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How can I get the application QmlEngine ?

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  • K Offline
    K Offline
    kmarconi
    wrote on last edited by kmarconi
    #3

    What I do actually is passing a reference of the engine into my class of translation. But since I never create an engine, could it be the reason why it is not working ?

    what's this supposed to be actually ?

    qobject_cast<QQmlApplicationEngine*>(qmlEngine(this));
    

    This is one of the way I found to get the engine.
    The problem here I think is that in each example I see which are restranlating their apps, they are using only one cpp file and one qml file so they just simply create an engine in the main and load the qml in it. But for me, it's not possible because I have a lot of classes and since one of them is already using my "main.qml" file (its a class heriting from QQuickView which use the qml file with the function "SetSource"), I canno't create another engine to load the qml file because it is making my app crash. I'm pretty sure that what I just wrote is not clear so don't hesitate don't ask me whatever you want.

    EDIT: If I try to qDebug my engine, I see : QObject(0x0) which means that my problem is with my way to get the engine.

    Thanks for your quick answer !

    J.HilkJ 1 Reply Last reply
    0
    • K kmarconi

      What I do actually is passing a reference of the engine into my class of translation. But since I never create an engine, could it be the reason why it is not working ?

      what's this supposed to be actually ?

      qobject_cast<QQmlApplicationEngine*>(qmlEngine(this));
      

      This is one of the way I found to get the engine.
      The problem here I think is that in each example I see which are restranlating their apps, they are using only one cpp file and one qml file so they just simply create an engine in the main and load the qml in it. But for me, it's not possible because I have a lot of classes and since one of them is already using my "main.qml" file (its a class heriting from QQuickView which use the qml file with the function "SetSource"), I canno't create another engine to load the qml file because it is making my app crash. I'm pretty sure that what I just wrote is not clear so don't hesitate don't ask me whatever you want.

      EDIT: If I try to qDebug my engine, I see : QObject(0x0) which means that my problem is with my way to get the engine.

      Thanks for your quick answer !

      J.HilkJ Online
      J.HilkJ Online
      J.Hilk
      Moderators
      wrote on last edited by
      #4

      @kmarconi
      true, I don't quite get it, do you have multiple QQmlEngines inside your Project ?


      Be aware of the Qt Code of Conduct, when posting : https://forum.qt.io/topic/113070/qt-code-of-conduct


      Q: What's that?
      A: It's blue light.
      Q: What does it do?
      A: It turns blue.

      K 1 Reply Last reply
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      • J.HilkJ J.Hilk

        @kmarconi
        true, I don't quite get it, do you have multiple QQmlEngines inside your Project ?

        K Offline
        K Offline
        kmarconi
        wrote on last edited by
        #5

        @J-Hilk Nop, sorry. I have for the moment none QQmlEngines inside my project. To display my app, I have a class heriting from QQuickView which is using OpenGL to display my app via the function myView.SetSources("qrc:/main.qml"). After some googling, every example I found for dynamic translation are done in three steps : remove the actual QTranslator, install the new one and then retranslate the app. But in each of these examples, they are doing this line : engine->load(QUrl("qrc:/main.qml")) at first. If i do this line, my app is immediatly crashing because the qml file is already in use in the class which display the app. Let's say this class's name is "myView", I also tried to get the engine by doing : QQmlEngine* engine = QQmlEngine::contextForObject(&myView)->engine(); but my app is directly crashing.

        J.HilkJ 1 Reply Last reply
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        • K kmarconi

          @J-Hilk Nop, sorry. I have for the moment none QQmlEngines inside my project. To display my app, I have a class heriting from QQuickView which is using OpenGL to display my app via the function myView.SetSources("qrc:/main.qml"). After some googling, every example I found for dynamic translation are done in three steps : remove the actual QTranslator, install the new one and then retranslate the app. But in each of these examples, they are doing this line : engine->load(QUrl("qrc:/main.qml")) at first. If i do this line, my app is immediatly crashing because the qml file is already in use in the class which display the app. Let's say this class's name is "myView", I also tried to get the engine by doing : QQmlEngine* engine = QQmlEngine::contextForObject(&myView)->engine(); but my app is directly crashing.

