Add abstraction for tile storage

src/jvmMain/kotlin/Main.kt

@@ -1,12 +1,16 @@
 // Copyright 2000-2021 JetBrains s.r.o. and contributors. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
 import androidx.compose.desktop.ui.tooling.preview.Preview
+import androidx.compose.foundation.layout.Column
 import androidx.compose.material.MaterialTheme
+import androidx.compose.material.Text
 import androidx.compose.material.icons.Icons
 import androidx.compose.material.icons.filled.Home
-import androidx.compose.runtime.Composable
+import androidx.compose.runtime.*
 import androidx.compose.ui.window.Window
 import androidx.compose.ui.window.application
 import centre.sciprog.maps.compose.*
+import io.ktor.client.HttpClient
+import io.ktor.client.engine.cio.CIO
 import java.nio.file.Path
 
 @Composable
@@ -26,7 +30,18 @@ fun App() {
             add(MapTextFeature(pointOne.toCoordinates(), "Home"))
             add(MapVectorImageFeature(pointOne.toCoordinates(), Icons.Filled.Home))
         }
-        MapView(viewPoint, features = features, cacheDirectory = Path.of("mapCache"))
+
+        val scope = rememberCoroutineScope()
+        val mapTileProvider = remember { OpenStreetMapTileProvider(scope, HttpClient(CIO), Path.of("mapCache")) }
+
+        var coordinates by remember { mutableStateOf<GeodeticMapCoordinates?>(null) }
+
+        Column {
+            Text(coordinates?.toString() ?: "")
+            MapView(viewPoint, mapTileProvider, features = features) {
+                coordinates = it
+            }
+        }
     }
 }
 

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

@@ -10,22 +10,22 @@ import androidx.compose.ui.graphics.vector.rememberVectorPainter
 import androidx.compose.ui.unit.IntSize
 
 //TODO replace zoom range with zoom-based representation change
-sealed class MapFeature(val zoomRange: ClosedFloatingPointRange<Double>)
+sealed class MapFeature(val zoomRange: IntRange)
 
-private val defaultZoomRange = 1.0..18.0
+private val defaultZoomRange = 1..18
 
 internal fun Pair<Double, Double>.toCoordinates() = GeodeticMapCoordinates.ofDegrees(first, second)
 
 class MapCircleFeature(
     val center: GeodeticMapCoordinates,
-    zoomRange: ClosedFloatingPointRange<Double> = defaultZoomRange,
+    zoomRange: IntRange = defaultZoomRange,
     val size: Float = 5f,
     val color: Color = Color.Red,
 ) : MapFeature(zoomRange)
 
 fun MapCircleFeature(
     centerCoordinates: Pair<Double, Double>,
-    zoomRange: ClosedFloatingPointRange<Double> = defaultZoomRange,
+    zoomRange: IntRange = defaultZoomRange,
     size: Float = 5f,
     color: Color = Color.Red,
 ) = MapCircleFeature(
@@ -38,21 +38,21 @@ fun MapCircleFeature(
 class MapLineFeature(
     val a: GeodeticMapCoordinates,
     val b: GeodeticMapCoordinates,
-    zoomRange: ClosedFloatingPointRange<Double> = defaultZoomRange,
+    zoomRange: IntRange = defaultZoomRange,
     val color: Color = Color.Red,
 ) : MapFeature(zoomRange)
 
 fun MapLineFeature(
     aCoordinates: Pair<Double, Double>,
     bCoordinates: Pair<Double, Double>,
-    zoomRange: ClosedFloatingPointRange<Double> = defaultZoomRange,
+    zoomRange: IntRange = defaultZoomRange,
     color: Color = Color.Red,
 ) = MapLineFeature(aCoordinates.toCoordinates(), bCoordinates.toCoordinates(), zoomRange, color)
 
 class MapTextFeature(
     val position: GeodeticMapCoordinates,
     val text: String,
-    zoomRange: ClosedFloatingPointRange<Double> = defaultZoomRange,
+    zoomRange: IntRange = defaultZoomRange,
     val color: Color = Color.Red,
 ) : MapFeature(zoomRange)
 
