Avoid unwanted point motion in Fline_beginning_position.

* lisp.h (scan_newline_from_point): Add prototype.
* search.c (scan_newline_from_point): New function, refactored from...
* cmds.c (Fforward_line): ...adjusted user.
* editfns.c (Fline_beginning_position): Use scan_newline_from_point
and simplify the former since the latter doesn't move point.

1 files changed, 3 insertions, 12 deletions

diff --git a/src/editfns.c b/src/editfns.c
index be1062dbbc5..376d8e3a0ea 100644
--- a/src/editfns.c
+++ b/src/editfns.c
@@ -787,26 +787,17 @@ boundaries, bind `inhibit-field-text-motion' to t.
 This function does not move point.  */)
   (Lisp_Object n)
 {
-  ptrdiff_t orig, orig_byte, end;
-  ptrdiff_t count = SPECPDL_INDEX ();
-  specbind (Qinhibit_point_motion_hooks, Qt);
+  ptrdiff_t charpos, bytepos;
 
   if (NILP (n))
     XSETFASTINT (n, 1);
   else
     CHECK_NUMBER (n);
 
-  orig = PT;
-  orig_byte = PT_BYTE;
-  Fforward_line (make_number (XINT (n) - 1));
-  end = PT;
-
-  SET_PT_BOTH (orig, orig_byte);
-
-  unbind_to (count, Qnil);
+  scan_newline_from_point (XINT (n) - 1, &charpos, &bytepos);
 
   /* Return END constrained to the current input field.  */
-  return Fconstrain_to_field (make_number (end), make_number (orig),
+  return Fconstrain_to_field (make_number (charpos), make_number (PT),
                               XINT (n) != 1 ? Qt : Qnil,
                               Qt, Qnil);
 }