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QPolygonF error

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  • Christian EhrlicherC Christian Ehrlicher

    Again: please provide a minimal, compilable example with the correct points.

    D Offline
    D Offline
    Daniil S.
    wrote on last edited by Daniil S.
    #8

    @Christian-Ehrlicher the above is complete code of the combine method, 30424848-5cf3-4662-967e-47e5ac8f9a26-image.png
    here are the points of the first call to this method, the result of the combine is passed to the second call, which results in an error, first call works correctly

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    0
    • Christian EhrlicherC Offline
      Christian EhrlicherC Offline
      Christian Ehrlicher
      Lifetime Qt Champion
      wrote on last edited by
      #9

      I don't see anything but a class function which does some calculation. What input points do you use? Why do you need the function above? You said QPolygonF::united(QPolygonF) triggers this error so write a reproducer which does use exactly only this function and nothing else.

      Qt Online Installer direct download: https://download.qt.io/official_releases/online_installers/
      Visit the Qt Academy at https://academy.qt.io/catalog

      D 1 Reply Last reply
      0
      • Christian EhrlicherC Christian Ehrlicher

        I don't see anything but a class function which does some calculation. What input points do you use? Why do you need the function above? You said QPolygonF::united(QPolygonF) triggers this error so write a reproducer which does use exactly only this function and nothing else.

        D Offline
        D Offline
        Daniil S.
        wrote on last edited by Daniil S.
        #10

        @Christian-Ehrlicher I wrote what points I use, in this method call "united", don't understand what else is needed

        QPolygonF united_low(low_polygon.united(high_polygon));
        united_low.erase(std::remove_if(united_low.begin(), united_low.end(), [](QPointF p) { return p.y() == -2; }), united_low.end());
        

        this function searches for the intersection of the upper (overlayed) graph with the lower, creates two polygons from the intersection and the upper graph and unite them, after which it clears the extra flags and adds the final result of the merge

        three steps of the loop, the first does not use the "HtrType" method, the other two use

        first step
        high QVector(QPointF(79,31), QPointF(182.303,139), QPointF(643,0), QPointF(673,31))
        low QVector(QPointF(0,-1), QPointF(1000,-1))

        second step
        high QVector(QPointF(293,0), QPointF(406.102,225), QPointF(556,0))
        low QVector(QPointF(0,-1), QPointF(79,-1), QPointF(79,31), QPointF(182.303,139), QPointF(182.303,139), QPointF(643,0), QPointF(643,0), QPointF(673,31), QPointF(673,-1), QPointF(1000,-1))

        third step
        high QVector(QPointF(293,0), QPointF(406.102,225), QPointF(556,0))
        low QVector(QPointF(0,-1), QPointF(79,-1), QPointF(79,31), QPointF(182.303,139), QPointF(182.303,139), QPointF(293,105), QPointF(338.857,91.2255), QPointF(406.102,225), QPointF(534.345,32.5048), QPointF(556,26), QPointF(643,0), QPointF(643,0), QPointF(673,31), QPointF(673,-1), QPointF(1000,-1))

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        • Christian EhrlicherC Offline
          Christian EhrlicherC Offline
          Christian Ehrlicher
          Lifetime Qt Champion
          wrote on last edited by
          #11

          @Daniil-S said in QPolygonF error:

          don't understand what else is needed

          If you want us to take a look on the problem then

          • create two QPolygonF with your points
          • call unite() on them
          • tells us what's wrong

          Noone will step through your code above, especially when the input is unknown.

          Qt Online Installer direct download: https://download.qt.io/official_releases/online_installers/
          Visit the Qt Academy at https://academy.qt.io/catalog

          D 2 Replies Last reply
          1
          • Christian EhrlicherC Christian Ehrlicher

            @Daniil-S said in QPolygonF error:

            don't understand what else is needed

            If you want us to take a look on the problem then

            • create two QPolygonF with your points
            • call unite() on them
            • tells us what's wrong

            Noone will step through your code above, especially when the input is unknown.

