You are not checking for the obj receiving the event.
This should not be a problem, but see if you get at all events from your list:
Qt Code: 
  1. bool MyDialog::eventFilter(QObject *obj, QEvent *event)
  2. {
  3.     qDebug() << "Event Filter called with " << event->type();
  4.     if(obj == ui->myList)
  5.    {
  6.        if (event->type() == QEvent::DragLeave) {
  7.         qDebug() << event->type() << "= drag leave event.";
  8.         return true;
  9.         } else if (event->type() == QEvent::DragEnter) {
  10.         qDebug() << event->type() << "= drag enter event.";
  11.         return true;
  12.        } 
  13.    }
  14.    else {
  15.         // standard event processing
  16.         return QObject::eventFilter(obj, event);
  17.     }
  18. }
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