implement drag and drop to file browser or desktop?

billconan

hello

I want to implement a program (windows only), such that a person can perform drag and drop from my qt program to desktop (or explorer).

the thing that needs to be dropped is a fake file. i.e. the file exists in memory, when dropping happens, a fake name will be created on the desktop with the data dumped from memory into the file.

I have found some ideas for QT4, but I tried with Qt5, doesn't really work

http://stackoverflow.com/questions/2724252/qt-4-x-how-to-implement-drag-and-drop-onto-the-desktop-or-into-a-folder

most of the ideas suggest using application/octet-stream as mime type. but if it is the only mime type, qt doesn't allow dropping.

only when text/uri-list is also included as a mime type, it allows dropping. but it only supports dropping an actual existing file, not a fake file with a piece of data in the memory.

here are some of my current codes:

one approach I tried is from here
http://stackoverflow.com/questions/24236768/how-can-i-drag-to-the-desktop-with-qt

    QDrag *drag = new QDrag(this);
    QString filename("file:///haha.dat");
    QMimeData *mimeData = new QMimeData;
    mimeData->setData(QString::fromUtf8("text/uri-list"),filename.toUtf8());
    QByteArray data;
    data.append(filename);
    mimeData->setData("application/octet-stream", data);

    drag->setMimeData(mimeData);

this doesn't work, no file can be dropped.

another way is implementing my own QMimeData, but doesn't work either

MyMimeData::MyMimeData()
{
  list << "application/x-qt-windows-mime;value=\"Shell IDList Array\"";
  list << "application/x-qt-windows-mime;value=\"DragImageBits\"";
  list << "application/x-qt-windows-mime;value=\"DragContext\"";
  list << "application/x-qt-windows-mime;value=\"DragSourceHelperFlags\"";
  list << "application/x-qt-windows-mime;value=\"InShellDragLoop\"";
  list << "text/uri-list";
  list << "application/octet-stream";
  list << "application/x-qt-windows-mime;value=\"FileName\"";
  list << "application/x-qt-windows-mime;value=\"FileContents\"";
  list << "application/x-qt-windows-mime;value=\"FileNameW\"";
  list << "application/x-qt-windows-mime;value=\"FileGroupDescriptorW\"";
}

QVariant MyMimeData::retrieveData(const QString &mimetype, QVariant::Type preferredType) const
{
    qDebug() << "retrieve data" << mimetype << preferredType;
    if (mimetype == "text/uri-list")
    {
        QVariantList urls;
        urls << QUrl::fromUserInput("file:///haha.dat");
        return ( urls);
    }
    return QString("haha");
}

bool MyMimeData::hasFormat(const QString &mimetype) const
{
    for(int i = 0;i<list.size();++i)
    {
        if (list[i] == mimetype)
        {
            return true;
        }
    }
    return false;
}

QStringList MyMimeData::formats() const
{
    return list;
}