ProjectDDD/Packages/SLUnity/SLUI/SLUILayoutElement.cs

using Superlazy.UI;
using UnityEngine;
using UnityEngine.UI;

[ExecuteAlways]
public class SLUILayoutElement : MonoBehaviour
{
    public bool useCanvasSize = false;

    private Canvas canvas;
    private LayoutElement element;
    private SLUILayoutScale scale;

    private void Awake()
    {
        canvas = GetComponentInParent<Canvas>();
        if (TryGetComponent(out element) == false)
        {
            element = gameObject.AddComponent<LayoutElement>();
            element.hideFlags = HideFlags.HideAndDontSave;
        }

        scale = GetComponent<SLUILayoutScale>();
    }

    private void Update()
    {
        if (element == null || canvas == null) return;

        if (useCanvasSize)
        {
            element.preferredWidth = canvas.pixelRect.width / canvas.scaleFactor;
            element.preferredHeight = canvas.pixelRect.height / canvas.scaleFactor;
            if (scale)
            {
                scale.startSize = new Vector2(element.preferredWidth, element.preferredHeight);
            }
        }
    }
}