Is there a bug in my code for populating a QTreeView?

Answer 1

I took a look at the Qt source (v4.5, though I don't expect much difference between v4.4 and v4.5) for QAbstractItemView and QTreeView, and I don't think they support incremental lazy loading of child nodes.

QAbstractItemView has no notion of trees, so it only calls fetchMore() on the top most index. It calls fetchMore() when:

• Geometry is updated
• The scroll bars are moved
• Rows are inserted
• The current item is changed as a result of an autoscrolling drag & drop operation

QTreeView additionally calls fetchMore() when:

• An item is expanded (this is essentially the only time it calls fetchMore() with a non-root index)
• The view's layout needs to be relaid, such as with expandAll() and collapseAll()

I think the best solution would be to subclass QTreeView to make it call fetchMore() in the appropriate places and with the appropriate indices.