MQL4/.github/instructions/mql4-indicators.instructions.md

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**/MQL4/Indicators/_Thivyam/**/*.mq4

Instructions for _Thivyam MQL4 Custom Indicators

CRITICAL: MQL4 Syntax Compliance

Before writing any MQL4 code, read and follow: mql4-syntax-critical.instructions.md

Key mandatory rules for indicators:

• Declare loop variables BEFORE for-loop: int i; for(i=0; i<n; i++)
• Use #property indicator_* directives correctly
• Declare indicator buffers properly with SetIndexBuffer()
• Use IndicatorBuffers() to specify total buffers
• Always validate buffer indices before accessing

---

Indicator Structure

Required Property Directives

//+------------------------------------------------------------------+
//|                                         YourIndicatorName.mq4    |
//|                                            Author: Your Name     |
//|                                     https://www.yourwebsite.com  |
//+------------------------------------------------------------------+
#property copyright "Your Name"
#property link      "https://www.yourwebsite.com"
#property version   "1.00"
#property strict
#property description "Brief description of indicator"

// Indicator window type
#property indicator_chart_window     // Main chart window
// OR
#property indicator_separate_window  // Separate window below chart

// For separate window indicators
#property indicator_minimum -100     // Minimum value
#property indicator_maximum 100      // Maximum value

// Number of plot buffers (visible lines)
#property indicator_buffers 2

// Plot properties
#property indicator_color1 clrBlue   // First line color
#property indicator_width1 2         // First line width
#property indicator_label1 "Signal"  // First line label

#property indicator_color2 clrRed
#property indicator_width2 1
#property indicator_label2 "Threshold"

---

Buffer Declaration

Indicator Buffers vs Plot Buffers

• Plot Buffers: Visible on chart (specified by #property indicator_buffers)
• Total Buffers: Plot buffers + calculation buffers (set with IndicatorBuffers())

Example: Moving Average Indicator

#property indicator_chart_window
#property indicator_buffers 1
#property indicator_color1 clrRed
#property indicator_width1 2

// Input parameters
input int InpMAPeriod = 20;          // MA Period
input int InpMAMethod = MODE_SMA;    // MA Method
input int InpMAAppliedPrice = PRICE_CLOSE;  // Applied Price

// Indicator buffers
double BufferMA[];  // Visible buffer

//+------------------------------------------------------------------+
int OnInit()
{
   // Set total buffers (1 plot + 0 calculation)
   IndicatorBuffers(1);
   
   // Bind buffer to indicator buffer array
   SetIndexBuffer(0, BufferMA);
   
   // Set plot style
   SetIndexStyle(0, DRAW_LINE, STYLE_SOLID, 2, clrRed);
   
   // Set indicator label
   SetIndexLabel(0, "MA(" + IntegerToString(InpMAPeriod) + ")");
   
   // Set empty value (gaps in line)
   SetIndexEmptyValue(0, 0.0);
   
   // Set indicator short name
   IndicatorShortName("MA(" + IntegerToString(InpMAPeriod) + ")");
   
   // Set precision
   IndicatorDigits(Digits);
   
   return INIT_SUCCEEDED;
}

//+------------------------------------------------------------------+
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[])
{
   // Calculate start position
   int limit = rates_total - prev_calculated;
   if(prev_calculated > 0) limit++;
   
   // Calculate MA
   int i;
   for(i = 0; i < limit; i++)
   {
      BufferMA[i] = iMA(NULL, 0, InpMAPeriod, 0, InpMAMethod, InpMAAppliedPrice, i);
   }
   
   return rates_total;
}

---

OnCalculate() Function

Function Signature (Time Series Version)

int OnCalculate(const int rates_total,       // Total bars available
                const int prev_calculated,   // Bars calculated on previous call
                const datetime &time[],      // Time array
                const double &open[],        // Open prices
                const double &high[],        // High prices
                const double &low[],         // Low prices
                const double &close[],       // Close prices
                const long &tick_volume[],   // Tick volumes
                const long &volume[],        // Real volumes
                const int &spread[])         // Spreads
{
   // Calculation logic here
   return rates_total;  // Return total bars processed
}

Efficient Calculation Pattern

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[])
{
   // Calculate how many bars need recalculation
   int limit;
   
   if(prev_calculated == 0)
   {
      // First calculation - process all bars
      limit = rates_total - 1;
      
