private void comboFlipMap_SelectedIndexChanged(object sender, EventArgs e)
        {
            if (_editor.SelectedRoom == null)
            {
                return;
            }

            var   room = _editor.SelectedRoom;
            short alternateGroupIndex = (short)(comboFlipMap.SelectedIndex - 1);

            if (room.Alternated)
            {
                if (alternateGroupIndex == -1)
                { // Delete flipped room
                    EditorActions.AlternateRoomDisableWithWarning(room, this);
                }
                else
                { // Change flipped map number, not much to do here
                    if (room.AlternateGroup != alternateGroupIndex &&
                        room.AlternateOpposite.AlternateGroup != alternateGroupIndex)
                    {
                        room.AlternateGroup = alternateGroupIndex;
                        room.AlternateOpposite.AlternateGroup = alternateGroupIndex;
                        _editor.RoomPropertiesChange(room);
                        _editor.RoomPropertiesChange(room.AlternateOpposite);
                    }
                }
            }
            else
            {
                if (alternateGroupIndex != -1)
                {// Create a new flipped room
                    EditorActions.AlternateRoomEnable(room, alternateGroupIndex);
                }
            }

            // Update combo box even if nothing changed internally
            // to correct invalid user input
            EditorEventRaised(new Editor.RoomPropertiesChangedEvent {
                Room = room
            });
        }