proc_setcallback
proc_setcallback(proc, control_dispatch_client, NULL);
proc_setcallback(p_priv, control_dispatch_priv, NULL);
proc_setcallback(p_frontend, engine_dispatch_frontend, NULL);
proc_setcallback(p_priv, engine_dispatch_priv, NULL);
proc_setcallback(p_priv, frontend_dispatch_priv, NULL);
proc_setcallback(p_engine, frontend_dispatch_engine, NULL);
proc_setcallback(p_control, priv_dispatch_control, NULL);
proc_setcallback(p_engine, priv_dispatch_engine, NULL);
proc_setcallback(p_frontend, priv_dispatch_frontend, NULL);
proc_setcallback(p, priv_dispatch_printer, p);
void proc_setcallback(struct imsgproc *,