Make it possible to add spacing to them from the theme without affecting
the center child should it happen to be a box.
self->start_box = gtk_box_new (GTK_ORIENTATION_HORIZONTAL, 0);
self->end_box = gtk_box_new (GTK_ORIENTATION_HORIZONTAL, 0);
+ gtk_widget_add_css_class (self->start_box, "start");
+ gtk_widget_add_css_class (self->end_box, "end");
+
self->center_box = gtk_center_box_new ();
gtk_center_box_set_start_widget (GTK_CENTER_BOX (self->center_box), self->start_box);
gtk_center_box_set_end_widget (GTK_CENTER_BOX (self->center_box), self->end_box);