Updating a view's proxy model when the source model changes

[graffy]

Hello,

I have a model that manages a list of files. It's viewed by two widgets (a combobox and a tableview). Each widget has it's own QSortFilterProxy to pick which files it's supposed to display.

The problem I'm encountering is related to drag and drop operations. After I perform a drag and drop (reordering list items), I've had trouble updating the views. For some reason, neither proxy model responds to the source model's dataChanged() signal (which I emit in the source model's setData() function, as well as the removeRows() function which is called last in the drag-drop operation). Anyway, I can solve the tableview refresh problem easily enough by adding a call to reset() in a slot in it's proxymodel, but the combo box is proving more difficult.

I can't use the reset() trick with the combobox's proxy model because it will reset the current index to -1, losing whatever item has been selected.

This leaves me with two possible solutions. Either I need to make a connection which ensures a proxy model is always synced with changes in it's source, or I need to save the current index of the combo box before the model is changed, then restore that index after the change is made. On the latter technique, I'm not sure how I can do that, nor am I certain that the view would update if I updated it's proxy model programmatically...

Any help would be much appreciated...

[Santosh Reddy]

The problem I'm encountering is related to drag and drop operations. After I perform a drag and drop (reordering list items), I've had trouble updating the views.

What do you mean by reordering?
If it is just inserting row(s), are you using beginInsertRows() and endInsertRows()?
If it is complete reordering, are you using beginModelReset() and endResetModel()?

[graffy]

I'm only inserting a row at a time. I still have to call reset() on each proxy (or in the source model alone) to get the view to refresh properly. That's fine for the table view, but not good for the combo box view...

[Santosh Reddy]

are you using beginInsertRows() and endInsertRows()?

[graffy]

Yes - sorry - I forgot to mention that. Here's some code...

Source model drag/drop and other relevant code...

Qt::ItemFlags EsxModel::ContentModel::flags(const QModelIndex &index) const
{
    if (!index.isValid())
        return Qt::NoItemFlags;
 
    EsmFile *file = item(index.row());
 
    if (!file)
        return Qt::NoItemFlags;
 
    Qt::ItemFlags dragDropFlags = Qt::ItemIsDragEnabled | Qt::ItemIsDropEnabled;
    Qt::ItemFlags checkFlags = Qt::ItemIsUserCheckable;
    Qt::ItemFlags defaultFlags = Qt::ItemIsDropEnabled | Qt::ItemIsSelectable;
 
    if (canBeChecked(file))
        return Qt::ItemIsEnabled | dragDropFlags | checkFlags | defaultFlags;
    else
        return defaultFlags;
}
 
bool EsxModel::ContentModel::setData(const QModelIndex &index, const QVariant &value, int role)
{
    if (index.isValid() && role == Qt::EditRole)
    {
        QString fname = value.value<QString>();
        mFiles.replace(index.row(), findItem(fname));
        emit dataChanged(index, index);
        return true;
    }
 
    return false;
}
 
bool EsxModel::ContentModel::insertRows(int position, int rows, const QModelIndex &parent)
{
    beginInsertRows(QModelIndex(), position, position+rows-1);
 
    for (int row = 0; row < rows; ++row)
        mFiles.insert(position, new EsmFile);
 
    endInsertRows();
    return true;
}
 
bool EsxModel::ContentModel::removeRows(int position, int rows, const QModelIndex &parent)
{
    beginRemoveRows(QModelIndex(), position, position+rows-1);
 
    for (int row = 0; row < rows; ++row)
        mFiles.removeAt(position);
 
    endRemoveRows();
    emit dataChanged(index(0,0,parent), index(rowCount()-1, 0, parent));
    return true;
}
 
Qt::DropActions EsxModel::ContentModel::supportedDropActions() const
{
    return Qt::CopyAction | Qt::MoveAction;
}
 
QStringList EsxModel::ContentModel::mimeTypes() const
{
    QStringList types;
    types << "application/omwcontent";
    return types;
}
 
QMimeData *EsxModel::ContentModel::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/omwcontent", encodedData);
    return mimeData;
}
 
bool EsxModel::ContentModel::dropMimeData(const QMimeData *data, Qt::DropAction action, int row, int column, const QModelIndex &parent)
{
    if (action == Qt::IgnoreAction)
        return true;
 
    if (!data->hasFormat("application/omwcontent"))
        return false;
 
    if (column > 0)
        return false;
 
    int beginRow;
 
    if (row != -1)
        beginRow = row;
    else if (parent.isValid())
        beginRow = parent.row();
    else
        beginRow = rowCount(QModelIndex());
 
    QByteArray encodedData = data->data("application/omwcontent");
    QDataStream stream(&encodedData, QIODevice::ReadOnly);
    QStringList newItems;
    int rows = 0;
 
    while (!stream.atEnd())
    {
        QString text;
        stream >> text;
        newItems << text;
        ++rows;
    }
 
    insertRows(beginRow, rows, QModelIndex());
 
    foreach (const QString &text, newItems)
    {
        QModelIndex idx = index(beginRow, 0, QModelIndex());
        setData(idx, text);
        beginRow++;
    }
 
    return true;
}

Qt::ItemFlags EsxModel::ContentModel::flags(const QModelIndex &index) const
{
    if (!index.isValid())
        return Qt::NoItemFlags;

    EsmFile *file = item(index.row());

    if (!file)
        return Qt::NoItemFlags;

