barlines - thickness and location

[Jarkko Sipilä (Koti)]

I would need for my use a software which draws the barlines over the
first note of the bars as a thin line. The barlines should not affect the
distances between the notes.

Like that:
http://webusers.siba.fi/~jsipila/trio.jpg

It is hard work to hack source codes of the lilypond so that I could draw the 
barlines in the above way with lilypond.
What classes do draw the barlines and control location and thickness of the 
barlines.

Thanks, Jarkko Sipilä