list in mimeData(const QModelIndexList& list) returns more items than selected in QTreeView

[Simonson]

Hi fellow Qt programmers,

I am using Qt 5.9.1 on Win10. The Tree I am implementing looks like this:

• RootElement
• • Product 1
• ++ Workpackage 1
• +++ Workstep 1
• +++ Workstep 2
• ...
• ++ Workpackage 2
• +++ Workstep 1
• +++ Workstep 2
• • Product 2
• ....

I reimplemented mimeTypes, mimeData, canDropMimeData and dropMimeData like this:

QStringList ProductTreeModel::mimeTypes() const
{
    QStringList mimeTypes;

    mimeTypes.append(Product::MIMETYPE_PRODUCT);
    mimeTypes.append(WorkStep::MIMETYPE_WORKSTEP);
    mimeTypes.append(WorkPackage::MIMETYPE_WORKPACKAGE);

    return mimeTypes;
}

QMimeData *ProductTreeModel::mimeData(const QModelIndexList &indexes) const
{
    //TODO add support for tool, material, qualification, instruction
    QByteArray encodedData;
    AbstractTreeNode* node;
    QMimeData* mimeData = new QMimeData();
    QDataStream mdStream(&encodedData, QIODevice::WriteOnly);

    for(QModelIndexList::const_iterator i=indexes.begin(); i!=indexes.end(); ++i) {
        node = indexToNode(*i);

        switch(node->getType()) {
        case AbstractTreeNode::TYPE_PRODUCT:
            mdStream << QJsonDocument(dynamic_cast<ProductTreeNode*>(node)->toJsonObject()).toBinaryData();
            break;

        case AbstractTreeNode::TYPE_WORKSTEP:
            mdStream << QJsonDocument(dynamic_cast<WorkStepTreeNode*>(node)->toJsonObject()).toBinaryData();
            break;

        case AbstractTreeNode::TYPE_WORKPACKAGE:
            mdStream << QJsonDocument(dynamic_cast<WorkPackageTreeNode*>(node)->toJsonObject()).toBinaryData();
            break;
        }
    }
    switch(node->getType()) {
    case AbstractTreeNode::TYPE_PRODUCT:
        mimeData->setData(Product::MIMETYPE_PRODUCT, encodedData);
        break;

    case AbstractTreeNode::TYPE_WORKSTEP:
        mimeData->setData(WorkStep::MIMETYPE_WORKSTEP, encodedData);
        break;

    case AbstractTreeNode::TYPE_WORKPACKAGE:
        mimeData->setData(WorkPackage::MIMETYPE_WORKPACKAGE, encodedData);
        break;
    }
    return mimeData;
}

bool ProductTreeModel::canDropMimeData(const QMimeData *data, Qt::DropAction action, int row, int column, const QModelIndex &parent) const
{
    Q_UNUSED(row)
    Q_UNUSED(action)
    Q_UNUSED(column);

    if((getType(parent)==AbstractTreeNode::TYPE_PRODUCT) && (data->hasFormat(WorkPackage::MIMETYPE_WORKPACKAGE))) {
        return true;
    }
    if((getType(parent)==AbstractTreeNode::TYPE_WORKPACKAGE) && (data->hasFormat(WorkStep::MIMETYPE_WORKSTEP))) {
        return true;
    }
    return false;
}

bool ProductTreeModel::dropMimeData(const QMimeData *data, Qt::DropAction action, int row, int column, const QModelIndex &parent)
{
    int i = 0;
    int insertRow;
    QByteArray encodedRow;
    QByteArray encodedData;
    QJsonDocument jsonRow;
    AbstractTreeNode* node;

    if(data->hasFormat(WorkPackage::MIMETYPE_WORKPACKAGE)) {
        encodedData = data->data(WorkPackage::MIMETYPE_WORKPACKAGE);
    }
    if(data->hasFormat(WorkStep::MIMETYPE_WORKSTEP)) {
        encodedData = data->data(WorkStep::MIMETYPE_WORKSTEP);
    }
    if(row<0) {
        insertRow = 0;
    }
    else {
        insertRow = row;
    }
    QDataStream mdStream(&encodedData, QIODevice::ReadOnly);

    if(!canDropMimeData(data, action, row, column, parent)) {
        return false;
    }
    if(action==Qt::IgnoreAction) {
        return true;
    }
    node = indexToNode(parent);

    while(!mdStream.atEnd()) {
        mdStream >> encodedRow;
        jsonRow = QJsonDocument::fromBinaryData(encodedRow);

        if(data->hasFormat(WorkPackage::MIMETYPE_WORKPACKAGE)) {
            insertWorkPackage(jsonRow.object(), insertRow+i, parent);
        }
        if(data->hasFormat(WorkStep::MIMETYPE_WORKSTEP)) {
            insertWorkStep(jsonRow.object(), insertRow+i, parent);
        }
        ++i;
    }
    return true;
}

Here is my problem: If I drag and drop Worksteps everythings works fine, but when I drag Workpackages indexes in mimeData() holds the very same index twice. And if I drag a Product, indexes even holds three times the index. I can't find any errors in the code. Is this behaviour intended by QTreeView?

Regards
Simonson

[Simonson]

ok found the error. The problems was that the columnCount() funktion returned a number > 1 for the alle other items than worksteps. Thats why indexes in mimeData() had more than one entries.