This is a Rust rewrite of Redshift, a screen color temperature adjustment tool. This initial version includes the core functionality needed to calculate and display color temperatures based on geographic location and time of day.

Current Status

Phase 1: Core Foundation ✅ Complete

Module structure set up with separate files for types, solar, colorramp, gamma, and location
Core types ported from C: Location, ColorSetting, Period, TransitionScheme, ProgramMode
Solar calculations fully ported with astronomical algorithms for day/night timing
Color ramp logic ported with blackbody color table for temperature-to-RGB conversion

Phase 2: Basic Functionality ✅ Complete

Dummy gamma method implemented (no-op for safe testing)
Manual location provider implemented (lat/lon specification)
CLI argument parsing using clap crate
Basic main loop that calculates solar position and applies color temperature

Phase 3: Basic Testing ✅ Complete

Solar calculations tested and working correctly
Color temperature output tested with dummy method

Phase 4: Continual Mode ✅ Complete

Main event loop implemented with periodic updates
Smooth fade animations between color temperatures
Intelligent sleep intervals (5s normal, 100ms during fades)
Period change detection and verbose status updates

Building

cd rewrite
cargo build --release

Installation

Quick Install (User Mode - Recommended)

The easiest way to install redshift-rebooted is using the installation script:

cd rewrite
./scripts/install.sh

This will:

Build the release binary
Install to ~/.local/bin/redshift-rebooted
Install systemd user service to ~/.config/systemd/user/
Provide instructions for enabling and starting the service

System-Wide Installation

For system-wide installation (requires root):

cd rewrite
sudo ./scripts/install.sh --system

This installs:

Binary to /usr/bin/redshift-rebooted
Systemd service to /usr/lib/systemd/user/ (still runs as user service)

Starting the Service

After installation, enable and start the service:

# Enable service to start automatically at login
systemctl --user enable redshift-rebooted

# Start the service now
systemctl --user start redshift-rebooted

# Check service status
systemctl --user status redshift-rebooted

# View logs
journalctl --user -u redshift-rebooted -f

Uninstallation

To uninstall redshift-rebooted:

# User mode
./scripts/uninstall.sh

# System mode
sudo ./scripts/uninstall.sh --system

Configuration

Before starting the service, configure your location in ~/.config/redshift/redshift.conf. See redshift.conf.sample for an example configuration.

The service will automatically:

Start when you log in (if enabled)
Restart on failure
Run in the background continuously
Adjust screen temperature based on time of day

Usage

The basic command matches the legacy C version:

# Print current color temperature for a location
./target/debug/redshift-rebooted -l 40.7:-74.0 -m dummy -pv

# Continual mode (continuously updates temperature)
./target/debug/redshift-rebooted -l 40.7:-74.0 -m dummy -v

# One-shot mode (set temperature once and exit)
./target/debug/redshift-rebooted -l 12:-34 -m dummy -o

# Custom day/night temperatures
./target/debug/redshift-rebooted -l 12:-34 -t 5500 --temp-night 3000 -p

Options

-l, --location <LAT:LON> - Location as latitude:longitude (required)
-m, --method <METHOD> - Gamma adjustment method (currently only 'dummy')
-o, --one-shot - Set temperature once and exit
-p, --print - Print current settings and exit
-v, --verbose - Verbose output
-t, --temp-day - Day temperature in Kelvin (default: 6500)
--temp-night - Night temperature in Kelvin (default: 3500)

Architecture

Module Structure

src/
├── main.rs         - Entry point, CLI parsing, main loop
├── types.rs        - Core type definitions
├── solar.rs        - Solar position calculations
├── colorramp.rs    - Color temperature to RGB conversion
├── gamma.rs        - Gamma adjustment method trait and implementations
└── location.rs     - Location provider trait and implementations

Key Components

Solar Module (solar.rs)

Implements astronomical algorithms from "Astronomical Algorithms" by Jean Meeus
Calculates solar elevation for any time and location
Determines day/night periods based on sun position

Color Ramp Module (colorramp.rs)

Contains blackbody color table (1000K-25100K in 100K intervals)
Interpolates between table values for precise temperatures
Applies brightness and gamma correction

Gamma Methods (gamma.rs)

Trait-based design for multiple adjustment methods
Currently implements dummy method (prints temperature, no display changes)
Ready for additional methods: DRM, RandR, VidMode

Location Providers (location.rs)

