[Solved again] Post a QGestureEvent to a QStateMachine

Malte J

Hello everybody,

i have a problem when posting QGestureEvents to a QStateMachine.
I implemented custom gesture recognizers, which a correctly registered and now i am receiving QGestureEvents in my application. I then do some processing and afterwards i would like to post one gesture event to my state machine.

QList<QGesture *> newGestureList;
newGestureList.append(g);
if (mp_stateMachine){
	QGestureEvent *ev = new QGestureEvent(newGestureList);
	mp_stateMachine->postEvent(ev);
}

So far so good. For Gestures with the state Qt::GestureStarted and Qt::GestureUpdated everything works fine.

Now the problem:
When the gesture has the state Qt::GestureFinished or Qt::GestureCancelled, it gets resetted by Qt, so that in custom transition, i receive the events, but the gestures have the state Qt::NoGesture. That is very critical to me since i need to check the state afterwards.

I found out, that in QGestureManager.cpp the cancelled and finished gestures are resetted:

    // reset gestures that ended
    QSet<QGesture *> endedGestures =
            finishedGestures + canceledGestures + undeliveredGestures + maybeToCanceledGestures;
    foreach (QGesture *gesture, endedGestures) {
        recycle(gesture);
        m_gestureTargets.remove(gesture);
    }

But I don't know why and how to solve my problem.

Any ideas are welcome!

Thank you in advance,
MalteJ

SGaist

Hi and welcome to devnet,

Shouldn't you rather decouple the two ? Handle the gesture in your widget, then send a custom event to your state machine so the machine doesn't need to know QGestureEvent and thus you can also change easily what triggers that custom event.

Hope it helps

Malte J

@SGaist Thank you for your fast answer.

In fact, I implemented custom gestures, which contain all important information for the decision.
My custom Transition class called GestureTransition triggers according to the specified gesture event.

Could I implement a custom event holding a QGesture object? If yes, how?

Thanks, Malte

Edit: I think i got it, subclassing QEvent was not that hard ;) Thank you for the idea!

Malte J

Okay... i have to reopen this issue.

like @SGaist proposed, I want to post a custom event to my state machine. However, I want this event to hold an instance of the causing QGesture object. Sadly, i see no way of copying such an object, and if I use a pointer, it is the same object that gets killed by Qt in the QGestureManager as said above..

Any ideas to solve this? I have like 8 custom gesture classes that hold different information, which are all subclasses of QGesture (for the information of the QGestureState). And I don't want to miss that..

PS: QGesture(const QGesture &) constructor does not work. It does not copy the state and properties...

SGaist

QGesture is a QObject thus it can't be copied.

I'd make these information separated objects (struct or class) and use them with your new events. This will avoid passing QGesture objects around.

Malte J

@SGaist So basically duplicating all the functionality provided by QGesture because i can't copy the objects? That doesn't sound very convenient to me.

SGaist

We might be misunderstanding each other. Is it correct that you have some custom data inside your custom gestures ?
If so, what I'm suggesting is to make these custom data easily accessible and copy them to the events you send to the state machine.

Malte J

Yes that is correct. Every of the 8 custom gestures defines its own set of data in addition to the QGestureState, which is set by the according gesture recognizer.

I now implemented an abstract superclass for all these gestures with a method getGestureData(). This method basically wraps all the data in a QMap<QString,QVariant> to make a general gesture treatment possible. The custom event GestureEvent now takes gesture type, the Qt::GestureState and the mentioned gesture data map.
It was a little bit circumstantial, but now it works.

Thanks again,
Malte