Add 2008 to copyright years.

[bpt/emacs.git] / src / undo.c

diff --git a/src/undo.c b/src/undo.c
index c09da9c..bf528e2 100644 (file)
--- a/src/undo.c
+++ b/src/undo.c
@@ -1,11 +1,12 @@
 /* undo handling for GNU Emacs.
 /* undo handling for GNU Emacs.

-   Copyright (C) 1990, 1993, 1994 Free Software Foundation, Inc.
+   Copyright (C) 1990, 1993, 1994, 2000, 2001, 2002, 2003, 2004,
+                 2005, 2006, 2007, 2008  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
 
 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)
+the Free Software Foundation; either version 3, or (at your option)

 any later version.
 
 GNU Emacs is distributed in the hope that it will be useful,
 any later version.
 
 GNU Emacs is distributed in the hope that it will be useful,


@@ -15,20 +16,36 @@ 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
 
 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.  */
+the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
+Boston, MA 02110-1301, USA.  */

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

+#include "window.h"
+
+/* Limits controlling how much undo information to keep.  */
+
+EMACS_INT undo_limit;
+EMACS_INT undo_strong_limit;
+
+Lisp_Object Vundo_outer_limit;
+
+/* Function to call when undo_outer_limit is exceeded.  */
+
+Lisp_Object Vundo_outer_limit_function;

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

+/* Marker for function call undo list elements.  */
+
+Lisp_Object Qapply;
+

 /* 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.
 /* 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.


@@ -36,19 +53,16 @@ Lisp_Object Qinhibit_read_only;
    an undo-boundary.  */
 Lisp_Object pending_boundary;
 
    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 point as it was at beginning of this command (if necessary)
+   And prepare the undo info for recording a change.
+   PT is the position of point that will naturally occur as a result of the
+   undo record that will be added just after this command terminates.  */

 
 

-void
-record_insert (beg, length)
-     int beg, length;
+static void
+record_point (pt)
+     int pt;

 {
 {

-  Lisp_Object lbeg, lend;
-
-  if (EQ (current_buffer->undo_list, Qt))
-    return;
+  int at_boundary;

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


@@ -59,9 +73,65 @@ record_insert (beg, length)
     Fundo_boundary ();
   XSETBUFFER (last_undo_buffer, current_buffer);
 
     Fundo_boundary ();
   XSETBUFFER (last_undo_buffer, current_buffer);
 

+  if (CONSP (current_buffer->undo_list))
+    {
+      /* Set AT_BOUNDARY to 1 only when we have nothing other than
+         marker adjustment before undo boundary.  */
+
+      Lisp_Object tail = current_buffer->undo_list, elt;
+
+      while (1)
+       {
+         if (NILP (tail))
+           elt = Qnil;
+         else
+           elt = XCAR (tail);
+         if (NILP (elt) || ! (CONSP (elt) && MARKERP (XCAR (elt))))
+           break;
+         tail = XCDR (tail);
+       }
+      at_boundary = NILP (elt);
+    }
+  else
+    at_boundary = 1;
+

   if (MODIFF <= SAVE_MODIFF)
     record_first_change ();
 
   if (MODIFF <= SAVE_MODIFF)
     record_first_change ();
 

+  /* If we are just after an undo boundary, and
+     point wasn't at start of deleted range, record where it was.  */
+  if (at_boundary
+      && BUFFERP (last_point_position_buffer)
+      /* If we're called from batch mode, this could be nil.  */
+      && current_buffer == XBUFFER (last_point_position_buffer))
+    {
+      /* If we have switched windows, use the point value
+        from the window we are in.  */
+      if (! EQ (last_point_position_window, selected_window))
+       last_point_position = marker_position (XWINDOW (selected_window)->pointm);
+
+      if (last_point_position != pt)
+       current_buffer->undo_list
+         = Fcons (make_number (last_point_position), current_buffer->undo_list);
+    }
+}
+
+/* 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.)  */
+
+void
+record_insert (beg, length)
+     int beg, length;
+{
+  Lisp_Object lbeg, lend;
+
+  if (EQ (current_buffer->undo_list, Qt))
+    return;
+
+  record_point (beg);
+

