[subset] set emptied CFF charstrings to 'endchar' with --retain-gids

Part of #1446

Lib/fontTools/subset/cff.py

@@ -104,37 +104,44 @@ def subset_glyphs(self, s):
 		font = cff[fontname]
 		cs = font.CharStrings
 
-		# Load all glyphs
-		for g in font.charset:
-			if g not in s.glyphs: continue
-			c, _ = cs.getItemAndSelector(g)
-
-		if cs.charStringsAreIndexed:
-			indices = [i for i,g in enumerate(font.charset) if g in s.glyphs]
-			csi = cs.charStringsIndex
-			csi.items = [csi.items[i] for i in indices]
-			del csi.file, csi.offsets
-			if hasattr(font, "FDSelect"):
-				sel = font.FDSelect
-				# XXX We want to set sel.format to None, such that the
-				# most compact format is selected. However, OTS was
-				# broken and couldn't parse a FDSelect format 0 that
-				# happened before CharStrings. As such, always force
-				# format 3 until we fix cffLib to always generate
-				# FDSelect after CharStrings.
-				# https://github.com/khaledhosny/ots/pull/31
-				#sel.format = None
-				sel.format = 3
-				sel.gidArray = [sel.gidArray[i] for i in indices]
-			cs.charStrings = {g:indices.index(v)
-					  for g,v in cs.charStrings.items()
-					  if g in s.glyphs}
+		if s.options.retain_gids:
+			for g in cs.keys():
+				if g in s.glyphs_emptied:
+					c = cs[g]
+					c.decompile()
+					c.program = ["endchar"]
 		else:
-			cs.charStrings = {g:v
-					  for g,v in cs.charStrings.items()
-					  if g in s.glyphs}
-		font.charset = [g for g in font.charset if g in s.glyphs]
-		font.numGlyphs = len(font.charset)
+			# Load all glyphs
+			for g in font.charset:
+				if g not in s.glyphs: continue
+				c, _ = cs.getItemAndSelector(g)
+
+			if cs.charStringsAreIndexed:
+				indices = [i for i,g in enumerate(font.charset) if g in s.glyphs]
+				csi = cs.charStringsIndex
+				csi.items = [csi.items[i] for i in indices]
+				del csi.file, csi.offsets
+				if hasattr(font, "FDSelect"):
+					sel = font.FDSelect
+					# XXX We want to set sel.format to None, such that the
+					# most compact format is selected. However, OTS was
+					# broken and couldn't parse a FDSelect format 0 that
+					# happened before CharStrings. As such, always force
+					# format 3 until we fix cffLib to always generate
+					# FDSelect after CharStrings.
+					# https://github.com/khaledhosny/ots/pull/31
+					#sel.format = None
+					sel.format = 3
+					sel.gidArray = [sel.gidArray[i] for i in indices]
+				cs.charStrings = {g:indices.index(v)
+						  for g,v in cs.charStrings.items()
+						  if g in s.glyphs}
+			else:
+				cs.charStrings = {g:v
+						  for g,v in cs.charStrings.items()
+						  if g in s.glyphs}
+			font.charset = [g for g in font.charset if g in s.glyphs]
+			font.numGlyphs = len(font.charset)
 
 	return True # any(cff[fontname].numGlyphs for fontname in cff.keys())
 

Tests/subset/subset_test.py

@@ -475,7 +475,7 @@ class SubsetTest(unittest.TestCase):
         subset.main([fontpath, "--recalc-timestamp", "--output-file=%s" % subsetpath, "*"])
         self.assertLess(modified, TTFont(subsetpath)['head'].modified)
 
-    def test_retain_gids(self):
+    def test_retain_gids_ttf(self):
         _, fontpath = self.compile_font(self.getpath("TestTTF-Regular.ttx"), ".ttf")
         font = TTFont(fontpath)
 
@@ -507,6 +507,41 @@ class SubsetTest(unittest.TestCase):
         self.assertGreater(glyf["A"].numberOfContours, 0)
         self.assertEqual(glyf["B"].numberOfContours, 0)
 
+    def test_retain_gids_otf(self):
+        _, fontpath = self.compile_font(self.getpath("TestOTF-Regular.ttx"), ".otf")
+        font = TTFont(fontpath)
+
+        self.assertEqual(font["hmtx"]["A"], (500, 132))
+        self.assertEqual(font["hmtx"]["B"], (400, 132))
+
+        font["CFF "].cff[0].decompileAllCharStrings()
+        cs = font["CFF "].cff[0].CharStrings
+        self.assertGreater(len(cs["A"].program), 0)
+        self.assertGreater(len(cs["B"].program), 0)
+
+        subsetpath = self.temp_path(".ttf")
+        subset.main(
+            [
+                fontpath,
+                "--retain-gids",
+                "--output-file=%s" % subsetpath,
+                "--glyph-names",
+                "A",
+            ]
+        )
+        subsetfont = TTFont(subsetpath)
+
+        self.assertEqual(subsetfont.getGlyphOrder(), font.getGlyphOrder())
+
+        hmtx = subsetfont["hmtx"]
+        self.assertEqual(hmtx["A"], (500, 132))
+        self.assertEqual(hmtx["B"], (0, 0))
+
+        subsetfont["CFF "].cff[0].decompileAllCharStrings()
+        cs = subsetfont["CFF "].cff[0].CharStrings
+        self.assertGreater(len(cs["A"].program), 0)
+        self.assertEqual(cs["B"].program, ["endchar"])
+
 
 if __name__ == "__main__":
     sys.exit(unittest.main())