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To: geda-user AT delorie DOT com
Subject: Re: [geda-user] gschem and metric sizes for symbols
In-reply-to: <20130630045911.22b7bbe8@warrawoona.sti>
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Comments: In-reply-to Alexey Shaposhnikov <avshap AT nerdshack DOT com>
   message dated "Sun, 30 Jun 2013 04:59:11 +0600."
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Message-Id: <20130630111548.4B71E8043961@turkos.aspodata.se>
Date: Sun, 30 Jun 2013 13:15:48 +0200 (CEST)
From: karl AT aspodata DOT se (Karl Hammar)
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Alexey Shaposhnikov:
> I'm trying to do ESKD (exUSSR standards for design documentation and
> technical drawing)-compliant symbols for gschem and encountered with such
> problem: in ESKD are using metric sizes for graphical symbols, so place
> components pins on 100 mils grid either difficult (for something like JFET
> symbol: http://i.imgur.com/b2P56qH.png) or practically impossible (for trimming
> resistor symbol: http://i.imgur.com/ZGbXqav.png)
> 
> So i must either use a custom grid size (40 mils) with scale 100 points = 2,5mm
> or recompile gEDA because at scale 100 points = 1 mm hardwired sizes for
> pins, nets and junctions became too small.
> 
> Is there exist a more elegant solution?

As a few other have said, the gschem unit is considered to arbritary.

==

There is one flaw in that thinking, since fonts are specified in points,
and fonts at different pointsizes don't look the same when you scale
them. So my opinion on the matter is that if you care about how things look
on paper, then 100 units = 2.54mm (but 2.5mm would be acceptable).

I don't know if that is relevant, gschems only font might be of
the dumbly scaling type.

==

Another flaw in that thinking is that you cannot possible scale a
drawing arbitrarily to make it readable.

When shrinking, I believe you cannot shrink a .sch more than 4 or
possible 8 times, else the symbols would be to small be readable.
I haven't tested the upper limit, but I think a .sch printed out
unscaled would have a little too big symbols.

I found out when doing my xfig to sym converter:
 http://www.delorie.com/archives/browse.cgi?p=geda-user/2013/04/27/18:57:38
that a scaling factor of about 4 is needed when converting a fig file to
sym.

==

So in essence there is a loose gschem to mm or inch relationship
with a possible span of perhaps 1:4.

///

Due to a DIN-standard, we in Europe are using the linewidths (mm)
0.12, 0.18, 0.25, 0.32, 0.5, 0.7, 1, 1.2 in technical drawings.

It would correspond to gschem sizes:

0.12 0.47
0.18 0.72
0.25 0.98
0.32 1.26
0.50 1.99
0.70 2.76
1.00 3.94
1.20 4.72

So gschem in the present state is not suitable for this, nor your
application.

///

I would like to be able to put nice looking schematics in ring
binders, A4, folded A3 etc in my case.

To that end I would like the following:

. be able to specify text font
. be able to measure and see distances in the drawing widget
. have the cap-styles back wich was recently removed
. have the "path" directive obey the cap-style
. have a (optional?) fixed scaling between gschem and paper
. have the possibility to specify whan 1 unit is in mm/inch
. sym's designed for that scaling

and possible a lot other stuff.

And it would be good to merge our different sym-file generators
and put that inside the repository.

///

I'm currently wound up in a lot of dreadful non technical issues,
like that the former state tv company wants everybody with a computer
to pay tv-licence fees, and that in spite you can prove that you
cannot see their so called broadcasts on the internet.

Well, my gschem work has stalled...

Regards,
/Karl Hammar

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