g_signal_connect (help_about, "activate", G_CALLBACK (about_new), toplevel);
g_signal_connect (help_ref, "activate", G_CALLBACK (reference_manual), NULL);
g_signal_connect (help_about, "activate", G_CALLBACK (about_new), toplevel);
g_signal_connect (help_ref, "activate", G_CALLBACK (reference_manual), NULL);