DarkRoom/docs/dev/windows.md

# DarkRoom — A Windows installer from the Linux CI

**Satisfies:** FR-PLAT-WIN-1 · FR-PLAT-WIN-2 · FR-PLAT-WIN-3 · NFR-COMPAT-2 (a stated channel)
**Companion to:** [distribution.md](distribution.md) · [requirements.md](requirements.md) §3.8, §4.4 ·
[android-signing.md](android-signing.md)

Spec for producing `DarkRoom-<version>-x86_64-setup.exe` from the same Gitea runner that builds the
Arch package and the APK, with no Windows machine in the loop. It names the toolchain, what the
tree has to change to compile for the target, what the installer does, how the CI job is shaped,
and — because there is no Windows hardware on the runner — exactly how much of the result can be
verified before a person double-clicks it.

**Written as a spec; §10 is the report.** Every step of §9 has since been run —
[`docker/windows/`](../../docker/windows/) is the container, [`packaging/windows/darkroom.nsi`](../../packaging/windows/darkroom.nsi)
the installer, [`.gitea/workflows/windows-image.yml`](../../.gitea/workflows/windows-image.yml) and
the `windows` job in `build-and-test.yml` the CI leg, and §6's gate passes through row 4 under
Wine. Four claims in the first draft were wrong and are corrected in place with a note; §10 lists
them. Where a claim still rests on reading rather than running, it says so.

---

## 1. Why this is nearly free, and where it is not

The reason to write this at all is that the tree is closer to Windows than a Linux-only project
usually is. The three things that ordinarily make a cross-build to Windows a week of work are all
absent:

| Usual obstacle | Here |
|---|---|
| A C image library (libraw, libjpeg-turbo, lcms) | `rawler`, `zune-jpeg`, `jpeg-encoder`, all pure Rust |
| OpenSSL, or a TLS stack with a system dependency | `reqwest` on `rustls` + `webpki-roots`; `ring` cross-compiles to the GNU target |
| A GUI toolkit with a platform-specific build | Slint on `winit` + wgpu, which already runs the same code on Linux and Android |

`rusqlite` is `bundled`, so SQLite compiles with whatever C compiler the target has; that is the one
place a cross C compiler is required, and it is a package install rather than a port. The inference
engine is tract, in Rust, which is what [faces.md §3](faces.md) chose it for — and this is the
second time that choice pays: the C++ ONNX Runtime would have needed a prebuilt Windows binary
fetched at build time.

**Where it is not free** is `dr-plat` and the handful of paths above it, which is exactly where
NFR-PORT-1 says platform code should be and where §3 finds it. That the list in §3 is short and
every item on it is already behind a `cfg` is the measure of whether NFR-PORT-3 ("a third platform
requires implementing the platform interfaces only") was met. It was, nearly: the gaps are in
things that grew *above* `dr-plat` — a settings file path, an `xdg-open` — rather than in the
interfaces themselves.

---

## 2. Toolchain: the GNU target, from a container

Two Rust targets can produce a Windows binary from Linux.

| Target | Linker | What it needs on the runner | What it costs |
|---|---|---|---|
| **`x86_64-pc-windows-gnu`** | MinGW-w64 `gcc` | `gcc-mingw-w64-x86-64` (Debian/Ubuntu), `mingw-w64-gcc` (Arch) — one apt/pacman install | Binaries link `libgcc_s` and `libwinpthread` unless told not to; the SEH unwinder is MinGW's rather than MSVC's; DirectX bindings are less exercised (not used — §2.1) |
| `x86_64-pc-windows-msvc` | `lld-link` via [`cargo-xwin`](https://github.com/rust-cross/cargo-xwin) | The MSVC CRT and Windows SDK headers, fetched from Microsoft's servers by `xwin` on first use (~1.5 GB, licence-accepted by flag) | A download step in CI that depends on Microsoft keeping those URLs stable, and a licence the runner accepts on the project's behalf |

**Decision: GNU.** It is a package install, it is what `rustup target add` supports out of the
box, and every crate in the dependency graph that carries a C component (`ring`, `libsqlite3-sys`,
`zstd-sys` if present) builds against MinGW today. The MSVC route produces a marginally more
conventional binary — the same CRT every other Windows application links — and costs a
1.5 GB fetch of Microsoft-licensed headers on every cold CI run. That is the wrong trade for a
channel whose users are, for now, the author.

Static-link the MinGW runtime so the installer carries one file rather than three. The
configuration lives in the container as environment variables rather than in a `.cargo/config.toml`
— that file is untracked here on purpose, and the Android image sets its linkers the same way:

```sh
CARGO_TARGET_X86_64_PC_WINDOWS_GNU_LINKER=x86_64-w64-mingw32-gcc-posix
CARGO_TARGET_X86_64_PC_WINDOWS_GNU_RUSTFLAGS="-C link-args=-static-libgcc -C link-args=-static-libstdc++"
```

**Corrected.** The first draft added `-Wl,--whole-archive -lwinpthread` "so nothing imports
`libwinpthread-1.dll`". That flag breaks the link: forcing the whole archive drags in unused
winpthread objects whose kernel32 and msvcrt references land after those libraries on the link
line, and the build dies on a hundred undefined `__imp_` symbols. It was also unnecessary —
rustc's windows-gnu target links its own winpthread in self-contained mode, and the built
executable imports no MinGW library at all (§10). `-posix` is stated because Debian's bare
`x86_64-w64-mingw32-gcc` is an alternatives symlink to either thread model.

Two more things the container needs that the draft did not name: a **host** `gcc`, because build
scripts and proc-macros compile for Linux whatever the target and the very first one fails with
"linker `cc` not found" without it; and **Wine 10**, because rustc's std imports
`bcryptprimitives.dll` for its random source and Debian bookworm's Wine 8.0 does not have it —
the smoke test dies at load with `c0000135` before the first instruction. So the image is
`debian:trixie-slim`, which also ships Node 20 natively.

### 2.1 What the binary reaches at runtime

Nothing the installer has to carry. wgpu opens **Vulkan** (`dr_gpu::new_shared`, D1 — Vulkan on
both targets, and the shared-device path permits nothing else), and on Windows the Vulkan loader
`vulkan-1.dll` is installed by every GPU vendor's driver. Slint's femtovg renderer finds system
fonts through `fontdb`, so the `fontconfig` the Linux CI job installs has no Windows counterpart.
There is no `libxkbcommon`, no display-server library: `winit` speaks Win32 directly.

**DirectX 12 is deliberately not enabled.** wgpu supports it and on Windows would be the
conventional choice, but the develop pipeline's compute shaders are written once for Vulkan
(NFR-PORT-2) and validated on two Vulkan drivers already; a third backend is a third set of
driver behaviours to characterise (NFR-R1's tolerance argument), and no Windows machine that can
run this application lacks a Vulkan ICD. The same reasoning that keeps GL out of `new_shared`
keeps DX12 out here. It is one flag away if that turns out to be wrong.

### 2.2 Where it builds

The same shape as the Android leg: a job container built from a Dockerfile in the tree and pushed
to the Gitea registry, tagged by the tree id of its directory so an unrelated push reuses it
([`android-image.yml`](../../.gitea/workflows/android-image.yml) already does this and the comment
there explains why).

```
docker/windows/
  Dockerfile        debian:trixie + rustup (1.92.0, target x86_64-pc-windows-gnu) + gcc + gcc-mingw-w64-x86-64 + nsis + wine
  build.sh          run a command in the container; caches registry, target and the Wine prefix
  package.sh        the LFS guard, staging, then makensis
```

`makensis` is a Linux binary; NSIS has always been buildable and runnable on POSIX hosts, and
Debian ships it as `nsis`. Wine is in the image for §6, not for the build. `osslsigncode` is not
in it until there is a certificate to give it (§5.4).

