Multi-listener drag

demo/maps/src/jvmMain/kotlin/Main.kt

@@ -64,35 +64,13 @@ fun App() {
 
             image(pointOne, Icons.Filled.Home)
 
-            var drag1 = Gmc.ofDegrees(55.744, 37.614)
+            val marker1 = rectangle(55.744 to 37.614, size = DpSize(10.dp, 10.dp), color = Color.Magenta)
+            val marker2 = rectangle(55.8 to 37.5, size = DpSize(10.dp, 10.dp), color = Color.Magenta)
+            val marker3 = rectangle(56.0 to 37.5, size = DpSize(10.dp, 10.dp), color = Color.Magenta)
 
-            var drag2 = Gmc.ofDegrees(55.8, 37.5)
+            draggableLine(marker1, marker2)
-
+            draggableLine(marker2, marker3)
-            var drag3 = Gmc.ofDegrees(56.0, 37.5)
+            draggableLine(marker3, marker1)
-
-            fun updateLine() {
-                line(drag1, drag2, id = "connection1", color = Color.Magenta)
-                line(drag2, drag3, id = "connection2", color = Color.Magenta)
-                line(drag3, drag1, id = "connection3", color = Color.Magenta)
-            }
-
-            rectangle(drag1, size = DpSize(10.dp, 10.dp)).draggable { _, end ->
-                drag1 = end
-                updateLine()
-            }
-
-            rectangle(drag2, size = DpSize(10.dp, 10.dp)).draggable { _, end ->
-                drag2 = end
-                updateLine()
-            }
-
-            rectangle(drag3, size = DpSize(10.dp, 10.dp)).draggable { _, end ->
-                drag3 = end
-                updateLine()
-            }
-
-
-            updateLine()
 
             points(
                 points = listOf(

demo/scheme/src/jvmMain/kotlin/Main.kt

@@ -8,7 +8,7 @@ import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.res.painterResource
 import androidx.compose.ui.window.Window
 import androidx.compose.ui.window.application
-import center.sciprog.maps.features.FeaturesState
+import center.sciprog.maps.features.FeatureCollection
 import center.sciprog.maps.features.ViewConfig
 import center.sciprog.maps.features.ViewPoint
 import center.sciprog.maps.features.computeBoundingBox
@@ -29,7 +29,7 @@ fun App() {
     MaterialTheme {
         val scope = rememberCoroutineScope()
 
-        val schemeFeaturesState = FeaturesState.remember(XYCoordinateSpace) {
+        val schemeFeaturesState = FeatureCollection.remember(XYCoordinateSpace) {
             background(1600f, 1200f) { painterResource("middle-earth.jpg") }
             circle(410.52737 to 868.7676, color = Color.Blue)
             text(410.52737 to 868.7676, "Shire", color = Color.Blue)

maps-kt-compose/src/commonMain/kotlin/center/sciprog/maps/compose/MapView.kt

@@ -18,7 +18,7 @@ import kotlin.math.min
 public expect fun MapView(
     mapTileProvider: MapTileProvider,
     initialViewPoint: MapViewPoint,
-    featuresState: FeaturesState<Gmc>,
+    featuresState: FeatureCollection<Gmc>,
     config: ViewConfig<Gmc> = ViewConfig(),
     modifier: Modifier = Modifier.fillMaxSize(),
 )
@@ -51,7 +51,7 @@ public fun MapView(
     modifier: Modifier = Modifier.fillMaxSize(),
 ) {
     val featuresState = key(featureMap) {
-        FeaturesState.build(GmcCoordinateSpace) {
+        FeatureCollection.build(GmcCoordinateSpace) {
             featureMap.forEach { feature(it.key.id, it.value) }
         }
     }
@@ -80,9 +80,9 @@ public fun MapView(
     initialRectangle: Rectangle<Gmc>? = null,
     config: ViewConfig<Gmc> = ViewConfig(),
     modifier: Modifier = Modifier.fillMaxSize(),
-    buildFeatures: FeaturesState<Gmc>.() -> Unit = {},
+    buildFeatures: FeatureCollection<Gmc>.() -> Unit = {},
 ) {
-    val featureState = FeaturesState.remember(GmcCoordinateSpace, buildFeatures)
+    val featureState = FeatureCollection.remember(GmcCoordinateSpace, buildFeatures)
 
     val viewPointOverride: MapViewPoint = remember(initialViewPoint, initialRectangle) {
         initialViewPoint

maps-kt-compose/src/commonMain/kotlin/center/sciprog/maps/compose/mapFeatures.kt

@@ -12,12 +12,12 @@ import center.sciprog.maps.features.*
 import center.sciprog.maps.features.Feature.Companion.defaultZoomRange
 
