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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
    #14

    Show us the implementation of your MyApp constructor, please.

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

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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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