Refactor papallel doanwload

settings.gradle.kts

@@ -13,5 +13,5 @@ pluginManagement {
     }
 }
 
-rootProject.name = "maps-kt-compose"
+rootProject.name = "maps-kt"
 

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

@@ -2,6 +2,7 @@ package centre.sciprog.maps.compose
 
 import androidx.compose.ui.graphics.ImageBitmap
 import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Deferred
 import kotlin.math.floor
 
 data class TileId(
@@ -16,7 +17,7 @@ data class MapTile(
 )
 
 interface MapTileProvider {
-    suspend fun loadTileAsync(tileIds: List<TileId>, scope: CoroutineScope, onTileLoad: (mapTile: MapTile) -> Unit)
+    fun CoroutineScope.loadTileAsync(tileId: TileId): Deferred<MapTile>
 
     val tileSize: Int get() = DEFAULT_TILE_SIZE
 

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

@@ -1,4 +1,4 @@
-package centre.sciprog.maps
+package centre.sciprog.maps.compose
 
 import kotlin.jvm.Synchronized
 
@@ -9,32 +9,14 @@ internal class LruCache<K, V>(
     private val cache = linkedMapOf<K, V>()
 
     @Synchronized
-    fun getCache() = cache.toMap()
+    fun put(key: K, value: V){
-
+        if (cache.size >= capacity) {
-    @Synchronized
+            cache.remove(cache.iterator().next().key)
-    fun put(key: K, value: V) = internalPut(key, value)
+        }
-
+        cache[key] = value
-    @Synchronized
-    operator fun get(key: K) = internalGet(key)
-
-    @Synchronized
-    fun remove(key: K) {
-        cache.remove(key)
     }
 
-    @Synchronized
+    operator fun get(key: K): V? {
-    fun getOrPut(key: K, callback: () -> V): V {
-        val internalGet = internalGet(key)
-        return internalGet ?: callback().also { internalPut(key, it) }
-    }
-
-    @Synchronized
-    fun clear(newCapacity: Int? = null) {
-        cache.clear()
-        capacity = newCapacity ?: capacity
-    }
-
-    private fun internalGet(key: K): V? {
         val value = cache[key]
         if (value != null) {
             cache.remove(key)
@@ -43,11 +25,18 @@ internal class LruCache<K, V>(
         return value
     }
 
-    private fun internalPut(key: K, value: V) {
+    @Synchronized
-        if (cache.size >= capacity) {
+    fun remove(key: K) {
-            cache.remove(cache.iterator().next().key)
+        cache.remove(key)
     }
-        cache[key] = value
+
+    @Synchronized
+    fun getOrPut(key: K, factory: () -> V): V = get(key) ?: factory().also { put(key, it) }
+
+    @Synchronized
+    fun reset(newCapacity: Int? = null) {
+        cache.clear()
+        capacity = newCapacity ?: capacity
     }
 
 }

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

@@ -17,6 +17,7 @@ import androidx.compose.ui.graphics.toArgb
 import androidx.compose.ui.input.pointer.*
 import androidx.compose.ui.unit.*
 import centre.sciprog.maps.*
+import kotlinx.coroutines.launch
 import mu.KotlinLogging
 import org.jetbrains.skia.Font
 import org.jetbrains.skia.Paint
@@ -28,6 +29,8 @@ private fun Color.toPaint(): Paint = Paint().apply {
     color = toArgb()
 }
 
+private fun IntRange.intersect(other: IntRange) = max(first, other.first)..min(last, other.last)
+
 private val logger = KotlinLogging.logger("MapView")
 
 /**
@@ -148,39 +151,40 @@ actual fun MapView(
 
     // 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 = mapTileProvider.toIndex(left)
+            val horizontalIndices: IntRange = (toIndex(left)..toIndex(right)).intersect(indexRange)
-            .rangeTo(mapTileProvider.toIndex(right))
-            .intersect(indexRange)
 
             val top = (centerCoordinates.y + canvasSize.height.value / 2 / tileScale)
             val bottom = (centerCoordinates.y - canvasSize.height.value / 2 / tileScale)
-        val verticalIndices = mapTileProvider.toIndex(bottom)
+            val verticalIndices: IntRange = (toIndex(bottom)..toIndex(top)).intersect(indexRange)
-            .rangeTo(mapTileProvider.toIndex(top))
-            .intersect(indexRange)
 
             mapTiles.clear()
 
-        val tileIds = verticalIndices
+            for (j in verticalIndices) {
-            .flatMap { j ->
+                for (i in horizontalIndices) {
-                horizontalIndices
+                    val id = TileId(zoom, i, j)
-                    .asSequence()
+                    //start all
-                    .map { TileId(zoom, it, j) }
+                    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" }
+                        }
+                    }
+                }
+            }
+        }
     }
 
-        mapTileProvider.loadTileAsync(
-            tileIds = tileIds,
-            scope = this
-        ) { mapTiles += it }
 
-    }
-
-    // d
     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()

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

@@ -2,12 +2,15 @@ package centre.sciprog.maps.compose
 
 import androidx.compose.ui.graphics.ImageBitmap
 import androidx.compose.ui.graphics.toComposeImageBitmap
-import centre.sciprog.maps.LruCache
+import io.ktor.client.HttpClient
-import io.ktor.client.*
+import io.ktor.client.request.get
-import io.ktor.client.request.*
+import io.ktor.client.statement.readBytes
-import io.ktor.client.statement.*
+import kotlinx.coroutines.CoroutineScope
-import kotlinx.coroutines.*
+import kotlinx.coroutines.Deferred
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.async
 import kotlinx.coroutines.sync.Semaphore
+import kotlinx.coroutines.sync.withPermit
 import mu.KotlinLogging
 import org.jetbrains.skia.Image
 import java.net.URL
@@ -45,6 +48,9 @@ class OpenStreetMapTileProvider(
             }
         }
 
+        try {
+            //semaphore works only for actual download
+            semaphore.withPermit {
                 val url = id.osmUrl()
                 val byteArray = client.get(url).readBytes()
 
@@ -59,34 +65,26 @@ class OpenStreetMapTileProvider(
 
                 Image.makeFromEncoded(byteArray).toComposeImageBitmap()
             }
-
-    override suspend fun loadTileAsync(
-        tileIds: List<TileId>,
-        scope: CoroutineScope,
-        onTileLoad: (mapTile: MapTile) -> Unit,
-    ) {
-        tileIds
-            .forEach { id ->
-                try {
-                    scope.launch {
-                        semaphore.acquire()
-                        try {
-                            val image = cache.getOrPut(id) { downloadImageAsync(id) }
-                            val result = MapTile(id, image.await())
-                            onTileLoad(result)
-                        } catch (e: Exception) {
-                            cache.remove(id)
-                            throw e
-                        } finally {
-                            semaphore.release()
-                        }
-                    }
         } catch (ex: Exception){
-                    logger.error(ex) { "Failed to load tile $id" }
+            //if loading is failed for some reason, clear the cache
+            cache.remove(id)
+            throw ex
         }
     }
+
+    override fun CoroutineScope.loadTileAsync(
+        tileId: TileId,
+    ): Deferred<MapTile> {
+        //start image download
+        val image = cache.getOrPut(tileId) {
+            downloadImageAsync(tileId)
         }
 
+        //collect the result asynchronously
+        return async { MapTile(tileId, image.await()) }
+    }
+
+
     companion object {
         private val logger = KotlinLogging.logger("OpenStreetMapCache")
     }