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Help with QWidget::show()

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  • M Offline
    M Offline
    mmikeinsantarosa
    wrote on 6 Nov 2021, 19:08 last edited by
    #1

    I need to call a function when a QWidget gets its show() method gets called and I have looked at examples for Mainwindow but I don't understand how this works.
    The widget that needs to implement show() is called ChartProperties. For declaring it in the header,
    void MainWindow::showEvent(QShowEvent *ev);
    doesn't work because this isn't a mainwindow and
    void ChartProperties::showEvent(QShowEvent *ev)
    complains about an extra member showevent.

    Any suggestions would be much appreciated.

    I'm clueless here and thanks for any response.

    1 Reply Last reply
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    • M mmikeinsantarosa
      6 Nov 2021, 19:43

      Sorry, I'm feeling pretty dumb here.

      Another class executes the ChartProperties->Show() method and when the dialog is rendered, I want to trap the ChartProperties show() event.
      I have irtual void showEvent(QShowEvent *event) override;
      in my ChartProperties header but I don't understand how to receive the showEvent..

      S Offline
      S Offline
      SGaist
      Lifetime Qt Champion
      wrote on 6 Nov 2021, 19:58 last edited by
      #10

      Hi,

      @mmikeinsantarosa said in Help with QWidget::show():

      I have irtual void showEvent(QShowEvent *event) override;

      This is just a declaration, you still have to implement the function itself.

      Interested in AI ? www.idiap.ch
      Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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      • C Offline
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        Christian Ehrlicher
        Lifetime Qt Champion
        wrote on 6 Nov 2021, 19:24 last edited by
        #2

        @mmikeinsantarosa said in Help with QWidget::show():

        void ChartProperties::showEvent(QShowEvent *ev)
        complains about an extra member showevent.

        What exact error message do you get?

        Qt Online Installer direct download: https://download.qt.io/official_releases/online_installers/
        Visit the Qt Academy at https://academy.qt.io/catalog

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        • M Offline
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          mmikeinsantarosa
          wrote on 6 Nov 2021, 19:27 last edited by
          #3

          @Christian-Ehrlicher said in Help with QWidget::show():

          void ChartProperties::showEvent(QShowEvent *ev)

          I get "extra qualification on member 'showEvent'"

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          • M Offline
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            mmikeinsantarosa
            wrote on 6 Nov 2021, 19:28 last edited by
            #4

            And the widget is actually a "QDialog".

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              Christian Ehrlicher
              Lifetime Qt Champion
              wrote on 6 Nov 2021, 19:30 last edited by
              #5

              And please show how you defined and declared this function.

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              Visit the Qt Academy at https://academy.qt.io/catalog

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              • M Offline
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                mmikeinsantarosa
                wrote on 6 Nov 2021, 19:34 last edited by
                #6

                Realizing that the class is actually a QDialog so I just changed the declaration to
                virtual void showEvent(QShowEvent *event) override;
                and it doesn't complain now.

                So now, how do I hook it up to execute another function?
                Right clicking on it and selecting refactor doesn't provide a way to create a function in my source. Do I need to create a slot to connect it to?

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                • C Offline
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                  Christian Ehrlicher
                  Lifetime Qt Champion
                  wrote on 6 Nov 2021, 19:36 last edited by
                  #7

                  @mmikeinsantarosa said in Help with QWidget::show():

                  So now, how do I hook it up to execute another function?

                  I don't understand this question. Simply create a function in your class and call it from within your other function.

                  Qt Online Installer direct download: https://download.qt.io/official_releases/online_installers/
                  Visit the Qt Academy at https://academy.qt.io/catalog

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                  • M Offline
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                    mmikeinsantarosa
                    wrote on 6 Nov 2021, 19:43 last edited by mmikeinsantarosa 11 Jun 2021, 19:43
                    #8

                    Sorry, I'm feeling pretty dumb here.

                    Another class executes the ChartProperties->Show() method and when the dialog is rendered, I want to trap the ChartProperties show() event.
                    I have irtual void showEvent(QShowEvent *event) override;
                    in my ChartProperties header but I don't understand how to receive the showEvent..

                    S 1 Reply Last reply 6 Nov 2021, 19:58
                    0
                    • C Offline
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                      Christian Ehrlicher
                      Lifetime Qt Champion
                      wrote on 6 Nov 2021, 19:47 last edited by
                      #9

                      As explained in the documentation this function is called when the widget is shown, you must not call it by yourself.

