The UI never touches the network. The sync engine runs in the background and writes to a local [Drift](https://drift.simonbinder.eu/) database. Screens observe reactive streams from that DB.
Download the latest release from the [Releases page](https://github.com/guettli/sharedinbox3/releases) *(not yet published)*.
Run the app, tap **+**, and enter your IMAP/SMTP server details. The app syncs your INBOX in the background using IMAP IDLE and works offline — the network is only needed during initial sync and when sending mail.
---
## For developers
### Prerequisites
[Nix](https://nixos.org/download) with flakes enabled, and [direnv](https://direnv.net/).
```bash
# One-time: allow direnv in this directory
direnv allow
```
`direnv` loads the Nix flake automatically — no manual `nix develop` needed after that. The flake pins **Flutter 3.41.6**, Android SDK, Stalwart mail server (for integration tests), and all Linux desktop build tools (GTK3, clang, cmake).
### First-time setup
```bash
# Generate the Drift database layer (required before first build)
`task check` runs `analyze` + `test` + `test-widget` + `build-linux` + `integration` in parallel — use it before every commit.
### Running the app on desktop in mobile screen resolution
Start the app on the Linux desktop target:
```bash
task run # or: flutter run -d linux
```
After the window opens, resize it to a phone-like size. Typical reference dimensions:
| Device profile | Width × Height |
| --- | --- |
| Compact phone (e.g. Pixel 6a) | 360 × 800 |
| Large phone (e.g. iPhone 14 Pro) | 393 × 852 |
| Tall phone (e.g. Samsung S24) | 360 × 780 |
Drag the window border to those dimensions, or use your window manager's "set window size" feature. The Flutter layout engine responds to the window size exactly as it would on a real device — breakpoints, overflow, and scrolling behave identically. Hot-reload (`r` in the terminal) preserves the window size between reloads.
1. Copy `app-release.apk` to the device (e.g. via USB file transfer, cloud storage, or `adb push`).
2. Open a file manager on the device, tap the `.apk` file, and confirm the install prompt.
> **Tip — split APKs for smaller size:** `flutter build apk --split-per-abi` produces three smaller APKs (one per CPU architecture). Install the one matching the device: `app-arm64-v8a-release.apk` covers almost all modern Android phones.
`test/widget/` contains [Flutter widget tests](https://docs.flutter.dev/testing/overview#widget-tests) for every screen. They run headlessly — no display server, no device, no database, no network. Each test pumps the screen into a virtual render canvas and uses in-memory fakes for the Riverpod repository providers.
Run them locally:
```bash
task test-widget # or: flutter test test/widget/
```
They also run in CI on every push (see the **Widget tests** step in `.github/workflows/ci.yml`).
Starts a local [Stalwart](https://stalw.art) mail server on random ports, runs the tests in `test/integration/`, then stops it. No manual setup needed — Stalwart is provided by the Nix flake.
