HorizontalHeaderView & VerticalHeaderView does not disconnect from QQmlTableModel::headerDataChanged in Loader

Volodymyr Mudryk

Hi

I have table view loaded dynamically. If it is without HorizontalHeaderView and VerticalHeaderView it works fine.
But if I use them in my real application it crash after same time. (but can not reproduce the crash in test app)
Investigation shows that connections from HorizontalHeaderView and VerticalHeaderView still are in model after the unload table view.
If you press many times the button "Reload" in test app you will see in output the model gets more and more connections.

Any ideas how to fix it?

Qt 6.4.0

main.qml

import QtQuick
import QtQuick.Controls
import Qt.labs.qmlmodels

import Helper

Window {
    id: window
    width: 640
    height: 480
    visible: true
    title: qsTr("Hello World")

    Helper {
        id: helper
    }

    Button {
        id: btnReload
        text: "Reload"
        anchors.left: loader.right
        onClicked: {
            loader.active = false
            loader.active = true
            helper.dumpObjectInfo(tableModel)
        }
    }

    TableModel {
        id: tableModel
        TableModelColumn {
            display: "name"
        }
        TableModelColumn {
            display: "color"
        }

        rows: [{
                "name": "cat",
                "color": "black"
            }, {
                "name": "dog",
                "color": "brown"
            }, {
                "name": "bird",
                "color": "white"
            }]
    }

    Loader {
        id: loader
        width: 100
        height: 300
        sourceComponent: comp
        active: true
    }

    Component {
        id: comp
        Item {
            anchors.fill: paren

            HorizontalHeaderView {
                id: horizontalHeader
                implicitHeight: 20
                syncView: tableView
                anchors.left: tableView.left

                delegate: Rectangle {
                    implicitHeight: 20
                    implicitWidth: 50
                    border.width: 1

                    Text {
                        text: "name"
                        anchors.fill: parent
                        horizontalAlignment: Text.AlignHCenter
                        verticalAlignment: Text.AlignVCenter
                        textFormat: Text.PlainText
                    }
                }
            }

            TableView {
                id: tableView
                anchors.left: parent.left
                anchors.right: parent.right
                anchors.top: horizontalHeader.bottom
                anchors.bottom: parent.bottom

                columnSpacing: 1
                rowSpacing: 1
                clip: true

                model: tableModel

                delegate: Rectangle {
                    implicitWidth: 100
                    implicitHeight: 50
                    border.width: 1

                    Text {
                        text: display
                        anchors.centerIn: parent
                    }
                }
            }
        }
    }
}

manu.cpp

#include <QGuiApplication>
#include <QQmlApplicationEngine>

#include "Helper.h"

int main(int argc, char *argv[])
{
    QGuiApplication app(argc, argv);

    QQmlApplicationEngine engine;
    const QUrl url(u"qrc:/untitled2/main.qml"_qs);
    QObject::connect(&engine, &QQmlApplicationEngine::objectCreated,
                     &app, [url](QObject *obj, const QUrl &objUrl) {
        if (!obj && url == objUrl)
            QCoreApplication::exit(-1);
    }, Qt::QueuedConnection);

    qmlRegisterType<Helper>("Helper", 1, 0, "Helper");

    engine.load(url);

    return app.exec();
}

Helper.h

#ifndef HELPER_H
#define HELPER_H

#include <QObject>

class Helper: public QObject
{
    Q_OBJECT
public:
    Helper();

    Q_INVOKABLE void dumpObjectInfo(QObject* obj);
};

#endif // HELPER_H

Helper.cpp

#include "Helper.h"

Helper::Helper()
{

}

void Helper::dumpObjectInfo(QObject *obj)
{
    obj->dumpObjectInfo();
}

Volodymyr Mudryk

@Volodymyr-Mudryk

I think the root cause is in qquickheaderview.cpp
Connect to &QAbstractItemModel::headerDataChanged as lambda but disconnect only from class instance.

How to notify Qt developers about it?

void QHeaderDataProxyModel::connectToModel()
{
    if (m_model.isNull())
        return;
    connect(m_model, &QAbstractItemModel::headerDataChanged,
        [this](Qt::Orientation orient, int first, int last) {
            if (orient != orientation())
                return;
            if (orient == Qt::Horizontal) {
                emit dataChanged(createIndex(0, first), createIndex(0, last));
            } else {
                emit dataChanged(createIndex(first, 0), createIndex(last, 0));
            }
        });
...

void QHeaderDataProxyModel::disconnectFromModel()
{
    if (m_model.isNull())
        return;
    m_model->disconnect(this);
}

Volodymyr Mudryk

I've created bug about it: https://bugreports.qt.io/browse/QTBUG-108610