Boolean axis properties do not respond to expressions

[jwoLondon]

Expanding on #6962 none of the Boolean axis properties appear to respond to expressions. Here is a minimal example to illustrate the problem:

{
  "$schema": "https://vega.github.io/schema/vega-lite/v4.json",
  "params": [
    {"name": "domain", "value": true, "bind": {"input": "checkbox"}},
    {"name": "labels", "value": true, "bind": {"input": "checkbox"}},
    {"name": "tickExtra", "value": true, "bind": {"input": "checkbox"}},
    {"name": "tickRound", "value": true, "bind": {"input": "checkbox"}},
    {"name": "ticks", "value": true, "bind": {"input": "checkbox"}},
    {"name": "grd", "value": true, "bind": {"input": "checkbox"}}
  ],
  "data": {
    "url": "https://cdn.jsdelivr.net/npm/[email protected]/data/movies.json"
  },
  "encoding": {
    "x": {
      "field": "IMDB Rating",
      "bin": true,
      "type": "ordinal",
      "axis": {
        "domain": {"expr": "domain"},
        "labels": {"expr": "labels"},
        "tickExtra": {"expr": "tickExtra"},
        "tickRound": {"expr": "tickRound"},
        "ticks": {"expr": "ticks"},
        "grid": {"expr": "grid"}
      }
    },
    "y": {"aggregate": "count"}
  },
  "mark": "bar"
}

Of the 6 Boolean properties, only grid has no claim in the schema not to accept expressions (although it would be nice if it could).

domain, labels, tickExtra, tickRound and ticks all allow expressions, but have no effect.

Looking at the compiled Vega Spec, it looks like the axes are being specified twice, and only one of them carries all the expressions through as signals (but tickExtra and tickRound are included in both). Perhaps this is part of the problem?

Vega specification:

 "axes": [
    {
      "scale": "x",
      "orient": "bottom",
      "grid": {"signal": "grid"},
      "tickExtra": {"signal": "tickExtra"},
      "tickRound": {"signal": "tickRound"},
      "gridScale": "y",
      "domain": false,
      "labels": false,
      "aria": false,
      "maxExtent": 0,
      "minExtent": 0,
      "ticks": false,
      "zindex": 0
    },
    {
      "scale": "y",
      "orient": "left",
      "gridScale": "x",
      "grid": true,
      "tickCount": {"signal": "ceil(height/40)"},
      "domain": false,
      "labels": false,
      "aria": false,
      "maxExtent": 0,
      "minExtent": 0,
      "ticks": false,
      "zindex": 0
    },
    {
      "scale": "x",
      "orient": "bottom",
      "grid": false,
      "title": "IMDB Rating (binned)",
      "domain": {"signal": "domain"},
      "labels": {"signal": "labels"},
      "tickExtra": {"signal": "tickExtra"},
      "tickRound": {"signal": "tickRound"},
      "ticks": {"signal": "ticks"},
      "labelAlign": "right",
      "labelAngle": 270,
      "labelBaseline": "middle",
      "zindex": 0
    },
    {
      "scale": "y",
      "orient": "left",
      "grid": false,
      "title": "Count of Records",
      "labelOverlap": true,
      "tickCount": {"signal": "ceil(height/40)"},
      "zindex": 0
    }
  ]

[domoritz]

We specify axes twice because of a limitation in Vega. One of the axes is just for the gridlines and the other is for the rest. See vega/vega#1865 for details.

The fact that axes don't respond to signal changes looks like an issue with Vega.

@jheer I don't see an issue in the generated Vega. Please return the issue if Vega-Lite is at fault here. Maybe this is a delicate of vega/vega#286.

[jheer]

Some of the axis parameters simply do not support signal values, as those values are currently needed at compile time (part of the parsing and dataflow graph generation process). The Vega schema should indicate if signals are or are not supported, so I would check there. Any changes to make some of these properties dynamic may be possible, but likely would require some substantial engineering / refactoring effort.

[domoritz]

We should make sure to only support expr for properties that support it then.

[kanitw]

The schema will be updated in #7148