Custom Editor Scripting

Overview

Creation of custom Unity Editor tools, Inspector extensions, and Property Drawers. Accelerates development by building project-specific tooling and improving the authoring experience.

When to Use

•Use when Inspector is cluttered
•Use for level design tools
•Use for data validation
•Use for efficient asset management
•Use for debugging visualization

Editor Classes Hierarchy

Class	Base	Use Case
Editor	`ScriptableObject`	Custom Inspector for Components
EditorWindow	`ScriptableObject`	Floating/Dockable Tool Windows
PropertyDrawer	`GUIDrawer`	Custom UI for Serializable fields
AssetPostprocessor	`AssetPostprocessor`	Import pipeline automation
ScriptableWizard	`EditorWindow`	Multi-step setup wizards

Immediate Mode GUI (IMGUI)

code

┌─────────────────────────────────────────────────────────────┐
│                     EDITOR GUI STACK                        │
├─────────────────────────────────────────────────────────────┤
│                                                             │
│  EditorGUILayout (Auto-layout)                              │
│  ┌──────────────────────┐                                   │
│  │ BeginVertical()      │                                   │
│  │  LabelField          │                                   │
│  │  PropertyField       │                                   │
│  │  HelpBox             │                                   │
│  │ EndVertical()        │                                   │
│  └──────────────────────┘                                   │
│             │                                               │
│             ▼                                               │
│  SerializedObject / SerializedProperty                      │
│  ┌──────────────────────┐                                   │
│  │ Update()             │                                   │
│  │ FindProperty()       │                                   │
│  │ ApplyModifiedProperties()                                │
│  └──────────────────────┘                                   │
│                                                             │
└─────────────────────────────────────────────────────────────┘

Best Practices

•✅ Wrap code in #if UNITY_EDITOR
•✅ Use SerializedObject / SerializedProperty for Undo support
•✅ Use OnEnable / OnDisable for initialization
•✅ Use EditorGUILayout for automatic layout
•✅ Clean up resources (textures, handles) immediately
•❌ NEVER modify target directly (breaks Undo/Prefab)
•❌ NEVER usage GetComponent in OnGUI (performance)
•❌ NEVER put Editor scripts in runtime folders

Few-Shot Examples

Example 1: Custom Inspector

User: "Improve the Enemy inspector."

Agent:

csharp

#if UNITY_EDITOR
using UnityEditor;
using UnityEngine;

[CustomEditor(typeof(Enemy))]
public class EnemyEditor : Editor
{
    private SerializedProperty _healthProp;
    private SerializedProperty _attackProp;

    private void OnEnable()
    {
        _healthProp = serializedObject.FindProperty("_maxHealth");
        _attackProp = serializedObject.FindProperty("_attackDamage");
    }

    public override void OnInspectorGUI()
    {
        serializedObject.Update();

        EditorGUILayout.LabelField("Stats", EditorStyles.boldLabel);
        
        EditorGUILayout.PropertyField(_healthProp);
        if (_healthProp.intValue < 0)
        {
            EditorGUILayout.HelpBox("Health cannot be negative!", MessageType.Error);
        }

        EditorGUILayout.PropertyField(_attackProp);

        if (GUILayout.Button("Reset Stats"))
        {
            _healthProp.intValue = 100;
            _attackProp.floatValue = 10f;
        }

        serializedObject.ApplyModifiedProperties();
    }
}
#endif

Example 2: Simple Editor Window

User: "Tool to bulk rename objects."

Agent:

csharp

#if UNITY_EDITOR
using UnityEditor;
using UnityEngine;

public class BulkRenamer : EditorWindow
{
    private string _baseName = "Enemy";
    private int _startIndex = 1;

    [MenuItem("Tools/Bulk Renamer")]
    public static void ShowWindow()
    {
        GetWindow<BulkRenamer>("Renamer");
    }

    private void OnGUI()
    {
        GUILayout.Label("Bulk Rename Selected", EditorStyles.boldLabel);
        
        _baseName = EditorGUILayout.TextField("Base Name", _baseName);
        _startIndex = EditorGUILayout.IntField("Start Index", _startIndex);

        if (GUILayout.Button("Rename"))
        {
            RenameSelected();
        }
    }

    private void RenameSelected()
    {
        var selected = Selection.gameObjects;
        for (int i = 0; i < selected.Length; i++)
        {
            Undo.RecordObject(selected[i], "Bulk Rename");
            selected[i].name = $"{_baseName}_{_startIndex + i}";
        }
    }
}
#endif

Example 3: Property Drawer

User: "Draw a range as a min-max slider."

Agent:

csharp

#if UNITY_EDITOR
[CustomPropertyDrawer(typeof(MinMaxRangeAttribute))]
public class MinMaxRangeDrawer : PropertyDrawer
{
    public override void OnGUI(Rect position, SerializedProperty property, GUIContent label)
    {
        var minProp = property.FindPropertyRelative("min");
        var maxProp = property.FindPropertyRelative("max");
        
        float minVal = minProp.floatValue;
        float maxVal = maxProp.floatValue;
        
        EditorGUI.MinMaxSlider(position, label, ref minVal, ref maxVal, 0f, 100f);
        
        minProp.floatValue = minVal;
        maxProp.floatValue = maxVal;
    }
}
#endif

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