* buffer.h (struct buffer_text): New field chars_modiff.

        (CHARS_MODIFF, BUF_CHARS_MODIFF): New macros.
        * buffer.c (Fbuffer_chars_modified_tick): New function returning
        value of BUF_CHARS_MODIFF.
        (syms_of_buffer): Defsubr it.
        (Fget_buffer_create): Initialize BUF_CHARS_MODIFF.
        * insdel.c (modify_region): New argument preserve_chars_modiff.
        Set CHARS_MODIFF to MODIFF provided preserve_chars_modiff is zero.
        (insert_1_both, insert_from_string_1, insert_from_buffer_1)
        (adjust_after_replace, adjust_after_replace_noundo)
        (replace_range, replace_range_2, del_range_2): Reset CHARS_MODIFF.
        * lisp.h (modify_region): Add fourth argument in extern.
        * casefiddle.c (casify_region): Call modify_region with fourth
        argument zero to assert that CHARS_MODIFF is updated.
        * editfns.c (Fsubst_char_in_region, Ftranslate_region_internal)
        (Ftranspose_regions): Likewise.
        * textprop.c (Fadd_text_properties, Fset_text_properties)
        (Fremove_text_properties, Fremove_list_of_text_properties):
        Call modify_region with fourth argument 1 to avoid that
        CHARS_MODIFF is updated.

1 files changed, 27 insertions, 0 deletions

diff --git a/src/buffer.c b/src/buffer.c
index 863b217d2b4..58c047a87ba 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -374,6 +374,7 @@ The value is never nil.  */)
   BUF_ZV_BYTE (b) = BEG_BYTE;
   BUF_Z_BYTE (b) = BEG_BYTE;
   BUF_MODIFF (b) = 1;
+  BUF_CHARS_MODIFF (b) = 1;
   BUF_OVERLAY_MODIFF (b) = 1;
   BUF_SAVE_MODIFF (b) = 1;
   BUF_INTERVALS (b) = 0;
@@ -1148,6 +1149,31 @@ No argument or nil as argument means use current buffer as BUFFER.  */)
 
   return make_number (BUF_MODIFF (buf));
 }
+
+DEFUN ("buffer-chars-modified-tick", Fbuffer_chars_modified_tick,
+       Sbuffer_chars_modified_tick, 0, 1, 0,
+       doc: /* Return BUFFER's character-change tick counter.
+Each buffer has a character-change tick counter, which is set to the
+value of the buffer's tick counter \(see `buffer-modified-tick'), each
+time text in that buffer is inserted or deleted.  By comparing the
+values returned by two individual calls of buffer-chars-modified-tick,
+you can tell whether a character change occurred in that buffer in
+between these calls.  No argument or nil as argument means use current
+buffer as BUFFER.  */)
+     (buffer)
+     register Lisp_Object buffer;
+{
+  register struct buffer *buf;
+  if (NILP (buffer))
+    buf = current_buffer;
+  else
+    {
+      CHECK_BUFFER (buffer);
+      buf = XBUFFER (buffer);
+    }
+
+  return make_number (BUF_CHARS_MODIFF (buf));
+}
 
 DEFUN ("rename-buffer", Frename_buffer, Srename_buffer, 1, 2,
        "sRename buffer (to new name): \nP",
@@ -6044,6 +6070,7 @@ The function `kill-all-local-variables' runs this before doing anything else.  *
   defsubr (&Sbuffer_modified_p);
   defsubr (&Sset_buffer_modified_p);
   defsubr (&Sbuffer_modified_tick);
+  defsubr (&Sbuffer_chars_modified_tick);
   defsubr (&Srename_buffer);
   defsubr (&Sother_buffer);
   defsubr (&Sbuffer_enable_undo);