
| 1416 | @end defopt |
| 1417 | |
| 1418 | @node Filling |
| 1419 | @comment node-name, next, previous, up |
| 1420 | @section Filling |
| 1421 | @cindex filling text |
| 1422 | |
| 1423 | @dfn{Filling} means adjusting the lengths of lines (by moving the line |
| 1424 | breaks) so that they are nearly (but no greater than) a specified |
| 1425 | maximum width. Additionally, lines can be @dfn{justified}, which means |
| 1426 | inserting spaces to make the left and/or right margins line up |
| 1427 | precisely. The width is controlled by the variable @code{fill-column}. |
| 1428 | For ease of reading, lines should be no longer than 70 or so columns. |
| 1429 | |
| 1430 | You can use Auto Fill mode (@pxref{Auto Filling}) to fill text |
| 1431 | automatically as you insert it, but changes to existing text may leave |
| 1432 | it improperly filled. Then you must fill the text explicitly. |
| 1433 | |
| 1434 | Most of the commands in this section return values that are not |
| 1435 | meaningful. All the functions that do filling take note of the current |
| 1436 | left margin, current right margin, and current justification style |
| 1437 | (@pxref{Margins}). If the current justification style is |
| 1438 | @code{none}, the filling functions don't actually do anything. |
| 1439 | |
| 1440 | Several of the filling functions have an argument @var{justify}. |
| 1441 | If it is non-@code{nil}, that requests some kind of justification. It |
| 1442 | can be @code{left}, @code{right}, @code{full}, or @code{center}, to |
| 1443 | request a specific style of justification. If it is @code{t}, that |
| 1444 | means to use the current justification style for this part of the text |
| 1445 | (see @code{current-justification}, below). Any other value is treated |
| 1446 | as @code{full}. |
| 1447 | |
| 1448 | When you call the filling functions interactively, using a prefix |
| 1449 | argument implies the value @code{full} for @var{justify}. |
| 1450 | |
| 1451 | @deffn Command fill-paragraph &optional justify region |
| 1452 | This command fills the paragraph at or after point. If |
| 1453 | @var{justify} is non-@code{nil}, each line is justified as well. |
| 1454 | It uses the ordinary paragraph motion commands to find paragraph |
| 1455 | boundaries. @xref{Paragraphs,,, emacs, The GNU Emacs Manual}. |
| 1456 | |
| 1457 | When @var{region} is non-@code{nil}, then if Transient Mark mode is |
| 1458 | enabled and the mark is active, this command calls @code{fill-region} |
| 1459 | to fill all the paragraphs in the region, instead of filling only the |
| 1460 | current paragraph. When this command is called interactively, |
| 1461 | @var{region} is @code{t}. |
| 1462 | @end deffn |
| 1463 | |
| 1464 | @deffn Command fill-region start end &optional justify nosqueeze to-eop |
| 1465 | This command fills each of the paragraphs in the region from @var{start} |
| 1466 | to @var{end}. It justifies as well if @var{justify} is |
| 1467 | non-@code{nil}. |
| 1468 | |
| 1469 | If @var{nosqueeze} is non-@code{nil}, that means to leave whitespace |
| 1470 | other than line breaks untouched. If @var{to-eop} is non-@code{nil}, |
| 1471 | that means to keep filling to the end of the paragraph---or the next hard |
| 1472 | newline, if @code{use-hard-newlines} is enabled (see below). |
| 1473 | |
| 1474 | The variable @code{paragraph-separate} controls how to distinguish |
| 1475 | paragraphs. @xref{Standard Regexps}. |
| 1476 | @end deffn |
| 1477 | |
| 1478 | @deffn Command fill-individual-paragraphs start end &optional justify citation-regexp |
| 1479 | This command fills each paragraph in the region according to its |
| 1480 | individual fill prefix. Thus, if the lines of a paragraph were indented |
| 1481 | with spaces, the filled paragraph will remain indented in the same |
| 1482 | fashion. |
| 1483 | |
| 1484 | The first two arguments, @var{start} and @var{end}, are the beginning |
| 1485 | and end of the region to be filled. The third and fourth arguments, |
| 1486 | @var{justify} and @var{citation-regexp}, are optional. If |
| 1487 | @var{justify} is non-@code{nil}, the paragraphs are justified as |
| 1488 | well as filled. If @var{citation-regexp} is non-@code{nil}, it means the |
| 1489 | function is operating on a mail message and therefore should not fill |
| 1490 | the header lines. If @var{citation-regexp} is a string, it is used as |
| 1491 | a regular expression; if it matches the beginning of a line, that line |
| 1492 | is treated as a citation marker. |
| 1493 | |
| 1494 | Ordinarily, @code{fill-individual-paragraphs} regards each change in |
| 1495 | indentation as starting a new paragraph. If |
| 1496 | @code{fill-individual-varying-indent} is non-@code{nil}, then only |
| 1497 | separator lines separate paragraphs. That mode can handle indented |
| 1498 | paragraphs with additional indentation on the first line. |
| 1499 | @end deffn |
| 1500 | |
| 1501 | @defopt fill-individual-varying-indent |
| 1502 | This variable alters the action of @code{fill-individual-paragraphs} as |
| 1503 | described above. |
| 1504 | @end defopt |
| 1505 | |
| 1506 | @deffn Command fill-region-as-paragraph start end &optional justify nosqueeze squeeze-after |
| 1507 | This command considers a region of text as a single paragraph and fills |
| 1508 | it. If the region was made up of many paragraphs, the blank lines |
| 1509 | between paragraphs are removed. This function justifies as well as |
| 1510 | filling when @var{justify} is non-@code{nil}. |
| 1511 | |
| 1512 | If @var{nosqueeze} is non-@code{nil}, that means to leave whitespace |
| 1513 | other than line breaks untouched. If @var{squeeze-after} is |
| 1514 | non-@code{nil}, it specifies a position in the region, and means don't |
| 1515 | canonicalize spaces before that position. |
| 1516 | |
| 1517 | In Adaptive Fill mode, this command calls @code{fill-context-prefix} to |
| 1518 | choose a fill prefix by default. @xref{Adaptive Fill}. |
| 1519 | @end deffn |
| 1520 | |
| 1521 | @deffn Command justify-current-line &optional how eop nosqueeze |
| 1522 | This command inserts spaces between the words of the current line so |
| 1523 | that the line ends exactly at @code{fill-column}. It returns |
| 1524 | @code{nil}. |
| 1525 | |
| 1526 | The argument @var{how}, if non-@code{nil} specifies explicitly the style |
| 1527 | of justification. It can be @code{left}, @code{right}, @code{full}, |
| 1528 | @code{center}, or @code{none}. If it is @code{t}, that means to do |
| 1529 | follow specified justification style (see @code{current-justification}, |
| 1530 | below). @code{nil} means to do full justification. |
| 1531 | |
| 1532 | If @var{eop} is non-@code{nil}, that means do only left-justification |
| 1533 | if @code{current-justification} specifies full justification. This is |
| 1534 | used for the last line of a paragraph; even if the paragraph as a |
| 1535 | whole is fully justified, the last line should not be. |
| 1536 | |
| 1537 | If @var{nosqueeze} is non-@code{nil}, that means do not change interior |
| 1538 | whitespace. |
| 1539 | @end deffn |
| 1540 | |
| 1541 | @defopt default-justification |
| 1542 | This variable's value specifies the style of justification to use for |
| 1543 | text that doesn't specify a style with a text property. The possible |
| 1544 | values are @code{left}, @code{right}, @code{full}, @code{center}, or |
| 1545 | @code{none}. The default value is @code{left}. |
| 1546 | @end defopt |
| 1547 | |
| 1548 | @defun current-justification |
| 1549 | This function returns the proper justification style to use for filling |
| 1550 | the text around point. |
| 1551 | |
| 1552 | This returns the value of the @code{justification} text property at |
| 1553 | point, or the variable @var{default-justification} if there is no such |
| 1554 | text property. However, it returns @code{nil} rather than @code{none} |
| 1555 | to mean ``don't justify''. |
| 1556 | @end defun |
| 1557 | |
| 1558 | @defopt sentence-end-double-space |
| 1559 | @anchor{Definition of sentence-end-double-space} |
| 1560 | If this variable is non-@code{nil}, a period followed by just one space |
| 1561 | does not count as the end of a sentence, and the filling functions |
| 1562 | avoid breaking the line at such a place. |
| 1563 | @end defopt |
| 1564 | |
| 1565 | @defopt sentence-end-without-period |
| 1566 | If this variable is non-@code{nil}, a sentence can end without a |
| 1567 | period. This is used for languages like Thai, where sentences end |
| 1568 | with a double space but without a period. |
| 1569 | @end defopt |
| 1570 | |
| 1571 | @defopt sentence-end-without-space |
| 1572 | If this variable is non-@code{nil}, it should be a string of |
| 1573 | characters that can end a sentence without following spaces. |
| 1574 | @end defopt |
| 1575 | |
| 1576 | @defvar fill-paragraph-function |
| 1577 | This variable provides a way to override the filling of paragraphs. |
| 1578 | If its value is non-@code{nil}, @code{fill-paragraph} calls this |
| 1579 | function to do the work. If the function returns a non-@code{nil} |
| 1580 | value, @code{fill-paragraph} assumes the job is done, and immediately |
| 1581 | returns that value. |
| 1582 | |
| 1583 | The usual use of this feature is to fill comments in programming |
| 1584 | language modes. If the function needs to fill a paragraph in the usual |
| 1585 | way, it can do so as follows: |
| 1586 | |
| 1587 | @example |
| 1588 | (let ((fill-paragraph-function nil)) |
| 1589 | (fill-paragraph arg)) |
| 1590 | @end example |
| 1591 | @end defvar |
| 1592 | |
| 1593 | @defvar fill-forward-paragraph-function |
| 1594 | This variable provides a way to override how the filling functions, |
| 1595 | such as @code{fill-region} and @code{fill-paragraph}, move forward to |
| 1596 | the next paragraph. Its value should be a function, which is called |
| 1597 | with a single argument @var{n}, the number of paragraphs to move, and |
| 1598 | should return the difference between @var{n} and the number of |
| 1599 | paragraphs actually moved. The default value of this variable is |
| 1600 | @code{forward-paragraph}. @xref{Paragraphs,,, emacs, The GNU Emacs |
| 1601 | Manual}. |
| 1602 | @end defvar |
| 1603 | |
| 1604 | @defvar use-hard-newlines |
| 1605 | If this variable is non-@code{nil}, the filling functions do not delete |
| 1606 | newlines that have the @code{hard} text property. These ``hard |
| 1607 | newlines'' act as paragraph separators. |
| 1608 | @end defvar |
| 1609 | |
| 1610 | @node Margins |
| 1611 | @section Margins for Filling |
| 1612 | |
| 1613 | @defopt fill-prefix |
| 1614 | This buffer-local variable, if non-@code{nil}, specifies a string of |
| 1615 | text that appears at the beginning of normal text lines and should be |
| 1616 | disregarded when filling them. Any line that fails to start with the |
| 1617 | fill prefix is considered the start of a paragraph; so is any line |
| 1618 | that starts with the fill prefix followed by additional whitespace. |
| 1619 | Lines that start with the fill prefix but no additional whitespace are |
| 1620 | ordinary text lines that can be filled together. The resulting filled |
| 1621 | lines also start with the fill prefix. |
| 1622 | |
| 1623 | The fill prefix follows the left margin whitespace, if any. |
| 1624 | @end defopt |
| 1625 | |
| 1626 | @defopt fill-column |
| 1627 | This buffer-local variable specifies the maximum width of filled lines. |
| 1628 | Its value should be an integer, which is a number of columns. All the |
| 1629 | filling, justification, and centering commands are affected by this |
| 1630 | variable, including Auto Fill mode (@pxref{Auto Filling}). |
| 1631 | |
| 1632 | As a practical matter, if you are writing text for other people to |
| 1633 | read, you should set @code{fill-column} to no more than 70. Otherwise |
| 1634 | the line will be too long for people to read comfortably, and this can |
| 1635 | make the text seem clumsy. |
| 1636 | |
| 1637 | The default value for @code{fill-column} is 70. |
| 1638 | @end defopt |
| 1639 | |
| 1640 | @deffn Command set-left-margin from to margin |
| 1641 | This sets the @code{left-margin} property on the text from @var{from} to |
| 1642 | @var{to} to the value @var{margin}. If Auto Fill mode is enabled, this |
| 1643 | command also refills the region to fit the new margin. |
| 1644 | @end deffn |
| 1645 | |
| 1646 | @deffn Command set-right-margin from to margin |
| 1647 | This sets the @code{right-margin} property on the text from @var{from} |
| 1648 | to @var{to} to the value @var{margin}. If Auto Fill mode is enabled, |
| 1649 | this command also refills the region to fit the new margin. |
| 1650 | @end deffn |
| 1651 | |
| 1652 | @defun current-left-margin |
| 1653 | This function returns the proper left margin value to use for filling |
| 1654 | the text around point. The value is the sum of the @code{left-margin} |
| 1655 | property of the character at the start of the current line (or zero if |
| 1656 | none), and the value of the variable @code{left-margin}. |
| 1657 | @end defun |
| 1658 | |
| 1659 | @defun current-fill-column |
| 1660 | This function returns the proper fill column value to use for filling |
| 1661 | the text around point. The value is the value of the @code{fill-column} |
| 1662 | variable, minus the value of the @code{right-margin} property of the |
| 1663 | character after point. |
| 1664 | @end defun |
| 1665 | |
| 1666 | @deffn Command move-to-left-margin &optional n force |
| 1667 | This function moves point to the left margin of the current line. The |
| 1668 | column moved to is determined by calling the function |
| 1669 | @code{current-left-margin}. If the argument @var{n} is non-@code{nil}, |
| 1670 | @code{move-to-left-margin} moves forward @var{n}@minus{}1 lines first. |
| 1671 | |
| 1672 | If @var{force} is non-@code{nil}, that says to fix the line's |
| 1673 | indentation if that doesn't match the left margin value. |
| 1674 | @end deffn |
| 1675 | |
| 1676 | @defun delete-to-left-margin &optional from to |
| 1677 | This function removes left margin indentation from the text between |
| 1678 | @var{from} and @var{to}. The amount of indentation to delete is |
| 1679 | determined by calling @code{current-left-margin}. In no case does this |
| 1680 | function delete non-whitespace. If @var{from} and @var{to} are omitted, |
| 1681 | they default to the whole buffer. |
| 1682 | @end defun |
| 1683 | |
| 1684 | @defun indent-to-left-margin |
| 1685 | This function adjusts the indentation at the beginning of the current |
| 1686 | line to the value specified by the variable @code{left-margin}. (That |
| 1687 | may involve either inserting or deleting whitespace.) This function |
| 1688 | is value of @code{indent-line-function} in Paragraph-Indent Text mode. |
| 1689 | @end defun |
| 1690 | |
| 1691 | @defopt left-margin |
| 1692 | This variable specifies the base left margin column. In Fundamental |
| 1693 | mode, @kbd{C-j} indents to this column. This variable automatically |
| 1694 | becomes buffer-local when set in any fashion. |
| 1695 | @end defopt |
| 1696 | |
| 1697 | @defopt fill-nobreak-predicate |
| 1698 | This variable gives major modes a way to specify not to break a line |
| 1699 | at certain places. Its value should be a list of functions. Whenever |
| 1700 | filling considers breaking the line at a certain place in the buffer, |
| 1701 | it calls each of these functions with no arguments and with point |
| 1702 | located at that place. If any of the functions returns |
| 1703 | non-@code{nil}, then the line won't be broken there. |
| 1704 | @end defopt |
| 1705 | |
| 1706 | @node Adaptive Fill |
| 1707 | @section Adaptive Fill Mode |
| 1708 | @c @cindex Adaptive Fill mode "adaptive-fill-mode" is adjacent. |
| 1709 | |
| 1710 | When @dfn{Adaptive Fill Mode} is enabled, Emacs determines the fill |
| 1711 | prefix automatically from the text in each paragraph being filled |
| 1712 | rather than using a predetermined value. During filling, this fill |
| 1713 | prefix gets inserted at the start of the second and subsequent lines |
| 1714 | of the paragraph as described in @ref{Filling}, and in @ref{Auto |
| 1715 | Filling}. |
| 1716 | |
| 1717 | @defopt adaptive-fill-mode |
| 1718 | Adaptive Fill mode is enabled when this variable is non-@code{nil}. |
| 1719 | It is @code{t} by default. |
| 1720 | @end defopt |
| 1721 | |
| 1722 | @defun fill-context-prefix from to |
| 1723 | This function implements the heart of Adaptive Fill mode; it chooses a |
| 1724 | fill prefix based on the text between @var{from} and @var{to}, |
| 1725 | typically the start and end of a paragraph. It does this by looking |
| 1726 | at the first two lines of the paragraph, based on the variables |
| 1727 | described below. |
| 1728 | @c The optional argument first-line-regexp is not documented |
| 1729 | @c because it exists for internal purposes and might be eliminated |
| 1730 | @c in the future. |
| 1731 | |
| 1732 | Usually, this function returns the fill prefix, a string. However, |
| 1733 | before doing this, the function makes a final check (not specially |
| 1734 | mentioned in the following) that a line starting with this prefix |
| 1735 | wouldn't look like the start of a paragraph. Should this happen, the |
| 1736 | function signals the anomaly by returning @code{nil} instead. |
| 1737 | |
| 1738 | In detail, @code{fill-context-prefix} does this: |
| 1739 | |
| 1740 | @enumerate |
| 1741 | @item |
| 1742 | It takes a candidate for the fill prefix from the first line---it |
| 1743 | tries first the function in @code{adaptive-fill-function} (if any), |
| 1744 | then the regular expression @code{adaptive-fill-regexp} (see below). |
| 1745 | The first non-@code{nil} result of these, or the empty string if |
| 1746 | they're both @code{nil}, becomes the first line's candidate. |
| 1747 | @item |
| 1748 | If the paragraph has as yet only one line, the function tests the |
| 1749 | validity of the prefix candidate just found. The function then |
| 1750 | returns the candidate if it's valid, or a string of spaces otherwise. |
| 1751 | (see the description of @code{adaptive-fill-first-line-regexp} below). |
| 1752 | @item |
| 1753 | When the paragraph already has two lines, the function next looks for |
| 1754 | a prefix candidate on the second line, in just the same way it did for |
| 1755 | the first line. If it doesn't find one, it returns @code{nil}. |
| 1756 | @item |
| 1757 | The function now compares the two candidate prefixes heuristically: if |
