gpuix-svelte

Write desktop apps in Svelte and render them straight into a native, GPU-accelerated window. gpuix-svelte is a Svelte custom renderer for GPUI, the UI framework behind the Zed editor. It talks to GPUI through @gpuix/native.

Warning
Experimental. gpuix-svelte is built on Svelte's unreleased custom renderer API, so every release ships the exact Svelte build it was tested against (see About the Svelte version). Expect breaking changes between minor versions.

Quick start

npm create gpuix-svelte@latest my-app
cd my-app
npm install
npm start

A counter opens in its own window. Edit App.svelte, save, and the window hot-reloads.

You need Node.js 24 or later or Bun 1.4 or later, on macOS (Apple Silicon), Windows (x64) or Linux (x64). The GPUI binary comes prebuilt from npm, so npm install is all the setup there is. On Bun, run bun create gpuix-svelte my-app, then cd my-app, bun install and bun run start. Building a standalone executable (npm run build) needs Bun whichever runtime you develop on.

What it looks like

<!-- App.svelte -->
<script lang="ts">
  let count = $state(0);
</script>

<div class="app">
  <text class="count">{count}</text>
  <div class="btn" onclick={() => count++}>Add one</div>
</div>

<style>
  .app { display: flex; flex-direction: column; align-items: center; gap: 16px; padding: 32px;
         width: 100%; height: 100%; background-color: #1e1e2e; }
  .count { font-size: 48px; color: #cdd6f4; }
  .btn { padding: 12px 24px; border-radius: 8px; background-color: #313244; color: #cdd6f4; }
  .btn:hover { background-color: #45475a; }
</style>

// app.ts
import { render_hot } from 'gpuix-svelte';

render_hot(new URL('./App.svelte', import.meta.url), { title: 'My app', width: 640, height: 480 });

npx gpuix-svelte app.ts          # Node
npx gpuix-svelte --bun app.ts    # Bun

Runes, snippets, {#each}, {#if}, {#await}, <svelte:boundary> and .svelte.ts state modules all work as you'd expect. Scoped <style> blocks work too, for class rules (the styling page has the details). Underneath, GPUI's element tree is painted on the GPU, and your UI shares its process with the whole of Node or Bun: files, processes, SQLite and native addons.

Coming from Svelte on the web

• Elements are GPUI's: div, text, img, svg, input, textarea, code, markdown, virtual-list, anchored and a few more. Any other tag renders as a div, with a one-time warning. <img src> takes a file path, a data: URL or an http(s) URL.
• Styling is CSS text for a flexbox layout in logical pixels. Lengths are px or rem (16 px), and sizes (width, height, min-*, max-*) also take % and auto. <style> blocks take class rules with :hover and :active. Values GPUI can't use are dropped with a warning. → docs/styling.md
• Theming is var(--token) in your styles plus one set_css_vars({ token: '#fff' }) call. → docs/styling.md#theming-with-css-variables
• Mouse events go to the element under the pointer. Put hitbox="self" on a clickable element and clicks on its decoration reach it. onclick is the primary button; right and middle clicks are onauxclick. → docs/styling.md (non-standard semantics)
• Inputs report through events, with the value in the payload: <input value={text} onchange={(e) => (text = e.value)} />. The compiler refuses bind: under a custom renderer, and {@attach} hands you the element. → docs/guide.md
• Keyboard shortcuts go through on_window_key('keydown', handler), which hears every key whatever has focus. → docs/guide.md
• Scroller, Portal, Tooltip and Popover ship with the package: a scroll column with a drawn scrollbar (virtualised on request), a wrapper that paints modals, menus and toasts on top from anywhere in the tree, and a hover tip and a controlled panel that hang beside their trigger. → docs/components.md
• Window and desktop APIs cover the title, fullscreen, the file picker, file drops, images from raw pixels, focus and accessibility attributes. → docs/guide.md

Documentation

For real code, the examples are the best reference (see Examples).

Adding it to an existing project

npm install gpuix-svelte

gpuix-svelte brings its own Svelte, so it's the only runtime dependency you add (see About the Svelte version). Run your entry through the package's bin, usually from package.json:

{
  "type": "module",
  "scripts": {
    "start": "gpuix-svelte app.ts",
    "test": "gpuix-svelte test.ts"
  }
}

The bin starts Node, or Bun when you pass --bun or launch it with bun run. Before your entry loads, it sets the custom-renderer module condition, which selects Svelte's client build with the renderer API, and installs the .svelte loader. Your .ts files need no loader: Node and Bun strip the types themselves, and the package ships as plain JavaScript.

