How to get the browser scroll offset?


I’m looking for the scroll offset of the browser window, but I can’t find any way to get it on the server-side. What I want to do:
Open a subwindow at the position where a click in the root window occours (works fine if the browser window is not scolled down), but if it’s scolled down, the position I get from the ClickEvent is relative to the top-left edge of the browsers viewport, but setPostionX/Y is relative to the applications top-left edge. To set the position of the new subwindow correct, I need the scroll offset of the browser.
Is there any way to get the offset, perhaps without a own widget?

Best regards