---

## 3. What the tree has to change

Read from the source, not run. Everything here is `dr-plat` or the thin layer above it — nothing
in `core/` is touched, which is NFR-PORT-1 holding.

### 3.1 Already handled

- **`volumes.rs`** — card detection reads `/proc/mounts` and `/sys/block` under
  `cfg(target_os = "linux")` and returns an empty list elsewhere. Windows gets no card detection
  in this pass; the import page's `Browse…` still reaches a card. (A `GetDriveType`/`DRIVE_REMOVABLE`
  implementation is a screen of code and a follow-up.)
- **Folder dialogues** — since 0.17.0 every folder the desktop asks for (the library, an import's
  source and second copy, Lightroom presets, an album's folder) is chosen in the platform's own
  dialogue through `rfd` ([`folder_dialog.rs`](../../ui/dr-ui/src/folder_dialog.rs)), which on
  Windows is the common item dialogue rather than the XDG portal. *Not verified*: nothing has
  opened one under Wine or on Windows.
- **`display.rs`** — the X11 and Wayland colour-profile readers are `cfg(all(unix, not(android)))`;
  the fallback is FR-DSP-8's stated one. Windows ICC profiles via `GetICMProfile` are a follow-up
  for the same reason.
- **`desktop_client.rs`** — the Nextcloud desktop client's Unix socket is `cfg(unix)`. On Windows
  the client listens on a named pipe (`\\.\pipe\...`); until that is implemented FR-NC-6c's
  integration is absent and the app behaves as it does on a Linux machine with no client running.
- **`secrets.rs`** — has a `PlatformSecretStore` for "any platform without an implementation"
  that returns `SecretError::Unavailable` on every call. It is loud on purpose, so a Windows build
  made with no further change *compiles*, starts, and fails at sign-in with a clear message. §3.2
  is what turns that into a working store.
- **`keyring`, `x11rb`, `wayland-*`** are target-scoped dependencies already, so the Linux-only
  crates are not even compiled.

### 3.2 Required before the installer is worth shipping

Ordered by what blocks a first sign-in. **All four are done**; each item says how.

1. **Secret store.** *Done.* `keyring` 4's `v1` feature set — the one the workspace already
   asks for — includes `windows-native-keyring-store`, so the Credential Manager backend needed
   no new feature name, only the crate as a `cfg(windows)` target dependency and the existing
   Secret Service implementation's `cfg` widened to include Windows. One implementation over
   both, because `keyring::Entry` is the same API over either; the only difference is that
   `is_available`'s probe always succeeds on Windows, which is correct — Credential Manager is
   always present, so FR-NC-2's degraded mode does not arise.

2. **Paths.** *Done* — [`platform/dr-plat/src/dirs.rs`](../../platform/dr-plat/src/dirs.rs). FR-PLAT-LIN-1
   says XDG, and the code said it in five places by reading `XDG_*_HOME` and falling back to
   `$HOME/.local/...`. On Windows `HOME` is normally unset, so every one of these degraded to a
   relative path from the working directory — which for a Start Menu launch is
   `C:\Windows\System32`. Now one function per kind of directory in `dr-plat`, with the Windows
   branch reading `%APPDATA%` (config; roams) and `%LOCALAPPDATA%` (data, cache, state; does
   not), and the five call sites using it. The Android overrides (`set_state_dir`,
   `set_data_dir`) stay where they were; only the fallback behind them moved. Both platforms'
   rules are unit-tested on either host, and the Windows one was confirmed by running the
   application under Wine: the log landed in `AppData\Local\darkroom\state` and nothing was
   written anywhere else.