| 1758 | the non-whitespace characters in the line 2 candidate occur in the |
| 1759 | same order in the line 1 candidate, the function returns the line 2 |
| 1760 | candidate. Otherwise, it returns the largest initial substring which |
| 1761 | is common to both candidates (which might be the empty string). |
| 1762 | @end enumerate |
| 1763 | @end defun |
| 1764 | |
| 1765 | @defopt adaptive-fill-regexp |
| 1766 | Adaptive Fill mode matches this regular expression against the text |
| 1767 | starting after the left margin whitespace (if any) on a line; the |
| 1768 | characters it matches are that line's candidate for the fill prefix. |
| 1769 | |
| 1770 | The default value matches whitespace with certain punctuation |
| 1771 | characters intermingled. |
| 1772 | @end defopt |
| 1773 | |
| 1774 | @defopt adaptive-fill-first-line-regexp |
| 1775 | Used only in one-line paragraphs, this regular expression acts as an |
| 1776 | additional check of the validity of the one available candidate fill |
| 1777 | prefix: the candidate must match this regular expression, or match |
| 1778 | @code{comment-start-skip}. If it doesn't, @code{fill-context-prefix} |
| 1779 | replaces the candidate with a string of spaces ``of the same width'' |
| 1780 | as it. |
| 1781 | |
| 1782 | The default value of this variable is @w{@code{"\\`[ \t]*\\'"}}, which |
| 1783 | matches only a string of whitespace. The effect of this default is to |
| 1784 | force the fill prefixes found in one-line paragraphs always to be pure |
| 1785 | whitespace. |
| 1786 | @end defopt |
| 1787 | |
| 1788 | @defopt adaptive-fill-function |
| 1789 | You can specify more complex ways of choosing a fill prefix |
| 1790 | automatically by setting this variable to a function. The function is |
| 1791 | called with point after the left margin (if any) of a line, and it |
| 1792 | must preserve point. It should return either ``that line's'' fill |
| 1793 | prefix or @code{nil}, meaning it has failed to determine a prefix. |
| 1794 | @end defopt |
| 1795 | |
| 1796 | @node Auto Filling |
| 1797 | @comment node-name, next, previous, up |
| 1798 | @section Auto Filling |
| 1799 | @cindex filling, automatic |
| 1800 | @cindex Auto Fill mode |
| 1801 | |
| 1802 | Auto Fill mode is a minor mode that fills lines automatically as text |
| 1803 | is inserted. This section describes the hook used by Auto Fill mode. |
| 1804 | For a description of functions that you can call explicitly to fill and |
| 1805 | justify existing text, see @ref{Filling}. |
| 1806 | |
| 1807 | Auto Fill mode also enables the functions that change the margins and |
| 1808 | justification style to refill portions of the text. @xref{Margins}. |
| 1809 | |
| 1810 | @defvar auto-fill-function |
| 1811 | The value of this buffer-local variable should be a function (of no |
| 1812 | arguments) to be called after self-inserting a character from the table |
| 1813 | @code{auto-fill-chars}. It may be @code{nil}, in which case nothing |
| 1814 | special is done in that case. |
| 1815 | |
| 1816 | The value of @code{auto-fill-function} is @code{do-auto-fill} when |
| 1817 | Auto-Fill mode is enabled. That is a function whose sole purpose is to |
| 1818 | implement the usual strategy for breaking a line. |
| 1819 | |
| 1820 | @quotation |
| 1821 | In older Emacs versions, this variable was named @code{auto-fill-hook}, |
| 1822 | but since it is not called with the standard convention for hooks, it |
| 1823 | was renamed to @code{auto-fill-function} in version 19. |
| 1824 | @end quotation |
| 1825 | @end defvar |
| 1826 | |
| 1827 | @defvar normal-auto-fill-function |
| 1828 | This variable specifies the function to use for |
| 1829 | @code{auto-fill-function}, if and when Auto Fill is turned on. Major |
| 1830 | modes can set buffer-local values for this variable to alter how Auto |
| 1831 | Fill works. |
| 1832 | @end defvar |
| 1833 | |
| 1834 | @defvar auto-fill-chars |
| 1835 | A char table of characters which invoke @code{auto-fill-function} when |
| 1836 | self-inserted---space and newline in most language environments. They |
| 1837 | have an entry @code{t} in the table. |
| 1838 | @end defvar |
| 1839 | |
| 1840 | @node Sorting |
| 1841 | @section Sorting Text |
| 1842 | @cindex sorting text |
| 1843 | |
| 1844 | The sorting functions described in this section all rearrange text in |
| 1845 | a buffer. This is in contrast to the function @code{sort}, which |
| 1846 | rearranges the order of the elements of a list (@pxref{Rearrangement}). |
| 1847 | The values returned by these functions are not meaningful. |
| 1848 | |
| 1849 | @defun sort-subr reverse nextrecfun endrecfun &optional startkeyfun endkeyfun predicate |
| 1850 | This function is the general text-sorting routine that subdivides a |
| 1851 | buffer into records and then sorts them. Most of the commands in this |
| 1852 | section use this function. |
| 1853 | |
| 1854 | To understand how @code{sort-subr} works, consider the whole accessible |
| 1855 | portion of the buffer as being divided into disjoint pieces called |
| 1856 | @dfn{sort records}. The records may or may not be contiguous, but they |
| 1857 | must not overlap. A portion of each sort record (perhaps all of it) is |
| 1858 | designated as the sort key. Sorting rearranges the records in order by |
| 1859 | their sort keys. |
| 1860 | |
| 1861 | Usually, the records are rearranged in order of ascending sort key. |
| 1862 | If the first argument to the @code{sort-subr} function, @var{reverse}, |
| 1863 | is non-@code{nil}, the sort records are rearranged in order of |
| 1864 | descending sort key. |
| 1865 | |
| 1866 | The next four arguments to @code{sort-subr} are functions that are |
| 1867 | called to move point across a sort record. They are called many times |
| 1868 | from within @code{sort-subr}. |
| 1869 | |
| 1870 | @enumerate |
| 1871 | @item |
| 1872 | @var{nextrecfun} is called with point at the end of a record. This |
| 1873 | function moves point to the start of the next record. The first record |
| 1874 | is assumed to start at the position of point when @code{sort-subr} is |
| 1875 | called. Therefore, you should usually move point to the beginning of |
| 1876 | the buffer before calling @code{sort-subr}. |
| 1877 | |
| 1878 | This function can indicate there are no more sort records by leaving |
| 1879 | point at the end of the buffer. |
| 1880 | |
| 1881 | @item |
| 1882 | @var{endrecfun} is called with point within a record. It moves point to |
| 1883 | the end of the record. |
| 1884 | |
| 1885 | @item |
| 1886 | @var{startkeyfun} is called to move point from the start of a record to |
| 1887 | the start of the sort key. This argument is optional; if it is omitted, |
| 1888 | the whole record is the sort key. If supplied, the function should |
| 1889 | either return a non-@code{nil} value to be used as the sort key, or |
| 1890 | return @code{nil} to indicate that the sort key is in the buffer |
| 1891 | starting at point. In the latter case, @var{endkeyfun} is called to |
| 1892 | find the end of the sort key. |
| 1893 | |
| 1894 | @item |
| 1895 | @var{endkeyfun} is called to move point from the start of the sort key |
| 1896 | to the end of the sort key. This argument is optional. If |
| 1897 | @var{startkeyfun} returns @code{nil} and this argument is omitted (or |
| 1898 | @code{nil}), then the sort key extends to the end of the record. There |
| 1899 | is no need for @var{endkeyfun} if @var{startkeyfun} returns a |
| 1900 | non-@code{nil} value. |
| 1901 | @end enumerate |
| 1902 | |
| 1903 | The argument @var{predicate} is the function to use to compare keys. |
| 1904 | If keys are numbers, it defaults to @code{<}; otherwise it defaults to |
| 1905 | @code{string<}. |
| 1906 | |
| 1907 | As an example of @code{sort-subr}, here is the complete function |
| 1908 | definition for @code{sort-lines}: |
| 1909 | |
| 1910 | @example |
| 1911 | @group |
| 1912 | ;; @r{Note that the first two lines of doc string} |
| 1913 | ;; @r{are effectively one line when viewed by a user.} |
| 1914 | (defun sort-lines (reverse beg end) |
| 1915 | "Sort lines in region alphabetically;\ |
| 1916 | argument means descending order. |
| 1917 | Called from a program, there are three arguments: |
| 1918 | @end group |
| 1919 | @group |
| 1920 | REVERSE (non-nil means reverse order),\ |
| 1921 | BEG and END (region to sort). |
| 1922 | The variable `sort-fold-case' determines\ |
| 1923 | whether alphabetic case affects |
| 1924 | the sort order." |
| 1925 | @end group |
| 1926 | @group |
| 1927 | (interactive "P\nr") |
| 1928 | (save-excursion |
| 1929 | (save-restriction |
| 1930 | (narrow-to-region beg end) |
| 1931 | (goto-char (point-min)) |
| 1932 | (let ((inhibit-field-text-motion t)) |
| 1933 | (sort-subr reverse 'forward-line 'end-of-line))))) |
| 1934 | @end group |
| 1935 | @end example |
| 1936 | |
| 1937 | Here @code{forward-line} moves point to the start of the next record, |
| 1938 | and @code{end-of-line} moves point to the end of record. We do not pass |
| 1939 | the arguments @var{startkeyfun} and @var{endkeyfun}, because the entire |
| 1940 | record is used as the sort key. |
| 1941 | |
| 1942 | The @code{sort-paragraphs} function is very much the same, except that |
| 1943 | its @code{sort-subr} call looks like this: |
| 1944 | |
| 1945 | @example |
| 1946 | @group |
| 1947 | (sort-subr reverse |
| 1948 | (function |
| 1949 | (lambda () |
| 1950 | (while (and (not (eobp)) |
| 1951 | (looking-at paragraph-separate)) |
| 1952 | (forward-line 1)))) |
| 1953 | 'forward-paragraph) |
| 1954 | @end group |
| 1955 | @end example |
| 1956 | |
| 1957 | Markers pointing into any sort records are left with no useful |
| 1958 | position after @code{sort-subr} returns. |
| 1959 | @end defun |
| 1960 | |
| 1961 | @defopt sort-fold-case |
| 1962 | If this variable is non-@code{nil}, @code{sort-subr} and the other |
| 1963 | buffer sorting functions ignore case when comparing strings. |
| 1964 | @end defopt |
| 1965 | |
| 1966 | @deffn Command sort-regexp-fields reverse record-regexp key-regexp start end |
| 1967 | This command sorts the region between @var{start} and @var{end} |
| 1968 | alphabetically as specified by @var{record-regexp} and @var{key-regexp}. |
| 1969 | If @var{reverse} is a negative integer, then sorting is in reverse |
| 1970 | order. |
| 1971 | |
| 1972 | Alphabetical sorting means that two sort keys are compared by |
| 1973 | comparing the first characters of each, the second characters of each, |
| 1974 | and so on. If a mismatch is found, it means that the sort keys are |
| 1975 | unequal; the sort key whose character is less at the point of first |
| 1976 | mismatch is the lesser sort key. The individual characters are compared |
| 1977 | according to their numerical character codes in the Emacs character set. |
| 1978 | |
| 1979 | The value of the @var{record-regexp} argument specifies how to divide |
| 1980 | the buffer into sort records. At the end of each record, a search is |
| 1981 | done for this regular expression, and the text that matches it is taken |
| 1982 | as the next record. For example, the regular expression @samp{^.+$}, |
| 1983 | which matches lines with at least one character besides a newline, would |
| 1984 | make each such line into a sort record. @xref{Regular Expressions}, for |
| 1985 | a description of the syntax and meaning of regular expressions. |
| 1986 | |
| 1987 | The value of the @var{key-regexp} argument specifies what part of each |
| 1988 | record is the sort key. The @var{key-regexp} could match the whole |
| 1989 | record, or only a part. In the latter case, the rest of the record has |
| 1990 | no effect on the sorted order of records, but it is carried along when |
| 1991 | the record moves to its new position. |
| 1992 | |
| 1993 | The @var{key-regexp} argument can refer to the text matched by a |
| 1994 | subexpression of @var{record-regexp}, or it can be a regular expression |
| 1995 | on its own. |
| 1996 | |
| 1997 | If @var{key-regexp} is: |
| 1998 | |
| 1999 | @table @asis |
| 2000 | @item @samp{\@var{digit}} |
| 2001 | then the text matched by the @var{digit}th @samp{\(...\)} parenthesis |
| 2002 | grouping in @var{record-regexp} is the sort key. |
| 2003 | |
| 2004 | @item @samp{\&} |
| 2005 | then the whole record is the sort key. |
| 2006 | |
| 2007 | @item a regular expression |
| 2008 | then @code{sort-regexp-fields} searches for a match for the regular |
| 2009 | expression within the record. If such a match is found, it is the sort |
| 2010 | key. If there is no match for @var{key-regexp} within a record then |
| 2011 | that record is ignored, which means its position in the buffer is not |
| 2012 | changed. (The other records may move around it.) |
| 2013 | @end table |
| 2014 | |
| 2015 | For example, if you plan to sort all the lines in the region by the |
| 2016 | first word on each line starting with the letter @samp{f}, you should |
| 2017 | set @var{record-regexp} to @samp{^.*$} and set @var{key-regexp} to |
| 2018 | @samp{\<f\w*\>}. The resulting expression looks like this: |
| 2019 | |
| 2020 | @example |
| 2021 | @group |
| 2022 | (sort-regexp-fields nil "^.*$" "\\<f\\w*\\>" |
| 2023 | (region-beginning) |
| 2024 | (region-end)) |
| 2025 | @end group |
| 2026 | @end example |
| 2027 | |
| 2028 | If you call @code{sort-regexp-fields} interactively, it prompts for |
| 2029 | @var{record-regexp} and @var{key-regexp} in the minibuffer. |
| 2030 | @end deffn |
| 2031 | |
| 2032 | @deffn Command sort-lines reverse start end |
| 2033 | This command alphabetically sorts lines in the region between |
| 2034 | @var{start} and @var{end}. If @var{reverse} is non-@code{nil}, the sort |
| 2035 | is in reverse order. |
| 2036 | @end deffn |
| 2037 | |
| 2038 | @deffn Command sort-paragraphs reverse start end |
| 2039 | This command alphabetically sorts paragraphs in the region between |
| 2040 | @var{start} and @var{end}. If @var{reverse} is non-@code{nil}, the sort |
| 2041 | is in reverse order. |
| 2042 | @end deffn |
| 2043 | |
| 2044 | @deffn Command sort-pages reverse start end |
| 2045 | This command alphabetically sorts pages in the region between |
| 2046 | @var{start} and @var{end}. If @var{reverse} is non-@code{nil}, the sort |
| 2047 | is in reverse order. |
| 2048 | @end deffn |
| 2049 | |
| 2050 | @deffn Command sort-fields field start end |
| 2051 | This command sorts lines in the region between @var{start} and |
| 2052 | @var{end}, comparing them alphabetically by the @var{field}th field |
| 2053 | of each line. Fields are separated by whitespace and numbered starting |
| 2054 | from 1. If @var{field} is negative, sorting is by the |
| 2055 | @w{@minus{}@var{field}th} field from the end of the line. This command |
| 2056 | is useful for sorting tables. |
| 2057 | @end deffn |
| 2058 | |
| 2059 | @deffn Command sort-numeric-fields field start end |
| 2060 | This command sorts lines in the region between @var{start} and |
| 2061 | @var{end}, comparing them numerically by the @var{field}th field of |
| 2062 | each line. Fields are separated by whitespace and numbered starting |
| 2063 | from 1. The specified field must contain a number in each line of the |
| 2064 | region. Numbers starting with 0 are treated as octal, and numbers |
| 2065 | starting with @samp{0x} are treated as hexadecimal. |
| 2066 | |
| 2067 | If @var{field} is negative, sorting is by the |
| 2068 | @w{@minus{}@var{field}th} field from the end of the line. This |
| 2069 | command is useful for sorting tables. |
| 2070 | @end deffn |
| 2071 | |
| 2072 | @defopt sort-numeric-base |
| 2073 | This variable specifies the default radix for |
| 2074 | @code{sort-numeric-fields} to parse numbers. |
| 2075 | @end defopt |
| 2076 | |
| 2077 | @deffn Command sort-columns reverse &optional beg end |
| 2078 | This command sorts the lines in the region between @var{beg} and |
| 2079 | @var{end}, comparing them alphabetically by a certain range of |
| 2080 | columns. The column positions of @var{beg} and @var{end} bound the |
| 2081 | range of columns to sort on. |
| 2082 | |
| 2083 | If @var{reverse} is non-@code{nil}, the sort is in reverse order. |
| 2084 | |
| 2085 | One unusual thing about this command is that the entire line |
| 2086 | containing position @var{beg}, and the entire line containing position |
| 2087 | @var{end}, are included in the region sorted. |
| 2088 | |
| 2089 | Note that @code{sort-columns} rejects text that contains tabs, because |
| 2090 | tabs could be split across the specified columns. Use @kbd{M-x |
| 2091 | untabify} to convert tabs to spaces before sorting. |
| 2092 | |
| 2093 | When possible, this command actually works by calling the @code{sort} |
| 2094 | utility program. |
| 2095 | @end deffn |
| 2096 | |
| 2097 | @node Columns |
| 2098 | @comment node-name, next, previous, up |
| 2099 | @section Counting Columns |
| 2100 | @cindex columns |
| 2101 | @cindex counting columns |
| 2102 | @cindex horizontal position |
| 2103 | |
| 2104 | The column functions convert between a character position (counting |
| 2105 | characters from the beginning of the buffer) and a column position |
| 2106 | (counting screen characters from the beginning of a line). |
| 2107 | |
| 2108 | These functions count each character according to the number of |
| 2109 | columns it occupies on the screen. This means control characters count |
| 2110 | as occupying 2 or 4 columns, depending upon the value of |
| 2111 | @code{ctl-arrow}, and tabs count as occupying a number of columns that |
| 2112 | depends on the value of @code{tab-width} and on the column where the tab |
| 2113 | begins. @xref{Usual Display}. |
| 2114 | |
| 2115 | Column number computations ignore the width of the window and the |
| 2116 | amount of horizontal scrolling. Consequently, a column value can be |
| 2117 | arbitrarily high. The first (or leftmost) column is numbered 0. They |
| 2118 | also ignore overlays and text properties, aside from invisibility. |
| 2119 | |
| 2120 | @defun current-column |
| 2121 | This function returns the horizontal position of point, measured in |
| 2122 | columns, counting from 0 at the left margin. The column position is the |
| 2123 | sum of the widths of all the displayed representations of the characters |
| 2124 | between the start of the current line and point. |
| 2125 | |
| 2126 | For an example of using @code{current-column}, see the description of |
| 2127 | @code{count-lines} in @ref{Text Lines}. |
