QuadTree.percent-range.html.svelte component

<!--
  @component
  Creates an interaction layer (in HTML) using [d3-quadtree](https://github.com/d3/d3-quadtree) to find the nearest datapoint to the mouse. This component creates a slot that exposes variables `x`, `y`, `found` (the found datapoint), `visible` (a Boolean whether any data was found) and `e` (the event object). This component works with a percent range so the `x` and `y` values coming back will be percentages.

  The quadtree searches across both the x and y dimensions at the same time. But if you want to only search across one, set the `x` and `y` props to the same value. For example, the [shared tooltip component](https://layercake.graphics/components/SharedTooltip.html.svelte) sets `y='x'` since it's nicer behavior to only pick up on the nearest x-value.
 -->
<script>
  import { getContext } from 'svelte';
  import { quadtree } from 'd3-quadtree';

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

  let visible = false;
  let found = {};
  let e = {};

  /** @type {String} [x='x'] - The dimension to search across when moving the mouse left and right. */
  export let x = 'x';

  /** @type {String} [y='y'] - The dimension to search across when moving the mouse up and down. */
  export let y = 'y';

  /** @type {String} [searchRadius] - The number of pixels to search around the mouse's location. This is the third argument passed to [`quadtree.find`](https://github.com/d3/d3-quadtree#quadtree_find) and by default a value of `undefined` means an unlimited range. */
  export let searchRadius = undefined;

  /** @type {Array} [dataset] - The dataset to work off of—defaults to $data if left unset. You can pass something custom in here in case you don't want to use the main data or it's in a strange format. */
  export let dataset = undefined;

  $: xGetter = x === 'x' ? $xGet : $yGet;
  $: yGetter = y === 'y' ? $yGet : $xGet;

  function findItem (evt) {
    e = evt;

    const xLayerKey = `layer${x.toUpperCase()}`;
    const yLayerKey = `layer${y.toUpperCase()}`;

    const xLayerVal = (evt[xLayerKey] / (x === 'x' ? $width : $height)) * 100;
    const yLayerVal = (evt[yLayerKey] / (y === 'y' ? $height : $width)) * 100;

    found = finder.find(xLayerVal, yLayerVal, searchRadius) || {};

    visible = Object.keys(found).length > 0;
  }

  $: finder = quadtree()
    .extent([[-1, -1], [$width + 1, $height + 1]])
    .x(xGetter)
    .y(yGetter)
    .addAll(dataset || $data);
</script>

<style>
  .bg {
    position: absolute;
    top: 0;
    right: 0;
    bottom: 0;
    left: 0;
  }
</style>

<div
  class="bg"
  on:mousemove="{findItem}"
  on:mouseout="{() => visible = false}"
  on:blur="{() => visible = false}"
></div>
<slot
  x={xGetter(found) || 0}
  y={yGetter(found) || 0}
  {found}
  {visible}
  {e}
></slot>