   | Kind | Linux today | Windows |
   |---|---|---|
   | config (`settings.json`, accounts) | `$XDG_CONFIG_HOME/darkroom` — `dr_sync::config_dir`, `settings_store.rs` | `%APPDATA%\darkroom` |
   | data (catalog, thumbnails, faces) | `$XDG_DATA_HOME/darkroom` — `library::data_root` | `%LOCALAPPDATA%\darkroom` |
   | state (crash reports, diagnostics) | `$XDG_STATE_HOME/darkroom` — `state.rs`, `crash.rs` | `%LOCALAPPDATA%\darkroom\state` |

   FR-PLAT-WIN-1 states this as the requirement. The catalog and thumbnail *formats* do not change,
   so a library directory copied from a Linux machine opens.

3. **Face models.** *Done.* `library::system_face_models_dirs` walked `$XDG_DATA_DIRS`, which
   does not exist on Windows. The rule moved to `dr_plat::system_data_dirs`: the installer puts
   the models beside the executable (§5), so the Windows branch returns the executable's own
   directory. The user-directory lookups above it are unchanged, so a hand-placed pair still
   outranks the installed one, exactly as on Linux.

4. **Opening the sign-in URL.** *Done.* `launch_ui.rs` shelled out to `xdg-open`. The Windows
   branch runs `rundll32 url.dll,FileProtocolHandler <url>`, which is `ShellExecute` on the URL
   and needs no crate — chosen over `cmd /C start`, whose quoting of `&` in a query string is a
   known trap, and over the `open` crate, which would be a dependency for one line. Android has
   its own Intent path already, so this is the third branch of a function that already had two.
   *Not verified*: Wine has no browser to open.

5. **`std::os::unix` uses outside a `cfg`.** `diagnostics.rs` and `presets.rs` use
   `PermissionsExt` for mode bits on written files. Most are inside `#[cfg(unix)]` blocks already;
   the first cross-compile will name any that are not, and the fix is a `cfg` rather than a
   Windows ACL equivalent — the files in question are the user's own.

6. **The executable's identity.** *Done.* Windows takes the icon and the version block from a
   resource compiled into the `.exe`, not from a `.desktop` file.
   [`apps/darkroom-desktop/build.rs`](../../apps/darkroom-desktop/build.rs) uses `winresource`
   (which invokes MinGW's `windres` when cross-compiling) to embed
   [`ui/dr-ui/ui/app-icon.png`](../../ui/dr-ui/ui/app-icon.png) — wrapped into an `.ico` in
   `OUT_DIR` at build time, since an ICO entry may be a PNG, so no generated binary is committed —
   plus the version from `CARGO_PKG_VERSION` and the product name. The script returns before
   touching the crate on every other target, and `winresource` is an unconditional
   build-dependency because **a `cfg(windows)` on a build-dependency is evaluated against the
   host**, which is Linux. This is the fifth place the identifier lives, and
   [`tools/set-version.sh`](../../tools/set-version.sh) does not need to learn it: the resource
   reads the version cargo already knows. The same commit made the release binary a GUI-subsystem
   executable (`windows_subsystem = "windows"`), or Windows keeps a console window open behind
   the application.

Everything in this list is `cfg(windows)` code in `dr-plat` or a call-site switch in `dr-ui`, and
none of it touches the image core, the catalog schema, or the edit pipeline. That is the NFR-PORT-3
test, and it should be stated in the commit that closes the list whether it passed.

**What the first cross-compile actually found** (§9 step 2): nothing in this list blocked the
link. The whole graph compiled; the only warnings were two constants — `SERVICE` in `secrets.rs`
and `TIMEOUT` in `desktop_client.rs` — left unused by the `cfg`s that already shadow their users,
now guarded the same way. Items 1–4 are still open, and the binary starts without them; it just
cannot sign in.

