Re: gEDA-user: DRC enforcement in PCB is wrong

["harry eaton" <bumpelo@xxxxxxxxxxx>]

> What does "rats must exist" mean? I thought they always exist.

When you launch pcb to start a new design, place some elements and load a
netlist (I think this is what gsch2pcb does), the rats do not yet exist. You
can hit the "w" key to draw the rats; they are called rats because you see a
tangled mess of lines showing all of the connections that need to be made.
They are very useful while placing the components because you can easily
judge what components should be near each other, how they are best oriented
etc. The idea is to place the parts such that the rats nest is the least
tangled.

As you add tracks to route the board you should update the rats nest. The
auto-DRC enforcement uses the connection finding routines in order to
determine what copper belongs to the net but the connection finder ("f" key)
traces only actual copper and rats. This is why auto-DRC requires that the
rats appear on the layout. For your purposes, simply hit the "w" key before
using the auto-DRC routing.

With that said I think I'd like to replace the auto-DRC routing with
interactive auto-routing instead. The idea would be to have the auto-router
route a single track from the starting point to the cursor, following the
cursor as you move it around; you could press a key (or maybe mouse button)
to change to a different (less optimal) route path if you didn't like the
candidate it was showing. When the path (or partial path) looked good you
would click to place it on the board. I think that this would be a very
powerful routing tool and it would help to debug and improve the auto-router
too.

h.