Explore how we would define a Q_GADGET

[ahayzen-kdab]

The main difference is that a gadget doesn't derive from a QObject and doesn't have any signals or slots

https://doc.qt.io/qt-6/qobject.html#Q_GADGET

Areas that would need API / changes

• cxx_qt::qobject we would need a cxx_qt::qgadget macro too
• Inside the struct when there are qproperty there should be no NOTIFY
• There should be no cxx_qt::qsignals(T) where T is a gadget
• What should happen to the qobject::T naming for both the "C++" context and the impl qobject::T ? should we have a qgadget::T ? or instead change things to something more generic like qt::T or cpp::T or cxx_qt::T ?
• What happens with the threading ? We use QMetaObject::invokeMethod(QObject* ptr, ... ) so this would need to be disabled ?
• We need to change our QObject assert to ensure it does not derive from a QObject ?
• Should you be able to still define custom base classes?
• Consider support for Q_GADGET-only features (e.g. QML_VALUE_TYPE)