On 2013–03–23 Wolfgang Schuster wrote:

> […]
> \startuseMPgraphic{framed:background}
>   fill unitsquare xyscaled(OverlayWidth,OverlayHeight) leftenlarged 1cm withcolor \MPcolor{lightgray};
>   setbounds currentpicture to OverlayBox ;
> \stopuseMPgraphic
> […]

How about making this configurable? It would be intuitive and
consistent. Suggestion:

content     background
-------     ----------
offset      backgroundoffset
loffset     backgroundloffset
roffset     backgroundroffset
toffset     backgroundtoffset
boffset     backgroundboffset


Marco