Crate document_graphics 

document-graphics

Bounded native Mermaid, SVG and optional SGF Go-board rendering for terminal and GUI applications. The crate returns straight RGBA pixels and logical dimensions. It has no UI framework, Markdown document model, application cache, broker or background service.

Mermaid supports flowcharts, sequence, class and state diagrams, ER attribute tables, pie charts, mind maps, timelines without sections, user journeys and quadrant charts. Bundled fonts cover Latin (including accents), Greek and Cyrillic labels. Unsupported syntax and unavailable glyphs return Ok(None) through the worker so callers can retain the original source. SVG rendering uses bundled KaTeX and Noto Sans fonts and rejects external resources, filters, reuse and foreign content.

Scope

The library renders the graphical content of documents independently of their layout or user interface. Today it supports Mermaid diagrams, a restricted SVG subset and Go positions from SGF records (sgf feature). Image decoding, other diagram formats and music notation are possible future modules; they are not implemented here yet. Applications own document layout, interaction, scheduling and cache budgets. Equation layout remains in katex-native.

New backends should remain optional and initialize only when used. Their own input limits and platform isolation requirements must be explicit. Future APIs may retain a bounded parsed model and render a selected fragment, position, page or tile without retaining an image for every item.

Integration

Requires Rust 1.90 or newer.

[dependencies]
document-graphics = "0.1"

Handle the private worker argument before initializing the application:

use document_graphics::{RasterOptions, worker::{self, Worker}};
use std::{sync::atomic::AtomicBool, time::Duration};

fn main() -> std::io::Result<()> {
    if std::env::args().nth(1).as_deref() == Some("--preview-worker") {
        return worker::worker_main();
    }
    // Run blocking rendering on a background thread in interactive applications.
    let mut worker = Worker::spawn(&std::env::current_exe()?, "--preview-worker")?;
    let cancelled = AtomicBool::new(false);
    let _image = worker.render(
        "flowchart LR; Read-->Preview", false,
        RasterOptions::scaled(2.), Duration::from_secs(2), &cancelled,
    )?;
    // Move image.rgba into the application's image type; no pixel copy is needed.
    Ok(())
}

RasterOptions::fit((width, height)) fits within physical bounds without upscaling. RasterOptions::scaled(2.) requests Retina output while preserving logical SVG size. Applications can set both fields explicitly. Source and raster limits apply to every mode: 16 KiB / 256 lines of Mermaid, 128 nodes, 256 edges, 256 KiB SVG, one million output pixels, and an 8,192-pixel edge. Additional nesting, geometry, annotation and label limits are enforced before expensive work. Pie charts allow 64 slices, mind maps 128 nodes/depth 32, timelines 64 periods/128 events, journeys 32 actors with scores 1–5, and quadrant charts 128 points with coordinates 0–1. Unsupported timeline sections retain source. Nonfinite chart numbers are rejected.

Use svg::rasterize(source, options) for bounded local SVG. It accepts no file paths and does not fetch resources. Only the internal Mermaid route permits bounded arrow markers. Mermaid parsing and layout are private to the worker; there is no public in-process Mermaid entry point.

SGF Go records

Enable the optional sgf feature (available from 0.1.1). It adds no dependencies, network access or runtime installation requirements. Parse a bounded collection, reconstruct the selected board, and render it off the application’s UI thread:

use document_graphics::{sgf::{Collection, RenderOptions, rasterize}, RasterOptions};
use std::sync::{Arc, atomic::AtomicBool};
let cancel = AtomicBool::new(false);
let source: Arc<[u8]> = Arc::from(&b"(;FF[4]GM[1]SZ[9];B[dd];W[ee])"[..]);
let collection = Collection::parse(source, &cancel)?;
let position = collection.position(2, &cancel)?;
let image = rasterize(&position, RenderOptions::default(), RasterOptions::scaled(2.), &cancel)?;

The compact index retains source ranges and tree links, including unknown properties; it does not store a board or bitmap for every node. Position::advance replays a direct child incrementally. Applications choose which positions to cache. Captures, passes, setup stones, handicap, move numbers, common board marks, labels, arrows and lines are supported. Replay follows SGF positions without checking competitive legality, ko or turn order. Comments and game information are exposed as text for the caller’s UI, not embedded in the diagram.

