[Greasemonkey] What DOM node is visable at the top of a window?

[Jeremy Dunck]

On 2/6/06, Roderick McGuire <mcguire at telerama.com> wrote:
> If I could figure out what DOM node is shown at the top of the window, I
> could use compareDocumentPosition to figure out what headerNode to
> scroll to.
>
> But I don't see how to find this info.
>
> Thanks in advance for any info.

I think this discussion will give you a good starting point:
http://www.quirksmode.org/js/findpos.html

The top of the viewport is window.scrollY, so given that page's
findPosY and window.scrollY, you should be able to find the next
header below the top of the scroll.