Simplify generate_fontconfig_pattern.

anntzer · anntzer · commit 22cfa695924b · 2022-10-29T14:22:56.000+02:00
- Switch _family_escape, _value_escape to be more similar to
  _family_escape, _value_escape.
- generate_fontconfig_pattern doesn't need to go through the generic
  escape_val, but instead rely on the fact that prop.get_family() always
  returns a list whereas the other getters always return a scalar value,
  and directly do the escaping and joining as needed.
diff --git a/lib/matplotlib/_fontconfig_pattern.py b/lib/matplotlib/_fontconfig_pattern.py
@@ -21,16 +21,18 @@
 
 family_punc = r'\\\-:,'
 _family_unescape = partial(re.compile(r'\\(?=[%s])' % family_punc).sub, '')
-family_escape = re.compile(r'([%s])' % family_punc).sub
+_family_escape = partial(re.compile(r'(?=[%s])' % family_punc).sub, r'\\')
 
 value_punc = r'\\=_:,'
 _value_unescape = partial(re.compile(r'\\(?=[%s])' % value_punc).sub, '')
-value_escape = re.compile(r'([%s])' % value_punc).sub
+_value_escape = partial(re.compile(r'(?=[%s])' % value_punc).sub, r'\\')
 
 # Remove after module deprecation elapses (3.8); then remove underscores
-# from _family_unescape and _value_unescape.
+# from _{family,value}_{un,}escape.
 family_unescape = re.compile(r'\\([%s])' % family_punc).sub
 value_unescape = re.compile(r'\\([%s])' % value_punc).sub
+family_escape = re.compile(r'([%s])' % family_punc).sub
+value_escape = re.compile(r'([%s])' % value_punc).sub
 
 
 class FontconfigPatternParser:
@@ -127,36 +129,12 @@ def parse(self, pattern):
 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)
-
-
 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)
+    """Convert a `.FontProperties` to a fontconfig pattern string."""
+    kvs = [(k, getattr(d, f"get_{k}")())
+           for k in ["style", "variant", "weight", "stretch", "file", "size"]]
+    # Families is given first without a leading keyword.  Other entries (which
+    # are necessarily scalar) are given as key=value, skipping Nones.
+    return (",".join(_family_escape(f) for f in d.get_family())
+            + "".join(f":{k}={_value_escape(str(v))}"
+                      for k, v in kvs if v is not None))
