Function reanchored 

pub fn reanchored(
    geometry: &RouteGeometry,
    anchors: &[(RouteLabelId, Pos2)],
) -> Vec<(RouteLabelId, FracVal)>

Each captured anchor re-projected onto the current geometry — the arc lengths a route edit commits. Re-projecting the same screen point keeps a horizontal label at the same X and a vertical one at the same Y (the perpendicular foot shares that coordinate).