The heuristic that Emacs uses to add an `undo-boundary' has been

reworked, as it interacts poorly with functions on `post-command-hook'
or `after-change-functions'.

* lisp/simple.el: New section added.
* src/cmds.c (remove_excessive_undo_boundaries): Now in lisp.
(self_insert_command): Calls simple.el to amalgamate.
(delete_char): Calls simple.el to amalgamate.
* src/keyboard.c (last_undo_boundary): Removed.
* src/undo.c (run_undoable_change): New function.

1 files changed, 17 insertions, 34 deletions

diff --git a/src/undo.c b/src/undo.c
index 750bc8afff2..364b37eeeb4 100644
--- a/src/undo.c
+++ b/src/undo.c
@@ -26,10 +26,6 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 #include "commands.h"
 #include "window.h"
 
-/* Last buffer for which undo information was recorded.  */
-/* BEWARE: This is not traced by the GC, so never dereference it!  */
-static struct buffer *last_undo_buffer;
-
 /* Position of point last time we inserted a boundary.  */
 static struct buffer *last_boundary_buffer;
 static ptrdiff_t last_boundary_position;
@@ -41,6 +37,12 @@ static ptrdiff_t last_boundary_position;
    an undo-boundary.  */
 static Lisp_Object pending_boundary;
 
+void
+run_undoable_change ()
+{
+  call0 (Qundo_auto__undoable_change);
+}
+
 /* 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
@@ -59,15 +61,7 @@ record_point (ptrdiff_t pt)
   if (NILP (pending_boundary))
     pending_boundary = Fcons (Qnil, Qnil);
 
-  if ((current_buffer != last_undo_buffer)
-      /* Don't call Fundo_boundary for the first change.  Otherwise we
-         risk overwriting last_boundary_position in Fundo_boundary with
-         PT of the current buffer and as a consequence not insert an
-         undo boundary because last_boundary_position will equal pt in
-         the test at the end of the present function (Bug#731).  */
-      && (MODIFF > SAVE_MODIFF))
-    Fundo_boundary ();
-  last_undo_buffer = current_buffer;
+  run_undoable_change ();
 
   at_boundary = ! CONSP (BVAR (current_buffer, undo_list))
                 || NILP (XCAR (BVAR (current_buffer, undo_list)));
@@ -139,9 +133,7 @@ record_marker_adjustments (ptrdiff_t from, ptrdiff_t to)
   if (NILP (pending_boundary))
     pending_boundary = Fcons (Qnil, Qnil);
 
-  if (current_buffer != last_undo_buffer)
-    Fundo_boundary ();
-  last_undo_buffer = current_buffer;
+  run_undoable_change ();
 
   for (m = BUF_MARKERS (current_buffer); m; m = m->next)
     {
@@ -228,10 +220,6 @@ record_first_change (void)
   if (EQ (BVAR (current_buffer, undo_list), Qt))
     return;
 
-  if (current_buffer != last_undo_buffer)
-    Fundo_boundary ();
-  last_undo_buffer = current_buffer;
-
   if (base_buffer->base_buffer)
     base_buffer = base_buffer->base_buffer;
 
@@ -259,15 +247,10 @@ record_property_change (ptrdiff_t beg, ptrdiff_t length,
   if (NILP (pending_boundary))
     pending_boundary = Fcons (Qnil, Qnil);
 
-  if (buf != last_undo_buffer)
-    boundary = true;
-  last_undo_buffer = buf;
-
   /* Switch temporarily to the buffer that was changed.  */
-  current_buffer = buf;
+  set_buffer_internal (buf);
 
-  if (boundary)
-    Fundo_boundary ();
+  run_undoable_change ();
 
   if (MODIFF <= SAVE_MODIFF)
     record_first_change ();
@@ -278,7 +261,8 @@ record_property_change (ptrdiff_t beg, ptrdiff_t length,
   bset_undo_list (current_buffer,
                   Fcons (entry, BVAR (current_buffer, undo_list)));
 
-  current_buffer = obuf;
+  /* Reset the buffer */
+  set_buffer_internal (obuf);
 }
 
 DEFUN ("undo-boundary", Fundo_boundary, Sundo_boundary, 0, 0, 0,
@@ -308,6 +292,8 @@ but another undo command will undo to the previous boundary.  */)
     }
   last_boundary_position = PT;
   last_boundary_buffer = current_buffer;
+
+  Fset (Qundo_auto__last_boundary_cause, Qexplicit);
   return Qnil;
 }
 
@@ -383,7 +369,6 @@ truncate_undo_list (struct buffer *b)
       && !NILP (Vundo_outer_limit_function))
     {
       Lisp_Object tem;
-      struct buffer *temp = last_undo_buffer;
 
       /* Normally the function this calls is undo-outer-limit-truncate.  */
       tem = call1 (Vundo_outer_limit_function, make_number (size_so_far));
@@ -394,10 +379,6 @@ truncate_undo_list (struct buffer *b)
           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))
@@ -455,6 +436,9 @@ void
 syms_of_undo (void)
 {
   DEFSYM (Qinhibit_read_only, "inhibit-read-only");
+  DEFSYM (Qundo_auto__undoable_change, "undo-auto--undoable-change");
+  DEFSYM (Qundo_auto__last_boundary_cause, "undo-auto--last-boundary-cause");
+  DEFSYM (Qexplicit, "explicit");
 
   /* Marker for function call undo list elements.  */
   DEFSYM (Qapply, "apply");
@@ -462,7 +446,6 @@ syms_of_undo (void)
   pending_boundary = Qnil;
   staticpro (&pending_boundary);
 
-  last_undo_buffer = NULL;
   last_boundary_buffer = NULL;
 
   defsubr (&Sundo_boundary);