Question

Are there any Qt based screen lockers on linux systems ?

i.e. 4 pin digit or password screen locker ?

Any reference will be greatly appreciated.

Answer 1

On linux, the screen locking is done by the screensavers, and the password is the one from the user linux account.

You can use QProcess to run a command line and check if it was successful:

• gnome-screensaver-command --lock
• xscreensaver-command --lock
• qdbus org.freedesktop.ScreenSaver /ScreenSaver Lock
• qdbus org.gnome.ScreenSaver /ScreenSaver Lock
• xlock

And/or use QtDBus module to do the same thing

// Tries to lock the screen and returns true if successful 
bool LockScreenWithDBus() {
    QDBusConnection bus = QDBusConnection::sessionBus();
    if(!bus.isConnected())
        return false;

    QStringList services;       
    services << "org.freedesktop.ScreenSaver"             
             << "org.gnome.ScreenSaver"
    // These last two are probably not necessary, because kde uses freedesktop
    // conventions for dbus
             << "org.kde.ScreenSaver"
             << "org.kde.krunner";           

    foreach(QString service, services) {        
        QDBusInterface screenSaverInterface(service, "/ScreenSaver",
                                            QString(), bus);
        if (!screenSaverInterface.isValid())
            continue;       
        QDBusReply<void> reply = screenSaverInterface.call("Lock");
        if (reply.isValid())
            return true;
    }
    return false;
}