vertical-motion not working with multi-line overlays

[Ralf Angeli]

Trying to move backward over an overlay covering more than one line
and having an image as display property with `previous-line' is not
possible anymore.  Emacs beeps and signals that it hit the beginning
of a buffer.  It seems that `vertical-motion' is not working correctly
as it returns 0.

Here is a testcase:

(progn
  (insert "\nfoo\nbar")
  (let ((ov (make-overlay (- (point) 7) (point))))
    (overlay-put ov 'display (create-image "splash.xpm" 'xpm))))

Execute it in the *scratch* buffer, e.g. with `C-x C-e', and try to
move point upwards over the image with `C-p'.



In GNU Emacs 21.3.50.1 (i686-pc-linux-gnu, GTK+ Version 2.4.14)
 of 2005-01-04 on neutrino
Distributor `The XFree86 Project, Inc', version 11.0.40300001
configured using `configure '--with-gtk''

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: en_US
  locale-coding-system: iso-latin-1
  default-enable-multibyte-characters: t

Major mode: Lisp Interaction

Minor modes in effect:
  mouse-wheel-mode: t
  unify-8859-on-encoding-mode: t
  utf-translate-cjk-mode: t
  line-number-mode: t
  transient-mark-mode: identity

Recent input:
<down> <down> <down> <left> C-x C-e <down> <down> <up> 
<up> <up> <up> <up> <up> <down> <down> <down> <up> 
<up> <up> <up> <up> <up> <down> <down> <up> <up> <up> 
<up> <up> <up> <down> <down> <up> <up> <up> <up> <up> 
<down> <down> <up> <up> <up> <up> <up> <up> <up> <up> 
<up> <up> <down> <down> <up> <up> <up> <up> <up> <up> 
<down> C-_ C-x C-e <up> <up> <up> <up> <down> <down> 
<down> C-_ <up> <up> <up> <right> <up> <down> <down> 
<down> <down> <left> C-x C-e <up> <up> C-_ <right> 
<down> <down> M-x r e p o r t - e m <tab> <return>

Recent messages:
Undo! [3 times]
(image :type xpm :file "splash.xpm")
Undo!
(image :type xpm :file "splash.xpm")
Undo!
(image :type xpm :file "splash.xpm")
Undo!
(image :type xpm :file "splash.xpm")
Undo!
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