Export variable instances as DSv5 variable-fonts

Lib/glyphsLib/builder/custom_params.py

@@ -1062,7 +1062,7 @@ def to_glyphs(self, glyphs, ufo):
 register(RenameGlyphsParamHandler())
 
 
-def to_ufo_custom_params(self, ufo, glyphs_object):
+def to_ufo_custom_params(self, ufo, glyphs_object, set_default_params=True):
     # glyphs_module=None because we shouldn't instanciate any Glyphs classes
     glyphs_proxy = GlyphsObjectProxy(glyphs_object, glyphs_module=None)
     ufo_proxy = UFOProxy(ufo)
@@ -1076,7 +1076,8 @@ def to_ufo_custom_params(self, ufo, glyphs_object):
         name = _normalize_custom_param_name(param.name)
         ufo.lib[CUSTOM_PARAM_PREFIX + glyphs_proxy.sub_key + name] = param.value
 
-    _set_default_params(ufo)
+    if set_default_params:
+        _set_default_params(ufo)
 
 
 def to_glyphs_custom_params(self, ufo, glyphs_object):

Lib/glyphsLib/builder/instances.py

@@ -56,13 +56,41 @@
 def to_designspace_instances(self):
     """Write instance data from self.font to self.designspace."""
     for instance in self.font.instances:
-        if instance.type == InstanceType.VARIABLE:
-            continue
         if self.minimize_glyphs_diffs or (
             is_instance_active(instance)
             and _is_instance_included_in_family(self, instance)
         ):
-            _to_designspace_instance(self, instance)
+            if instance.type == InstanceType.VARIABLE:
+                _to_designspace_varfont(self, instance)
+            else:
+                _to_designspace_instance(self, instance)
+
+
+def _to_designspace_varfont(self, instance):
+    from fontTools.designspaceLib import RangeAxisSubsetDescriptor
+    from fontTools.ufoLib import fontInfoAttributesVersion3
+
+    ds = self.designspace
+    ufo_varfont = self.designspace.addVariableFontDescriptor(
+        name=instance.name,
+        filename=instance.customParameters["fileName"],
+        axisSubsets=[RangeAxisSubsetDescriptor(name=axis.name) for axis in ds.axes],
+    )
+
+    # to_ufo_custom_params() wants a UFO, create a dummy one
+    ufo = self.ufo_module.Font()
+    to_ufo_custom_params(self, ufo, instance, set_default_params=False)
+
+    info = {}
+    for attr in fontInfoAttributesVersion3:
+        if (value := getattr(ufo.info, attr, None)) is not None:
+            info[attr] = value
+
+    if info:
+        ufo_varfont.lib["public.fontInfo"] = info
+
+    for key in ufo.lib:
+        ufo_varfont.lib[key] = ufo.lib[key]
 
 
 def _to_designspace_instance(self, instance):

Lib/glyphsLib/classes.py

@@ -3372,6 +3372,8 @@ def fullName(self, value):
 
     # v2 compatibility
     def _get_axis_value(self, index):
+        if self.type == InstanceType.VARIABLE:
+            return None
         if index < len(self.axes):
             return self.axes[index]
         if index < len(self._axis_defaults):

tests/builder/axes_test.py

@@ -667,10 +667,8 @@ def test_axis_with_no_mapping_does_not_error_in_roundtrip_with_2_axes(ufo_module
 
 
 def test_variable_instance(ufo_module):
-    """Glyphs 3 introduced a so-called "variable" instance which is a
-    pseudo-instance that holds various VF settings.
-    This messed with the instance_mapping creation as it would overwrite the designLoc
-    of a default instance of an axis back to 0.
+    """Glyphs 3 introduced a "variable" instance which is a special instance
+    that holds various VF settings. We export it to Design Space variable-font.
     """
     source_path = os.path.join("tests", "data", "VariableInstance.glyphs")
     font = GSFont(source_path)
@@ -681,6 +679,21 @@ def test_variable_instance(ufo_module):
     assert doc.axes[0].default == 400
     assert len(doc.instances) == 27  # The VF setting should not be in the DS
 
