From 9cc3689fb16504921075666861dccee5a9dcefaa Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Tue, 19 Dec 2023 16:07:27 -0700
Subject: [PATCH] [VARC] Towards drawing new design

---
 Lib/fontTools/ttLib/tables/otTables.py | 24 +++++++++++-
 Lib/fontTools/ttLib/ttGlyphSet.py      | 53 ++++++++++++++++----------
 2 files changed, 56 insertions(+), 21 deletions(-)

diff --git a/Lib/fontTools/ttLib/tables/otTables.py b/Lib/fontTools/ttLib/tables/otTables.py
index 5dd52cd2c..4e073bac7 100644
--- a/Lib/fontTools/ttLib/tables/otTables.py
+++ b/Lib/fontTools/ttLib/tables/otTables.py
@@ -143,6 +143,8 @@ class VarTransform:
         else:
             flags = self.flags
 
+        data.append(struct.pack(">H", flags))
+
         if flags & VarTransformFlags.HAVE_VARIATIONS:
             data.append(struct.pack(">L", self.varIndex))
 
@@ -158,7 +160,7 @@ class VarTransform:
             value = getattr(self.transform, attr_name)
             data.append(write_transform_component(value, mapping_values))
 
-        return struct.pack(">H", flags) + bytesjoin(data)
+        return bytesjoin(data)
 
     def toXML(self, writer, ttFont, attrs, name):
         if self.varIndex != NO_VARIATION_INDEX:
@@ -184,6 +186,26 @@ class VarTransform:
             v = str2fl(safeEval(attrs[attr_name]), mapping.fractionalBits)
             setattr(self.transform, attr_name, v)
 
+    def applyDeltas(deltas):
+        i = 0
+
+        def read_transform_component_delta(data, values):
+            nonlocal i
+            if self.flags & values.flag:
+                v = fi2fl(data[i], values.fractionalBits) * values.scale
+                i += 1
+                return v
+            else:
+                return 0
+
+        for attr_name, mapping_values in VAR_TRANSFORM_MAPPING.items():
+            value = read_transform_component_delta(data, mapping_values)
+            setattr(
+                self.transform, attr_name, getattr(self.transform, attr_name) + value
+            )
+
+        assert i == len(deltas)
+
     def __eq__(self, other):
         if type(self) != type(other):
             return NotImplemented
diff --git a/Lib/fontTools/ttLib/ttGlyphSet.py b/Lib/fontTools/ttLib/ttGlyphSet.py
index d848c8670..d5107236b 100644
--- a/Lib/fontTools/ttLib/ttGlyphSet.py
+++ b/Lib/fontTools/ttLib/ttGlyphSet.py
@@ -5,9 +5,10 @@ from collections.abc import Mapping
 from contextlib import contextmanager
 from copy import copy
 from types import SimpleNamespace
+from fontTools.misc.vector import Vector
 from fontTools.misc.fixedTools import otRound
 from fontTools.misc.loggingTools import deprecateFunction
-from fontTools.misc.transform import Transform
+from fontTools.misc.transform import Transform, DecomposedTransform
 from fontTools.pens.transformPen import TransformPen, TransformPointPen
 from fontTools.pens.recordingPen import (
     DecomposingRecordingPen,
@@ -288,42 +289,54 @@ class _TTGlyphVARC(_TTGlyph):
         glyphSet = self.glyphSet
         varc = glyphSet.varcTable
         idx = varc.Coverage.glyphs.index(self.name)
-        glyph = varc.VarCompositeGlyphs.glyphs[idx]
+        glyph = varc.VarCompositeGlyphs.VarCompositeGlyph[idx]
 
         from fontTools.varLib.multiVarStore import MultiVarStoreInstancer
 
+        fvarAxes = glyphSet.font["fvar"].axes
         instancer = MultiVarStoreInstancer(
-            varc.MultiVarStore, self.glyphSet.font["fvar"].axes, self.glyphSet.location
+            varc.MultiVarStore, fvarAxes, self.glyphSet.location
         )
-        instancer.setLocation(self.glyphSet.location)
 
         for comp in glyph.components:
-            comp = copy(comp)  # Shallow copy
-            locationValues, transformValues = comp.getComponentValues()
+            location = {}
+            assert (comp.AxisIndicesIndex is None) == (comp.AxisValuesIndex is None)
+            if comp.AxisIndicesIndex is not None:
+                axisIndices = varc.AxisIndicesList.Item[comp.AxisIndicesIndex]
+                axisValues = Vector(varc.AxisValuesList.Item[comp.AxisValuesIndex])
+                # Apply variations
+                varIdx = NO_VARIATION_INDEX
+                if comp.AxisValuesIndex < varc.AxisValuesList.VarIndicesCount:
+                    varIdx = varc.AxisValuesList.VarIndices[comp.AxisValuesIndex]
+                if varIdx != NO_VARIATION_INDEX:
+                    axisValues = (
+                        axisValues + instancer[varIdx]
+                    )  # TODO Implement __iadd__ for Vector
+                location = {
+                    fvarAxes[i].axisTag: v for i, v in zip(axisIndices, axisValues)
+                }
 
-            if comp.locationVarIndex != NO_VARIATION_INDEX:
-                assert len(locationValues)
-                locationDeltas = instancer[comp.locationVarIndex]
-                locationValues = list(locationValues + locationDeltas)
-            if comp.transformVarIndex != NO_VARIATION_INDEX:
-                assert len(transformValues)
-                transformDeltas = instancer[comp.transformVarIndex]
-                transformValues = list(transformValues + transformDeltas)
-
-            comp.setComponentValues(locationValues, transformValues)
+            transform = DecomposedTransform()
+            if comp.TransformIndex is not None:
+                varTransform = varc.TransformList.VarTransform[comp.TransformIndex]
+                varIdx = varTransform.varIndex
+                if varIdx != NO_VARIATION_INDEX:
+                    deltas = instancer[varIdx]
+                    varTransform.applyDeltas(deltas)
+                transform = varTransform.transform
 
             with self.glyphSet.glyphSet.pushLocation(
-                comp.location, comp.flags & VarComponentFlags.RESET_UNSPECIFIED_AXES
+                location, comp.flags & VarComponentFlags.RESET_UNSPECIFIED_AXES
             ):
                 with self.glyphSet.pushLocation(
-                    comp.location, comp.flags & VarComponentFlags.RESET_UNSPECIFIED_AXES
+                    location, comp.flags & VarComponentFlags.RESET_UNSPECIFIED_AXES
                 ):
                     try:
                         pen.addVarComponent(
-                            comp.glyphName, comp.transform, self.glyphSet.rawLocation
+                            comp.glyphName, transform, self.glyphSet.rawLocation
                         )
                     except AttributeError:
-                        t = comp.transform.toTransform()
+                        t = transform.toTransform()
                         compGlyphSet = (
                             self.glyphSet
                             if comp.glyphName != self.name