verticalOffsetForFlattenChange static method

double? verticalOffsetForFlattenChange({ required FlattenChange change, required double currentOffset, required double itemExtent, required double topPadding, required double minScrollExtent, required double maxScrollExtent, })

New vertical offset after an incremental single-node change, or null when the change happened at/below the viewport top (so nothing visible moves).

Implementation

static double? verticalOffsetForFlattenChange({
  required FlattenChange change,
  required double currentOffset,
  required double itemExtent,
  required double topPadding,
  required double minScrollExtent,
  required double maxScrollExtent,
}) {
  final changePixel = topPadding + (change.index + 1) * itemExtent;
  if (changePixel <= currentOffset) {
    final delta = change.deltaItems * itemExtent;
    return (currentOffset + delta).clamp(minScrollExtent, maxScrollExtent);
  }
  return null;
}