Function _parse_char_metrics

lib/matplotlib/_afm.py:201–252

Parse the given filehandle for character metrics information. It is assumed that the file cursor is on the line behind 'StartCharMetrics'. Returns ------- ascii_d : dict A mapping "ASCII num of the character" to `.CharMetrics`. name_d : dict A mapping "ch

(fh: BinaryIO)

def _parse_char_metrics(fh: BinaryIO) -> tuple[dict[CharacterCodeType, CharMetrics],
                                               dict[str, CharMetrics]]:
    """
    Parse the given filehandle for character metrics information.

    It is assumed that the file cursor is on the line behind 'StartCharMetrics'.

    Returns
    -------
    ascii_d : dict
         A mapping "ASCII num of the character" to `.CharMetrics`.
    name_d : dict
         A mapping "character name" to `.CharMetrics`.

    Notes
    -----
    This function is incomplete per the standard, but thus far parses
    all the sample afm files tried.
    """
    required_keys = {'C', 'WX', 'N', 'B'}

    ascii_d: dict[CharacterCodeType, CharMetrics] = {}
    name_d: dict[str, CharMetrics] = {}
    for bline in fh:
        # We are defensively letting values be utf8. The spec requires
        # ascii, but there are non-compliant fonts in circulation
        line = _to_str(bline.rstrip())
        if line.startswith('EndCharMetrics'):
            return ascii_d, name_d
        # Split the metric line into a dictionary, keyed by metric identifiers
        vals = dict(s.strip().split(' ', 1) for s in line.split(';') if s)
        # There may be other metrics present, but only these are needed
        if not required_keys.issubset(vals):
            raise RuntimeError('Bad char metrics line: %s' % line)
        num = _to_int(vals['C'])
        wx = _to_float(vals['WX'])
        name = vals['N']
        bbox = tuple(map(int, _to_list_of_floats(vals['B'])))
        if len(bbox) != 4:
            raise RuntimeError(f'Bad parse: bbox has {len(bbox)} elements, should be 4')
        metrics = CharMetrics(wx, name, bbox)
        # Workaround: If the character name is 'Euro', give it the
        # corresponding character code, according to WinAnsiEncoding (see PDF
        # Reference).
        if name == 'Euro':
            num = 128
        elif name == 'minus':
            num = ord("\N{MINUS SIGN}")  # 0x2212
        if num != -1:
            ascii_d[num] = metrics
        name_d[name] = metrics
    raise RuntimeError('Bad parse')


def _parse_kern_pairs(fh: BinaryIO) -> dict[tuple[str, str], float]: