1 /* undo handling for GNU Emacs.
2 Copyright (C) 1990, 1993, 1994, 2000, 2001, 2002, 2003, 2004,
3 2005, 2006, 2007, 2008, 2009, 2010, 2011 Free Software Foundation, Inc.
5 This file is part of GNU Emacs.
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.
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.
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/>. */
28 /* Last buffer for which undo information was recorded. */
29 /* BEWARE: This is not traced by the GC, so never dereference it! */
30 struct buffer
*last_undo_buffer
;
32 /* Position of point last time we inserted a boundary. */
33 struct buffer
*last_boundary_buffer
;
34 EMACS_INT last_boundary_position
;
36 Lisp_Object Qinhibit_read_only
;
38 /* Marker for function call undo list elements. */
42 /* The first time a command records something for undo.
43 it also allocates the undo-boundary object
44 which will be added to the list at the end of the command.
45 This ensures we can't run out of space while trying to make
47 Lisp_Object pending_boundary
;
49 /* Record point as it was at beginning of this command (if necessary)
50 and prepare the undo info for recording a change.
51 PT is the position of point that will naturally occur as a result of the
52 undo record that will be added just after this command terminates. */
55 record_point (EMACS_INT pt
)
59 /* Don't record position of pt when undo_inhibit_record_point holds. */
60 if (undo_inhibit_record_point
)
63 /* Allocate a cons cell to be the undo boundary after this command. */
64 if (NILP (pending_boundary
))
65 pending_boundary
= Fcons (Qnil
, Qnil
);
67 if ((current_buffer
!= last_undo_buffer
)
68 /* Don't call Fundo_boundary for the first change. Otherwise we
69 risk overwriting last_boundary_position in Fundo_boundary with
70 PT of the current buffer and as a consequence not insert an
71 undo boundary because last_boundary_position will equal pt in
72 the test at the end of the present function (Bug#731). */
73 && (MODIFF
> SAVE_MODIFF
))
75 last_undo_buffer
= current_buffer
;
77 if (CONSP (current_buffer
->undo_list
))
79 /* Set AT_BOUNDARY to 1 only when we have nothing other than
80 marker adjustment before undo boundary. */
82 Lisp_Object tail
= current_buffer
->undo_list
, elt
;
90 if (NILP (elt
) || ! (CONSP (elt
) && MARKERP (XCAR (elt
))))
94 at_boundary
= NILP (elt
);
99 if (MODIFF
<= SAVE_MODIFF
)
100 record_first_change ();
102 /* If we are just after an undo boundary, and
103 point wasn't at start of deleted range, record where it was. */
105 && current_buffer
== last_boundary_buffer
106 && last_boundary_position
!= pt
)
107 current_buffer
->undo_list
108 = Fcons (make_number (last_boundary_position
), current_buffer
->undo_list
);
111 /* Record an insertion that just happened or is about to happen,
112 for LENGTH characters at position BEG.
113 (It is possible to record an insertion before or after the fact
114 because we don't need to record the contents.) */
117 record_insert (EMACS_INT beg
, EMACS_INT length
)
119 Lisp_Object lbeg
, lend
;
121 if (EQ (current_buffer
->undo_list
, Qt
))
126 /* If this is following another insertion and consecutive with it
127 in the buffer, combine the two. */
128 if (CONSP (current_buffer
->undo_list
))
131 elt
= XCAR (current_buffer
->undo_list
);
133 && INTEGERP (XCAR (elt
))
134 && INTEGERP (XCDR (elt
))
135 && XINT (XCDR (elt
)) == beg
)
137 XSETCDR (elt
, make_number (beg
+ length
));
142 XSETFASTINT (lbeg
, beg
);
143 XSETINT (lend
, beg
+ length
);
144 current_buffer
->undo_list
= Fcons (Fcons (lbeg
, lend
),
145 current_buffer
->undo_list
);
148 /* Record that a deletion is about to take place,
149 of the characters in STRING, at location BEG. */
152 record_delete (EMACS_INT beg
, Lisp_Object string
)
156 if (EQ (current_buffer
->undo_list
, Qt
))
159 if (PT
== beg
+ SCHARS (string
))
161 XSETINT (sbeg
, -beg
);
166 XSETFASTINT (sbeg
, beg
);
170 current_buffer
->undo_list
171 = Fcons (Fcons (string
, sbeg
), current_buffer
->undo_list
);
174 /* Record the fact that MARKER is about to be adjusted by ADJUSTMENT.
