Reuse the same scene in SceneContext by switching root nodes

client/src/main/java/envoy/client/ui/SceneContext.java

@@ -4,7 +4,6 @@ import java.io.IOException;
 import java.util.Stack;
 import java.util.logging.Level;
 
-import javafx.application.Platform;
 import javafx.fxml.FXMLLoader;
 import javafx.scene.*;
 import javafx.stage.Stage;
@@ -29,11 +28,10 @@ import envoy.client.event.*;
 public final class SceneContext implements EventListener {
 
 	private final Stage			stage;
-	private final FXMLLoader	loader			= new FXMLLoader();
+	private final Stack<Parent>	roots		= new Stack<>();
-	private final Stack<Scene>	sceneStack		= new Stack<>();
+	private final Stack<Object>	controllers	= new Stack<>();
-	private final Stack<Object>	controllerStack	= new Stack<>();
 
-	private static final Settings settings = Settings.getInstance();
+	private Scene scene;
 
 	/**
 	 * Initializes the scene context.
@@ -49,41 +47,47 @@ public final class SceneContext implements EventListener {
 	/**
 	 * Loads a new scene specified by a scene info.
 	 *
-	 * @param sceneInfo specifies the scene to load
+	 * @param info specifies the scene to load
 	 * @throws RuntimeException if the loading process fails
 	 * @since Envoy Client v0.1-beta
 	 */
-	public void load(SceneInfo sceneInfo) {
+	public void load(SceneInfo info) {
-		EnvoyLog.getLogger(SceneContext.class).log(Level.FINER, "Loading scene " + sceneInfo);
+		EnvoyLog.getLogger(SceneContext.class).log(Level.FINER, "Loading scene " + info);
-		loader.setRoot(null);
-		loader.setController(null);
 
 		try {
-			final var	rootNode	=
-				(Parent) loader.load(getClass().getResourceAsStream(sceneInfo.path));
-			final var	scene		= new Scene(rootNode);
-			final var	controller	= loader.getController();
-			controllerStack.push(controller);
 
-			sceneStack.push(scene);
+			// Load root node and controller
-			stage.setScene(scene);
+			var		loader		= new FXMLLoader();
+			Parent	root		= loader.load(getClass().getResourceAsStream(info.path));
+			Object	controller	= loader.getController();
+			roots.push(root);
+			controllers.push(controller);
+
+			if (scene == null) {
+
+				// One-time scene initialization
+				scene = new Scene(root);
+				applyCSS();
+				stage.setScene(scene);
+			} else {
+				scene.setRoot(root);
+				stage.sizeToScene();
+			}
+
+			stage.setResizable(info.resizable);
+
+			// Remove previous keyboard shortcuts
+			scene.getAccelerators().clear();
 
 			// Supply the global custom keyboard shortcuts for that scene
 			scene.getAccelerators()
-				.putAll(GlobalKeyShortcuts.getInstance().getKeyboardShortcuts(sceneInfo));
+				.putAll(GlobalKeyShortcuts.getInstance().getKeyboardShortcuts(info));
 
 			// Supply the scene specific keyboard shortcuts
 			if (controller instanceof KeyboardMapping)
 				scene.getAccelerators()
 					.putAll(((KeyboardMapping) controller).getKeyboardShortcuts());
-
+		} catch (IOException e) {
-			Platform.runLater(() -> stage.setResizable(sceneInfo.resizable));
-			stage.sizeToScene();
-			applyCSS();
-			stage.show();
-		} catch (final IOException e) {
-			EnvoyLog.getLogger(SceneContext.class).log(Level.SEVERE,
-				String.format("Could not load scene for %s: ", sceneInfo), e);
 			throw new RuntimeException(e);
 		}
 	}
@@ -95,29 +99,30 @@ public final class SceneContext implements EventListener {
 	 */
 	public void pop() {
 
-		// Pop scene and controller
+		// Pop current root node and controller
-		sceneStack.pop();
+		roots.pop();
-		controllerStack.pop();
+		controllers.pop();
 
 		// Apply new scene if present
-		if (!sceneStack.isEmpty()) {
+		if (!roots.isEmpty()) {
-			final var newScene = sceneStack.peek();
+			scene.setRoot(roots.peek());
-			stage.setScene(newScene);
+
-			applyCSS();
+			// Invoke restore if controller is restorable
-			stage.sizeToScene();
+			var controller = controllers.peek();
-			// If the controller implements the Restorable interface,
-			// the actions to perform on restoration will be executed here
-			final var controller = controllerStack.peek();
 			if (controller instanceof Restorable)
 				((Restorable) controller).onRestore();
+		} else {
+
+			// Remove the current scene entirely
+			scene = null;
+			stage.setScene(null);
 		}
-		stage.show();
 	}
 
 	private void applyCSS() {
-		if (!sceneStack.isEmpty()) {
+		if (scene != null) {
-			final var	styleSheets	= stage.getScene().getStylesheets();
+			var	styleSheets	= scene.getStylesheets();
-			final var	themeCSS	= "/css/" + settings.getCurrentTheme() + ".css";
+			var	themeCSS	= "/css/" + Settings.getInstance().getCurrentTheme() + ".css";
 			styleSheets.clear();
 			styleSheets.addAll(getClass().getResource("/css/base.css").toExternalForm(),
 				getClass().getResource(themeCSS).toExternalForm());
@@ -126,8 +131,8 @@ public final class SceneContext implements EventListener {
 
 	@Event(eventType = Logout.class, priority = 150)
 	private void onLogout() {
-		sceneStack.clear();
+		roots.clear();
-		controllerStack.clear();
+		controllers.clear();
 	}
 
 	@Event(priority = 150, eventType = ThemeChangeEvent.class)
@@ -140,7 +145,7 @@ public final class SceneContext implements EventListener {
 	 * @return the controller used by the current scene
 	 * @since Envoy Client v0.1-beta
 	 */
-	public <T> T getController() { return (T) controllerStack.peek(); }
+	public <T> T getController() { return (T) controllers.peek(); }
 
 	/**
 	 * @return the stage in which the scenes are displayed
@@ -152,5 +157,5 @@ public final class SceneContext implements EventListener {
 	 * @return whether the scene stack is empty
 	 * @since Envoy Client v0.2-beta
 	 */
-	public boolean isEmpty() { return sceneStack.isEmpty(); }
+	public boolean isEmpty() { return roots.isEmpty(); }
 }

client/src/main/java/envoy/client/ui/Startup.java

@@ -93,7 +93,7 @@ public final class Startup extends Application {
 		final var sceneContext = new SceneContext(stage);
 		context.setSceneContext(sceneContext);
 
-		// Authenticate with token if present
+		// Authenticate with token if present or load login scene
 		if (localDB.getAuthToken() != null) {
 			logger.info("Attempting authentication with token...");
 			localDB.loadUserData();
@@ -102,8 +102,9 @@ public final class Startup extends Application {
 					VERSION, localDB.getLastSync())))
 				sceneContext.load(SceneInfo.LOGIN_SCENE);
 		} else
-			// Load login scene
 			sceneContext.load(SceneInfo.LOGIN_SCENE);
+
+		stage.show();
 	}
 
 	/**