feat: Camera's Viewfinder can now be affected by rotation effects (#1527

)

packages/flame/lib/effects.dart

@@ -22,7 +22,7 @@ export 'src/effects/move_along_path_effect.dart';
 export 'src/effects/move_effect.dart';
 export 'src/effects/opacity_effect.dart';
 export 'src/effects/provider_interfaces.dart'
- show PositionProvider, ScaleProvider;
+ show PositionProvider, ScaleProvider, AngleProvider;
 export 'src/effects/remove_effect.dart';
 export 'src/effects/rotate_effect.dart';
 export 'src/effects/scale_effect.dart';

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

@@ -59,7 +59,7 @@ import 'component.dart';
 /// do not specify the size of a PositionComponent, then it will be
 /// equal to zero and the component won't be able to respond to taps.
 class PositionComponent extends Component
- implements PositionProvider, ScaleProvider {
+ implements AngleProvider, PositionProvider, ScaleProvider {
  PositionComponent({
  Vector2? position,
  Vector2? size,
@@ -110,7 +110,9 @@ class PositionComponent extends Component
  /// Rotation angle (in radians) of the component. The component will be
  /// rotated around its anchor point in the clockwise direction if the
  /// angle is positive, or counterclockwise if the angle is negative.
+ @override
  double get angle => transform.angle;
+ @override
  set angle(double a) => transform.angle = a;
 
  /// The scale factor of this component. The scale can be different along

packages/flame/lib/src/effects/provider_interfaces.dart

@@ -11,3 +11,9 @@ abstract class ScaleProvider {
  Vector2 get scale;
  set scale(Vector2 value);
 }
+
+/// Interface for a component that can be affected by rotation effects.
+abstract class AngleProvider {
+ double get angle;
+ set angle(double value);
+}

packages/flame/lib/src/effects/rotate_effect.dart

@@ -1,6 +1,8 @@
 import 'controllers/effect_controller.dart';
+import 'effect.dart';
+import 'effect_target.dart';
 import 'measurable_effect.dart';
-import 'transform2d_effect.dart';
+import 'provider_interfaces.dart';
 
 /// Rotate a component around its anchor.
 ///
@@ -16,7 +18,9 @@ import 'transform2d_effect.dart';
 /// This effect applies incremental changes to the component's angle, and
 /// requires that any other effect or update logic applied to the same component
 /// also used incremental updates.
-class RotateEffect extends Transform2DEffect implements MeasurableEffect {
+class RotateEffect extends Effect
+ with EffectTarget<AngleProvider>
+ implements MeasurableEffect {
  RotateEffect.by(double angle, EffectController controller)
  : _angle = angle,
  super(controller);

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

@@ -15,7 +15,8 @@ import 'camera_component.dart';
 /// The viewfinder contains the game point that is currently at the
 /// "cross-hairs" of the viewport ([position]), the [zoom] level, and the
 /// [angle] of rotation of the camera.
-class Viewfinder extends Component implements PositionProvider, ScaleProvider {
+class Viewfinder extends Component
+ implements AngleProvider, PositionProvider, ScaleProvider {
  /// Internal transform matrix used by the viewfinder.
  final Transform2D _transform = Transform2D();
 
@@ -47,7 +48,9 @@ class Viewfinder extends Component implements PositionProvider, ScaleProvider {
  /// Rotation angle of the game world, in radians.
  ///
  /// The rotation is around the axis that is perpendicular to the screen.
+ @override
  double get angle => -_transform.angle;
+ @override
  set angle(double value) => _transform.angle = -value;
 
  /// The point within the viewport that is considered the "logical center" of

packages/flame/test/experimental/viewfinder_test.dart

@@ -179,6 +179,23 @@ void main() {
  }
  },
  );
+
+ testWithFlameGame(
+ 'camera rotate effect',
+ (game) async {
+ final world = World()..addToParent(game);
+ final camera = CameraComponent(world: world)..addToParent(game);
+ camera.viewfinder.add(
+ RotateEffect.by(1, EffectController(duration: 1)),
+ );
+ await game.ready();
+
+ for (var t = 0.0; t < 1.0; t += 0.1) {
+ expect(camera.viewfinder.angle, closeTo(t, 1e-15));
+ game.update(0.1);
+ }
+ },
+ );
  });
 }