[cairo] Questions about very thin lines

[Stefan Salewski]

Is there a detailed documentation how cairo draws thin lines (smaller
than one pixel) available?

I read the explanation about
http://cairographics.org/FAQ/#sharp_lines
I think I understand that.

But what is about width below 1? For PNG output the lines fade out and
finally vanish, OK. But I do not really understand what will happen for
PostScript and PDF output. I think for these devices one device unit is
defined as 1/72 inch, but device resolution of printers is much higher.
What will happen for thin lines, will I get  1/72 inch width lines which
fade out? Or thinner lines with full color intensity. And how can I
produce the thinnest hardware limited line for a printer output?

Maybe it would be fine to have multiple drawing modes for lines? For
example one mode for lines which fade out and vanish, and one mode where
lines become thin, but always remain visible. (This later mode is what I
currently emulate by converting line width to device units and ensure
that width is at least one in device units -- works OK for PNG output,
but I have currently no idea if that is a good method for PDF.
(Application is drawing schematics for electronics.)

Best regards

Stefan Salewski