[Solved] Having troubles connecting dbus signal to qt slot

LinGreg

I'm not sure where I should post this -- my appologies it I'm in the wrong place. I'm having loads of troubles trying to connect a dbus signal to a qt slot. Basically I want to connect a qt slot the a KDE dbus signal (this is on a linux system running KDE). I included code to try to exemplify my problem.

In the code below, I'm trying to connect "wakeup" of "my_obj" to the dBus signal "profileChanged". But, even though I'm sure (via qbusviewer) that this signal is being emitted, "wakeup" will not run. Here is my header:

@
class my_wake_up_class : public QObject
{
Q_OBJECT
public slots:
void wakeup(QString); //Does not run!
};
@

and my main code:

@
#include "test.h"

const QString service = "org.kde.Solid.PowerManagement";
const QString path = "/org/kde/Solid/PowerManagement";
const QString interface = "org.kde.Solid.PowerManagement";

void my_wake_up_class::wakeup(QString a)
{
std::cout << "this should run" << std::endl;
}

int main()
{
QDBusConnection bus = QDBusConnection::sessionBus();

    if (!bus.isConnected()) 
    {
            qDebug() << "Can't connect to the D-Bus session bus.\n";
    }                

    my_wake_up_class my_obj;
    
    bool conn = bus.connect(service, path, interface, "profileChanged", &my_obj, SLOT(wakeup(QString)));

    if (!conn) 
            qDebug() << "not connected";
    
    for(;;)
    {
            usleep(100000);
    }
    
    return 0;

}
@

So when "profileChanged" is emited (which I'm sure it is from qdbusviewer) the "wakeup" is not being called (as it should) and I not getting any error nor warnings. I'm sure that "profileChanged"'s sigature is of the form "void (QString)" from the qdbus output, which is:

bq. signal void org.kde.Solid.PowerManagement.profileChanged(QString)

I've no clue what I've done wrong (I haven't found anything in the documentation that is remotedly helpful). Does anyone know how to do this? Thanks.

p3c0

Hi,

To make this work you will need to enable Qt Event system. The best way would be to wrap your code inside QApplication.

eg:
@
QApplication a(argc, argv);
QDBusConnection bus = QDBusConnection::sessionBus();

if (!bus.isConnected()) {
...

return a.exec();
@

Also adding sleep functions would block that system and the events would never be delivered.

LinGreg

THANKS! I knew I was missing a rather simple, yet very important (and fundamental), piece of information. Thanks for humoring my ignorance!

p3c0

You're Welcome :) You can mark the post as solved by editing the post title and prepending [Solved].