scroll-preserve-screen-position doesn't work with a header-line-format

[jbyler+emacs-lists]

There seems to be an off-by-one error triggered by using a header line
together with scroll-preserve-screen-position.  The symptom: instead of
staying in the same position on the screen when scrolling, the cursor
moves one screen line down each time the buffer is scrolled.  Put
another way: repeatedly typing C-v M-v or using a mouse scroll wheel to
scroll up and down causes the cursor to migrate slowly down the screen
instead of staying put as it should.

To reproduce:

emacs -q --no-site-file
(setq scroll-preserve-screen-position t)
(setq header-line-format "")
C-v M-v C-v M-v C-v M-v etc.

I think this problem has existed for a while (already existed in CVS
5/25/2003); I only noticed it recently because I started using a header
line.  A brief source search indicates the
scroll-preserve-screen-position is implemented in the C source in
window.c.

Thanks,
Jesse
-----

The information contained in this electronic mail
and any attached document is the confidential and
proprietary business information of Forum Systems,
Inc. It is intended solely for the addressed
recipient listed above. It may not be distributed
in any manner without the express written consent
of Forum Systems, Inc.