175 This is done only when a marker points within text being deleted,
176 because that's the only case where an automatic marker adjustment
177 won't be inverted automatically by undoing the buffer modification. */
180 record_marker_adjustment (Lisp_Object marker
, EMACS_INT adjustment
)
182 if (EQ (current_buffer
->undo_list
, Qt
))
185 /* Allocate a cons cell to be the undo boundary after this command. */
186 if (NILP (pending_boundary
))
187 pending_boundary
= Fcons (Qnil
, Qnil
);
189 if (current_buffer
!= last_undo_buffer
)
191 last_undo_buffer
= current_buffer
;
193 current_buffer
->undo_list
194 = Fcons (Fcons (marker
, make_number (adjustment
)),
195 current_buffer
->undo_list
);
198 /* Record that a replacement is about to take place,
199 for LENGTH characters at location BEG.
200 The replacement must not change the number of characters. */
203 record_change (EMACS_INT beg
, EMACS_INT length
)
205 record_delete (beg
, make_buffer_string (beg
, beg
+ length
, 1));
206 record_insert (beg
, length
);
209 /* Record that an unmodified buffer is about to be changed.
210 Record the file modification date so that when undoing this entry
211 we can tell whether it is obsolete because the file was saved again. */
214 record_first_change (void)
216 Lisp_Object high
, low
;
217 struct buffer
*base_buffer
= current_buffer
;
219 if (EQ (current_buffer
->undo_list
, Qt
))
222 if (current_buffer
!= last_undo_buffer
)
224 last_undo_buffer
= current_buffer
;
226 if (base_buffer
->base_buffer
)
227 base_buffer
= base_buffer
->base_buffer
;
229 XSETFASTINT (high
, (base_buffer
->modtime
>> 16) & 0xffff);
230 XSETFASTINT (low
, base_buffer
->modtime
& 0xffff);
231 current_buffer
->undo_list
= Fcons (Fcons (Qt
, Fcons (high
, low
)), current_buffer
->undo_list
);
234 /* Record a change in property PROP (whose old value was VAL)
235 for LENGTH characters starting at position BEG in BUFFER. */
238 record_property_change (EMACS_INT beg
, EMACS_INT length
,
239 Lisp_Object prop
, Lisp_Object value
,
242 Lisp_Object lbeg
, lend
, entry
;
243 struct buffer
*obuf
= current_buffer
, *buf
= XBUFFER (buffer
);
246 if (EQ (buf
->undo_list
, Qt
))
249 /* Allocate a cons cell to be the undo boundary after this command. */
250 if (NILP (pending_boundary
))
251 pending_boundary
= Fcons (Qnil
, Qnil
);
253 if (buf
!= last_undo_buffer
)
255 last_undo_buffer
= buf
;
257 /* Switch temporarily to the buffer that was changed. */
258 current_buffer
= buf
;
263 if (MODIFF
<= SAVE_MODIFF
)
264 record_first_change ();
267 XSETINT (lend
, beg
+ length
);
268 entry
= Fcons (Qnil
, Fcons (prop
, Fcons (value
, Fcons (lbeg
, lend
))));
269 current_buffer
->undo_list
= Fcons (entry
, current_buffer
->undo_list
);
271 current_buffer
= obuf
;
274 DEFUN ("undo-boundary", Fundo_boundary
, Sundo_boundary
, 0, 0, 0,
275 doc
: /* Mark a boundary between units of undo.
