fix: Fix CircleShape.computeDistanceToOut and add some tests. (#100)

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Fixes #99.

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Co-authored-by: drrnbrns <dburns@example.com>

Author: drrnbrns

packages/forge2d/lib/src/collision/shapes/circle_shape.dart

@@ -55,11 +55,10 @@ class CircleShape extends Shape {
     int childIndex,
     Vector2 normalOut,
   ) {
-    final xfq = xf.q;
-    final centerX = xfq.cos * p.x - xfq.sin * p.y + xf.p.x;
-    final centerY = xfq.sin * p.x + xfq.cos * p.y + xf.p.y;
-    final dx = p.x - centerX;
-    final dy = p.y - centerY;
+    final q = xf.q;
+    final tp = xf.p;
+    final dx = -(q.cos * position.x - q.sin * position.y + tp.x - p.x);
+    final dy = -(q.sin * position.x + q.cos * position.y + tp.y - p.y);
     final d1 = sqrt(dx * dx + dy * dy);
     normalOut.x = dx * 1 / d1;
     normalOut.y = dy * 1 / d1;

packages/forge2d/test/collision/shapes/circle_shape_test.dart

@@ -23,5 +23,32 @@ void main() {
       expect(clonedCircleShape.radius, equals(radius));
       expect(clonedCircleShape.position, equals(position));
     });
+
+    test('Test computeDistanceToOut', () {
+      void checkDistance(
+        Transform tf,
+        Vector2 testPoint,
+        double expectedDistance,
+        Vector2 expectedNormal,
+      ) {
+        const radius = 3.0;
+        final position = Vector2(1.0, 2.0);
+        final circleShape = CircleShape(radius: radius, position: position);
+        final normal = Vector2.zero();
+        final distance =
+            circleShape.computeDistanceToOut(tf, testPoint, 0, normal);
+        expect(distance, closeTo(expectedDistance, 0.01));
+        expect(normal.x, closeTo(expectedNormal.x, 0.01));
+        expect(normal.y, closeTo(expectedNormal.y, 0.01));
+      }
+
+      final tfZero = Transform.zero();
+      checkDistance(tfZero, Vector2(10, 7), 7.3, Vector2(0.87, 0.49));
+      checkDistance(tfZero, Vector2(1, -5), 4.0, Vector2(0.0, -1.0));
+
+      final tf2 = Transform.zero()..setVec2Angle(Vector2(10, 10), 0.2);
+      checkDistance(tf2, Vector2(10, 7), 7.59, Vector2(0.89, 0.46));
+      checkDistance(tf2, Vector2(1, -5), 4.17, Vector2(0.06, -1.0));
+    });
   });
 }

packages/forge2d/test/collision/shapes/polygon_shape_test.dart

@@ -0,0 +1,61 @@
+import 'package:forge2d/forge2d.dart';
+import 'package:test/test.dart';
+
+void main() {
+  group('PolygonShape', () {
+    test('Test setAsBoxXY', () {
+      final polygonShape = PolygonShape()..setAsBoxXY(3, 4);
+      expect(
+        polygonShape.vertices,
+        equals([
+          Vector2(-3.0, -4.0),
+          Vector2(3.0, -4.0),
+          Vector2(3.0, 4.0),
+          Vector2(-3.0, 4.0),
+        ]),
+      );
+      expect(
+        polygonShape.normals,
+        equals([
+          Vector2(0.0, -1.0),
+          Vector2(1.0, 0.0),
+          Vector2(0.0, 1.0),
+          Vector2(-1.0, 0.0),
+        ]),
+      );
+    });
+
+    test('Test clone', () {
+      final polygonShape = PolygonShape()..setAsBoxXY(3, 4);
+      final clonedPolygonShape = polygonShape.clone() as PolygonShape;
+      expect(clonedPolygonShape.radius, equals(polygonShape.radius));
+      expect(clonedPolygonShape.vertices, equals(polygonShape.vertices));
+      expect(clonedPolygonShape.normals, equals(polygonShape.normals));
+    });
+
+    test('Test computeDistanceToOut', () {
+      void checkDistance(
+        Transform tf,
+        Vector2 testPoint,
+        double expectedDistance,
+        Vector2 expectedNormal,
+      ) {
+        final polygonShape = PolygonShape()..setAsBoxXY(3, 4);
+        final normal = Vector2.zero();
+        final distance =
+            polygonShape.computeDistanceToOut(tf, testPoint, 0, normal);
+        expect(distance, closeTo(expectedDistance, 0.01));
+        expect(normal.x, closeTo(expectedNormal.x, 0.01));
+        expect(normal.y, closeTo(expectedNormal.y, 0.01));
+      }
+
+      final tfZero = Transform.zero();
+      checkDistance(tfZero, Vector2(10, 7), 7.0, Vector2(1.0, 0.0));
+      checkDistance(tfZero, Vector2(1, -5), 1.0, Vector2(0.0, -1.0));
+
+      final tf2 = Transform.zero()..setVec2Angle(Vector2(10, 10), 0.2);
+      checkDistance(tf2, Vector2(10, 7), 8.2, Vector2(0.98, 0.2));
+      checkDistance(tf2, Vector2(1, -5), 1.1, Vector2(0.2, -0.98));
+    });
+  });
+}