# RFCP — Iteration 3.10.3: Calculator Shortcut & Ruler Limit

## Two small UX changes, no backend.

---

## 1. Link Budget Calculator — Quick Access Button

Move calculator access to a visible toolbar button, not buried in Map Tools panel.

**Location:** Top-left corner of the map, below the zoom controls (+/- buttons). Similar to how Fit, Reset, Topo, Grid, Ruler, Elev buttons are in the top-right.

**Implementation:**
Add a button to the left toolbar (or create a small floating button group):

```typescript
// Top-left button, below zoom controls
<button
  className="map-tool-btn"
  onClick={() => setShowLinkBudget(!showLinkBudget)}
  title="Link Budget Calculator"
>
  {/* Calculator icon — use an emoji or SVG */}
  🔗 {/* or a small "LB" text label, or a calculator SVG icon */}
</button>
```

**Styling:** Same visual style as the right-side tool buttons (Fit, Reset, Topo, Grid, Ruler, Elev) — dark rounded rectangle with light text/icon.

**Position options (pick one):**
- **Option A:** Add to the RIGHT toolbar stack below "Elev" button — keeps all tools together
- **Option B:** Floating button top-left below zoom — separate but prominent
- **Option C:** Add to the measurement overlay bar (near the ruler distance display)

Recommend **Option A** — add "LB" or calculator icon button to the right toolbar stack, below Elev. Consistent with existing UI pattern.

Also: Remove the "Hide Link Budget Calculator" button from Map Tools panel (or keep it as secondary toggle — but primary access should be the toolbar button).

---

## 2. Ruler — Maximum 2 Points Only

**Problem:** Ruler currently allows unlimited points, creating a web of measurement lines. For RF point-to-point measurement, only 2 points make sense: start and end.

**Fix:** Limit ruler to exactly 2 points. When both points are placed, the measurement is complete. To start a new measurement, clicking again replaces the first point and clears the old measurement.

```typescript
// In the map click handler for ruler mode:
function handleRulerClick(e: L.LeafletMouseEvent) {
  const currentPoints = rulerPoints;
  
  if (currentPoints.length === 0) {
    // First point
    setRulerPoints([snappedLatLng]);
  } else if (currentPoints.length === 1) {
    // Second point — measurement complete
    setRulerPoints([currentPoints[0], snappedLatLng]);
    // Optionally: auto-deactivate ruler mode after 2nd point
    // clearTool();  // uncomment if you want one-shot behavior
  } else {
    // Already 2 points — start new measurement
    // Replace: clear old points, start fresh with new first point
    setRulerPoints([snappedLatLng]);
  }
}
```

**Behavior:**
1. Click 1: Place start point (show marker)
2. Click 2: Place end point (show marker + line + distance label + Terrain Profile button)
3. Click 3: Clear previous, start new measurement from this click
4. Right-click or Escape: Cancel/clear ruler entirely

**Remove:**
- Remove "Right-click to finish" instruction (no longer needed — measurement auto-completes at 2 points)
- Remove multi-point polyline rendering (only single line between 2 points)

**Visual:**
- Show a single straight line between 2 points (green dashed, as current)
- Distance label at midpoint
- Terrain Profile button appears after 2nd point is placed
- Small circle markers at both endpoints

---

## Testing Checklist

- [ ] Calculator button visible in toolbar (right side, below Elev)
- [ ] Click calculator button opens/closes Link Budget panel
- [ ] Ruler allows exactly 2 points, no more
- [ ] Third click starts new measurement (replaces old)
- [ ] Escape clears ruler
- [ ] Distance + Terrain Profile button appears after 2nd point
- [ ] No multi-point web/polygon possible
- [ ] Ruler still snaps to site markers

## Commit Message

```
fix(ux): add calculator toolbar button, limit ruler to 2 points

- Add Link Budget Calculator button to right toolbar
- Limit ruler to exactly 2 points (point-to-point only)
- Third click starts new measurement, clears previous
- Remove multi-point polyline behavior
```