Generalize map control logic

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

@@ -57,7 +57,7 @@ fun App() {
 //                50.kilometers,
 //                50.kilometers
 //            ),
-            config = MapViewConfig(
+            config = ViewConfig(
                 onViewChange = { centerCoordinates = focus },
             )
         ) {

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

@@ -4,17 +4,44 @@ import androidx.compose.ui.unit.DpSize
 import center.sciprog.maps.coordinates.*
 import center.sciprog.maps.features.CoordinateSpace
 import center.sciprog.maps.features.Rectangle
+import center.sciprog.maps.features.ViewPoint
+import kotlin.math.pow
 
 public object GmcCoordinateSpace : CoordinateSpace<Gmc> {
-    override fun buildRectangle(first: Gmc, second: Gmc): GmcRectangle = GmcRectangle(first, second)
+    override fun Rectangle(first: Gmc, second: Gmc): GmcRectangle = GmcRectangle(first, second)
 
-    override fun buildRectangle(center: Gmc, zoom: Double, size: DpSize): GmcRectangle{
+    override fun Rectangle(center: Gmc, zoom: Double, size: DpSize): GmcRectangle {
         val scale = WebMercatorProjection.scaleFactor(zoom)
-        return buildRectangle(center, (size.width.value/scale).radians, (size.height.value / scale).radians)
+        return buildRectangle(center, (size.width.value / scale).radians, (size.height.value / scale).radians)
     }
 
+    override fun ViewPoint(center: Gmc, zoom: Double): ViewPoint<Gmc> = MapViewPoint(center, zoom)
+
+    override fun ViewPoint<Gmc>.moveBy(delta: Gmc): ViewPoint<Gmc> {
+        val newCoordinates = GeodeticMapCoordinates(
+            (focus.latitude + delta.latitude).coerceIn(
+                -MercatorProjection.MAXIMUM_LATITUDE,
+                MercatorProjection.MAXIMUM_LATITUDE
+            ),
+            focus.longitude + delta.longitude
+        )
+        return MapViewPoint(newCoordinates, zoom)
+    }
+
+    override fun ViewPoint<Gmc>.zoomBy(zoomDelta: Double, invariant: Gmc): ViewPoint<Gmc> = if (invariant == focus) {
+        ViewPoint(focus, (zoom + zoomDelta).coerceIn(2.0, 18.0) )
+    } else {
+        val difScale = (1 - 2.0.pow(-zoomDelta))
+        val newCenter = GeodeticMapCoordinates(
+            focus.latitude + (invariant.latitude - focus.latitude) * difScale,
+            focus.longitude + (invariant.longitude - focus.longitude) * difScale
+        )
+        MapViewPoint(newCenter, (zoom + zoomDelta).coerceIn(2.0, 18.0))
+    }
+
+
     override fun Rectangle<Gmc>.withCenter(center: Gmc): GmcRectangle {
-            return buildRectangle(center, height = latitudeDelta, width = longitudeDelta)
+        return buildRectangle(center, height = latitudeDelta, width = longitudeDelta)
     }
 
     override fun Collection<Rectangle<Gmc>>.wrapRectangles(): Rectangle<Gmc>? {
@@ -45,7 +72,7 @@ public fun CoordinateSpace<Gmc>.buildRectangle(
     center: Gmc,
     height: Distance,
     width: Distance,
-    ellipsoid: GeoEllipsoid = GeoEllipsoid.WGS84
+    ellipsoid: GeoEllipsoid = GeoEllipsoid.WGS84,
 ): GmcRectangle {
     val reducedRadius = ellipsoid.reducedRadius(center.latitude)
     return buildRectangle(center, (height / ellipsoid.polarRadius).radians, (width / reducedRadius).radians)

