Scroll view of vaadin app from widget (client side)

In a widget, I’d like to listen to window scroll events. Putting GWT’s window.addScrollHandler does not work because the vaadin application is inside of a Widget and the window is not actually scrolling, but the UI. Thus, in client side development, how can I access the UI widget to attach a scroll listener? I am actually looking for a client side equivalent of UI.getCurrent().