Merge pull request #451 from googlei18n/map-width-using-os2

Use the OS/2 width class to map the wdth axis

Lib/glyphsLib/builder/axes.py

@@ -311,42 +311,45 @@ def get_user_loc(self, master_or_instance):
         """Get the user location of a Glyphs master or instance.
         Masters in Glyphs can have a user location in the "Axis Location"
         custom parameter.
+
         The user location is what the user sees on the slider in his
         variable-font-enabled UI. For weight it is a value between 0 and 1000,
         400 being Regular and 700 Bold.
-        For width it's the same as the design location, a percentage of
-        extension with respect to the normal width.
+
+        For width it's a percentage of extension with respect to the normal
+        width, 100 being normal, 200 Ultra-expanded = twice as wide.
+        It may or may not match the design location.
         """
         user_loc = self.default_user_loc
 
         if self.tag != "wght":
             # The user location is by default the same as the design location.
             user_loc = self.get_design_loc(master_or_instance)
 
-        # For the width, the user location should be the same as the design
-        # location (regardless of the OS/2 width class and prescribed mapping
-        # to a percentage), as enforced by DesignspaceTest::test_twoAxes
-        # in tests/builder/interpolation_test.py
-        if self.tag != "wdth":
-            if self.user_loc_key is not None and hasattr(
-                master_or_instance, self.user_loc_key
-            ):
-                # Instances have special ways to specify a user location.
-                # Only weight and with have a custom user location via a key.
-                # The `user_loc_key` gives a "location code" = Glyphs UI string
-                user_loc_str = getattr(master_or_instance, self.user_loc_key)
-                new_user_loc = user_loc_string_to_value(self.tag, user_loc_str)
-                if new_user_loc is not None:
-                    user_loc = new_user_loc
-
-            # The custom param takes over the key if it exists
-            # e.g. for weight:
-            #       key = "weight" -> "Bold" -> 700
-            # but param = "weightClass" -> 600       => 600 wins
-            if self.user_loc_param is not None:
-                class_ = master_or_instance.customParameters[self.user_loc_param]
-                if class_ is not None:
-                    user_loc = class_to_value(self.tag, class_)
+        # Try to guess the user location by looking at the OS/2 weightClass
+        # and widthClass. If a weightClass is found, it translates directly
+        # to a user location in 0..1000. If a widthClass is found, it
+        # translate to a percentage of extension according to the spec, see
+        # the mapping named `WIDTH_CLASS_TO_VALUE` at the top.
+        if self.user_loc_key is not None and hasattr(
+            master_or_instance, self.user_loc_key
+        ):
+            # Instances have special ways to specify a user location.
+            # Only weight and with have a custom user location via a key.
+            # The `user_loc_key` gives a "location code" = Glyphs UI string
+            user_loc_str = getattr(master_or_instance, self.user_loc_key)
+            new_user_loc = user_loc_string_to_value(self.tag, user_loc_str)
+            if new_user_loc is not None:
+                user_loc = new_user_loc
+
+        # The custom param takes over the key if it exists
+        # e.g. for weight:
+        #       key = "weight" -> "Bold" -> 700
+        # but param = "weightClass" -> 600       => 600 wins
+        if self.user_loc_param is not None:
+            class_ = master_or_instance.customParameters[self.user_loc_param]
+            if class_ is not None:
+                user_loc = class_to_value(self.tag, class_)
 
         # Masters have a customParameter that specifies a user location
         # along custom axes. If this is present it takes precedence over

tests/data/DesignspaceTestTwoAxes.designspace

@@ -7,7 +7,10 @@
             <map input="600" output="128" />
             <map input="900" output="190" />
         </axis>
-        <axis default="100" maximum="100" minimum="70" name="Width" tag="wdth" />
+        <axis default="100" maximum="100" minimum="62.500000" name="Width" tag="wdth">
+            <map input="62.500000" output="70" />
+            <map input="100" output="100" />
+        </axis>
     </axes>
     <sources>
         <source familyname="DesignspaceTest TwoAxes" filename="DesignspaceTestTwoAxes-Regular.ufo" name="DesignspaceTest TwoAxes Regular" stylename="Regular">