 
-internal fun FeaturesState<Gmc>.coordinatesOf(pair: Pair<Number, Number>) =
+internal fun FeatureCollection<Gmc>.coordinatesOf(pair: Pair<Number, Number>) =
     GeodeticMapCoordinates.ofDegrees(pair.first.toDouble(), pair.second.toDouble())
 
 public typealias MapFeature = Feature<Gmc>
 
-public fun FeaturesState<Gmc>.circle(
+public fun FeatureCollection<Gmc>.circle(
     centerCoordinates: Pair<Number, Number>,
     zoomRange: DoubleRange = defaultZoomRange,
     size: Dp = 5.dp,
@@ -27,7 +27,7 @@ public fun FeaturesState<Gmc>.circle(
     id, CircleFeature(coordinateSpace, coordinatesOf(centerCoordinates), zoomRange, size, color)
 )
 
-public fun FeaturesState<Gmc>.rectangle(
+public fun FeatureCollection<Gmc>.rectangle(
     centerCoordinates: Pair<Number, Number>,
     zoomRange: DoubleRange = defaultZoomRange,
     size: DpSize = DpSize(5.dp, 5.dp),
@@ -38,7 +38,7 @@ public fun FeaturesState<Gmc>.rectangle(
 )
 
 
-public fun FeaturesState<Gmc>.draw(
+public fun FeatureCollection<Gmc>.draw(
     position: Pair<Number, Number>,
     zoomRange: DoubleRange = defaultZoomRange,
     id: String? = null,
@@ -49,7 +49,7 @@ public fun FeaturesState<Gmc>.draw(
 )
 
 
-public fun FeaturesState<Gmc>.line(
+public fun FeatureCollection<Gmc>.line(
     curve: GmcCurve,
     zoomRange: DoubleRange = defaultZoomRange,
     color: Color = Color.Red,
@@ -60,7 +60,7 @@ public fun FeaturesState<Gmc>.line(
 )
 
 
-public fun FeaturesState<Gmc>.line(
+public fun FeatureCollection<Gmc>.line(
     aCoordinates: Pair<Double, Double>,
     bCoordinates: Pair<Double, Double>,
     zoomRange: DoubleRange = defaultZoomRange,
@@ -72,7 +72,7 @@ public fun FeaturesState<Gmc>.line(
 )
 
 
-public fun FeaturesState<Gmc>.arc(
+public fun FeatureCollection<Gmc>.arc(
     center: Pair<Double, Double>,
     radius: Distance,
     startAngle: Angle,
@@ -92,7 +92,7 @@ public fun FeaturesState<Gmc>.arc(
     )
 )
 
-public fun FeaturesState<Gmc>.points(
+public fun FeatureCollection<Gmc>.points(
     points: List<Pair<Double, Double>>,
     zoomRange: DoubleRange = defaultZoomRange,
     stroke: Float = 2f,
@@ -102,7 +102,7 @@ public fun FeaturesState<Gmc>.points(
 ): FeatureId<PointsFeature<Gmc>> =
     feature(id, PointsFeature(coordinateSpace, points.map(::coordinatesOf), zoomRange, stroke, color, pointMode))
 
-public fun FeaturesState<Gmc>.image(
+public fun FeatureCollection<Gmc>.image(
     position: Pair<Double, Double>,
     image: ImageVector,
     size: DpSize = DpSize(20.dp, 20.dp),
@@ -119,7 +119,7 @@ public fun FeaturesState<Gmc>.image(
     )
 )
 
-public fun FeaturesState<Gmc>.text(
+public fun FeatureCollection<Gmc>.text(
     position: Pair<Double, Double>,
     text: String,
     zoomRange: DoubleRange = defaultZoomRange,

