Re: gEDA-user: Polygon islands in PCB

[Dave N6NZ <n6nz@xxxxxxxx>]

Ben Jackson wrote:
> On Tue, Aug 26, 2008 at 11:21:47PM -0700, Dave N6NZ wrote:
>> Is there some trick I don't know for insetting a smaller rectangle 
>> inside a larger one that gives me automatic clearance?
> 
> Sure, draw an enclosed box with traces (not connected to anything).  The
> hole will be removed.  The trace (which is probably harmless, but might
> accidentally be some kind of great waveguide antenna at some wavelength)
> will still be there.  The rule for that is that the largest part of the
> polygon will remain (you can see this if you just draw a rectangle and
> slice it in half with a line).  If your hole is big enough, constructing
> other polys to fit is your only hope.

So, I thought briefly of doing exactly that trick.  But I didn't want a 
floating trace.  I suppose you could do it twice -- once with "new lines 
clear poly" and then do another set of tracks overlapping the outer 
track by the min-overlap rule with "new lines clear poly" set to off. 
Then the inside that the island poly could touch the non-clearing line. 
  Kind of a hassle.

In the end, for the design I was working on the island was small enough 
that I just set a track width to 75 mil and did my own poly fill with 
that.  Works OK for small islands, would get tedious for large ones.

> 
> The easiest way to add this feature might be to have a tool which slices
> a polygon for you to make holes, rather than an element that clears
> polygons but is otherwise invisible (?).
> 

So, why is it hard to have poly clear poly?  That may be a dumb question 
since I don't know the internals of PCB... They would have to be drawn 
in the correct order, of course.  But I could see a simple dialog that 
contains a list of net names associated with polygons.  Drag the names 
up/down the list to adjust order.  Personally, I would set it up so the 
one at the top of the list is drawn last, clearing anybody it is drawn 
on top of.

While we're talking about polygons... I always seem to need to tweak the 
corners and the easiest way is to bring up vi and hand edit.  Is there 
some nice polygon editing function I'm not aware of?  If not, I'd 
suggest an "edit polygon" tool that lit up grabbers at polygon corners 
which then became the only thing the select tool would be sensitive to.

-dave


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