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

@@ -0,0 +1,85 @@
+package center.sciprog.maps.compose
+
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.remember
+import androidx.compose.ui.unit.Dp
+import androidx.compose.ui.unit.DpOffset
+import androidx.compose.ui.unit.DpSize
+import androidx.compose.ui.unit.dp
+import center.sciprog.maps.coordinates.*
+import center.sciprog.maps.features.*
+import kotlin.math.*
+
+internal class MapState internal constructor(
+    config: ViewConfig<Gmc>,
+    canvasSize: DpSize,
+    viewPoint: ViewPoint<Gmc>,
+    public val tileSize: Int,
+) : CoordinateViewState<Gmc>(config, canvasSize, viewPoint) {
+    override val space: CoordinateSpace<Gmc> get() = GmcCoordinateSpace
+
+    public val zoom: Int
+        get() = floor(viewPoint.zoom).toInt()
+
+    public val scaleFactor: Double
+        get() = WebMercatorProjection.scaleFactor(viewPoint.zoom)
+
+    public val centerCoordinates: WebMercatorCoordinates
+        get() = WebMercatorProjection.toMercator(viewPoint.focus, zoom)
+
+    internal val tileScale: Double
+        get() = 2.0.pow(viewPoint.zoom - zoom)
+
+    private fun DpOffset.toMercator(): WebMercatorCoordinates = WebMercatorCoordinates(
+        zoom,
+        (x - canvasSize.width / 2).value / tileScale + centerCoordinates.x,
+        (y - canvasSize.height / 2).value / tileScale + centerCoordinates.y,
+    )
+
+    /*
+     * Convert screen independent offset to GMC, adjusting for fractional zoom
+     */
+    override fun DpOffset.toCoordinates(): Gmc =
+        WebMercatorProjection.toGeodetic(toMercator())
+
+    internal fun WebMercatorCoordinates.toOffset(): DpOffset = DpOffset(
+        (canvasSize.width / 2 + (x.dp - centerCoordinates.x.dp) * tileScale.toFloat()),
+        (canvasSize.height / 2 + (y.dp - centerCoordinates.y.dp) * tileScale.toFloat())
+    )
+
+    override fun Gmc.toDpOffset(): DpOffset =
+        WebMercatorProjection.toMercator(this, zoom).toOffset()
+
+    override fun viewPointFor(rectangle: Rectangle<Gmc>): ViewPoint<Gmc> {
+        val zoom = log2(
+            min(
+                canvasSize.width.value / rectangle.longitudeDelta.radians.value,
+                canvasSize.height.value / rectangle.latitudeDelta.radians.value
+            ) * PI / tileSize
+        )
+        return MapViewPoint(rectangle.center, zoom)
+    }
+
+    override fun ViewPoint<Gmc>.moveBy(x: Dp, y: Dp): ViewPoint<Gmc> {
+        val deltaX = x.value / tileScale
+        val deltaY = y.value / tileScale
+        val newCoordinates = GeodeticMapCoordinates(
+            (focus.latitude + (deltaY / scaleFactor).radians).coerceIn(
+                -MercatorProjection.MAXIMUM_LATITUDE,
+                MercatorProjection.MAXIMUM_LATITUDE
+            ),
+            focus.longitude + (deltaX / scaleFactor).radians
+        )
+        return MapViewPoint(newCoordinates, zoom)
+    }
+}
+
+@Composable
+internal fun rememberMapState(
+    config: ViewConfig<Gmc>,
+    canvasSize: DpSize,
+    viewPoint: ViewPoint<Gmc>,
+    tileSize: Int,
+):MapState = remember {
+    MapState(config, canvasSize, viewPoint, tileSize)
+}

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

@@ -5,7 +5,6 @@ import androidx.compose.runtime.Composable
 import androidx.compose.runtime.key
 import androidx.compose.runtime.remember
 import androidx.compose.ui.Modifier
-import androidx.compose.ui.input.pointer.PointerEvent
 import androidx.compose.ui.unit.DpSize
 import androidx.compose.ui.unit.dp
 import center.sciprog.maps.coordinates.Gmc
@@ -15,25 +14,12 @@ import kotlin.math.log2
 import kotlin.math.min
 
 
-//TODO consider replacing by modifier
-/**
- */
-public data class MapViewConfig(
-    val zoomSpeed: Double = 1.0 / 3.0,
-    val onClick: MapViewPoint.(PointerEvent) -> Unit = {},
-    val dragHandle: DragHandle<Gmc> = DragHandle.bypass(),
-    val onViewChange: MapViewPoint.() -> Unit = {},
-    val onSelect: (GmcRectangle) -> Unit = {},
-    val zoomOnSelect: Boolean = true,
-    val onCanvasSizeChange: (DpSize) -> Unit = {},
-)
-
 @Composable
 public expect fun MapView(
     mapTileProvider: MapTileProvider,
     initialViewPoint: MapViewPoint,
     featuresState: FeaturesState<Gmc>,
-    config: MapViewConfig = MapViewConfig(),
+    config: ViewConfig<Gmc> = ViewConfig(),
     modifier: Modifier = Modifier.fillMaxSize(),
 )
 
@@ -61,7 +47,7 @@ public fun MapView(
     initialViewPoint: MapViewPoint? = null,
     initialRectangle: GmcRectangle? = null,
     featureMap: Map<FeatureId<*>, MapFeature>,
-    config: MapViewConfig = MapViewConfig(),
+    config: ViewConfig<Gmc> = ViewConfig(),
     modifier: Modifier = Modifier.fillMaxSize(),
 ) {
     val featuresState = key(featureMap) {
@@ -92,7 +78,7 @@ public fun MapView(
     mapTileProvider: MapTileProvider,
     initialViewPoint: MapViewPoint? = null,
     initialRectangle: GmcRectangle? = null,
-    config: MapViewConfig = MapViewConfig(),
+    config: ViewConfig<Gmc> = ViewConfig(),
     modifier: Modifier = Modifier.fillMaxSize(),
     buildFeatures: FeaturesState<Gmc>.() -> Unit = {},
 ) {

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

@@ -1,20 +1,20 @@
 package center.sciprog.maps.compose
 
 import androidx.compose.foundation.Canvas
-import androidx.compose.foundation.gestures.drag
-import androidx.compose.foundation.gestures.forEachGesture
 import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.runtime.*
-import androidx.compose.ui.ExperimentalComposeUiApi
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.geometry.Offset
-import androidx.compose.ui.geometry.Rect
 import androidx.compose.ui.geometry.Size
 import androidx.compose.ui.graphics.*
 import androidx.compose.ui.graphics.drawscope.*
-import androidx.compose.ui.input.pointer.*
-import androidx.compose.ui.unit.*
-import center.sciprog.maps.coordinates.*
+import androidx.compose.ui.unit.IntOffset
+import androidx.compose.ui.unit.IntSize
+import androidx.compose.ui.unit.dp
+import center.sciprog.maps.coordinates.GeodeticMapCoordinates
+import center.sciprog.maps.coordinates.Gmc
+import center.sciprog.maps.coordinates.radians
+import center.sciprog.maps.coordinates.toFloat
 import center.sciprog.maps.features.*
 import kotlinx.coroutines.launch
 import kotlinx.coroutines.supervisorScope
@@ -31,17 +31,6 @@ private fun Color.toPaint(): Paint = Paint().apply {
 
 private fun IntRange.intersect(other: IntRange) = max(first, other.first)..min(last, other.last)
 
