Hierarchy Example (ActiveQt)


  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:
      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.


  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.


  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.


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


  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.


  #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>

Files: