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How to refresh data on horizontal header of QTableWidget?

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  • mrjjM mrjj

    @tovax
    Hi
    For each setHeaderData, you emit a headerDataChanged
    so i would guess on lots of view repaints are issued. (for each axisIndex)
    Since you always want to refresh whole header, i was wondering if you could test with
    delaying the headerDataChanged signal until after the loop.

    for (int32_t axisIndex = Axis::Index::Min; axisIndex <= Axis::Index::Max; axisIndex++) {
            tableModel->setHeaderData(axisIndex, Qt::Horizontal, posCmd.at(axisIndex), Qt::DisplayRole);
        }
     
    tableModel->HeaderChange(Axis::Index::Min, Axis::Index::Max ); // this issues the signal with 
                      headerDataChanged(orientation,Min,Max );
    
    
    tovaxT Offline
    tovaxT Offline
    tovax
    wrote on last edited by
    #10

    @mrjj
    Hi,
    According to your suggestion, I blocked "headerDataChanged" signal, and add this public function to Model Class:

    void MotionSheetTableModel::HeaderChange(int32_t first, int32_t last)
    {
        emit headerDataChanged(Qt::Horizontal, first, last);
    }
    

    But no significant improvement in test results.
    Is my understanding right, please?

    Best Regards!

    mrjjM 1 Reply Last reply
    0
    • tovaxT tovax

      @mrjj
      Hi,
      According to your suggestion, I blocked "headerDataChanged" signal, and add this public function to Model Class:

      void MotionSheetTableModel::HeaderChange(int32_t first, int32_t last)
      {
          emit headerDataChanged(Qt::Horizontal, first, last);
      }
      

      But no significant improvement in test results.
      Is my understanding right, please?

      Best Regards!

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

      @tovax
      If by blocked you mean
      // emit headerDataChanged(orientation, section, section);
      and call your new function (HeaderChange) after the loop then we are on same page.

      Ok so that didnt speed it up. :(
      Im not sure how altering the list
      posCmdList[section] = QString::number(value.value<double>(), 'f', 2);
      would be slow.

      I think i would insert some timing functions
      (https://doc.qt.io/qt-5/qelapsedtimer.html is handy for that)
      and see where the time is spend.
      Now we know its not from pure updates so we need to find the spot where the time is used.

      Also 10 times pr second does not sound that massive but I would try other values to see
      where the sweet spot it.

      tovaxT 1 Reply Last reply
      0
      • mrjjM mrjj

        @tovax
        If by blocked you mean
        // emit headerDataChanged(orientation, section, section);
        and call your new function (HeaderChange) after the loop then we are on same page.

        Ok so that didnt speed it up. :(
        Im not sure how altering the list
        posCmdList[section] = QString::number(value.value<double>(), 'f', 2);
        would be slow.

        I think i would insert some timing functions
        (https://doc.qt.io/qt-5/qelapsedtimer.html is handy for that)
        and see where the time is spend.
        Now we know its not from pure updates so we need to find the spot where the time is used.

        Also 10 times pr second does not sound that massive but I would try other values to see
        where the sweet spot it.

        tovaxT Offline
        tovaxT Offline
        tovax
        wrote on last edited by
        #12

        @mrjj
        I add this debug code:

        bool MotionSheetTableModel::setHeaderData(int32_t section, Qt::Orientation orientation, const QVariant &value, int32_t role)
        {
            Q_UNUSED(orientation);
            if (role == Qt::DisplayRole) {
                QElapsedTimer timer;
                timer.start();
                posCmdList[section] = QString::number(value.value<double>(), 'f', 2);
                qDebug() << "MotionSheetTableModel::setHeaderData" << timer.nsecsElapsed();
                // emit headerDataChanged(orientation, section, section);
            }
        
            return true;
        }
        

        Result as follow:

        MotionSheetTableModel::setHeaderData 28158
        MotionSheetTableModel::setHeaderData 27646
        MotionSheetTableModel::setHeaderData 28158
        MotionSheetTableModel::setHeaderData 27646
        MotionSheetTableModel::setHeaderData 28158
        MotionSheetTableModel::setHeaderData 28670
        MotionSheetTableModel::setHeaderData 53244
        MotionSheetTableModel::setHeaderData 31741
        MotionSheetTableModel::setHeaderData 28158
        MotionSheetTableModel::setHeaderData 28158
        MotionSheetTableModel::setHeaderData 28670
        MotionSheetTableModel::setHeaderData 28158
        MotionSheetTableModel::setHeaderData 28158
        MotionSheetTableModel::setHeaderData 27646
        MotionSheetTableModel::setHeaderData 28158
        MotionSheetTableModel::setHeaderData 28158
        MotionSheetTableModel::setHeaderData 28670
        MotionSheetTableModel::setHeaderData 27646
        MotionSheetTableModel::setHeaderData 28670
        MotionSheetTableModel::setHeaderData 28670
        

        Nanoseconds, It looks fast enough.

        Best Regards!

