Re: gEDA-user: General Layers questions

[Stephan Boettcher <boettcher@xxxxxxxxxxxxxxxxxx>]

Martin Kupec <martin.kupec@xxxxxxxxx> writes:

> On Fri, Mar 18, 2011 at 09:00:04PM +0100, Stephan Boettcher wrote:
>> Martin Kupec <martin.kupec@xxxxxxxxx> writes:
>> 
>> > On Fri, Mar 18, 2011 at 07:18:52PM +0100, Stephan Boettcher wrote:
>> >> The file format need not know about these distictions.  Both are
>> >> graphical layers, with different attributes.  The one has attributes to
>> >> tell DRC to flag overlapping components, the other has attributes to
>> >> tell some autorouter not to put copper there, and attributes to tell DRC
>> >> to check for intruding copper.  Future plugins need more layers to tell
>> >> about different constraints.
>> >> 
>> >> Ideally, any layer type is fully defined via attributes.  The most
>> >> common attribute may be "net:conductive" for normal copper layers, so
>> >> that the HIDs know that the layer contributes to the implementation of
>> >> the netlist.  Copper layers need a second attribute "gbr:layer=inner5"
>> >> to tell the (gerber) exporter where to put it.  A third attribute
>> >> defines the DRC rules that apply "drc:rules=default", plus per layer
>> >> override "drc:minwidth=6mil".
>> >> 
>> >> "drc:courtyard=front"
>> >> "drc:keepout=front"
>> >> "route:keepout=front"
>> >
>> >
>> > That is a bit complicated. I need a clean definition of layer types, so
>> > one can pick the right layer when needed. But some attributes in
>> > addition to layer type are possible.
>> 
>> I do not understand that argument.
>
> Ok. We probably don't understand each other, so I will just state my fears.
>
> I would like to know about each drawing layer where it belongs to.
>
> So when I am performing DRC check, I will know, that it is conductive
> layer and I should consider it. I can take care of special DRC rules for
> some conductive layers later.

So we do need layer specific DRC rules.  Silk layers get the silk rules
attached.  Copper layers get copper rules attached.

> If layers types would be defined by attributes, someone would be able to
> declare one layer both as conductive and as silk for example. That could
> cause me a nighmares. 

Well, that would be a DRC violation :-) The DRC tool shall not suffer
from nightmares if it finds positives.

> That is why I insist on 'typed' layers, not 'tagged' layer.

As long as the user can define arbitrary types, the type becomes an
attribute.  If the user cannot define new types, then there shall be
only very few very abstract types, connected to basic properies, e.g.,
"conductive", "hole/via", "other".

> That example is probably silly, but someone would probably come up with
> something more realistic, but still giving me nightmares.

-- 
Stephan


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