tpt-text

Deterministic text shaping and layout in pure Rust. The same input produces the same glyph positions on every platform, including WebAssembly, so PDFs, CAD drawings and browser previews agree byte for byte.

Hello

use tpt_text::{layout_text, FontRegistry, Fx, TextStyle};

let registry = FontRegistry::new();
let font = std::fs::read("NotoSans-Regular.ttf")?;
let face = registry.load_font(font, 0)?;

let style = TextStyle::new(face.family(), Fx::from_int(16));
let layout = layout_text(&registry, "Hello, world", &style, Fx::from_int(200))?;

for line in &layout.lines {
    println!("line at y={} holds {} runs", line.top, line.runs.len());
}
println!("digest {:016x}", layout.digest());
# Ok::<(), Box<dyn std::error::Error>>(())

Features

Area	What you get
Shaping	rustybuzz, OpenType features, letter spacing, variable-font axes
Bidi	UAX #9 resolution, visual reordering, per-line rule L1
Line breaking	UAX #14 (Unicode 18), soft hyphens, caller-supplied hyphenation
Fallback	caller-configured per-script chains, per-cluster font choice
Layout	alignment (start, end, left, right, centre, justify), tab stops, line height, truncation with ellipsis
Editing	caret from a point, point from a byte, selection rectangles
Output	positions, glyph outlines, SVG, JSON with the serde feature, layout digests
Documents	several paragraphs with incremental relayout and a shape cache
Fonts	in-memory registry, collections (.ttc), names read from the file, system fonts with fontdb
Targets	std, no_std + alloc, wasm32-unknown-unknown

Cargo features:

Feature	Default	Adds
std	yes	std::error::Error impls
fontdb	no	tpt_text::system::SystemFonts, OS font discovery
serde	no	Serialize for layouts and styles; Deserialize for styles

Determinism

Layout arithmetic is fixed-point (Fx, 16.16) and integer-only. Floating point appears only where values enter or leave the crate, such as font variation values and conversions for display. CI runs a digest check that compares native output with output recorded from the WebAssembly build.

Crates in this repository

Crate	Purpose
tpt-text	The library
tpt-text-linebreak	UAX #14 line breaking, no_std
tpt-text-wasm	WebAssembly bindings and a browser demo
tpt-text-cli	Command-line layout: JSON, SVG, digest, break explanations
tpt-text-snapshot	Text snapshots of layouts for tests
tpt-text-golden	JSON golden files for tests

Examples: layout_svg, caret_selection, bidi_emoji. A renderer starter using tiny-skia is in templates/tiny-skia.

Guides: cookbook and migration.

Working on the repository

cargo xtask ci          # formatting, lints, tests, no_std and wasm builds, docs, digests
cargo xtask bench-check # benchmarks against crates/tpt-text/benches/baseline.txt

See CONTRIBUTING.md. Dual-licensed under MIT or Apache-2.0.