emacs / src / undo.c

  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
/* undo handling for GNU Emacs.
   Copyright (C) 1990, 1993, 1994 Free Software Foundation, Inc.

This file is part of GNU Emacs.

GNU Emacs is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.

GNU Emacs is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with GNU Emacs; see the file COPYING.  If not, write to
the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.  */


#include <config.h>
#include "lisp.h"
#include "buffer.h"
#include "commands.h"

/* Last buffer for which undo information was recorded.  */
Lisp_Object last_undo_buffer;

Lisp_Object Qinhibit_read_only;

/* The first time a command records something for undo.
   it also allocates the undo-boundary object
   which will be added to the list at the end of the command.
   This ensures we can't run out of space while trying to make
   an undo-boundary.  */
Lisp_Object pending_boundary;

/* Record an insertion that just happened or is about to happen,
   for LENGTH characters at position BEG.
   (It is possible to record an insertion before or after the fact
   because we don't need to record the contents.)  */

record_insert (beg, length)
     int beg, length;
{
  Lisp_Object lbeg, lend;

  if (EQ (current_buffer->undo_list, Qt))
    return;

  /* Allocate a cons cell to be the undo boundary after this command.  */
  if (NILP (pending_boundary))
    pending_boundary = Fcons (Qnil, Qnil);

  if (current_buffer != XBUFFER (last_undo_buffer))
    Fundo_boundary ();
  XSETBUFFER (last_undo_buffer, current_buffer);

  if (MODIFF <= SAVE_MODIFF)
    record_first_change ();

  /* If this is following another insertion and consecutive with it
     in the buffer, combine the two.  */
  if (CONSP (current_buffer->undo_list))
    {
      Lisp_Object elt;
      elt = XCONS (current_buffer->undo_list)->car;
      if (CONSP (elt)
	  && INTEGERP (XCONS (elt)->car)
	  && INTEGERP (XCONS (elt)->cdr)
	  && XINT (XCONS (elt)->cdr) == beg)
	{
	  XSETINT (XCONS (elt)->cdr, beg + length);
	  return;
	}
    }

  XSETFASTINT (lbeg, beg);
  XSETINT (lend, beg + length);
  current_buffer->undo_list = Fcons (Fcons (lbeg, lend),
                                     current_buffer->undo_list);
}

/* Record that a deletion is about to take place,
   for LENGTH characters at location BEG.  */

record_delete (beg, length)
     int beg, length;
{
  Lisp_Object lbeg, lend, sbeg;
  int at_boundary;

  if (EQ (current_buffer->undo_list, Qt))
    return;

  /* Allocate a cons cell to be the undo boundary after this command.  */
  if (NILP (pending_boundary))
    pending_boundary = Fcons (Qnil, Qnil);

  if (current_buffer != XBUFFER (last_undo_buffer))
    Fundo_boundary ();
  XSETBUFFER (last_undo_buffer, current_buffer);

  at_boundary = (CONSP (current_buffer->undo_list)
		 && NILP (XCONS (current_buffer->undo_list)->car));

  if (MODIFF <= SAVE_MODIFF)
    record_first_change ();

  if (PT == beg + length)
    XSETINT (sbeg, -beg);
  else
    XSETFASTINT (sbeg, beg);
  XSETFASTINT (lbeg, beg);
  XSETFASTINT (lend, beg + length);

  /* If we are just after an undo boundary, and 
     point wasn't at start of deleted range, record where it was.  */
  if (at_boundary
      && last_point_position != XFASTINT (sbeg)
      && current_buffer == XBUFFER (last_point_position_buffer))
    current_buffer->undo_list
      = Fcons (make_number (last_point_position), current_buffer->undo_list);

  current_buffer->undo_list
    = Fcons (Fcons (Fbuffer_substring (lbeg, lend), sbeg),
	     current_buffer->undo_list);
}

/* Record the fact that MARKER is about to be adjusted by ADJUSTMENT.
   This is done only when a marker points within text being deleted,
   because that's the only case where an automatic marker adjustment
   won't be inverted automatically by undoing the buffer modification.  */

record_marker_adjustment (marker, adjustment)
     Lisp_Object marker;
     int adjustment;
{
  if (EQ (current_buffer->undo_list, Qt))
    return;