+    assert len(doc.variableFonts) == 1
+
+    varfont = doc.variableFonts[0]
+    assert len(varfont.axisSubsets) == len(doc.axes)
+    assert "public.fontInfo" in varfont.lib
+
+    info = varfont.lib["public.fontInfo"]
+    assert len(info.get("openTypeNameRecords")) == 1
+    assert info["openTypeNameRecords"][0].string == "Variable"
+    assert info["openTypeNameRecords"][0].nameID == 1
+    assert info["openTypeNameRecords"][0].platformID == 1
+    assert info["openTypeNameRecords"][0].languageID == 0
+    assert info["openTypeNameRecords"][0].encodingID == 0
+    assert info.get("openTypeNamePreferredFamilyName") == "Cairo Variable"
+
 
 def test_virtual_masters_extend_min_max_for_unmapped_axis(ufo_module, datadir):
     # https://github.com/googlefonts/glyphsLib/issues/859

tests/classes_test.py

@@ -40,6 +40,7 @@
     GSPath,
     GSSmartComponentAxis,
     GSBackgroundImage,
+    InstanceType,
     segment,
     LayerComponentsProxy,
     LayerGuideLinesProxy,
@@ -187,6 +188,20 @@ def test_font_master_proxy(self):
         self.assertEqual(master.font, font)
 
 
+class GSInstanceTest(unittest.TestCase):
+    def test_variable_instance(self):
+        instance = GSInstance()
+        instance.name = "Variable"
+        instance.type = InstanceType.VARIABLE
+
+        assert instance.weightValue is None
+        assert instance.widthValue is None
+        assert instance.customValue is None
+        assert instance.customValue1 is None
+        assert instance.customValue2 is None
+        assert instance.customValue3 is None
+
+
 class GSObjectsTestCase(unittest.TestCase):
     def setUp(self):
         self.font = GSFont(TESTFILE_PATH)

tests/data/VariableInstance.glyphs

@@ -1,5 +1,5 @@
 {
-.appVersion = "3139";
+.appVersion = "3234";
 .formatVersion = 3;
 axes = (
 {
@@ -777,14 +777,24 @@ name = "ExtraBlack Slant Left";
 weightClass = 1000;
 },
 {
-axesValues = (
-0,
-0
+customParameters = (
+{
+name = "Name Table Entry";
+value = "1 1 0 0; Variable";
+}
+);
+name = Variable;
+properties = (
+{
+key = preferredFamilyNames;
+values = (
+{
+language = dflt;
+value = "Cairo Variable";
+}
+);
+}
 );
-instanceInterpolations = {
-"459CA063-FA7D-4205-A795-7B6CE244EAAB" = 1;
-};
-name = Regular;
 type = variable;
 }
 );
@@ -832,34 +842,34 @@ key = designerURL;
 value = "https://gaber.design";
 },
 {
-key = manufacturers;
+key = licenses;
 values = (
 {
 language = dflt;
-value = "Kief Type Foundry, Accademia di Belle Arti di Urbino";
+value = "This Font Software is licensed under the SIL Open Font License, Version 1.1. This license is available with a FAQ at: http://scripts.sil.org/OFL";
 }
 );
 },
 {
-key = manufacturerURL;
-value = "https://gaber.design";
+key = licenseURL;
+value = "http://scripts.sil.org/OFL";
 },
 {
-key = licenses;
+key = manufacturers;
 values = (
 {
 language = dflt;
-value = "This Font Software is licensed under the SIL Open Font License, Version 1.1. This license is available with a FAQ at: http://scripts.sil.org/OFL";
+value = "Kief Type Foundry, Accademia di Belle Arti di Urbino";
 }
 );
 },
 {
-key = licenseURL;
-value = "http://scripts.sil.org/OFL";
+key = manufacturerURL;
+value = "https://gaber.design";
 },
 {
 key = vendorID;
-value = "1KTF";
+value = 1KTF;
 }
 );
 settings = {