Encoding

Text encoding helpers and cross-platform font discovery.

This module is the bridge between Python str objects and the byte streams that ESC/POS commands expect, plus a tiny utility for locating a usable truetype font on the host system without relying on system-specific APIs.

Exports:

• CODEPAGE_TO_ENCODING: map from CodePage to the name of the matching Python codec.

• text_to_bytes(): encode a string with a graceful UTF-8 fallback.

• find_system_font(): return the first existing font path from FONT_CANDIDATES.

goojprt.encoding.CODEPAGE_TO_ENCODING: dict[int, str] = {CodePage.PC437: 'cp437', CodePage.PC850: 'cp850', CodePage.WPC1250: 'cp1250', CodePage.PC866: 'cp866', CodePage.PC852: 'cp852', CodePage.PC858: 'cp858'}

ESC/POS code page → Python codec name (as accepted by str.encode).

goojprt.encoding.find_system_font() → str | None

Return the path to the first available fallback system font.

Iterates FONT_CANDIDATES in order (macOS → Linux → Windows) and returns the first path that exists on disk.

Returns:

Absolute path to a usable .ttf/.ttc file, or None when no candidate exists (in which case callers should fall back to PIL.ImageFont.load_default()).

goojprt.encoding.text_to_bytes(text: str, encoding: str = 'gb2312') → bytes

Encode text into bytes suitable for the printer’s data stream.

The PT-210 firmware usually expects GB2312/GBK (Chinese) for native text output, but plain ASCII also works with "ascii" or "utf-8". When the chosen codec cannot represent a character (UnicodeEncodeError) or is unknown to Python (LookupError) the function falls back to UTF-8 with errors="replace" so callers never receive an exception.

Parameters:

• text – Input string.

• encoding – Name of the Python codec to try first, e.g. "gb2312", "cp1250" or "ascii".

Returns:

Raw bytes for inclusion in an ESC/POS payload.