  /* Allocate a cons cell to be the undo boundary after this command.  */
  if (NILP (pending_boundary))
    pending_boundary = Fcons (Qnil, Qnil);

  if (current_buffer != XBUFFER (last_undo_buffer))
    Fundo_boundary ();
  XSETBUFFER (last_undo_buffer, current_buffer);

  current_buffer->undo_list
    = Fcons (Fcons (marker, make_number (adjustment)),
	     current_buffer->undo_list);
}

/* Record that a replacement is about to take place,
   for LENGTH characters at location BEG.
   The replacement does not change the number of characters.  */

record_change (beg, length)
     int beg, length;
{
  record_delete (beg, length);
  record_insert (beg, length);
}

/* Record that an unmodified buffer is about to be changed.
   Record the file modification date so that when undoing this entry
   we can tell whether it is obsolete because the file was saved again.  */

record_first_change ()
{
  Lisp_Object high, low;
  struct buffer *base_buffer = current_buffer;

  if (EQ (current_buffer->undo_list, Qt))
    return;

  if (current_buffer != XBUFFER (last_undo_buffer))
    Fundo_boundary ();
  XSETBUFFER (last_undo_buffer, current_buffer);

  if (base_buffer->base_buffer)
    base_buffer = base_buffer->base_buffer;

  XSETFASTINT (high, (base_buffer->modtime >> 16) & 0xffff);
  XSETFASTINT (low, base_buffer->modtime & 0xffff);
  current_buffer->undo_list = Fcons (Fcons (Qt, Fcons (high, low)), current_buffer->undo_list);
}

/* Record a change in property PROP (whose old value was VAL)
   for LENGTH characters starting at position BEG in BUFFER.  */

record_property_change (beg, length, prop, value, buffer)
     int beg, length;
     Lisp_Object prop, value, buffer;
{
  Lisp_Object lbeg, lend, entry;
  struct buffer *obuf = current_buffer;
  int boundary = 0;

  if (EQ (XBUFFER (buffer)->undo_list, Qt))
    return;

  /* Allocate a cons cell to be the undo boundary after this command.  */
  if (NILP (pending_boundary))
    pending_boundary = Fcons (Qnil, Qnil);

  if (!EQ (buffer, last_undo_buffer))
    boundary = 1;
  last_undo_buffer = buffer;

  /* Switch temporarily to the buffer that was changed.  */
  current_buffer = XBUFFER (buffer);

  if (boundary)
    Fundo_boundary ();

  if (MODIFF <= SAVE_MODIFF)
    record_first_change ();

  XSETINT (lbeg, beg);
  XSETINT (lend, beg + length);
  entry = Fcons (Qnil, Fcons (prop, Fcons (value, Fcons (lbeg, lend))));
  current_buffer->undo_list = Fcons (entry, current_buffer->undo_list);

  current_buffer = obuf;
}

DEFUN ("undo-boundary", Fundo_boundary, Sundo_boundary, 0, 0, 0,
  "Mark a boundary between units of undo.\n\
An undo command will stop at this point,\n\
but another undo command will undo to the previous boundary.")
  ()
{
  Lisp_Object tem;
  if (EQ (current_buffer->undo_list, Qt))
    return Qnil;
  tem = Fcar (current_buffer->undo_list);
  if (!NILP (tem))
    {
      /* One way or another, cons nil onto the front of the undo list.  */
      if (!NILP (pending_boundary))
	{
	  /* If we have preallocated the cons cell to use here,
	     use that one.  */
	  XCONS (pending_boundary)->cdr = current_buffer->undo_list;
	  current_buffer->undo_list = pending_boundary;
	  pending_boundary = Qnil;
	}
      else
	current_buffer->undo_list = Fcons (Qnil, current_buffer->undo_list);
    }
  return Qnil;
}

/* At garbage collection time, make an undo list shorter at the end,
   returning the truncated list.
   MINSIZE and MAXSIZE are the limits on size allowed, as described below.
   In practice, these are the values of undo-limit and
   undo-strong-limit.  */

Lisp_Object
truncate_undo_list (list, minsize, maxsize)
     Lisp_Object list;
     int minsize, maxsize;
{
  Lisp_Object prev, next, last_boundary;
  int size_so_far = 0;

  prev = Qnil;
  next = list;
  last_boundary = Qnil;

  /* Always preserve at least the most recent undo record.
     If the first element is an undo boundary, skip past it.

