ebrowse hangs emacs w/ scrolling option conflict

[Michael L. Labbe]

oboy, my first bug!

emacs-version: Emacs 21.2.1 (i386-msvc-nt5.0.2195) on buffy
also affected: Emacs 21.1.1 (i386-msvc-nt5.0.2195) on buffy

Configure commands: Downloaded binary install from
http://ftp.gnu.org/gnu/windows/emacs/latest/

Modifications to source: None

The complete text of any files needed to reproduce the bug:
http://creativeforces.dhs.org/~sludge/BROWSE.bz2 
Please un-bzip it before reproducing the bug.  In order to use the
dribble file, copy the file to "~".

Description:

Setting the scroll margin to a large number causes some sort of a
logic error in the display code of an ebrowse buffer.  The browse file
I have given you is of my current project, which contains enough data
to need to be scrolled on the default window size. ( Of course I
produced this dribble file with emacs -q! )

The freeze is tough enough that I can't seem to get out of it with
C-g, and C-break doesn't work on my keyboard.  Emacs does seem to be
getting the window redraw commands though, so it isn't a stiff lock.
100% cpu usage does ensue, however.

Scrolling to the bottom of the buffer with next-line doesn't cause the
hang.  The scroll-margin with the addition of the mouse wheel hopping
multiple lines is what gets it stuck in an infinite loop.

Dribble file:
http://creativeforces.dhs.org/~sludge/dribble

Don't hesitate to ask if you have any questions.  I check my email
more frequently than is healthy.

-- 
Michael L. Labbe
http://www.threewavesoftware.com