Simplify preferences pages and DisplayBox via Gtk.Buildable
Make PreferencesPage
into a template and make it implement Gtk.Buildable
so that pages don't have to duplicate scrolled window, column etc.
Extract FullscreenBox
from DisplayView
.
Make PreferencesPage
into a template and make it implement Gtk.Buildable
so that pages don't have to duplicate scrolled window, column etc.
Extract FullscreenBox
from DisplayView
.