car-interface-android/docs/IMPLEMENTATION_PLAN.md

CarDash implementation plan

Last updated: 2026-10-29

1. What we are building

CarDash is a Flutter/Dart Android home-screen launcher for a landscape car tablet. It deliberately trades the reference head-unit chrome for maximum compatibility:

• One home page. No top bar, no bottom dock, no pages.
• Clock/date, battery/charging and Wi-Fi on the page.
• A prominent media-volume card (ring, slider, −/+, mute).
• Up to 16 home buttons: Navigation, Music, Radio, Settings, All apps, plus apps pinned from All Apps.
• Navigation/Music/Radio are app slots with show/hide switches. They can be assigned, changed and cleared. Settings and All apps are always present.
• Pinned apps are added by long-pressing an app in All Apps and removed by long-pressing the added button on Home. Settings and All apps are always last. Only pinned apps show their own icon by default; the fixed buttons and predefined slots stay stylized.
• The grid adapts from 2 to 6 columns and shrinks its tiles as the count grows.
• Every external app opens full-screen through a normal Android Intent.
• Settings: light/dark/automatic theme, six accent colors, battery visibility, fixed night window, home-button switches, slot assignment, HOME-role setup, four-digit PIN.
• The stylized Music tile shows an animated equalizer while media audio is active.
• The long-press hint fades away two minutes after app start.
• The Home-role banner is gone; a one-time first-run tip points to Settings.
• Long-pressing a pinned app opens Rename, Change icon and Remove. Rename/icon changes persist; Remove needs no confirmation.
• Optional OBD-II over a paired Bluetooth Classic ELM327: digital speed, throttle bar, rolling 5 km MAF economy and ambient temperature.
• Optional location weather fallback when OBD has no ambient value; red below 3°C; no row when unavailable.
• Dark surfaces are tinted by the selected accent instead of retaining a green base.
• PIN is requested only on a cold start, never on resume or screen-off.
• The screen stays awake while CarDash is the foreground window.
• Landscape-only; tablet-first 1280×800; Android 10 minimum.
• Package: com.wasp.cardash_launcher. Display name: CarDash.

2. Decisions and why

Decision	Choice	Rationale
Central app content	Launcher-native; apps open full-screen	Android cannot embed another app; overlay chrome was rejected as fragile and app-obstructing.
UI chrome	None (no bars)	Removes the mismatch between launcher chrome and full-screen apps; cleaner, more compatible.
Home layout	Single page, info + volume + up to 16 buttons	Matches the refined brief; tiles scale from 2 to 6 columns.
App slots	Navigation, Music, Radio with visibility switches	Kept from the original brief; Settings and All apps are fixed.
Pinned apps	All Apps long-press adds, Home long-press removes	Makes any installed app reachable from Home without editing a separate layout screen.
Home cap	16 buttons total, including Settings and All apps	Keeps the single page legible at tablet resolutions; enforced in LauncherController.
Icons	Only pinned apps show their own icon by default; fixed slots stay stylized	Keeps the dashboard consistent while making added apps recognizable.
Accent	Six curated choices, persisted in Settings	Changes the whole theme without a color picker or arbitrary contrast failures.
Battery visibility	One switch hides level and charging bolt	One control for both indicators, as requested.
Media feedback	Stylized Music tile + animated bars while media is active	Compact visual feedback without adding a media control surface.
Hint lifetime	Two minutes from process start, then fade out	Avoids permanent onboarding chrome; survives widget rebuilds via AppClock.
Home role	Settings row only; one-time first-run tip	Removes permanent dashboard chrome while keeping discovery.
Pinned editing	Long-press menu: Rename / Change icon / Remove	Keeps the home page clean; removal remains immediate.
Custom icon source	Default app icon plus 29 bundled monochrome line icons	Matches the stylized dashboard and follows light/dark theme colors.
OBD transport	Bluetooth Classic SPP, bonded ELM327 only, read-only	No scanning, BLE, USB or Wi-Fi; one native worker serializes requests.
OBD values	Speed, throttle (49/11), MAF economy, ambient (46)	The requested dashboard subset; unsupported PIDs stay hidden.
Economy	5 km MAF rolling window, petrol constants, fuel-cut guard	Matches the design note; show — until 0.5 km.
Weather fallback	Open-Meteo + one-shot device location, Settings toggle	No API key/account; hide the row on any failure.
Temperature priority	OBD ambient, else location weather	OBD wins whenever a fresh value exists.
Accent background	Dark canvas/surfaces/borders blend toward the accent	Fixes the green base showing through when Blue is selected.
Screen	FLAG_KEEP_SCREEN_ON while foreground	The dashboard is the car display; no wake-lock permission needed.
Theme	Light / Dark / Automatic with fixed 19:00–07:00 window	No location permission or network; time pickers make the window adjustable.
PIN	Four digits, salted PBKDF2 hash, cold start only	Matches the explicit instruction; no re-lock while running.
Min Android	API 29 (Android 10)	Requested minimum; no in-scope API requires newer.
Target/compile	36	Current Flutter toolchain defaults; runs on API 29.
Orientation	sensorLandscape + Dart orientation lock	Car/tablet form factor; portrait is intentionally unsupported.
AVD	10.1" WXGA tablet, 1280×800, 160 dpi, API 35 and API 29	Matches a dashboard tablet and the reference resolution class.
HOME role	Standard RoleManager request + Settings row	A launcher must be chosen as the system home app; never silently forced.
Overlay/kiosk/root	Out of scope	Rejected for compatibility.

