docs: public boolean openAbove(Element referenceElement) {
  
          int windowTop = Window.getScrollTop();
          int windowBottom = Window.getScrollTop() + Window.getClientHeight();
          int spaceAbove = referenceElement.getAbsoluteTop() - windowTop;
          int spaceBelow = windowBottom - referenceElement.getAbsoluteBottom();
          return spaceAbove > spaceBelow;
      }