Drop item from view outside the window

[folibis]

I have application with QTreeView which contents an image of remote file system (webdav) and QTreeView contents local file system.
I want to implement drag'n'drop actions for my app.
It works perfectly when i move items between my app's widgets or from outside my app. in QAbstractItemModel::dropMimeData i can control all activity. It looks like that:

bool MyModel::dropMimeData (const QMimeData * data, Qt::DropAction action, int row, int column, const QModelIndex & parent)
{
	QList<QUrl> urls = data->urls();
    foreach(const QUrl url,urls)
    {
        LocalFileItem * item = static_cast<RemoteFileItem *>(parent.internalPointer());
        if(url.scheme() == "file") 
            copeLocalFile(item,url);
        // url looks like dav:///public/test.txt
        else if(url.scheme() == "dav")
        {
			QString remoteFile = url.path();
			copyRemoteFile(remoteFile,item);
        }
    }
    return false;
}

bool MyModel::dropMimeData (const QMimeData * data, Qt::DropAction action, int row, int column, const QModelIndex & parent)
{
	QList<QUrl> urls = data->urls();
    foreach(const QUrl url,urls)
    {
        LocalFileItem * item = static_cast<RemoteFileItem *>(parent.internalPointer());
        if(url.scheme() == "file") 
            copeLocalFile(item,url);
        // url looks like dav:///public/test.txt
        else if(url.scheme() == "dav")
        {
			QString remoteFile = url.path();
			copyRemoteFile(remoteFile,item);
        }
    }
    return false;
}

To copy to clipboard, switch view to plain text mode 

It also works good when I copy file from local tree to the desktop, or even to another place outside my app. I just set correct url like that:

QMimeData * MyModel::mimeData (const QModelIndexList & indexes) const
{
    QMimeData * mimeData = new QMimeData();
    QList<QUrl> urls;
    foreach (const QModelIndex index, indexes)
    {
        if (index.isValid())
        {
            FileItem * item = static_cast<FileItem*>(index.internalPointer());
            urls.append(item.url()); // url looks like file://c://test.txt
        }
    }
    mimeData->setUrls(urls);
    return mimeData;
}
QStringList MyModel::mimeTypes() const
{
    QStringList types;
    types << "text/uri-list";
    return types;
}

QMimeData * MyModel::mimeData (const QModelIndexList & indexes) const
{
    QMimeData * mimeData = new QMimeData();
    QList<QUrl> urls;
    foreach (const QModelIndex index, indexes)
    {
        if (index.isValid())
        {
            FileItem * item = static_cast<FileItem*>(index.internalPointer());
            urls.append(item.url()); // url looks like file://c://test.txt
        }
    }
    mimeData->setUrls(urls);
    return mimeData;
}
QStringList MyModel::mimeTypes() const
{
    QStringList types;
    types << "text/uri-list";
    return types;
}

To copy to clipboard, switch view to plain text mode 

But the problem is to copy from remote tree to desktop. All drop actions are controlled by OS. So I cannot handle the moment when my item actually was dropped.
It should be noted that coppied file not exists in local file system while dropping.

I have an idea how to solve this problem:

reimplement QMimeData and method retrieveData() like that:

QVariant MimeData::retrieveData (const QString & mimeType, QVariant::Type type) const
{
    //Qt::MouseButtons buttons = QApplication::mouseButtons ();
    // here i need check if mouse buttom was release(item was dropped), create temporary file, copy content of remote file into temp file and return path to this file; 
    return QMimeData::retrieveData(mimeType,type);
}

QVariant MimeData::retrieveData (const QString & mimeType, QVariant::Type type) const
{
    //Qt::MouseButtons buttons = QApplication::mouseButtons ();
    // here i need check if mouse buttom was release(item was dropped), create temporary file, copy content of remote file into temp file and return path to this file; 
    return QMimeData::retrieveData(mimeType,type);
}

To copy to clipboard, switch view to plain text mode 

but I cannot find the way to get state of mouse button, QApplication::mouseButtons does not returns actual state.

Any other ideas?