          J.HilkJ Online
          J.HilkJ Online
          J.Hilk
          Moderators
          wrote on last edited by
          #6

          @kmarconi ok I get it,

          QQuickView has a getter for the internal QQmlEngine
          https://doc.qt.io/qt-5/qquickview.html#engine

          call that and simply call retranslate on that returned object, and you should be fine


          Be aware of the Qt Code of Conduct, when posting : https://forum.qt.io/topic/113070/qt-code-of-conduct


          Q: What's that?
          A: It's blue light.
          Q: What does it do?
          A: It turns blue.

          K 1 Reply Last reply
          1
          • J.HilkJ J.Hilk

            @kmarconi ok I get it,

            QQuickView has a getter for the internal QQmlEngine
            https://doc.qt.io/qt-5/qquickview.html#engine

            call that and simply call retranslate on that returned object, and you should be fine

            K Offline
            K Offline
            kmarconi
            wrote on last edited by
            #7

            @J-Hilk Wow I think you saved my life here, thanks ^^ My app is finally not crashing anymore but I have now an error from my main.qml file : QML StackView: Binding loop detected for property "button". Any idea on why this could happen ?

            Big thanks.

            J.HilkJ 1 Reply Last reply
            0
            • K kmarconi

              @J-Hilk Wow I think you saved my life here, thanks ^^ My app is finally not crashing anymore but I have now an error from my main.qml file : QML StackView: Binding loop detected for property "button". Any idea on why this could happen ?

              Big thanks.

              J.HilkJ Online
              J.HilkJ Online
              J.Hilk
              Moderators
              wrote on last edited by
              #8

              @kmarconi hard to tell without knowing your qml file content,

              retranslate does not only reevaluate your text bindings, but all bindings
              https://doc.qt.io/qt-5/qqmlengine.html#retranslate

              Note: Due to a limitation in the implementation, this function refreshes all the engine's bindings, not only those that use strings marked for translation. This may be optimized in a future release.
              

              so, the bug is probably there from the binging :D


              Be aware of the Qt Code of Conduct, when posting : https://forum.qt.io/topic/113070/qt-code-of-conduct


              Q: What's that?
              A: It's blue light.
              Q: What does it do?
              A: It turns blue.

              1 Reply Last reply
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              • K Offline
                K Offline
                kmarconi
                wrote on last edited by kmarconi
                #9

                Here is my main.qml file :

                Item {
                id:root
                visible: true
                width: 640
                height: 480

                property var mainMenu: Menu{rootStack: root}
                
                StackView {
                    anchors.fill: parent
                    id: menuStack
                
                    property var button: hmiclass.button
                    initialItem: mainMenu
                
                    onButtonChanged: {
                        mainMenu.onButtonPushed(button)
                    }
                }
                

                }

                EDIT: I need to find where that loop is coming from.. Or to find a patch to refresh only the bindings which are in the translation file.

                K 2 Replies Last reply
                0
                • K kmarconi

                  Here is my main.qml file :

                  Item {
                  id:root
                  visible: true
                  width: 640
                  height: 480

                  property var mainMenu: Menu{rootStack: root}
                  
                  StackView {
                      anchors.fill: parent
                      id: menuStack
                  
                      property var button: hmiclass.button
                      initialItem: mainMenu
                  
                      onButtonChanged: {
                          mainMenu.onButtonPushed(button)
                      }
                  }
                  

                  }

                  EDIT: I need to find where that loop is coming from.. Or to find a patch to refresh only the bindings which are in the translation file.

                  K Offline
                  K Offline
                  kmarconi
                  wrote on last edited by
                  #10

                  @kmarconi Last question : When I check the definition of the retranslate function, it says : Refreshes all binding expressions that use strings marked for translation. What is that "marked" thing and how to apply it ? Thanks

                  J.HilkJ 1 Reply Last reply
                  0
                  • K kmarconi

                    @kmarconi Last question : When I check the definition of the retranslate function, it says : Refreshes all binding expressions that use strings marked for translation. What is that "marked" thing and how to apply it ? Thanks

                    J.HilkJ Online
                    J.HilkJ Online
                    J.Hilk
                    Moderators
                    wrote on last edited by
                    #11

                    @kmarconi
                    take a look here:
                    https://doc.qt.io/qt-5/qtquick-internationalization.html


                    Be aware of the Qt Code of Conduct, when posting : https://forum.qt.io/topic/113070/qt-code-of-conduct


                    Q: What's that?
                    A: It's blue light.
                    Q: What does it do?
                    A: It turns blue.

