Copy font info attributes from default font to instance selectively

Lib/fontmake/instantiator.py

@@ -40,7 +40,6 @@
 import fontMath
 import fontTools.designspaceLib as designspaceLib
 import fontTools.misc.fixedTools
-import fontTools.ufoLib as ufoLib
 import fontTools.varLib as varLib
 import ufoLib2
 
@@ -76,6 +75,78 @@
     200: 9,
 }
 
+# Font info fields that are not interpolated and should be copied from the
+# default font to the instance.
+#
+# fontMath at the time of this writing handles the following attributes:
+# https://github.com/robotools/fontMath/blob/0.5.0/Lib/fontMath/mathInfo.py#L360-L422
+#
+# From the attributes that are left, we skip instance-specific ones on purpose:
+# - guidelines
+# - postscriptFontName
+# - styleMapFamilyName
+# - styleMapStyleName
+# - styleName
+# - openTypeNameCompatibleFullName
+# - openTypeNamePreferredFamilyName
+# - openTypeNamePreferredSubfamilyName
+# - openTypeNameUniqueID
+# - openTypeNameWWSFamilyName
+# - openTypeNameWWSSubfamilyName
+# - openTypeOS2Panose
+# - postscriptFullName
+# - postscriptUniqueID
+# - woffMetadataUniqueID
+#
+# Some, we skip because they are deprecated:
+# - macintoshFONDFamilyID
+# - macintoshFONDName
+# - year
+#
+# This means we implicitly require the `stylename` attribute in the Designspace
+# `<instance>` element.
+UFO_INFO_ATTRIBUTES_TO_COPY_TO_INSTANCES = {
+    "copyright",
+    "familyName",
+    "note",
+    "openTypeGaspRangeRecords",
+    "openTypeHeadCreated",
+    "openTypeHeadFlags",
+    "openTypeNameDescription",
+    "openTypeNameDesigner",
+    "openTypeNameDesignerURL",
+    "openTypeNameLicense",
+    "openTypeNameLicenseURL",
+    "openTypeNameManufacturer",
+    "openTypeNameManufacturerURL",
+    "openTypeNameRecords",
+    "openTypeNameSampleText",
+    "openTypeNameVersion",
+    "openTypeOS2CodePageRanges",
+    "openTypeOS2FamilyClass",
+    "openTypeOS2Selection",
+    "openTypeOS2Type",
+    "openTypeOS2UnicodeRanges",
+    "openTypeOS2VendorID",
+    "postscriptDefaultCharacter",
+    "postscriptForceBold",
+    "postscriptIsFixedPitch",
+    "postscriptWindowsCharacterSet",
+    "trademark",
+    "versionMajor",
+    "versionMinor",
+    "woffMajorVersion",
+    "woffMetadataCopyright",
+    "woffMetadataCredits",
+    "woffMetadataDescription",
+    "woffMetadataExtensions",
+    "woffMetadataLicense",
+    "woffMetadataLicensee",
+    "woffMetadataTrademark",
+    "woffMetadataVendor",
+    "woffMinorVersion",
+}
+
 
 # Custom exception for this module
 class InstantiatorError(Exception):
@@ -292,9 +363,7 @@ def _generate_instance_info(
         info_instance.extractInfo(font.info)
 
         # Copy non-interpolating metadata from the default font.
-        for attribute in ufoLib.fontInfoAttributesVersion3:
-            if hasattr(info_instance, attribute):
-                continue  # Skip interpolated info attributes.
+        for attribute in UFO_INFO_ATTRIBUTES_TO_COPY_TO_INSTANCES:
             if hasattr(self.copy_info, attribute):
                 setattr(
                     font.info,
@@ -305,7 +374,15 @@ def _generate_instance_info(
         # TODO: multilingual names to replace possibly existing name records.
         if instance.familyName:
             font.info.familyName = instance.familyName
-        if instance.styleName:
+        if instance.styleName is None:
+            logger.warning(
+                "The given instance or instance at location %s is missing the "
+                "stylename attribute, which is required. Copying over the styleName "
+                "from the default font, which is probably wrong.",
+                location,
+            )
+            font.info.styleName = self.copy_info.styleName
+        else:
             font.info.styleName = instance.styleName
         if instance.postScriptFontName:
             font.info.postscriptFontName = instance.postScriptFontName

