computeDisplayRows<T extends DataGridRow> function

List<GridDisplayRow<T>> computeDisplayRows<T extends DataGridRow>({ required List<double> displayOrder, required Map<double, T> rowsById, required List<DataGridColumn<T>> columns, required GroupState group, })

Turns displayOrder into the flat list of visual row slots the virtualized grid body renders, applying row grouping when group.hasGroups is true.

Ungrouped rows pass through unchanged, one GridDataRow per id. Grouped rows are partitioned by the grouped column's value via a stable bucket-by-value pass over displayOrder (not a re-sort), so both the order groups first appear in and the relative order of rows within a group are preserved regardless of the current sort column. A GridGroupHeaderRow precedes each group's GridDataRow members; members are omitted when the group is collapsed.

Implementation

List<GridDisplayRow<T>> computeDisplayRows<T extends DataGridRow>({
  required List<double> displayOrder,
  required Map<double, T> rowsById,
  required List<DataGridColumn<T>> columns,
  required GroupState group,
}) {
  if (!group.hasGroups) {
    return [for (final id in displayOrder) GridDataRow<T>(id)];
  }

  DataGridColumn<T>? column;
  for (final c in columns) {
    if (c.id == group.groupedColumnIds.first) {
      column = c;
      break;
    }
  }
  if (column == null) {
    return [for (final id in displayOrder) GridDataRow<T>(id)];
  }
  final groupColumn = column;

  final bucketOrder = <String>[];
  final bucketIds = <String, List<double>>{};
  final bucketValues = <String, dynamic>{};

  for (final id in displayOrder) {
    final row = rowsById[id];
    if (row == null) continue;

    final value = groupColumn.valueAccessor?.call(row);
    final groupKey = '${groupColumn.id}:$value';

    final bucket = bucketIds.putIfAbsent(groupKey, () {
      bucketOrder.add(groupKey);
      bucketValues[groupKey] = value;
      return <double>[];
    });
    bucket.add(id);
  }

  final result = <GridDisplayRow<T>>[];
  for (final groupKey in bucketOrder) {
    final ids = bucketIds[groupKey]!;
    final value = bucketValues[groupKey];
    final isExpanded = group.isGroupExpanded(groupKey);
    final firstRow = rowsById[ids.first]!;
    final formatter = groupColumn.cellFormatter as CellFormatter<T>?;
    final displayLabel =
        formatter?.call(firstRow, groupColumn) ?? value.toString();

    result.add(
      GridGroupHeaderRow<T>(
        groupKey: groupKey,
        columnId: groupColumn.id,
        columnTitle: groupColumn.title,
        value: value,
        displayLabel: displayLabel,
        rowCount: ids.length,
        isExpanded: isExpanded,
      ),
    );

    if (isExpanded) {
      for (final id in ids) {
        result.add(GridDataRow<T>(id));
      }
    }
  }

  return result;
}