Unity uGUI frame line

FrameView.cs

// This code is released under CC0 1.0 Universal (Public Domain Dedication).
// https://creativecommons.org/publicdomain/zero/1.0/

using UnityEngine;
using UnityEngine.UI;

namespace Rector.UI.Components
{
    public sealed class FrameView : Graphic
    {
        [SerializeField, Range(0, 100f)] float lineWidthVertical = 1f;
        [SerializeField, Range(0, 100f)] float lineWidthHorizontal = 1f;
        [SerializeField] bool uniform = true;

        protected override void OnPopulateMesh(VertexHelper vh)
        {
            var left = 0f;
            var right = 1f;
            var bottom = 0f;
            var top = 1f;

            var rectTrans = rectTransform;
            var pivot = rectTrans.pivot;
            var rect = rectTrans.rect;
            var w = rect.width;
            var h = rect.height;

            left -= pivot.x;
            right -= pivot.x;
            bottom -= pivot.y;
            top -= pivot.y;

            left *= w;
            right *= w;
            top *= h;
            bottom *= h;

            vh.Clear();
            var hor = uniform ? lineWidthVertical : lineWidthHorizontal;
            AddQuad(vh, new Vector2(left, bottom), new Vector2(left + hor, top), 0);
            AddQuad(vh, new Vector2(left + hor, bottom), new Vector2(right - hor, bottom + lineWidthVertical), 4);
            AddQuad(vh, new Vector2(right - hor, bottom), new Vector2(right, top), 8);
            AddQuad(vh, new Vector2(left + hor, top - lineWidthVertical), new Vector2(right - lineWidthVertical, top), 12);
        }

        void AddQuad(VertexHelper vh, Vector2 leftBottom, Vector2 rightTop, int offset)
        {
            var vert = UIVertex.simpleVert;
            vert.color = color;
            vert.position = leftBottom;
            vh.AddVert(vert);
            vert.position = new Vector2(rightTop.x, leftBottom.y);
            vh.AddVert(vert);
            vert.position = rightTop;
            vh.AddVert(vert);
            vert.position = new Vector2(leftBottom.x, rightTop.y);
            vh.AddVert(vert);
            vh.AddTriangle(0 + offset, 1 + offset, 2 + offset);
            vh.AddTriangle(2 + offset, 3 + offset, 0 + offset);
        }
    }
}