[Snippets] Add layout-features.py that prints GSUB/GPOS features

Snippets/layout-features.py

@@ -0,0 +1,47 @@
+#! /usr/bin/env python
+
+from __future__ import print_function, division, absolute_import
+from fontTools.misc.py23 import *
+from fontTools.ttLib import TTFont
+from fontTools.ttLib.tables import otTables
+import sys
+
+if len(sys.argv) != 2:
+	print("usage: layout-features.py fontfile.ttf")
+	sys.exit(1)
+fontfile = sys.argv[1]
+font = TTFont(fontfile)
+
+for tag in ('GSUB', 'GPOS'):
+	if not tag in font: continue
+	print("Table:", tag)
+	table = font[tag].table
+	if not table.ScriptList or not table.FeatureList: continue
+	featureRecords = table.FeatureList.FeatureRecord
+	for script in table.ScriptList.ScriptRecord:
+		print("  Script:", script.ScriptTag)
+		if not script.Script:
+			print ("    Null script.")
+			continue
+		languages = list(script.Script.LangSysRecord)
+		if script.Script.DefaultLangSys:
+			defaultlangsys = otTables.LangSysRecord()
+			defaultlangsys.LangSysTag = "default"
+			defaultlangsys.LangSys = script.Script.DefaultLangSys
+			languages.insert(0, defaultlangsys)
+		for langsys in languages:
+			print("    Language:", langsys.LangSysTag)
+			if not langsys.LangSys:
+				print ("    Null language.")
+				continue
+			features = [featureRecords[index] for index in langsys.LangSys.FeatureIndex]
+			if langsys.LangSys.ReqFeatureIndex != 0xFFFF:
+				record = featureRecords[langsys.LangSys.ReqFeatureIndex]
+				requiredfeature = otTables.FeatureRecord()
+				requiredfeature.FeatureTag = 'required(%s)' % record.FeatureTag
+				requiredfeature.Feature = record.Feature
+				features.insert(0, requiredfeature)
+			for feature in features:
+				print("      Feature:", feature.FeatureTag)
+				lookups = feature.Feature.LookupListIndex
+				print("        Lookups:", ','.join(str(l) for l in lookups))