nf-metro 1.1.0

Generate metro-map-style SVG diagrams from Mermaid graph definitions

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Generate metro-map-style SVG diagrams from Mermaid graph definitions with %%metro directives. Designed for visualizing bioinformatics pipeline workflows (e.g., nf-core pipelines) as transit-style maps where each analysis route is a colored "metro line."

Try it without installing: the nf-metro playground runs the full layout engine in your browser. Edit a .mmd file, preview the result live, import a Nextflow -with-dag diagram directly, and tweak layout options - no Python, no CLI needed.

What nf-metro does

• Static SVG - a self-contained diagram you can commit, embed in a README, or drop into docs.
• Interactive HTML - pan, zoom, hover for station details, click a line in the legend to isolate it and zoom to its extent.
• Live progress overlay - light up stations in real time as a Nextflow pipeline runs, using nf-metro serve with Nextflow's -with-weblog.
• Dashboard mode - nf-metro serve-multi hosts many pipelines or runs side by side on one page.
• Nextflow DAG import - convert a -with-dag Mermaid export into a metro map with nf-metro convert (or --from-nextflow on render).
• Embedded data manifest - every SVG carries a machine-readable JSON manifest so overlays and downstream tools can address stations without re-running the layout engine.

Installation

pip (PyPI)

pip install nf-metro

Conda (Bioconda)

conda install bioconda::nf-metro

Container (Seqera Containers)

A pre-built container is available via Seqera Containers:

docker pull community.wave.seqera.io/library/pip_nf-metro:611b1ba39c6007f1

Development

pip install -e ".[dev]"

Requires Python 3.10+.

Quick start

Render a metro map from a .mmd file:

nf-metro render examples/simple_pipeline.mmd -o pipeline.svg

Validate your input without rendering:

nf-metro validate examples/simple_pipeline.mmd

Inspect structure (sections, lines, stations):

nf-metro info examples/simple_pipeline.mmd

See the Guide for a step-by-step walkthrough of writing .mmd files.

CLI reference

nf-metro render

Render a Mermaid metro map definition to SVG or interactive HTML.

nf-metro render [OPTIONS] INPUT_FILE

Every layout/render option below also has a %%metro directive equivalent in the .mmd file; an explicitly-passed flag overrides the directive.

Option	Default	Description
-o, --output PATH	<input>.<format>	Output file path
--format [svg|html]	svg	Output format: svg or interactive html
--theme [nfcore|light|seqera]	from style:, else nfcore	Visual theme
--legend TEXT	auto	Legend+logo position (keyword, keyword | canvas, keyword | dx,dy, or x,y)
--line-spread [bundle|centered|rails]	bundle	How lines sharing a station relate vertically
--width INTEGER	auto	SVG width in pixels
--height INTEGER	auto	SVG height in pixels
--x-spacing FLOAT	auto	Horizontal spacing between layers
--y-spacing FLOAT	auto	Vertical spacing between tracks
--fold-threshold INTEGER	15	Max station-columns a section row may reach before wrapping to the next row
--animate / --no-animate	off	Add animated balls traveling along lines
--directional / --no-directional	off	Draw static chevrons along each route pointing in the flow direction
--strict / --no-strict	off	Treat a layout-invariant violation as an error instead of a warning
--debug / --no-debug	off	Show debug overlay (ports, hidden stations, edge waypoints)
--logo PATH	none	Logo image path (overrides %%metro logo: directive)
--line-order [definition|span]	definition	Line ordering strategy: definition preserves .mmd order, span sorts by section span
--diamond-style [straight|symmetric]	straight	Fork-join layout: straight keeps the top branch on the main track; symmetric fans evenly
--center-ports / --no-center-ports	off	Centre inter-section ports on the shorter of the two connected sections
--compact-offsets / --no-compact-offsets	off	Size each station only for the lines actually passing through it
--section-x-gap FLOAT	50	Horizontal gap between sections
--section-y-gap FLOAT	50	Vertical gap between sections
--label-angle FLOAT	theme default	Station-label angle in degrees
--font-scale FLOAT	1.0	Scale text and the label metrics that drive layout spacing
--logo-scale FLOAT	1.0	Scale the logo within the legend
--legend-min-height FLOAT	0	Minimum legend content height in pixels
--legend-logo-gap FLOAT	auto	Gap between the logo and the legend entries
--validate	off	Run the render-geometry oracle over the drawn SVG and report violations
--from-nextflow	off	Convert Nextflow -with-dag mermaid input before rendering
--title TEXT	none	Pipeline title (overrides the %%metro title: directive)

Embedding options

Flags for producing an SVG to embed in another page or application. See the embedding guide for when to use each.

