anchor.diff:  	    PixelsPerEvent = Range / EventsPerPage,
   	    Share = EventsPerPage / N,
   	    wxScrollBar:setScrollbar(ScrollBar,
  -				     trunc(EventPos * Share * PixelsPerEvent),
  +                                     trunc(EventPos * Share * PixelsPerEvent),
   				     round(Share * Range),
   				     Range,
   				     round(Share * Range),
  
positive.code:     end.
  
  jump_up(S, OldKey, OldPos, NewPos) ->
      Try = NewPos - OldPos,
      Order = S#state.event_order,
      Fun = fun(Event, #e{pos = P}) when P >= NewPos ->
  		  Key = et_collector:make_key(Order, Event),
  		  #e{event = Event, key = Key, pos = P - 1};
  	     (_, Acc) ->
  		  Acc
  	  end,
      PrevE = et_collector:iterate(S#state.collector_pid,
  				 OldKey, 
  				 Try, 
  				 Fun,
  				 #e{key = OldKey, pos = OldPos}),
      case collect_more_events(S, PrevE, S#state.events_per_page) of
  	{_, []} ->
  	    S;
  
negative.code:     N = round(S#state.n_events * Pos / Range),
      Diff = 
  	case N - event_pos(S) of
  	    D when D < 0 -> D;
  	    D            -> D
  	end,
      S2 = scroll_changed(S, Diff),
      noreply(S2);
  