[cffLib] Add a simple (and quite possibly incomplete) convertCFF2ToCFF()

Lib/fontTools/cffLib/__init__.py

@@ -458,6 +458,11 @@ class CFFFontSet(object):
                         if hasattr(privateDict, key):
                             delattr(privateDict, key)
                             # print "Removing privateDict attr", key
+
+        # TODO(behdad): What does the following comment even mean? Both CFF and CFF2
+        # use the same T2Charstring class.
+        # What I see missing is dropping the endchar and return operators...
+
         # At this point, the Subrs and Charstrings are all still T2Charstring class
         # easiest to fix this by compiling, then decompiling again
         file = BytesIO()
@@ -465,6 +470,42 @@ class CFFFontSet(object):
         file.seek(0)
         self.decompile(file, otFont, isCFF2=True)
 
+    def convertCFF2ToCFF(self, otFont):
+        """Converts this object from CFF2 format to CFF format. This conversion
+        is done 'in-place'. The conversion cannot be reversed.
+
+        The CFF2 font cannot be variable. This method will remove the VarStore,
+        but will not process the CharStrings in any way (TODO instantiate to default).
+
+        This assumes a decompiled CFF table. (i.e. that the object has been
+        filled via :meth:`decompile`.)"""
+        self.major = 1
+        topDictData = TopDictIndex(None)
+        topDictData.items = self.topDictIndex.items
+        self.topDictIndex = topDictData
+        topDict = topDictData[0]
+        if hasattr(topDict, "Private"):
+            privateDict = topDict.Private
+        else:
+            privateDict = None
+        opOrder = buildOrder(topDictOperators)
+        topDict.order = opOrder
+
+        fdArray = topDict.FDArray
+        charStrings = topDict.CharStrings
+
+        for cs in charStrings.values():
+            cs.program.append("endchar")
+
+        # TODO Add "return" to subrs that don't end in endchar?
+
+        # At this point, the Subrs and Charstrings are all still T2Charstring class
+        # easiest to fix this by compiling, then decompiling again
+        # file = BytesIO()
+        # self.compile(file, otFont, isCFF2=False)
+        # file.seek(0)
+        # self.decompile(file, otFont, isCFF2=False)
+
     def desubroutinize(self):
         for fontName in self.fontNames:
             font = self[fontName]

Lib/fontTools/varLib/instancer/__init__.py

@@ -89,7 +89,7 @@ from fontTools.misc.fixedTools import (
     otRound,
 )
 from fontTools.varLib.models import normalizeValue, piecewiseLinearMap
-from fontTools.ttLib import TTFont
+from fontTools.ttLib import TTFont, getTableClass
 from fontTools.ttLib.tables.TupleVariation import TupleVariation
 from fontTools.ttLib.tables import _g_l_y_f
 from fontTools import varLib
@@ -574,7 +574,13 @@ def changeTupleVariationAxisLimit(var, axisTag, axisLimit):
 
 
 def instantiateCFF2(
-    varfont, axisLimits, *, round=round, specialize=True, generalize=False
+    varfont,
+    axisLimits,
+    *,
+    round=round,
+    specialize=True,
+    generalize=False,
+    downgrade=False,
 ):
     # The algorithm here is rather simple:
     #
@@ -594,7 +600,11 @@ def instantiateCFF2(
     topDict = cff.topDictIndex[0]
     varStore = topDict.VarStore.otVarStore
     if not varStore:
-        # TODO Downgrade to CFF if requested.
+        if downgrade:
+            table = varfont["CFF "] = getTableClass("CFF ")()
+            table.cff = cff
+            cff.convertCFF2ToCFF(varfont)
+            del varfont["CFF2"]
         return
 
     cff.desubroutinize()
@@ -653,7 +663,6 @@ def instantiateCFF2(
         newDefaults = []
         newDeltas = []
         for i in range(count):
-
             defaultValue = arg[i]
 
             major = vsindex
@@ -804,12 +813,18 @@ def instantiateCFF2(
 
     # Remove empty VarStore
     if not varStore.VarData:
+        if "VarStore" in topDict.rawDict:
+            del topDict.rawDict["VarStore"]
         del topDict.VarStore
         del topDict.CharStrings.varStore
         for private in privateDicts:
             del private.vstore
 
-        # TODO Downgrade to CFF if requested.
+        if downgrade:
+            table = varfont["CFF "] = getTableClass("CFF ")()
+            table.cff = cff
+            cff.convertCFF2ToCFF(varfont)
+            del varfont["CFF2"]
 
 
 def _instantiateGvarGlyph(

Tests/varLib/instancer/data/test_results/CFF2Instancer-VF-1-instance-400.ttx

@@ -208,27 +208,6 @@
           256 70 -256 hlineto
         </CharString>
       </CharStrings>
-      <VarStore Format="1">
-        <Format value="1"/>
-        <VarRegionList>
-          <!-- RegionAxisCount=1 -->
-          <!-- RegionCount=1 -->
-          <Region index="0">
-            <VarRegionAxis index="0">
-              <StartCoord value="0.0"/>
-              <PeakCoord value="1.0"/>
-              <EndCoord value="1.0"/>
-            </VarRegionAxis>
-          </Region>
-        </VarRegionList>
-        <!-- VarDataCount=1 -->
-        <VarData index="0">
-          <!-- ItemCount=0 -->
-          <NumShorts value="0"/>
-          <!-- VarRegionCount=1 -->
-          <VarRegionIndex index="0" value="0"/>
-        </VarData>
-      </VarStore>
     </CFFFont>
 
     <GlobalSubrs>

Tests/varLib/instancer/data/test_results/CFF2Instancer-VF-3-instance-400.ttx

@@ -234,27 +234,6 @@
           -45 25 -14 -3 rlineto
         </CharString>
       </CharStrings>
-      <VarStore Format="1">
-        <Format value="1"/>
-        <VarRegionList>
-          <!-- RegionAxisCount=1 -->
-          <!-- RegionCount=1 -->
-          <Region index="0">
-            <VarRegionAxis index="0">
-              <StartCoord value="0.0"/>
-              <PeakCoord value="1.0"/>
-              <EndCoord value="1.0"/>
-            </VarRegionAxis>
-          </Region>
-        </VarRegionList>
-        <!-- VarDataCount=1 -->
-        <VarData index="0">
-          <!-- ItemCount=0 -->
-          <NumShorts value="0"/>
-          <!-- VarRegionCount=1 -->
-          <VarRegionIndex index="0" value="0"/>
-        </VarData>
-      </VarStore>
     </CFFFont>
 
     <GlobalSubrs>