Constant Range Channel

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#define     MName          "Constant Range Channel"

#define     MVersion       "1.0"

#define     MBuild         "2022-05-11 11:31 WEST"

#define     MCopyright     "Copyright \x00A9 2022, Fernando M. I. Carreiro, All rights reserved"

#define     MProfile       "https://www.mql5.com/en/users/FMIC"

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#property   strict

#property   version        MVersion

#property   description    MName

#property   description    "MetaTrader Indicator (Build "MBuild")"

#property   copyright      MCopyright

#property   link           MProfile

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//--- Setup



   #property indicator_chart_window



   // Define number of buffers and plots

      #define MPlots    3

      #define MBuffers  3

      #ifndef __MQL4__

         #property indicator_buffers   MBuffers

         #property indicator_plots     MPlots

      #else

         #property indicator_buffers   MPlots

      #endif



   // Display properties

      #define     MClrUpper         C'38, 166,154'

      #define     MClrMiddle        C'239,166,154'

      #define     MClrLower         C'239, 83, 80'

      #property   indicator_label1  "Upper"

      #property   indicator_label2  "Middle"

      #property   indicator_label3  "Lower"

      #property   indicator_color1  MClrUpper

      #property   indicator_color2  MClrMiddle

      #property   indicator_color3  MClrLower

      #property   indicator_width1  1

      #property   indicator_width2  1

      #property   indicator_width3  1

      #property   indicator_style1  STYLE_SOLID

      #property   indicator_style2  STYLE_DOT

      #property   indicator_style3  STYLE_SOLID

      #property   indicator_type1   DRAW_LINE

      #property   indicator_type2   DRAW_LINE

      #property   indicator_type3   DRAW_LINE



//--- Parameter settings



   input uint i_nStepTicks = 50; // Channel range step size (ticks)



//--- Macro definitions



   // Define OnCalculate loop sequencing macros

      #ifdef __MQL4__   // for MQL4 (as series)

         #define MOnCalcNext(  _index          ) ( _index--             )

         #define MOnCalcBack(  _index, _offset ) ( _index + _offset     )

         #define MOnCalcCheck( _index          ) ( _index >= 0          )

         #define MOnCalcValid( _index          ) ( _index < rates_total )

         #define MOnCalcStart \

            ( rates_total - ( prev_calculated < 1 ? 1 : prev_calculated ) )

      #else             // for MQL5 (as non-series)

         #define MOnCalcNext(  _index          ) ( _index++             )

         #define MOnCalcBack(  _index, _offset ) ( _index - _offset     )

         #define MOnCalcCheck( _index          ) ( _index < rates_total )

         #define MOnCalcValid( _index          ) ( _index >= 0          )

         #define MOnCalcStart \

            ( prev_calculated < 1 ? 0 : prev_calculated - 1 )

      #endif



   // Define macro for invalid parameter values

      #define MCheckParameter( _condition, _text ) if( _condition ) \

         { Print( "Error: Invalid ", _text ); return INIT_PARAMETERS_INCORRECT; }



//--- Global variable declarations



   // Indicator buffers

      double

         g_dbStepRange,                // Channel range step size

         g_adbUpper[],                 // Buffer for channel's upper level

         g_adbMiddle[],                // Buffer for channel's middle level

         g_adbLower[];                 // Buffer for channel's lower level



//--- Event handling functions



   // Initialisation event handler

      int OnInit(void)

      {

         // Validate input parameters

            MCheckParameter( i_nStepTicks < 1, "Range step size!" );



         // Set initial values

            g_dbStepRange = WRONG_VALUE;



         // Set number of significant digits (precision)

            IndicatorSetInteger( INDICATOR_DIGITS, _Digits );



         // Set buffers

            #ifdef __MQL4__

               IndicatorBuffers( MBuffers ); // Set total number of buffers (MQL4 Only)

            #endif

            int iBuffer = 0;

            SetIndexBuffer( iBuffer++, g_adbUpper,  INDICATOR_DATA );

            SetIndexBuffer( iBuffer++, g_adbMiddle, INDICATOR_DATA );

            SetIndexBuffer( iBuffer++, g_adbLower,  INDICATOR_DATA );



         // Set indicator name

            IndicatorSetString( INDICATOR_SHORTNAME,

               MName + "(" + (string) i_nStepTicks + ")" );



         return INIT_SUCCEEDED;  // Successful initialisation of indicator

      };



   // Calculation event handler

      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[]

         )

      {

         // Convert rang step siz from ticks to price quote difference

            if( ( g_dbStepRange < 0 ) && ( rates_total > 0 ) )

            {

               double dbTickSize = WRONG_VALUE;

               if( SymbolInfoDouble( _Symbol, SYMBOL_TRADE_TICK_SIZE, dbTickSize ) && ( dbTickSize > 0 ) )

                  g_dbStepRange = dbTickSize * i_nStepTicks;

               else

                  return 0;

            };



         // Main loop   fill in the buffer arrays with data values

            for( int iCur  = MOnCalcStart, iPrev = MOnCalcBack( iCur, 1 );

                 !IsStopped() && MOnCalcCheck( iCur );

                 MOnCalcNext( iCur ), MOnCalcNext( iPrev ) )

            {

               // Calculate middle value

                  double dbLow    = low[  iCur ],

                         dbHigh   = high[ iCur ],

                         dbMiddle = MOnCalcValid( iPrev )

                                  ? ( dbLow  > g_adbUpper[ iPrev ] ? dbLow

                                    : dbHigh < g_adbLower[ iPrev ] ? dbHigh : g_adbMiddle[ iPrev ] )

                                  : close[ iCur ];



               // Set buffer values

                  g_adbMiddle[ iCur ] = dbMiddle;

                  g_adbUpper[  iCur ] = dbMiddle + g_dbStepRange;

                  g_adbLower[  iCur ] = dbMiddle - g_dbStepRange;

            };



         return rates_total;  // Return value for prev_calculated of next call

      };



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