What am I missing? Is there a "and now 'Make it So Number One!'!" command to change the display?

update? Try ->update;

*barf* https://developer.gnome.org/search?q=set_from_file

https://developer.gnome.org/gtk3/stable/GtkImage.html#gtk-image-set-from-file See gtk_image_new_from_file() for details.

...
void     gtk_image_set_from_surface ()
void     gtk_image_clear ()
GtkWidget *     gtk_image_new ()
void     gtk_image_set_pixel_size ()
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https://developer.gnome.org/gtk3/stable/GtkImage.html#gtk-image-clear Resets the image to be empty.

So I'd try clear/set

Object Hierarchy

    GObject
    ╰── GInitiallyUnowned
        ╰── GtkWidget
            ╰── GtkMisc
                ╰── GtkImage

void     gtk_widget_show ()
void     gtk_widget_show_now ()
void     gtk_widget_hide ()
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eeh https://developer.gnome.org/gtk3/stable/GtkWidget.html#gtk-widget-show-all

umm Gtk ->update refresh

meh https://developer.gnome.org/gtk3/stable/GtkWidget.html#gtk-widget-queue-draw

weird no update? Ha :p