dataToPoint method
Implementation
Offset dataToPoint(DynamicData data) {
double xy = scale.rangeValue(data).toDouble();
double at = atan2(props.end.dy - props.start.dy, props.end.dx - props.start.dx);
double x = props.start.dx + xy * cos(at);
double y = props.start.dy + xy * sin(at);
return Offset(x, y);
}