MQL5Book/Indicators/p7/SubFolder/NonEmbeddedIndicator.mq5

//+------------------------------------------------------------------+
//|                                         NonEmbeddedIndicator.mq5 |
//|                                  Copyright 2022, MetaQuotes Ltd. |
//|                                             https://www.mql5.com |
//+------------------------------------------------------------------+
#property indicator_chart_window
#property indicator_buffers 0
#property indicator_plots   0

input int Reference = 0;

int handle = 0;

//+------------------------------------------------------------------+
//| Indicator initialization function                                |
//+------------------------------------------------------------------+
int OnInit()
{
   const string name = MQLInfoString(MQL_PROGRAM_NAME);
   const string path = MQLInfoString(MQL_PROGRAM_PATH);
   Print(Reference);
   Print("Name: " + name);
   Print("Full path: " + path);
   
   if(Reference == 0)
   {
      handle = iCustom(_Symbol, _Period, name, 1);
      if(handle == INVALID_HANDLE)
      {
         return INIT_FAILED;
      }
   }
   Print("Success");
   return INIT_SUCCEEDED;
}

//+------------------------------------------------------------------+
//| Indicator calculation function (dummy here)                      |
//+------------------------------------------------------------------+
int OnCalculate(const int rates_total,
                const int prev_calculated,
                const int begin,
                const double &price[])
{
   return rates_total;
}

//+------------------------------------------------------------------+
//| Indicator finalization function                                  |
//+------------------------------------------------------------------+
void OnDeinit(const int)
{
   IndicatorRelease(handle);
}
//+------------------------------------------------------------------+