request.security in MQL5: higher-timeframe data without repainting

//@version=6
indicator("Higher-timeframe close and EMA, no repainting", overlay = true)

htf = input.timeframe("D", "Higher timeframe")
emaLen = input.int(20, "HTF EMA length", minval = 1)

// [1] with lookahead_on: the last COMPLETED higher-timeframe bar, the same on history and in real time
htfClose = request.security(syminfo.tickerid, htf, close[1], lookahead = barmerge.lookahead_on)
htfEma = request.security(syminfo.tickerid, htf, ta.ema(close, emaLen)[1], lookahead = barmerge.lookahead_on)

plot(htfClose, "Previous HTF close", color.gray, 2, plot.style_stepline)
plot(htfEma, "HTF EMA (closed bar)", color.orange, 2, plot.style_stepline)

//+------------------------------------------------------------------+
//| Higher-timeframe close and EMA without repainting                |
//| = request.security(..., close[1], lookahead = lookahead_on)       |
//| Custom indicator: save in MQL5/Indicators and compile (F7).      |
//+------------------------------------------------------------------+
#property indicator_chart_window
#property indicator_buffers 2
#property indicator_plots   2

#property indicator_label1  "Previous HTF close"
#property indicator_type1   DRAW_LINE
#property indicator_color1  clrGray
#property indicator_width1  2

#property indicator_label2  "HTF EMA (closed bar)"
#property indicator_type2   DRAW_LINE
#property indicator_color2  clrOrange
#property indicator_width2  2

input ENUM_TIMEFRAMES InpHtf    = PERIOD_D1; // Higher timeframe
input int             InpEmaLen = 20;        // HTF EMA length

double CloseBuf[], EmaBuf[];
int    emaHandle = INVALID_HANDLE;

int OnInit()
  {
   if(PeriodSeconds(InpHtf) <= PeriodSeconds(_Period) || InpEmaLen < 1)
     {
      Print("Pick a timeframe higher than the chart's, and an EMA length of at least 1");
      return INIT_PARAMETERS_INCORRECT;
     }
   SetIndexBuffer(0, CloseBuf, INDICATOR_DATA);
   SetIndexBuffer(1, EmaBuf, INDICATOR_DATA);
   PlotIndexSetDouble(0, PLOT_EMPTY_VALUE, EMPTY_VALUE);
   PlotIndexSetDouble(1, PLOT_EMPTY_VALUE, EMPTY_VALUE);

   // ta.ema() evaluated on the higher timeframe = an iMA handle on that timeframe
   emaHandle = iMA(_Symbol, InpHtf, InpEmaLen, 0, MODE_EMA, PRICE_CLOSE);
   if(emaHandle == INVALID_HANDLE)
     {
      Print("Could not create the higher-timeframe EMA, error ", GetLastError());
      return INIT_FAILED;
     }
   return INIT_SUCCEEDED;
  }

void OnDeinit(const int reason)
  {
   IndicatorRelease(emaHandle);
  }

int OnCalculate(const int rates_total,
                const int prev_calculated,
                const datetime &time[],
                const double &open[],
                const double &high[],
                const double &low[],
                const double &close[],
                const long &tick_volume[],
                const long &volume[],
                const int &spread[])
  {
   int htfBars = Bars(_Symbol, InpHtf);
   if(htfBars < 2 || BarsCalculated(emaHandle) < htfBars)
      return prev_calculated;  // higher timeframe still loading: try again on the next tick

   int start = prev_calculated > 0 ? prev_calculated - 1 : 0;

   // How far back on the higher timeframe the oldest bar to calculate goes, plus the bar before it
   int oldest = iBarShift(_Symbol, InpHtf, time[start]);
   int need   = oldest < 0 ? htfBars : MathMin(oldest + 2, htfBars);

   double htfClose[], htfEma[];
   ArraySetAsSeries(htfClose, true);  // [0] = forming HTF bar, [1] = last completed one
   ArraySetAsSeries(htfEma, true);
   if(CopyClose(_Symbol, InpHtf, 0, need, htfClose) != need || CopyBuffer(emaHandle, 0, 0, need, htfEma) != need)
      return prev_calculated;

   for(int i = start; i < rates_total; i++)
     {
      CloseBuf[i] = EMPTY_VALUE;
      EmaBuf[i]   = EMPTY_VALUE;
      int shift = iBarShift(_Symbol, InpHtf, time[i]);  // the HTF bar that contains this chart bar
      if(shift < 0 || shift + 1 >= need)
         continue;
      // shift + 1 is close[1] in Pine: the HTF bar before it, already closed
      CloseBuf[i] = htfClose[shift + 1];
      EmaBuf[i]   = htfEma[shift + 1];
     }
   return rates_total;
  }
//+------------------------------------------------------------------+