tests/test_instantiator.py

@@ -1,3 +1,5 @@
+import logging
+
 import fontTools.designspaceLib as designspaceLib
 import pytest
 import ufoLib2
@@ -299,15 +301,18 @@ def test_instance_attributes(data_dir):
     assert instance_font.info.styleMapStyleName == "xxx"
 
 
-def test_instance_no_attributes(data_dir):
+def test_instance_no_attributes(data_dir, caplog):
     designspace = designspaceLib.DesignSpaceDocument.fromfile(
         data_dir / "DesignspaceTest" / "DesignspaceTest-bare.designspace"
     )
     generator = fontmake.instantiator.Instantiator.from_designspace(
         designspace, round_geometry=True
     )
 
-    instance_font = generator.generate_instance(designspace.instances[0])
+    with caplog.at_level(logging.WARNING):
+        instance_font = generator.generate_instance(designspace.instances[0])
+    assert "missing the stylename attribute" in caplog.text
+
     assert instance_font.info.familyName == "MyFont"
     assert instance_font.info.styleName == "Light"
     assert instance_font.info.postscriptFontName is None
@@ -459,10 +464,8 @@ def test_data_independence(data_dir):
 
     assert generator.copy_info.openTypeOS2Panose == [2, 11, 5, 4, 2, 2, 2, 2, 2, 4]
     generator.copy_info.openTypeOS2Panose.append(1000)
-    assert instance_font1.info.openTypeOS2Panose == [2, 11, 5, 4, 2, 2, 2, 2, 2, 4]
-    assert instance_font2.info.openTypeOS2Panose == [2, 11, 5, 4, 2, 2, 2, 2, 2, 4]
-    instance_font1.info.openTypeOS2Panose.append(2000)
-    assert instance_font2.info.openTypeOS2Panose == [2, 11, 5, 4, 2, 2, 2, 2, 2, 4]
+    assert instance_font1.info.openTypeOS2Panose is None
+    assert instance_font2.info.openTypeOS2Panose is None
 
     # copy_feature_text not tested because it is a(n immutable) string
 
@@ -472,3 +475,38 @@ def test_data_independence(data_dir):
     assert not instance_font2.lib["public.skipExportGlyphs"]
     instance_font1.lib["public.skipExportGlyphs"].append("z")
     assert not instance_font2.lib["public.skipExportGlyphs"]
+
+
+def test_skipped_fontinfo_attributes():
+    """Test that we consider all available font info attributes for copying."""
+    import fontTools.ufoLib
+    import fontMath.mathInfo
+
+    SKIPPED_ATTRS = {
+        "guidelines",
+        "macintoshFONDFamilyID",
+        "macintoshFONDName",
+        "openTypeNameCompatibleFullName",
+        "openTypeNamePreferredFamilyName",
+        "openTypeNamePreferredSubfamilyName",
+        "openTypeNameUniqueID",
+        "openTypeNameWWSFamilyName",
+        "openTypeNameWWSSubfamilyName",
+        "openTypeOS2Panose",
+        "postscriptFontName",
+        "postscriptFullName",
+        "postscriptUniqueID",
+        "styleMapFamilyName",
+        "styleMapStyleName",
+        "styleName",
+        "woffMetadataUniqueID",
+        "year",
+    }
+
+    assert (
+        fontTools.ufoLib.fontInfoAttributesVersion3
+        - set(fontMath.mathInfo._infoAttrs.keys())
+        - {"postscriptWeightName"}  # Handled in fontMath specially.
+        - fontmake.instantiator.UFO_INFO_ATTRIBUTES_TO_COPY_TO_INSTANCES
+        == SKIPPED_ATTRS
+    )