Fix tile loading lock

maps-kt-compose/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 io.ktor.utils.io.CancellationException
 import kotlinx.coroutines.launch
 import mu.KotlinLogging
 import org.jetbrains.skia.Font
@@ -185,6 +186,7 @@ actual fun MapView(
                         try {
                             mapTiles += deferred.await()
                         } catch (ex: Exception) {
+                            if (ex !is CancellationException) {
                                 //displaying the error is maps responsibility
                                 logger.error(ex) { "Failed to load tile with id=$id" }
                             }
@@ -193,6 +195,7 @@ actual fun MapView(
                 }
             }
         }
+    }
 
 
     Canvas(canvasModifier) {

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

@@ -5,6 +5,7 @@ import androidx.compose.ui.graphics.toComposeImageBitmap
 import io.ktor.client.HttpClient
 import io.ktor.client.request.get
 import io.ktor.client.statement.readBytes
+import io.ktor.utils.io.CancellationException
 import kotlinx.coroutines.CoroutineScope
 import kotlinx.coroutines.Deferred
 import kotlinx.coroutines.Dispatchers
@@ -37,6 +38,7 @@ class OpenStreetMapTileProvider(
      * Download and cache the tile image
      */
     private fun CoroutineScope.downloadImageAsync(id: TileId) = async(Dispatchers.IO) {
+
         id.cacheFilePath()?.let { path ->
             if (path.exists()) {
                 try {
@@ -48,7 +50,6 @@ class OpenStreetMapTileProvider(
             }
         }
 
-        try {
         //semaphore works only for actual download
         semaphore.withPermit {
             val url = id.osmUrl()
@@ -65,23 +66,30 @@ class OpenStreetMapTileProvider(
 
             Image.makeFromEncoded(byteArray).toComposeImageBitmap()
         }
-        } catch (ex: Exception){
-            //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) {
+        val imageDeferred = cache.getOrPut(tileId) {
             downloadImageAsync(tileId)
         }
 
         //collect the result asynchronously
-        return async { MapTile(tileId, image.await()) }
+        return async {
+            val image = try {
+                imageDeferred.await()
+            } catch (ex: Exception) {
+                cache.remove(tileId)
+                if(ex !is CancellationException) {
+                    logger.error(ex) { "Failed to load tile image with id=$tileId" }
+                }
+                throw ex
+            }
+            MapTile(tileId, image)
+        }
     }