QAbstractItemView calls fetchMore() when scrolling side-to-side

Scrolling to the maximum position of a horizontal scrollbar triggers a call to canFetchMore() + fetchMore() in QAbstractItemView. This means that if you scroll back and forth side-to-side, without ever scrolling down, the model will continually be fetching more items that are not actually being displayed.

The canFetchMore() + fetchMore() should only be called when scrolling down.

Either that, or there should be an "orientation" argument to canFetchMore() / fetchMore() which takes either Qt::Vertical or Qt::Horizontal.