Scatter.canvas.svelte component

<!--
  @component
  Generates a canvas scatter plot.
 -->
<script>
  import { getContext, onMount, untrack } from 'svelte';
  import { scaleCanvas } from 'layercake';

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

  const { ctx } = getContext('canvas');

  /**
   * @typedef {Object} Props
   * @property {number} [r=5] - The circle's radius.
   * @property {string} [fill='#0cf'] - The circle's fill color.
   * @property {string} [stroke='#000'] - The circle's stroke color.
   * @property {number} [strokeWidth=1] - The circle's stroke width.
   */

  /** @type {Props} */
  let { r = 5, fill = '#0cf', stroke = '#000', strokeWidth = 1 } = $props();

  onMount(() => {
    $effect(() => {
      if ($width && $height) {
        untrack(() => {
          if (!$ctx) return;

          /**
           * If you were to have multiple canvas layers
           * maybe for some artistic layering purposes
           * put these reset functions in the first layer, not each one
           * since they should only run once per update
           */
          scaleCanvas($ctx, $width, $height);
          $ctx.clearRect(0, 0, $width, $height);

          /**
           * Draw our scatterplot
           */
          $data.forEach((/** @type {any} d */ d) => {
            $ctx.beginPath();
            $ctx.arc($xGet(d), $yGet(d), r, 0, 2 * Math.PI, false);
            $ctx.lineWidth = strokeWidth;
            $ctx.strokeStyle = stroke;
            $ctx.stroke();
            $ctx.fillStyle = fill;
            $ctx.fill();
          });
        });
      }
    });
  });
</script>