tabler/shared/ui/Signature.astro

---
import Icon from './Icon.astro'
import CaptureScript from '../components/CaptureScript.astro'

interface Props {
  id?: string
  class?: string
  clear?: boolean
  width?: number
  height?: number
  event?: string
  /** extra-js param — raw JS appended inside the init callback */
  extraJs?: string
}

const { id = 'default', class: className, clear, width = 400, height = 400, event = 'DOMContentLoaded', extraJs } = Astro.props

const signatureClass = ['signature position-relative', className]

const clearSnippet = clear
  ? `		document.querySelector(${JSON.stringify(`#signature-${id}-clear`)}).addEventListener("click", function () {
		  signaturePad.clear();
		});
`
  : ''

// extraJs is a documented escape hatch for raw JS (see Props) — not user data, so it
// stays interpolated verbatim rather than JSON-serialized.
const extraSnippet = extraJs
  ? `${extraJs}
`
  : ''

// set:html (below) is genuinely required here: extraJs is a documented raw-JS escape
// hatch that must land *inside* the init callback body (it references canvas /
// signaturePad), so the whole script has to be assembled as text — <script define:vars>
// can only inject variables, not splice caller-supplied code into the function body.
const script = `<!-- BEGIN SIGNATURE PAD -->
<script>
  document.addEventListener(${JSON.stringify(event)}, function () {
    const canvas = document.getElementById(${JSON.stringify(`signature-${id}`)});

    if (canvas) {
      const signaturePad = new SignaturePad(canvas, {
        backgroundColor: "transparent",
		  penColor: getComputedStyle(canvas).color
      });

${clearSnippet}
		function resizeCanvas() {
        const ratio = Math.max(window.devicePixelRatio || 1, 1);

		  console.log(canvas.offsetWidth, canvas.offsetHeight);

        canvas.width = canvas.offsetWidth * ratio;
        canvas.height = canvas.offsetHeight * ratio;
        canvas.getContext("2d").scale(ratio, ratio);
        signaturePad.fromData(signaturePad.toData());
      }

		window.addEventListener("resize", resizeCanvas);
		resizeCanvas();

${extraSnippet}
    }
  });
</script>
<!-- END SIGNATURE PAD -->`
---

<div class:list={signatureClass}>
  {
    clear && (
      <div class="position-absolute top-0 end-0 p-2">
        <div class="btn btn-icon" id={`signature-${id}-clear`} title="Clear signature" data-bs-toggle="tooltip">
          <Icon name="trash" />{' '}
        </div>
      </div>
    )
  }
  <canvas id={`signature-${id}`} width={width} height={height} class="signature-canvas"></canvas>
</div>
<CaptureScript>
  <Fragment set:html={script} />
</CaptureScript>