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QPainterPath from list of points

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  • M Offline
    M Offline
    mrjj
    Lifetime Qt Champion
    wrote on 27 Dec 2015, 18:41 last edited by mrjj
    #7

    Ok. i see.
    So it is not enough to actually test for mouse click on line
    http://stackoverflow.com/questions/26849632/see-if-a-point-lies-on-a-linevector

    I have no good suggestions for easy way. so let's wait and see
    if someone has a nice trick before resorting calculating offsets for each line segments :)

    J 1 Reply Last reply 27 Dec 2015, 18:46
    0
    • M mrjj
      27 Dec 2015, 18:41

      Ok. i see.
      So it is not enough to actually test for mouse click on line
      http://stackoverflow.com/questions/26849632/see-if-a-point-lies-on-a-linevector

      I have no good suggestions for easy way. so let's wait and see
      if someone has a nice trick before resorting calculating offsets for each line segments :)

      J Offline
      J Offline
      Joel Bodenmann
      wrote on 27 Dec 2015, 18:46 last edited by
      #8

      Thanks for your help, very appreciated!

      I hope that somebody has a better, easier way to get this done :/

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

      M 1 Reply Last reply 27 Dec 2015, 18:54
      0
      • J Joel Bodenmann
        27 Dec 2015, 18:46

        Thanks for your help, very appreciated!

        I hope that somebody has a better, easier way to get this done :/

        M Offline
        M Offline
        mrjj
        Lifetime Qt Champion
        wrote on 27 Dec 2015, 18:54 last edited by
        #9

        @Joel-Bodenmann
        well if no neat tricks comes, here is easy to understand
        implementation of click a line which would be easy to adapt to
        trigger when near a line as it uses vectors.
        https://msdn.microsoft.com/en-us/library/ms969920.aspx

        J 1 Reply Last reply 27 Dec 2015, 19:02
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        • M mrjj
          27 Dec 2015, 18:54

          @Joel-Bodenmann
          well if no neat tricks comes, here is easy to understand
          implementation of click a line which would be easy to adapt to
          trigger when near a line as it uses vectors.
          https://msdn.microsoft.com/en-us/library/ms969920.aspx

          J Offline
          J Offline
          Joel Bodenmann
          wrote on 27 Dec 2015, 19:02 last edited by
          #10

          @mrjj I don't think that that's going to help because the mouse-click-detection should be handled by the QGraphicsView/QGraphicsScene and for that they use QGraphcisItem::shape().

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

          M K 2 Replies Last reply 27 Dec 2015, 19:04
          0
          • J Joel Bodenmann
            27 Dec 2015, 19:02

            @mrjj I don't think that that's going to help because the mouse-click-detection should be handled by the QGraphicsView/QGraphicsScene and for that they use QGraphcisItem::shape().

            M Offline
            M Offline
            mrjj
            Lifetime Qt Champion
            wrote on 27 Dec 2015, 19:04 last edited by
            #11

            @Joel-Bodenmann
            ok, so you must have an actual polygon to return
            for hit-testing/handles to work.

            1 Reply Last reply
            0
            • J Joel Bodenmann
              27 Dec 2015, 19:02

              @mrjj I don't think that that's going to help because the mouse-click-detection should be handled by the QGraphicsView/QGraphicsScene and for that they use QGraphcisItem::shape().

              K Offline
              K Offline
              kshegunov
              Moderators
              wrote on 27 Dec 2015, 19:10 last edited by kshegunov
              #12

              @Joel-Bodenmann
              Let me first clarify something, you want to get an envelope around your path, that is larger (respectful to the lines) by some fixed pixel offset? Or you're talking about enveloping a polygon?

              Right, I read your post again and understand what you mean now. I believe you should implement that yourself, at least I don't know any easy way. I assume your points are ordered, so it's a simple linear algebra problem. You take the points by pairs, and from that pair you can easily calculate the alongside and normal vector for each line. From those two vectors (after normalization) you can build up your envelope. I hope that helps.

              Kind regards.

              Read and abide by the Qt Code of Conduct

              J 1 Reply Last reply 27 Dec 2015, 19:18
              0
              • K kshegunov
                27 Dec 2015, 19:10

                @Joel-Bodenmann
                Let me first clarify something, you want to get an envelope around your path, that is larger (respectful to the lines) by some fixed pixel offset? Or you're talking about enveloping a polygon?

