How to detect a long hover in Godot with C#

While trying out the Godot Engine I wanted to implement a custom "long hover" event. The event is fired if the user hovers over a button for 3 seconds. The event shouldn't fire if the user stops hovering before the 3 seconds have ended.

The logic for the event emission is contained inside the MaybeEmitSuperHover method. I'm running MaybeEmitSuperHover() inside the _Process method to check if the button is still hovered on every single frame.

This is the class that is attached to the Button inside the Godot project.

using Godot;
using System.Threading;
using System.Threading.Tasks;

public class ButtonBehaviour : Button
{
    private CancellationTokenSource _cancellationTokenSource;

    [Signal]
    public delegate void SuperHover();

    private void MaybeEmitSuperHover()
    {
        var hasActiveTimer = _cancellationTokenSource != null;

        // (3.) Reset the timer if button isn't hovered
        if (!IsHovered())
        {
            if (hasActiveTimer)
            {
                _cancellationTokenSource.Cancel();
                _cancellationTokenSource = null;
            }

            return;
        }

        // (2.) Do nothing if there is an active timer while hovering
        if (hasActiveTimer) return;

        // (1.) Create a new Delayed Task (timer)
        _cancellationTokenSource = new CancellationTokenSource();
        Task.Delay(3000).ContinueWith(async (t) =>
        {
            GD.Print("SUPER HOVER");
            EmitSignal("SuperHover");
        }, _cancellationTokenSource.Token);
    }

    public override void _Process(float delta)
    {
        MaybeEmitSuperHover();
    }
}

MaybeEmitSuperHover() explained

The function is best read, block by block, from bottom to top. We detect if the user hovers over the button during the current frame with IsHovered.

(1.) Create a new Delayed Task (timer)

In this block we already know that the user is Hovering over the button and doesn't have an active timer. As we can't find an existing timer reference inside _cancellationTokenSource we create a new timer with Task.Delay(3000).ContinueWith(...) and store a reference in _cancellationTokenSource. This is necessary because we need _cancellationTokenSource to Cancel the timer later.

(2.) Do nothing if there is an active timer while hovering

We do nothing (early return) if the button is hovered but there is already an existing timer. This prevents that we create additional timers if there is already one running.

(3.) Reset the timer if button isn't hovered

If the button isn't hovered we generally don't want to do anything, except if there is a reference to the current timer inside _cancellationTokenSource. This means we need to cancel the timer and reset the reference because:

• If the timer hasn't elapsed yet but the user has stopped hovering, we don't want to fire the event. So we need to Cancel it prematurely.
• If the timer has elapsed we need to reset its reference to null so we can set a new one, once the user hovers again.

In this example we printed the appearance of the SuperHover event with:

GD.Print("SUPER HOVER")

In a real game you would probably emit a custom event. To emit the SuperHover event we first need register it and manually emit it:

// register the event
[Signal]
public delegate void SuperHover();

// emit the event
EmitSignal("SuperHover");

This way you can react to the event in another Class, Node or Scene.