[Qt-interest] Can't post a user event from compute thread to GUI thread

[Moinier, Pierre (UK)]

Hi!
 
I have done what you suggested, but the behaviour is the same. Nothing
seems to go to event()...
 
So I commented out the call to installEventFilter and to evenFilter and
here is my reimplementation of event():
 
 bool UpdateView::event(QEvent *event)
 {
       std::cout << "hello" << std::endl;
     if (event->type() == QEvent::User) {
       std::cout << "hello ... found the event!" << std::endl;
             return true;
         }
 
     else 
       return false;
 }

If it is easier, I could tar up the couple of files and send it to
you...
 
Regards,
 
    -Pierre.

________________________________

From: Mihail Naydenov [mailto:mlists at ymail.com] 
Sent: 10 November 2009 12:35
To: Moinier, Pierre (UK); qt-interest at trolltech.com
Subject: Re: [Qt-interest] Can't post a user event from compute thread
to GUI thread


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After just a quick look, why do you use an event filter, when you are
sending events directly to that object?
Just reimplement event() in UpdateView and you will be ok.

Also note that your implementation of instance() is NOT thread safe. You
can Q_GLOBAL_STATIC macro to help you out in that.
(no how to use it, look at QThreadPool or some other singleton in qt's
src)

MihailNaydenov



	From: "Moinier, Pierre (UK)" <Pierre.Moinier at baesystems.com>
	To: qt-interest at trolltech.com
	Sent: Tue, November 10, 2009 1:14:03 PM
	Subject: [Qt-interest] Can't post a user event from compute
thread to GUI thread
	
	
	
	Hi!
	 
	I am trying to figure out how to send an event fom a thread to
the main visualisation thread using postEvent, installEventFilter and
eventFilter.
	I am pasting parts of the test code I am using, which compiles,
but somehow, the event is probably not reaching the filter, beause I am
not geting any messages from eventFilter.
	 
	Could anyone tell me what I am doing wrong?
	 
	Regards,
	 
	    -Pierre.
	 
	-------------------------------------------------------------
Test Code
------------------------------------------------------------------
	main.cpp:
	 
	#include <QApplication>
	 
	#include "ComputeThread.h"
	#include <qpushbutton.h>
	 
	int main(int argc, char* argv[])
	{
	  QApplication app(argc, argv);
	  ComputeThread thread;
	  thread.start();
	 
	  QPushButton hello("Hello world!");
	  hello.resize(100, 30);
	 
	  hello.show();
	  return app.exec();
	}
	
	ComputeThread.cpp:
	 
	
	#include <iostream>
	#include <QApplication>
	#include <QEvent>
	 
	

	#include "ComputeThread.h"
	#include "UpdateView.h"
	 
	void ComputeThread::run()
	{
	  for (int i=0;i<100;i++)
	    {
	      sleep(1);
	      std::cout << "sending Event...." << UpdateView::UPDATE_EV1
<< std::endl;
	      QEvent *e = new QEvent(QEvent::User);
	      QApplication::postEvent(&UpdateView::instance(), e);
	      //  QCoreApplication::postEvent(&UpdateView::instance(),
new QEvent(static_cast<QEvent::Type>(UpdateView::UPDATE_EV1)));
	    }
	}
	
	UpdateView.cpp:
	 
	#include <iostream>
	#include <QEvent>
	 
	#include "UpdateView.h"
	 
	

	UpdateView::UpdateView()
	{
	  std::cout << "hello sailor" << std::endl;
	  installEventFilter(this);
	}
	 
	bool UpdateView::eventFilter(QObject *obj, QEvent *event)
	{
	  std::cout << "hello" << std::endl;
!!! I should get Hello on the sceen.....
	  const Event ev = static_cast<Event>(event->type());
	  switch(ev)
	    {
	    case UPDATE_EV1:
	      std::cout << "Updating the scene..." << std::endl;
	      break;
	 
	    default:
	      return false;
	    }
	  return true;
	}
	
	UpdateView.h:
	 
	#ifndef UPDATEVIEW_H
	#define UPDATEVIEW_H
	 
	#include <QEvent>
	#include <QObject>
	 
	class UpdateView : public QObject
	{
	  Q_OBJECT
	    public:
	  UpdateView(); 
	  static UpdateView& instance()
	    {
	      static UpdateView theinstance;
	      return theinstance;
	    }
	 
	  enum Event {UPDATE_EV1 = 1000 , UPDATE_EV2 = 1001};
	 
	  bool eventFilter(QObject *obj, QEvent *event);
	 
	};
	 
	#endif
	
	 
	

	
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