From e88e47f8ffb783c2e9b17b8cbe8939f87dbfb8d7 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Wed, 20 Dec 2023 13:00:15 -0700
Subject: [PATCH] [VARC] Take a stab at instancing

---
 Lib/fontTools/varLib/instancer/__init__.py | 69 +++++-----------------
 Tests/varLib/instancer/instancer_test.py   | 18 ++++--
 2 files changed, 27 insertions(+), 60 deletions(-)

diff --git a/Lib/fontTools/varLib/instancer/__init__.py b/Lib/fontTools/varLib/instancer/__init__.py
index c692433ed..92e9c4737 100644
--- a/Lib/fontTools/varLib/instancer/__init__.py
+++ b/Lib/fontTools/varLib/instancer/__init__.py
@@ -475,70 +475,31 @@ def instantiateVARC(varfont, axisLimits):
 
     varc = varfont["VARC"].table
     fvarAxes = varfont["fvar"].axes if "fvar" in varfont else []
-    if varc.VarCompositeGlyphs is not None:
-        for glyph in varc.VarCompositeGlyphs.VarCompositeGlyph:
-            for comp in glyph.components:
-                if comp.axisIndicesIndex is None:
-                    continue
 
-                axisIndices = varc.AxisIndicesList.Item[comp.axisIndicesIndex]
-                axisValues = comp.axisValues
+    location = axisLimits.pinnedLocation()
+    axisMap = [i for i, axis in enumerate(fvarAxes) if axis.axisTag not in location]
+    reverseAxisMap = {i: j for j, i in enumerate(axisMap)}
 
-                comp.axisValues = []
-                for axisIndex, axisValue in zip(axisIndices, axisValues):
-                    tag = fvarAxes[axisIndex].axisTag
-                    if tag in axisLimits:
-                        axisValue = axisLimits[tag].renormalizeValue(
-                            axisValue, extrapolate=False
-                        )
-                    comp.axisValues.append(axisValue)
-
-                """
-                newLocation = {}
-                for tag, loc in component.location.items():
-                    if tag not in axisLimits:
-                        newLocation[tag] = loc
-                        continue
-                    if comp.flags & VarComponentFlags.AXIS_VALUES_HAVE_VARIATION:
-                        raise NotImplementedError(
-                            "Instancing accross VarComponent axes with variation is not supported."
-                        )
-                    limits = axisLimits[tag]
-                    loc = limits.renormalizeValue(loc, extrapolate=False)
-                    newLocation[tag] = loc
-                component.location = newLocation
-                """
+    if varc.AxisIndicesList:
+        axisIndicesList = varc.AxisIndicesList.Item
+        for i, axisIndices in enumerate(axisIndicesList):
+            if any(fvarAxes[j].axisTag in axisLimits for j in axisIndices):
+                raise NotImplementedError(
+                    "Instancing across VarComponent axes is not supported."
+                )
+            axisIndicesList[i] = [reverseAxisMap[j] for j in axisIndices]
 
     store = varc.MultiVarStore
     if store:
-        store.prune_regions()  # Needed?
-
-        fvar = varfont["fvar"]
-        location = axisLimits.pinnedLocation()
         for region in store.SparseVarRegionList.Region:
             newRegionAxis = []
             for regionRecord in region.SparseVarRegionAxis:
-                tag = fvar.axes[regionRecord.AxisIndex].axisTag
-                if tag in location:
-                    continue
+                tag = fvarAxes[regionRecord.AxisIndex].axisTag
                 if tag in axisLimits:
-                    limits = axisLimits[tag]
-                    triple = (
-                        regionRecord.StartCoord,
-                        regionRecord.PeakCoord,
-                        regionRecord.EndCoord,
+                    raise NotImplementedError(
+                        "Instancing across VarComponent axes is not supported."
                     )
-                    triple = tuple(
-                        limits.renormalizeValue(v, extrapolate=False) for v in triple
-                    )
-                    (
-                        regionRecord.StartCoord,
-                        regionRecord.PeakCoord,
-                        regionRecord.EndCoord,
-                    ) = triple
-                newRegionAxis.append(regionRecord)
-            region.VarRegionAxis = newRegionAxis
-            region.VarRegionAxisCount = len(newRegionAxis)
+                regionRecord.AxisIndex = reverseAxisMap[regionRecord.AxisIndex]
 
 
 def instantiateTupleVariationStore(
diff --git a/Tests/varLib/instancer/instancer_test.py b/Tests/varLib/instancer/instancer_test.py
index 809d6bd35..b9a45058b 100644
--- a/Tests/varLib/instancer/instancer_test.py
+++ b/Tests/varLib/instancer/instancer_test.py
@@ -1699,22 +1699,28 @@ class InstantiateVariableFontTest(object):
 
     def test_varComposite(self):
         input_path = os.path.join(
-            TESTDATA, "..", "..", "..", "ttLib", "data", "varc-ac00-ac01.ttf"
+            TESTDATA, "..", "..", "..", "ttLib", "data", "varc-6868.ttf"
         )
         varfont = ttLib.TTFont(input_path)
 
         location = {"wght": 600}
 
-        instance = instancer.instantiateVariableFont(
-            varfont,
-            location,
-        )
+        # We currently do not allow this either; although in theory
+        # it should be possible.
+        with pytest.raises(
+            NotImplementedError,
+            match="is not supported.",
+        ):
+            instance = instancer.instantiateVariableFont(
+                varfont,
+                location,
+            )
 
         location = {"0000": 0.5}
 
         with pytest.raises(
             NotImplementedError,
-            match="Instancing accross VarComponent axes with variation is not supported.",
+            match="is not supported.",
         ):
             instance = instancer.instantiateVariableFont(
                 varfont,