Retrieve QComboBox index from QCompletion popup - c++

Question

I have a QComboBox with a QCompleter. The QCompleter displays suggestions in a popup list and I'm drawing the elements in a custom way.
The problem is: I can't get the index in the original combobox even if I did store it into the UserData of the item.
Complete code follows:
class MyItemDelegate: public QItemDelegate {
public:
MyItemDelegate(QWidget *parent) :
QItemDelegate(parent) {}
void paint(QPainter *painter, const QStyleOptionViewItem &option,
const QModelIndex &index ) const Q_DECL_OVERRIDE
{
if (index.row() == 0) { // If this is the first item in the POPUP VIEW
auto comboIndex = index.data(Qt::UserRole).toInt();
qDebug() << "Combobox index is " << comboIndex; // WRONG!!
}
... custom styling code omitted since off-topic ...
}
};
MyWindow::MyWindow(QStringList words, QMainWindow *parent) :
QDialog((QWidget*)parent),
ui(new Ui::MyWindow) {
ui->setupUi(this);
int comboBoxIndex = 0;
for(auto& word : words) {
ui->myComboBox->addItem(word, comboBoxIndex); // This is stored in UserData
++comboBoxIndex;
}
completer = new QCompleter(words, this);
// Use a TreeView for the popup of the completer
QTreeView *treeView = new QTreeView(this);
completer->setPopup(treeView);
treeView->setItemDelegate(new MyItemDelegate(this));
}
No matter what element I have first in the QCompletion popup list, the qDebug() line always returns 0 as index.
Isn't index.data() referring to the original item data of the combobox?

Answer 1

As i see, your problem is that you retrieve comboIndex from model where you didn't set UserData. You set UserData for items of internal QComboBox model (see QComboBox), but when you try to retrieve this data, you do that in code of MyItemDelegate, which you set for QTreeView for QCompleter. That's why index in paint method of delegate is index of QCompleter internal model, not index of QComboBox internal model. And that's why comboIndex is always 0.
To solve your problem you can add UserData in QCompleter internal model. For example, you can create your own model and set this model for QCompleter with method setModel.