    path.closestPointLength(point [, opt])

Return the length of the path up to the point that lies closest to `point`.

Invisible segments (e.g. Moveto segments) have no length and are therefore skipped by the algorithm; if the path contains no visible segments, `0` is returned. If the path has no segments at all, `0` is returned.

The function finds a visible segment whose identified closest point lies at the lowest distance from `point`. It then determines the length of the path up to the identified closest point.

The `opt` argument is optional. Two properties may be specified, `opt.precision` and `opt.segmentSubdivisions`, which determine maximum error allowed in segment `closestPoint` calculations for curved segments (default precision is 3; this corresponds to maximum observed error of 0.1%). The `opt.segmentSubdivisions` property is an array of individual segments' subdivision arrays. The `path.getSegmentSubdivisions()` function may be used to obtain the `segmentSubdivisions` array. The `opt.precision` property is still necessary, however; it determines the precision of the point search algorithm in curved segments.