Problem with selection in TreeView Qt6

[A Former User]

I'm trying to implement a TreeView in which i want to highlight the selected row.
The model is a c++ implemented QAbstractItemModel which is set to the qml context from the main.cpp

Here is the main.qml

import QtQuick 
import QtQuick.Controls

Window {
    id: mainWin
    visible: true
    width: 640
    height: 480
    title: qsTr("QML Test")

    TreeView {
        id: treeView
        anchors.fill: parent
        model: projectModel
    

        selectionModel: ItemSelectionModel {
            model: treeView.model
        }
    
    
        delegate: TreeViewDelegate {
            id: treeDelegate
        
            required property bool selected
            required property int row
            
            background: Rectangle {
                opacity: treeDelegate.selected ? 1 : 0
                color: "red"
            }
            onClicked: {
                treeView.selectionModel.select(treeView.modelIndex(treeDelegate.row, 0),  ItemSelectionModel.Toggle | ItemSelectionModel.Rows)
                console.log("clicked:", treeView.model.data(treeView.modelIndex(treeDelegate.row, 0)))
                console.log("Selection model selected? ", treeView.selectionModel.isSelected(treeView.modelIndex(treeDelegate.row, 0)))
                console.log("Delegate selected? ", treeDelegate.selected)
            }
      
        }
}

this is how the model is shown by the TreeView, which is ok

If i click on Parent1 it get selected properly and it becomes red

If i click on Parent2, the item Child1 is higlighed in red instead

The log present in the onClicked slot show this:

qml: clicked:  Parent2
qml: Selection model selected?  true
qml: Delegate selected?  false

So it seems the the proper item is actully retrived by the model, and the selection model should properly use it, BUT the selected property is set to the wrong delegate, to the Child1 delegate instead that to the Parent2 one.
I guess it's somehow reletaed to the fact that Child1 is in row=1 in the view and Parent2 has also row=1 in the QModelIndex; infact if i hide the child1 the selection of parent2 works, but how can i fix this?

[bee65]

TreeView is implement on top of TableView, and you have to be careful with modelIndex's which might refer to the index in the tree or in the table. I have not used selectionModel, but I would guess it expects to work with table indexes.

[A Former User]

@bee65 Thanks for the asnwer.
the selection model seem to work properly. in fact the log of clicked item state is always coherent:

onClicked: {
     ...
    console.log("Selection model selected? ", treeView.selectionModel.isSelected(treeView.modelIndex(treeDelegate.row, 0)))
}

i get true on the first click (when it's selected) and false on the second (when is toggled). This is always correct, no matter if it's on a child or parent item or if expand/reduce the tree in between clicks. It seems selection model is doing its job.

What is wrong is how the selected state of the delegate is syncronized (not sure by who). I'm not sure but i think that it's the TreeViewDelegate that should properly transalte the model QModelIndex into "view" row but it consider the QModel indx as a "linear" table index (as you point that out).
Anyway, how can i fix this?

[China_JuJu]

you can record the currentIndex int model and the currentViewIndex in view, and when you click the item and expand or collapse the item in treeview, converts index in the view to the index in the model