Added proper file cache and map drag

.gitignore

@@ -1,5 +1,6 @@
 build/
 .gradle/
 .idea/
+mapCache/
 
 *.iml

src/jvmMain/kotlin/Main.kt

@@ -11,16 +11,17 @@ import androidx.compose.ui.window.application
 import centre.sciprog.maps.compose.GeodeticMapCoordinates
 import centre.sciprog.maps.compose.MapRectangle
 import centre.sciprog.maps.compose.MapView
+import java.nio.file.Path
 
 @Composable
 @Preview
 fun App() {
     MaterialTheme {
-        val map = MapRectangle(
+        val map = MapRectangle.of(
             GeodeticMapCoordinates.ofDegrees(66.513260, 0.0),
             GeodeticMapCoordinates.ofDegrees(40.979897, 44.999999),
         )
-        MapView(map, modifier = Modifier.fillMaxSize())
+        MapView(map,  modifier = Modifier.fillMaxSize(), initialZoom = 4.0, cacheDirectory = Path.of("mapCache"))
     }
 }
 

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

@@ -1,18 +1,21 @@
 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.material.Text
 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.ImageBitmap
+import androidx.compose.ui.graphics.drawscope.clipRect
 import androidx.compose.ui.graphics.toComposeImageBitmap
 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
@@ -24,6 +27,8 @@ 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.*
 import kotlin.math.*
 
 
@@ -36,26 +41,48 @@ private data class OsMapTileId(
     val j: Int,
 )
 
-private fun OsMapTileId.osmUrl() = URL("https://tile.openstreetmap.org/${zoom.toInt()}/${i}/${j}.png")
-
 private data class OsMapTile(
     val id: OsMapTileId,
     val image: ImageBitmap,
 )
 
-private class OsMapCache(val scope: CoroutineScope, val client: HttpClient) {
+private class OsMapCache(val scope: CoroutineScope, val client: HttpClient, private val cacheDirectory: Path? = null) {
     private val cache = HashMap<OsMapTileId, Deferred<ImageBitmap>>()
 
-    public suspend fun loadTile(id: OsMapTileId): OsMapTile {
+    private fun OsMapTileId.osmUrl() = URL("https://tile.openstreetmap.org/${zoom}/${i}/${j}.png")
-        val image = cache.getOrPut(id) {
+
-            scope.async(Dispatchers.IO) {
+    private fun OsMapTileId.cacheFilePath() = cacheDirectory?.resolve("${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)
@@ -71,15 +98,14 @@ fun MapView(
     initialRectangle: MapRectangle,
     modifier: Modifier,
     client: HttpClient = remember { HttpClient(CIO) },
+    cacheDirectory: Path? = null,
     initialZoom: Double? = null,
 ) {
-    val mapRectangle by remember { mutableStateOf(initialRectangle) }
-
     val scope = rememberCoroutineScope()
-    val mapCache = remember { OsMapCache(scope, client) }
+    val mapCache = remember { OsMapCache(scope, client, cacheDirectory) }
-
+    val mapTiles = remember {  mutableStateListOf<OsMapTile>()}
-    val mapTiles = mutableStateListOf<OsMapTile>()
 
+    var mapRectangle by remember { mutableStateOf(initialRectangle) }
     var canvasSize by remember { mutableStateOf(Size(512f, 512f)) }
 
     //TODO provide override for tiling
@@ -107,11 +133,11 @@ fun MapView(
         )
     }
 
-    //val scaleFactor = WebMercatorProjection.scaleFactor(computedZoom)
+    val scaleFactor by derivedStateOf { WebMercatorProjection.scaleFactor(zoom) }
 
     val topLeft by derivedStateOf { with(WebMercatorProjection) { mapRectangle.topLeft.toMercator(zoom) } }
 
-    LaunchedEffect(canvasSize, zoom) {
+    LaunchedEffect(mapRectangle, canvasSize, zoom) {
 
         val startIndexHorizontal = (topLeft.x / TILE_SIZE).toInt()
         val startIndexVertical = (topLeft.y / TILE_SIZE).toInt()
@@ -142,17 +168,12 @@ fun MapView(
         }
     }.onPointerEvent(PointerEventType.Press) {
         println(coordinates)
+    }.pointerInput(Unit) {
+        detectDragGestures { change: PointerInputChange, dragAmount: Offset ->
+            mapRectangle = mapRectangle.move(dragAmount.y / scaleFactor, -dragAmount.x / scaleFactor)
+        }
     }.fillMaxSize()
-//        .pointerInput(Unit) {
+
-//        forEachGesture {
-//            awaitPointerEventScope {
-//                val down = awaitFirstDown()
-//                drag(down.id) {
-//                    println(currentEvent.mouseEvent?.button)
-//                }
-//            }
-//        }
-//    }
 