@@ -60,7 +60,7 @@ class MapBitmapImageFeature(
     val position: GeodeticMapCoordinates,
     val image: ImageBitmap,
     val size: IntSize = IntSize(15, 15),
-    zoomRange: ClosedFloatingPointRange<Double> = defaultZoomRange,
+    zoomRange: IntRange = defaultZoomRange,
     val color: Color = Color.Red,
 ) : MapFeature(zoomRange)
 
@@ -69,7 +69,7 @@ class MapVectorImageFeature internal constructor(
     val position: GeodeticMapCoordinates,
     val painter: VectorPainter,
     val size: Size,
-    zoomRange: ClosedFloatingPointRange<Double> = defaultZoomRange,
+    zoomRange: IntRange = defaultZoomRange,
     val color: Color = Color.Red,
 ) : MapFeature(zoomRange)
 
@@ -78,6 +78,6 @@ fun MapVectorImageFeature(
     position: GeodeticMapCoordinates,
     image: ImageVector,
     size: Size = Size(20f,20f),
-    zoomRange: ClosedFloatingPointRange<Double> = defaultZoomRange,
+    zoomRange: IntRange = defaultZoomRange,
     color: Color = Color.Red,
 ): MapVectorImageFeature = MapVectorImageFeature(position, rememberVectorPainter(image), size, zoomRange, color)

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

@@ -0,0 +1,27 @@
+package centre.sciprog.maps.compose
+
+import androidx.compose.ui.graphics.ImageBitmap
+import kotlin.math.floor
+
+data class TileId(
+    val zoom: Int,
+    val i: Int,
+    val j: Int,
+)
+
+data class MapTile(
+    val id: TileId,
+    val image: ImageBitmap,
+)
+
+
+
+interface MapTileProvider {
+    suspend fun loadTile(id: TileId): MapTile
+    fun toIndex(d: Double): Int = floor(d / DEFAULT_TILE_SIZE).toInt()
+    fun toCoordinate(i: Int): Double = (i * DEFAULT_TILE_SIZE).toDouble()
+
+    companion object{
+        const val DEFAULT_TILE_SIZE = 256
+    }
+}

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

@@ -2,136 +2,71 @@ package centre.sciprog.maps.compose
 
 import androidx.compose.foundation.Canvas
 import androidx.compose.foundation.gestures.detectDragGestures
-import androidx.compose.foundation.layout.Column
 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.Size
-import androidx.compose.ui.graphics.*
+import androidx.compose.ui.graphics.Color
 import androidx.compose.ui.graphics.drawscope.clipRect
 import androidx.compose.ui.graphics.drawscope.drawIntoCanvas
 import androidx.compose.ui.graphics.drawscope.translate
+import androidx.compose.ui.graphics.nativeCanvas
+import androidx.compose.ui.graphics.toArgb
 import androidx.compose.ui.input.pointer.PointerEventType
 import androidx.compose.ui.input.pointer.PointerInputChange
 import androidx.compose.ui.input.pointer.onPointerEvent
 import androidx.compose.ui.input.pointer.pointerInput
-import io.ktor.client.HttpClient
-import io.ktor.client.engine.cio.CIO
-import io.ktor.client.request.get
-import io.ktor.client.statement.readBytes
-import kotlinx.coroutines.CoroutineScope
-import kotlinx.coroutines.Deferred
-import kotlinx.coroutines.Dispatchers
-import kotlinx.coroutines.async
 import mu.KotlinLogging
 import org.jetbrains.skia.Font
-import org.jetbrains.skia.Image
 import org.jetbrains.skia.Paint
-import java.net.URL
-import java.nio.file.Path
-import kotlin.io.path.*
-import kotlin.math.floor
 import kotlin.math.pow
+import kotlin.math.round
+import kotlin.math.roundToInt
 
