QPen pen(Qt::black, 2, Qt::SolidLine, Qt::MiterJoin);
QPen pen(Qt::red, 2, Qt::SolidLine, Qt::RoundJoin);
QPen pen(Qt::blue, 2, Qt::SolidLine, Qt::BevelJoin);These examples are all using the Qt package library, specifically the QPainter class which is used for drawing graphics in Qt applications.