[Interest] [External] Proxied view not updating live when source model does

[Murphy, Sean]

> I'm having an issue where my proxy model and its associated view aren't
> updating live when changes are made in the source model.
> 
> My proxy model simply is attempting to invert the rows of the source model. So
> it inherits from a QSortFilterProxyModel and implements mapFromSource() and
> mapToSource() as follows:
> 
>     QModelIndex invertRowsModel::mapFromSource(const QModelIndex
> &sourceIndex) const
>     {
>         if(sourceIndex.isValid() && rowCount() > 0)
>         {
>             return this->index(rowCount() - sourceIndex.row() - 1,
> sourceIndex.column());
>         }
> 
>         return QModelIndex();
>     }
> 

Small update here, but I'm not sure what it actually means... I added a debug 
statement at the top of my mapFromSource() function, so now that function reads like so:  

    QModelIndex invertRowsModel::mapFromSource(const QModelIndex &sourceIndex) const
    {
        if(sourceIndex.isValid() && rowCount() > 0)
        {
            qDebug() << __FUNCTION__ << "valid index" << sourceIndex;
            return this->index(rowCount() - sourceIndex.row() - 1, sourceIndex.column());
        } else {
            qDebug() << __FUNCTION__ << "invalid index" << sourceIndex;
        }

        return QModelIndex();
    }

With this in place, while modifying the data in the source view, I NEVER see the 
mapFromSource() "valid index" debug message from the proxy model. Right after 
setData() is called in the source model, I see a couple of these messages come out 
and that's it:

  invertRowsModel::mapFromSource invalid index QModelIndex(-1,-1,0x0,QObject(0x0))  

I'm not sure exactly what that means or how to address it, but it is a new data point...

Sean