| 1 | /* undo handling for GNU Emacs. |
| 2 | Copyright (C) 1990, 1993-1994, 2000-2014 Free Software Foundation, |
| 3 | Inc. |
| 4 | |
| 5 | This file is part of GNU Emacs. |
| 6 | |
| 7 | GNU Emacs is free software: you can redistribute it and/or modify |
| 8 | it under the terms of the GNU General Public License as published by |
| 9 | the Free Software Foundation, either version 3 of the License, or |
| 10 | (at your option) any later version. |
| 11 | |
| 12 | GNU Emacs is distributed in the hope that it will be useful, |
| 13 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 14 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 15 | GNU General Public License for more details. |
| 16 | |
| 17 | You should have received a copy of the GNU General Public License |
| 18 | along with GNU Emacs. If not, see <http://www.gnu.org/licenses/>. */ |
| 19 | |
| 20 | |
| 21 | #include <config.h> |
| 22 | |
| 23 | #include "lisp.h" |
| 24 | #include "character.h" |
| 25 | #include "buffer.h" |
| 26 | #include "commands.h" |
| 27 | #include "window.h" |
| 28 | |
| 29 | /* Last buffer for which undo information was recorded. */ |
| 30 | /* BEWARE: This is not traced by the GC, so never dereference it! */ |
| 31 | static struct buffer *last_undo_buffer; |
| 32 | |
| 33 | /* Position of point last time we inserted a boundary. */ |
| 34 | static struct buffer *last_boundary_buffer; |
| 35 | static ptrdiff_t last_boundary_position; |
| 36 | |
| 37 | Lisp_Object Qinhibit_read_only; |
| 38 | |
| 39 | /* Marker for function call undo list elements. */ |
| 40 | |
| 41 | Lisp_Object Qapply; |
| 42 | |
| 43 | /* The first time a command records something for undo. |
| 44 | it also allocates the undo-boundary object |
| 45 | which will be added to the list at the end of the command. |
| 46 | This ensures we can't run out of space while trying to make |
| 47 | an undo-boundary. */ |
| 48 | static Lisp_Object pending_boundary; |
| 49 | |
| 50 | /* Record point as it was at beginning of this command (if necessary) |
| 51 | and prepare the undo info for recording a change. |
| 52 | PT is the position of point that will naturally occur as a result of the |
| 53 | undo record that will be added just after this command terminates. */ |
| 54 | |
| 55 | static void |
| 56 | record_point (ptrdiff_t pt) |
| 57 | { |
| 58 | bool at_boundary; |
| 59 | |
| 60 | /* Don't record position of pt when undo_inhibit_record_point holds. */ |
| 61 | if (undo_inhibit_record_point) |
| 62 | return; |
| 63 | |
| 64 | /* Allocate a cons cell to be the undo boundary after this command. */ |
| 65 | if (NILP (pending_boundary)) |
| 66 | pending_boundary = Fcons (Qnil, Qnil); |
| 67 | |
| 68 | if ((current_buffer != last_undo_buffer) |
| 69 | /* Don't call Fundo_boundary for the first change. Otherwise we |
| 70 | risk overwriting last_boundary_position in Fundo_boundary with |
| 71 | PT of the current buffer and as a consequence not insert an |
| 72 | undo boundary because last_boundary_position will equal pt in |
| 73 | the test at the end of the present function (Bug#731). */ |
| 74 | && (MODIFF > SAVE_MODIFF)) |
| 75 | Fundo_boundary (); |
| 76 | last_undo_buffer = current_buffer; |
| 77 | |
| 78 | at_boundary = ! CONSP (BVAR (current_buffer, undo_list)) |
| 79 | || NILP (XCAR (BVAR (current_buffer, undo_list))); |
| 80 | |
| 81 | if (MODIFF <= SAVE_MODIFF) |