 
-private const val TILE_SIZE = 256
-
-
-private data class OsMapTileId(
-    val zoom: Int,
-    val i: Int,
-    val j: Int,
-)
-
-private data class OsMapTile(
-    val id: OsMapTileId,
-    val image: ImageBitmap,
-)
-
-private class OsMapCache(val scope: CoroutineScope, val client: HttpClient, private val cacheDirectory: Path? = null) {
-    private val cache = HashMap<OsMapTileId, Deferred<ImageBitmap>>()
-
-    private fun OsMapTileId.osmUrl() = URL("https://tile.openstreetmap.org/${zoom}/${i}/${j}.png")
-
-    private fun OsMapTileId.cacheFilePath() = cacheDirectory?.resolve("${zoom}/${i}/${j}.png")
-
-    private fun CoroutineScope.downloadImageAsync(id: OsMapTileId) = scope.async(Dispatchers.IO) {
-        id.cacheFilePath()?.let { path ->
-            if (path.exists()) {
-                try {
-                    return@async Image.makeFromEncoded(path.readBytes()).toComposeImageBitmap()
-                } catch (ex: Exception) {
-                    logger.debug { "Failed to load image from $path" }
-                    path.deleteIfExists()
-                }
-            }
-        }
-
-        val url = id.osmUrl()
-        val byteArray = client.get(url).readBytes()
-
-        logger.debug { "Finished downloading map tile with id $id from $url" }
-
-        id.cacheFilePath()?.let { path ->
-            logger.debug { "Caching map tile $id to $path" }
-
-            path.parent.createDirectories()
-            path.writeBytes(byteArray)
-        }
-
-        Image.makeFromEncoded(byteArray).toComposeImageBitmap()
-    }
-
-    public suspend fun loadTile(id: OsMapTileId): OsMapTile {
-        val image = cache.getOrPut(id) {
-            scope.downloadImageAsync(id)
-        }.await()
-
-        return OsMapTile(id, image)
-    }
-}
-
 private fun Color.toPaint(): Paint = Paint().apply {
     isAntiAlias = true
     color = toArgb()
 }
 
-private fun Double.toIndex(): Int = floor(this / TILE_SIZE).toInt()
-private fun Int.toCoordinate(): Double = (this * TILE_SIZE).toDouble()
-
 private val logger = KotlinLogging.logger("MapView")
 
+/**
+ * A component that renders map and provides basic map manipulation capabilities
+ */
 @OptIn(ExperimentalComposeUiApi::class)
 @Composable
 fun MapView(
     initialViewPoint: MapViewPoint,
+    mapTileProvider: MapTileProvider,
     features: Collection<MapFeature> = emptyList(),
     modifier: Modifier = Modifier.fillMaxSize(),
-    client: HttpClient = remember { HttpClient(CIO) },
+    onClick: (GeodeticMapCoordinates) -> Unit = {},
-    cacheDirectory: Path? = null,
 ) {
     var viewPoint by remember { mutableStateOf(initialViewPoint) }
 
-    val scope = rememberCoroutineScope()
+    val zoom: Int by derivedStateOf { viewPoint.zoom.roundToInt() }
-    val mapCache = remember { OsMapCache(scope, client, cacheDirectory) }
+
-    val mapTiles = remember { mutableStateListOf<OsMapTile>() }
+    val mapTiles = remember { mutableStateListOf<MapTile>() }
 
     //var mapRectangle by remember { mutableStateOf(initialRectangle) }
     var canvasSize by remember { mutableStateOf(Size(512f, 512f)) }
 
-    val centerCoordinates by derivedStateOf { viewPoint.toMercator() }
+    val centerCoordinates by derivedStateOf { WebMercatorProjection.toMercator(viewPoint.focus, zoom) }
 
