src/undo.c

   1 /* undo handling for GNU Emacs.
   2    Copyright (C) 1990, 1993, 1994, 2000 Free Software Foundation, Inc.
   3
   4 This file is part of GNU Emacs.
   5
   6 GNU Emacs is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU Emacs is distributed in the hope that it will be useful,
  12 but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 GNU General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Emacs; see the file COPYING.  If not, write to
  18 the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  19 Boston, MA 02111-1307, USA.  */
  20
  21
  22 #include <config.h>
  23 #include "lisp.h"
  24 #include "buffer.h"
  25 #include "commands.h"
  26
  27 /* Limits controlling how much undo information to keep.  */
  28
  29 EMACS_INT undo_limit;
  30 EMACS_INT undo_strong_limit;
  31
  32 Lisp_Object Vundo_outer_limit;
  33
  34 /* Function to call when undo_outer_limit is exceeded.  */
  35
  36 Lisp_Object Vundo_outer_limit_function;
  37
  38 /* Last buffer for which undo information was recorded.  */
  39 Lisp_Object last_undo_buffer;
  40
  41 Lisp_Object Qinhibit_read_only;
  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 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 (pt)
  57      int pt;
  58 {
  59   int at_boundary;
  60
  61   /* Allocate a cons cell to be the undo boundary after this command.  */
  62   if (NILP (pending_boundary))
  63     pending_boundary = Fcons (Qnil, Qnil);
  64
  65   if (!BUFFERP (last_undo_buffer)
  66       || current_buffer != XBUFFER (last_undo_buffer))
  67     Fundo_boundary ();
  68   XSETBUFFER (last_undo_buffer, current_buffer);
  69
  70   if (CONSP (current_buffer->undo_list))
  71     {
  72       /* Set AT_BOUNDARY to 1 only when we have nothing other than
  73          marker adjustment before undo boundary.  */
  74
  75       Lisp_Object tail = current_buffer->undo_list, elt;
  76
  77       while (1)
  78         {
  79           if (NILP (tail))
  80             elt = Qnil;
  81           else
  82             elt = XCAR (tail);
  83           if (NILP (elt) || ! (CONSP (elt) && MARKERP (XCAR (elt))))
  84             break;
  85           tail = XCDR (tail);
  86         }
  87       at_boundary = NILP (elt);
  88     }
  89   else
  90     at_boundary = 1;
  91
  92   if (MODIFF <= SAVE_MODIFF)
  93     record_first_change ();
  94
  95   /* If we are just after an undo boundary, and
  96      point wasn't at start of deleted range, record where it was.  */
  97   if (at_boundary
  98       && last_point_position != pt
  99       /* If we're called from batch mode, this could be nil.  */
 100       && BUFFERP (last_point_position_buffer)
 101       && current_buffer == XBUFFER (last_point_position_buffer))
 102     current_buffer->undo_list
 103       = Fcons (make_number (last_point_position), current_buffer->undo_list);
 104 }
 105
 106 /* Record an insertion that just happened or is about to happen,
 107    for LENGTH characters at position BEG.
