QTreeView / QAbstractItemModel => release nodes which move out of the visible area

Hi,

I am currently on a visualization tool for a massive amount of records using a QTreeView with a custom QAbstractItemModel.

As I successfully implemented the "canFetchMore()" and "fetchMore()" methods of the QAbstractItemModel for dynamic (or, in other words, incremental) loading of the model as the user scrolls through the QTreeView I was wondering if there are counterparts to the "*fetchMore()" methods to free/release/unload elements which move out of the visible area?

Best regards and thanks in advance,
Rainer