| 2128 | @end defun |
| 2129 | |
| 2130 | @deffn Command move-to-column column &optional force |
| 2131 | This function moves point to @var{column} in the current line. The |
| 2132 | calculation of @var{column} takes into account the widths of the |
| 2133 | displayed representations of the characters between the start of the |
| 2134 | line and point. |
| 2135 | |
| 2136 | When called interactively, @var{column} is the value of prefix numeric |
| 2137 | argument. If @var{column} is not an integer, an error is signaled. |
| 2138 | |
| 2139 | If column @var{column} is beyond the end of the line, point moves to |
| 2140 | the end of the line. If @var{column} is negative, point moves to the |
| 2141 | beginning of the line. |
| 2142 | |
| 2143 | If it is impossible to move to column @var{column} because that is in |
| 2144 | the middle of a multicolumn character such as a tab, point moves to the |
| 2145 | end of that character. However, if @var{force} is non-@code{nil}, and |
| 2146 | @var{column} is in the middle of a tab, then @code{move-to-column} |
| 2147 | converts the tab into spaces so that it can move precisely to column |
| 2148 | @var{column}. Other multicolumn characters can cause anomalies despite |
| 2149 | @var{force}, since there is no way to split them. |
| 2150 | |
| 2151 | The argument @var{force} also has an effect if the line isn't long |
| 2152 | enough to reach column @var{column}; if it is @code{t}, that means to |
| 2153 | add whitespace at the end of the line to reach that column. |
| 2154 | |
| 2155 | The return value is the column number actually moved to. |
| 2156 | @end deffn |
| 2157 | |
| 2158 | @node Indentation |
| 2159 | @section Indentation |
| 2160 | @cindex indentation |
| 2161 | |
| 2162 | The indentation functions are used to examine, move to, and change |
| 2163 | whitespace that is at the beginning of a line. Some of the functions |
| 2164 | can also change whitespace elsewhere on a line. Columns and indentation |
| 2165 | count from zero at the left margin. |
| 2166 | |
| 2167 | @menu |
| 2168 | * Primitive Indent:: Functions used to count and insert indentation. |
| 2169 | * Mode-Specific Indent:: Customize indentation for different modes. |
| 2170 | * Region Indent:: Indent all the lines in a region. |
| 2171 | * Relative Indent:: Indent the current line based on previous lines. |
| 2172 | * Indent Tabs:: Adjustable, typewriter-like tab stops. |
| 2173 | * Motion by Indent:: Move to first non-blank character. |
| 2174 | @end menu |
| 2175 | |
| 2176 | @node Primitive Indent |
| 2177 | @subsection Indentation Primitives |
| 2178 | |
| 2179 | This section describes the primitive functions used to count and |
| 2180 | insert indentation. The functions in the following sections use these |
| 2181 | primitives. @xref{Width}, for related functions. |
| 2182 | |
| 2183 | @defun current-indentation |
| 2184 | @comment !!Type Primitive Function |
| 2185 | @comment !!SourceFile indent.c |
| 2186 | This function returns the indentation of the current line, which is |
| 2187 | the horizontal position of the first nonblank character. If the |
| 2188 | contents are entirely blank, then this is the horizontal position of the |
| 2189 | end of the line. |
| 2190 | @end defun |
| 2191 | |
| 2192 | @deffn Command indent-to column &optional minimum |
| 2193 | @comment !!Type Primitive Function |
| 2194 | @comment !!SourceFile indent.c |
| 2195 | This function indents from point with tabs and spaces until @var{column} |
| 2196 | is reached. If @var{minimum} is specified and non-@code{nil}, then at |
| 2197 | least that many spaces are inserted even if this requires going beyond |
| 2198 | @var{column}. Otherwise the function does nothing if point is already |
| 2199 | beyond @var{column}. The value is the column at which the inserted |
| 2200 | indentation ends. |
| 2201 | |
| 2202 | The inserted whitespace characters inherit text properties from the |
| 2203 | surrounding text (usually, from the preceding text only). @xref{Sticky |
| 2204 | Properties}. |
| 2205 | @end deffn |
| 2206 | |
| 2207 | @defopt indent-tabs-mode |
| 2208 | @comment !!SourceFile indent.c |
| 2209 | If this variable is non-@code{nil}, indentation functions can insert |
| 2210 | tabs as well as spaces. Otherwise, they insert only spaces. Setting |
| 2211 | this variable automatically makes it buffer-local in the current buffer. |
| 2212 | @end defopt |
| 2213 | |
| 2214 | @node Mode-Specific Indent |
| 2215 | @subsection Indentation Controlled by Major Mode |
| 2216 | |
| 2217 | An important function of each major mode is to customize the @key{TAB} |
| 2218 | key to indent properly for the language being edited. This section |
| 2219 | describes the mechanism of the @key{TAB} key and how to control it. |
| 2220 | The functions in this section return unpredictable values. |
| 2221 | |
| 2222 | @defvar indent-line-function |
| 2223 | This variable's value is the function to be used by @key{TAB} (and |
| 2224 | various commands) to indent the current line. The command |
| 2225 | @code{indent-according-to-mode} does no more than call this function. |
| 2226 | |
| 2227 | In Lisp mode, the value is the symbol @code{lisp-indent-line}; in C |
| 2228 | mode, @code{c-indent-line}; in Fortran mode, @code{fortran-indent-line}. |
| 2229 | The default value is @code{indent-relative}. |
| 2230 | @end defvar |
| 2231 | |
| 2232 | @deffn Command indent-according-to-mode |
| 2233 | This command calls the function in @code{indent-line-function} to |
| 2234 | indent the current line in a way appropriate for the current major mode. |
| 2235 | @end deffn |
| 2236 | |
| 2237 | @deffn Command indent-for-tab-command &optional rigid |
| 2238 | This command calls the function in @code{indent-line-function} to |
| 2239 | indent the current line; however, if that function is |
| 2240 | @code{indent-to-left-margin}, @code{insert-tab} is called instead. |
| 2241 | (That is a trivial command that inserts a tab character.) If |
| 2242 | @var{rigid} is non-@code{nil}, this function also rigidly indents the |
| 2243 | entire balanced expression that starts at the beginning of the current |
| 2244 | line, to reflect change in indentation of the current line. |
| 2245 | @end deffn |
| 2246 | |
| 2247 | @deffn Command newline-and-indent |
| 2248 | This function inserts a newline, then indents the new line (the one |
| 2249 | following the newline just inserted) according to the major mode. |
| 2250 | |
| 2251 | It does indentation by calling the current @code{indent-line-function}. |
| 2252 | In programming language modes, this is the same thing @key{TAB} does, |
| 2253 | but in some text modes, where @key{TAB} inserts a tab, |
| 2254 | @code{newline-and-indent} indents to the column specified by |
| 2255 | @code{left-margin}. |
| 2256 | @end deffn |
| 2257 | |
| 2258 | @deffn Command reindent-then-newline-and-indent |
| 2259 | @comment !!SourceFile simple.el |
| 2260 | This command reindents the current line, inserts a newline at point, |
| 2261 | and then indents the new line (the one following the newline just |
| 2262 | inserted). |
| 2263 | |
| 2264 | This command does indentation on both lines according to the current |
| 2265 | major mode, by calling the current value of @code{indent-line-function}. |
| 2266 | In programming language modes, this is the same thing @key{TAB} does, |
| 2267 | but in some text modes, where @key{TAB} inserts a tab, |
| 2268 | @code{reindent-then-newline-and-indent} indents to the column specified |
| 2269 | by @code{left-margin}. |
| 2270 | @end deffn |
| 2271 | |
| 2272 | @node Region Indent |
| 2273 | @subsection Indenting an Entire Region |
| 2274 | |
| 2275 | This section describes commands that indent all the lines in the |
| 2276 | region. They return unpredictable values. |
| 2277 | |
| 2278 | @deffn Command indent-region start end &optional to-column |
| 2279 | This command indents each nonblank line starting between @var{start} |
| 2280 | (inclusive) and @var{end} (exclusive). If @var{to-column} is |
| 2281 | @code{nil}, @code{indent-region} indents each nonblank line by calling |
| 2282 | the current mode's indentation function, the value of |
| 2283 | @code{indent-line-function}. |
| 2284 | |
| 2285 | If @var{to-column} is non-@code{nil}, it should be an integer |
| 2286 | specifying the number of columns of indentation; then this function |
| 2287 | gives each line exactly that much indentation, by either adding or |
| 2288 | deleting whitespace. |
| 2289 | |
| 2290 | If there is a fill prefix, @code{indent-region} indents each line |
| 2291 | by making it start with the fill prefix. |
| 2292 | @end deffn |
| 2293 | |
| 2294 | @defvar indent-region-function |
| 2295 | The value of this variable is a function that can be used by |
| 2296 | @code{indent-region} as a short cut. It should take two arguments, the |
| 2297 | start and end of the region. You should design the function so |
| 2298 | that it will produce the same results as indenting the lines of the |
| 2299 | region one by one, but presumably faster. |
| 2300 | |
| 2301 | If the value is @code{nil}, there is no short cut, and |
| 2302 | @code{indent-region} actually works line by line. |
| 2303 | |
| 2304 | A short-cut function is useful in modes such as C mode and Lisp mode, |
| 2305 | where the @code{indent-line-function} must scan from the beginning of |
| 2306 | the function definition: applying it to each line would be quadratic in |
| 2307 | time. The short cut can update the scan information as it moves through |
| 2308 | the lines indenting them; this takes linear time. In a mode where |
| 2309 | indenting a line individually is fast, there is no need for a short cut. |
| 2310 | |
| 2311 | @code{indent-region} with a non-@code{nil} argument @var{to-column} has |
| 2312 | a different meaning and does not use this variable. |
| 2313 | @end defvar |
| 2314 | |
| 2315 | @deffn Command indent-rigidly start end count |
| 2316 | This command indents all lines starting between @var{start} |
| 2317 | (inclusive) and @var{end} (exclusive) sideways by @var{count} columns. |
| 2318 | This ``preserves the shape'' of the affected region, moving it as a |
| 2319 | rigid unit. Consequently, this command is useful not only for indenting |
| 2320 | regions of unindented text, but also for indenting regions of formatted |
| 2321 | code. |
| 2322 | |
| 2323 | For example, if @var{count} is 3, this command adds 3 columns of |
| 2324 | indentation to each of the lines beginning in the region specified. |
| 2325 | |
| 2326 | In Mail mode, @kbd{C-c C-y} (@code{mail-yank-original}) uses |
| 2327 | @code{indent-rigidly} to indent the text copied from the message being |
| 2328 | replied to. |
| 2329 | @end deffn |
| 2330 | |
| 2331 | @deffn Command indent-code-rigidly start end columns &optional nochange-regexp |
| 2332 | This is like @code{indent-rigidly}, except that it doesn't alter lines |
| 2333 | that start within strings or comments. |
| 2334 | |
| 2335 | In addition, it doesn't alter a line if @var{nochange-regexp} matches at |
| 2336 | the beginning of the line (if @var{nochange-regexp} is non-@code{nil}). |
| 2337 | @end deffn |
| 2338 | |
| 2339 | @node Relative Indent |
| 2340 | @subsection Indentation Relative to Previous Lines |
| 2341 | |
| 2342 | This section describes two commands that indent the current line |
| 2343 | based on the contents of previous lines. |
| 2344 | |
| 2345 | @deffn Command indent-relative &optional unindented-ok |
| 2346 | This command inserts whitespace at point, extending to the same |
| 2347 | column as the next @dfn{indent point} of the previous nonblank line. An |
| 2348 | indent point is a non-whitespace character following whitespace. The |
| 2349 | next indent point is the first one at a column greater than the current |
| 2350 | column of point. For example, if point is underneath and to the left of |
| 2351 | the first non-blank character of a line of text, it moves to that column |
| 2352 | by inserting whitespace. |
| 2353 | |
| 2354 | If the previous nonblank line has no next indent point (i.e., none at a |
| 2355 | great enough column position), @code{indent-relative} either does |
| 2356 | nothing (if @var{unindented-ok} is non-@code{nil}) or calls |
| 2357 | @code{tab-to-tab-stop}. Thus, if point is underneath and to the right |
| 2358 | of the last column of a short line of text, this command ordinarily |
| 2359 | moves point to the next tab stop by inserting whitespace. |
| 2360 | |
| 2361 | The return value of @code{indent-relative} is unpredictable. |
| 2362 | |
| 2363 | In the following example, point is at the beginning of the second |
| 2364 | line: |
| 2365 | |
| 2366 | @example |
| 2367 | @group |
| 2368 | This line is indented twelve spaces. |
| 2369 | @point{}The quick brown fox jumped. |
| 2370 | @end group |
| 2371 | @end example |
| 2372 | |
| 2373 | @noindent |
| 2374 | Evaluation of the expression @code{(indent-relative nil)} produces the |
| 2375 | following: |
| 2376 | |
| 2377 | @example |
| 2378 | @group |
| 2379 | This line is indented twelve spaces. |
| 2380 | @point{}The quick brown fox jumped. |
| 2381 | @end group |
| 2382 | @end example |
| 2383 | |
| 2384 | In this next example, point is between the @samp{m} and @samp{p} of |
| 2385 | @samp{jumped}: |
| 2386 | |
| 2387 | @example |
| 2388 | @group |
| 2389 | This line is indented twelve spaces. |
| 2390 | The quick brown fox jum@point{}ped. |
| 2391 | @end group |
| 2392 | @end example |
| 2393 | |
| 2394 | @noindent |
| 2395 | Evaluation of the expression @code{(indent-relative nil)} produces the |
| 2396 | following: |
| 2397 | |
| 2398 | @example |
| 2399 | @group |
| 2400 | This line is indented twelve spaces. |
| 2401 | The quick brown fox jum @point{}ped. |
| 2402 | @end group |
| 2403 | @end example |
| 2404 | @end deffn |
| 2405 | |
| 2406 | @deffn Command indent-relative-maybe |
| 2407 | @comment !!SourceFile indent.el |
| 2408 | This command indents the current line like the previous nonblank line, |
| 2409 | by calling @code{indent-relative} with @code{t} as the |
| 2410 | @var{unindented-ok} argument. The return value is unpredictable. |
| 2411 | |
| 2412 | If the previous nonblank line has no indent points beyond the current |
| 2413 | column, this command does nothing. |
| 2414 | @end deffn |
| 2415 | |
| 2416 | @node Indent Tabs |
| 2417 | @comment node-name, next, previous, up |
| 2418 | @subsection Adjustable ``Tab Stops'' |
| 2419 | @cindex tabs stops for indentation |
| 2420 | |
| 2421 | This section explains the mechanism for user-specified ``tab stops'' |
| 2422 | and the mechanisms that use and set them. The name ``tab stops'' is |
| 2423 | used because the feature is similar to that of the tab stops on a |
| 2424 | typewriter. The feature works by inserting an appropriate number of |
| 2425 | spaces and tab characters to reach the next tab stop column; it does not |
| 2426 | affect the display of tab characters in the buffer (@pxref{Usual |
| 2427 | Display}). Note that the @key{TAB} character as input uses this tab |
| 2428 | stop feature only in a few major modes, such as Text mode. |
| 2429 | @xref{Tab Stops,,, emacs, The GNU Emacs Manual}. |
| 2430 | |
| 2431 | @deffn Command tab-to-tab-stop |
| 2432 | This command inserts spaces or tabs before point, up to the next tab |
| 2433 | stop column defined by @code{tab-stop-list}. It searches the list for |
| 2434 | an element greater than the current column number, and uses that element |
| 2435 | as the column to indent to. It does nothing if no such element is |
| 2436 | found. |
| 2437 | @end deffn |
| 2438 | |
| 2439 | @defopt tab-stop-list |
| 2440 | This variable is the list of tab stop columns used by |
| 2441 | @code{tab-to-tab-stops}. The elements should be integers in increasing |
| 2442 | order. The tab stop columns need not be evenly spaced. |
| 2443 | |
| 2444 | Use @kbd{M-x edit-tab-stops} to edit the location of tab stops |
| 2445 | interactively. |
| 2446 | @end defopt |
| 2447 | |
| 2448 | @node Motion by Indent |
| 2449 | @subsection Indentation-Based Motion Commands |
| 2450 | |
| 2451 | These commands, primarily for interactive use, act based on the |
| 2452 | indentation in the text. |
| 2453 | |
| 2454 | @deffn Command back-to-indentation |
| 2455 | @comment !!SourceFile simple.el |
| 2456 | This command moves point to the first non-whitespace character in the |
| 2457 | current line (which is the line in which point is located). It returns |
| 2458 | @code{nil}. |
| 2459 | @end deffn |
| 2460 | |
| 2461 | @deffn Command backward-to-indentation &optional arg |
| 2462 | @comment !!SourceFile simple.el |
| 2463 | This command moves point backward @var{arg} lines and then to the |
| 2464 | first nonblank character on that line. It returns @code{nil}. |
| 2465 | If @var{arg} is omitted or @code{nil}, it defaults to 1. |
| 2466 | @end deffn |
| 2467 | |
| 2468 | @deffn Command forward-to-indentation &optional arg |
| 2469 | @comment !!SourceFile simple.el |
| 2470 | This command moves point forward @var{arg} lines and then to the first |
| 2471 | nonblank character on that line. It returns @code{nil}. |
| 2472 | If @var{arg} is omitted or @code{nil}, it defaults to 1. |
| 2473 | @end deffn |
| 2474 | |
| 2475 | @node Case Changes |
| 2476 | @comment node-name, next, previous, up |
| 2477 | @section Case Changes |
| 2478 | @cindex case conversion in buffers |
| 2479 | |
| 2480 | The case change commands described here work on text in the current |
| 2481 | buffer. @xref{Case Conversion}, for case conversion functions that work |
| 2482 | on strings and characters. @xref{Case Tables}, for how to customize |
| 2483 | which characters are upper or lower case and how to convert them. |
| 2484 | |
| 2485 | @deffn Command capitalize-region start end |
| 2486 | This function capitalizes all words in the region defined by |
| 2487 | @var{start} and @var{end}. To capitalize means to convert each word's |
| 2488 | first character to upper case and convert the rest of each word to lower |
| 2489 | case. The function returns @code{nil}. |
| 2490 | |
| 2491 | If one end of the region is in the middle of a word, the part of the |
| 2492 | word within the region is treated as an entire word. |
| 2493 | |
| 2494 | When @code{capitalize-region} is called interactively, @var{start} and |
| 2495 | @var{end} are point and the mark, with the smallest first. |
| 2496 | |
| 2497 | @example |
| 2498 | @group |
| 2499 | ---------- Buffer: foo ---------- |
| 2500 | This is the contents of the 5th foo. |
