How come this slot doesn't get called every second?

[ShaChris23]

Why is it that, for the code below, the Thread1.printEvent() gets printed as often as Thread2.printEvent()? My thought is that since it's 2 separate event loops (due to 2 threads), Thread1.printEvent() should keep on going even though Thread2.printEvent() takes a long time?

Here's how everything is connected:

--> denotes is connected to

Thread1.timer.timeout() --> Thread1.doSomething(); // times out every 1 second
Thread1.doSomething() --> Thread1.printEvent(); // takes "zero" time
Thread1.doSomething() --> Thread2.printEvent(); // takes 10 seconds


This is the code for Thread1

#include <QThread>
#include <QTimer>
 
class Thread1 : public QThread
{
  Q_OBJECT
 
public:
  void run();
 
private:
  QTimer*   timer;
 
signals:
  void doSomething();
 
private slots:
  void printEvent();
 
private:
  int number; 
};
 
#include <iostream>
 
void Thread1::run()
{
  number = 0;
 
  // We create QTimer here because it has thread-affinity
  timer = new QTimer();
  if(!QObject::connect( timer,
                    SIGNAL(timeout()),
                    this,
                    SIGNAL(doSomething())))
  {
    throw std::runtime_error( "ERROR!" );
  }
  if(!QObject::connect( this,
    SIGNAL(doSomething()),
    this,
    SLOT(printEvent())))
  {
    throw std::runtime_error( "ERROR!" );
  }
 
  timer->start(1000);
  this->exec();
 
  delete timer;
}
 
void Thread1::printEvent()
{
  std::cout << "Thread1: sending event... " << number++ << std::endl;
}

#include <QThread>
#include <QTimer>

class Thread1 : public QThread
{
  Q_OBJECT

public:
  void run();

private:
  QTimer*   timer;

signals:
  void doSomething();
  
private slots:
  void printEvent();

private:
  int number; 
};

#include <iostream>

void Thread1::run()
{
  number = 0;

  // We create QTimer here because it has thread-affinity
  timer = new QTimer();
  if(!QObject::connect( timer,
                    SIGNAL(timeout()),
                    this,
                    SIGNAL(doSomething())))
  {
    throw std::runtime_error( "ERROR!" );
  }
  if(!QObject::connect( this,
    SIGNAL(doSomething()),
    this,
    SLOT(printEvent())))
  {
    throw std::runtime_error( "ERROR!" );
  }

  timer->start(1000);
  this->exec();

  delete timer;
}

void Thread1::printEvent()
{
  std::cout << "Thread1: sending event... " << number++ << std::endl;
}

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This is the code for Thread2..

#include <QThread>
 
class Thread2 : public QThread
{
  Q_OBJECT
 
public:
  void run();
 
public slots:
  void  printEvent();
 
private:
  int number;
};
 
#include <iostream>
 
void Thread2::run()
{
  number = 0;
  exec();
}
 
void Thread2::printEvent()
{
  std::cout << "Thread2: Received event... " << number++ << std::endl;
  if( number < 3 )
  {
    msleep(10000);
  }
}

#include <QThread>

class Thread2 : public QThread
{
  Q_OBJECT

public:
  void run();

public slots:
  void  printEvent();

private:
  int number;
};

#include <iostream>

void Thread2::run()
{
  number = 0;
  exec();
}

void Thread2::printEvent()
{
  std::cout << "Thread2: Received event... " << number++ << std::endl;
  if( number < 3 )
  {
    msleep(10000);
  }
}

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Lastly, this is the code for main.cpp

#include <QObject>
#include <QtCore/QCoreApplication>
 
int main( int   argc,
          char* argv[] )
{
  QCoreApplication  a( argc,
                       argv );
 
  Thread1           thread1;
  Thread2           thread2;
 
  // Connect the 2 threads signal slot here
  if (!QObject::connect(&thread1, SIGNAL(doSomething()),
      &thread2, SLOT(printEvent())))
  {
    throw std::runtime_error( "ERROR!" );
  }
 
  thread1.start();
  thread2.start();
 
  return a.exec();
}

#include <QObject>
#include <QtCore/QCoreApplication>

int main( int   argc,
          char* argv[] )
{
  QCoreApplication  a( argc,
                       argv );

  Thread1           thread1;
  Thread2           thread2;

  // Connect the 2 threads signal slot here
  if (!QObject::connect(&thread1, SIGNAL(doSomething()),
      &thread2, SLOT(printEvent())))
  {
    throw std::runtime_error( "ERROR!" );
  }

  thread1.start();
  thread2.start();

  return a.exec();
}

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[caduel]

read up on that 5th argument to the connect call.... (and use the queued connction)

[ShaChris23]

@caduel:

Thanks for your suggestion. I will look into that 5th argument.