Vernier

A native Linux desktop tool for measuring and taking off quantities from PDF drawings (architectural floor plans and other CAD-exported PDFs): render a page, set a real-world scale from one known dimension, then measure lengths with CAD-style snapping — the cursor locks onto the drawing's real vector geometry instead of eyeballed pixels.

Name: after the vernier scale (Pierre Vernier, 1631) — the little sliding scale that lets a ruler read precisely. Precision measurement is the whole point.

Why

PDF viewers and editors do measurement badly: their measure tools have no snapping and no fluid "set scale → measure" loop, so every takeoff is eyeballed pixel-clicking. CAD-exported PDFs carry the real line geometry inside the file — Vernier extracts it, indexes it, and snaps to it, so a measurement means the same thing it meant in the CAD model.

Features

• Open a PDF; page navigation with a thumbnail sidebar.
• Smooth pan/zoom, crisp at any magnification (pages re-render at the current zoom — never an upscaled bitmap).
• Set scale from a known dimension: click its two endpoints (snapped), type the real length (3000 mm, 3 m, 10 ft), or enter a drawing ratio like 1:50 directly.
• Measure two-point dimensions with vertex/endpoint snapping, on-page labels, and a live readout in real units.
• Written as a pure, headless, unit-tested Rust core with a thin GTK4/libadwaita shell — see docs/architecture.md.

Build

Rust stable plus the GTK stack development libraries are required: GTK4 ≥ 4.14, libadwaita ≥ 1.5, and (for MuPDF's build) clang, fontconfig and freetype headers. On Fedora: gtk4-devel libadwaita-devel clang-devel fontconfig-devel freetype-devel cmake.

cargo build --release
cargo run --release            # optionally: vernier <file.pdf>
cargo test                     # headless core tests, incl. a synthetic PDF fixture

Flatpak packaging (the intended distribution route) lives in packaging/.

Status

MVP: render → scale → snap-measure works end to end on real multi-thousand-segment floor plans. Planned next: areas/perimeters, counts, midpoint/intersection/perpendicular snaps, ortho lock, categories, CSV/annotated-PDF export, annotation persistence.

License

AGPL-3.0-or-later (a consequence of rendering with MuPDF, which is AGPL). The MuPDF dependency is isolated behind a single PdfBackend trait, so a differently-licensed backend could be swapped in without touching the rest of the app.