API Reference: Hooks

Three callbacks and signals. They are all attached at call sites, not on objects: there is no "subscribe to an object" API, and progress information can only come in through these parameters.

Environment-level readiness (capabilities / runtime / KaTeX / package fetching) does not attach at call sites; see Environment Status.

onLoading(names)

Progress callback while third-party packages are fetched for an import. Three mounting points, in increasing precedence:

1. createManimRenderer({ onLoading })
2. createSurface(container, { onLoading })
3. run(code, { onLoading })

onLoading?: (names: string[]) => void

Parameters names: the package names being fetched; called once more with an empty array when done.

Example

const surface = await renderer.createSurface(container, {
  onLoading: (names) => {
    if (names.length === 0) return hideLoading()
    // Bundled packages and cache hits are fast; showing it immediately makes it flash. Delay ~300 ms.
    window.setTimeout(() => showLoading(names), 300)
  },
})

Notes

• Covers package fetching only, not render progress. "Rendering now" has to be tracked at the call site around run().
• print from user code does not come through here; the core writes it to console.info.

onProgress(note)

Stage updates during an export; attached on the request passed to exporter.run().

onProgress?: (note: string) => void

Parameters note: one line of progress text, e.g. "playing from the top and recording…" or "recorded 32 KB".

Example

await recorder.run({ python, controller, onProgress: (note) => setStatus(note) })

signal

Cancels one export. Only exporter.run() accepts it; surface.run() does not.

run(request: ExportRequest, signal?: AbortSignal): Promise<ExportResult>

Example

const abort = new AbortController()
stopButton.onclick = () => abort.abort()
await recorder.run({ python, controller }, abort.signal)

After an abort the recorder stops and returns { ok: false, reason: 'error', error: 'cancelled' }.

Notes

• It cancels the export action, not the render in flight. Cancelling "the piece that is running right now" has no corresponding capability in this version; see the gap table at the end of Low-Level Exports.