[Bug-readline] [PATCH] fix cursor position after completion

[Miroslav Lichvar]

Hi,

there is a bug in cursor placement after completion if the following
conditions are met:
- multibyte locale is used
- prompt has invisible characters
- number of characters after the cursor is greater than number of
  invisible characters in the prompt

Steps to reproduce the problem in bash can be found here:
https://bugzilla.redhat.com/show_bug.cgi?id=249987

It's caused by line 1048 in redisplay()
        _rl_col_width(&visible_line[pos], 0, nleft)

nleft is nonzero, but visible_line[pos] is empty string and
_rl_col_width returns negative number.

As the functionality around this line seems to be implemented also in
_rl_move_cursor_relative which is called afterwards, I'm suggesting
the following patch to fix the bug.

--- display.c.redisplay 2007-11-28 17:16:50.000000000 +0100
+++ display.c   2007-11-29 13:42:18.000000000 +0100
@@ -1038,23 +1038,6 @@
             position that doesn't take invisible characters in the prompt
             into account.  We use a fudge factor to compensate. */
 
-         /* Since _rl_backspace() doesn't know about invisible characters in 
the
-            prompt, and there's no good way to tell it, we compensate for
-            those characters here and call _rl_backspace() directly. */
-         if (wrap_offset && cursor_linenum == 0 && nleft < _rl_last_c_pos)
-           {
-             /* TX == new physical cursor position in multibyte locale. */
-             if (MB_CUR_MAX > 1 && rl_byte_oriented == 0)
-               tx = _rl_col_width (&visible_line[pos], 0, nleft) - 
visible_wrap_offset;
-             else
-               tx = nleft;
-             if (_rl_last_c_pos > tx)
-               {
-                 _rl_backspace (_rl_last_c_pos - tx);  /* XXX */
-                 _rl_last_c_pos = tx;
-               }
-           }
-
          /* We need to note that in a multibyte locale we are dealing with
             _rl_last_c_pos as an absolute cursor position, but moving to a
             point specified by a buffer position (NLEFT) that doesn't take

-- 
Miroslav Lichvar