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  4. How to create a line between 2 points with QLabel?
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How to create a line between 2 points with QLabel?

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  • F frnklu20

    yes! instead of using QPainter, represent this line as a QLabel

    mrjjM Offline
    mrjjM Offline
    mrjj
    Lifetime Qt Champion
    wrote on last edited by mrjj
    #4

    @frnklu20
    Well QLabel can show a pixmap. It can not show line by itself.
    So the idea to draw on pixmap and show in label is fine enough.
    you can do that directly

      int h =100;
      int w = 100;
      QPixmap pix(w, h);
      QPainter paint(&pix);
      pix.fill( Qt::white );
      paint.setPen(QColor(0, 0, 0, 255));
      paint.drawLine(xxx) 
      ui->label->setPixmap(pix);
    

    But what are you actually doing?
    Maybe a custom widget would work far better.

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    • F Offline
      F Offline
      frnklu20
      wrote on last edited by
      #5

      I guess a custom widget will be better, but i don't have any ideia to do that

      I want is to deal with the line as an object and to be clickable, i want to click in any part of the line and my program recognizes it.

      What i thought was to use a CustomLabel class that it emits a signal when it is clicked and create an obect of this class between 2 points.
      So the way you said before, i create a line inside my QLabel but it becomes to big for being a rect

      mrjjM 1 Reply Last reply
      0
      • F frnklu20

        I guess a custom widget will be better, but i don't have any ideia to do that

        I want is to deal with the line as an object and to be clickable, i want to click in any part of the line and my program recognizes it.

        What i thought was to use a CustomLabel class that it emits a signal when it is clicked and create an obect of this class between 2 points.
        So the way you said before, i create a line inside my QLabel but it becomes to big for being a rect

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

        @frnklu20
        Well the image has to be as big as the points
        like 0,0 and 100,100 , the pixmap must be 100x100
        But if you want to click on it, an image is not so good as it
        has no idea where line is. so it needs the point anyway.

        Even with a custom widget, it must still be as big as the span between the points.

        So what should happen when you click the line at any part of it ?

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        • F Offline
          F Offline
          frnklu20
          wrote on last edited by
          #7

          It's not pretty yet, but that's what my program does
          I add objects on the screen and draw lines between then

          0_1557239421701_daede2d6-eb37-4671-887c-e4d02e0c4430-image.png

          but this line has to be treated as an object as well, when i click in any point of the line it should open a window with its data

          mrjjM 1 Reply Last reply
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          • F frnklu20

            It's not pretty yet, but that's what my program does
            I add objects on the screen and draw lines between then

            0_1557239421701_daede2d6-eb37-4671-887c-e4d02e0c4430-image.png

            but this line has to be treated as an object as well, when i click in any point of the line it should open a window with its data

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

            @frnklu20
            well you need to store the 2 points for each line and
            then use math to find out if the user hits a line on mousePressed.
            How is the lines stored now ? ( the points you use to draw it )

            This explains it well
            http://www.jeffreythompson.org/collision-detection/line-point.php

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            • SGaistS Offline
              SGaistS Offline
              SGaist
              Lifetime Qt Champion
              wrote on last edited by
              #9

              Hi,

              Since you seem to want to interact and have things working dynamically, did you consider the Graphics View Framework ?

              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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              • F Offline
                F Offline
                frnklu20
                wrote on last edited by
                #10

                Exactly!

                Graphics View Framework would help me a lot, i guess

                Do you know some book or site that i can learn more about it?with some examples and everything

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                • SGaistS Offline
                  SGaistS Offline
                  SGaist
                  Lifetime Qt Champion
                  wrote on last edited by
                  #11

                  Did you check the Qt documentation and related examples ?

                  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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                  • F Offline
                    F Offline
                    frnklu20
                    wrote on last edited by
                    #12

                    Yes!
                    But i'm having a problem.

                    I saw in a video a guy using the the graphic view framework in a QDialog

                    That's the code:

                    dialog.h

                    class Dialog : public QDialog
                    {
                        Q_OBJECT
                    
                    public:
                        explicit Dialog(QWidget *parent = nullptr);
                        ~Dialog();
                    
                    private:
                        Ui::Dialog *ui;
                        QGraphicsScene *scene;
                        QGraphicsEllipseItem *ellipse;
                        QGraphicsRectItem *rectangle;
                        
                    };
                    

                    dialog.cpp

                        QDialog(parent),
                        ui(new Ui::Dialog)
                    {
                        ui->setupUi(this);
                    
                        scene= new QGraphicsScene(this);
                        ui->graphicsView->setScene(scene);////the problem is here!
                        QBrush redBrush(Qt::red);
                        QPen blackpen(Qt::black);
                    
                        ellipse=scene->addEllipse(10,10,100,100,blackpen,redBrush);
                    
                    }
                    

                    It says that no member named 'graphicView' in Ui::Dialog, so how can i fix it?
                    i want to use the application in qwidget or qdialog class

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                    • SGaistS Offline
                      SGaistS Offline
                      SGaist
                      Lifetime Qt Champion
                      wrote on last edited by
                      #13

                      Did you add a QGraphicsView widget name graphicsView through designer to your dialog ?

                      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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                      0
                      • F Offline
                        F Offline
                        frnklu20
                        wrote on last edited by
                        #14

                        no, how can i do this?

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                        0
                        • SGaistS Offline
                          SGaistS Offline
                          SGaist
                          Lifetime Qt Champion
                          wrote on last edited by
                          #15

                          Well, use designer as explained here.

                          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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