Guides

Events

Engine events for state, limits, errors and imports, and chart view events for user gestures.

Engine events

engine.on(event, listener) returns a function that removes the listener.

Event	Payload and moment
`change`	`EngineState`. After every effective state change (same moment as `subscribe`), and once when the license check finishes.
`limit`	`{ reason: LimitReason }`. An action was refused by a limit; the call also throws `limit_reached`.
`error`	`{ error, context }`. Failures that have no caller to reject: a file in an import batch (`context: 'import'`) or a math-channel store call (`'mathChannels.create'`, …).
`import`	`{ file, phase, datasetId?, error? }`, with `phase` `'start'`, `'done'` or `'error'`, per file.

TypeScript

const offs = [
  engine.on('limit', ({ reason }) => openUpgradeDialog(reason)),
  engine.on('import', ({ file, phase }) => setStatusLine(`${file}: ${phase}`)),
  engine.on('error', ({ error, context }) => report(context, error)),
]
// later: offs.forEach((off) => off())

Chart view events

view.on(event, listener) also returns an unsubscribe function.

Event	Payload and moment
`status`	`'no-data' \| 'empty' \| 'ready'`, when it changes.
`contextmenu`	`{ clientX, clientY, zoomXRange? }`. The user right-clicked the plot. On a multi-band chart a right-drag selects an X span, passed as `zoomXRange`. Emitted in every status.
`viewchange`	`[x0, x1] \| null`. The user zoomed or panned a multi-band chart. The worksheet’s linked zoom is already updated.