Files
DarkRoom/docker/android/README.md
T
dtourolleandClaude Opus 5 b044a8c067 Build the Android CI image in CI, not on a laptop
The Android job ran in gitea.tourolle.paris/dtourolle/darkroom-android:latest,
a tag that had never been pushed. The image existed only as a local
darkroom-android:latest on one machine, so every Android job died at docker
pull with "manifest unknown" before reaching a step. The registry API confirms
it: that manifest is a 404 while the other builder images answer 200.

android-image.yml now builds and pushes it, following KPN's docker.yaml — host
runner rather than a container, so it has the Docker daemon and the host's
cached registry credentials, and a plain-git checkout because that host has no
Node for actions/checkout.

Where it diverges from KPN: that workflow gates on dorny/paths-filter running
inside the builder image, which here would need the very image that is missing.
The tag is the git tree hash of docker/android instead, which changes when and
only when a file there changes. An unrelated push reuses the image, a Dockerfile
edit cannot keep serving a stale latest, and a missing tag rebuilds itself
without a manual step.

The presence probe is curl against the registry API, not `docker manifest
inspect`. The latter exits 1 on this registry even for tags that are plainly
there — jellytau-builder:latest answers HTTP 200 while docker reports "manifest
unknown" for it — and trusting it would have rebuilt 7 GB on every push. The
HEAD request also yields Docker-Content-Digest, so latest is repointed only when
the digests actually disagree, without pulling any layers.

A probe that cannot authenticate falls through to building. Rebuilding when it
was unnecessary costs minutes; skipping a build that was needed is the failure
this commit exists to remove.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
2026-08-16 14:59:57 +02:00

89 lines
3.3 KiB
Markdown

# Android build environment
Reproducible container for cross-compiling DarkRoom to Android. CI and local builds use the same
image, so a break appears in one place rather than two.
## Use
```bash
# Cross-compile for a device ABI
./docker/android/build.sh cargo ndk -t arm64-v8a build --release
# All four ABIs
./docker/android/build.sh cargo ndk -t arm64-v8a -t armeabi-v7a -t x86_64 -t x86 build --release
# Type-check without linking
./docker/android/build.sh cargo check --target aarch64-linux-android
# Interactive shell
./docker/android/build.sh
# After editing the Dockerfile
./docker/android/build.sh --rebuild
```
Prefers `podman`, falls back to `docker`. First run builds the image, which takes several minutes;
after that it is cached.
## In CI
`.gitea/workflows/android-image.yml` builds this image and pushes it to
`gitea.tourolle.paris/dtourolle/darkroom-android`, which the Android job then runs inside. It is
called on every push and finishes in seconds unless something here changed — the image is tagged
with the git tree hash of `docker/android/`, so a rebuild happens when and only when a file in this
directory does.
Nothing needs pushing by hand. Editing the Dockerfile is the trigger; `latest` follows
automatically. To force a rebuild without a content change, run the workflow from the Gitea UI with
`force` set to `true`.
The job runs on the host runner rather than in a container, because it needs the Docker daemon and
the runner host's cached registry credentials.
## Pinned versions
| Component | Version | Why this one |
|---|---|---|
| JDK | 17 | AGP's stable target. The host's JDK 25 breaks Gradle. |
| Compile SDK | API 36 | Required for Play distribution |
| **Min API** | **28** (Android 9) | Floor where Vulkan support is dependable (NFR-COMPAT-1) |
| Build tools | 36.0.0 | Matches compile SDK |
| NDK | 27.2.12479018 (r27c) | Current LTS |
| Rust | 1.92.0 | Slint 1.17 requires it; cargo-ndk 4.1.x needs ≥ 1.86 |
| cargo-ndk | 4.1.2 | |
Bumping any of these is a reviewable change, not silent drift.
### Compile SDK versus min API
These are different and both matter. `ANDROID_API` (36) is what the SDK compiles against — the
newest APIs available. `MIN_API` (28) is what native code *links* against, and determines the
oldest device that can run the result.
cargo-ndk defaults to **API 21** if not told otherwise, which is far below what this app needs.
`CARGO_NDK_PLATFORM` and the per-target linker paths both pin it to `MIN_API`. Verify with:
```bash
file target/aarch64-linux-android/release/*.so
# → "... for Android 28, built by NDK r27c"
```
## Caching
The cargo registry and target directory persist in `~/.cache/darkroom-android`, so rebuilds do not
re-download the crate index. Clear with:
```bash
rm -rf ~/.cache/darkroom-android
```
The Android target dir is kept separate from the host's `target/` — sharing one directory between
host and container builds causes constant rebuilds as they invalidate each other's fingerprints.
## What is not here
No emulator, no `adb` device access. This image cross-compiles; it does not run or deploy. Device
testing (spikes S2 and S10, which need two GPU vendors) happens on real hardware — the emulator's
GPU behaviour is not representative of Adreno or Mali, which is precisely what those spikes exist
to test.