Expose Fit Internals

[curran]

Faced with the task of adding fit methods to geo-albers-usa-territories , I'm a bit stuck.

Ideally I could follow the pattern found in albersUsa.js, namely

import {fitExtent, fitSize, fitWidth, fitHeight} from "./fit.js";

However, since the projection is not inside this repository, and those internals from fit.js are not exported from the top level of this package, I see no way to access them. Am I missing an approach that would work?

FWIW I did try

import { fitExtent, fitSize, fitWidth, fitHeight } from 'd3-geo/src/fit.js';

But that feels janky, and caused some headaches with Rollup (here's what I tried, for reference).

I propose to export these methods from the d3-geo package, for use by projections defined outside this project.

Thoughts?

[curran]

That might look something like adding the following to index.js:

(long names as this is probably a rare use case, and because these will end up on d3 itself)

export {
  fitExtent as geoProjectionFitExtent,
  fitSize as geoProjectionFitSize,
  fitWidth as geoProjectionFitWidth,
  fitHeight as geoProjectionFitHeight
} from "./projection/fit.js";

Then in the externally defined projection I could say:

import {
  geoProjectionFitExtent as fitExtent,
  geoProjectionFitSize as fitSize,
  geoProjectionFitWidth as fitWidth,
  geoProjectionFitHeight as fitHeight
} from 'd3-geo';

[Fil]

An alternative approach would be to finally offer a composite projections construct, that would deal with all the peculiarities (clipping, inverse, etc).

[curran]

Interesting idea! Were there already discussions along the lines of a composite projections construct?

More sleuthing reveals another approach, though not sure if this is applicable https://github.com/d3/d3-geo-projection/blob/master/src/gilbert.js#L37

Maybe I could just say

  property("fitExtent");
  property("fitHeight");
  property("fitSize");
  property("fitWidth");

[curran]

Considering submitting a PR with the change to expose these.

[Fil]

It looks like @HarryStevens has an alternative here https://observablehq.com/@washpostgraphics/geo-albers-usa-pr

[HarryStevens]

It looks like @HarryStevens has an alternative here https://observablehq.com/@washpostgraphics/geo-albers-usa-pr

Yep, I just kept copy-pasting code from d3-geo until it stopped throwing errors.

[nthitz]

apologies slightly off topic, but any chance of publishing https://observablehq.com/@washpostgraphics/geo-albers-usa-pr to npm for easier use off of observable?