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Date: Tue, 22 Dec 2015 17:52:08 +0000
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Subject: Re: [geda-user] Cross project collaboration on data models
From: "Peter Clifton (petercjclifton AT googlemail DOT com) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
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On 22 December 2015 at 17:38, John Doty <jpd AT noqsi DOT com> wrote:

> The one thing that led to many corrupted schematics in one of my projects was a change in the attribute promotion policy, promoting attributes that I had intended to control in heavy symbols. That made a real mess. I suppose that the developer who made the change thought it would be helpful, but it was a naughty thing to do.

Urg... I will go bang my head hard against a wall if that turned out
to be something _I_ was responsible for. Definitely a naughty thing to
do.

Was this recently, or some time back? (Peter B and I always pushed
very hard to avoid breaking things like that - existing user designs
not breaking was a golden golden rule).

There was a dumb case of this in PCB, when the polygon clipper was
introduced. The prior graphical subtraction based code, would keep all
the segmented cut pieces of a given polygon. After the clipper was
introduced, it discarded all bit the single largest piece. (And added
a config flag on an object to revert to the OLD behaviour). Why ever
would that be a _good_ idea... a new flag, to get the OLD behaviour?
Sadly. the change was made before my involvement - and  changing the
sense of the flag after the fact would have broken all the boards
designed since the clipper was introduced.



>> (And IMO, we ought to rip
>> out all the flattened net-list, PCB like work-flow specific hacks out
>> of gnetlist).
>
> Except that most layout tools (not just pcb) take flattened netlists as input. So, that’s a generally useful capability.

Generally useful, but needs to be explicitly called out by the target
netlister I think. (I recall gnetlist flattens by default, and acts on
attributes that have their meaning pretty hard-coded).

Another example, our implementation of slotting, makes makes shudder
somewhat. It is one of the few cases where gEDA throws away its
complete core agnosticism over attached attributes etc..  We should
have introduced a more generic mechanism, then "activated" (probably
with a work-flow specific plugin) it for designs which need that
behaviour.


Peter