apparently impossible qobject_cast is working!?

[FS Lover]

Can you show me a case where you would "need" to use the QAbstractProxyModel API of the completion model ?

<qt installation dir>/examples/tools/treemodelcompleter/mainwindow.cpp: highlight member function.

every time we need to map the highlighted completion item to the original model the completion is performed for,
we need to use the QAbstractProxyModel API of the completion model.

in this qt's own example we need to do so in order to highlight the user's choice of the completion in the original model.

Of course they are. For instance the "private" sections of classes in C++ are examples of such case.

it is access to them in the programming environment that is restricted, not the knowledge about the existence and function of them in the documentation.
at least for those that programmer can makes use of them (e.g. in subclassing).