[Qt-interest] Nested widget disappears when I add a spacer item / dynamically adding widgets to widgets

[Kustaa Nyholm]

Related to my unanswered question yesterday here is a more specific
test case:

I've got following simple code:

    gLayout = new QBoxLayout(QBoxLayout::TopToBottom, this);

    QWidget* top=new QWidget();
    new QPushButton("A",top);

    gLayout->addWidget(top);

    gLayout->addWidget(new QPushButton("B"));


This works, and displays two buttons, A and B.

But if I add a spacer to the mix by adding a single line:

gLayout->addItem(
   new QSpacerItem(20, 40, QSizePolicy::Minimum, QSizePolicy::Expanding));

then button A disappers!

What is going on?

Note that button A is a child of the widget 'top' which is what I add
to the layout. If I add A button to gLayout directly then there is no
problem but inmy bigger application that is not feasible because 'top' is a
form maintained with Qt Designer...

So what is the proper way to add a widget that contains widgets
to a layout?

br Kusti