Creating Custom Widget Extensions

Creating an Extension Factory

The QExtensionFactory class provides a standard extension factory, but it can also be used as an interface for custom extension factories.

The purpose is to reimplement the QExtensionFactory::createExtension() function, making it able to create your extension, such as a MultiPageWidget container extension.

You can either create a new QExtensionFactory and reimplement the QExtensionFactory::createExtension() function:

 QObject *ANewExtensionFactory::createExtension(QObject *object,
         const QString &iid, QObject *parent) const
 {
     if (iid != Q_TYPEID(QDesignerContainerExtension))
         return 0;

     if (MyCustomWidget *widget = qobject_cast<MyCustomWidget*>
             (object))
         return new MyContainerExtension(widget, parent);

     return 0;
 }

or you can use an existing factory, expanding the QExtensionFactory::createExtension() function to enable the factory to create your custom extension as well:

 QObject *AGeneralExtensionFactory::createExtension(QObject *object,
         const QString &iid, QObject *parent) const
 {
     MyCustomWidget *widget = qobject_cast<MyCustomWidget*>(object);

     if (widget && (iid == Q_TYPEID(QDesignerTaskMenuExtension))) {
          return new MyTaskMenuExtension(widget, parent);

     } else if (widget && (iid == Q_TYPEID(QDesignerContainerExtension))) {
         return new MyContainerExtension(widget, parent);

     } else {
         return 0;
     }
 }

 void MyPlugin::initialize(QDesignerFormEditorInterface *formEditor)
 {
     if (initialized)
         return;

     QExtensionManager *manager = formEditor->extensionManager();
     Q_ASSERT(manager != 0);

     manager->registerExtensions(new MyExtensionFactory(manager),
                                 Q_TYPEID(QDesignerTaskMenuExtension));

     initialized = true;
 }