Artem SolidAlloy

Unity hotswapping notes

Unity has built-in support for hotswapping, which is a huge productivity booster. This feature works not only with graphics assets like bitmaps and meshes, but also with code: if you edit the source and save it, the editor will save the state of the running game, compile and load the new code, then load the saved state and continue where it left off. Unfortunately, this feature is very easy to break, and most available 3rd party plugins have little regard for it.

It looks like there’s a lot of confusion about hotswapping in Unity, and many developers are not even aware of its existence – which is no wonder if their only experience is seeing lots of errors on the console when they forget to stop the game before recompiling... This document is an attempt to clear up some of this confusion.

Nota bene, I’m not a Unity developer, so everything below is based on blog posts and experimentation. Corrections are most welcome!

	/* MIT License

	Copyright (c) 2022 David Tattersall

	Permission is hereby granted, free of charge, to any person obtaining a copy
	of this software and associated documentation files (the "Software"), to deal
	in the Software without restriction, including without limitation the rights
	to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
	copies of the Software, and to permit persons to whom the Software is
	furnished to do so, subject to the following conditions:

	static Lifecycle() => Debug.Log(Prefix + "Static Constructor");
	[RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.SubsystemRegistration)] static void Subs() => Debug.Log(Prefix + "Subsystem Registration");
	[RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.AfterAssembliesLoaded)] static void AfterAsm() => Debug.Log(Prefix + "AfterAssembliesLoaded");
	[RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.BeforeSplashScreen)] static void BeforeSlash() => Debug.Log(Prefix + "Before Splash");
	[RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.BeforeSceneLoad)] static void BeforeScene() => Debug.Log(Prefix + "BeforeScene");
	private void Awake() => Debug.Log(Prefix + "Awake");
	private void OnEnable() => Debug.Log(Prefix + "OnEnable");
	[RuntimeInitializeOnLoadMethod(RuntimeInitializeLoadType.AfterSceneLoad)] static void AfterScene() => Debug.Log(Prefix + "AfterSceneLoad");
	[RuntimeInitializeOnLoadMethod] static void DefaultLog() => Debug.Log(Prefix + "RuntimeInit Default");
	void Start() => Debug

	// void* src = https://gist.github.com/andrew-raphael-lukasik/e4ae9b45a2c24672c0d1218f77235948
	using System.Collections.Generic;
	using System.Linq;

	using UnityEngine;
	using UnityEngine.UIElements;
	using UnityEngine.Localization;
	using UnityEngine.Localization.Settings;
	using UnityEngine.ResourceManagement.AsyncOperations;

	using System;
	using System.Collections.Concurrent;
	using System.Collections.Generic;
	using System.Reflection;
	using System.Runtime.InteropServices;
	using Unity.Collections.LowLevel.Unsafe;
	using UnityEditor;
	using UnityEditor.IMGUI.Controls;
	using UnityEngine;
	using Unity.Entities;

	using UnityEngine;
	using UnityEngine.UI;

	/// A concrete subclass of the Unity UI `Graphic` class that just skips drawing.
	/// Useful for providing a raycast target without actually drawing anything.
	public class NonDrawingGraphic : Graphic
	{
	public override void SetMaterialDirty() { return; }
	public override void SetVerticesDirty() { return; }

	using System;
	using System.Diagnostics.Contracts;
	using System.Runtime.CompilerServices;

	public static class SpanSplitExtensions
	{
	public ref struct Enumerable1<T> where T : IEquatable<T>
	{
	public Enumerable1(ReadOnlySpan<T> span, T separator)
	{

	using UnityEngine;
	using UnityEditor;
	using UnityEditorInternal;
	using UnityEngine.Events;
	using System.Reflection;


	namespace Test
	{
	[CustomPropertyDrawer (typeof (UnityEventBase), true)]

	Shader "UI/Fast-Default"
	{
	Properties
	{
	[PerRendererData] _MainTex ("Sprite Texture", 2D) = "white" {}
	_Color ("Tint", Color) = (1,1,1,1)
	}

	SubShader
	{

	using UnityEngine;
	using UnityEditor;
	using UnityEditorInternal;

	public static class ReorderableListUtility {

	public static ReorderableList GetListWithFoldout(SerializedObject serializedObject, SerializedProperty property, bool draggable, bool displayHeader, bool displayAddButton, bool displayRemoveButton) {
	var list = new ReorderableList(serializedObject, property, draggable, displayHeader, displayAddButton, displayRemoveButton);

	list.drawHeaderCallback = (Rect rect) => {

Artem SolidAlloy

Unity hotswapping notes

The basic flow of hotswapping