GameScreen.cs

using System;
using System.Reflection;
using UnityEngine;

#if UNITY_EDITOR
using UnityEditor;
#endif

namespace Tonari.Unity
{
    public static class GameScreen
    {
#if UNITY_EDITOR
        private static Vector2 _sizeOfMainGameView;

        static GameScreen()
        {
            var type = Type.GetType("UnityEditor.GameView, UnityEditor");
            if (type != null)
            {
                var method = type.GetMethod("GetSizeOfMainGameView", BindingFlags.NonPublic | BindingFlags.Static);
                var getSizeOfMainGameView = Delegate.CreateDelegate(typeof(Func<Vector2>), method) as Func<Vector2>;

                if (getSizeOfMainGameView == null)
                    throw new InvalidOperationException("GetSizeOfMainGameViewを取得できません");

                _sizeOfMainGameView = getSizeOfMainGameView();
            }
        }
#endif

        public static Vector2 Size
        {
            get
            {
#if UNITY_EDITOR
                return _sizeOfMainGameView;
#else
                return new Vector2(Width, Height);
#endif
            }
        }

        public static float Width
        {
            get
            {
#if UNITY_EDITOR
                return _sizeOfMainGameView.x;
#else
                return Screen.width;
#endif
            }
        }

        public static float Height
        {
            get
            {
#if UNITY_EDITOR
                return _sizeOfMainGameView.y;
#else
                return Screen.height;
#endif
            }
        }
    }
}