Signals are not emitted if QAxControl is put on D-Bus and no other slots connect to the signals

If QAxControl is used to load an ActiveX control, and this object is then put on the D-Bus with QDBusConnection::registerObject() then slots and signals are all visible via the D-Bus interface, and you can call the object's slots via the D-Bus as you would expect, but QAxControl never emits any of the signals defined by the underlying ActiveX control.

If you then connect one of these signals to a regular slot, they are emitted, both on the normal slot, and via the D-Bus.

Pseudocode:

auto ax = new QAxObject(this);
if (!ax->setControl("someaxcontrol")) {
    delete ax;
    return false;
}

QDBusConnection::sessionBus().registerObject("/MyAXObject,
    "org.qtproject.Qt.QAxObject",
    ax,
    QDBusConnection::ExportAllContents);

// at this point, if someaxcontrol dispatches an event, ax will not emit a Qt signal

// now, connect any other slot to the signal
QObject::connect(ax, SIGNAL(somesignal()), this, SLOT(dummy()));

// and now, if somecontrol dispatches the somesignal event, it will be
// emitted as Qt signal, so dummy() will be called, and the corresponding
// signal will be emitted on the D-Bus as well

The problem seems to be a combination of factors:

1. After QDBusConnection::registerObject tries to connect the object's signals, QObject::receivers() still returns 0. Apparently it does not count the receivers connected in this manner.
2. In QAxEventSink::Invoke, signalHasReceivers is called, which again calls QObject::receivers(). As this returns 0, QAxEventSink decides that no on is listening for the signal, and skips emitting it.

I'm unsure if the root cause is that QObject::receivers() doesn't count connections made through QDBusConnection::registerObject, or if QAxEventSink should be smarter about how it tests if anything is connected to the signal.

If the object being registered on the D-Bus is a regular QObject with statically defined slots, it works correctly. The signals are then emitted through QMetaObject::activate, which uses different logic to determine if anyone is connected to the signal, which correctly count the QDBusConnection as being connected.