Trait-based design for multiple location sources
Currently implements manual provider (user-specified lat/lon)
Ready for additional provider: GeoClue2

Systemd Service

The systemd service integration allows redshift-rebooted to run automatically in the background:

Service Features

Automatic startup: Starts at login when enabled
Auto-restart: Restarts automatically if it crashes (3-second delay)
User service: Runs as your user account with display access
Graphical session: Only starts after graphical session is available

Service Management

# Enable auto-start at login
systemctl --user enable redshift-rebooted

# Start immediately
systemctl --user start redshift-rebooted

# Stop the service
systemctl --user stop redshift-rebooted

# Disable auto-start
systemctl --user disable redshift-rebooted

# Restart after config changes
systemctl --user restart redshift-rebooted

# View status and recent logs
systemctl --user status redshift-rebooted

# Follow logs in real-time
journalctl --user -u redshift-rebooted -f

# View all logs
journalctl --user -u redshift-rebooted

Troubleshooting

Service fails to start:

Check logs: journalctl --user -u redshift-rebooted
Verify configuration file exists: ~/.config/redshift/redshift.conf
Test manually: redshift-rebooted -v to see errors

Screen temperature not changing:

Ensure you're using the correct gamma method for your system
Check that location is configured correctly
Verify service is running: systemctl --user status redshift-rebooted

Service not starting at login:

Enable the service: systemctl --user enable redshift-rebooted
Ensure systemd user services are enabled (should be default on most systems)

Next Steps

To complete the rewrite, the following work remains:

Real Gamma Methods - Port Linux gamma adjustment methods:
- DRM (Direct Rendering Manager for TTY/framebuffer)
- RandR (X11 RandR extension, preferred, multi-output)
- VidMode (X11 VidMode extension, legacy, single output)
Additional Location Provider - Port automatic location detection:
- GeoClue2 (Linux location service)
~~Configuration File Support~~ ✅ Complete - INI-style config files supported
~~Signal Handling~~ ✅ Complete - SIGUSR1 (toggle), SIGINT/SIGTERM (restore & exit)
Hook Scripts - Execute user scripts on period changes

Testing

The Rust rewrite has been tested and verified to:

Parse command-line arguments correctly
Calculate solar elevation accurately
Determine day/night/transition periods
Compute appropriate color temperatures
Display verbose output with solar information
Run continuously with smooth fade transitions
Update temperature based on changing solar position

Example test (print mode - shows current status and exits):

$ ./target/debug/redshift-rebooted -l 12:-34 -m dummy -pv
Location: 12.00, -34.00
Period: Night
Color temperature: 3500K
Brightness: 1.00
Gamma: 1.00, 1.00, 1.00
Solar elevation: -44.03°

Example test (continual mode - runs forever with updates):

$ ./target/debug/redshift-rebooted -l 40:-74 -m dummy -v
Location: 40.00, -74.00
Period: Night
Color temperature: 3500K
# Smooth fade from initial 6500K to target 3500K over ~4 seconds
Temperature: 6494
Temperature: 6478
...
Temperature: 3500
# Then continues monitoring, sleeping 5 seconds between checks

Unit Tests

Comprehensive test suites have been created for all non-dummy/non-placeholder code:

cargo test

Test Coverage:

types_tests.rs (9 tests): Core type definitions, bounds checking, defaults
solar_tests.rs (8 tests): Solar elevation calculations, time-based variations
colorramp_tests.rs (13 tests): Color temperature conversions, gamma/brightness adjustments
location_tests.rs (19 tests): Manual location provider functionality, option parsing
continual_mode_tests.rs (24 tests): Event loop logic, transition progress, fade animations, color interpolation

Total: 73 passing tests

All tests verify correct behavior against the legacy C implementation, including:

Solar position calculations at various latitudes/longitudes
Color temperature interpolation from blackbody table
Gamma ramp adjustments with brightness and gamma correction
Location provider initialization and configuration
Transition progress calculation from solar elevation
Fade animation smoothness and easing functions
Color setting interpolation and major difference detection
Complete event loop iteration logic

Compatibility

This rewrite maintains compatibility with the legacy C version's command-line interface for basic operations. The output format and calculation methods are designed to match the original implementation.

Credits

Original author of Redshift for C source code Simple Maps for the country/city data under Creative Commons 4.0 liscense https://creativecommons.org/licenses/by/4.0/ https://simplemaps.com/data/world-cities