protected function makeCallables(
        $listener,
        $callable,
        /*# int */ $priority
    )/*# : array */ {
        $result = [];
        if (is_array($callable)) {
            if (isset($callable[1]) && is_int($callable[1])) {
                $priority = $callable[1];
                $xc = $callable[0];
            } else {
                foreach ($callable as $cc) {
                    $result = array_merge(
                        $result,
                        $this->makeCallables($listener, $cc, $priority)
                    );
                }
                return $result;
            }
        } elseif (is_string($callable)) {
            $xc = $callable;
        }

        if (isset($xc)) {
            if (!is_callable($xc)) {
                $xc = array($listener, $xc);
            }
            if (is_callable($xc)) {
                $result[] = [ $xc, $priority ];
            }
        }
        return $result;
    }