Skip to content
  • Categories
  • Recent
  • Tags
  • Popular
  • Users
  • Groups
  • Search
  • Get Qt Extensions
  • Unsolved
Collapse
Brand Logo
  1. Home
  2. Qt Development
  3. General and Desktop
  4. Unwanted vertical offset with with QRubberBand
Forum Updated to NodeBB v4.3 + New Features

Unwanted vertical offset with with QRubberBand

Scheduled Pinned Locked Moved Unsolved General and Desktop
18 Posts 3 Posters 5.6k Views 2 Watching
  • Oldest to Newest
  • Newest to Oldest
  • Most Votes
Reply
  • Reply as topic
Log in to reply
This topic has been deleted. Only users with topic management privileges can see it.
  • mrjjM mrjj

    @Bidski
    well from fast read- it looks and seems ok.
    If this on windows 10, it might be a bug.
    We had questions of incorrect frame thickness. 7 and not 1.
    Not sure this is related.
    You code looks fine. Try debug it and look at the values.

    B Offline
    B Offline
    Bidski
    wrote on last edited by
    #7

    @mrjj said in Unwanted vertical offset with with QRubberBand:

    @Bidski
    well from fast read- it looks and seems ok.
    If this on windows 10, it might be a bug.
    We had questions of incorrect frame thickness. 7 and not 1.
    Not sure this is related.
    You code looks fine. Try debug it and look at the values.

    This is actually on linux (Arch Linux to be precise) and Gnome 3 desktop environment and Qt5.8.

    I will get to debugging and dumping some values tomorrow and get back to you.

    mrjjM 1 Reply Last reply
    1
    • B Bidski

      @mrjj said in Unwanted vertical offset with with QRubberBand:

      @Bidski
      well from fast read- it looks and seems ok.
      If this on windows 10, it might be a bug.
      We had questions of incorrect frame thickness. 7 and not 1.
      Not sure this is related.
      You code looks fine. Try debug it and look at the values.

      This is actually on linux (Arch Linux to be precise) and Gnome 3 desktop environment and Qt5.8.

      I will get to debugging and dumping some values tomorrow and get back to you.

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

      @Bidski
      Super.
      Also if you can upload the small? project and give link here then
      its just to run and see for oneself also.

      B 1 Reply Last reply
      0
      • mrjjM mrjj

        @Bidski
        Super.
        Also if you can upload the small? project and give link here then
        its just to run and see for oneself also.

        B Offline
        B Offline
        Bidski
        wrote on last edited by
        #9

        @mrjj said in Unwanted vertical offset with with QRubberBand:

        @Bidski
        Super.
        Also if you can upload the small? project and give link here then
        its just to run and see for oneself also.

        Ok, I have dumped some quick values.
        The (x, y, width, height) of the QLabel geometry is reported as (188, 9, 613, 512)
        When the QRubberBand is stretched above the QLabel (as shown in the original image), its geometry is reported as (335, 9, 62, 175)
        When attempting to stretch the QRubberBand down to the bottom of the QLabel, the extent of its geometry reaches (340, 364, 272, 157)

        The black border of the QLabel (where the QRubberBand should be stopping) has top coordinate of 31 and a bottom coordinate of 544.
        Based on this, the QRubberBand is overshooting the top by 22 pixels and undershooting the bottom by 22 pixels.

        These measurements were taken with the window in a non-maximised state. When maximised, the offset remains the same.

        I will organise you a link to the code shortly

        1 Reply Last reply
        1
        • B Offline
          B Offline
          Bidski
          wrote on last edited by
          #10

          Hopefully you should be able to view this repo.
          Bitbucket Repo

          mrjjM 1 Reply Last reply
          0
          • B Bidski

            Hopefully you should be able to view this repo.
            Bitbucket Repo

            mrjjM Offline
            mrjjM Offline
            mrjj
            Lifetime Qt Champion
            wrote on last edited by mrjj
            #11

            @Bidski
            It still sounds as difference between client coordinates and global coordinates :)
            Like the height of the caption.

            It will let me into
            https://bitbucket.org/Bidski/imageannotator/src

            but i cant seem to find the download as zip ?
            I guess bitbucket do not offer such option. :)

            Called Downloads :) ( doh)

            B 1 Reply Last reply
            0
            • mrjjM mrjj

              @Bidski
              It still sounds as difference between client coordinates and global coordinates :)
              Like the height of the caption.