Option	Default	Description
--responsive / --no-responsive	off	Emit viewBox only (no fixed width/height) so the host can scale with CSS
--embed-font / --no-embed-font	off	Inline Inter as a base64 @font-face so the SVG renders identically on any host
--text-to-paths / --no-text-to-paths	off	Convert text to vector paths (no font dependency; loses selectable text; needs fonttools[woff])
--bare / --no-bare	off	Omit the title and outer padding so the canvas hugs the content (keeps the watermark)
--svg-class-prefix TEXT	none	Prefix every SVG presentation class so multiple maps on one page don't collide
--no-dark-mode-css	off	Suppress the prefers-color-scheme: dark block when the host manages its own theme
--no-chrome-css	off	Bake concrete chrome colors instead of --nfm-* var() (needed for raster export, e.g. cairosvg)

The --logo flag lets you use the same .mmd file with different logos per theme:

nf-metro render pipeline.mmd -o pipeline_dark.svg --theme nfcore --logo logo_dark.png
nf-metro render pipeline.mmd -o pipeline_light.svg --theme light --logo logo_light.png

Interactive HTML output

--format html produces a self-contained .html file with the SVG inlined plus a small JS/CSS layer (no external dependencies, no network):

nf-metro render pipeline.mmd --format html -o pipeline.html

The page provides:

• Drag to pan, scroll to zoom (Cmd/Ctrl+scroll in embedded mode).
• Hover a station to see its label, section, and the lines passing through it.
• Click a line in the legend to isolate it. Stations and sections not carrying that line disappear and the view zooms to the bounding box of what remains. Click again, hit Esc, or use the Reset button to restore.
• Embed... opens a copy-snippet panel with three options:
  • Inline HTML - a self-contained <div> you paste into any HTML host (MkDocs, Confluence, Notion, blog templates). Keeps full interactivity, no iframe.
  • iframe - a one-liner pointing at the hosted .html file.
  • Static SVG - the raw <svg> markup for contexts that strip scripts.

GitHub READMEs strip <script> tags, so embed there as a static SVG (or link out to a hosted version). Most static-site generators and internal wikis run the inline-HTML snippet as-is.

Embedded data manifest

Every rendered SVG carries a machine-readable manifest so the committed file is a self-contained artifact - a downstream tool can position overlays, restyle nodes, or look up which processes a node represents without re-running the layout engine. The data is carried as a JSON block in a <metadata id="diagram-manifest"> element and as data-node-* attributes on each station's <g> element.

Set %%metro manifest: false (or --no-manifest) to emit the drawn map without a manifest. See the Data manifest docs for the full schema and how to consume it.

nf-metro validate

Check a .mmd file for errors without producing output.

nf-metro validate [OPTIONS] INPUT_FILE

Option	Default	Description
--with-layout	off	Also run the layout engine with its full invariant suite
--strict	off	Treat warnings as errors

nf-metro validate-svg

Run geometry checks on an already-rendered SVG (without re-running the layout engine).

nf-metro validate-svg [OPTIONS] SVG_FILE

Option	Default	Description
--geometry	off	Check that routes don't pass through station labels or markers, and that distinct lines don't collapse onto one stroke

nf-metro info

Print a summary of the parsed map: sections, lines, stations, and edges.

nf-metro info INPUT_FILE

nf-metro convert

Convert a Nextflow -with-dag mermaid file to nf-metro .mmd format. The output can be rendered directly or hand-tuned first.

nf-metro convert [OPTIONS] INPUT_FILE

Option	Default	Description
-o, --output PATH	stdout	Output .mmd file path
--title TEXT	auto	Pipeline title for the converted output

To convert and render in one step, use the --from-nextflow flag on render instead. See Importing from Nextflow for details.

nf-metro serve

Host a metro map and light up stations in real time as a Nextflow pipeline runs. Point Nextflow's -with-weblog at the server; stations transition from pending to running to done as tasks complete. No Seqera Platform, no plugin required.

