fix: Camera no longer "sticks" to boundary with BoundedPositionBehavior

packages/flame/lib/src/camera/behaviors/bounded_position_behavior.dart

@@ -74,18 +74,9 @@ class BoundedPositionBehavior extends Component {
     if (isValidPoint(currentPosition)) {
       _previousPosition.setFrom(currentPosition);
     } else {
-      var inBoundsPoint = _previousPosition;
-      var outOfBoundsPoint = currentPosition;
-      while (inBoundsPoint.taxicabDistanceTo(outOfBoundsPoint) > _precision) {
-        final newPoint = (inBoundsPoint + outOfBoundsPoint)..scale(0.5);
-        if (isValidPoint(newPoint)) {
-          inBoundsPoint = newPoint;
-        } else {
-          outOfBoundsPoint = newPoint;
-        }
-      }
-      _previousPosition.setFrom(inBoundsPoint);
-      _target!.position = inBoundsPoint;
+      final closestBoundaryPoint = _bounds.nearestPoint(currentPosition);
+      _previousPosition.setFrom(closestBoundaryPoint);
+      _target!.position = closestBoundaryPoint;
     }
   }
 }

packages/flame/lib/src/experimental/geometry/shapes/circle.dart

@@ -82,6 +82,16 @@ class Circle extends Shape {
       ..add(_center);
   }
 
+  @override
+  Vector2 nearestPoint(Vector2 point) {
+    if (_radius == 0) {
+      return _center;
+    }
+    final vectorToPoint = point - _center;
+    final distance = vectorToPoint.length;
+    return _center + vectorToPoint * (_radius / distance);
+  }
+
   @override
   String toString() => 'Circle([${_center.x}, ${_center.y}], $_radius)';
 }

packages/flame/lib/src/experimental/geometry/shapes/polygon.dart

@@ -215,6 +215,25 @@ class Polygon extends Shape {
     return bestVertex;
   }
 
+  @override
+  Vector2 nearestPoint(Vector2 point) {
+    final result = Vector2.zero();
+    var shortestDistance2 = double.infinity;
+    for (var i = 0; i < _vertices.length; i++) {
+      final vertex = _vertices[i];
+      final edge = _edges[i];
+      final dotProduct = (point - vertex).dot(edge);
+      final t = (dotProduct / edge.length2).clamp(-1.0, 0.0);
+      final edgePoint = vertex + edge * t;
+      final distance2 = (edgePoint - point).length2;
+      if (distance2 < shortestDistance2) {
+        shortestDistance2 = distance2;
+        result.setFrom(edgePoint);
+      }
+    }
+    return result;
+  }
+
   @override
   String toString() => 'Polygon($vertices)';
 }

packages/flame/lib/src/experimental/geometry/shapes/rectangle.dart

@@ -123,6 +123,13 @@ class Rectangle extends Shape {
     return Vector2(vx, vy);
   }
 
+  @override
+  Vector2 nearestPoint(Vector2 point) {
+    final xx = (point.x).clamp(_left, _right);
+    final yy = (point.y).clamp(_top, _bottom);
+    return Vector2(xx, yy);
+  }
+
   @override
   String toString() => 'Rectangle([$_left, $_top], [$_right, $_bottom])';
 }

packages/flame/lib/src/experimental/geometry/shapes/rounded_rectangle.dart

@@ -171,6 +171,24 @@ class RoundedRectangle extends Shape {
     return result;
   }
 
+  @override
+  Vector2 nearestPoint(Vector2 point) {
+    final xx = (point.x).clamp(_left, _right);
+    final yy = (point.y).clamp(_top, _bottom);
+    final result = Vector2(xx, yy);
+    if (containsPoint(result)) {
+      return result;
+    }
+    final center = result
+      ..setValues(
+        result.x <= _left + _radius ? _left + _radius : _right - _radius,
+        result.y <= _top + _radius ? _top + _radius : _bottom - _radius,
+      );
+    final vectorToPoint = point - center;
+    final distance = vectorToPoint.length;
+    return center..addScaled(vectorToPoint, _radius / distance);
+  }
+
   @override
   String toString() =>
       'RoundedRectangle([$_left, $_top], [$_right, $_bottom], $_radius)';

packages/flame/lib/src/experimental/geometry/shapes/shape.dart

@@ -82,4 +82,11 @@ abstract class Shape {
   ///
   /// This method is only used for convex shapes.
   Vector2 support(Vector2 direction);
+
+  /// Returns a point on the shape's boundary which is closest to the given
+  /// [externalPoint].
+  ///
+  /// The [externalPoint] must lie outside of the shape. If there are multiple
+  /// nearest points, any one can be returned.
+  Vector2 nearestPoint(Vector2 externalPoint);
 }

packages/flame/test/camera/behaviors/bounded_position_behavior_test.dart

@@ -26,7 +26,7 @@ void main() {
       expect(component.position, Vector2(0, 3));
       component.position = Vector2(-1, 2);
       game.update(0);
-      expect(component.position, Vector2(0, 3));
+      expect(component.position, Vector2(0, 2));
     });
 
     test('bad precision', () {

packages/flame/test/camera/camera_component_test.dart

@@ -150,8 +150,11 @@ void main() {
 
       camera.moveTo(Vector2(-20, 0), speed: 10);
       for (var i = 0; i < 20; i++) {
-        expect(camera.viewfinder.position, closeToVector(Vector2(0, 10), 0.5));
-        game.update(0.5);
+        expect(
+          camera.viewfinder.position,
+          closeToVector(Vector2(0, 10 - i * 0.45), 0.5),
+        );
+        game.update(0.1);
       }
 