     Column {
         //Text(coordinates.toString())
@@ -161,7 +182,7 @@ fun MapView(
                 canvasSize = size
                 logger.debug { "Redraw canvas. Size: $size" }
             }
-
+            clipRect {
                 mapTiles.forEach { (id, image) ->
                     //converting back from tile index to screen offset
                     logger.debug { "Drawing tile $id" }
@@ -177,3 +198,4 @@ fun MapView(
             }
         }
     }
+}

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

@@ -27,13 +27,13 @@ public class GeodeticMapCoordinates private constructor(public val latitude: Dou
     }
 
     override fun toString(): String {
-        return "GeodeticCoordinates(latitude=${latitude / PI * 180}, longitude=${longitude / PI * 180})"
+        return "GeodeticCoordinates(latitude=${latitude / PI * 180} deg, longitude=${longitude / PI * 180} deg)"
     }
 
 
     public companion object {
         public fun ofRadians(latitude: Double, longitude: Double): GeodeticMapCoordinates {
-            require(longitude in (-PI)..(PI)) { "Longitude $longitude is not in (-PI)..(PI)" }
+            require(latitude in (-PI/2)..(PI/2)) { "Latitude $latitude is not in (-PI/2)..(PI/2)" }
             return GeodeticMapCoordinates(latitude, longitude.rem(PI / 2))
         }
 

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

@@ -1,8 +1,9 @@
 package centre.sciprog.maps.compose
 
-import kotlin.math.abs
+import kotlin.math.max
+import kotlin.math.min
 
-class MapRectangle(
+class MapRectangle private constructor(
     var topLeft: GeodeticMapCoordinates,
     var bottomRight: GeodeticMapCoordinates,
 ) {
@@ -10,8 +11,39 @@ class MapRectangle(
         require(topLeft.latitude >= bottomRight.latitude)
         require(topLeft.longitude <= bottomRight.longitude)
     }
-    val topRight: GeodeticMapCoordinates = GeodeticMapCoordinates.ofRadians(topLeft.latitude, bottomRight.longitude)
+
-    val bottomLeft: GeodeticMapCoordinates = GeodeticMapCoordinates.ofRadians(bottomRight.latitude, topLeft.longitude)
+    val topRight: GeodeticMapCoordinates get() = GeodeticMapCoordinates.ofRadians(topLeft.latitude, bottomRight.longitude)
+    val bottomLeft: GeodeticMapCoordinates get() = GeodeticMapCoordinates.ofRadians(bottomRight.latitude, topLeft.longitude)
+
+    val topLatitude get() = topLeft.latitude
+    val bottomLatitude get() = bottomRight.latitude
+
+    val leftLongitude get() = topLeft.longitude
+    val rightLongitude get() = bottomRight.longitude
+
+    companion object{
+        fun of(
+            a: GeodeticMapCoordinates,
+            b: GeodeticMapCoordinates
+        ) = MapRectangle(
+            GeodeticMapCoordinates.ofRadians(max(a.latitude, b.latitude), min(a.longitude,b.longitude)),
+            GeodeticMapCoordinates.ofRadians(min(a.latitude, b.latitude), max(a.longitude,b.longitude)),
+        )
+    }
+}
+
+internal fun MapRectangle.move(latitudeDelta: Double, longitudeDelta: Double): MapRectangle {
+    val safeLatitudeDelta: Double = if(topLatitude + latitudeDelta > MercatorProjection.MAXIMUM_LATITUDE){
+        0.0
+    } else if(bottomLatitude + latitudeDelta < -MercatorProjection.MAXIMUM_LATITUDE){
+        0.0
+    } else {
+        latitudeDelta
+    }
+    return MapRectangle.of(
+        GeodeticMapCoordinates.ofRadians(topLeft.latitude + safeLatitudeDelta, topLeft.longitude + longitudeDelta),
+        GeodeticMapCoordinates.ofRadians(bottomRight.latitude + safeLatitudeDelta, bottomRight.longitude + longitudeDelta)
+    )
 }
 
 sealed interface MapFeature