Function: pollingOnStatus()

function pollingOnStatus(
   printer: Pick<PrinterAdapter, "getStatus">, 
   cb: (status: PrinterStatus) => void, 
   intervalMs?: number): () => void;

Build an onStatus implementation for drivers whose printers don't push spontaneous status frames (LM / LW today; anything where getStatus() is a discrete request/response cycle).

Returns a function with the same shape as PrinterAdapter.onStatus — subscribe a callback, get back an unsubscribe function. Internally it kicks an immediate getStatus() so the subscriber resolves quickly, then polls at intervalMs until the unsubscribe handle fires.

Errors during a poll are swallowed silently — a missed read keeps the last-known status visible upstream rather than flickering the pill on every transient timeout. The cadence matches the harness shell's pre-plan-11 polling timer (4 s) so visible status freshness is unchanged.

Multi-subscriber: each call returns its own unsubscribe; the underlying poll loop runs once per subscriber. Drivers that need a shared loop should implement their own onStatus directly.

Usage on a driver-web printer class:

onStatus(cb: (s: PrinterStatus) => void): () => void {
  return pollingOnStatus(this, cb);
}

Per plan 11 §onStatus parity: lifting the harness's pull-side timer into each driver collapses the shell's push-vs-pull branch down to a single subscription path. Every driver looks like a push driver to the shell.

Parameters

Parameter	Type	Default value
printer	Pick<PrinterAdapter, "getStatus">	undefined
cb	(status: PrinterStatus) => void	undefined
intervalMs	number	DEFAULT_POLLING_INTERVAL_MS

Returns

() => void