com.misaki.ao-volume/Editor/View/VolumeObjectView.cs

using UnityEditor;
using UnityEditor.IMGUI.Controls;
using UnityEngine;
using UnityEngine.UIElements;

namespace Misaki.AoVolume.Editor
{
    [CustomEditor(typeof(VolumeObject))]
    [CanEditMultipleObjects]
    public class VolumeObjectView : UnityEditor.Editor
    {
        [SerializeField]
        private VisualTreeAsset _viewAsset;

        private readonly BoxBoundsHandle _boundsHandle = new()
        {
            wireframeColor = Color.green,
            handleColor = Color.green
        };

        public override VisualElement CreateInspectorGUI()
        {
            if (_viewAsset == null)
            {
                return null;
            }

            var view = _viewAsset.Instantiate();
            view.dataSource = target;

            view.Q<Button>("force-update-button").clicked += () =>
            {
                var volumeObject = target as VolumeObject;
                volumeObject.ForceDataUpdate();
            };

            return view;
        }

        private void OnSceneGUI()
        {
            var volume = (VolumeObject)target;

            using (new Handles.DrawingScope(volume.transform.localToWorldMatrix))
            {
                _boundsHandle.center = Vector3.zero;
                _boundsHandle.size = volume.data.size;

                EditorGUI.BeginChangeCheck();
                _boundsHandle.DrawHandle();
                if (EditorGUI.EndChangeCheck())
                {
                    Undo.RecordObject(volume, string.Format("Change {0} Volume Size", target.name));
                    volume.data.size = _boundsHandle.size;
                }
            }
        }
    }
}