[morx] Change MorphType to uint8, to comply with the spec

Lib/fontTools/ttLib/tables/otConverters.py

@@ -24,8 +24,11 @@ def buildConverters(tableSpec, tableNamespace):
 			assert tp == "uint16"
 			converterClass = ValueFormat
 		elif name.endswith("Count") or name == "MorphType":
-			assert tp in ("uint16", "uint32")
-			converterClass = ComputedUShort if tp == 'uint16' else ComputedULong
+			converterClass = {
+				"uint8": ComputedUInt8,
+				"uint16": ComputedUShort,
+				"uint32": ComputedULong,
+			}[tp]
 		elif name == "SubTable":
 			converterClass = SubTable
 		elif name == "ExtSubTable":
@@ -218,6 +221,8 @@ class ComputedInt(IntValue):
 			xmlWriter.comment("%s=%s" % (name, value))
 			xmlWriter.newline()
 
+class ComputedUInt8(ComputedInt, UInt8):
+	pass
 class ComputedUShort(ComputedInt, UShort):
 	pass
 class ComputedULong(ComputedInt, ULong):

Lib/fontTools/ttLib/tables/otData.py

@@ -1,3 +1,4 @@
+# coding: utf-8
 from __future__ import print_function, division, absolute_import
 from fontTools.misc.py23 import *
 
@@ -1247,11 +1248,14 @@ otData = [
 		('Flags32', 'DisableFlags', None, None, 'Complement of flags for the settings that this feature and setting disable.'),
 	]),
 
+	# Apple TrueType Reference Manual, chapter “The ‘morx’ table”,
+	# section “Metamorphosis Subtables”.
+	# https://developer.apple.com/fonts/TrueType-Reference-Manual/RM06/Chap6morx.html
 	('MorphSubtable', [
 		('uint32', 'StructLength', None, None, 'Total subtable length, including this header.'),
 		('uint8', 'CoverageFlags', None, None, 'Most significant byte of coverage flags.'),
-		('uint8', 'Reserved', None, None, 'Unused.'),
-		('uint16', 'MorphType', None, None, 'Subtable type.'),
+		('uint16', 'Reserved', None, None, 'Unused.'),
+		('uint8', 'MorphType', None, None, 'Subtable type.'),
 		('Flags32', 'SubFeatureFlags', None, None, 'The 32-bit mask identifying which subtable this is (the subtable being executed if the AND of this value and the processed defaultFlags is nonzero).'),
 		('SubStruct', 'SubStruct', None, None, 'SubTable.'),
         ]),