Intercept QML keys on C++ side.

egor.utsov

QApplication app(argc, argv);
KeysInterceptor *ki = new KeysInterceptor;
app.installEventFilter(ki);

KeyInterceptor.cpp:

bool KeysInterceptor::eventFilter(QObject *watched, QEvent *event)
{
    if (event->type() == QEvent::Type::KeyPress || event->type() == QEvent::KeyRelease)
        qDebug() << __FUNCTION__ << ":" << watched << " - " << event->type();

    return QObject::eventFilter(watched, event);
}

egor.utsov

@dheerendra i just checked it on desktop and it works like a charm

dheerendra

This should work. What is the issue ? Sorry i missed seeing your response.
Question - To blackout your screen are you dependent on the key events ?

egor.utsov

@dheerendra yes. Blackout should happen if no activity on keyboard is observed for ten minutes for example

dheerendra

You can do this with simple timer which fires after 10 minutes. Inside the handler just check whether key event happened. I'm not in favor of event filter in QApplication becz, every event goes there, checks & then responds. It is risky & performance hit.

egor.utsov

@dheerendra how i can save time of last key event in this case?

dheerendra

you can use the following

Window {
    visible: true
    width: 640
    height: 480
    title: qsTr("Hello World")
    property date startDate :new Date();
    property int mils;
    Timer{
        id : tim
        interval: 10000
        repeat: true
        running: true
        onTriggered: {
            var end  = new Date();
            var elapsed = end.getTime() - startDate.getTime()
            if (elapsed>=10000){
                console.log("Blackout")
            }else {
                console.log("No blackout")
                startDate = new Date()
            }
        }
    }

    Rectangle{
        anchors.fill: parent
        focus: true
        objectName: "Dheerendra"
        Keys.onPressed: {
            console.log("Key is pressed")
            startDate = new Date();
        }
    }
}

egor.utsov

@dheerendra i have many places, where key processed. It is hard to put such code everywhere

dheerendra

It can be componetized as well. If it is everywhere, catch at the source only with qApp.

egor.utsov

@dheerendra once again - key events does not appear in filter. Think it is worth to mention that i use linuxfb plugin withOUT libinput.

dheerendra

basic question - In your program are you able to catch/handle the keyboard events ?

egor.utsov

@dheerendra qml ui react to key presses.

dheerendra

@egor.utsov said in Intercept QML keys on C++ side.:

if (event->type() == QEvent::Type::KeyPress || event->type() == QEvent::KeyRelease)

Can you just print the event type in eventFilter function ? Right now it is condition based. When you press the keyboard let us see what type events are coming. This may give us hint. If not we will do something else.

egor.utsov

@dheerendra i am also tried to enable QT_LOGGING_RULES="qt.qpa.input=true", but key events still not printed, however i see beginning of qpa logs

dheerendra

while we debug this issue, another option what you can try is Keys.forwardTo option in qml. We can make all the key events forward to one common object. This common object can handle your blackout logic.

what is happening in eventfilter function ? Is it printing the type as key event or not ?

egor.utsov

@dheerendra Hi. I reboot the unit and now key events appeared in filter. I don't know whats changed, but it works now. Thank you for help and sorry for bothering