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59 lines
2.7 KiB
Markdown
59 lines
2.7 KiB
Markdown
<img src="docs/icon/gearslip-icon.png" alt="Gearslip icon" width="96" height="96">
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# Gearslip
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Bring any app to your car screen.
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## What this is
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Gearslip is a phone-side Android Auto client. It speaks the Android Auto protocol directly
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to a car head unit over USB and acts as a **Car App Library host**: apps that ship an
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Android Auto car UI (navigation and media apps) hand Gearslip a template, and Gearslip
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renders it natively on the car screen, full quality, no phone-screen mirroring. A separate
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screen-sharing mode is included for apps that don't ship a car UI at all.
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Built by reverse-engineering the protocol for interoperability - getting a non-Google client
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talking to a car head unit that only expects Google's own app.
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## Status
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Real progress, with one hard limit that's worth knowing before you build on this:
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- **Templated app hosting works.** All 16 template types the Car App Library defines are
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rendered, including a keyboard Gearslip draws itself for search and sign-in. Verified
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against several real navigation and media apps.
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- **Media playback works.** Car-enabled media apps are browsable and controllable from the
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car UI, with lyrics and playback state, over the same host connection.
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- **The connection to a real head unit needs a certificate Google controls, and Gearslip
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doesn't ship one.** A head unit only accepts a phone identity that chains to Google's
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Automotive Link certificate authority - something only Google issues. Without one, Gearslip
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still runs and renders everything correctly against a debug harness, but a real car will
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reject the connection outright. See [docs/SPIKE_FINDINGS.md](docs/SPIKE_FINDINGS.md) for what was
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tested, including one publicly-known leaked certificate that works on some older head
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units and is rejected by newer firmware and by Google's own reference tooling.
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- **No adb, root, or Shizuku is required to run it.** Every feature is gated on an ordinary
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Android permission or an on-device consent dialog - nothing needs privileged access, on
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the phone or in the car.
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## Building
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```
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./gradlew :gearslip:assembleDebug
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```
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The APK lands at `build/Gearslip-debug.apk`.
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## Further reading
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- [docs/BUILDING_APPS.md](docs/BUILDING_APPS.md) - how to write apps Gearslip can render:
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templated apps, media apps, and the Gearslip app protocol.
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- [docs/SPIKE_FINDINGS.md](docs/SPIKE_FINDINGS.md) - the certificate investigation in full: what was
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tried, what a real head unit does and doesn't accept, and why.
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- [docs/CUSTOM_HEADUNIT_SCOPING.md](docs/CUSTOM_HEADUNIT_SCOPING.md) - the original scoping of what a
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custom head unit client would need.
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## License
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AGPL-3.0 - see [LICENSE](LICENSE). A separate commercial license is available for private
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use outside the AGPL's terms; see [NOTICE.md](NOTICE.md).
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