Bauhaus

A daily artwork wallpaper app for Android.

Each morning the bauhaus service takes a CC0 landscape from the Metropolitan Museum of Art or the Art Institute of Chicago, runs AdaIN neural style transfer against a curated reference (Monet, Hokusai, Cezanne, Turner, …), and publishes it. This app fetches that artwork and sets it as your wallpaper.

Features

• Daily artwork from the bauhaus Cloudflare Workers service
• Set as home screen, lock screen, or both
• Browse, favorite, and re-apply any day from the archive
• Save to gallery or share, with the artwork's source and licence linked
• Background updates via WorkManager
• Quick Settings tile for a one-tap update from the notification shade
• Home-screen widget (Glance) showing the current artwork
• Launcher shortcuts for "set today's" and "browse the archive"
• Per-app language support (localeConfig)
• Baseline profile for optimized startup

Tech Stack

• Jetpack Compose with Material 3
• Coil 3 for image loading, sharing one OkHttp 5 client (and its disk cache) with the API layer
• WorkManager for background wallpaper updates
• DataStore Preferences
• kotlinx-serialization

Requirements

Min SDK	35 (Android 15)
compileSdk / targetSdk	37
JDK	21 (Temurin — pinned in .mise.toml)
Android SDK	platforms;android-37.0, build-tools;37.0.0

Authoritative versions live in gradle/libs.versions.toml; this table is a summary, so prefer the catalog if they ever disagree.

Note: AGP currently tracks an alpha (9.4.0-alpha06). Behaviour can change between alphas.

Build variants

Two product flavors on the mode dimension. Every Gradle task is flavored — there is no bare assembleDebug or testDebugUnitTest.

Flavor	Contents
foss	No Google or proprietary dependencies. This is what CI builds, releases, and ships.
full	Adds Firebase Crashlytics and Analytics. Not built by CI.

Build types: debug, release, and benchmark (a non-debuggable release used by the macrobenchmark module).

Build

# Debug APK
./gradlew assembleFossDebug

# Unit tests
./gradlew testFossDebugUnitTest

# Lint (warnings are errors)
./gradlew lintFossDebug

# Coverage report -> app/build/reports/jacoco/jacocoTestReport/
./gradlew jacocoTestReport

# Install on a connected device
./gradlew installFossDebug

Or with Just:

just build          # assemble
just test           # unit tests
just lint           # lint
just coverage       # jacoco report
just check          # everything CI runs, in one go
just install        # install on a connected device
just build-full     # the Firebase-carrying flavor
just deps           # refresh gradle/libs.versions.toml
just                # list all recipes

Recipes default to the foss flavor; override with just flavor=full build.

CodeQL

The CodeQL workflow uses advanced setup to build assembleFossDebug explicitly. Disable CodeQL default setup in Settings > Code security > CodeQL analysis before enabling this workflow: default autobuild runs assemble, which also builds full and fails without google-services.json. The analysis build disables Gradle build/configuration caches and reruns tasks so CodeQL observes compilation rather than restored outputs.

Development environment

Install mise to get the pinned JDK, then point Gradle at an Android SDK — either via ANDROID_HOME or a local.properties containing sdk.dir=/path/to/Android/sdk.

mise install
./gradlew assembleFossDebug

Alternatively, open the repo in VS Code and choose Reopen in Container. The .devcontainer/ setup provisions a Debian base with JDK 21 plus the Android SDK platform and build-tools this project needs. That image is built and asserted on in CI whenever .devcontainer/ changes.

just install reads an optional android.device.serial= line from local.properties to target a specific device when several are attached.

Release signing

Release builds are signed only when signing material is present. Without it the release APK is produced unsigned — and an unsigned APK cannot be installed.

Locally, copy keystore.properties.example to keystore.properties (it is git-ignored) and fill in storeFile, storePassword, keyAlias, and keyPassword.

In CI the equivalent environment variables take precedence: KEYSTORE_PATH, KEYSTORE_PASSWORD, KEY_ALIAS, KEY_PASSWORD.

Project Structure

Module	Description
:app	Main application
:benchmark	Macrobenchmark tests and baseline profile generation

Service contract

Two properties of the bauhaus service's contract shape this code and are easy to get wrong:

• Artwork is keyed by UTC date, published at 04:00 UTC. The device clock names a different day than the service does for part of every day, so the app never calls LocalDate.now(). It seeds from serviceToday() and then anchors to the date the service itself returns in /api/today.json. See ServiceCalendar.kt.
• Image responses Vary: Accept. Every image request must carry the same Accept header or Coil and the API layer cache-miss each other and double the request count. An OkHttp interceptor enforces this — see HttpModule.kt.

License

MIT — Cascadia Collections

Artwork is not covered by that licence: images from the daily scheduled runs are CC0-1.0, and each image's own licence and upstream source are published in its metadata and shown in the app.

Nightly APK

Download the signed FOSS APK or view the nightly release. Builds publish on pushes to main and daily at 10:23 UTC; Actions also supports manual runs. Enable installation from unknown sources on your device, then open the APK. Nightlies keep the same signing key so subsequent builds install as updates. Switching from a store or locally signed build may require uninstalling it first.

Maintainers: NIGHTLY_KEYSTORE_BASE64 holds a persistent JKS with alias androiddebugkey and store/key password android. Preserve this secret to keep installed nightlies updateable. The workflow verifies APK signatures and publishes SHA256SUMS.