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

@@ -42,7 +42,7 @@ private val logger = KotlinLogging.logger("MapView")
 public actual fun MapView(
     mapTileProvider: MapTileProvider,
     initialViewPoint: MapViewPoint,
-    featuresState: FeaturesState<Gmc>,
+    featuresState: FeatureCollection<Gmc>,
     config: ViewConfig<Gmc>,
     modifier: Modifier,
 ): Unit = key(initialViewPoint) {

maps-kt-features/src/commonMain/kotlin/center/sciprog/maps/features/AttributeMap.kt

@@ -5,8 +5,6 @@ import androidx.compose.ui.graphics.Color
 
 public object ZAttribute : Feature.Attribute<Float>
 
-public object DraggableAttribute : Feature.Attribute<DragHandle<Any>>
-
 public object SelectableAttribute : Feature.Attribute<(FeatureId<*>, SelectableFeature<*>) -> Unit>
 
 public object VisibleAttribute : Feature.Attribute<Boolean>

maps-kt-features/src/commonMain/kotlin/center/sciprog/maps/features/DraggableAttribute.kt

@@ -0,0 +1,6 @@
+package center.sciprog.maps.features
+
+
+public object DraggableAttribute : Feature.Attribute<DragHandle<Any>>
+
+public object DragListenerAttribute : Feature.Attribute<Set<(begin: Any, end: Any) -> Unit>>

maps-kt-features/src/commonMain/kotlin/center/sciprog/maps/features/Feature.kt

@@ -49,6 +49,13 @@ public interface DraggableFeature<T : Any> : SelectableFeature<T> {
     public fun withCoordinates(newCoordinates: T): Feature<T>
 }
 
+/**
+ * A draggable marker feature. Other features could be bound to this one.
+ */
+public interface MarkerFeature<T: Any>: DraggableFeature<T>{
+    public val center: T
+}
+
 public fun <T : Any> Iterable<Feature<T>>.computeBoundingBox(
     space: CoordinateSpace<T>,
     zoom: Float,
@@ -115,12 +122,12 @@ public class PointsFeature<T : Any>(
 
 public data class CircleFeature<T : Any>(
     override val space: CoordinateSpace<T>,
-    public val center: T,
+    override val center: T,
     override val zoomRange: FloatRange = defaultZoomRange,
     public val size: Dp = 5.dp,
     public val color: Color = Color.Red,
     override var attributes: AttributeMap = AttributeMap(),
-) : DraggableFeature<T> {
+) : MarkerFeature<T> {
     override fun getBoundingBox(zoom: Float): Rectangle<T> =
         space.Rectangle(center, zoom, DpSize(size, size))
 
@@ -130,12 +137,12 @@ public data class CircleFeature<T : Any>(
 
 public class RectangleFeature<T : Any>(
     override val space: CoordinateSpace<T>,
-    public val center: T,
+    override val center: T,
     override val zoomRange: FloatRange = defaultZoomRange,
     public val size: DpSize = DpSize(5.dp, 5.dp),
     public val color: Color = Color.Red,
     override var attributes: AttributeMap = AttributeMap(),
-) : DraggableFeature<T> {
+) : MarkerFeature<T> {
     override fun getBoundingBox(zoom: Float): Rectangle<T> =
         space.Rectangle(center, zoom, size)
 
@@ -193,35 +200,35 @@ public data class DrawFeature<T : Any>(
 
 public data class BitmapImageFeature<T : Any>(
     override val space: CoordinateSpace<T>,
-    public val position: T,
+    override val center: T,
     public val size: DpSize,
     public val image: ImageBitmap,
     override val zoomRange: FloatRange = defaultZoomRange,
     override var attributes: AttributeMap = AttributeMap(),
-) : DraggableFeature<T> {
+) : MarkerFeature<T> {
-    override fun getBoundingBox(zoom: Float): Rectangle<T> = space.Rectangle(position, zoom, size)
+    override fun getBoundingBox(zoom: Float): Rectangle<T> = space.Rectangle(center, zoom, size)
 
