Main Scene Auto Loading

Main, initial, loader, boot, bootstrap - you name it.

Whenever you enter playmode this tool firstly loads the main scene, and only after that loads desired scene(s).

load.single.scene.mp4

load.multiple.scenes.mp4

For more details why you need this and how to implement it: https://forum.unity.com/threads/executing-first-scene-in-build-settings-when-pressing-play-button-in-editor.157502/

Features:

• Persist hierarchy state(selected and expanded objects) on entering/exiting playmode.
• Convinient settings UI located in ProjectSettings window.
• UPM support, simple install.
• Highly extendable for any project.

Dependencies:

• Unity 2019.4+ (uses SerializeReference attribute, docs)
• EditorCoroutines package, docs

Installation

Install via git url by adding this entry in your manifest.json

"com.sag.main-scene-auto-loading": "https://github.com/STARasGAMES/unity-main-scene-auto-loading.git#upm"

Or using PackageManager window:

1. copy this link https://github.com/STARasGAMES/unity-main-scene-auto-loading.git#upm,
2. open PackageManager window,
3. click + button in top-left corner,
4. select Add package from git URL,
5. in appeared field paste the link you copied before (https://github.com/STARasGAMES/unity-main-scene-auto-loading.git#upm).

How it works

After installing this package it will create Assets/MainSceneAutoLoadingSettings.asset asset. You can change settings by selecting this asset or by using ProjectSettings window.

MainSceneAutoLoader listens for play button click. When this happens it asks MainSceneProvider for main scene and sets the EditorSceneManager.playModeStartScene(docs) to received value. After that Unity directly loads specified scene by itself.

When main scene loaded MainSceneLoadedHandler receives notification with additional information about preveiously opened scenes, selected and expanded objects. This handler decides what to do with provided arguments. Default handler will load all previously loaded scenes.

MainSceneAutoLoader also listens for exiting playmode. It will notify PlaymodeExitedHandler when editor fully exited playmode. Default handler will restore previously opened scenes, selected and expanded objects.

Extending

For now, there are 3 ways to extend:

• IMainSceneProvider
• IMainSceneLoadedHandler
• IPlaymodeExitedHandler

Main thing to remember - all extended scripts should be in editor assemblies! e.g. under Editor folder or within editor .asmdef

IMainSceneProvider

Responsible for providing the main scene, that will be loaded first when entering playmode. It's quite simple:

public interface IMainSceneProvider
{
    SceneAsset Get();
}

To implement your own realization you just need to derive from this interface. Remember to place this script under Editor folder.

using SaG.MainSceneAutoLoading.MainSceneProviders;
using UnityEditor;
using UnityEngine;

public class Sample_MainSceneProvider : IMainSceneProvider
{
    [SerializeField]
    private bool _setting1;

    [SerializeField]
    private int _setting2;

    [SerializeField]
    private Object _setting3;

    public SceneAsset Get()
    {
        // implementation
        throw new System.NotImplementedException();
    }
}

And after that you could find your option in settings's dropdown:

Also, you could write custom property drawer if you'd like to remove setting's folding and provide additional information:

[CustomPropertyDrawer(typeof(Sample_MainSceneProvider))]
public class Sample_MainSceneProviderPropertyDrawer : PropertyDrawer
{
    private const int FieldsCount = 4;
    private const int FieldHeightSelf = 18;
    private const int FieldHeightTotal = 20;


    public override float GetPropertyHeight(SerializedProperty property, GUIContent label)
    {
        return FieldHeightTotal * FieldsCount;
    }

    public override void OnGUI(Rect position, SerializedProperty property, GUIContent label)
    {
        EditorGUI.indentLevel++;

        position.height = FieldHeightSelf;
        GUI.enabled = false;
        EditorGUI.LabelField(position, "Custom description");
        GUI.enabled = true;
        position.y += FieldHeightTotal;
        EditorGUI.PropertyField(position, property.FindPropertyRelative("_setting1"));
        position.y += FieldHeightTotal;
        EditorGUI.PropertyField(position, property.FindPropertyRelative("_setting2"));
        position.y += FieldHeightTotal;
        EditorGUI.PropertyField(position, property.FindPropertyRelative("_setting3"));

        EditorGUI.indentLevel--;
    }
}

IMainSceneLoadedHandler

The same as above, just implement this interface and you are good to go.

However, you could also create an in-scnene handler and combine with DelegateToInSceneImplementations option.

#if UNITY_EDITOR // this script should not be present in builds
using System.Collections;
using SaG.MainSceneAutoLoading;
using SaG.MainSceneAutoLoading.MainSceneLoadedHandlers;
using SaG.MainSceneAutoLoading.Utilities;
using UnityEngine;
using UnityEngine.SceneManagement;

public class InSceneMainSceneLoadedHandler : MonoBehaviour, IMainSceneLoadedHandler
{
    public void OnMainSceneLoaded(LoadMainSceneArgs args)
    {
        Debug.Log($"OnMainSceneLoaded! Now decide what to do with args.SceneSetups...");
        StartCoroutine(LoadDesiredScenes(args));
    }

    IEnumerator LoadDesiredScenes(LoadMainSceneArgs args)
    {
        yield return new WaitForSeconds(1f);
        foreach (var sceneSetup in args.SceneSetups)
        {
            SceneManager.LoadScene(sceneSetup.path, LoadSceneMode.Additive);
        }

        // call this to restore previously selected and expanded GameObjects 
        SceneHierarchyStateUtility.RestoreHierarchyState(args);
    }
}
#endif

IPlaymodeExitedHandler

Look at the default implementation: https://github.com/STARasGAMES/unity-main-scene-auto-loading/blob/main/Packages/SaG.MainSceneAutoLoading/Editor/PlaymodeExitedHandlers/RestoreSceneManagerSetup.cs