| 2501 | ---------- Buffer: foo ---------- |
| 2502 | @end group |
| 2503 | |
| 2504 | @group |
| 2505 | (capitalize-region 1 44) |
| 2506 | @result{} nil |
| 2507 | |
| 2508 | ---------- Buffer: foo ---------- |
| 2509 | This Is The Contents Of The 5th Foo. |
| 2510 | ---------- Buffer: foo ---------- |
| 2511 | @end group |
| 2512 | @end example |
| 2513 | @end deffn |
| 2514 | |
| 2515 | @deffn Command downcase-region start end |
| 2516 | This function converts all of the letters in the region defined by |
| 2517 | @var{start} and @var{end} to lower case. The function returns |
| 2518 | @code{nil}. |
| 2519 | |
| 2520 | When @code{downcase-region} is called interactively, @var{start} and |
| 2521 | @var{end} are point and the mark, with the smallest first. |
| 2522 | @end deffn |
| 2523 | |
| 2524 | @deffn Command upcase-region start end |
| 2525 | This function converts all of the letters in the region defined by |
| 2526 | @var{start} and @var{end} to upper case. The function returns |
| 2527 | @code{nil}. |
| 2528 | |
| 2529 | When @code{upcase-region} is called interactively, @var{start} and |
| 2530 | @var{end} are point and the mark, with the smallest first. |
| 2531 | @end deffn |
| 2532 | |
| 2533 | @deffn Command capitalize-word count |
| 2534 | This function capitalizes @var{count} words after point, moving point |
| 2535 | over as it does. To capitalize means to convert each word's first |
| 2536 | character to upper case and convert the rest of each word to lower case. |
| 2537 | If @var{count} is negative, the function capitalizes the |
| 2538 | @minus{}@var{count} previous words but does not move point. The value |
| 2539 | is @code{nil}. |
| 2540 | |
| 2541 | If point is in the middle of a word, the part of the word before point |
| 2542 | is ignored when moving forward. The rest is treated as an entire word. |
| 2543 | |
| 2544 | When @code{capitalize-word} is called interactively, @var{count} is |
| 2545 | set to the numeric prefix argument. |
| 2546 | @end deffn |
| 2547 | |
| 2548 | @deffn Command downcase-word count |
| 2549 | This function converts the @var{count} words after point to all lower |
| 2550 | case, moving point over as it does. If @var{count} is negative, it |
| 2551 | converts the @minus{}@var{count} previous words but does not move point. |
| 2552 | The value is @code{nil}. |
| 2553 | |
| 2554 | When @code{downcase-word} is called interactively, @var{count} is set |
| 2555 | to the numeric prefix argument. |
| 2556 | @end deffn |
| 2557 | |
| 2558 | @deffn Command upcase-word count |
| 2559 | This function converts the @var{count} words after point to all upper |
| 2560 | case, moving point over as it does. If @var{count} is negative, it |
| 2561 | converts the @minus{}@var{count} previous words but does not move point. |
| 2562 | The value is @code{nil}. |
| 2563 | |
| 2564 | When @code{upcase-word} is called interactively, @var{count} is set to |
| 2565 | the numeric prefix argument. |
| 2566 | @end deffn |
| 2567 | |
| 2568 | @node Text Properties |
| 2569 | @section Text Properties |
| 2570 | @cindex text properties |
| 2571 | @cindex attributes of text |
| 2572 | @cindex properties of text |
| 2573 | |
| 2574 | Each character position in a buffer or a string can have a @dfn{text |
| 2575 | property list}, much like the property list of a symbol (@pxref{Property |
| 2576 | Lists}). The properties belong to a particular character at a |
| 2577 | particular place, such as, the letter @samp{T} at the beginning of this |
| 2578 | sentence or the first @samp{o} in @samp{foo}---if the same character |
| 2579 | occurs in two different places, the two occurrences in general have |
| 2580 | different properties. |
| 2581 | |
| 2582 | Each property has a name and a value. Both of these can be any Lisp |
| 2583 | object, but the name is normally a symbol. Typically each property |
| 2584 | name symbol is used for a particular purpose; for instance, the text |
| 2585 | property @code{face} specifies the faces for displaying the character |
| 2586 | (@pxref{Special Properties}). The usual way to access the property |
| 2587 | list is to specify a name and ask what value corresponds to it. |
| 2588 | |
| 2589 | If a character has a @code{category} property, we call it the |
| 2590 | @dfn{property category} of the character. It should be a symbol. The |
| 2591 | properties of the symbol serve as defaults for the properties of the |
| 2592 | character. |
| 2593 | |
| 2594 | Copying text between strings and buffers preserves the properties |
| 2595 | along with the characters; this includes such diverse functions as |
| 2596 | @code{substring}, @code{insert}, and @code{buffer-substring}. |
| 2597 | |
| 2598 | @menu |
| 2599 | * Examining Properties:: Looking at the properties of one character. |
| 2600 | * Changing Properties:: Setting the properties of a range of text. |
| 2601 | * Property Search:: Searching for where a property changes value. |
| 2602 | * Special Properties:: Particular properties with special meanings. |
| 2603 | * Format Properties:: Properties for representing formatting of text. |
| 2604 | * Sticky Properties:: How inserted text gets properties from |
| 2605 | neighboring text. |
| 2606 | * Lazy Properties:: Computing text properties in a lazy fashion |
| 2607 | only when text is examined. |
| 2608 | * Clickable Text:: Using text properties to make regions of text |
| 2609 | do something when you click on them. |
| 2610 | * Fields:: The @code{field} property defines |
| 2611 | fields within the buffer. |
| 2612 | * Not Intervals:: Why text properties do not use |
| 2613 | Lisp-visible text intervals. |
| 2614 | @end menu |
| 2615 | |
| 2616 | @node Examining Properties |
| 2617 | @subsection Examining Text Properties |
| 2618 | |
| 2619 | The simplest way to examine text properties is to ask for the value of |
| 2620 | a particular property of a particular character. For that, use |
| 2621 | @code{get-text-property}. Use @code{text-properties-at} to get the |
| 2622 | entire property list of a character. @xref{Property Search}, for |
| 2623 | functions to examine the properties of a number of characters at once. |
| 2624 | |
| 2625 | These functions handle both strings and buffers. Keep in mind that |
| 2626 | positions in a string start from 0, whereas positions in a buffer start |
| 2627 | from 1. |
| 2628 | |
| 2629 | @defun get-text-property pos prop &optional object |
| 2630 | This function returns the value of the @var{prop} property of the |
| 2631 | character after position @var{pos} in @var{object} (a buffer or |
| 2632 | string). The argument @var{object} is optional and defaults to the |
| 2633 | current buffer. |
| 2634 | |
| 2635 | If there is no @var{prop} property strictly speaking, but the character |
| 2636 | has a property category that is a symbol, then @code{get-text-property} returns |
| 2637 | the @var{prop} property of that symbol. |
| 2638 | @end defun |
| 2639 | |
| 2640 | @defun get-char-property position prop &optional object |
| 2641 | This function is like @code{get-text-property}, except that it checks |
| 2642 | overlays first and then text properties. @xref{Overlays}. |
| 2643 | |
| 2644 | The argument @var{object} may be a string, a buffer, or a window. If |
| 2645 | it is a window, then the buffer displayed in that window is used for |
| 2646 | text properties and overlays, but only the overlays active for that |
| 2647 | window are considered. If @var{object} is a buffer, then overlays in |
| 2648 | that buffer are considered first, in order of decreasing priority, |
| 2649 | followed by the text properties. If @var{object} is a string, only |
| 2650 | text properties are considered, since strings never have overlays. |
| 2651 | @end defun |
| 2652 | |
| 2653 | @defun get-char-property-and-overlay position prop &optional object |
| 2654 | This is like @code{get-char-property}, but gives extra information |
| 2655 | about the overlay that the property value comes from. |
| 2656 | |
| 2657 | Its value is a cons cell whose @sc{car} is the property value, the |
| 2658 | same value @code{get-char-property} would return with the same |
| 2659 | arguments. Its @sc{cdr} is the overlay in which the property was |
| 2660 | found, or @code{nil}, if it was found as a text property or not found |
| 2661 | at all. |
| 2662 | |
| 2663 | If @var{position} is at the end of @var{object}, both the @sc{car} and |
| 2664 | the @sc{cdr} of the value are @code{nil}. |
| 2665 | @end defun |
| 2666 | |
| 2667 | @defvar char-property-alias-alist |
| 2668 | This variable holds an alist which maps property names to a list of |
| 2669 | alternative property names. If a character does not specify a direct |
| 2670 | value for a property, the alternative property names are consulted in |
| 2671 | order; the first non-@code{nil} value is used. This variable takes |
| 2672 | precedence over @code{default-text-properties}, and @code{category} |
| 2673 | properties take precedence over this variable. |
| 2674 | @end defvar |
| 2675 | |
| 2676 | @defun text-properties-at position &optional object |
| 2677 | This function returns the entire property list of the character at |
| 2678 | @var{position} in the string or buffer @var{object}. If @var{object} is |
| 2679 | @code{nil}, it defaults to the current buffer. |
| 2680 | @end defun |
| 2681 | |
| 2682 | @defvar default-text-properties |
| 2683 | This variable holds a property list giving default values for text |
| 2684 | properties. Whenever a character does not specify a value for a |
| 2685 | property, neither directly, through a category symbol, or through |
| 2686 | @code{char-property-alias-alist}, the value stored in this list is |
| 2687 | used instead. Here is an example: |
| 2688 | |
| 2689 | @example |
| 2690 | (setq default-text-properties '(foo 69) |
| 2691 | char-property-alias-alist nil) |
| 2692 | ;; @r{Make sure character 1 has no properties of its own.} |
| 2693 | (set-text-properties 1 2 nil) |
| 2694 | ;; @r{What we get, when we ask, is the default value.} |
| 2695 | (get-text-property 1 'foo) |
| 2696 | @result{} 69 |
| 2697 | @end example |
| 2698 | @end defvar |
| 2699 | |
| 2700 | @node Changing Properties |
| 2701 | @subsection Changing Text Properties |
| 2702 | |
| 2703 | The primitives for changing properties apply to a specified range of |
| 2704 | text in a buffer or string. The function @code{set-text-properties} |
| 2705 | (see end of section) sets the entire property list of the text in that |
| 2706 | range; more often, it is useful to add, change, or delete just certain |
| 2707 | properties specified by name. |
| 2708 | |
| 2709 | Since text properties are considered part of the contents of the |
| 2710 | buffer (or string), and can affect how a buffer looks on the screen, |
| 2711 | any change in buffer text properties marks the buffer as modified. |
| 2712 | Buffer text property changes are undoable also (@pxref{Undo}). |
| 2713 | Positions in a string start from 0, whereas positions in a buffer |
| 2714 | start from 1. |
| 2715 | |
| 2716 | @defun put-text-property start end prop value &optional object |
| 2717 | This function sets the @var{prop} property to @var{value} for the text |
| 2718 | between @var{start} and @var{end} in the string or buffer @var{object}. |
| 2719 | If @var{object} is @code{nil}, it defaults to the current buffer. |
| 2720 | @end defun |
| 2721 | |
| 2722 | @defun add-text-properties start end props &optional object |
| 2723 | This function adds or overrides text properties for the text between |
| 2724 | @var{start} and @var{end} in the string or buffer @var{object}. If |
| 2725 | @var{object} is @code{nil}, it defaults to the current buffer. |
| 2726 | |
| 2727 | The argument @var{props} specifies which properties to add. It should |
| 2728 | have the form of a property list (@pxref{Property Lists}): a list whose |
| 2729 | elements include the property names followed alternately by the |
| 2730 | corresponding values. |
| 2731 | |
| 2732 | The return value is @code{t} if the function actually changed some |
| 2733 | property's value; @code{nil} otherwise (if @var{props} is @code{nil} or |
| 2734 | its values agree with those in the text). |
| 2735 | |
| 2736 | For example, here is how to set the @code{comment} and @code{face} |
| 2737 | properties of a range of text: |
| 2738 | |
| 2739 | @example |
| 2740 | (add-text-properties @var{start} @var{end} |
| 2741 | '(comment t face highlight)) |
| 2742 | @end example |
| 2743 | @end defun |
| 2744 | |
| 2745 | @defun remove-text-properties start end props &optional object |
| 2746 | This function deletes specified text properties from the text between |
| 2747 | @var{start} and @var{end} in the string or buffer @var{object}. If |
| 2748 | @var{object} is @code{nil}, it defaults to the current buffer. |
| 2749 | |
| 2750 | The argument @var{props} specifies which properties to delete. It |
| 2751 | should have the form of a property list (@pxref{Property Lists}): a list |
| 2752 | whose elements are property names alternating with corresponding values. |
| 2753 | But only the names matter---the values that accompany them are ignored. |
| 2754 | For example, here's how to remove the @code{face} property. |
| 2755 | |
| 2756 | @example |
| 2757 | (remove-text-properties @var{start} @var{end} '(face nil)) |
| 2758 | @end example |
| 2759 | |
| 2760 | The return value is @code{t} if the function actually changed some |
| 2761 | property's value; @code{nil} otherwise (if @var{props} is @code{nil} or |
| 2762 | if no character in the specified text had any of those properties). |
| 2763 | |
| 2764 | To remove all text properties from certain text, use |
| 2765 | @code{set-text-properties} and specify @code{nil} for the new property |
| 2766 | list. |
| 2767 | @end defun |
| 2768 | |
| 2769 | @defun remove-list-of-text-properties start end list-of-properties &optional object |
| 2770 | Like @code{remove-text-properties} except that |
| 2771 | @var{list-of-properties} is a list of property names only, not an |
| 2772 | alternating list of property names and values. |
| 2773 | @end defun |
| 2774 | |
| 2775 | @defun set-text-properties start end props &optional object |
| 2776 | This function completely replaces the text property list for the text |
| 2777 | between @var{start} and @var{end} in the string or buffer @var{object}. |
| 2778 | If @var{object} is @code{nil}, it defaults to the current buffer. |
| 2779 | |
| 2780 | The argument @var{props} is the new property list. It should be a list |
| 2781 | whose elements are property names alternating with corresponding values. |
| 2782 | |
| 2783 | After @code{set-text-properties} returns, all the characters in the |
| 2784 | specified range have identical properties. |
| 2785 | |
| 2786 | If @var{props} is @code{nil}, the effect is to get rid of all properties |
| 2787 | from the specified range of text. Here's an example: |
| 2788 | |
| 2789 | @example |
| 2790 | (set-text-properties @var{start} @var{end} nil) |
| 2791 | @end example |
| 2792 | |
| 2793 | Do not rely on the return value of this function. |
| 2794 | @end defun |
| 2795 | |
| 2796 | The easiest way to make a string with text properties |
| 2797 | is with @code{propertize}: |
| 2798 | |
| 2799 | @defun propertize string &rest properties |
| 2800 | This function returns a copy of @var{string} which has the text |
| 2801 | properties @var{properties}. These properties apply to all the |
| 2802 | characters in the string that is returned. Here is an example that |
| 2803 | constructs a string with a @code{face} property and a @code{mouse-face} |
| 2804 | property: |
| 2805 | |
| 2806 | @smallexample |
| 2807 | (propertize "foo" 'face 'italic |
| 2808 | 'mouse-face 'bold-italic) |
| 2809 | @result{} #("foo" 0 3 (mouse-face bold-italic face italic)) |
| 2810 | @end smallexample |
| 2811 | |
| 2812 | To put different properties on various parts of a string, you can |
| 2813 | construct each part with @code{propertize} and then combine them with |
| 2814 | @code{concat}: |
| 2815 | |
| 2816 | @smallexample |
| 2817 | (concat |
| 2818 | (propertize "foo" 'face 'italic |
| 2819 | 'mouse-face 'bold-italic) |
| 2820 | " and " |
| 2821 | (propertize "bar" 'face 'italic |
| 2822 | 'mouse-face 'bold-italic)) |
| 2823 | @result{} #("foo and bar" |
| 2824 | 0 3 (face italic mouse-face bold-italic) |
| 2825 | 3 8 nil |
| 2826 | 8 11 (face italic mouse-face bold-italic)) |
| 2827 | @end smallexample |
| 2828 | @end defun |
| 2829 | |
| 2830 | See also the function @code{buffer-substring-no-properties} |
| 2831 | (@pxref{Buffer Contents}) which copies text from the buffer |
| 2832 | but does not copy its properties. |
| 2833 | |
| 2834 | @node Property Search |
| 2835 | @subsection Text Property Search Functions |
| 2836 | |
| 2837 | In typical use of text properties, most of the time several or many |
| 2838 | consecutive characters have the same value for a property. Rather than |
| 2839 | writing your programs to examine characters one by one, it is much |
| 2840 | faster to process chunks of text that have the same property value. |
| 2841 | |
| 2842 | Here are functions you can use to do this. They use @code{eq} for |
| 2843 | comparing property values. In all cases, @var{object} defaults to the |
| 2844 | current buffer. |
| 2845 | |
| 2846 | For high performance, it's very important to use the @var{limit} |
| 2847 | argument to these functions, especially the ones that search for a |
| 2848 | single property---otherwise, they may spend a long time scanning to the |
| 2849 | end of the buffer, if the property you are interested in does not change. |
| 2850 | |
| 2851 | These functions do not move point; instead, they return a position (or |
| 2852 | @code{nil}). Remember that a position is always between two characters; |
| 2853 | the position returned by these functions is between two characters with |
| 2854 | different properties. |
| 2855 | |
| 2856 | @defun next-property-change pos &optional object limit |
| 2857 | The function scans the text forward from position @var{pos} in the |
| 2858 | string or buffer @var{object} till it finds a change in some text |
| 2859 | property, then returns the position of the change. In other words, it |
| 2860 | returns the position of the first character beyond @var{pos} whose |
| 2861 | properties are not identical to those of the character just after |
| 2862 | @var{pos}. |
| 2863 | |
| 2864 | If @var{limit} is non-@code{nil}, then the scan ends at position |
