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Capture scroll event in textEditor

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  • D danga96

    hello to the whole community Qt Forum,
    I would like to know if there is a way to capture the scroll event in a text editor; I have tried installing an eventfilter and captured these events:

    bool TextEdit::eventFilter(QObject* obj, QEvent* event) {
    	if (event->type() == QEvent::GraphicsSceneWheel){}
    	if (event->type() == QEvent::Wheel){}
    	if (event->type() == QEvent::Scroll){}
    	return true;
    }
    

    but they don't work, only "Wheel" is captured when you reach the beginning and the end of the scroll area
    Thanks in advance :)

    raven-worxR Offline
    raven-worxR Offline
    raven-worx
    Moderators
    wrote on last edited by
    #2

    @danga96 said in Capture scroll event in textEditor:

    I have tried installing an eventfilter

    installed where? on the widget itself or on it's viewport widget?

    --- SUPPORT REQUESTS VIA CHAT WILL BE IGNORED ---
    If you have a question please use the forum so others can benefit from the solution in the future

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    • D Offline
      D Offline
      danga96
      wrote on last edited by
      #3

      Thanks for the reply; I did it like this:

      textEdit = new QTextEdit(this);
      textEdit->installEventFilter(this);
      
      raven-worxR 1 Reply Last reply
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      • D danga96

        Thanks for the reply; I did it like this:

        textEdit = new QTextEdit(this);
        textEdit->installEventFilter(this);
        
        raven-worxR Offline
        raven-worxR Offline
        raven-worx
        Moderators
        wrote on last edited by
        #4

        @danga96
        then try
        textEdit->viewport()->installEventFilter(this);

        --- SUPPORT REQUESTS VIA CHAT WILL BE IGNORED ---
        If you have a question please use the forum so others can benefit from the solution in the future

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        • D Offline
          D Offline
          danga96
          wrote on last edited by
          #5

          @raven-worx said in Capture scroll event in textEditor:

          textEdit->viewport()->installEventFilter(this);

          thanks a lot, now it goes with the mouse, but if a user uses the scrollbar the event is not captured, how can I do?

          raven-worxR 1 Reply Last reply
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          • D danga96

            @raven-worx said in Capture scroll event in textEditor:

            textEdit->viewport()->installEventFilter(this);

            thanks a lot, now it goes with the mouse, but if a user uses the scrollbar the event is not captured, how can I do?

            raven-worxR Offline
            raven-worxR Offline
            raven-worx
            Moderators
            wrote on last edited by
            #6

            @danga96
            What are you exactly trying to achieve?

            --- SUPPORT REQUESTS VIA CHAT WILL BE IGNORED ---
            If you have a question please use the forum so others can benefit from the solution in the future

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            • D Offline
              D Offline
              danga96
              wrote on last edited by
              #7

              @raven-worx said in Capture scroll event in textEditor:

              What are you exactly trying to achieve?

              in practice, I would like to launch a function whenever a scroll occurs; in particular, on my text I have labels, which act as some kind of little clouds, which must follow the text, so if this scrolls upwards the label must also follow it;

              raven-worxR 1 Reply Last reply
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              • D danga96

                @raven-worx said in Capture scroll event in textEditor:

                What are you exactly trying to achieve?

                in practice, I would like to launch a function whenever a scroll occurs; in particular, on my text I have labels, which act as some kind of little clouds, which must follow the text, so if this scrolls upwards the label must also follow it;

                raven-worxR Offline
                raven-worxR Offline
                raven-worx
                Moderators
                wrote on last edited by raven-worx
                #8

                @danga96
                then its easier to subclass QTextEdit:

                void MyTextEdit::scrollContentsBy(int dx, int dy) {
                   // scroll happened, do whatever you want here
                   QTextEdit::scrollContentsBy(dx, dy);
                }
                

                --- SUPPORT REQUESTS VIA CHAT WILL BE IGNORED ---
                If you have a question please use the forum so others can benefit from the solution in the future

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                • D Offline
                  D Offline
                  danga96
                  wrote on last edited by
                  #9

                  @raven-worx
                  sorry again, but how can I use this virtual method? do i need to make a connect?

                  jsulmJ 1 Reply Last reply
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                  • D danga96

                    @raven-worx
                    sorry again, but how can I use this virtual method? do i need to make a connect?

                    jsulmJ Online
                    jsulmJ Online
                    jsulm
                    Lifetime Qt Champion
                    wrote on last edited by
                    #10

                    @danga96 said in Capture scroll event in textEditor:

                    do i need to make a connect?

