Temperlux

A brightness controller for external (DDC/CI) and internal (backlight) displays, written in Rust with GTK4/Libadwaita GUI.

Based on Luminance by sidevesh — rewritten from scratch with FFI-based DDC for performance and a testable architecture.

Features

• GUI — per-display brightness sliders with live hardware control
• CLI — get/set/increase/decrease brightness from the command line
• JSON output — temperlux list --json for scripting/waybar/polybar
• Sync modes — Off, Same Value, or Proportional across all displays
• Min/Max caps — per-display brightness range limits
• Display rename — custom names persisted in config
• Autostart — optional "Start on login" via Preferences
• Error auto-expiry — error messages auto-clear after 5 seconds

Install

From source

# Install dependencies
sudo apt install ddcutil libddcutil-dev libgtk-4-dev libadwaita-1-dev pkg-config

# Build and install (CLI + GUI)
make && sudo make install

This installs:

• temperlux (CLI) → /usr/local/bin/
• temperlux-gui (GUI) → /usr/local/bin/
• Desktop entry → /usr/local/share/applications/
• App icon → /usr/local/share/icons/hicolor/

From crates.io

# CLI only (no GUI)
cargo install temperlux

# With GUI
cargo install temperlux --features gui

Uninstall

sudo make uninstall

Usage

GUI

temperlux-gui

CLI

# List all displays
temperlux list

# JSON output for scripting
temperlux list --json

# Get brightness of display 1
temperlux get 1

# Set display 1 to 75%
temperlux set 1 --percent 75

# Set all displays to 50%
temperlux set --percent 50

# Increase all displays by 10%
temperlux increase --percent 10

# Rename a display
temperlux rename 1 "Left Monitor"

Shell completions

# Bash
temperlux completions bash > ~/.local/share/bash-completion/completions/temperlux

# Zsh
temperlux completions zsh > ~/.zfunc/_temperlux

# Fish
temperlux completions fish > ~/.config/fish/completions/temperlux.fish

Build

# CLI only (default)
cargo build --release

# With GUI
cargo build --release --features gui

# Run tests
cargo test

Requirements

• Rust 1.82+
• libddcutil development headers
• GTK4 + Libadwaita 1.2+ (for GUI feature)

Install dependencies (Debian/Ubuntu)

sudo apt install ddcutil libddcutil-dev libgtk-4-dev libadwaita-1-dev pkg-config

Architecture

src/
  main.rs          CLI entry point
  cli.rs           clap argument definitions + shell completions
  autostart.rs     Autostart .desktop file management
  lib.rs           Library root
  settings.rs      JSON config (~/.config/temperlux/settings.json)
  sync.rs          Sync mode math (proportional map, delta apply)
  caps.rs          Min/max brightness clamping
  display/
    ddc_ffi.rs     DdcService (FFI libddcutil, parallel writes, command coalescing)
    backlight.rs   RealBacklightProvider (/sys/class/backlight)
    manager.rs     DisplayManager (unified display operations)
    provider.rs    BacklightProvider trait
  gui/
    window.rs      Main window, display rows, dialogs
    viewmodel.rs   DisplayRow data model
    debounce.rs    Slider debouncing + worker pool

Both CLI and GUI use DdcService (FFI libddcutil) for reliable display detection and fast parallel DDC writes with command coalescing. Hardware access is behind provider traits with mock implementations for testing.

Configuration

Config file: ~/.config/temperlux/settings.json

{
  "sync_mode": "Proportional",
  "show_display_numbers": true,
  "autostart": false,
  "display_order": ["ddc:2", "ddc:1", "ddc:3"],
  "displays": {
    "ddc:1": {
      "min_brightness": 20.0,
      "max_brightness": 80.0,
      "custom_name": "Left Monitor"
    },
    "ddc:2": {
      "min_brightness": 0.0,
      "max_brightness": 100.0,
      "custom_name": "Right Monitor"
    }
  }
}

License

GPL-3.0-or-later. See LICENSE and NOTICE.

This project is a rewrite of Luminance by sidevesh, which is also licensed under GPL-3.0-or-later.