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c++qteventsqml
rbaleksandar
rbaleksandar

Reputation: 9701

Handling Qt C++ events in QML context

The C++ API has QEvent along with multiple other classes derived from it (QMouseEvent, QGestureEvent etc.). QML on the other hand has events too. However I am struggling to find an elegant way of directly processing C++ events in QML.

Usually what I do is I create a custom QQuickWidget (or similar including QQmlEngine), override the QWidget::event(QEvent* event) and upon receiving a specific C++ event I propagate it through signals to QML slots with the QML code being loaded through that widget. This seems like a lot of work and I'm wondering if there is some sort of QML built-in event handling for events that come from C++ context.

In particular I'm interested in handling QGestureEvents in QML but I guess what works for this type of events should also work for any other type of event.

Upvotes: 2

Views: 1464

Answers (2)

Kevin Krammer
Kevin Krammer

Reputation: 5207

If QGestureEvent can be copy-constructed you could simply create a Q_GADGET based adapter:

class QmlGestureEvent : public QGestureEvent
{
    Q_GADGET
    Q_PROPERTY(...) // for the things you want to access from QML

public:
    QmlGestureEvent(const QGestureEvent &other) : QGestureEvent(other) {}
};

If it is not copy-constructable you'll have to add data members to the adapter and copy the values from the event.

Upvotes: 1

dtech
dtech

Reputation: 49329

There is no direct support for event handling in QML, even keyboard and mouse are accessible through auxiliary objects.

QEvent itself is not a QObject derived, and as such, the same applies to all the derived events as well. That means no meta-information and no easy way to use from QML.

Since you are interested in a particular type of events, it would be easiest to create your own auxiliary object for those type of events, implement it in C++ and interface it to QML via signals you can attach handlers to.

Upvotes: 1

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