CameraController.cs

namespace SpaceGame;

public partial class CameraController : Node
{
    public event Action ZoomChanged;

    [ExportGroup("Zoom")]
    [Export(PropertyHint.Range, "0.02, 0.16")]
    float zoomIncrementDefault = 0.02f;

    [Export(PropertyHint.Range, "0.01, 10")]
    float minZoom = 0.01f;

    [Export(PropertyHint.Range, "0.1, 10")]
    public float MaxZoom = 4.0f;

    [Export(PropertyHint.Range, "0.01, 1")]
    float smoothFactor = 0.25f;

    float zoomIncrement = 0.02f;
    float targetZoom;

    Vector2 prevZoom;
    Camera2D camera;

    public override void _Ready()
    {
        camera = GetParent<Camera2D>();

        // Make sure the camera zoom does not go past MinZoom
        // Note that a higher MinZoom value means the camera can zoom out more
        float maxZoom = Mathf.Max(camera.Zoom.X, minZoom);
        camera.Zoom = Vector2.One * maxZoom;

        // Set the initial target zoom value on game start
        targetZoom = camera.Zoom.X;
    }

    public override void _PhysicsProcess(double delta)
    {
        // Prevent zoom from becoming too fast when zooming out
        zoomIncrement = zoomIncrementDefault * camera.Zoom.X;

        // Lerp to the target zoom for a smooth effect
        prevZoom = camera.Zoom;
        camera.Zoom = camera.Zoom.Lerp(
            to: new Vector2(targetZoom, targetZoom), 
            weight: smoothFactor);

        if (prevZoom != camera.Zoom)
            ZoomChanged?.Invoke();
    }

    // Not sure if this should be done in _Input or _UnhandledInput
    public override void _UnhandledInput(InputEvent @event)
    {
        if (@event is InputEventMouseButton mouseButton)
            InputEventMouseButton(mouseButton);
    }

    void InputEventMouseButton(InputEventMouseButton @event)
    {
        HandleZoom(@event);
    }

    void HandleZoom(InputEventMouseButton @event)
    {
        // Not sure why or if this is required
        if (!@event.IsPressed())
            return;

        // Zoom in
        if (@event.ButtonIndex == MouseButton.WheelUp)
            targetZoom += zoomIncrement;

        // Zoom out
        if (@event.ButtonIndex == MouseButton.WheelDown)
            targetZoom -= zoomIncrement;

        // Clamp the zoom
        targetZoom = Mathf.Clamp(targetZoom, minZoom, MaxZoom);
    }
}