RokidXRUnity/Editor/InterfaceSupport/OptionalDrawer.cs

using UnityEngine;
using UnityEditor;
using Rokid.UXR.Interaction;

namespace Rokid.UXR.Editor
{
    /// <summary>
    /// Adds an [Optional] label in the inspector over any SerializedField with this attribute.
    /// </summary>
    [CustomPropertyDrawer(typeof(OptionalAttribute))]
    public class OptionalDrawer : DecoratorDrawer
    {
        private static readonly float HEADER_SIZE_AS_PERCENT = 0.25f;

        public override float GetHeight()
        {
            return base.GetHeight() * (1f + HEADER_SIZE_AS_PERCENT);
        }

        public override void OnGUI(Rect position)
        {
            position.y += GetHeight() * HEADER_SIZE_AS_PERCENT / (1f + HEADER_SIZE_AS_PERCENT);
            EditorGUI.LabelField(position, "[Optional]");
        }
    }
}