            D Offline
            D Offline
            Daniil S.
            wrote on last edited by Daniil S.
            #12

            @Christian-Ehrlicher

            move the slider and graph will sometimes bug

            .pro file

            QT  += core gui
            
            greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
            
            CONFIG += c++11
            
            # You can make your code fail to compile if it uses deprecated APIs.
            # In order to do so, uncomment the following line.
            #DEFINES += QT_DISABLE_DEPRECATED_BEFORE=0x060000    # disables all the APIs deprecated before Qt 6.0.0
            
            SOURCES += \
                main.cpp \
                mainwindow.cpp
            
            HEADERS += \
                mainwindow.h
            
            FORMS += \
                mainwindow.ui
            
            # Default rules for deployment.
            qnx: target.path = /tmp/$${TARGET}/bin
            else: unix:!android: target.path = /opt/$${TARGET}/bin
            !isEmpty(target.path): INSTALLS += target
            
            

            main.cpp

            #include "mainwindow.h"
            
            #include <QApplication>
            #include <QWidget>
            
            int main(int argc, char *argv[])
            {
              QApplication a(argc, argv);
              MainWindow w;
              w.show();
              return a.exec();
            }
            

            mainwindow.h

            #pragma once
            
            #include <QMainWindow>
            #include <QPainterPath>
            
            QT_BEGIN_NAMESPACE
            namespace Ui { class MainWindow; }
            QT_END_NAMESPACE
            
            class MainWindow : public QMainWindow
            {
              Q_OBJECT
            
              static QVector<QPointF> HtpType(QVector<QPointF> low_graphic, QVector<QPointF> high_graphic);
              static int GetTimeProjection(qreal x_coord, QPointF left_point, QPointF right_point);
            
            public:
              MainWindow(QWidget *parent = nullptr);
              ~MainWindow();
            
            public slots:
              void recalculate(int value);
            
            private:
              Ui::MainWindow *ui;
            };
            

            mainwindow.cpp

            #include "mainwindow.h"
            #include "ui_mainwindow.h"
            
            QVector<QPointF> MainWindow::HtpType(QVector<QPointF> low_graphic, QVector<QPointF> high_graphic)
            {
              QVector<QPointF> combined, intersected_low, after_high;
            
              QPointF before_enter(-1,-1), after_exit(-1,-1);
              auto low_iterator(low_graphic.begin());
              while (low_iterator != low_graphic.end()) {
            
                if (low_iterator->x() < high_graphic.first().x()) {
            
                  combined.push_back(*low_iterator); 
                  before_enter = *low_iterator; 
                }
                else if (low_iterator->x() >= high_graphic.first().x() && low_iterator->x() <= high_graphic.last().x()) {
            
                  intersected_low.push_back(*low_iterator); 
            
                } else if (low_iterator->x() > high_graphic.last().x()) {
            
                  if (after_exit == QPointF(-1,-1))  
                    after_exit = *low_iterator;
            
                  after_high.push_back(*low_iterator); 
                }
                low_iterator++;
              }
            
              if (intersected_low.isEmpty()) {
            
                if (before_enter.y() == -1 && after_exit.y() == -1) { 
                  high_graphic.push_front(QPointF(high_graphic.first().x(), -1));
                  high_graphic.push_back(QPointF(high_graphic.last().x(), -1));
            
                  Q_FOREACH(QPointF point, high_graphic)
                    if (combined.last() != point)
                      combined.push_back(point);
            
                  Q_FOREACH(QPointF point, after_high)
                    if (combined.last() != point)
                      combined.push_back(point);
            
                  return combined;
                } else { 
            
                  intersected_low.push_back(QPointF(high_graphic.first().x(), GetTimeProjection(high_graphic.first().x(), before_enter, after_exit)));
                  intersected_low.push_back(QPointF(high_graphic.last().x(), GetTimeProjection(high_graphic.last().x(), before_enter, after_exit)));
                }
              }
            
              QPolygonF low_polygon(intersected_low), high_polygon(high_graphic);
            
