"""
A module for parsing and generating `fontconfig patterns`_.
.. _fontconfig patterns:
https://www.freedesktop.org/software/fontconfig/fontconfig-user.html
"""
# This class logically belongs in `matplotlib.font_manager`, but placing it
# there would have created cyclical dependency problems, because it also needs
# to be available from `matplotlib.rcsetup` (for parsing matplotlibrc files).
from functools import lru_cache
import re
import numpy as np
from pyparsing import (Literal, ZeroOrMore, Optional, Regex, StringEnd,
ParseException, Suppress)
family_punc = r'\\\-:,'
family_unescape = re.compile(r'\\([%s])' % family_punc).sub
family_escape = re.compile(r'([%s])' % family_punc).sub
value_punc = r'\\=_:,'
value_unescape = re.compile(r'\\([%s])' % value_punc).sub
value_escape = re.compile(r'([%s])' % value_punc).sub
[docs]class FontconfigPatternParser:
"""
A simple pyparsing-based parser for `fontconfig patterns`_.
.. _fontconfig patterns:
https://www.freedesktop.org/software/fontconfig/fontconfig-user.html
"""
_constants = {
'thin': ('weight', 'light'),
'extralight': ('weight', 'light'),
'ultralight': ('weight', 'light'),
'light': ('weight', 'light'),
'book': ('weight', 'book'),
'regular': ('weight', 'regular'),
'normal': ('weight', 'normal'),
'medium': ('weight', 'medium'),
'demibold': ('weight', 'demibold'),
'semibold': ('weight', 'semibold'),
'bold': ('weight', 'bold'),
'extrabold': ('weight', 'extra bold'),
'black': ('weight', 'black'),
'heavy': ('weight', 'heavy'),
'roman': ('slant', 'normal'),
'italic': ('slant', 'italic'),
'oblique': ('slant', 'oblique'),
'ultracondensed': ('width', 'ultra-condensed'),
'extracondensed': ('width', 'extra-condensed'),
'condensed': ('width', 'condensed'),
'semicondensed': ('width', 'semi-condensed'),
'expanded': ('width', 'expanded'),
'extraexpanded': ('width', 'extra-expanded'),
'ultraexpanded': ('width', 'ultra-expanded')
}
def __init__(self):
family = Regex(
r'([^%s]|(\\[%s]))*' % (family_punc, family_punc)
).setParseAction(self._family)
size = Regex(
r"([0-9]+\.?[0-9]*|\.[0-9]+)"
).setParseAction(self._size)
name = Regex(
r'[a-z]+'
).setParseAction(self._name)
value = Regex(
r'([^%s]|(\\[%s]))*' % (value_punc, value_punc)
).setParseAction(self._value)
families = (
family
+ ZeroOrMore(
Literal(',')
+ family)
).setParseAction(self._families)
point_sizes = (
size
+ ZeroOrMore(
Literal(',')
+ size)
).setParseAction(self._point_sizes)
property = (
(name
+ Suppress(Literal('='))
+ value
+ ZeroOrMore(
Suppress(Literal(','))
+ value))
| name
).setParseAction(self._property)
pattern = (
Optional(
families)
+ Optional(
Literal('-')
+ point_sizes)
+ ZeroOrMore(
Literal(':')
+ property)
+ StringEnd()
)
self._parser = pattern
self.ParseException = ParseException
[docs] def parse(self, pattern):
"""
Parse the given fontconfig *pattern* and return a dictionary
of key/value pairs useful for initializing a
`.font_manager.FontProperties` object.
"""
props = self._properties = {}
try:
self._parser.parseString(pattern)
except self.ParseException as e:
raise ValueError(
"Could not parse font string: '%s'\n%s" % (pattern, e)) from e
self._properties = None
self._parser.resetCache()
return props
def _family(self, s, loc, tokens):
return [family_unescape(r'\1', str(tokens[0]))]
def _size(self, s, loc, tokens):
return [float(tokens[0])]
def _name(self, s, loc, tokens):
return [str(tokens[0])]
def _value(self, s, loc, tokens):
return [value_unescape(r'\1', str(tokens[0]))]
def _families(self, s, loc, tokens):
self._properties['family'] = [str(x) for x in tokens]
return []
def _point_sizes(self, s, loc, tokens):
self._properties['size'] = [str(x) for x in tokens]
return []
def _property(self, s, loc, tokens):
if len(tokens) == 1:
if tokens[0] in self._constants:
key, val = self._constants[tokens[0]]
self._properties.setdefault(key, []).append(val)
else:
key = tokens[0]
val = tokens[1:]
self._properties.setdefault(key, []).extend(val)
return []
# `parse_fontconfig_pattern` is a bottleneck during the tests because it is
# repeatedly called when the rcParams are reset (to validate the default
# fonts). In practice, the cache size doesn't grow beyond a few dozen entries
# during the test suite.
parse_fontconfig_pattern = lru_cache()(FontconfigPatternParser().parse)
def _escape_val(val, escape_func):
"""
Given a string value or a list of string values, run each value through
the input escape function to make the values into legal font config
strings. The result is returned as a string.
"""
if not np.iterable(val) or isinstance(val, str):
val = [val]
return ','.join(escape_func(r'\\\1', str(x)) for x in val
if x is not None)
[docs]def generate_fontconfig_pattern(d):
"""
Given a dictionary of key/value pairs, generates a fontconfig
pattern string.
"""
props = []
# Family is added first w/o a keyword
family = d.get_family()
if family is not None and family != []:
props.append(_escape_val(family, family_escape))
# The other keys are added as key=value
for key in ['style', 'variant', 'weight', 'stretch', 'file', 'size']:
val = getattr(d, 'get_' + key)()
# Don't use 'if not val' because 0 is a valid input.
if val is not None and val != []:
props.append(":%s=%s" % (key, _escape_val(val, value_escape)))
return ''.join(props)
