How to handle resize of Gtk::Window

Is there a way to handle Gtk::Window resize event? We don't have an event controller for it, nor we can override Gtk::Widget::size_allocate function because it's not virtual.

#include <gtkmm.h>

class Window : public Gtk::Window {
public:
    Window() {
        // connecting on_resize to the window
    };
    
    void on_resize(int width, int height) {
        
    };
};


int main(int argc, char **argv) {
    auto app = Gtk::Application::create("hu.azsn.window");
    return app->make_window_and_run<Window>(argc, argv);
}

size_allocate is a signal. The corresponding handler is size_allocate_vfunc.

class Window : public Gtk::Window {
public:
    void on_resize(int width, int height) {  
    }

protected:
    void size_allocate_vfunc(int width, int height, int baseline) override {
        on_resize(width, height);
        Gtk::Widget::size_allocate_vfunc(width, height, baseline);
    }
};