# J621 desktop (Electron)

An Electron shell around the web build. The main process serves the SPA from
the privileged `app://j621` scheme — a real origin, so `localStorage`, OPFS,
Web Workers and WebCodecs all behave exactly like they do in Chrome — and the
SPA keeps its normal first-run flow: on launch it asks where the backend is
(or runs in local mode with no backend at all).

The renderer code is not forked: the shell loads `frontend/dist` as built by
`npm run build` in `frontend/`.

## Layout

```
src/main.ts      window, app:// protocol handler, menu, external links
src/preload.ts   window.j621Desktop bridge
electron-builder.yml   deb + pacman + nsis packaging
```

## Development

```bash
# terminal 1: the SPA with its /api proxy (needs the backend for library pages)
cd frontend && npm run dev

# terminal 2
cd desktop && npm run dev
```

`npm run dev` builds the main process and points the window at
`http://localhost:5173` (`J621_DEV_SERVER`). Without the dev server,
`npm start` builds both halves and serves the bundled SPA over `app://j621`.

## Builds

```bash
npm run dist:linux   # release/*.deb + release/*.pkg.tar.zst
npm run dist:win     # release/J621-Setup-*.exe (cross-built with wine; untested)
npm run dist:all
```

The Arch package can be installed and removed with pacman:

```bash
sudo pacman -U release/j621-*.pkg.tar.zst
```

## Smoke test

`npm run smoke` builds everything, runs Electron headless through `xvfb-run`
and checks that the bundled SPA loads over `app://j621`: the SPA fallback, an
asset fetch, `localStorage`, OPFS, WebCodecs and the preload bridge. It exits
non-zero on failure.

## Backend CORS

A desktop app is cross-origin to the backend, exactly like the frontend-only
Docker deployment. Add the shell's origin to the backend:

```
CORS_ALLOWED_ORIGINS=app://j621
```

The setup screen shows this hint (with the actual origin) when the connection
test fails. Without a backend, choose "Continue without a backend" — the
e621-facing pages work the same as in the browser.