#include <QApplication>

#include <QDebug>
#include <QFont>
#include <QFontDatabase>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);

    QFont font;
    font.setStyleHint(QFont::Serif);
    // QFont::defaultFamily() returns an empty string on Linux
    qDebug() << font.defaultFamily();

    // This is a workaround: if QFontDatabase is instantiated QFont::defaultFamily() returns a non empty string
    QFontDatabase fdb;
    // Choose other styleHint than QFont::Serif otherwise the family string would be loaded from the fallback cache
    font.setStyleHint(QFont::Monospace);
    qDebug() << font.defaultFamily();

    return a.exec();
}