Display Layout Editor

A focused drag-and-drop display layout editor. It provides a sparse, spatial workflow without turning display placement into a full settings dashboard.

Display Layout is an independent project. NVIDIA is not affiliated with, does not endorse, and does not own this project. No NVIDIA source code, artwork, trademarks, or other proprietary assets are included, and no infringement of or ownership claim over NVIDIA's works is intended or implied.

Compositor support

Display Layout selects a backend from the current desktop automatically. The supported compositor families are:

Compositor	Backend/API
niri	niri msg IPC
Sway	swaymsg IPC
Hyprland	hyprctl IPC
River, Wayfire, labwc	wlroots output management via wlr-randr
GNOME Shell	Mutter DisplayConfig via gdctl
KDE Plasma	KScreen via kscreen-doctor

Display Layout is Wayland-only: both the editor and display identification overlays are native Wayland clients, and XWayland is neither used nor required. X11 sessions and XRandR are intentionally unsupported.

wlr-randr is included in the Nix package. The other tools are supplied by their compositor or desktop session. Explicit backend names are niri, sway, hyprland, wlr, gnome, and kscreen; river, wayfire, labwc, mutter, kde, and plasma are accepted aliases.

Features

• Logical-pixel, to-scale display previews
• Drag-and-drop placement with proximity snapping for edges and centerlines
• Animated alignment guides while displays line up horizontally or vertically
• Reset, close, and atomic user-confirmed apply workflow
• Numbered output badges plus simultaneous, per-output identification overlays
• Dark and light themes
• Pixel- or percentage-based default window dimensions
• Configurable font, font size, and snap distance
• Small C codebase and runtime closure

Run

nix run github:johnrichardrinehart/display-layout

Or build locally:

nix build
./result/bin/display-layout

Configuration

Copy config.example.ini to $XDG_CONFIG_HOME/display-layout/config.ini (normally ~/.config/display-layout/config.ini). The application never creates or rewrites its configuration automatically.

Dimensions independently accept pixels or percentages:

width = 1060px
height = 87%
font-size = 16
# font = /path/to/a/monospace-font.ttf
theme = system
snap-distance = 14
identify-duration-ms = 2000
backend = auto

Use theme = dark, light, or system. System mode checks common desktop and GTK preferences and falls back to dark. An explicit config can be selected with --config PATH, and a backend can be selected with --backend NAME.

Backend architecture

The generic application owns rendering, interaction, configuration, and the display layout model:

• src/main.c — native Wayland UI, software rendering, and interaction
• src/model.h — backend-neutral display data
• src/backend.h / src/backend.c — backend contract and selection
• src/backend_niri.c — niri IPC
• src/backend_sway.c — Sway IPC
• src/backend_hyprland.c — Hyprland IPC
• src/backend_wlr.c — wlroots output management
• src/backend_gnome.c — GNOME/Mutter integration
• src/backend_kscreen.c — KDE/KScreen integration
• src/backend_common.c — safe command execution, JSON helpers, and shared identification
• tests/backend_test.c — parser and backend-selection regression tests
• tests/nixos/backend-matrix.nix — NixOS VM render/apply matrix with a screenshot for every backend

A backend implements only load, apply, and lifecycle operations. Commands are invoked directly without shell interpolation, output is parsed in-process, and multi-output APIs are applied atomically where the compositor API permits it.

Development

The flake follows the same dev-input partitioning used by the author's other projects. Consumer evaluation does not fetch development-only inputs.

direnv allow
nix flake check

On x86-64, the flake check includes a NixOS VM test. It launches the packaged editor without XWayland under a headless Sway compositor, exercises contract fixtures for all six backend APIs, captures backend-*.png screenshots, activates Apply through the compositor's Wayland seat, and verifies that each compositor command receives the layout.

Development tooling uses:

• flake-parts
• treefmt-nix
• nix-direnv
• git-hooks.nix
• clang-format

License

MIT. The vendored jsmn parser retains its own MIT license notice in src/third_party/jsmn.h.