using UnityEngine;
using UnityEngine.UI;

namespace JCUnityLib.UI
{
    [ExecuteAlways]
    [RequireComponent(typeof(Image))]
    public class VernierCaliper : MonoBehaviour 
    {
        const string _SHADER_NAME = "JC/UI/VernierCaliper";
        RectTransform _rectTransform;
        Image _image;
        public float lineWidth = 5;  
        public float lineSpace = 10;
        public float lineHeight = 50;
        public Color lineColor = Color.black;

        void Update()
        {
            if (!_rectTransform) _rectTransform = GetComponent<RectTransform>();
            if (!_image) _image = GetComponent<Image>();
            if (_image.material == null || _image.material.shader.name != _SHADER_NAME)
                _image.material = new Material(Shader.Find(_SHADER_NAME));
            Material imageMaterial = _image.material;
            if (!imageMaterial) return;
            imageMaterial.SetFloat("_rectWidth", _rectTransform.rect.width);
            imageMaterial.SetFloat("_rectHeight", _rectTransform.rect.height);
            imageMaterial.SetFloat("_LineWidth", lineWidth);
            imageMaterial.SetFloat("_LineSpace", lineSpace);
            imageMaterial.SetFloat("_LineHeight", lineHeight);
            imageMaterial.SetColor("_LineColor", lineColor);
        }
    }
}