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, 18 insertions, 0 deletions

diff --git a/src/search.c b/src/search.c
index 9eed390244f..c6ae9d7e922 100644
--- a/src/search.c
+++ b/src/search.c
@@ -985,6 +985,24 @@ scan_newline (ptrdiff_t start, ptrdiff_t start_byte,
   return shortage;
 }
 
+/* Like above, but always scan from point and report the
+   resulting position in *CHARPOS and *BYTEPOS.  */
+
+ptrdiff_t
+scan_newline_from_point (ptrdiff_t count, ptrdiff_t *charpos,
+                         ptrdiff_t *bytepos)
+{
+  ptrdiff_t shortage;
+
+  if (count <= 0)
+    *charpos = find_newline (PT, PT_BYTE, BEGV, BEGV_BYTE, count - 1,
+                             &shortage, bytepos, 1);
+  else
+    *charpos = find_newline (PT, PT_BYTE, ZV, ZV_BYTE, count,
+                             &shortage, bytepos, 1);
+  return shortage;
+}
+
 /* Like find_newline, but doesn't allow QUITting and doesn't return
    SHORTAGE.  */
 ptrdiff_t