name: mql5-indicator-patterns description: Develop custom MQL5 indicators with proper patterns. Use when creating indicators, debugging OnCalculate(), working with buffers, or implementing multi-timeframe indicators in MetaTrader 5. allowed-tools: Read, Grep, Edit, Write

MQL5 Visual Indicator Patterns

Battle-tested patterns for creating custom MQL5 indicators with proper display, buffer management, and real-time updates.

Quick Reference

Essential Patterns

Display Scale (for small values < 1.0):

IndicatorSetDouble(INDICATOR_MINIMUM, 0.0);
IndicatorSetDouble(INDICATOR_MAXIMUM, 0.1);

Buffer Setup (visible + hidden):

SetIndexBuffer(0, BufVisible, INDICATOR_DATA);        // Visible
SetIndexBuffer(1, BufHidden, INDICATOR_CALCULATIONS); // Hidden

New Bar Detection (prevents drift):

static int last_processed_bar = -1;
bool is_new_bar = (i > last_processed_bar);

Warmup Calculation:

int StartCalcPosition = underlying_warmup + own_warmup;
PlotIndexSetInteger(0, PLOT_DRAW_BEGIN, StartCalcPosition);

Common Pitfalls

Blank Display: Set explicit scale (see Display Scale reference)

Rolling Window Drift: Use new bar detection with hidden buffer (see Recalculation reference)

Misaligned Plots: Calculate correct PLOT_DRAW_BEGIN (see Complete Template reference)

Forward-Indexed Arrays: Always set ArraySetAsSeries(buffer, false)

Key Patterns

For production MQL5 indicators:

1. Explicit scale for small values (< 1.0 range)
2. Hidden buffers for recalculation tracking
3. New bar detection prevents rolling window drift
4. Static variables maintain state efficiently
5. Proper warmup calculation prevents misalignment
6. Forward indexing for code clarity

These patterns solve the most common indicator development issues encountered in real-world MT5 development.

Reference Documentation

For detailed information, see:

• Display Scale - Fix blank indicator windows for small values
• Buffer Patterns - Visible and hidden buffer architecture
• Recalculation - Bar detection and rolling window state management
• Complete Template - Full working example with all patterns
• Debugging - Checklist for troubleshooting display issues