MapLabels.svg.svelte component

<!--
  @component
  Adds SVG text labels based features in the data or a custom GeoJSON Feature Collection.
 -->
<script>
  import { getContext } from 'svelte';

  const { data, width, height } = getContext('LayerCake');

  /** @type {Function} projection - A D3 projection function. Pass this in as an uncalled function, e.g. `projection={geoAlbersUsa}`. */
  export let projection;

  /** @type {Function} getLabel - An accessor function to get the field to display. */
  export let getLabel;

  /** @type {Number} [fixedAspectRatio] - By default, the map fills to fit the $width and $height. If instead you want a fixed-aspect ratio, like for a server-side rendered map, set that here. */
  export let fixedAspectRatio = undefined;

  /** @type {Function} [getCoordinates=d => d.geometry.coordinates] - An accessor function to get the `[x, y]` coordinate field. Defaults to a GeoJSON feature format. */
  export let getCoordinates;

  /** @type {Array} [features] - A list of labels as GeoJSON features. If unset, the plotted features will defaults to those in `$data.features`, assuming this field a list of GeoJSON features. */
  export let features = undefined;

  $: fitSizeRange = fixedAspectRatio ? [100, 100 / fixedAspectRatio] : [$width, $height];

  $: projectionFn = projection()
    .fitSize(fitSizeRange, $data);
</script>

<g class="map-labels">
{#each (features || $data.features) as d}
  {@const coords = projectionFn(getCoordinates(d))}
  <text
    class="map-label"
    x="{coords[0]}"
    y="{coords[1]}"
  >{getLabel(d)}</text>
{/each}
</g>

<style>
  .map-labels {
    pointer-events: none;
  }
  .map-label {
    color: #333;
    /**
     * If you render this in an ScaledSvg layout component, you'll
     * want to make this like 1px bc it's actually being zoomed by about 10x
     */
    font-size: 8px;
    text-anchor: middle;
  }
</style>