    Qt::ItemFlags dragDropFlags = Qt::ItemIsDragEnabled | Qt::ItemIsDropEnabled;
    Qt::ItemFlags checkFlags = Qt::ItemIsUserCheckable;
    Qt::ItemFlags defaultFlags = Qt::ItemIsDropEnabled | Qt::ItemIsSelectable;

    if (canBeChecked(file))
        return Qt::ItemIsEnabled | dragDropFlags | checkFlags | defaultFlags;
    else
        return defaultFlags;
}

bool EsxModel::ContentModel::setData(const QModelIndex &index, const QVariant &value, int role)
{
    if (index.isValid() && role == Qt::EditRole)
    {
        QString fname = value.value<QString>();
        mFiles.replace(index.row(), findItem(fname));
        emit dataChanged(index, index);
        return true;
    }

    return false;
}

bool EsxModel::ContentModel::insertRows(int position, int rows, const QModelIndex &parent)
{
    beginInsertRows(QModelIndex(), position, position+rows-1);

    for (int row = 0; row < rows; ++row)
        mFiles.insert(position, new EsmFile);

    endInsertRows();
    return true;
}

bool EsxModel::ContentModel::removeRows(int position, int rows, const QModelIndex &parent)
{
    beginRemoveRows(QModelIndex(), position, position+rows-1);

    for (int row = 0; row < rows; ++row)
        mFiles.removeAt(position);

    endRemoveRows();
    emit dataChanged(index(0,0,parent), index(rowCount()-1, 0, parent));
    return true;
}

Qt::DropActions EsxModel::ContentModel::supportedDropActions() const
{
    return Qt::CopyAction | Qt::MoveAction;
}

QStringList EsxModel::ContentModel::mimeTypes() const
{
    QStringList types;
    types << "application/omwcontent";
    return types;
}

QMimeData *EsxModel::ContentModel::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/omwcontent", encodedData);
    return mimeData;
}

bool EsxModel::ContentModel::dropMimeData(const QMimeData *data, Qt::DropAction action, int row, int column, const QModelIndex &parent)
{
    if (action == Qt::IgnoreAction)
        return true;

    if (!data->hasFormat("application/omwcontent"))
        return false;

    if (column > 0)
        return false;

    int beginRow;

    if (row != -1)
        beginRow = row;
    else if (parent.isValid())
        beginRow = parent.row();
    else
        beginRow = rowCount(QModelIndex());

    QByteArray encodedData = data->data("application/omwcontent");
    QDataStream stream(&encodedData, QIODevice::ReadOnly);
    QStringList newItems;
    int rows = 0;

    while (!stream.atEnd())
    {
        QString text;
        stream >> text;
        newItems << text;
        ++rows;
    }

    insertRows(beginRow, rows, QModelIndex());

    foreach (const QString &text, newItems)
    {
        QModelIndex idx = index(beginRow, 0, QModelIndex());
        setData(idx, text);
        beginRow++;
    }

    return true;
}

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And the proxy model:

EsxModel::MasterProxyModel::MasterProxyModel(QObject *parent, QAbstractTableModel* model) :
    QSortFilterProxyModel(parent)
{
    setFilterRegExp(QString("game"));
    setFilterRole (Qt::UserRole);
 
    if (model)
         setSourceModel (model);
 }
 
QVariant EsxModel::MasterProxyModel::data(const QModelIndex &index, int role) const
{
    return QSortFilterProxyModel::data (index, role);
}

EsxModel::MasterProxyModel::MasterProxyModel(QObject *parent, QAbstractTableModel* model) :
    QSortFilterProxyModel(parent)
{
    setFilterRegExp(QString("game"));
    setFilterRole (Qt::UserRole);

    if (model)
         setSourceModel (model);
 }

QVariant EsxModel::MasterProxyModel::data(const QModelIndex &index, int role) const
{
    return QSortFilterProxyModel::data (index, role);
}

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[Santosh Reddy]

Can you show the rowCount()? Is it based on anything other than mFiles.size()?

[graffy]

Nope.

int EsxModel::ContentModel::rowCount(const QModelIndex &parent) const
{
    return mFiles.size();
}

int EsxModel::ContentModel::rowCount(const QModelIndex &parent) const
{
    return mFiles.size();
}

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[Santosh Reddy]

Add this

int EsxModel::ContentModel::rowCount(const QModelIndex &parent) const
{
    if(parent.isValid())
        return 0;
 
    return mFiles.size();
}

int EsxModel::ContentModel::rowCount(const QModelIndex &parent) const
{
    if(parent.isValid())
        return 0;

    return mFiles.size();
}

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also do the corresponding changes in parent() and index()

[graffy]

Being new to Qt in general, I'm a bit lost... The parent() and index() functions have not been implemented in the source model. I presume that's something that needs to be done? Any examples you could point to that might fill in the gaps in my understanding on this?

[graffy]

I may not have a clear enough understanding of Qt, but could it be that the proxied view gets messed up because the item is being manipulated w.r.t the source model parent index and not the proxy model? That is, I presume each proxy has a local parent for it's filtered version of the source model (since it will have it's own unique index values)... So, if the drag/drop and related operations reference the items according to the source model's parent, then it would make sense that they would get screwed up when rendered in a view that is filtered by a proxy...

Which would suggest implementing the source model methods that take a parent() parameter in the proxy and calling the source model method with mapToSource() ... ?

[Santosh Reddy]

What is you model based on QAbstractItemModel/QAbstractTableModel/QStandardItemModel?