        1 Reply Last reply
        0
        • mrjjM Offline
          mrjjM Offline
          mrjj
          Lifetime Qt Champion
          wrote on last edited by
          #13

          Hi
          Yes it does indeed look ok fast.
          I would then disable the new function to check if app still feels
          laggy and its related to View redrawing.
          ( not send the headerDataChanged signal)

          i know you wont see the updates then but its a ok test to see if you are stressing
          the event loop anyways.

          If app still laggy with View not repainting it means the event loop is stressed.

          tovaxT 3 Replies Last reply
          0
          • mrjjM mrjj

            Hi
            Yes it does indeed look ok fast.
            I would then disable the new function to check if app still feels
            laggy and its related to View redrawing.
            ( not send the headerDataChanged signal)

            i know you wont see the updates then but its a ok test to see if you are stressing
            the event loop anyways.

            If app still laggy with View not repainting it means the event loop is stressed.

            tovaxT Offline
            tovaxT Offline
            tovax
            wrote on last edited by
            #14

            @mrjj
            Hi,
            When not send the headerDataChanged signal, the app run smoothly.
            By the way, if the data display in the table cell, the app run smoothly too.

            1 Reply Last reply
            0
            • mrjjM mrjj

              Hi
              Yes it does indeed look ok fast.
              I would then disable the new function to check if app still feels
              laggy and its related to View redrawing.
              ( not send the headerDataChanged signal)

              i know you wont see the updates then but its a ok test to see if you are stressing
              the event loop anyways.

              If app still laggy with View not repainting it means the event loop is stressed.

              tovaxT Offline
              tovaxT Offline
              tovax
              wrote on last edited by
              #15

              @mrjj
              Here is the system time in relevent function:

              onPosCmd - start "22:06:33:908"
              setHeaderData 0 "22:06:33:908"
              setHeaderData 1 "22:06:33:908"
              setHeaderData 2 "22:06:33:909"
              setHeaderData 3 "22:06:33:909"
              setHeaderData 4 "22:06:33:909"
              setHeaderData 5 "22:06:33:910"
              setHeaderData 6 "22:06:33:910"
              setHeaderData 7 "22:06:33:910"
              setHeaderData 8 "22:06:33:911"
              setHeaderData 9 "22:06:33:911"
              setHeaderData 10 "22:06:33:911"
              setHeaderData 11 "22:06:33:911"
              setHeaderData 12 "22:06:33:912"
              setHeaderData 13 "22:06:33:912"
              setHeaderData 14 "22:06:33:912"
              setHeaderData 15 "22:06:33:913"
              onPosCmd - end "22:06:33:913"
              headerData 0 "22:06:33:953"
              headerData 1 "22:06:33:954"
              headerData 8 "22:06:33:956"
              headerData 9 "22:06:33:957"
              headerData 10 "22:06:33:958"
              headerData 11 "22:06:33:959"
              headerData 12 "22:06:33:960"
              headerData 13 "22:06:33:961"
              headerData 14 "22:06:33:962"
              headerData 15 "22:06:33:963"
              headerData 0 "22:06:33:976"
              headerData 1 "22:06:33:978"
              headerData 8 "22:06:33:980"
              headerData 9 "22:06:33:982"
              headerData 10 "22:06:33:984"
              headerData 11 "22:06:33:985"
              headerData 12 "22:06:33:987"
              headerData 13 "22:06:33:989"
              headerData 14 "22:06:33:990"
              headerData 15 "22:06:33:992"
              

              It doesn't seem to waste much time on signaling.

              1 Reply Last reply
              0
              • Christian EhrlicherC Online
                Christian EhrlicherC Online
                Christian Ehrlicher
                Lifetime Qt Champion
                wrote on last edited by Christian Ehrlicher
                #16

                What resize mode do you use? And can you provide a small test example so we can run it e.g. with callgrind to see where the time is spend.

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

                tovaxT 1 Reply Last reply
                0
                • mrjjM mrjj

                  Hi
                  Yes it does indeed look ok fast.
                  I would then disable the new function to check if app still feels
                  laggy and its related to View redrawing.
                  ( not send the headerDataChanged signal)

                  i know you wont see the updates then but its a ok test to see if you are stressing
                  the event loop anyways.

                  If app still laggy with View not repainting it means the event loop is stressed.

                  tovaxT Offline
                  tovaxT Offline
                  tovax
                  wrote on last edited by
                  #17

                  @mrjj
                  From "setHeaderData" to "headerData" waste 40ms. Will this have an impact, please?

