#include <QtWidgets/QtWidgets>

class SomeMainWindow : public QMainWindow
{
  using QMainWindow::QMainWindow;
  void closeEvent(QCloseEvent *) override {
    qDebug() << "closeEvent";
  }
};

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

  QMenu *menu = new QMenu("File");
  w.menuBar()->addMenu(menu);

  QAction *action = menu->addAction("Action 1");
  w.connect(action, &QAction::triggered, &w, []() { qDebug() << "Action triggered"; });
  w.setGeometry(100, 100, 150, 150);
  w.setCentralWidget(new QLabel(QString("Main Window - Qt %1").arg(qVersion())));
  w.show();

  QDialog *d1 = new QDialog(&w, Qt::Window | Qt::WindowTitleHint);
  QVBoxLayout *vbox1 = new QVBoxLayout(d1);
  vbox1->addWidget(new QLabel("Dialog d1"));
  vbox1->addStretch(1);
  d1->setWindowTitle("Window 1");
  d1->setGeometry(250, 250, 300, 300);
  d1->show();

  QDialog *d2 = new QDialog(d1, Qt::Window | Qt::WindowTitleHint);
  QVBoxLayout *vbox2 = new QVBoxLayout(d2);
  vbox2->addWidget(new QLabel("Dialog d2"));
  vbox2->addStretch(1);
  d2->setWindowTitle("Window 2");
  QPushButton *okbtn = new QPushButton("Ok");
  vbox2->addWidget(okbtn);
  d2->connect(okbtn, &QPushButton::clicked, d2, &QDialog::accept);
  d2->setGeometry(500, 500, 200, 200);
  d2->setWindowModality(Qt::WindowModal);
  d2->exec();

  int res = a.exec();
  return res;
}