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brother-ql

brother-ql / web/src / WebBrotherQLPrinter

Class: WebBrotherQLPrinter ​

WebUSB PrinterAdapter for Brother QL printers.

Mirrors the node driver's behaviour — renderMultiPlaneImage() runs internally when the resolved media carries a palette, and pickRotation auto-rotates landscape input on media tagged defaultOrientation: 'horizontal'.

Implements ​

Constructors ​

Constructor ​

new WebBrotherQLPrinter(device, transport): WebBrotherQLPrinter

Parameters ​

device ​

DeviceEntry

transport ​

Transport

Returns ​

WebBrotherQLPrinter

Properties ​

device ​

readonly device: DeviceEntry

The device entry for the connected printer.

Useful for logging, diagnostics, and displaying VID/PID. Undefined if the connection was established without device matching (e.g. a raw TCP connection to a known IP).

Implementation of ​

PrinterAdapter.device

family ​

readonly family: "brother-ql"

Driver family identifier, e.g. 'brother-ql' or 'labelwriter'.

Implementation of ​

PrinterAdapter.family

Accessors ​

connected ​

Get Signature ​

get connected(): boolean

Whether the printer is currently connected.

Returns ​

boolean

Implementation of ​

PrinterAdapter.connected

model ​

Get Signature ​

get model(): string

Human-readable model name from the driver's device registry.

Returns ​

string

Implementation of ​

PrinterAdapter.model

Methods ​

close() ​

close(): Promise<void>

Close the connection. Always call in finally blocks.

Returns ​

Promise<void>

Implementation of ​

PrinterAdapter.close

createPreview() ​

createPreview(image, options?): Promise<PreviewResult>

Generate a preview showing how this printer would reproduce the design on the given media. Returns separated 1bpp planes with display colours.

The driver uses its own colour-splitting logic (the same code that print() uses internally) to produce the planes. The consuming app renders whatever planes come back without needing to know the splitting rules.

For offline preview without a live connection, use the static createPreviewOffline() function exported from the driver's *-core package instead.

Parameters ​

image ​

RawImageData

— full RGBA, typically from designer.render().

options? ​

PreviewOptions

— optional media override. If media is omitted, uses detected media from the last getStatus(). If no status is available, the driver defaults to single-colour at the printer's native head width and sets PreviewResult.assumed = true.

Returns ​

Promise<PreviewResult>

Implementation of ​

PrinterAdapter.createPreview

getStatus() ​

getStatus(): Promise<PrinterStatus>

Send ESC iS and resolve with the next status frame the printer emits. The read loop is the sole reader of the bulk-IN pipe — getStatus() subscribes transiently, writes the request, and the subscription receives the response (alongside any spontaneous frames; see onStatus()).

The QL preamble (200×0x00 invalidate + ESC @ initialize) is sent only when the parser hasn't been confirmed clean — first call of the session, or after a previous timeout. Steady-state polls send bare ESC iS. Bench observation: a freshly-opened QL doesn't reply to bare ESC iS until the invalidate flushes any stale parser state from a prior session.

Returns ​

Promise<PrinterStatus>

Implementation of ​

PrinterAdapter.getStatus

onStatus() ​

onStatus(cb): () => void

Subscribe to status updates. A polling shim built on pollingOnStatus from contracts — it calls getStatus() on first subscribe and then every DEFAULT_POLLING_INTERVAL_MS, matching the labelwriter and labelmanager web drivers (plan 11 §onStatus parity).

An earlier revision skipped polling and relied solely on the printer's unsolicited frames. That was a workaround for the Chromium WebUSB sub-packet stall — getStatus()'s read() would hang, so polling looked unreliable and was dropped. WebUsbTransport.read() now rounds reads up to the endpoint packet size, so getStatus() is dependable and polling is restored.

Parameters ​

cb ​

(status) => void

Returns ​

() => void

Implementation of ​

PrinterAdapter.onStatus

print() ​

print(image, media?, options?): Promise<void>

Print from a full-colour RGBA image.

The driver converts to its native format internally:

  • Single-colour media (media.palette undefined) — threshold/dither RGBA to a single 1bpp plane via renderImage.
  • Multi-ink media (media.palette defined) — split into planes via renderMultiPlaneImage using that palette.

Orientation: drivers compute the rotation via pickRotation (see ./orientation.ts) — the input image is treated as the intended visual; the driver auto-rotates landscape input on media tagged defaultOrientation: 'horizontal'.

Multi-ink splitting: the palette on the media descriptor names every ink the driver should classify pixels into; the contracts package does not pick "red" or "black" — those facts live with the media entry.

Batch printing: call print() once per label. The driver handles job framing internally (e.g. Brother QL page-break commands between sequential print() calls within the same session).

Parameters ​

image ​

RawImageData

— full RGBA, typically from designer.render().

media? ​

MediaDescriptor

— which media to print on. Determines dimensions, margins, and colour mode. If omitted, uses detected media from the last getStatus().

options? ​

BrotherQLPrintOptions

— per-call options (copies, density, etc.).

Returns ​

Promise<void>

Throws ​

MediaNotSpecifiedError if no media is known.

Implementation of ​

PrinterAdapter.print