wickchart-coview

Cross-tab co-view for wickchart, as an opt-in plugin — charts that share a room name keep each other briefed. Every pan/zoom broadcasts the visible window (throttled to ~8/s, heartbeat every 4 s), each chart renders the others' viewports as labeled bands along the top of the plot, and the crosshair is shared live — a dashed ghost mirrors the pointer of the tab you are pairing with. Closed tabs say goodbye; crashed tabs fade via the 12 s presence TTL. Zero dependencies.

npm install wickchart wickchart-coview

import 'wickchart';
import { attachCoview } from 'wickchart-coview';

// declarative — the room is the attribute:
// <wick-chart co-view="btc-warroom" co-view-name="Maya"></wick-chart>
const coview = attachCoview(chart);

chart.getPeers();
// [{ id, name: 'Maya', range: { from, to }, at }] — oldest sighting first

chart.addEventListener('wick:peers', (e) => {
  // { peers, joined, left } — membership changes only, not every move
});

coview.detach();

Until wickchart 2.0 the core element ships its own identical machinery; attaching shadows it with the same behavior (this package is the home it moves into at the cut — see ROADMAP-V2.md in the repo).

The protocol

Public and tiny — anything that can postMessage can join a room: channel wick-co-view:<room>, messages { v: 1, peer, … } where peer is a random per-chart id:

| type | payload | meaning | | ---- | ------- | ------- | | view | from, to, name | the sender's visible window (presence heartbeat) | | cross | time, yFrac — or time: null | pointer moved / left | | bye | — | sender is leaving the room |

Wrong-version, self-echoed, and unknown messages are ignored — the envelope check lives in coUnwrap() and is safe by construction.

API

attachCoview(chart, { channel?, ttl?, beatMs? }) returns the controller:

| Method | Meaning | | ------ | ----------------------------------------------------------- | | chart.getPeers() | live peers with their viewports, oldest first | | coview.detach() | goodbye, close, restore the element's own machinery |

channel is an injectable transport factory (tests, WebSocket bridges); ttl is the presence timeout (default 12 s); beatMs the heartbeat (default 4 s). Events on the chart: wick:peers with { peers, joined, left }.

The pure half — PresenceTracker (TTL bookkeeping) and the protocol envelope (coWrap/coUnwrap) — is a separate import with no DOM: import { PresenceTracker } from 'wickchart-coview/core'.

MIT.