-internal fun MapViewPoint.move(deltaX: Double, deltaY: Double): MapViewPoint {
-    val newCoordinates = GeodeticMapCoordinates(
-        (focus.latitude + (deltaY / scaleFactor).radians).coerceIn(
-            -MercatorProjection.MAXIMUM_LATITUDE,
-            MercatorProjection.MAXIMUM_LATITUDE
-        ),
-        focus.longitude + (deltaX / scaleFactor).radians
-    )
-    return MapViewPoint(newCoordinates, zoom)
-}
-
 private val logger = KotlinLogging.logger("MapView")
 
 /**
@@ -52,320 +41,208 @@ public actual fun MapView(
     mapTileProvider: MapTileProvider,
     initialViewPoint: MapViewPoint,
     featuresState: FeaturesState<Gmc>,
-    config: MapViewConfig,
+    config: ViewConfig<Gmc>,
     modifier: Modifier,
 ): Unit = key(initialViewPoint) {
-    var canvasSize by remember { mutableStateOf(defaultCanvasSize) }
 
-    var viewPoint by remember { mutableStateOf(initialViewPoint) }
-
-    require(viewPoint.zoom in 1.0..18.0) { "Zoom value of ${viewPoint.zoom} is not valid" }
-
-    fun setViewPoint(newViewPoint: MapViewPoint) {
-        config.onViewChange(newViewPoint)
-        viewPoint = newViewPoint
-    }
-
-    val zoom: Int by derivedStateOf {
-        require(viewPoint.zoom in 1.0..18.0) { "Zoom value of ${viewPoint.zoom} is not valid" }
-        floor(viewPoint.zoom).toInt()
-    }
-
-    val tileScale: Double by derivedStateOf { 2.0.pow(viewPoint.zoom - zoom) }
-
-    val mapTiles = remember(mapTileProvider) { mutableStateListOf<MapTile>() }
-
-    val centerCoordinates by derivedStateOf { WebMercatorProjection.toMercator(viewPoint.focus, zoom) }
-
-    fun DpOffset.toMercator(): WebMercatorCoordinates = WebMercatorCoordinates(
-        zoom,
-        (x - canvasSize.width / 2).value / tileScale + centerCoordinates.x,
-        (y - canvasSize.height / 2).value / tileScale + centerCoordinates.y,
+    val state = rememberMapState(
+        config,
+        defaultCanvasSize,
+        initialViewPoint,
+        mapTileProvider.tileSize
     )
+    val canvasModifier = modifier.mapControls(state).fillMaxSize()
 
-    /*
-     * Convert screen independent offset to GMC, adjusting for fractional zoom
-     */
-    fun DpOffset.toGeodetic() = WebMercatorProjection.toGeodetic(toMercator())
+    with(state) {
 
-    // Selection rectangle. If null - no selection
-    var selectRect by remember { mutableStateOf<Rect?>(null) }
+        val mapTiles = remember(mapTileProvider) { mutableStateListOf<MapTile>() }
 
-    @OptIn(ExperimentalComposeUiApi::class)
-    val canvasModifier = modifier.pointerInput(Unit) {
-        forEachGesture {
-            awaitPointerEventScope {
-                fun Offset.toDpOffset() = DpOffset(x.toDp(), y.toDp())
+        // Load tiles asynchronously
+        LaunchedEffect(viewPoint, canvasSize) {
+            with(mapTileProvider) {
+                val indexRange = 0 until 2.0.pow(zoom).toInt()
 
-                val event: PointerEvent = awaitPointerEvent()
+                val left = centerCoordinates.x - canvasSize.width.value / 2 / tileScale
+                val right = centerCoordinates.x + canvasSize.width.value / 2 / tileScale
+                val horizontalIndices: IntRange = (toIndex(left)..toIndex(right)).intersect(indexRange)
 
-                event.changes.forEach { change ->
-                    val dragStart = change.position
-                    val dpPos = DpOffset(dragStart.x.toDp(), dragStart.y.toDp())
+                val top = (centerCoordinates.y + canvasSize.height.value / 2 / tileScale)
+                val bottom = (centerCoordinates.y - canvasSize.height.value / 2 / tileScale)
+                val verticalIndices: IntRange = (toIndex(bottom)..toIndex(top)).intersect(indexRange)
 
-                    //start selection
-                    var selectionStart: Offset? =
-                        if (event.buttons.isPrimaryPressed && event.keyboardModifiers.isShiftPressed) {
-                            change.position
-                        } else {
-                            null
-                        }
+                mapTiles.clear()
 
