[LSC] Ambiguities in the draft BFC spec

[Lars C. Hassing]

William Howard wrote:
> To address point 1, I would like to see the syntax definition changed to
>     0 BFC NOCERTIFY
>     0 BFC CERTIFY [CW|{CCW}]
>     0 BFC [CLIP|NOCLIP] [CW|CCW] [INVERTNEXT]
> where [] indicates an optional item and {} the default value

We might event change it to
     0 BFC NOCERTIFY
     0 BFC CERTIFY [CW|{CCW}]
     0 BFC CLIP|NOCLIP
     0 BFC CW|CCW
     0 BFC INVERTNEXT
since I don't think it gives much sense specifying the last three together.
Maybe "CLIP CW" would make sense, but NOCLIP doesn't fit with any.
Even if "CLIP CW" could be fine, it would be no big deal to specify them on two lines.


> What does "0 BFC" mean (it's valid syntax, so it must mean something)?

No longer an issue with the above change.


> Do we need to explicity state that the CERTIFY/NOCERTIFY variants of the BFC
> meta-commands  must occur before any "Operational Command-Lines"?

I think it already say so in the first section,
but no harm to explicitly state it.


> And what to do about point 2?  If rendering tools can cope with changes in
> winding within a file should we care if parts are singularly wound?

I think it should be allowed to change winding.
Some part of a part may be easier to write in a certain winding,
e.g. if you do some hand-crafted mirroring.
/Lars