     Skip, skip, skip the undo, skip, skip, skip the undo,
     Skip, skip, skip the undo, skip to the undo bound'ry. 
     (Get it?  "Skip to my Loo?")  */
  if (CONSP (next) && NILP (XCONS (next)->car))
    {
      /* Add in the space occupied by this element and its chain link.  */
      size_so_far += sizeof (struct Lisp_Cons);

      /* Advance to next element.  */
      prev = next;
      next = XCONS (next)->cdr;
    }
  while (CONSP (next) && ! NILP (XCONS (next)->car))
    {
      Lisp_Object elt;
      elt = XCONS (next)->car;

      /* Add in the space occupied by this element and its chain link.  */
      size_so_far += sizeof (struct Lisp_Cons);
      if (CONSP (elt))
	{
	  size_so_far += sizeof (struct Lisp_Cons);
	  if (STRINGP (XCONS (elt)->car))
	    size_so_far += (sizeof (struct Lisp_String) - 1
			    + XSTRING (XCONS (elt)->car)->size);
	}

      /* Advance to next element.  */
      prev = next;
      next = XCONS (next)->cdr;
    }
  if (CONSP (next))
    last_boundary = prev;

  while (CONSP (next))
    {
      Lisp_Object elt;
      elt = XCONS (next)->car;

      /* When we get to a boundary, decide whether to truncate
	 either before or after it.  The lower threshold, MINSIZE,
	 tells us to truncate after it.  If its size pushes past
	 the higher threshold MAXSIZE as well, we truncate before it.  */
      if (NILP (elt))
	{
	  if (size_so_far > maxsize)
	    break;
	  last_boundary = prev;
	  if (size_so_far > minsize)
	    break;
	}

      /* Add in the space occupied by this element and its chain link.  */
      size_so_far += sizeof (struct Lisp_Cons);
      if (CONSP (elt))
	{
	  size_so_far += sizeof (struct Lisp_Cons);
	  if (STRINGP (XCONS (elt)->car))
	    size_so_far += (sizeof (struct Lisp_String) - 1
			    + XSTRING (XCONS (elt)->car)->size);
	}

      /* Advance to next element.  */
      prev = next;
      next = XCONS (next)->cdr;
    }

  /* If we scanned the whole list, it is short enough; don't change it.  */
  if (NILP (next))
    return list;

  /* Truncate at the boundary where we decided to truncate.  */
  if (!NILP (last_boundary))
    {
      XCONS (last_boundary)->cdr = Qnil;
      return list;
    }
  else
    return Qnil;
}

DEFUN ("primitive-undo", Fprimitive_undo, Sprimitive_undo, 2, 2, 0,
  "Undo N records from the front of the list LIST.\n\
Return what remains of the list.")
  (n, list)
     Lisp_Object n, list;
{
  struct gcpro gcpro1, gcpro2;
  Lisp_Object next;
  int count = specpdl_ptr - specpdl;
  register int arg;
#if 0  /* This is a good feature, but would make undo-start
	  unable to do what is expected.  */
  Lisp_Object tem;

  /* If the head of the list is a boundary, it is the boundary
     preceding this command.  Get rid of it and don't count it.  */
  tem = Fcar (list);
  if (NILP (tem))
    list = Fcdr (list);
#endif

  CHECK_NUMBER (n, 0);
  arg = XINT (n);
  next = Qnil;
  GCPRO2 (next, list);

  /* Don't let read-only properties interfere with undo.  */
  if (NILP (current_buffer->read_only))
    specbind (Qinhibit_read_only, Qt);

  while (arg > 0)
    {
      while (1)
	{
	  next = Fcar (list);
	  list = Fcdr (list);
	  /* Exit inner loop at undo boundary.  */
	  if (NILP (next))
	    break;
	  /* Handle an integer by setting point to that value.  */
	  if (INTEGERP (next))
	    SET_PT (clip_to_bounds (BEGV, XINT (next), ZV));
	  else if (CONSP (next))
	    {
	      Lisp_Object car, cdr;

	      car = Fcar (next);
	      cdr = Fcdr (next);
	      if (EQ (car, Qt))
		{
		  /* Element (t high . low) records previous modtime.  */
		  Lisp_Object high, low;
		  int mod_time;
		  struct buffer *base_buffer = current_buffer;

		  high = Fcar (cdr);
		  low = Fcdr (cdr);
		  mod_time = (XFASTINT (high) << 16) + XFASTINT (low);

		  if (current_buffer->base_buffer)
		    base_buffer = current_buffer->base_buffer;

