undo.c 11.8 KB
Newer Older
Jim Blandy's avatar
Jim Blandy committed
1
/* undo handling for GNU Emacs.
Jim Blandy's avatar
Jim Blandy committed
2
   Copyright (C) 1990, 1993 Free Software Foundation, Inc.
Jim Blandy's avatar
Jim Blandy committed
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

This file is part of GNU Emacs.

GNU Emacs is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY.  No author or distributor
accepts responsibility to anyone for the consequences of using it
or for whether it serves any particular purpose or works at all,
unless he says so in writing.  Refer to the GNU Emacs General Public
License for full details.

Everyone is granted permission to copy, modify and redistribute
GNU Emacs, but only under the conditions described in the
GNU Emacs General Public License.   A copy of this license is
supposed to have been given to you along with GNU Emacs so you
can know your rights and responsibilities.  It should be in a
file named COPYING.  Among other things, the copyright notice
and this notice must be preserved on all copies.  */


#include "config.h"
#include "lisp.h"
#include "buffer.h"

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

29 30
Lisp_Object Qinhibit_read_only;

Jim Blandy's avatar
Jim Blandy committed
31 32 33 34 35 36 37 38 39 40
/* 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)
     Lisp_Object beg, length;
{
  Lisp_Object lbeg, lend;

41 42 43
  if (EQ (current_buffer->undo_list, Qt))
    return;

Jim Blandy's avatar
Jim Blandy committed
44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59
  if (current_buffer != XBUFFER (last_undo_buffer))
    Fundo_boundary ();
  XSET (last_undo_buffer, Lisp_Buffer, current_buffer);

  if (MODIFF <= current_buffer->save_modified)
    record_first_change ();

  /* If this is following another insertion and consecutive with it
     in the buffer, combine the two.  */
  if (XTYPE (current_buffer->undo_list) == Lisp_Cons)
    {
      Lisp_Object elt;
      elt = XCONS (current_buffer->undo_list)->car;
      if (XTYPE (elt) == Lisp_Cons
	  && XTYPE (XCONS (elt)->car) == Lisp_Int
	  && XTYPE (XCONS (elt)->cdr) == Lisp_Int
60
	  && XINT (XCONS (elt)->cdr) == XINT (beg))
Jim Blandy's avatar
Jim Blandy committed
61
	{
62
	  XSETINT (XCONS (elt)->cdr, XINT (beg) + XINT (length));
Jim Blandy's avatar
Jim Blandy committed
63 64 65 66
	  return;
	}
    }

67 68 69 70
  lbeg = beg;
  XSET (lend, Lisp_Int, XINT (beg) + XINT (length));
  current_buffer->undo_list = Fcons (Fcons (lbeg, lend),
                                     current_buffer->undo_list);
Jim Blandy's avatar
Jim Blandy committed
71 72 73 74 75 76 77 78 79 80
}

/* 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;

81 82 83
  if (EQ (current_buffer->undo_list, Qt))
    return;

Jim Blandy's avatar
Jim Blandy committed
84 85 86 87 88 89 90 91 92 93 94 95 96
  if (current_buffer != XBUFFER (last_undo_buffer))
    Fundo_boundary ();
  XSET (last_undo_buffer, Lisp_Buffer, current_buffer);

  if (MODIFF <= current_buffer->save_modified)
    record_first_change ();

  if (point == beg + length)
    XSET (sbeg, Lisp_Int, -beg);
  else
    XFASTINT (sbeg) = beg;
  XFASTINT (lbeg) = beg;
  XFASTINT (lend) = beg + length;
97 98

  /* If point isn't at start of deleted range, record where it is.  */
99
  if (PT != XFASTINT (sbeg))
100 101 102
    current_buffer->undo_list
      = Fcons (make_number (PT), current_buffer->undo_list);

