Qt QMenu lazy initialization

Question

In my QMenu I have a submenu that may contain potentially hunderds of items, and it is not always used, so I am considering initalizing it only on demand:

I suspect that this can be done by implementing a QAbstractItemModel and overriding the methods canFetchMore fetchMore.

Is there an easier way using some trick? I don't mind if it is a little hackish (like replacing a dummy menu after clicking it with the good one, or something like that).

Answer 1

A hackish way, but it works well in my initial tests, would be something like:

//    menuBar->addMenu(Slow::APIMenu()); //old way

    auto emptyApiMenu = new QMenu("API");
    emptyApiMenu->addAction("API"); //dummy item to avoid qt warning of invisible menu
    QObject::connect(emptyApiMenu, &QMenu::aboutToShow, [=]() //lazy initialization of API menu
    {
        menuBar->insertMenu(emptyApiMenu->menuAction(), Slow::APIMenu());
        menuBar->removeAction(emptyApiMenu->menuAction());
    });
    menuBar->addMenu(emptyApiMenu);

It even opens the recently spawned menu so it is seamless