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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] PCB data structures
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Date: Fri, 22 Jan 2016 13:10:24 +0100
In-Reply-To: <20160122094909.08704cd6e4dfc8a35e1ac734@gmail.com> (Nicklas
	Karlsson's message of "Fri, 22 Jan 2016 09:49:09 +0100")
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"Nicklas Karlsson (nicklas DOT karlsson17 AT gmail DOT com) [via
geda-user AT delorie DOT com]" <geda-user AT delorie DOT com> writes:

>> > The PCB layout has an object of type pcb_layout as the root object, which can contain an arbitrary number of pcb_layer objects--which in turn contain the geometric primitives--and pcb_element objects which aren't associated with a layer.  Objects of type pcb_polygon can have child objects of type pcb_polygon_hole:
>> >
>> > pcb_layout
>> > +- pcb_layer
>> >    +- pcb_arc
>> >    +- pcb_line
>> >    +- pcb_pad
>> >    +- pcb_pin
>> >    +- pcb_polygon
>> >       +- pcb_polygon_hole
>> >    +- pcb_rat
>> >    +- pcb_text
>> >    +- pcb_via
>> > +- pcb_element
>> 
>> Sounds reasonable, and similar to what we have now but with much cleaned up
>> naming and hierarchy.
>
> I would say then looking at data layer by layer there are: arc, line,
> circle, polygon and cutout of these drawing primitives.
>
> Pad/pin/via is a composite of these drawing primitives on different
> layer, this is the case no matter how they are represented. 

I believe it is a mistake to have pcb_layer contain the drawing
primitives.  A pcb_via or pcb_element shall contain the same drawing
primitives, for any layers.  There may be a (hierarchy of) container(s)
for drawing elements not contained in a pcb_via or pcb_element.  pcb_via
and pcb_element shall be subclasses of such containers.

> A hole is equal to a round cut out usually thru all board layers with
> or without plating. Text is probably also a composite of other drawing
> primitives.

A hole is a connection between layers.  No further assumptions about
holes is needed before an export HID or a DRC ruleset is called.

-- 
Stephan