| 82 | record_first_change (); |
| 83 | |
| 84 | /* If we are just after an undo boundary, and |
| 85 | point wasn't at start of deleted range, record where it was. */ |
| 86 | if (at_boundary |
| 87 | && current_buffer == last_boundary_buffer |
| 88 | && last_boundary_position != pt) |
| 89 | bset_undo_list (current_buffer, |
| 90 | Fcons (make_number (last_boundary_position), |
| 91 | BVAR (current_buffer, undo_list))); |
| 92 | } |
| 93 | |
| 94 | /* Record an insertion that just happened or is about to happen, |
| 95 | for LENGTH characters at position BEG. |
| 96 | (It is possible to record an insertion before or after the fact |
| 97 | because we don't need to record the contents.) */ |
| 98 | |
| 99 | void |
| 100 | record_insert (ptrdiff_t beg, ptrdiff_t length) |
| 101 | { |
| 102 | Lisp_Object lbeg, lend; |
| 103 | |
| 104 | if (EQ (BVAR (current_buffer, undo_list), Qt)) |
| 105 | return; |
| 106 | |
| 107 | record_point (beg); |
| 108 | |
| 109 | /* If this is following another insertion and consecutive with it |
| 110 | in the buffer, combine the two. */ |
| 111 | if (CONSP (BVAR (current_buffer, undo_list))) |
| 112 | { |
| 113 | Lisp_Object elt; |
| 114 | elt = XCAR (BVAR (current_buffer, undo_list)); |
| 115 | if (CONSP (elt) |
| 116 | && INTEGERP (XCAR (elt)) |
| 117 | && INTEGERP (XCDR (elt)) |
| 118 | && XINT (XCDR (elt)) == beg) |
| 119 | { |
| 120 | XSETCDR (elt, make_number (beg + length)); |
| 121 | return; |
| 122 | } |
| 123 | } |
| 124 | |
| 125 | XSETFASTINT (lbeg, beg); |
| 126 | XSETINT (lend, beg + length); |
| 127 | bset_undo_list (current_buffer, |
| 128 | Fcons (Fcons (lbeg, lend), BVAR (current_buffer, undo_list))); |
| 129 | } |
| 130 | |
| 131 | /* Record the fact that markers in the region of FROM, TO are about to |
| 132 | be adjusted. This is done only when a marker points within text |
| 133 | being deleted, because that's the only case where an automatic |
| 134 | marker adjustment won't be inverted automatically by undoing the |
| 135 | buffer modification. */ |
| 136 | |
| 137 | static void |
| 138 | record_marker_adjustments (ptrdiff_t from, ptrdiff_t to) |
| 139 | { |
| 140 | Lisp_Object marker; |
| 141 | register struct Lisp_Marker *m; |
| 142 | register ptrdiff_t charpos, adjustment; |
| 143 | |
| 144 | /* Allocate a cons cell to be the undo boundary after this command. */ |
| 145 | if (NILP (pending_boundary)) |
| 146 | pending_boundary = Fcons (Qnil, Qnil); |
| 147 | |
| 148 | if (current_buffer != last_undo_buffer) |
| 149 | Fundo_boundary (); |
| 150 | last_undo_buffer = current_buffer; |
| 151 | |
| 152 | for (m = BUF_MARKERS (current_buffer); m; m = m->next) |
| 153 | { |
| 154 | charpos = m->charpos; |
| 155 | eassert (charpos <= Z); |
| 156 | |
| 157 | if (from <= charpos && charpos <= to) |
| 158 | { |
| 159 | /* insertion_type nil markers will end up at the beginning of |
| 160 | the re-inserted text after undoing a deletion, and must be |
| 161 | adjusted to move them to the correct place. |
| 162 | |
| 163 | insertion_type t markers will automatically move forward |
| 164 | upon re-inserting the deleted text, so we have to arrange |
| 165 | for them to move backward to the correct position. */ |
| 166 | adjustment = (m->insertion_type ? to : from) - charpos; |
| 167 | |
| 168 | if (adjustment) |
| 169 | { |
| 170 | XSETMISC (marker, m); |
| 171 | bset_undo_list |
