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The same code works under Windows and fails under GNU/Linux

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  • G Offline
    G Offline
    goetz
    wrote on last edited by
    #15

    [quote author="vishwajeet" date="1298555161"]
    Problem seems simple here i guess, its just you have to check the difference between win and Linux in terms of main() code execution, max u might have to go 1 layer down but that should resolve ur problem. [/quote]

    [Highlighting by me]

    Can you please use correct english in your writings. It's hard to read these non obvious abbreviations, especially for non-native speakers. This is neither Twitter nor SMS, we do have far more than 140 available :-) so no need to confuse people.

    http://www.catb.org/~esr/faqs/smart-questions.html

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    • J Offline
      J Offline
      jerome.bouat
      wrote on last edited by
      #16

      Now the MyApp class has the below declaration :
      @class MyApp : public QApplication
      {
      private:

      Q_OBJECT

      public:
      bool tested;
      QString program;
      streambuf *coutbuf;
      virtual ~MyApp();
      MyApp(int &,char **);
      };@

      And below is its definition :
      @MyApp::MyApp(int &argc,char **argv) : QApplication(argc,argv),program(argv[0]),coutbuf(cout.rdbuf()),tested(false)

      {

      MainWindow *mainWindow = new MainWindow(argc,argv);

      mainWindow->show();

      }@

      I recompiled all but I still get the same issue.

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      • G Offline
        G Offline
        goetz
        wrote on last edited by
        #17

        It's common to instantiate your UI class in the main function after the QApplication (-derived) object has been created.

        I have not tested if that is the cause of your problem, but at least it's common coding style in Qt world.

        http://www.catb.org/~esr/faqs/smart-questions.html

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        • V Offline
          V Offline
          vishwajeet
          wrote on last edited by
          #18

          Ohhhh i apologies for too many abbreviations in my writing.
          [quote author="Volker" date="1298556541"][quote author="vishwajeet" date="1298555161"]
          Problem seems simple here i guess, its just you have to check the difference between win and Linux in terms of main() code execution, max u might have to go 1 layer down but that should resolve ur problem. [/quote]

          [Highlighting by me]

          Can you please use correct english in your writings. It's hard to read these non obvious abbreviations, especially for non-native speakers. This is neither Twitter nor SMS, we do have far more than 140 available :-) so no need to confuse people.
          [/quote]

          To jerome.bouat

          Could you please check if @MyApp app(argc,argv);
          return app.exec(); // event loop@ is getting executed in case of windows and Linux ?

          Born To Code !!!

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          • J Offline
            J Offline
            jerome.bouat
            wrote on last edited by
            #19

            The below code fragment is being executed
            on Windows (because the application works properly)
            and Linux (because I don't get the error if I comment it) :
            @MyApp app(argc,argv);
            return app.exec(); // event loop@

            I moved the GUI initialization in a separate method (createWindow) :
            @class MyApp : public QApplication

            {

            private:

            Q_OBJECT

            public:

            bool tested;

            QString program;

            streambuf *coutbuf;

            virtual ~MyApp();

            // empty, just call super class constructor
            // and initialize object attributes

            MyApp(int &,char **);

            void createWindow(int &,char **);

            };@

            Into this new method, I don't get the error message
            if I comment the "show()" call
            @void MyApp::createWindow(int &argc,char **argv)

            {

            MainWindow *mainWindow = new MainWindow(argc,argv);

            mainWindow->show(); // no error if commented

            }@

            Thus, the issue seems to be located into the super-super class method QWidget::show().

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            • G Offline
              G Offline
              goetz
              wrote on last edited by
              #20

              No way to analyze this here. Can you please:

              • make a small test case
              • put it into a complete project
              • make sure it compiles, runs and shows the error
              • put the sources (and only these) into a ZIP
              • put the ZIP on dropbox, pastebin or make it available somewhere else
              • post the link here

              http://www.catb.org/~esr/faqs/smart-questions.html

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              • J Offline
                J Offline
                jerome.bouat
                wrote on last edited by
                #21

                It seems to be an OpenGL issue but the error message I reported is far from that.

                I'm investigating.

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                • J Offline
                  J Offline
                  jerome.bouat
                  wrote on last edited by
                  #22

                  Just a Qt newbie question : I assume that all calls like below should be located into header files only and not cpp files :
                  @QObject::connect(scrollBar, SIGNAL(valueChanged(int)), label, SLOT(setNum(int)));@
                  ?

                  Or could we possibly use this call into cpp files by including the right Qt file ?

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                  • G Offline
                    G Offline
                    goetz
                    wrote on last edited by
                    #23

                    It's an ordinary call of a static method. You put it into regular method bodies. That happens mostly in the .cpp files, but can be put into headers too.

                    http://www.catb.org/~esr/faqs/smart-questions.html

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                    • A Offline
                      A Offline
                      andre
                      wrote on last edited by
                      #24

                      What's more, in most cases the right file is already included when you call this: the header of either of the objects you want to connect. If you find that you can not use the connect call: it is to be found in the QObject header.

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                      • J Offline
                        J Offline
                        jerome.bouat
                        wrote on last edited by
                        #25

                        I assume the "emit" keyword can be used in cpp files ?

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                        • A Offline
                          A Offline
                          andre
                          wrote on last edited by
                          #26

                          Perhaps you should work through one of the basic Qt tutorials. This is all explained very well in the documentation, there is even a section called "Signals & Slots" that explains in detail how this all works.

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