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Subject: Re: [geda-user] The nature of gEDA layers
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From: John Griessen <john AT ecosensory DOT com>
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Date: Thu, 28 Jan 2016 09:44:19 -0600
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On 01/28/2016 07:59 AM, Chad Parker (parker DOT charles AT gmail DOT com) [via geda-user AT delorie DOT com] wrote:
>     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.
>
>     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 package, 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 connectivity and geometry are interdependent.  If you move a layer up the stack, what is adjacent changes and some of the 
netlist/ratlines data is now stale.  That data can be updated and reconciled by running DRCs usually. Since we almost always use
netlist/ratlines data and DRCs, the connectivity doesn't really NEED to be in core data structures -- it can be an attribute 
associated with a trace or pad's unique ID.

One thing needed in core data structures is room for and a mechanism for a unique ID for each atomic board element such as
trace, pad, polygon, text...

Which brings us to text.  Should text be a separate type of atomic board element still?  With fonts to swapping out?
Could it reduce to a small bitmap and the idea of text and fonts be handled at a higher abstraction level in the code?

What about bitmaps?  Allow them to be made from square pixels of arbitrary size, or only from other bits of trace atomic board 
elements?