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I am attempting to change Gtk::Image -derived object by giving it pixbuf, but i cannot figure out how to approach that.

The simple setup can be mimicked as:

#include <gtkmm.h>
#include <iostream>
class MyImage : public Gtk::Image
public:
    void setPixBuf(Glib::RefPtr<Gdk::Pixbuf> pixbuf);
void MyImage::setPixBuf(Glib::RefPtr<Gdk::Pixbuf> pixbuf)
    // How can i override the existing pixbuf here?
void freeImagePixelData(const guint8* data)
    delete[] data;
Glib::RefPtr<Gdk::Pixbuf> generateTestImage()
    guint8 *data = new guint8[40*40*4];
    for(int i=0; i<40*40*4; )
        data[i++] = (guint8)255;    // R
        data[i++] = (guint8)255;    // G
        data[i++] = (guint8)0;      // B
        data[i++] = (guint8)255;    // A
    Glib::RefPtr<Gdk::Pixbuf> pixbuf = Gdk::Pixbuf::create_from_data(
        data, Gdk::Colorspace::COLORSPACE_RGB, true, 8, 40, 40,  40*4, sigc::ptr_fun(&freeImagePixelData));
    return pixbuf;
int main(int argc, char** argv)
    Glib::RefPtr<Gtk::Application> app = Gtk::Application::create(argc, argv, "com.almost-university.gtkmm.image.pixbuf");
    Gtk::Window window;
    MyImage im1;
    im1.setPixBuf(generateTestImage());
    window.add(im1);
    window.show_all_children();
    app->run(window);
    return 0;
(Please note that this is an oversimplified version of what i am trying to figure out, i do know that i should be using Gtk::manage and not add things directly to the window without another container, this is just a mock-up).
I know that if i were to generate the image using a constructor as so:
    Gtk::Image im2(generateTestImage());
    window.add(im2);
then i would in fact be getting a yellow square.
Somehow i refuse to believe that one can only use pixbuf at the time of object creation. There must be a way to set the image data somehow, and i just cannot find the needed function.
To set Pixbuf in an Gtk::Image you can use Gtk::Image::set(const Glib::RefPtr< Gdk::Pixbuf >& pixbuf) method:
void MyImage::setPixBuf(Glib::RefPtr<Gdk::Pixbuf> pixbuf)
    set(pixbuf);
        
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