anchor.diff:    );
   }
   
  +///
  +/// Nejakym takovym chytristikou bysme meli delat vsechny dropdowny.
  +///
   class DropdownTracker {
   
     Element _element;
  
positive.code:     this._dropdown = dropdown;
      this._onHide = onHide;
      Stream<Event> mergedRelevant = StreamGroup.merge([window.onMouseWheel, window.onResize, window.onScroll]);
      FnxStreamDebouncer db = new FnxStreamDebouncer(new Duration(milliseconds: 20));
      subscription = mergedRelevant.transform(db).listen(updatePosition);
    }
  
  
negative.code:       }
        left = el.left.toInt();
  
        if (dropdownH + el.top + el.height < scrHeight) {
          // vejde se dolu
          top = el.top.toInt() + el.height.toInt();
  
        } else {
          if (el.top - dropdownH > 0) {
            // vejde se nahoru
            top = el.top.toInt() - dropdownH;
  
          } else {
            top = (scrHeight - dropdownH)~/2;
          }
        }
      }
    }
  