Godot Signals (C#)

Godot 4.6 C# Signal Patterns

1. Built-in Signals

Connect in the editor or in code. Disconnect on cleanup to avoid leaks.

button.Pressed += OnButtonPressed;   // connect
button.Pressed -= OnButtonPressed;   // disconnect

2. Custom Signals

[Signal]
public delegate void HealthChangedEventHandler(int newHealth);

Godot 4.6 generates EmitSignalHealthChanged() from the delegate name. Connect from another node with player.HealthChanged += OnHealthChanged;.

3. Signal vs Direct Call

• Signals for loose coupling — UI reacting to game events, decoupled observers.
• Direct calls for tight coupling — coordinator calling controller methods.

CrystalMagica uses direct calls within the coordinator pattern and Rx for cross-system events.

4. Signal Bus Singleton

An AutoLoad node that centralizes game-wide events. Avoids deep signal chains through the scene tree.

public partial class SignalBus : Node
{
    [Signal]
    public delegate void GamePausedEventHandler(bool paused);
    public static SignalBus Instance { get; private set; }
    public override void _Ready() => Instance = this;
}

Use sparingly. Too many signals on one bus becomes spaghetti.

5. Async Signal Awaiting

await ToSignal(animPlayer, AnimationPlayer.SignalName.AnimationFinished);

Useful for cutscenes, animation sequences, and one-shot waits.

6. Rx Integration

CrystalMagica uses System.Reactive Subject<T> instead of Godot signals for ViewModel-to-View communication.

// In RemoteCharacterVM
public Subject<CharacterAction> Updates { get; } = new();
Updates.OnNext(new CharacterAction.Move(position));

// In View — subscribe
_vm.Updates
    .OfType<CharacterAction.Move>()
    .Subscribe(action => MoveSprite(action.Position));

Why Rx over signals:

• Full type safety (no string-based signal names)
• Composability — Select, OfType, CombineLatest, Throttle
• Familiar .NET pattern for C# developers

7. Thread Safety

Signals fire on the thread that emits them. If OnNext is called from the main thread (_Process drain loop), subscribers run on main thread. Never emit signals or call OnNext from a background thread if subscribers touch nodes — Godot scene tree access is main-thread-only.