GUI: Cancel old rendering tasks on reload

This bug probably got introduced during the last GUI rendering refactoring.

BlockMap-gui/src/main/java/de/piegames/blockmap/gui/RenderedMap.java

@@ -5,6 +5,7 @@
 import java.util.Map;
 import java.util.Objects;
 import java.util.Set;
+import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ExecutorService;
 import java.util.stream.Collectors;
@@ -42,6 +43,7 @@ public class RenderedMap implements Runnable {
 	protected ReadOnlySetWrapper<Vector2ic>									rendering		= new ReadOnlySetWrapper<>(FXCollections.observableSet());
 	/** Where the mouse currently points to, in world coordinates */
 	protected ReadOnlyObjectProperty<Vector2dc>								mouseWorldProperty;
+	private final AtomicBoolean cancelRendering = new AtomicBoolean(false);
 
 	public RenderedMap(RegionFolder regionFolder, ExecutorService executor, ReadOnlyObjectProperty<Vector2dc> mouseWorldProperty) {
 		this.regionFolder = Objects.requireNonNull(regionFolder);
@@ -76,10 +78,18 @@ public void draw(GraphicsContext gc, int level, AABBd frustum, double scale) {
 				.filter(r -> r.isVisible(frustum))
 				.forEach(r -> r.drawForeground(gc, frustum, scale));
 	}
+
+	/* Cancel existing rendering tasks and already free up some memory */
+	public void cancel() {
+		cancelRendering.set(true);
+		regions.clear();
+	}
 
 	/* Render the next region file on a worker thread */
 	@Override
 	public void run() {
+		if (cancelRendering.get())
+			return;
 		RenderedRegion region = nextRegion();
 		Platform.runLater(() -> rendering.getValue().add(region.position));
 		try {

BlockMap-gui/src/main/java/de/piegames/blockmap/gui/WorldRendererCanvas.java

@@ -47,17 +47,24 @@ public WorldRendererCanvas() {
 		progress.addListener(e -> repaint());
 
 		this.regionFolder.addListener((obs, prev, val) -> {
+			if (map != null) {
+				/* Cancel existing tasks */
+				for (Runnable task : executor.getQueue())
+					executor.remove(task);
+				/* Free up the old map */
+				map.cancel();
+			}
 			if (val == null || val.listRegions().isEmpty()) {
 				map = null;
-				status.set("No regions loaded");
+				executor.execute(() -> Platform.runLater(() -> status.set("No regions loaded")));
 				chunkMetadata.unbind();
 				chunkMetadata.clear();
 			} else {
+				executor.execute(() -> Platform.runLater(() -> status.set("Rendering")));
 				map = new RenderedMap(val, executor, viewport.mouseWorldProperty);
 				map.getCurrentlyRendering().addListener((InvalidationListener) e -> repaint());
 				progress.bind(map.getProgress());
 				chunkMetadata.bind(map.getChunkMetadata());
-				status.set("Rendering");
 				executor.execute(() -> Platform.runLater(() -> status.set("Done")));
 			}
 			repaint();