kicad-developers team mailing list archive

[Brian <lotharyx@xxxxxxxxx>]

On 11/14/19 5:20 PM, Kevin Cozens wrote:
> It is always possible to draw with four contraints if you were to use 
> center point, radius, start angle, end angle.
There are different sets of constraints from which to pick.  The set of 
four you described are indeed immune from self-inconsistency problems, 
but as such they don't answer the question of >180 or <180 sweep (unless 
again one uses an implicit constraint, e.g. always draw counterclockwise).

As I think about it, your suggested set is the minimal set, if one 
treats cartesian start/endpoints as two constraints each (i.e. start X, 
start Y, etc.).  I don't think there's a way to get away with fewer than 
five numbers, regardless of what those numbers represent.  I do remain 
convinced that no more than five are required to be unambiguous, 
alongside the "always travel CCW" rule (which one could call an 
externally-applied, or implicit, constraint).

As I was typing this, Avishay added:

> Kicad does not adhere to direction

Ah, I missed that nuance.  In that case yes, definitely there is 
ambiguity.  But I've never seen a symbol get drawn with a wrong arc, so 
how does it resolve the ambiguity?  Is it just dumb luck that I've never 
seen it happen?

Cheers,
-Brian