		  /* If this records an obsolete save
		     (not matching the actual disk file)
		     then don't mark unmodified.  */
		  if (mod_time != base_buffer->modtime)
		    continue;
#ifdef CLASH_DETECTION
		  Funlock_buffer ();
#endif /* CLASH_DETECTION */
		  Fset_buffer_modified_p (Qnil);
		}
#ifdef USE_TEXT_PROPERTIES
	      else if (EQ (car, Qnil))
		{
		  /* Element (nil prop val beg . end) is property change.  */
		  Lisp_Object beg, end, prop, val;

		  prop = Fcar (cdr);
		  cdr = Fcdr (cdr);
		  val = Fcar (cdr);
		  cdr = Fcdr (cdr);
		  beg = Fcar (cdr);
		  end = Fcdr (cdr);

		  Fput_text_property (beg, end, prop, val, Qnil);
		}
#endif /* USE_TEXT_PROPERTIES */
	      else if (INTEGERP (car) && INTEGERP (cdr))
		{
		  /* Element (BEG . END) means range was inserted.  */
		  Lisp_Object end;

		  if (XINT (car) < BEGV
		      || XINT (cdr) > ZV)
		    error ("Changes to be undone are outside visible portion of buffer");
		  /* Set point first thing, so that undoing this undo
		     does not send point back to where it is now.  */
		  Fgoto_char (car);
		  Fdelete_region (car, cdr);
		}
	      else if (STRINGP (car) && INTEGERP (cdr))
		{
		  /* Element (STRING . POS) means STRING was deleted.  */
		  Lisp_Object membuf;
		  int pos = XINT (cdr);

		  membuf = car;
		  if (pos < 0)
		    {
		      if (-pos < BEGV || -pos > ZV)
			error ("Changes to be undone are outside visible portion of buffer");
		      SET_PT (-pos);
		      Finsert (1, &membuf);
		    }
		  else
		    {
		      if (pos < BEGV || pos > ZV)
			error ("Changes to be undone are outside visible portion of buffer");
		      SET_PT (pos);

		      /* Now that we record marker adjustments
			 (caused by deletion) for undo,
			 we should always insert after markers,
			 so that undoing the marker adjustments
			 put the markers back in the right place.  */
		      Finsert (1, &membuf);
		      SET_PT (pos);
		    }
		}
	      else if (MARKERP (car) && INTEGERP (cdr))
		{
		  /* (MARKER . INTEGER) means a marker MARKER
		     was adjusted by INTEGER.  */
		  if (XMARKER (car)->buffer)
		    Fset_marker (car,
				 make_number (marker_position (car) - XINT (cdr)),
				 Fmarker_buffer (car));
		}
	    }
	}
      arg--;
    }

  UNGCPRO;
  return unbind_to (count, list);
}

syms_of_undo ()
{
  Qinhibit_read_only = intern ("inhibit-read-only");
  staticpro (&Qinhibit_read_only);

  pending_boundary = Qnil;
  staticpro (&pending_boundary);

  defsubr (&Sprimitive_undo);
  defsubr (&Sundo_boundary);
}
Tip: Filter by directory path e.g. /media app.js to search for public/media/app.js.
Tip: Use camelCasing e.g. ProjME to search for ProjectModifiedEvent.java.
Tip: Filter by extension type e.g. /repo .js to search for all .js files in the /repo directory.
Tip: Separate your search with spaces e.g. /ssh pom.xml to search for src/ssh/pom.xml.
Tip: Use ↑ and ↓ arrow keys to navigate and return to view the file.
Tip: You can also navigate files with Ctrl+j (next) and Ctrl+k (previous) and view the file with Ctrl+o.
Tip: You can also navigate files with Alt+j (next) and Alt+k (previous) and view the file with Alt+o.