| 172 | (current_buffer, |
| 173 | Fcons (Fcons (marker, make_number (adjustment)), |
| 174 | BVAR (current_buffer, undo_list))); |
| 175 | } |
| 176 | } |
| 177 | } |
| 178 | } |
| 179 | |
| 180 | /* Record that a deletion is about to take place, of the characters in |
| 181 | STRING, at location BEG. Optionally record adjustments for markers |
| 182 | in the region STRING occupies in the current buffer. */ |
| 183 | |
| 184 | void |
| 185 | record_delete (ptrdiff_t beg, Lisp_Object string, bool record_markers) |
| 186 | { |
| 187 | Lisp_Object sbeg; |
| 188 | |
| 189 | if (EQ (BVAR (current_buffer, undo_list), Qt)) |
| 190 | return; |
| 191 | |
| 192 | if (PT == beg + SCHARS (string)) |
| 193 | { |
| 194 | XSETINT (sbeg, -beg); |
| 195 | record_point (PT); |
| 196 | } |
| 197 | else |
| 198 | { |
| 199 | XSETFASTINT (sbeg, beg); |
| 200 | record_point (beg); |
| 201 | } |
| 202 | |
| 203 | /* primitive-undo assumes marker adjustments are recorded |
| 204 | immediately before the deletion is recorded. See bug 16818 |
| 205 | discussion. */ |
| 206 | if (record_markers) |
| 207 | record_marker_adjustments (beg, beg + SCHARS (string)); |
| 208 | |
| 209 | bset_undo_list |
| 210 | (current_buffer, |
| 211 | Fcons (Fcons (string, sbeg), BVAR (current_buffer, undo_list))); |
| 212 | } |
| 213 | |
| 214 | /* Record that a replacement is about to take place, |
| 215 | for LENGTH characters at location BEG. |
| 216 | The replacement must not change the number of characters. */ |
| 217 | |
| 218 | void |
| 219 | record_change (ptrdiff_t beg, ptrdiff_t length) |
| 220 | { |
| 221 | record_delete (beg, make_buffer_string (beg, beg + length, 1), false); |
| 222 | record_insert (beg, length); |
| 223 | } |
| 224 | \f |
| 225 | /* Record that an unmodified buffer is about to be changed. |
| 226 | Record the file modification date so that when undoing this entry |
| 227 | we can tell whether it is obsolete because the file was saved again. */ |
| 228 | |
| 229 | void |
| 230 | record_first_change (void) |
| 231 | { |
| 232 | struct buffer *base_buffer = current_buffer; |
| 233 | |
| 234 | if (EQ (BVAR (current_buffer, undo_list), Qt)) |
| 235 | return; |
| 236 | |
| 237 | if (current_buffer != last_undo_buffer) |
| 238 | Fundo_boundary (); |
| 239 | last_undo_buffer = current_buffer; |
| 240 | |
| 241 | if (base_buffer->base_buffer) |
| 242 | base_buffer = base_buffer->base_buffer; |
| 243 | |
| 244 | bset_undo_list (current_buffer, |
| 245 | Fcons (Fcons (Qt, Fvisited_file_modtime ()), |
| 246 | BVAR (current_buffer, undo_list))); |
| 247 | } |
| 248 | |
| 249 | /* Record a change in property PROP (whose old value was VAL) |
| 250 | for LENGTH characters starting at position BEG in BUFFER. */ |
| 251 | |
| 252 | void |
| 253 | record_property_change (ptrdiff_t beg, ptrdiff_t length, |
| 254 | Lisp_Object prop, Lisp_Object value, |
| 255 | Lisp_Object buffer) |
| 256 | { |
| 257 | Lisp_Object lbeg, lend, entry; |
| 258 | struct buffer *obuf = current_buffer, *buf = XBUFFER (buffer); |
| 259 | bool boundary = 0; |
| 260 | |
| 261 | if (EQ (BVAR (buf, undo_list), Qt)) |
| 262 | return; |
| 263 | |
| 264 | /* Allocate a cons cell to be the undo boundary after this command. */ |
| 265 | if (NILP (pending_boundary)) |
| 266 | pending_boundary = Fcons (Qnil, Qnil); |
| 267 | |
| 268 | if (buf != last_undo_buffer) |