### 3.3 Explicitly not in this pass

- **MIME/file-type registration** — FR-PLAT-LIN-1's `.desktop` MIME entries have a registry
  equivalent (`HKCU\Software\Classes\.cr2` etc.). Not until the application opens a file from the
  command line usefully, which `main.rs` accepts but the launch flow does not yet act on.
- **High-DPI declaration** — winit sets per-monitor-v2 awareness through its manifest by default.
  Verified in winit's source, not on a monitor; if text is blurry on a 150% display this is the
  first suspect.
- **Card detection, ICC profiles, the desktop-client pipe** — §3.1's three follow-ups.
- **A GL or DX12 fallback** — §2.1. A machine without Vulkan gets the library and no develop
  path, which is what it gets on Linux too.

---

## 4. The build script

`docker/windows/build.sh`, in the shape of the Android one and with the same rules:

```sh
cargo build --release --target x86_64-pc-windows-gnu -p darkroom-desktop
```

Release only, with `CARGO_TARGET_DIR` inside the workspace so the CI cache key
(`windows-${{ hashFiles('**/Cargo.lock') }}`) covers it. The whole workspace is *not* built for
the target: `darkroom-android` cannot be, and the examples that need a display or a catalog on
disk have nothing to run against. `cargo clippy --target x86_64-pc-windows-gnu -p darkroom-desktop`
is worth running in the same job, because the `cfg(windows)` branches from §3 are otherwise
never linted — the Linux job cannot see them.

Not `cargo test --target x86_64-pc-windows-gnu`: the test binaries would be Windows executables,
and running them means Wine. §6 does that for exactly one binary, deliberately.

---

## 5. The installer

[`packaging/windows/darkroom.nsi`](../../packaging/windows/darkroom.nsi), compiled by `makensis` on
the runner into `DarkRoom-<version>-x86_64-setup.exe`. `package.sh` passes the version in
(`/DVERSION=…`, from `tools/set-version.sh`'s single source, the workspace `Cargo.toml`) and refuses
to run if any `models/face/*.onnx` is smaller than 100 KB — the LFS-pointer guard every other
packager carries, for the reason [distribution.md §1](distribution.md) gives.

### 5.1 Per-user, not per-machine

Install to `$LOCALAPPDATA\Programs\DarkRoom`, register the uninstaller under
`HKCU\Software\Microsoft\Windows\CurrentVersion\Uninstall\DarkRoom`, `RequestExecutionLevel user`.
No UAC prompt, no `Program Files`, no writes outside the user's profile. This is the shape VS Code's
"User Installer" and most Electron applications use, and it is right for this project for two
reasons: an unsigned installer that also asks for administrator rights is the most alarming thing
Windows can show a user (§5.4), and a per-user install means the application's own data directories
(§3.2) and its binaries are governed by the same account, which is what NFR-SEC-5's
"the user's own hardware" means on a shared machine.

### 5.2 What it puts on disk

```
$LOCALAPPDATA\Programs\DarkRoom\
  darkroom.exe
  models\
    scrfd_500m_640.onnx   scrfd_2.5g_640.onnx   scrfd_10g_640.onnx   arcface_mbf_b1.onnx
    2d106det_b1.onnx   ocec_s_b1.onnx   sgc_l_48_b1.onnx
    yolo26s-sem-ade20k.onnx   yolo26s-sem-ade20k.classes.json   categories.txt
    migan-512.onnx
  manual\
    index.html   media\   (the rendered manual and its pictures)
  LICENSE
  uninstall.exe
```

Plus a Start Menu shortcut, and nothing on the desktop unless the user ticks it. The models are
the f32 files the APK bundles and the PKGBUILD installs — not the APK's quantised siblings, which
only a Hexagon runs; `models\` beside the executable is
where §3.2's lookup finds them. **No `LICENSE` yet**: the repository has no licence file at its
root (the Arch package points at the system's shared GPL text), so the installer has no licence
page until one is added — a one-file change, and the `.nsi` says where the page then goes. The face weights carry the research-only grant that
[faces.md §2](faces.md) records, and this channel changes nothing about that: the installer is
for the author's own machines until §2.2a's caveat is resolved, exactly as the APK is.