3. Architecture

Flutter
  HomeScreen
    ClockBlock / StatusCluster / VolumeCard / ShortcutGrid
    LauncherController  -> apps, slots, pinned apps, 16-button cap, default-home state
    SystemController    -> battery/Wi-Fi/volume/media polling
  AllAppsScreen / AppPickerSheet
  SettingsScreen -> General / Security
  PinSetupScreen / LockScreen -> LockController -> PinService
Android (Kotlin)
  MainActivity -> keep-screen-on, volume keys, permission forwarding
               -> LauncherBridge (packages, icons, system flag, role)
               -> SystemBridge (battery, Wi-Fi, volume, media activity)
               -> TelemetryBridge (Bluetooth devices, OBD, location)
               -> ObdService (Classic SPP ELM327 worker)

• SettingsRepository is the only persistence path for theme, night window, slot visibility/assignments and pinned apps. flutter_secure_storage holds the salted PIN hash.
• Package enumeration and icon rendering happen on a worker thread in Kotlin and are returned as PNG bytes.
• Timers for volume/status are stopped when the app leaves the foreground.
• The PIN check is awaited before runApp, so there is no dashboard flash on a locked cold start.
• Network access is limited to the optional Open-Meteo weather fallback; no telemetry.

4. Milestones

#	Milestone	State
M0	Local git repo, Flutter scaffold, launcher config, package ID, icons, docs	Done
M1	x86_64 API 35/API 29 images, 1280×800 landscape tablet AVDs, emulator/install scripts	Done
M2	Theme system, single home layout, clock/status, volume card, shortcut grid	Done (initial visual pass)
M3	Kotlin bridges: app list/icons/launch, HOME role, volume, battery/Wi-Fi	Done
M4	App picker, All Apps, slot persistence, long-press flows, launch errors	Done
M5	Settings, theme auto window, PIN setup/change/remove, cold-start lock	Done
M6	Interaction testing, light/dark screenshots, layout polish, API 29 verification	Done
M7	Release build, final docs, screenshots, last commits	Done
M8	Home-button visibility switches, All Apps pinning, 16-button adaptive grid, keep-awake	Done
M9	Accent colors, battery toggle, fading hint, user icons, Media equalizer, install rule	Done
M10	Remove Home-role banner, one-time first-run tip, pinned Rename/icon/remove menu	Done
M11	Restore stylized fixed icons; pinned apps show own icons by default; 29-icon selector	Done
M12	Accent-tinted dark theme, OBD-II adapter/telemetry, location weather fallback, Car data Settings	Done

5. Verification checklist

• flutter analyze clean.
• Unit/widget tests pass (23 tests: PIN, repository, theme/accent, battery, first-run state, slot visibility, pinned apps, custom labels/icons, cap, dense grid, equalizer).
• Debug APK builds with JDK 21.
• Installs on API 35 1280×800 tablet.
• HOME role granted; Home opens CarDash.
• Immersive full-screen; no Android bars.
• Real app list and icons in All Apps.
• App picker assign / long-press change / clear, with persistence across restart.
• Launch Navigation/Music/Radio full-screen and return Home (verified with Maps and YouTube Music).
• Volume slider, mute and hardware-key synchronization (keys are routed to STREAM_MUSIC while the dashboard is foreground).
• Light theme, dark theme and automatic switch.
• PIN set/change/remove; cold start shows lock; wrong PIN; no re-lock after returning from an app.
• Verify 1024×600 compact layout (adb shell wm size 1024x600).
• Boot and verify on Android 10 (API 29) AVD, including PIN and release APK.
• Release APK on both AVDs (54 MB universal APK).
• Navigation/Music/Radio switches hide/show buttons, persist, and preserve assignments.
• All Apps long-press pins apps; the 16-button cap rejects a 17th button.
• Long-press on an added app removes it; it can be re-added from All Apps.
• 16 buttons fit at 1280×800 and 1024×600; the grid uses 2–6 columns.
• FLAG_KEEP_SCREEN_ON is present on the dashboard window.
• Six accent choices change the Material theme immediately and persist.
• Battery switch hides both the battery level and charging bolt.
• Settings/All apps are the last two Home buttons.
• A user-installed app (F-Droid) shows its own icon; system apps stay generic.
• Music equalizer widget animates; native media-active polling is wired.
• Home hint is gone after two minutes from process start.
• All Apps search icon is visibly smaller.
• No Home-role banner; the first-run tip appears once, then never again.
• Long-press pinned app shows Rename, Change icon and Remove.
• Rename updates the Home label; Change icon persists a stylized icon; Remove is immediate.
• Fixed buttons stay stylized; pinned apps show their own icons by default.
• Change icon offers Default plus 29 monochrome icons and applies the chosen icon.
• Accent-tinted dark background changes from green to blue when Blue is chosen.
• OBD Settings device dropdown and Bluetooth permission action are present.
• OBD economy/card tests pass; native ELM327 path compiles.
• Location permission, reverse geocoding and Open-Meteo fallback verified live (Ukiah, 17°C).
• Temperature row renders below the date and follows OBD/weather priority.
• Release 0.6.0 installed on the emulator and physical Android 17 tablet.
• Screenshots in docs/screenshots/; README/AGENTS/plan/OBD doc updated.

