[cairo] Obtaining two parallel paths from a single curve

[John Ellson]

archee at 126 wrote:
> Hi,
>
> How to obtain two parallel paths from a single curve?
> Say, these two parallel paths are N pixels away from each other.
>
> Thanks!
Perhaps a dumb idea, with all these math wiz's around describing
envelopes of circles....,
but couldn't you just draw a wide line in the color of your parallel
lines, then draw another
slightly narrower wide line with the same coordinates in the color for
the road, leaving just parallel borders?

John