cadcraft/packaging/web

Hosting CADCraft for the web

cadcraft-web-<version>.zip (from the GitHub release, or packaging/web/package.sh) holds a static site in cadcraft-web-<version>/:

File	What it is
index.html	The page. It loads everything through relative URLs.
cadcraft-web-<hash>.js	wasm-bindgen glue (generated, ES module)
cadcraft-web-<hash>_bg.wasm	The app, about 13 MB, or 5 MB with compression
_headers, .htaccess	Sample header rules for Netlify/Cloudflare Pages and Apache

There is no server-side code. Upload the folder's contents anywhere that serves static files.

Any path works

All URLs in index.html are relative (public_url = "./" in apps/cadcraft-web/Trunk.toml), so the site works at a domain root (https://example.com/), under a prefix (https://example.com/tools/cadcraft/) and from a CDN bucket. The asset names carry a content hash, so they can be cached forever. Only index.html needs revalidation.

Required server settings

• MIME type: serve .wasm as application/wasm. Browsers refuse to stream-compile it under any other type, and the app then loads slowly or not at all. Serve .js as text/javascript. Most hosts already do both. For nginx, check that mime.types has application/wasm wasm;.
• Compression: turn on gzip or Brotli for .wasm, .js and .html. That takes the download from about 13 MB to about 5 MB. You can also precompress (brotli -k *.wasm) and let the server send Content-Encoding: br.
• Caching: Cache-Control: public, max-age=31536000, immutable on the hashed .wasm and .js files, and no-cache on index.html.
• HTTPS: WebGPU (and the clipboard) only work in a secure context, which means https:// or http://localhost. Over plain HTTP elsewhere, the app falls back to WebGL2.
• No special isolation headers: CADCraft doesn't use SharedArrayBuffer, so it doesn't need Cross-Origin-Opener-Policy or Cross-Origin-Embedder-Policy. If your site already sends COEP require-corp, also send Cross-Origin-Resource-Policy: same-origin (or cross-origin when the files live on a CDN) on the app's files.

nginx example:

location /cadcraft/ {
    types { application/wasm wasm; text/javascript js; text/html html; }
    gzip on;
    gzip_types application/wasm text/javascript text/html;
    location ~* \.(wasm|js)$ { add_header Cache-Control "public, max-age=31536000, immutable"; }
    location ~* index\.html$ { add_header Cache-Control "no-cache"; }
}

Local test: python3 -m http.server 8765 inside the folder, then open http://localhost:8765/.

Panel layout storage

The browser host saves docked, floating and hidden palette arrangements alongside interface preferences in its local storage. Floating palettes remain embedded in the browser canvas; they do not become native operating-system windows. Window > Reset Palettes restores the default arrangement. This record contains panel placement and visibility, not drawing data.

The optional cadcraft.panel-layout record uses the shared docking layout version and is limited to 64 KiB. Malformed, incompatible or invalid arrangements are ignored atomically, leaving the startup defaults usable. Storage availability and autosave follow the browser host's existing eframe persistence; clearing site data removes the saved layout.

Embedding in a page (iframe)

<iframe
  src="https://example.com/cadcraft/"
  title="CADCraft image editor"
  style="width: 100%; height: 720px; border: 0;"
  allow="fullscreen; clipboard-read; clipboard-write"
  allowfullscreen>
</iframe>

• The app fills the iframe and follows its size, so size the iframe and not the app.
• Keyboard shortcuts go to the iframe after the user clicks into it, as with any embedded app.
• Cross-origin embeds work. Preferences are kept in the iframe's localStorage. Browsers that partition or block third-party storage may forget them between visits, and the app then starts with defaults.
• Sandboxed iframes need at least sandbox="allow-scripts allow-same-origin allow-downloads allow-popups". Without allow-same-origin there's no storage. Without allow-downloads, Save and Export (browser downloads) are blocked.
• Don't send X-Frame-Options: DENY or a frame-ancestors CSP that excludes the embedding page.

