Adding a right-click menu for specific items in QTreeView

I'm writing a Qt desktop application in c++ with Qt Creator.

I declared in my main window a treeView, and a compatible model.

Now, I would like to have a right-click menu for the tree item. Not for all of the items, but for a part of them, for example: for the tree elements with an even index.

I tried adding a simple context menu with the following code:

in the .h file:

QStandardItemModel* model;
QMenu* contextMenu;
QAction* uninstallAction;
private slots:
    void uninstallAppletClickedSlot();

and in the .cpp file:

in the constructor:

ui->treeView->setModel(model);
contextMenu = new QMenu(ui->treeView);
ui->treeView->setContextMenuPolicy(Qt::ActionsContextMenu);
uninstallAction = new QAction("Uninstall TA",contextMenu);
ui->treeView->addAction(uninstallAction);
connect(uninstallAction, SIGNAL(triggered()), this, SLOT(uninstallAppletClickedSlot()));

and a slot:

void MainWindow::uninstallAppletClickedSlot()
{

}

this code gives me a context menu with the wanted action, but do you have any idea how can I add this action only for the QStandardItems with the even indexes??

BTW, I'm adding items to the treeView by the following way:

void MainWindow::AddItem(QString name)
{
QStandardItem *parentItem = model->invisibleRootItem();
QStandardItem *app = new QStandardItem(name);
parentItem->appendRow(app);
}

I googled a lot, but found nothing :(

thanks in advance!

I would do this in the following way:

Configure the context menu

ui->treeView->setContextMenuPolicy(Qt::CustomContextMenu);
connect(ui->treeView, SIGNAL(customContextMenuRequested(const QPoint &)), this, SLOT(onCustomContextMenu(const QPoint &)));

Implement the context menu handling

void MainWindow::onCustomContextMenu(const QPoint &point)
{
    QModelIndex index = ui->treeView->indexAt(point);
    if (index.isValid() && index.row() % 2 == 0) {
        contextMenu->exec(ui->treeView->viewport()->mapToGlobal(point));
    }    
}