Gearslip/README.md

Gearslip

Bring any app to your car screen.

What Gearslip is

Gearslip is an Android Auto client for the phone. It speaks the Android Auto protocol directly to a car head unit over USB, with no Google software in the path. Gearslip acts as a Car App Library host: an app that ships a car interface hands Gearslip a template, and Gearslip renders that template natively on the car screen. Nothing is mirrored from the phone. For apps without a car interface, Gearslip offers a separate screen-sharing mode.

The author reverse-engineered the protocol for interoperability, so that a client other than Google's own can talk to a car head unit.

Features

• Phone calls. Dial from a keypad, or search your contacts, then confirm before the call goes out.
• Navigation. Gearslip hosts real Car App Library map apps on the car screen; Organic Maps and OsmAnd both work today.
• Music. Browse, play, and queue tracks from a car-enabled media app, with a Now Playing view, an Up Next queue, and lyrics.
• The web. A browser template with its own on-screen keyboard, for anything that doesn't ship a car interface of its own.
• Weather and the day ahead. A dashboard screen shows the week's calendar next to the current and coming weather.
• Notifications. Read and reply to notifications from the car screen, using the same on-screen keyboard.

Status

• The connection is wired only, for now. Plug the phone into the head unit's USB port; Gearslip does not yet offer a wireless option.
• Setup walks you through it. First launch asks for the Android Auto certificate, then one permission at a time, each with a plain reason and an Allow or Skip. A help screen inside the car answers anything setup didn't cover.
• Templated apps work. Gearslip renders all 16 template types that the Car App Library defines, and it draws its own keyboard for search, sign-in, and text fields. It has been tested against several real navigation and media apps.
• Audio reaches the car by capturing playback, not by mirroring the screen. Android requires a screen-share style consent dialog and indicator for this, even though Gearslip never reads the screen; that grant is the only way a non-privileged app can tap another app's audio. The consent normally repeats every drive; two optional adb commands in the setup guide reduce it to a one-time grant.
• Gearslip needs no adb, root, or Shizuku. Every feature relies on an ordinary Android permission or an on-device consent dialog. The two adb commands mentioned above, for audio, are the sole exception: both are optional, and both only remove a dialog that the driver would otherwise see once per drive.

Building

./gradlew :gearslip:assembleDebug

The APK lands at build/Gearslip-debug.apk.

A release build needs a signing key. Copy keystore.properties.example to keystore.properties, fill in your own values, and run ./gradlew :gearslip:assembleRelease. Git ignores both the properties file and the keystore. Without them, the debug build still works.

Writing apps for Gearslip

docs/BUILDING_APPS.md specifies how to write apps that Gearslip can render: templated apps, media apps, and the Gearslip app protocol.

License

Gearslip is licensed under AGPL-3.0; see LICENSE. The author offers a separate commercial license for private use outside the AGPL's terms; see NOTICE.md.