                    No, you simply override it in your class (scrollContentsBy is called by Qt framework). This is how virtual methods are used: if a subclass overrides it then its own implementation is called, else the implementation in the base class is called.

                    https://forum.qt.io/topic/113070/qt-code-of-conduct

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                    • D Offline
                      D Offline
                      danga96
                      wrote on last edited by
                      #11

                      @raven-worx said in Capture scroll event in textEditor:
                      @jsulm
                      thanks for answering me, but I can't get it to work; if I declare the method like this:

                      QTextEdit::scrollContentsBy(int dx,int dy);
                      

                      it works, but not belonging to the class I can't exceed the private variables;
                      do i have to do anything in .h, adding some define?
                      in the .h I have tried:

                      void scrollContentsBy(int dx, int dy) override;
                      

                      and in .cpp:

                      void TextEdit::scrollContentsBy(int dx, int dy) { }
                      

                      and I get this error in compilation: "method with override specifier 'override' did not override any base class methods"

                      jsulmJ 1 Reply Last reply
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                      • D danga96

                        @raven-worx said in Capture scroll event in textEditor:
                        @jsulm
                        thanks for answering me, but I can't get it to work; if I declare the method like this:

                        QTextEdit::scrollContentsBy(int dx,int dy);
                        

                        it works, but not belonging to the class I can't exceed the private variables;
                        do i have to do anything in .h, adding some define?
                        in the .h I have tried:

                        void scrollContentsBy(int dx, int dy) override;
                        

                        and in .cpp:

                        void TextEdit::scrollContentsBy(int dx, int dy) { }
                        

                        and I get this error in compilation: "method with override specifier 'override' did not override any base class methods"

                        jsulmJ Online
                        jsulmJ Online
                        jsulm
                        Lifetime Qt Champion
                        wrote on last edited by jsulm
                        #12

                        @danga96 Is your class derived from QTextEdit?

                        class MyTextEdit : public QTextEdit
                        {
                        ...
                        };
                        

                        https://forum.qt.io/topic/113070/qt-code-of-conduct

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                        • D Offline
                          D Offline
                          danga96
                          wrote on last edited by
                          #13

                          now yes, but the class already inherits from QMainWindow, and I don't know if this creates conflicts, so is there a way to do it through a connect?

                          jsulmJ 1 Reply Last reply
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                          • D danga96

                            now yes, but the class already inherits from QMainWindow, and I don't know if this creates conflicts, so is there a way to do it through a connect?

                            jsulmJ Online
                            jsulmJ Online
                            jsulm
                            Lifetime Qt Champion
                            wrote on last edited by jsulm
                            #14

                            @danga96 I don't get it: you want to capture scroll events in QTextEdit but in your QMainWindow? That can't work.
                            Create a new class as subclass of QTextEdit and use that subclass instead of QTextEdit...
                            Also, is MyTextEdit really derived from QMainWindow?! If so then this is really a bad name.

                            https://forum.qt.io/topic/113070/qt-code-of-conduct

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                            • D Offline
                              D Offline
                              danga96
                              wrote on last edited by
                              #15

                              @jsulm
                              I'm referring to this example: richtext-textedit
                              I'm using it to do tests; at this point I would ask you how I can adapt this with the solution proposed by you?

                              jsulmJ 1 Reply Last reply
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                              • D danga96

                                @jsulm
                                I'm referring to this example: richtext-textedit
                                I'm using it to do tests; at this point I would ask you how I can adapt this with the solution proposed by you?

                                jsulmJ Online
                                jsulmJ Online
                                jsulm
                                Lifetime Qt Champion
                                wrote on last edited by
                                #16

                                @danga96 The solution wasn't proposed by me.
                                In the textedit.h file you will find this line:

                                QTextEdit *textEdit;
                                

                                Replace it with your own class derived from QTextEdit:

                                MyOwnTextEdit *textEdit;
                                

                                In myowntextedit.h

                                class MyOwnTextEdit : public QTextEdit
                                {
                                    ...
                                    void scrollContentsBy(int dx, int dy) override;
                                    ...
                                }
                                

                                https://forum.qt.io/topic/113070/qt-code-of-conduct

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                                • D Offline
                                  D Offline
                                  danga96
                                  wrote on last edited by
                                  #17

                                  @jsulm said in Capture scroll event in textEditor:
                                  thank you very much, and I apologize in advance for the insistence, but in this way I have to modify almost everything, because I will have to create a new class and adapt all the changes I have made with this new type, only to manage the scroll event;
                                  Therefore I would like to know if there is another way.

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                                  • D Offline
                                    D Offline
                                    danga96
                                    wrote on last edited by
                                    #18

                                    finally I solved this way:

                                    connect(textEdit->verticalScrollBar(), &QScrollBar::valueChanged, this, &TextEdit::handleUsersCursors);
                                    	
                                    connect(textEdit->horizontalScrollBar(), &QScrollBar::valueChanged, this, &TextEdit::handleUsersCursors);
                                    

                                    without creating a new class;
                                    thanks anyway for the tips;

                                    1 Reply Last reply
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