Using Handles to edit line segments

using UnityEngine;
using System.Collections;
using System.Collections.Generic;

public class SimpleLine : MonoBehaviour
{
    public List<Vector3> controlPoints;
}

.....

using UnityEngine;
using UnityEditor;
using System.Collections;
using System.Collections.Generic;

[CustomEditor(typeof(SimpleLine))]
public class SimpleLineEditor : Editor
{
    SimpleLine sl;
    private bool listenToControlId;

    private int[] controlIds;

    public void OnEnable()
    {
        sl = (SimpleLine)target;
    }

    public void OnSceneGUI()
    {

        if (sl == null || sl.controlPoints == null)
            return;

        Undo.RecordObject(target, "Move");

        Vector3 offset = sl.transform.position;
        offset.z = 0;

        Handles.color = Color.cyan;
        Handles.DrawLine(offset - Vector3.up * 10, offset + Vector3.up * 10);
        Handles.DrawLine(offset, offset + Vector3.right * 10);

        float scale = HandleUtility.GetHandleSize(sl.transform.position);
        float handleSize = 0.02f * scale;

        Vector3 lastPoint = Vector3.zero;

        if (Event.current.type == EventType.MouseDown)
            listenToControlId = true;

        if (controlIds == null || controlIds.Length != sl.controlPoints.Count)
            controlIds = new int[sl.controlPoints.Count];

        // point editor
        for (int i = 0; i < sl.controlPoints.Count; i++)
        {
            var point = sl.controlPoints[i];

            Handles.color = Color.yellow;


            point = Handles.FreeMoveHandle(point + offset, Quaternion.identity, handleSize, Vector3.zero, (controlID, position, rotation, size) =>
            {
                controlIds[i] = controlID;
                Handles.RectangleCap(controlID, position, rotation, size);
            }) - offset;

            if (GUIUtility.keyboardControl == controlIds[i] && GUIUtility.keyboardControl != 0)
                activeNode = i;

            sl.controlPoints[i] = point;

            if (i > 0)
                Handles.DrawLine(lastPoint + offset, point + offset);
            lastPoint = point;
        }


        for (int i = 0; i < sl.controlPoints.Count; i++)
        {
            if (activeNode == i)
            {
                var point = sl.controlPoints[i];

                Handles.color = Color.yellow;
                point = Handles.PositionHandle(point + offset, Quaternion.identity) - offset;
                sl.controlPoints[i] = point;
            }
        }

        if (GUI.changed)
            EditorUtility.SetDirty(sl);

    }

    public void CustomRectangleCap(int controlID, Vector3 position, Quaternion rotation, float size)
    {
        Handles.RectangleCap(controlID, position, rotation, size);
    }

    public int activeNode { get; set; }
}