From 830cff62532ad9e7d85aaaeba7352d514ac6d038 Mon Sep 17 00:00:00 2001
From: Behdad Esfahbod <behdad@behdad.org>
Date: Wed, 21 Apr 2021 14:10:27 -0600
Subject: [PATCH] [ttLib] Add Value.getEffectiveFormat()

This ignores 0/None values that don't need to be encoded.
---
 Lib/fontTools/ttLib/tables/otBase.py | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/Lib/fontTools/ttLib/tables/otBase.py b/Lib/fontTools/ttLib/tables/otBase.py
index 3c07f9e11..dd8b724d7 100644
--- a/Lib/fontTools/ttLib/tables/otBase.py
+++ b/Lib/fontTools/ttLib/tables/otBase.py
@@ -970,6 +970,13 @@ class ValueRecord(object):
 			format = format | valueRecordFormatDict[name][0]
 		return format
 
+	def getEffectiveFormat(self):
+		format = 0
+		for name,value in self.__dict__.items():
+			if value:
+				format = format | valueRecordFormatDict[name][0]
+		return format
+
 	def toXML(self, xmlWriter, font, valueName, attrs=None):
 		if attrs is None:
 			simpleItems = []