              It will let me into
              https://bitbucket.org/Bidski/imageannotator/src

              but i cant seem to find the download as zip ?
              I guess bitbucket do not offer such option. :)

              Called Downloads :) ( doh)

              B Offline
              B Offline
              Bidski
              wrote on last edited by
              #12

              @mrjj said in Unwanted vertical offset with with QRubberBand:

              @Bidski
              It still sounds as difference between client coordinates and global coordinates :)
              Like the height of the caption.

              What is the correct way to handle the difference in coordinate systems?

              J.HilkJ mrjjM 2 Replies Last reply
              0
              • B Bidski

                @mrjj said in Unwanted vertical offset with with QRubberBand:

                @Bidski
                It still sounds as difference between client coordinates and global coordinates :)
                Like the height of the caption.

                What is the correct way to handle the difference in coordinate systems?

                J.HilkJ Offline
                J.HilkJ Offline
                J.Hilk
                Moderators
                wrote on last edited by
                #13

                @Bidski

                for some reason, the QMenuBar is the problem. You can verify this, if you add

                ui->menubar->hide();
                

                in your constructor.

                No Offset with that.

                Not sure why thats the case, but now we can narrow it down :)


                Be aware of the Qt Code of Conduct, when posting : https://forum.qt.io/topic/113070/qt-code-of-conduct


                Q: What's that?
                A: It's blue light.
                Q: What does it do?
                A: It turns blue.

                B 1 Reply Last reply
                1
                • B Bidski

                  @mrjj said in Unwanted vertical offset with with QRubberBand:

                  @Bidski
                  It still sounds as difference between client coordinates and global coordinates :)
                  Like the height of the caption.

                  What is the correct way to handle the difference in coordinate systems?

                  mrjjM Offline
                  mrjjM Offline
                  mrjj
                  Lifetime Qt Champion
                  wrote on last edited by mrjj
                  #14

                  @Bidski

                  Hi
                  Its these functions.
                  http://doc.qt.io/qt-5/qwidget.html#mapFromGlobal
                  QPoint QWidget::mapToParent(const QPoint &pos) const

                  I didnt get to run it ( will tonight) but my best guess is that parent for RubberBand and
                  parent for Label is not the same and the offset comes from that.

                  A Child is relative to its parent. So its x,y is from the parent x,y. and not from zero,zero

                  So I think its where the diff comes from.
                  The mouse is in global, but the Label is in local with x,y.
                  I think RubberBand is relative to parent (if any) and not 0,0.

                  Its talked about here
                  http://stackoverflow.com/questions/16527248/qrubberband-on-a-definite-label

                  1 Reply Last reply
                  0
                  • J.HilkJ J.Hilk

                    @Bidski

                    for some reason, the QMenuBar is the problem. You can verify this, if you add

                    ui->menubar->hide();
                    

                    in your constructor.

                    No Offset with that.

                    Not sure why thats the case, but now we can narrow it down :)

                    B Offline
                    B Offline
                    Bidski
                    wrote on last edited by
                    #15

                    @J.Hilk @mrjj

                    I had a look at my code again. The QMenuBar, QLabel, and QRubberBand all share the same parent (which is AnnotateApp), so the mouse event position should have been in the same coordinate system as everything else? It appears that the QMenuBar is somehow absent in the calculation of the coordinates?

                    However, I made some code changes based on the SO link @mrjj provided. The QLabel is now the parent of QRubberBand and the mouse event coordinates are now mapped to global and then mapped from global to QLabel, as shown below.

                    void AnnotateApp::mousePressEvent(QMouseEvent *event)
                    {
                        // Create a rubber band if the mouse event is happening inside the image.
                        if (ui->image->geometry().contains(event->pos()))
                        {
                            origin = ui->image->mapFromGlobal(this->mapToGlobal(event->pos()));
                    
                            if (!rubberBand)
                            {
                                rubberBand = new QRubberBand(QRubberBand::Rectangle, ui->image);
                            }
                    
                            rubberBand->setGeometry(QRect(origin, QSize()));
                            rubberBand->show();
                        }
                    }
                    
                    void AnnotateApp::mouseMoveEvent(QMouseEvent *event)
                    {
                        // Only act if we actually have a rubber band to work with.
                        if (rubberBand && rubberBand->isVisible())
                        {
                            QPoint pos = ui->image->mapFromGlobal(this->mapToGlobal(event->pos());
                    
                            // Check to see if the mouse is still inside the iamge or not.
                            // If it is, then update the rubber band to the new coordinates.
                            if (ui->image->geometry().contains(pos))
                            {
                                rubberBand->setGeometry(QRect(origin, pos).normalized());
                            }
                    
