opencode-skill/skills/mql-developer/fibo-zone-indicator/SKILL.md

name, description, category

name	description	category
fibo-zone-indicator	Multi-timeframe Fibonacci retracement + S/R indicator for MetaTrader 5. Draws buy zones (61.8-80.1% retracement) on lower portion of bars with TP/SL lines, plus support/resistance levels and psychological price levels. Built for XAUUSD (gold) but works on any symbol.	mql5

FiboZone Indicator — MQL5 Implementation

Overview

Indicator สำหรับ XAUUSD — แสดง Fibonacci retracement zones จาก D1/H4/H1 พร้อม:

• Buy zone (61.8-80.1%) อยู่ lower portion ของแท่ง
• TP/SL lines
• Support/Resistance levels (จาก 20 bars ย้อนหลัง)
• Psychological price levels

Key Code Patterns

MQL5 Array Parameter Syntax

CRITICAL: When passing arrays OUT of a function (output parameters), use reference-to-array syntax:

// WRONG — treats as reference to single element
int FindSRLevels(const double &highs[], const double &lows[], int count,
                 SSRLevel &srOut, int maxOut)

// CORRECT — reference to array
int FindSRLevels(const double &highs[], const double &lows[], int count,
                 SSRLevel &srOut[], int maxOut)

Every declaration, definition, and call site must use [] on array parameters. Mismatch causes compile errors: cannot convert 'double[]' to 'double&'.

ArrayResize Before Indexing

Always ArrayResize on output arrays BEFORE writing to them:

// WRONG — array out of range
for(int i = 0; i < outCount; i++)
   srOut[i] = filtered[i];

// CORRECT
ArrayResize(srOut, outCount);
for(int i = 0; i < outCount; i++)
   srOut[i] = filtered[i];

Fibo Zone Calculation — Lower Portion

User clarified: Fibo tool 0% = TOP, 100% = BOTTOM. Zone 61.8-80.1% must be in LOWER portion of the bar.

Bullish bar (close > open): Zone near LOW → subtract from HIGH

r.zoneHigh = high - barHeight * 0.618;  // closer to high
r.zoneLow  = high - barHeight * 0.801;  // closer to low (lower portion)

Bearish bar (close < open): Zone near LOW of the bar → add from LOW

r.zoneHigh = low + barHeight * 0.801;   // closer to high
r.zoneLow  = low + barHeight * 0.618;   // closer to low (lower portion)

Calculation Test (Manual)

Bullish bar: High=4766, Low=4664, Bar=102

// Lower portion of bullish bar:
zoneHigh = 4766 - 102 * 0.618 = 4702.96
zoneLow  = 4766 - 102 * 0.801 = 4684.30
// Zone: [4684, 4703] ✅ in lower portion (closer to low)

Bearish bar: High=4766, Low=4664, Bar=102

// Lower portion of bearish bar:
zoneHigh = 4664 + 102 * 0.801 = 4745.70
zoneLow  = 4664 + 102 * 0.618 = 4727.04
// Zone: [4727, 4746] ✅ in lower portion

OBJ_RECTANGLE for Price Zones

OBJ_RECTANGLE needs distinct time1 and time2 to span chart width:

// WRONG — time1 == time2 → zero-width (looks like vertical line)
ObjectCreate(0, name, OBJ_RECTANGLE, 0, anchorTime, zoneLow, anchorTime, zoneHigh);

// CORRECT — time2 = far future → spans full chart width
datetime rightTime = D'2099.12.31 23:59:59';
ObjectCreate(0, name, OBJ_RECTANGLE, 0, anchorTime, zoneLow, rightTime, zoneHigh);
ObjectSetInteger(0, name, OBJPROP_FILL,  true);
ObjectSetInteger(0, name, OBJPROP_COLOR, ColorToARGB(zoneColor, 60));

S/R Zone Width Parameter

InpSRZoneWidth groups similar prices into one S/R zone. Must be smaller than the actual price range:

// Example: XAUUSD range ~100 points over 20 bars
// zoneWidth = 200 → all bars in ONE zone → only 1-3 S/R lines
// zoneWidth = 50  → ~2 zones → more S/R lines
input int InpSRZoneWidth = 50;
input int InpSRMinHits   = 2;   // lower from 5 to see more lines
input int InpMaxSR       = 4;

Common Bugs Fixed

Bug	Fix
cannot convert double[] to double&	Change all array params to &arr[] syntax
array out of range at line N	Add ArrayResize(srOut, count) before srOut[i] =
Rectangle looks like vertical line	Set time2 = D'2099.12.31' not anchorTime
Fibo zone in wrong portion	Use high-subtract for bullish, low-add for bearish
S/R zoneWidth=200, only 3 lines	Reduce to ~50 for XAUUSD range