-                    drag(change.id) { dragChange ->
-                        val dragAmount = dragChange.position - dragChange.previousPosition
-                        val dpStart = dragChange.previousPosition.toDpOffset()
-                        val dpEnd = dragChange.position.toDpOffset()
-
-                        //apply drag handle and check if it prohibits the drag even propagation
-                        if (selectionStart == null && !config.dragHandle.handle(
-                                event,
-                                MapViewPoint(dpStart.toGeodetic(), viewPoint.zoom),
-                                MapViewPoint(dpEnd.toGeodetic(), viewPoint.zoom)
-                            )
-                        ) {
-                            return@drag
-                        }
-
-                        if (event.buttons.isPrimaryPressed) {
-                            //If selection process is started, modify the frame
-                            selectionStart?.let { start ->
-                                val offset = dragChange.position
-                                selectRect = Rect(
-                                    min(offset.x, start.x),
-                                    min(offset.y, start.y),
-                                    max(offset.x, start.x),
-                                    max(offset.y, start.y)
-                                )
-                                return@drag
+                for (j in verticalIndices) {
+                    for (i in horizontalIndices) {
+                        val id = TileId(zoom, i, j)
+                        //ensure that failed tiles do not fail the application
+                        supervisorScope {
+                            //start all
+                            val deferred = loadTileAsync(id)
+                            //wait asynchronously for it to finish
+                            launch {
+                                try {
+                                    mapTiles += deferred.await()
+                                } catch (ex: Exception) {
+                                    //displaying the error is maps responsibility
+                                    logger.error(ex) { "Failed to load tile with id=$id" }
+                                }
                             }
-
-//                            config.onClick(MapViewPoint(dpPos.toGeodetic(), viewPoint.zoom), event)
-                            //If no selection, drag map
-                            setViewPoint(
-                                viewPoint.move(
-                                    -dragAmount.x.toDp().value / tileScale,
-                                    +dragAmount.y.toDp().value / tileScale
-                                )
-                            )
                         }
+
                     }
 
-                    // evaluate selection
-                    selectRect?.let { rect ->
-                        //Use selection override if it is defined
-                        val gmcBox = GmcRectangle(
-                            rect.topLeft.toDpOffset().toGeodetic(),
-                            rect.bottomRight.toDpOffset().toGeodetic()
+                }
+            }
+        }
+
+        val painterCache = key(featuresState) {
+            featuresState.features.values.filterIsInstance<VectorImageFeature<Gmc>>().associateWith { it.painter() }
+        }
+
+        Canvas(canvasModifier) {
+            fun GeodeticMapCoordinates.toOffset(): Offset = toOffset(this@Canvas)
+
+            fun DrawScope.drawFeature(zoom: Int, feature: MapFeature) {
+                when (feature) {
+                    is FeatureSelector -> drawFeature(zoom, feature.selector(zoom))
+                    is CircleFeature -> drawCircle(
+                        feature.color,
+                        feature.size.toPx(),
+                        center = feature.center.toOffset()
+                    )
+
+                    is RectangleFeature -> drawRect(
+                        feature.color,
+                        topLeft = feature.center.toOffset() - Offset(
+                            feature.size.width.toPx() / 2,
+                            feature.size.height.toPx() / 2
+                        ),
+                        size = feature.size.toSize()
+                    )
+
+                    is LineFeature -> drawLine(feature.color, feature.a.toOffset(), feature.b.toOffset())
+                    is ArcFeature -> {
+                        val topLeft = feature.oval.topLeft.toOffset()
+                        val bottomRight = feature.oval.bottomRight.toOffset()
+
+                        val size = Size(abs(topLeft.x - bottomRight.x), abs(topLeft.y - bottomRight.y))
+
+                        drawArc(
+                            color = feature.color,
+                            startAngle = feature.startAngle.radians.degrees.toFloat(),
+                            sweepAngle = feature.arcLength.radians.degrees.toFloat(),
+                            useCenter = false,
+                            topLeft = topLeft,
+                            size = size,
+                            style = Stroke()
                         )
-                        config.onSelect(gmcBox)
-                        if (config.zoomOnSelect) {
-                            setViewPoint(gmcBox.computeViewPoint(mapTileProvider, canvasSize))
-                        }
-                        selectRect = null
+
                     }
-                }
-            }
-        }
-    }.onPointerEvent(PointerEventType.Scroll) {
-        val change = it.changes.first()
-        val (xPos, yPos) = change.position
-        //compute invariant point of translation
-        val invariant = DpOffset(xPos.toDp(), yPos.toDp()).toGeodetic()
-        setViewPoint(viewPoint.zoom(-change.scrollDelta.y.toDouble() * config.zoomSpeed, invariant))
-    }.fillMaxSize()
 
+                    is BitmapImageFeature -> drawImage(feature.image, feature.position.toOffset())
 
-    // Load tiles asynchronously
-    LaunchedEffect(viewPoint, canvasSize) {
-        with(mapTileProvider) {
-            val indexRange = 0 until 2.0.pow(zoom).toInt()
-
-            val left = centerCoordinates.x - canvasSize.width.value / 2 / tileScale
-            val right = centerCoordinates.x + canvasSize.width.value / 2 / tileScale
-            val horizontalIndices: IntRange = (toIndex(left)..toIndex(right)).intersect(indexRange)
-
-            val top = (centerCoordinates.y + canvasSize.height.value / 2 / tileScale)
-            val bottom = (centerCoordinates.y - canvasSize.height.value / 2 / tileScale)
-            val verticalIndices: IntRange = (toIndex(bottom)..toIndex(top)).intersect(indexRange)
-
-            mapTiles.clear()
-
-            for (j in verticalIndices) {
-                for (i in horizontalIndices) {
-                    val id = TileId(zoom, i, j)
-                    //ensure that failed tiles do not fail the application
-                    supervisorScope {
-                        //start all
-                        val deferred = loadTileAsync(id)
-                        //wait asynchronously for it to finish
-                        launch {
-                            try {
-                                mapTiles += deferred.await()
-                            } catch (ex: Exception) {
-                                //displaying the error is maps responsibility
-                                logger.error(ex) { "Failed to load tile with id=$id" }
+                    is VectorImageFeature -> {
+                        val offset = feature.position.toOffset()
+                        val size = feature.size.toSize()
+                        translate(offset.x - size.width / 2, offset.y - size.height / 2) {
+                            with(painterCache[feature]!!) {
+                                draw(size)
                             }
                         }
                     }
 