-    override fun withCoordinates(newCoordinates: T): Feature<T> = copy(position = newCoordinates)
+    override fun withCoordinates(newCoordinates: T): Feature<T> = copy(center = newCoordinates)
 }
 
 public data class VectorImageFeature<T : Any>(
     override val space: CoordinateSpace<T>,
-    public val position: T,
+    override val center: T,
     public val size: DpSize,
     public val image: ImageVector,
     override val zoomRange: FloatRange = defaultZoomRange,
     override var attributes: AttributeMap = AttributeMap(),
-) : DraggableFeature<T>, PainterFeature<T> {
+) : MarkerFeature<T>, PainterFeature<T> {
-    override fun getBoundingBox(zoom: Float): Rectangle<T> = space.Rectangle(position, zoom, size)
+    override fun getBoundingBox(zoom: Float): Rectangle<T> = space.Rectangle(center, zoom, size)
 
-    override fun withCoordinates(newCoordinates: T): Feature<T> = copy(position = newCoordinates)
+    override fun withCoordinates(newCoordinates: T): Feature<T> = copy(center = newCoordinates)
 
     @Composable
     override fun painter(): VectorPainter = rememberVectorPainter(image)
 }
 
 /**
- * A background image that is bound to coordinates and is scaled together with them
+ * An image that is bound to coordinates and is scaled together with them
  *
  * @param rectangle the size of background in scheme size units. The screen units to scheme units ratio equals scale.
  */

maps-kt-features/src/commonMain/kotlin/center/sciprog/maps/features/FeatureCollection.kt

@@ -18,10 +18,23 @@ import kotlinx.coroutines.isActive
 import kotlinx.coroutines.launch
 
 @JvmInline
-public value class FeatureId<out MapFeature>(public val id: String)
+public value class FeatureId<out F : Feature<*>>(public val id: String)
 
-public class FeaturesState<T : Any>(public val coordinateSpace: CoordinateSpace<T>) :
+public interface FeatureBuilder<T : Any> {
-    CoordinateSpace<T> by coordinateSpace {
+
+    public val coordinateSpace: CoordinateSpace<T>
+
+    public fun <F : Feature<T>> feature(id: String?, feature: F): FeatureId<F>
+
+    public fun <F : Feature<T>, V> setAttribute(id: FeatureId<F>, key: Feature.Attribute<V>, value: V?)
+}
+
+public fun <T : Any, F : Feature<T>> FeatureBuilder<T>.feature(id: FeatureId<F>, feature: F): FeatureId<F> =
+    feature(id.id, feature)
+
+public class FeatureCollection<T : Any>(
+    override val coordinateSpace: CoordinateSpace<T>,
+) : CoordinateSpace<T> by coordinateSpace, FeatureBuilder<T> {
 
     @PublishedApi
     internal val featureMap: MutableMap<String, Feature<T>> = mutableStateMapOf()
@@ -30,21 +43,21 @@ public class FeaturesState<T : Any>(public val coordinateSpace: CoordinateSpace<
         get() = featureMap.mapKeys { FeatureId<Feature<T>>(it.key) }
 
     @Suppress("UNCHECKED_CAST")
-    public fun <F : Feature<T>> getFeature(id: FeatureId<F>): F = featureMap[id.id] as F
+    public operator fun <F : Feature<T>> get(id: FeatureId<F>): F = featureMap[id.id] as F
 
     private fun generateID(feature: Feature<T>): String = "@feature[${feature.hashCode().toUInt()}]"
 
-    public fun <F : Feature<T>> feature(id: String?, feature: F): FeatureId<F> {
+    override fun <F : Feature<T>> feature(id: String?, feature: F): FeatureId<F> {
         val safeId = id ?: generateID(feature)
         featureMap[safeId] = feature
         return FeatureId(safeId)
     }
 
-    public fun <F : Feature<T>> feature(id: FeatureId<F>?, feature: F): FeatureId<F> = feature(id?.id, feature)
+    public fun <F : Feature<T>> feature(id: FeatureId<F>, feature: F): FeatureId<F> = feature(id.id, feature)
 
 
-    public fun <F : Feature<T>, V> setAttribute(id: FeatureId<F>, key: Feature.Attribute<V>, value: V?) {
+    override fun <F : Feature<T>, V> setAttribute(id: FeatureId<F>, key: Feature.Attribute<V>, value: V?) {
-        getFeature(id).attributes[key] = value
+        get(id).attributes[key] = value
     }
 
