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  4. Why does my QGraphicsSimpleTextItem not display any plot information when I move my mouse?
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Why does my QGraphicsSimpleTextItem not display any plot information when I move my mouse?

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  • mrjjM mrjj

    @engsml
    Nope, that's perfect. Normally it wont send mouseMove to QWidgets as far as i recall
    and you need to set mouseTracking to true to have them come without mouse buttons being pressed.

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    engsml
    wrote on last edited by
    #5

    @mrjj Yeah, the mouseMoveEvent works on everything but the actual QChart. I can only get the x and y points to display when I left click and drag it into the chart area. Otherwise it won't work. Would I have to include this function: QChartView::mouseMoveEvent(event) for it to work?

    mrjjM 1 Reply Last reply
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    • E engsml

      @mrjj Yeah, the mouseMoveEvent works on everything but the actual QChart. I can only get the x and y points to display when I left click and drag it into the chart area. Otherwise it won't work. Would I have to include this function: QChartView::mouseMoveEvent(event) for it to work?

      mrjjM Offline
      mrjjM Offline
      mrjj
      Lifetime Qt Champion
      wrote on last edited by
      #6

      @engsml
      hi
      Its only sent to the widget under the mouse cursor.
      So yes, if you want to trap them there, you need to subclass and override that.
      However, if you need mouse info a global scope , maybe look into event filters.
      That allows to capture it across various Widgets without subclassing.
      If you already subclassed QChartView, override is ofcourse most easy.

      http://doc.qt.io/qt-5/eventsandfilters.html

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      • mrjjM mrjj

        @engsml
        hi
        Its only sent to the widget under the mouse cursor.
        So yes, if you want to trap them there, you need to subclass and override that.
        However, if you need mouse info a global scope , maybe look into event filters.
        That allows to capture it across various Widgets without subclassing.
        If you already subclassed QChartView, override is ofcourse most easy.

        http://doc.qt.io/qt-5/eventsandfilters.html

        E Offline
        E Offline
        engsml
        wrote on last edited by
        #7

        @mrjj How would I subclass QChartView? I think that is what I am missing.

        mrjjM 1 Reply Last reply
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        • E engsml

          @mrjj How would I subclass QChartView? I think that is what I am missing.

          mrjjM Offline
          mrjjM Offline
          mrjj
          Lifetime Qt Champion
          wrote on last edited by mrjj
          #8

          hi

          class MyQChartView : public QChartView {
            Q_OBJECT
           public:
            explicit MyQChartView (QWidget* parent = 0) : QChartView(parent) {}
            ~QChartView() {}
          protected:
           virtual void moveEvent(QMoveEvent* event) override {
                  .....
           }
          };
          

          If you have the QChartView in UI file, you can use promotion to easy replace it at runtime with your version.
          http://doc.qt.io/qt-5/designer-using-custom-widgets.html
          just give it MyQChartView as class name and MyQChartView .h (if you put it in own file)
          else what ever .h file it lives in.

          update: you might want to call base class version as it might use it.

          virtual void moveEvent(QMoveEvent* event) override {
                  QChartView::moveEvent(event); // call base first
          ...
           }
          
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          • mrjjM Offline
            mrjjM Offline
            mrjj
            Lifetime Qt Champion
            wrote on last edited by
            #9

            updated code. paste error.
            explicit QChartView (QWidget* parent = 0) : QChartView(parent) {}
            --->
            explicit MyQChartView (QWidget* parent = 0) : QChartView(parent) {}

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            • mrjjM mrjj

              hi

              class MyQChartView : public QChartView {
                Q_OBJECT
               public:
                explicit MyQChartView (QWidget* parent = 0) : QChartView(parent) {}
                ~QChartView() {}
              protected:
               virtual void moveEvent(QMoveEvent* event) override {
                      .....
               }
              };
              

              If you have the QChartView in UI file, you can use promotion to easy replace it at runtime with your version.
              http://doc.qt.io/qt-5/designer-using-custom-widgets.html
              just give it MyQChartView as class name and MyQChartView .h (if you put it in own file)
              else what ever .h file it lives in.

              update: you might want to call base class version as it might use it.

              virtual void moveEvent(QMoveEvent* event) override {
                      QChartView::moveEvent(event); // call base first
              ...
               }
              
              E Offline
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              engsml
              wrote on last edited by
              #10

              @mrjj Thank you! Do I create another .cpp and header file and include this in my project?

              mrjjM 1 Reply Last reply
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              • E engsml

                @mrjj Thank you! Do I create another .cpp and header file and include this in my project?

                mrjjM Offline
                mrjjM Offline
                mrjj
                Lifetime Qt Champion
                wrote on last edited by mrjj
                #11

                @engsml
                Yes, that is the cleanest. (IMHO)
                and then just promote it. ( it sounds complex but really easy after first time)

                E 2 Replies Last reply
                1
                • mrjjM mrjj

                  @engsml
                  Yes, that is the cleanest. (IMHO)
                  and then just promote it. ( it sounds complex but really easy after first time)

                  E Offline
                  E Offline
                  engsml
                  wrote on last edited by
                  #12

                  @mrjj Thank you! I will try that

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                  0
                  • mrjjM mrjj

                    @engsml
                    Yes, that is the cleanest. (IMHO)
                    and then just promote it. ( it sounds complex but really easy after first time)

                    E Offline
                    E Offline
                    engsml
                    wrote on last edited by
                    #13

                    @mrjj When I create the new class, what do I make the base class? Also, what does promoting accomplish in the sense that it overrides the QChartView class?

                    mrjjM 1 Reply Last reply
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                    • E engsml

                      @mrjj When I create the new class, what do I make the base class? Also, what does promoting accomplish in the sense that it overrides the QChartView class?

                      mrjjM Offline
                      mrjjM Offline
                      mrjj
                      Lifetime Qt Champion
                      wrote on last edited by mrjj
                      #14

                      @engsml
                      just see code snippet ?
                      Like that. its complete override. with mousemove.

                      promotion is just easy way to get your type into the UI file.
                      Creator just note the actual type you want and at runtime, its your new widget instead.
                      Like a runtime replace.
                      if you insert the Chart via code, you have no use for promotion.

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                      • mrjjM mrjj

                        @engsml
                        just see code snippet ?
                        Like that. its complete override. with mousemove.

                        promotion is just easy way to get your type into the UI file.
                        Creator just note the actual type you want and at runtime, its your new widget instead.
                        Like a runtime replace.
                        if you insert the Chart via code, you have no use for promotion.

                        E Offline
                        E Offline
                        engsml
                        wrote on last edited by
                        #15

                        @mrjj Hi. thanks for your help! I ended up not being able to figure it out, but am currently looking into the event filters option. I added QtCharts::QChartView::mouseMoveEvent(event); to my function to pass the event to the chartView but it still won't display any information when the mouse is on the plot. Any ideas? I'm following the "callout" example which has a similar structure.

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                        • mrjjM Offline
                          mrjjM Offline
                          mrjj
                          Lifetime Qt Champion
                          wrote on last edited by mrjj
                          #16

                          Hi
                          ah, QChartView is basically a QAbstractScrollArea which means it has the

                          https://doc.qt.io/qt-5/qabstractscrollarea.html#viewport

                          There is a high chance that this viewport objects uses/eats the mouseMove and hence the Widget dont see them
                          or viewport have no mouse tracking.

                          i might be able to test it tonight.

                          Else event filter sounds like a plan. set it on viewport().

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