Add feature group

maps-kt-compose/src/commonMain/kotlin/centre/sciprog/maps/compose/FeatureBuilder.kt

@@ -75,3 +75,13 @@ fun FeatureBuilder.image(
     zoomRange: IntRange = defaultZoomRange,
     id: FeatureId? = null,
 ) = addFeature(id, MapVectorImageFeature(position.toCoordinates(), image, size, zoomRange))
+
+fun FeatureBuilder.group(
+    zoomRange: IntRange = defaultZoomRange,
+    id: FeatureId? = null,
+    builder: FeatureBuilder.() -> Unit,
+): FeatureId {
+    val map = MapFeatureBuilder(emptyMap()).apply(builder).build()
+    val feature = MapFeatureGroup(map, zoomRange)
+    return addFeature(id, feature)
+}

maps-kt-compose/src/commonMain/kotlin/centre/sciprog/maps/compose/MapFeature.kt

@@ -16,10 +16,11 @@ import centre.sciprog.maps.wrapAll
 
 //TODO replace zoom range with zoom-based representation change
 sealed class MapFeature(val zoomRange: IntRange) {
-    abstract fun getBoundingBox(zoom: Int): GmcBox
+    abstract fun getBoundingBox(zoom: Int): GmcBox?
 }
 
-fun Iterable<MapFeature>.computeBoundingBox(zoom: Int): GmcBox? = map { it.getBoundingBox(zoom) }.wrapAll()
+fun Iterable<MapFeature>.computeBoundingBox(zoom: Int): GmcBox? =
+    mapNotNull { it.getBoundingBox(zoom) }.wrapAll()
 
 internal fun Pair<Double, Double>.toCoordinates() = GeodeticMapCoordinates.ofDegrees(first, second)
 
@@ -29,7 +30,7 @@ internal val defaultZoomRange = 1..18
  * A feature that decides what to show depending on the zoom value (it could change size of shape)
  */
 class MapFeatureSelector(val selector: (zoom: Int) -> MapFeature) : MapFeature(defaultZoomRange) {
-    override fun getBoundingBox(zoom: Int): GmcBox = selector(zoom).getBoundingBox(zoom)
+    override fun getBoundingBox(zoom: Int): GmcBox? = selector(zoom).getBoundingBox(zoom)
 }
 
 class MapDrawFeature(
@@ -79,7 +80,6 @@ class MapBitmapImageFeature(
     override fun getBoundingBox(zoom: Int): GmcBox = GmcBox(position, position)
 }
 
-
 class MapVectorImageFeature(
     val position: GeodeticMapCoordinates,
     val painter: Painter,
@@ -96,3 +96,13 @@ fun MapVectorImageFeature(
     size: Size = Size(20f, 20f),
     zoomRange: IntRange = defaultZoomRange,
 ): MapVectorImageFeature = MapVectorImageFeature(position, rememberVectorPainter(image), size, zoomRange)
+
+/**
+ * A group of other features
+ */
+class MapFeatureGroup(
+    val children: Map<FeatureId, MapFeature>,
+    zoomRange: IntRange = defaultZoomRange,
+) : MapFeature(zoomRange) {
+    override fun getBoundingBox(zoom: Int): GmcBox? = children.values.mapNotNull { it.getBoundingBox(zoom) }.wrapAll()
+}

maps-kt-compose/src/jvmMain/kotlin/centre/sciprog/maps/compose/MapViewJvm.kt

@@ -48,7 +48,7 @@ private val logger = KotlinLogging.logger("MapView")
 /**
  * A component that renders map and provides basic map manipulation capabilities
  */
-@OptIn(ExperimentalComposeUiApi::class)
+
 @Composable
 actual fun MapView(
     mapTileProvider: MapTileProvider,
@@ -102,6 +102,7 @@ actual fun MapView(
     // Selection rectangle. If null - no selection
     var selectRect by remember { mutableStateOf<Rect?>(null) }
 
+    @OptIn(ExperimentalComposeUiApi::class)
     val canvasModifier = modifier.pointerInput(Unit) {
         forEachGesture {
             awaitPointerEventScope {
@@ -240,6 +241,11 @@ actual fun MapView(
                     val offset = feature.position.toOffset()
                     feature.drawFeature(this, offset)
                 }
+                is MapFeatureGroup -> {
+                    feature.children.values.forEach {
+                        drawFeature(zoom, it)
+                    }
+                }
             }
         }