gaemstone/src/gaemstone.Client/Systems/FreeCameraController.cs

using System;
using System.Linq;
using System.Numerics;
using gaemstone.ECS;
using static gaemstone.Client.Components.CameraComponents;
using static gaemstone.Client.Components.InputComponents;
using static gaemstone.Components.TransformComponents;

namespace gaemstone.Client.Systems;

[Module]
[DependsOn<gaemstone.Client.Components.CameraComponents>]
[DependsOn<gaemstone.Client.Components.InputComponents>]
[DependsOn<gaemstone.Components.TransformComponents>]
public class FreeCameraController
{
	[Component]
	public struct CameraController
	{
		public float MouseSensitivity { get; set; }
	}

	[System]
	public static void UpdateCamera(
		Universe universe, TimeSpan delta,
		in Camera camera, ref GlobalTransform transform, ref CameraController controller)
	{
		var input    = universe.LookupByType<Input>();
		var mouse    = universe.LookupByType<Mouse>();
		var keyboard = universe.LookupByType<Keyboard>();
		if ((input == null) || (mouse == null) || (keyboard == null)) return;

		var module = universe.LookupByTypeOrThrow<FreeCameraController>();
		var capturedBy      = input.GetTargets<CursorCapturedBy>().FirstOrDefault();
		var inputCapturedBy = input.GetTargets<MouseInputCapturedBy>().FirstOrDefault();
		var isCaptured = (capturedBy != null);
		// If another system has the mouse captured, don't do anything here.
		if (isCaptured && (capturedBy != module)) return;

		var isMouseDown = ((inputCapturedBy == null) || (inputCapturedBy == module))
			           && mouse.LookupChild("Buttons/Right")?.Has<Active>() == true;
		if (isMouseDown != isCaptured) {
			if (isMouseDown)
				input.Add<CursorCapturedBy>(module);
			else {
				input.Remove<CursorCapturedBy>(module);
				input.Remove<InputCapturedBy>(module);
				input.Remove<MouseInputCapturedBy>(module);
			}
		}

		var mouseMovement = Vector2.Zero;
		if (isCaptured) {
			var raw = (Vector2?)mouse.LookupChild("Delta")?.GetOrThrow<RawValue2D>() ?? default;
			mouseMovement = raw * controller.MouseSensitivity * (float)delta.TotalSeconds;
		}

		if (camera.IsOrthographic) {
			transform *= Matrix4x4.CreateTranslation(-mouseMovement.X, -mouseMovement.Y, 0);
		} else {
			var shift = keyboard.LookupChild("ShiftLeft")?.Has<Active>() == true;
			var w = keyboard.LookupChild("W")?.Has<Active>() == true;
			var a = keyboard.LookupChild("A")?.Has<Active>() == true;
			var s = keyboard.LookupChild("S")?.Has<Active>() == true;
			var d = keyboard.LookupChild("D")?.Has<Active>() == true;

			var speed = (shift ? 12 : 4) * (float)delta.TotalSeconds;
			var forwardMovement = ((w ? -1 : 0) + (s ? 1 : 0)) * speed;
			var sideMovement    = ((a ? -1 : 0) + (d ? 1 : 0)) * speed;

			var curTranslation = new Vector3(transform.Value.M41, transform.Value.M42, transform.Value.M43);
			var yawRotation   = Matrix4x4.CreateRotationY(-mouseMovement.X / 100, curTranslation);
			var pitchRotation = Matrix4x4.CreateRotationX(-mouseMovement.Y / 100);
			var translation   = Matrix4x4.CreateTranslation(sideMovement, 0, forwardMovement);

			transform = translation * pitchRotation * transform * yawRotation;
		}
	}
}