     /**
@@ -54,26 +67,38 @@ public class FeaturesState<T : Any>(public val coordinateSpace: CoordinateSpace<
      *
      * TODO use context receiver for that
      */
+    @Suppress("UNCHECKED_CAST")
     public fun FeatureId<DraggableFeature<T>>.draggable(
         constraint: ((T) -> T)? = null,
-        callback: ((start: T, end: T) -> Unit) = { _, _ -> },
+        callback: ((start: T, end: T) -> Unit)? = null,
     ) {
-        @Suppress("UNCHECKED_CAST")
+        if (getAttribute(this, DraggableAttribute) == null) {
-        val handle = DragHandle.withPrimaryButton<Any> { _, start, end ->
+            val handle = DragHandle.withPrimaryButton<Any> { _, start, end ->
-            val startPosition = start.focus as T
+                val feature = featureMap[id] as? DraggableFeature ?: return@withPrimaryButton DragResult(end)
-            val endPosition = end.focus as T
+                val startPosition = start.focus as T
-            val feature = featureMap[id] as? DraggableFeature ?: return@withPrimaryButton DragResult(end)
+                val endPosition = end.focus as T
-            val boundingBox = feature.getBoundingBox(start.zoom) ?: return@withPrimaryButton DragResult(end)
+                val boundingBox = feature.getBoundingBox(start.zoom) ?: return@withPrimaryButton DragResult(end)
-            if (startPosition in boundingBox) {
+                if (startPosition in boundingBox) {
-                val finalPosition = constraint?.invoke(endPosition) ?: endPosition
+                    val finalPosition = constraint?.invoke(endPosition) ?: endPosition
-                feature(id, feature.withCoordinates(finalPosition))
+                    feature(id, feature.withCoordinates(finalPosition))
-                callback(startPosition, finalPosition)
+                    feature.attributes[DragListenerAttribute]?.forEach {
-                DragResult(ViewPoint(finalPosition, end.zoom), false)
+                        it.invoke(startPosition, endPosition)
-            } else {
+                    }
-                DragResult(end, true)
+                    DragResult(ViewPoint(finalPosition, end.zoom), false)
+                } else {
+                    DragResult(end, true)
+                }
             }
+            setAttribute(this, DraggableAttribute, handle)
+        }
+
+        //Apply callback
+        if (callback != null) {
+            setAttribute(
+                this, DragListenerAttribute,
+                ((getAttribute(this, DragListenerAttribute) ?: emptySet()) + callback) as Set<(Any, Any) -> Unit>
+            )
         }
-        setAttribute(this, DraggableAttribute, handle)
     }
 
     /**
@@ -84,7 +109,7 @@ public class FeaturesState<T : Any>(public val coordinateSpace: CoordinateSpace<
         update: suspend (F) -> F,
     ): Job = scope.launch {
         while (isActive) {
-            feature(this@updated, update(getFeature(this@updated)))
+            feature(this@updated, update(get(this@updated)))
         }
     }
 
@@ -98,15 +123,7 @@ public class FeaturesState<T : Any>(public val coordinateSpace: CoordinateSpace<
 
     @Suppress("UNCHECKED_CAST")
     public fun <A> getAttribute(id: FeatureId<Feature<T>>, key: Feature.Attribute<A>): A? =
-        getFeature(id).attributes[key]
+        get(id).attributes[key]
-
-
-//    @Suppress("UNCHECKED_CAST")
-//    public fun <T> findAllWithAttribute(key: Attribute<T>, condition: (T) -> Boolean): Set<FeatureId> {
-//        return attributes.filterValues {
-//            condition(it[key] as T)
-//        }.keys
-//    }
 
     /**
      * Process all features with a given attribute from the one with highest [z] to lowest
@@ -129,8 +146,8 @@ public class FeaturesState<T : Any>(public val coordinateSpace: CoordinateSpace<
          */
         public fun <T : Any> build(
             coordinateSpace: CoordinateSpace<T>,
-            builder: FeaturesState<T>.() -> Unit = {},
+            builder: FeatureCollection<T>.() -> Unit = {},
-        ): FeaturesState<T> = FeaturesState(coordinateSpace).apply(builder)
+        ): FeatureCollection<T> = FeatureCollection(coordinateSpace).apply(builder)
 
