Brightness

App and system screen brightness

One.Brightness reads and writes the screen brightness on iOS and Android. It has get(), set(value), getSystem(), setSystem(value), getSystemMode(), setSystemMode(mode), isUsingSystem(), restoreSystem(), getPermissions(), requestPermissions(), isAvailable(), and addListener(fn).

import { One } from 'one'

const initial = await One.Brightness.get()
await One.Brightness.set(0.5)
// later
await One.Brightness.set(initial)

get() and set(value) take and return a number between 0 and 1; out-of-range values throw synchronously. On iOS the setting persists until the device locks. On Android it applies to the current activity while the app is in the foreground.

The getSystem family is Android only: getSystem() reads the global brightness, setSystem(value) writes it and switches the mode to manual, getSystemMode() resolves 'unknown', 'automatic', or 'manual', setSystemMode(mode) switches between 'manual' and 'automatic', isUsingSystem() reports whether the activity follows the system value, and restoreSystem() drops the app override. On iOS these resolve the app value or the matching empty value ('unknown' mode, always using system) and do nothing. addListener(fn) receives { brightness } and fires on iOS only; the iOS simulator never posts brightness notifications for programmatic sets, so listeners stay quiet there while get still reads back every set.

System writes need the Android write-settings grant. getPermissions() and requestPermissions() resolve { status, granted, canAskAgain }, where status is 'granted', 'denied', or 'undetermined'. requestPermissions() opens system settings; read the grant back when the app resumes. On iOS permissions resolve granted with no prompt.

System writes also need WRITE_SETTINGS in the Android manifest, which prebuild does not declare yet. Until it does, grant the access from the system settings screen that requestPermissions() opens; on dev builds adb shell appops set <package> WRITE_SETTINGS allow grants it directly. Without the declaration and the grant, setSystem and setSystemMode reject with E_BRIGHTNESS_PERMISSIONS. On web, reads resolve 1, effects resolve without doing anything, permissions resolve denied, and listeners never fire.