                            // If it is not, then clamp the coordinates to the image boundary.
                            else
                            {
                                int x = std::min(ui->image->geometry().right(),  std::max(pos.x(), ui->image->geometry().left()));
                                int y = std::min(ui->image->geometry().bottom(), std::max(pos.y(), ui->image->geometry().top()));
                    
                                rubberBand->setGeometry(QRect(origin, QPoint(x, y)).normalized());
                            }
                        }
                    }
                    

                    This simply changes where the offset occurs. In the first image, I can't drag the left and top sides of the rubber band past where they are (started dragging from the middle of the QLabel). In the second image I started dragging from the top-left of the QLabel, immediately a small x-offset is appears and the width of the QRubberBand snaps to where the x-boundary occurs in the first image.

                    More offset issues
                    Even more issues

                    J.HilkJ 1 Reply Last reply
                    0
                    • B Bidski

                      @J.Hilk @mrjj

                      I had a look at my code again. The QMenuBar, QLabel, and QRubberBand all share the same parent (which is AnnotateApp), so the mouse event position should have been in the same coordinate system as everything else? It appears that the QMenuBar is somehow absent in the calculation of the coordinates?

                      However, I made some code changes based on the SO link @mrjj provided. The QLabel is now the parent of QRubberBand and the mouse event coordinates are now mapped to global and then mapped from global to QLabel, as shown below.

                      void AnnotateApp::mousePressEvent(QMouseEvent *event)
                      {
                          // Create a rubber band if the mouse event is happening inside the image.
                          if (ui->image->geometry().contains(event->pos()))
                          {
                              origin = ui->image->mapFromGlobal(this->mapToGlobal(event->pos()));
                      
                              if (!rubberBand)
                              {
                                  rubberBand = new QRubberBand(QRubberBand::Rectangle, ui->image);
                              }
                      
                              rubberBand->setGeometry(QRect(origin, QSize()));
                              rubberBand->show();
                          }
                      }
                      
                      void AnnotateApp::mouseMoveEvent(QMouseEvent *event)
                      {
                          // Only act if we actually have a rubber band to work with.
                          if (rubberBand && rubberBand->isVisible())
                          {
                              QPoint pos = ui->image->mapFromGlobal(this->mapToGlobal(event->pos());
                      
                              // Check to see if the mouse is still inside the iamge or not.
                              // If it is, then update the rubber band to the new coordinates.
                              if (ui->image->geometry().contains(pos))
                              {
                                  rubberBand->setGeometry(QRect(origin, pos).normalized());
                              }
                      
                              // If it is not, then clamp the coordinates to the image boundary.
                              else
                              {
                                  int x = std::min(ui->image->geometry().right(),  std::max(pos.x(), ui->image->geometry().left()));
                                  int y = std::min(ui->image->geometry().bottom(), std::max(pos.y(), ui->image->geometry().top()));
                      
                                  rubberBand->setGeometry(QRect(origin, QPoint(x, y)).normalized());
                              }
                          }
                      }
                      

                      This simply changes where the offset occurs. In the first image, I can't drag the left and top sides of the rubber band past where they are (started dragging from the middle of the QLabel). In the second image I started dragging from the top-left of the QLabel, immediately a small x-offset is appears and the width of the QRubberBand snaps to where the x-boundary occurs in the first image.

                      More offset issues
                      Even more issues

                      J.HilkJ Offline
                      J.HilkJ Offline
                      J.Hilk
                      Moderators
                      wrote on last edited by J.Hilk
                      #16

                      @Bidski

                      I don't have a bugfix for you, but a workaround.

                      reverte mousePressEvent back to how it was and

                      void AnnotateApp::mouseMoveEvent(QMouseEvent *event)
                      {
                          // Only act if we actually have a rubber band to work with.
                          if (rubberBand && rubberBand->isVisible())
                          {
                              // Check to see if the mouse is still inside the iamge or not.
                              // If it is, then update the rubber band to the new coordinates.
                              QRect fixedRect (ui->image->x(),
                                               ui->image->y()+ui->menubar->height(),
                                               ui->image->width(),
                                               ui->image->height());
                              if (fixedRect.contains(event->pos()))
                              {
                                  rubberBand->setGeometry(QRect(origin, event->pos()).normalized());
                              }
                      
                              // If it is not, then clamp the coordinates to the image boundary.
                              else
                              {
                                  int x = std::min(fixedRect.right(),  std::max(event->pos().x(), fixedRect.left()));
                                  int y = std::min(fixedRect.bottom(), std::max(event->pos().y(), fixedRect.top()));
                      
                                  rubberBand->setGeometry(QRect(origin, QPoint(x, y)).normalized());
                              }
                          }
                      }
                      

                      but its a workaround! Hopefully someone can give you a better solution.


