'Update information about a directory as it is expanded.'

def index_expanded(self, index):

    item = self.item_from_index(index)
    self.saved_open_folders.add(item.path)
    self.size_columns()
    if item.cached:
        return
    path = item.path
    model = self.model()
    model.populate(item)
    model.update_entry(path)
    for row in range(item.rowCount()):
        path = item.child(row, 0).path
        model.update_entry(path)
    item.cached = True
