QSortFilterProxyModel with sorting and initially suppressing filter (with testcase)

#include <QStringListModel>
#include <QSortFilterProxyModel>
#include <QDebug>

int main(int argc, char *argv[])
{
  QStringListModel slm;
  QSortFilterProxyModel sfm;

  sfm.setSourceModel(&slm);

  // make sure the filter does not match any entry
  sfm.setFilterRegExp(QRegExp("[0-9]+"));

  sfm.setDynamicSortFilter(true);
  sfm.sort(0);
  slm.setStringList(QStringList() << "z" << "x" << "a" << "b");

  // this will make all entries visible - but unsorted
  sfm.setFilterRegExp(QRegExp("[a-z]+"));

  for (int i = 0; i < sfm.rowCount(); ++i)
    qDebug() << sfm.index(i, 0).data();
}