Generate QTouchEvents to simulate touches

SGaist

Hi and welcome to devnet,

I can't comment about whether your idea will work or not, however after a quick look at QTouchEvent's documentation, it seems wrong to instantiate your own QTouchDevice. It's the platform plugin that should do that

Nex46

Hi, thank you.
What do you mean by the platform plugin? I assumed that QTouchEvents could be used just like QMouseEvents.

Any other ideas on how to create an interface for a custom touch device?

SGaist

Qt uses QPA the Q Platform Abstraction concept to implement support for current/new platform. The platform plugins are build based on that. I didn't say the QTouchEvent couldn't be used like that. Just that the QTouchDevice you are creating is probably invalid since it's the QPA part that will create one if a touch device is available

Nex46

Ok, I see. The touch device I'm trying to connect does not have a standard interface so it can not be automatically recognized as a touch device.
The computer communicating with the device receives the coordinates of touchpoints via serial interface and are then sent to my Qt app over dBus.

Maybe writing a custom plugin using the QPA API is the only way. Anyone who has got any experience or thoughts on this approach?

SGaist

If it's already working through D-Bus then you can use the QtDBus module to write a helper class that will send the coordinates through D-Bus. Doing so you can keep your current implementation the same and not fiddle with low-level stuff

Nex46

Yes, it's already working with dBus. I'm using the QtDBus module to receive the coordinates in a helper class, but how do I generate the touches in the qml layer. That's what I need help with, and that's why I wrote the test code above to try to generate touch events. Or is it possible to generate an event directly via qbus?

SGaist

Ok, all right, I misunderstood you, sorry.

For your last question, no it's not. From your test code, I would remove the QTouchDevice, since there are non, giving an "invalid" one could sabotage the event processing.

Next, I wouldn't use a while loop, you can use a worker object, and give it to a QThread if needed, to implement the event generation.

agocs

Use QWindowSystemInterface::handleTouchEvent to inject touches into the QPA event system. Unlike the sendEvent approach shown above, it is also thread-safe.

Nex46

Hi agocs,

I cant seem to find any documentation on QWindowSystemInterface. How do I import the class?
I can only find old examples from <2010 and I'm using Qt 5.3. Is QWindowSystemInterface still valid?

SGaist

You'll have to dig in the sources, it's part of the QPA (QPlatform Abstraction) which isn't application API. You can find it under src/gui/kernel

Nex46

After several attempts to inject QTouchEvents I gave up and went for another solution. By defining a new qml element in C++ that emits a signal (touchActive) when the coordinates are changed and listening to this signal in qml layer (onTouchActive).
The drawback is that every multi-touch gesture will have to be interpreted in the C++ class; pinch, zoom etc.
For reference see:
http://qt-project.org/doc/qt-4.8/qtbinding.html#defining-new-qml-elements