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From: geda AT psjt DOT org (Stephan =?utf-8?Q?B=C3=B6ttcher?=)
To: <geda-user AT delorie DOT com>
Subject: Re: [geda-user] (features: layers stack, padstack/vias)
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Date: Sat, 09 Jan 2016 10:14:06 +0100
In-Reply-To: <20160109020345.1e07cb84@jive> (Lev's message of "Sat, 9 Jan 2016
	02:03:45 +0100")
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"Lev (leventelist AT gmail DOT com) [via geda-user AT delorie DOT com]"
<geda-user AT delorie DOT com> writes:

> On Fri, 8 Jan 2016 17:52:59 +0100
> "Nicklas Karlsson (nicklas DOT karlsson17 AT gmail DOT com) [via
> geda-user AT delorie DOT com]" <geda-user AT delorie DOT com> wrote:
>
>> In preferences-->Layers-->Groups some of the layers are listed but
>> not all are listed. What do you think is missing?
>
> I would add explicitly the insulation layers, and documentation layers, silks,
> etc. I'd add user defined layers as well. I'd add some logic like "XOR this
> layer with that, and use it as conductive 2."

I'd prefer the format/data model to become more general and orthogonal,
not more explicit layer types.  All layers that need to be described
needs an explicit entry in the layerlist and can be drawn on.

If you want to draw on an insulation layer, just add it.  If you do not
want to draw on it, there is little reason to add it.  It should not be
required to describe the board, unless the data model/format lacks other
attachment points for its dialectric properties attributes.

NB: Since the primary target export is Gerber, I propose to implement
the level concept from that standard somehow.  Each object shall be
explicitly assigned to a layer, and a level on the layer.  Even levels
draw, odd levels clear. Standard library level assignment could be:

  level 10: polygons
  level 25: holes in polygons
  level 35: clearances around lines
  level 40: lines.
  level 50: pads

A Line object would not need to include its clearance directly, but
there would be a second line on the clearance layer.  But those two
objects must be linked to each other both in the file format and the
data model, so maybe that is not a good idea.

OTOH, generic compond objects are require too, for Vias, Elements, and
hierarchy, why not for Lines and Arcs as well?

In other words, please think more generic not more special case.  The
GUI shall encapsulate all that with more specialized tools and
defaults.   

Line( (("attribute" value) ...) (("layer1" level1 width1) ("layer2" level2 width2) ...) ((x1 y1) (x2 y2) ...) )

-- 
Stephan