Smart components

Lib/glyphsLib/builder/components.py

@@ -20,6 +20,7 @@
 from glyphsLib.classes import GSBackgroundLayer
 from glyphsLib.types import Transform
 
+from .smart_components import to_ufo_smart_component
 from .constants import GLYPHS_PREFIX, COMPONENT_INFO_KEY, SMART_COMPONENT_AXES_LIB_KEY
 
 logger = logging.getLogger(__name__)
@@ -61,7 +62,14 @@ def to_ufo_components(self, ufo_glyph, layer):
 
     pen = ufo_glyph.getPointPen()
     for index, component in enumerate(layer.components):
-        pen.addComponent(component.name, component.transform)
+        # XXX We may also want to test here if we're compiling a font (and decompose
+        # if so) or changing the representation format (in which case we leave it
+        # as a component and save the smart component values).
+        # See https://github.com/googlefonts/glyphsLib/pull/822
+        if component.smartComponentValues and component.component.smartComponentAxes:
+            to_ufo_smart_component(self, layer, component, pen)
+        else:
+            pen.addComponent(component.name, component.transform)
 
         if not (component.anchor or component.alignment):
             continue

Lib/glyphsLib/builder/smart_components.py

@@ -0,0 +1,138 @@
+"""Convert Glyphs smart components.
+
+Smart components (https://glyphsapp.com/learn/smart-components) are a
+feature within Glyphs whereby a component can essentially define its
+own private designspace - each master of a component glyph can
+define its own axes and masters. When the component is used, instead
+of simply scaling or transforming the component, the designer can
+*interpolate* the component by specifying the location in the private
+designspace.
+
+For example, a font might define a ``_part.serif`` glyph component with
+"left width" and "right width" axes, and for each master in the font,
+define layers for the ``_part.serif`` at some default left width and
+right width, one with an extended left width, and one with an extended
+right width, and use the "smart components settings" to assign locations
+to these additional layers. (Unlike a full interpolation model, the
+locations of smart component layers can only be at the axis extremes.)
+
+We handle smart components by decomposing them and then applying a standard
+OpenType interpolation model to adjust the node positions.
+"""
+
+from enum import IntEnum
+
+# We're going to use pickle/unpickle to copy the node objects because
+# it's considerably faster than copy.deepcopy
+import pickle
+
+from fontTools.varLib.models import VariationModel, normalizeValue
+from fontTools.ttLib.tables._g_l_y_f import GlyphCoordinates
+
+from glyphsLib.classes import GSLayer
+
+
+# smartComponentPoleMapping returns 1 for bottom of axis and 2 for top.
+class Pole(IntEnum):
+    MIN = 1
+    MAX = 2
+
+
+# This normalizes the location of a "master" (additional smart component
+# layer). Because these are defined to be at the "poles", this is always
+# 0.0, 1.0 or -1.0. But working out which it should be is slightly tricky:
+# the axes don't define their own defaults, but the location of the
+# default layer of the glyph tells you whether the default value of the
+# axis is at the top or the bottom.
+def normalized_location(layer, base_layer):
+    loc = {}
+    for axis_name, current_value in layer.smartComponentPoleMapping.items():
+        base_value = base_layer.smartComponentPoleMapping[axis_name]
+        if current_value == base_value:
+            loc[axis_name] = 0.0
+        elif base_value == Pole.MIN and current_value == Pole.MAX:
+            loc[axis_name] = 1.0
+        elif base_value == Pole.MAX and current_value == Pole.MIN:
+            loc[axis_name] = -1.0
+        else:
+            raise ValueError(
+                f"Strange axis mapping for axis {axis_name} in smart layer {base_layer}"
+            )
+    return loc
+
+
+def variation_model(glyph, smart_layers):
+    master_locations = [normalized_location(l, smart_layers[0]) for l in smart_layers]
+    axis_order = [ax.name for ax in glyph.smartComponentAxes]
+    return VariationModel(master_locations, axisOrder=axis_order, extrapolate=True)
+
+
+# Two slightly horrible functions for turning a GSLayer into a
+# GlyphCoordinates object and back again.
+def get_coordinates(layer):
+    gc = GlyphCoordinates([])
+    for path in layer.paths:
+        gc.extend(
+            GlyphCoordinates([(pt.position.x, pt.position.y) for pt in path.nodes])
+        )
+    return gc
+
+
+def set_coordinates(layer, coords):
+    counter = 0
+    for path in layer.paths:
+        for node in path.nodes:
+            node.position.x, node.position.y = coords[counter]
+            counter += 1
+
+
+def to_ufo_smart_component(self, layer, component, pen):
+    # Find the GSGlyph that is being used as a component by this GSComponent
+    root = component.component
+
+    masters = [l for l in root.layers if l.smartComponentPoleMapping]
+    if layer.associatedMasterId:
+        # Each master in the font can have its own set of smart component
+        # "master layers", so we need to filter by those smart components
+        # which are in the same font master as the current one
+        masters = [
+            l for l in masters if l.associatedMasterId == layer.associatedMasterId
+        ]
+    if not masters:
+        raise ValueError(
+            "Could not find any masters for the smart component %s used in %s"
+            % (root.name, layer.name)
+        )
+    model = variation_model(root, masters)
+
+    # Determine the normalized location of the interpolant within the
+    # mini-designspace, remembering that we have to work out where the
+    # default value is by looking at the first "master"
+    axes_tuples = {}
+    for ax in root.smartComponentAxes:
+        if masters[0].smartComponentPoleMapping[ax.name] == Pole.MIN:
+            defaultValue = ax.bottomValue
+        else:
+            defaultValue = ax.topValue
+        axes_tuples[ax.name] = (ax.bottomValue, defaultValue, ax.topValue)
+    normalized_location = {
+        name: normalizeValue(value, axes_tuples[name], extrapolate=True)
+        for name, value in component.smartComponentValues.items()
+    }
+    coordinates = [get_coordinates(l) for l in masters]
+    new_coords = model.interpolateFromMasters(normalized_location, coordinates)
+
+    # Decompose by creating a new layer, copying its shapes and applying
+    # the new coordinates
+    new_layer = GSLayer()
+    new_layer._shapes = pickle.loads(pickle.dumps(masters[0]._shapes))
+    set_coordinates(new_layer, new_coords)
+
+    # Don't forget that the GSComponent might also be transformed, so
+    # we need to apply that transformation to the new layer as well
+    if component.transform:
+        for p in new_layer.paths:
+            p.applyTransform(component.transform)
+
+    # And we are done
+    new_layer.drawPoints(pen)

