graphviz-anywhere (Rust crate)

Rust crate published as graphviz-anywhere on crates.io.

Status

This crate currently builds against the legacy C-ABI wrapper (capi/graphviz_api.{h,c}). A follow-up PR will switch the FFI surface to the CGraphviz C++ class via the cxx crate so all platforms share one Graphviz implementation.

Usage (native)

use graphviz_anywhere::{Engine, Format, GraphvizContext};

let ctx = GraphvizContext::new()?;
let svg = ctx.render_to_string(
    r#"digraph G { a -> b; }"#,
    Engine::Dot,
    Format::Svg,
)?;
println!("{svg}");

Ship native binaries via one of:

• Environment: GRAPHVIZ_ANYWHERE_DIR=/path/with/lib+include
• Prebuilt: drop libgraphviz_api.a under packages/rust/prebuilt/<os>/
• Repo build: ./scripts/build-<os>.sh populates output/<os>*/lib/

Usage (wasm32)

When compiled for wasm32-unknown-unknown the crate does not link the native C library. Instead, GraphvizContext::render delegates to a JavaScript function the host environment must install on globalThis:

// Contract (TypeScript):
declare global {
  function __graphviz_anywhere_render(
    dot: string,
    engine: string,   // "dot" | "neato" | "fdp" | "sfdp" | "circo" |
                      // "twopi" | "osage" | "patchwork"
    format: string,   // "svg" | "png" | "pdf" | "ps" | "json" |
                      // "dot" | "xdot" | "plain"
  ): string;
}

The function must return the rendered output as a string (for svg, the SVG source; for binary formats the consumer is expected to interpret the returned string as raw bytes). On failure, throw a JavaScript Error; the thrown error is reported to Rust as GraphvizError::RenderFailed.

Example wire-up with @kookyleo/graphviz-anywhere-web

import { Graphviz } from "@kookyleo/graphviz-anywhere-web";

const graphviz = await Graphviz.load();
globalThis.__graphviz_anywhere_render = (dot, engine, format) =>
  graphviz.layout(dot, format, engine);

// Now any wasm-bindgen consumer that depends on `graphviz-anywhere`
// (e.g. `plantuml-little-web`) can call .render(...) normally.

Context lifetime on wasm32

GraphvizContext::new() on wasm32 is a zero-cost no-op that returns a marker value; the real Graphviz context is owned by the JavaScript side. Dropping a GraphvizContext is likewise a no-op on wasm32.