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How to update QTableView when rows are inserted to it

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  • RatzzR Ratzz

    @kshegunov
    The beginInsertRows doc http://doc.qt.io/qt-4.8/qabstractitemmodel.html#beginInsertRows says

    Note: This function emits the rowsAboutToBeInserted() signal which connected views (or proxies) must handle before the data is inserted. Otherwise, the views may end up in an invalid state.
    

    Will it help?

    kshegunovK Offline
    kshegunovK Offline
    kshegunov
    Moderators
    wrote on last edited by kshegunov
    #9

    @Ratzz
    Yes, I saw that, but this is to notify the view insertions will be happening. The question is whether endInsertRows() emits rowsInserted() thus telling the view the insertion has finished and it can actually update itself. Unfortunately, the documentation doesn't state anything specific about endInsertRows(), unless I completely missed it ...

    PS. I just noticed something in your code:

    QTreeView * view= dynamic_cast<QTreeView*>(event->source());
    

    Is this a typo?

    Read and abide by the Qt Code of Conduct

    RatzzR 1 Reply Last reply
    1
    • SGaistS Offline
      SGaistS Offline
      SGaist
      Lifetime Qt Champion
      wrote on last edited by
      #10

      Hi,

      The documentation doesn't specify but the implementation does emit rowsInserted. However in this case insertRows doesn't do anything so I wonder if there isn't a caching mechanism that avoids to update the view if in fact nothing has changed.

      Interested in AI ? www.idiap.ch
      Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

      RatzzR kshegunovK 2 Replies Last reply
      1
      • kshegunovK kshegunov

        @Ratzz
        Yes, I saw that, but this is to notify the view insertions will be happening. The question is whether endInsertRows() emits rowsInserted() thus telling the view the insertion has finished and it can actually update itself. Unfortunately, the documentation doesn't state anything specific about endInsertRows(), unless I completely missed it ...

        PS. I just noticed something in your code:

        QTreeView * view= dynamic_cast<QTreeView*>(event->source());
        

        Is this a typo?

        RatzzR Offline
        RatzzR Offline
        Ratzz
        wrote on last edited by
        #11

        @kshegunov said:

        Is this a typo?

        I drag the items from another QTreeView .The cast is for that..
        Did you mean that?

        --Alles ist gut.

        1 Reply Last reply
        0
        • SGaistS SGaist

          Hi,

          The documentation doesn't specify but the implementation does emit rowsInserted. However in this case insertRows doesn't do anything so I wonder if there isn't a caching mechanism that avoids to update the view if in fact nothing has changed.

          RatzzR Offline
          RatzzR Offline
          Ratzz
          wrote on last edited by
          #12

          @SGaist said:
          Thanks for the reply.
          So there is no way with insertRows?

          --Alles ist gut.

          1 Reply Last reply
          0
          • SGaistS SGaist

            Hi,

            The documentation doesn't specify but the implementation does emit rowsInserted. However in this case insertRows doesn't do anything so I wonder if there isn't a caching mechanism that avoids to update the view if in fact nothing has changed.

            kshegunovK Offline
            kshegunovK Offline
            kshegunov
            Moderators
            wrote on last edited by kshegunov
            #13

            @SGaist

            However in this case insertRows doesn't do anything so I wonder if there isn't a caching mechanism that avoids to update the view if in fact nothing has changed.

            After a quick look (without pretense to be complete) I couldn't clearly see any such caching done.
            Here's what I peeked at (for Qt 5.6):
            http://code.qt.io/cgit/qt/qtbase.git/tree/src/corelib/itemmodels/qabstractitemmodel.cpp#n2601
            http://code.qt.io/cgit/qt/qtbase.git/tree/src/corelib/itemmodels/qabstractitemmodel.cpp#n582

            @Ratzz

            I drag the items from another QTreeView .The cast is for that..
            Did you mean that?

            Indeed I did. Have you considered handling the drag/drop events through the ordinary mechanism? Serializing on drag, then deserializing the mime data on drop?

            Read and abide by the Qt Code of Conduct

            RatzzR 1 Reply Last reply
            1
            • kshegunovK kshegunov

              @SGaist

              However in this case insertRows doesn't do anything so I wonder if there isn't a caching mechanism that avoids to update the view if in fact nothing has changed.

              After a quick look (without pretense to be complete) I couldn't clearly see any such caching done.
              Here's what I peeked at (for Qt 5.6):
              http://code.qt.io/cgit/qt/qtbase.git/tree/src/corelib/itemmodels/qabstractitemmodel.cpp#n2601
              http://code.qt.io/cgit/qt/qtbase.git/tree/src/corelib/itemmodels/qabstractitemmodel.cpp#n582

              @Ratzz

              I drag the items from another QTreeView .The cast is for that..
              Did you mean that?

              Indeed I did. Have you considered handling the drag/drop events through the ordinary mechanism? Serializing on drag, then deserializing the mime data on drop?

              RatzzR Offline
              RatzzR Offline
              Ratzz
              wrote on last edited by
              #14

              @kshegunov said:

              Serializing on drag, then deserializing the mime data on drop?

