Re: gEDA-user: DRC vs shorted nets?

["harry eaton" <bumpelo@comcast.net>]

> Ok, but it would be nice if something gave the location of the short.
Change
> color, or X/Y points.

Yes, but as I point out, that is a very hard problem which in general
doesn't have a solution (think about many simultaneous shorts).

> What defines "tenuous" distances?  Zero is apparently not a tenuous
distance.
> How do the tenuous distances relate to the "DRC Minimium..." under the
size
> menu?  A distance of one gets a warning but zero does not?

The minimum overlap rule is less important today, but there are still cases
where it matters. Consider a rounded trace end just kissing a circular via;
it touches at an infinitesimal point. If any extra etching were to occur,
the trace would be broken.

In the old days, the photo-plotter was a mechanical device with real optical
aperatures and it had mechanical slop, so if there wasn't enough overlap of
two lines they might not be connected in the physical circuit. In the
current age of laser photo-plotters, it's pretty much a non issue, but there
is still the etch rate issues where this matters.

The "adjust acitve sizes/minimum overlap" in the sizes menu basically
provides how much any track can shrink by before it's allowed to break
connection. What I would call a "tenuous short" is one which if the trace
making the short were to shrink by "minimup overlap" e.g. 4 mils, it would
no longer be a short. The DRC checker would point out this tenous short
telling you  there is potential for a broken trace (never mind you want this
trace broken!).

harry