(Fconstrain_to_field): Fix behaviour on field boundaries.

(find_field): Set before_field to after_field when pos is at BEGV.

2 files changed, 33 insertions, 13 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 9829d7162da..b7e3640934a 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,7 +1,7 @@
 2006-01-26  L$,1 q(Brentey K,Aa(Broly  <lorentey@elte.hu>
 
-        * editfns.c (Fconstrain_to_field): Use get_pos_property, not
-        Fget_char_property.  Fix bogus comment.
+        * editfns.c (Fconstrain_to_field): Fix behaviour on field boundaries.
+        (find_field): Set before_field to after_field when pos is at BEGV.
         (Fline_beginning_position, Fline_end_position): Clarify 
         confusing doc string.
 
diff --git a/src/editfns.c b/src/editfns.c
index 1ee7c968884..9be9232a9c7 100644
--- a/src/editfns.c
+++ b/src/editfns.c
@@ -526,7 +526,9 @@ find_field (pos, merge_at_boundary, beg_limit, beg, end_limit, end)
     = (XFASTINT (pos) > BEGV
        ? get_char_property_and_overlay (make_number (XINT (pos) - 1),
                                         Qfield, Qnil, NULL)
-       : Qnil);
+       /* Using nil here would be a more obvious choice, but it would
+          fail when the buffer starts with a non-sticky field.  */
+       : after_field);
 
   /* See if we need to handle the case where MERGE_AT_BOUNDARY is nil
      and POS is at beginning of a field, which can also be interpreted
@@ -717,7 +719,8 @@ Field boundaries are not noticed if `inhibit-field-text-motion' is non-nil.  */)
 {
   /* If non-zero, then the original point, before re-positioning.  */
   int orig_point = 0;
-
+  int fwd, prev_old, prev_new;
+  
   if (NILP (new_pos))
     /* Use the current point, and afterwards, set it.  */
     {
@@ -725,23 +728,40 @@ Field boundaries are not noticed if `inhibit-field-text-motion' is non-nil.  */)
       XSETFASTINT (new_pos, PT);
     }
 
+  CHECK_NUMBER_COERCE_MARKER (new_pos);
+  CHECK_NUMBER_COERCE_MARKER (old_pos);
+
+  fwd = (XFASTINT (new_pos) > XFASTINT (old_pos));
+
+  prev_old = make_number (XFASTINT (old_pos) - 1);
+  prev_new = make_number (XFASTINT (new_pos) - 1);
+  
   if (NILP (Vinhibit_field_text_motion)
       && !EQ (new_pos, old_pos)
-      && (!NILP (get_pos_property (new_pos, Qfield, Qnil))
-          || !NILP (get_pos_property (old_pos, Qfield, Qnil)))
+      && (!NILP (Fget_text_property (new_pos, Qfield, Qnil))
+          || !NILP (Fget_text_property (old_pos, Qfield, Qnil))
+          /* To recognize field boundaries, we must also look at the
+             previous positions; we could use `get_pos_property'
+             instead, but in itself that would fail inside non-sticky
+             fields (like comint prompts).  */
+          || (XFASTINT (new_pos) > BEGV
+              && !NILP (Fget_text_property (prev_new, Qfield, Qnil)))
+          || (XFASTINT (old_pos) > BEGV
+              && !NILP (Fget_text_property (prev_old, Qfield, Qnil))))
       && (NILP (inhibit_capture_property)
-          || NILP (get_pos_property (old_pos, inhibit_capture_property, Qnil))))
+          /* Field boundaries are again a problem; but now we must
+             decide the case exactly, so we need to call
+             `get_pos_property' as well.  */
+          || (NILP (get_pos_property (old_pos, inhibit_capture_property, Qnil))
+              && (XFASTINT (old_pos) <= BEGV
+                  || NILP (Fget_text_property (old_pos, inhibit_capture_property, Qnil))
+                  || NILP (Fget_text_property (prev_old, inhibit_capture_property, Qnil))))))
     /* It is possible that NEW_POS is not within the same field as
        OLD_POS; try to move NEW_POS so that it is.  */
     {
-      int fwd, shortage;
+      int shortage;
       Lisp_Object field_bound;
 
-      CHECK_NUMBER_COERCE_MARKER (new_pos);
-      CHECK_NUMBER_COERCE_MARKER (old_pos);
-
-      fwd = (XFASTINT (new_pos) > XFASTINT (old_pos));
-
       if (fwd)
         field_bound = Ffield_end (old_pos, escape_from_edge, new_pos);
       else