Merge pull request #1195 from googlefonts/decompose-components

Implement decompose-components action

src/fontra/core/instancer.py

@@ -15,13 +15,15 @@
 from .classes import (
     Component,
     GlobalAxis,
+    GlobalDiscreteAxis,
     Layer,
     LocalAxis,
     Source,
     StaticGlyph,
     VariableGlyph,
 )
 from .path import InterpolationError, PackedPath, joinPaths
+from .protocols import ReadableFontBackend
 
 
 class LocationCoordinateSystem(Enum):
@@ -31,11 +33,11 @@ class LocationCoordinateSystem(Enum):
 
 @dataclass
 class FontInstancer:
-    backend: Any
+    backend: ReadableFontBackend
 
     def __post_init__(self) -> None:
         self.glyphInstancers: dict[str, GlyphInstancer] = {}
-        self.globalAxes: list[GlobalAxis] | None = None
+        self.globalAxes: list[GlobalAxis | GlobalDiscreteAxis] | None = None
 
     async def getGlyphInstancer(
         self, glyphName: str, addToCache: bool = False
@@ -45,6 +47,7 @@ async def getGlyphInstancer(
             if self.globalAxes is None:
                 self.globalAxes = await self.backend.getGlobalAxes()
             glyph = await self.backend.getGlyph(glyphName)
+            assert glyph is not None, glyphName
             glyph = await self._ensureComponentLocationCompatibility(glyph)
             glyphInstancer = GlyphInstancer(glyph, self)
             if addToCache:
@@ -194,7 +197,7 @@ def instantiate(
         )
 
     @cached_property
-    def globalAxes(self) -> list[GlobalAxis]:
+    def globalAxes(self) -> list[GlobalAxis | GlobalDiscreteAxis]:
         assert self.fontInstancer.globalAxes is not None
         return self.fontInstancer.globalAxes
 
@@ -204,6 +207,8 @@ def componentTypes(self) -> list[bool]:
         variable (has a non-empty location) and False if it is a "classic"
         component.
         """
+        # TODO: also return True for components that vary their non-translate
+        # transformation fields
         numComponents = len(self.activeLayerGlyphs[0].components)
         return [
             any(

src/fontra/workflow/actions.py

@@ -14,6 +14,8 @@
 from ..backends import getFileSystemBackend, newFileSystemBackend
 from ..backends.copy import copyFont
 from ..core.classes import GlobalAxis, GlobalDiscreteAxis, VariableGlyph
+from ..core.instancer import FontInstancer, LocationCoordinateSystem
+from ..core.path import PackedPathPointPen
 from ..core.protocols import ReadableFontBackend
 
 # All actions should use this logger, regardless of where they are defined
@@ -347,7 +349,7 @@ def _renameAxis(axis, axes):
 @dataclass(kw_only=True)
 class DropInactiveSourcesAction(BaseFilterAction):
     async def processGlyph(self, glyph: VariableGlyph) -> VariableGlyph:
-        usedSources = [source for source in glyph.sources if not source.inactive]
+        usedSources = getActiveSources(glyph.sources)
         usedLayerNames = {source.layerName for source in usedSources}
         usedLayers = {
             layerName: layer
@@ -471,3 +473,47 @@ async def processGlobalAxes(self, axes) -> list[GlobalAxis | GlobalDiscreteAxis]
 
     async def processGlyph(self, glyph: VariableGlyph) -> VariableGlyph:
         return _remapSourceLocations(glyph, self._axisValueMapFunctions)
+
+
+@registerActionClass("decompose-components")
+@dataclass(kw_only=True)
+class DecomposeComponentsAction(BaseFilterAction):
+    onlyVariableComponents: bool = False
+
+    @cached_property
+    def fontInstancer(self):
+        return FontInstancer(self.validatedInput)
+
+    async def getGlyph(self, glyphName: str) -> VariableGlyph:
+        instancer = await self.fontInstancer.getGlyphInstancer(glyphName)
+        glyph = instancer.glyph
+
+        if not instancer.componentTypes or (
+            self.onlyVariableComponents and not any(instancer.componentTypes)
+        ):
+            return glyph
+
+        newLayers = {}
+        for source in instancer.activeSources:
+            pen = PackedPathPointPen()
+            await instancer.drawPoints(
+                pen,
+                source.location,
+                coordSystem=LocationCoordinateSystem.SOURCE,
+                flattenComponents=True,
+                flattenVarComponents=True,
+            )
+
+            layer = glyph.layers[source.layerName]
+            newLayers[source.layerName] = replace(
+                layer,
+                glyph=replace(layer.glyph, path=pen.getPath(), components=[]),
+            )
+
+        glyph = replace(glyph, layers=newLayers)
+
+        return glyph
+
+
+def getActiveSources(sources):
+    return [source for source in sources if not source.inactive]

test-py/data/workflow/input-components.fontra/font-data.json

@@ -0,0 +1,43 @@
+{
+"unitsPerEm": 1000,
+"customData": {},
+"axes": [
+{
+"name": "width",
+"label": "width",
+"tag": "wdth",
+"minValue": 0,
+"defaultValue": 0,
+"maxValue": 1000
+},
+{
+"name": "weight",
+"label": "weight",
+"tag": "wght",
+"minValue": 100,
+"defaultValue": 100,
+"maxValue": 900,
+"mapping": [
+[
+100,
+150
+],
+[
+900,
+850
+]
+]
+},
+{
+"name": "italic",
+"label": "italic",
+"tag": "ital",
+"values": [
+0,
+1
+],
+"defaultValue": 0
+}
+],
+"sources": []
+}

test-py/data/workflow/input-components.fontra/glyph-info.csv

@@ -0,0 +1,5 @@
+glyph name;code points
+A;U+0041,U+0061
+Adieresis;U+00C4,U+00E4
+dieresis;U+00A8
+dot;U+27D1