XGIMI Elfin Plus (WK03C, Android 11): gear button needs settings_key_scancodes 66; keycode route did nothing #3613

Part: Launcher (the home screen), install script

TV: XGIMI Elfin Plus projector (WK03C, device altai, MediaTek), Android 11, kernel 4.19.116, remote "XGIMI RC"

What happened

With the stock Google TV home (launcherx) disabled, the remote's gear button never opened the launcher's quick settings panel, even with settings_key_panel on, HomeKeyService enabled and bound (dumpsys accessibility listed it under Bound services) and settings_key_keycodes set.

• getevent -lt shows the gear as /dev/input/event3 EV_KEY KEY_F8 (MSC_SCAN 00070041), so the press does reach Android.
• A keycode list was no use: the key layout file for this remote (/vendor/usr/keylayout/Vendor_000d_Product_3838.kl) can't be read from adb shell, and logcat prints no key lines here, so I could not tell which Android keycode scancode 66 becomes. [139] (F8) did nothing, and injected keys (input keyevent) don't go through the helper on this set, so they proved nothing either.
• Separately, launcherx was switched back on repeatedly, within minutes of pm disable-user. Each time it was on, the gear (and Home) opened Google TV, and the helper never saw the key. This looks like the XGIMI xrmservice behaviour described in examples: XGIMI MoGo 3 Pro profile button crashes xrmservice and sets off autofocus; "KEYCODE_F6:ignore" stops it #3121 (it starts a launcherx activity and re-enables launcherx on its remote keys).
• launcherx was also enabled again after some tools/theme.sh runs; I could not tell why.

What fixed it

settings_key_scancodes (config.xml only) with the gear's scancode:

<integer-array name="settings_key_scancodes">
    <item>66</item>
</integer-array>

Rebuilt (tools/docker-build.sh), reinstalled with SKIP_BUILD=1 HOME_KEY_SERVICE=1 RESTORE_KEY_SERVICES=1 launcher/build-and-install.sh, launcherx and setupwraith disabled, theme with "settings_key_panel": true. Pressing the real gear button then opens the quick settings panel, over Home and over Netflix.

Suggestions

• docs: say that when the keycode can't be found (key layout unreadable, no InputReader log), the evdev code from getevent -lt (here KEY_F8 = 66) works as a scancode entry in settings_key_scancodes. That entry only exists in config.xml, so it needs a rebuild; Config.java does not read it from a theme's config.json. Reading it from config.json like settings_key_keycodes would remove the rebuild.
• an examples/ entry for the Elfin Plus (WK03C) would be useful: gear is scancode 66 / KEY_F8.
• launcherx re-enable after pm disable-user on XGIMI (see examples: XGIMI MoGo 3 Pro profile button crashes xrmservice and sets off autofocus; "KEYCODE_F6:ignore" stops it #3121 and Launcher: keep accessibility helpers enabled across a reboot #3199): the gear press and Home both end up on Google TV until it is disabled again.

Output (getevent -lt, gear pressed three times):

/dev/input/event3: EV_MSC  MSC_SCAN  00070041
/dev/input/event3: EV_KEY  KEY_F8    DOWN
/dev/input/event3: EV_KEY  KEY_F8    UP