| 2865 | @var{limit}. If there is no property change before that point, |
| 2866 | @code{next-property-change} returns @var{limit}. |
| 2867 | |
| 2868 | The value is @code{nil} if the properties remain unchanged all the way |
| 2869 | to the end of @var{object} and @var{limit} is @code{nil}. If the value |
| 2870 | is non-@code{nil}, it is a position greater than or equal to @var{pos}. |
| 2871 | The value equals @var{pos} only when @var{limit} equals @var{pos}. |
| 2872 | |
| 2873 | Here is an example of how to scan the buffer by chunks of text within |
| 2874 | which all properties are constant: |
| 2875 | |
| 2876 | @smallexample |
| 2877 | (while (not (eobp)) |
| 2878 | (let ((plist (text-properties-at (point))) |
| 2879 | (next-change |
| 2880 | (or (next-property-change (point) (current-buffer)) |
| 2881 | (point-max)))) |
| 2882 | @r{Process text from point to @var{next-change}@dots{}} |
| 2883 | (goto-char next-change))) |
| 2884 | @end smallexample |
| 2885 | @end defun |
| 2886 | |
| 2887 | @defun previous-property-change pos &optional object limit |
| 2888 | This is like @code{next-property-change}, but scans back from @var{pos} |
| 2889 | instead of forward. If the value is non-@code{nil}, it is a position |
| 2890 | less than or equal to @var{pos}; it equals @var{pos} only if @var{limit} |
| 2891 | equals @var{pos}. |
| 2892 | @end defun |
| 2893 | |
| 2894 | @defun next-single-property-change pos prop &optional object limit |
| 2895 | The function scans text for a change in the @var{prop} property, then |
| 2896 | returns the position of the change. The scan goes forward from |
| 2897 | position @var{pos} in the string or buffer @var{object}. In other |
| 2898 | words, this function returns the position of the first character |
| 2899 | beyond @var{pos} whose @var{prop} property differs from that of the |
| 2900 | character just after @var{pos}. |
| 2901 | |
| 2902 | If @var{limit} is non-@code{nil}, then the scan ends at position |
| 2903 | @var{limit}. If there is no property change before that point, |
| 2904 | @code{next-single-property-change} returns @var{limit}. |
| 2905 | |
| 2906 | The value is @code{nil} if the property remains unchanged all the way to |
| 2907 | the end of @var{object} and @var{limit} is @code{nil}. If the value is |
| 2908 | non-@code{nil}, it is a position greater than or equal to @var{pos}; it |
| 2909 | equals @var{pos} only if @var{limit} equals @var{pos}. |
| 2910 | @end defun |
| 2911 | |
| 2912 | @defun previous-single-property-change pos prop &optional object limit |
| 2913 | This is like @code{next-single-property-change}, but scans back from |
| 2914 | @var{pos} instead of forward. If the value is non-@code{nil}, it is a |
| 2915 | position less than or equal to @var{pos}; it equals @var{pos} only if |
| 2916 | @var{limit} equals @var{pos}. |
| 2917 | @end defun |
| 2918 | |
| 2919 | @defun next-char-property-change pos &optional limit |
| 2920 | This is like @code{next-property-change} except that it considers |
| 2921 | overlay properties as well as text properties, and if no change is |
| 2922 | found before the end of the buffer, it returns the maximum buffer |
| 2923 | position rather than @code{nil} (in this sense, it resembles the |
| 2924 | corresponding overlay function @code{next-overlay-change}, rather than |
| 2925 | @code{next-property-change}). There is no @var{object} operand |
| 2926 | because this function operates only on the current buffer. It returns |
| 2927 | the next address at which either kind of property changes. |
| 2928 | @end defun |
| 2929 | |
| 2930 | @defun previous-char-property-change pos &optional limit |
| 2931 | This is like @code{next-char-property-change}, but scans back from |
| 2932 | @var{pos} instead of forward, and returns the minimum buffer |
| 2933 | position if no change is found. |
| 2934 | @end defun |
| 2935 | |
| 2936 | @defun next-single-char-property-change pos prop &optional object limit |
| 2937 | This is like @code{next-single-property-change} except that it |
| 2938 | considers overlay properties as well as text properties, and if no |
| 2939 | change is found before the end of the @var{object}, it returns the |
| 2940 | maximum valid position in @var{object} rather than @code{nil}. Unlike |
| 2941 | @code{next-char-property-change}, this function @emph{does} have an |
| 2942 | @var{object} operand; if @var{object} is not a buffer, only |
| 2943 | text-properties are considered. |
| 2944 | @end defun |
| 2945 | |
| 2946 | @defun previous-single-char-property-change pos prop &optional object limit |
| 2947 | This is like @code{next-single-char-property-change}, but scans back |
| 2948 | from @var{pos} instead of forward, and returns the minimum valid |
| 2949 | position in @var{object} if no change is found. |
| 2950 | @end defun |
| 2951 | |
| 2952 | @defun text-property-any start end prop value &optional object |
| 2953 | This function returns non-@code{nil} if at least one character between |
| 2954 | @var{start} and @var{end} has a property @var{prop} whose value is |
| 2955 | @var{value}. More precisely, it returns the position of the first such |
| 2956 | character. Otherwise, it returns @code{nil}. |
| 2957 | |
| 2958 | The optional fifth argument, @var{object}, specifies the string or |
| 2959 | buffer to scan. Positions are relative to @var{object}. The default |
| 2960 | for @var{object} is the current buffer. |
| 2961 | @end defun |
| 2962 | |
| 2963 | @defun text-property-not-all start end prop value &optional object |
| 2964 | This function returns non-@code{nil} if at least one character between |
| 2965 | @var{start} and @var{end} does not have a property @var{prop} with value |
| 2966 | @var{value}. More precisely, it returns the position of the first such |
| 2967 | character. Otherwise, it returns @code{nil}. |
| 2968 | |
| 2969 | The optional fifth argument, @var{object}, specifies the string or |
| 2970 | buffer to scan. Positions are relative to @var{object}. The default |
| 2971 | for @var{object} is the current buffer. |
| 2972 | @end defun |
| 2973 | |
| 2974 | @node Special Properties |
| 2975 | @subsection Properties with Special Meanings |
| 2976 | |
| 2977 | Here is a table of text property names that have special built-in |
| 2978 | meanings. The following sections list a few additional special property |
| 2979 | names that control filling and property inheritance. All other names |
| 2980 | have no standard meaning, and you can use them as you like. |
| 2981 | |
| 2982 | Note: the properties @code{composition}, @code{display}, |
| 2983 | @code{invisible} and @code{intangible} can also cause point to move to |
| 2984 | an acceptable place, after each Emacs command. @xref{Adjusting |
| 2985 | Point}. |
| 2986 | |
| 2987 | @table @code |
| 2988 | @cindex property category of text character |
| 2989 | @kindex category @r{(text property)} |
| 2990 | @item category |
| 2991 | If a character has a @code{category} property, we call it the |
| 2992 | @dfn{property category} of the character. It should be a symbol. The |
| 2993 | properties of this symbol serve as defaults for the properties of the |
| 2994 | character. |
| 2995 | |
| 2996 | @item face |
| 2997 | @cindex face codes of text |
| 2998 | @kindex face @r{(text property)} |
| 2999 | You can use the property @code{face} to control the font and color of |
| 3000 | text. @xref{Faces}, for more information. |
| 3001 | |
| 3002 | In the simplest case, the value is a face name. It can also be a list; |
| 3003 | then each element can be any of these possibilities; |
| 3004 | |
| 3005 | @itemize @bullet |
| 3006 | @item |
| 3007 | A face name (a symbol or string). |
| 3008 | |
| 3009 | @item |
| 3010 | A property list of face attributes. This has the |
| 3011 | form (@var{keyword} @var{value} @dots{}), where each @var{keyword} is a |
| 3012 | face attribute name and @var{value} is a meaningful value for that |
| 3013 | attribute. With this feature, you do not need to create a face each |
| 3014 | time you want to specify a particular attribute for certain text. |
| 3015 | @xref{Face Attributes}. |
| 3016 | |
| 3017 | @item |
| 3018 | A cons cell with the form @code{(foreground-color . @var{color-name})} |
| 3019 | or @code{(background-color . @var{color-name})}. These are old, |
| 3020 | deprecated equivalents for @code{(:foreground @var{color-name})} and |
| 3021 | @code{(:background @var{color-name})}. Please convert code that uses |
| 3022 | them. |
| 3023 | @end itemize |
| 3024 | |
| 3025 | It works to use the latter two forms directly as the value |
| 3026 | of the @code{face} property. |
| 3027 | |
| 3028 | Font Lock mode (@pxref{Font Lock Mode}) works in most buffers by |
| 3029 | dynamically updating the @code{face} property of characters based on |
| 3030 | the context. |
| 3031 | |
| 3032 | @item font-lock-face |
| 3033 | @kindex font-lock-face @r{(text property)} |
| 3034 | The @code{font-lock-face} property is equivalent to the @code{face} |
| 3035 | property when Font Lock mode is enabled. When Font Lock mode is disabled, |
| 3036 | @code{font-lock-face} has no effect. |
| 3037 | |
| 3038 | The @code{font-lock-face} property is useful for special modes that |
| 3039 | implement their own highlighting. @xref{Precalculated Fontification}. |
| 3040 | |
| 3041 | @item mouse-face |
| 3042 | @kindex mouse-face @r{(text property)} |
| 3043 | The property @code{mouse-face} is used instead of @code{face} when the |
| 3044 | mouse is on or near the character. For this purpose, ``near'' means |
| 3045 | that all text between the character and where the mouse is have the same |
| 3046 | @code{mouse-face} property value. |
| 3047 | |
| 3048 | @item fontified |
| 3049 | @kindex fontified @r{(text property)} |
| 3050 | This property says whether the text is ready for display. If |
| 3051 | @code{nil}, Emacs's redisplay routine calls the functions in |
| 3052 | @code{fontification-functions} (@pxref{Auto Faces}) to prepare this |
| 3053 | part of the buffer before it is displayed. It is used internally by |
| 3054 | the ``just in time'' font locking code. |
| 3055 | |
| 3056 | @item display |
| 3057 | This property activates various features that change the |
| 3058 | way text is displayed. For example, it can make text appear taller |
| 3059 | or shorter, higher or lower, wider or narrow, or replaced with an image. |
| 3060 | @xref{Display Property}. |
| 3061 | |
| 3062 | @item help-echo |
| 3063 | @kindex help-echo @r{(text property)} |
| 3064 | @cindex tooltip |
| 3065 | @anchor{Text help-echo} |
| 3066 | If text has a string as its @code{help-echo} property, then when you |
| 3067 | move the mouse onto that text, Emacs displays that string in the echo |
| 3068 | area, or in the tooltip window (@pxref{Tooltips,,, emacs, The GNU Emacs |
| 3069 | Manual}). |
| 3070 | |
| 3071 | If the value of the @code{help-echo} property is a function, that |
| 3072 | function is called with three arguments, @var{window}, @var{object} and |
| 3073 | @var{pos} and should return a help string or @code{nil} for |
| 3074 | none. The first argument, @var{window} is the window in which |
| 3075 | the help was found. The second, @var{object}, is the buffer, overlay or |
| 3076 | string which had the @code{help-echo} property. The @var{pos} |
| 3077 | argument is as follows: |
| 3078 | |
| 3079 | @itemize @bullet{} |
| 3080 | @item |
| 3081 | If @var{object} is a buffer, @var{pos} is the position in the buffer. |
| 3082 | @item |
| 3083 | If @var{object} is an overlay, that overlay has a @code{help-echo} |
| 3084 | property, and @var{pos} is the position in the overlay's buffer. |
| 3085 | @item |
| 3086 | If @var{object} is a string (an overlay string or a string displayed |
| 3087 | with the @code{display} property), @var{pos} is the position in that |
| 3088 | string. |
| 3089 | @end itemize |
| 3090 | |
| 3091 | If the value of the @code{help-echo} property is neither a function nor |
| 3092 | a string, it is evaluated to obtain a help string. |
| 3093 | |
| 3094 | You can alter the way help text is displayed by setting the variable |
| 3095 | @code{show-help-function} (@pxref{Help display}). |
| 3096 | |
| 3097 | This feature is used in the mode line and for other active text. |
| 3098 | |
| 3099 | @item keymap |
| 3100 | @cindex keymap of character |
| 3101 | @kindex keymap @r{(text property)} |
| 3102 | The @code{keymap} property specifies an additional keymap for |
| 3103 | commands. When this keymap applies, it is used for key lookup before |
| 3104 | the minor mode keymaps and before the buffer's local map. |
| 3105 | @xref{Active Keymaps}. If the property value is a symbol, the |
| 3106 | symbol's function definition is used as the keymap. |
| 3107 | |
| 3108 | The property's value for the character before point applies if it is |
| 3109 | non-@code{nil} and rear-sticky, and the property's value for the |
| 3110 | character after point applies if it is non-@code{nil} and |
| 3111 | front-sticky. (For mouse clicks, the position of the click is used |
| 3112 | instead of the position of point.) |
| 3113 | |
| 3114 | @item local-map |
| 3115 | @kindex local-map @r{(text property)} |
| 3116 | This property works like @code{keymap} except that it specifies a |
| 3117 | keymap to use @emph{instead of} the buffer's local map. For most |
| 3118 | purposes (perhaps all purposes), it is better to use the @code{keymap} |
| 3119 | property. |
| 3120 | |
| 3121 | @item syntax-table |
| 3122 | The @code{syntax-table} property overrides what the syntax table says |
| 3123 | about this particular character. @xref{Syntax Properties}. |
| 3124 | |
| 3125 | @item read-only |
| 3126 | @cindex read-only character |
| 3127 | @kindex read-only @r{(text property)} |
| 3128 | If a character has the property @code{read-only}, then modifying that |
| 3129 | character is not allowed. Any command that would do so gets an error, |
| 3130 | @code{text-read-only}. If the property value is a string, that string |
| 3131 | is used as the error message. |
| 3132 | |
| 3133 | Insertion next to a read-only character is an error if inserting |
| 3134 | ordinary text there would inherit the @code{read-only} property due to |
| 3135 | stickiness. Thus, you can control permission to insert next to |
| 3136 | read-only text by controlling the stickiness. @xref{Sticky Properties}. |
| 3137 | |
| 3138 | Since changing properties counts as modifying the buffer, it is not |
| 3139 | possible to remove a @code{read-only} property unless you know the |
| 3140 | special trick: bind @code{inhibit-read-only} to a non-@code{nil} value |
| 3141 | and then remove the property. @xref{Read Only Buffers}. |
| 3142 | |
| 3143 | @item invisible |
| 3144 | @kindex invisible @r{(text property)} |
| 3145 | A non-@code{nil} @code{invisible} property can make a character invisible |
| 3146 | on the screen. @xref{Invisible Text}, for details. |
| 3147 | |
| 3148 | @item intangible |
| 3149 | @kindex intangible @r{(text property)} |
| 3150 | If a group of consecutive characters have equal and non-@code{nil} |
| 3151 | @code{intangible} properties, then you cannot place point between them. |
| 3152 | If you try to move point forward into the group, point actually moves to |
| 3153 | the end of the group. If you try to move point backward into the group, |
| 3154 | point actually moves to the start of the group. |
| 3155 | |
| 3156 | If consecutive characters have unequal non-@code{nil} |
| 3157 | @code{intangible} properties, they belong to separate groups; each |
| 3158 | group is separately treated as described above. |
| 3159 | |
| 3160 | When the variable @code{inhibit-point-motion-hooks} is non-@code{nil}, |
| 3161 | the @code{intangible} property is ignored. |
| 3162 | |
| 3163 | @item field |
| 3164 | @kindex field @r{(text property)} |
| 3165 | Consecutive characters with the same @code{field} property constitute a |
| 3166 | @dfn{field}. Some motion functions including @code{forward-word} and |
| 3167 | @code{beginning-of-line} stop moving at a field boundary. |
| 3168 | @xref{Fields}. |
| 3169 | |
| 3170 | @item cursor |
| 3171 | @kindex cursor @r{(text property)} |
| 3172 | Normally, the cursor is displayed at the end of any overlay and text |
| 3173 | property strings present at the current buffer position. You can |
| 3174 | place the cursor on any desired character of these strings by giving |
| 3175 | that character a non-@code{nil} @code{cursor} text property. In |
| 3176 | addition, if the value of the @code{cursor} property of an overlay |
| 3177 | string is an integer number, it specifies the number of buffer's |
| 3178 | character positions associated with the overlay string; this way, |
| 3179 | Emacs will display the cursor on the character with that property |
| 3180 | regardless of whether the current buffer position is actually covered |
| 3181 | by the overlay. Specifically, if the value of the @code{cursor} |
| 3182 | property of a character is the number @var{n}, the cursor will be |
| 3183 | displayed on this character for any buffer position in the range |
| 3184 | @code{[@var{ovpos}..@var{ovpos}+@var{n}]}, where @var{ovpos} is the |
| 3185 | starting buffer position covered by the overlay (@pxref{Managing |
| 3186 | Overlays}). |
| 3187 | |
| 3188 | @item pointer |
| 3189 | @kindex pointer @r{(text property)} |
| 3190 | This specifies a specific pointer shape when the mouse pointer is over |
| 3191 | this text or image. @xref{Pointer Shape}, for possible pointer |
| 3192 | shapes. |
| 3193 | |
| 3194 | @item line-spacing |
| 3195 | @kindex line-spacing @r{(text property)} |
| 3196 | A newline can have a @code{line-spacing} text or overlay property that |
| 3197 | controls the height of the display line ending with that newline. The |
| 3198 | property value overrides the default frame line spacing and the buffer |
| 3199 | local @code{line-spacing} variable. @xref{Line Height}. |
| 3200 | |
| 3201 | @item line-height |
| 3202 | @kindex line-height @r{(text property)} |
| 3203 | A newline can have a @code{line-height} text or overlay property that |
| 3204 | controls the total height of the display line ending in that newline. |
| 3205 | @xref{Line Height}. |
| 3206 | |
| 3207 | @item wrap-prefix |
| 3208 | If text has a @code{wrap-prefix} property, the prefix it defines will |
| 3209 | be added at display-time to the beginning of every continuation line |
| 3210 | due to text wrapping (so if lines are truncated, the wrap-prefix is |
| 3211 | never used). It may be a string, an image, or a stretch-glyph such as |
