QSortFilterProxyModel not mapping properly

zmurphy

I'm having an issue with calls to a QSortFilterProxyModel's mapFromSource function always returning an invalid QModelIndex, regardless of the index provided. In my test case, the model has exactly 1 valid entry, but regardless of what QModelIndex I provide, it always returns invalid. Below is some of the test code I've been using.

            auto src = _sorted_view->sourceModel();
            for (int i = 0; i < src->rowCount(QModelIndex()); ++i) {
                for (int j = 0; j < src->columnCount(QModelIndex()); ++j) {
                    QModelIndex s = src->index(i, j);
                    QModelIndex m = _meta_model->index(i, j);
                    QModelIndex v = _sorted_view->mapFromSource(s);
                    QModelIndex t = _sorted_view->mapFromSource(m);

                    std::string st = src->data(s).toString().toStdString();
                    std::string mt = _meta_model->data(m).toString().toStdString();
                    if (v.isValid()) { //Always invalid
                        std::string vt = _sorted_view->data(v).toString().toStdString();
                    }    
                    if (t.isValid()) { //Always invalid
                        std::string tt = _sorted_view->data(t).toString().toStdString();
                    }    
                }    
            }

In this case, _sorted_view is the QSortFilterProxyModel and _meta_model is a subclass of QAbstractItemModel. Would anyone with a better understanding of QT's model-view setup be able to tell me why the mapping here is not working? As a note, calls to mapToSource generate perfectly valid QModelIndexes, but trying to go the other way does not.

SGaist

Hi and welcome to devnet,

Why are you using indexes from two different models and map them with _sorted_view ?

zmurphy

In this case src and _meta_model point to the same object. It's just some leftover from when I was trying to track down the issue and wanted to make sure that the view was using the model I thought it was.

SGaist

Are you sure of that ? Because if they point to the same object, then the index returned should be the same. If not, then your custom model does something wrong.

zmurphy

Yes, the indexes returned from src and _meta_model are the same. The issue is that none of the indexes returned by _sorted_view->mapFromSource are valid even though I know there is 1 valid entry and I'm iterating over every entry.

SGaist

Can you show how the source model is implemented ?

zmurphy

Yes, here's the top level class. There's a handful of subclasses but I don't believe they do interactions with the Model/View aspects.

class CxFVariableItemModel : public QAbstractItemModel {

public:

    CxFVariableItemModel () : QAbstractItemModel ()
    {   
    }   
    virtual ~CxFVariableItemModel () {}

    const QList <QString> &headers () const { return _headers; }

    virtual const QList <QString> &possibleHeaders () const = 0;

    void setHeaders (const QList <QString> &headers) { 
        emit layoutAboutToBeChanged (); 
        _headers = headers; 
        emit layoutChanged (); 
    }

    virtual const bool useLabels (int whichSensor) = 0;

    virtual const QList <LabelReturnType> &getUsefulStrings (bool returnLabels, int whichSensor) = 0;

    virtual const char *getVariableName (int whichSensor) = 0;

    virtual const int getWhichRow (const char *name) = 0;

    virtual const int depVarSize (int whichSensor, int i) = 0;

    virtual const char *getRealDependName (const int whichSensor, const int whichDependSensor) = 0;

/// Will return a list of all possible timing variable names
    virtual const QList <QString> getListOfTimingVariableNames () = 0;

/// Will return a list of all possible variable names
    virtual const QList <QString> getListOfVariableNames () = 0;

    QModelIndex index (int row, int column, const QModelIndex &parent = QModelIndex ()) const
    {   
        if (!hasIndex (row, column, parent)) {
            return QModelIndex ();
        }   
        if (parent == QModelIndex ()) {
            return createIndex(row, column);
        }   
        if (_headers [column] == "Other") {
            return createIndex (row, column, reinterpret_cast <void *> (parent.row () + 1));
        }   

        return QModelIndex ();
    }   

    QModelIndex parent (const QModelIndex &index) const
    {   
// We used to have index.parent ().row () but that causes an issue when we only had one variable in the GUI.
        long parentRow = index.row ();
        if (parentRow == 0) return QModelIndex ();
        else {
            return createIndex (parentRow - 1, 0);
        }
    }

    virtual int rowCount (const QModelIndex &parent) const = 0;
    int columnCount (const QModelIndex &) const { return _headers.size (); }

    virtual QVariant data (const QModelIndex &index, int role = Qt::DisplayRole) const = 0;

    QVariant headerData (int section, Qt::Orientation orientation, int role = Qt::DisplayRole) const
    {
        if (role == Qt::DisplayRole) {
            if (orientation == Qt::Horizontal) {
                return QVariant (_headers [section]);
            } else { // vertical
                return (QVariant (section));
            }
        }
        return (QVariant ());
    }

protected :

    QList <QString> _headers;
};

Some of this code is quite old so it may not necessarily be correct according to current Qt Model/View standards which is where I think the problem lies.

SGaist

You can check you model implementation with the QAbstractItemModelTester. See this wiki entry.