anchor.diff:      if
           (BufCnt == 0) andalso (SN == filling) ->
               ?Debug("~p waiting for the fetch to complete ~p", [SN, <<">">>]),
  -            State0#state{stack={button,<<">">>,ReplyTo}};
  +            State1 = prefetch(SN, State0),
  +            State1#state{stack={button,<<">">>,ReplyTo}};
           (BufCnt == 0) ->
               %% no data, serve empty gui
               State1 = prefetch(SN,State0),
  
positive.code: serve_stack( _, #state{stack=undefined}=State) -> 
      % no stack, nothing .. do
      State;
  serve_stack( _, #state{nav=ind,bufBot=B,guiBot=B}=State) -> 
      % gui is current at the end of the buffer, no new interesting data, nothing .. do
      State;
  
negative.code:     State1 = data_append(filling, {Recs,false},State0),
      NewBufBot = State1#state.bufBot,
      NewGuiBot = State1#state.guiBot,
      State2 = if
          (Button == <<">">>) ->      prefetch(filling,State1);
          (Button == <<">>">>) ->     prefetch(filling,State1);
          (Button == <<"<">>) ->      prefetch(filling,State1);
          (Button == <<"<<">>) ->     prefetch(filling,State1);
          (NewGuiBot == NewBufBot) -> prefetch(filling,State1);
          true ->                     State1
      end,    
  