Vernier

Native pixel-measurement overlay written in Rust. Currently supported:

• macOS — Apple Silicon, macOS 11+ (tested on 15 Sequoia).
• Linux Wayland — Hyprland is the primary development target; other wlroots compositors should work via the GlobalShortcuts portal.

Linux X11 and Windows backends exist as stubs and aren't usable yet.

Site: https://usevernier.com

Install

macOS

Download Vernier-X.Y.Z-aarch64.dmg from the latest release, drag Vernier.app into Applications, and launch it. The bundle is ad-hoc signed — the first launch shows a Gatekeeper prompt; right-click the app → Open to dismiss it once.

The daemon runs as a menu-bar item (no Dock icon). Press Cmd+, or click the V in the menu bar → Preferences to configure shortcuts and integrations.

Arch Linux (AUR)

Three flavors:

Package	Source
vernier	Builds from the tagged source tarball.
vernier-bin	Drops in the prebuilt x86_64 / aarch64 binary from the GitHub Release.
vernier-git	Builds the tip of main.

paru -S vernier-bin    # or `yay -S vernier-bin`

Cargo (any Linux distro)

For distros without a native package, install from crates.io:

cargo install vernier-rs    # compiles from source, installs the `vernier` binary

The crate is vernier-rs because the bare vernier name was already taken; the installed binary is still vernier. You need Rust 1.85+ and the system build/runtime libraries — pkgconf plus the wayland, libxkbcommon, pipewire, fontconfig, freetype2 and libglvnd (OpenGL) dev packages (see Build from source for the exact Arch names; other distros name them similarly).

The first time you run vernier, the daemon registers itself with your application launcher — it writes vernier.desktop and the icon theme under ~/.local/share, no extra step needed. To register it before the first launch, run vernier install-desktop.

cargo install can't pull in the optional capture/clipboard tools (grim, slurp, wl-clipboard, libnotify). Run vernier doctor to see which are missing — the related features degrade gracefully until you install them.

Build from source

Rust 1.85+ (stable). System packages on Arch:

sudo pacman -S --needed \
  rust base-devel pkgconf \
  wayland wayland-protocols libxkbcommon \
  pipewire xdg-desktop-portal xdg-desktop-portal-hyprland \
  libx11 libxcb dbus \
  gtk3 libayatana-appindicator

cargo build --release
./target/release/vernier

On macOS, packaging/macos/package.sh builds the .app bundle and DMG using iconutil + create-dmg (brew install create-dmg librsvg).

Use

Ctrl+Shift+Alt+Super+F (Linux) / Ctrl+Shift+Alt+Cmd+F (macOS) toggles measure mode. Rebindable in Preferences → Shortcuts.

While measuring:

• Drag to draw a measurement rectangle. The pill shows W×H in configurable units.
• Hover the pill on a held rect → camera icon; click to capture just that region and hand off to a screenshot tool (screencapture -i on macOS, Satty / Swappy / Annotator on Wayland).
• Shift (alone) — extend the live crosshair to full-screen alignment lines.
• B / V — drop a horizontal / vertical guide; drag the guide to reposition, double-click to delete.
• Right-click — context menu (freeze stuck measurements, add guides, change edge-detection tolerance, change capture handoff target).
• Esc — clear the current rect and leave measure mode.
• Cmd+, / Ctrl+, — open the Preferences window.

The Preferences window is a separate subprocess (eframe + egui) so the long-running daemon stays tiny and the heavier UI toolkit only loads when you open it. On macOS it promotes itself to a foreground app via TransformProcessType so it can take key focus despite the daemon being LSUIElement.

Hyprland setup

The tray icon registers as a StatusNotifierItem. waybar's tray module renders it; the default Omarchy waybar config is already wired up — the V appears in the tray-expander group on the right side. Left-click for the menu (Preferences, Quit).

If your waybar lacks the tray module:

{ "modules-right": ["tray", ...],
  "tray": { "icon-size": 16, "spacing": 8 } }

Hotkey wiring (three options)

Zero setup on Hyprland. On startup the daemon runs hyprctl keyword bind = …, exec, vernier toggle itself and re-applies the bind on configreloaded, so the shortcut Just Works. The runtime bind is cleared when the daemon exits.

Portal-based (other wlroots compositors). The daemon registers a GlobalShortcuts portal entry named hk_1 via xdg-desktop-portal-hyprland (1.3+). Map a key to it:

bind = SHIFT CTRL ALT SUPER, F, global, vernier:hk_1

Manual CLI bind. Skip the portal entirely:

bind = SHIFT CTRL ALT SUPER, F, exec, vernier toggle

vernier toggle talks to the running daemon over a Unix domain socket at $XDG_RUNTIME_DIR/vernier.sock — no portal required.

Layout

Cargo workspace:

crates/
├── vernier-core/      algorithms, geometry, settings
├── vernier-platform/  Platform trait + per-OS impls
│                      (macOS + Linux Wayland; X11 + Windows are stubs)
├── vernier-ui/        egui prefs window (separate subprocess)
└── vernier-app/       binary

vernier-platform exposes a Platform trait the rest of the codebase binds against. The HUD is rasterized in vernier-platform via tiny-skia and split into a cached static layer (held rects, guides, stuck pills) and a dynamic layer (live crosshair, cursor, toast) so most frames skip the expensive stroke pass — only the small dynamic layer re-renders when the cursor moves.

Linux backend autoselects Wayland when $WAYLAND_DISPLAY is set; the X11 fallback isn't implemented yet.

License

MIT OR Apache-2.0, at your option. See LICENSE-MIT and LICENSE-APACHE.