   /* If this is following another insertion and consecutive with it
      in the buffer, combine the two.  */
   if (CONSP (current_buffer->undo_list))
   /* If this is following another insertion and consecutive with it
      in the buffer, combine the two.  */
   if (CONSP (current_buffer->undo_list))


@@ -73,7 +143,7 @@ record_insert (beg, length)
          && INTEGERP (XCDR (elt))
          && XINT (XCDR (elt)) == beg)
        {
          && INTEGERP (XCDR (elt))
          && XINT (XCDR (elt)) == beg)
        {

-         XSETINT (XCDR (elt), beg + length);
+         XSETCDR (elt, make_number (beg + length));

          return;
        }
     }
          return;
        }
     }


@@ -93,56 +163,20 @@ record_delete (beg, string)
      Lisp_Object string;
 {
   Lisp_Object sbeg;
      Lisp_Object string;
 {
   Lisp_Object sbeg;

-  int at_boundary;

 
   if (EQ (current_buffer->undo_list, Qt))
     return;
 
 
   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 (CONSP (current_buffer->undo_list))
+  if (PT == beg + SCHARS (string))

     {
     {

-      /* Set AT_BOUNDARY to 1 only when we have nothing other than
-         marker adjustment before undo boundary.  */
-
-      Lisp_Object tail = current_buffer->undo_list, elt;
-
-      while (1)
-       {
-         if (NILP (tail))
-           elt = Qnil;
-         else
-           elt = XCAR (tail);
-         if (NILP (elt) || ! (CONSP (elt) && MARKERP (XCAR (elt))))
-           break;
-         tail = XCDR (tail);
-       }
-      at_boundary = NILP (elt);
+      XSETINT (sbeg, -beg);
+      record_point (PT);

     }
   else
     }
   else

-    at_boundary = 0;
-
-  if (MODIFF <= SAVE_MODIFF)
-    record_first_change ();
-
-  if (PT == beg + XSTRING (string)->size)
-    XSETINT (sbeg, -beg);
-  else
-    XSETFASTINT (sbeg, beg);
-
-  /* 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);
+    {
+      XSETFASTINT (sbeg, beg);
+      record_point (beg);
+    }

 
   current_buffer->undo_list
     = Fcons (Fcons (string, sbeg), current_buffer->undo_list);
 
   current_buffer->undo_list
     = Fcons (Fcons (string, sbeg), current_buffer->undo_list);


@@ -165,7 +199,8 @@ record_marker_adjustment (marker, adjustment)
   if (NILP (pending_boundary))
     pending_boundary = Fcons (Qnil, Qnil);
 
   if (NILP (pending_boundary))
     pending_boundary = Fcons (Qnil, Qnil);
 

-  if (current_buffer != XBUFFER (last_undo_buffer))
+  if (!BUFFERP (last_undo_buffer)
+      || current_buffer != XBUFFER (last_undo_buffer))

     Fundo_boundary ();
   XSETBUFFER (last_undo_buffer, current_buffer);
 
     Fundo_boundary ();
   XSETBUFFER (last_undo_buffer, current_buffer);
 


@@ -199,7 +234,8 @@ record_first_change ()
   if (EQ (current_buffer->undo_list, Qt))
     return;
 
   if (EQ (current_buffer->undo_list, Qt))
     return;
 

-  if (current_buffer != XBUFFER (last_undo_buffer))
+  if (!BUFFERP (last_undo_buffer)
+      || current_buffer != XBUFFER (last_undo_buffer))

     Fundo_boundary ();
   XSETBUFFER (last_undo_buffer, current_buffer);
 
     Fundo_boundary ();
   XSETBUFFER (last_undo_buffer, current_buffer);
 


@@ -252,10 +288,10 @@ record_property_change (beg, length, prop, value, buffer)
 }
 
 DEFUN ("undo-boundary", Fundo_boundary, Sundo_boundary, 0, 0, 0,
 }
 
 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.")
-  ()
+       doc: /* Mark a boundary between units of undo.
+An undo command will stop at this point,
+but another undo command will undo to the previous boundary.  */)
+     ()

 {
   Lisp_Object tem;
   if (EQ (current_buffer->undo_list, Qt))
 {
   Lisp_Object tem;
   if (EQ (current_buffer->undo_list, Qt))


@@ -268,7 +304,7 @@ but another undo command will undo to the previous boundary.")
        {
          /* If we have preallocated the cons cell to use here,
             use that one.  */
        {
          /* If we have preallocated the cons cell to use here,
             use that one.  */

-         XCDR (pending_boundary) = current_buffer->undo_list;
+         XSETCDR (pending_boundary, current_buffer->undo_list);

          current_buffer->undo_list = pending_boundary;
          pending_boundary = Qnil;
        }
          current_buffer->undo_list = pending_boundary;
          pending_boundary = Qnil;
        }


@@ -279,29 +315,35 @@ but another undo command will undo to the previous boundary.")
 }
 
 /* At garbage collection time, make an undo list shorter at the end,
 }
 
 /* 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;
+   returning the truncated list.  How this is done depends on the
+   variables undo-limit, undo-strong-limit and undo-outer-limit.
+   In some cases this works by calling undo-outer-limit-function.  */
+
+void
+truncate_undo_list (b)
+     struct buffer *b;

 {
 {

+  Lisp_Object list;

   Lisp_Object prev, next, last_boundary;
   int size_so_far = 0;
 
   Lisp_Object prev, next, last_boundary;
   int size_so_far = 0;
 

+  /* Make sure that calling undo-outer-limit-function
+     won't cause another GC.  */
+  int count = inhibit_garbage_collection ();
+
+  /* Make the buffer current to get its local values of variables such
+     as undo_limit.  Also so that Vundo_outer_limit_function can
+     tell which buffer to operate on.  */
+  record_unwind_protect (set_buffer_if_live, Fcurrent_buffer ());
+  set_buffer_internal (b);
+
+  list = b->undo_list;
+

   prev = Qnil;
   next = list;
   last_boundary = Qnil;
 
   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 the first element is an undo boundary, skip past it.  */

   if (CONSP (next) && NILP (XCAR (next)))
     {
       /* Add in the space occupied by this element and its chain link.  */
   if (CONSP (next) && NILP (XCAR (next)))
     {
       /* Add in the space occupied by this element and its chain link.  */


@@ -311,6 +353,13 @@ truncate_undo_list (list, minsize, maxsize)
       prev = next;
       next = XCDR (next);
     }
       prev = next;
       next = XCDR (next);
     }

+
+  /* Always preserve at least the most recent undo record
+     unless it is really horribly big.
+
+     Skip, skip, skip the undo, skip, skip, skip the undo,
+     Skip, skip, skip the undo, skip to the undo bound'ry.  */
+

   while (CONSP (next) && ! NILP (XCAR (next)))
     {
       Lisp_Object elt;
   while (CONSP (next) && ! NILP (XCAR (next)))
     {
       Lisp_Object elt;


@@ -323,31 +372,56 @@ truncate_undo_list (list, minsize, maxsize)
          size_so_far += sizeof (struct Lisp_Cons);
          if (STRINGP (XCAR (elt)))
            size_so_far += (sizeof (struct Lisp_String) - 1
          size_so_far += sizeof (struct Lisp_Cons);
          if (STRINGP (XCAR (elt)))
            size_so_far += (sizeof (struct Lisp_String) - 1

-                           + XSTRING (XCAR (elt))->size);
+                           + SCHARS (XCAR (elt)));

        }
 
       /* Advance to next element.  */
       prev = next;
       next = XCDR (next);
     }
        }
 
       /* Advance to next element.  */
       prev = next;
       next = XCDR (next);
     }

