jpeg-save.c

pg.preview = toggle =
  gtk_check_button_new_with_mnemonic
    (_("Sho_w preview in image window"));

gtk_toggle_button_set_active
    (GTK_TOGGLE_BUTTON (toggle),
     jsvals.preview);

gtk_box_pack_start (GTK_BOX (vbox),
                    toggle, FALSE,
                    FALSE, 0);

gtk_widget_show (toggle);