Outline

using System.Collections.Generic;

namespace UnityEngine.UI.Extensions
{
    public class Outline : BaseVertexEffect
    {
        [SerializeField]
        private Color m_EffectColor = new Color(0f, 0f, 0f, 0.5f);

        [SerializeField]
        private bool m_Precise;

        [SerializeField]
        private Vector2 m_EffectDistance = new Vector2(1f, -1f);

        protected Outline()
        {
        }

#if UNITY_EDITOR
        protected override void OnValidate()
        {
            effectDistance = m_EffectDistance;
            base.OnValidate();
        }
#endif

        public Color effectColor
        {
            get { return m_EffectColor; }
            set
            {
                m_EffectColor = value;
                if (graphic != null)
                    graphic.SetVerticesDirty();
            }
        }

        public Vector2 effectDistance
        {
            get { return m_EffectDistance; }
            set
            {
                if (value.x > 600)
                    value.x = 600;
                if (value.x < -600)
                    value.x = -600;

                if (value.y > 600)
                    value.y = 600;
                if (value.y < -600)
                    value.y = -600;

                if (m_EffectDistance == value)
                    return;

                m_EffectDistance = value;

                if (graphic != null)
                    graphic.SetVerticesDirty();
            }
        }

        protected void ApplyOutline(List<UIVertex> verts, Color32 color, int num, float x, float y)
        {
            var count = verts.Count;
            var index = 0;

            for (int pos = (num - 1) * 4; index < count; index++, pos += num * 4)
            {
                if (pos >= verts.Count)
                    break;
                var first = verts[pos];
                var second = verts[pos + 1];
                var third = verts[pos + 2];
                var fourth = verts[pos + 3];

                first.color = color;
                second.color = color;
                third.color = color;
                fourth.color = color;
                first.position += new Vector3(x, y);
                second.position += new Vector3(x, y);
                third.position += new Vector3(x, y);
                fourth.position += new Vector3(x, y);

                verts.Insert(pos, first);
                verts.Insert(pos, second);
                verts.Insert(pos, third);
                verts.Insert(pos, fourth);
                pos += 4;
            }
        }

        public override void ModifyVertices(List<UIVertex> verts)
        {
            if (!IsActive())
                return;

            ApplyOutline(verts, effectColor, 1, effectDistance.x, effectDistance.y);
            ApplyOutline(verts, effectColor, 2, -effectDistance.x, -effectDistance.y);
            ApplyOutline(verts, effectColor, 3, -effectDistance.x, effectDistance.y);
            ApplyOutline(verts, effectColor, 4, effectDistance.x, -effectDistance.y);
            if (m_Precise)
            {
                ApplyOutline(verts, effectColor, 5, 0, -effectDistance.y);
                ApplyOutline(verts, effectColor, 6, 0, effectDistance.y);
                ApplyOutline(verts, effectColor, 7, -effectDistance.x, 0);
                ApplyOutline(verts, effectColor, 8, effectDistance.x, 0);
            }
        }
    }
}