Qt Widget Hierarchy (in-process)

The ActiveX control in this example is a QWidget subclass with child widgets that are accessible as sub types.

The QParentWidget class provides slots to create a widget with a name, and to return a pointer to a named widget.

    class QParentWidget : public QWidget
    {
        Q_OBJECT
    public:
        QParentWidget( QWidget *parent = 0, const char *name = 0, WFlags f = 0 );

        QSize sizeHint() const;

    public slots:
        void createSubWidget( const QString &name );

        QSubWidget *subWidget( const QString &name );

    private:
        QVBoxLayout *vbox;
    };

The constructor of QParentWidget creates a vertical box layout. New child widgets are automatically added to the layout.

    QParentWidget::QParentWidget( QWidget *parent, const char *name, WFlags f )
    : QWidget( parent, name, f )
    {
        vbox = new QVBoxLayout( this );
        vbox->setAutoAdd( TRUE );
    }

The createSubWidget slot creates a new QSubWidget with the name provided in the parameter, and sets the label to that name. The widget is also shown explicitly.

    void QParentWidget::createSubWidget( const QString &name )
    {
        QSubWidget *sw = new QSubWidget( this, name );
        sw->setLabel( name );
        sw->show();
    }

The subWidget slot uses the QObject::child() function and returns the first child of type QSubWidget that has the requested name.

    QSubWidget *QParentWidget::subWidget( const QString &name )
    {
        return (QSubWidget*)child( name, "QSubWidget" );
    }

The QSubWidget class has a single string-property label, and implements the paintEvent to draw the label.

    class QSubWidget : public QWidget
    {
        Q_OBJECT
        Q_PROPERTY( QString label READ label WRITE setLabel )
    public:
        QSubWidget( QWidget *parent = 0, const char *name = 0, WFlags f = 0 );

        void setLabel( const QString &text );
        QString label() const;

        QSize sizeHint() const;

    protected:
        void paintEvent( QPaintEvent *e );

    private:
        QString lbl;
    };

The implementation of the QSubWidget class is self-explanatory.

    QSubWidget::QSubWidget( QWidget *parent, const char *name, WFlags f )
    : QWidget( parent, name, f )
    {
    }

    void QSubWidget::setLabel( const QString &text )
    {
        lbl = text;
        setName( text );
        update();
    }

    QString QSubWidget::label() const
    {
        return lbl;
    }

    QSize QSubWidget::sizeHint() const
    {
        QFontMetrics fm( font() );
        return QSize( fm.width(lbl), fm.height() );
    }

    void QSubWidget::paintEvent( QPaintEvent * )
    {
        QPainter painter(this);
        painter.setPen( colorGroup().text() );
        painter.drawText( rect(), AlignCenter, lbl );
    }

The ActiveQtFactory class implements a QAxFactory. It returns the class names of all supported types, QParentWidget and QSubWidget, from the featureList() reimplementation.

    class ActiveQtFactory : public QAxFactory
    {
    public:
        ActiveQtFactory( const QUuid &lib, const QUuid &app )
            : QAxFactory( lib, app )
        {}
        QStringList featureList() const
        {
            QStringList list;
            list << "QParentWidget";
            list << "QSubWidget";
            return list;
        }

The factory can however only create objects of the QParentWidget type directly - objects of subtypes can only be created through the interface of QParentWidget objects.

        QWidget *create( const QString &key, QWidget *parent, const char *name )
        {
            if ( key == "QParentWidget" )
                return new QParentWidget( parent, name );

            return 0;
        }

COM however requires the IDs for the interfaces of the sub types as well to be able to marshal calls correctly.

        QUuid classID( const QString &key ) const
        {
            if ( key == "QParentWidget" )
                return QUuid( "{d574a747-8016-46db-a07c-b2b4854ee75c}" );
            if ( key == "QSubWidget" )
                return QUuid( "{850652f4-8f71-4f69-b745-bce241ccdc30}" );

            return QUuid();
        }
        QUuid interfaceID( const QString &key ) const
        {
            if ( key == "QParentWidget" )
                return QUuid( "{4a30719d-d9c2-4659-9d16-67378209f822}" );
            if ( key == "QSubWidget" )
                return QUuid( "{2d76cc2f-3488-417a-83d6-debff88b3c3f}" );

            return QUuid();
        }
        QUuid eventsID( const QString &key ) const
        {
            if ( key == "QParentWidget" )
                return QUuid( "{aac9f855-c3dc-4cae-b747-c77f4d509f4c}" );
            if ( key == "QSubWidget" )
                return QUuid( "{25fac47e-c723-4696-8c74-6185903bdf65}" );

            return QUuid();
        }

Objects of the QSubWidget type should not expose the full functionality of e.g. QWidget. Only those properties and slots explicitly declared in the type are accessible.

        QString exposeToSuperClass( const QString &key ) const
        {
            if ( key == "QSubWidget" )
                return key;
            return QAxFactory::exposeToSuperClass(key);
        }
    };

The factory is then exported using the QAXFACTORY_EXPORT macro.

To build the example you must first build the QAxServer library. Then run qmake and your make tool in examples/multiple.

---

The demonstration requires your WebBrowser to support ActiveX controls, and scripting to be enabled.

    <script language=javascript>
    function createSubWidget( form )
    {
        ParentWidget.createSubWidget( form.nameEdit.value );
    }

    function renameSubWidget( form )
    {
        var SubWidget = ParentWidget.subWidget( form.nameEdit.value );
        if ( !SubWidget ) {
            alert( "No such widget " + form.nameEdit.value + "!" );
            return;
        }
        SubWidget.label = form.labelEdit.value;
        form.nameEdit.value = SubWidget.label;
    }

    function setFont( form )
    {
        ParentWidget.font = form.fontEdit.value;
    }
    </script>

    <p>
    This widget can have many children!<br>
    <object ID="ParentWidget" CLASSID="CLSID:d574a747-8016-46db-a07c-b2b4854ee75c"
    CODEBASE=http://www.trolltech.com/demos/hierarchy.cab>
    [Object not available! Did you forget to build and register the server?]
    </object><br>
    <form>
    <input type="edit" ID="nameEdit" value = "<enter object name>">
    <input type="button" value = "Create" onClick="createSubWidget(this.form)">
    <input type="edit" ID="labelEdit">
    <input type="button" value = "Rename" onClick="renameSubWidget(this.form)">
    <br>
    <input type="edit" ID="fontEdit" value = "MS Sans Serif">
    <input type="button" value = "Set Font" onClick="setFont(this.form)">
    </form>

See also The QAxServer Examples.