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

[Eli Zaretskii <eliz@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.)

I will look into fixing this soon.  Thanks for reporting this.