Lios

Lios is a polished Rust GTK4/VTE terminal emulator by KnottDynamics and Trevor Knott. It keeps the terminal core reliable by using VTE, then focuses on what should feel better day to day: beautiful built-in themes, glass/background controls, fast same-directory windows, simple config, and an opt-in GPU renderer switch without making unstable GPU paths the default.

Why Lios

• Uses VTE for real terminal behavior instead of a toy parser.
• Keeps Cairo as the reliable default renderer, with explicit opt-in GPU modes for GTK auto, OpenGL, or Vulkan.
• Treats theming as a core feature, not a plugin: built-in palettes, opacity, background images, accent tint, and live preferences are baked in.
• Opens new windows in the active terminal directory, which keeps shell workflows smooth.
• Stays small: SSH and other extra workflows belong in optional lios-* helpers, not the core terminal.
• Avoids telemetry, background downloads, and secret storage.

Features

• GTK4 window with a VTE terminal widget.
• Spawns $SHELL, with common Unix shell fallbacks.
• Optional -- COMMAND ... and --command "..." launch modes.
• Dark readable defaults: white-on-black palette, opaque dark backing layer, Monospace 12, block cursor, 1,000 lines of scrollback.
• Built-in themes: xfce, xterm, green-on-black, white-on-black, dark-pastels, solarized-dark, solarized-light, black-on-white.
• Slider-based master/full-window opacity plus nested image, terminal shade, and accent opacity controls.
• Background image support with ~ path expansion, fixed color tint, or per-launch random accent tint.
• Packaged default background image for first launch on new machines.
• Explicit visible mouse pointer over the terminal instead of VTE's dark text cursor shape.
• GPU acceleration toggle: reliable cairo by default, with opt-in auto, OpenGL (gl), or Vulkan (vulkan) through GSK_RENDERER before GTK starts.
• Child shells get TERM=xterm-256color, COLORTERM=truecolor, and TERM_PROGRAM=lios; VTE Sixel rendering is enabled.
• Desktop launcher install with lios --install or lios ---install.
• App icon installed from assets/logo.png.
• Optional window decoration/topbar removal.
• Slim topbar with a collapsible in-window preferences drawer for common live theme/background changes.
• Ctrl+Shift+N and New Window open a borderless terminal in the active terminal directory.
• Right-click appearance submenus for background images, terminal glass, accent presets, random tint, and themes.
• Right-click diagnostics for active windows, RSS, scrollback, terminal identity, image protocol, theme, background, and config path.
• Terminal-driven config commands for theming from a shell or script.
• Clipboard/context actions for copy, copy as HTML, paste, select all.
• Keyboard shortcuts for Ctrl+Shift+C, Ctrl+Shift+V, Ctrl+Shift+A, Ctrl+Shift+N, Ctrl+Shift+Q, Ctrl+Shift+,, Esc while preferences are open, Ctrl++, Ctrl+-, and Ctrl+0.

System Dependencies

Install Rust plus GTK4/VTE libraries and headers.

Debian/Ubuntu names:

sudo apt install pkg-config libgtk-4-dev libvte-2.91-gtk4-dev

Arch names:

sudo pacman -S rust pkgconf gtk4 vte4

Run

Install from crates.io:

cargo install lios
lios

Run from source:

cargo run
cargo run -- --working-directory "$HOME"
cargo run -- -- htop
cargo run -- --command "ls -la"
cargo run -- --theme solarized-dark
cargo run -- --gpu
cargo run -- --gpu-mode vulkan
cargo run -- --renderer gl
cargo run -- --opacity 0.88
cargo run -- --background-image ~/Pictures/wallpaper.jpg --background-opacity 0.50 --random-overlay
cargo run -- --hide-titlebar
cargo run -- config init
cargo run -- config set gpu on
cargo run -- config set gpu_mode gl
cargo run -- config set theme solarized-dark
cargo run -- config set renderer gl
cargo run -- config set background.image ~/Pictures/wallpaper.jpg
cargo run -- config set topbar false

Optional Plugins

Core Lios stays small. Optional helpers use separate lios-* packages.

lios-ssh launches OpenSSH inside Lios without storing hosts, passwords, keys, or SSH config:

cargo install lios-ssh
lios-ssh user@example.com
lios-ssh -p 2222 user@example.com
lios-ssh --theme solarized-dark -- -J jump.example.com user@example.com

The helper wraps lios -- ssh ... using argv. OpenSSH still handles ~/.ssh/config, SSH agent, known hosts, keys, jump hosts, and verification.

Configuration

Lios reads ~/.config/lios/config.toml by default when it exists. Use --config path/to/config.toml to load another file.

[window]
title = "Lios"
width = 960
height = 640
decorated = false # set true to show the topbar/window decorations
renderer = "cairo" # cairo disables GPU; auto, gl, or vulkan enable GPU
opacity = 1.00 # master/full-window opacity

[terminal]
font = "Monospace 12"
scrollback_lines = 1000 # max 100000

[theme]
name = "xfce"
# Optional custom overrides:
# foreground = "#ffffff"
# background = "#000000"
# Optional XFCE Red cursor preset values:
# cursor_background = "#e6192e"
# cursor_foreground = "#a51d2d"
# cursor = "#e6192e" # legacy alias for cursor_background
# palette = ["#000000", "#aa0000", "#00aa00", "#aa5500", "#0000aa", "#aa00aa", "#00aaaa", "#aaaaaa", "#555555", "#ff5555", "#55ff55", "#ffff55", "#5555ff", "#ff55ff", "#55ffff", "#ffffff"]

[background]
image = "/home/example/Pictures/wallpaper.jpg"
image_opacity = 1.00
terminal_opacity = 0.50
# Use lower values for more glass/desktop transparency.
# overlay_color = "#7c3aed"
overlay_opacity = 0.00
random_overlay = true

CLI flags override the config file for one run. Use --gpu for GTK GPU auto-selection, --gpu-mode gl or --gpu-mode vulkan to force a GPU backend, and --no-gpu to force the reliable Cairo renderer. The text config stores this as window.renderer so older configs remain valid.