-                }
+                    is TextFeature -> drawIntoCanvas { canvas ->
+                        val offset = feature.position.toOffset()
+                        canvas.nativeCanvas.drawString(
+                            feature.text,
+                            offset.x + 5,
+                            offset.y - 5,
+                            Font().apply(feature.fontConfig),
+                            feature.color.toPaint()
+                        )
+                    }
 
-            }
-        }
-    }
-
-    val painterCache = key(featuresState) {
-        featuresState.features.values.filterIsInstance<VectorImageFeature<Gmc>>().associateWith { it.painter() }
-    }
-
-    Canvas(canvasModifier) {
-        fun WebMercatorCoordinates.toOffset(): Offset = Offset(
-            (canvasSize.width / 2 + (x.dp - centerCoordinates.x.dp) * tileScale.toFloat()).toPx(),
-            (canvasSize.height / 2 + (y.dp - centerCoordinates.y.dp) * tileScale.toFloat()).toPx()
-        )
-
-        //Convert GMC to offset in pixels (not DP), adjusting for zoom
-        fun GeodeticMapCoordinates.toOffset(): Offset = WebMercatorProjection.toMercator(this, zoom).toOffset()
-
-
-        fun DrawScope.drawFeature(zoom: Int, feature: MapFeature) {
-            when (feature) {
-                is FeatureSelector -> drawFeature(zoom, feature.selector(zoom))
-                is CircleFeature -> drawCircle(
-                    feature.color,
-                    feature.size.toPx(),
-                    center = feature.center.toOffset()
-                )
-
-                is RectangleFeature -> drawRect(
-                    feature.color,
-                    topLeft = feature.center.toOffset() - Offset(
-                        feature.size.width.toPx() / 2,
-                        feature.size.height.toPx() / 2
-                    ),
-                    size = feature.size.toSize()
-                )
-
-                is LineFeature -> drawLine(feature.color, feature.a.toOffset(), feature.b.toOffset())
-                is ArcFeature -> {
-                    val topLeft = feature.oval.topLeft.toOffset()
-                    val bottomRight = feature.oval.bottomRight.toOffset()
-
-                    val size = Size(abs(topLeft.x - bottomRight.x), abs(topLeft.y - bottomRight.y))
-
-                    drawArc(
-                        color = feature.color,
-                        startAngle = feature.startAngle.radians.degrees.toFloat(),
-                        sweepAngle = feature.arcLength.radians.degrees.toFloat(),
-                        useCenter = false,
-                        topLeft = topLeft,
-                        size = size,
-                        style = Stroke()
-                    )
-
-                }
-
-                is BitmapImageFeature -> drawImage(feature.image, feature.position.toOffset())
-
-                is VectorImageFeature -> {
-                    val offset = feature.position.toOffset()
-                    val size = feature.size.toSize()
-                    translate(offset.x - size.width / 2, offset.y - size.height / 2) {
-                        with(painterCache[feature]!!) {
-                            draw(size)
+                    is DrawFeature -> {
+                        val offset = feature.position.toOffset()
+                        translate(offset.x, offset.y) {
+                            feature.drawFeature(this)
                         }
                     }
-                }
 
-                is TextFeature -> drawIntoCanvas { canvas ->
-                    val offset = feature.position.toOffset()
-                    canvas.nativeCanvas.drawString(
-                        feature.text,
-                        offset.x + 5,
-                        offset.y - 5,
-                        Font().apply(feature.fontConfig),
-                        feature.color.toPaint()
-                    )
-                }
-
-                is DrawFeature -> {
-                    val offset = feature.position.toOffset()
-                    translate(offset.x, offset.y) {
-                        feature.drawFeature(this)
+                    is FeatureGroup -> {
+                        feature.children.values.forEach {
+                            drawFeature(zoom, it)
+                        }
                     }
-                }
 
-                is FeatureGroup -> {
-                    feature.children.values.forEach {
-                        drawFeature(zoom, it)
-                    }
-                }
-
-                is PathFeature -> {
-                    TODO("MapPathFeature not implemented")
+                    is PathFeature -> {
+                        TODO("MapPathFeature not implemented")
 //                    val offset = feature.rectangle.center.toOffset() - feature.targetRect.center
 //                    translate(offset.x, offset.y) {
 //                        sca
 //                        drawPath(feature.path, brush = feature.brush, style = feature.style)
 //                    }
-                }
+                    }
 
-                is PointsFeature -> {
-                    val points = feature.points.map { it.toOffset() }
-                    drawPoints(
-                        points = points,
-                        color = feature.color,
-                        strokeWidth = feature.stroke,
-                        pointMode = feature.pointMode
-                    )
-                }
+                    is PointsFeature -> {
+                        val points = feature.points.map { it.toOffset() }
+                        drawPoints(
+                            points = points,
+                            color = feature.color,
+                            strokeWidth = feature.stroke,
+                            pointMode = feature.pointMode
+                        )
+                    }
 
