[HOWTO] How To: Use Corgi / TopDown Engine MMSceneLoadingManager

[Tony Li]

If you're using More Mountains' Corgi Engine or TopDown Engine and want to use its MMSceneLoadingManager instead of the Pixel Crusher save system's StandardSceneTransitionManager:

• Untick the Save System component's Save Current Scene checkbox.
• If you're using MMSceneLoadingManager/LoadingSceneManager to load a scene on start, make a subclass and override the LoadAsynchronously() coroutine. At the beginning of the coroutine, call:

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  PixelCrushers.SaveSystem.RecordSavedGameData();
  PixelCrushers.SaveSystem.BeforeSceneChange();

  At the end of the coroutine, call:

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  PixelCrushers.SaveSystem.ApplySavedGameData();

• If you're calling LoadingSceneManager.LoadScene manually, you'll need to call

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  PixelCrushers.SaveSystem.RecordSavedGameData();
  PixelCrushers.SaveSystem.BeforeSceneChange();

  before calling LoadingSceneManager.LoadScene. Also add a script that hooks into SceneManager.sceneLoaded. Example:

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  using UnityEngine;
  using UnityEngine.SceneManagement;
  public class ApplySaveDataOnSceneLoad : MonoBehaviour
  {
      void Awake() { SceneManager.sceneLoaded += OnLoaded; }
      void OnLoaded(Scene scene, LoadSceneMode mode)
      {
          PixelCrushers.SaveSystem.ApplySavedGameData();
      }
  }

The Pixel Crushers/Common/Third Party Support/TopDown Engine Support package folder contains a prewritten subclass for you. In your LoadingScreen scene, replace the MMLoadingSceneManager component with your subclass. You can replace it in-place.

[Peter Drake]

I'm using MM's FinishLevel class, so I'm trying to apply this.

I created a subclass of FinishLevel to attach to my level exit GameObject:

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public class FinishLevelUsingPixelCrusherSaveSystem : FinishLevel
{
    /// <summary>
    /// Loads the next level
    /// </summary>
    public override void GoToNextLevel()
    {
        if (LevelManager.HasInstance)
        {
            LevelManager.Instance.GotoLevel(LevelName);
        }
        else
        {
            MMSceneLoadingManagerUsingPixelCrusherSaveSystem.LoadScene(LevelName); // This line is different
        }
    }
}

The new class I'm calling LoadScene on there is:

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public class MMSceneLoadingManagerUsingPixelCrusherSaveSystem :  MMSceneLoadingManager
{
    protected override IEnumerator LoadAsynchronously()
    {
        PixelCrushers.SaveSystem.RecordSavedGameData();
        PixelCrushers.SaveSystem.BeforeSceneChange();
        yield return base.LoadAsynchronously();
    }
}

(Is that the right way to call a superclass method in an IEnumerator?)

Can you elaborate on what you mean by "hooks into SceneManager.sceneLoaded"? Do you just mean that I have to attach this script to any GameObject in the scene being loaded?

Apologies for my ignorance. The number of things that have to be glued together to produce a Unity game can be overwhelming.

[Tony Li]

Hi,

You're absolutely right. Putting together a complete game is a big undertaking with a lot of moving parts. It's just a matter of tackling it piece by piece. Your subclasses looks perfect.

In your loading screen scene, remember to replace the MMSceneLoadingManager with your custom subclass.

[Peter Drake]

I hammered on this for a while, but I kept having to create subclasses of MM classes, which smelled bad, OOP-wise.

I think I found a simpler solution. Simply subclass MM's FinishLevel:

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using MoreMountains.Tools;
using MoreMountains.TopDownEngine;

public class FinishLevelUsingPixelCrusherSaveSystem : FinishLevel
{
    /// <summary>
    /// Loads the next level
    /// </summary>
    public override void GoToNextLevel()
    {
        PixelCrushers.SaveSystem.RecordSavedGameData();
        PixelCrushers.SaveSystem.BeforeSceneChange();
        if (LevelManager.HasInstance)
        {
            LevelManager.Instance.GotoLevel(LevelName);
        }
        else
        {
            MMSceneLoadingManager.LoadScene(LevelName);
        }
        PixelCrushers.SaveSystem.ApplySavedGameData();
    }
}

This seems to work, in that the item in my inventory is still there when I leave and return to the scene. There is one catch: the capacity of the inventory has been reduced from 6 to 1 -- just enough to hold the one item I put in there.

Thoughts?

[Tony Li]

It's fine to subclass FinishLevel, except for two changes:

1. Don't call PixelCrushers.SaveSystem.ApplySavedGameData() in it. TDE loads asynchronously, which means the scene won't be loaded right away, so you shouldn't call ApplySavedGameData() right away.

2. You must subclass MMSceneLoadingManager and, in the LoadingScreen scene, replace MMSceneLoadingManager with your subclass. Since you're calling RecordSavedGameData() in your FinishLevel subclass, you can make your coroutine look like this instead:

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protected override IEnumerator LoadAsynchronously()
{
    yield return base.LoadAsynchronously();
    yield return new WaitForEndOfFrame(); // Let components in newly-loaded scene initialize themselves first. //[FIXED TYPO]
    PixelCrushers.SaveSystem.ApplySavedGameData();
}

[Peter Drake]

I'm getting an error message on that.

[Peter Drake]

Oh, I see. That has to be yield return new WaitForEndofFrame();

[Peter Drake]

Nope, the inventory still isn't returning properly. See before and after screenshots attached.

Screen Shot 2022-05-20 at 2.54.48 PM.png (132.24 KiB) Viewed 1848 times

Screen Shot 2022-05-20 at 2.55.13 PM.png (140.93 KiB) Viewed 1848 times

[Tony Li]

Hi,

Thanks for noting the typo. I fixed it in the code above.

For your InventoryEngineSaver components, make sure you've assigned a unique Key to each one (e.g., "MainInventory", "WeaponInventory", etc.). Also set the Player ID. If you're making a single player game, "Player1" is fine. And tick Save Across Scene Changes:

inventoryEngineSaver.png (21.19 KiB) Viewed 1845 times

[Peter Drake]

Okay, I did that.

Now when I return to the scene I do have six inventory slots ... but I don't have the item I picked up previously.