| 269 | boundary = 1; |
| 270 | last_undo_buffer = buf; |
| 271 | |
| 272 | /* Switch temporarily to the buffer that was changed. */ |
| 273 | current_buffer = buf; |
| 274 | |
| 275 | if (boundary) |
| 276 | Fundo_boundary (); |
| 277 | |
| 278 | if (MODIFF <= SAVE_MODIFF) |
| 279 | record_first_change (); |
| 280 | |
| 281 | XSETINT (lbeg, beg); |
| 282 | XSETINT (lend, beg + length); |
| 283 | entry = Fcons (Qnil, Fcons (prop, Fcons (value, Fcons (lbeg, lend)))); |
| 284 | bset_undo_list (current_buffer, |
| 285 | Fcons (entry, BVAR (current_buffer, undo_list))); |
| 286 | |
| 287 | current_buffer = obuf; |
| 288 | } |
| 289 | |
| 290 | DEFUN ("undo-boundary", Fundo_boundary, Sundo_boundary, 0, 0, 0, |
| 291 | doc: /* Mark a boundary between units of undo. |
| 292 | An undo command will stop at this point, |
| 293 | but another undo command will undo to the previous boundary. */) |
| 294 | (void) |
| 295 | { |
| 296 | Lisp_Object tem; |
| 297 | if (EQ (BVAR (current_buffer, undo_list), Qt)) |
| 298 | return Qnil; |
| 299 | tem = Fcar (BVAR (current_buffer, undo_list)); |
| 300 | if (!NILP (tem)) |
| 301 | { |
| 302 | /* One way or another, cons nil onto the front of the undo list. */ |
| 303 | if (!NILP (pending_boundary)) |
| 304 | { |
| 305 | /* If we have preallocated the cons cell to use here, |
| 306 | use that one. */ |
| 307 | XSETCDR (pending_boundary, BVAR (current_buffer, undo_list)); |
| 308 | bset_undo_list (current_buffer, pending_boundary); |
| 309 | pending_boundary = Qnil; |
| 310 | } |
| 311 | else |
| 312 | bset_undo_list (current_buffer, |
| 313 | Fcons (Qnil, BVAR (current_buffer, undo_list))); |
| 314 | } |
| 315 | last_boundary_position = PT; |
| 316 | last_boundary_buffer = current_buffer; |
| 317 | return Qnil; |
| 318 | } |
| 319 | |
| 320 | /* At garbage collection time, make an undo list shorter at the end, |
| 321 | returning the truncated list. How this is done depends on the |
| 322 | variables undo-limit, undo-strong-limit and undo-outer-limit. |
| 323 | In some cases this works by calling undo-outer-limit-function. */ |
| 324 | |
| 325 | void |
| 326 | truncate_undo_list (struct buffer *b) |
| 327 | { |
| 328 | Lisp_Object list; |
| 329 | Lisp_Object prev, next, last_boundary; |
| 330 | EMACS_INT size_so_far = 0; |
| 331 | dynwind_begin (); |
| 332 | static const size_t sizeof_cons = sizeof (scm_t_cell); |
| 333 | |
| 334 | /* Make the buffer current to get its local values of variables such |
| 335 | as undo_limit. Also so that Vundo_outer_limit_function can |
| 336 | tell which buffer to operate on. */ |
| 337 | record_unwind_current_buffer (); |
| 338 | set_buffer_internal (b); |
| 339 | |
| 340 | list = BVAR (b, undo_list); |
| 341 | |
| 342 | prev = Qnil; |
| 343 | next = list; |
| 344 | last_boundary = Qnil; |
| 345 | |
| 346 | /* If the first element is an undo boundary, skip past it. */ |
| 347 | if (CONSP (next) && NILP (XCAR (next))) |
| 348 | { |
| 349 | /* Add in the space occupied by this element and its chain link. */ |
| 350 | size_so_far += sizeof_cons; |
| 351 | |
| 352 | /* Advance to next element. */ |
| 353 | prev = next; |
| 354 | next = XCDR (next); |
| 355 | } |
| 356 | |
| 357 | /* Always preserve at least the most recent undo record |
| 358 | unless it is really horribly big. |
| 359 | |
| 360 | Skip, skip, skip the undo, skip, skip, skip the undo, |