+
+  /* If by the first boundary we have already passed undo_outer_limit,
+     we're heading for memory full, so offer to clear out the list.  */
+  if (INTEGERP (Vundo_outer_limit)
+      && size_so_far > XINT (Vundo_outer_limit)
+      && !NILP (Vundo_outer_limit_function))
+    {
+      Lisp_Object temp = last_undo_buffer, tem;
+
+      /* Normally the function this calls is undo-outer-limit-truncate.  */
+      tem = call1 (Vundo_outer_limit_function, make_number (size_so_far));
+      if (! NILP (tem))
+       {
+         /* The function is responsible for making
+            any desired changes in buffer-undo-list.  */
+         unbind_to (count, Qnil);
+         return;
+       }
+      /* That function probably used the minibuffer, and if so, that
+        changed last_undo_buffer.  Change it back so that we don't
+        force next change to make an undo boundary here.  */
+      last_undo_buffer = temp;
+    }
+

   if (CONSP (next))
     last_boundary = prev;
 
   if (CONSP (next))
     last_boundary = prev;
 

+  /* Keep additional undo data, if it fits in the limits.  */

   while (CONSP (next))
     {
       Lisp_Object elt;
       elt = XCAR (next);
 
       /* When we get to a boundary, decide whether to truncate
   while (CONSP (next))
     {
       Lisp_Object elt;
       elt = XCAR (next);
 
       /* When we get to a boundary, decide whether to truncate

-        either before or after it.  The lower threshold, MINSIZE,
+        either before or after it.  The lower threshold, undo_limit,

         tells us to truncate after it.  If its size pushes past
         tells us to truncate after it.  If its size pushes past

-        the higher threshold MAXSIZE as well, we truncate before it.  */
+        the higher threshold undo_strong_limit, we truncate before it.  */

       if (NILP (elt))
        {
       if (NILP (elt))
        {

-         if (size_so_far > maxsize)
+         if (size_so_far > undo_strong_limit)

            break;
          last_boundary = prev;
            break;
          last_boundary = prev;

-         if (size_so_far > minsize)
+         if (size_so_far > undo_limit)

            break;
        }
 
            break;
        }
 


@@ -358,7 +432,7 @@ truncate_undo_list (list, minsize, maxsize)
          size_so_far += sizeof (struct Lisp_Cons);
          if (STRINGP (XCAR (elt)))
            size_so_far += (sizeof (struct Lisp_String) - 1
          size_so_far += sizeof (struct Lisp_Cons);
          if (STRINGP (XCAR (elt)))
            size_so_far += (sizeof (struct Lisp_String) - 1

-                           + XSTRING (XCAR (elt))->size);
+                           + SCHARS (XCAR (elt)));

        }
 
       /* Advance to next element.  */
        }
 
       /* Advance to next element.  */


@@ -368,28 +442,30 @@ truncate_undo_list (list, minsize, maxsize)
 
   /* If we scanned the whole list, it is short enough; don't change it.  */
   if (NILP (next))
 
   /* 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.  */
   /* Truncate at the boundary where we decided to truncate.  */

-  if (!NILP (last_boundary))
-    {
-      XCDR (last_boundary) = Qnil;
-      return list;
-    }
+  else if (!NILP (last_boundary))
+    XSETCDR (last_boundary, Qnil);
+  /* There's nothing we decided to keep, so clear it out.  */

   else
   else

-    return Qnil;
+    b->undo_list = Qnil;
+
+  unbind_to (count, Qnil);

 }
 \f
 DEFUN ("primitive-undo", Fprimitive_undo, Sprimitive_undo, 2, 2, 0,
 }
 \f
 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)
+       doc: /* Undo N records from the front of the list LIST.
+Return what remains of the list.  */)
+     (n, list)

      Lisp_Object n, list;
 {
   struct gcpro gcpro1, gcpro2;
   Lisp_Object next;
      Lisp_Object n, list;
 {
   struct gcpro gcpro1, gcpro2;
   Lisp_Object next;

-  int count = specpdl_ptr - specpdl;
+  int count = SPECPDL_INDEX ();

   register int arg;
   register int arg;

+  Lisp_Object oldlist;
+  int did_apply = 0;
+

 #if 0  /* This is a good feature, but would make undo-start
          unable to do what is expected.  */
   Lisp_Object tem;
 #if 0  /* This is a good feature, but would make undo-start
          unable to do what is expected.  */
   Lisp_Object tem;


