Drag Drop problem with model views

[Jeffb]

Hi Guys

I've got a QTreeView that I've setup so that I can drag and drop a node within the tree.
That included reimplementing supportedDropActions(), mimeTypes(), mimeData(const QModelIndexList &indexes), bool dropMimeData(...) and removeRows().

Most of it works fine:
When I start the drag, mimeData() is called.
When I drop the node, dropMimeData(...) gets called - It creates a new node from the mimeData and insert the node into the data structure (between beginInsertRows() and endInsertRows() ).
It then automatically calls removeRows() which removes the original node.

But there are some occasions where I need to reject the drop. If I simply return false in dropMimeData,
the dragged node returns to its original position but then removeRows() is still called and the node gets removed.
If I set up a flag so that the node isn't removed within removeRows(), it leaves the row there but makes it invisible.

Does anyone know how to fix this?

Thanks
Jeff

[high_flyer]

post the relevant code.
Specially your dropMimeData().

[Jeffb]

The model (JB_NodeModel) uses a helper class (dragDropHelper) that handles the various drag drop methods e.g. dropMimeData.

bool JB_NodeModel::dropMimeData(const QMimeData *data,
                                Qt::DropAction action,
                                int row,
                                int column,
                                const QModelIndex &parent)
{
    if (dragDropHelper)
        return dragDropHelper->dropMimeData(data,
                                            action,
                                            row,
                                            column,
                                            parent,
                                            this);
    else
        return QAbstractItemModel::dropMimeData(data,
                                                action,
                                                row,
                                                column,
                                                parent);
}

bool JB_NodeModel::dropMimeData(const QMimeData *data,
                                Qt::DropAction action,
                                int row,
                                int column,
                                const QModelIndex &parent)
{
    if (dragDropHelper)
        return dragDropHelper->dropMimeData(data,
                                            action,
                                            row,
                                            column,
                                            parent,
                                            this);
    else
        return QAbstractItemModel::dropMimeData(data,
                                                action,
                                                row,
                                                column,
                                                parent);
}

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bool JB_NMHP_DD_KwGrpsWidget::dropMimeData(const QMimeData *data,
                                           Qt::DropAction action,
                                           int row,
                                           int column,
                                           const QModelIndex &parent,
                                           JB_NodeModel *aNodeModel)
{
    Q_CHECK_PTR(aNodeModel);
    bool handleDrop = true;
    JB_Node* movedNode = 0;
 
    if (action == Qt::IgnoreAction)
        handleDrop = true;
 
    if (!data->hasFormat("text/plain"))
        handleDrop = false;
    else if (column > 0)
        handleDrop = false;
    else
    {
        JB_Node* aParentNode = 0;
        if (modelWrapper->getJBNodeModel() == aNodeModel)
        {
            aParentNode = aNodeModel->nodeFromIndex(parent);
            Q_CHECK_PTR(aParentNode);
        }
        else
            JB_Utilities::getJBUtilities()->debugMB("ERROR: The Drag&Drop modelWrapper and nodeModel do not match", 0);
 
        int beginRow;
        if (row >= 0)
            beginRow = row;
        else
            beginRow = 0;
            //beginRow = aParentNode->children.count();
 
        QString aFirstNodePrimaryTableName;
        QString aFirstNodeLineage;
        QString aFirstNodeRowIDFieldName;
        QHash<QString, QVariant> aFirstNodeFieldValues;
 
        QStringList nodesMimeDataTextList = JB_Utilities::getJBUtilities()->getTextListFromMimeData(data);
        QString firstNodeText = nodesMimeDataTextList.value(0);
        JB_Utilities::getJBUtilities()->getInfoFromMIMEDataText(firstNodeText,
                                                                aFirstNodePrimaryTableName,
                                                                aFirstNodeLineage,
                                                                aFirstNodeRowIDFieldName,
                                                                aFirstNodeFieldValues);
 
        if (aFirstNodePrimaryTableName == "KeywordGroup")
        {
            if (nodesMimeDataTextList.size() > 1)
                JB_Utilities::getJBUtilities()->debugMB("ERROR: The Drag&Drop is trying to move more than one Keyword Group", 0);
            else
            {
                movedNode = aNodeModel->getNodeForNodeLineage(aFirstNodeLineage);
                Q_CHECK_PTR(movedNode);
                if (movedNode->parent == aParentNode)
                    handleDrop = false;
                else
                {
                    handleDrop = true;
                    JB_Node* newFromMovedNode = new JB_Node(*movedNode);
                    newFromMovedNode->children = movedNode->children;
                    for (int i = 0; i < newFromMovedNode->children.count(); i++)
                        newFromMovedNode->children.value(i)->parent = newFromMovedNode;
 
                    int parentRowID = aParentNode->getRowID();
                    int unhashedParentRowID = JB_Utilities::getJBUtilities()->getUnHashedTreeLevelID(parentRowID);
 