| 361 | Skip, skip, skip the undo, skip to the undo bound'ry. */ |
| 362 | |
| 363 | while (CONSP (next) && ! NILP (XCAR (next))) |
| 364 | { |
| 365 | Lisp_Object elt; |
| 366 | elt = XCAR (next); |
| 367 | |
| 368 | /* Add in the space occupied by this element and its chain link. */ |
| 369 | size_so_far += sizeof_cons; |
| 370 | if (CONSP (elt)) |
| 371 | { |
| 372 | size_so_far += sizeof_cons; |
| 373 | if (STRINGP (XCAR (elt))) |
| 374 | size_so_far += (sizeof (struct Lisp_String) - 1 |
| 375 | + SCHARS (XCAR (elt))); |
| 376 | } |
| 377 | |
| 378 | /* Advance to next element. */ |
| 379 | prev = next; |
| 380 | next = XCDR (next); |
| 381 | } |
| 382 | |
| 383 | /* If by the first boundary we have already passed undo_outer_limit, |
| 384 | we're heading for memory full, so offer to clear out the list. */ |
| 385 | if (INTEGERP (Vundo_outer_limit) |
| 386 | && size_so_far > XINT (Vundo_outer_limit) |
| 387 | && !NILP (Vundo_outer_limit_function)) |
| 388 | { |
| 389 | Lisp_Object tem; |
| 390 | struct buffer *temp = last_undo_buffer; |
| 391 | |
| 392 | /* Normally the function this calls is undo-outer-limit-truncate. */ |
| 393 | tem = call1 (Vundo_outer_limit_function, make_number (size_so_far)); |
| 394 | if (! NILP (tem)) |
| 395 | { |
| 396 | /* The function is responsible for making |
| 397 | any desired changes in buffer-undo-list. */ |
| 398 | dynwind_end (); |
| 399 | return; |
| 400 | } |
| 401 | /* That function probably used the minibuffer, and if so, that |
| 402 | changed last_undo_buffer. Change it back so that we don't |
| 403 | force next change to make an undo boundary here. */ |
| 404 | last_undo_buffer = temp; |
| 405 | } |
| 406 | |
| 407 | if (CONSP (next)) |
| 408 | last_boundary = prev; |
| 409 | |
| 410 | /* Keep additional undo data, if it fits in the limits. */ |
| 411 | while (CONSP (next)) |
| 412 | { |
| 413 | Lisp_Object elt; |
| 414 | elt = XCAR (next); |
| 415 | |
| 416 | /* When we get to a boundary, decide whether to truncate |
| 417 | either before or after it. The lower threshold, undo_limit, |
| 418 | tells us to truncate after it. If its size pushes past |
| 419 | the higher threshold undo_strong_limit, we truncate before it. */ |
| 420 | if (NILP (elt)) |
| 421 | { |
| 422 | if (size_so_far > undo_strong_limit) |
| 423 | break; |
| 424 | last_boundary = prev; |
| 425 | if (size_so_far > undo_limit) |
| 426 | break; |
| 427 | } |
| 428 | |
| 429 | /* Add in the space occupied by this element and its chain link. */ |
| 430 | size_so_far += sizeof_cons; |
| 431 | if (CONSP (elt)) |
| 432 | { |
| 433 | size_so_far += sizeof_cons; |
| 434 | if (STRINGP (XCAR (elt))) |
| 435 | size_so_far += (sizeof (struct Lisp_String) - 1 |
| 436 | + SCHARS (XCAR (elt))); |
| 437 | } |
| 438 | |
| 439 | /* Advance to next element. */ |
| 440 | prev = next; |
| 441 | next = XCDR (next); |
| 442 | } |
| 443 | |
| 444 | /* If we scanned the whole list, it is short enough; don't change it. */ |
| 445 | if (NILP (next)) |
| 446 | ; |
| 447 | /* Truncate at the boundary where we decided to truncate. */ |
| 448 | else if (!NILP (last_boundary)) |
| 449 | XSETCDR (last_boundary, Qnil); |
| 450 | /* There's nothing we decided to keep, so clear it out. */ |
| 451 | else |
| 452 | bset_undo_list (b, Qnil); |
| 453 | |
| 454 | dynwind_end (); |
| 455 | } |
| 456 | |
| 457 | \f |
| 458 | void |
| 459 | syms_of_undo (void) |