nf-metro serve path/to/map.mmd --port 8080
# then in another shell:
nextflow run my/pipeline -with-weblog http://localhost:8080/events

Option	Default	Description
--port	8080	Port to listen on
--host	127.0.0.1	Interface to bind (0.0.0.0 to accept remote connections)
--theme	nfcore	Visual theme (nfcore, light, seqera)
--overlay	ring	Status overlay style: ring, pulse, dot, led
--token	none	Require ?token= or X-Metro-Token header on /events

Stations must be mapped to Nextflow process names with %%metro process: directives (see the directive reference and the live progress guide).

nf-metro serve-multi

Long-lived dashboard mode: each pipeline or run registers its own map and gets a stable /r/<id>/ URL. Useful for running many pipelines side by side or keeping a history of runs.

nf-metro serve-multi --port 8080

# register a map (returns JSON with "id" and "events")
curl -s --data-binary @map.mmd "http://localhost:8080/maps?name=myrun"
# point Nextflow at the per-run events endpoint
nextflow run my/pipeline -with-weblog "http://localhost:8080/r/<id>/events"

See the live progress guide for the full dashboard workflow and the optional Nextflow plugin that handles registration automatically.

nf-metro check-mapping

Audit a .mmd file's %%metro process: directives against a real Nextflow process graph and report drift: processes with no station (invisible), stale patterns that match nothing, and processes matching more than one station (duplicated progress). Exits non-zero when it finds problems, so it can gate CI.

nextflow run my/pipeline -with-dag dag.mmd -preview
nf-metro check-mapping path/to/map.mmd --dag dag.mmd

Option	Default	Description
--dag <file>	-	Nextflow -with-dag Mermaid export
--processes <file>	-	Newline-delimited list of process names (alternative to --dag)
--ignore <regex>	-	Processes deliberately left unmapped (e.g. .*:DUMPSOFTWAREVERSIONS). Repeatable.

Examples

The examples/ directory contains ready-to-render .mmd files:

Example	Description
simple_pipeline.mmd	Minimal two-line pipeline with no sections
rnaseq_auto.mmd	nf-core/rnaseq with fully auto-inferred layout
rnaseq_sections.mmd	nf-core/rnaseq with manual grid overrides

Topology gallery

The examples/topologies/ directory has 38 examples covering a range of layout patterns. See the topology README for descriptions and rendered previews, or browse the online gallery.

A few highlights:

Wide Fan-Out	Section Diamond	Variant Calling
Fold Serpentine	Multi-Line Bundle	RNA-seq Lite

Input format

Input files use a subset of Mermaid graph LR syntax extended with %%metro directives. The format has three layers: global directives that configure the overall map, section directives inside subgraph blocks that control section layout, and edges that define connections between stations.

The Guide walks through the format step by step, from a minimal flat pipeline to a multi-section map with custom grid layout. The walkthrough below covers the key ideas.

Walkthrough: nf-core/rnaseq

The full example is at examples/rnaseq_sections.mmd.

Global directives

%%metro title: nf-core/rnaseq
%%metro logo: examples/nf-core-rnaseq_logo_dark.png
%%metro style: dark

• title: sets the map title (shown top-left unless a logo is provided)
• logo: embeds a PNG image in place of the text title
• style: selects a theme (dark or light)

Lines (routes)

Each metro line represents a distinct path through the pipeline:

%%metro line: star_rsem | Aligner: STAR, Quantification: RSEM | #0570b0
%%metro line: star_salmon | Aligner: STAR, Quantification: Salmon (default) | #2db572
%%metro line: hisat2 | Aligner: HISAT2, Quantification: None | #f5c542
%%metro line: pseudo_salmon | Pseudo-aligner: Salmon, Quantification: Salmon | #e63946
%%metro line: pseudo_kallisto | Pseudo-aligner: Kallisto, Quantification: Kallisto | #7b2d3b

An optional fourth field sets the stroke style: solid (default), dashed, or dotted.

Grid placement

Sections are placed automatically via topological sort, but explicit positions can be set:

%%metro grid: postprocessing | 2,0,2
%%metro grid: qc_report | 1,2,1,2

The format is section_id | col,row[,rowspan[,colspan]].

