private static boolean isLengthDefined(final StyleKey key, final StyleSheet styleSheet) {
    if (key.isInheritable()) {
      if (styleSheet.isLocalKey(key) == false) {
        return false;
      }
    }

    final Object o = styleSheet.getStyleProperty(key, null);
    if (o == null) {
      return false;
    }
    if (o instanceof Number == false) {
      return false;
    }
    final Number n = (Number) o;
    return n.doubleValue() != 0;
  }