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# Hierarchy Example (ActiveQt)

The Hierarchy example is shows how to write an in-process ActiveX control. The control is a QWidget subclass with child widgets that are accessible as sub-types.

    class QParentWidget : public QWidget
    {
        Q_OBJECT
        Q_CLASSINFO("ClassID", "{d574a747-8016-46db-a07c-b2b4854ee75c}");
        Q_CLASSINFO("InterfaceID", "{4a30719d-d9c2-4659-9d16-67378209f822}");
    public:
        QParentWidget(QWidget *parent = 0);

        QSize sizeHint() const;

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

        QSubWidget *subWidget( const QString &name );

    private:
        QVBoxLayout *vbox;
    };

The `QParentWidget` class provides slots to create a widget with a name, and to return a pointer to a named widget. The class declaration uses `Q_CLASSINFO()` to provide the COM identifiers for this class.
The following code example is written in c++.

    QParentWidget::QParentWidget(QWidget *parent)
    : QWidget(parent)
    {
        vbox = new QVBoxLayout(this);
    }

The constructor of QParentWidget creates a vertical box layout. New child widgets are automatically added to the layout.
The following code example is written in c++.

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

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.
The following code example is written in c++.

    QSubWidget *QParentWidget::subWidget(const QString &name)
    {
        return qFindChild<QSubWidget*>(this, name);
    }

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

    class QSubWidget : public QWidget
    {
        Q_OBJECT
        Q_PROPERTY( QString label READ label WRITE setLabel )

        Q_CLASSINFO("ClassID", "{850652f4-8f71-4f69-b745-bce241ccdc30}");
        Q_CLASSINFO("InterfaceID", "{2d76cc2f-3488-417a-83d6-debff88b3c3f}");
        Q_CLASSINFO("ToSuperClass", "QSubWidget");

    public:
        QSubWidget(QWidget *parent = 0, const QString &name = QString());

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

        QSize sizeHint() const;

    protected:
        void paintEvent( QPaintEvent *e );

    private:
        QString lbl;
    };

The `QSubWidget` class has a single string-property `label`, and implements the paintEvent to draw the label. The class uses again `Q_CLASSINFO` to provide the COM identifiers, and also sets the ToSuperClass attribute to QSubWidget, to ensure that only no slots of any superclasses (i.e. QWidget) are exposed.
The following code example is written in c++.

    QSubWidget::QSubWidget(QWidget *parent, const QString &name)
    : QWidget(parent)
    {
        setObjectName(name);
    }

    void QSubWidget::setLabel(const QString &text)
    {
        lbl = text;
        setObjectName(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(palette().text().color());
        painter.drawText(rect(), Qt::AlignCenter, lbl);

    }

The implementation of the QSubWidget class is self-explanatory.
The following code example is written in c++.

    #include "objects.h"
    #include <QAxFactory>

    QAXFACTORY_BEGIN("{9e626211-be62-4d18-9483-9419358fbb03}", "{75c276de-1df5-451f-a004-e4fa1a587df1}")
        QAXCLASS(QParentWidget)
        QAXTYPE(QSubWidget)
    QAXFACTORY_END()

The classes are then exported using a QAxFactory. `QParentWidget` is exported as a full class (which can be created ), while `QSubWidget` is only exported as a type, which can only be created indirectly through APIs of `QParentWidget`.

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

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!
    </p>
    <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>