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Documentation Index

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The Tauri Plugin Thermal Printer acts as a translator between a developer-friendly TypeScript API and the raw ESC/POS binary commands that thermal printers understand. Understanding the architecture helps you reason about platform differences, debug unexpected output, and make the most of the plugin’s capabilities.

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Architecture Diagram

The following diagram shows the full data path from your frontend code to the physical printer across both the desktop and Android paths: 
Frontend (JavaScript/TypeScript)
    ↓ (IPC Commands)
Tauri Core (Rust)  ←— ESC/POS generation (shared across all platforms)
    ↓ (Platform-specific implementations)
    ├── Desktop: Operating System (Linux/macOS/Windows)
    │       ↓ (Raw binary data)
    │   Thermal Printer (ESC/POS protocol)
    │
    └── Android: Kotlin Plugin
            ↓ (Bluetooth SPP / RFCOMM)
        Thermal Printer (ESC/POS protocol)
ESC/POS generation lives entirely in Rust and is shared across every platform — the same ProcessPrint pipeline runs whether you are targeting Windows, Linux, macOS, or Android. Only the final delivery mechanism changes.

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Core Components

The plugin is built from four tightly-coupled layers.

Data Models

Defined in src/models/. Contains PrintJobRequest (the main print descriptor), the PrintSections enum (all printable content types), and GlobalStyles (font, alignment, size, etc.). These types are shared between Rust and TypeScript via Tauri’s serialisation layer.

Tauri Commands

Defined in src/commands.rs. Exposes three #[command] functions to the frontend — list_thermal_printers, print_thermal_printer, and test_thermal_printer — that delegate immediately to the platform implementation.

Print Processing

Defined in src/process/process_print.rs. The ProcessPrint struct iterates over every section in a PrintJobRequest and converts each one into ESC/POS byte sequences, applying the current GlobalStyles context and running text through the configured TextEncoder.

OS Integration

Defined in src/desktop_printers/ (desktop) and android/ (Kotlin). Receives the finished Vec<u8> from ProcessPrint and hands it to the operating system or Bluetooth stack for transmission.

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Desktop Flow

1

Frontend sends PrintJobRequest

Your TypeScript code calls print_thermal_printer(job). The plugin invokes plugin:thermal-printer|print_thermal_printer over Tauri’s IPC bridge, serialising the PrintJobRequest struct as JSON.
2

Tauri receives and routes the command

The Rust #[command] handler in src/commands.rs deserialises the request and calls app.thermal_printer().print_thermal_printer(print_job_request) on the desktop implementation.
3

ProcessPrint generates ESC/POS bytes

ProcessPrint::generate_document initialises the printer (\x1B\x40), writes the code-page select command (\x1B\x74\x{n}), then processes every section in order — converting titles, text, tables, QR codes, barcodes, and images into their corresponding byte sequences.
4

Operating System sends binary data to the printer

On Linux/macOS the finished Vec<u8> is piped to lp -d {printer_name} -o raw via CUPS. On Windows it is sent directly using the WinAPI sequence OpenPrinterW → StartDocPrinterW → StartPagePrinter → WritePrinter → teardown.
5

Thermal printer interprets ESC/POS commands and prints

The printer’s firmware reads the byte stream, executes each ESC/POS command in sequence (set alignment, enable bold, print text, render QR, cut paper…), and produces the physical output.

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Android Flow

1

Frontend sends PrintJobRequest

Same as desktop — print_thermal_printer(job) is called in TypeScript. The printer field must be the Bluetooth MAC address of the target device (e.g. "AA:BB:CC:DD:EE:FF").
2

Rust generates ESC/POS binary data

The mobile implementation in src/mobile.rs runs the identical ProcessPrint::generate_document pipeline, producing the same Vec<u8> byte stream as the desktop path.
3

Kotlin plugin receives binary data and MAC address

The Rust layer calls run_mobile_plugin("print_raw_data", PrintRawRequest { identifier, data }). The Kotlin Thermal_Printer_Plugin receives the identifier string and raw byte array.
4

Bluetooth SPP connection is established

BluetoothPrinter.printRawData retrieves the remote device by MAC address, cancels any in-progress discovery, then opens an RFCOMM socket using the standard SPP UUID (00001101-0000-1000-8000-00805F9B34FB).
5

Thermal printer interprets ESC/POS and prints

The byte stream is written to the socket’s output stream. The printer firmware executes each command identically to the desktop path.

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ESC/POS Protocol

ESC/POS (Escape Sequence for Point of Sale) is the de-facto binary command language for thermal printers, originally developed by Epson in the 1980s. Every formatting action — alignment, bold text, QR codes, paper cuts — is encoded as a short sequence of bytes beginning with the ESC control character (\x1B). The plugin generates all ESC/POS commands internally so you never write raw bytes yourself. Here are a few examples of what the ProcessPrint layer emits:
Hex sequenceEffect
\x1B\x40Initialise printer (sent at the start of every job)
\x1B\x74\x06Select code page 6 (Windows-1252) via ESC t n
\x1B\x61\x00Left-align text
\x1B\x61\x01Centre-align text
\x1B\x61\x02Right-align text
\x1B\x45\x01Enable bold
\x1B\x45\x00Disable bold
\x1B\x64\x03Feed 3 lines (ESC d n)
\x1D\x56\x41\x00Partial paper cut
Each printer model may interpret certain ESC/POS commands slightly differently. If a feature (such as a specific cut mode or font) does not produce the expected result, consult your printer’s programming manual for the correct command values.

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Platform Implementations

PlatformPrinter DiscoveryPrint DeliveryConnection Types
Linuxlpstat -p + lpstat -v (CUPS)lp -d {name} -o rawUSB, Network, Parallel
macOSlpstat -p + lpstat -v (CUPS)lp -d {name} -o rawUSB, Network
WindowsEnumPrintersW (WinAPI)OpenPrinterW + WritePrinterUSB, Network, Serial
AndroidPrinterDiscovery (USB + Bluetooth)BluetoothPrinter via RFCOMM SPPBluetooth, USB (discovery only)
iOS❌ Not implemented❌ Not implemented—
On desktop, the printer field in PrintJobRequest must match the printer name exactly as it appears in the system — use list_thermal_printers() to retrieve the correct name for your platform.

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