[Qt-interest] Custom widget in designer with simple container

[mario]

2010/9/16 mario <dodiesis at gmail.com>:
> 2010/9/16 Friedemann Kleint <Friedemann.Kleint at nokia.com>:
>> Hi Mario,
>>
>> you need to make the internal widget known to Qt Designer as  a container page
>> by implementing the QDesignerContainerExtension for your widget (see
>> http://doc.qt.nokia.com/4.6/qdesignercontainerextension.html and examples).
>> The XML returned by QDesignerCustomWidgetInterface::domXml () should already
>> contain one the page.
>>
I tried but the result is not so good.

Then: even deriving a basic container Qframe/QWidget and putting it in
the designer is not enough to make it layout-able.
So I searched into the QT's code to copy the code of the QGroupBox (or
QFrame). Seems that it does not have a QDesignerContainerExtension
implementation (in tools/designer directory).
QScrollArea, QTab*, QStackedWidget... they do. But they are all
multi-page widgets.

Where is the code to make these default widgets visible as "container" ?
Tnx
Mario