Kotlin pour le développement d’un jeu avec libGDX : avantage & inconvénient

libGDX est un framework de développement de jeux vidéo Java. Mais quand on développe un jeu, on veut se concentrer sur le design du jeu, itérer rapidement : on ne veut pas perdre de temps avec des problèmes de syntaxes ou autre. Mais Kotlin s’intègre t’il facilement avec les APIs Java de libGDX ? Qu’apporte Kotlin dans ce contexte et surtout. Les avantages de Kotlin sont-ils toujours des avantages dans le code d’un jeu vidéo ?

(Kotlin Paris Meetup - https://www.meetup.com/fr-FR/Kotlin-Paris-Meetup/events/247733641/ )

Transcript

1. Kotlin pour le développement d’un jeu avec libGDX Avantages & inconvénients
2. David Wursteisen
4. John Carmack
10. ❤
11. PRODUCTIVITYYYYYYYY
12. Core iOS GWT Android Desktop
13. Core Android Desktop
14. class HelloWorld : ScreenAdapter() { override fun show() { } override fun render(delta: Float) { } } Initialisation de l’écran de jeu Rendu de l’écran de jeu
15. class HelloWorld : ScreenAdapter() { var batch: SpriteBatch? override fun show() { batch = SpriteBatch() } override fun render(delta: Float) { batch!!.begin() // ... batch!!.end() } }
16. class HelloWorld : ScreenAdapter() { var batch: SpriteBatch? override fun show() { batch = SpriteBatch() } override fun render(delta: Float) { batch!!.begin() // ... batch!!.end() } }
17. class HelloWorld : ScreenAdapter() { lateinit var batch: SpriteBatch override fun show() { batch = SpriteBatch() } override fun render(delta: Float) { batch.begin() // ... batch.end() } }
18. class HelloWorld : ScreenAdapter() { lateinit var batch: SpriteBatch override fun show() { batch = SpriteBatch() } override fun render(delta: Float) { batch.begin() // ... batch.end() } }
19. fun String.toColor(): Color = Color.valueOf(this) val background = « 0089d5".toColor() fun ShapeRenderer.rect(pos: Vector2, size: Vector2) { this.rect(pos.x, pos.y, size.x, size.y) } batch.rect(pos1, pos2)
20. fun String.toColor(): Color = Color.valueOf(this) val background = « 0089d5".toColor() fun ShapeRenderer.rect(pos: Vector2, size: Vector2) { this.rect(pos.x, pos.y, size.x, size.y) } batch.rect(pos1, pos2) Méthode d’extension = étendre une API à son besoin
21. Hexagonal Architecture ?
22. object EntityFactory { fun player(engine: PooledEngine, assets: AssetManager): Unit { // … } Couplage ! Couplage !
23. const val TOUCH_DOWN = 1 const val TOUCH_UP = 2 const val TOUCH_MOVE = 3 Compile-Time Constants Properties the value of which is known at compile time can be marked as compile time constants using the const modifier. Such properties need to fulfil the following requirements: Top-level or member of an object Initialized with a value of type String or a primitive type No custom getter
24. private void readMeasureHeader(InputStream is, int measureIndex) throws IOException { int header = helper.readUnsignedByte(is); boolean repeatStart = ((header & ParserHelper.BITMASK_3) != 0); boolean doubleBar = ((header & ParserHelper.BITMASK_8) != 0); int numerator = 0; if ((header & ParserHelper.BITMASK_1) != 0) { numerator = helper.readByte(is); } int denominator = 0; if ((header & ParserHelper.BITMASK_2) != 0) { denominator = helper.readByte(is); } }
25. private void readMeasureHeader(InputStream is, int measureIndex) throws IOException { int header = helper.readUnsignedByte(is); boolean repeatStart = ((header & ParserHelper.BITMASK_3) != 0); boolean doubleBar = ((header & ParserHelper.BITMASK_8) != 0); int numerator = 0; if ((header & ParserHelper.BITMASK_1) != 0) { numerator = helper.readByte(is); } int denominator = 0; if ((header & ParserHelper.BITMASK_2) != 0) { denominator = helper.readByte(is); } }
26. TOUCH_DOWN shl 3 TOUCH_DOWN and 2 TOUCH_DOWN << 3 TOUCH_DOWN & 2
27. Direction Position
28. Vector2(3f, 5f).set(entity[cameraData].direction) .scl(5f) .add(entity[position].value) .add(halfX, halfY val v1 = Vector2(3f, 5f) + Vector2(4f, 2f) v2 = v1 * 5f
29. Vector2(3f, 5f).set(entity[cameraData].direction) .scl(5f) .add(entity[position].value) .add(halfX, halfY val v1 = Vector2(3f, 5f) + Vector2(4f, 2f) v2 = v1 * 5f Surcharge d’opérateur (add) Surcharge d’opérateur (scl)
30. engine.addEntity({ e -> val left = spriteDef.slices("left") val leftRegion = left.textureRegion(assets["sheets/pico8/keyboard.png"]) e.add(Controller()) e.add(Position(42 v2 26)) e.add(Size(16 v2 16)) e.add(EntityRender(texture = leftRegion)) e.add(ButtonComponent(ButtonSystem.LEFT)) e.add(StateComponent()) }) Vector2
31. engine.addEntity({ e -> val left = spriteDef.slices("left") val leftRegion = left.textureRegion(assets["sheets/pico8/keyboard.png"]) e.add(Controller()) e.add(Position(42 v2 26)) e.add(Size(16 v2 16)) e.add(EntityRender(texture = leftRegion)) e.add(ButtonComponent(ButtonSystem.LEFT)) e.add(StateComponent()) }) infix fun Int.v2(that: Int): Vector2 = Vector2(this.toFloat(), that.toFloat())
34. Position Couleur Joueur Etat
35. val player = Entity() player.add(Player())) player.add(Position(100 v2 100)) player.add(ColorSplash(Color.GREEN)) player.add(StateComponent()) Position Couleur Joueur Etat
36. ComponentMapper<PositionComponent> pm = ComponentMapper.getFor(PositionComponent.class); ComponentMapper<VelocityComponent> vm = ComponentMapper.getFor(VelocityComponent.class); ... PositionComponent position = pm.get(entity); VelocityComponent velocity = vm.get(entity); Extracteur Extraction
37. inline fun <reified T : Component> EntitySystem.get(): ComponentMapper<T> = ComponentMapper.getFor(T::class.java) private val move: ComponentMapper<TurnMove> = ComponentMapper.getFor(TurnMove::class.java) Extracteur
38. inline fun <reified T : Component> EntitySystem.get(): ComponentMapper<T> = ComponentMapper.getFor(T::class.java) private val move: ComponentMapper<TurnMove> = ComponentMapper.getFor(TurnMove::class.java) Inline + reified
39. inline fun <reified T : Component> EntitySystem.get(): ComponentMapper<T> = ComponentMapper.getFor(T::class.java) private val move: ComponentMapper<TurnMove> = get()
40. private val move: ComponentMapper<TurnMove> = get() private val position: ComponentMapper<Position> = get() private val state: ComponentMapper<StateComponent> = get() private val direction: ComponentMapper<Direction> = get()
41. PositionComponent position = pm.get(entity); Extraction
42. val position: Position = pm.get(entity)
43. val position: Position = entity.get(pm)
44. val position: Position = entity[pm]
45. entity[move].turn(entity[direction].value) entity[state].time = 0f entity[animated].animation = animation["dragon_move"] Direction Etat …
46. public void render(float delta) {
 movePlayer(delta);
 moveEnemies(delta);
 moveWorld(delta);
 
