#include <QtCore>
#include <QtWidgets>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QFileSystemModel model;
    model.setNameFilters(QStringList{"*.foo"});
    model.setNameFilterDisables(false);
    model.setFilter(QDir::AllDirs | QDir::Files | QDir::NoDotAndDotDot);
    
    QSortFilterProxyModel pm;
    pm.setRecursiveFilteringEnabled(true);
    pm.setSourceModel(&model);
    pm.setFilterKeyColumn(0);

    QTreeView w;
    w.setModel(&pm);
    w.show();

    return a.exec();
}