@domicile-desktop/system-backlight

Screen brightness for a Domicile shell, on the system calls of @domicile-desktop/sdk/system. See SHELL-SYSTEM-ACCESS.md.

Usage

import { system } from "@domicile-desktop/sdk/system";
import { brightnessSetter } from "@domicile-desktop/system-backlight/set-brightness";
import { watchBrightness } from "@domicile-desktop/system-backlight/watch-brightness";

const host = system(domicile);
const watch = await watchBrightness(host, (level) => show(level));
const set = brightnessSetter(host);
await set(0.5);

• readBacklight (./read-backlight): the preferred device under /sys/class/backlight: firmware, then platform, then raw, in systemd's order; ties by name. None without one.
• watchBrightness: the level (0 to 1) now and on each change of a whole percent. Re-reads on each udevadm monitor uevent and every two minutes.
• brightnessSetter: sets a level through logind's org.freedesktop.login1.Session.SetBrightness. Never sets zero, which turns most panels off. Sends one level at a time; a level superseded while waiting resolves SetOutcome.Superseded.
• Every call resolves a Result<…, SystemError>. A level that is not a number throws.

Requirements

• udevadm on the compositor's PATH (systemd).
• A logind session.
• Watching and setting work while the desktop is locked, so a lock screen can adjust the brightness (LOCK.md).

Testing

bun run turbo test --filter @domicile-desktop/system-backlight. Tests answer the system calls from files recorded on a ThinkPad (src/fake-system.ts).