Bind a lot of widgets in the box.

Simple Code

#include <gtkmm.h>

int main (int argc, char **argv) {
    auto app = Gtk::Application::create(argc, argv, "sjLin");

    Gtk::Window window;
    Gtk::Box box_1;
    Gtk::Button btn("test");

    window.set_default_size(800, 600);

    window.add(box_1);
    box_1.add(btn);

    btn.show();
    box_1.show();
    return app->run(window);
}