How to use task_error ? (Writing pretty hooks)

[Thomas Neumann]

hiya

It seems the documentation is a bit patchy about this. (At least regarding
fai-wiki and the webpage.)

Am I allowed to use task_error in self-written hooks?

If yes: What exactly means e.g. "task_error 801 $RETVAL" ?

Is there a list of error codes already in use? May I invent new ones?

Background: I'm in the process of polishing up my custom extrbase hook. It
would be nice to properly signal 'something went wrong' (like missing
requirements, runtime errors etc.)

tschüß
thomas