                  1 Reply Last reply
                  0
                  • Christian EhrlicherC Christian Ehrlicher

                    What resize mode do you use? And can you provide a small test example so we can run it e.g. with callgrind to see where the time is spend.

                    tovaxT Offline
                    tovaxT Offline
                    tovax
                    wrote on last edited by
                    #18

                    @Christian-Ehrlicher
                    Hi,
                    The resize mode is QHeaderView::Stretch, this is the config of tableView:

                        tableView = new QTableView(this);
                        tableView->setModel(tableModel);
                    
                        tableView->setFrameShape(QFrame::NoFrame);
                    
                        tableView->horizontalHeader()->setVisible(true); 
                        tableView->horizontalHeader()->setSectionResizeMode(QHeaderView::Stretch);
                    
                        tableView->verticalHeader()->setVisible(true); 
                        tableView->verticalHeader()->setSectionResizeMode(QHeaderView::Stretch);
                    
                        tableView->setSelectionBehavior(QAbstractItemView::SelectItems);
                        tableView->setSelectionMode(QAbstractItemView::ExtendedSelection);
                        tableView->setAlternatingRowColors(true);
                    
                    1 Reply Last reply
                    0
                    • Christian EhrlicherC Online
                      Christian EhrlicherC Online
                      Christian Ehrlicher
                      Lifetime Qt Champion
                      wrote on last edited by
                      #19

                      @tovax said in How to refresh data on horizontal header of QTableWidget?:

                      The resize mode is QHeaderView::Stretch

                      Ok, this is at least not a problem for the update. So please provide a small testcase.

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

                      tovaxT 2 Replies Last reply
                      0
                      • Christian EhrlicherC Christian Ehrlicher

                        @tovax said in How to refresh data on horizontal header of QTableWidget?:

                        The resize mode is QHeaderView::Stretch

                        Ok, this is at least not a problem for the update. So please provide a small testcase.

                        tovaxT Offline
                        tovaxT Offline
                        tovax
                        wrote on last edited by
                        #20
                        This post is deleted!
                        1 Reply Last reply
                        0
                        • Christian EhrlicherC Christian Ehrlicher

                          @tovax said in How to refresh data on horizontal header of QTableWidget?:

                          The resize mode is QHeaderView::Stretch

                          Ok, this is at least not a problem for the update. So please provide a small testcase.

                          tovaxT Offline
                          tovaxT Offline
                          tovax
                          wrote on last edited by tovax
                          #21

                          @Christian-Ehrlicher
                          Here is the github link:
                          TableView
                          Best Regards!

                          1 Reply Last reply
                          1
                          • Christian EhrlicherC Online
                            Christian EhrlicherC Online
                            Christian Ehrlicher
                            Lifetime Qt Champion
                            wrote on last edited by
                            #22

                            @tovax: I'll give it a try today, thx

                            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
                            1
                            • Christian EhrlicherC Online
                              Christian EhrlicherC Online
                              Christian Ehrlicher
                              Lifetime Qt Champion
                              wrote on last edited by
                              #23

                              Looks like the culprit is that a header data change triggers a complete repaint through QAbstractItemView::updateGeometries() which is very expensive. It doesn't matter if you call headerDataChanged() once per section or completely - it's a delayed trigger.

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

                              tovaxT 1 Reply Last reply
                              2
                              • Christian EhrlicherC Christian Ehrlicher

                                Looks like the culprit is that a header data change triggers a complete repaint through QAbstractItemView::updateGeometries() which is very expensive. It doesn't matter if you call headerDataChanged() once per section or completely - it's a delayed trigger.

                                tovaxT Offline
                                tovaxT Offline
                                tovax
                                wrote on last edited by
                                #24

                                @Christian-Ehrlicher
                                Hi,
                                In other words, can't I update the data on the horizontal header, please?
                                Best Regards!

                                mrjjM 1 Reply Last reply
                                0
                                • tovaxT tovax

                                  @Christian-Ehrlicher
                                  Hi,
                                  In other words, can't I update the data on the horizontal header, please?
                                  Best Regards!

                                  mrjjM Offline
                                  mrjjM Offline
                                  mrjj
                                  Lifetime Qt Champion
                                  wrote on last edited by mrjj
                                  #25

                                  @tovax
                                  Hi
                                  Nope, not as fast as you wish.
                                  On my (albeit old) gamer pc, it uses 28% CPU to refresh it.
                                  So for less powerful system, you will have to find another way to do the same
                                  than using the headers. Its too expensive to be used in this way.
                                  ( even 'just' 10 times pr second )

                                  So basically its not a supported use case with Qt to have high-speed header refresh. That said you might be able to fix it with a custom HeaderView
                                  but if there is enough virtual function to override this behavior, i cannot say currently.

                                  1 Reply Last reply
                                  0
                                  • Christian EhrlicherC Online
                                    Christian EhrlicherC Online
                                    Christian Ehrlicher
                                    Lifetime Qt Champion
                                    wrote on last edited by
                                    #26

                                    Or, as we said already more times - don't try to update at 100Hz - noone can ever read this...

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

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                                    • tovaxT Offline
                                      tovaxT Offline
                                      tovax
                                      wrote on last edited by
                                      #27

                                      OK, Thanks for both of you! I'll think about other ways.
                                      Best Regards!

                                      1 Reply Last reply
                                      0
                                      • tovaxT Offline
                                        tovaxT Offline
                                        tovax
                                        wrote on last edited by
                                        #28

                                        Solved:

                                        1. Derived from QAbstractTableModel + QTableView
                                        2. Create two QTableView, one for cell's data, another for header data.
                                        3. Frozen the first row of the QTableView used for header data, and refresh data in it (100Hz).
                                        4. (Refer to official demo: Frozen Column Example)
                                        1 Reply Last reply
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