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}");
    Q_CLASSINFO("EventsID", "{4a30719d-d9c2-4659-9d16-67378209f823}");
public:
    explicit QParentWidget(QWidget *parent = nullptr);

    QSize sizeHint() const override;

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

    QSubWidget *subWidget(const QString &name);

private:
    QVBoxLayout *m_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.

QParentWidget::QParentWidget(QWidget *parent)
: QWidget(parent),
  m_vbox(new QVBoxLayout(this))
{
}

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

void QParentWidget::createSubWidget(const QString &name)
{
    QSubWidget *sw = new QSubWidget(this, name);
    m_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.

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

The subWidget slot uses the QObject::findChild() 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 = nullptr, const QString &name = QString());

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

    QSize sizeHint() const override;

protected:
    void paintEvent(QPaintEvent *e) override;

private:
    QString m_label;
};

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.

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

void QSubWidget::setLabel(const QString &text)
{
    m_label = text;
    setObjectName(text);
    update();
}

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

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

void QSubWidget::paintEvent(QPaintEvent *)
{
    QPainter painter(this);
    painter.setPen(palette().text().color());
    painter.drawText(rect(), Qt::AlignCenter, m_label);
}

The implementation of the QSubWidget class is self-explanatory.

#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 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.qt-project.org/demos/hierarchy.cab">
[Object not available! Did you forget to build and register the server?]
</object><br />
<form>
<input type="edit" ID="nameEdit" value="&lt;enter object name&gt;" />
<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>

Example project @ code.qt.io

© 2024 The Qt Company Ltd. Documentation contributions included herein are the copyrights of their respective owners. The documentation provided herein is licensed under the terms of the GNU Free Documentation License version 1.3 as published by the Free Software Foundation. Qt and respective logos are trademarks of The Qt Company Ltd. in Finland and/or other countries worldwide. All other trademarks are property of their respective owners.