Jim Blandy's avatar
Jim Blandy committed
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
  current_buffer->undo_list
    = Fcons (Fcons (Fbuffer_substring (lbeg, lend), sbeg),
	     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;
  XFASTINT (high) = (current_buffer->modtime >> 16) & 0xffff;
  XFASTINT (low) = current_buffer->modtime & 0xffff;
  current_buffer->undo_list = Fcons (Fcons (Qt, Fcons (high, low)), current_buffer->undo_list);
}

131 132 133 134 135 136 137 138 139 140 141
/* 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;

142 143 144
  if (EQ (current_buffer->undo_list, Qt))
    return;

145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165
  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 <= current_buffer->save_modified)
    record_first_change ();

  XSET (lbeg, Lisp_Int, beg);
  XSET (lend, Lisp_Int, 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;
}

Jim Blandy's avatar
Jim Blandy committed
166 167 168 169 170 171 172 173 174 175
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);
Jim Blandy's avatar
Jim Blandy committed
176
  if (!NILP (tem))
Jim Blandy's avatar
Jim Blandy committed
177 178 179 180 181 182 183
    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.
Jim Blandy's avatar
Jim Blandy committed
184 185
   In practice, these are the values of undo-limit and
   undo-strong-limit.  */
Jim Blandy's avatar
Jim Blandy committed
186 187 188 189 190 191 192 193 194 195 196 197 198 199

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.
Jim Blandy's avatar
Jim Blandy committed
200 201 202
     If the first element is an undo boundary, skip past it.

     Skip, skip, skip the undo, skip, skip, skip the undo,
Jim Blandy's avatar
Jim Blandy committed
203 204
     Skip, skip, skip the undo, skip to the undo bound'ry. 
     (Get it?  "Skip to my Loo?")  */
Jim Blandy's avatar
Jim Blandy committed
205
  if (XTYPE (next) == Lisp_Cons
206
      && NILP (XCONS (next)->car))
Jim Blandy's avatar
Jim Blandy committed
207 208 209 210 211 212 213 214 215
    {
      /* 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 (XTYPE (next) == Lisp_Cons
216
	 && ! NILP (XCONS (next)->car))
Jim Blandy's avatar
Jim Blandy committed
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
    {
      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 (XTYPE (elt) == Lisp_Cons)
	{
	  size_so_far += sizeof (struct Lisp_Cons);
	  if (XTYPE (XCONS (elt)->car) == Lisp_String)
	    size_so_far += (sizeof (struct Lisp_String) - 1
			    + XSTRING (XCONS (elt)->car)->size);
	}

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

  while (XTYPE (next) == Lisp_Cons)
    {
      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.  */
Jim Blandy's avatar
Jim Blandy committed
247
      if (NILP (elt))
Jim Blandy's avatar
Jim Blandy committed
248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271
	{
	  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 (XTYPE (elt) == Lisp_Cons)
	{
	  size_so_far += sizeof (struct Lisp_Cons);
	  if (XTYPE (XCONS (elt)->car) == Lisp_String)
	    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.  */
Jim Blandy's avatar
Jim Blandy committed
272
  if (NILP (next))
Jim Blandy's avatar
Jim Blandy committed
273 274 275
    return list;

  /* Truncate at the boundary where we decided to truncate.  */
Jim Blandy's avatar
Jim Blandy committed
276
  if (!NILP (last_boundary))
Jim Blandy's avatar
Jim Blandy committed
277 278 279 280 281 282 283 284 285 286 287
    {
      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.")
288 289
  (n, list)
     Lisp_Object n, list;
Jim Blandy's avatar
Jim Blandy committed
290
{
291
  int count = specpdl_ptr - specpdl;
292
  register int arg = XINT (n);
Jim Blandy's avatar
Jim Blandy committed
293 294 295 296 297 298 299
#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);
Jim Blandy's avatar
Jim Blandy committed
300
  if (NILP (tem))
Jim Blandy's avatar
Jim Blandy committed
301 302 303
    list = Fcdr (list);
#endif

304 305 306 307
  /* Don't let read-only properties interfere with undo.  */
  if (NILP (current_buffer->read_only))
    specbind (Qinhibit_read_only, Qt);

