@mytec: stack done, rust next

docs/devlog/gpu_supp/RFCP-3.10.3-Calculator-Ruler-UX.md

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+# 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
+```