[whatwg] Canvas - Exception on arc with negative radius

Dirk Schulze vbs85 at gmx.de
Sun Mar 29 11:34:29 PDT 2009

Am Freitag, den 27.03.2009, 13:44 -0700 schrieb Martin Atkins:
> Dirk Schulze wrote:
> > 
> > Another example is: http://blahbleh.com/molecools.php?name=1,2%
> > 20dimethylcyclopropane
> > 
> > If you turn the molecule a bit, the circles disappear with a
> > INDEX_SIZE_ERR exception.
> > 
> > Isn't it better to just ignore the arc and go on with the drawing, like
> > Firefox does? And perhaps the same for arcTo?
> > 
> Assuming that we desire a "do what I mean" approach, it seems sane to me 
> for a negative radius to be normalized to a positive radius with the 
> same magnitude.
> It goes from being the distance from the center to the edge to being the 
> distance from the center to the "opposite" edge.
> You might also like to visualize this as drawing the "back" of the circle.

A negative value doesn't mean, that you want an arc. They can happen
during the automatic calculation process. There is no reason, that a
developers takes negative values and wants to see an arc otherwise he
could cut of the sign.
I'm just speaking of ignoring negative arcs instead of giving an
exception to continue further drawings.


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