feat(ai): Add Pursue behavior from gdx-ai

examples/lib/main.dart

@@ -2,6 +2,7 @@ import 'package:dashbook/dashbook.dart';
 import 'package:flutter/material.dart';
 
 import 'stories/animations/animations.dart';
+import 'stories/behaviors/behaviors.dart';
 import 'stories/camera_and_viewport/camera_and_viewport.dart';
 import 'stories/collision_detection/collision_detection.dart';
 import 'stories/components/components.dart';
@@ -21,6 +22,7 @@ void main() async {
   );
 
   addAnimationStories(dashbook);
+  addBehaviorStories(dashbook);
   addCameraAndViewportStories(dashbook);
   addCollisionDetectionStories(dashbook);
   addComponentsStories(dashbook);

examples/lib/stories/behaviors/behaviors.dart

@@ -0,0 +1,15 @@
+import 'package:dashbook/dashbook.dart';
+import 'package:flame/game.dart';
+
+import '../../commons/commons.dart';
+import 'pursue_example.dart';
+
+void addBehaviorStories(Dashbook dashbook) {
+  dashbook.storiesOf('Behaviors')
+    .add(
+      'Pursue',
+      (_) => GameWidget(game: PursueExample()),
+      codeLink: baseLink('behaviors/pursue_example.dart'),
+      info: PursueExample.description,
+    );
+}

examples/lib/stories/behaviors/pursue_example.dart

@@ -0,0 +1,107 @@
+import 'dart:math';
+import 'dart:ui';
+
+import 'package:flame/components.dart';
+import 'package:flame/game.dart';
+import 'package:flame/steer.dart';
+
+class PursueExample extends FlameGame {
+  static const description = '''
+    In this example the red square (Predator) chases after blue circles (Prey)
+    using the Pursue behavior. Thin blue line shows the current predator's
+    velocity, and yellow line is its acceleration.
+  ''';
+
+  late Predator predator;
+
+  @override
+  Future<void> onLoad() async {
+    super.onLoad();
+    // camera.viewport = FixedResolutionViewport(Vector2(400, 800));
+    predator = Predator(position: Vector2(200, 400))
+      ..behavior = Pursue(maxPredictionTime: 3)
+      ..maxLinearSpeed = 100
+      ..maxLinearAcceleration = 50;
+    add(predator);
+    makePrey();
+  }
+
+  void makePrey() {
+    const tau = 2 * pi;
+    final random = Random();
+
+    final preyX = random.nextDouble() * 200 + 100.0;
+    final preyY = random.nextDouble() * 300 + 100.0;
+    final prey = Prey(
+      position: Vector2(preyX, preyY),
+      velocity: Vector2(0, 30)..rotate(random.nextDouble() * tau),
+    )..maxLinearSpeed = 30;
+    add(prey);
+    predator.target = prey;
+  }
+}
+
+class Prey extends SteerableComponent {
+  Prey({Vector2? position, Vector2? velocity})
+      : super(position: position, velocity: velocity, size: Vector2.all(20));
+
+  final bgPaint = Paint()..color = const Color(0xff74c3ff);
+
+  @override
+  void render(Canvas canvas) {
+    final radius = width / 2;
+    canvas.drawCircle(Offset(radius, radius), radius, bgPaint);
+  }
+}
+
+class Predator extends SteerableComponent with HasGameRef<PursueExample> {
+  Predator({Vector2? position})
+      : super(size: Vector2.all(20), position: position);
+
+  final bgPaint = Paint()..color = const Color(0xffe21515);
+  final speedPaint = Paint()
+    ..color = const Color(0xff52a569)
+    ..style = PaintingStyle.stroke
+    ..strokeWidth = 1;
+  final accelerationPaint = Paint()
+    ..color = const Color(0xffe8bf28)
+    ..style = PaintingStyle.stroke
+    ..strokeWidth = 2;
+
+  Steerable? get target => (behavior! as Pursue).target;
+  set target(Steerable? target) {
+    (behavior! as Pursue).target = target;
+  }
+
+  @override
+  void render(Canvas canvas) {
+    // print(linearVelocity);
+    canvas.drawRect(Rect.fromLTWH(0, 0, width, height), bgPaint);
+    canvas.drawPath(
+      Path()
+        ..moveTo(width / 2, height / 2)
+        ..relativeLineTo(linearVelocity.x, linearVelocity.y),
+      speedPaint,
+    );
+    final acceleration = steering.linearAcceleration;
+    canvas.drawPath(
+      Path()
+        ..moveTo(width / 2, height / 2)
+        ..relativeLineTo(acceleration.x, acceleration.y),
+      accelerationPaint,
+    );
+  }
+
+  @override
+  void update(double dt) {
+    super.update(dt);
+    final prey = target;
+    if (prey != null) {
+      if (position.distanceToSquared(prey.position) < 64) {
+        (prey as SteerableComponent).removeFromParent();
+        target = null;
+        gameRef.makePrey();
+      }
+    }
+  }
+}

packages/flame/lib/components.dart

@@ -23,6 +23,7 @@ export 'src/components/sprite_animation_group_component.dart';
 export 'src/components/sprite_batch_component.dart';
 export 'src/components/sprite_component.dart';
 export 'src/components/sprite_group_component.dart';
+export 'src/components/steerable_component.dart';
 export 'src/components/text_box_component.dart';
 export 'src/components/text_component.dart';
 export 'src/components/timer_component.dart';

packages/flame/lib/src/ai/README.md

@@ -0,0 +1,186 @@
+
+Most of the code in this directory was ported from [gdxAI] project by libGDX, licensed under
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