Duplicating the number of classes is a high price to pay to be able to
have some QAction functionality behave differently, or be only available
in widgets applications.
Instead, declare the entire API in QtGui in QAction* classes, and
delegate the implementation of QtWidgets specific functionality to
the private. The creation of the private is then delegated to the
Q(Gui)ApplicationPrivate instance through a virtual factory function.
Change some public APIs that are primarily useful for specialized tools
such as Designer to operate on QObject* rather than QWidget*. APIs that
depend on QtWidgets types have been turned into inline template
functions, so that they are instantiated only at the caller side, where
we can expect the respective types to be fully defined. This way, we
only need to forward declare a few classes in the header, and don't
need to generate any additional code for e.g. language bindings.
Change-Id: Id0b27f9187652ec531a2e8b1b9837e82dc81625c
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
bcaff2b06f