Exception is raised when intervalXY is used on cells

[RyanChapman2x]

The underlying issue is that the invert.js code expects a scale.invert function. But cell marks use d3.scaleBand, which doesn't have a invert function. Here's a quick monkeypatch/proof-of-concept fix (I don't make any adjustments for pixelSize; also note that this won't work if the domain isn't sorted low to high):

invert.js

export function invert(value, scale, pixelSize = 1) {
  if (scale.type == 'band') {
    return Math.round(( (value - scale.range[0]) / (scale.range[1] - scale.range[0]) ) * (scale.domain.slice(-1) - scale.domain[0]));
  } else {
    return scale.invert(pixelSize * Math.floor(value / pixelSize));
  }
}

[jheer]

Thanks! And, yes, this is a known limitation. Interval interactors are currently only valid over a continuous domain.

Long ago in Vega I implemented inversion methods for ordinal band and point scales, but they were not accepted into D3 and so unfortunately not available by default here, either. We could consider bringing custom logic into the interval implementation, assuming we can properly accept the scale type. Or, at minimum, we should check the scale type and proactively raise helpful error messages.