                      Qt Online Installer direct download: https://download.qt.io/official_releases/online_installers/
                      Visit the Qt Academy at https://academy.qt.io/catalog

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                      • M mmikeinsantarosa
                        6 Nov 2021, 19:43

                        Sorry, I'm feeling pretty dumb here.

                        Another class executes the ChartProperties->Show() method and when the dialog is rendered, I want to trap the ChartProperties show() event.
                        I have irtual void showEvent(QShowEvent *event) override;
                        in my ChartProperties header but I don't understand how to receive the showEvent..

                        S Offline
                        S Offline
                        SGaist
                        Lifetime Qt Champion
                        wrote on 6 Nov 2021, 19:58 last edited by
                        #10

                        Hi,

                        @mmikeinsantarosa said in Help with QWidget::show():

                        I have irtual void showEvent(QShowEvent *event) override;

                        This is just a declaration, you still have to implement the function itself.

                        Interested in AI ? www.idiap.ch
                        Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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                        • M Offline
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                          mmikeinsantarosa
                          wrote on 6 Nov 2021, 20:03 last edited by
                          #11

                          Do I create a slot then connect this event to my slot?

                          M 1 Reply Last reply 6 Nov 2021, 20:16
                          0
                          • C Offline
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                            Christian Ehrlicher
                            Lifetime Qt Champion
                            wrote on 6 Nov 2021, 20:05 last edited by
                            #12

                            @mmikeinsantarosa said in Help with QWidget::show():

                            Do I create a slot then connect this event to my slot?

                            What slot? showEvent() is a class function, not a slot. Please learn C++ basics first.

                            Qt Online Installer direct download: https://download.qt.io/official_releases/online_installers/
                            Visit the Qt Academy at https://academy.qt.io/catalog

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                            • M mmikeinsantarosa
                              6 Nov 2021, 20:03

                              Do I create a slot then connect this event to my slot?

                              M Offline
                              M Offline
                              mpergand
                              wrote on 6 Nov 2021, 20:16 last edited by mpergand 11 Jun 2021, 20:17
                              #13

                              @mmikeinsantarosa

                              Your question seems pretty close this this one

                              As an alternative, you can simply do:

                              MyDialog::show()
                              {
                                myFunction();
                                QDialog::show();
                              }
                              

                              Using showEvent is dangerous cause it can be called multi times !

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                              • M Offline
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                                mmikeinsantarosa
                                wrote on 6 Nov 2021, 20:19 last edited by
                                #14

                                The method name is "showEvent" which leads me to think it's a signal. It's also listed in the signals list in the documentation for QDialog so I thought it might actually be a signal.

                                thanks for clearing this up SGaist.

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                                • S Offline
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                                  SGaist
                                  Lifetime Qt Champion
                                  wrote on 6 Nov 2021, 20:24 last edited by
                                  #15

                                  @mmikeinsantarosa said in Help with QWidget::show():

                                  It's also listed in the signals list in the documentation for QDialog

                                  That's wrong, neither in the Qt 5 nor in the Qt 6 documentation.

                                  It is listed under Reimplemented Protected Functions.

                                  Beside that, signals name do not finish in "event". They usually have a name in relation to some action like rejected in QDialog.

                                  Interested in AI ? www.idiap.ch
                                  Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

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                                  • M Offline
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                                    mmikeinsantarosa
                                    wrote on 6 Nov 2021, 22:37 last edited by
                                    #16

                                    I stand corrected. entering QDialog in the Qt help and selecting signals reveals signals at the top, with 3 items under it then Reimplemented Protected Functions where the showEvent function is listed.

                                    J 1 Reply Last reply 7 Nov 2021, 07:26
                                    0
                                    • M mmikeinsantarosa
                                      6 Nov 2021, 22:37

                                      I stand corrected. entering QDialog in the Qt help and selecting signals reveals signals at the top, with 3 items under it then Reimplemented Protected Functions where the showEvent function is listed.

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                                      JonB
                                      wrote on 7 Nov 2021, 07:26 last edited by
                                      #17

                                      @mmikeinsantarosa
                                      Indeed, that is how Qt documentation lays out its methods.

                                      To reiterate something @Christian-Ehrlicher said. In Qt nomenclature:

                                      • Methods ending in Event (showEvent(), mouseMoveEvent()) are not signals. Instead they are protected virtual methods. You must sub-class and override if you want to access them.

                                      • Signals tend to be named as the past tense of something that has happened (clicked(), customContextMenuRequested()). You cannot override them. You can connect() to them, without needing to sub-class.

                                      • And slots are just named as an action to be performed (show(), setDiabled()).

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                                      6 Nov 2021, 19:47

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