Unity上からiOS端末の画面輝度を取得/設定

UIScreenBridge.cs

using System.Runtime.InteropServices;
using UnityEngine;

namespace iOSNative
{
    /// <summary>
    /// `UIScreen`のBridge
    /// </summary>
    /// <remarks>
    /// - https://developer.apple.com/documentation/uikit/uiscreen
    /// </remarks>
    public static class UIScreenBridge
    {
        /// <summary>
        /// 画面の輝度
        /// </summary>
        /// <remarks>
        /// NOTE: 
        ///  - 値は[0f~1f]の範囲
        ///  - iOS実機以外は常に1fを返す
        ///  - APIの性質からアプリ上で設定した輝度は端末がロックされるまで有効
        /// </remarks>
        public static float Brightness
        {
            get
            {
#if !UNITY_EDITOR && UNITY_IOS
                return GetBrightnessNative();
#else
                return 1f;
#endif
            }
            set
            {
                var val = Mathf.Clamp01(value);
#if !UNITY_EDITOR && UNITY_IOS
                SetBrightnessNative(val);
#endif
            }
        }

        #region P/Invoke

        [DllImport("__Internal", EntryPoint = "getBrightness")]
        static extern float GetBrightnessNative();

        [DllImport("__Internal", EntryPoint = "setBrightness")]
        static extern void SetBrightnessNative(float brightness);

        #endregion P/Invoke
    }
}

UIScreenBridge.mm

#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>

#ifdef __cplusplus
extern "C" {
#endif

// 画面の輝度の取得
// NOTE: 値は[0f~1f]の範囲
// ref: https://developer.apple.com/documentation/uikit/uiscreen/1617830-brightness?language=objc
float getBrightness() {
    return [[UIScreen mainScreen] brightness];
}

// 画面の輝度の設定
// NOTE: 値は[0f~1f]の範囲
// ref: https://developer.apple.com/documentation/uikit/uiscreen/1617830-brightness?language=objc
void setBrightness(float brightness) {
    [UIScreen mainScreen].brightness = brightness;
}

#ifdef __cplusplus
}
#endif