requirements-dev.in

@@ -6,6 +6,7 @@ pytest>=2.8
 pytest-randomly
 pytest-xdist
 xmldiff>=2.2
+fonttools[ufo,unicode] >= 4.38.0
 # extras
 ufoNormalizer>=0.3.2
 defcon>=0.6.0

requirements-dev.txt

@@ -1,5 +1,5 @@
 #
-# This file is autogenerated by pip-compile with python 3.7
+# This file is autogenerated by pip-compile with python 3.9
 # To update, run:
 #
 #    pip-compile requirements-dev.in
@@ -32,8 +32,9 @@ flake8==4.0.1
     #   flake8-bugbear
 flake8-bugbear==22.3.23
     # via -r requirements-dev.in
-fonttools[ufo,unicode]==4.34.4
+fonttools[ufo,unicode]==4.38.0
     # via
+    #   -r requirements-dev.in
     #   booleanoperations
     #   cffsubr
     #   cu2qu
@@ -42,12 +43,7 @@ fonttools[ufo,unicode]==4.34.4
 fs==2.4.15
     # via fonttools
 importlib-metadata==4.2.0
-    # via
-    #   click
-    #   flake8
-    #   pluggy
-    #   pytest
-    #   pytest-randomly
+    # via pytest-randomly
 iniconfig==1.1.1
     # via pytest
 lxml==4.8.0
@@ -100,12 +96,8 @@ tomli==2.0.1
     # via
     #   black
     #   pytest
-typed-ast==1.5.3
-    # via black
 typing-extensions==4.2.0
-    # via
-    #   black
-    #   importlib-metadata
+    # via black
 ufo2ft==2.27.0
     # via -r requirements-dev.in
 ufonormalizer==0.6.1

requirements.txt

@@ -1,5 +1,5 @@
 #
-# This file is autogenerated by pip-compile with python 3.7
+# This file is autogenerated by pip-compile with python 3.9
 # To update, run:
 #
 #    pip-compile setup.cfg
@@ -8,7 +8,7 @@ appdirs==1.4.4
     # via fs
 attrs==21.4.0
     # via ufolib2
-fonttools[ufo,unicode]==4.34.4
+fonttools[ufo,unicode]==4.38.0
     # via
     #   glyphsLib (setup.cfg)
     #   ufolib2
@@ -20,8 +20,6 @@ pytz==2022.1
     # via fs
 six==1.16.0
     # via fs
-typing-extensions==4.2.0
-    # via ufolib2
 ufolib2==0.13.1
     # via glyphsLib (setup.cfg)
 unicodedata2==14.0.0

setup.cfg

@@ -32,7 +32,7 @@ setup_requires =
     setuptools_scm
 install_requires =
     ufoLib2 >= 0.6.2
-    fonttools[ufo,unicode] >= 4.33.0
+    fonttools[ufo,unicode] >= 4.38.0
     openstep-plist >= 0.3.0
 
 [options.extras_require]