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Date:	Mon, 25 Jan 2016 20:46:00 +0100
From:	"Bert Timmerman (bert DOT timmerman AT xs4all DOT nl) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
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To:	geda-user AT delorie DOT com
Subject:	Re: [geda-user] pcb_fprintf mixes mm and mils for same output object
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Reply-To:	geda-user AT delorie DOT com

Britton Kerin (britton DOT kerin AT gmail DOT com) [via geda-user AT delorie DOT com] wrote:
> This code:
>
>        pcb_fprintf (FP, "\tArc[%mr %mr %mr %mr %mr %mr %ma %ma %s]\n",
>                         arc->X, arc->Y, arc->Width,
>                         arc->Height, arc->Thickness,
>                         arc->Clearance, arc->StartAngle,
>                         arc->Delta, F2S (arc, ARC_TYPE));
>
> outputs this:
>
>        Arc[176.6100mm 926.41mil 86.38mil 86.38mil 0.1540mm 0.3080mm -90 -90 ""]
>
> It looks intentional.  The culprit code is in CoordsToString():
>
>      /* Check our freedom in choosing units */
>      if ((allow&  ALLOW_IMPERIAL) == 0)
>        family = METRIC;
>      else if ((allow&  ALLOW_METRIC) == 0)
>        family = IMPERIAL;
>      else
>        {
>          int met_votes = 0,
>              imp_votes = 0;
>
>          if ( coord[0] == 23530814 ) {
>            printf ("%s:%i:%s: checkpoint\n", __FILE__, __LINE__, __func__);
>          }
>
>          for (i = 0; i<  n_coords; ++i)
>            if(min_sig_figs(COORD_TO_MIL(coord[i]))<
> min_sig_figs(COORD_TO_MM(coord[i])))
>              ++imp_votes;
>            else
>              ++met_votes;
>
>          if (imp_votes>  met_votes)
>            family = IMPERIAL;
>          else
>            family = METRIC;
>        }
>
> So we're voting based on sig figs to decide whether to use metric or
> imperial units.  I wouldn't do this for the disk file format, if
> anywhere.  I guess maybe the intention was to maintain exactness in
> case some objects were created with mil sizes and some with metric but
> it's not worth it.
>
> There are other format codes besides %mr that force either metric or
> imperial.  I think for file format one of those should be used, or
> else plain ints in the internal unit (nm).  Fixing this is a file
> format change though so I though I'd ask if there's any appetite for
> or strong aversion to it.
>
> Britton
>
>    
Hi Britton,

A nice find.

I for one would like to hear the rationale for implementing in this way, 
best from the author (if possible) of the code under review.

Kind regards,

Bert Timmeman

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