#include <QtGui>
#include <QLabel>
class Label : public QLabel {
 protected:
  void mouseMoveEvent(QMouseEvent* event) {
    QTemporaryFile file;
    if (file.open()) {
      QUrl url = QUrl::fromLocalFile(file.fileName());
      file.write(text().toUtf8());
      file.close();

      QDrag* drag = new QDrag(this);
      QMimeData* mimeData = new QMimeData;
      mimeData->setUrls(QList<QUrl>() << url);
      drag->setMimeData(mimeData);
      drag->exec(Qt::CopyAction);
    }
  }
};

int main(int argc, char* argv[]) {
  QApplication app(argc, argv);
  Label label;
  label.setText("DRAG HERE");
  label.show();
  return app.exec();
}

With pure Qt API ? No, I don't know, but since it's something Windows specific you should look at the native API for that part.

Why did you delete this thread just to ask the same question again ?