thread problem

[^NyAw^]

Hi,

If the heavy computation performs GUI, use SIGNAL SLOT mechanism to let the main thread do the GUI operations. It's not difficult.

But if you really want to do it as you tell, why use a thread that starts a timer? Only start a timer on the main thread and try if the calls to "processEvents" work.

[talk2amulya]

looks like a revising in the heavy-computation algorithm is in order....a connect in the main also doesnt work..its really strange....thanks guys for ur time!

[^NyAw^]

Hi,

a connect in the main also doesnt work

Is "yourClassThread" defining the "Q_OBJECT" macro?

You can take a look at console output to see why it don't connect. Note that the connections have to be "Qt::QueuedConnection" or let it autodetect.

[talk2amulya]

i meant i cant use connect(...) in main() because where would i put Q_OBJECT?? about Qt::QueuedConnection , yes i used that too..still didnt work..i m sure if i get to call processEvents() at a certain interval until the processing is over, i can animate the icon..but for sm reason, none of my attempts to call processEvents(), either from main() or other thread is working....

[spirit]

create an object in main thread (in main.cpp) which will call qApp->processEvents by QTimer::timeOut.

....
class MyProcessEventDispatcher: public QObject
{
    Q_OBJECT
 
public:
       MyProcessEventDispatcher(QObject *parent = 0) 
          : QObject (parent) 
        {
                m_timer.setInterval(100);
                connect(&m_timer, SIGNAL(timeout()), SLOT(updateEvents()));
                m_timer.start();
       }
 
private slots:
      void updateEvents() 
      {
            m_timer.start();
            qApp->processEvents();
       }
private:
     QTimer m_timer;
};
#include "main.moc" 
int main(int argc, char **argv)
{
      QApplication app(argc, argv);
      MyProcessEventDispatcher mpee;
      ...  
      return app.exec();
}

....
class MyProcessEventDispatcher: public QObject
{
    Q_OBJECT

public:
       MyProcessEventDispatcher(QObject *parent = 0) 
          : QObject (parent) 
        {
                m_timer.setInterval(100);
                connect(&m_timer, SIGNAL(timeout()), SLOT(updateEvents()));
                m_timer.start();
       }

private slots:
      void updateEvents() 
      {
            m_timer.start();
            qApp->processEvents();
       }
private:
     QTimer m_timer;
};
#include "main.moc" 
int main(int argc, char **argv)
{
      QApplication app(argc, argv);
      MyProcessEventDispatcher mpee;
      ...  
      return app.exec();
}

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[talk2amulya]

for some reason

connect(&m_timer, SIGNAL(timeout()), SLOT(updateEvents()));

connect(&m_timer, SIGNAL(timeout()), SLOT(updateEvents()));

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isnt getting connected..

[spirit]

I've updated code and also tested it. a slot is called normal.

[talk2amulya]

yeh, i made those changes too but still updateEvents() is only getting called once, until whole of the processing is done..so no help from this either..thanks though, spirit...

[talk2amulya]

actually there is only one function call(which makes further calls) that is doing all the heavy processing..and that function call is in main()..perhaps the control isnt going back to the other objects or timers cuz of it..could that be true? just cuz one particular function has to execute, the control will go nowhere else?

[spirit]

yes this is possible. so, try to call processEvents in that "havy" function.

[^NyAw^]

Hi,

Calling "processEvents" is not a good idea. I think if you call it many times it ignore some of them.

Have you ported your heavy computation inside the thread? You will not need to call "processEvents" then. You emit SIGNALs and let the main thread do its work.

[spirit]

maybe this can help you Keeping the GUI Responsive

[talk2amulya]

that is EXACTLY what i did sm days back..and the icon animates cuz of it as desired..although intermittently ..but i had to place like 30 calls to processEvents() here and there inside it..and if i want it to be done smoothly i might need more..so thats why i was wondering there should be a better way to do it in QT..so i went with using timers and on timeout, calling processEvents(), but evidently it also has no effect..which i find really surprising...anyone has anymore info about processEvents()??or smth else that could resolve this issue?

[talk2amulya]

i have already read that link..and i have tried sm of the ways that fits my needs..but none of them worked..

[talk2amulya]

hi oscar,

the heavy processing code contains some GUI calls, so i cant put that in another thread.. even if it was to be done..it'd be a lot of work..i m looking for a solution that bypasses me having to change anything in the way the things are done currently

[^NyAw^]

Hi,

#include <QThread>
class myThread : public QThread
{
  Q_OBJECT
public:
  //Redefine this method with your computation
  void run()
  {
     while(!bStop)
     {
       //Do some work
       emit (emitShowText(QString("Hello Thread"));
       ...
     }
 
  }
 
signals:
  void emitShowText(QString);            //Define all the signals you want to emit
  void emitShowProcessProgress(int);
}

#include <QThread>
class myThread : public QThread
{
  Q_OBJECT
public:
  //Redefine this method with your computation
  void run()
  {
     while(!bStop)
     {
       //Do some work
       emit (emitShowText(QString("Hello Thread"));
       ...
     }

  }

signals:
  void emitShowText(QString);            //Define all the signals you want to emit
  void emitShowProcessProgress(int);
}

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myAppWindow::myAppWindow(QWidget *parent, Qt::WFlags flags) : QMainWindow(parent, flags)
{
  ui.setupUi(this);  //Setup UI if used a GUI editor like QDesigner
 
  //Create the thread and connect it's signals to "this" slots
  m_pThread = new myThread(this);
  bool bC = connect(m_pThread,SIGNAL(emitShowText(QString)),this,SLOT(showText(QString)),Qt::QueuedConnection); //Insert a debug point and take a look at console out. If connection fail it will reach error message on it
 
  m_pThread->start();  //Enter the Thread "run" method
}

myAppWindow::myAppWindow(QWidget *parent, Qt::WFlags flags) : QMainWindow(parent, flags)
{
  ui.setupUi(this);  //Setup UI if used a GUI editor like QDesigner

  //Create the thread and connect it's signals to "this" slots
  m_pThread = new myThread(this);
  bool bC = connect(m_pThread,SIGNAL(emitShowText(QString)),this,SLOT(showText(QString)),Qt::QueuedConnection); //Insert a debug point and take a look at console out. If connection fail it will reach error message on it

  m_pThread->start();  //Enter the Thread "run" method
}

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