using UnityEngine;
using UnityEngine.SceneManagement;
using UnityEditor;
using UnityEditor.Experimental.SceneManagement; 
 
[InitializeOnLoad]
class CustomPrefabEnvironment
{
    static CustomPrefabEnvironment()
    {
        // Uncomment this to dynamically create a plane when entering Prefab Mode
        PrefabStage.prefabStageOpened += OnPrefabStageOpened;
    }
 
    static void OnPrefabStageOpened(PrefabStage prefabStage)
    {
        Debug.Log("OnPrefabStageOpened     " + prefabStage.prefabAssetPath);
 
        // Get info from the PrefabStage
        var root = prefabStage.prefabContentsRoot;
        var scene = prefabStage.scene;
        GameObject sceneRootCanvas = null;

        if (root.GetComponent<Canvas>() == null)
            return;

        var sceneRootObjs = scene.GetRootGameObjects();
        for (int i = 0; i < sceneRootObjs.Length; i++)
        {
            var sceneRootObj = sceneRootObjs[i];
            if (sceneRootObj == root)
                continue;
            if (sceneRootObj.GetComponent<Canvas>())
            {
                sceneRootCanvas = sceneRootObj;
                break;
            }
        }

        if (sceneRootCanvas)
        {
            root.transform.SetParent(sceneRootCanvas.transform);

            GameObject obj = AssetDatabase.LoadAssetAtPath<GameObject>(prefabStage.prefabAssetPath);

            RectTransform rcTrans = root.GetComponent<RectTransform>();
            RectTransform srcRcTrans = obj.GetComponent<RectTransform>();

            rcTrans.localPosition = srcRcTrans.localPosition;
            rcTrans.localScale = srcRcTrans.localScale;
            rcTrans.localRotation = srcRcTrans.localRotation;
            rcTrans.pivot = srcRcTrans.pivot;
            rcTrans.anchorMin = srcRcTrans.anchorMin;
            rcTrans.anchorMax = srcRcTrans.anchorMax;
            rcTrans.offsetMax = srcRcTrans.offsetMax;
            rcTrans.offsetMin = srcRcTrans.offsetMin;
            rcTrans.anchoredPosition = srcRcTrans.anchoredPosition;
            rcTrans.anchoredPosition3D = srcRcTrans.anchoredPosition3D;
            rcTrans.sizeDelta = srcRcTrans.sizeDelta;  
        }
    }
}