GameHost HelloWorld! (first version).cs

namespace PataponGameHost.Systems
{
	public struct Character
	{
	}

	[RestrictToApplication(typeof(GameSimulationThreadingHost))]
	public class MoveCharacterSystem : AppSystem
	{
		private GameInputThreadingClient client;
		private EntitySet                characterSet;

		private System system;

		protected override void OnInit()
		{
			base.OnInit();

			client = new GameInputThreadingClient();
			characterSet = World.Mgr.GetEntities()
			                    .With<Character>()
			                    .With<Vector3>()
			                    .AsSet();
			
			system = new System(characterSet);

			for (var i = 0; i != 1_000_000; i++)
			{
				var ch = World.Mgr.CreateEntity();
				ch.Set(new Character());
				ch.Set(new Vector3());
			}
		}

		protected override void OnUpdate()
		{
			base.OnUpdate();

			var moveVector = new Vector2();
			using (client.SynchronizeThread())
			{
				var openTkBackend = client.Listener.worldCollection.GetOrCreate<OpenTkInputBackend>();
				if (openTkBackend.IsKeyDown(Key.Left))
					moveVector.X -= 1;
				if (openTkBackend.IsKeyDown(Key.Right))
					moveVector.X += 1;
				if (openTkBackend.IsKeyDown(Key.Down))
					moveVector.Y -= 1;
				if (openTkBackend.IsKeyDown(Key.Up))
					moveVector.Y += 1;
			}

			var dt = World.Mgr.Get<WorldTime>()[0].Delta;
			
			moveVector = Vector2.Normalize(moveVector) * dt;
			if (float.IsNaN(moveVector.X))
				moveVector = default;

			system.Update(new Vector3(moveVector, 0));
		}

		private class System : AEntitySystem<Vector3>
		{
			public System(EntitySet set) : base(set, new DefaultParallelRunner(Environment.ProcessorCount / 4))
			{
			}

			protected override void Update(Vector3 state, in Entity entity)
			{
				entity.Get<Vector3>() += state;
			}
		}
	}
}