 //                else -> {
 //                    logger.error { "Unrecognized feature type: ${feature::class}" }
 //                }
-            }
-        }
-
-        if (canvasSize != size.toDpSize()) {
-            logger.debug { "Recalculate canvas. Size: $size" }
-            config.onCanvasSizeChange(canvasSize)
-            canvasSize = size.toDpSize()
-        }
-
-        clipRect {
-            val tileSize = IntSize(
-                ceil((mapTileProvider.tileSize.dp * tileScale.toFloat()).toPx()).toInt(),
-                ceil((mapTileProvider.tileSize.dp * tileScale.toFloat()).toPx()).toInt()
-            )
-            mapTiles.forEach { (id, image) ->
-                //converting back from tile index to screen offset
-                val offset = IntOffset(
-                    (canvasSize.width / 2 + (mapTileProvider.toCoordinate(id.i).dp - centerCoordinates.x.dp) * tileScale.toFloat()).roundToPx(),
-                    (canvasSize.height / 2 + (mapTileProvider.toCoordinate(id.j).dp - centerCoordinates.y.dp) * tileScale.toFloat()).roundToPx()
-                )
-                drawImage(
-                    image = image.toComposeImageBitmap(),
-                    dstOffset = offset,
-                    dstSize = tileSize
-                )
+                }
             }
 
-            featuresState.features.values.filter { viewPoint.zoom in it.zoomRange }.forEach { feature ->
-                drawFeature(zoom, feature)
+            if (canvasSize != size.toDpSize()) {
+                logger.debug { "Recalculate canvas. Size: $size" }
+                config.onCanvasSizeChange(canvasSize)
+                canvasSize = size.toDpSize()
             }
-        }
 
-        selectRect?.let { rect ->
-            drawRect(
-                color = Color.Blue,
-                topLeft = rect.topLeft,
-                size = rect.size,
-                alpha = 0.5f,
-                style = Stroke(
-                    width = 2f,
-                    pathEffect = PathEffect.dashPathEffect(floatArrayOf(10f, 10f), 0f)
+            clipRect {
+                val tileSize = IntSize(
+                    ceil((mapTileProvider.tileSize.dp * tileScale.toFloat()).toPx()).toInt(),
+                    ceil((mapTileProvider.tileSize.dp * tileScale.toFloat()).toPx()).toInt()
                 )
-            )
+                mapTiles.forEach { (id, image) ->
+                    //converting back from tile index to screen offset
+                    val offset = IntOffset(
+                        (canvasSize.width / 2 + (mapTileProvider.toCoordinate(id.i).dp - centerCoordinates.x.dp) * tileScale.toFloat()).roundToPx(),
+                        (canvasSize.height / 2 + (mapTileProvider.toCoordinate(id.j).dp - centerCoordinates.y.dp) * tileScale.toFloat()).roundToPx()
+                    )
+                    drawImage(
+                        image = image.toComposeImageBitmap(),
+                        dstOffset = offset,
+                        dstSize = tileSize
+                    )
+                }
+
+                featuresState.features.values.filter { viewPoint.zoom in it.zoomRange }.forEach { feature ->
+                    drawFeature(zoom, feature)
+                }
+            }
+
+            selectRect?.let { dpRect ->
+                val rect = dpRect.toRect()
+                drawRect(
+                    color = Color.Blue,
+                    topLeft = rect.topLeft,
+                    size = rect.size,
+                    alpha = 0.5f,
+                    style = Stroke(
+                        width = 2f,
+                        pathEffect = PathEffect.dashPathEffect(floatArrayOf(10f, 10f), 0f)
+                    )
+                )
+            }
         }
     }
 }

maps-kt-features/build.gradle.kts

@@ -17,6 +17,9 @@ kotlin {
             dependencies {
                 api(compose.foundation)
             }
+        }
+        val jvmMain by getting{
+
         }
         val jvmTest by getting {
             dependencies {

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

@@ -3,7 +3,7 @@ package center.sciprog.maps.features
 import androidx.compose.ui.unit.DpSize
 
 
-public interface Area<T: Any>{
+public interface Area<T : Any> {
     public operator fun contains(point: T): Boolean
 }
 
@@ -11,7 +11,7 @@ public interface Area<T: Any>{
  * A map coordinates rectangle. [a] and [b] represent opposing angles
  * of the rectangle without specifying which ones.
  */
-public interface Rectangle<T : Any>: Area<T> {
+public interface Rectangle<T : Any> : Area<T> {
     public val a: T
     public val b: T
 }
@@ -24,12 +24,24 @@ public interface CoordinateSpace<T : Any> {
     /**
      * Build a rectangle by two opposing corners
      */
-    public fun buildRectangle(first: T, second: T): Rectangle<T>
+    public fun Rectangle(first: T, second: T): Rectangle<T>
 
     /**
      * Build a rectangle of visual size [size]
      */
-    public fun buildRectangle(center: T, zoom: Double, size: DpSize): Rectangle<T>
+    public fun Rectangle(center: T, zoom: Double, size: DpSize): Rectangle<T>
+
+    /**
+     * Create a [ViewPoint] associated with this coordinate space.
+     */
+    public fun ViewPoint(center: T, zoom: Double): ViewPoint<T>
+
+    public fun ViewPoint<T>.moveBy(delta: T): ViewPoint<T>
+
+    public fun ViewPoint<T>.zoomBy(
+        zoomDelta: Double,
+        invariant: T = focus,
+    ): ViewPoint<T>
 
