when we can delete a class derived from Gtk::Window or others

I want to create some windows on demand with "new". If the user closes
the window, when I can call delete on that class derived from
Gtk::Dialog or Gtk::Window?

Example:
#include <iostream>
#include <string>
#include <gtkmm.h>


class ExampleWindow : public Gtk::Dialog
{
     protected:
         Gtk::Box m_VBox;
         Gtk::Button m_button;
         std::string mytext;
         Gtk::Frame frame;
         Gtk::Grid grid;
         Gtk::ScrolledWindow sw;

     public:
         ExampleWindow(const std::string& text_):
             m_VBox{ Gtk::ORIENTATION_VERTICAL }
         ,m_button{ text_ }
         ,mytext{ text_ }
         {
             set_title("Example");
             set_border_width(10);
             set_default_size(400, 200);

             get_vbox()->add(sw);
             sw.add(m_VBox);
             m_VBox.add( frame );
             frame.add( m_button );


m_button.signal_clicked().connect(sigc::mem_fun(this,&ExampleWindow::my_clicked));

             show_all_children();
         }

         void my_clicked()
         {
             ExampleWindow* win2 = new ExampleWindow("Stand Alone Win");
             win2->show();
         }

         virtual ~ExampleWindow() override
         {
             // Not called for the stand alone win while closing it. How
to achieve that?
             std::cout << "Destructor called for " << mytext << std::endl;
         }

         bool on_delete_event( GdkEventAny* ) override
         {
             std::cout << "sighandler on_delete called"  << mytext <<
std::endl;
             //delete this; // that did not work, the window did not hide!

             return false;
         }

         void on_hide() override
         {
             std::cout << "Hide event" << std::endl;
             delete this;    // is it safe to delete our self here?????
         }

};


int main(int argc, char *argv[])
{
     auto app = Gtk::Application::create(argc, argv, "some.base");

     // Create win with new
     ExampleWindow* window = new ExampleWindow{ "Press to create new win" };

     //Shows the window and returns when it is closed.
     return app->run(*window);
}