Incrementing the length of a QLineF in the negative direction?



  • The documentation seems to be spotty on this. Below is how I did it. Is this the correct way?

    @
    QLineF refLine(100,100, 500,500);
    QLineF perpLine = refLine.normalVector(); //create a perpendicular line to the refLine
    perpLine.setLength(-1); //this seems to set it in the negative direction and it stays in the negative direction

    for(int i = 0; i < 50; i++)
    {
    perpLine.setLength(perpLine.Length + 1); // this will increment perpLine in a negative direction
    }

    @


  • Moderators

    i read the docs of QLineF::setLength() pretty clear:
    [quote]
    Sets the length of the line to the given length. QLineF will move the end point (p2) of the line to give the line its new length
    [/quote]

    The following code would rotate the line by 180° (around p1):
    @
    QLineF line(100,100, 500,500);
    line.setLength( - line.length() );
    @



  • Thanks for the reply. I always find Qt documentation to be top notch. I'm having trouble inferring from the documentation on this topic to mean negative numbers will invert/rotate the line.


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