HelpBoxAttribute.cs

using System;
using UnityEngine;
#if UNITY_EDITOR
using UnityEditor;
#endif

/// <summary>
/// ヘルプボックスの種類
/// </summary>
public enum HelpBoxType
{ 
    /// <summary>
    /// 通常
    /// </summary>
    None,

    /// <summary>
    /// 情報
    /// </summary>
    Info,

    /// <summary>
    /// 警告
    /// </summary>
    Warning,

    /// <summary>
    /// エラー
    /// </summary>
    Error,
}

/// <summary>
/// Inspector ビューに HelpBox を表示します
/// </summary>
/// <example>
/// <code>
/// [HelpBox( "通常メッセージ",   HelpBoxType.None,    0 )]\n
/// [HelpBox( "情報メッセージ",   HelpBoxType.Info,    1 )]\n
/// [HelpBox( "警告メッセージ",   HelpBoxType.Warning, 2 )]\n
/// [HelpBox( "エラーメッセージ", HelpBoxType.Error,   3 )]\n
/// </code>
/// </example>
[AttributeUsage( AttributeTargets.Field, Inherited = true, AllowMultiple = true )]
public sealed class HelpBoxAttribute : PropertyAttribute
{
    /// <summary>
    /// 表示するメッセージ
    /// </summary>
    public string Message;

    /// <summary>
    /// メッセージのタイプ
    /// </summary>
    public HelpBoxType Type;

    /// <summary>
    /// コンストラクタ
    /// </summary>
    /// <param name="message">表示するメッセージ</param>
    /// <param name="type">メッセージのタイプ</param>
    /// <param name="order">表示順位</param>
    public HelpBoxAttribute( string message, HelpBoxType type = HelpBoxType.None, int order = 0 )
    {
        Message     = message;
        Type        = type;
        this.order  = order;
    }
}

#if UNITY_EDITOR
[CustomPropertyDrawer( typeof( HelpBoxAttribute ) )]
public sealed class HelpBoxDrawer : DecoratorDrawer
{
    private HelpBoxAttribute HelpBoxAttribute { get { return attribute as HelpBoxAttribute; } }

    public override void OnGUI( Rect position )
    {
        var helpBoxPosition = EditorGUI.IndentedRect( position );
        helpBoxPosition.height = GetHelpBoxHeight();

        EditorGUI.HelpBox( helpBoxPosition, HelpBoxAttribute.Message, GetMessageType( HelpBoxAttribute.Type ) );
    }
    
    public override float GetHeight()
    {
        return GetHelpBoxHeight();
    }

    public MessageType GetMessageType( HelpBoxType type )
    {
        switch ( type )
        {
            case HelpBoxType.Error:     return MessageType.Error;
            case HelpBoxType.Info:      return MessageType.Info;
            case HelpBoxType.None:      return MessageType.None;
            case HelpBoxType.Warning:   return MessageType.Warning;
        }
        return 0;
    }

    public float GetHelpBoxHeight()
    {
        var style   = new GUIStyle( "HelpBox" );
        var content = new GUIContent( HelpBoxAttribute.Message );
        return Mathf.Max( style.CalcHeight( content, Screen.width - ( HelpBoxAttribute.Type != HelpBoxType.None ? 53 : 21) ), 40);
    }
}
#endif