neo4j-nvl-skill

## When to Use
- Rendering a Neo4j graph in a browser (vanilla JS, React, Vite) with custom interactions, rendering, or data shapes
- Visualizing `driver.executeQuery` results as an interactive graph
- Wiring zoom, pan, drag, click, hover, lasso, or box-select interactions
- Embedding NVL inside an existing app and synchronizing graph state

## When NOT to Use
- **Pre-styled embedded graph view with default behavior, no custom interactions** → `GraphVisualization` from `@neo4j-ndl/react` (Neo4j Needle / NDL design system) — wraps NVL with default Neo4j styling. See [Use NVL or the Needle Component?](#use-nvl-or-the-needle-component) below.
- **Python / Jupyter notebook graph visualization** → `neo4j/python-graph-visualization` (the Python port of NVL)
- **Writing/optimizing Cypher** → `neo4j-cypher-skill`
- **Driver setup / executeQuery / sessions** → `neo4j-driver-javascript-skill`
- **Server-side data fetching with no rendering** → `neo4j-driver-javascript-skill`
- **GDS algorithm execution** → `neo4j-gds-skill` or `neo4j-aura-graph-analytics-skill`
- **GraphQL API** → `neo4j-graphql-skill`

---

## Use NVL or the Needle Component?

| Need | Use |
|---|---|
| Embed a graph view with default Neo4j styling, no custom interactions or rendering | `GraphVisualization` from `@neo4j-ndl/react` (Neo4j Needle / NDL design system) — wraps NVL and accepts records shaped `{ id, labels, properties: { key: { stringified, type } } }` (`NeoNode`) |
| Custom interactions, custom rendering, non-standard data shapes, or framework-agnostic embedding | This skill — use NVL directly |

If the answer is the first row, install and use the Needle component instead of NVL — do not duplicate styling work.

---

## Install

```bash
npm install @neo4j-nvl/base                  # core (required)
npm install @neo4j-nvl/interaction-handlers  # standard interactions (optional, vanilla JS)
npm install @neo4j-nvl/react                 # React wrappers (optional)
```

Peer requirements: **React 19** for `@neo4j-nvl/react`. The published peerDependency range still permits React 18, but mixing major versions is not recommended — target 19. `@neo4j-nvl/layout-workers` is a transitive dependency — never install directly. `neo4j-driver` is a peer of `@neo4j-nvl/base` only when using `nvlResultTransformer`.

Starter templates: https://github.com/neo4j-devtools/nvl-boilerplates — official per-framework scaffolds; prefer these over hand-rolled setups.

License: NVL ships under the **Neo4j Visualization Library License** — for use with Neo4j products only. Cannot be used against other graph backends.

---

## Pick the Right Paradigm

| Need | Use |
|---|---|
| React app, default interactions | `<InteractiveNvlWrapper>` from `@neo4j-nvl/react` |
| React app, custom interaction wiring | `<BasicNvlWrapper>` + own handlers via `ref` |
| Vanilla JS, standard interactions | `NVL` + `@neo4j-nvl/interaction-handlers` |
| Vanilla JS, fully custom event logic | `NVL` + `container.addEventListener` + `nvl.getHits()` |
| Static PNG/SVG image export | `<StaticPictureWrapper>` or `nvl.saveToFile()` / `nvl.saveToSvg()` |

---

## Pick the Right Renderer

| Renderer | Max nodes | Detail | Use case |
|---|---|---|---|
| `'canvas'` (default) | ~1,000 | Full captions, icons, arrows, pixel-perfect hit-testing | Detail investigation, small graphs |
| `'webgl'` | 100,000+ | Reduced label fidelity (bound by GPU max texture size) | Large-scale pattern exploration |

```javascript
const nvl = new NVL(container, nodes, rels, { renderer: 'webgl' })
nvl.setRenderer('canvas')   // swap at runtime
```

---

## Container Setup

The container must have an explicit `width` AND `height`. Missing height → container collapses to `0` → graph invisible. Most-reported NVL bug.

```html
<!-- ❌ height defaults to 0; graph invisible -->
<div id="viz"></div>

<!-- ✅ explicit dimensions -->
<div id="viz" style="width: 100%; height: 600px;"></div>
```

---

## Vanilla — Base Library

```javascript
import { NVL } from '@neo4j-nvl/base'

const container = document.getElementById('viz')
const nodes = [{ id: '1' }, { id: '2' }]
const relationships = [{ id: '12', from: '1', to: '2', type: 'KNOWS' }]

const nvl = new NVL(container, nodes, relationships)
```

With options + callbacks:

```javascript
import { NVL } from '@neo4j-nvl/base'

const options = {
  initialZoom: 1.0,
  minZoom: 0.1,
  maxZoom: 8,
  layout: 'forceDirected',
  renderer: 'canvas',
  styling: { defaultNodeColor: '#0e86d4', defaultRelationshipColor: '#888' }
}
const callbacks = {
  onInitialization: () => console.log('NVL ready'),
  onLayoutDone: () => nvl.fit([]),
  onError: (err) => console.error('NVL error', err)
}

const nvl = new NVL(container, nodes, relationships, options, callbacks)

// On teardown — always:
nvl.destroy()
```

`NVL` constructor signature: `new NVL(frame, nvlNodes?, nvlRels?, options?, callbacks?)`. All but `frame` are optional and default to empty.

---

## Vanilla — Interaction Handlers

Compose handlers onto an existing `NVL` instance. Each handler registers callbacks via `.updateCallback(name, fn)` and must be torn down with `.destroy()`.

```javascript
import { NVL } from '@neo4j-nvl/base'
import {
  ZoomInteraction, PanInteraction, DragNodeInteraction,
  ClickInteraction, HoverInteraction, BoxSelectInteraction,
  LassoInteraction, KeyboardInteraction
} from '@neo4j-nvl/interaction-handlers'

const nvl = new NVL(container, nodes, relationships)

const zoom  = new ZoomInteraction(nvl)
const pan   = new PanInteraction(nvl)
const drag  = new DragNodeInteraction(nvl)
const click = new ClickInteraction(nvl, { selectOnClick: true })
const hover = new HoverInteraction(nvl, { drawShadowOnHover: true })

click.updateCallback('onNodeClick',         (node, hits, evt) => console.log('node',  node.id))
click.updateCallback('onRelationshipClick', (rel,  hits, evt) => console.log('rel',   rel.id))
click.updateCallback('onCanvasClick',       (evt)             => console.log('canvas'))
hover.update