fix: symbols/text stay fixed on compass rotation, polygon area display in label box

src/components/map/map-view.tsx

@@ -23,6 +23,19 @@ function formatDistance(meters: number): string {
   return `${(meters / 1000).toFixed(2)} km`
 }
 
+// Approximate polygon area in m² using the Shoelace formula on spherical coordinates
+function polygonArea(ring: number[][]): number {
+  const toRad = Math.PI / 180
+  const R = 6371000
+  let area = 0
+  const n = ring.length - 1 // exclude closing duplicate
+  for (let i = 0; i < n; i++) {
+    const j = (i + 1) % n
+    area += (ring[j][0] - ring[i][0]) * toRad * (2 + Math.sin(ring[i][1] * toRad) + Math.sin(ring[j][1] * toRad))
+  }
+  return Math.abs(area * R * R / 2)
+}
+
 // Point-to-segment distance in screen pixels (for click detection on lines)
 function pointToSegmentDist(px: number, py: number, x1: number, y1: number, x2: number, y2: number): number {
   const dx = x2 - x1, dy = y2 - y1
@@ -1396,7 +1409,7 @@ export function MapView({
             pointer-events: none;
           `
 
-          const marker = new maplibregl.Marker({ element: arrowEl, anchor: 'center' })
+          const marker = new maplibregl.Marker({ element: arrowEl, anchor: 'center', rotationAlignment: 'viewport' })
             .setLngLat(p2 as [number, number])
             .addTo(map.current)
           markersRef.current.push(marker)
@@ -1468,7 +1481,21 @@ export function MapView({
           el.appendChild(labelLine)
           el.appendChild(infoLine)
         } else {
-          el.textContent = label
+          // Polygon: show label + area
+          const ring = (f.geometry.coordinates as number[][][])[0]
+          const area = polygonArea(ring)
+          const areaText = area < 10000 ? `${Math.round(area)} m²` : `${(area / 10000).toFixed(2)} ha`
+
+          const labelLine = document.createElement('div')
+          labelLine.textContent = label
+          labelLine.style.cssText = 'font-size:11px;font-weight:600;line-height:1.2;'
+
+          const infoLine = document.createElement('div')
+          infoLine.textContent = areaText
+          infoLine.style.cssText = 'font-size:8px;opacity:0.8;line-height:1.2;font-weight:400;'
+
+          el.appendChild(labelLine)
+          el.appendChild(infoLine)
         }
 
         // Double-click to edit label — only in select mode
@@ -1481,7 +1508,7 @@ export function MapView({
           })
         }
 
-        const marker = new maplibregl.Marker({ element: el, anchor: 'center' })
+        const marker = new maplibregl.Marker({ element: el, anchor: 'center', rotationAlignment: 'viewport' })
           .setLngLat(midpoint)
           .addTo(map.current)
         markersRef.current.push(marker)
@@ -1568,7 +1595,7 @@ export function MapView({
           }
 
           try {
-            const marker = new maplibregl.Marker({ element: wrapper, draggable: canEdit, anchor: 'center' })
+            const marker = new maplibregl.Marker({ element: wrapper, draggable: canEdit, anchor: 'center', rotationAlignment: 'viewport' })
               .setLngLat(coords)
               .addTo(map.current)
 
@@ -1634,7 +1661,7 @@ export function MapView({
           el.textContent = (f.properties.text as string) || ''
           wrapper.appendChild(el)
 
-          const marker = new maplibregl.Marker({ element: wrapper, draggable: canEdit, anchor: 'center' })
+          const marker = new maplibregl.Marker({ element: wrapper, draggable: canEdit, anchor: 'center', rotationAlignment: 'viewport' })
             .setLngLat(coords)
             .addTo(map.current)