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screen colour temperature daemon for X11
location from the timezone · single instance · reapplies after suspend
Version 0.2.0. The daemon provides timezone based location, a single instance D-Bus lock, gamma ramps over XRandR, reapplication on resume from suspend, and a
--statusreadout. Three clients ship with it, a tray icon, a settings panel, and a terminal dashboard. A release with a.deband an AUR package are available. Flatpak is planned. Young software, tested on one machine so far. Report what breaks.
In the default live theme the dashboard's accent colour is the tint the daemon is currently applying, so the interface reads warmer as evening comes on. Every other colour on screen is derived from that one.
The reel above is nightlight-tui --demo, a day compressed into twenty-eight seconds, no daemon required. Each keypress the tour makes is shown in the corner as it happens.
This tool writes gamma ramps through XRandR. That mechanism does not exist under GNOME's or KDE's Wayland sessions. Wayland support, if it lands, will cover wlroots compositors only (Sway, Hyprland, river) through a separate backend.
If you are on Wayland today, use wl-gammarelay-rs.
redshift was archived in April 2026. gammastep took its place and is maintained, packaged everywhere, and works. A maintained redshift already exists, and this is not one.
This project fixes three defects that gammastep inherited from redshift's architecture. Each one was measured, not assumed. The evidence, with commands and outputs, is in docs/PRIOR-ART.md.
1. It will not start without being told where you live.
With no config file and no -l, gammastep prints its settings, hangs at location acquisition, and applies nothing. No error is emitted. Geoclue2, its only automatic provider, is unavailable on most desktops.
nightlightd reads /etc/localtime and looks the coordinate up in the timezone database every Linux system ships. No network, no permissions, no questions. Sunset lands within a few minutes of correct, which is all the transition curve needs.
2. Two copies can run at once, and the screen flickers. Nothing prevents it. On a stock Mint Xfce install, four redshift instances had accumulated from three autostart mechanisms that do not know about each other.
nightlightd claims a D-Bus name on startup. A second instance finds the name taken and exits.
3. It does not react when the ramp is wiped.
nm -D on the gammastep binary shows no xcb_randr_select_input. It never subscribes to RandR events, so it cannot notice a resume from suspend, a resolution change, or a monitor being plugged in. It recovers on its next polling tick, if at all. It reads get_screen_resources_current, so hotplugged monitors are likely never seen.
nightlightd subscribes to screen events and rewrites the ramp when they fire.
Everything else (packaging, systemd units, solar elevation scheduling) gammastep already does well, and none of it is a selling point here.
The daemon runs headless and needs no interface. Three thin clients ship with it. Each is a separate process that holds no state and talks only over D-Bus, so if one crashes the filter keeps running.
nightlight-trayputs on/off, automatic/manual and the current temperature in the notification area.nightlight-paneldraws the day/night curve with sliders for the temperature bounds, gamma and night brightness.nightlight-tuiis a terminal dashboard built with ratatui.
The dashboard has five tabs.
now plots the day as a square wave over the sun's crossing arcs, with a strip along the floor showing the screen's colour at every hour. today derives the day's milestones (night's end, sunrise, full day, solar noon, sunset) from the same solar maths the daemon schedules on. location shows the city the timezone resolved to and takes a manual pin on the map. settings adjusts the day and night bounds, gamma and night dim. T cycles the themes. live follows the screen; the rest (tokyo, mocha, nord, gruvbox, synth, ember, phosphor) are fixed palettes.
Every knob is a number in ~/.config/nightlightd/config.toml. All fields are optional. These are the defaults, except the two shaping examples.
day_temp = 6500
night_temp = 4500
gamma = 0.9 # bend the ramp's curve, constant all day
night_brightness = 0.9 # dim to 90% at night, easing with the sunGamma and brightness ride the same gamma ramp write as the colour, so they cost nothing extra and reset with it. Nothing is adaptive. No screen sampling, no backlight control, by design.
Every change of target, a toggle, a manual set, the daemon starting at night, eases onto the screen over about two seconds rather than landing in one frame. The walk is taken on the mired scale, so the glide looks even to the eye the whole way down.
A daemon does the work. Thin clients talk to it over D-Bus.
tray icon ─┐
panel ─┤
dashboard ─┼─► DBus ─► nightlightd ─► gamma ramp
CLI ─┘ ▲ ▲
│ └─ RandR events
└────── timer
The daemon has no interface of its own. If a client dies, the filter keeps running.
docs/HOW-IT-WORKS.md is the long version, written for someone who has never heard of a gamma ramp.
Grab the .deb from the latest release, then
sudo apt install ./nightlightd_0.2.0-1_amd64.deb
systemctl --user enable --now nightlightd
The package installs all four binaries, the systemd user unit, and the tray's
autostart entry. A user unit cannot be enabled at install time, so the
daemon needs that one systemctl --user line (or a log-out/log-in plus the
panel's "Start at login" box).
yay -S nightlightd
systemctl --user enable --now nightlightd
The release also carries a musl tarball, fully static builds of the daemon and the terminal dashboard with no library dependencies, for x86_64 Linux of any age. Unpack and follow the bundled INSTALL.
Requires a Rust toolchain.
cargo install --path cli # the daemon + CLI: nightlightd
cargo install --path tray # tray icon: nightlight-tray
cargo install --path panel # settings panel: nightlight-panel
cargo install --path tui # terminal dashboard: nightlight-tui
mkdir -p ~/.config/systemd/user
cp dist/nightlightd.service ~/.config/systemd/user/
systemctl --user daemon-reload
systemctl --user enable --now nightlightd
Tracked in docs/ISSUES.md.
| M-1 | Upstream fix to gammastep | 🔶 MR open, awaiting review (below) |
| M0 | Skeleton | ✅ done |
| M1 | Core library (colour, sun, timezone) | ✅ done |
| M2 | X11 backend | ✅ done |
| M3 | Daemon and event loop | ✅ done |
| M4 | DBus, CLI, systemd, suspend | ✅ done |
| M5 | Tray icon, settings panel, terminal dashboard | ✅ done |
| M6 | Packaging and release | 🔶 v0.2.0 released, on the AUR, announced. Flatpak remains |
The timezone fallback went upstream before the Rust port of it was written. chinstrap/gammastep!28, opened 2026-07-10, adds the same provider in C, where it helps far more people. It has been awaiting review since. Upstream's last commit is from March 2025 and its oldest open merge request dates to 2020, so a long wait is expected. What the attempt revealed is recorded in docs/PRIOR-ART.md under "Upstream attempt". If it lands and the remaining defects prove fixable upstream, this repository becomes obsolete, which was always an acceptable outcome.
See LICENSE.