Fix: S1API OnTick Event Fails After Hot Reload

by Alex Johnson 47 views

If you're a developer working with the S1API in Schedule I and have encountered an issue where the S1API.GameTime.TimeManager.OnTick event stops firing after a hot reload, you're not alone. This article dives deep into the bug, its causes, and potential solutions. We'll explore the technical details in a way that's easy to understand, so you can get back to building your awesome mods!

Understanding the S1API OnTick Bug

The core problem lies in how the OnTick event is handled within the S1API, specifically in the context of hot reloads. In simple terms, a hot reload is when you return to the main menu and load a save again without closing the game entirely. The initial load (cold start) works perfectly fine – the OnTick event fires as expected, and your handlers (the code that reacts to the event) are triggered correctly. However, after a hot reload, the OnTick event mysteriously stops firing, leaving your handlers in the dark. This can be incredibly frustrating, especially when you've built functionality that relies on this event. Understanding the root cause is the first step towards a solution.

The Technical Details: Why OnTick Fails After Hot Reload

To understand why this happens, we need to delve into the technical aspects of the S1API and how it interacts with the game's time management system. The S1API.GameTime.TimeManager class is responsible for managing the OnTick event. This event is supposed to fire regularly, providing a heartbeat for your mods to synchronize with the game's passage of time. When the game initially loads, the TimeManager class hooks into the underlying ScheduleOne.GameTime.TimeManager.Instance (the game's time manager). This connection is established within the static constructor of the S1API.GameTime.TimeManager class. The critical issue is that this static constructor runs only once during the entire game process lifecycle. Therefore, it only sets up the OnTick event wiring for the first instance of ScheduleOne.GameTime.TimeManager.Instance. The problem arises because, in Schedule I, the ScheduleOne.GameTime.TimeManager.Instance is recreated every time the Main gameplay scene is reloaded (during a hot reload). This means that after returning to the main menu and loading a save again, a new instance of the game's time manager is created. However, the S1API's OnTick event is still wired to the old instance, which is no longer active. This disconnect is the heart of the bug – the event is firing on an object that no longer exists in the current scene, so no one hears it!

Reproduction Steps: Witnessing the OnTick Bug in Action

To see this bug in action, you can follow a simple set of reproduction steps. This will help you verify the issue and ensure that any fixes you implement are indeed working correctly. Here’s a step-by-step guide:

  1. Create a tiny test mod: This mod will simply subscribe to the OnTick event and log a message whenever it fires. This allows you to clearly see when the event is being triggered.

    using MelonLoader;
using S1API.GameTime;

public sealed class TickTesterMod : MelonMod
{
    public override void OnInitializeMelon()
    {
        MelonLogger.Msg("[TickTester] Initialized.");
        TimeManager.OnTick -= OnTick;
        TimeManager.OnTick += OnTick;
        MelonLogger.Msg("[TickTester] TimeManager.OnTick handler registered.");
    }

    private static void OnTick()
    {
        MelonLogger.Msg("[TickTester] OnTick fired.");
    }
}

  2. Start the game and load a save: Launch Schedule I and load any save game from the main menu. This will start the first gameplay session.

  3. Observe the OnTick event firing: Once in the gameplay scene, wait for a few in-game minutes. You should see the message [TickTester] OnTick fired. repeatedly appearing in your MelonLoader console log. This confirms that the OnTick event is working as expected in the initial session.

  4. Return to the main menu (hot reload): Press the Esc key to open the game menu and select “Quit to Main Menu.” Important: Do not close the game entirely. This simulates a hot reload.

  5. Load the same save again: From the main menu, load the same save game you used earlier. This will start the second gameplay session.

  6. Observe the OnTick event failing: Wait again for a few in-game minutes. This time, you will notice that no [TickTester] OnTick fired. messages appear in the console log. This clearly demonstrates that the OnTick event has stopped firing after the hot reload, even though your handler is still subscribed.

By following these steps, you can reliably reproduce the bug and test potential solutions. The key takeaway is that the OnTick event only works in the first gameplay session after the game starts, highlighting the issue with the static constructor and instance rebinding.

The Solution: Rebinding OnTick After Scene Loads

The key to fixing this issue lies in ensuring that the S1API.GameTime.TimeManager's OnTick event is re-wired to the correct ScheduleOne.GameTime.TimeManager.Instance whenever a new scene is loaded, particularly after a hot reload. There are a couple of ways to achieve this rebinding:

1. Scene-Loaded Hook

One approach is to use a scene-loaded hook. This involves subscribing to an event that fires whenever a new scene is loaded in the game. Within this hook, you can then re-establish the connection between the S1API's OnTick event and the current ScheduleOne.GameTime.TimeManager.Instance. This ensures that the event is always wired to the active time manager.

2. Lazy Check Before Access

Another method is to implement a lazy check before accessing the TimeManager.Instance. This means that instead of hooking the event only once in the static constructor, you would check if the ScheduleOne.GameTime.TimeManager.Instance has changed whenever you need to access the OnTick event. If it has changed, you would then rebind the event. This approach adds a small overhead to each access, but it guarantees that you are always using the correct instance.

Suggested Implementation

A practical implementation might involve creating a dedicated method within the S1API.GameTime.TimeManager class to handle the rebinding. This method would detach the existing OnTick handler and reattach it to the current ScheduleOne.GameTime.TimeManager.Instance. You could then call this method either from a scene-loaded hook or within the lazy check. Here’s a conceptual example:

public static class TimeManager
{
    public static Action OnTick = delegate { };

    private static void RebindOnTick()
    {
        // Detach existing handler (if any)
        S1GameTime.TimeManager.Instance.onTick -= (Action)(() => OnTick());

        // Attach handler to the current instance
        S1GameTime.TimeManager.Instance.onTick += (Action)(() => OnTick());
    }

    // Call RebindOnTick() from a scene-loaded hook or a lazy check
}

This is a simplified example, and the exact implementation might vary depending on the specific framework and game structure. However, the core principle remains the same: you need to ensure that the OnTick event is re-wired whenever the ScheduleOne.GameTime.TimeManager.Instance changes.

Conclusion: Keeping OnTick Ticking

The S1API.GameTime.TimeManager.OnTick bug is a common pitfall for mod developers working with Schedule I. By understanding the underlying cause – the static constructor and instance rebinding issue – you can effectively address the problem. Implementing a scene-loaded hook or a lazy check before access are viable solutions to ensure that your OnTick event continues to fire reliably, even after hot reloads. This allows you to build more robust and predictable mods for Schedule I.

For more information on game development and debugging, check out helpful resources like the Unity Documentation. This resource can provide additional insights into scene management and event handling, helping you become a more effective game developer. Remember, a little bit of understanding can go a long way in squashing bugs and building amazing experiences!