| 3212 | used by the @code{display} text-property. @xref{Display Property}. |
| 3213 | |
| 3214 | A wrap-prefix may also be specified for an entire buffer using the |
| 3215 | @code{wrap-prefix} buffer-local variable (however, a |
| 3216 | @code{wrap-prefix} text-property takes precedence over the value of |
| 3217 | the @code{wrap-prefix} variable). @xref{Truncation}. |
| 3218 | |
| 3219 | @item line-prefix |
| 3220 | If text has a @code{line-prefix} property, the prefix it defines will |
| 3221 | be added at display-time to the beginning of every non-continuation |
| 3222 | line. It may be a string, an image, or a stretch-glyph such as used |
| 3223 | by the @code{display} text-property. @xref{Display Property}. |
| 3224 | |
| 3225 | A line-prefix may also be specified for an entire buffer using the |
| 3226 | @code{line-prefix} buffer-local variable (however, a |
| 3227 | @code{line-prefix} text-property takes precedence over the value of |
| 3228 | the @code{line-prefix} variable). @xref{Truncation}. |
| 3229 | |
| 3230 | @item modification-hooks |
| 3231 | @cindex change hooks for a character |
| 3232 | @cindex hooks for changing a character |
| 3233 | @kindex modification-hooks @r{(text property)} |
| 3234 | If a character has the property @code{modification-hooks}, then its |
| 3235 | value should be a list of functions; modifying that character calls all |
| 3236 | of those functions. Each function receives two arguments: the beginning |
| 3237 | and end of the part of the buffer being modified. Note that if a |
| 3238 | particular modification hook function appears on several characters |
| 3239 | being modified by a single primitive, you can't predict how many times |
| 3240 | the function will be called. |
| 3241 | |
| 3242 | If these functions modify the buffer, they should bind |
| 3243 | @code{inhibit-modification-hooks} to @code{t} around doing so, to |
| 3244 | avoid confusing the internal mechanism that calls these hooks. |
| 3245 | |
| 3246 | Overlays also support the @code{modification-hooks} property, but the |
| 3247 | details are somewhat different (@pxref{Overlay Properties}). |
| 3248 | |
| 3249 | @item insert-in-front-hooks |
| 3250 | @itemx insert-behind-hooks |
| 3251 | @kindex insert-in-front-hooks @r{(text property)} |
| 3252 | @kindex insert-behind-hooks @r{(text property)} |
| 3253 | The operation of inserting text in a buffer also calls the functions |
| 3254 | listed in the @code{insert-in-front-hooks} property of the following |
| 3255 | character and in the @code{insert-behind-hooks} property of the |
| 3256 | preceding character. These functions receive two arguments, the |
| 3257 | beginning and end of the inserted text. The functions are called |
| 3258 | @emph{after} the actual insertion takes place. |
| 3259 | |
| 3260 | See also @ref{Change Hooks}, for other hooks that are called |
| 3261 | when you change text in a buffer. |
| 3262 | |
| 3263 | @item point-entered |
| 3264 | @itemx point-left |
| 3265 | @cindex hooks for motion of point |
| 3266 | @kindex point-entered @r{(text property)} |
| 3267 | @kindex point-left @r{(text property)} |
| 3268 | The special properties @code{point-entered} and @code{point-left} |
| 3269 | record hook functions that report motion of point. Each time point |
| 3270 | moves, Emacs compares these two property values: |
| 3271 | |
| 3272 | @itemize @bullet |
| 3273 | @item |
| 3274 | the @code{point-left} property of the character after the old location, |
| 3275 | and |
| 3276 | @item |
| 3277 | the @code{point-entered} property of the character after the new |
| 3278 | location. |
| 3279 | @end itemize |
| 3280 | |
| 3281 | @noindent |
| 3282 | If these two values differ, each of them is called (if not @code{nil}) |
| 3283 | with two arguments: the old value of point, and the new one. |
| 3284 | |
| 3285 | The same comparison is made for the characters before the old and new |
| 3286 | locations. The result may be to execute two @code{point-left} functions |
| 3287 | (which may be the same function) and/or two @code{point-entered} |
| 3288 | functions (which may be the same function). In any case, all the |
| 3289 | @code{point-left} functions are called first, followed by all the |
| 3290 | @code{point-entered} functions. |
| 3291 | |
| 3292 | It is possible with @code{char-after} to examine characters at various |
| 3293 | buffer positions without moving point to those positions. Only an |
| 3294 | actual change in the value of point runs these hook functions. |
| 3295 | |
| 3296 | @defvar inhibit-point-motion-hooks |
| 3297 | When this variable is non-@code{nil}, @code{point-left} and |
| 3298 | @code{point-entered} hooks are not run, and the @code{intangible} |
| 3299 | property has no effect. Do not set this variable globally; bind it with |
| 3300 | @code{let}. |
| 3301 | @end defvar |
| 3302 | |
| 3303 | @defvar show-help-function |
| 3304 | @anchor{Help display} If this variable is non-@code{nil}, it specifies a |
| 3305 | function called to display help strings. These may be @code{help-echo} |
| 3306 | properties, menu help strings (@pxref{Simple Menu Items}, |
| 3307 | @pxref{Extended Menu Items}), or tool bar help strings (@pxref{Tool |
| 3308 | Bar}). The specified function is called with one argument, the help |
| 3309 | string to display. Tooltip mode (@pxref{Tooltips,,, emacs, The GNU Emacs |
| 3310 | Manual}) provides an example. |
| 3311 | @end defvar |
| 3312 | |
| 3313 | @item composition |
| 3314 | @kindex composition @r{(text property)} |
| 3315 | This text property is used to display a sequence of characters as a |
| 3316 | single glyph composed from components. But the value of the property |
| 3317 | itself is completely internal to Emacs and should not be manipulated |
| 3318 | directly by, for instance, @code{put-text-property}. |
| 3319 | |
| 3320 | @end table |
| 3321 | |
| 3322 | @node Format Properties |
| 3323 | @subsection Formatted Text Properties |
| 3324 | |
| 3325 | These text properties affect the behavior of the fill commands. They |
| 3326 | are used for representing formatted text. @xref{Filling}, and |
| 3327 | @ref{Margins}. |
| 3328 | |
| 3329 | @table @code |
| 3330 | @item hard |
| 3331 | If a newline character has this property, it is a ``hard'' newline. |
| 3332 | The fill commands do not alter hard newlines and do not move words |
| 3333 | across them. However, this property takes effect only if the |
| 3334 | @code{use-hard-newlines} minor mode is enabled. @xref{Hard and Soft |
| 3335 | Newlines,, Hard and Soft Newlines, emacs, The GNU Emacs Manual}. |
| 3336 | |
| 3337 | @item right-margin |
| 3338 | This property specifies an extra right margin for filling this part of the |
| 3339 | text. |
| 3340 | |
| 3341 | @item left-margin |
| 3342 | This property specifies an extra left margin for filling this part of the |
| 3343 | text. |
| 3344 | |
| 3345 | @item justification |
| 3346 | This property specifies the style of justification for filling this part |
| 3347 | of the text. |
| 3348 | @end table |
| 3349 | |
| 3350 | @node Sticky Properties |
| 3351 | @subsection Stickiness of Text Properties |
| 3352 | @cindex sticky text properties |
| 3353 | @cindex inheritance of text properties |
| 3354 | |
| 3355 | Self-inserting characters normally take on the same properties as the |
| 3356 | preceding character. This is called @dfn{inheritance} of properties. |
| 3357 | |
| 3358 | In a Lisp program, you can do insertion with inheritance or without, |
| 3359 | depending on your choice of insertion primitive. The ordinary text |
| 3360 | insertion functions such as @code{insert} do not inherit any properties. |
| 3361 | They insert text with precisely the properties of the string being |
| 3362 | inserted, and no others. This is correct for programs that copy text |
| 3363 | from one context to another---for example, into or out of the kill ring. |
| 3364 | To insert with inheritance, use the special primitives described in this |
| 3365 | section. Self-inserting characters inherit properties because they work |
| 3366 | using these primitives. |
| 3367 | |
| 3368 | When you do insertion with inheritance, @emph{which} properties are |
| 3369 | inherited, and from where, depends on which properties are @dfn{sticky}. |
| 3370 | Insertion after a character inherits those of its properties that are |
| 3371 | @dfn{rear-sticky}. Insertion before a character inherits those of its |
| 3372 | properties that are @dfn{front-sticky}. When both sides offer different |
| 3373 | sticky values for the same property, the previous character's value |
| 3374 | takes precedence. |
| 3375 | |
| 3376 | By default, a text property is rear-sticky but not front-sticky; thus, |
| 3377 | the default is to inherit all the properties of the preceding character, |
| 3378 | and nothing from the following character. |
| 3379 | |
| 3380 | You can control the stickiness of various text properties with two |
| 3381 | specific text properties, @code{front-sticky} and @code{rear-nonsticky}, |
| 3382 | and with the variable @code{text-property-default-nonsticky}. You can |
| 3383 | use the variable to specify a different default for a given property. |
| 3384 | You can use those two text properties to make any specific properties |
| 3385 | sticky or nonsticky in any particular part of the text. |
| 3386 | |
| 3387 | If a character's @code{front-sticky} property is @code{t}, then all |
| 3388 | its properties are front-sticky. If the @code{front-sticky} property is |
| 3389 | a list, then the sticky properties of the character are those whose |
| 3390 | names are in the list. For example, if a character has a |
| 3391 | @code{front-sticky} property whose value is @code{(face read-only)}, |
| 3392 | then insertion before the character can inherit its @code{face} property |
| 3393 | and its @code{read-only} property, but no others. |
| 3394 | |
| 3395 | The @code{rear-nonsticky} property works the opposite way. Most |
| 3396 | properties are rear-sticky by default, so the @code{rear-nonsticky} |
| 3397 | property says which properties are @emph{not} rear-sticky. If a |
| 3398 | character's @code{rear-nonsticky} property is @code{t}, then none of its |
| 3399 | properties are rear-sticky. If the @code{rear-nonsticky} property is a |
| 3400 | list, properties are rear-sticky @emph{unless} their names are in the |
| 3401 | list. |
| 3402 | |
| 3403 | @defvar text-property-default-nonsticky |
| 3404 | This variable holds an alist which defines the default rear-stickiness |
| 3405 | of various text properties. Each element has the form |
| 3406 | @code{(@var{property} . @var{nonstickiness})}, and it defines the |
| 3407 | stickiness of a particular text property, @var{property}. |
| 3408 | |
| 3409 | If @var{nonstickiness} is non-@code{nil}, this means that the property |
| 3410 | @var{property} is rear-nonsticky by default. Since all properties are |
| 3411 | front-nonsticky by default, this makes @var{property} nonsticky in both |
| 3412 | directions by default. |
| 3413 | |
| 3414 | The text properties @code{front-sticky} and @code{rear-nonsticky}, when |
| 3415 | used, take precedence over the default @var{nonstickiness} specified in |
| 3416 | @code{text-property-default-nonsticky}. |
| 3417 | @end defvar |
| 3418 | |
| 3419 | Here are the functions that insert text with inheritance of properties: |
| 3420 | |
| 3421 | @defun insert-and-inherit &rest strings |
| 3422 | Insert the strings @var{strings}, just like the function @code{insert}, |
| 3423 | but inherit any sticky properties from the adjoining text. |
| 3424 | @end defun |
| 3425 | |
| 3426 | @defun insert-before-markers-and-inherit &rest strings |
| 3427 | Insert the strings @var{strings}, just like the function |
| 3428 | @code{insert-before-markers}, but inherit any sticky properties from the |
| 3429 | adjoining text. |
| 3430 | @end defun |
| 3431 | |
| 3432 | @xref{Insertion}, for the ordinary insertion functions which do not |
| 3433 | inherit. |
| 3434 | |
| 3435 | @node Lazy Properties |
| 3436 | @subsection Lazy Computation of Text Properties |
| 3437 | |
| 3438 | Instead of computing text properties for all the text in the buffer, |
| 3439 | you can arrange to compute the text properties for parts of the text |
| 3440 | when and if something depends on them. |
| 3441 | |
| 3442 | The primitive that extracts text from the buffer along with its |
| 3443 | properties is @code{buffer-substring}. Before examining the properties, |
| 3444 | this function runs the abnormal hook @code{buffer-access-fontify-functions}. |
| 3445 | |
| 3446 | @defvar buffer-access-fontify-functions |
| 3447 | This variable holds a list of functions for computing text properties. |
| 3448 | Before @code{buffer-substring} copies the text and text properties for a |
| 3449 | portion of the buffer, it calls all the functions in this list. Each of |
| 3450 | the functions receives two arguments that specify the range of the |
| 3451 | buffer being accessed. (The buffer itself is always the current |
| 3452 | buffer.) |
| 3453 | @end defvar |
| 3454 | |
| 3455 | The function @code{buffer-substring-no-properties} does not call these |
| 3456 | functions, since it ignores text properties anyway. |
| 3457 | |
| 3458 | In order to prevent the hook functions from being called more than |
| 3459 | once for the same part of the buffer, you can use the variable |
| 3460 | @code{buffer-access-fontified-property}. |
| 3461 | |
| 3462 | @defvar buffer-access-fontified-property |
| 3463 | If this variable's value is non-@code{nil}, it is a symbol which is used |
| 3464 | as a text property name. A non-@code{nil} value for that text property |
| 3465 | means, ``the other text properties for this character have already been |
| 3466 | computed.'' |
| 3467 | |
| 3468 | If all the characters in the range specified for @code{buffer-substring} |
| 3469 | have a non-@code{nil} value for this property, @code{buffer-substring} |
| 3470 | does not call the @code{buffer-access-fontify-functions} functions. It |
| 3471 | assumes these characters already have the right text properties, and |
| 3472 | just copies the properties they already have. |
| 3473 | |
| 3474 | The normal way to use this feature is that the |
| 3475 | @code{buffer-access-fontify-functions} functions add this property, as |
| 3476 | well as others, to the characters they operate on. That way, they avoid |
| 3477 | being called over and over for the same text. |
| 3478 | @end defvar |
| 3479 | |
| 3480 | @node Clickable Text |
| 3481 | @subsection Defining Clickable Text |
| 3482 | @cindex clickable text |
| 3483 | @cindex follow links |
| 3484 | @cindex mouse-1 |
| 3485 | |
| 3486 | @dfn{Clickable text} is text that can be clicked, with either the |
| 3487 | mouse or via a keyboard command, to produce some result. Many major |
| 3488 | modes use clickable text to implement textual hyper-links, or |
| 3489 | @dfn{links} for short. |
| 3490 | |
| 3491 | The easiest way to insert and manipulate links is to use the |
| 3492 | @code{button} package. @xref{Buttons}. In this section, we will |
| 3493 | explain how to manually set up clickable text in a buffer, using text |
| 3494 | properties. For simplicity, we will refer to the clickable text as a |
| 3495 | @dfn{link}. |
| 3496 | |
| 3497 | Implementing a link involves three separate steps: (1) indicating |
| 3498 | clickability when the mouse moves over the link; (2) making @kbd{RET} |
| 3499 | or @kbd{Mouse-2} on that link do something; and (3) setting up a |
| 3500 | @code{follow-link} condition so that the link obeys |
| 3501 | @code{mouse-1-click-follows-link}. |
| 3502 | |
| 3503 | To indicate clickability, add the @code{mouse-face} text property to |
| 3504 | the text of the link; then Emacs will highlight the link when the |
| 3505 | mouse moves over it. In addition, you should define a tooltip or echo |
| 3506 | area message, using the @code{help-echo} text property. @xref{Special |
| 3507 | Properties}. For instance, here is how Dired indicates that file |
| 3508 | names are clickable: |
| 3509 | |
| 3510 | @smallexample |
| 3511 | (if (dired-move-to-filename) |
| 3512 | (add-text-properties |
| 3513 | (point) |
| 3514 | (save-excursion |
| 3515 | (dired-move-to-end-of-filename) |
| 3516 | (point)) |
| 3517 | '(mouse-face highlight |
| 3518 | help-echo "mouse-2: visit this file in other window"))) |
| 3519 | @end smallexample |
| 3520 | |
| 3521 | To make the link clickable, bind @key{RET} and @kbd{Mouse-2} to |
| 3522 | commands that perform the desired action. Each command should check |
| 3523 | to see whether it was called on a link, and act accordingly. For |
| 3524 | instance, Dired's major mode keymap binds @kbd{Mouse-2} to the |
| 3525 | following command: |
| 3526 | |
| 3527 | @smallexample |
| 3528 | (defun dired-mouse-find-file-other-window (event) |
| 3529 | "In Dired, visit the file or directory name you click on." |
| 3530 | (interactive "e") |
| 3531 | (let ((window (posn-window (event-end event))) |
| 3532 | (pos (posn-point (event-end event))) |
| 3533 | file) |
| 3534 | (if (not (windowp window)) |
| 3535 | (error "No file chosen")) |
| 3536 | (with-current-buffer (window-buffer window) |
| 3537 | (goto-char pos) |
| 3538 | (setq file (dired-get-file-for-visit))) |
| 3539 | (if (file-directory-p file) |
| 3540 | (or (and (cdr dired-subdir-alist) |
| 3541 | (dired-goto-subdir file)) |
| 3542 | (progn |
| 3543 | (select-window window) |
| 3544 | (dired-other-window file))) |
| 3545 | (select-window window) |
| 3546 | (find-file-other-window (file-name-sans-versions file t))))) |
| 3547 | @end smallexample |
| 3548 | |
| 3549 | @noindent |
| 3550 | This command uses the functions @code{posn-window} and |
| 3551 | @code{posn-point} to determine where the click occurred, and |
| 3552 | @code{dired-get-file-for-visit} to determine which file to visit. |
| 3553 | |
| 3554 | Instead of binding the mouse command in a major mode keymap, you can |
| 3555 | bind it within the link text, using the @code{keymap} text property |
| 3556 | (@pxref{Special Properties}). For instance: |
| 3557 | |
| 3558 | @example |
| 3559 | (let ((map (make-sparse-keymap))) |
| 3560 | (define-key map [mouse-2] 'operate-this-button) |
| 3561 | (put-text-property link-start link-end 'keymap map)) |
| 3562 | @end example |
| 3563 | |
| 3564 | @noindent |
| 3565 | With this method, you can easily define different commands for |
| 3566 | different links. Furthermore, the global definition of @key{RET} and |
