disable mouse polling when window is inactive

KavTest/Engines/InputEngine.cs

@@ -13,6 +13,13 @@ namespace KavTest.Engines
     )]
     public class InputEngine : Engine
     {
+        private Game Game { get; }
+
+        public InputEngine(Game game)
+        {
+            Game = game;
+        }
+
         public override void Update(double dt)
         {
             var keyboardState = Keyboard.GetState();
@@ -38,6 +45,8 @@ namespace KavTest.Engines
                 SendMessage(new MoveCameraMessage(new Vector3(5, 0, 0)));
             }
 
+            if (Game.IsActive)
+            {
                 if (SomeComponent<CameraComponent>())
                 {
                     var cameraEntity = ReadEntity<CameraComponent>();
@@ -45,4 +54,5 @@ namespace KavTest.Engines
                 }
             }
         }
+    }
 }

KavTest/KavTestGame.cs

@@ -50,7 +50,7 @@ namespace KavTest
                 Smuggler.Importer.ImportGLB(GraphicsDevice, File.OpenRead("Content/rustysphere.glb"))
             );
 
-            WorldBuilder.AddEngine(new InputEngine());
+            WorldBuilder.AddEngine(new InputEngine(this));
             WorldBuilder.AddEngine(new AngularVelocityEngine());
             WorldBuilder.AddEngine(new MotionEngine());
             WorldBuilder.AddEngine(new CameraEngine());