protected function resolveMinMax($min, $max, $adder)
    {
        if (!$max || $min > $max) {
            $max = $min + $adder;
        } elseif (!$min || $min > $max) {
            $min = $max - $adder;
            if ($min < 0) {
                $min = 0;
            }
        }

        return array($min, $max);
    }