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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

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