[varLib] Add optimizeVarData()

Though not really effective right now since we don't split into
multiple VarData sets.

Lib/fontTools/ttLib/tables/otTables.py

@@ -193,11 +193,14 @@ class VarData(BaseTable):
 		rawTable = self.__dict__.copy()
 
 		numShorts = 0
+		count = self.VarRegionCount
 		for item in self.Item:
-			for i in range(len(item) - 1, numShorts - 1, -1):
+			for i in range(count - 1, numShorts - 1, -1):
 				if not (-128 <= item[i] <= 127):
 					numShorts = i + 1
 					break
+			if numShorts == count:
+				break
 
 		rawTable['NumShorts'] = numShorts
 		return rawTable

Lib/fontTools/varLib/__init__.py

@@ -488,6 +488,11 @@ def _add_HVAR(font, model, master_ttfs, axes):
 		items.append(hAdvanceDeltas.get(glyphName, zeroes))
 	while items and items[-1] is zeroes:
 		del items[-1]
+
+	# TODO Add indirect mapping to save on duplicates
+	#uniq = set(items)
+	#if (len(items) - len(uniq)) * len(varTupleIndexs)) > len(items) * 2:
+
 	varData = builder.buildVarData(varTupleIndexes, items)
 	varStore = builder.buildVarStore(varTupleList, [varData])
 

Lib/fontTools/varLib/builder.py

@@ -26,7 +26,38 @@ def buildVarRegionList(supports, axisTags):
 	self.VarRegionCount = len(self.VarRegion)
 	return self
 
-def buildVarData(varRegionIndices, items):
+
+def _reorderItem(lst, narrows):
+	out = []
+	count = len(lst)
+	for i in range(count):
+		if i not in narrows:
+			out.append(lst[i])
+	for i in range(count):
+		if i in narrows:
+			out.append(lst[i])
+	return out
+
+def optimizeVarData(self):
+	# Reorder columns such that all SHORT columns come before UINT8
+	count = self.VarRegionCount
+	items = self.Item
+	narrows = set(range(count))
+	for item in items:
+		for i in narrows:
+			if not (-128 <= item[i] <= 127):
+				narrows.remove(i)
+				break
+		if not narrows:
+			break
+
+	self.VarRegionIndex = _reorderItem(self.VarRegionIndex, narrows)
+	for i in range(self.ItemCount):
+		items[i] = _reorderItem(items[i], narrows)
+
+	return self
+
+def buildVarData(varRegionIndices, items, optimize=True):
 	self = ot.VarData()
 	self.VarRegionIndex = list(varRegionIndices)
 	regionCount = self.VarRegionCount = len(self.VarRegionIndex)
@@ -35,8 +66,11 @@ def buildVarData(varRegionIndices, items):
 		assert len(item) == regionCount
 		records.append(list(item))
 	self.ItemCount = len(self.Item)
+	if optimize:
+		optimizeVarData(self)
 	return self
 
+
 def buildVarStore(varTupleList, varDataList):
 	self = ot.VarStore()
 	self.Format = 1