Turn a flat table into a tree with QIdentityProxyModel - c++

Question

I want to write a proxy model that groups a flat table into a tree by the first (n) columns, similar to this UI library for React.
I am struggling to get this to work, even in its simplest form:
First question is: do i need to implement all four of the following or only mapToSource and mapFromSource?
https://doc.qt.io/qt-6/qidentityproxymodel.html#parent
https://doc.qt.io/qt-6/qidentityproxymodel.html#index
https://doc.qt.io/qt-6/qidentityproxymodel.html#mapToSource
https://doc.qt.io/qt-6/qidentityproxymodel.html#mapFromSource
If so, how can I achieve the behavior with the following code? I am trying around but I always come up with deadlocks or weird behavior.
#include <QApplication>
#include <QSqlDatabase>
#include <QSqlTableModel>
#include <QSqlError>
#include <QSqlQuery>
#include <QTreeView>
#include <QIdentityProxyModel>
class GroupByFirstColumnProxyModel : public QIdentityProxyModel {
Q_OBJECT
public:
GroupByFirstColumnProxyModel(QObject *parent = nullptr)
: QIdentityProxyModel{parent} {}
~GroupByFirstColumnProxyModel() {}
void setSourceModel(QAbstractItemModel* sourceModel) override {
return QIdentityProxyModel::setSourceModel(sourceModel);
}
int columnCount (const QModelIndex &parent=QModelIndex()) const override {
auto cols = QIdentityProxyModel::columnCount(parent);
qDebug() << "columnCount" << parent << cols << parent.isValid();
return cols;
}
QModelIndex index(int row, int column, const QModelIndex &parent = QModelIndex()) const override {
qDebug() << "index" << row << column << parent;
return QIdentityProxyModel::index(row, column, parent);
}
QModelIndex parent(const QModelIndex &child) const override {
if (!child.isValid()) {
return QModelIndex();
}
qDebug() << "parent" << child;
return QIdentityProxyModel::parent(child);
}
QModelIndex mapFromSource(const QModelIndex &sourceIndex) const override {
qDebug() << "mapFromSource" << sourceIndex;
return QIdentityProxyModel::mapFromSource(sourceIndex);
}
QModelIndex mapToSource(const QModelIndex &proxyIndex) const override {
if (!proxyIndex.isValid()) {
return QModelIndex();
}
qDebug() << "mapToSource" << proxyIndex;
return QIdentityProxyModel::mapToSource(proxyIndex);
}
};
static bool createConnection()
{
QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE");
db.setDatabaseName(":memory:");
if (!db.open()) {
return false;
}
QSqlQuery query;
query.exec("create table simple (A int, B int)");
query.exec("insert into simple values(1, 2)");
return true;
}
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
if (!createConnection())
return EXIT_FAILURE;
QSqlTableModel *model = new QSqlTableModel;
model->setTable("simple");
model->select();
QTreeView *view = new QTreeView;
GroupByFirstColumnProxyModel *proxy = new GroupByFirstColumnProxyModel;
proxy->setSourceModel(model);
view->setModel(proxy);
view->show();
return a.exec();
}
#include "main.moc"