From 926f7218320f2541a00b13b7f4a9024c51396492 Mon Sep 17 00:00:00 2001
From: Cosimo Lupo <clupo@google.com>
Date: Thu, 20 May 2021 10:01:58 +0100
Subject: [PATCH] return True from SinglePos.prune_post_subset to not change
 semantics

the useless subtable might have been there to stop the next subtable from applying...
https://github.com/fonttools/fonttools/pull/2313#issuecomment-844497422
---
 Lib/fontTools/subset/__init__.py | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/Lib/fontTools/subset/__init__.py b/Lib/fontTools/subset/__init__.py
index 1b61fefc7..65415e2e9 100644
--- a/Lib/fontTools/subset/__init__.py
+++ b/Lib/fontTools/subset/__init__.py
@@ -555,8 +555,9 @@ def subset_glyphs(self, s):
 
 @_add_method(otTables.SinglePos)
 def prune_post_subset(self, font, options):
-	if not self.Value:
-		return False
+	if self.Value is None:
+		assert self.ValueFormat == 0
+		return True
 
 	# Shrink ValueFormat
 	if self.Format == 1:
@@ -575,7 +576,7 @@ def prune_post_subset(self, font, options):
 		self.Value = self.Value[0] if self.ValueFormat != 0 else None
 		del self.ValueCount
 
-	return bool(self.ValueFormat)
+	return True
 
 @_add_method(otTables.PairPos)
 def subset_glyphs(self, s):