Add late-behavior initialization (fastjengine#201)

- (fastjengine#172) add mid-game init calls

examples/java/tech/fastj/examples/bullethell/scenes/GameScene.java

@@ -165,7 +165,6 @@ private void newWave() {
         enemyCount = calculateEnemyCount(wave);
         for (int i = 0; i < enemyCount; i++) {
             Model2D enemy = createEnemy();
-            enemy.initBehaviors();
             enemies.put(enemy.getID(), enemy);
         }
 
@@ -183,7 +182,7 @@ private Model2D createEnemy() {
         );
 
         Model2D enemy = Model2D.fromPolygons(ModelUtil.loadModel(Path.of(FilePaths.PathToResources + "enemy.psdf")));
-        enemy.addBehavior(new EnemyMovement(this), this);
+        enemy.addLateBehavior(new EnemyMovement(this), this);
         enemy.setTranslation(randomPosition);
         drawableManager.addGameObject(enemy);
         return enemy;

examples/java/tech/fastj/examples/bullethell/scripts/PlayerCannon.java

@@ -58,12 +58,10 @@ private void createBullet(GameObject player) {
 
         Polygon2D bullet = (Polygon2D) Polygon2D.fromPoints(bulletMesh)
                 .setFill(Color.red)
-                .addBehavior(bulletMovementScript, gameScene)
+                .addLateBehavior(bulletMovementScript, gameScene)
                 .<GameObject>addTag(Tags.Bullet, gameScene);
 
         gameScene.drawableManager.addGameObject(bullet);
-        bullet.initBehaviors();
-
         bulletCount++;
     }
 

src/main/java/tech/fastj/engine/FastJEngine.java

@@ -654,17 +654,16 @@ private static void initEngine() {
     /** Runs the game loop -- the heart of the engine. */
     private static void gameLoop() {
         float elapsedTime;
+        float elapsedFixedTime;
         float accumulator = 0f;
         float updateInterval = 1f / targetUPS;
 
         while (display.getWindow().isVisible()) {
             elapsedTime = deltaTimer.evalDeltaTime();
-            FastJEngine.log("Delta: {}", FastJEngine.getDeltaTime());
             accumulator += elapsedTime;
 
             while (accumulator >= updateInterval) {
-                fixedDeltaTimer.evalDeltaTime();
-                FastJEngine.log("Fixed Delta: {}", FastJEngine.getFixedDeltaTime());
+                elapsedFixedTime = fixedDeltaTimer.evalDeltaTime();
                 gameManager.fixedUpdate(canvas);
                 gameManager.updateBehaviors();
 
@@ -677,7 +676,7 @@ private static void gameLoop() {
                     AfterUpdateList.clear();
                 }
 
-                accumulator -= updateInterval;
+                accumulator -= elapsedFixedTime;
             }
 
             gameManager.processInputEvents();
@@ -712,7 +711,7 @@ private static void gameLoop() {
     private static void sync() {
         final float loopSlot = 1f / targetFPS;
         final double endTime = deltaTimer.getLastTimestamp() + loopSlot;
-        final double currentTime = deltaTimer.getTime();
+        final double currentTime = deltaTimer.getCurrentTime();
         if (currentTime < endTime) {
             try {
                 TimeUnit.MILLISECONDS.sleep((long) ((endTime - currentTime) * 1000L));

src/main/java/tech/fastj/engine/internals/Timer.java

@@ -1,9 +1,10 @@
 package tech.fastj.engine.internals;
 
 /**
- * Timer that accurately specifies time.
+ * Timekeeping class, primarily used to track the time between the previous and current game frames.
  * <p>
- * This class is based on Antonio Hernández Bejarano's Timer class: https://ahbejarano.gitbook.io/lwjglgamedev/
+ * This class is based on Antonio Hernández Bejarano's Timer class:
+ * <a href="https://ahbejarano.gitbook.io/lwjglgamedev/">https://ahbejarano.gitbook.io/lwjglgamedev/</a>
  * <p>
  * Didn't make too many changes.
  *
@@ -17,7 +18,7 @@ public class Timer {
 
     /** Initializes the Timer. */
     public void init() {
-        lastTimestamp = getTime();
+        lastTimestamp = getCurrentTime();
         deltaTime = 0f;
     }
 
@@ -26,7 +27,7 @@ public void init() {
      *
      * @return The current time (nanoseconds) as a double.
      */
-    public double getTime() {
+    public double getCurrentTime() {
         return System.nanoTime() / 1_000_000_000d;
     }
 
