fix: `Plunger`'s pull not correctly working on some devices (#321)

* fix: plunger's pull not correctly working on some devices

* fix: plunger's pull not correctly working on some devices

* fix: plunger's pull not correctly working on some devices

Co-authored-by: Tom Arra <tarra3@gmail.com>

packages/pinball_components/lib/src/components/plunger.dart

@@ -97,7 +97,7 @@ class Plunger extends BodyComponent with InitialPosition, Layered, ZIndex {
   void update(double dt) {
     // Ensure that we only pull or release when the time is greater than zero.
     if (_pullingDownTime > 0) {
-      _pullingDownTime -= dt;
+      _pullingDownTime -= PinballForge2DGame.clampDt(dt);
       if (_pullingDownTime <= 0) {
         release();
       } else {

packages/pinball_components/test/src/components/plunger_test.dart

@@ -141,7 +141,11 @@ void main() {
 
           expect(plunger.body.linearVelocity.y, isPositive);
 
-          await tester.pump(const Duration(seconds: 2));
+          // Call game update at 120 FPS, so that the plunger will act as if it
+          // was pulled for 2 seconds.
+          for (var i = 0.0; i < 2; i += 1 / 120) {
+            game.update(1 / 20);
+          }
 
           expect(plunger.body.linearVelocity.y, isZero);
         },

packages/pinball_flame/lib/src/pinball_forge2d_game.dart

@@ -24,7 +24,7 @@ class PinballForge2DGame extends FlameGame implements Forge2DGame {
   @override
   void update(double dt) {
     super.update(dt);
-    world.stepDt(min(dt, 1 / 60));
+    world.stepDt(clampDt(dt));
   }
 
   @override
@@ -41,4 +41,14 @@ class PinballForge2DGame extends FlameGame implements Forge2DGame {
   Vector2 worldToScreen(Vector2 position) {
     throw UnimplementedError();
   }
+
+  /// Clamp the [dt] in such a way that it would never exceed the minimal of
+  /// 1/60th of a second.
+  ///
+  /// Note: this is a static method because composing this class as a generic
+  /// on `BodyComponent` and mixins for that class will crash the Dart analyzer
+  /// server.
+  static double clampDt(double dt) {
+    return min(dt, 1 / 60);
+  }
 }

packages/pinball_flame/test/src/pinball_forge2d_game_test.dart

@@ -47,5 +47,17 @@ void main() {
         );
       },
     );
+
+    group('clampDt', () {
+      test('returns dt', () {
+        const dt = 0.0001;
+        expect(PinballForge2DGame.clampDt(dt), equals(dt));
+      });
+
+      test('returns result of 1/60 as dt is to high', () {
+        const dt = 1.0;
+        expect(PinballForge2DGame.clampDt(dt), equals(1 / 60));
+      });
+    });
   });
 }