 108    (It is possible to record an insertion before or after the fact
 109    because we don't need to record the contents.)  */
 110
 111 void
 112 record_insert (beg, length)
 113      int beg, length;
 114 {
 115   Lisp_Object lbeg, lend;
 116
 117   if (EQ (current_buffer->undo_list, Qt))
 118     return;
 119
 120   record_point (beg);
 121
 122   /* If this is following another insertion and consecutive with it
 123      in the buffer, combine the two.  */
 124   if (CONSP (current_buffer->undo_list))
 125     {
 126       Lisp_Object elt;
 127       elt = XCAR (current_buffer->undo_list);
 128       if (CONSP (elt)
 129           && INTEGERP (XCAR (elt))
 130           && INTEGERP (XCDR (elt))
 131           && XINT (XCDR (elt)) == beg)
 132         {
 133           XSETCDR (elt, make_number (beg + length));
 134           return;
 135         }
 136     }
 137
 138   XSETFASTINT (lbeg, beg);
 139   XSETINT (lend, beg + length);
 140   current_buffer->undo_list = Fcons (Fcons (lbeg, lend),
 141                                      current_buffer->undo_list);
 142 }
 143
 144 /* Record that a deletion is about to take place,
 145    of the characters in STRING, at location BEG.  */
 146
 147 void
 148 record_delete (beg, string)
 149      int beg;
 150      Lisp_Object string;
 151 {
 152   Lisp_Object sbeg;
 153
 154   if (EQ (current_buffer->undo_list, Qt))
 155     return;
 156
 157   if (PT == beg + SCHARS (string))
 158     {
 159       XSETINT (sbeg, -beg);
 160       record_point (PT);
 161     }
 162   else
 163     {
 164       XSETFASTINT (sbeg, beg);
 165       record_point (beg);
 166     }
 167
 168   current_buffer->undo_list
 169     = Fcons (Fcons (string, sbeg), current_buffer->undo_list);
 170 }
 171
 172 /* Record the fact that MARKER is about to be adjusted by ADJUSTMENT.
 173    This is done only when a marker points within text being deleted,
 174    because that's the only case where an automatic marker adjustment
 175    won't be inverted automatically by undoing the buffer modification.  */
 176
 177 void
 178 record_marker_adjustment (marker, adjustment)
 179      Lisp_Object marker;
 180      int adjustment;
 181 {
 182   if (EQ (current_buffer->undo_list, Qt))
 183     return;
 184
 185   /* Allocate a cons cell to be the undo boundary after this command.  */
 186   if (NILP (pending_boundary))
 187     pending_boundary = Fcons (Qnil, Qnil);
 188
 189   if (!BUFFERP (last_undo_buffer)
 190       || current_buffer != XBUFFER (last_undo_buffer))
 191     Fundo_boundary ();
 192   XSETBUFFER (last_undo_buffer, current_buffer);
 193
 194   current_buffer->undo_list
 195     = Fcons (Fcons (marker, make_number (adjustment)),
 196              current_buffer->undo_list);
 197 }
 198
 199 /* Record that a replacement is about to take place,
 200    for LENGTH characters at location BEG.
 201    The replacement must not change the number of characters.  */
 202
 203 void
 204 record_change (beg, length)
 205      int beg, length;
 206 {
 207   record_delete (beg, make_buffer_string (beg, beg + length, 1));
 208   record_insert (beg, length);
 209 }
 210 \f
 211 /* Record that an unmodified buffer is about to be changed.
 212    Record the file modification date so that when undoing this entry
 213    we can tell whether it is obsolete because the file was saved again.  */
 214
 215 void
 216 record_first_change ()
 217 {
 218   Lisp_Object high, low;
 219   struct buffer *base_buffer = current_buffer;
 220
 221   if (EQ (current_buffer->undo_list, Qt))
 222     return;
 223
 224   if (!BUFFERP (last_undo_buffer)
 225       || current_buffer != XBUFFER (last_undo_buffer))
 226     Fundo_boundary ();
 227   XSETBUFFER (last_undo_buffer, current_buffer);
 228
 229   if (base_buffer->base_buffer)
 230     base_buffer = base_buffer->base_buffer;
 231
 232   XSETFASTINT (high, (base_buffer->modtime >> 16) & 0xffff);
 233   XSETFASTINT (low, base_buffer->modtime & 0xffff);
 234   current_buffer->undo_list = Fcons (Fcons (Qt, Fcons (high, low)), current_buffer->undo_list);
 235 }
 236
 237 /* Record a change in property PROP (whose old value was VAL)
 238    for LENGTH characters starting at position BEG in BUFFER.  */
 239
 240 void
 241 record_property_change (beg, length, prop, value, buffer)
 242      int beg, length;
 243      Lisp_Object prop, value, buffer;
 244 {
 245   Lisp_Object lbeg, lend, entry;
 246   struct buffer *obuf = current_buffer;
 247   int boundary = 0;
 248
 249   if (EQ (XBUFFER (buffer)->undo_list, Qt))
 250     return;
 251
 252   /* Allocate a cons cell to be the undo boundary after this command.  */
 253   if (NILP (pending_boundary))
 254     pending_boundary = Fcons (Qnil, Qnil);
 255
 256   if (!EQ (buffer, last_undo_buffer))
 257     boundary = 1;
 258   last_undo_buffer = buffer;
 259
 260   /* Switch temporarily to the buffer that was changed.  */
 261   current_buffer = XBUFFER (buffer);
 262
 263   if (boundary)
 264     Fundo_boundary ();
 265
 266   if (MODIFF <= SAVE_MODIFF)
 267     record_first_change ();
 268
 269   XSETINT (lbeg, beg);
 270   XSETINT (lend, beg + length);
 271   entry = Fcons (Qnil, Fcons (prop, Fcons (value, Fcons (lbeg, lend))));
 272   current_buffer->undo_list = Fcons (entry, current_buffer->undo_list);
 273
 274   current_buffer = obuf;
 275 }
 276
 277 DEFUN ("undo-boundary", Fundo_boundary, Sundo_boundary, 0, 0, 0,
 278        doc: /* Mark a boundary between units of undo.