Limits: 8 MiB source, 100,000 nodes, 1,024 games, 256 levels of variation nesting, 300,000 properties (128 per node), 500,000 values, 128 KiB per value, boards up to 52 × 52, 512 marks and 512 lines per position, and 32 characters per board label. Position reconstruction has a 20-million-step work limit. SVG and raster limits also apply, so dense annotated boards can exceed the diagram budget. UTF-8 and ISO-8859-1 are accepted; missing CA uses UTF-8 when valid, otherwise ISO-8859-1. Other games/encodings return an explicit error. VW cropping and legacy markup are retained in source but not interpreted. Board labels use bundled fonts.

Unlike Mermaid’s layout engine, this bounded, iterative parser and replay loop run in-process with cooperative cancellation, followed by the restricted SVG renderer. They are not isolated by the Mermaid worker’s OS sandbox. Callers must schedule them off-thread, coalesce requests and retain readable source on failure. There is no hard wall-clock deadline on this in-process API.

The repository’s sgf_probe example reads an SGF directory, checks every node and renders roots and leaves without modifying any input:

cargo run --release --features sgf --example sgf_probe -- path/to/sgf-directory

Worker lifecycle

Applications choose cache sizes, scheduling, idle retirement and total invocation budgets. Each worker handles at most worker::MAX_REQUESTS (32) requests; check requests_completed() and replace the worker when needed. Rejected syntax does not break the worker. An I/O error, cancellation or deadline stops and reaps it before returning; an errored handle must be replaced. Dropping a healthy handle also stops and reaps its child. Process creation itself is outside the per-render deadline.

The child receives source, theme and raster options over bounded private pipes; its inherited environment is cleared. Unix workers disable core dumps and have an eight-second cumulative CPU backstop. On macOS the worker’s sandbox profile allows everything by default, then denies file-data reads, writes, networking and child processes; other operations, such as Mach service lookups, remain allowed. The parent samples resident memory against 256 MiB. Other platforms retain input/output bounds and deadlines, but do not yet have equivalent OS sandbox and resident-memory enforcement.

The library owns these mechanisms. A terminal app can retain a five-second total budget; a desktop app can reuse a worker through a bounded queue and retire it on idle. Neither policy is imposed on the other application.

Development

This is a standalone library repository, shared by mdviewer and Plastext. The Mermaid backend comes from the published document-graphics-mermaid crate, maintained in a separate fork. It provides caller-supplied font metrics, complete ER key badges and chart-label contrast fixes. Its default features stay disabled: this library owns SVG rasterization and does not need the backend’s CLI or PNG renderer. All dependencies come from crates.io; no sibling checkout is required.

cargo fmt --all --check
cargo clippy --all-targets --all-features --no-deps --locked -- -D warnings
cargo test --all-features --locked
cargo +1.90.0 check --all-targets --all-features --locked

Shared renderer, SVG and protocol tests belong here. Application integration and policy tests stay with the consumers. On macOS, worker tests must run outside an enclosing sandbox so the child can install its own sandbox.

See release checks for testing changes in the consumers, packaging and consumer validation.

MIT; see LICENSE. katex-native includes KaTeX fonts under OFL-1.1. Noto Sans assets and their license/provenance are in fonts.

Modules

mermaid

Bounded native Mermaid subset. Parsing and layout belong in the worker process.

svg

Restricted SVG rendering with bundled fonts and no external resources.

worker

Isolated rendering, shared wire protocol and process supervision.

Structs

Raster

Straight RGBA pixels and unscaled SVG dimensions. Moving this value transfers its pixel buffer; callers need not copy it into an intermediate image format.

RasterOptions

Raster fitting is independent of logical layout. Bounds are physical pixels; scale is the requested physical pixels per logical SVG unit (1x or Retina). All output remains subject to the crate’s pixel, edge and source-size caps.

Constants

MAX_EDGE

MAX_PIXELS