- From: Justin Novosad <junov@google.com>
- Date: Mon, 17 Mar 2014 11:45:05 -0400
- To: Dirk Schulze <dschulze@adobe.com>
- Cc: WHATWG List <whatwg@whatwg.org>, Ian Hickson <ian@hixie.ch>
On Mon, Mar 17, 2014 at 11:35 AM, Dirk Schulze <dschulze@adobe.com> wrote: > > > Hmmm, I gave this a bit more thought... To apply the construction > > algorithm in transformed space, the ellipse parameters (radiusX, radiusY, > > rotation) would have to be transformed. Transforming the parameters would > > be intractable under a projective transform (e.g. perspective), but since > > we are limitted to affine transforms, it can be done. Now, in the case > of > > a non-invertible CTM, we would end up with radiusX or radiusY or both > equal > > to zero. And what happens when you have that? Your arcTo just turned > into > > lineTo(x1, y1). Tada! > > Why does radiusX or radiusY need to be zero? Because you define it that > way for a non-invertible matrix? That makes sense for scale(0,0). What > about infinity or NaN? If Ian didn’t update the spec then this is still > undefined and therefore up to the UA to decide. > > Oh yeah, I was totally forgetting about singularities caused by non-finite values. Could we just the same agree to resolve that case by treating arcTo as lineTo(x1, y1) in the case of a non-invertible CTM? Or do you think there is a more logical thing to do?
Received on Monday, 17 March 2014 15:53:36 UTC