 279 An undo command will stop at this point,
 280 but another undo command will undo to the previous boundary.  */)
 281      ()
 282 {
 283   Lisp_Object tem;
 284   if (EQ (current_buffer->undo_list, Qt))
 285     return Qnil;
 286   tem = Fcar (current_buffer->undo_list);
 287   if (!NILP (tem))
 288     {
 289       /* One way or another, cons nil onto the front of the undo list.  */
 290       if (!NILP (pending_boundary))
 291         {
 292           /* If we have preallocated the cons cell to use here,
 293              use that one.  */
 294           XSETCDR (pending_boundary, current_buffer->undo_list);
 295           current_buffer->undo_list = pending_boundary;
 296           pending_boundary = Qnil;
 297         }
 298       else
 299         current_buffer->undo_list = Fcons (Qnil, current_buffer->undo_list);
 300     }
 301   return Qnil;
 302 }
 303
 304 /* At garbage collection time, make an undo list shorter at the end,
 305    returning the truncated list.  How this is done depends on the
 306    variables undo-limit, undo-strong-limit and undo-outer-limit.
 307    In some cases this works by calling undo-outer-limit-function.  */
 308
 309 void
 310 truncate_undo_list (b)
 311      struct buffer *b;
 312 {
 313   Lisp_Object list;
 314   Lisp_Object prev, next, last_boundary;
 315   int size_so_far = 0;
 316
 317   /* Make sure that calling undo-outer-limit-function
 318      won't cause another GC.  */
 319   int count = inhibit_garbage_collection ();
 320
 321   /* Make the buffer current to get its local values of variables such
 322      as undo_limit.  Also so that Vundo_outer_limit_function can
 323      tell which buffer to operate on.  */
 324   record_unwind_protect (set_buffer_if_live, Fcurrent_buffer ());
 325   set_buffer_internal (b);
 326
 327   list = b->undo_list;
 328
 329   prev = Qnil;
 330   next = list;
 331   last_boundary = Qnil;
 332
 333   /* If the first element is an undo boundary, skip past it.  */
 334   if (CONSP (next) && NILP (XCAR (next)))
 335     {
 336       /* Add in the space occupied by this element and its chain link.  */
 337       size_so_far += sizeof (struct Lisp_Cons);
 338
 339       /* Advance to next element.  */
 340       prev = next;
 341       next = XCDR (next);
 342     }
 343
 344   /* Always preserve at least the most recent undo record
 345      unless it is really horribly big.
