RichTextAreaAttribute #unity

RichTextAreaAttribute.cs

using System;
using UnityEngine;
using Sirenix.OdinInspector.Editor;
using UnityEditor;

[AttributeUsage(AttributeTargets.Field | AttributeTargets.Property)]
public class RichTextAreaAttribute : Attribute
{
    public bool ShowHelp { get; private set; }
    public RichTextAreaAttribute()
    {
        ShowHelp = false;
    }

    public RichTextAreaAttribute(bool showHelp)
    {
        ShowHelp = showHelp;
    }
}

public class RichTextAreaAttributeDrawer : OdinAttributeDrawer<RichTextAreaAttribute, string>
{
    protected override void DrawPropertyLayout(GUIContent label)
    {
        GUIStyle style = new GUIStyle(GUI.skin.textArea);
        style.richText = true;

        if (this.Attribute.ShowHelp && GUILayout.Button("Rich Text Help"))
        {
            Application.OpenURL("http://digitalnativestudios.com/textmeshpro/docs/rich-text/");
        }
        EditorGUILayout.PrefixLabel("Text");
        ValueEntry.SmartValue = EditorGUILayout.TextArea(ValueEntry.SmartValue, style);
    }
}