276 An undo command will stop at this point,
277 but another undo command will undo to the previous boundary. */)
281 if (EQ (current_buffer
->undo_list
, Qt
))
283 tem
= Fcar (current_buffer
->undo_list
);
286 /* One way or another, cons nil onto the front of the undo list. */
287 if (!NILP (pending_boundary
))
289 /* If we have preallocated the cons cell to use here,
291 XSETCDR (pending_boundary
, current_buffer
->undo_list
);
292 current_buffer
->undo_list
= pending_boundary
;
293 pending_boundary
= Qnil
;
296 current_buffer
->undo_list
= Fcons (Qnil
, current_buffer
->undo_list
);
298 last_boundary_position
= PT
;
299 last_boundary_buffer
= current_buffer
;
303 /* At garbage collection time, make an undo list shorter at the end,
304 returning the truncated list. How this is done depends on the
305 variables undo-limit, undo-strong-limit and undo-outer-limit.
306 In some cases this works by calling undo-outer-limit-function. */
309 truncate_undo_list (struct buffer
*b
)
312 Lisp_Object prev
, next
, last_boundary
;
315 /* Make sure that calling undo-outer-limit-function
316 won't cause another GC. */
317 int count
= inhibit_garbage_collection ();
319 /* Make the buffer current to get its local values of variables such
320 as undo_limit. Also so that Vundo_outer_limit_function can
321 tell which buffer to operate on. */
322 record_unwind_protect (set_buffer_if_live
, Fcurrent_buffer ());
323 set_buffer_internal (b
);
329 last_boundary
= Qnil
;
331 /* If the first element is an undo boundary, skip past it. */
332 if (CONSP (next
) && NILP (XCAR (next
)))
334 /* Add in the space occupied by this element and its chain link. */
335 size_so_far
+= sizeof (struct Lisp_Cons
);
337 /* Advance to next element. */
342 /* Always preserve at least the most recent undo record
343 unless it is really horribly big.
345 Skip, skip, skip the undo, skip, skip, skip the undo,
346 Skip, skip, skip the undo, skip to the undo bound'ry. */
348 while (CONSP (next
) && ! NILP (XCAR (next
)))
353 /* Add in the space occupied by this element and its chain link. */
354 size_so_far
+= sizeof (struct Lisp_Cons
);
357 size_so_far
+= sizeof (struct Lisp_Cons
);
358 if (STRINGP (XCAR (elt
)))
359 size_so_far
+= (sizeof (struct Lisp_String
) - 1
360 + SCHARS (XCAR (elt
)));
363 /* Advance to next element. */
368 /* If by the first boundary we have already passed undo_outer_limit,
369 we're heading for memory full, so offer to clear out the list. */
370 if (INTEGERP (Vundo_outer_limit
)
371 && size_so_far
> XINT (Vundo_outer_limit
)
372 && !NILP (Vundo_outer_limit_function
))
375 struct buffer
*temp
= last_undo_buffer
;
377 /* Normally the function this calls is undo-outer-limit-truncate. */
378 tem
= call1 (Vundo_outer_limit_function
, make_number (size_so_far
));
381 /* The function is responsible for making
382 any desired changes in buffer-undo-list. */
383 unbind_to (count
, Qnil
);
386 /* That function probably used the minibuffer, and if so, that
387 changed last_undo_buffer. Change it back so that we don't
388 force next change to make an undo boundary here. */
389 last_undo_buffer
= temp
;
393 last_boundary
= prev
;
395 /* Keep additional undo data, if it fits in the limits. */
401 /* When we get to a boundary, decide whether to truncate
402 either before or after it. The lower threshold, undo_limit,
403 tells us to truncate after it. If its size pushes past
404 the higher threshold undo_strong_limit, we truncate before it. */
407 if (size_so_far
> undo_strong_limit
)
409 last_boundary
= prev
;
410 if (size_so_far
> undo_limit
)
414 /* Add in the space occupied by this element and its chain link. */
415 size_so_far
+= sizeof (struct Lisp_Cons
);
418 size_so_far
+= sizeof (struct Lisp_Cons
);
419 if (STRINGP (XCAR (elt
)))
420 size_so_far
+= (sizeof (struct Lisp_String
) - 1
421 + SCHARS (XCAR (elt
)));
424 /* Advance to next element. */
429 /* If we scanned the whole list, it is short enough; don't change it. */
432 /* Truncate at the boundary where we decided to truncate. */
433 else if (!NILP (last_boundary
))
434 XSETCDR (last_boundary
, Qnil
);
435 /* There's nothing we decided to keep, so clear it out. */
439 unbind_to (count
, Qnil
);
442 DEFUN ("primitive-undo", Fprimitive_undo
, Sprimitive_undo
, 2, 2, 0,
443 doc
: /* Undo N records from the front of the list LIST.