 renderWorld();
 renderEnemies();
 renderPlayer();
 }
47. public void render(float delta) {
 movePlayer(delta);
 moveEnemies(delta);
 moveWorld(delta);
 
 renderWorld();
 renderEnemies();
 renderPlayer();
 } 60x
 secondes
48. Garbage Collector Garbage Collector Garbage Collector Garbage Collecto arbage C Garbage STOP THE WORLD
49. altLayers = map.layers .mapIndexed { index, layer -> index to layer } .filter { it.second.name.startsWith("alt_") } .map { it.first } .toIntArray() mutableList !
50. val a = Array<String>(5, { "" }) val b = Array<String>() Différence ? Array libGDX
51. import com.badlogic.gdx.utils.Array as GdxArray val a = Array<String>(5, { "" }) val b = GdxArray<String>()
52. interface EventListener { fun onEvent(event: Event, eventData: EventData) } fun register(eventListener: EventListener, vararg events: Event) { events.forEach { val lst = listeners[it] if (lst == null) { listeners.put(it, listOf(eventListener)) } else { listeners.put(it, lst + eventListener) } } }
53. interface EventListener { fun onEvent(event: Event, eventData: EventData) } fun register(eventListener: EventListener, vararg events: Event) { events.forEach { val lst = listeners[it] if (lst == null) { listeners.put(it, listOf(eventListener)) } else { listeners.put(it, lst + eventListener) } } } Interface avec une méthode
54. eventBus.register(object : EventListener { override fun onEvent(event: Event, eventData: EventData) { game.loadingScreen() } }, GameEvents.EVENT_GAME_MAIN_MENU) Class anonyme
55. fun on(event: Int, block: Transition): OnState { var currentTransitions = parent.transitions[state] ?: emptyMap() currentTransitions += event to block parent.transitions += state to currentTransitions return this } Lambda
56. startWith(WAIT) onState(WAIT).on(GameEvents.EVENT_COMPUTER_ALLOW_MOVE) { entity, event -> if (entity[dragon].currentTurn > 3) { entity[dragon].currentTurn = -1 go(FIRE, entity, event) } else { go(MOVE, entity, event) } } onState(FIRE).on(GameEvents.EVENT_DRAGON_FIRE_BALL) { entity, event -> go(MOVE, entity, event) } Lambda
57. startWith(WAIT) onState(WAIT).on(GameEvents.EVENT_COMPUTER_ALLOW_MOVE) { entity, event -> if (entity[dragon].currentTurn > 3) { entity[dragon].currentTurn = -1 go(FIRE, entity, event) } else { go(MOVE, entity, event) } } onState(FIRE).on(GameEvents.EVENT_DRAGON_FIRE_BALL) { entity, event -> go(MOVE, entity, event) } Etat Event Transition
58. ❤
59. On reste en contact ? @dwursteisen
60. https://goo.gl/4UcQYx En attendant… téléchargez 
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