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Forum Update on Monday, May 27th 2025

QUndoStack across 2 cpps? QTreeView and QGraphicsScene

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qundostackqundocommandc++qtqtreeviewqgraphicsscene
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  • S StudentScripter

    bumping this

    SGaistS Offline
    SGaistS Offline
    SGaist
    Lifetime Qt Champion
    wrote on last edited by
    #16

    @StudentScripter your tree view has no reason to be doing that setup with the scene. They share a model, they don't need to know about each other.

    As for the delegate, your goal is clear, and again, the editorEvent is what you want to use to implement the behavior you want.

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

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    • SGaistS SGaist

      @StudentScripter your tree view has no reason to be doing that setup with the scene. They share a model, they don't need to know about each other.

      As for the delegate, your goal is clear, and again, the editorEvent is what you want to use to implement the behavior you want.

      S Offline
      S Offline
      StudentScripter
      wrote on last edited by
      #17

      @SGaist Well but as i understand it with

      model = new ViewLayerStandartItemModel(0,1,this);
      

      im creating a new instance of this class, a new object. So in order to have access to the same model i have to pass the object i create in the treeview trough to the scene.
      Is this a mistake? How should i do it instead?

      SGaistS 1 Reply Last reply
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      • S StudentScripter

        @SGaist Well but as i understand it with

        model = new ViewLayerStandartItemModel(0,1,this);
        

        im creating a new instance of this class, a new object. So in order to have access to the same model i have to pass the object i create in the treeview trough to the scene.
        Is this a mistake? How should i do it instead?

        SGaistS Offline
        SGaistS Offline
        SGaist
        Lifetime Qt Champion
        wrote on last edited by
        #18

        @StudentScripter you should create the model in the class that manages the ViewLayerList object and set it on both objects there. In the absolute, with the code you show, ViewLayerList is not even needed unless there are some additional function you are implementing. If not, then just use QTreeView directly and configure it in the class managing it.

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

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        • SGaistS SGaist

          @StudentScripter you should create the model in the class that manages the ViewLayerList object and set it on both objects there. In the absolute, with the code you show, ViewLayerList is not even needed unless there are some additional function you are implementing. If not, then just use QTreeView directly and configure it in the class managing it.

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          StudentScripter
          wrote on last edited by
          #19

          @SGaist Yes im implementing additional functions in the qtreeview/ViewLayerList, thats why i subclassed it. Im creating the model object directly in ViewLayerLists constructor, cause i use that model mostly in this cpp.

          So i guess my approach with giving the model from there to the scene is okish?

          SGaistS 1 Reply Last reply
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          • S StudentScripter

            @SGaist Yes im implementing additional functions in the qtreeview/ViewLayerList, thats why i subclassed it. Im creating the model object directly in ViewLayerLists constructor, cause i use that model mostly in this cpp.

            So i guess my approach with giving the model from there to the scene is okish?

            SGaistS Offline
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            SGaist
            Lifetime Qt Champion
            wrote on last edited by
            #20

            @StudentScripter no, it makes that class know another one just for the purpose of sharing the model. That's tight coupling for the bad reasons.

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

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            • JonBJ JonB

              @StudentScripter
              It seems to me you have two possible general approaches:

              • Use signals & slots to communicate between the tree view and the graphics scene. This can alleviate the need for each side to know too much about the other side. But be careful not to get into an "infinite loop", where each side "ping pongs" signals between themselves for some change.

              • As @SGaist says, create a common model and share the model between both sides. For example, QStandardItem is part of a QStandardItemModel. You can already have multiple views (e.g. QTreeView) attached to the same model, make it so (some wrapper around) the QGraphicsScene shares that model with your one QTreeView. All your operations, like selecting or clicking a checkbox, should be implemented in the model, not the view or scene. Then that emits signals like dataChanged() or selectionChanged() in response to your actions and both views get notified about it and react in their own ways. The model code can be kept in its own/class/module/file, that is included into both the tree view & graphics scene classes, they should not need to see each other directly. This would be my inclination.

              JonBJ Offline
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              JonB
              wrote on last edited by
              #21

              @JonB said in QUndoStack across 2 cpps? QTreeView and QGraphicsScene:

              The model code can be kept in its own/class/module/file, that is included into both the tree view & graphics scene classes, they should not need to see each other directly. This would be my inclination.

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              • JonBJ JonB

                @JonB said in QUndoStack across 2 cpps? QTreeView and QGraphicsScene:

                The model code can be kept in its own/class/module/file, that is included into both the tree view & graphics scene classes, they should not need to see each other directly. This would be my inclination.

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                StudentScripter
                wrote on last edited by
                #22

                @JonB Ok and from their i add an setter in the qtreeview class and the viewlayerlist to retrieve the model.

                JonBJ SGaistS 2 Replies Last reply
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                • S StudentScripter

                  @JonB Ok and from their i add an setter in the qtreeview class and the viewlayerlist to retrieve the model.

                  JonBJ Offline
                  JonBJ Offline
                  JonB
                  wrote on last edited by
                  #23

                  @StudentScripter Yes, a suitable public getter & setter for the model called from each of the QTreeView and QGraphicsScene modules.

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                  • S StudentScripter

                    @JonB Ok and from their i add an setter in the qtreeview class and the viewlayerlist to retrieve the model.

                    SGaistS Offline
                    SGaistS Offline
                    SGaist
                    Lifetime Qt Champion
                    wrote on last edited by
                    #24

                    @StudentScripter QTreeView already has a setter for the model. You just need to add one to your QGraphicsScene subclass.

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

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                    • SGaistS SGaist

                      @StudentScripter QTreeView already has a setter for the model. You just need to add one to your QGraphicsScene subclass.

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                      StudentScripter
                      wrote on last edited by
                      #25

                      @SGaist Yep done everything and works fine. :D

                      SGaistS 1 Reply Last reply
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                      • S StudentScripter

                        @SGaist Yep done everything and works fine. :D

                        SGaistS Offline
                        SGaistS Offline
                        SGaist
                        Lifetime Qt Champion
                        wrote on last edited by
                        #26

                        @StudentScripter great !

                        Then please mark the model as solved using the "Topic Tools" button or the dotted menu beside the answer you deem correct so that other forum users may know a solution has been found :-)

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

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