                      Be aware of the Qt Code of Conduct, when posting : https://forum.qt.io/topic/113070/qt-code-of-conduct


                      Q: What's that?
                      A: It's blue light.
                      Q: What does it do?
                      A: It turns blue.

                      B 1 Reply Last reply
                      0
                      • J.HilkJ J.Hilk

                        @Bidski

                        I don't have a bugfix for you, but a workaround.

                        reverte mousePressEvent back to how it was and

                        void AnnotateApp::mouseMoveEvent(QMouseEvent *event)
                        {
                            // Only act if we actually have a rubber band to work with.
                            if (rubberBand && rubberBand->isVisible())
                            {
                                // Check to see if the mouse is still inside the iamge or not.
                                // If it is, then update the rubber band to the new coordinates.
                                QRect fixedRect (ui->image->x(),
                                                 ui->image->y()+ui->menubar->height(),
                                                 ui->image->width(),
                                                 ui->image->height());
                                if (fixedRect.contains(event->pos()))
                                {
                                    rubberBand->setGeometry(QRect(origin, event->pos()).normalized());
                                }
                        
                                // If it is not, then clamp the coordinates to the image boundary.
                                else
                                {
                                    int x = std::min(fixedRect.right(),  std::max(event->pos().x(), fixedRect.left()));
                                    int y = std::min(fixedRect.bottom(), std::max(event->pos().y(), fixedRect.top()));
                        
                                    rubberBand->setGeometry(QRect(origin, QPoint(x, y)).normalized());
                                }
                            }
                        }
                        

                        but its a workaround! Hopefully someone can give you a better solution.

                        B Offline
                        B Offline
                        Bidski
                        wrote on last edited by
                        #17

                        @J.Hilk
                        Is this actually a bug?

                        mrjjM 1 Reply Last reply
                        0
                        • B Bidski

                          @J.Hilk
                          Is this actually a bug?

                          mrjjM Offline
                          mrjjM Offline
                          mrjj
                          Lifetime Qt Champion
                          wrote on last edited by mrjj
                          #18

                          @Bidski
                          Hi
                          Not in Qt. ( maybe if old)

                          I would guess from the attempt to snap the
                          coordinates but cant say for sure.

                          However, please see this sample

                          https://www.dropbox.com/s/gp9rvylkb18xnl3/myrubberband.zip?dl=0

                          alt text

                          Drag the rubberband and release
                          It cuts what is expected and show in label
                          So all seems to be fine :)

                          #include <QMouseEvent>
                          
                          MainWindow::MainWindow(QWidget *parent) :
                              QMainWindow(parent),
                              ui(new Ui::MainWindow)
                          {
                              ui->setupUi(this);
                              move_rubberband = false;
                              rubberBand = new QRubberBand(QRubberBand::Rectangle, this);
                              rubberBand->setGeometry(0,0,50,50);
                              rubberBand->show();
                          }
                          
                          void MainWindow::mousePressEvent(QMouseEvent *e)
                          {
                              if(rubberBand->geometry().contains(e->pos()))
                              {
                                  rubberband_offset = e->pos() - rubberBand->pos();
                                  move_rubberband = true;
                              }
                          }
                          
                          void MainWindow::mouseMoveEvent(QMouseEvent *e)
                          {
                              if(move_rubberband)
                              {
                                  rubberBand->move(e->pos() - rubberband_offset);
                              }
                          }
                          
                          void MainWindow::mouseReleaseEvent(QMouseEvent *e)
                          {
                              move_rubberband = false;
                          
                              QRect r=rubberBand->geometry();
                              rubberBand->hide();
                              QPixmap p=grab(r); // no need for mapTo here. 
                              ui->label->setPixmap(p);
                              rubberBand->show();
                              rubberBand->raise();
                          }
                          
                          
                          1 Reply Last reply
                          0

                          • Login

                          • Login or register to search.
                          • First post
                            Last post
                          0
                          • Categories
                          • Recent
                          • Tags
                          • Popular
                          • Users
                          • Groups
                          • Search
                          • Get Qt Extensions
                          • Unsolved