dagre-dgl-rs

A faithful Rust port of dagre-js — a directed graph layout library that produces layered, hierarchical graph drawings.

What it does

dagre-dgl-rs takes a directed graph with node sizes and edge constraints, runs a multi-stage layout pipeline, and outputs x/y coordinates for each node and a list of waypoints for each edge. It does not render anything — it is a pure layout engine.

Layout pipeline

The stages mirror dagre-js exactly:

Acyclic — reverse edges to make the graph a DAG
Rank — assign each node to a horizontal layer (network simplex)
Nesting — handle compound/nested graphs
Normalize — insert dummy nodes on long edges
Order — minimise edge crossings within each layer
Position — assign x/y coordinates (Brandes-Köpf)
Edge routing — compute waypoints through dummy nodes

Usage

use dagre_rs::{Graph, GraphLabel, NodeLabel, EdgeLabel, layout};

let mut g = Graph::with_options(false, true, false);

g.set_graph(GraphLabel {
    rankdir: Some("TB".to_string()),
    nodesep: Some(50.0),
    ranksep: Some(50.0),
    ..Default::default()
});

g.set_node("a", NodeLabel { width: 100.0, height: 40.0, ..Default::default() });
g.set_node("b", NodeLabel { width: 100.0, height: 40.0, ..Default::default() });

g.set_edge("a", "b", EdgeLabel { minlen: Some(1), weight: Some(1.0), ..Default::default() }, None);

layout(&mut g);

let a = g.node("a");
println!("a => x={:.1}, y={:.1}", a.x.unwrap(), a.y.unwrap());

Graph options

Graph::with_options(multigraph, directed, compound):

Parameter	Description
`multigraph`	Allow multiple edges between the same pair of nodes
`directed`	Treat edges as directed (required for layout)
`compound`	Enable parent/child node relationships

GraphLabel fields

Field	Default	Description
`rankdir`	`"TB"`	Layout direction: `TB`, `BT`, `LR`, `RL`
`nodesep`	`50`	Minimum gap between nodes in the same rank
`edgesep`	`10`	Minimum gap between edge splines
`ranksep`	`50`	Minimum gap between ranks
`marginx`	`0`	Graph margin (x)
`marginy`	`0`	Graph margin (y)

Output

After layout(), each node has x and y set to its centre coordinates, and each edge label has points: Vec<Point> containing the waypoints.

Running tests

The test suite is ported from dagre-js/test/ and covers the rank, network simplex, and layout algorithms.

Run all tests:

cargo test

Run with output visible (useful for debugging):

cargo test -- --nocapture

Run a specific test by name:

cargo test network_simplex

Run tests matching a pattern:

cargo test rank

Dependencies

petgraph — underlying graph data structure
indexmap — deterministic iteration order

dagre-dgl-rs 0.1.0