fix: Auto-resize SpriteComponent on sprite change

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

@@ -15,12 +15,46 @@ export '../sprite.dart';
 class SpriteComponent extends PositionComponent
  with HasPaint
  implements SizeProvider {
+ /// When set to true, the component is auto-resized to match the
+ /// size of underlying sprite.
+ late bool _autoResize;
+
+ /// Returns current value of auto resize flag.
+ bool get autoResize => _autoResize;
+
+ /// Sets the given value of autoResize flag. Will update the [size]
+ /// to fit srcSize of [sprite] if set to true.
+ set autoResize(bool value) {
+ _autoResize = value;
+ if (value) {
+ size.setFrom(sprite?.srcSize ?? Vector2.zero());
+ }
+ }
+
  /// The [sprite] to be rendered by this component.
- Sprite? sprite;
+ Sprite? _sprite;
+
+ /// Returns the current sprite rendered by this component.
+ Sprite? get sprite => _sprite;
+
+ /// Sets the given sprite as the new [sprite] of this component.
+ /// Will update the size if [autoResize] is set to true.
+ set sprite(Sprite? value) {
+ _sprite = value;
+
+ if (_autoResize) {
+ if (value != null) {
+ size.setFrom(value.srcSize);
+ } else {
+ size.setZero();
+ }
+ }
+ }
 
  /// Creates a component with an empty sprite which can be set later
  SpriteComponent({
- this.sprite,
+ Sprite? sprite,
+ bool? autoResize,
  Paint? paint,
  super.position,
  Vector2? size,
@@ -30,9 +64,14 @@ class SpriteComponent extends PositionComponent
  super.anchor,
  super.children,
  super.priority,
- }) : super(
- size: size ?? sprite?.srcSize,
- ) {
+ }) : assert(
+ (size == null && (autoResize ?? true)) ||
+ (size != null && !(autoResize ?? false)),
+ '''If size is set, autoResize should be false or size should be null when autoResize is true.''',
+ ),
+ _autoResize = autoResize ?? size == null,
+ _sprite = sprite,
+ super(size: size ?? sprite?.srcSize) {
  if (paint != null) {
  this.paint = paint;
  }
@@ -42,6 +81,7 @@ class SpriteComponent extends PositionComponent
  Image image, {
  Vector2? srcPosition,
  Vector2? srcSize,
+ bool? autoResize,
  Paint? paint,
  Vector2? position,
  Vector2? size,
@@ -56,6 +96,7 @@ class SpriteComponent extends PositionComponent
  srcPosition: srcPosition,
  srcSize: srcSize,
  ),
+ autoResize: autoResize,
  paint: paint,
  position: position,
  size: size ?? srcSize ?? image.size,

packages/flame/test/components/sprite_component_test.dart

@@ -1,6 +1,6 @@
 import 'package:flame/components.dart';
 import 'package:flame_test/flame_test.dart';
-import 'package:test/test.dart';
+import 'package:flutter_test/flutter_test.dart';
 
 Future<void> main() async {
  final image = await generateImage();
@@ -37,4 +37,34 @@ Future<void> main() async {
  expect(component6.size, Vector2(2, 2));
  });
  });
+
+ group('SpriteComponent.autoResize', () {
+ test('mutual exclusive with size while construction', () {
+ expect(
+ () => SpriteComponent(autoResize: true, size: Vector2.all(2)),
+ throwsAssertionError,
+ );
+
+ expect(() => SpriteComponent(autoResize: false), throwsAssertionError);
+ });
+
+ test('default value set correctly when not provided explicitly', () {
+ final component1 = SpriteComponent();
+ final component2 = SpriteComponent(size: Vector2.all(2));
+
+ expect(component1.autoResize, true);
+ expect(component2.autoResize, false);
+ });
+
+ test('resizes on sprite change', () {
+ final sprite1 = Sprite(image);
+ final sprite2 = Sprite(image, srcSize: Vector2.all(13));
+
+ final component = SpriteComponent()..sprite = sprite1;
+ expect(component.size, sprite1.srcSize);
+
+ component.sprite = sprite2;
+ expect(component.size, sprite2.srcSize);
+ });
+ });
 }