validate method

String? validate()

Returns a validation error, or null when this value can be submitted.

Implementation

String? validate() {
  if (pages.isEmpty || pages.any((page) => page < 0)) {
    return 'Header/footer pages must contain zero-based page indexes.';
  }
  if (slots.isEmpty) {
    return 'Header/footer slots cannot be empty.';
  }
  final positions = <CPDFHeaderFooterPosition>{};
  for (final slot in slots) {
    if (!positions.add(slot.position)) {
      return 'Header/footer slots cannot use duplicate positions.';
    }
    if (slot.fontSize <= 0) {
      return 'Header/footer fontSize must be greater than zero.';
    }
  }
  return null;
}