[whatwg] Canvas - Exception on arc with negative radius

Martin Atkins mart at degeneration.co.uk
Fri Mar 27 13:44:12 PDT 2009

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.

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