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  4. Visualization of dynamic c++ list with positions as set of Items in QML-app at corresponding positions.
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Visualization of dynamic c++ list with positions as set of Items in QML-app at corresponding positions.

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qmllistc++exposing qmldata visualizat
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  • I ilyaik

    Some c++ class periodically sends a list of items with positions inside (x and y). It needs to be visualized on grids and axis I've created in QML.
    For representation of item I've prepared black rectangle in Rect.qml file.
    Is it possible to:

    • represent each item using rect.qml (like appearance of item)
    • not using paint(...) from QQuickPaintedItem and updatePaintNode(...) from QQuickItem respectively
    • place each item in some QML container (like Rectangle) with corresponding (x and y) from list ?
      I didn't find any straight way to do this.

    I know i could use QGraphicsScene and QPainter with QMainWindow GUI without any "qml" but i want to use benefits of QML interface.

    p3c0P Offline
    p3c0P Offline
    p3c0
    Moderators
    wrote on last edited by
    #2

    @ilyaik How does the list of items look like ?
    One way to implement would be using Connections. Set the target as your C++ class which I assume you have set as a context property. Then when ever the new list is sent through as signal, grab it inside the corresponding handler in QML. Once you get the list iterate over it and then set x and y coordinates of the Black rectangles. For this you can keep a list of Black rectangles in QML array.

    157

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    1
    • p3c0P p3c0

      @ilyaik How does the list of items look like ?
      One way to implement would be using Connections. Set the target as your C++ class which I assume you have set as a context property. Then when ever the new list is sent through as signal, grab it inside the corresponding handler in QML. Once you get the list iterate over it and then set x and y coordinates of the Black rectangles. For this you can keep a list of Black rectangles in QML array.

      I Offline
      I Offline
      ilyaik
      wrote on last edited by
      #3

      @p3c0 This is an idea!
      List is a QList<struct {int x; int y}>

      But as it always happens... after 1 day of searching solution appears only after asking a question on forum =)

      I did as you said: a C++ class myList with QList inside. I made this class as a context property. Class has Q_PROPERTY (int count READ count NOTIFY countChanged) that is the size of QList.
      In QML part i've placed

      Repeater { 
         model: myList.count;
         Rectangle {
            // black rectangle
              ...
              x: myList.xPosition(index)
              y: myList.yPosition(index)
         }
      }
      

      myList has xPosition(index) and yPosition(index) slots recpectively.

      And it works.
      Thank you for help!

      p3c0P 1 Reply Last reply
      0
      • I ilyaik

        @p3c0 This is an idea!
        List is a QList<struct {int x; int y}>

        But as it always happens... after 1 day of searching solution appears only after asking a question on forum =)

        I did as you said: a C++ class myList with QList inside. I made this class as a context property. Class has Q_PROPERTY (int count READ count NOTIFY countChanged) that is the size of QList.
        In QML part i've placed

        Repeater { 
           model: myList.count;
           Rectangle {
              // black rectangle
                ...
                x: myList.xPosition(index)
                y: myList.yPosition(index)
           }
        }
        

        myList has xPosition(index) and yPosition(index) slots recpectively.

        And it works.
        Thank you for help!

        p3c0P Offline
        p3c0P Offline
        p3c0
        Moderators
        wrote on last edited by
        #4

        @ilyaik You're Welcome :)
        Using Repeater is also a good idea. You can mark the post as solved if done.

        157

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        • I Offline
          I Offline
          ilyaik
          wrote on last edited by
          #5

          I've faces a new problem.

          If QList inside myClass changed it's values, but count myList.count didn't, Repeater doesn't updates. That's ok... strictly speaking the Repeater's model myList.count didn't change.
          I made a signal from myClass updateSignal. updateSignal emits when data inside list in myClass is updated. In QML this signal is exposed in Connections part.

          Connections {
                  target: myClass
                  onUpdateSignal {
                      repeater.model = 0
                      repeater.model = myClass.count
                  }
          }
          
          // And Repeater part
          
          Repeater { 
              id: repeater
              model: 0
              Rectangle {
                // black rectangle
                  ...
                  x: myList.xPosition(index)
                  y: myList.yPosition(index)
              }
          }
          

          It renewsrepeater.
          But it seams that it's like a crutch.
          Is there any proper way to renew Repeater?

          P.S. repeater.update() didn't help.

          p3c0P 1 Reply Last reply
          0
          • I ilyaik

            I've faces a new problem.

            If QList inside myClass changed it's values, but count myList.count didn't, Repeater doesn't updates. That's ok... strictly speaking the Repeater's model myList.count didn't change.
            I made a signal from myClass updateSignal. updateSignal emits when data inside list in myClass is updated. In QML this signal is exposed in Connections part.

            Connections {
                    target: myClass
                    onUpdateSignal {
                        repeater.model = 0
                        repeater.model = myClass.count
                    }
            }
            
            // And Repeater part
            
            Repeater { 
                id: repeater
                model: 0
                Rectangle {
                  // black rectangle
                    ...
                    x: myList.xPosition(index)
                    y: myList.yPosition(index)
                }
            }
            

            It renewsrepeater.
            But it seams that it's like a crutch.
            Is there any proper way to renew Repeater?

            P.S. repeater.update() didn't help.

            p3c0P Offline
            p3c0P Offline
            p3c0
            Moderators
            wrote on last edited by
            #6

            @ilyaik That is a valid way. Bindings are meant for that.
            Also it should work even without first assigning model to 0 in Connections.

            157

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            • I Offline
              I Offline
              ilyaik
              wrote on last edited by
              #7

              No. Repeater doesn't renew without assigning model to 0 in Connections. It seems like nothing changes for Repeater if myClass.count stays unchanged.

              p3c0P 1 Reply Last reply
              0
              • I ilyaik

                No. Repeater doesn't renew without assigning model to 0 in Connections. It seems like nothing changes for Repeater if myClass.count stays unchanged.

                p3c0P Offline
                p3c0P Offline
                p3c0
                Moderators
                wrote on last edited by
                #8

                @ilyaik That means the count didnot change

                repeater.model = myClass.count
                

                the Repeater will update only when the property changes. That is how Binding works.

                157

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                • I Offline
                  I Offline
                  ilyaik
                  wrote on last edited by
                  #9

                  So that's why i use assigning model to 0 in Connections to force Repeater to renew itself when count stays unchanged.

                  p3c0P 1 Reply Last reply
                  0
                  • I ilyaik

                    So that's why i use assigning model to 0 in Connections to force Repeater to renew itself when count stays unchanged.

                    p3c0P Offline
                    p3c0P Offline
                    p3c0
                    Moderators
                    wrote on last edited by
                    #10

                    @ilyaik Ok. So is it that you only want to update x and y positions even if no new item is added ?

                    157

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                    • I Offline
                      I Offline
                      ilyaik
                      wrote on last edited by
                      #11

                      Yes. If myClass's QList changes inside

                      p3c0P 1 Reply Last reply
                      0
                      • I ilyaik

                        Yes. If myClass's QList changes inside

                        p3c0P Offline
                        p3c0P Offline
                        p3c0
                        Moderators
                        wrote on last edited by
                        #12

                        @ilyaik then I think my first post could be the possible way.

                        157

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