Gtk::Builder: Add helper functions for getting widgets and objects more cleanly [master]
See #43 (closed) and the individual commits, but in brief, this adds new overloads enabling
auto button = builder->get_widget<Gtk::Button>(id);
auto derived = Gtk::Builder::get_derived<Derived>(builder, id, args);
auto adjustment = builder->get_object<Gtk::Adjustment>(id);
and makes tests/builder
use these, as well as demos/gtk-demo/example_builder
use the new widget
overloads.
If this is accepted, I'd like if we can get it into gtkmm-3-24
(or 3.26 if that's around by then) too. I've not backported it yet though until it's definitely worthwhile.