feat: Adding ability for a SpawnComponent to not auto start (#2947)

`SpawnComponent` didn't had the ability to not auto start. This PR adds
a new attribute in order to customize that.

Co-authored-by: Lukas Klingsbo <me@lukas.fyi>

packages/flame/lib/src/components/spawn_component.dart

@@ -25,6 +25,7 @@ class SpawnComponent extends Component {
     this.area,
     this.within = true,
     this.selfPositioning = false,
+    this.autoStart = true,
     Random? random,
     super.key,
   })  : assert(
@@ -46,6 +47,7 @@ class SpawnComponent extends Component {
     this.area,
     this.within = true,
     this.selfPositioning = false,
+    this.autoStart = true,
     Random? random,
     super.key,
   })  : assert(
@@ -102,6 +104,9 @@ class SpawnComponent extends Component {
   /// The amount of spawned components.
   int amount = 0;
 
+  /// Whether the timer automatically starts or not.
+  final bool autoStart;
+
   @override
   FutureOr<void> onLoad() async {
     if (area == null && !selfPositioning) {
@@ -147,6 +152,7 @@ class SpawnComponent extends Component {
         updatePeriod();
         amount++;
       },
+      autoStart: autoStart,
     );
     timer = timerComponent.timer;
     add(timerComponent);

packages/flame/test/components/spawn_component_test.dart

@@ -140,5 +140,31 @@ void main() {
         isTrue,
       );
     });
+
+    testWithFlameGame('Does not spawns when auto start is false', (game) async {
+      final random = Random(0);
+      final shape = Rectangle.fromCenter(
+        center: Vector2(100, 200),
+        size: Vector2.all(200),
+      );
+      final spawn = SpawnComponent(
+        factory: (_) => PositionComponent(),
+        period: 1,
+        area: shape,
+        random: random,
+        autoStart: false,
+      );
+      final world = game.world;
+      await world.ensureAdd(spawn);
+      game.update(1.5);
+      await game.ready();
+      expect(world.children.length, 1);
+
+      spawn.timer.start();
+
+      game.update(1);
+      await game.ready();
+      expect(world.children.length, 2);
+    });
   });
 }