[whatwg] Canvas arcTo method

Michael Day mikeday at yeslogic.com
Mon Aug 20 21:24:59 PDT 2012

Hi Rik,

> Yes you can go to absolute canvas coordinates but you need to remember
> that the radius is transformed too.

You cannot transform the three control points, and then generate the 
arc. If you do this, you will always get circular arcs, whereas a 
scale(2, 1) will produce an elliptical arc. You have to generate the 
arc, then scale it.

> I am sure that it's supposed to work. Do you have an example where this
> is not the case? (Maybe you're using PDFL?)

This is getting off-topic, but in the PDF 1.7 specification, section 4.1 
"Graphics Objects", it states that inside a path object the only allowed 
operators are the path construction operators, followed by the path 
painting operators. This does not include page description level 
operators that change the graphics state, such as the transformation.



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