This discussion is in no small part strengthening my = suggestion that the layer data structure be agnostic to how it is ultimatel= y realized. "Layer" clearly means different things to different p= eople.

> = So, if one generic container of data holds a 2D conductor on insulator patt= ern, and one holds
> solder mask and one holds top-to-bottom-via connectivity they don'= t all get talked about as layers or it
> is confusing.

I wouldn'= t include inter-layer connectivity as a layer. I think that's a fundame= ntally different idea. I would suggest implementing connectivity within a f= ootprint/pattern/group as something like a netlist. pcb implements connec= tivity awareness for other reasons, so you might as well reuse the idea her= e. But I think that is a discussion for a different thread.

Otherwise, yes, I do think you call a solder mask pattern a layer, I do = think you call a copper pattern a layer, I do think you call a drill drawin= g a layer, I do think you call assembly data a layer.

=C2=A0=

A layer is a flat surface made of particular material for example: c= opper foil, solder mask, insulating board.

My suggest= ion is that you modify your statement slightly and replace "A layer is= a flat surface..." with "A layer -represents- a flat surface&quo= t;. To the software, a layer is really just a collection of primitives that= can be operated on and are frequently exported together.

A Group is a collection of properties, attributes and objects on
multible layers.

=C2=A0 Librecad used the term "Block"
=C2=A0 Inkscape uses the term "Group"

Let me point out that Inkscape also has the concept of layers. The= Inkscape concept of a group is more like what pcb would call a footprint/p= attern, with the exception that Inkscape groups are restricted to a single = layer. Creating an Inkscape group brings all of the grouped objects into th= e same layer. I've actually found that to be really annoying on multipl= e occasions. Believe it or not, I've actually laid out a board with Ink= scape...

I think that perhaps one sticking poi= nt may be that in the concept of layer that I have presented, an individual= primitive can be in multiple containers. A circular piece of copper could = be in a group/pattern container (e.g. a component footprint) and also in a = layer container. You would be able to access the primitive from either cont= ainer.

I don't think there should be a "buried-via" property.= =C2=A0 I don't think

those should be attached to the pads.

I agree. A buried via is just a collection of objects on par= ticular layers and a hit on a particular drill layer.

We export a plated-drill file.=C2=A0=C2=A0

In other software packages, I have always exported just a drill file,= and the board house determines if it should be plated based on the presenc= e of copper pads around it.

We should have a layer that corresponds
to the geometry exported in that file. And we be able draw on them (in
expert mode).

Yes, I completely agree. You could even have multiple drill = layers if you wanted to. For example, a drill layer for the top side, a dri= ll layer for the bottom side, and drill layers for any or all inner layers.= This could be useful in implementing blind/buried vias.

The drill-layers are marked as such with a property that is hardwired to the code that handled connectivity.

I would = try to keep connectivity and geometry separate if possible.

<= br>

Geometry and connectivity needs to be hardwired in the core data
structures. That is the core of what is needed to be efficient while
drawing.

Ultimately a layout tool is a connectivity aware drawing pac= kage, although some would argue that the connectivity awareness is optional= . You certainly -can- layout a board without net lines, but I think many if= not most board designers find them quite useful.

The via editor will help the user to define all required via layers

and apply designrules that test for manufacturability.

I would just say footprint/pattern editor. A via is really = no different from a footprint/pattern when it comes down to it.=C2=A0
<= /div>

--Chad

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