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Date: Wed, 13 May 2015 17:37:03 -0400
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From: DJ Delorie <dj AT delorie DOT com>
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Subject: Re: [geda-user] Free rotate and exported centroid (XY) file question
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> So a part's rotation from its initial positioning is not a separately
> stored parameter,

Right, this is the root cause of the limitation.  We've contemplated
putting in a native center/angle but haven't yet.  It would solve a
few problems, but any change in the file format has its drawbacks, and
it's difficult to know how to "migrate" old designs as you see and
edit them.

> The obvious question now is if there's a relatively easy way to get the
> correct angle definitions for free-rotated parts in the XY file.

If you go by the IPC spec, there's no way to know the *starting* angle
of the footprint when you load it, aside from some "rules of thumb".
Otherwise, you could re-load the original footprint and compare pin
orientations to try to guess, I suppose.

Or, you could hack in something to keep a rotation attribute around,
and update it as needed.  Attributes don't need file format changes at
least.

> Anyway, thank you again for your explanation. Things like this remind me
> why open source can so very pleasant to work with.

Heh.  Try getting such an explanation out of Microsoft ;-)