Umbriel

Umbriel is a Wayland compositor designed for daily use, with scrolling, dwindle, and master layouts, per-output workspaces, window rules, blur, shadows, and fluid animations.

It runs independently and can be paired with Noctalia, which provides a first-class desktop shell experience for Umbriel. Umbriel is built in C++23 on wlroots and umbrielfx, its independently maintained, in-tree hard fork of SceneFX. Xwayland support comes from wlroots' Xwayland server, which starts on demand and needs the Xwayland binary installed and on PATH. Portal screen capture and sharing is provided by xdg-desktop-portal-umbriel, an xdg-desktop-portal backend for Umbriel.

When people ask what Umbriel's selling point is, the honest answer is that there is no single killer feature. We were simply disappointed with the choices available to us, so we built the compositor we wanted to live in. The plan is not to conquer the world or take over the big names; it is to feel at home with something we have a say in, with less friction. That is exactly how Noctalia came to life, and Umbriel is its compositor side.

We want one desktop for productivity and gaming: flexible layouts, tab groups, and scratchpads for organizing work, alongside HDR, variable refresh rate, and configurable fullscreen presentation for games.

To understand the values and philosophy guiding the project, read our ethos.

• Scrolling, dwindle, and master layouts with per-workspace selection, width presets, animated navigation, and mouse-driven resizing and tiled reordering
• Tab groups that stack, move, and resize like any row in the scrolling layout, and tab whole areas in the master layout, with a clickable, scrollable, draggable tab bar that can be hidden
• Independent workspaces per output, with dynamic or named workspaces, hotplug restoration, fractional scaling, and configurable modes, positions, and transforms
• Floating, pinned, and fullscreen windows with configurable placement, focus, sizing, opacity, and visual effects
• Window rules and layer rules for application placement, focus, decorations, and effects
• Global named scratchpads for temporarily hiding window groups and summoning them on any output
• An animated overview, directional focus, configurable keybinds, submaps, and activation policy
• Blur, shadows, rounded corners, double borders, opacity, and animated position, size, and fade transitions
• Keyboard, pointer, touch, touchpad gestures, XKB configuration, and text-input-v3/input-method-v2 input method support
• Tablet and pad input, relative pointer motion, pointer locking, and per-window pointer confinement
• Color-managed HDR with automatic fullscreen activation, configurable SDR reference white, and SDR screen capture, plus optional 10-bit SDR rendering
• Variable refresh rate, opt-in tearing, and direct scanout for eligible fullscreen content
• Explicit GPU synchronization through linux-drm-syncobj when supported by the renderer and backend
• Restricted Wayland connections for sandbox engines through security-context-v1, with per-application protocol grants
• Layer shell, session locking, clipboard management, screen capture, output control, and gamma control
• On-demand X11 application support through Xwayland, with optional native-resolution rendering on scaled outputs
• Virtual outputs for screen sharing and Sunshine/Moonlight game streaming
• Live-reloaded TOML configuration with diagnostics and includes, plus local IPC and runtime inspection commands
• GLSL effect presets for animations, borders, windows, screens, and cursors, with effect pools, runtime selection, and inspection
• Runs as a nested Wayland compositor inside an existing Wayland or X11 desktop for development, or directly on DRM for daily use

HDR, VRR, tearing, direct scanout, and explicit synchronization depend on the display, graphics stack, and client. HDR, VRR, and tearing are opt-in; see the output reference for policies and fallback behavior.

Distribution maintainers should also read PACKAGING.md for the installed layout, dependency notes, and config fallback.

The scene graph and renderer live in umbrielfx/ and build as part of the tree. They are maintained as part of Umbriel rather than rebased onto upstream SceneFX; no separate SceneFX package is needed.

