SVG paths: parsing NaN and Infinity

[nicoburns]

Allows paths like M0,0 L0,0 L90,0 LNaN,NaN to be parsed. This is useful for deserializing paths encoded in AnyRender serialized scenes. Otherwise deserializing panics.

(one might argue that we ought to strip NaN's and Infinity's from scene's, but we may also want to specifically test for them, so I think it is best to at least have the capability to preserve them)

[jneem]

I went to see if the svg spec had anything to say about this, but AFAICT the grammar doesn't even mention decimal points? Although the paragraph after the grammar clearly assumes that they're in there 😕

[raphlinus]

This doesn't feel right to me, I would consider non-finite values to be invalid. I think ideally deserialization should fail but not panic.

I confirm @jneem's observation, the SVG 2 "spec" is obviously defective. However, SVG 1.1 has a clear grammar in which these would be rejected.

[nicoburns]

I've vendored a copy of kurbo's path parsing code into anyrender_serialize. So I guess if this is a "no" then we should just close it.