@@ -401,21 +477,29 @@ Return what remains of the list.")
     list = Fcdr (list);
 #endif
 
     list = Fcdr (list);
 #endif
 

-  CHECK_NUMBER (n, 0);
+  CHECK_NUMBER (n);

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

+  /* I don't think we need to gcpro oldlist, as we use it only
+     to check for EQ.  ++kfs  */

 
 

-  /* Don't let read-only properties interfere with undo.  */
+  /* In a writable buffer, enable undoing read-only text that is so
+     because of text properties.  */

   if (NILP (current_buffer->read_only))
     specbind (Qinhibit_read_only, Qt);
 
   if (NILP (current_buffer->read_only))
     specbind (Qinhibit_read_only, Qt);
 

+  /* Don't let `intangible' properties interfere with undo.  */
+  specbind (Qinhibit_point_motion_hooks, Qt);
+
+  oldlist = current_buffer->undo_list;
+

   while (arg > 0)
     {
   while (arg > 0)
     {

-      while (1)
+      while (CONSP (list))

        {
        {

-         next = Fcar (list);
-         list = Fcdr (list);
+         next = XCAR (list);
+         list = XCDR (list);

          /* Exit inner loop at undo boundary.  */
          if (NILP (next))
            break;
          /* Exit inner loop at undo boundary.  */
          if (NILP (next))
            break;


@@ -426,8 +510,8 @@ Return what remains of the list.")
            {
              Lisp_Object car, cdr;
 
            {
              Lisp_Object car, cdr;
 

-             car = Fcar (next);
-             cdr = Fcdr (next);
+             car = XCAR (next);
+             cdr = XCDR (next);

              if (EQ (car, Qt))
                {
                  /* Element (t high . low) records previous modtime.  */
              if (EQ (car, Qt))
                {
                  /* Element (t high . low) records previous modtime.  */


@@ -454,7 +538,7 @@ Return what remains of the list.")
                }
              else if (EQ (car, Qnil))
                {
                }
              else if (EQ (car, Qnil))
                {

-                 /* Element (nil prop val beg . end) is property change.  */
+                 /* Element (nil PROP VAL BEG . END) is property change.  */

                  Lisp_Object beg, end, prop, val;
 
                  prop = Fcar (cdr);
                  Lisp_Object beg, end, prop, val;
 
                  prop = Fcar (cdr);


@@ -464,12 +548,13 @@ Return what remains of the list.")
                  beg = Fcar (cdr);
                  end = Fcdr (cdr);
 
                  beg = Fcar (cdr);
                  end = Fcdr (cdr);
 

+                 if (XINT (beg) < BEGV || XINT (end) > ZV)
+                   error ("Changes to be undone are outside visible portion of buffer");

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

-                 Lisp_Object end;

 
                  if (XINT (car) < BEGV
                      || XINT (cdr) > ZV)
 
                  if (XINT (car) < BEGV
                      || XINT (cdr) > ZV)


@@ -479,6 +564,41 @@ Return what remains of the list.")
                  Fgoto_char (car);
                  Fdelete_region (car, cdr);
                }
                  Fgoto_char (car);
                  Fdelete_region (car, cdr);
                }

+             else if (EQ (car, Qapply))
+               {
+                 /* Element (apply FUN . ARGS) means call FUN to undo.  */
+                 struct buffer *save_buffer = current_buffer;
+
+                 car = Fcar (cdr);
+                 cdr = Fcdr (cdr);
+                 if (INTEGERP (car))
+                   {
+                     /* Long format: (apply DELTA START END FUN . ARGS).  */
+                     Lisp_Object delta = car;
+                     Lisp_Object start = Fcar (cdr);
+                     Lisp_Object end   = Fcar (Fcdr (cdr));
+                     Lisp_Object start_mark = Fcopy_marker (start, Qnil);
+                     Lisp_Object end_mark   = Fcopy_marker (end, Qt);
+
+                     cdr = Fcdr (Fcdr (cdr));
+                     apply1 (Fcar (cdr), Fcdr (cdr));
+
+                     /* Check that the function did what the entry said it
+                        would do.  */
+                     if (!EQ (start, Fmarker_position (start_mark))
+                         || (XINT (delta) + XINT (end)
+                             != marker_position (end_mark)))
+                       error ("Changes to be undone by function different than announced");
+                     Fset_marker (start_mark, Qnil, Qnil);
+                     Fset_marker (end_mark, Qnil, Qnil);
+                   }
+                 else
+                   apply1 (car, cdr);
+
+                 if (save_buffer != current_buffer)
+                   error ("Undo function switched buffer");
+                 did_apply = 1;
+               }

