I would like to write a simple Qt app (in Python with PySide6) that will generate a midi file such that the user can drag it directly into their DAW (e.g. Reaper, Ableton, Bitwig).

I have got

  def mousePressEvent(self,e):
    if e.button() == Qt.LeftButton:
      drag = QDrag(self)
      mimeData = QMimeData()
      mimeData.setData("audio/midi",mid)
      drag.setMimeData(mimeData)
      drag.exec(Qt.CopyAction)

in my mousePressEvent, and this seems to get halfway there: Reaper reacts as if a MIDI file is being dragged over. But what do I do next so that the MIDI arrives in Reaper when I release the drag?