+    // Load tiles asynchronously
     LaunchedEffect(viewPoint, canvasSize) {
-        val z = viewPoint.zoom.toInt()
+        //remember zoom state to avoid races
+        val z = zoom
         val left = centerCoordinates.x - canvasSize.width / 2
         val right = centerCoordinates.x + canvasSize.width / 2
-        val horizontalIndices = left.toIndex()..right.toIndex()
+        val horizontalIndices = mapTileProvider.toIndex(left)..mapTileProvider.toIndex(right)
 
         val top = (centerCoordinates.y + canvasSize.height / 2)
         val bottom = (centerCoordinates.y - canvasSize.height / 2)
-        val verticalIndices = bottom.toIndex()..top.toIndex()
+        val verticalIndices = mapTileProvider.toIndex(bottom)..mapTileProvider.toIndex(top)
 
         mapTiles.clear()
 
@@ -139,9 +74,9 @@ fun MapView(
 
         for (j in verticalIndices) {
             for (i in horizontalIndices) {
-                if (z == viewPoint.zoom.toInt() && i in indexRange && j in indexRange) {
+                if (z == zoom && i in indexRange && j in indexRange) {
-                    val tileId = OsMapTileId(z, i, j)
+                    val tileId = TileId(z, i, j)
-                    val tile = mapCache.loadTile(tileId)
+                    val tile = mapTileProvider.loadTile(tileId)
                     mapTiles.add(tile)
                 }
             }
@@ -150,7 +85,7 @@ fun MapView(
     }
 
     fun Offset.toMercator(): WebMercatorCoordinates = WebMercatorCoordinates(
-        viewPoint.zoom,
+        zoom,
         x + centerCoordinates.x - canvasSize.width / 2,
         y + centerCoordinates.y - canvasSize.height / 2,
     )
@@ -162,15 +97,10 @@ fun MapView(
         (canvasSize.height / 2 - centerCoordinates.y + y).toFloat()
     )
 
-    fun GeodeticMapCoordinates.toOffset(): Offset = WebMercatorProjection.toMercator(this, viewPoint.zoom).toOffset()
+    fun GeodeticMapCoordinates.toOffset(): Offset = WebMercatorProjection.toMercator(this, zoom).toOffset()
 
-    var coordinates by remember { mutableStateOf<GeodeticMapCoordinates?>(null) }
+    val canvasModifier = modifier.onPointerEvent(PointerEventType.Press) {
-
+        onClick(it.changes.first().position.toGeodetic())
-    val canvasModifier = modifier.onPointerEvent(PointerEventType.Move) {
-        val position = it.changes.first().position
-        coordinates = position.toGeodetic()
-    }.onPointerEvent(PointerEventType.Press) {
-        println(coordinates)
     }.onPointerEvent(PointerEventType.Scroll) {
         viewPoint = viewPoint.zoom(-it.changes.first().scrollDelta.y.toDouble())
     }.pointerInput(Unit) {
@@ -180,8 +110,6 @@ fun MapView(
     }.fillMaxSize()
 
 
-    Column {
-        //Text(coordinates.toString())
     Canvas(canvasModifier) {
         if (canvasSize != size) {
             canvasSize = size
@@ -190,17 +118,16 @@ fun MapView(
         clipRect {
             mapTiles.forEach { (id, image) ->
                 //converting back from tile index to screen offset
-                    logger.debug { "Drawing tile $id" }
                 val offset = Offset(
-                        (canvasSize.width / 2 - centerCoordinates.x + id.i.toCoordinate()).toFloat(),
+                    (canvasSize.width / 2 - centerCoordinates.x + mapTileProvider.toCoordinate(id.i)).toFloat(),
-                        (canvasSize.height / 2 - centerCoordinates.y + id.j.toCoordinate()).toFloat()
+                    (canvasSize.height / 2 - centerCoordinates.y + mapTileProvider.toCoordinate(id.j)).toFloat()
                 )
                 drawImage(
                     image = image,
                     topLeft = offset
                 )
             }
-                features.filter { viewPoint.zoom in it.zoomRange }.forEach { feature ->
+            features.filter { zoom in it.zoomRange }.forEach { feature ->
                 when (feature) {
                     is MapCircleFeature -> drawCircle(
                         feature.color,
@@ -233,4 +160,3 @@ fun MapView(
         }
     }
 }
-}

