apply method

@override Delta? apply(Delta document, int index, String text)

Applies heuristic rule to an insert operation on a document and returns resulting Delta.

Implementation

@override
Delta? apply(Delta document, int index, String text) {
  final iter = DeltaIterator(document);
  final previous = iter.skip(index);
  final target = iter.next();
  final beforeEmbed = target?.data == EmbedNode.kPlainTextPlaceholder;
  final afterEmbed = previous?.data == EmbedNode.kPlainTextPlaceholder;
  if (beforeEmbed || afterEmbed) {
    final delta = Delta()..retain(index);
    if (beforeEmbed && !text.endsWith('\n')) {
      return delta..insert(text)..insert('\n');
    }
    if (afterEmbed && !text.startsWith('\n')) {
      return delta..insert('\n')..insert(text);
    }
    return delta..insert(text);
  }
  return null;
}