how do I rotate text about an arbitrary point?

PsylumDan

The image is the start of a compass display. It's also my first step into drawing on a QPainter.
The line works fine. It rotates around the center of the image. I would like the text to rotate around the center point as well. As it is, the text is rotating around 0, 0 (upper left corner). The forum won't let me attach the zipped project so here is my paintEvent code. This is a subclass of a QLabel.

void AZ_Label::paintEvent(QPaintEvent *ev)
{
    Q_UNUSED(ev);
    QPainter p(this);
    p.setPen(QPen(Qt::white, 2));
    p.rotate(lineAngle);
    p.save();
    p.translate(translateX, translateY);
    p.drawText(50, 50, "North");
    p.restore();
    p.rotate(-lineAngle);
    p.drawEllipse(xPosition, yPosition, cSize, cSize);
    line.setAngle(qreal(lineAngle));
    p.drawLine(line);
    emit sigSizechanged(xPosition, yPosition, cSize);
}

translateX and translateY are set from a slider on the main window.

JonB

@PsylumDan
Does https://stackoverflow.com/questions/31760995/how-to-set-transform-origin-for-qpainter-in-qt, https://stackoverflow.com/a/46180679 address your issue?

PsylumDan

@JonB said in how do I rotate text about an arbitrary point?:

@PsylumDan
Does https://stackoverflow.com/questions/31760995/how-to-set-transform-origin-for-qpainter-in-qt, https://stackoverflow.com/a/46180679 address your issue?

Thanks for the reply but no. The line works as expected. It's the text that I'm having trouble with.

mrjj

Hi
Qt is not "holding" the text in its center.
You have to calculate the center.
Please try code here.
https://stackoverflow.com/questions/40300346/qt-rotating-text-around-its-center-point

PsylumDan

@mrjj said in how do I rotate text about an arbitrary point?:

Hi
Qt is not "holding" the text in its center.
You have to calculate the center.
Please try code here.
https://stackoverflow.com/questions/40300346/qt-rotating-text-around-its-center-point

That's exactly what I needed. Thanks!