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

[Louai Al-Khanji]

Hi

The attached works for me.

-- Louai

On Tue, Nov 10, 2009 at 8:48 AM, Moinier, Pierre (UK)
<Pierre.Moinier at baesystems.com> wrote:
> 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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>
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>       Keep this in mind if you answer this message.
>
> 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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-- 
- Louai Al-Khanji
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