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QPainterPath from list of points

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  • kshegunovK kshegunov

    @Joel-Bodenmann
    Sorry for updating a previous post, I didn't realize you were writing at that same time. Look up my suggestion, and if there's something unclear I'll try to expand.

    Kind regards.

    Joel BodenmannJ Offline
    Joel BodenmannJ Offline
    Joel Bodenmann
    wrote on last edited by
    #15

    @kshegunov
    Thanks for your answer. I guess I'll have to figure out how to properly implement this in the next couple of days then. I'll definitely publish results here so people don't have to do that in the future themselves :)

    Industrial process automation software: https://simulton.com
    Embedded Graphics & GUI library: https://ugfx.io

    kshegunovK 1 Reply Last reply
    0
    • Joel BodenmannJ Joel Bodenmann

      @kshegunov
      Thanks for your answer. I guess I'll have to figure out how to properly implement this in the next couple of days then. I'll definitely publish results here so people don't have to do that in the future themselves :)

      kshegunovK Offline
      kshegunovK Offline
      kshegunov
      Moderators
      wrote on last edited by
      #16

      @Joel-Bodenmann
      Also QPainterPathStroker::createStroke coupled with QPainterPath::toFillPolygon might be the easiest way to get what you're after.

      Read and abide by the Qt Code of Conduct

      Joel BodenmannJ 1 Reply Last reply
      0
      • kshegunovK kshegunov

        @Joel-Bodenmann
        Also QPainterPathStroker::createStroke coupled with QPainterPath::toFillPolygon might be the easiest way to get what you're after.

        Joel BodenmannJ Offline
        Joel BodenmannJ Offline
        Joel Bodenmann
        wrote on last edited by
        #17

        @kshegunov
        Can you elaborate? I still need to get the outline of the stroked polygon somehow, no?

        Industrial process automation software: https://simulton.com
        Embedded Graphics & GUI library: https://ugfx.io

        kshegunovK 1 Reply Last reply
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        • Joel BodenmannJ Joel Bodenmann

          @kshegunov
          Can you elaborate? I still need to get the outline of the stroked polygon somehow, no?

          kshegunovK Offline
          kshegunovK Offline
          kshegunov
          Moderators
          wrote on last edited by kshegunov
          #18

          @Joel-Bodenmann
          Hello,
          Surely, note however that I've not tried this. Set the pen width with your desired offset. Create the stroke, with the createStroke method. The outline of the stroke is supposed to be (as per the documentation) the painter path you get from it. Convert the path to a polygon with the toFillPolygon method. If it doesn't work, you can always revert to implementing it yourself, but if it does, well, it looks simpler. :)

          Kind regards.

          Read and abide by the Qt Code of Conduct

          Joel BodenmannJ 1 Reply Last reply
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          • kshegunovK kshegunov

            @Joel-Bodenmann
            Hello,
            Surely, note however that I've not tried this. Set the pen width with your desired offset. Create the stroke, with the createStroke method. The outline of the stroke is supposed to be (as per the documentation) the painter path you get from it. Convert the path to a polygon with the toFillPolygon method. If it doesn't work, you can always revert to implementing it yourself, but if it does, well, it looks simpler. :)

            Kind regards.

            Joel BodenmannJ Offline
            Joel BodenmannJ Offline
            Joel Bodenmann
            wrote on last edited by
            #19

            @kshegunov
            Thanks for the explanation. The trouble I am having is getting the QPainterPath (that needs to be passed to QPainterPathStroker::createStroke() from my list of lines. The only reasonable option I see is QPainterPath::addPolygon() but that I can't use as I don't have a polygon, I only have a polyline (like a non-closed polygon).

            Any thoughts?

            Industrial process automation software: https://simulton.com
            Embedded Graphics & GUI library: https://ugfx.io

            1 Reply Last reply
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            • kshegunovK Offline
              kshegunovK Offline
              kshegunov
              Moderators
              wrote on last edited by
              #20

              @Joel-Bodenmann
              Hello,
              One thing is to create the path from a polygon (no one says it has to be a closed one ;)). You could also perhaps get it by constructing the path from your points with QPainterPath::moveTo and QPainterPath::lineTo. The latter would be my choice if I were supposed to compose a painter path.

              Kind regards.

              Read and abide by the Qt Code of Conduct

              1 Reply Last reply
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              • Chris KawaC Offline
                Chris KawaC Offline
                Chris Kawa
                Lifetime Qt Champion
                wrote on last edited by Chris Kawa
                #21

                As mentioned above you can use QPainterPathStroker. The problem is it will create tiny loops on the inside of the joints, so you need to simplify the path afterwards.
                Sample code:

                QVector<QPoint> points { QPoint(30,30), QPoint(100, 100), QPoint(200,50) };
                
                QPainterPath basePath;
                basePath.addPolygon(QPolygon(points));
                
                QPainterPathStroker str;
                str.setCapStyle(Qt::RoundCap);
                str.setWidth(10.0);
                
                QPainterPath resultPath = str.createStroke(basePath).simplified();
                
                Joel BodenmannJ 1 Reply Last reply
                2
                • Chris KawaC Chris Kawa

                  As mentioned above you can use QPainterPathStroker. The problem is it will create tiny loops on the inside of the joints, so you need to simplify the path afterwards.
                  Sample code:

                  QVector<QPoint> points { QPoint(30,30), QPoint(100, 100), QPoint(200,50) };
                  
                  QPainterPath basePath;
                  basePath.addPolygon(QPolygon(points));
                  
                  QPainterPathStroker str;
                  str.setCapStyle(Qt::RoundCap);
                  str.setWidth(10.0);
                  
                  QPainterPath resultPath = str.createStroke(basePath).simplified();
                  
                  Joel BodenmannJ Offline
                  Joel BodenmannJ Offline
                  Joel Bodenmann
                  wrote on last edited by
                  #22

                  Wow, I am deeply impressed. Using the code shown by @Chris-Kawa gave exactly the desired result:
                  Alt text

                  Thank you very much for your help, guys. Very appreciated!

                  Industrial process automation software: https://simulton.com
                  Embedded Graphics & GUI library: https://ugfx.io

                  1 Reply Last reply
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                  • mrjjM Offline
                    mrjjM Offline
                    mrjj
                    Lifetime Qt Champion
                    wrote on last edited by
                    #23

                    well what can we say ?
                    Chris rules :)

                    Joel BodenmannJ 1 Reply Last reply
                    1
                    • mrjjM mrjj

                      well what can we say ?
                      Chris rules :)

                      Joel BodenmannJ Offline
                      Joel BodenmannJ Offline
                      Joel Bodenmann
                      wrote on last edited by
                      #24

                      @mrjj Well, thanks to you and @kshegunov too. You guys are amazing!

                      Industrial process automation software: https://simulton.com
                      Embedded Graphics & GUI library: https://ugfx.io

                      1 Reply Last reply
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