Dropping file onto Dockitem of App

My app processes any file that are being dragged onto the window and with the open dialog. But dropping one onto to app’s dockitem does not even launch the app.

I searched in the documents and forum here, but other than to handle that in the Opendocument event handler (which I did), and that there should be a filetypegroup indicated (why?), I find no useful coding or instruction.
Does anyone has such a thing?

You need a file type because it is there that you indicate what role your app takes for opening the files. Just open the editor, drop one of the files in there and then change the role to edit or run (default is for the owner of the type).

Mhh, the app has to take the same role no matter what kind of file: open it.
So far my file type group is special/any (.*). What else is needed, so that the app launches at all?

First you define a file type, where you app is has the role to view/edit it.
I added special/any, picked role view and alternate and got it working:

Thanks Christian, did not set Role to View as you did.