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Hi,

while we're on the topic of public APIs and kdelibs cleanups: Here's a neat=
=20
little moc trick that we use in Qt 4 and that we can very well also use in=
=20
kdelibs.

It is very common to need slots in public classes. Take KDateWidget for=20
example:

=2E..
protected Q_SLOTS:
  void slotDateChanged();
=2E..
private:
    KDateWidgetPrivate *d;
=2E..

This slot is not intended for applications to call/use and it is connected =
to=20
the internal widgets. There's no need to have it in the public API and=20
exported. You can use the following instead:

=2E..
private:
    Q_PRIVATE_SLOT(d, void slotDateChanged())

    KDateWidgetPrivate *d;
=2E..

This macro expands to nothing but moc reads it nevertheless. It will genera=
te=20
a slot with the given signature in the metaobject, so you can connect to it=
=2E=20
But it assumes that the method itself is a member function of the first=20
argument of the macro. So the generated code will look like

=2E.. [deep in the metacall ]
	d->slotDateChanged();
=2E..

If that moc generated code is included from within the .cpp file (like we=20
fortunately do most of the time in KDE) d is well-defined and the compiler=
=20
can call your private slot, which is now just a member function of your d=20
pointer.

And of course in general I suggest not to have any private methods in our=20
public API at all. Putting it into your d-pointer gives you more flexibilit=
y=20
in the future to change the implementation. There is really no good reason=
=20
for exporting private functions.

I've heard gcc 4.2 will apply the default (hidden) visibility to private=20
members, so they won't exported anymore. But I hope that at some point in t=
he=20
future we can provide binary compatibility in kdelibs with more than just g=
cc=20
> 4.2 :)


Simon

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