Printing with a coordinate system given in millimeters

[_Jack_]

Thanks for reply.
I resolved my problem in this way: taking in account printer resolution (hoping this is a general solution) :

QTransform TPiXEL = QTransform::fromScale(
painter.device()->physicalDpiX() / 25.400,
painter.device()->physicalDpiY() / 25.400);
painter.setWorldTransform(TPiXEL, false);

Thanks.

[doberkofler]

Are you now using setWorldTransform together with setWindow/setViewport or instead of the method suggested by wysota?