### 5.3 Uninstall

Removes the install directory, the shortcut and the registry key. **Does not touch
`%LOCALAPPDATA%\darkroom` or `%APPDATA%\darkroom`** — the catalog, the thumbnails, the face
index, the settings. An uninstaller that deletes a library index the user spent two hours building
is the kind of destructive default FR-CULL-12 and NFR-SEC-5's "disabling deletes nothing" both
argue against. The uninstaller says so on its one page, and names the two directories so a user who
does want them gone knows where they are.

### 5.4 Signing, and the warning that results from not doing it

An unsigned installer triggers SmartScreen's "Windows protected your PC" interstitial, dismissable
through "More info → Run anyway". Signing needs an Authenticode certificate, which is paid and
identity-verified; from Linux the signing itself is `osslsigncode`, which is why it is in the
container image, but there is no certificate to give it. **This spec ships unsigned** and the
release notes say what the interstitial looks like. An OV certificate is a cost decision to make
if this channel ever has a user who is not the author; an EV one buys instant reputation and costs
a hardware token. Neither is a build problem.

The APK went through the same sequence — [android-signing.md](android-signing.md) records a
debug-signed build becoming a release-signed one when it mattered — and this channel should be
allowed to do the same.

### 5.5 What NSIS is chosen over

WiX produces an MSI, which is what enterprise deployment tooling wants and what nobody deploying
a photo editor to their own laptop cares about; its Linux story is `wixl` from msitools, which is
real but thinly used. Inno Setup runs only under Wine. NSIS is scriptable in plain text, builds
natively on Linux, produces a single self-contained `.exe`, and the script for §5.2 is under a
hundred lines. It is the conventional answer for exactly this situation.

One choice inside NSIS: `Target amd64-unicode`, a 64-bit installer rather than the default 32-bit
stub. The application is x86_64 only so nothing is lost, and it is what lets §6's install test run
under a 64-bit-only Wine — the 32-bit stub needs an i386 multiarch Wine and dies loading the WoW64
`ntdll` without one.

---

## 6. Verifying without Windows

This is the part to be honest about. The runner has no Windows, no GPU it can hand to a Windows
process, and no display. What *can* be checked, in increasing cost and decreasing certainty:

| Check | How | What it proves |
|---|---|---|
| **It links** | the build succeeds | Every `cfg(windows)` branch compiles; no `unix`-only symbol leaked past a `cfg` |
| **It is a Windows executable** | `file darkroom.exe` reports PE32+; `x86_64-w64-mingw32-objdump -p` lists the DLLs it imports and none are MinGW's | The static-runtime flags in §2 held |
| **It starts** | `wine64 darkroom.exe --version` exits 0 and prints the version | The CRT, the resource block and `main` are sound; paths in §3.2 resolve (Wine sets `LOCALAPPDATA`) |
| **The installer runs** | `wine64 DarkRoom-setup.exe /S` then the install directory exists with the eight files, and `wine64 uninstall.exe /S` removes it | The NSIS script's file list, sections and uninstaller are right |
| **It draws a window** | `xvfb-run wine64 darkroom.exe` with `SLINT_WGPU_CPU` and a lavapipe ICD exposed through `winevulkan` | That Slint's winit backend initialises on Win32 — and this is where the chain gets long enough that a failure says more about Wine than about DarkRoom |

The first four are the CI gate. The fifth is worth trying once by hand and not putting in CI:
it needs `winevulkan` to find a host ICD, `xvfb`, and a Wine prefix warmed up in the container,
and every one of those is a moving part that has nothing to do with whether the application works
on Windows.

`--version` exists for this — a smoke test needs an exit that opens no window and touches no
directory — and it is answered before the logger and the crash hook install, so it proves the CRT
and the resource block and nothing above them.

