Source code for matplotlib.fontconfig_pattern

A module for parsing and generating `fontconfig patterns`_.

.. _fontconfig patterns:

# 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: """ _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)