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

@@ -1,13 +1,15 @@
 package centre.sciprog.maps.compose
 
+import kotlin.math.roundToInt
+
 /**
- * Observable position on the map
+ * Observable position on the map. Includes observation coordinate and [zoom] factor
  */
 data class MapViewPoint(
     val focus: GeodeticMapCoordinates,
     val zoom: Double,
 ) {
-    val scaleFactor by lazy { WebMercatorProjection.scaleFactor(zoom) }
+    val scaleFactor by lazy { WebMercatorProjection.scaleFactor(zoom.roundToInt()) }
 }
 
 fun MapViewPoint.move(deltaX: Float, deltaY: Float): MapViewPoint {
@@ -32,8 +34,4 @@ fun MapViewPoint.move(delta: GeodeticMapCoordinates): MapViewPoint {
     return MapViewPoint(newCoordinates, zoom)
 }
 
-fun MapViewPoint.zoom(zoomDelta: Double): MapViewPoint {
+fun MapViewPoint.zoom(zoomDelta: Double): MapViewPoint = copy(zoom = (zoom + zoomDelta).coerceIn(2.0, 18.0))
-    return copy(zoom = (zoom + zoomDelta).coerceIn(2.0, 18.0))
-}
-
-fun MapViewPoint.toMercator() = WebMercatorProjection.toMercator(focus, zoom)

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

@@ -20,16 +20,16 @@ public open class MercatorProjection(
     private val correctedRadius: ((GeodeticMapCoordinates) -> Double)? = null,
 ) {
 
-    public fun MercatorCoordinates.toGeodetic(): GeodeticMapCoordinates {
+    public fun toGeodetic(mc: MercatorCoordinates): GeodeticMapCoordinates {
         val res = GeodeticMapCoordinates.ofRadians(
-            atan(sinh(y / radius)),
+            atan(sinh(mc.y / radius)),
-            baseLongitude + x / radius,
+            baseLongitude + mc.x / radius,
         )
         return if (correctedRadius != null) {
             val r = correctedRadius.invoke(res)
             GeodeticMapCoordinates.ofRadians(
-                atan(sinh(y / r)),
+                atan(sinh(mc.y / r)),
-                baseLongitude + x / r,
+                baseLongitude + mc.x / r,
             )
         } else {
             res
@@ -39,12 +39,12 @@ public open class MercatorProjection(
     /**
      * https://en.wikipedia.org/wiki/Web_Mercator_projection#Formulas
      */
-    public fun GeodeticMapCoordinates.toMercator(): MercatorCoordinates {
+    public fun toMercator(gmc: GeodeticMapCoordinates): MercatorCoordinates {
-        require(abs(latitude) <= MAXIMUM_LATITUDE) { "Latitude exceeds the maximum latitude for mercator coordinates" }
+        require(abs(gmc.latitude) <= MAXIMUM_LATITUDE) { "Latitude exceeds the maximum latitude for mercator coordinates" }
-        val r = correctedRadius?.invoke(this) ?: radius
+        val r = correctedRadius?.invoke(gmc) ?: radius
         return MercatorCoordinates(
-            x = r * (longitude - baseLongitude),
+            x = r * (gmc.longitude - baseLongitude),
-            y = r * ln(tan(PI / 4 + latitude / 2))
+            y = r * ln(tan(PI / 4 + gmc.latitude / 2))
         )
     }
 

