Added function to draw custom markers with Kotlin DSL Canvas API. FeatureId can be extended to hold info about a feature??? I added unused onFeatureClick, which can be latter implemented with pointer input, where it will check coordinates with offset? Features need to hold info about their coordinates?

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

@@ -3,9 +3,12 @@ package centre.sciprog.maps.compose
 import androidx.compose.runtime.Composable
 import androidx.compose.runtime.mutableStateMapOf
 import androidx.compose.runtime.snapshots.SnapshotStateMap
+import androidx.compose.ui.geometry.Offset
 import androidx.compose.ui.geometry.Size
 import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.graphics.drawscope.DrawScope
 import androidx.compose.ui.graphics.vector.ImageVector
+import centre.sciprog.maps.GmcBox
 
 typealias FeatureId = String
 
@@ -15,7 +18,7 @@ interface FeatureBuilder {
     fun build(): SnapshotStateMap<FeatureId, MapFeature>
 }
 
-internal class MapFeatureBuilder(initialFeatures: Map<FeatureId,MapFeature>) : FeatureBuilder {
+internal class MapFeatureBuilder(initialFeatures: Map<FeatureId, MapFeature>) : FeatureBuilder {
 
     private val content: SnapshotStateMap<FeatureId, MapFeature> = mutableStateMapOf<FeatureId, MapFeature>().apply {
         putAll(initialFeatures)
@@ -41,6 +44,21 @@ fun FeatureBuilder.circle(
     id, MapCircleFeature(centerCoordinates.toCoordinates(), zoomRange, size, color)
 )
 
+fun FeatureBuilder.custom(
+    position: Pair<Double, Double>,
+    id: FeatureId? = null,
+    customFeatureBuilder: DrawScope.(Offset) -> Unit,
+) = addFeature(id, object : MapCustomFeature(position = position.toCoordinates()) {
+    override fun drawFeature(drawScope: DrawScope, offset: Offset) {
+        customFeatureBuilder(drawScope, offset)
+    }
+
+    override fun getBoundingBox(zoom: Int): GmcBox {
+        return GmcBox(position.toCoordinates(), position.toCoordinates())
+    }
+
+})
+
 fun FeatureBuilder.line(
     aCoordinates: Pair<Double, Double>,
     bCoordinates: Pair<Double, Double>,

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

@@ -1,9 +1,11 @@
 package centre.sciprog.maps.compose
 
 import androidx.compose.runtime.Composable
+import androidx.compose.ui.geometry.Offset
 import androidx.compose.ui.geometry.Size
 import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.graphics.ImageBitmap
+import androidx.compose.ui.graphics.drawscope.DrawScope
 import androidx.compose.ui.graphics.painter.Painter
 import androidx.compose.ui.graphics.vector.ImageVector
 import androidx.compose.ui.graphics.vector.rememberVectorPainter
@@ -31,6 +33,13 @@ class MapFeatureSelector(val selector: (zoom: Int) -> MapFeature) : MapFeature(d
 
 }
 
+abstract class MapCustomFeature(
+    zoomRange: IntRange = defaultZoomRange,
+    val position: GeodeticMapCoordinates
+) : MapFeature(zoomRange) {
+    abstract fun drawFeature(drawScope: DrawScope, offset: Offset)
+}
+
 class MapCircleFeature(
     val center: GeodeticMapCoordinates,
     zoomRange: IntRange = defaultZoomRange,
@@ -68,7 +77,7 @@ class MapBitmapImageFeature(
 }
 
 
-class MapVectorImageFeature (
+class MapVectorImageFeature(
     val position: GeodeticMapCoordinates,
     val painter: Painter,
     val size: Size,

