candela [WIP]

Smooth color temperature transitions for hyprsunset.

Features

• Automatic sunrise/sunset calculation based on location
• Fixed schedule mode for explicit wakeup/bedtime times
• Smooth easing transitions (linear, ease_in, ease_out, ease_in_out)
• Simple TOML configuration
• Environment variable overrides
• UNIX philosophy: simple, composable, efficient
• Optimized updates (only calls hyprctl when temperature changes)

Installation

From Source

git clone https://github.com/candela/candela
cd candela
cargo build --release
cargo install --path .

From Crates.io

cargo install candela

Configuration

Create a config file at ~/.config/candela/config.toml:

mode = "auto"

[location]
latitude = 48.516
longitude = 9.12

[schedule]
wakeup = "07:00"
bedtime = "22:00"

[transition]
duration_minutes = 60
easing = "linear"

[temperature]
day = 6500
night = 1500

[daemon]
tick_interval_seconds = 5
optimize_updates = true
status_update_interval = 1

Configuration Options

Option	Description	Default
mode	auto or fixed	auto
location.latitude	Latitude for sunrise/sunset	0.0
location.longitude	Longitude for sunrise/sunset	0.0
schedule.wakeup	Wake time (HH:MM)	07:00
schedule.bedtime	Bed time (HH:MM)	22:00
transition.duration_minutes	Transition duration	60
transition.easing	Easing function	linear
temperature.day	Day temperature (K)	6500
temperature.night	Night temperature (K)	1500
daemon.tick_interval_seconds	Update interval	5
daemon.optimize_updates	Only call hyprctl when temp changes	true
daemon.status_update_interval	Status file update frequency (0=every tick)	1

Environment Variables

All config options can be overridden via environment variables:

CANDELA_MODE=auto
CANDELA_LATITUDE=48.516
CANDELA_LONGITUDE=9.12
CANDELA_DAY_TEMP=6500
CANDELA_NIGHT_TEMP=1500
CANDELA_TRANSITION_DURATION=60
CANDELA_EASING=linear
CANDELA_TICK_INTERVAL=5
CANDELA_OPTIMIZE_UPDATES=true
CANDELA_STATUS_UPDATE_INTERVAL=1

Usage

candela daemon    # Run the daemon (default)
candela now       # Show current temperature
candela status    # Show status (temp, phase, target, progress)
candela set 3000  # Set temperature immediately
candela pause     # Pause transition
candela resume    # Resume transition
candela config    # Print current config

Status File

The daemon writes status to /tmp/candela.status:

temp=5432
phase=night
target=1500
progress=0.75

Use this for waybar integration:

"custom/candela": {
    "exec": "candela status",
    "interval": 5,
    "format": "{}K"
}

Or simply:

watch -n 5 candela status

Hyprland Integration

Add to your ~/.config/hypr/hyprland.conf:

exec-once = candela daemon

Or as a systemd user service:

[Unit]
Description=candela daemon
After=graphical-session.target

[Service]
ExecStart=%h/.cargo/bin/candela daemon
Restart=on-failure

[Install]
WantedBy=default.target

Then enable:

systemctl --user daemon-reload
systemctl --user enable --now candela

Optimization

candela follows UNIX philosophy:

• Optimized updates: By default, hyprctl is only called when the temperature actually changes
• Configurable status updates: Control how often the status file is updated (0 = every tick, N = every N ticks)
• Simple status file: Easy to parse with shell tools, suitable for waybar modules

License

MIT