444 Return what remains of the list. */)
445 (Lisp_Object n
, Lisp_Object list
)
447 struct gcpro gcpro1
, gcpro2
;
449 int count
= SPECPDL_INDEX ();
454 #if 0 /* This is a good feature, but would make undo-start
455 unable to do what is expected. */
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. */
469 /* I don't think we need to gcpro oldlist, as we use it only
470 to check for EQ. ++kfs */
472 /* In a writable buffer, enable undoing read-only text that is so
473 because of text properties. */
474 if (NILP (current_buffer
->read_only
))
475 specbind (Qinhibit_read_only
, Qt
);
477 /* Don't let `intangible' properties interfere with undo. */
478 specbind (Qinhibit_point_motion_hooks
, Qt
);
480 oldlist
= current_buffer
->undo_list
;
488 /* Exit inner loop at undo boundary. */
491 /* Handle an integer by setting point to that value. */
493 SET_PT (clip_to_bounds (BEGV
, XINT (next
), ZV
));
494 else if (CONSP (next
))
496 Lisp_Object car
, cdr
;
502 /* Element (t high . low) records previous modtime. */
503 Lisp_Object high
, low
;
505 struct buffer
*base_buffer
= current_buffer
;
509 mod_time
= (XFASTINT (high
) << 16) + XFASTINT (low
);
511 if (current_buffer
->base_buffer
)
512 base_buffer
= current_buffer
->base_buffer
;
514 /* If this records an obsolete save
515 (not matching the actual disk file)
516 then don't mark unmodified. */
517 if (mod_time
!= base_buffer
->modtime
)
519 #ifdef CLASH_DETECTION
521 #endif /* CLASH_DETECTION */
522 Fset_buffer_modified_p (Qnil
);
524 else if (EQ (car
, Qnil
))
526 /* Element (nil PROP VAL BEG . END) is property change. */
527 Lisp_Object beg
, end
, prop
, val
;
536 if (XINT (beg
) < BEGV
|| XINT (end
) > ZV
)
537 error ("Changes to be undone are outside visible portion of buffer");
538 Fput_text_property (beg
, end
, prop
, val
, Qnil
);
540 else if (INTEGERP (car
) && INTEGERP (cdr
))
542 /* Element (BEG . END) means range was inserted. */
544 if (XINT (car
) < BEGV
546 error ("Changes to be undone are outside visible portion of buffer");
547 /* Set point first thing, so that undoing this undo
548 does not send point back to where it is now. */
550 Fdelete_region (car
, cdr
);
552 else if (EQ (car
, Qapply
))
554 /* Element (apply FUN . ARGS) means call FUN to undo. */
555 struct buffer
*save_buffer
= current_buffer
;
561 /* Long format: (apply DELTA START END FUN . ARGS). */
562 Lisp_Object delta
= car
;
563 Lisp_Object start
= Fcar (cdr
);
564 Lisp_Object end
= Fcar (Fcdr (cdr
));
565 Lisp_Object start_mark
= Fcopy_marker (start
, Qnil
);
566 Lisp_Object end_mark
= Fcopy_marker (end
, Qt
);
568 cdr
= Fcdr (Fcdr (cdr
));
569 apply1 (Fcar (cdr
), Fcdr (cdr
));
571 /* Check that the function did what the entry said it
573 if (!EQ (start
, Fmarker_position (start_mark
))
574 || (XINT (delta
) + XINT (end
)
575 != marker_position (end_mark
)))
576 error ("Changes to be undone by function different than announced");
577 Fset_marker (start_mark
, Qnil
, Qnil
);
578 Fset_marker (end_mark
, Qnil
, Qnil
);
583 if (save_buffer
!= current_buffer
)
584 error ("Undo function switched buffer");
587 else if (STRINGP (car
) && INTEGERP (cdr
))
589 /* Element (STRING . POS) means STRING was deleted. */
591 EMACS_INT pos
= XINT (cdr
);
596 if (-pos
< BEGV
|| -pos
> ZV
)
597 error ("Changes to be undone are outside visible portion of buffer");
599 Finsert (1, &membuf
);
603 if (pos
< BEGV
|| pos
> ZV
)
604 error ("Changes to be undone are outside visible portion of buffer");
607 /* Now that we record marker adjustments
608 (caused by deletion) for undo,
609 we should always insert after markers,
610 so that undoing the marker adjustments
