UnityEditor.HandleUtility.GetHandleSize C# (CSharp) Method

        public static float GetHandleSize(Vector3 position)
        {
            Camera current = Camera.current;
            position = Handles.matrix.MultiplyPoint(position);
            if (current != null)
            {
                Transform transform = current.transform;
                Vector3 vector = transform.position;
                float z = Vector3.Dot(position - vector, transform.TransformDirection(new Vector3(0f, 0f, 1f)));
                Vector3 vector2 = current.WorldToScreenPoint(vector + transform.TransformDirection(new Vector3(0f, 0f, z)));
                Vector3 vector3 = current.WorldToScreenPoint(vector + transform.TransformDirection(new Vector3(1f, 0f, z)));
                Vector3 vector4 = vector2 - vector3;
                float magnitude = vector4.magnitude;
                return ((80f / Mathf.Max(magnitude, 0.0001f)) * EditorGUIUtility.pixelsPerPoint);
            }
            return 20f;
        }

        private void CollisionPlanesSceneGUI()
        {
            if (m_ScenePlanes.Count == 0)
            {
                return;
            }

            Event evt = Event.current;

            Color origCol = Handles.color;
            Color col     = new Color(1, 1, 1, 0.5F);

            for (int i = 0; i < m_ScenePlanes.Count; ++i)
            {
                if (m_ScenePlanes[i] == null)
                {
                    continue;
                }

                Transform  transform          = m_ScenePlanes[i];
                Vector3    position           = transform.position;
                Quaternion rotation           = transform.rotation;
                Vector3    right              = rotation * Vector3.right;
                Vector3    up                 = rotation * Vector3.up;
                Vector3    forward            = rotation * Vector3.forward;
                bool       isPlayingAndStatic = EditorApplication.isPlaying && transform.gameObject.isStatic;
                if (editingPlanes)
                {
                    if (Object.ReferenceEquals(s_SelectedTransform, transform))
                    {
                        EditorGUI.BeginChangeCheck();
                        var newPosition = transform.position;
                        var newRotation = transform.rotation;

                        using (new EditorGUI.DisabledScope(isPlayingAndStatic))
                        {
                            if (isPlayingAndStatic)
                            {
                                Handles.ShowStaticLabel(position);
                            }
                            if (EditMode.editMode == EditMode.SceneViewEditMode.ParticleSystemCollisionModulePlanesMove)
                            {
                                newPosition = Handles.PositionHandle(position, rotation);
                            }
                            else if (EditMode.editMode == EditMode.SceneViewEditMode.ParticleSystemCollisionModulePlanesRotate)
                            {
                                newRotation = Handles.RotationHandle(rotation, position);
                            }
                        }
                        if (EditorGUI.EndChangeCheck())
                        {
                            Undo.RecordObject(transform, "Modified Collision Plane Transform");
                            transform.position = newPosition;
                            transform.rotation = newRotation;
                            ParticleSystemEditorUtils.PerformCompleteResimulation();
                        }
                    }
                    else
                    {
                        float handleSize = HandleUtility.GetHandleSize(position) * 0.6f;

                        EventType oldEventType = evt.type;

                        // we want ignored mouse up events to check for dragging off of scene view
                        if (evt.type == EventType.Ignore && evt.rawType == EventType.MouseUp)
                        {
                            oldEventType = evt.rawType;
                        }

                        Handles.FreeMoveHandle(position, Quaternion.identity, handleSize, Vector3.zero, Handles.RectangleHandleCap);

                        // Detect selected plane (similar to TreeEditor)
                        if (oldEventType == EventType.MouseDown && evt.type == EventType.Used)
                        {
                            s_SelectedTransform   = transform;
                            oldEventType          = EventType.Used;
                            GUIUtility.hotControl = 0; // Reset hot control or the FreeMoveHandle will prevent input to the new Handles. (case 873514)
                        }
                    }
                }

                Handles.color = col;
                Color color = Handles.s_ColliderHandleColor * 0.9f;
                if (isPlayingAndStatic)
                {
                    color.a *= 0.2f;
                }

                if (m_PlaneVisualizationType == PlaneVizType.Grid)
                {
                    DrawGrid(position, right, forward, up, color);
                }
                else
                {
                    DrawSolidPlane(position, rotation, color, Color.yellow);
                }
            }

            Handles.color = origCol;
        }