---
name: fibo-zone-indicator
description: >
  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.
category: 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:

```mql5
// 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:

```mql5
// 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
```mql5
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
```mql5
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
```mql5
// 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
```mql5
// 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:

```mql5
// 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:

```mql5
// 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 |