Turning on and off the screen of MeeGo Harmattan using QML and C++

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This article explains how to turn on and off the screen of a MeeGo Harmattan device programatically from QML using C++ and QML binding.

Article Metadata

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Tested with

SDK: Nokia Qt SDK 1.1.3

Devices(s): Nokia N950

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Compatibility

Platform(s): MeeGo Harmattan

Device(s): All

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Article

Keywords: QmDisplayState,qmdisplaystate.h,qmsystem

Created: sabb0ur ()

Last edited: hamishwillee (11 Oct 2012)

Introduction

This code snippet will enable you to programatically query the display state of the device, whether it is On or Off (or Dimmed), as well as turn On/Off the display from button clicks on the QML interface.

It uses QML/C++ binding and the QmDisplayState class to do so.

Project file

CONFIG+= qmsystem2

mycustomclass.h

#ifndef MYCUSTOMCLASS_H 
#define MYCUSTOMCLASS_H
 
#include <qmdisplaystate.h>
#include <QDebug>
#include <QObject>
 
class MyCustomclass : public QObject
{
    Q_OBJECT
public:
    MyCustomclass();
 
    MeeGo::QmDisplayState displayState;
 
    Q_INVOKABLE void printDisplayState();
    Q_INVOKABLE void turnOffDisplay();
    Q_INVOKABLE void turnOnDisplay();
 
};
 
#endif // MYCUSTOMCLASS_H

myscustomclass.cpp

#include "mycustomclass.h"
 
MyCustomclass::MyCustomclass() {
}
 
 
void MyCustomclass::printDisplayState() {
    if (displayState.get() == MeeGo::QmDisplayState::On) {
        qDebug() << "The display is on!";
    }
    else if(displayState.get() == MeeGo::QmDisplayState::Off) {
        qDebug() << "The display is off!";
    }
}
 
void MyCustomclass::turnOffDisplay() {
    qDebug() << "Turning off display";
    displayState.set(MeeGo::QmDisplayState::Off);
}
 
void MyCustomclass::turnOnDisplay() {
    qDebug() << "Turning on display";
    displayState.set(MeeGo::QmDisplayState::On);
}

main.cpp

#include <QDebug>
#include <QtGui/QApplication>
#include "qmlapplicationviewer.h"
#include <QDeclarativeContext>
#include "mycustomclass.h"
 
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
 
    QmlApplicationViewer viewer;
    viewer.setOrientation(QmlApplicationViewer::ScreenOrientationAuto);    
 
    MyCustomclass myObject;
    viewer.setMainQmlFile(QLatin1String("qml/WakeUpAndSleep/main.qml"));
    viewer.rootContext()->setContextProperty("myObject", &myObject);
 
    viewer.showExpanded();
 
    return app.exec();
}

main.qml

import QtQuick 1.1 
import com.nokia.meego 1.0
 
PageStackWindow {
    id: appWindow
 
    initialPage: mainPage
 
    MainPage {
        id: mainPage
    }
}

MainPage.qml

import QtQuick 1.1 
import com.nokia.meego 1.0
 
Page {
 
    Timer {
        id: turnOnScreenTimer
        interval: 5000; running: false; repeat: false
        onTriggered: {
            console.log("Timer running to turn on screen");
            myObject.turnOnDisplay();
            myObject.printDisplayState();
        }
    }
 
    Label {
        id: label
        anchors.centerIn: parent
        text: qsTr("Sleep and wakeup demo")
        visible: false
    }
 
    Button{
        id: displayStateButton
        anchors {
            horizontalCenter: parent.horizontalCenter
            top: label.bottom
            topMargin: 10
        }
        text: qsTr("Display state")
 
        onClicked: {
            myObject.printDisplayState();
        }
    }
 
    Button{
        id: turnOffScreenButton
        anchors {
            horizontalCenter: parent.horizontalCenter
            top: displayStateButton.bottom
            topMargin: 10
        }
        text: qsTr("Turn off screen")
        onClicked: {
            myObject.printDisplayState();
            myObject.turnOffDisplay();
            myObject.printDisplayState();
        }
    }
 
    Button{
        id: turnOffForFiveButton
        anchors {
            horizontalCenter: parent.horizontalCenter
            top: turnOffScreenButton.bottom
            topMargin: 10
        }
        text: qsTr("Turn off screen for 5 seconds")
        onClicked: {
            myObject.printDisplayState();
            myObject.turnOffDisplay();
            myObject.printDisplayState();
            turnOnScreenTimer.start();
        }
 
    }
}

Test application

Download the zipped project here File:WakeUpAndSleep.zip which includes a .deb installation.