Dragging out of a QTreeView with a ProxyModel

[jmichiel]

I'm trying to get dragging to work using a QTreeView and a custom ProxyModel that contains a QSqlQueryModel. I'm using the ProxyModel to do grouping based on the values of some column of the data.
Now I want the user to be able to drag leafs of the tree out of the tree to another widget in my app.

I read http://doc.qt.nokia.com/4.7/model-vi...ith-item-views and did everything stated there, but dragging (and dropping for that matter) doesn't work in the least: the drag is never started, startDrag() is never called (placed a breakpoint in QAbstractItemView code). The only thing that happens is that the item is selected.
What could I be doing wrong?
I don't need to subclass QTreeView since it should be able to handle it out-of-the-box, right?
The QTreeView is inside a QDockWidget, if that matters.

The drag and drop examples work, but they don't use a View, just plain Widgets.

---

Added after 50 minutes:

If I set the selectionBehaviour to SelectItems, it works...
Can it have something to do with the fact that I remove columns in my proxymodel, so that SelectRows has trouble selecting the entire row somehow?
Should I override mapSelectionFromSource/mapSelectionToSource to make it work on rows perhaps?

[wysota]

How did you implement flags() for your model? What is the value of the dragEnabled property for the view? How did you implement mimeData() for the model?

[jmichiel]

dragEnabled is true, and these are the flags and mimeData methods (pretty much as in the documentation:

Qt::ItemFlags ThemaLesModel::flags(const QModelIndex &index) const
{
    Qt::ItemFlags defaultFlags = sourceModel()->flags(mapToSource(index));
    if (index.isValid())
        return Qt::ItemIsDragEnabled | Qt::ItemIsDropEnabled | defaultFlags;
    return defaultFlags;
}
 
 
QMimeData *ThemaLesModel::mimeData(const QModelIndexList &indexes) const
 {
     QMimeData *mimeData = new QMimeData();
     QByteArray encodedData;
 
     QDataStream stream(&encodedData, QIODevice::WriteOnly);
 
     foreach (const QModelIndex &index, indexes) {
         if (index.isValid()) {
             QString text = data(index, Qt::DisplayRole).toString();
             stream << text;
         }
     }
 
     mimeData->setData("application/vnd.text.list", encodedData);
     return mimeData;
}

Qt::ItemFlags ThemaLesModel::flags(const QModelIndex &index) const
{
    Qt::ItemFlags defaultFlags = sourceModel()->flags(mapToSource(index));
    if (index.isValid())
        return Qt::ItemIsDragEnabled | Qt::ItemIsDropEnabled | defaultFlags;
    return defaultFlags;
}


QMimeData *ThemaLesModel::mimeData(const QModelIndexList &indexes) const
 {
     QMimeData *mimeData = new QMimeData();
     QByteArray encodedData;

     QDataStream stream(&encodedData, QIODevice::WriteOnly);

     foreach (const QModelIndex &index, indexes) {
         if (index.isValid()) {
             QString text = data(index, Qt::DisplayRole).toString();
             stream << text;
         }
     }

     mimeData->setData("application/vnd.text.list", encodedData);
     return mimeData;
}

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If I use 'SelectRows', than I can't do anything. Using SelectItems, it works, but only for the original data rows, not for the 'virtual' ones I introduced myself for the grouping. While debugging, I saw that apparently it's the selectionModel that tells the view there are no selections when in SelectRows mode.

[wysota]

Is ThemaLesModel the proxy or the base model?

[jmichiel]

ThemaLesModel is derived from the Grouping proxy. The sourceModel is a QSqlQueryModel