Created attachment 95178 [details]
shot

Only happens when scrolling up.

I did some bisecting and it looks like this commit introduced the problem:

Thu Aug 23 15:32:09 2007  Tim Janik  <timj@imendio.com>

        * gdk/x11/gdkgeometry-x11.c (_gdk_window_process_expose): fix
        X serial handling to cope with wraparounds and maintain referential
        integrity when removing list nodes. based on a patch by Hui Wang,
        fixes #461648.

http://svn.gnome.org/viewcvs/gtk%2B?view=revision&revision=18693

We don't do anything special in devhelp, just embedding gtkmozembed. The special overlay on top might trigger some bug though. I just tried with epiphany and it has the exact same bug.

The math in the patch is not correct if serial and item->serial are equal.  It should be inverted.  Attaching patch.

Created attachment 95296 [details] [review]
patch

Committed after updating to trunk.

2007-09-10  Behdad Esfahbod  <behdad@gnome.org>

        * gdk/x11/gdkgeometry-x11.c (gdk_window_queue),
        (_gdk_window_process_expose): Fix serial number comparison regression
        introduced recently. (#474897)

Thanks, that was a quick turnaround :)

Yep.  Thanks for doing the hard part of bisecting.

Do you use a git-svn checkout?  How do you handle the build/ subdir that is svn:external?   Last time I tried (two months ago), glib git-svn checkout didn't build because of that.  Thanks.

(In reply to comment #8)

> Do you use a git-svn checkout?  How do you handle the build/ subdir that is
> svn:external?   Last time I tried (two months ago), glib git-svn checkout
> didn't build because of that.  Thanks.

I usually just copy it into a git-svn repository from a SVN checkout and then git-ignore it. 

I only have gtk+ in git-svn, and not glib so I don't really get hit by that.

Thanks.  I'll give it another try.