fix: World component can now be queried with componentsAtPoint (#1739)

The componentsAtPoint function allows us to find a component located at a specific position. Usually it is applied to the top-level Game, but there are instances when it could also be useful to apply this function to the World component. This PR enables such functionality.

packages/flame/lib/src/experimental/camera_component.dart

@@ -122,7 +122,7 @@ class CameraComponent extends Component {
  if (viewport.containsLocalPoint(viewportPoint)) {
  currentCameras.add(this);
  final worldPoint = viewfinder.transform.globalToLocal(viewportPoint);
- yield* world.componentsAtPointFromCamera(worldPoint, nestedPoints);
+ yield* world.componentsAtPoint(worldPoint, nestedPoints);
  yield* viewfinder.componentsAtPoint(worldPoint, nestedPoints);
  currentCameras.removeLast();
  }

packages/flame/lib/src/experimental/world.dart

@@ -1,6 +1,7 @@
 import 'dart:ui';
 
 import 'package:flame/src/components/component.dart';
+import 'package:flame/src/components/mixins/coordinate_transform.dart';
 import 'package:flame/src/experimental/camera_component.dart';
 import 'package:meta/meta.dart';
 import 'package:vector_math/vector_math_64.dart';
@@ -10,7 +11,7 @@ import 'package:vector_math/vector_math_64.dart';
 /// The primary feature of this component is that it disables regular rendering,
 /// and allows itself to be rendered through a [CameraComponent] only. The
 /// updates proceed through the world tree normally.
-class World extends Component {
+class World extends Component implements CoordinateTransform {
  @override
  void renderTree(Canvas canvas) {}
 
@@ -25,18 +26,8 @@ class World extends Component {
  bool containsLocalPoint(Vector2 point) => true;
 
  @override
- Iterable<Component> componentsAtPoint(
- Vector2 point, [
- List<Vector2>? nestedPoints,
- ]) {
- return const Iterable.empty();
- }
+ Vector2? localToParent(Vector2 point) => null;
 
- @internal
- Iterable<Component> componentsAtPointFromCamera(
- Vector2 point,
- List<Vector2>? nestedPoints,
- ) {
- return super.componentsAtPoint(point, nestedPoints);
- }
+ @override
+ Vector2? parentToLocal(Vector2 point) => null;
 }

packages/flame/test/experimental/camera_component_test.dart

@@ -139,6 +139,17 @@ void main() {
  expect(it.current, game);
  expect(nested, [Vector2(400, 300)]);
  expect(it.moveNext(), false);
+
+ // Check that `componentsAtPoint` is usable with non-top-level components
+ // also.
+ expect(
+ world.componentsAtPoint(Vector2(100, 100)).toList(),
+ [component, world],
+ );
+ expect(
+ component.componentsAtPoint(Vector2(100, 50)).toList(),
+ [component],
+ );
  });
  });
 }