Theme cursor colors can be configured as a pair with theme.cursor_background and theme.cursor_foreground; leaving both unset keeps the normal inherited VTE cursor. The red XFCE-style pair shown above is available as an optional preset. Existing configs that use theme.cursor still work as a cursor-background alias. Preferences include cursor background/foreground fields with clickable color swatches plus XFCE Red and clear controls.

Use window.opacity or --opacity as the main full-window opacity. This affects the whole terminal UI and is the primary control for app transparency.

Background images are rendered against the theme background and composited below a transparent VTE terminal. image_opacity controls how strongly the image blends into the theme-colored base. terminal_opacity is the nested terminal shade layer over that image; lower values show more image while preserving readable text. Without an image, use the master opacity for reliable transparent-terminal behavior, then use terminal_opacity only as the inner shade. If an older config has an image with terminal_opacity = 1.00, Lios uses the image shade at runtime so the image is not hidden by a fully opaque terminal background.

On a new machine with no existing Lios config, the packaged default background is written to the user data directory and used automatically. Existing config files are respected.

The topbar is hidden by default. Ctrl+Shift+, opens the collapsible in-window preferences drawer, and the right-click menu also includes Open Preferences.... Ctrl+Shift+N opens another borderless terminal window in the active terminal directory using the current live settings. Ctrl+Shift+Q closes the current window. The drawer can change GPU acceleration mode, theme, cursor colors, font, topbar visibility, background image path, master opacity, terminal shade opacity, image opacity, accent opacity, overlay color, and random overlay. Cursor color rows include text fields and color-picker swatches; clearing both fields restores the normal inherited cursor. Opacity controls are sliders. The background row includes Browse and Clear controls; chosen images apply immediately and lower terminal shade opacity if needed so the image is visible. Other edits enable Apply and Save plus Revert, and Esc closes the drawer. Theme/background/font/cursor changes apply live after Apply; renderer changes are saved and apply on the next launch. Changes are written back to ~/.config/lios/config.toml when a config path is available.

Right-click inside the terminal for quick actions. New Window opens a borderless terminal in the active terminal directory. Close Window manages terminal windows. Diagnostics prints resource state into the terminal. Reset to Dark Default returns the current window to the plain dark default look. The Opacity submenu starts with master/full-window opacity controls, then nests terminal shade controls under Terminal Shade. The Background submenu changes/clears images, adjusts image brightness, or resets the whole background. Cursor can apply the optional XFCE Red cursor pair or restore the inherited default. Accent switches fixed accent presets (Violet, Cyan, Emerald, Amber, Rose), toggles random accent tint, and adjusts accent strength. The Theme submenu switches built-in terminal themes. These actions apply live and persist to the active config path when one is available.

Desktop Launcher

Install or build the binary first, then run lios --install to add Lios to the desktop app menu without launching it from another terminal. lios ---install is also accepted.

cargo install --path .
lios --install

The command writes dev.lios.Terminal.desktop under $XDG_DATA_HOME/applications or ~/.local/share/applications with Terminal=false and Exec pointing at the exact binary that ran the command. It also installs the app icon from assets/logo.png as dev.lios.Terminal under the user icon theme and requests a desktop/icon cache refresh when the standard desktop tools are available. Normal GUI startup also makes the packaged icon available to GTK so direct cargo run launches can resolve the same icon name. Running cargo run -- --install creates a launcher for target/debug/lios; use the installed lios --install command for a stable app-menu entry. Use lios --uninstall or lios ---uninstall to remove that launcher and icon.

Resource Policy

• Terminal scrollback is bounded. scrollback_lines must be between 0 and 100000; the default is 1000.
• Runtime diagnostics show active windows, process RSS, scrollback limit, renderer, terminal identity, image protocol, theme, background image, opacity, overlay state, and config path.
• GTK callbacks that can outlive their parent window use weak window references to avoid reference cycles during repeated open/close cycles.
• Segmented preference controls store weak button references internally, avoiding self-cycles between buttons and their click closures.
• No Tokio tasks or channels are used; child processes are owned by VTE and tied to the terminal widget/window lifecycle.
• VTE Sixel rendering is enabled. Lios exports its own VTE/Sixel identity and strips inherited Kitty, WezTerm, and iTerm marker variables so child apps do not detect unsupported image protocols. Image tools still need to run outside tmux or inside tmux configured to pass image protocols through.

Rust 1.88.0 can ICE while compiling generated GTK binding crates with heavy debug or optimization settings. Cargo.toml keeps the workaround scoped to the affected GTK crates. If cargo install still crashes while compiling GTK dependencies with a rustc stack trace, retry with a larger compiler stack:

RUST_MIN_STACK=16777216 cargo install --path .

Terminal config commands:

lios config path
lios config sample
lios config init
lios config init --force
lios config show
lios config set gpu on
lios config set gpu_mode vulkan
lios config set renderer gl
lios config set theme solarized-dark
lios config set opacity 0.88
lios config set background_opacity 0.80
lios config set overlay_color '#7c3aed'
lios config set overlay_opacity 0.18
lios config set random_overlay true
lios config set topbar false
lios --install
lios ---install
lios --uninstall

Useful keys include gpu, gpu_mode, renderer, theme, font, opacity, background.image, background_opacity, background_image_opacity, overlay_color, overlay_opacity, random_overlay, and topbar.

Package

The Cargo package is named lios and includes crate metadata for packaging.

cargo publish --dry-run
cargo publish