showHandlerOutter property
draw a outter container for the handler, the outter shape could be either a rectangle or circle the shape will always match the default handler shape which is control by using the this.shape default value is always false unless defined if set to true then the handlerOutterRadius also needs to get set unless you want to use the default value showHandlerOutter enable then both this.shadow and this.icon are expected to be null. we are keeping this as backwards compatibility since similar effect could be generate by using
Icon(Icons.filter_tilt_shift, size: iconSize, color: Colors.teal[700]);
Implementation
final bool showHandlerOutter;