documentation error - callback not optional

I get "function takes exactly 2 arguments, 1 given" if I leave callback off as I discovered leaving it off accidentally

Incidentally, one has room for 4 chars in the tab title and two are shown at a time.

Some other Series60 programs that use tabs have pictures not text and consequently show more tabs. I wonder if this will be added to appuifw ? Not that I can draw meaningful pictures =)