fix: don't crash if entering multiple enemies range

game/core/src/main/de/dhbw/tinf22b6/gameobject/bullet/Bullet.java

@@ -1,8 +1,5 @@
 package de.dhbw.tinf22b6.gameobject.bullet;
 
-import static com.badlogic.gdx.math.MathUtils.cosDeg;
-import static com.badlogic.gdx.math.MathUtils.sinDeg;
-
 import com.badlogic.gdx.graphics.g2d.Batch;
 import com.badlogic.gdx.math.Vector2;
 import com.badlogic.gdx.physics.box2d.FixtureDef;
@@ -13,85 +10,94 @@
 import de.dhbw.tinf22b6.world.Box2dWorld;
 import de.dhbw.tinf22b6.world.WorldParser;
 
+import static com.badlogic.gdx.math.MathUtils.cosDeg;
+import static com.badlogic.gdx.math.MathUtils.sinDeg;
+
 public abstract class Bullet extends GameObject {
-    protected float speed;
-    protected final int damage;
-    protected boolean active;
-    protected float angle;
-    protected float r;
-    // be careful when adjusting this parameter, as this is not the range in tiles but rather a
-    // counting of delta times
-    // speed until the "range" is reached
-    // TODO: this needs to be refactored to actually represent a value in tiles
-    protected float range = 2.3f;
+  protected final int damage;
+  protected float speed;
+  protected boolean active;
+  protected float angle;
+  protected float r;
+  // be careful when adjusting this parameter, as this is not the range in tiles but rather a
+  // counting of delta times
+  // speed until the "range" is reached
+  // TODO: this needs to be refactored to actually represent a value in tiles
+  protected float range = 2.3f;
 
-    public Bullet(String region, Vector2 position, float angle, int damage, short mask) {
-        super(region, new Vector2(position.x / Constants.TILE_SIZE, position.y / Constants.TILE_SIZE), mask);
-        this.angle = angle;
-        this.damage = damage;
-        active = true;
-        speed = 3;
-        width = 3;
-        height = 6;
-        // wait until world is unlocked before adding body
-        World world = Box2dWorld.instance.getWorld();
-        boolean isLocked;
-        do {
-            isLocked = world.isLocked();
-        } while (isLocked);
-        body = world.createBody(WorldParser.getDynamicBodyDef(pos.x + width / 2, pos.y + height / 2));
-        PolygonShape polygonShape = new PolygonShape();
-        polygonShape.setAsBox(3 - 2, 3 - 2);
+  public Bullet(String region, Vector2 position, float angle, int damage, short mask) {
+    super(region, new Vector2(position.x / Constants.TILE_SIZE, position.y / Constants.TILE_SIZE), mask);
+    this.angle = angle;
+    this.damage = damage;
+    active = true;
+    speed = 3;
+    width = 3;
+    height = 6;
+    // This is arcane wizardry! It might fix the crash which happened at random when
+    // the player gets into the range of multiple enemies at the same time, and they start shooting
+    // in the same tick - effectively locking up the world (inserting body) and causing a data race
+    // this "fix" works for me and needs throughout testing as I suspect it breaking something further
+    // when the #render() call is done and the body is not created yet.
+    new Thread(() -> {
+      World world = Box2dWorld.instance.getWorld();
+      boolean isLocked;
+      do {
+        isLocked = world.isLocked();
+      } while (isLocked);
+      body = world.createBody(WorldParser.getDynamicBodyDef(pos.x + width / 2, pos.y + height / 2));
+      PolygonShape polygonShape = new PolygonShape();
+      polygonShape.setAsBox(3 - 2, 3 - 2);
 
-        FixtureDef fixtureDef = new FixtureDef();
-        fixtureDef.shape = polygonShape;
-        fixtureDef.filter.categoryBits = collisionMask;
-        fixtureDef.isSensor = true;
+      FixtureDef fixtureDef = new FixtureDef();
+      fixtureDef.shape = polygonShape;
+      fixtureDef.filter.categoryBits = collisionMask;
+      fixtureDef.isSensor = true;
 
-        body.createFixture(fixtureDef).setUserData(this);
-        body.setBullet(true);
-        polygonShape.dispose();
-    }
+      body.createFixture(fixtureDef).setUserData(this);
+      body.setBullet(true);
+      polygonShape.dispose();
+    }).start();
+  }
 
-    @Override
-    public void render(Batch batch) {
-        float rotation = 90 + angle + 180;
-        batch.draw(
-                currentAnimation.getKeyFrame(stateTime, true),
-                pos.x,
-                pos.y,
-                width / 2,
-                height / 2,
-                width,
-                height,
-                1,
-                1,
-                rotation);
-    }
+  @Override
+  public void render(Batch batch) {
+    float rotation = 90 + angle + 180;
+    batch.draw(
+        currentAnimation.getKeyFrame(stateTime, true),
+        pos.x,
+        pos.y,
+        width / 2,
+        height / 2,
+        width,
+        height,
+        1,
+        1,
+        rotation);
+  }
 
-    @Override
-    public void tick(float delta) {
-        super.tick(delta); // play the animation
-        r += delta;
+  @Override
+  public void tick(float delta) {
+    super.tick(delta); // play the animation
+    r += delta;
 
-        if (active) {
-            Vector2 tmp = new Vector2(pos);
-            tmp.y = r * sinDeg(angle);
-            tmp.x = r * cosDeg(angle);
-            tmp.setLength(speed);
+    if (active) {
+      Vector2 tmp = new Vector2(pos);
+      tmp.y = r * sinDeg(angle);
+      tmp.x = r * cosDeg(angle);
+      tmp.setLength(speed);
 
-            pos.add(tmp);
-            body.setTransform(pos.x + width / 2, pos.y + height / 2, 0);
+      pos.add(tmp);
+      body.setTransform(pos.x + width / 2, pos.y + height / 2, 0);
 
-            if (r * speed > range) {
-                // Remove Bullet
-                remove = true;
-                active = false;
-            }
-        }
+      if (r * speed > range) {
+        // Remove Bullet
+        remove = true;
+        active = false;
+      }
     }
+  }
 
-    public int getDamage() {
-        return damage;
-    }
+  public int getDamage() {
+    return damage;
+  }
 }