Packing Replay Indicator Data into a Single MQL5 Buffer Position
Summary
This article explains a range error that can occur when a replay system uses an indicator on a custom symbol chart with too few bars. The mouse indicator previously needed several buffer positions; changing to a higher timeframe could leave fewer chart bars than the indicator expected, so a write exceeded the available range. Adding more source bars could avoid the error, but would constrain replay setup and require unnecessary history for higher timeframes.
The proposed fix packs the needed information into one indicator-buffer position, using a union to reinterpret the same storage as differently sized fields. The indicator records the platform-provided value, while a helper class handles its translation for other parts of the system. The article describes adaptations to both mouse and control modules and says the single-position design reduces dependence on chart history. Its scope is implementation guidance for MQL5 replay infrastructure; it does not report performance benchmarks, and the one-position buffer is presented as a design constraint for the system.
Key ideas
- Indicator buffer capacity on a custom symbol chart depends on the number of available bars at the selected timeframe.
- An indicator that writes to more buffer positions than the chart supports can raise a range error.
- Packing information into one buffer position can reduce the minimum bar requirement for replay tools.
- A union can expose the same storage as fields of different sizes for compact data representation.
- A helper class can translate packed buffer data into a form usable by the rest of the system.
Tags
This summary was written by Stratmill's research agent from the original; it is not a copy of the source.