Femto Car Launcher

A glanceable Android home launcher for in-car displays.

Femto Car Launcher replaces the Android home screen with a single fixed dashboard designed for automotive viewing distances and touch accuracy. The dashboard combines a live map, driving data, weather, calendar, and media control on one screen, so a driver reads the essentials at a glance instead of navigating between apps.

Femto Car Launcher targets three hardware classes: aftermarket CarPlay / Android Auto AI boxes that inject Android into a factory display, built-in Android head units, and smartphones mounted as a car-navigation display. On a smartphone the launcher also runs as a regular app; becoming the default home screen stays optional. The minimum supported platform is Android 13 (Application Programming Interface — API — level 33). No single market is privileged: language, units, and locale-specific behaviour adapt per device.

_{The dashboard on a head-unit display, light and dark. The map style follows the theme. These images are the project's own screenshot-test references, regenerated from the current code on every UI change, so they cannot drift from the build. The map behind the interface is a still capture of this app's OpenStreetMap backend — the map itself renders in a WebView, which the screenshot harness cannot run (see app/src/test/resources).}

Live map

The dashboard background is a full-bleed live map that follows the vehicle.

• Two map providers. OpenStreetMap data rendered through the keyless OpenFreeMap service works out of the box with no account and no API key. A Google Maps provider (roadmap, satellite, hybrid, and terrain map types with a traffic overlay) activates when the user enters a personal Google Maps Platform API key in Settings → Map. Usage of the paid provider bills the key owner's own account; Femto Car Launcher adds no fees.
• A car-navigation camera. The camera follows the Global Positioning System (GPS) position with smooth easing, keeps the travel direction pointing up (heading-up), and offers a north-up mode. A drag detaches the camera for free panning; the camera re-attaches automatically after a pause, or immediately via the locate button. Zoom buttons and a compass sit at the screen edge in reach of the driver.
• Depth and style. Optional three-dimensional buildings and terrain relief add depth on the OpenStreetMap provider. Map colours can follow the launcher accent and the light/dark theme, or use the provider's own styles.
• Self-healing. A map that fails to load — an unstable link, a provider outage, a missing key — shows a clear notice in the visible map area and recovers automatically: reloads retry with a capped backoff while the network reports connectivity, and a reconnect after an offline period reloads the map without user action.

Driving data and trips

• Speed overlay. Current speed, trip distance, average speed, altitude, and the reverse-geocoded address of the current position, rendered in high-contrast numerals. A tap on the reset button starts a new trip with a "Since" timestamp.
• Trip recording. An on-device track log records the route at one fix per second while driving, with a configurable retention period. Recorded trips export as GPS Exchange Format (GPX) files through the system file picker.
• Trip flythrough. A tap on the speed panel opens a three-dimensional wireframe replay of the recorded track — a flythrough with a speed-coloured trail and altitude curtain, rendered natively for smooth motion, with a two-dimensional fallback on devices without the required graphics support.

Glanceable panels

• Weather. Current conditions, feels-like temperature, wind, and humidity from the Norwegian Meteorological Institute (MET Norway), with an hourly strip on the card and a full-screen panel built around a 24-hour temperature curve, precipitation nowcast, and daily range bars. Forecasts stay readable offline through an on-device cache.
• Calendar. A multi-day strip plus upcoming events read from the device calendar, with per-calendar visibility selection and a full-screen agenda panel. Event colours match the calendar colours.
• Now playing. The active media session of any music app: title, artist, album, cover art, and transport controls, including shuffle and repeat where the source app supports them. Cover art opens a full-screen player. Long titles scroll only while the vehicle is parked and truncate while moving. A spectrum visualisation renders on devices whose audio stack supports capture.
• Clock. A self-updating clock honouring the system 12/24-hour preference, with optional seconds.
• Status cluster. Wi-Fi and cellular signal, Bluetooth state, GPS reception, and battery level with charging state.

Apps and voice

• Dock. An application dock attaches to any screen edge. A long-press edits the dock: buttons and status icons reorder or hide individually, and a reset restores the default layout.
• App panel. A full-screen application panel offers search, a pinned-apps row, recently used apps, an A–Z fast-scroll index, and three icon-size presets. A long-press on an app opens App info or uninstalls the app.
• Voice assistant. A microphone button captures speech in-launcher with a live transcript, and falls back to the system voice assistant when no on-device recognizer exists or the microphone permission is denied.

Made for the car — and adjustable

Automotive defaults keep the dashboard legible and operable while driving: at the default display size, body text stays at or above 16 sp and touch targets stay at or above 64 dp, and the layout anchors cards clear of the driver's view with a left- and right-hand-drive switch. Every default remains a user choice rather than a lockout:

• Layout. Any orientation and aspect ratio, from wide head units to portrait phone mounts; the dashboard reflows across a matrix of screen sizes. Display size offers small / medium / large scales, and the small scale deliberately trades the automotive floors for density.
• Appearance. Material You dynamic colour by default, fixed accent presets as an alternative, light / dark / automatic theme, and a configurable glass look (blur, borders, drop shadows) for the floating cards.
• Typography. The system font by default, any Google Fonts family per slot (a Latin face plus a Chinese-Japanese-Korean fallback face) downloaded on demand, or any font already installed on the device — plus user-adjustable text size, weight, and letter spacing. No fonts ship inside the APK and no Play Services are required.
• Motion. A reduced-motion setting calms animations across the dashboard.
• Panels. Calendar, weather, and music cards toggle individually; the music card's spectrum, album name, and cover art each have a visibility switch.
• Units. Speed and temperature units and the clock format follow the user, independent of the system locale.

Every panel degrades gracefully: a denied permission or an unavailable data source renders a reduced state instead of an error screen. The dashboard renders identically regardless of vehicle motion — distraction responsibility stays with the driver and the vehicle's own instruments.

Privacy and data

• Femto Car Launcher requires no account and contains no advertising and no analytics.
• Location, calendar, and media data stay on the device. Network traffic goes only to the services the user selects: map tiles from the chosen map provider, weather from MET Norway, and — only when the user configures a self-hosted geocoding host — reverse-geocoding queries; the default reverse geocoder runs on-device.
• Google Maps keys are entered by the user, stored only on the device, and sent only to Google.
• Notification access, when granted, is used solely to read and control the active media session for the now-playing card.
• An in-app diagnostics report (Settings → System) summarises device and runtime facts for troubleshooting, and the open-source licenses screen lists every bundled third-party component.

Installation

Every merge to main publishes a release-signed APK as a rolling prerelease tagged nightly. Install the APK by sideloading on the head unit or with adb install -r femto-car-launcher-nightly.apk. Play Store publication is not planned at present; sideloading is the supported installation path. Android 13 or later is required.

To enable the optional paid map provider in Settings → Map:

• Google Maps — enter a personal Google Maps Platform API key with the Maps JavaScript API enabled and an HTTP-referrer restriction allowing https://appassets.androidplatform.net/*. An optional Map ID (created in the Google Cloud console) renders a vector map with heading-up rotation, tilt, and 3D; a blank Map ID renders a flat north-up raster map.

Building from source

A Java Development Kit (JDK) 21 and an Android 13+ device or emulator are the only prerequisites; the Gradle build provisions Node.js and pnpm on demand for the bundled map page.

./gradlew assembleDebug   # debug APK at app/build/outputs/apk/debug/
./gradlew test lint       # unit tests and Android Lint

Contributor documentation, including verification commands and coding rules, lives in AGENTS.md and .claude/rules/.