                    K 1 Reply Last reply
                    0
                    • J.HilkJ J.Hilk

                      @kmarconi
                      take a look here:
                      https://doc.qt.io/qt-5/qtquick-internationalization.html

                      K Offline
                      K Offline
                      kmarconi
                      wrote on last edited by
                      #12

                      @J-Hilk Yeah I already been there but every string which needs to be translated are already marked as qsTr so ...

                      J.HilkJ KroMignonK 2 Replies Last reply
                      0
                      • K kmarconi

                        @J-Hilk Yeah I already been there but every string which needs to be translated are already marked as qsTr so ...

                        J.HilkJ Online
                        J.HilkJ Online
                        J.Hilk
                        Moderators
                        wrote on last edited by
                        #13

                        @kmarconi said in How can I get the application QmlEngine ?:

                        Yeah I already been there but every string which needs to be translated are already marked as qsTr so ...

                        so, you answered your own question

                        Refreshes all binding expressions that use strings marked for translation. What is that "marked" thing and how to apply it ? Thanks

                        😉


                        Be aware of the Qt Code of Conduct, when posting : https://forum.qt.io/topic/113070/qt-code-of-conduct


                        Q: What's that?
                        A: It's blue light.
                        Q: What does it do?
                        A: It turns blue.

                        K 1 Reply Last reply
                        0
                        • J.HilkJ J.Hilk

                          @kmarconi said in How can I get the application QmlEngine ?:

                          Yeah I already been there but every string which needs to be translated are already marked as qsTr so ...

                          so, you answered your own question

                          Refreshes all binding expressions that use strings marked for translation. What is that "marked" thing and how to apply it ? Thanks

                          😉

                          K Offline
                          K Offline
                          kmarconi
                          wrote on last edited by
                          #14

                          @J-Hilk Yeah but I thought that maybe there was another thing to do ... I'm stuck now so I'm trying everything I can Haha

                          1 Reply Last reply
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                          • K kmarconi

                            @J-Hilk Yeah I already been there but every string which needs to be translated are already marked as qsTr so ...

                            KroMignonK Offline
                            KroMignonK Offline
                            KroMignon
                            wrote on last edited by
                            #15

                            @kmarconi said in How can I get the application QmlEngine ?:

                            Yeah I already been there but every string which needs to be translated are already marked as qsTr so ...

                            My way to ensure translation is the define a global Object which handle language changes.
                            This object is exposed to QML with engine->rootContext()->setContextProperty("translation", &myLocalesHandler).

                            This object has a property called emptyString:

                                Q_PROPERTY(QString emptyString     READ emptyString     NOTIFY languageChanged)
                            ....
                                QString emptyString() const
                                {
                                    return QString();
                                }
                            

                            On language change signal languageChanged() is emitted and in QML I have something like this:

                            Label {
                                text: qsTr("This is a message") + translation.emptyString
                            }
                            

                            Works great for me, hope this could also helps you.

                            It is an old maxim of mine that when you have excluded the impossible, whatever remains, however improbable, must be the truth. (Sherlock Holmes)

                            K 1 Reply Last reply
                            2
                            • fcarneyF Offline
                              fcarneyF Offline
                              fcarney
                              wrote on last edited by
                              #16

                              When I have objects that live in qml space such as a plain QObject, I will make it based upon QQuickItem in order to get the qml engine. I often do this for image providers that provide QImages to qml. I think any QQuick based object should be able to do this.

                              C++ is a perfectly valid school of magic.

                              1 Reply Last reply
                              0
                              • KroMignonK KroMignon

                                @kmarconi said in How can I get the application QmlEngine ?:

                                Yeah I already been there but every string which needs to be translated are already marked as qsTr so ...

                                My way to ensure translation is the define a global Object which handle language changes.
                                This object is exposed to QML with engine->rootContext()->setContextProperty("translation", &myLocalesHandler).

                                This object has a property called emptyString:

                                    Q_PROPERTY(QString emptyString     READ emptyString     NOTIFY languageChanged)
                                ....
                                    QString emptyString() const
                                    {
                                        return QString();
                                    }
                                

                                On language change signal languageChanged() is emitted and in QML I have something like this:

                                Label {
                                    text: qsTr("This is a message") + translation.emptyString
                                }
                                

                                Works great for me, hope this could also helps you.

                                K Offline
                                K Offline
                                kmarconi
                                wrote on last edited by
                                #17

                                @KroMignon Thanks for your help, will try it now. I just have question on your translation class. Where do you emit the signal languageChanged and how do you link it to your function which retranslate the app with the engine ? Thanks !