| 3567 | @kbd{Mouse-2} remain available for the rest of the text in the buffer. |
| 3568 | |
| 3569 | @vindex mouse-1-click-follows-link |
| 3570 | The basic Emacs command for clicking on links is @kbd{Mouse-2}. |
| 3571 | However, for compatibility with other graphical applications, Emacs |
| 3572 | also recognizes @kbd{Mouse-1} clicks on links, provided the user |
| 3573 | clicks on the link quickly without moving the mouse. This behavior is |
| 3574 | controlled by the user option @code{mouse-1-click-follows-link}. |
| 3575 | @xref{Mouse References,,, emacs, The GNU Emacs Manual}. |
| 3576 | |
| 3577 | To set up the link so that it obeys |
| 3578 | @code{mouse-1-click-follows-link}, you must either (1) apply a |
| 3579 | @code{follow-link} text or overlay property to the link text, or (2) |
| 3580 | bind the @code{follow-link} event to a keymap (which can be a major |
| 3581 | mode keymap or a local keymap specified via the @code{keymap} text |
| 3582 | property). The value of the @code{follow-link} property, or the |
| 3583 | binding for the @code{follow-link} event, acts as a ``condition'' for |
| 3584 | the link action. This condition tells Emacs two things: the |
| 3585 | circumstances under which a @kbd{Mouse-1} click should be regarded as |
| 3586 | occurring ``inside'' the link, and how to compute an ``action code'' |
| 3587 | that says what to translate the @kbd{Mouse-1} click into. The link |
| 3588 | action condition can be one of the following: |
| 3589 | |
| 3590 | @table @asis |
| 3591 | @item @code{mouse-face} |
| 3592 | If the condition is the symbol @code{mouse-face}, a position is inside |
| 3593 | a link if there is a non-@code{nil} @code{mouse-face} property at that |
| 3594 | position. The action code is always @code{t}. |
| 3595 | |
| 3596 | For example, here is how Info mode handles @key{Mouse-1}: |
| 3597 | |
| 3598 | @smallexample |
| 3599 | (define-key Info-mode-map [follow-link] 'mouse-face) |
| 3600 | @end smallexample |
| 3601 | |
| 3602 | @item a function |
| 3603 | If the condition is a function, @var{func}, then a position @var{pos} |
| 3604 | is inside a link if @code{(@var{func} @var{pos})} evaluates to |
| 3605 | non-@code{nil}. The value returned by @var{func} serves as the action |
| 3606 | code. |
| 3607 | |
| 3608 | For example, here is how pcvs enables @kbd{Mouse-1} to follow links on |
| 3609 | file names only: |
| 3610 | |
| 3611 | @smallexample |
| 3612 | (define-key map [follow-link] |
| 3613 | (lambda (pos) |
| 3614 | (eq (get-char-property pos 'face) 'cvs-filename-face))) |
| 3615 | @end smallexample |
| 3616 | |
| 3617 | @item anything else |
| 3618 | If the condition value is anything else, then the position is inside a |
| 3619 | link and the condition itself is the action code. Clearly, you should |
| 3620 | specify this kind of condition only when applying the condition via a |
| 3621 | text or property overlay on the link text (so that it does not apply |
| 3622 | to the entire buffer). |
| 3623 | @end table |
| 3624 | |
| 3625 | @noindent |
| 3626 | The action code tells @kbd{Mouse-1} how to follow the link: |
| 3627 | |
| 3628 | @table @asis |
| 3629 | @item a string or vector |
| 3630 | If the action code is a string or vector, the @kbd{Mouse-1} event is |
| 3631 | translated into the first element of the string or vector; i.e., the |
| 3632 | action of the @kbd{Mouse-1} click is the local or global binding of |
| 3633 | that character or symbol. Thus, if the action code is @code{"foo"}, |
| 3634 | @kbd{Mouse-1} translates into @kbd{f}. If it is @code{[foo]}, |
| 3635 | @kbd{Mouse-1} translates into @key{foo}. |
| 3636 | |
| 3637 | @item anything else |
| 3638 | For any other non-@code{nil} action code, the @kbd{Mouse-1} event is |
| 3639 | translated into a @kbd{Mouse-2} event at the same position. |
| 3640 | @end table |
| 3641 | |
| 3642 | To define @kbd{Mouse-1} to activate a button defined with |
| 3643 | @code{define-button-type}, give the button a @code{follow-link} |
| 3644 | property. The property value should be a link action condition, as |
| 3645 | described above. @xref{Buttons}. For example, here is how Help mode |
| 3646 | handles @kbd{Mouse-1}: |
| 3647 | |
| 3648 | @smallexample |
| 3649 | (define-button-type 'help-xref |
| 3650 | 'follow-link t |
| 3651 | 'action #'help-button-action) |
| 3652 | @end smallexample |
| 3653 | |
| 3654 | To define @kbd{Mouse-1} on a widget defined with |
| 3655 | @code{define-widget}, give the widget a @code{:follow-link} property. |
| 3656 | The property value should be a link action condition, as described |
| 3657 | above. For example, here is how the @code{link} widget specifies that |
| 3658 | a @key{Mouse-1} click shall be translated to @key{RET}: |
| 3659 | |
| 3660 | @smallexample |
| 3661 | (define-widget 'link 'item |
| 3662 | "An embedded link." |
| 3663 | :button-prefix 'widget-link-prefix |
| 3664 | :button-suffix 'widget-link-suffix |
| 3665 | :follow-link "\C-m" |
| 3666 | :help-echo "Follow the link." |
| 3667 | :format "%[%t%]") |
| 3668 | @end smallexample |
| 3669 | |
| 3670 | @defun mouse-on-link-p pos |
| 3671 | This function returns non-@code{nil} if position @var{pos} in the |
| 3672 | current buffer is on a link. @var{pos} can also be a mouse event |
| 3673 | location, as returned by @code{event-start} (@pxref{Accessing Mouse}). |
| 3674 | @end defun |
| 3675 | |
| 3676 | @node Fields |
| 3677 | @subsection Defining and Using Fields |
| 3678 | @cindex fields |
| 3679 | |
| 3680 | A field is a range of consecutive characters in the buffer that are |
| 3681 | identified by having the same value (comparing with @code{eq}) of the |
| 3682 | @code{field} property (either a text-property or an overlay property). |
| 3683 | This section describes special functions that are available for |
| 3684 | operating on fields. |
| 3685 | |
| 3686 | You specify a field with a buffer position, @var{pos}. We think of |
| 3687 | each field as containing a range of buffer positions, so the position |
| 3688 | you specify stands for the field containing that position. |
| 3689 | |
| 3690 | When the characters before and after @var{pos} are part of the same |
| 3691 | field, there is no doubt which field contains @var{pos}: the one those |
| 3692 | characters both belong to. When @var{pos} is at a boundary between |
| 3693 | fields, which field it belongs to depends on the stickiness of the |
| 3694 | @code{field} properties of the two surrounding characters (@pxref{Sticky |
| 3695 | Properties}). The field whose property would be inherited by text |
| 3696 | inserted at @var{pos} is the field that contains @var{pos}. |
| 3697 | |
| 3698 | There is an anomalous case where newly inserted text at @var{pos} |
| 3699 | would not inherit the @code{field} property from either side. This |
| 3700 | happens if the previous character's @code{field} property is not |
| 3701 | rear-sticky, and the following character's @code{field} property is not |
| 3702 | front-sticky. In this case, @var{pos} belongs to neither the preceding |
| 3703 | field nor the following field; the field functions treat it as belonging |
| 3704 | to an empty field whose beginning and end are both at @var{pos}. |
| 3705 | |
| 3706 | In all of these functions, if @var{pos} is omitted or @code{nil}, the |
| 3707 | value of point is used by default. If narrowing is in effect, then |
| 3708 | @var{pos} should fall within the accessible portion. @xref{Narrowing}. |
| 3709 | |
| 3710 | @defun field-beginning &optional pos escape-from-edge limit |
| 3711 | This function returns the beginning of the field specified by @var{pos}. |
| 3712 | |
| 3713 | If @var{pos} is at the beginning of its field, and |
| 3714 | @var{escape-from-edge} is non-@code{nil}, then the return value is |
| 3715 | always the beginning of the preceding field that @emph{ends} at @var{pos}, |
| 3716 | regardless of the stickiness of the @code{field} properties around |
| 3717 | @var{pos}. |
| 3718 | |
| 3719 | If @var{limit} is non-@code{nil}, it is a buffer position; if the |
| 3720 | beginning of the field is before @var{limit}, then @var{limit} will be |
| 3721 | returned instead. |
| 3722 | @end defun |
| 3723 | |
| 3724 | @defun field-end &optional pos escape-from-edge limit |
| 3725 | This function returns the end of the field specified by @var{pos}. |
| 3726 | |
| 3727 | If @var{pos} is at the end of its field, and @var{escape-from-edge} is |
| 3728 | non-@code{nil}, then the return value is always the end of the following |
| 3729 | field that @emph{begins} at @var{pos}, regardless of the stickiness of |
| 3730 | the @code{field} properties around @var{pos}. |
| 3731 | |
| 3732 | If @var{limit} is non-@code{nil}, it is a buffer position; if the end |
| 3733 | of the field is after @var{limit}, then @var{limit} will be returned |
| 3734 | instead. |
| 3735 | @end defun |
| 3736 | |
| 3737 | @defun field-string &optional pos |
| 3738 | This function returns the contents of the field specified by @var{pos}, |
| 3739 | as a string. |
| 3740 | @end defun |
| 3741 | |
| 3742 | @defun field-string-no-properties &optional pos |
| 3743 | This function returns the contents of the field specified by @var{pos}, |
| 3744 | as a string, discarding text properties. |
| 3745 | @end defun |
| 3746 | |
| 3747 | @defun delete-field &optional pos |
| 3748 | This function deletes the text of the field specified by @var{pos}. |
| 3749 | @end defun |
| 3750 | |
| 3751 | @defun constrain-to-field new-pos old-pos &optional escape-from-edge only-in-line inhibit-capture-property |
| 3752 | This function ``constrains'' @var{new-pos} to the field that |
| 3753 | @var{old-pos} belongs to---in other words, it returns the position |
| 3754 | closest to @var{new-pos} that is in the same field as @var{old-pos}. |
| 3755 | |
| 3756 | If @var{new-pos} is @code{nil}, then @code{constrain-to-field} uses |
| 3757 | the value of point instead, and moves point to the resulting position |
| 3758 | as well as returning it. |
| 3759 | |
| 3760 | If @var{old-pos} is at the boundary of two fields, then the acceptable |
| 3761 | final positions depend on the argument @var{escape-from-edge}. If |
| 3762 | @var{escape-from-edge} is @code{nil}, then @var{new-pos} must be in |
| 3763 | the field whose @code{field} property equals what new characters |
| 3764 | inserted at @var{old-pos} would inherit. (This depends on the |
| 3765 | stickiness of the @code{field} property for the characters before and |
| 3766 | after @var{old-pos}.) If @var{escape-from-edge} is non-@code{nil}, |
| 3767 | @var{new-pos} can be anywhere in the two adjacent fields. |
| 3768 | Additionally, if two fields are separated by another field with the |
| 3769 | special value @code{boundary}, then any point within this special |
| 3770 | field is also considered to be ``on the boundary.'' |
| 3771 | |
| 3772 | Commands like @kbd{C-a} with no argumemt, that normally move backward |
| 3773 | to a specific kind of location and stay there once there, probably |
| 3774 | should specify @code{nil} for @var{escape-from-edge}. Other motion |
| 3775 | commands that check fields should probably pass @code{t}. |
| 3776 | |
| 3777 | If the optional argument @var{only-in-line} is non-@code{nil}, and |
| 3778 | constraining @var{new-pos} in the usual way would move it to a different |
| 3779 | line, @var{new-pos} is returned unconstrained. This used in commands |
| 3780 | that move by line, such as @code{next-line} and |
| 3781 | @code{beginning-of-line}, so that they respect field boundaries only in |
| 3782 | the case where they can still move to the right line. |
| 3783 | |
| 3784 | If the optional argument @var{inhibit-capture-property} is |
| 3785 | non-@code{nil}, and @var{old-pos} has a non-@code{nil} property of that |
| 3786 | name, then any field boundaries are ignored. |
| 3787 | |
| 3788 | You can cause @code{constrain-to-field} to ignore all field boundaries |
| 3789 | (and so never constrain anything) by binding the variable |
| 3790 | @code{inhibit-field-text-motion} to a non-@code{nil} value. |
| 3791 | @end defun |
| 3792 | |
| 3793 | @node Not Intervals |
| 3794 | @subsection Why Text Properties are not Intervals |
| 3795 | @cindex intervals |
| 3796 | |
| 3797 | Some editors that support adding attributes to text in the buffer do |
| 3798 | so by letting the user specify ``intervals'' within the text, and adding |
| 3799 | the properties to the intervals. Those editors permit the user or the |
| 3800 | programmer to determine where individual intervals start and end. We |
| 3801 | deliberately provided a different sort of interface in Emacs Lisp to |
| 3802 | avoid certain paradoxical behavior associated with text modification. |
| 3803 | |
| 3804 | If the actual subdivision into intervals is meaningful, that means you |
| 3805 | can distinguish between a buffer that is just one interval with a |
| 3806 | certain property, and a buffer containing the same text subdivided into |
| 3807 | two intervals, both of which have that property. |
| 3808 | |
| 3809 | Suppose you take the buffer with just one interval and kill part of |
| 3810 | the text. The text remaining in the buffer is one interval, and the |
| 3811 | copy in the kill ring (and the undo list) becomes a separate interval. |
| 3812 | Then if you yank back the killed text, you get two intervals with the |
| 3813 | same properties. Thus, editing does not preserve the distinction |
| 3814 | between one interval and two. |
| 3815 | |
| 3816 | Suppose we ``fix'' this problem by coalescing the two intervals when |
| 3817 | the text is inserted. That works fine if the buffer originally was a |
| 3818 | single interval. But suppose instead that we have two adjacent |
| 3819 | intervals with the same properties, and we kill the text of one interval |
| 3820 | and yank it back. The same interval-coalescence feature that rescues |
| 3821 | the other case causes trouble in this one: after yanking, we have just |
| 3822 | one interval. One again, editing does not preserve the distinction |
| 3823 | between one interval and two. |
| 3824 | |
| 3825 | Insertion of text at the border between intervals also raises |
| 3826 | questions that have no satisfactory answer. |
| 3827 | |
| 3828 | However, it is easy to arrange for editing to behave consistently for |
| 3829 | questions of the form, ``What are the properties of this character?'' |
| 3830 | So we have decided these are the only questions that make sense; we have |
| 3831 | not implemented asking questions about where intervals start or end. |
| 3832 | |
| 3833 | In practice, you can usually use the text property search functions in |
| 3834 | place of explicit interval boundaries. You can think of them as finding |
| 3835 | the boundaries of intervals, assuming that intervals are always |
| 3836 | coalesced whenever possible. @xref{Property Search}. |
| 3837 | |
| 3838 | Emacs also provides explicit intervals as a presentation feature; see |
| 3839 | @ref{Overlays}. |
| 3840 | |
| 3841 | @node Substitution |
| 3842 | @section Substituting for a Character Code |
| 3843 | |
| 3844 | The following functions replace characters within a specified region |
| 3845 | based on their character codes. |
| 3846 | |
| 3847 | @defun subst-char-in-region start end old-char new-char &optional noundo |
| 3848 | @cindex replace characters |
| 3849 | This function replaces all occurrences of the character @var{old-char} |
| 3850 | with the character @var{new-char} in the region of the current buffer |
| 3851 | defined by @var{start} and @var{end}. |
| 3852 | |
| 3853 | @cindex undo avoidance |
| 3854 | If @var{noundo} is non-@code{nil}, then @code{subst-char-in-region} does |
| 3855 | not record the change for undo and does not mark the buffer as modified. |
| 3856 | This was useful for controlling the old selective display feature |
| 3857 | (@pxref{Selective Display}). |
| 3858 | |
| 3859 | @code{subst-char-in-region} does not move point and returns |
| 3860 | @code{nil}. |
| 3861 | |
| 3862 | @example |
| 3863 | @group |
| 3864 | ---------- Buffer: foo ---------- |
| 3865 | This is the contents of the buffer before. |
| 3866 | ---------- Buffer: foo ---------- |
| 3867 | @end group |
| 3868 | |
| 3869 | @group |
| 3870 | (subst-char-in-region 1 20 ?i ?X) |
| 3871 | @result{} nil |
| 3872 | |
| 3873 | ---------- Buffer: foo ---------- |
| 3874 | ThXs Xs the contents of the buffer before. |
| 3875 | ---------- Buffer: foo ---------- |
| 3876 | @end group |
| 3877 | @end example |
| 3878 | @end defun |
| 3879 | |
| 3880 | @deffn Command translate-region start end table |
| 3881 | This function applies a translation table to the characters in the |
| 3882 | buffer between positions @var{start} and @var{end}. |
| 3883 | |
| 3884 | The translation table @var{table} is a string or a char-table; |
| 3885 | @code{(aref @var{table} @var{ochar})} gives the translated character |
| 3886 | corresponding to @var{ochar}. If @var{table} is a string, any |
| 3887 | characters with codes larger than the length of @var{table} are not |
| 3888 | altered by the translation. |
| 3889 | |
| 3890 | The return value of @code{translate-region} is the number of |
| 3891 | characters that were actually changed by the translation. This does |
| 3892 | not count characters that were mapped into themselves in the |
| 3893 | translation table. |
| 3894 | @end deffn |
| 3895 | |
| 3896 | @node Registers |
| 3897 | @section Registers |
| 3898 | @cindex registers |
| 3899 | |
| 3900 | A register is a sort of variable used in Emacs editing that can hold a |
| 3901 | variety of different kinds of values. Each register is named by a |
| 3902 | single character. All @acronym{ASCII} characters and their meta variants |
| 3903 | (but with the exception of @kbd{C-g}) can be used to name registers. |
| 3904 | Thus, there are 255 possible registers. A register is designated in |
| 3905 | Emacs Lisp by the character that is its name. |
| 3906 | |
| 3907 | @defvar register-alist |
| 3908 | This variable is an alist of elements of the form @code{(@var{name} . |
| 3909 | @var{contents})}. Normally, there is one element for each Emacs |
| 3910 | register that has been used. |
| 3911 | |
| 3912 | The object @var{name} is a character (an integer) identifying the |
| 3913 | register. |
| 3914 | @end defvar |
| 3915 | |
| 3916 | The @var{contents} of a register can have several possible types: |
| 3917 | |
| 3918 | @table @asis |
| 3919 | @item a number |
| 3920 | A number stands for itself. If @code{insert-register} finds a number |
