D-Bus Adaptor Example

The following example code shows how a D-Bus interface can be implemented using an adaptor.

A sample usage of QDBusAbstractAdaptor is as follows:

         class MainApplicationAdaptor: public QDBusAbstractAdaptor
         {
             Q_OBJECT
             Q_CLASSINFO("D-Bus Interface", "org.kde.DBus.MainApplication")
             Q_PROPERTY(QString caption READ caption WRITE setCaption)
             Q_PROPERTY(QString organizationName READ organizationName)
             Q_PROPERTY(QString organizationDomain READ organizationDomain)

         private:
             QApplication *app;

         public:
             MainApplicationAdaptor(QApplication *application)
                 : QDBusAbstractAdaptor(application), app(application)
             {
                 connect(application, SIGNAL(aboutToQuit()), SIGNAL(aboutToQuit()));
                 connect(application, SIGNAL(focusChanged(QWidget*, QWidget*)),
                         SLOT(focusChangedSlot(QWidget*, QWidget*)));
             }

             QString caption()
             {
                 if (app->hasMainWindow())
                     return app->mainWindow()->caption();
                 return QString(""); // must not return a null QString
             }

             void setCaption(const QString &newCaption)
             {
                 if (app->hasMainWindow())
                     app->mainWindow()->setCaption(newCaption);
             }

             QString organizationName()
             {
                 return app->organizationName();
             }

             QString organizationDomain()
             {
                 return app->organizationDomain();
             }

         public slots:
             Q_NOREPLY void quit()
             { app->quit(); }

             void reparseConfiguration()
             { app->reparseConfiguration(); }

             QString mainWindowObject()
             {
                 if (app->hasMainWindow())
                     return QString("/%1/mainwindow").arg(app->applicationName());
                 return QString();
             }

             void setSessionManagement(bool enable)
             {
                 if (enable)
                    app->enableSessionManagement();
                 else
                    app->disableSessionManagement();
             }

         private slots:
             void focusChangedSlot(QWidget *, QWidget *now)
             {
                 if (now == app->mainWindow())
                     emit mainWindowHasFocus();
             }

         signals:
             void aboutToQuit();
             void mainWindowHasFocus();
         };

The code above would create an interface that could be represented more or less in the following canonical representation:

 interface org.kde.DBus.MainApplication
 {
     property readwrite STRING caption
     property read STRING organizationName
     property read STRING organizationDomain

     method quit() annotation("org.freedesktop.DBus.Method.NoReply", "true")
     method reparseConfiguration()
     method mainWindowObject(out STRING)
     method disableSessionManagement(in BOOLEAN enable)

     signal aboutToQuit()
     signal mainWindowHasFocus()
 }

This adaptor could be used in the application's main function as follows

 int main(int argc, char **argv)
 {
     // create the QApplication object
     QApplication app(argc, argv);

     // create the MainApplication adaptor:
     new MainApplicationAdaptor(app);

     // connect to D-Bus and register as an object:
     QDBusConnection::sessionBus().registerObject("/MainApplication", app);

     // add main window, etc.
     [...]

     app.exec();
 }

Break-down analysis:

• The header
• The properties
• The constructor
• Slots/methods
• Signals

 class MainApplicationAdaptor: public QDBusAbstractAdaptor
 {
     Q_OBJECT
     Q_CLASSINFO("D-Bus Interface", "org.kde.DBus.MainApplication")

     Q_PROPERTY(QString caption READ caption WRITE setCaption)
     Q_PROPERTY(QString organizationName READ organizationName)
     Q_PROPERTY(QString organizationDomain READ organizationDomain)

 QString caption()
 {
     if (app->hasMainWindow())
         return app->mainWindow()->caption();
     return QString();
 }

 void setCaption(const QString &newCaption)
 {
     if (app->hasMainWindow())
         app->mainWindow()->setCaption(newCaption);
 }

 QString organizationName()
 {
     return app->organizationName();
 }

 QString organizationDomain()
 {
     return app->organizationDomain();
 }

 MyInterfaceAdaptor(QApplication *application)
     : QDBusAbstractAdaptor(application), app(application)
 {
     connect(application, SIGNAL(aboutToQuit()), SIGNAL(aboutToQuit());
     connect(application, SIGNAL(focusChanged(QWidget*, QWidget*)),
             SLOT(focusChangedSlot(QWidget*, QWidget*)));
 }

 public slots:
     Q_NOREPLY void quit()
     { app->quit(); }

     void reparseConfiguration()
     { app->reparseConfiguration(); }

     QString mainWindowObject()
     {
         if (app->hasMainWindow())
             return QString("/%1/mainwindow").arg(app->applicationName());
         return QString();
     }

     void setSessionManagement(bool enable)
     {
         if (enable)
            app->enableSessionManagement();
         else
            app->disableSessionManagement();
     }

 signals:
     void aboutToQuit();
     void mainWindowHasFocus();

 private slots:
     void focusChangedSlot(QWidget *, QWidget *now)
     {
         if (now == app->mainWindow())
             emit mainWindowHasFocus();
     }