Interface: PrintEngine
A print engine — one printhead with one protocol.
Most devices have a single engine. The LabelWriter Duo has two (label + tape) with different protocols and different USB interfaces. The Twin Turbo also has two (left + right) sharing one transport with in-band protocol-level addressing.
Extended by
Properties
| Property | Type | Description |
|---|---|---|
bind? | EngineBind | Per-engine routing hints. Omit on single-engine devices. See EngineBind for transport-layer vs protocol-layer routing. |
capabilities? | PrintEngineCapabilities | Engine-level capability flags. See PrintEngineCapabilities. |
dpi | number | - |
forcedTrailingFeedMm? | number | Post-print tape advance the printer (or this driver's encoder) forces after the printed bitmap, in mm. Distinct from printableArea: - printableArea describes where the head can't reach during the print; - forcedTrailingFeedMm describes tape eaten after the print so content clears the cutter / tear bar. Populated where the suite has a known fixed post-print feed (cat-printer's DEFAULT_FEED_LINES, labelmanager's encoder-side trailing pad, LabelManager PnP's firmware-enforced advance). Absent / 0 when the trailing feed is variable (e.g. labelwriter ESC E advances to the next tear bar — distance depends on the label gap-sensor position) or when the suite has no measurement. Use getForcedTrailingFeedMm(engine) from @thermal-label/contracts to resolve with the zero default. |
headDots | number | Native dot count across the head. |
mediaCompatibility? | readonly string[] | Filter for which entries from the driver's media registry this engine accepts. Resolved against MediaDescriptor.targetModels. Driver-defined string set; undefined = engine accepts every media in the driver's registry. |
printableArea? | PrintableArea | Chassis-physical dead zones around the printable rectangle (mm). Insets the head physically cannot reach — head-to-cutter offsets, head-vs-tape-width geometry, sensor-window keep-outs. Encoders use this to crop / shift the bitmap so authored content lands where the user expects. Distinct from MediaDescriptor.printMargins (per-media design-tool inset), from forcedTrailingFeedMm (post-print tape advance), and from any wire-protocol "feed margin" command the firmware enacts on its own (e.g. Brother QL/PT ESC i d). Absent means "not measured" rather than "measured to zero". Use getPrintableArea(engine, media?) from @thermal-label/contracts to resolve a fully-populated value with the standard zero defaults and per-roll media-tag override applied. |
protocol | string | Driver-family-specific wire-protocol tag. |
role | string | Semantic role identifier — used as the lookup key on the runtime adapter (printer.engines[role]). For single-engine devices: 'primary'. For composite devices: descriptive ('label', 'tape', 'left', 'right'). |