#unitytips: HelpBox Attribute (with docs button)

HelpBoxAttribute.cs

using UnityEngine;
using System;

namespace Giacomelli.Framework
{
    public enum HelpBoxType
    {
        /// <summary>
        ///   <para>Neutral message.</para>
        /// </summary>
        None,
        /// <summary>
        ///   <para>Info message.</para>
        /// </summary>
        Info,
        /// <summary>
        ///   <para>Warning message.</para>
        /// </summary>
        Warning,
        /// <summary>
        ///   <para>Error message.</para>
        /// </summary>
        Error
    }

    [AttributeUsage(AttributeTargets.Field)]
    public class HelpBoxAttribute : PropertyAttribute
    {
        public HelpBoxAttribute(string text, string docsUrl = null, HelpBoxType type = HelpBoxType.Info)
        {
            Text = text;
            DocsUrl = docsUrl;
            Type = type;
        }

        public string Text { get; }
        public string DocsUrl { get; }
        public HelpBoxType Type { get; }
    }
}

HelpBoxDrawer.cs

using UnityEngine;
using UnityEditor;
using System;

namespace Giacomelli.Framework
{
    [CustomPropertyDrawer(typeof(HelpBoxAttribute))]
    public class HelpBoxDrawer : PropertyDrawer
    {
        const float XPadding = 30f;
        const float YPadding = 5f;
        const float DefaultHeight = 20f;
        const float DocsButtonHeight = 20f;
        float _height;
     
        public override void OnGUI(Rect position,
                                   SerializedProperty property,
                                   GUIContent label)
        {

            var attr = attribute as HelpBoxAttribute;
            CalculateHeight(attr);

            EditorGUI.PropertyField(position, property, label, true);

            position = new Rect(
                XPadding,
                position.y + EditorGUI.GetPropertyHeight(property, label, true) + YPadding,
                position.width - XPadding,
                _height);

            EditorGUI.HelpBox(position, attr.Text, (MessageType) attr.Type);

            if (!string.IsNullOrEmpty(attr.DocsUrl))
            {
                position = new Rect(
                    position.x + position.width - 40,
                    position.y + position.height - DocsButtonHeight,
                    40,
                    DocsButtonHeight);


                if(GUI.Button(position, "Docs"))
                {
                    if (attr.DocsUrl.StartsWith("http"))
                        Application.OpenURL(attr.DocsUrl);
                    else
                        Application.OpenURL($"https://docs.unity3d.com/ScriptReference/{attr.DocsUrl}");
                }
             }
        }

        public override float GetPropertyHeight(SerializedProperty property, GUIContent label)
        {
            return EditorGUI.GetPropertyHeight(property, label, true) + _height + 10;
        }

        void CalculateHeight(HelpBoxAttribute attr)
        {
            _height = (attr.Text.Split(new string[] { "\n" }, StringSplitOptions.RemoveEmptyEntries).Length + 1) * DefaultHeight;

            if (!string.IsNullOrEmpty(attr.DocsUrl))
                _height += DocsButtonHeight;
        }
    }
}

SampleComponent.cs

using Giacomelli.Framework;
using UnityEngine;

public class SampleComponent : MonoBehaviour
{
    [SerializeField]
    [HelpBox("Values are 0 for the primary button (often the left button), 1 for secondary button, and 2 for the middle button.", "Input.GetMouseButtonDown.html")]
    int _button;

    [SerializeField]
    [HelpBox("Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. esse cillum dolore eu fugiat nulla pariatur.", "http://diegogiacomelli.com.br/", HelpBoxType.Info)]
    string _infoSample;

    [SerializeField]
    [HelpBox("Warning sample HelpBox with docs button", "http://diegogiacomelli.com.br/unitytips-helpbox-attribute/", HelpBoxType.Warning)]
    string _warningSample;

    [SerializeField]
    [HelpBox("Error sample HelpBox with docs button", "http://diegogiacomelli.com.br/unitytips-helpbox-attribute/", HelpBoxType.Error)]
    string _errorSample;
}