@@ -36,7 +37,7 @@ public double getTime() {
      * @return The time elapsed since the last time evaluation.
      */
     public float evalDeltaTime() {
-        double time = getTime();
+        double time = getCurrentTime();
         deltaTime = (float) (time - lastTimestamp);
         lastTimestamp = time;
         return deltaTime;

src/main/java/tech/fastj/graphics/game/GameObject.java

@@ -86,12 +86,31 @@ public GameObject addBehavior(Behavior behavior, BehaviorHandler behaviorHandler
         return this;
     }
 
+    /**
+     * Adds the specified {@link Behavior} to the {@code GameObject}'s list of {@code Behavior}s, and initializes it.
+     * <p>
+     * This does not check to make sure the game is running -- it only initializes the given behavior.
+     * <p>
+     * {@code Behavior}s can be added as many times as needed.
+     *
+     * @param behavior        {@code Behavior} parameter to be added.
+     * @param behaviorHandler Handler that the {@code GameObject} will be added to, as a behavior listener.
+     * @return the {@code GameObject} is returned for method chaining.
+     */
+    public GameObject addLateBehavior(Behavior behavior, BehaviorHandler behaviorHandler) {
+        behaviors.add(behavior);
+        behaviorHandler.addBehaviorListener(this);
+        behavior.init(this);
+
+        return this;
+    }
+
     /**
      * Removes the specified {@link Behavior} from the {@code GameObject}'s list of {@code Behavior}s.
      *
      * @param behavior        {@code Behavior} parameter to be removed from.
-     * @param behaviorHandler Handler that, if the {@code GameObject} no longer has any Behaviors, the {@code
-     *                        GameObject} will be removed from as a behavior listener.
+     * @param behaviorHandler Handler that, if the {@code GameObject} no longer has any Behaviors, the
+     *                        {@code GameObject} will be removed from as a behavior listener.
      * @return the {@code GameObject} is returned for method chaining.
      */
     public GameObject removeBehavior(Behavior behavior, BehaviorHandler behaviorHandler) {
@@ -127,8 +146,8 @@ protected void destroyTheRest(Scene origin) {
     }
 
     /**
-     * Destroys all references of the {@code GameObject}'s behaviors and removes its references from the {@code
-     * SimpleManager}.
+     * Destroys all references of the {@code GameObject}'s behaviors and removes its references from the
+     * {@code SimpleManager}.
      *
      * @param origin {@code SimpleManager} parameter that will have all references to this {@code GameObject} removed.
      */

src/test/java/unittest/testcases/graphics/game/GameObjectTests.java

@@ -141,6 +141,47 @@ void checkDestroyBehaviors_shouldMakePointfNull() {
         assertNull(mockBehavior.getPointf(), "After destroying the GameObject's behaviors, the Pointf should be null.");
     }
 
+    @Test
+    void checkInitBehavior_withAddLateBehavior_shouldInitializePointf() {
+        GameObject gameObject = new MockGameObject();
+        MockBehavior mockBehavior = new MockBehavior();
+        Scene mockScene = new MockEmptyScene();
+
+        gameObject.addLateBehavior(mockBehavior, mockScene);
+
+        assertNotNull(mockBehavior.getPointf(), "After initializing the GameObject's behaviors, its Pointf should not be null.");
+    }
+
+    @Test
+    void checkUpdateBehavior_withAddLateBehavior_shouldIncrementPointf() {
+        GameObject gameObject = new MockGameObject();
+        MockBehavior mockBehavior = new MockBehavior();
+        Scene mockScene = new MockEmptyScene();
+
+        gameObject.addLateBehavior(mockBehavior, mockScene);
+
+        int expectedIncrement = 15;
+        for (int i = 0; i < expectedIncrement; i++) {
+            gameObject.updateBehaviors();
+        }
+
+        boolean condition = Maths.floatEquals(expectedIncrement, mockBehavior.getPointf().x) && Maths.floatEquals(expectedIncrement, mockBehavior.getPointf().y);
+        assertTrue(condition, "After updating, the behavior's Pointf should have incremented.");
+    }
+
+    @Test
+    void checkDestroyBehavior_withAddLateBehavior_shouldMakePointfNull() {
+        GameObject gameObject = new MockGameObject();
+        MockBehavior mockBehavior = new MockBehavior();
+        Scene mockScene = new MockEmptyScene();
+
+        gameObject.addLateBehavior(mockBehavior, mockScene); // pointf is not null here
+        assertNotNull(mockBehavior.getPointf());
+
+        gameObject.destroyAllBehaviors(); // pointf is null here
+        assertNull(mockBehavior.getPointf(), "After destroying the GameObject's behaviors, the Pointf should be null.");
+    }
+
     @Test
     void tryUpdateBehaviorWithoutInitializing_shouldThrowNullPointerException() {
         GameObject gameObject = new MockGameObject();