capmargin for multiline captions but centered for oneline

Question

The koma class scrbook centers oneline captions if not given captions=nooneline. However, settings setcapmargin (\setcapmargin{0.05\textwidth}), also one line captions are left aligned with the additional margin.

How do I have multiline captions with a fixed margin but one line captions centered?

I may use the subfig package, if so, I want koma to handle the captions, therefore settings caption=false.

Answer 1

The "trick" is to set the caption width instead of the margin with "center" as optional position argument:

\setcapwidth[c]{0.9\textwidth}