Timer QML Component event blocks UI?

[diorahman]

Hi there!

I have Timer component with event onTriggered event connected to a C++ process. The C++ has event loop in it. Somehow, it blocks the UI thread (validated from the busy indicator stops running; please take a look at the code from: http://cl.ly/A1RZ) whenever the timer is triggered. (The process doesn't block the UI when it is connected to a onClicked event of a Button element). I'm on N950 Harmattan device.

The complete code can be downloaded from here: http://cl.ly/A1RZ

Is there a way to not block the UI when I call the C++ process?

To prove that the onClicked doesn't block the UI (whenever it runs the C++ process) you can change the onClicked event from:

@onClicked: loopTimer.start();@

to

@onClicked: dummyLoop.process();@

The C++ process is as follows:

@void DummyProcessWithLocalEventLoop::process()
{
qDebug() << "run local event loop";

QEventLoop loop;
QTimer timer;
timer.setSingleShot(true);
connect(&timer, SIGNAL(timeout()), &loop, SLOT(quit()));
timer.start(5000);
loop.exec();

qDebug() << "local event loop done";

}
@

The page asking the process

@import QtQuick 1.1
import com.nokia.meego 1.0
import dummy 1.0

Page {
tools: commonTools

id: container

DummyLoop{
    id: dummyLoop
}

BusyIndicator{
    id: busy
    anchors.centerIn: parent
    running: true
}

Timer{
    id: loopTimer
    interval: 1000
    running: false

    onTriggered: {
        dummyLoop.process();
    }

}

Button{
    anchors {
        horizontalCenter: parent.horizontalCenter
        top: busy.bottom
        topMargin: 10
    }

    text: qsTr("run dummy loop")
    onClicked: loopTimer.start();
}

}
@

[giesbert]

That the main event loop (for the UI) is blocked is absolutly clear. Your timer runns 5 seconds and you spin a sub event loop inside DummyProcessWithLocalEventLoop::process(). This event loop will not üprocess events from the main event loop.

[diorahman]

Thanks for your quick reply :-)

What I couldn't understand is: the behavior between onClicked event and onTriggered is different. What is the explanation?