Handling stylus input in QML

Larvae

Hi,

I'm trying to handle the input of a stylus on a tablet in QML, but I'm stuck.

Qt has an example on how to use classic C++ to draw on a tablet. In the example they inherit QWidget to create a canvas which can handle QTabletEvent-events, allowing you to draw thick and thin lines based on the pen preassure. It works fine on my tablet.

I'm trying to get the same in modern QML. From what I have found, the QML element to handle this would be PointHandler. I can't get it to handle pen input, though. This is my last code to test this:

Window {
    visible: true
    width: 640
    height: 480
    id: main
    title: qsTr("Hello World")

    Label {
        id: label
        anchors.centerIn: parent
    }

    Rectangle {
        anchors.left: main.left
        anchors.top: main.top
        width: main.width
        height: main.height
        opacity: 0
        PointHandler {
            acceptedDevices: PointerDevice.AllDevices
            onActiveChanged: {
                label.text = (active == true ) ? "AllDevices" : ""
            }
        }
        PointHandler {
            acceptedDevices: PointerDevice.UnknownDevice
            onActiveChanged: {
                label.text = (active == true ) ? "UnknownDevice" : ""
            }
        }
        PointHandler {
            acceptedDevices: PointerDevice.Mouse
            onActiveChanged: {
                label.text = (active == true ) ? "Mouse " + point.pressure : ""
            }
        }
        PointHandler {
            acceptedDevices: PointerDevice.TouchScreen
            onActiveChanged: {
                label.text = (active == true ) ? "TouchScreen" : ""
            }
        }
        PointHandler {
            acceptedDevices: PointerDevice.TouchPad
            onActiveChanged: {
                label.text = (active == true ) ? "TouchPad" : ""
            }
        }
        PointHandler {
            acceptedDevices: PointerDevice.Stylus
            onActiveChanged: {
                label.text = (active == true ) ? "Stylus" : ""
            }
        }
        PointHandler {
            acceptedDevices: PointerDevice.Airbrush
            onActiveChanged: {
                label.text = (active == true ) ? "Airbrush" : ""
            }
        }
        PointHandler {
            acceptedDevices: PointerDevice.Puck
            onActiveChanged: {
                label.text = (active == true ) ? "Puck" : ""
            }
        }
    }

}

Since it didn't work I added a PointHandler for each type to see what happens. Turns out, the stylus triggers the PointHandler for Mouse instead of Stylus. So far I wasn't able to find out how to change this. I hope someone here can give me some pointers on that.

Regards

Thorsten

Larvae

After some try-and-error I found out that QGuiApplication recieves QTabletEvents, but they are not sent to the QQmlApplicationEngine.

At least installing an eventfilter that sends a message to qDebug when QTabletEvents are encountered reacts this way.

Marek

@Larvae Hi
Have you beeen able to handle stylus input in QML ? Here is some documentation HandlerPoint I'm starting some project which require pressure velocity measurement with hand writing so I wonder how it worked for you.
Best,
Marek