       expect(

packages/flame/test/experimental/geometry/shapes/circle_test.dart

@@ -147,5 +147,21 @@ void main() {
         closeToVector(Vector2(2 - 20 / sqrt(5), 1 - 10 / sqrt(5))),
       );
     });
+
+    test('nearestPoint', () {
+      final circle = Circle(Vector2(1, 1), 1);
+      const a = 0.7071067811865475; // sqrt(1/2)
+      expect(circle.nearestPoint(Vector2(0, 0)), Vector2.all(1 - a));
+      expect(circle.nearestPoint(Vector2(1, 0)), Vector2(1, 0));
+      expect(circle.nearestPoint(Vector2(2, 0)), Vector2(1 + a, 1 - a));
+      expect(circle.nearestPoint(Vector2(2, 2)), Vector2(1 + a, 1 + a));
+    });
+
+    test('nearestPoint for zero-radius circle', () {
+      final circle = Circle(Vector2(3, 4), 0);
+      expect(circle.nearestPoint(Vector2(3, 4)), Vector2(3, 4));
+      expect(circle.nearestPoint(Vector2(5, 7)), Vector2(3, 4));
+      expect(circle.nearestPoint(Vector2(0, 0)), Vector2(3, 4));
+    });
   });
 }

packages/flame/test/experimental/geometry/shapes/polygon_test.dart

@@ -271,5 +271,29 @@ void main() {
       expect(result.edges, [z, z, z, z, z]);
       expect(result.isConvex, true);
     });
+
+    test('nearestPoint', () {
+      final polygon = Polygon([
+        Vector2(10, 10),
+        Vector2(20, 30),
+        Vector2(10, 40),
+        Vector2(40, 40),
+        Vector2(50, 0),
+      ]);
+
+      expect(polygon.nearestPoint(Vector2(0, 0)), Vector2(10, 10));
+      expect(
+        polygon.nearestPoint(Vector2(10, 0)),
+        Vector2(12.352941176470589, 9.411764705882353),
+      );
+      expect(polygon.nearestPoint(Vector2(60, 0)), Vector2(50, 0));
+      expect(polygon.nearestPoint(Vector2(10, 30)), Vector2(15, 35));
+      expect(polygon.nearestPoint(Vector2(30, 50)), Vector2(30, 40));
+      expect(polygon.nearestPoint(Vector2(50, 50)), Vector2(40, 40));
+      expect(
+        polygon.nearestPoint(Vector2(50, 20)),
+        Vector2(45.294117647058826, 18.823529411764707),
+      );
+    });
   });
 }

packages/flame/test/experimental/geometry/shapes/rectangle_test.dart

@@ -208,5 +208,20 @@ void main() {
       );
       expect(rectangle.support(Vector2(9, -200)), closeToVector(Vector2(9, 2)));
     });
+
+    test('nearestPoint', () {
+      final rectangle = Rectangle.fromLTRB(0, 0, 5, 4);
+
+      expect(rectangle.nearestPoint(Vector2(0, 0)), Vector2(0, 0));
+      expect(rectangle.nearestPoint(Vector2(1, -1)), Vector2(1, 0));
+      expect(rectangle.nearestPoint(Vector2(-1, -1)), Vector2(0, 0));
+      expect(rectangle.nearestPoint(Vector2(-3, 2)), Vector2(0, 2));
+      expect(rectangle.nearestPoint(Vector2(-3, 7)), Vector2(0, 4));
+      expect(rectangle.nearestPoint(Vector2(-3, 7)), Vector2(0, 4));
+      expect(rectangle.nearestPoint(Vector2(3, 7)), Vector2(3, 4));
+      expect(rectangle.nearestPoint(Vector2(7, 7)), Vector2(5, 4));
+      expect(rectangle.nearestPoint(Vector2(17, 1)), Vector2(5, 1));
+      expect(rectangle.nearestPoint(Vector2(8, -2)), Vector2(5, 0));
+    });
   });
 }

packages/flame/test/experimental/geometry/shapes/rounded_rectangle_test.dart

@@ -228,5 +228,27 @@ void main() {
         throwsUnimplementedError,
       );
     });
+
+    test('nearestPoint', () {
+      final rrect = RoundedRectangle.fromLTRBR(0, 0, 50, 30, 10);
+
+      expect(
+        rrect.nearestPoint(Vector2(0, 0)),
+        Vector2(2.9289321881345254, 2.9289321881345254),
+      );
+      expect(
+        rrect.nearestPoint(Vector2(0, -10)),
+        Vector2(5.52786404500042, 1.0557280900008408),
+      );
+      expect(rrect.nearestPoint(Vector2(10, -10)), Vector2(10, 0));
+      expect(rrect.nearestPoint(Vector2(30, -10)), Vector2(30, 0));
+      expect(
+        rrect.nearestPoint(Vector2(55, 5)),
+        Vector2(49.48683298050514, 6.83772233983162),
+      );
+      expect(rrect.nearestPoint(Vector2(60, 15)), Vector2(50, 15));
+      expect(rrect.nearestPoint(Vector2(20, 150)), Vector2(20, 30));
+      expect(rrect.nearestPoint(Vector2(100, 100)), Vector2(46, 28));
+    });
   });
 }