bug#13277: 24.2.91; -nw display bug with overlay-arrow

[Eli Zaretskii <eliz@gnu.org>]

> Date: Tue, 25 Dec 2012 21:03:22 +0200
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: 13277@debbugs.gnu.org
> 
> > From: Andreas Schwab <schwab@linux-m68k.org>
> > Date: Tue, 25 Dec 2012 19:13:44 +0100
> > 
> > This is a regression from emacs 23, already present in 24.1:
> > 
> > $ cat bug.el
> > (set (make-local-variable 'overlay-arrow-string) "=>")
> > (set (make-local-variable 'overlay-arrow-position) (point-marker))
> > ;;(setq truncate-lines t)
> > (insert-char ?- (window-width))
> > (goto-char (point-min))
> > $ emacs -nw -l ./bug.el
> > 
> > The cursor is placed at the right margin.  Either moving forward two
> > characters or deleting one character (so that the line fits in the
> > window) puts the cursor after the arrow, where it belongs.
> 
> It's a consequence of the bidirectional display, under which we can no
> longer assume that, if point is at position P, and that position is
> not visible, the cursor should be put on the first visible glyph whose
> position is >= P.  (In this case, the first 2 characters are obscured
> by the overlay arrow, and don't appear on the line.)

Should be fixed in revision 111082 on the emacs-24 branch.  (The fix
is a simple one-liner, and is so obviously correct that it can only
cause problems if it exposes another bug, so I think it's appropriate
for the branch.)