Access class returned by QGenericPlugin::create



  • Hi All,

    I am just getting familiar with the Qt plugin architecture. Currently I am checking out the tuiotouch plugin, which receives UDP packets and parses out tuio protocol messages to forward tracked data into the applictaion as touch events. I was able to get it all up and running, but I was wondering if it is possible to access the data maintained by the plugin itself.

    I looked into the plugin source and noticed that the QTuioTouchPlugin returns a QTuioHandler when QTuioTouchPlugin::create(...) is called. Here is the code copied from C:\Qt\5.8\Src\qtbase\src\plugins\generic\tuiotouch\main.cpp:

    #include <QtGui/qgenericplugin.h>
    #include <QCoreApplication>
    
    #include "qtuiohandler_p.h"
    
    QT_BEGIN_NAMESPACE
    
    class QTuioTouchPlugin : public QGenericPlugin
    {
        Q_OBJECT
        Q_PLUGIN_METADATA(IID QGenericPluginFactoryInterface_iid FILE "tuiotouch.json")
    
    public:
        QTuioTouchPlugin();
    
        QObject* create(const QString &key, const QString &specification);
    };
    
    QTuioTouchPlugin::QTuioTouchPlugin()
    {
    }
    
    QObject* QTuioTouchPlugin::create(const QString &key,
                                             const QString &spec)
    {
        if (!key.compare(QLatin1String("TuioTouch"), Qt::CaseInsensitive))
            return new QTuioHandler(spec);
    
        return 0;
    }
    
    QT_END_NAMESPACE
    

    Using the QPluginLoader class I am loading the tuiotouch dll and then instaciate a QGenericPlugin from it:

    QPluginLoader loader("path/to/dll");
    QObject *plugin_obj = loader.instance();
    auto plugin = qobject_cast<QGenericPlugin*>(plugin_obj);
    

    I then proceed to create the plugin using the interface described from the plugin source main (see above):

    QObject* plugin_handle = plugin->create("TuioTouch",  "udp=3333");
    

    I want to access the class interface of QTuioHandler. Can I somehow make my compiler familiar with this QObject subclass returned by create? Can I somehow create a class header for QTuioHandler, so I can cast auto plugin_tuio_handle = qobject_cast<QTuioHandler*>(plugin_handle)?

    The plugin is compiled as a dll, so I am realizing that what I am asking might be a bit difficult to say the least.


  • Lifetime Qt Champion

    Hi,

    Do you mean the qtuiohandler_p.h header file ?

    Out of curiosity, why do you want to do that?


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