     /**
      * Move given rectangle to be centered at [center]
@@ -39,4 +51,8 @@ public interface CoordinateSpace<T : Any> {
     public fun Collection<Rectangle<T>>.wrapRectangles(): Rectangle<T>?
 
     public fun Collection<T>.wrapPoints(): Rectangle<T>?
-}
+
+}
+
+public fun <T : Any> CoordinateSpace<T>.Rectangle(viewPoint: ViewPoint<T>, size: DpSize): Rectangle<T> =
+    Rectangle(viewPoint.focus, viewPoint.zoom, size)

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

@@ -116,7 +116,7 @@ public data class CircleFeature<T : Any>(
     override var attributes: AttributeMap = AttributeMap(),
 ) : DraggableFeature<T> {
     override fun getBoundingBox(zoom: Double): Rectangle<T> =
-        space.buildRectangle(center, zoom, DpSize(size, size))
+        space.Rectangle(center, zoom, DpSize(size, size))
 
     override fun withCoordinates(newCoordinates: T): Feature<T> =
         CircleFeature(space, newCoordinates, zoomRange, size, color, attributes)
@@ -131,7 +131,7 @@ public class RectangleFeature<T : Any>(
     override var attributes: AttributeMap = AttributeMap(),
 ) : DraggableFeature<T> {
     override fun getBoundingBox(zoom: Double): Rectangle<T> =
-        space.buildRectangle(center, zoom, size)
+        space.Rectangle(center, zoom, size)
 
     override fun withCoordinates(newCoordinates: T): Feature<T> =
         RectangleFeature(space, newCoordinates, zoomRange, size, color, attributes)
@@ -146,7 +146,7 @@ public class LineFeature<T : Any>(
     override var attributes: AttributeMap = AttributeMap(),
 ) : SelectableFeature<T> {
     override fun getBoundingBox(zoom: Double): Rectangle<T> =
-        space.buildRectangle(a, b)
+        space.Rectangle(a, b)
 
     override fun contains(point: ViewPoint<T>): Boolean {
         return super.contains(point)
@@ -181,7 +181,7 @@ public data class DrawFeature<T : Any>(
     override var attributes: AttributeMap = AttributeMap(),
     public val drawFeature: DrawScope.() -> Unit,
 ) : DraggableFeature<T> {
-    override fun getBoundingBox(zoom: Double): Rectangle<T> = space.buildRectangle(position, position)
+    override fun getBoundingBox(zoom: Double): Rectangle<T> = space.Rectangle(position, position)
 
     override fun withCoordinates(newCoordinates: T): Feature<T> = copy(position = newCoordinates)
 }
@@ -194,7 +194,7 @@ public data class BitmapImageFeature<T : Any>(
     override val zoomRange: ClosedFloatingPointRange<Double> = defaultZoomRange,
     override var attributes: AttributeMap = AttributeMap(),
 ) : DraggableFeature<T> {
-    override fun getBoundingBox(zoom: Double): Rectangle<T> = space.buildRectangle(position, zoom, size)
+    override fun getBoundingBox(zoom: Double): Rectangle<T> = space.Rectangle(position, zoom, size)
 
     override fun withCoordinates(newCoordinates: T): Feature<T> = copy(position = newCoordinates)
 }
@@ -207,7 +207,7 @@ public data class VectorImageFeature<T : Any>(
     override val zoomRange: ClosedFloatingPointRange<Double> = defaultZoomRange,
     override var attributes: AttributeMap = AttributeMap(),
 ) : DraggableFeature<T> {
-    override fun getBoundingBox(zoom: Double): Rectangle<T> = space.buildRectangle(position, zoom, size)
+    override fun getBoundingBox(zoom: Double): Rectangle<T> = space.Rectangle(position, zoom, size)
 
     override fun withCoordinates(newCoordinates: T): Feature<T> = copy(position = newCoordinates)
 
@@ -238,7 +238,7 @@ public class TextFeature<T : Any>(
     override var attributes: AttributeMap = AttributeMap(),
     public val fontConfig: FeatureFont.() -> Unit,
 ) : DraggableFeature<T> {
-    override fun getBoundingBox(zoom: Double): Rectangle<T> = space.buildRectangle(position, position)
+    override fun getBoundingBox(zoom: Double): Rectangle<T> = space.Rectangle(position, position)
 
     override fun withCoordinates(newCoordinates: T): Feature<T> =
         TextFeature(space, newCoordinates, text, zoomRange, color, attributes, fontConfig)

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

@@ -0,0 +1,14 @@
+package center.sciprog.maps.features
+
+import androidx.compose.ui.input.pointer.PointerEvent
+import androidx.compose.ui.unit.DpSize
+
+public data class ViewConfig<T : Any>(
+    val zoomSpeed: Double = 1.0 / 3.0,
+    val onClick: ViewPoint<T>.(PointerEvent) -> Unit = {},
+    val dragHandle: DragHandle<T> = DragHandle.bypass(),
+    val onViewChange: ViewPoint<T>.() -> Unit = {},
+    val onSelect: (Rectangle<T>) -> Unit = {},
+    val zoomOnSelect: Boolean = true,
+    val onCanvasSizeChange: (DpSize) -> Unit = {},
+)

