using UnityEngine;
using UnityEngine.UI;

[RequireComponent(typeof(RectTransform), typeof(TrailRenderer))]
public class ScreenSpaceTrail : MonoBehaviour
{
    private RectTransform rectTransform;
    private TrailRenderer trail;
    private Camera uiCamera;

    void Start()
    {
        rectTransform = GetComponent<RectTransform>();
        trail = GetComponent<TrailRenderer>();
        uiCamera = GetComponentInParent<Canvas>().worldCamera;
    }

    void Update()
    {
        UpdateTrailPosition();
    }

    void UpdateTrailPosition()
    {
        // 将UI坐标转换为世界坐标
        Vector3 screenPos = RectTransformUtility.WorldToScreenPoint(
            uiCamera,
            rectTransform.position);

        // 设置Z值在相机近裁剪面稍前方
        Vector3 worldPos = uiCamera.ScreenToWorldPoint(
            new Vector3(screenPos.x, screenPos.y, uiCamera.nearClipPlane + 0.1f));

        transform.position = worldPos;
    }

    public void ClearTrail()
    {
        trail.Clear();
    }
}