         /**
          * Build and remember map feature state
@@ -138,15 +155,15 @@ public class FeaturesState<T : Any>(public val coordinateSpace: CoordinateSpace<
         @Composable
         public fun <T : Any> remember(
             coordinateSpace: CoordinateSpace<T>,
-            builder: FeaturesState<T>.() -> Unit = {},
+            builder: FeatureCollection<T>.() -> Unit = {},
-        ): FeaturesState<T> = remember(builder) {
+        ): FeatureCollection<T> = remember(builder) {
             build(coordinateSpace, builder)
         }
 
     }
 }
 
-public fun <T : Any> FeaturesState<T>.circle(
+public fun <T : Any> FeatureBuilder<T>.circle(
     center: T,
     zoomRange: FloatRange = defaultZoomRange,
     size: Dp = 5.dp,
@@ -156,7 +173,7 @@ public fun <T : Any> FeaturesState<T>.circle(
     id, CircleFeature(coordinateSpace, center, zoomRange, size, color)
 )
 
-public fun <T : Any> FeaturesState<T>.rectangle(
+public fun <T : Any> FeatureBuilder<T>.rectangle(
     centerCoordinates: T,
     zoomRange: FloatRange = defaultZoomRange,
     size: DpSize = DpSize(5.dp, 5.dp),
@@ -166,7 +183,7 @@ public fun <T : Any> FeaturesState<T>.rectangle(
     id, RectangleFeature(coordinateSpace, centerCoordinates, zoomRange, size, color)
 )
 
-public fun <T : Any> FeaturesState<T>.draw(
+public fun <T : Any> FeatureBuilder<T>.draw(
     position: T,
     zoomRange: FloatRange = defaultZoomRange,
     id: String? = null,
@@ -176,7 +193,7 @@ public fun <T : Any> FeaturesState<T>.draw(
     DrawFeature(coordinateSpace, position, zoomRange, drawFeature = draw)
 )
 
-public fun <T : Any> FeaturesState<T>.line(
+public fun <T : Any> FeatureBuilder<T>.line(
     aCoordinates: T,
     bCoordinates: T,
     zoomRange: FloatRange = defaultZoomRange,
@@ -187,7 +204,7 @@ public fun <T : Any> FeaturesState<T>.line(
     LineFeature(coordinateSpace, aCoordinates, bCoordinates, zoomRange, color)
 )
 
-public fun <T : Any> FeaturesState<T>.arc(
+public fun <T : Any> FeatureBuilder<T>.arc(
     oval: Rectangle<T>,
     startAngle: Float,
     arcLength: Float,
@@ -199,7 +216,7 @@ public fun <T : Any> FeaturesState<T>.arc(
     ArcFeature(coordinateSpace, oval, startAngle, arcLength, zoomRange, color)
 )
 
-public fun <T : Any> FeaturesState<T>.points(
+public fun <T : Any> FeatureBuilder<T>.points(
     points: List<T>,
     zoomRange: FloatRange = defaultZoomRange,
     stroke: Float = 2f,
@@ -209,7 +226,7 @@ public fun <T : Any> FeaturesState<T>.points(
 ): FeatureId<PointsFeature<T>> =
     feature(id, PointsFeature(coordinateSpace, points, zoomRange, stroke, color, pointMode))
 
-public fun <T : Any> FeaturesState<T>.image(
+public fun <T : Any> FeatureBuilder<T>.image(
     position: T,
     image: ImageVector,
     zoomRange: FloatRange = defaultZoomRange,
@@ -227,17 +244,17 @@ public fun <T : Any> FeaturesState<T>.image(
         )
     )
 
-public fun <T : Any> FeaturesState<T>.group(
+public fun <T : Any> FeatureBuilder<T>.group(
     zoomRange: FloatRange = defaultZoomRange,
     id: String? = null,
-    builder: FeaturesState<T>.() -> Unit,
+    builder: FeatureCollection<T>.() -> Unit,
 ): FeatureId<FeatureGroup<T>> {
-    val map = FeaturesState(coordinateSpace).apply(builder).features
+    val map = FeatureCollection(coordinateSpace).apply(builder).features
     val feature = FeatureGroup(coordinateSpace, map, zoomRange)
     return feature(id, feature)
 }
 