src/commonMain/kotlin/centre/sciprog/maps/compose/MapView.kt

@@ -21,6 +21,7 @@ expect fun MapView(
     computeViewPoint: (canvasSize: DpSize) -> MapViewPoint,
     features: Map<FeatureId, MapFeature>,
     onClick: MapViewPoint.() -> Unit = {},
+    onFeatureClick: (FeatureId) -> Unit = {},
     //TODO consider replacing by modifier
     config: MapViewConfig = MapViewConfig(),
     modifier: Modifier = Modifier.fillMaxSize(),
@@ -32,13 +33,14 @@ fun MapView(
     initialViewPoint: MapViewPoint,
     features: Map<FeatureId, MapFeature> = emptyMap(),
     onClick: MapViewPoint.() -> Unit = {},
+    onFeatureClick: (FeatureId) -> Unit = {},
     config: MapViewConfig = MapViewConfig(),
     modifier: Modifier = Modifier.fillMaxSize(),
     buildFeatures: @Composable (FeatureBuilder.() -> Unit) = {},
 ) {
     val featuresBuilder = MapFeatureBuilder(features)
     featuresBuilder.buildFeatures()
-    MapView(mapTileProvider, { initialViewPoint }, featuresBuilder.build(), onClick, config, modifier)
+    MapView(mapTileProvider, { initialViewPoint }, featuresBuilder.build(), onClick, onFeatureClick, config, modifier)
 }
 
 @Composable
@@ -47,6 +49,7 @@ fun MapView(
     box: GmcBox,
     features: Map<FeatureId, MapFeature> = emptyMap(),
     onClick: MapViewPoint.() -> Unit = {},
+    onFeatureClick: (FeatureId) -> Unit = {},
     config: MapViewConfig = MapViewConfig(),
     modifier: Modifier = Modifier.fillMaxSize(),
     buildFeatures: @Composable (FeatureBuilder.() -> Unit) = {},
@@ -62,5 +65,5 @@ fun MapView(
         )
         MapViewPoint(box.center, zoom)
     }
-    MapView(mapTileProvider, computeViewPoint, featuresBuilder.build(), onClick, config, modifier)
+    MapView(mapTileProvider, computeViewPoint, featuresBuilder.build(), onClick, onFeatureClick, config, modifier)
 }

src/jvmMain/kotlin/Main.kt

@@ -6,14 +6,15 @@ import androidx.compose.material.Text
 import androidx.compose.material.icons.Icons
 import androidx.compose.material.icons.filled.Home
 import androidx.compose.runtime.*
+import androidx.compose.ui.geometry.Size
 import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.window.Window
 import androidx.compose.ui.window.application
 import centre.sciprog.maps.GeodeticMapCoordinates
 import centre.sciprog.maps.MapViewPoint
 import centre.sciprog.maps.compose.*
-import io.ktor.client.HttpClient
-import io.ktor.client.engine.cio.CIO
+import io.ktor.client.*
+import io.ktor.client.engine.cio.*
 import kotlinx.coroutines.delay
 import kotlinx.coroutines.isActive
 import kotlinx.coroutines.launch
@@ -44,15 +45,25 @@ fun App() {
                 mapTileProvider,
                 viewPoint,
                 onClick = { coordinates = focus },
+                onFeatureClick = {
+
+                },
                 config = MapViewConfig(inferViewBoxFromFeatures = true)
             ) {
                 val pointOne = 55.568548 to 37.568604
                 val pointTwo = 55.929444 to 37.518434
+                val pointThree = 60.929444 to 37.518434
 
                 image(pointOne, Icons.Filled.Home)
 
                 //remember feature Id
-                val circleId: FeatureId = circle(pointTwo)
+                val circleId: FeatureId = custom(position = pointThree) {
+                    drawRect(
+                        color = Color.Red,
+                        topLeft = it,
+                        size = Size(20f, 20f)
+                    )
+                }
 
                 line(pointOne, pointTwo)
                 text(pointOne, "Home")

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

@@ -41,6 +41,7 @@ actual fun MapView(
     computeViewPoint: (canvasSize: DpSize) -> MapViewPoint,
     features: Map<FeatureId, MapFeature>,
     onClick: MapViewPoint.() -> Unit,
+    onFeatureClick: (FeatureId) -> Unit,
     config: MapViewConfig,
     modifier: Modifier,
 ) {
@@ -219,7 +220,10 @@ actual fun MapView(
                         feature.color.toPaint()
                     )
                 }
-
+                is MapCustomFeature -> drawIntoCanvas { canvas ->
+                    val offset = feature.position.toOffset()
+                    feature.drawFeature(this, offset)
+                }
             }
         }