                Right, I read your post again and understand what you mean now. I believe you should implement that yourself, at least I don't know any easy way. I assume your points are ordered, so it's a simple linear algebra problem. You take the points by pairs, and from that pair you can easily calculate the alongside and normal vector for each line. From those two vectors (after normalization) you can build up your envelope. I hope that helps.

                Kind regards.

                J Offline
                J Offline
                Joel Bodenmann
                wrote on 27 Dec 2015, 19:18 last edited by
                #13

                @kshegunov You are correct, I need an envelope around the path that has a few pixels of padding on each side of the line. Like the green line in this crude drawing that I made earlier: http://paste.ugfx.org/sores/7505d64a54e0/264c3e10630e.jpg

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

                K 1 Reply Last reply 27 Dec 2015, 19:32
                0
                • J Joel Bodenmann
                  27 Dec 2015, 19:18

                  @kshegunov You are correct, I need an envelope around the path that has a few pixels of padding on each side of the line. Like the green line in this crude drawing that I made earlier: http://paste.ugfx.org/sores/7505d64a54e0/264c3e10630e.jpg

                  K Offline
                  K Offline
                  kshegunov
                  Moderators
                  wrote on 27 Dec 2015, 19:32 last edited by
                  #14

                  @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.

                  Read and abide by the Qt Code of Conduct

                  J 1 Reply Last reply 27 Dec 2015, 19:45
                  0
                  • K kshegunov
                    27 Dec 2015, 19:32

                    @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.

                    J Offline
                    J Offline
                    Joel Bodenmann
                    wrote on 27 Dec 2015, 19:45 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

                    K 1 Reply Last reply 27 Dec 2015, 21:53
                    0
                    • J Joel Bodenmann
                      27 Dec 2015, 19:45

                      @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 :)

                      K Offline
                      K Offline
                      kshegunov
                      Moderators
                      wrote on 27 Dec 2015, 21:53 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

                      J 1 Reply Last reply 28 Dec 2015, 00:09
                      0
                      • K kshegunov
                        27 Dec 2015, 21:53

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

                        J Offline
                        J Offline
                        Joel Bodenmann
                        wrote on 28 Dec 2015, 00:09 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

                        K 1 Reply Last reply 28 Dec 2015, 00:18
                        0
                        • J Joel Bodenmann
                          28 Dec 2015, 00:09

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

                          K Offline
                          K Offline
                          kshegunov
                          Moderators
                          wrote on 28 Dec 2015, 00:18 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

                          J 1 Reply Last reply 28 Dec 2015, 13:12
                          0
                          • K kshegunov
                            28 Dec 2015, 00:18

                            @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.

                            J Offline
                            J Offline
                            Joel Bodenmann
                            wrote on 28 Dec 2015, 13:12 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
                            0
                            • K Offline
                              K Offline
                              kshegunov
                              Moderators
                              wrote on 28 Dec 2015, 15:23 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
                              0
                              • C Offline
                                C Offline
                                Chris Kawa
                                Lifetime Qt Champion
                                wrote on 28 Dec 2015, 15:49 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();
                                
                                J 1 Reply Last reply 28 Dec 2015, 16:27
                                2
                                • C Chris Kawa
                                  28 Dec 2015, 15:49

                                  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();
                                  
                                  J Offline
                                  J Offline
                                  Joel Bodenmann
                                  wrote on 28 Dec 2015, 16:27 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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                                  • M Offline
                                    M Offline
                                    mrjj
                                    Lifetime Qt Champion
                                    wrote on 28 Dec 2015, 16:28 last edited by
                                    #23

                                    well what can we say ?
                                    Chris rules :)

                                    J 1 Reply Last reply 28 Dec 2015, 16:30
                                    1
                                    • M mrjj
                                      28 Dec 2015, 16:28

                                      well what can we say ?
                                      Chris rules :)

                                      J Offline
                                      J Offline
                                      Joel Bodenmann
                                      wrote on 28 Dec 2015, 16:30 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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                                      27 Dec 2015, 21:53

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