| 3921 | in the register, it converts the number to decimal. |
| 3922 | |
| 3923 | @item a marker |
| 3924 | A marker represents a buffer position to jump to. |
| 3925 | |
| 3926 | @item a string |
| 3927 | A string is text saved in the register. |
| 3928 | |
| 3929 | @item a rectangle |
| 3930 | A rectangle is represented by a list of strings. |
| 3931 | |
| 3932 | @item @code{(@var{window-configuration} @var{position})} |
| 3933 | This represents a window configuration to restore in one frame, and a |
| 3934 | position to jump to in the current buffer. |
| 3935 | |
| 3936 | @item @code{(@var{frame-configuration} @var{position})} |
| 3937 | This represents a frame configuration to restore, and a position |
| 3938 | to jump to in the current buffer. |
| 3939 | |
| 3940 | @item (file @var{filename}) |
| 3941 | This represents a file to visit; jumping to this value visits file |
| 3942 | @var{filename}. |
| 3943 | |
| 3944 | @item (file-query @var{filename} @var{position}) |
| 3945 | This represents a file to visit and a position in it; jumping to this |
| 3946 | value visits file @var{filename} and goes to buffer position |
| 3947 | @var{position}. Restoring this type of position asks the user for |
| 3948 | confirmation first. |
| 3949 | @end table |
| 3950 | |
| 3951 | The functions in this section return unpredictable values unless |
| 3952 | otherwise stated. |
| 3953 | |
| 3954 | @defun get-register reg |
| 3955 | This function returns the contents of the register |
| 3956 | @var{reg}, or @code{nil} if it has no contents. |
| 3957 | @end defun |
| 3958 | |
| 3959 | @defun set-register reg value |
| 3960 | This function sets the contents of register @var{reg} to @var{value}. |
| 3961 | A register can be set to any value, but the other register functions |
| 3962 | expect only certain data types. The return value is @var{value}. |
| 3963 | @end defun |
| 3964 | |
| 3965 | @deffn Command view-register reg |
| 3966 | This command displays what is contained in register @var{reg}. |
| 3967 | @end deffn |
| 3968 | |
| 3969 | @deffn Command insert-register reg &optional beforep |
| 3970 | This command inserts contents of register @var{reg} into the current |
| 3971 | buffer. |
| 3972 | |
| 3973 | Normally, this command puts point before the inserted text, and the |
| 3974 | mark after it. However, if the optional second argument @var{beforep} |
| 3975 | is non-@code{nil}, it puts the mark before and point after. |
| 3976 | You can pass a non-@code{nil} second argument @var{beforep} to this |
| 3977 | function interactively by supplying any prefix argument. |
| 3978 | |
| 3979 | If the register contains a rectangle, then the rectangle is inserted |
| 3980 | with its upper left corner at point. This means that text is inserted |
| 3981 | in the current line and underneath it on successive lines. |
| 3982 | |
| 3983 | If the register contains something other than saved text (a string) or |
| 3984 | a rectangle (a list), currently useless things happen. This may be |
| 3985 | changed in the future. |
| 3986 | @end deffn |
| 3987 | |
| 3988 | @node Transposition |
| 3989 | @section Transposition of Text |
| 3990 | |
| 3991 | This subroutine is used by the transposition commands. |
| 3992 | |
| 3993 | @defun transpose-regions start1 end1 start2 end2 &optional leave-markers |
| 3994 | This function exchanges two nonoverlapping portions of the buffer. |
| 3995 | Arguments @var{start1} and @var{end1} specify the bounds of one portion |
| 3996 | and arguments @var{start2} and @var{end2} specify the bounds of the |
| 3997 | other portion. |
| 3998 | |
| 3999 | Normally, @code{transpose-regions} relocates markers with the transposed |
| 4000 | text; a marker previously positioned within one of the two transposed |
| 4001 | portions moves along with that portion, thus remaining between the same |
| 4002 | two characters in their new position. However, if @var{leave-markers} |
| 4003 | is non-@code{nil}, @code{transpose-regions} does not do this---it leaves |
| 4004 | all markers unrelocated. |
| 4005 | @end defun |
| 4006 | |
| 4007 | @node Base 64 |
| 4008 | @section Base 64 Encoding |
| 4009 | @cindex base 64 encoding |
| 4010 | |
| 4011 | Base 64 code is used in email to encode a sequence of 8-bit bytes as |
| 4012 | a longer sequence of @acronym{ASCII} graphic characters. It is defined in |
| 4013 | Internet RFC@footnote{ |
| 4014 | An RFC, an acronym for @dfn{Request for Comments}, is a numbered |
| 4015 | Internet informational document describing a standard. RFCs are |
| 4016 | usually written by technical experts acting on their own initiative, |
| 4017 | and are traditionally written in a pragmatic, experience-driven |
| 4018 | manner. |
| 4019 | }2045. This section describes the functions for |
| 4020 | converting to and from this code. |
| 4021 | |
| 4022 | @deffn Command base64-encode-region beg end &optional no-line-break |
| 4023 | This function converts the region from @var{beg} to @var{end} into base |
| 4024 | 64 code. It returns the length of the encoded text. An error is |
| 4025 | signaled if a character in the region is multibyte, i.e.@: in a |
| 4026 | multibyte buffer the region must contain only characters from the |
| 4027 | charsets @code{ascii}, @code{eight-bit-control} and |
| 4028 | @code{eight-bit-graphic}. |
| 4029 | |
| 4030 | Normally, this function inserts newline characters into the encoded |
| 4031 | text, to avoid overlong lines. However, if the optional argument |
| 4032 | @var{no-line-break} is non-@code{nil}, these newlines are not added, so |
| 4033 | the output is just one long line. |
| 4034 | @end deffn |
| 4035 | |
| 4036 | @deffn Command base64-encode-string string &optional no-line-break |
| 4037 | This function converts the string @var{string} into base 64 code. It |
| 4038 | returns a string containing the encoded text. As for |
| 4039 | @code{base64-encode-region}, an error is signaled if a character in the |
| 4040 | string is multibyte. |
| 4041 | |
| 4042 | Normally, this function inserts newline characters into the encoded |
| 4043 | text, to avoid overlong lines. However, if the optional argument |
| 4044 | @var{no-line-break} is non-@code{nil}, these newlines are not added, so |
| 4045 | the result string is just one long line. |
| 4046 | @end deffn |
| 4047 | |
| 4048 | @defun base64-decode-region beg end |
| 4049 | This function converts the region from @var{beg} to @var{end} from base |
| 4050 | 64 code into the corresponding decoded text. It returns the length of |
| 4051 | the decoded text. |
| 4052 | |
| 4053 | The decoding functions ignore newline characters in the encoded text. |
| 4054 | @end defun |
| 4055 | |
| 4056 | @defun base64-decode-string string |
| 4057 | This function converts the string @var{string} from base 64 code into |
| 4058 | the corresponding decoded text. It returns a unibyte string containing the |
| 4059 | decoded text. |
| 4060 | |
| 4061 | The decoding functions ignore newline characters in the encoded text. |
| 4062 | @end defun |
| 4063 | |
| 4064 | @node MD5 Checksum |
| 4065 | @section MD5 Checksum |
| 4066 | @cindex MD5 checksum |
| 4067 | @cindex message digest computation |
| 4068 | |
| 4069 | MD5 cryptographic checksums, or @dfn{message digests}, are 128-bit |
| 4070 | ``fingerprints'' of a document or program. They are used to verify |
| 4071 | that you have an exact and unaltered copy of the data. The algorithm |
| 4072 | to calculate the MD5 message digest is defined in Internet |
| 4073 | RFC@footnote{ |
| 4074 | For an explanation of what is an RFC, see the footnote in @ref{Base |
| 4075 | 64}. |
| 4076 | }1321. This section describes the Emacs facilities for computing |
| 4077 | message digests. |
| 4078 | |
| 4079 | @defun md5 object &optional start end coding-system noerror |
| 4080 | This function returns the MD5 message digest of @var{object}, which |
| 4081 | should be a buffer or a string. |
| 4082 | |
| 4083 | The two optional arguments @var{start} and @var{end} are character |
| 4084 | positions specifying the portion of @var{object} to compute the |
| 4085 | message digest for. If they are @code{nil} or omitted, the digest is |
| 4086 | computed for the whole of @var{object}. |
| 4087 | |
| 4088 | The function @code{md5} does not compute the message digest directly |
| 4089 | from the internal Emacs representation of the text (@pxref{Text |
| 4090 | Representations}). Instead, it encodes the text using a coding |
| 4091 | system, and computes the message digest from the encoded text. The |
| 4092 | optional fourth argument @var{coding-system} specifies which coding |
| 4093 | system to use for encoding the text. It should be the same coding |
| 4094 | system that you used to read the text, or that you used or will use |
| 4095 | when saving or sending the text. @xref{Coding Systems}, for more |
| 4096 | information about coding systems. |
| 4097 | |
| 4098 | If @var{coding-system} is @code{nil} or omitted, the default depends |
| 4099 | on @var{object}. If @var{object} is a buffer, the default for |
| 4100 | @var{coding-system} is whatever coding system would be chosen by |
| 4101 | default for writing this text into a file. If @var{object} is a |
| 4102 | string, the user's most preferred coding system (@pxref{Recognize |
| 4103 | Coding, prefer-coding-system, the description of |
| 4104 | @code{prefer-coding-system}, emacs, GNU Emacs Manual}) is used. |
| 4105 | |
| 4106 | Normally, @code{md5} signals an error if the text can't be encoded |
| 4107 | using the specified or chosen coding system. However, if |
| 4108 | @var{noerror} is non-@code{nil}, it silently uses @code{raw-text} |
| 4109 | coding instead. |
| 4110 | @end defun |
| 4111 | |
| 4112 | @node Atomic Changes |
| 4113 | @section Atomic Change Groups |
| 4114 | @cindex atomic changes |
| 4115 | |
| 4116 | In data base terminology, an @dfn{atomic} change is an indivisible |
| 4117 | change---it can succeed entirely or it can fail entirely, but it |
| 4118 | cannot partly succeed. A Lisp program can make a series of changes to |
| 4119 | one or several buffers as an @dfn{atomic change group}, meaning that |
| 4120 | either the entire series of changes will be installed in their buffers |
| 4121 | or, in case of an error, none of them will be. |
| 4122 | |
| 4123 | To do this for one buffer, the one already current, simply write a |
| 4124 | call to @code{atomic-change-group} around the code that makes the |
| 4125 | changes, like this: |
| 4126 | |
| 4127 | @example |
| 4128 | (atomic-change-group |
| 4129 | (insert foo) |
| 4130 | (delete-region x y)) |
| 4131 | @end example |
| 4132 | |
| 4133 | @noindent |
| 4134 | If an error (or other nonlocal exit) occurs inside the body of |
| 4135 | @code{atomic-change-group}, it unmakes all the changes in that buffer |
| 4136 | that were during the execution of the body. This kind of change group |
| 4137 | has no effect on any other buffers---any such changes remain. |
| 4138 | |
| 4139 | If you need something more sophisticated, such as to make changes in |
| 4140 | various buffers constitute one atomic group, you must directly call |
| 4141 | lower-level functions that @code{atomic-change-group} uses. |
| 4142 | |
| 4143 | @defun prepare-change-group &optional buffer |
| 4144 | This function sets up a change group for buffer @var{buffer}, which |
| 4145 | defaults to the current buffer. It returns a ``handle'' that |
| 4146 | represents the change group. You must use this handle to activate the |
| 4147 | change group and subsequently to finish it. |
| 4148 | @end defun |
| 4149 | |
| 4150 | To use the change group, you must @dfn{activate} it. You must do |
| 4151 | this before making any changes in the text of @var{buffer}. |
| 4152 | |
| 4153 | @defun activate-change-group handle |
| 4154 | This function activates the change group that @var{handle} designates. |
| 4155 | @end defun |
| 4156 | |
| 4157 | After you activate the change group, any changes you make in that |
| 4158 | buffer become part of it. Once you have made all the desired changes |
| 4159 | in the buffer, you must @dfn{finish} the change group. There are two |
| 4160 | ways to do this: you can either accept (and finalize) all the changes, |
| 4161 | or cancel them all. |
| 4162 | |
| 4163 | @defun accept-change-group handle |
| 4164 | This function accepts all the changes in the change group specified by |
| 4165 | @var{handle}, making them final. |
| 4166 | @end defun |
| 4167 | |
| 4168 | @defun cancel-change-group handle |
| 4169 | This function cancels and undoes all the changes in the change group |
| 4170 | specified by @var{handle}. |
| 4171 | @end defun |
| 4172 | |
| 4173 | Your code should use @code{unwind-protect} to make sure the group is |
| 4174 | always finished. The call to @code{activate-change-group} should be |
| 4175 | inside the @code{unwind-protect}, in case the user types @kbd{C-g} |
| 4176 | just after it runs. (This is one reason why |
| 4177 | @code{prepare-change-group} and @code{activate-change-group} are |
| 4178 | separate functions, because normally you would call |
| 4179 | @code{prepare-change-group} before the start of that |
| 4180 | @code{unwind-protect}.) Once you finish the group, don't use the |
| 4181 | handle again---in particular, don't try to finish the same group |
| 4182 | twice. |
| 4183 | |
| 4184 | To make a multibuffer change group, call @code{prepare-change-group} |
| 4185 | once for each buffer you want to cover, then use @code{nconc} to |
| 4186 | combine the returned values, like this: |
| 4187 | |
| 4188 | @example |
| 4189 | (nconc (prepare-change-group buffer-1) |
| 4190 | (prepare-change-group buffer-2)) |
| 4191 | @end example |
| 4192 | |
| 4193 | You can then activate the multibuffer change group with a single call |
| 4194 | to @code{activate-change-group}, and finish it with a single call to |
| 4195 | @code{accept-change-group} or @code{cancel-change-group}. |
| 4196 | |
| 4197 | Nested use of several change groups for the same buffer works as you |
| 4198 | would expect. Non-nested use of change groups for the same buffer |
| 4199 | will get Emacs confused, so don't let it happen; the first change |
| 4200 | group you start for any given buffer should be the last one finished. |
| 4201 | |
| 4202 | @node Change Hooks |
| 4203 | @section Change Hooks |
| 4204 | @cindex change hooks |
| 4205 | @cindex hooks for text changes |
| 4206 | |
| 4207 | These hook variables let you arrange to take notice of all changes in |
| 4208 | all buffers (or in a particular buffer, if you make them buffer-local). |
| 4209 | See also @ref{Special Properties}, for how to detect changes to specific |
| 4210 | parts of the text. |
| 4211 | |
| 4212 | The functions you use in these hooks should save and restore the match |
| 4213 | data if they do anything that uses regular expressions; otherwise, they |
| 4214 | will interfere in bizarre ways with the editing operations that call |
| 4215 | them. |
| 4216 | |
| 4217 | @defvar before-change-functions |
| 4218 | This variable holds a list of functions to call before any buffer |
| 4219 | modification. Each function gets two arguments, the beginning and end |
| 4220 | of the region that is about to change, represented as integers. The |
| 4221 | buffer that is about to change is always the current buffer. |
| 4222 | @end defvar |
| 4223 | |
| 4224 | @defvar after-change-functions |
| 4225 | This variable holds a list of functions to call after any buffer |
| 4226 | modification. Each function receives three arguments: the beginning and |
| 4227 | end of the region just changed, and the length of the text that existed |
| 4228 | before the change. All three arguments are integers. The buffer that's |
| 4229 | about to change is always the current buffer. |
| 4230 | |
| 4231 | The length of the old text is the difference between the buffer positions |
| 4232 | before and after that text as it was before the change. As for the |
| 4233 | changed text, its length is simply the difference between the first two |
| 4234 | arguments. |
| 4235 | @end defvar |
| 4236 | |
| 4237 | Output of messages into the @samp{*Messages*} buffer does not |
| 4238 | call these functions. |
| 4239 | |
| 4240 | @defmac combine-after-change-calls body@dots{} |
| 4241 | The macro executes @var{body} normally, but arranges to call the |
| 4242 | after-change functions just once for a series of several changes---if |
| 4243 | that seems safe. |
| 4244 | |
| 4245 | If a program makes several text changes in the same area of the buffer, |
| 4246 | using the macro @code{combine-after-change-calls} around that part of |
| 4247 | the program can make it run considerably faster when after-change hooks |
| 4248 | are in use. When the after-change hooks are ultimately called, the |
| 4249 | arguments specify a portion of the buffer including all of the changes |
| 4250 | made within the @code{combine-after-change-calls} body. |
| 4251 | |
| 4252 | @strong{Warning:} You must not alter the values of |
| 4253 | @code{after-change-functions} within |
| 4254 | the body of a @code{combine-after-change-calls} form. |
| 4255 | |
| 4256 | @strong{Warning:} if the changes you combine occur in widely scattered |
| 4257 | parts of the buffer, this will still work, but it is not advisable, |
| 4258 | because it may lead to inefficient behavior for some change hook |
| 4259 | functions. |
| 4260 | @end defmac |
| 4261 | |
| 4262 | @defvar first-change-hook |
| 4263 | This variable is a normal hook that is run whenever a buffer is changed |
| 4264 | that was previously in the unmodified state. |
| 4265 | @end defvar |
| 4266 | |
| 4267 | @defvar inhibit-modification-hooks |
| 4268 | If this variable is non-@code{nil}, all of the change hooks are |
| 4269 | disabled; none of them run. This affects all the hook variables |
| 4270 | described above in this section, as well as the hooks attached to |
| 4271 | certain special text properties (@pxref{Special Properties}) and overlay |
| 4272 | properties (@pxref{Overlay Properties}). |
| 4273 | |
| 4274 | Also, this variable is bound to non-@code{nil} while running those |
| 4275 | same hook variables, so that by default modifying the buffer from |
| 4276 | a modification hook does not cause other modification hooks to be run. |
| 4277 | If you do want modification hooks to be run in a particular piece of |
| 4278 | code that is itself run from a modification hook, then rebind locally |
| 4279 | @code{inhibit-modification-hooks} to @code{nil}. |
| 4280 | @end defvar |
| 4281 | |
| 4282 | |