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

@@ -0,0 +1,140 @@
+package center.sciprog.maps.features
+
+import androidx.compose.foundation.gestures.drag
+import androidx.compose.foundation.gestures.forEachGesture
+import androidx.compose.runtime.*
+import androidx.compose.ui.ExperimentalComposeUiApi
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.geometry.Offset
+import androidx.compose.ui.input.pointer.*
+import androidx.compose.ui.unit.*
+import kotlin.math.max
+import kotlin.math.min
+
+
+public abstract class CoordinateViewState<T : Any>(
+    public val config: ViewConfig<T>,
+    canvasSize: DpSize,
+    viewPoint: ViewPoint<T>,
+) {
+
+    public abstract val space: CoordinateSpace<T>
+
+    public var canvasSize: DpSize by mutableStateOf(canvasSize)
+    protected var viewPointState: MutableState<ViewPoint<T>> = mutableStateOf(viewPoint)
+
+    public var viewPoint: ViewPoint<T>
+        get() = viewPointState.value
+        set(value) {
+            config.onViewChange(value)
+            viewPointState.value = value
+        }
+
+    public abstract fun DpOffset.toCoordinates(): T
+
+    public abstract fun T.toDpOffset(): DpOffset
+
+    public fun T.toOffset(density: Density): Offset = with(density){
+        val dpOffset = this@toOffset.toDpOffset()
+        Offset(dpOffset.x.toPx(), dpOffset.y.toPx())
+    }
+
+    public abstract fun ViewPoint<T>.moveBy(x: Dp, y: Dp): ViewPoint<T>
+
+    public abstract fun viewPointFor(rectangle: Rectangle<T>): ViewPoint<T>
+
+    // Selection rectangle. If null - no selection
+    public var selectRect: DpRect? by mutableStateOf<DpRect?>(null)
+}
+
+public val DpRect.topLeft: DpOffset get() = DpOffset(left, top)
+public val DpRect.bottomRight: DpOffset get() = DpOffset(right, bottom)
+
+
+@OptIn(ExperimentalComposeUiApi::class)
+public fun <T : Any> Modifier.mapControls(
+    state: CoordinateViewState<T>,
+): Modifier = with(state) {
+    pointerInput(Unit) {
+        forEachGesture {
+            awaitPointerEventScope {
+                fun Offset.toDpOffset() = DpOffset(x.toDp(), y.toDp())
+
+                val event: PointerEvent = awaitPointerEvent()
+
+                event.changes.forEach { change ->
+                    val dragStart = change.position
+                    val dpPos = DpOffset(dragStart.x.toDp(), dragStart.y.toDp())
+
+                    //start selection
+                    val selectionStart: Offset? =
+                        if (event.buttons.isPrimaryPressed && event.keyboardModifiers.isShiftPressed) {
+                            change.position
+                        } else {
+                            null
+                        }
+
+                    drag(change.id) { dragChange ->
+                        val dragAmount: Offset = dragChange.position - dragChange.previousPosition
+                        val dpStart = dragChange.previousPosition.toDpOffset()
+                        val dpEnd = dragChange.position.toDpOffset()
+
+                        //apply drag handle and check if it prohibits the drag even propagation
+                        if (selectionStart == null && !config.dragHandle.handle(
+                                event,
+                                space.ViewPoint(dpStart.toCoordinates(), viewPoint.zoom),
+                                space.ViewPoint(dpEnd.toCoordinates(), viewPoint.zoom)
+                            )
+                        ) {
+                            return@drag
+                        }
+
+                        if (event.buttons.isPrimaryPressed) {
+                            //If selection process is started, modify the frame
+                            selectionStart?.let { start ->
+                                val offset = dragChange.position
+                                selectRect = DpRect(
+                                    min(offset.x, start.x).dp,
+                                    min(offset.y, start.y).dp,
+                                    max(offset.x, start.x).dp,
+                                    max(offset.y, start.y).dp
+                                )
+                                return@drag
+                            }
+
+//                            config.onClick(MapViewPoint(dpPos.toGeodetic(), viewPoint.zoom), event)
+                            //If no selection, drag map
+                            viewPoint = viewPoint.moveBy(
+                                -dragAmount.x.toDp(),
+                                dragAmount.y.toDp()
+                            )
+
+                        }
+                    }
+
+                    // evaluate selection
+                    selectRect?.let { rect ->
+                        //Use selection override if it is defined
+                        val coordinateRect = space.Rectangle(
+                            rect.topLeft.toCoordinates(),
+                            rect.bottomRight.toCoordinates()
+                        )
+                        config.onSelect(coordinateRect)
+                        if (config.zoomOnSelect) {
+                            viewPoint = viewPointFor(coordinateRect)
+                        }
+                        selectRect = null
+                    }
+                }
+            }
+        }
+    }.onPointerEvent(PointerEventType.Scroll) {
+        val change = it.changes.first()
+        val (xPos, yPos) = change.position
+        //compute invariant point of translation
+        val invariant = DpOffset(xPos.toDp(), yPos.toDp()).toCoordinates()
+        viewPoint = with(space) {
+            viewPoint.zoomBy(-change.scrollDelta.y.toDouble() * config.zoomSpeed, invariant)
+        }
+    }
+}

maps-kt-scheme/build.gradle.kts

@@ -1,4 +1,3 @@
-import org.jetbrains.compose.compose
 import space.kscience.gradle.KScienceVersions.JVM_TARGET
 
 
@@ -30,6 +29,6 @@ kotlin {
     }
 }
 
-java{
+java {
     targetCompatibility = JVM_TARGET
 }