font_to_py.py Implement fix for iss #23.

font_to_py.py

@@ -6,11 +6,11 @@
 
 # Some code adapted from Daniel Bader's work at the following URL
 # http://dbader.org/blog/monochrome-font-rendering-with-freetype-and-python
-# With thanks to Stephen Irons @ironss for fix for leading left pixels.
+# With thanks to Stephen Irons @ironss for various improvements.
 
 # The MIT License (MIT)
 #
-# Copyright (c) 2016 Peter Hinch
+# Copyright (c) 2016-2019 Peter Hinch
 #
 # Permission is hereby granted, free of charge, to any person obtaining a copy
 # of this software and associated documentation files (the "Software"), to deal
@@ -275,9 +275,9 @@ class Font(dict):
         elif charset == '':
             self.charset = [chr(defchar)] + [chr(ordv) for ordv in self.crange]
         else:
-            cl = [ord(x) for x in chr(defchar) + charset]
+            cl = [ord(x) for x in chr(defchar) + charset if self._face.get_char_index(x) != 0 ]
             self.crange = range(min(cl), max(cl) + 1)  # Inclusive ordinal value range
-            cs = [chr(ordv) if chr(ordv) in charset else '' for ordv in self.crange]
+            cs = [chr(ordv) if chr(ordv) in charset and self._face.get_char_index(chr(ordv)) != 0 else '' for ordv in self.crange]
             # .charset has an item for all chars in range. '' if unsupported.
             # item 0 is the default char. Subsequent chars are in increasing ordinal value.
             self.charset = [chr(defchar)] + cs