              QPointF prepend_point(before_enter.y() != -1 ? QPointF(high_graphic.first().x(), GetTimeProjection(high_graphic.first().x(), before_enter, intersected_low.first()))
                                                           : QPointF(high_graphic.first().x(), -1));
            
              low_polygon.prepend(prepend_point);
              if (combined.last() != prepend_point)
                combined.push_back(prepend_point);
            
              low_polygon.prepend(QPointF(high_graphic.first().x(), -2));
              low_polygon.append(after_exit.y() != -1 ? QPointF(high_graphic.last().x(), GetTimeProjection(high_graphic.last().x(), intersected_low.last(), after_exit))
                                                      : QPointF(high_graphic.last().x(), -1));
              low_polygon.append(QPointF(high_graphic.last().x(), -2));
            
              for(int i(0); i < low_polygon.count(); i++)
                if (low_polygon.at(i).y() == -1)
                  low_polygon[i].ry() = 0;
            
              high_polygon.prepend(QPointF(high_graphic.first().x(), -2));
              high_polygon.append(QPointF(high_graphic.last().x(), -2));
            
              QPolygonF united_low(low_polygon.united(high_polygon));
              united_low.erase(std::remove_if(united_low.begin(), united_low.end(), [](QPointF p) { return p.y() == -2; }), united_low.end());
            
              if (united_low.last() == united_low.first())
                united_low.removeLast(); 
            
              QPointF after_high_point(high_graphic.last().x(), -1);
              if (after_exit.y() != -1)
                after_high_point.ry() = GetTimeProjection(high_graphic.last().x(), intersected_low.last(), after_exit);
              united_low.push_back(after_high_point);
            
              Q_FOREACH(QPointF point, united_low)
                if (combined.last() != point)
                  combined.push_back(point);
            
              Q_FOREACH(QPointF point, after_high)
                if (combined.last() != point)
                  combined.push_back(point);
            
              return combined;
            }
            
            int MainWindow::GetTimeProjection(qreal x_coord, QPointF left_point, QPointF right_point)
            {
              if (left_point.y() == -1)
                left_point.ry() = 0;
              if (right_point.y() == -1)
                right_point.ry() = 0;
            
              qreal x_min = (( right_point.x() <= left_point.x() ) ? right_point.x() : left_point.x());
              qreal x_max = (( right_point.x() >= left_point.x() ) ? right_point.x() : left_point.x());
              qreal y_min = (( right_point.y() <= left_point.y() ) ? right_point.y() : left_point.y());
              qreal y_max = (( right_point.y() >= left_point.y() ) ? right_point.y() : left_point.y());
            
              int direction = 0;
            
              if (left_point.y() != right_point.y())
                direction = ((left_point.y() < right_point.y()) ? 1 : -1);
            
              qreal delta_x = x_max - x_min;
              qreal delta_y = y_max - y_min;
            
              int value = 0;
            
              direction == -1 ? value = (delta_x ? y_min + delta_y - (delta_y / delta_x) * (x_coord - x_min) : y_min + delta_y)
                                        : value = (delta_x ? y_min + (delta_y / delta_x) * (x_coord - x_min) : y_min);
            
              return value;
            }
            
            MainWindow::MainWindow(QWidget *parent)
              : QMainWindow(parent)
              , ui(new Ui::MainWindow)
            {
              ui->setupUi(this);
              ui->graphicsView->setScene(new QGraphicsScene(ui->graphicsView));
            
              ui->horizontalSlider->setRange(0, 255);
              connect(ui->horizontalSlider, &QSlider::valueChanged, this, &MainWindow::recalculate);
            }
            
            MainWindow::~MainWindow()
            {
              delete ui;
            }
            
            void MainWindow::recalculate(int value)
            {
              QVector<QPointF> high, low1;
              high << QPointF(293,0) << QPointF(406.102, 225) << QPointF(556,0);
              low1 << QPointF(0,-1) << QPointF(79,-1) << QPointF(79,31) << QPointF(182.303,value) << QPointF(643,0) << QPointF(673,31) << QPointF(673,-1) << QPointF(1000,- 1);
            
              QVector<QPointF> result(HtpType(HtpType(low1, high), high));
            
              QPointF first(result.first());
              first.ry() = std::abs(255 - first.y());
              QPainterPath path(first);
              for(int i(1); i < result.count(); i++) {
            
