I would like to have a padding of ~5 pixels for all the widgets inside
frame, but I am not sure how to do that easily without .pack_start
Gtk::Frame is a child of Gtk::Container → Gtk::Bin so you have to use
the add or “<<” methodes to add a child and not pack_start. If you want
to add more than one child, you have to add an other container like a
Gtk::VBox or a Gtk::Table first.
The padding on all sides is controlled with Gtk::Containers
set_border_width method.