UnityEditor.HandleUtility.AddControl C# (CSharp) Method

        public static void AddControl(int controlId, float distance)
        {
            if ((distance < s_CustomPickDistance) && (distance > 5f))
            {
                distance = 5f;
            }
            if (distance <= s_NearestDistance)
            {
                s_NearestDistance = distance;
                s_NearestControl = controlId;
            }
        }

        internal static void DoBoneHandle(Transform target, Dictionary <Transform, bool> validBones, BoneRenderer renderer)
        {
            int   id  = target.name.GetHashCode();
            Event evt = Event.current;

            bool hasValidChildBones = false;

            if (validBones != null)
            {
                foreach (Transform child in target)
                {
                    if (validBones.ContainsKey(child))
                    {
                        hasValidChildBones = true;
                        break;
                    }
                }
            }

            Vector3 basePoint = target.position;

            List <Vector3> endPoints = new List <Vector3>();

            // [case 525602] do not draw root.
            if (!hasValidChildBones && target.parent != null)
            {
                endPoints.Add(target.position + (target.position - target.parent.position) * 0.4f);
            }
            else
            {
                foreach (Transform child in target)
                {
                    // Only render bone connections to valid bones
                    // (except if no child bones are valid - then draw all connections)
                    if (validBones != null && !validBones.ContainsKey(child))
                    {
                        continue;
                    }

                    endPoints.Add(child.position);
                }
            }

            for (int i = 0; i < endPoints.Count; i++)
            {
                Vector3 endPoint = endPoints[i];


                switch (evt.GetTypeForControl(id))
                {
                case EventType.Layout:
                {
                    // TODO : This is slow and should be revisited prior to exposing bone handles
                    Vector3[] vertices = BoneRenderer.GetBoneWireVertices(basePoint, endPoint);
                    if (vertices != null)
                    {
                        HandleUtility.AddControl(id, DistanceToPolygone(vertices));
                    }

                    break;
                }

                case EventType.MouseMove:
                    if (id == HandleUtility.nearestControl)
                    {
                        HandleUtility.Repaint();
                    }
                    break;

                case EventType.MouseDown:
                {
                    // am I closest to the thingy?
                    if (!evt.alt && HandleUtility.nearestControl == id && evt.button == 0)
                    {
                        GUIUtility.hotControl = id;     // Grab mouse focus
                        if (evt.shift)
                        {
                            Object[] selected = Selection.objects;
                            if (ArrayUtility.Contains(selected, target) == false)
                            {
                                ArrayUtility.Add(ref selected, target);
                                Selection.objects = selected;
                            }
                        }
                        else
                        {
                            Selection.activeObject = target;
                        }

                        EditorGUIUtility.PingObject(target);

                        evt.Use();
                    }
                    break;
                }

                case EventType.MouseDrag:
                {
                    if (!evt.alt && GUIUtility.hotControl == id)
                    {
                        DragAndDrop.PrepareStartDrag();
                        DragAndDrop.objectReferences = new UnityEngine.Object[] { target };
                        DragAndDrop.StartDrag(ObjectNames.GetDragAndDropTitle(target));

                        // having a hot control set during drag makes the control eat the drag events
                        // and dragging of bones no longer works over the avatar configure window
                        // see case 912016
                        GUIUtility.hotControl = 0;

                        evt.Use();
                    }
                    break;
                }

                case EventType.MouseUp:
                {
                    if (GUIUtility.hotControl == id && (evt.button == 0 || evt.button == 2))
                    {
                        GUIUtility.hotControl = 0;
                        evt.Use();
                    }
                    break;
                }

                case EventType.Repaint:
                {
                    color = GUIUtility.hotControl == 0 && HandleUtility.nearestControl == id ? Handles.preselectionColor : color;
                    if (hasValidChildBones)
                    {
                        renderer.AddBoneInstance(basePoint, endPoint, color);
                    }
                    else
                    {
                        renderer.AddBoneLeafInstance(basePoint, target.rotation, (endPoint - basePoint).magnitude, color);
                    }
                }
                break;
                }
            }
        }