                QPointF next(result.at(i));
                next.ry() = std::abs(255 - next.y());
                path.lineTo(next);
              }
            
              ui->graphicsView->scene()->clear();
              ui->graphicsView->scene()->addPath(path);
            }
            

            mainwindow.ui

            <?xml version="1.0" encoding="UTF-8"?>
            <ui version="4.0">
             <class>MainWindow</class>
             <widget class="QMainWindow" name="MainWindow">
              <property name="geometry">
               <rect>
                <x>0</x>
                <y>0</y>
                <width>800</width>
                <height>600</height>
               </rect>
              </property>
              <property name="windowTitle">
               <string>MainWindow</string>
              </property>
              <widget class="QWidget" name="centralwidget">
               <widget class="QGraphicsView" name="graphicsView">
                <property name="geometry">
                 <rect>
                  <x>50</x>
                  <y>50</y>
                  <width>681</width>
                  <height>461</height>
                 </rect>
                </property>
               </widget>
               <widget class="QSlider" name="horizontalSlider">
                <property name="geometry">
                 <rect>
                  <x>290</x>
                  <y>520</y>
                  <width>160</width>
                  <height>16</height>
                 </rect>
                </property>
                <property name="orientation">
                 <enum>Qt::Horizontal</enum>
                </property>
               </widget>
              </widget>
              <widget class="QMenuBar" name="menubar">
               <property name="geometry">
                <rect>
                 <x>0</x>
                 <y>0</y>
                 <width>800</width>
                 <height>20</height>
                </rect>
               </property>
              </widget>
              <widget class="QStatusBar" name="statusbar"/>
             </widget>
             <resources/>
             <connections/>
            </ui>
            
            
            1 Reply Last reply
            0
            • Christian EhrlicherC Christian Ehrlicher

              @Daniil-S said in QPolygonF error:

              don't understand what else is needed

              If you want us to take a look on the problem then

              • create two QPolygonF with your points
              • call unite() on them
              • tells us what's wrong

              Noone will step through your code above, especially when the input is unknown.

              D Offline
              D Offline
              Daniil S.
              wrote on last edited by
              #13

              @Christian-Ehrlicher what you need or a smaller example?

              JonBJ 1 Reply Last reply
              0
              • D Daniil S.

                @Christian-Ehrlicher what you need or a smaller example?

                JonBJ Offline
                JonBJ Offline
                JonB
                wrote on last edited by
                #14

                @Daniil-S said in QPolygonF error:

                or a smaller example?

                Do you really need about 100 lines of code to draw a polygon to illustrate whatever your problem is? Have you reduced this to some minimum which exemplifies the problem? Any example to illustrate a point which is longer than about 20 lines is suspect....

                1 Reply Last reply
                0
                • Christian EhrlicherC Offline
                  Christian EhrlicherC Offline
                  Christian Ehrlicher
                  Lifetime Qt Champion
                  wrote on last edited by
                  #15

                  I will not debug your code, as @JonB said (and also me some time ago) a simple list with the polygons as input and the (wrong) and correct output is the way to go.

                  Qt Online Installer direct download: https://download.qt.io/official_releases/online_installers/
                  Visit the Qt Academy at https://academy.qt.io/catalog

                  1 Reply Last reply
                  2
                  • D Offline
                    D Offline
                    Daniil S.
                    wrote on last edited by Daniil S.
                    #16
                      QVector<QPointF> high, low;
                      high << QPointF(293,0) << QPointF(406.102, 225) << QPointF(556,0);
                      low << QPointF(79,-1) << QPointF(182.303, 57) << QPointF(673,-1);
                    
                      qDebug() << HtpType(HtpType(low, high), high);
                    
                      QVector<QPointF> high1, low1;
                      high1 << QPointF(293,0) << QPointF(406.102, 225) << QPointF(556,0);
                      low1 << QPointF(79,-1) << QPointF(182.303, 60) << QPointF(673,-1);
                    
                      qDebug() << HtpType(HtpType(low1, high1), high1);
                    

                    first qDebug() (second point of low Y = 57) bad result

                    QVector(QPointF(79,-1), QPointF(182.303,57), QPointF(293,44), QPointF(293,0), QPointF(293,44), QPointF(313.881,41.5388), QPointF(293,0), QPointF(313.881,41.5388), QPointF(406.102,225), QPointF(546.601,14.1078), QPointF(556,13), QPointF(556,0), QPointF(406.102,225), QPointF(313.881,41.5388), QPointF(556,-1), QPointF(673,-1))

                    second qDebug() (second point of low Y = 60) right result

                    QVector(QPointF(79,-1), QPointF(182.303,60), QPointF(293,46), QPointF(314.79,43.3487), QPointF(406.102,225), QPointF(545.85,15.2349), QPointF(556,14), QPointF(556,-1), QPointF(673,-1))

                    to combine two plots, I need to use this method, because graphs has flags that cannot be changed during combine, so the intersection is first searched and it is combined to the top

