Shows empty game objects in the hierarchy

HierarchyEmptyObjectDisplay.cs

// MIT License
// 
// Copyright (c) 2020 Sabresaurus
// 
// 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:
// 
//  The above copyright notice and this permission notice shall be included in all
//  copies or substantial portions of the Software.
// 
//  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
//  SOFTWARE.

using UnityEditor;
using UnityEngine;

[InitializeOnLoad]
public static class HierarchyEmptyObjectDisplay
{
    static HierarchyEmptyObjectDisplay()
    {
        EditorApplication.hierarchyWindowItemOnGUI += OnHierarchyItemGUI;
    }

    private static void OnHierarchyItemGUI(int instanceID, Rect selectionRect)
    {
        GameObject gameObject = EditorUtility.InstanceIDToObject(instanceID) as GameObject;
        
        if (gameObject == null) return;
        
        Component[] components = gameObject.GetComponents<Component>();
        // Transform counts as a component, so an empty game object has exactly one component
        if (components.Length != 1) return;
        
        Rect drawRect = selectionRect;
        drawRect.xMax -= 2;
        drawRect.xMin = drawRect.xMax - 38;
        drawRect.height = 16;
        
        
        Color lastColor = GUI.contentColor;
        GUI.contentColor = Color.green;
        GUI.Label(drawRect, new GUIContent(), EditorStyles.helpBox);
        GUI.Label(drawRect, "Empty", EditorStyles.miniLabel);
        GUI.contentColor = lastColor;
    }
}