Re: gEDA-user: Recap of remaining metric-conversion work

[Andrew Poelstra <asp11@xxxxxx>]

On Sat, Jul 23, 2011 at 06:47:23PM +0100, Peter Clifton wrote:
> On Sat, 2011-07-23 at 19:38 -0700, Andrew Poelstra wrote:
> > 
> > Anyway, here are the commits I have made but not pushed:
> > 
> >   1. Introduce Coord and Angle units, set a bunch of BDimension,
> >      LocationType and int variables in global.h to one of these.
> >      Convert pcb-printf to use these (including adding %ma spec
> >      to print angles).
> 
> Oops, I've just been playing with the grid snap code and no doubt
> introducing additional uses of "LocationType" which you will need to fix
> up.
> 
> Any chance you could push this one ASAP, or does it cause regressions?
>

This causes no regressions, though if you are playing with grids
you may need commit #2 below, which does cause regressions.

In any case, I will push the first commit so that others will have
the Coord and Angle units for their work.
 
> >   2. Convert grid units to Coord. Set mm/mil autodetect code to
> >      look for multiples of 127nm (see bug lp-811393), though I
> >      doubt this will work properly with cmil base units.
> 
> Unlikely I would imagine.
> 
> >   3. Add scale-factor lookup functions to pcb-printf and make
> >      GetValue use this instead of its own table. Now there is
> >      only one table of units, in pcb-printf.c, and everything
> >      should be using it.
> >
> >   4. Upgrade unit structures in pcb-printf. Now units have a
> >      "real" suffix that pcb uses internally and in file.c, and
> >      an internationalized copy of the same suffix.
> 
> Is there any use-case for I18N suffixes? I would imagine units are
> pretty much universal and language agnostic - unless you are spelling
> them out, e.g. "mètre" (French) vs. "metre" (English) /
> "meter" (American).
> 

The Gtk GUI uses _("mm") and _("mil") in its current code. I
did not want to change this, so I internationalized all the units.

Whether there is any actual justification, I don't know.

> > In principle, just audits. The ones I have done so far have been quick
> > and easy, essentially just replacing LocationType/BDimension with Coord,
> > using Angle, using NormalizeAngle() and Distance() instead of repeating
> > code. Nothing deep.
> > 
> > I may even have been done by now except that when auditing search.c, I
> > found the arc-intersection problems that lead to a recent long thread
> > on this board. When I get a free moment (probably not till tomorrow) I
> > will just post a bug report and move on, "fixing" the unit handling
> > without fixing the actual algorithm.
> 
> Always *BLEEPING* arcs which cause grief. If you could describe a
> perfect circle with B-Splines, I would be up for killing the "arc"
> primitive and replacing it with something a little more robust (unique)
> in how it may be defined.
> 

I think we need to convert stretched arcs to elliptical arcs internally
when reading files to avoid angle inconsistencies, and link in a proper
mathematical library to look for distances and intersections.

That would probably eliminate a lot of grief beyond this one problem.

But I also think that is a project for another day, unless we can find
a volunteer to work on it...

> > I expect that aside from that, everything left will be easy. I just need
> > to spend some time and git'er'done.
> > 
> > After all the source has been audited, I can commit the small changes to
> > const.h that actually do the conversion. Then I'll push and you guys can
> > jump on me for all the bugs I've caused.
> 
> I'm looking forward to opening my "mm" designs with a "mm" grid and not
> chasing lost of off-grid gremlins ;)
>

As am I :)
 
> Let me know if I can be of any help.
> 

-- 
Andrew Poelstra
Email: asp11 at sfu.ca OR apoelstra at wpsoftware.net
Web:   http://www.wpsoftware.net/andrew/



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