Jim Blandy's avatar
Jim Blandy committed
308 309 310 311
  while (arg > 0)
    {
      while (1)
	{
312
	  Lisp_Object next;
Jim Blandy's avatar
Jim Blandy committed
313 314
	  next = Fcar (list);
	  list = Fcdr (list);
315
	  /* Exit inner loop at undo boundary.  */
Jim Blandy's avatar
Jim Blandy committed
316
	  if (NILP (next))
Jim Blandy's avatar
Jim Blandy committed
317
	    break;
318 319 320 321
	  /* Handle an integer by setting point to that value.  */
	  if (XTYPE (next) == Lisp_Int)
	    SET_PT (clip_to_bounds (BEGV, XINT (next), ZV));
	  else if (XTYPE (next) == Lisp_Cons)
Jim Blandy's avatar
Jim Blandy committed
322
	    {
323 324 325 326 327
	      Lisp_Object car, cdr;

	      car = Fcar (next);
	      cdr = Fcdr (next);
	      if (EQ (car, Qt))
Jim Blandy's avatar
Jim Blandy committed
328
		{
329 330 331 332 333 334
		  /* Element (t high . low) records previous modtime.  */
		  Lisp_Object high, low;
		  int mod_time;

		  high = Fcar (cdr);
		  low = Fcdr (cdr);
335
		  mod_time = (XFASTINT (high) << 16) + XFASTINT (low);
336 337 338 339 340
		  /* If this records an obsolete save
		     (not matching the actual disk file)
		     then don't mark unmodified.  */
		  if (mod_time != current_buffer->modtime)
		    break;
341
#ifdef CLASH_DETECTION
342
		  Funlock_buffer ();
343
#endif /* CLASH_DETECTION */
344
		  Fset_buffer_modified_p (Qnil);
Jim Blandy's avatar
Jim Blandy committed
345
		}
346 347
#ifdef USE_TEXT_PROPERTIES
	      else if (EQ (car, Qnil))
348
		{
349
		  /* Element (nil prop val beg . end) is property change.  */
350 351 352 353 354 355 356 357 358 359 360
		  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);
		}
361
#endif /* USE_TEXT_PROPERTIES */
362
	      else if (XTYPE (car) == Lisp_Int && XTYPE (cdr) == Lisp_Int)
Jim Blandy's avatar
Jim Blandy committed
363
		{
364 365 366 367 368
		  /* Element (BEG . END) means range was inserted.  */
		  Lisp_Object end;

		  if (XINT (car) < BEGV
		      || XINT (cdr) > ZV)
Jim Blandy's avatar
Jim Blandy committed
369
		    error ("Changes to be undone are outside visible portion of buffer");
370 371
		  /* Set point first thing, so that undoing this undo
		     does not send point back to where it is now.  */
372
		  Fgoto_char (car);
373
		  Fdelete_region (car, cdr);
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
		}
	      else if (XTYPE (car) == Lisp_String && XTYPE (cdr) == Lisp_Int)
		{
		  /* 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);

		      /* Insert before markers so that if the mark is
			 currently on the boundary of this deletion, it
			 ends up on the other side of the now-undeleted
			 text from point.  Since undo doesn't even keep
			 track of the mark, this isn't really necessary,
			 but it may lead to better behavior in certain
			 situations.  */
		      Finsert_before_markers (1, &membuf);
		      SET_PT (pos);
		    }
Jim Blandy's avatar
Jim Blandy committed
405 406 407 408 409 410
		}
	    }
	}
      arg--;
    }

411
  return unbind_to (count, list);
Jim Blandy's avatar
Jim Blandy committed
412 413 414 415
}

syms_of_undo ()
{
416 417 418
  Qinhibit_read_only = intern ("inhibit-read-only");
  staticpro (&Qinhibit_read_only);

Jim Blandy's avatar
Jim Blandy committed
419 420 421
  defsubr (&Sprimitive_undo);
  defsubr (&Sundo_boundary);
}