-public fun <T : Any> FeaturesState<T>.scalableImage(
+public fun <T : Any> FeatureBuilder<T>.scalableImage(
     box: Rectangle<T>,
     zoomRange: FloatRange = defaultZoomRange,
     id: String? = null,
@@ -247,7 +264,7 @@ public fun <T : Any> FeaturesState<T>.scalableImage(
     ScalableImageFeature<T>(coordinateSpace, box, zoomRange, painter = painter)
 )
 
-public fun <T : Any> FeaturesState<T>.text(
+public fun <T : Any> FeatureBuilder<T>.text(
     position: T,
     text: String,
     zoomRange: FloatRange = defaultZoomRange,

maps-kt-features/src/commonMain/kotlin/center/sciprog/maps/features/compositeFeatures.kt

@@ -0,0 +1,34 @@
+package center.sciprog.maps.features
+
+import androidx.compose.ui.graphics.Color
+
+
+public fun <T : Any> FeatureCollection<T>.draggableLine(
+    aId: FeatureId<MarkerFeature<T>>,
+    bId: FeatureId<MarkerFeature<T>>,
+    zoomRange: FloatRange = Feature.defaultZoomRange,
+    color: Color = Color.Red,
+    id: String? = null,
+): FeatureId<LineFeature<T>> {
+    var lineId: FeatureId<LineFeature<T>>? = null
+
+    fun drawLine(): FeatureId<LineFeature<T>> = line(
+        get(aId).center,
+        get(bId).center,
+        zoomRange,
+        color,
+        lineId?.id ?: id
+    ).also {
+        lineId = it
+    }
+
+    aId.draggable { _, _ ->
+        drawLine()
+    }
+
+    bId.draggable { _, _ ->
+        drawLine()
+    }
+
+    return drawLine()
+}

maps-kt-features/src/jvmMain/kotlin/center/sciprog/maps/features/drawFeature.kt

@@ -62,10 +62,10 @@ public fun <T : Any> DrawScope.drawFeature(
 
         }
 
-        is BitmapImageFeature -> drawImage(feature.image, feature.position.toOffset())
+        is BitmapImageFeature -> drawImage(feature.image, feature.center.toOffset())
 
         is VectorImageFeature -> {
-            val offset = feature.position.toOffset()
+            val offset = feature.center.toOffset()
             val size = feature.size.toSize()
             translate(offset.x - size.width / 2, offset.y - size.height / 2) {
                 with(painterCache[feature]!!) {

maps-kt-scheme/src/commonMain/kotlin/center/sciprog/maps/scheme/schemeFeatures.kt

@@ -12,7 +12,7 @@ import center.sciprog.maps.features.*
 
 internal fun Pair<Number, Number>.toCoordinates(): XY = XY(first.toFloat(), second.toFloat())
 
-fun FeaturesState<XY>.background(
+fun FeatureCollection<XY>.background(
     width: Float,
     height: Float,
     offset: XY = XY(0f, 0f),
@@ -31,7 +31,7 @@ fun FeaturesState<XY>.background(
     )
 }
 
-fun FeaturesState<XY>.circle(
+fun FeatureCollection<XY>.circle(
     centerCoordinates: Pair<Number, Number>,
     zoomRange: FloatRange = Feature.defaultZoomRange,
     size: Dp = 5.dp,
@@ -39,14 +39,14 @@ fun FeaturesState<XY>.circle(
     id: String? = null,
 ): FeatureId<CircleFeature<XY>> = circle(centerCoordinates.toCoordinates(), zoomRange, size, color, id = id)
 
-fun FeaturesState<XY>.draw(
+fun FeatureCollection<XY>.draw(
     position: Pair<Number, Number>,
     zoomRange: FloatRange = Feature.defaultZoomRange,
     id: String? = null,
     draw: DrawScope.() -> Unit,
 ): FeatureId<DrawFeature<XY>> = draw(position.toCoordinates(), zoomRange = zoomRange, id = id, draw = draw)
 
