Missing touch events for QScrollArea

// compile as: g++ test.cpp -o a -O0 -g3 -fPIC $(pkg-config --cflags --libs Qt5Gui Qt5Widgets)
#include <QApplication>
#include <QLabel>
#include <QScrollArea>
#include <QDebug>
#include <QMetaEnum>

void gen_label_text(QLabel& label) {
    const char sentence[] = "'th sentence here\n";
    QString text;
    for (int line = 0; line < 1e3; ++line) {
        text += QString::number(line) + sentence;
    }
    label.setText(text);
}

/// Gives human-readable event type information.
// Credits to https://stackoverflow.com/a/22535470/2388257
QDebug operator<<(QDebug str, const QEvent * ev) {
   static int eventEnumIndex = QEvent::staticMetaObject
         .indexOfEnumerator("Type");
   str << "QEvent";
   if (ev) {
      QString name = QEvent::staticMetaObject
            .enumerator(eventEnumIndex).valueToKey(ev->type());
      if (!name.isEmpty()) str << name; else str << ev->type();
   } else {
      str << (void*)ev;
   }
   return str.maybeSpace();
}

struct QScrollAreaWrapper : public QScrollArea {
    bool event(QEvent* ev) override {
        qDebug() << "handling an event " << ev;
        return QScrollArea::event(ev);
    }
};

int main(int argc, char **argv) {
    QApplication app (argc, argv);
    QLabel label;
    gen_label_text(label);
    QScrollAreaWrapper qsa;
    qsa.setWidget(&label);
    qsa.show();
    // set Qt::WA_AcceptTouchEvents wherever possible
    label.setAttribute          (Qt::WA_AcceptTouchEvents, true);
    qsa.setAttribute            (Qt::WA_AcceptTouchEvents, true);
    qsa.viewport()->setAttribute(Qt::WA_AcceptTouchEvents, true);

    return app.exec();
}