Unit
data class UnitBezier(val x1: Double = 0.0, val y1: Double = 0.0, val x2: Double = 0.0, val y2: Double = 0.0)
A timing curve from (0, 0) to (1, 1), with the control points (x1, y1) and (x2, y2).
x1 and x2 are between 0 and 1.
See mln_unit_bezier in the C API reference.