PositionViewer/Assets/Draw/DrawText.cs

using System.Collections.Generic;
using System.Linq;
using UnityEngine;
using UnityEngine.UI;

public class DrawText : DrawShape
{
    private RectTransform rectTransform_;

    private Vector3[] lineCorners_;

    // Start and end vertices (in absolute coordinates)
    private readonly List<Vector2> _vertices = new List<Vector2>(2);

    private void Awake()
    {
        rectTransform_ = GetComponent<RectTransform>();
        Debug.Log("DrawText awake");
        lineCorners_ = new Vector3[4];
        // 2 вершины будут рассчитываться, другие 2 получаться
        lineCorners_[1] = new Vector3();
        lineCorners_[3] = new Vector3();
    }

    public override void StartDraw(Vector2 position)
    {
        _vertices.Add(position);
        _vertices.Add(position);
    }
    public override void StopDraw(Vector2 position)
    {
        Image image = GetComponent<Image>();
        image.enabled = false;
    }
    public override void UpdateShape(Vector2 newPosition)
    {
        _vertices[_vertices.Count - 1] = newPosition;

        rectTransform_.sizeDelta = new Vector2(Mathf.Abs(_vertices[0].x - _vertices[1].x), Mathf.Abs(_vertices[0].y - _vertices[1].y));
        rectTransform_.transform.position = new Vector2(Mathf.Min(_vertices[0].x, _vertices[1].x), Mathf.Min(_vertices[0].y, _vertices[1].y));
    }

    public override void Clear()
    {
    }
}