-fun FeaturesState<XY>.line(
+fun FeatureCollection<XY>.line(
     aCoordinates: Pair<Number, Number>,
     bCoordinates: Pair<Number, Number>,
     scaleRange: FloatRange = Feature.defaultZoomRange,
@@ -55,7 +55,7 @@ fun FeaturesState<XY>.line(
 ): FeatureId<LineFeature<XY>> = line(aCoordinates.toCoordinates(), bCoordinates.toCoordinates(), scaleRange, color, id)
 
 
-public fun FeaturesState<XY>.arc(
+public fun FeatureCollection<XY>.arc(
     center: Pair<Double, Double>,
     radius: Float,
     startAngle: Float,
@@ -71,7 +71,7 @@ public fun FeaturesState<XY>.arc(
     color = color
 )
 
-fun FeaturesState<XY>.image(
+fun FeatureCollection<XY>.image(
     position: Pair<Number, Number>,
     image: ImageVector,
     size: DpSize = DpSize(image.defaultWidth, image.defaultHeight),
@@ -80,7 +80,7 @@ fun FeaturesState<XY>.image(
 ): FeatureId<VectorImageFeature<XY>> =
     image(position.toCoordinates(), image, size = size, zoomRange = zoomRange, id = id)
 
-fun FeaturesState<XY>.text(
+fun FeatureCollection<XY>.text(
     position: Pair<Number, Number>,
     text: String,
     zoomRange: FloatRange = Feature.defaultZoomRange,

maps-kt-scheme/src/jvmMain/kotlin/center/sciprog/maps/scheme/SchemeView.kt

@@ -23,7 +23,7 @@ private val logger = KotlinLogging.logger("SchemeView")
 @Composable
 public fun SchemeView(
     initialViewPoint: ViewPoint<XY>,
-    featuresState: FeaturesState<XY>,
+    featuresState: FeatureCollection<XY>,
     config: ViewConfig<XY>,
     modifier: Modifier = Modifier.fillMaxSize(),
 ) = key(initialViewPoint) {
@@ -96,7 +96,7 @@ public fun SchemeView(
     modifier: Modifier = Modifier.fillMaxSize(),
 ) {
     val featuresState = key(featureMap) {
-        FeaturesState.build(XYCoordinateSpace) {
+        FeatureCollection.build(XYCoordinateSpace) {
             featureMap.forEach { feature(it.key.id, it.value) }
         }
     }
@@ -124,9 +124,9 @@ public fun SchemeView(
     initialRectangle: Rectangle<XY>? = null,
     config: ViewConfig<XY> = ViewConfig(),
     modifier: Modifier = Modifier.fillMaxSize(),
-    buildFeatures: FeaturesState<XY>.() -> Unit = {},
+    buildFeatures: FeatureCollection<XY>.() -> Unit = {},
 ) {
-    val featureState = FeaturesState.remember(XYCoordinateSpace, buildFeatures)
+    val featureState = FeatureCollection.remember(XYCoordinateSpace, buildFeatures)
 
     val viewPointOverride: ViewPoint<XY> = remember(initialViewPoint, initialRectangle) {
         initialViewPoint

maps-kt-scheme/src/jvmMain/kotlin/center/sciprog/maps/svg/exportToSvg.kt

@@ -22,7 +22,7 @@ class FeatureStateSnapshot<T : Any>(
 )
 
 @Composable
-fun <T: Any> FeaturesState<T>.snapshot(): FeatureStateSnapshot<T> = FeatureStateSnapshot(
+fun <T: Any> FeatureCollection<T>.snapshot(): FeatureStateSnapshot<T> = FeatureStateSnapshot(
     features,
     features.values.filterIsInstance<PainterFeature<T>>().associateWith { it.painter() }
 )
@@ -83,10 +83,10 @@ fun FeatureStateSnapshot<XY>.generateSvg(
                 )
             }
 
-            is BitmapImageFeature -> drawImage(feature.image, feature.position.toOffset())
+            is BitmapImageFeature -> drawImage(feature.image, feature.center.toOffset())
 
             is VectorImageFeature -> {
-                val offset = feature.position.toOffset()
+                val offset = feature.center.toOffset()
                 val imageSize = feature.size.toSize()
                 translate(offset.x - imageSize.width / 2, offset.y - imageSize.height / 2) {
                     with(painterCache[feature]!!) {