Re: gEDA-user: General Layers questions

[Stephan Boettcher <boettcher@xxxxxxxxxxxxxxxxxx>]

DJ Delorie <dj@xxxxxxxxxxx> writes:

>> But at the core, they work all just the same.
>
> The "core" includes the autorouters, optimizers, DRC, exporters,
> reports, and even simple editing - we have a "hide vias" button.  How
> does that work if you no longer have "vias" as an inherent type?

Hide all composites with attribute "type=via".  The GUI probably
maintains an extra list of those, as well as a list of elements, for
performance.

The autorouter is told to route on all enable conductive layers, and
choose from a set of selected vias to go between those layers.

Exporters can only export what they know about.  All layers can be
turned into gerbers.  More complicated exports may need a technology
description, like an advanced concept of the current layer groups. An
exporter shall define a set of attibutes it expects to find on layers
and objects to do its special deeds, and those attribute shall not be
overloaded attributes that the core tool needs.

> PCB has a lot of tools that know a lot about how PCBs are designed.
> These tools are essential to making PCB a viable layout editor.  The
> input we need at this stage is from people who design a lot of PCBs,
> so we know what kinds of abstractions make sense to expose and what
> kinds need to be hidden behind other data structures.

At the bottom, a layout is a set of layers with attributes, containing
shapes, maybe with attributes.

The semantics of those attributes is what encapsulates the builtin
knowledge how to make PCBs, and the tool must fully exploit that
knowledge when presenting a layout to the user.

When we morph the current pcb towards such an abstract layer concept,
the user shall not see the difference unless she activates the new
features that become available with these concepts.

> Maybe to the rendering engines they all work the same, but saying
> "they all work the same" *in general* just isn't applicable here.
> They don't.

-- 
Stephan


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