ESC/POS for Kotlin Multiplatform

Basic ESC/POS command generator and device connection support for various connection types: Bluetooth, USB, TCP.

This library is not a wrapper around established ESC/POS libraries, but rather a green field implementation.

• ESC/POS for Kotlin Multiplatform
  • Setup
  • What is ESC/POS?
  • Feature/Platform matrix

Setup

The library is available at Maven Central.

repositories {
    mavenCentral()
}

implementation("cz.multiplatform.escpos4k:escpos4k:0.3.0")

TLDR Android Bluetooth example

suspend fun awaitPrint(): MyError? {
  val btManager = BluetoothPrinterManager(requireContext())
  val device = btManager.pairedPrinters().firstOrNull() 
      ?: return MyError.NotFound
  val connection = btManager.openConnection(device)?.takeIf { it.isOpen } // (1)
      ?: return MynError.Disconnected
  
  val config = PrinterConfiguration(charactersPerLine = 32)
  val libraryError: PrintError? = connection.print(configuration) {       // (2)
    // MULTIPLE TEXT ALIGNMENTS PER LINE
    line("Famous bridges:")
    charset(Charset.CP865) // Can encode Ø, but not ů
    segmentedLine(
      LineSegment("Øresundsbroen", TextAlignment.LEFT),
      LineSegment("7845m", TextAlignment.RIGHT),
    )
    charset(Charset.CP852) // Can encode ů, but not Ø
    segmentedLine(
      LineSegment("Karlův most", TextAlignment.LEFT),
      LineSegment("515m", TextAlignment.RIGHT),
    )
    
    // STANDARD TEXT STYLING, CAN BE SCOPED USING
    // with-STYLE BUILDERS
    withTextSize(width = 2, height = 3) {
      line("Me big!")
    }
    line("Me small again!")
    
    bold(true)
    line("Normal and bald. Wait.. I wanted BOLD!")
    bold(false)

    // BARCODES - SUPPORTS A NUMBER OF 1D and 2D CODES
    val qrCode: Either<QRCodeError, QRCodeSpec> = 
        BarcodeSpec.QRCodeSpec("Hello from the QR Code!")
    qrCode
      .onRight(::barcode)
      .onLeft { err ->
        line("Could not construct QR code:")
        line(err.toString())
    }
  }
  
  return libraryError?.let(::mapToMyError)
}

fun mapToMyError(libraryError: PrintError): MyError {
    // ...
}

(1) Use the PrinterManager to open a Bluetooth connection
(2) Print using the CommandBuilder

What is ESC/POS?

ESC/POS is a set of printer commands developed by Epson for use in thermal printers. It has been adopted as a "standard" by virtually all thermal printer manufacturers across the globe.

ESC/POS is similar in this regard to the QR code - QR codes were invented by Denso Wave for use in their automotive manufacturing plants, but are now used just about everywhere.

Most thermal printers work with a subset of ESC/POS. The set of actually supported ESC/POS commands varies among OEMs and printer models.

Feature/Platform matrix

The following table summarizes connector implementation status on each platform.

• ✔️ - Implemented
• ❌ - Not yet implemented
• N/A - Technology not available on that platform

	Android	Java	iOS	macOS
Command builder	✔️	✔️	✔️	✔️
Bluetooth connector	✔️	❌	N/A	❌
USB connector	✔️	❌	N/A	❌
TCP connector	✔️	✔️	✔️	✔️