      // Initialize buffers
      ArrayInitialize(BufferMA, 0);
   }
   else
   {
      // Subsequent calculations - process new bars only
      limit = rates_total - prev_calculated;
   }
   
   // Process bars from oldest to newest
   int i;
   for(i = limit; i >= 0; i--)
   {
      // Calculate indicator value for bar i
      BufferMA[i] = CalculateValue(i);
   }
   
   // Return value for next call
   return rates_total;
}

---

Drawing Styles

Available Draw Styles

DRAW_LINE          // Line connecting points
DRAW_SECTION       // Sections (gaps at empty values)
DRAW_HISTOGRAM     // Histogram from zero line
DRAW_ARROW         // Arrows at points
DRAW_ZIGZAG        // ZigZag line
DRAW_NONE          // No drawing (calculation buffer)

Example: Multi-Buffer Indicator

#property indicator_separate_window
#property indicator_buffers 3
#property indicator_color1 clrGreen
#property indicator_color2 clrRed
#property indicator_color3 clrGray

// Buffers
double BufferUp[];      // Bullish signal
double BufferDown[];    // Bearish signal
double BufferZero[];    // Zero line

int OnInit()
{
   IndicatorBuffers(3);
   
   // Buffer 0: Bullish histogram
   SetIndexBuffer(0, BufferUp);
   SetIndexStyle(0, DRAW_HISTOGRAM, STYLE_SOLID, 2, clrGreen);
   SetIndexLabel(0, "Bullish");
   
   // Buffer 1: Bearish histogram
   SetIndexBuffer(1, BufferDown);
   SetIndexStyle(1, DRAW_HISTOGRAM, STYLE_SOLID, 2, clrRed);
   SetIndexLabel(1, "Bearish");
   
   // Buffer 2: Zero line
   SetIndexBuffer(2, BufferZero);
   SetIndexStyle(2, DRAW_LINE, STYLE_DOT, 1, clrGray);
   SetIndexLabel(2, "Zero");
   
   IndicatorShortName("Multi Signal");
   
   return INIT_SUCCEEDED;
}

---

Arrow Drawing

Using Arrow Symbols

#property indicator_chart_window
#property indicator_buffers 2
#property indicator_color1 clrGreen
#property indicator_color2 clrRed

double BufferBuy[];   // Buy arrows
double BufferSell[];  // Sell arrows

int OnInit()
{
   IndicatorBuffers(2);
   
   // Buy arrows (up arrow)
   SetIndexBuffer(0, BufferBuy);
   SetIndexStyle(0, DRAW_ARROW);
   SetIndexArrow(0, 233);  // Up arrow symbol code
   SetIndexLabel(0, "Buy Signal");
   SetIndexEmptyValue(0, 0.0);
   
   // Sell arrows (down arrow)
   SetIndexBuffer(1, BufferSell);
   SetIndexStyle(1, DRAW_ARROW);
   SetIndexArrow(1, 234);  // Down arrow symbol code
   SetIndexLabel(1, "Sell Signal");
   SetIndexEmptyValue(1, 0.0);
   
   return INIT_SUCCEEDED;
}

int OnCalculate(/* ... */)
{
   int i;
   for(i = limit; i >= 0; i--)
   {
      // Place buy arrow below candle low
      if(IsBuySignal(i))
      {
         BufferBuy[i] = low[i] - 10 * Point;
      }
      else
      {
         BufferBuy[i] = 0;  // Empty value (no arrow)
      }
      
      // Place sell arrow above candle high
      if(IsSellSignal(i))
      {
         BufferSell[i] = high[i] + 10 * Point;
      }
      else
      {
         BufferSell[i] = 0;
      }
   }
   
   return rates_total;
}

Common Arrow Codes

233 - Up arrow
234 - Down arrow
159 - Circle
158 - Square
168 - Triangle up
170 - Triangle down

---

Multi-Timeframe Indicators

Getting Data from Other Timeframes

int OnCalculate(/* ... */)
{
   int i;
   for(i = limit; i >= 0; i--)
   {
      // Get H4 data while indicator is on M15 chart
      double h4High = iHigh(Symbol(), PERIOD_H4, iBarShift(Symbol(), PERIOD_H4, time[i]));
      double h4Low = iLow(Symbol(), PERIOD_H4, iBarShift(Symbol(), PERIOD_H4, time[i]));
      