Sections

Sections are Mermaid subgraph blocks. Entry and exit hints control which side the port appears on:

graph LR
    subgraph preprocessing [Pre-processing]
        %%metro exit: right | star_salmon, star_rsem, hisat2
        %%metro exit: bottom | pseudo_salmon, pseudo_kallisto
        cat_fastq[cat fastq]
        fastqc_raw[FastQC]
        ...
    end

• %%metro entry: <side> | <line_ids> - which lines enter and from which side (left, right, top, bottom)
• %%metro exit: <side> | <line_ids> - which lines exit and to which side
• %%metro direction: <dir> - section flow direction: LR (default), RL (right-to-left), or TB (top-to-bottom)

Stations and edges

Stations use Mermaid node syntax. Edges carry comma-separated line IDs:

        cat_fastq -->|star_salmon,star_rsem,hisat2,pseudo_salmon,pseudo_kallisto| fastqc_raw
        star -->|star_rsem| rsem
        star -->|star_salmon| umi_tools_dedup

Inter-section edges

Edges between stations in different sections go outside all subgraph/end blocks. They are automatically rewritten into port-to-port connections with junction stations at fan-out points:

    sortmerna -->|star_salmon,star_rsem| star
    sortmerna -->|hisat2| hisat2_align
    sortmerna -->|pseudo_salmon| salmon_pseudo
    sortmerna -->|pseudo_kallisto| kallisto

Directive reference

Directive	Scope	Description
%%metro title: <text>	Global	Map title
%%metro logo: <path>	Global	Logo image (replaces title text)
%%metro logo_scale: <factor>	Global	Scale the logo within the legend block
%%metro style: <name>	Global	Theme: dark, light
%%metro line: <id> | <name> | <color> [| <style>]	Global	Define a metro line. Optional style: solid (default), dashed, dotted
%%metro grid: <section> | <col>,<row>[,<rowspan>[,<colspan>]]	Global	Pin section to grid position
%%metro legend: <position>	Global	Legend position: tl, tr, bl, br, bottom, right, none (append | canvas, | <dx>,<dy>, or use <x>,<y> - see the guide)
%%metro line_order: <strategy>	Global	Line ordering: definition (default) or span
%%metro file: <station> | <label> [| <name>] [| banner]	Global	Mark a station as a file terminus with a document icon
%%metro files: <station> | <label> [| <name>] [| banner]	Global	Mark a station with a stacked-documents icon (e.g. paired files)
%%metro dir: <station> | <label> [| <name>]	Global	Mark a station with a folder icon
%%metro off_track: <station>[, <station>...]	Global	Lift listed stations above the main track, anchored to their producer/consumer
%%metro process: <station> | <regex>	Global	Map a station to a Nextflow process name regex for live progress; repeatable
%%metro compact_offsets: true	Global	Use compact per-station offsets instead of global line-priority slots
%%metro center_ports: true	Global	Centre inter-section ports on the shorter of the two connected sections
%%metro line_spread: <mode>[ | <section>...]	Global / Section	How lines sharing a station relate vertically: bundle (default), centered, rails
%%metro animate: true	Global	Add animated balls traveling along lines (same as --animate)
%%metro directional: true	Global	Draw static flow-direction chevrons (same as --directional)
%%metro manifest: false	Global	Omit the embedded data manifest from the rendered SVG
%%metro legend_min_height: <pixels>	Global	Minimum legend content height in pixels
%%metro entry: <side> | <lines>	Section	Entry port hint
%%metro exit: <side> | <lines>	Section	Exit port hint
%%metro direction: <dir>	Section	Flow direction: LR, RL, TB

Live progress

nf-metro can light up a metro map in real time as a Nextflow pipeline runs. Map stations to Nextflow processes with %%metro process: directives, then start the server:

nf-metro serve path/to/map.mmd
nextflow run my/pipeline -with-weblog http://localhost:8080/events

Stations transition from pending to running to done as tasks are submitted and complete. The layout is computed once; the overlay is drawn on top, so the map never re-flows during a run.

For multi-pipeline dashboards, persistent history, and the optional Nextflow plugin that handles wiring automatically, see the live progress guide.

Python API

nf-metro is a command-line tool. Its Python modules are importable, but the internal API (parser, layout engine, renderer) is not part of the public, semver-stable surface and may change between releases without notice. Drive nf-metro through the nf-metro CLI (or python -m nf_metro) for stable behaviour.

Contributing

See the Contributing guide for setup, testing, how to add topology fixtures, working with layout invariants, and the visual review process.

License

MIT