First step was:
Qt Code: 
  1. MainWindow::MainWindow()
  2. {
  3.     textEdit = new QTextEdit;
  4.     setCentralWidget(textEdit);
  5.  
  6.     textEdit->setAcceptDrops(false);
  7.     setAcceptDrops(true);
  8.  
  9.     setWindowTitle(tr("Text Editor"));
  10. }
  11.  
  12. void MainWindow::dragEnterEvent(QDragEnterEvent *event)
  13. {    
  14.      event->accept();
  15. }
  16.  
  17. void MainWindow::dragMoveEvent(QDragMoveEvent *event)
  18. {
  19.      event->accept();
  20. }
  21.  
  22. void MainWindow::dropEvent(QDropEvent *event)
  23. {
  24.     if (event->mimeData()->hasFormat("text/uri-list")) {
  25.     QList<QUrl> urls = event->mimeData()->urls();
  26.     if (urls.isEmpty())
  27.         return;
  28.  
  29.     QString fileName = urls.first().toLocalFile();
  30.     if (fileName.isEmpty())
  31.         return;
  32.  
  33.     if (readFile(fileName))
  34.         setWindowTitle(tr("%1 - %2").arg(fileName)
  35.                                     .arg(tr("Drag File")));
  36.     }
  37. }
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In the second step I enabled drops for textEdit
Qt Code: 
  1. textEdit->setAcceptDrops(true)
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and subclassed it, so now it's possible to move/copy a text from a line to another:
Qt Code: 
  1. ...dragEnterEvent(QDragEnterEvent *e)
  2. {
  3.     if (e->source()) {
  4.         if (e->source()->objectName() == "qt_scrollarea_viewport") {
  5.             e->accept();
  6.         }
  7.     }
  8. }
  9.  
  10. ...dragMoveEvent(QDragMoveEvent *e)
  11. {
  12.     e->accept();
  13. }
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My questions:
1. During drag the cursor stays hidden: is this due to the non-propagation of the event to the parent?
2. Why subclassing dropEvent() like this
Qt Code: 
  1. ...dropEvent(QDropEvent *e)
  2. {
  3.     e->accept();
  4. }
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text is not copied/moved?
3. Are there any alternatives to get this task?
I hope this thread will be useful for others.
Thank you so much.