      // Use H4 data for calculation
      BufferSignal[i] = CalculateFromMTF(h4High, h4Low, close[i]);
   }
   
   return rates_total;
}

---

Using Other Indicators

Calling Built-in Indicators

int OnCalculate(/* ... */)
{
   int i;
   for(i = limit; i >= 0; i--)
   {
      // Get Moving Average value
      double ma = iMA(Symbol(), PERIOD_CURRENT, 20, 0, MODE_SMA, PRICE_CLOSE, i);
      
      // Get RSI value
      double rsi = iRSI(Symbol(), PERIOD_CURRENT, 14, PRICE_CLOSE, i);
      
      // Get Stochastic values
      double stochMain = iStochastic(Symbol(), PERIOD_CURRENT, 5, 3, 3, MODE_SMA, 0, MODE_MAIN, i);
      double stochSignal = iStochastic(Symbol(), PERIOD_CURRENT, 5, 3, 3, MODE_SMA, 0, MODE_SIGNAL, i);
      
      // Use values for calculation
      BufferSignal[i] = (close[i] > ma && rsi > 50) ? 1 : -1;
   }
   
   return rates_total;
}

MA Method Constants

MODE_SMA  = 0  // Simple Moving Average
MODE_EMA  = 1  // Exponential Moving Average
MODE_SMMA = 2  // Smoothed Moving Average
MODE_LWMA = 3  // Linear Weighted Moving Average

Applied Price Constants

PRICE_CLOSE    = 0  // Close price
PRICE_OPEN     = 1  // Open price
PRICE_HIGH     = 2  // High price
PRICE_LOW      = 3  // Low price
PRICE_MEDIAN   = 4  // (High + Low) / 2
PRICE_TYPICAL  = 5  // (High + Low + Close) / 3
PRICE_WEIGHTED = 6  // (High + Low + Close + Close) / 4

---

Zone Detection Indicator Example

Supply/Demand Zone Indicator

#property indicator_chart_window
#property indicator_buffers 0  // No plot buffers (we'll draw objects)

input int InpZoneBars = 3;          // Bars to form zone
input color InpDemandColor = clrGreen;
input color InpSupplyColor = clrRed;

datetime g_lastBarTime = 0;

int OnInit()
{
   return INIT_SUCCEEDED;
}

int OnCalculate(/* ... */)
{
   // Detect new bar
   if(time[0] != g_lastBarTime)
   {
      g_lastBarTime = time[0];
      
      // Check for zone patterns
      DetectZones();
   }
   
   return rates_total;
}

void DetectZones()
{
   // Scan recent bars for demand zones
   int i;
   for(i = 1; i < 50; i++)
   {
      if(IsDemandZone(i))
      {
         DrawZone("Demand_" + IntegerToString(iTime(Symbol(), PERIOD_CURRENT, i)),
                  iTime(Symbol(), PERIOD_CURRENT, i),
                  iHigh(Symbol(), PERIOD_CURRENT, i),
                  iLow(Symbol(), PERIOD_CURRENT, i),
                  InpDemandColor);
      }
      
      if(IsSupplyZone(i))
      {
         DrawZone("Supply_" + IntegerToString(iTime(Symbol(), PERIOD_CURRENT, i)),
                  iTime(Symbol(), PERIOD_CURRENT, i),
                  iHigh(Symbol(), PERIOD_CURRENT, i),
                  iLow(Symbol(), PERIOD_CURRENT, i),
                  InpSupplyColor);
      }
   }
}

void DrawZone(string name, datetime time, double high, double low, color zoneColor)
{
   if(ObjectFind(0, name) >= 0) return;  // Already drawn
   
   datetime time2 = time + PeriodSeconds() * 100;
   
   ObjectCreate(0, name, OBJ_RECTANGLE, 0, time, high, time2, low);
   ObjectSetInteger(0, name, OBJPROP_COLOR, zoneColor);
   ObjectSetInteger(0, name, OBJPROP_STYLE, STYLE_SOLID);
   ObjectSetInteger(0, name, OBJPROP_WIDTH, 1);
   ObjectSetInteger(0, name, OBJPROP_BACK, true);
   ObjectSetInteger(0, name, OBJPROP_SELECTABLE, false);
   ObjectSetInteger(0, name, OBJPROP_RAY_RIGHT, true);
}