                    QString kwGrpParentIDFieldName = "kwGrp_KwGrpParentID";
                    if (newFromMovedNode->getMappedDBFieldNames().contains(kwGrpParentIDFieldName))
                    {
                        newFromMovedNode->setData("kwGrp_KwGrpParentID", QVariant(unhashedParentRowID));
                        newFromMovedNode->setDragDropStatus(JB_DRAGDROP);
                        aNodeModel->insertNode(aParentNode, beginRow, newFromMovedNode, false, true);
                    }
                    else
                        JB_Utilities::getJBUtilities()->debugMB("ERROR: newFromMovedNode should have a kwGrp_KwGrpParentID field", 0);
                }
            }
        }
    }
 
    if (handleDrop == false && movedNode)
        movedNode->setDragDropStatus(JB_CANCEL_DRAGDROP);
 
    return handleDrop;
}

bool JB_NMHP_DD_KwGrpsWidget::dropMimeData(const QMimeData *data,
                                           Qt::DropAction action,
                                           int row,
                                           int column,
                                           const QModelIndex &parent,
                                           JB_NodeModel *aNodeModel)
{
    Q_CHECK_PTR(aNodeModel);
    bool handleDrop = true;
    JB_Node* movedNode = 0;

    if (action == Qt::IgnoreAction)
        handleDrop = true;

    if (!data->hasFormat("text/plain"))
        handleDrop = false;
    else if (column > 0)
        handleDrop = false;
    else
    {
        JB_Node* aParentNode = 0;
        if (modelWrapper->getJBNodeModel() == aNodeModel)
        {
            aParentNode = aNodeModel->nodeFromIndex(parent);
            Q_CHECK_PTR(aParentNode);
        }
        else
            JB_Utilities::getJBUtilities()->debugMB("ERROR: The Drag&Drop modelWrapper and nodeModel do not match", 0);

        int beginRow;
        if (row >= 0)
            beginRow = row;
        else
            beginRow = 0;
            //beginRow = aParentNode->children.count();

        QString aFirstNodePrimaryTableName;
        QString aFirstNodeLineage;
        QString aFirstNodeRowIDFieldName;
        QHash<QString, QVariant> aFirstNodeFieldValues;

        QStringList nodesMimeDataTextList = JB_Utilities::getJBUtilities()->getTextListFromMimeData(data);
        QString firstNodeText = nodesMimeDataTextList.value(0);
        JB_Utilities::getJBUtilities()->getInfoFromMIMEDataText(firstNodeText,
                                                                aFirstNodePrimaryTableName,
                                                                aFirstNodeLineage,
                                                                aFirstNodeRowIDFieldName,
                                                                aFirstNodeFieldValues);

        if (aFirstNodePrimaryTableName == "KeywordGroup")
        {
            if (nodesMimeDataTextList.size() > 1)
                JB_Utilities::getJBUtilities()->debugMB("ERROR: The Drag&Drop is trying to move more than one Keyword Group", 0);
            else
            {
                movedNode = aNodeModel->getNodeForNodeLineage(aFirstNodeLineage);
                Q_CHECK_PTR(movedNode);
                if (movedNode->parent == aParentNode)
                    handleDrop = false;
                else
                {
                    handleDrop = true;
                    JB_Node* newFromMovedNode = new JB_Node(*movedNode);
                    newFromMovedNode->children = movedNode->children;
                    for (int i = 0; i < newFromMovedNode->children.count(); i++)
                        newFromMovedNode->children.value(i)->parent = newFromMovedNode;

                    int parentRowID = aParentNode->getRowID();
                    int unhashedParentRowID = JB_Utilities::getJBUtilities()->getUnHashedTreeLevelID(parentRowID);

                    QString kwGrpParentIDFieldName = "kwGrp_KwGrpParentID";
                    if (newFromMovedNode->getMappedDBFieldNames().contains(kwGrpParentIDFieldName))
                    {
                        newFromMovedNode->setData("kwGrp_KwGrpParentID", QVariant(unhashedParentRowID));
                        newFromMovedNode->setDragDropStatus(JB_DRAGDROP);
                        aNodeModel->insertNode(aParentNode, beginRow, newFromMovedNode, false, true);
                    }
                    else
                        JB_Utilities::getJBUtilities()->debugMB("ERROR: newFromMovedNode should have a kwGrp_KwGrpParentID field", 0);
                }
            }
        }
    }

    if (handleDrop == false && movedNode)
        movedNode->setDragDropStatus(JB_CANCEL_DRAGDROP);

    return handleDrop;
}

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Qt::DropActions JB_NMHP_DD_KwGrpsWidget::supportedDropActions() const
{
    return Qt::MoveAction;
}

Qt::DropActions JB_NMHP_DD_KwGrpsWidget::supportedDropActions() const
{
    return Qt::MoveAction;
}

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[high_flyer]

can you show your removeRows() as well?