Allow embedding a sveltekit page as a widget in a third party website

[unlocomqx]

Implements #13589

This (draft) PR brings the possibility to embed a sveltekit page as a widget in a third party website in a convenient manner.

It's just a proof-of-concept, showing how easy (or how hard) it is to implement.

How it works

Any +page.server.js can export an embed function and return an object containing a target (a dom selector)

// /routes/embed/+page.server.js
export const embed = (event) => {
  const target = event.url.searchParams.get('target');
  if (target) {
    return {
      target
    };
  }

  return null;
};

In this case, the page can be embedded by including this script

<!-- The /embed page will be embedded into section#main -->
<script defer src="http://my-app.com/embed?target=section%23main"></script>

What works

• Server data loading and invalidation
• SSR
• Form actions
• Navigation between routes (currently without the url bar reflecting the navigation)

How to test

I added a test app in kit/packages/kit/test/apps/embedded-widget

Stackblitz

pnpm install
cd packages/kit/test/apps/embedded-widget/
pnpm run dev

Todo

• Use url hashes for navigation (because we can't change the pathname of the third party app)
• Respect browser back/forward button

Extra details

The code adds the embed script origin to the app base

The code also uses the document.currentScript.src instead of the location to determine if a url is external to the widget. There might be other places where this should be done and I've missed it.

Feel free to test, I would love to know what you think about this and if it's a good feature

Cheers

---

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Tests

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Latest commit: 0440806

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[svelte-docs-bot]

Preview: https://svelte-dev-git-preview-kit-13638-svelte.vercel.app/