GTK4 popover menu size

Dear all ,
for some reason something is wrong with the size of the popover menus of my GTK4 app.
I create the menus using:

GMenu * menu = create_menu (); // Setting up my menu and items.
GtkWidget * popover =  gtk_popover_menu_new_from_model_full ((GMenuModel *)menu, GTK_POPOVER_MENU_NESTED); 
// I need to use the ' gtk_popover_menu_new_from_model_full' command here, 
// the menu created using the 'gtk_popover_menu_new_from_model' does not behave properly, 
// that might be a bug, some items of the menu having the same name, 
// It is not possible to navigate the menu properly and some elements remains inaccessible, 
// this was solved with this  '_full' command.
gtk_popover_set_has_arrow (GTK_POPOVER(popover), FALSE);
gtk_popover_set_pointing_to (GTK_POPOVER(popover), & rect);
gtk_popover_popup (GTK_POPOVER(popover));

My issue comes from the size of the menu, which appear much smaller than it should be,
by the way that size is always the same no matter the window / menu size in my app,
so how can I ensure that the menu will have the proper size and that all items will be accessible ?

Thanks in advance for your help.

Sébastien