emit singnals from another thread

Hi everybody!

I want to know if I emit a signal from another thread which event loop is responsible for emitting the signal. in other words, this signal emitted from which thread?

for example mysignal in below code

Code:

---

class O2;
 
class O1 : public QObject
{
Q_OBJECT
public:
O1(QObject *parent = 0): olocal(new O2(this)), QObject(parent) 
{
     m_thread = new QThread;
     olocal->moveToThread(m_thread);
     connect(m_thread, SIGNAL(started()), olocal, SLOT(start()));
     connect(olocal, SIGNAL(finished()), m_thread, SLOT(quit()));
 
....
}
 
~O1() {
   olocal->finish();
   m_thread->wait();
  delete olocal;
  delete m_thread;
}
 
signals:
   void mysignal();
};
 
class O2 : public QObject
{
Q_OBJECT
public:
O2(O1 *parent) : q_ptr(parent) {}
 
signals:
   void finished();
 
public slots:
    void start() { b_start = true; QTimer::singleShot(0, this, SLOT(run())); }
    void finish() { b_finish = true; }
 
    void run() {
        if(b_finished) {
             emit finished();
             return;
         }
 
        // do some staff
        if( /* something */)
             emit q_ptr->mysignal();
 
        if(b_start)
             QTimer::singleShot(0, this, run());
    }
};

---

thanks in advance

The signal would be emitted from the thread that is executing your code that does the emit. Your connect statements above will used queued connections when the sender/receiver are in different threads. You can force the connection type, but I would recommend that you use the default queued connection type unless you have very specific requirements.

Just to clarify: there is no event loop involved with emitting
However, with a QueuedConnection the slot it called by the event loop of the thread "owning" the receiver object.

The same is true for an AutoConnection when the thread executing the emit is a different one than the "receiver" thread, as jefftee said.

Cheers,
_