| 460 | { |
| 461 | #include "undo.x" |
| 462 | |
| 463 | DEFSYM (Qinhibit_read_only, "inhibit-read-only"); |
| 464 | DEFSYM (Qapply, "apply"); |
| 465 | |
| 466 | pending_boundary = Qnil; |
| 467 | staticpro (&pending_boundary); |
| 468 | |
| 469 | last_undo_buffer = NULL; |
| 470 | last_boundary_buffer = NULL; |
| 471 | |
| 472 | DEFVAR_INT ("undo-limit", undo_limit, |
| 473 | doc: /* Keep no more undo information once it exceeds this size. |
| 474 | This limit is applied when garbage collection happens. |
| 475 | When a previous command increases the total undo list size past this |
| 476 | value, the earlier commands that came before it are forgotten. |
| 477 | |
| 478 | The size is counted as the number of bytes occupied, |
| 479 | which includes both saved text and other data. */); |
| 480 | undo_limit = 80000; |
| 481 | |
| 482 | DEFVAR_INT ("undo-strong-limit", undo_strong_limit, |
| 483 | doc: /* Don't keep more than this much size of undo information. |
| 484 | This limit is applied when garbage collection happens. |
| 485 | When a previous command increases the total undo list size past this |
| 486 | value, that command and the earlier commands that came before it are forgotten. |
| 487 | However, the most recent buffer-modifying command's undo info |
| 488 | is never discarded for this reason. |
| 489 | |
| 490 | The size is counted as the number of bytes occupied, |
| 491 | which includes both saved text and other data. */); |
| 492 | undo_strong_limit = 120000; |
| 493 | |
| 494 | DEFVAR_LISP ("undo-outer-limit", Vundo_outer_limit, |
| 495 | doc: /* Outer limit on size of undo information for one command. |
| 496 | At garbage collection time, if the current command has produced |
| 497 | more than this much undo information, it discards the info and displays |
| 498 | a warning. This is a last-ditch limit to prevent memory overflow. |
| 499 | |
| 500 | The size is counted as the number of bytes occupied, which includes |
| 501 | both saved text and other data. A value of nil means no limit. In |
| 502 | this case, accumulating one huge undo entry could make Emacs crash as |
| 503 | a result of memory overflow. |
| 504 | |
| 505 | In fact, this calls the function which is the value of |
| 506 | `undo-outer-limit-function' with one argument, the size. |
| 507 | The text above describes the behavior of the function |
| 508 | that variable usually specifies. */); |
| 509 | Vundo_outer_limit = make_number (12000000); |
| 510 | |
| 511 | DEFVAR_LISP ("undo-outer-limit-function", Vundo_outer_limit_function, |
| 512 | doc: /* Function to call when an undo list exceeds `undo-outer-limit'. |
| 513 | This function is called with one argument, the current undo list size |
| 514 | for the most recent command (since the last undo boundary). |
| 515 | If the function returns t, that means truncation has been fully handled. |
| 516 | If it returns nil, the other forms of truncation are done. |
| 517 | |
| 518 | Garbage collection is inhibited around the call to this function, |
| 519 | so it must make sure not to do a lot of consing. */); |
| 520 | Vundo_outer_limit_function = Qnil; |
| 521 | |
| 522 | DEFVAR_BOOL ("undo-inhibit-record-point", undo_inhibit_record_point, |
| 523 | doc: /* Non-nil means do not record `point' in `buffer-undo-list'. */); |
| 524 | undo_inhibit_record_point = 0; |
| 525 | } |