              No i have not considered this part.

              --Alles ist gut.

              kshegunovK 1 Reply Last reply
              0
              • SGaistS Offline
                SGaistS Offline
                SGaist
                Lifetime Qt Champion
                wrote on last edited by
                #15

                @kshegunov : I mean't view side caching.

                @Ratzz currently you are not inserting anything through it. Like @kshegunov suggested, implement the drag and drop through the mechanism provided for model/view classes. It's described here

                Interested in AI ? www.idiap.ch
                Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

                RatzzR 1 Reply Last reply
                0
                • SGaistS SGaist

                  @kshegunov : I mean't view side caching.

                  @Ratzz currently you are not inserting anything through it. Like @kshegunov suggested, implement the drag and drop through the mechanism provided for model/view classes. It's described here

                  RatzzR Offline
                  RatzzR Offline
                  Ratzz
                  wrote on last edited by
                  #16

                  @SGaist
                  I will try to implement through (link you provided ) this.

                  --Alles ist gut.

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                  • RatzzR Ratzz

                    @kshegunov said:

                    Serializing on drag, then deserializing the mime data on drop?

                    No i have not considered this part.

                    kshegunovK Offline
                    kshegunovK Offline
                    kshegunov
                    Moderators
                    wrote on last edited by kshegunov
                    #17

                    @Ratzz

                    No i have not considered this part.

                    Then I suggest you try it out. It may prove to be easier and better behaved than pulling the records directly from the tree widget. As for your current implementation, I'm at a loss why it doesn't work. Maybe the tree view is losing the selection when dragging and the selection model returns no records?

                    @SGaist

                    I mean't view side caching.

                    I see, well I didn't look at the view (obviously) but I suppose it's possible.

                    Read and abide by the Qt Code of Conduct

                    RatzzR 1 Reply Last reply
                    1
                    • mrjjM Offline
                      mrjjM Offline
                      mrjj
                      Lifetime Qt Champion
                      wrote on last edited by
                      #18

                      Hi
                      I am still wondering. Sorry.
                      Lets say If I dont have drag&drop.

                      I simply append to my internal list used in model.

                      How will I tell the view(s) that?

                      I though dataChanged would do it but not even begin/endInsertRow
                      does it.

                      Thanks

                      kshegunovK 1 Reply Last reply
                      0
                      • kshegunovK kshegunov

                        @Ratzz

                        No i have not considered this part.

                        Then I suggest you try it out. It may prove to be easier and better behaved than pulling the records directly from the tree widget. As for your current implementation, I'm at a loss why it doesn't work. Maybe the tree view is losing the selection when dragging and the selection model returns no records?

                        @SGaist

                        I mean't view side caching.

                        I see, well I didn't look at the view (obviously) but I suppose it's possible.

                        RatzzR Offline
                        RatzzR Offline
                        Ratzz
                        wrote on last edited by
                        #19

                        @kshegunov said:

                        Maybe the tree view is losing the selection when dragging and the selection model returns no records?

                        I don't think so because the rowCount is getting updated as and when the new drop takes place.

                        --Alles ist gut.

                        1 Reply Last reply
                        0
                        • mrjjM mrjj

                          Hi
                          I am still wondering. Sorry.
                          Lets say If I dont have drag&drop.

                          I simply append to my internal list used in model.

                          How will I tell the view(s) that?

                          I though dataChanged would do it but not even begin/endInsertRow
                          does it.

                          Thanks

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

                          @mrjj

                          I simply append to my internal list used in model.

                          I'm by no means an expert, but possibly calling submit() (I don't know if it works I'm just guessing)?

                          Read and abide by the Qt Code of Conduct

                          1 Reply Last reply
                          0
                          • SGaistS Offline
                            SGaistS Offline
                            SGaist
                            Lifetime Qt Champion
                            wrote on last edited by
                            #21

                            On a side note, your rowCount implementation should rather return the size of your TableList, that way it's one less thing to manage.

                            Interested in AI ? www.idiap.ch
                            Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct

                            RatzzR 1 Reply Last reply
                            1
                            • SGaistS SGaist

                              On a side note, your rowCount implementation should rather return the size of your TableList, that way it's one less thing to manage.

                              RatzzR Offline
                              RatzzR Offline
                              Ratzz
                              wrote on last edited by
                              #22

                              @SGaist
                              Yes ,now i am returning the size of TableList .

                              --Alles ist gut.

                              RatzzR 1 Reply Last reply
                              1
                              • RatzzR Ratzz

                                @SGaist
                                Yes ,now i am returning the size of TableList .

                                RatzzR Offline
                                RatzzR Offline
                                Ratzz
                                wrote on last edited by Ratzz
                                #23

                                In dropEvent called a new function from model which stores all the parameter of item when droped and emitted layoutAboutToBeChanged() before appending to my TableList and then emitted layoutChanged() which worked for me.

                                Thanks to @kshegunov , @SGaist , @mrjj for the help.

                                --Alles ist gut.

                                1 Reply Last reply
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