Root
|-v A1
| |-- textA
|
|-v B1
| |-- textB

Root
|-> A1

Root
|-v A1
| |-- textA

bool MySortFilterProxyModel::filterAcceptsRow(
  int sourceRow,
  const QModelIndex &sourceParent
) const {
  bool result = QSortFilterProxyModel::filterAcceptsRow(sourceRow, sourceParent);

  if (m_tree) {
  //   if (result)
       m_tree->expand(sourceParent);
  }
 return result;
}