Hide empty facets?

[mbostock]

E.g., here:

It’s relatively easy to do this for marks, but it’ll be a little more work to do it for grid lines.

[Fil]

I suppose this should be an option?

For the mark, it seems that it's just a matter of testing if (marksIndexByFacet.has(key)) in

plot/src/facet.js

Line 108 in 4dd62d2

for (let i = 0; i < marks.length; ++i) {

(reference: 96ad3fe )

For the grid lines, I'm struggling to find a solution that would use only a marginal change. The correct solution might be to move the grid lines from the axes' render loop to the facets'.

[mbostock]

Fixed in #516.