Qt: Multiple windows in a parent/child chain, parent does not close children?

Question

I am trying to create multiple windows in a chain: window 1 is the parent of window 2, window 2 is the parent of window 3, etc. When I close one window, I would like all its children to close as well. Currently, if I close the top level window, all others close, as hoped, but closing, for example, window 2, only closes window 2, not window 3, etc. How should I be doing this? Thanks for your help!

main_window.cpp

MainWindow::MainWindow(QWidget *parent) : QMainWindow(parent)
{
    QPushButton* button = new QPushButton("Open 1", this);
    connect(button, SIGNAL(clicked()), this, SLOT(on_button_clicked()));
}

void MainWindow::on_button_clicked() {
    window1 *w = new window1(this);
    w->show();
}

window1.cpp

window1::window1(QWidget *parent) : QWidget(parent)
{
    this->setWindowFlags(Qt::Window); // in order to have a free-standing window

    QPushButton* button = new QPushButton("Open 2", this);
    connect(button, SIGNAL(clicked()), this, SLOT(on_button_clicked()));
}

void window1::on_button_clicked() {
    window2 *w = new window2(this);
    w->show();
}

window2.cpp

window2::window2(QWidget *parent) : QWidget(parent)
{
    this->setWindowFlags(Qt::Window);

    QLabel* label = new QLabel("Window 2", this);
}

Answer 1

By default QApplication quits when the last primary window (window with no parent) is closed (see QApplication::lastWindowClosed signal), that is why closing your MainWindow closes everything.

Closing a widget doesn't delete it, unless the attribute Qt::WA_DeleteOnClose is set (see QWidget::close()). If you just want your windows to be closed, I think you have to reimplement closeEvent() to call close() on the children.

But if you want to delete them when closed, then set the attribute Qt::WA_DeleteOnClose. The children are automatically deleted when the parent is deleted.