                    1 Reply Last reply
                    0
                    • Christian EhrlicherC Offline
                      Christian EhrlicherC Offline
                      Christian Ehrlicher
                      Lifetime Qt Champion
                      wrote on last edited by Christian Ehrlicher
                      #17

                      This is a testcase similar to what we want to see:

                      int main(int argc, char **argv)
                      {
                        QCoreApplication app(argc, argv);
                      
                        QPolygonF p1 = QVector<QPointF>({{1., 0.}, {2., 1.}, {3., 1.}, {4., 1.}});
                        QPolygonF p2 = QVector<QPointF>({{2., 2.}, {3., 2.}, {4., 5.}, {3., 2.}});
                        QPolygonF united = p1.united(p2);
                        QPolygonF expected = QVector<QPointF>({{1., 0.}, {2., 1.}, {3., 1.}, {4., 1.}, {1., 0.}, {2., 2.}, {3., 2.}, {4., 5.}, {3., 2.}, {2., 2.}, {1., 0.}});
                        qDebug() << (united == expected);
                        qDebug() << united;
                        qDebug() << expected;
                      
                        return 0;
                      }
                      

                      Qt Online Installer direct download: https://download.qt.io/official_releases/online_installers/
                      Visit the Qt Academy at https://academy.qt.io/catalog

                      D 2 Replies Last reply
                      1
                      • Christian EhrlicherC Christian Ehrlicher

                        This is a testcase similar to what we want to see:

                        int main(int argc, char **argv)
                        {
                          QCoreApplication app(argc, argv);
                        
                          QPolygonF p1 = QVector<QPointF>({{1., 0.}, {2., 1.}, {3., 1.}, {4., 1.}});
                          QPolygonF p2 = QVector<QPointF>({{2., 2.}, {3., 2.}, {4., 5.}, {3., 2.}});
                          QPolygonF united = p1.united(p2);
                          QPolygonF expected = QVector<QPointF>({{1., 0.}, {2., 1.}, {3., 1.}, {4., 1.}, {1., 0.}, {2., 2.}, {3., 2.}, {4., 5.}, {3., 2.}, {2., 2.}, {1., 0.}});
                          qDebug() << (united == expected);
                          qDebug() << united;
                          qDebug() << expected;
                        
                          return 0;
                        }
                        
                        D Offline
                        D Offline
                        Daniil S.
                        wrote on last edited by
                        #18

                        @Christian-Ehrlicher

                        int main(int argc, char *argv[])
                        {
                          QPolygonF high, low;
                          high << QPointF(293, 0) << QPointF(406.102, 225) << QPointF(556, 0);
                          low << QPointF(79, -1) << QPointF(182.303, 60) << QPointF(673, -1);
                        
                        
                        
                          QPolygonF low1(low.united(high).united(high))
                              , expected({ QPointF(79,-1), QPointF(182.303,60), QPointF(314.876,43.5194), QPointF(406.102,225), QPointF(546.162,14.7677), QPointF(673,-1), QPointF(79,-1) });
                        
                          qDebug() << low1;
                          qDebug() << expected;
                          qDebug() << (expected == low1);
                        
                          return 0;
                        }
                        

                        qDebug()

                        QPolygonF(QPointF(79,-1)QPointF(182.303,60)QPointF(314.876,43.5194)QPointF(293,0)QPointF(556,0)QPointF(406.102,225)QPointF(314.876,43.5194)QPointF(182.303,60)QPointF(79,-1)QPointF(314.876,43.5194)QPointF(406.102,225)QPointF(546.162,14.7677)QPointF(673,-1)QPointF(79,-1)QPointF(182.303,60)QPointF(314.876,43.5194)QPointF(293,0)QPointF(556,0)QPointF(406.102,225)QPointF(314.876,43.5194)QPointF(79,-1))
                        
