CODEWITHSUNDEEP
qt
diverger
diverger

Reputation: 176

Multiple inheritance of QApplication and QAbstractNativeEventFilter

I want to filter the USB device insert/removal events in my Qt application. So I need to use installNativeEventFilter() to install a native even filter (derived from QAbstractNativeEventFilter) to my app. The problem is I need emit some signals from my event filter, and connect them to the slots in my app. So, if I can inherent from both QApplication and QAbstractNativeEventFilter, then both the signals and slots are in the same class, and it's more convenient to connect them. But is the code below safe or not?

class QApp  : public QApplication, public QAbstractNativeEventFilter
{
    virtual bool nativeEventFilter(const QByteArray &eventType, void *message, long *) Q_DECL_OVERRIDE;
signals:
    void deviceChanged();
    ...
};

QApp a(argc, argv);
a.installNativeEventFilter( &a );

Upvotes: 2

Views: 1952

Answers (1)

Kuba hasn't forgotten Monica
Kuba hasn't forgotten Monica

Reputation: 98435

Why would you want to derive from QApplication? To emit signals, all you need is to derive from QObject:

class NativeEventFilter : public QObject, public QAbstractNativeEventFilter {
  Q_OBJECT
  ...
public:
  Q_SIGNAL void signal1();
  explicit NativeEventFilter(QObject * parent = 0) : QObject(parent) {}
  bool nativeEventFilter(const QByteArray & et, void * msg, long * result) override {
    ...
  };
  ...
};

int main(int argc, char ** argv) {
  QApplication app(argc, argv);
  NativeEventFilter filter;
  app.installNativeEventFilter(&filter);
  ...
  return app.exec();
}

Upvotes: 5

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