Heya, we at the SVGWG just resolved today to add equivalents for the CanvasPathMethods interface arc/ellipse/arcTo commands to the <path> element's syntax.
Ideally, we'd be able to use the same names as Path, for minimal confusion - "<path d='M0 0 arc 30 30 10 0 90 0'>" producing a line from (0,0) to (40,30), then a quarter-arc to (30,40). However, this is problematic for arcTo(), as it has both a 5-arg (for circular arcs) and a 7-arg (for elliptical arcs) version. For one, this is somewhat inconsistent with the pattern established by the existing arc() and ellipse() functions. For two, and worse for SVG, SVG typically allows you to omit the name of the path command if the immediately previous command was the same name. To do this, the command needs to have a constant number of arguments, so you can just split on every Nth arg. So, we're going to have to name the 7-arg version something different. The obvious answer is "ellipseTo". Could we change the CanvasPathMethods interface to do the same? To the best of my knowledge, no implementations exist yet for the 7-arg version, so there's no backwards-compat issues. ~TJ