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

@@ -0,0 +1,66 @@
+package centre.sciprog.maps.compose
+
+import androidx.compose.ui.graphics.ImageBitmap
+import androidx.compose.ui.graphics.toComposeImageBitmap
+import io.ktor.client.HttpClient
+import io.ktor.client.request.get
+import io.ktor.client.statement.readBytes
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Deferred
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.async
+import mu.KotlinLogging
+import org.jetbrains.skia.Image
+import java.net.URL
+import java.nio.file.Path
+import kotlin.io.path.*
+
+/**
+ * A [MapTileProvider] based on Open Street Map API. With in-memory and file cache
+ */
+public class OpenStreetMapTileProvider(private val scope: CoroutineScope, private val client: HttpClient, private val cacheDirectory: Path): MapTileProvider {
+    private val cache = HashMap<TileId, Deferred<ImageBitmap>>()
+
+    private fun TileId.osmUrl() = URL("https://tile.openstreetmap.org/${zoom}/${i}/${j}.png")
+
+    private fun TileId.cacheFilePath() = cacheDirectory.resolve("${zoom}/${i}/${j}.png")
+
+    private fun downloadImageAsync(id: TileId) = scope.async(Dispatchers.IO) {
+        id.cacheFilePath()?.let { path ->
+            if (path.exists()) {
+                try {
+                    return@async Image.makeFromEncoded(path.readBytes()).toComposeImageBitmap()
+                } catch (ex: Exception) {
+                    logger.debug { "Failed to load image from $path" }
+                    path.deleteIfExists()
+                }
+            }
+        }
+
+        val url = id.osmUrl()
+        val byteArray = client.get(url).readBytes()
+
+        logger.debug { "Finished downloading map tile with id $id from $url" }
+
+        id.cacheFilePath()?.let { path ->
+            logger.debug { "Caching map tile $id to $path" }
+
+            path.parent.createDirectories()
+            path.writeBytes(byteArray)
+        }
+
+        Image.makeFromEncoded(byteArray).toComposeImageBitmap()
+    }
+
+    override suspend fun loadTile(id: TileId): MapTile {
+        val image = cache.getOrPut(id) {
+            downloadImageAsync(id)
+        }.await()
+
+        return MapTile(id, image)
+    }
+
+    companion object{
+        private val logger = KotlinLogging.logger("OpenStreetMapCache")
+    }
+}

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

@@ -7,14 +7,14 @@ package centre.sciprog.maps.compose
 
 import kotlin.math.*
 
-public data class WebMercatorCoordinates(val zoom: Double, val x: Double, val y: Double)
+public data class WebMercatorCoordinates(val zoom: Int, val x: Double, val y: Double)
 
 public object WebMercatorProjection  {
 
     /**
      * Compute radians to projection coordinates ratio for given [zoom] factor
      */
-    public fun scaleFactor(zoom: Double) = 256.0 / 2 / PI * 2.0.pow(zoom)
+    public fun scaleFactor(zoom: Int) = 256.0 / 2 / PI * 2.0.pow(zoom)
 
     public fun toGeodetic(mercator: WebMercatorCoordinates): GeodeticMapCoordinates {
         val scaleFactor = scaleFactor(mercator.zoom)
@@ -26,7 +26,7 @@ public object WebMercatorProjection  {
     /**
      * https://en.wikipedia.org/wiki/Web_Mercator_projection#Formulas
      */
-    public fun toMercator(gmc: GeodeticMapCoordinates, zoom: Double): WebMercatorCoordinates {
+    public fun toMercator(gmc: GeodeticMapCoordinates, zoom: Int): WebMercatorCoordinates {
         require(abs(gmc.latitude) <= MercatorProjection.MAXIMUM_LATITUDE) { "Latitude exceeds the maximum latitude for mercator coordinates" }
 
         val scaleFactor = scaleFactor(zoom)