**One more row the table missed:** the Start Menu shortcut. `CreateShortcut` is `IShellLink`,
which does nothing under a headless Wine while the `CreateDirectory` beside it succeeds, so an
installer that installs and uninstalls cleanly here can still have a broken shortcut. That row is
on Windows only.

**What none of this proves:** that wgpu opens a Vulkan device on a real driver, that a 6000-px
render completes, that fonts are found, that the secret store round-trips. Those are a person with
a Windows machine, once per release, until there is a Windows runner — and a self-hosted Windows
act_runner is how that would be done, not a cloud service. The release notes for the first build
say which of these were checked and on what.

---

## 7. The CI job

A fourth leg of [`build-and-test.yml`](../../.gitea/workflows/build-and-test.yml), beside desktop,
Android and traceability:

```yaml
  windows-image:
    uses: ./.gitea/workflows/windows-image.yml     # same shape as android-image.yml

  windows:
    runs-on: linux/amd64
    name: Windows (x86_64, cross)
    needs: windows-image
    container:
      image: gitea.tourolle.paris/dtourolle/darkroom-windows:latest
    steps:
      - checkout, LFS pull                           # copied from the desktop leg
      - cache: ~/.cargo, target                      # key: windows-${{ hashFiles('**/Cargo.lock') }}
      - docker/windows/build.sh                      # cargo build + clippy, --target x86_64-pc-windows-gnu
      - smoke: file, objdump, wine64 --version       # §6 rows 1–3
      - docker/windows/package.sh                    # LFS guard, makensis
      - smoke: wine64 setup.exe /S; ls; uninstall    # §6 row 4
      - upload artefact: DarkRoom-*-setup.exe        # on tags only, like the APK
```

Same gotchas as the Android leg, which its comments already record: the host has no Node, so the
checkout is plain `git`; workflow inputs arrive as strings; the image build needs the host Docker
daemon and runs outside a container. None of that is new.

**Cost.** A cold build of the whole graph for a second target is roughly the desktop leg again —
tract, Slint's compiler, wgpu — so with the cargo cache warm it is minutes and cold it is the
better part of half an hour. Worth noting because the runner is one machine and the legs run in
parallel on it; if it starts starving the desktop leg, `needs: desktop` serialises them.

**Disk is the tighter budget.** The runner has one 99 GB disk shared with its container images. At
rest it holds about 23 GB; the desktop leg's restored target cache, the models and the dependency
build bring it to about 78 GB before a test runs, and v0.18.0's run ended at 92 GB used. v0.18.1's
release build then died with "No space left on device", so that tag has no release page. Since
then the desktop leg deletes its test executables, `target/debug/examples` and
`target/debug/incremental` after the Test step and before the release build — they are relinked
whenever a source changes, and the cache exists for the dependency rlibs — and prints the disk
again beside its Disk before and after lines. A second target's cache on the same disk is the
first thing to look at if a leg runs out again.

---

## 8. Requirements

Three, added to [requirements.md §3.8](requirements.md) under a `#### Windows` heading beside the
Linux ones. Phrased to be testable, and each one is something §3 or §5 would otherwise leave as a
convention.

**FR-PLAT-WIN-1 — Known folders.** Configuration under `%APPDATA%\darkroom`; data, cache and
state under `%LOCALAPPDATA%\darkroom`. No file under the user's profile root and nothing relative
to the working directory. The directory *layout* beneath those roots is the same as under XDG, so
a library directory moves between platforms unchanged.

**FR-PLAT-WIN-2 — Installer.** A per-user installer that needs no elevation, registers an
uninstaller, and whose uninstaller removes what the installer wrote and nothing the application
wrote. Models are installed beside the executable and found there last, after the user's own
directories.

**FR-PLAT-WIN-3 — Built from Linux.** The Windows binary and its installer are produced by the
Linux CI from the same commit as every other channel, with no Windows machine in the build.
Verification on Windows is a release step, recorded per release, not a build step.

