trigger event on scroll wheel

lib/src/gestures/gestures.dart

@@ -37,7 +37,8 @@ abstract class MapGestureMixin extends State<FlutterMap>
             : max(mapState.options.minZoom ?? 0, mapState.zoom + delta);
         final newZoom = mapState.fitZoomToBounds(zoom);
         // Move the map to the new zoom level
-        mapState.move(mapState.center, newZoom, source: MapEventSource.custom);
+        mapState.move(mapState.center, newZoom,
+            source: MapEventSource.scrollWheel);
       }
     }
   }

lib/src/gestures/map_events.dart

@@ -19,7 +19,8 @@ enum MapEventSource {
   interactiveFlagsChanged,
   fitBounds,
   initialization,
-  custom
+  custom,
+  scrollWheel,
 }
 
 /// Base event class which is emitted by MapController instance, the event
@@ -183,6 +184,23 @@ class MapEventDoubleTapZoom extends MapEventWithMove {
         );
 }
 
+/// Event which is fired when scroll wheel is used to zoom
+class MapEventScrollWheelZoom extends MapEventWithMove {
+  MapEventScrollWheelZoom({
+    required LatLng targetCenter,
+    required double targetZoom,
+    required MapEventSource source,
+    required LatLng center,
+    required double zoom,
+  }) : super(
+          targetCenter: targetCenter,
+          targetZoom: targetZoom,
+          source: source,
+          center: center,
+          zoom: zoom,
+        );
+}
+
 /// Event which is fired when animation for double tap gesture is started
 class MapEventDoubleTapZoomStart extends MapEvent {
   MapEventDoubleTapZoomStart(

lib/src/map/map.dart

@@ -200,6 +200,16 @@ class MapState {
           source: source,
         ),
       );
+    } else if (source == MapEventSource.scrollWheel) {
+      emitMapEvent(
+        MapEventScrollWheelZoom(
+          center: _lastCenter!,
+          zoom: _zoom,
+          targetCenter: targetCenter,
+          targetZoom: targetZoom,
+          source: source,
+        ),
+      );
     } else if (source == MapEventSource.onDrag ||
         source == MapEventSource.onMultiFinger) {
       emitMapEvent(