Function encodeTextForFont

src/document/forms/appearance-utils.ts:705–734

(text: string, font: FormFont)

 * Encode text for use in a PDF content stream with the given font.
 */
export function encodeTextForFont(text: string, font: FormFont): PdfString {
  if (isEmbeddedFont(font)) {
    font.markUsedInForm();

    if (!font.canEncode(text)) {
      const unencodable = font.getUnencodableCharacters(text);
      const firstBad = unencodable[0];

      throw new Error(
        `Font cannot encode character '${firstBad}' (U+${firstBad.codePointAt(0)?.toString(16).toUpperCase().padStart(4, "0")})`,
      );
    }

    const gids = font.encodeTextToGids(text);
    const bytes = new Uint8Array(gids.length * 2);

    for (let i = 0; i < gids.length; i++) {
      bytes[i * 2] = (gids[i] >> 8) & 0xff;
      bytes[i * 2 + 1] = gids[i] & 0xff;
    }

    return PdfString.fromBytes(bytes);
  }

  if (isExistingFont(font) && font.isCIDFont) {
    return PdfString.fromBytes(font.encodeTextToBytes(text));
  }

  return PdfString.fromString(text);
}

/**
 * Generate color operators for text rendering.