static double CalcSignedDistance(QLineF line, QPointF p)
{
// scalar projection on line. in case of co-linear
// vectors this is equal to the signed distance.
return((p.x() - line.p1().x()) * (line.p2().x() - line.p1().x()) + (p.y() - line.p1().y()) * (line.p2().y() - line.p1().y()));
}
static LineSide GetSideOfLine(QLineF line, QPointF pt)
{
double d = (pt.x() - line.p1().x()) * (line.p2().y() - line.p1().y()) - (pt.y() - line.p1().y()) * (line.p2().x() - line.p1().x());
return((Math.Sign(d) >= 0) ? LineSide.Right : ((Math.Sign(d) < 0) ? LineSide.Left : LineSide.On));
}