Transparently instantiating derived widgets with Gtk::Builder

[Roger Leigh <rleigh codelibre net>]

Hi folks,

I'm currently in the process of updating a 15 year old tutorial¹ to the 
current GTK+ 3.x release.  Part of that is updating the use of libglade 
to use Gtk::Builder.  I have read the documentation about using derived 
widgets² and the Gtk::Builder documentation³.  However, I'm not entirely 
satisfied with the result.

I would like to be able to instantiate my derived widget directly with 
the Gtk::Builder stuff managed internally in the constructor so that the 
end user does not need to know about it.  Is this technically possible? 
Can I use e.g. move-assignment with wrap() or get_widget_derived?  It 
looks possible, but I'm unsure how safe it would be.  Has anyone done 
this, or have any examples?

What I'm thinking of is something like:

MyWidget::MyWidget:
  Gtk::Window()
{
  Gtk::Builder builder;
  builder.add_from_resource(res);
  MyWidget *tmp
  build.get_widget_derived(name, tmp);
  *this = std::move(*tmp);
}

but I'm not sure about the safety of it.


Thanks all,
Roger


¹https://gitlab.com/codelibre/ogcalc/tree/master/gtk/C++
²https://developer.gnome.org/gtkmm-tutorial/stable/sec-builder-using-derived-widgets.html.en
³https://developer.gnome.org/gtkmm/stable/classGtk_1_1Builder.html#af8b9510f6146cde5364f830494114191