 346
 347      Skip, skip, skip the undo, skip, skip, skip the undo,
 348      Skip, skip, skip the undo, skip to the undo bound'ry.  */
 349
 350   while (CONSP (next) && ! NILP (XCAR (next)))
 351     {
 352       Lisp_Object elt;
 353       elt = XCAR (next);
 354
 355       /* Add in the space occupied by this element and its chain link.  */
 356       size_so_far += sizeof (struct Lisp_Cons);
 357       if (CONSP (elt))
 358         {
 359           size_so_far += sizeof (struct Lisp_Cons);
 360           if (STRINGP (XCAR (elt)))
 361             size_so_far += (sizeof (struct Lisp_String) - 1
 362                             + SCHARS (XCAR (elt)));
 363         }
 364
 365       /* Advance to next element.  */
 366       prev = next;
 367       next = XCDR (next);
 368     }
 369
 370   /* If by the first boundary we have already passed undo_outer_limit,
 371      we're heading for memory full, so offer to clear out the list.  */
 372   if (INTEGERP (Vundo_outer_limit)
 373       && size_so_far > XINT (Vundo_outer_limit)
 374       && !NILP (Vundo_outer_limit_function))
 375     {
 376       Lisp_Object temp = last_undo_buffer;
 377
 378       /* Normally the function this calls is undo-outer-limit-truncate.  */
 379       if (! NILP (call1 (Vundo_outer_limit_function,
 380                          make_number (size_so_far))))
 381         {
 382           /* The function is responsible for making
 383              any desired changes in buffer-undo-list.  */
 384           unbind_to (count, Qnil);
 385           return;
 386         }
 387       /* That function probably used the minibuffer, and if so, that
 388          changed last_undo_buffer.  Change it back so that we don't
 389          force next change to make an undo boundary here.  */
 390       last_undo_buffer = temp;
 391     }
 392
 393   if (CONSP (next))
 394     last_boundary = prev;
 395
 396   /* Keep additional undo data, if it fits in the limits.  */
 397   while (CONSP (next))
 398     {
 399       Lisp_Object elt;
 400       elt = XCAR (next);
 401
 402       /* When we get to a boundary, decide whether to truncate
 403          either before or after it.  The lower threshold, undo_limit,
 404          tells us to truncate after it.  If its size pushes past
 405          the higher threshold undo_strong_limit, we truncate before it.  */
 406       if (NILP (elt))
 407         {
 408           if (size_so_far > undo_strong_limit)
 409             break;
 410           last_boundary = prev;
 411           if (size_so_far > undo_limit)
 412             break;
 413         }
 414
 415       /* Add in the space occupied by this element and its chain link.  */
 416       size_so_far += sizeof (struct Lisp_Cons);
 417       if (CONSP (elt))
 418         {
 419           size_so_far += sizeof (struct Lisp_Cons);
 420           if (STRINGP (XCAR (elt)))
 421             size_so_far += (sizeof (struct Lisp_String) - 1
 422                             + SCHARS (XCAR (elt)));
 423         }
 424
 425       /* Advance to next element.  */
 426       prev = next;
 427       next = XCDR (next);
 428     }
 429
 430   /* If we scanned the whole list, it is short enough; don't change it.  */
 431   if (NILP (next))
 432     ;
 433   /* Truncate at the boundary where we decided to truncate.  */
 434   else if (!NILP (last_boundary))
 435     XSETCDR (last_boundary, Qnil);
 436   /* There's nothing we decided to keep, so clear it out.  */
 437   else
 438     b->undo_list = Qnil;
 439
 440   unbind_to (count, Qnil);
 441 }
 442 \f
 443 DEFUN ("primitive-undo", Fprimitive_undo, Sprimitive_undo, 2, 2, 0,
 444        doc: /* Undo N records from the front of the list LIST.
