Re: gEDA-user: Working on a tiny schematics editor

[John Doty <jpd@xxxxxxxxx>]

Stephan, this project is interesting. I'll try it on Ubuntu when I get back to Noqsi. I  think I'll pass on trying it on a Mac for now (all I have here in Cambridge).

I am puzzled, however, by your motivation:

On Dec 26, 2010, at 8:48 AM, Stefan Salewski wrote:

> I think one reason for start writing it was my desire to assign
> attributes/classes to subnets, to transfer this information to PCB to
> support manually- and auto-routing with already specified parameters for
> traces.

Semantics like this are the responsibility of gnetlist back ends, not gschem. Indeed, the limits of our ability to continue to extend gEDA seem primarily to derive from semantics inappropriately "wired in" to the gnetlist front end, and to a lesser extent in gschem. The kludginess of some back ends derives from the same problem.

There is nothing in gschem that prevents attaching arbitrary attributes to net segments. Unfortunately, the gnetlist front end insists on digesting the data according to rigid (and sometimes wrong!) theories of its semantics before handing it to the back end. In most cases the digested data is just what the back end writer needs (that's why simple back ends are easy to write with just a tiny bit of Scheme knowledge), but if it's not things become difficult. In this case, there appears to be no way to access net segments or their attributes from a gnetlist back end.

John Doty              Noqsi Aerospace, Ltd.
http://www.noqsi.com/
jpd@xxxxxxxxx




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