Merge pull request #1652 from anthrotype/varlib-set-default-OS2-classes

varLib: add set_default_weight_width_slant

Lib/fontTools/varLib/__init__.py

@@ -857,6 +857,45 @@ def load_designspace(designspace):
 	)
 
 
+# https://docs.microsoft.com/en-us/typography/opentype/spec/os2#uswidthclass
+WDTH_VALUE_TO_OS2_WIDTH_CLASS = {
+	50: 1,
+	62.5: 2,
+	75: 3,
+	87.5: 4,
+	100: 5,
+	112.5: 6,
+	125: 7,
+	150: 8,
+	200: 9,
+}
+
+
+def set_default_weight_width_slant(font, location):
+	if "OS/2" in font:
+		if "wght" in location:
+			weight_class = otRound(max(1, min(location["wght"], 1000)))
+			if font["OS/2"].usWeightClass != weight_class:
+				log.info("Setting OS/2.usWidthClass = %s", weight_class)
+				font["OS/2"].usWeightClass = weight_class
+
+		if "wdth" in location:
+			# map 'wdth' axis (50..200) to OS/2.usWidthClass (1..9), rounding to closest
+			widthValue = min(max(location["wdth"], 50), 200)
+			widthClass = otRound(
+				models.piecewiseLinearMap(widthValue, WDTH_VALUE_TO_OS2_WIDTH_CLASS)
+			)
+			if font["OS/2"].usWidthClass != widthClass:
+				log.info("Setting OS/2.usWidthClass = %s", widthClass)
+				font["OS/2"].usWidthClass = widthClass
+
+	if "slnt" in location and "post" in font:
+		italicAngle = max(-90, min(location["slnt"], 90))
+		if font["post"].italicAngle != italicAngle:
+			log.info("Setting post.italicAngle = %s", italicAngle)
+			font["post"].italicAngle = italicAngle
+
+
 def build(designspace, master_finder=lambda s:s, exclude=[], optimize=True):
 	"""
 	Build variation font from a designspace file.
@@ -930,6 +969,10 @@ def build(designspace, master_finder=lambda s:s, exclude=[], optimize=True):
 				post.extraNames = []
 				post.mapping = {}
 
+	set_default_weight_width_slant(
+		vf, location={axis.axisTag: axis.defaultValue for axis in vf["fvar"].axes}
+	)
+
 	for tag in exclude:
 		if tag in vf:
 			del vf[tag]

Tests/varLib/data/test_results/BuildMain.ttx

@@ -55,7 +55,7 @@
          will be recalculated by the compiler -->
     <version value="4"/>
     <xAvgCharWidth value="506"/>
-    <usWeightClass value="400"/>
+    <usWeightClass value="368"/>
     <usWidthClass value="5"/>
     <fsType value="00000000 00000100"/>
     <ySubscriptXSize value="650"/>

Tests/varLib/data/test_results/SparseMasters.ttx

@@ -55,7 +55,7 @@
          will be recalculated by the compiler -->
     <version value="4"/>
     <xAvgCharWidth value="580"/>
-    <usWeightClass value="400"/>
+    <usWeightClass value="350"/>
     <usWidthClass value="5"/>
     <fsType value="00000000 00000100"/>
     <ySubscriptXSize value="650"/>

Tests/varLib/varLib_test.py

@@ -4,6 +4,7 @@ from fontTools.ttLib import TTFont, newTable
 from fontTools.varLib import build
 from fontTools.varLib.mutator import instantiateVariableFont
 from fontTools.varLib import main as varLib_main, load_masters
+from fontTools.varLib import set_default_weight_width_slant
 from fontTools.designspaceLib import (
     DesignSpaceDocumentError, DesignSpaceDocument, SourceDescriptor,
 )
@@ -661,5 +662,81 @@ def _extract_flat_kerning(font, pairpos_table):
     return extracted_kerning
 
 
+@pytest.fixture
+def ttFont():
+    f = TTFont()
+    f["OS/2"] = newTable("OS/2")
+    f["OS/2"].usWeightClass = 400
+    f["OS/2"].usWidthClass = 100
+    f["post"] = newTable("post")
+    f["post"].italicAngle = 0
+    return f
+
+
+class SetDefaultWeightWidthSlantTest(object):
+    @pytest.mark.parametrize(
+        "location, expected",
+        [
+            ({"wght": 0}, 1),
+            ({"wght": 1}, 1),
+            ({"wght": 100}, 100),
+            ({"wght": 1000}, 1000),
+            ({"wght": 1001}, 1000),
+        ],
+    )
+    def test_wght(self, ttFont, location, expected):
+        set_default_weight_width_slant(ttFont, location)
+
+        assert ttFont["OS/2"].usWeightClass == expected
+
+    @pytest.mark.parametrize(
+        "location, expected",
+        [
+            ({"wdth": 0}, 1),
+            ({"wdth": 56}, 1),
+            ({"wdth": 57}, 2),
+            ({"wdth": 62.5}, 2),
+            ({"wdth": 75}, 3),
+            ({"wdth": 87.5}, 4),
+            ({"wdth": 100}, 5),
+            ({"wdth": 112.5}, 6),
+            ({"wdth": 125}, 7),
+            ({"wdth": 150}, 8),
+            ({"wdth": 200}, 9),
+            ({"wdth": 201}, 9),
+            ({"wdth": 1000}, 9),
+        ],
+    )
+    def test_wdth(self, ttFont, location, expected):
+        set_default_weight_width_slant(ttFont, location)
+
+        assert ttFont["OS/2"].usWidthClass == expected
+
+    @pytest.mark.parametrize(
+        "location, expected",
+        [
+            ({"slnt": -91}, -90),
+            ({"slnt": -90}, -90),
+            ({"slnt": 0}, 0),
+            ({"slnt": 11.5}, 11.5),
+            ({"slnt": 90}, 90),
+            ({"slnt": 91}, 90),
+        ],
+    )
+    def test_slnt(self, ttFont, location, expected):
+        set_default_weight_width_slant(ttFont, location)
+
+        assert ttFont["post"].italicAngle == expected
+
+    def test_all(self, ttFont):
+        set_default_weight_width_slant(
+            ttFont, {"wght": 500, "wdth": 150, "slnt": -12.0}
+        )
+
+        assert ttFont["OS/2"].usWeightClass == 500
+        assert ttFont["OS/2"].usWidthClass == 8
+        assert ttFont["post"].italicAngle == -12.0
+
+
 if __name__ == "__main__":
     sys.exit(unittest.main())