Gtk.FontButton

const Gtk = imports.gi.Gtk;

let font_button = new Gtk.FontButton({
    font_name: value,
    show_size: value,
    show_style: value,
    title: value,
    use_font: value,
    use_size: value,
});
  

The Gtk.FontButton is a button which displays the currently selected font an allows to open a font chooser dialog to change the font. It is suitable widget for selecting a font in a preference dialog.