From 0218e07f76e3ff413a220a71a5d4f8102a90f17b Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Mon, 19 Nov 2018 16:22:49 -0500
Subject: [PATCH] [varLib.mutator] Move some code out of merger

---
 Lib/fontTools/varLib/merger.py  | 63 +++------------------------------
 Lib/fontTools/varLib/mutator.py | 58 ++++++++++++++++++++++++++----
 2 files changed, 57 insertions(+), 64 deletions(-)

diff --git a/Lib/fontTools/varLib/merger.py b/Lib/fontTools/varLib/merger.py
index 3270bf519..e5f02fede 100644
--- a/Lib/fontTools/varLib/merger.py
+++ b/Lib/fontTools/varLib/merger.py
@@ -813,7 +813,9 @@ def merge(merger, self, lst):
 
 class MutatorMerger(AligningMerger):
 	"""A merger that takes a variable font, and instantiates
-	an instance."""
+	an instance.  While there's no "merging" to be done per se,
+	the operation can benefit from many operations that the
+	aligning merger does."""
 
 	def __init__(self, font, location):
 		Merger.__init__(self, font)
@@ -827,63 +829,10 @@ class MutatorMerger(AligningMerger):
 
 		self.instancer = VarStoreInstancer(store, font['fvar'].axes, location)
 
-	def instantiate(self):
-		font = self.font
-
-		for tableTag in 'GSUB','GPOS':
-			if not tableTag in font:
-				continue
-			table = font[tableTag].table
-			if not hasattr(table, 'FeatureVariations'):
-				continue
-			variations = table.FeatureVariations
-			for record in variations.FeatureVariationRecord:
-				applies = True
-				for condition in record.ConditionSet.ConditionTable:
-					if condition.Format == 1:
-						axisIdx = condition.AxisIndex
-						axisTag = self.font['fvar'].axes[axisIdx].axisTag
-						Min = condition.FilterRangeMinValue
-						Max = condition.FilterRangeMaxValue
-						loc = self.location[axisTag]
-						if not (Min <= loc <= Max):
-							applies = False
-					else:
-						applies = False
-					if not applies:
-						break
-
-				if applies:
-					assert record.FeatureTableSubstitution.Version == 0x00010000
-					for rec in record.FeatureTableSubstitution.SubstitutionRecord:
-						table.FeatureList.FeatureRecord[rec.FeatureIndex].Feature = rec.Feature
-					break
-			del table.FeatureVariations
-
-
-		self.mergeTables(font, [font], ['GPOS'])
-
-		if 'GDEF' in font:
-			gdef = font['GDEF'].table
-			if gdef.Version >= 0x00010003:
-				del gdef.VarStore
-				gdef.Version = 0x00010002
-				if gdef.MarkGlyphSetsDef is None:
-					del gdef.MarkGlyphSetsDef
-					gdef.Version = 0x00010000
-			if not (gdef.LigCaretList or
-				gdef.MarkAttachClassDef or
-				gdef.GlyphClassDef or
-				gdef.AttachList or
-				(gdef.Version >= 0x00010002 and gdef.MarkGlyphSetsDef)):
-				del font['GDEF']
-
 @MutatorMerger.merger(ot.Anchor)
 def merge(merger, self, lst):
 
-	# Most other structs are merged with self pointing to a copy of base font.
-	# Anchors are sometimes created later and initialized to have 0/None members.
-	# Hence the copy.
+	# Hack till we become selfless.
 	self.__dict__ = lst[0].__dict__.copy()
 
 	if self.Format != 3:
@@ -911,9 +860,7 @@ def merge(merger, self, lst):
 @MutatorMerger.merger(otBase.ValueRecord)
 def merge(merger, self, lst):
 
-	# Most other structs are merged with self pointing to a copy of base font.
-	# ValueRecords are sometimes created later and initialized to have 0/None members.
-	# Hence the copy.
+	# Hack till we become selfless.
 	self.__dict__ = lst[0].__dict__.copy()
 
 	instancer = merger.instancer
diff --git a/Lib/fontTools/varLib/mutator.py b/Lib/fontTools/varLib/mutator.py
index 9616dbb0c..cabb92b73 100644
--- a/Lib/fontTools/varLib/mutator.py
+++ b/Lib/fontTools/varLib/mutator.py
@@ -115,12 +115,59 @@ def instantiateVariableFont(varfont, location, inplace=False):
 			setattr(varfont[tableTag], itemName,
 				getattr(varfont[tableTag], itemName) + delta)
 
-	if 'GDEF' in varfont:
-		log.info("Mutating GDEF/GPOS/GSUB tables")
-		merger = MutatorMerger(varfont, loc)
+	log.info("Mutating FeatureVariations")
+	for tableTag in 'GSUB','GPOS':
+		if not tableTag in varfont:
+			continue
+		table = varfont[tableTag].table
+		if not hasattr(table, 'FeatureVariations'):
+			continue
+		variations = table.FeatureVariations
+		for record in variations.FeatureVariationRecord:
+			applies = True
+			for condition in record.ConditionSet.ConditionTable:
+				if condition.Format == 1:
+					axisIdx = condition.AxisIndex
+					axisTag = fvar.axes[axisIdx].axisTag
+					Min = condition.FilterRangeMinValue
+					Max = condition.FilterRangeMaxValue
+					v = loc[axisTag]
+					if not (Min <= v <= Max):
+						applies = False
+				else:
+					applies = False
+				if not applies:
+					break
+
+			if applies:
+				assert record.FeatureTableSubstitution.Version == 0x00010000
+				for rec in record.FeatureTableSubstitution.SubstitutionRecord:
+					table.FeatureList.FeatureRecord[rec.FeatureIndex].Feature = rec.Feature
+				break
+		del table.FeatureVariations
+
+	if 'GDEF' in varfont and varfont['GDEF'].table.Version >= 0x00010003:
+		log.info("Mutating GDEF/GPOS/GSUB tables")
+		gdef = varfont['GDEF'].table
+		instancer = VarStoreInstancer(gdef.VarStore, fvar.axes, loc)
+
+		merger = MutatorMerger(varfont, loc)
+		merger.mergeTables(varfont, [varfont], ['GPOS'])
+
+		# Downgrade GDEF.
+		del gdef.VarStore
+		gdef.Version = 0x00010002
+		if gdef.MarkGlyphSetsDef is None:
+			del gdef.MarkGlyphSetsDef
+			gdef.Version = 0x00010000
+
+		if not (gdef.LigCaretList or
+			gdef.MarkAttachClassDef or
+			gdef.GlyphClassDef or
+			gdef.AttachList or
+			(gdef.Version >= 0x00010002 and gdef.MarkGlyphSetsDef)):
+			del varfont['GDEF']
 
-		log.info("Building interpolated tables")
-		merger.instantiate()
 
 	addidef = False
 	for glyph in glyf.glyphs.values():
@@ -130,7 +177,6 @@ def instantiateVariableFont(varfont, location, inplace=False):
 			addidef = any(op.startswith("GETVARIATION") for op in instructions)
 			if addidef:
 				break
-
 	if addidef:
 		log.info("Adding IDEF to fpgm table for GETVARIATION opcode")
 		asm = []