Instantiator support for non-default layer sources

Lib/fontmake/instantiator.py

@@ -147,6 +147,8 @@
  "woffMinorVersion",
 }
 
+DEFAULT_LAYER_NAME = "foreground"
+
 
 # Custom exception for this module
 class InstantiatorError(Exception):
@@ -224,21 +226,33 @@ def from_designspace(
  # because the math behind varLib and MutatorMath uses the default font as the
  # point of reference for all data.
  default_font = designspace.default.font
+ non_default_layer_name = designspace.default.layerName
+ non_default_layer_flag = (
+ non_default_layer_name is not None
+ and non_default_layer_name != DEFAULT_LAYER_NAME
+ )
+
  glyph_names: Set[str] = set(default_font.keys())
 
- for source in designspace.sources:
- other_names = set(source.font.keys())
- diff_names = other_names - glyph_names
- if diff_names:
- logger.warning(
- "The source %s (%s) contains glyphs that are missing from the "
- "default source, which will be ignored: %s. If this is unintended, "
- "check that these glyphs have the exact same name as the "
- "corresponding glyphs in the default source.",
- source.name,
- source.filename,
- ", ".join(sorted(diff_names)),
- )
+ if non_default_layer_flag:
+ if non_default_layer_name in default_font.layers:
+ layer = default_font.layers[non_default_layer_name]
+ glyph_names = layer.keys()
+ logger.info(f"Building from layer {layer.name}")
+ else:
+ for source in designspace.sources:
+ other_names = set(source.font.keys())
+ diff_names = other_names - glyph_names
+ if diff_names:
+ logger.warning(
+ "The source %s (%s) contains glyphs that are missing from the "
+ "default source, which will be ignored: %s. If this is unintended, "
+ "check that these glyphs have the exact same name as the "
+ "corresponding glyphs in the default source.",
+ source.name,
+ source.filename,
+ ", ".join(sorted(diff_names)),
+ )
 
  # Construct Variators
  axis_bounds: AxisBounds = {} # Design space!
@@ -517,9 +531,11 @@ def collect_info_masters(
 ) -> List[Tuple[Location, FontMathObject]]:
  """Return master Info objects wrapped by MathInfo."""
  locations_and_masters = []
+
  for source in designspace.sources:
- if source.layerName is not None:
- continue # No font info in source layers.
+ if source.layerName is not None and source.layerName != DEFAULT_LAYER_NAME:
+ if source != designspace.default:
+ continue # No font info in source layers.
 
  normalized_location = varLib.models.normalizeLocation(
  source.location, axis_bounds
@@ -541,9 +557,11 @@ def collect_kerning_masters(
  groups = designspace.default.font.groups
 
  locations_and_masters = []
+
  for source in designspace.sources:
- if source.layerName is not None:
- continue # No kerning in source layers.
+ if source.layerName is not None and source.layerName != DEFAULT_LAYER_NAME:
+ if source != designspace.default:
+ continue # No kerning in source layers.
 
  # If a source has groups, they should match the default's.
  if source.font.groups and source.font.groups != groups:

tests/data/MutatorSans/MutatorSans-non-default-layer.designspace

@@ -0,0 +1,29 @@
+<?xml version='1.0' encoding='UTF-8'?>
+<designspace format="4.0">
+ <axes>
+ <axis tag="wdth" name="width" minimum="0" maximum="1000" default="0"/>
+ <axis tag="wght" name="weight" minimum="0" maximum="1000" default="0"/>
+ </axes>
+ <sources>
+ <source filename="MutatorSansLightCondensed.ufo" name="master.MutatorMathTest.LightCondensed.0" familyname="MutatorMathTest" stylename="LightCondensed" layer="support">
+ <lib copy="1"/>
+ <groups copy="1"/>
+ <features copy="1"/>
+ <info copy="1"/>
+ <location>
+ <dimension name="width" xvalue="0"/>
+ <dimension name="weight" xvalue="0"/>
+ </location>
+ </source>
+ </sources>
+ <instances>
+ <instance familyname="MutatorMathTest" stylename="LightCondensed" filename="instances/MutatorMathTest-LightCondensed.ufo" postscriptfontname="MutatorMathTest-LightCondensed">
+ <location>
+ <dimension name="width" xvalue="0"/>
+ <dimension name="weight" xvalue="0"/>
+ </location>
+ <kerning/>
+ <info/>
+ </instance>
+ </instances>
+</designspace>

tests/test_instantiator.py

@@ -420,6 +420,18 @@ def test_interpolation_masters_as_instances(data_dir):
  assert instance_font["l"].width == 280
 
 
+def test_non_default_layer(data_dir, caplog):
+ designspace = designspaceLib.DesignSpaceDocument.fromfile(
+ data_dir / "MutatorSans" / "MutatorSans-non-default-layer.designspace"
+ )
+ designspace.loadSourceFonts(ufoLib2.Font.open)
+ generator = fontmake.instantiator.Instantiator.from_designspace(
+ designspace, round_geometry=True
+ )
+ instance_font = generator.generate_instance(designspace.instances[0])
+ assert {g.name for g in instance_font} == {"A", "S", "W"}
+
+
 def test_instance_attributes(data_dir):
  designspace = designspaceLib.DesignSpaceDocument.fromfile(
  data_dir / "DesignspaceTest" / "DesignspaceTest-instance-attrs.designspace"