The QAxServer Module

ActiveX controls provided by ActiveQt servers support a minimal set of COM interfaces to implement the OLE specifications. When the ActiveX class inherits from the QAxBindable class it can also implement additional COM interfaces.

Create a new subclass of QAxAggregated and use multiple inheritance to subclass additional COM interface classes.

    class AxImpl : public QAxAggregated, public ISomeCOMInterface
    {
    public:
        AxImpl() {}

        long queryInterface( const QUuid &iid, void **iface );

        // IUnknown
        QAXAGG_IUNKNOWN

        // ISomeCOMInterface
        ...
    }
    

Reimplement the queryInterface() function to support the additional COM interfaces.

    long AxImpl::queryInterface( const QUuid &iid, void **iface )
    {
        *iface = 0;
        if ( iid == IID_ISomeCOMInterface )
            *iface = (ISomeCOMInterface*)this;
        else
            return E_NOINTERFACE;

        AddRef();
        return S_OK;
    }
    

Since ISomeCOMInterface is a subclass of IUnknown you will have to implement the QueryInterface, AddRef and Release functions. Use the QAXAGG_IUNKNOWN macro in your class definition to do that. If you implement the IUnknown functions manually, delegate the calls to the interface pointer returned by the controllingUnknown() function, e.g.

    HRESULT AxImpl::QueryInterface( REFIID iid, void **iface )
    {
        return controllingUnknown()->QueryInterface( iid, iface );
    }
    

Implement the methods of the COM interfaces, and use QAxAggregated::Object() if you need to make calls to the QObject subclass implementing the control.

In your QAxBindable subclass, implement createAggregate() to return a new object of the QAxAggregated subclass.

    class MyActiveX : public QWidget,                       
                      public QAxBindable
    {
    	Q_OBJECT
    public:
        MyActiveX( QWidget *parent, const char *name = 0 );

        QAxAggregated *createAggregate()
        {
            return new AxImpl();
        }
        
    };
    

1. If a standard constructor is not present the compiler will issue an error "no overloaded function takes 2 parameters" when using the default factory through the QAXFACTORY_DEFAULT macro. If you cannot provide a standard constructor you must implement a QAxFactory custom factory and call the constructor you have in your implementation of QAxFactory::create. Back...
2. COM cannot marshal IPictureDisp accross process boundaries, so QPixmap properties cannot be called for out-of-process servers. You can however marshal the image data via e.g. temporary files. See the Microsoft KB article Q150034 for more information. Back...
3. OLE needs to marshal user defined types by reference (ByRef), and cannot marshal them by value (ByVal). This is why const-references and object parameters are not supported for QRect, QSize and QPoint. Also note that servers with this datatype require Windows 98 or DCOM 1.2 to be installed. Back...
4. This is not required, but gives the client more control over the ActiveX control. Back...