---

Alerts and Notifications

Alert Implementation

datetime g_lastAlertTime = 0;

int OnCalculate(/* ... */)
{
   // Check for signal on most recent bar
   if(IsSignal(0) && time[0] != g_lastAlertTime)
   {
      g_lastAlertTime = time[0];
      
      // Sound alert
      Alert("Signal detected on ", Symbol(), " ", PeriodToString());
      
      // Email notification (if enabled)
      if(InpSendEmail)
      {
         SendMail("Indicator Alert: " + Symbol(),
                  "Signal detected at " + TimeToString(TimeCurrent()));
      }
      
      // Push notification (if enabled)
      if(InpSendPush)
      {
         SendNotification("Signal: " + Symbol() + " " + PeriodToString());
      }
   }
   
   return rates_total;
}

string PeriodToString()
{
   switch(Period())
   {
      case PERIOD_M1:  return "M1";
      case PERIOD_M5:  return "M5";
      case PERIOD_M15: return "M15";
      case PERIOD_M30: return "M30";
      case PERIOD_H1:  return "H1";
      case PERIOD_H4:  return "H4";
      case PERIOD_D1:  return "D1";
      default:         return "Unknown";
   }
}

---

Best Practices for Indicators

Performance Optimization

1. Minimize calculations: Only recalculate changed bars
2. Use efficient algorithms: Avoid nested loops where possible
3. Cache values: Store frequently used calculations
4. Avoid unnecessary repaints: Use prev_calculated correctly

Repaint vs Non-Repaint

// NON-REPAINT: Use closed bar data
int OnCalculate(/* ... */)
{
   // Calculate from bar 1 onwards (skip bar 0)
   int i;
   for(i = limit; i >= 1; i--)  // Start from 1, not 0
   {
      BufferSignal[i] = CalculateSignal(i);
   }
   
   return rates_total;
}

// REPAINT: Include current bar (bar 0)
int OnCalculate(/* ... */)
{
   // Calculate from bar 0 (current bar)
   int i;
   for(i = limit; i >= 0; i--)  // Include bar 0
   {
      BufferSignal[i] = CalculateSignal(i);
   }
   
   return rates_total;
}

User-Friendly Features

1. Clear input descriptions: Use descriptive input names
2. Reasonable defaults: Set sensible default values
3. Visual customization: Allow color/style customization
4. Alert options: Provide optional alerts
5. Multi-timeframe support: Make indicator timeframe-agnostic

---

Common Pitfalls

Issue 1: Wrong Array Indexing

// ❌ WRONG - Arrays are not time-series by default
BufferMA[rates_total - 1 - i] = value;

// ✅ CORRECT - If not set as series
BufferMA[i] = value;

// ✅ CORRECT - Or explicitly set as series
ArraySetAsSeries(BufferMA, true);
BufferMA[i] = value;  // Now i=0 is newest bar

Issue 2: Not Handling Empty Values

// ✅ CORRECT - Set empty value and use it
SetIndexEmptyValue(0, 0.0);

if(noSignal)
   BufferSignal[i] = 0.0;  // Empty value (gap in line)
else
   BufferSignal[i] = calculatedValue;

Issue 3: Incorrect Buffer Count

// ❌ WRONG - Mismatch between property and actual
#property indicator_buffers 2
// But only using 1 buffer

// ✅ CORRECT - Match declaration
#property indicator_buffers 2
double Buffer1[], Buffer2[];

int OnInit()
{
   IndicatorBuffers(2);
   SetIndexBuffer(0, Buffer1);
   SetIndexBuffer(1, Buffer2);
   return INIT_SUCCEEDED;
}

---

Summary: MQL4 Indicator Best Practices

1. ✅ Use correct #property directives
2. ✅ Match buffer count between property and SetIndexBuffer calls
3. ✅ Return rates_total from OnCalculate()
4. ✅ Use prev_calculated for efficient recalculation
5. ✅ Set empty values for gaps in plots
6. ✅ Use descriptive labels with SetIndexLabel()
7. ✅ Implement non-repaint logic when appropriate
8. ✅ Provide user customization options
9. ✅ Test on multiple timeframes
10. ✅ Optimize for performance (minimize calculations)

Following these practices ensures professional, efficient, and reliable MQL4 custom indicators.