                        QPolygonF(QPointF(79,-1)QPointF(182.303,60)QPointF(314.876,43.5194)QPointF(406.102,225)QPointF(546.162,14.7677)QPointF(673,-1)QPointF(79,-1))
                        
                        false
                        
                        1 Reply Last reply
                        1
                        • Christian EhrlicherC Christian Ehrlicher

                          This is a testcase similar to what we want to see:

                          int main(int argc, char **argv)
                          {
                            QCoreApplication app(argc, argv);
                          
                            QPolygonF p1 = QVector<QPointF>({{1., 0.}, {2., 1.}, {3., 1.}, {4., 1.}});
                            QPolygonF p2 = QVector<QPointF>({{2., 2.}, {3., 2.}, {4., 5.}, {3., 2.}});
                            QPolygonF united = p1.united(p2);
                            QPolygonF expected = QVector<QPointF>({{1., 0.}, {2., 1.}, {3., 1.}, {4., 1.}, {1., 0.}, {2., 2.}, {3., 2.}, {4., 5.}, {3., 2.}, {2., 2.}, {1., 0.}});
                            qDebug() << (united == expected);
                            qDebug() << united;
                            qDebug() << expected;
                          
                            return 0;
                          }
                          
                          D Offline
                          D Offline
                          Daniil S.
                          wrote on last edited by
                          #19

                          @Christian-Ehrlicher still not what you need?

                          kshegunovK 1 Reply Last reply
                          0
                          • D Daniil S.

                            @Christian-Ehrlicher still not what you need?

                            kshegunovK Offline
                            kshegunovK Offline
                            kshegunov
                            Moderators
                            wrote on last edited by
                            #20

                            low.united(high).united(high)?

                            Why the second call? What does calling it only once produce?

                            Read and abide by the Qt Code of Conduct

                            D 1 Reply Last reply
                            0
                            • kshegunovK kshegunov

                              low.united(high).united(high)?

                              Why the second call? What does calling it only once produce?

                              D Offline
                              D Offline
                              Daniil S.
                              wrote on last edited by Daniil S.
                              #21

                              @kshegunov I have an application that combines graphs of changing values, nothing prevents different "scenes" with same graphs that can combined more times. now I have 3 scenes, on 3 lines, the top two scenes have exactly the same graph, and if i combine them all, this leads to this error

                              kshegunovK 1 Reply Last reply
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                              • D Daniil S.

                                @kshegunov I have an application that combines graphs of changing values, nothing prevents different "scenes" with same graphs that can combined more times. now I have 3 scenes, on 3 lines, the top two scenes have exactly the same graph, and if i combine them all, this leads to this error

                                kshegunovK Offline
                                kshegunovK Offline
                                kshegunov
                                Moderators
                                wrote on last edited by kshegunov
                                #22

                                Okay, this answers the first question, what about the second? Does calling .union only once produce the correct result?

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                                Christian EhrlicherC D 2 Replies Last reply
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                                • kshegunovK kshegunov

                                  Okay, this answers the first question, what about the second? Does calling .union only once produce the correct result?

                                  Christian EhrlicherC Offline
                                  Christian EhrlicherC Offline
                                  Christian Ehrlicher
                                  Lifetime Qt Champion
                                  wrote on last edited by
                                  #23

                                  @kshegunov said in QPolygonF error:

                                  Does calling .union only once produce the correct result?

                                  Yes, but with slightly different numbers (not visible in a plain debug output). I would guess somewhere in the clipping logic a rounding error triggers this bug (e.g. 314.87615740 / 43.51943745 <-> 314.87600000 / 43.51940000)

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                                  kshegunovK 1 Reply Last reply
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                                  • kshegunovK kshegunov

                                    Okay, this answers the first question, what about the second? Does calling .union only once produce the correct result?