Runtime flags go before the entry, and a flag that takes a value needs the = form (gpuix-svelte --experimental-ffi app.ts, gpuix-svelte --import=tsx app.ts). Arguments after the entry go to your script. Spelled out, the bin runs:

node --conditions custom-renderer --conditions development --import gpuix-svelte/register app.ts
bun  --conditions custom-renderer --conditions development --preload gpuix-svelte/plugin app.ts

On Bun, preload = ["gpuix-svelte/plugin"] in a bunfig.toml does the job of --preload for ad-hoc bun file.ts runs.

TypeScript

The package ships type declarations. Your tsconfig.json needs a paths entry that points at the Svelte build nested inside the package. For the editor and svelte-check to type your markup as GPUI elements, it also needs the gpuixHTML namespace:

{
  "compilerOptions": {
    "module": "nodenext",
    "strict": true,
    "noEmit": true,
    "allowImportingTsExtensions": true,
    "erasableSyntaxOnly": true,
    "verbatimModuleSyntax": true,
    "customConditions": ["custom-renderer", "development"],
    "types": ["node", "gpuix-svelte/html"],
    "skipLibCheck": true,
    "paths": {
      "svelte": ["./node_modules/gpuix-svelte/node_modules/svelte"],
      "svelte/*": ["./node_modules/gpuix-svelte/node_modules/svelte/*"]
    }
  },
  "svelteOptions": { "namespace": "gpuixHTML" }
}

You'll also want a *.svelte module declaration and a svelte.config.js that turns off Svelte's DOM accessibility advice. starter/ has all three, ready to copy.

With this config, tsc rejects what Node's built-in type stripping can't run. erasableSyntaxOnly catches enums, namespaces and parameter properties, verbatimModuleSyntax catches a type imported without import type, and module: nodenext requires a file extension on relative imports, which allowImportingTsExtensions lets you spell .ts. If your app needs that syntax anyway, install tsx and load it through the bin: gpuix-svelte --import=tsx app.ts.

Event handlers take a GpuixEvent and {@attach} gets a ShadowNode. Both are exported as types:

<script lang="ts">
  import type { GpuixEvent, ShadowNode } from 'gpuix-svelte';
</script>

Examples

Clone the repository to run them (bun install, then the command):

Each of these, apart from demo:web (which always runs on Bun), has a Bun twin under a bun: prefix, such as npm run bun:demo:counter.

About the Svelte version

Custom renderers live on an open Svelte pull request that moves on its own schedule. So each release of this package bundles the exact build of that pull request it was tested against, inside node_modules/gpuix-svelte/node_modules/svelte. Its loaders resolve every svelte import (yours, the compiled components' and its own) to that copy.

In practice:

• gpuix-svelte is your one dependency, and the Svelte you import is the one it brings. Keep svelte itself out of your package.json.
• Upgrading gpuix-svelte can move the Svelte build underneath you, so read the changelog before a minor bump.
• svelte-check installs the registry's Svelte as its own peer dependency and uses it to read your components. The paths entry in your tsconfig points type imports at the bundled build.

Good to know

• Scrollbars come from Scroller. Context menus are drawn by the app: a Popover with position, or a <Portal>, placed at the onauxclick coordinates.
• left, top, right and bottom take pixels only. A progress bar's fill sizes with width: 50%.
• <svg> takes its color from the nearest ancestor's style, which the renderer copies over. Hover is handled natively, so give hover tones to the <svg> itself.
• Headless tests run on macOS and Windows.
• Standalone binaries and web bundles are built with Bun, from a script modelled on the repository's. See docs/shipping.md.

How it works

Svelte's custom renderer API hands the renderer DOM-shaped operations: create an element, insert it before an anchor, set an attribute, add a comment node. GPUI's tree is flat, keyed by numeric id, and holds elements and text. gpuix-svelte keeps a lightweight shadow tree in JavaScript and projects it onto GPUI. Only elements and non-blank text get native nodes, and they're created lazily, once they're attached to the window. Every change in a frame is queued and shipped as one batch, which Rust applies before the next paint.

Around that sit a .svelte loader for Node (module.registerHooks) and one for Bun (Bun.plugin), which compile components with the renderer baked in and turn <style> blocks into class rules. There's also a translator from CSS text to GPUI styles that expands shorthands and drops what GPUI would reject, a ~125 fps frame loop, and in-process hot reload. The full design notes are in CLAUDE.md.

Contributing

See docs/contributing.md for running the demos and tests, moving the vendored Svelte build, and how releases are cut.

License

MIT