 445 Return what remains of the list.  */)
 446      (n, list)
 447      Lisp_Object n, list;
 448 {
 449   struct gcpro gcpro1, gcpro2;
 450   Lisp_Object next;
 451   int count = SPECPDL_INDEX ();
 452   register int arg;
 453
 454 #if 0  /* This is a good feature, but would make undo-start
 455           unable to do what is expected.  */
 456   Lisp_Object tem;
 457
 458   /* If the head of the list is a boundary, it is the boundary
 459      preceding this command.  Get rid of it and don't count it.  */
 460   tem = Fcar (list);
 461   if (NILP (tem))
 462     list = Fcdr (list);
 463 #endif
 464
 465   CHECK_NUMBER (n);
 466   arg = XINT (n);
 467   next = Qnil;
 468   GCPRO2 (next, list);
 469
 470   /* In a writable buffer, enable undoing read-only text that is so
 471      because of text properties.  */
 472   if (NILP (current_buffer->read_only))
 473     specbind (Qinhibit_read_only, Qt);
 474
 475   /* Don't let `intangible' properties interfere with undo.  */
 476   specbind (Qinhibit_point_motion_hooks, Qt);
 477
 478   while (arg > 0)
 479     {
 480       while (CONSP (list))
 481         {
 482           next = XCAR (list);
 483           list = XCDR (list);
 484           /* Exit inner loop at undo boundary.  */
 485           if (NILP (next))
 486             break;
 487           /* Handle an integer by setting point to that value.  */
 488           if (INTEGERP (next))
 489             SET_PT (clip_to_bounds (BEGV, XINT (next), ZV));
 490           else if (CONSP (next))
 491             {
 492               Lisp_Object car, cdr;
 493
 494               car = XCAR (next);
 495               cdr = XCDR (next);
 496               if (EQ (car, Qt))
 497                 {
 498                   /* Element (t high . low) records previous modtime.  */
 499                   Lisp_Object high, low;
 500                   int mod_time;
 501                   struct buffer *base_buffer = current_buffer;
 502
 503                   high = Fcar (cdr);
 504                   low = Fcdr (cdr);
 505                   mod_time = (XFASTINT (high) << 16) + XFASTINT (low);
 506
 507                   if (current_buffer->base_buffer)
 508                     base_buffer = current_buffer->base_buffer;
 509
 510                   /* If this records an obsolete save
 511                      (not matching the actual disk file)
 512                      then don't mark unmodified.  */
 513                   if (mod_time != base_buffer->modtime)
 514                     continue;
 515 #ifdef CLASH_DETECTION
 516                   Funlock_buffer ();
 517 #endif /* CLASH_DETECTION */
 518                   Fset_buffer_modified_p (Qnil);
 519                 }
 520               else if (EQ (car, Qnil))
 521                 {
 522                   /* Element (nil PROP VAL BEG . END) is property change.  */
 523                   Lisp_Object beg, end, prop, val;
 524
 525                   prop = Fcar (cdr);
 526                   cdr = Fcdr (cdr);
 527                   val = Fcar (cdr);
 528                   cdr = Fcdr (cdr);
 529                   beg = Fcar (cdr);
 530                   end = Fcdr (cdr);
 531
 532                   Fput_text_property (beg, end, prop, val, Qnil);
 533                 }
 534               else if (INTEGERP (car) && INTEGERP (cdr))
 535                 {
 536                   /* Element (BEG . END) means range was inserted.  */
 537
 538                   if (XINT (car) < BEGV
 539                       || XINT (cdr) > ZV)
 540                     error ("Changes to be undone are outside visible portion of buffer");
 541                   /* Set point first thing, so that undoing this undo
 542                      does not send point back to where it is now.  */
 543                   Fgoto_char (car);
 544                   Fdelete_region (car, cdr);
 545                 }
 546               else if (SYMBOLP (car))
 547                 {
 548                   Lisp_Object oldlist = current_buffer->undo_list;
 549                   /* Element (FUNNAME . ARGS) means call FUNNAME to undo.  */
 550                   apply1 (car, cdr);
 551                   /* Make sure this produces at least one undo entry,
 552                      so the test in `undo' for continuing an undo series
 553                      will work right.  */
 554                   if (EQ (oldlist, current_buffer->undo_list))
 555                     current_buffer->undo_list
 556                       = Fcons (list2 (Qcdr, Qnil), current_buffer->undo_list);
 557                 }
 558               else if (STRINGP (car) && INTEGERP (cdr))
 559                 {
 560                   /* Element (STRING . POS) means STRING was deleted.  */
 561                   Lisp_Object membuf;
