The callback function you specify here will be called like a standard MUI Royale event callback, but with the following extra arguments:
Your callback function then has to return a value that indicates how the two entries should be aligned in the listview. If entry 1 should be placed before 2, your callback has to return -1. If entry 1 should be placed after entry 2, your callback has to return 1. If the two entries are the same, return 0.
Note that you always have to pass a string specifying the name of a Hollywood function to this attribute. Never pass the function directly but always pass the name of the function as a string!
Also note that you must also set up a notification on this attribute. Otherwise the callback function will never get called.
See Notifications for details.