Host mode: let the page open and store drawings

A page can take over the file side of the app instead of the browser's downloads. The iframe embed above opts in by adding ?host=parent to the iframe's URL (https://example.com/cadcraft/?host=parent); the app then talks to its same-origin framing page over postMessage, with plain window messages that carry a type:

Message	Direction	Fields
cadcraft:ready	app → page	version, appVersion: the app is listening; send a drawing now
cadcraft:open	page → app	name, bytes (an ArrayBuffer or Uint8Array): open like File › Open
cadcraft:save	app → page	name, bytes (a transferred ArrayBuffer): every file the app would otherwise download (SAVE, SAVEAS, exports). The page stores it and reports failures itself.
cadcraft:dirty	app → page	dirty: unsaved changes appeared or went away
cadcraft:failed	app → page	error: the app couldn't start

In host mode the app starts on the Start tab instead of an empty Drawing1, so the page should guard leaving it while changes are unsaved (that is what cadcraft:dirty reports).

Same-document host mode (no iframe)

A page can also run the app in its own document — its own <canvas id="cadcraft_canvas"> inside a component, no iframe — by loading the wasm-bindgen module itself. It opts in with data-host="page" on that canvas — the exact value page; anything else, and an unframed ?host=parent, keeps the normal app with downloads. The behaviour is the same as the parent bridge, except the transport is DOM CustomEvents on the canvas instead of postMessage: the app dispatches cadcraft:ready, cadcraft:save, cadcraft:dirty and cadcraft:failed on the canvas with the message fields (without the type) as the event's detail, and the page dispatches a cadcraft:open event with detail: { name, bytes } to open a drawing. Events don't bubble, so two editors on one page can't hear each other; listen on the canvas itself.

<canvas id="cadcraft_canvas" data-host="page" style="width: 100%; height: 600px; border: 0;"></canvas>

import init from "./cadcraft-web-<hash>.js"; // the wasm-bindgen glue shipped with the app

const canvas = document.getElementById("cadcraft_canvas");
// The app announces itself while `init` runs, so add the listeners first.
canvas.addEventListener("cadcraft:ready", () => {
  // The app is listening; hand it a drawing of the page's own now, if you have one.
  canvas.dispatchEvent(new CustomEvent("cadcraft:open", {
    detail: { name: "plan.dxf", bytes: drawingBytes }, // ArrayBuffer or Uint8Array
  }));
});
// Every file the app would otherwise download (SAVE, SAVEAS, exports) arrives here.
canvas.addEventListener("cadcraft:save", (event) => {
  const { name, bytes } = event.detail; // bytes is an ArrayBuffer
  storeFile(name, bytes);
});
canvas.addEventListener("cadcraft:dirty", (event) => {
  warnBeforeLeaving(event.detail.dirty);
});
canvas.addEventListener("cadcraft:failed", (event) => {
  showError(event.detail.error);
});

// If the wasm cannot be fetched or instantiated, `init` rejects before the app can post
// `cadcraft:failed`, so report that here too.
try {
  await init({ module_or_path: "./cadcraft-web-<hash>_bg.wasm" });
} catch (error) {
  showError(String(error));
}

The messages and both transports are the shared contract of craft-web-host (storytold/craft-libs#420), the same for every Craft app: its README lists every message, including saved, with the compatibility notes. In cadcraft:ready, version is the contract's ("1") and appVersion is this app's release. CADCraft reads bytes, so a host sends bytes, not a File.

Trust and limits

• Who is trusted. In page host mode the page and CADCraft share one document, so any script on the page can drive the app: open files in it and receive what it saves. Use this mode only for a page you control. The iframe mode (?host=parent) answers only the parent window, on the page's own origin.
• Files from the host are untrusted input. An opened file goes through the same reading as one picked with File ▸ Open or dropped on the window, with the same format limits; before it is copied into the app's memory, its size is checked against the app's open size limit and a larger drawing is refused, and a name is cut to 255 characters.
• The event and message names are the interface. cadcraft:ready, cadcraft:open, cadcraft:save, cadcraft:dirty and cadcraft:failed, and the fields they carry (the same as the ?host=parent messages), stay stable; changing one is a breaking change.

Renderer selection and fallback flags

CADCraft renders with wgpu. It uses WebGPU when the browser has it and falls back to WebGL2 on its own. URL query flags override this, and they work on the iframe src too:

Flag	Effect
(none)	WebGPU if available, otherwise WebGL2
?webgl	Force the WebGL2 backend (useful when a WebGPU driver misbehaves)
?cpu	Force the CPU canvas path (slowest, most compatible)

For example: <iframe src="https://example.com/cadcraft/?webgl" ...>.

A browser with neither WebGPU nor WebGL2 gets a message in place of the app.