mql5-indicator-patterns_skill

Overview

This skill provides battle-tested MQL5 indicator development patterns to build reliable, well-behaved MetaTrader 5 indicators. It focuses on buffer management, display scaling, warmup alignment, and robust OnCalculate behavior so indicators render correctly and avoid common runtime drift. The patterns are practical and targeted at production-ready indicators.

How this skill works

The skill documents concrete code patterns and configuration steps that inspect and control indicator state: explicit display scale settings, visible and hidden buffer architecture, forward-indexed arrays, and new-bar detection using static state. It explains how to compute PLOT_DRAW_BEGIN from underlying and own warmup and how OnCalculate should return rates_total to indicate successful updates. The guidance prevents blank displays, rolling-window drift, misaligned plots, and indexing errors.

When to use it

• Creating a custom MQL5 indicator for MetaTrader 5 from scratch
• Fixing a blank or mis-scaled indicator window for small-value plots
• Stopping value drift caused by rolling-window recalculation
• Aligning plot start using correct warmup calculation
• Converting array indexing from series mode to forward-indexed logic

Best practices

• Set INDICATOR_MINIMUM and INDICATOR_MAXIMUM explicitly for small-value ranges
• Use separate visible and hidden buffers: INDICATOR_DATA for plots, INDICATOR_CALCULATIONS for internal state
• Detect new bars with a static last_processed_bar and only reset rolling state on bar change
• Call ArraySetAsSeries(buffer, false) to use forward indexing consistently
• Compute StartCalcPosition = underlying_warmup + own_warmup and set PLOT_DRAW_BEGIN accordingly
• Return rates_total from OnCalculate and only recalc bars from prev_calculated onwards

Example use cases

• A volatility indicator whose values are <1.0 and currently displays a blank chart
• An oscillator that slowly drifts because it recalculates all bars on each tick
• A multi-buffer indicator that needs hidden buffers to track recalculation state
• Porting an indicator that used series arrays to forward-indexed logic for clarity
• Creating a template indicator with correct PLOT_DRAW_BEGIN so plots align with price bars