611 put the markers back in the right place. */
612 Finsert (1, &membuf
);
616 else if (MARKERP (car
) && INTEGERP (cdr
))
618 /* (MARKER . INTEGER) means a marker MARKER
619 was adjusted by INTEGER. */
620 if (XMARKER (car
)->buffer
)
622 make_number (marker_position (car
) - XINT (cdr
)),
623 Fmarker_buffer (car
));
631 /* Make sure an apply entry produces at least one undo entry,
632 so the test in `undo' for continuing an undo series
635 && EQ (oldlist
, current_buffer
->undo_list
))
636 current_buffer
->undo_list
637 = Fcons (list3 (Qapply
, Qcdr
, Qnil
), current_buffer
->undo_list
);
640 return unbind_to (count
, list
);
646 Qinhibit_read_only
= intern_c_string ("inhibit-read-only");
647 staticpro (&Qinhibit_read_only
);
649 Qapply
= intern_c_string ("apply");
652 pending_boundary
= Qnil
;
653 staticpro (&pending_boundary
);
655 last_undo_buffer
= NULL
;
656 last_boundary_buffer
= NULL
;
658 defsubr (&Sprimitive_undo
);
659 defsubr (&Sundo_boundary
);
661 DEFVAR_INT ("undo-limit", undo_limit
,
662 doc
: /* Keep no more undo information once it exceeds this size.
663 This limit is applied when garbage collection happens.
664 When a previous command increases the total undo list size past this
665 value, the earlier commands that came before it are forgotten.
667 The size is counted as the number of bytes occupied,
668 which includes both saved text and other data. */);
671 DEFVAR_INT ("undo-strong-limit", undo_strong_limit
,
672 doc
: /* Don't keep more than this much size of undo information.
673 This limit is applied when garbage collection happens.
674 When a previous command increases the total undo list size past this
675 value, that command and the earlier commands that came before it are forgotten.
676 However, the most recent buffer-modifying command's undo info
677 is never discarded for this reason.
679 The size is counted as the number of bytes occupied,
680 which includes both saved text and other data. */);
681 undo_strong_limit
= 120000;
683 DEFVAR_LISP ("undo-outer-limit", Vundo_outer_limit
,
684 doc
: /* Outer limit on size of undo information for one command.
685 At garbage collection time, if the current command has produced
686 more than this much undo information, it discards the info and displays
687 a warning. This is a last-ditch limit to prevent memory overflow.
689 The size is counted as the number of bytes occupied, which includes
690 both saved text and other data. A value of nil means no limit. In
691 this case, accumulating one huge undo entry could make Emacs crash as
692 a result of memory overflow.
694 In fact, this calls the function which is the value of
695 `undo-outer-limit-function' with one argument, the size.
696 The text above describes the behavior of the function
697 that variable usually specifies. */);
698 Vundo_outer_limit
= make_number (12000000);
700 DEFVAR_LISP ("undo-outer-limit-function", Vundo_outer_limit_function
,
701 doc
: /* Function to call when an undo list exceeds `undo-outer-limit'.
702 This function is called with one argument, the current undo list size
703 for the most recent command (since the last undo boundary).
704 If the function returns t, that means truncation has been fully handled.
705 If it returns nil, the other forms of truncation are done.
707 Garbage collection is inhibited around the call to this function,
708 so it must make sure not to do a lot of consing. */);
709 Vundo_outer_limit_function
= Qnil
;
711 DEFVAR_BOOL ("undo-inhibit-record-point", undo_inhibit_record_point
,
712 doc
: /* Non-nil means do not record `point' in `buffer-undo-list'. */);
713 undo_inhibit_record_point
= 0;