Features

Opens HepMC files in a custom editor
Shows one event at a time with next/previous navigation
Supports pan and zoom
Right-click in the graph to save the current event as SVG
Layout and styling follow pyhepmc's graphviz view:
- unicode particle names for every PDG ID pyhepmc knows (6,496 entries incl. nuclei)
- track thickness scales with energy relative to the event's most energetic particle
- color by category (hadron, quark/gluon, lepton/boson, generator-internal, …), dashed neutrals, arrowheads on beam and final-state particles only
Shows particle hover tooltips with:
- name
- PDG ID
- status
- mass
- 4-momentum
- electric charge

Supported input

The parser handles the common HepMC3 ASCII records used in this project:

E event headers
U units
W event weights
A attributes
P particles
V vertices

Architecture

src/common/ contains the portable HepMC parser, PDG lookup (pdg.ts + generated pdg-data.json), graph construction, the DOT builder (dot.ts) and the graphviz WASM wrapper (render.ts).
src/webview/ contains the browser-side shell: it injects the SVG produced by the host and adds zoom and tooltips.
src/extension.ts contains the VS Code custom editor host layer; it parses the file, lays events out with graphviz on request, and serves the theme stylesheet (src/common/theme.ts).
Vocabulary is in CONTEXT.md; design decisions are recorded in docs/adr/.

Build

npm install
npm run build

Regenerating particle data

src/common/pdg-data.json is generated from pyhepmc's unicode name table and the particle package. It is committed, so a normal build needs no Python. To refresh it:

uv run --with "pyhepmc,particle" python scripts/generate_pdg_data.py

Notes

The UI is intentionally browser-native so it can be reused in a standalone website later (@hpcc-js/wasm-graphviz runs in both Node and browsers).
d3-selection and d3-zoom are used for the lightweight interactive view layer.

Third-party notices

Particle names in src/common/pdg-data.json come from pyhepmc (BSD-3-Clause), with categories and charges derived from particle (BSD-3-Clause).
Layout uses Graphviz (EPL-1.0) via @hpcc-js/wasm-graphviz (Apache-2.0).