Added ability to execute code when a scene is restored

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

@@ -0,0 +1,25 @@
+package envoy.client.ui;
+
+/**
+ * This interface defines an action that should be performed when a scene gets
+ * restored from the scene stack in {@link SceneContext}.
+ * <p>
+ * Project: <strong>envoy-client</strong><br>
+ * File: <strong>Restorable.java</strong><br>
+ * Created: <strong>03.07.2020</strong><br>
+ *
+ * @author Leon Hofmeister
+ * @since Envoy Client v0.1-beta
+ */
+@FunctionalInterface
+public interface Restorable {
+
+	/**
+	 * This method is getting called when a scene gets restored.<br>
+	 * Hence, it can contain anything that should be done when the underlying scene
+	 * gets restored.
+	 *
+	 * @since Envoy Client v0.1-beta
+	 */
+	void onRestore();
+}

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

@@ -92,6 +92,7 @@ public final class SceneContext {
 	private final Stage			stage;
 	private final FXMLLoader	loader			= new FXMLLoader();
 	private final Stack<Scene>	sceneStack		= new Stack<>();
+	private final Stack<Object>	controllerStack	= new Stack<>();
 
 	private static final Settings settings = Settings.getInstance();
 
@@ -120,6 +121,7 @@ public final class SceneContext {
 		try {
 			final var	rootNode	= (Parent) loader.load(getClass().getResourceAsStream(sceneInfo.path));
 			final var	scene		= new Scene(rootNode);
+			controllerStack.push(loader.getController());
 
 			sceneStack.push(scene);
 			stage.setScene(scene);
@@ -139,10 +141,18 @@ public final class SceneContext {
 	 */
 	public void pop() {
 		sceneStack.pop();
+		controllerStack.pop();
 		if (!sceneStack.isEmpty()) {
-			stage.setScene(sceneStack.peek());
+			final var newScene = sceneStack.peek();
+			stage.setScene(newScene);
 			applyCSS();
 			stage.sizeToScene();
+			// If the controller implements the Restorable interface,
+			// the actions to perform on restoration will be executed here
+			try {
+				final Restorable restorable = (Restorable) controllerStack.peek();
+				restorable.onRestore();
+			} catch (final ClassCastException e) {}
 		}
 		stage.show();
 	}
@@ -161,7 +171,7 @@ public final class SceneContext {
 	 * @return the controller used by the current scene
 	 * @since Envoy Client v0.1-beta
 	 */
-	public <T> T getController() { return loader.getController(); }
+	public <T> T getController() { return (T) controllerStack.peek(); }
 
 	/**
 	 * @return the stage in which the scenes are displayed

src/main/java/envoy/client/ui/controller/ChatScene.java

@@ -24,6 +24,7 @@ import envoy.client.event.MessageCreationEvent;
 import envoy.client.net.Client;
 import envoy.client.net.WriteProxy;
 import envoy.client.ui.IconUtil;
+import envoy.client.ui.Restorable;
 import envoy.client.ui.SceneContext;
 import envoy.client.ui.listcell.ContactListCellFactory;
 import envoy.client.ui.listcell.MessageControl;
@@ -43,7 +44,7 @@ import envoy.util.EnvoyLog;
  * @author Kai S. K. Engelbart
  * @since Envoy Client v0.1-beta
  */
-public final class ChatScene {
+public final class ChatScene implements Restorable {
 
 	@FXML
 	private Label contactLabel;
@@ -173,6 +174,9 @@ public final class ChatScene {
 		if (!client.isOnline()) updateInfoLabel("You are offline", "infoLabel-info");
 	}
 
+	@Override
+	public void onRestore() { updateRemainingCharsLabel(); }
+
 	/**
 	 * Actions to perform when the list of contacts has been clicked.
 	 *