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, 7 insertions, 34 deletions

diff --git a/src/cmds.c b/src/cmds.c
index a975a8ed4e0..6f19a046893 100644
--- a/src/cmds.c
+++ b/src/cmds.c
@@ -220,36 +220,6 @@ to t.  */)
   return Qnil;
 }
 
-static int nonundocount;
-
-static void
-remove_excessive_undo_boundaries (void)
-{
-  bool remove_boundary = true;
-
-  if (!EQ (Vthis_command, KVAR (current_kboard, Vlast_command)))
-    nonundocount = 0;
-
-  if (NILP (Vexecuting_kbd_macro))
-    {
-      if (nonundocount <= 0 || nonundocount >= 20)
-        {
-          remove_boundary = false;
-          nonundocount = 0;
-        }
-      nonundocount++;
-    }
-
-  if (remove_boundary
-      && CONSP (BVAR (current_buffer, undo_list))
-      && NILP (XCAR (BVAR (current_buffer, undo_list)))
-      /* Only remove auto-added boundaries, not boundaries
-         added by explicit calls to undo-boundary.  */
-      && EQ (BVAR (current_buffer, undo_list), last_undo_boundary))
-    /* Remove the undo_boundary that was just pushed.  */
-    bset_undo_list (current_buffer, XCDR (BVAR (current_buffer, undo_list)));
-}
-
 DEFUN ("delete-char", Fdelete_char, Sdelete_char, 1, 2, "p\nP",
        doc: /* Delete the following N characters (previous if N is negative).
 Optional second arg KILLFLAG non-nil means kill instead (save in kill ring).
@@ -265,7 +235,7 @@ because it respects values of `delete-active-region' and `overwrite-mode'.  */)
   CHECK_NUMBER (n);
 
   if (abs (XINT (n)) < 2)
-    remove_excessive_undo_boundaries ();
+    call0 (Qundo_auto__amalgamate);
 
   pos = PT + XINT (n);
   if (NILP (killflag))
@@ -311,7 +281,7 @@ At the end, it runs `post-self-insert-hook'.  */)
     error ("Negative repetition argument %"pI"d", XFASTINT (n));
 
   if (XFASTINT (n) < 2)
-    remove_excessive_undo_boundaries ();
+    call0 (Qundo_auto__amalgamate);
 
   /* Barf if the key that invoked this was not a character.  */
   if (!CHARACTERP (last_command_event))
@@ -321,7 +291,7 @@ At the end, it runs `post-self-insert-hook'.  */)
                                     XINT (last_command_event));
     int val = internal_self_insert (character, XFASTINT (n));
     if (val == 2)
-      nonundocount = 0;
+      Fset (Qundo_auto__this_command_amalgamating, Qnil);
     frame_make_pointer_invisible (SELECTED_FRAME ());
   }
 
@@ -526,6 +496,10 @@ internal_self_insert (int c, EMACS_INT n)
 void
 syms_of_cmds (void)
 {
+  DEFSYM (Qundo_auto__amalgamate, "undo-auto--amalgamate");
+  DEFSYM (Qundo_auto__this_command_amalgamating,
+          "undo-auto--this-command-amalgamating");
+
   DEFSYM (Qkill_forward_chars, "kill-forward-chars");
 
   /* A possible value for a buffer's overwrite-mode variable.  */
@@ -555,7 +529,6 @@ keys_of_cmds (void)
 {
   int n;
 
-  nonundocount = 0;
   initial_define_key (global_map, Ctl ('I'), "self-insert-command");
   for (n = 040; n < 0177; n++)
     initial_define_key (global_map, n, "self-insert-command");