Merge pull request matplotlib#7931 from kshramt/font_weight

FIX: consider 'weight-as-string' more highly than 'weight-as-number'

 - Internally store the text weight as a string
 - if compare weight as strings before comparing as number, apply bias against numeric but not string match

Slight concern that our font selection method is getting farther away from 'standard', but it fixes the handling of fonts that do not correctly report their weights or use non-standard weights and does not obviously break anything els.

Author: tacaswell

lib/matplotlib/font_manager.py

@@ -346,6 +346,7 @@ def findSystemFonts(fontpaths=None, fontext='ttf'):
     return [fname for fname in fontfiles if os.path.exists(fname)]
 
 
+@cbook.deprecated("2.1")
 def weight_as_number(weight):
     """
     Return the weight property as a numeric value.  String values
@@ -435,17 +436,12 @@ def ttfFontProperty(font):
     else:
         variant = 'normal'
 
-    #  Weights are: 100, 200, 300, 400 (normal: default), 500 (medium),
-    #    600 (semibold, demibold), 700 (bold), 800 (heavy), 900 (black)
-    #    lighter and bolder are also allowed.
-
     weight = next((w for w in weight_dict if sfnt4.find(w) >= 0), None)
     if not weight:
         if font.style_flags & ft2font.BOLD:
             weight = 700
         else:
             weight = 400
-    weight = weight_as_number(weight)
 
     #  Stretch can be absolute and relative
     #  Absolute stretches are: ultra-condensed, extra-condensed, condensed,
@@ -511,11 +507,7 @@ def afmFontProperty(fontpath, font):
     else:
         variant = 'normal'
 
-    #  Weights are: 100, 200, 300, 400 (normal: default), 500 (medium),
-    #    600 (semibold, demibold), 700 (bold), 800 (heavy), 900 (black)
-    #    lighter and bolder are also allowed.
-
-    weight = weight_as_number(font.get_weight().lower())
+    weight = font.get_weight().lower()
 
     #  Stretch can be absolute and relative
     #  Absolute stretches are: ultra-condensed, extra-condensed, condensed,
@@ -855,7 +847,6 @@ def set_weight(self, weight):
         except ValueError:
             if weight not in weight_dict:
                 raise ValueError("weight is invalid")
-            weight = weight_dict[weight]
         self._weight = weight
 
     def set_stretch(self, stretch):
@@ -1204,10 +1195,19 @@ def score_weight(self, weight1, weight2):
         """
         Returns a match score between *weight1* and *weight2*.
 
-        The result is the absolute value of the difference between the
+        The result is 0.0 if both weight1 and weight 2 are given as strings
+        and have the same value.
+
+        Otherwise, the result is the absolute value of the difference between the
         CSS numeric values of *weight1* and *weight2*, normalized
-        between 0.0 and 1.0.
+        between 0.05 and 1.0.
         """
+
+        # exact match of the weight names (e.g. weight1 == weight2 == "regular")
+        if (isinstance(weight1, six.string_types) and
+                isinstance(weight2, six.string_types) and
+                weight1 == weight2):
+            return 0.0
         try:
             weightval1 = int(weight1)
         except ValueError:
@@ -1216,7 +1216,7 @@ def score_weight(self, weight1, weight2):
             weightval2 = int(weight2)
         except ValueError:
             weightval2 = weight_dict.get(weight2, 500)
-        return abs(weightval1 - weightval2) / 1000.0
+        return 0.95*(abs(weightval1 - weightval2) / 1000.0) + 0.05
 
     def score_size(self, size1, size2):
         """

lib/matplotlib/tests/test_font_manager.py

@@ -38,6 +38,17 @@ def test_font_priority():
     assert cmap[8729] == 30
 
 
+def test_score_weight():
+    assert 0 == fontManager.score_weight("regular", "regular")
+    assert 0 == fontManager.score_weight("bold", "bold")
+    assert (0 < fontManager.score_weight(400, 400) <
+            fontManager.score_weight("normal", "bold"))
+    assert (0 < fontManager.score_weight("normal", "regular") <
+            fontManager.score_weight("normal", "bold"))
+    assert (fontManager.score_weight("normal", "regular") ==
+            fontManager.score_weight(400, 400))
+
+
 def test_json_serialization():
     # on windows, we can't open a file twice, so save the name and unlink
     # manually...