createPath method
Implementation
@override
Path createPath(Offset offset, double size, Neighbors neighbors) {
double cSizeFraction = radiusFraction.coerceIn(0.0, 1.0);
double padding = size * (1 - cSizeFraction) / 2;
var sSize = size - 2 * padding;
return Path()..addOval(Rect.fromLTWH(offset.dx + padding, offset.dy + padding, sSize, sSize));
}