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reterminal-dm4/emmc-provisioning/docs/SCREEN-BRIGHTNESS-SUMMARY.md
nearxos 0844adbcbe Update cloud-init scripts and documentation for enhanced DNS management and provisioning steps</message> 
<message>Modify the first-boot.sh script to include an additional step for managing screen brightness during the provisioning process. Update user-data.bootstrap to improve DNS configuration by ensuring NetworkManager manages /etc/resolv.conf correctly, and remove obsolete scripts related to systemd-resolved. Enhance documentation to reflect these changes and clarify the setup process for users, improving overall network boot functionality and user experience.
2026-03-06 14:45:23 +02:00

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Screen Brightness Control — Summary

Short overview of how the reTerminal DM brightness system works.

What it does

Components

Component Role
screen-brightness (daemon) Reads sensor and override, drives backlight and buzzer; writes /run/screen-brightness/state.
brightness-api (HTTP) Listens on 127.0.0.1:8765. POST sets override (level 1–5 or auto); GET returns current state.
brightness-overlay (UI) Small icon in bottom-right of screen; click to expand/collapse panel with buttons 1–5 and Auto. Talks to the API.

Levels and modes

  • Levels 1–5: 1 = dimmest, 5 = brightest. Written to /sys/class/backlight/lcd_backlight/brightness (0 is never used).
  • Auto: Override file set to auto (or missing). Daemon uses ambient light to pick level.
  • Manual: Override file contains 1–5. Daemon keeps that level until user switches back to Auto.

Override file: /run/screen-brightness/override
State file (read-only): /run/screen-brightness/state (mode, level, lux, override=0|1).

On-screen overlay

  • Icon: Brightness (sun) icon in the bottom-right corner; transparent when retracted.
  • Click icon: Panel expands with “Brightness”, buttons 1 2 3 4 5, and Auto. Semi-transparent background behind the buttons.
  • Active state: The current level or Auto is highlighted so you can see which is active.
  • Click again: Panel retracts to icon only.

Overlay uses the local API; if GtkLayerShell is available (Wayland), it stays on top of fullscreen apps.

Services and boot

  • screen-brightness.service — Starts the daemon. ExecStartPre writes auto into the override file so every boot starts in Auto.
  • brightness-api.service — Starts the HTTP API (after screen-brightness).
  • brightness-overlay — Started from the user session (e.g. autostart) so it appears on the desktop.

Quick reference

Action How
Set level 3 Overlay: expand → click 3. Or: echo 3 > /run/screen-brightness/override (root).
Set Auto Overlay: expand → click Auto. Or: echo auto > /run/screen-brightness/override.
Read state curl http://127.0.0.1:8765/state or cat /run/screen-brightness/state.
Config /etc/screen-brightness.conf (optional); systemctl reload screen-brightness to apply.

For full setup and regulations, see SCREEN-BRIGHTNESS-MANUAL-SETUP.md and SCREEN-BRIGHTNESS-REGULATIONS.md.