Infinite Canvas

Overview

@xnet/canvas provides an infinite, zoomable 2D surface where users can place, connect, and arrange nodes. The canvas supports real-time collaboration via Yjs — multiple users can simultaneously add, move, and connect nodes.

Canvas component

import { Canvas } from '@xnet/canvas'

;<Canvas
  doc={ydoc} // Required: Yjs document
  awareness={awareness} // Cursor presence
  renderNode={(node) => <MyCard />} // Custom node content
  onNodeDoubleClick={(id) => open(id)}
  onBackgroundClick={() => deselect()}
  config={{
    minZoom: 0.1,
    maxZoom: 3,
    gridSize: 20,
    showGrid: true
  }}
/>

Keyboard shortcuts

Shortcut	Action
`Delete` / `Backspace`	Delete selected nodes
`Cmd+A`	Select all
`Escape`	Clear selection
`Cmd+1`	Fit to content
`Cmd+0`	Reset view

Mouse interaction

Scroll — Pan the canvas
Ctrl/Cmd + Scroll — Zoom (pinch-to-zoom)
Click node — Select it
Shift/Cmd + Click — Additive selection
Drag node — Move it
Drag resize handles — Resize (8 handles on selection)
Double-click — Open node

useCanvas hook

The primary hook that wires together the store, viewport, and layout engine:

const {
  // State
  nodes,
  edges,
  selectedNodeIds,
  viewport,

  // Node operations
  addNode,
  updateNodePosition,
  removeNode,

  // Edge operations
  addEdge,
  removeEdge,

  // Selection
  selectNode,
  selectAll,
  clearSelection,
  deleteSelected,

  // Viewport
  pan,
  zoomAt,
  fitToContent,
  resetView,

  // Layout
  autoLayout,
  layoutSelected,

  // Queries
  findNodeAt,
  findNodesInRect,
  getVisibleNodes
} = useCanvas({ doc: ydoc, config })

Spatial index

The canvas uses an R-tree (rbush) for efficient spatial queries. This enables viewport culling — only nodes visible on screen need to be rendered.

// Find all nodes in the current viewport
const visibleIds = store.getVisibleNodes(viewport.getVisibleRect())

// Find the topmost node at a point
const nodeId = store.findNodeAt(point)

// Find all nodes overlapping with a given node
const overlapping = store.findIntersecting(nodeId)

The spatial index is automatically updated when nodes are added, moved, or removed.

Layout algorithms

The LayoutEngine supports automatic layout via ELK.js and two built-in algorithms:

ELK.js layouts

await autoLayout({
  algorithm: 'layered', // Sugiyama/hierarchical
  direction: 'RIGHT', // RIGHT, LEFT, DOWN, UP
  nodeSpacing: 50,
  layerSpacing: 100,
  edgeRouting: 'ORTHOGONAL' // POLYLINE, ORTHOGONAL, SPLINES
})

Available algorithms: layered, force, mrtree, radial, stress, box.

Grid layout

layoutEngine.layoutGrid(nodes, {
  columns: 4,
  spacing: 20,
  padding: 50
})

Circle layout

layoutEngine.layoutCircle(nodes, {
  radius: 300 // Auto-calculated if omitted
})

Nodes with properties.fixed = true keep their positions during layout.

Viewport

The Viewport class manages the camera:

pan(dx, dy) — Move by screen-space delta
zoomAt(x, y, factor) — Zoom while keeping the point under cursor stationary
fitToRect(rect, padding) — Fit viewport to show a rectangle (never zooms beyond 100%)
reset() — Return to origin at zoom 1
screenToCanvas(x, y) — Convert screen coordinates to canvas space
canvasToScreen(x, y) — Convert canvas coordinates to screen space
getVisibleRect() — The canvas-space rectangle currently on screen

Data storage

Canvas state is stored in three Yjs maps inside the Y.Doc:

Map	Contents
`metadata`	Title, created/updated timestamps
`nodes`	`CanvasNode` objects keyed by ID
`edges`	`CanvasEdge` objects keyed by ID

All mutations go through Yjs transactions, so changes sync automatically to other peers. The spatial index updates reactively when the Yjs maps change.

Node types

interface CanvasNode {
  id: string
  type: string // 'page', 'database', 'note', etc.
  position: {
    x: number
    y: number
    width: number // Default: 200
    height: number // Default: 100
    rotation?: number
    zIndex?: number
    collapsed?: boolean
  }
  properties: Record<string, unknown>
  linkedNodeId?: string // Link to a page/database node
}

Edges connect nodes with optional labels, arrow markers, and routing styles (bezier or orthogonal).

Comments

The canvas supports spatial comments via useCanvasComments:

Position pins — Fixed canvas coordinates. Never orphaned.
Object-attached pins — Follow a node’s position. Become orphaned when the node is deleted.