NFR-COMPAT-2's channel table in [distribution.md §1](distribution.md) gains a row. NFR-PORT-3 gets
its first real test, and the commit that closes §3.2 records the answer.

---

## 9. Order

1. `--version` in `main.rs`, and the `.cargo/config.toml` target block. Trivial, and the smoke
   test in §6 needs both before anything else can be measured.
2. `rustup target add x86_64-pc-windows-gnu`, `pacman -S mingw-w64-gcc`, and a first
   `cargo build --target …` on the developer machine — **before the container exists**, because
   the list in §3.2 is a reading of the source and the compiler's list will be longer. Fix the
   `cfg` fallout as it appears. This is the afternoon that decides whether §1's optimism holds.
3. §3.2 items 1–4, each its own commit, each stating which NFR-PORT interface it implemented.
4. §3.2 item 6 — the resource block — and the NSIS script; `makensis` by hand; `wine64 setup.exe /S`
   by hand. Now there is an artefact.
5. The container, the image workflow, the CI leg. Only after 4 works locally, for the same reason
   the Android image was reproduced from the tree after it had lived on one laptop.
6. A build on a real Windows machine, and a note in the release saying what was checked.

Steps 1–2 are cheap and either confirm this document or replace §3.2 with the true list. Nothing
past step 2 should be started on the strength of this document alone.

---

## 10. Report · 2026-09-12

Steps 1, 2 and 4 run, in the container rather than on the developer machine, because the
container was the cheaper way to get a pinned MinGW and a Wine that could be thrown away.

| §6 row | Result |
|---|---|
| It links | Yes, first attempt once the link flags were right. 115 MB, `PE32+ … (GUI)`. Two dead-code warnings, both `cfg`-shadowed constants, fixed. |
| It is a Windows executable | 26 imports, all Windows system DLLs. No MinGW runtime. `.rsrc` carries `PRODUCTVERSION 0,12,0,0`, `ProductName DarkRoom`, the icon. |
| It starts | `wine darkroom-desktop.exe --version` → `darkroom-desktop 0.12.0`, exit 0, 0.1 s. |
| The installer runs | `makensis` → 105 MB. `/S` installs the exe and ten models to `AppData\Local\Programs\DarkRoom`, writes the `HKCU` uninstall key; the installed exe runs; `uninstall.exe /S` removes directory and key. Shortcut unverifiable (§6). |
| It draws a window | Not attempted. |

**What the first draft got wrong**, kept in place above with a note rather than rewritten, because
the reasoning that produced each mistake is the thing a reader will otherwise repeat:

1. The `--whole-archive -lwinpthread` link flag (§2) — breaks the link and was never needed.
2. No host C compiler in the image (§2) — build scripts are host binaries.
3. Debian bookworm's Wine (§2) — lacks `bcryptprimitives.dll`, which rustc's std imports.
4. A `cfg(windows)` on the `winresource` build-dependency (§3.2 item 6) — evaluated against the
   host, so the crate was silently absent from the cross-build.

And two things it did not know to say: NSIS's default stub is 32-bit (§5.5), and `CreateShortcut`
cannot be verified headless (§6).

**Closed since**, same day: all four §3.2 items (each says how), a `LICENSE` at the repository
root so the installer has its licence page, and §7's CI leg — `windows-image.yml` and the
`windows` job, every step of which was run by hand in the same container first. The Windows
target is also linted now, with `cargo clippy --target x86_64-pc-windows-gnu -- -D warnings` in
that job, which is the only place the `cfg(windows)` branches are ever compiled by CI.

**What the first real Windows run has to check**, in order, because Wine cannot: that a Vulkan
device opens on a real driver and a render completes; that fonts are found; that Credential
Manager round-trips a sign-in and the browser opens for Login Flow v2; that the Start Menu
shortcut exists; and that text is sharp on a scaled display (§3.3). The release notes for the
first build should say which of these were checked and on what machine.