fontc crashes on super bezier segments (3+ off-curve points before a curve)

[cmyr]

fontc rejects glyphs that contain "super bezier" segments (cubic curve segments with more than 2 consecutive off-curve control points). These exist in some sources, and are supported by fontmake.

python3 -m ttx_diff 'https://github.com/Omnibus-Type/Barrio?8f33bf10cb#Barriecito/sources/Barriecito.glyphs'

fontTools handles this via decomposeSuperBezierSegment in fonttools/Lib/fontTools/pens/basePen.py:389. When BasePen.curveTo receives more than 3 points (i.e. more than 2 control points), it decomposes the super bezier into multiple standard cubic bezier segments that together reproduce the same curve.

[rsheeter]

I see code for quads with lots of off-curves in

fontc/fontir/src/ir/path_builder.rs

Line 120 in 911eb9e

pub fn qcurve_to(&mut self, p: impl Into<Point>) -> Result<(), PathConversionError> {

... perhaps we're just missing the cubic equivalent?