6. Known risks and mitigations

1. Media-volume polling is every 900 ms while foreground. It is cheap and handles hardware keys, but a future native ContentObserver would remove the polling. No global play/pause is in scope.
2. QUERY_ALL_PACKAGES is required for a launcher app list. It is documented and acceptable for sideloading; a Play distribution needs policy work.
3. PIN security scope: cold-start only by design; it does not replace the Android keyguard or protect against adb/data extraction. README explains it.
4. Emulator stability: headless emulators can be killed by the host; scripts use managed boot and the host GPU. SwiftShader is only a fallback.
5. Flutter 3.47 / AGP 9.1 / JDK 21: works on this machine; Java 27 is not the validated toolchain. The emulator uses the host GPU; SwiftShader segfaulted on the API 35 image, so the helper script defaults to -gpu host.
6. 16-button density: small labels and mixed pinned-app icons are the trade-off for a single page. The Settings count and grid scaling make the limit explicit.
7. Screen-on battery use: the flag applies only while the dashboard is foreground; it is not a background wake lock.
8. Media attribution: the equalizer follows AudioManager.isMusicActive, not a specific package. Exact attribution would require notification access.
9. Pinned customizations: Rename affects only the Home label. Default restores the app icon; a chosen stylized icon is a bundled asset and cannot become unavailable.
10. OBD hardware is untested here. No ELM327 adapter is available on this machine; the native socket/protocol path compiles and the parser/economy UI is unit-tested, but a real-car soak test is still required.
11. Weather depends on location, permission and network. Any failure hides the row; OBD ambient is always preferred when available.
12. Uninstall/reinstall may drop the HOME role; Settings and the installer script can restore it.

7. Out of scope (for now)

• Embedded third-party apps, overlay bars, split screen, kiosk/device-owner.
• Global play/pause or now-playing metadata.
• Wi-Fi/BLE/USB OBD adapters, DTC contents, RPM/coolant/voltage/MIL, fuel level/range.
• Calls, climate, reverse camera.
• An app drawer with folders/pages; a single searchable All Apps page is enough.
• Play Store packaging/signing, remote git, CI.

8. Change log

• 2026-10-29: Pivoted from an overlay/head-unit chrome design to a launcher-native single home page, no top/bottom bars, full-screen external apps. Implemented core UI, Kotlin bridges, settings, PIN and documentation. Verified initial home, app picker, All Apps, volume, themes and cold-start PIN on the API 35 AVD; then verified the release build and PIN flows on the API 29 AVD. Added hardware volume-key routing and PIN verification progress. Screenshots captured at 1280×800 and 1024×600.
• 2026-10-29: Added home-button visibility switches, All Apps long-press pinning, a 16-button cap with an adaptive 2–6 column grid, pinned-app removal, and a foreground keep-screen-on flag. Verified 17 tests, 16-button layouts at 1280×800 and 1024×600, cap/removal/re-add, and 0.2.0 on the physical tablet.
• 2026-10-29: Added six accent choices, battery/charging visibility, a two-minute fading hint anchored to process start, Settings/All apps last, user-app icons, a media-active equalizer, and a smaller All Apps search icon. Added the two-attempt ADB install rule. Verified 21 tests, accent/battery toggles, a user-app icon (F-Droid), hint expiry, and 0.3.0 on the emulator/tablet.
• 2026-10-29: Removed the Home-role banner; added a once-only first-run tip. Replaced immediate removal with a pinned-app menu (Rename, Change icon, Remove), custom Home labels and up to 25 installed-app icon choices. Verified 23 tests and the full menu flow at 1280×800; 0.4.0 installed on the tablet.
• 2026-10-29: Clarified icon policy: fixed/predefined buttons are always stylized; only pinned apps show their own icon by default. The Change icon grid now offers Default plus 29 bundled monochrome line icons. Verified 0.5.0 on the emulator and tablet.
• 2026-10-29: Fixed the dark accent background. Added optional ELM327 OBD-II (speed, throttle, rolling MAF economy, ambient), location/Open-Meteo fallback, Car data Settings with adapter dropdown and weather toggle, and permission flows. Verified 30 tests, live weather on the emulator and 0.6.0 installation; OBD hardware remains a car test.