              else if (STRINGP (car) && INTEGERP (cdr))
                {
                  /* Element (STRING . POS) means STRING was deleted.  */
              else if (STRINGP (car) && INTEGERP (cdr))
                {
                  /* Element (STRING . POS) means STRING was deleted.  */


@@ -522,19 +642,84 @@ Return what remains of the list.")
       arg--;
     }
 
       arg--;
     }
 

+
+  /* Make sure an apply entry produces at least one undo entry,
+     so the test in `undo' for continuing an undo series
+     will work right.  */
+  if (did_apply
+      && EQ (oldlist, current_buffer->undo_list))
+    current_buffer->undo_list
+      = Fcons (list3 (Qapply, Qcdr, Qnil), current_buffer->undo_list);
+

   UNGCPRO;
   return unbind_to (count, list);
 }
   UNGCPRO;
   return unbind_to (count, list);
 }

-
+\f

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

+  Qapply = intern ("apply");
+  staticpro (&Qapply);
+

   pending_boundary = Qnil;
   staticpro (&pending_boundary);
 
   defsubr (&Sprimitive_undo);
   defsubr (&Sundo_boundary);
   pending_boundary = Qnil;
   staticpro (&pending_boundary);
 
   defsubr (&Sprimitive_undo);
   defsubr (&Sundo_boundary);

+
+  DEFVAR_INT ("undo-limit", &undo_limit,
+             doc: /* Keep no more undo information once it exceeds this size.
+This limit is applied when garbage collection happens.
+When a previous command increases the total undo list size past this
+value, the earlier commands that came before it are forgotten.
+
+The size is counted as the number of bytes occupied,
+which includes both saved text and other data.  */);
+  undo_limit = 20000;
+
+  DEFVAR_INT ("undo-strong-limit", &undo_strong_limit,
+             doc: /* Don't keep more than this much size of undo information.
+This limit is applied when garbage collection happens.
+When a previous command increases the total undo list size past this
+value, that command and the earlier commands that came before it are forgotten.
+However, the most recent buffer-modifying command's undo info
+is never discarded for this reason.
+
+The size is counted as the number of bytes occupied,
+which includes both saved text and other data.  */);
+  undo_strong_limit = 30000;
+
+  DEFVAR_LISP ("undo-outer-limit", &Vundo_outer_limit,
+             doc: /* Outer limit on size of undo information for one command.
+At garbage collection time, if the current command has produced
+more than this much undo information, it discards the info and displays
+a warning.  This is a last-ditch limit to prevent memory overflow.
+
+The size is counted as the number of bytes occupied, which includes
+both saved text and other data.  A value of nil means no limit.  In
+this case, accumulating one huge undo entry could make Emacs crash as
+a result of memory overflow.
+
+In fact, this calls the function which is the value of
+`undo-outer-limit-function' with one argument, the size.
+The text above describes the behavior of the function
+that variable usually specifies.  */);
+  Vundo_outer_limit = make_number (3000000);
+
+  DEFVAR_LISP ("undo-outer-limit-function", &Vundo_outer_limit_function,
+              doc: /* Function to call when an undo list exceeds `undo-outer-limit'.
+This function is called with one argument, the current undo list size
+for the most recent command (since the last undo boundary).
+If the function returns t, that means truncation has been fully handled.
+If it returns nil, the other forms of truncation are done.
+
+Garbage collection is inhibited around the call to this function,
+so it must make sure not to do a lot of consing.  */);
+  Vundo_outer_limit_function = Qnil;

 }
 }

+
+/* arch-tag: d546ee01-4aed-4ffb-bb8b-eefaae50d38a
+   (do not change this comment) */