Easiest way to find the distance between two parallel QLineF?

Before delving deeper and looking at creating perpendicular lines and walking them, is there an easy solution for finding the parallel distance between 2 QLineFs?

From the math point of view, I guess the following should work (I'm tempted to say it's impossible to do it "simpler", but implementing the same operations using your own specialized code might be more performant):
@QLineF normal = line1,normal();.
QPointF crossPoint;
if (normal.intersect(line2, &crossPoint) != QLineF::NoIntersection) {
QLineF distanceLine(line1.p1(), crossPoint);
qreal distance = distanceLine.length();
}@
Please note there is no check for actual parallelity; you can add it be comparison of the inclinations:
@if (line1.dy() * line2.dx() == line1.dx() * line2.dy()) {
// parallel
} else {
// not parallel
}@