 562                   int pos = XINT (cdr);
 563
 564                   membuf = car;
 565                   if (pos < 0)
 566                     {
 567                       if (-pos < BEGV || -pos > ZV)
 568                         error ("Changes to be undone are outside visible portion of buffer");
 569                       SET_PT (-pos);
 570                       Finsert (1, &membuf);
 571                     }
 572                   else
 573                     {
 574                       if (pos < BEGV || pos > ZV)
 575                         error ("Changes to be undone are outside visible portion of buffer");
 576                       SET_PT (pos);
 577
 578                       /* Now that we record marker adjustments
 579                          (caused by deletion) for undo,
 580                          we should always insert after markers,
 581                          so that undoing the marker adjustments
 582                          put the markers back in the right place.  */
 583                       Finsert (1, &membuf);
 584                       SET_PT (pos);
 585                     }
 586                 }
 587               else if (MARKERP (car) && INTEGERP (cdr))
 588                 {
 589                   /* (MARKER . INTEGER) means a marker MARKER
 590                      was adjusted by INTEGER.  */
 591                   if (XMARKER (car)->buffer)
 592                     Fset_marker (car,
 593                                  make_number (marker_position (car) - XINT (cdr)),
 594                                  Fmarker_buffer (car));
 595                 }
 596             }
 597         }
 598       arg--;
 599     }
 600
 601   UNGCPRO;
 602   return unbind_to (count, list);
 603 }
 604 \f
 605 void
 606 syms_of_undo ()
 607 {
 608   Qinhibit_read_only = intern ("inhibit-read-only");
 609   staticpro (&Qinhibit_read_only);
 610
 611   pending_boundary = Qnil;
 612   staticpro (&pending_boundary);
 613
 614   defsubr (&Sprimitive_undo);
 615   defsubr (&Sundo_boundary);
 616
 617   DEFVAR_INT ("undo-limit", &undo_limit,
 618               doc: /* Keep no more undo information once it exceeds this size.
 619 This limit is applied when garbage collection happens.
 620 When a previous command increases the total undo list size past this
 621 value, the earlier commands that came before it are forgotten.
 622
 623 The size is counted as the number of bytes occupied,
 624 which includes both saved text and other data.  */);
 625   undo_limit = 20000;
 626
 627   DEFVAR_INT ("undo-strong-limit", &undo_strong_limit,
 628               doc: /* Don't keep more than this much size of undo information.
 629 This limit is applied when garbage collection happens.
 630 When a previous command increases the total undo list size past this
 631 value, that command and the earlier commands that came before it are forgotten.
 632 However, the most recent buffer-modifying command's undo info
 633 is never discarded for this reason.
 634
 635 The size is counted as the number of bytes occupied,
 636 which includes both saved text and other data.  */);
 637   undo_strong_limit = 30000;
 638
 639   DEFVAR_LISP ("undo-outer-limit", &Vundo_outer_limit,
 640               doc: /* Outer limit on size of undo information for one command.
 641 At garbage collection time, if the current command has produced
 642 more than this much undo information, it discards the info and displays
 643 a warning.  This is a last-ditch limit to prevent memory overflow.
 644
 645 The size is counted as the number of bytes occupied, which includes
 646 both saved text and other data.  A value of nil means no limit.  In
 647 this case, accumulating one huge undo entry could make Emacs crash as
 648 a result of memory overflow.
 649
 650 In fact, this calls the function which is the value of
 651 `undo-outer-limit-function' with one argument, the size.
 652 The text above describes the behavior of the function
 653 that variable usually specifies.  */);
 654   Vundo_outer_limit = make_number (3000000);
 655
 656   DEFVAR_LISP ("undo-outer-limit-function", &Vundo_outer_limit_function,
 657                doc: /* Function to call when an undo list exceeds `undo-outer-limit'.
 658 This function is called with one argument, the current undo list size
 659 for the most recent command (since the last undo boundary).
 660 If the function returns t, that means truncation has been fully handled.
 661 If it returns nil, the other forms of truncation are done.
 662
 663 Garbage collection is inhibited around the call to this function,
 664 so it must make sure not to do a lot of consing.  */);
 665   Vundo_outer_limit_function = Qnil;
 666 }
 667
 668 /* arch-tag: d546ee01-4aed-4ffb-bb8b-eefaae50d38a
 669    (do not change this comment) */