Qt Code: 
  1. #include <QtGui>
  2.  
  3. int main(int argc, char *argv[])
  4. {
  5.     QApplication app(argc, argv);
  6.  
  7.     QFileSystemModel model;
  8.     model.setRootPath("");
  9.     QTreeView tree;
  10.     tree.setModel(&model);
  11.  
  12.     // Demonstrating look and feel features
  13.     tree.setAnimated(false);
  14.     tree.setIndentation(20);
  15.     tree.setSortingEnabled(true);
  16.  
  17.     tree.setWindowTitle(QObject::tr("Dir View"));
  18.     tree.resize(640, 480);
  19.     tree.show();
  20.  
  21.     return app.exec();
  22. }
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The above code is the entire code for the dir view demo, on Windows 7, when expanding to the qt dir, I experience several seconds delay as well.