code: public static void positionElement(Element elem, Element referenceElement, int dx, int dy) {
  
          com.google.gwt.dom.client.Style style = elem.getStyle();
          style.setLeft(0, Unit.PX);
          style.setTop(0, Unit.PX);
          int myX = elem.getAbsoluteLeft();
          int myY = elem.getAbsoluteTop();
          int refX = referenceElement.getAbsoluteLeft();
          int refY = referenceElement.getAbsoluteTop();
          int newX = (refX - myX) + dx;
          int newY = (refY - myY) + dy;
          style.setLeft(newX, Unit.PX);
          style.setTop(newY, Unit.PX);
      }
docs: Positions an element in the DOM relative to another element.<p>
  
  @param elem the element to position
  @param referenceElement the element relative to which the first element should be positioned
  @param dx the x offset relative to the reference element
  @param dy the y offset relative to the reference element