                                J.HilkJ 1 Reply Last reply
                                0
                                • K kmarconi

                                  @KroMignon Thanks for your help, will try it now. I just have question on your translation class. Where do you emit the signal languageChanged and how do you link it to your function which retranslate the app with the engine ? Thanks !

                                  J.HilkJ Online
                                  J.HilkJ Online
                                  J.Hilk
                                  Moderators
                                  wrote on last edited by
                                  #18

                                  @kmarconi what @KroMignon described was the way you had to go before Qt 5.10

                                  you can take a look at this blog post, I think its rather good:

                                  https://retifrav.github.io/blog/2017/01/04/translating-qml-app/


                                  Be aware of the Qt Code of Conduct, when posting : https://forum.qt.io/topic/113070/qt-code-of-conduct


                                  Q: What's that?
                                  A: It's blue light.
                                  Q: What does it do?
                                  A: It turns blue.

                                  K 1 Reply Last reply
                                  1
                                  • J.HilkJ J.Hilk

                                    @kmarconi what @KroMignon described was the way you had to go before Qt 5.10

                                    you can take a look at this blog post, I think its rather good:

                                    https://retifrav.github.io/blog/2017/01/04/translating-qml-app/

                                    K Offline
                                    K Offline
                                    kmarconi
                                    wrote on last edited by
                                    #19

                                    @J-Hilk Yeah I've seen this post but it's kinda dirty way to retranslate the whole app I think ... I still will try it but I hope to find a way to use the retranslate function properly.

                                    J.HilkJ 1 Reply Last reply
                                    0
                                    • K kmarconi

                                      @J-Hilk Yeah I've seen this post but it's kinda dirty way to retranslate the whole app I think ... I still will try it but I hope to find a way to use the retranslate function properly.

                                      J.HilkJ Online
                                      J.HilkJ Online
                                      J.Hilk
                                      Moderators
                                      wrote on last edited by
                                      #20

                                      @kmarconi
                                      what would you consider a proper retranslate functionality ?

                                      You can either,

                                      • call retranslate() on the QQmlEngine,
                                      • update the strings via the empty string property workaround
                                      • reload the qml file entirely

                                      there are not other ways, at least that I know of


                                      Be aware of the Qt Code of Conduct, when posting : https://forum.qt.io/topic/113070/qt-code-of-conduct


                                      Q: What's that?
                                      A: It's blue light.
                                      Q: What does it do?
                                      A: It turns blue.

                                      K 1 Reply Last reply
                                      0
                                      • J.HilkJ J.Hilk

                                        @kmarconi
                                        what would you consider a proper retranslate functionality ?

                                        You can either,

                                        • call retranslate() on the QQmlEngine,
                                        • update the strings via the empty string property workaround
                                        • reload the qml file entirely

                                        there are not other ways, at least that I know of

                                        K Offline
                                        K Offline
                                        kmarconi
                                        wrote on last edited by kmarconi
                                        #21

                                        @J-Hilk Calling retranslate for me is the cleanest way. No need to add "+trans.emptyString" on each of my qsTr object and I have a lot. I need to figure out how to solve this infinite binding loop. Is reloading the whole qml a heavy task for the system ?

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                                        • KroMignonK Offline
                                          KroMignonK Offline
                                          KroMignon
                                          wrote on last edited by KroMignon
                                          #22

                                          @kmarconi said in How can I get the application QmlEngine ?:

                                          I still will try it but I hope to find a way to use the retranslate function properly.

                                          I can not figure out what your problem is.
                                          @J-Hilk have give you all information you need to do it.

                                          If you are using Qt 5.10 and upper (which is not my case) simply follow documentation
                                          That's not so complicated to follow, you could create a class which handle the locales, for example let it call LocalHandler, when you have install the new translator with QCoreApplication::installTranslator() then emit a signal for example called translationUpated().
                                          Then in your main.cpp:

                                          LocalHandler loc;
                                          
                                          QObject::connect(&loc, &LocalHandler::translationUpated, engine, &QQmlEngine::retranslate);
                                          

                                          Alternatively you can use a app->installEventFilter() to catch QEvent::LanguageChange and then trigger QQmlEngine::retranslate().

                                          For prior version, you have to do more work ==> https://retifrav.github.io/blog/2017/01/04/translating-qml-app/

                                          It is an old maxim of mine that when you have excluded the impossible, whatever remains, however improbable, must be the truth. (Sherlock Holmes)

                                          K 1 Reply Last reply
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