[pstricks] Accessing key/value parameters set using \pssetincustom macros?

[Richard Hensh]

> 
> > your macro still _overwrites_ a preceding global setting by \psset.
> > This can only be changed by a local option, like your 
> linecolor=green.
> 
> And instead of \addbefore at par, one could use the preset 
> system, which allows users to change variables globally. See 
> an example below. Notice 2 things:
> 

This is more or less what I need. Thanks.

BTW, I made the following modifications to the code and it worked...but I'm
not sure why.

\makeatletter
\pst at addfams{rjh}

\def\rjhLine{\pst at object{rjhLine}}
\def\rjhLine at i(#1,#2){%
  \pst at killglue
  \begingroup
  \expandafter\@psset\pst at par,\@nil
  \psline(#1,#2)%
  \endgroup
} \makeatother

\presetkeys[psset]{rjh}{%
  linecolor=blue,linewidth=1.25pt,arrowscale=1.25,arrows=->%
}{}

\makeatother

How does the line

	\expandafter\@psset\pst at par,\@nil

know which family to use? Or is that the wrong question to ask?

Thanks
ricky