                                    D Offline
                                    D Offline
                                    Daniil S.
                                    wrote on last edited by Daniil S.
                                    #24

                                    @kshegunov yes, but I cant check top polygons are equal, because they must be combined in order in the loop and can have different overlay types, and checking high by points before united is not entirely correct, because a polygon can contain a point, but not a union

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                                    • Christian EhrlicherC Christian Ehrlicher

                                      @kshegunov said in QPolygonF error:

                                      Does calling .union only once produce the correct result?

                                      Yes, but with slightly different numbers (not visible in a plain debug output). I would guess somewhere in the clipping logic a rounding error triggers this bug (e.g. 314.87615740 / 43.51943745 <-> 314.87600000 / 43.51940000)

                                      kshegunovK Offline
                                      kshegunovK Offline
                                      kshegunov
                                      Moderators
                                      wrote on last edited by kshegunov
                                      #25

                                      @Christian-Ehrlicher said in QPolygonF error:

                                      Yes, but with slightly different numbers (not visible in a plain debug output). I would guess somewhere in the clipping logic a rounding error triggers this bug (e.g. 314.87615740 / 43.51943745 <-> 314.87600000 / 43.51940000)

                                      Looks truncated more than a rounding error.

                                      @Daniil-S said in QPolygonF error:

                                      yes, but I cant check top polygons are equal, because they must be combined in order in the loop and can have different overlay types, and checking high by points before united is not entirely correct, because a polygon can contain a point, but not a union

                                      I was asking to discern whether the problem is that the two unions apply the same polygon only, there's a lot of edge cases whenever you're dealing with lines which are almost parallel (e.g. https://codereview.qt-project.org/c/qt/qtbase/+/292807).

                                      Please search the tracker and if this isn't reported, do so. Attach the minimal code to reproduce as well. Whenever I finish with that QLineF thing, given time I'll take a look.

                                      Read and abide by the Qt Code of Conduct

                                      Christian EhrlicherC D 2 Replies Last reply
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                                      • kshegunovK kshegunov

                                        @Christian-Ehrlicher said in QPolygonF error:

                                        Yes, but with slightly different numbers (not visible in a plain debug output). I would guess somewhere in the clipping logic a rounding error triggers this bug (e.g. 314.87615740 / 43.51943745 <-> 314.87600000 / 43.51940000)

                                        Looks truncated more than a rounding error.

                                        @Daniil-S said in QPolygonF error:

                                        yes, but I cant check top polygons are equal, because they must be combined in order in the loop and can have different overlay types, and checking high by points before united is not entirely correct, because a polygon can contain a point, but not a union

                                        I was asking to discern whether the problem is that the two unions apply the same polygon only, there's a lot of edge cases whenever you're dealing with lines which are almost parallel (e.g. https://codereview.qt-project.org/c/qt/qtbase/+/292807).

                                        Please search the tracker and if this isn't reported, do so. Attach the minimal code to reproduce as well. Whenever I finish with that QLineF thing, given time I'll take a look.

                                        Christian EhrlicherC Offline
                                        Christian EhrlicherC Offline
                                        Christian Ehrlicher
                                        Lifetime Qt Champion
                                        wrote on last edited by
                                        #26

                                        @kshegunov said in QPolygonF error:

                                        Looks truncated more than a rounding error.

                                        No error - qDebug() prints not the complete double value, I guess the values are taken from there. Mine are the exact ones :)

                                        So basically a polygon is united with a polygon which nearly matches parts of the first polygon which fails sometimes.

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                                        kshegunovK 1 Reply Last reply
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                                        • Christian EhrlicherC Christian Ehrlicher

                                          @kshegunov said in QPolygonF error:

                                          Looks truncated more than a rounding error.

                                          No error - qDebug() prints not the complete double value, I guess the values are taken from there. Mine are the exact ones :)

                                          So basically a polygon is united with a polygon which nearly matches parts of the first polygon which fails sometimes.

                                          kshegunovK Offline
                                          kshegunovK Offline
                                          kshegunov
                                          Moderators
                                          wrote on last edited by
                                          #27

                                          @Christian-Ehrlicher said in QPolygonF error:

                                          So basically a polygon is united with a polygon which nearly matches parts of the first polygon which fails sometimes.

                                          Yes, what I imagine happens. Probably somewhere in the clip/intersection code there's some numerical instability that breaks it silently.

                                          Read and abide by the Qt Code of Conduct

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