Install a C++23 compiler, Meson, Ninja, Just, pkg-config, wayland-scanner, and development packages for wlroots 0.20 (0.20.1 or newer, built with Xwayland support), Wayland, wayland-protocols, xkbcommon, libinput, pixman, libdrm, libdisplay-info, EGL, GLES2, GBM, Cairo, Pango, tomlplusplus, nlohmann-json, xcb, xcb-icccm, and xcb-ewmh. Native [drm] GPU exclusions also require libudev. lcms2 is optional. See PACKAGING.md for dependency version requirements and test-only dependencies. Then build Umbriel:

just release
just install

jemalloc is optional but recommended on glibc: it returns freed memory to the OS promptly and bounds heap fragmentation in long-running sessions. Meson's -Djemalloc=enabled or -Djemalloc=disabled forces the choice; the default (auto) uses it when the development package is installed and skips it otherwise (non-glibc libc builds always skip it).

The binaries are written to build-debug/umbriel and build-release/umbriel.

Build the package directly:

nix build

The resulting binary is available at result/bin/umbriel. For development, enter the project shell and use the same Just recipes as a system build:

nix develop
just debug

For unit tests, the headless compositor harness, and contributor checks, see Development Commands.

Installed display-manager sessions start through start-umbriel. For supported account shells, it loads the noninteractive login environment, then runs the compositor as a user service on systemd or directly on other init systems. In a managed systemd session, the launcher imports that login environment into the user manager before starting Umbriel. Login-profile values take precedence over values with the same names from environment.d, including PATH; variables found only in the user manager remain available.

Start an installed native session from a TTY with:

start-umbriel

From an existing Wayland or X11 session, Umbriel opens a nested window (mod = Alt). From a TTY it takes over the seat (mod = Super).

Apps that capture the screen through xdg-desktop-portal (browser screen sharing, OBS, portal-aware screenshot tools) are served by xdg-desktop-portal-umbriel, which implements the Screencast and Screenshot interfaces for Umbriel.

just run debug kitty

Or run the binary directly:

./build-debug/umbriel -s kitty

With the packaged starting configuration:

kitty is an optional startup command. Replace it with another command, or omit it by running just run debug or ./build-debug/umbriel. The packaged configuration binds mod+Return to spawn:kitty and mod alone to the Noctalia launcher. Change those commands under [keybinds] if you use another terminal or shell (see examples/config.toml).

Stop with mod+Escape or Ctrl+C from the parent terminal.

Umbriel first checks $XDG_CONFIG_HOME/umbriel/config.toml, then $XDG_CONFIG_DIRS, and finally its packaged share/umbriel/config.toml. These paths remain watched, so creating a higher-priority config switches to it without a session restart. Pass -c path/to/config.toml to pin another file. Config files can include files with [include] files = ["theme.toml", "keybinds.toml"]; later files and the main file override earlier values.

See examples/config.toml for the packaged starting configuration and our online documentation for the full reference.

Declarative configuration uses Nix attrsets serialized to TOML with pkgs.formats.toml.

# flake inputs
umbriel.url = "git+https://github.com/noctalia-dev/umbriel";

# NixOS
imports = [ inputs.umbriel.nixosModules.default ];
programs.umbriel.enable = true;

# home-manager
imports = [ inputs.umbriel.homeModules.default ];
programs.umbriel = {
  enable = true;
  settings = {
    general.autostart = [ "noctalia" ];
    layout.gap = 5;
    input.keyboard.layout = "de";
    keybinds = {
      "Mod+Return" = "spawn:kitty";
      "Mod+Q" = "window-close";
      "Mod" = "spawn:noctalia msg panel-toggle launcher";
    };
  };
};

The portal lives in a separate repository and comes with the NixOS module: enabling Umbriel installs it, configures it as the xdg.portal backend, and writes the portal configuration screencasting needs. You can set programs.umbriel.portalPackage to null if you don't want the portal.

When settings is omitted, the Home Manager and hjem modules leave the user path untouched so Umbriel loads its packaged configuration. Home Manager also accepts a raw TOML string or a path. The hjem module is exported as inputs.umbriel.hjemModules.default.

See CONTRIBUTING.md for code style, naming conventions, the dependency stack, and debugging helpers, and SCOPE.md for what the project takes on and what it declines. Umbriel shares its conventions with noctalia. For general help and design discussion, join the community on Discord.

Bug reports are always welcome. Feature requests are read against SCOPE.md, so please skim it before opening one, and ask on Discord if you are unsure whether an idea fits.

MIT License. See LICENSE for details.