(gobject:define-gflags "GdkDragAction" drag-action
  (:export t
   :type-initializer "gdk_drag_action_get_type")
  (:none 0)
  (:copy #.(ash 1 0))
  (:move #.(ash 1 1))
  (:link #.(ash 1 2))
  (:ask #.(ash 1 3)))    
  

:copy

Copy the data.

:move

Move the data, that is, first copy it, then delete it from the source using the DELETE target of the X selection protocol.

:link

Add a link to the data. Note that this is only useful if source and destination agree on what it means, and is not supported on all platforms.

:ask

Ask the user what to do with the data.