Set font on QTreeWidget will cause the first column to ridiculously expand its width.

int main( int argc, char **argv )
{
    QApplication app( argc, argv );

    QTreeWidget w;
    QStringList headerLabels;
    headerLabels << "Column 1" << "Column 2" << "Column 3";

    w.setFont(QFont ("Courier", 9));

    w.setHeaderLabels(headerLabels);

    QTreeWidgetItem* item = new QTreeWidgetItem(&w);
    item->setText(0, "test1");
    item->setText(1, "test2");
    item->setText(2, "test3");
    w.addTopLevelItem(item);
    w.show();

    return app.exec();
}