pointerX can fail with faceting

[Fil]

as reported by @yurivish in https://observablehq.com/d/3264dbb558b44080, using pointerX (e.g. to browse faceted timelines) fails when the facets are aligned vertically can in some cases feel “wrong”.

minimal repro:

Plot.lineY(industries, {
  x: "date",
  y: "unemployed",
  fx: (d) => d.date.getDay(),
  fy: (d) => d.date.getFullYear(),
  stroke: "industry",
  tip: true
}).plot()

Enregistrement.de.l.ecran.2023-08-01.a.11.37.39.mov