Incorrect axes merging rule for facet of facet

[kanitw]

{
  "$schema": "https://vega.github.io/schema/vega-lite/v2.json",
  "data": {"url": "data/cars.json"},
  "facet": {"row": {"field": "Origin","type": "ordinal"}},
  "spec": {
    "facet": {"row": {"field": "Cylinders","type": "ordinal"}},
    "spec": {
      "mark": "point",
      "encoding": {
        "x": {"field": "Horsepower","type": "quantitative"},
        "y": {"field": "Acceleration","type": "quantitative"}
      }
    }
  }
}

X-Axis should be shared for all of the facets

[domoritz]

Column of column leads to Error: Unrecognized signal name: "undefined"

{
  "$schema": "https://vega.github.io/schema/vega-lite/v2.json",
  "data": {"url": "data/cars.json"},
  "facet": {"column": {"field": "Origin","type": "ordinal"}},
  "spec": {
    "facet": {"column": {"field": "Cylinders","type": "ordinal"}},
    "spec": {
      "mark": "point",
      "encoding": {
        "x": {"field": "Horsepower","type": "quantitative"},
        "y": {"field": "Acceleration","type": "quantitative"}
      }
    }
  }
}

[domoritz]

Here is another example we should support.

Facet of facet where the inside facet uses a shared y scale but every row uses a different scale.

{
  "data": {"url": "https://vega.github.io/vega-lite/examples/data/cars.json"},
  "transform": [{
    "filter": "year(datum.Year) > 1977"
  }],
  "facet": {
    "row": {"type": "nominal", "field": "Origin"}
  },
  "spec": {
    "facet": {
      "column": {"type": "ordinal", "field": "Year"}
    },
    "spec": {
      "mark": {"type": "circle", "size": 60},
      "encoding": {
        "color": {"type": "nominal", "field": "Origin"},
        "x": {"type": "quantitative", "field": "Horsepower"},
        "y": {"type": "quantitative", "field": "Miles_per_Gallon", "scale": {"zero": false}}
      },
      "height": 100,
      "width": 100
    },
    "resolve": {"scale": {"y": "shared"}}
  },
  "resolve": {"scale": {"y": "independent"}},
  "$schema": "https://vega.github.io/schema/vega-lite/v4.json"
}

Right now, this produces

[nmaar]

Hello, here is a summary of issue #7407.

In the current version of vega lite, multiple axis are displayed in the case of a facet of a facet:

Facet of facet visualizaitons will improve if one (shared) axis is displayed, like the following Tableau example.

Currently this issue has a P4 "nice to have" label.
I can't estimate how much work it is (or even possible) to implement a common axis.
But (if possible) I suggest implementing this feature would expand the possibilities of vega lite greatly.

nmaar

[bigfacewo]

Are there any updates or plans regarding this issue?