Merge pull request #673 from anthrotype/subset-passthrough-tables

[subset] add --passthrough-tables option

Lib/fontTools/subset/__init__.py

@@ -216,11 +216,17 @@ Font table options:
       they do not need subsetting (ignore the fact that 'loca' is listed
       here): 'gasp', 'head', 'hhea', 'maxp', 'vhea', 'OS/2', 'loca',
       'name', 'cvt ', 'fpgm', 'prep', 'VMDX', 'DSIG' and 'CPAL'.
-      Tables that the tool does not know how to subset and are not specified
+      By default, tables that the tool does not know how to subset and are not
-      here will be dropped from the font.
+      specified here will be dropped from the font, unless --passthrough-tables
+      option is passed.
       Example:
          --no-subset-tables+=FFTM
             * Keep 'FFTM' table in the font by preventing subsetting.
+  --passthrough-tables
+      Do not drop tables that the tool does not know how to subset.
+  --no-passthrough-tables
+      Tables that the tool does not know how to subset and are not specified
+      in --no-subset-tables will be dropped from the font. [default]
   --hinting-tables[-]=<table>[,<table>...]
       Specify (=), add to (+=) or exclude from (-=) the list of font-wide
       hinting tables that will be dropped if --no-hinting is specified,
@@ -2444,6 +2450,7 @@ class Options(object):
 
         self.drop_tables = self._drop_tables_default[:]
         self.no_subset_tables = self._no_subset_tables_default[:]
+        self.passthrough_tables = False  # keep/drop tables we can't subset
         self.hinting_tables = self._hinting_tables_default[:]
         self.legacy_kern = False    # drop 'kern' table if GPOS available
         self.layout_features = self._layout_features_default[:]
@@ -2722,6 +2729,8 @@ class Subsetter(object):
                     del font[tag]
                 else:
                     log.info("%s subsetted", tag)
+            elif self.options.passthrough_tables:
+                log.info("%s NOT subset; don't know how to subset", tag)
             else:
                 log.info("%s NOT subset; don't know how to subset; dropped", tag)
                 del font[tag]

Lib/fontTools/subset/subset_test.py

@@ -1,7 +1,7 @@
 from __future__ import print_function, division, absolute_import
 from fontTools.misc.py23 import *
 from fontTools import subset
-from fontTools.ttLib import TTFont
+from fontTools.ttLib import TTFont, newTable
 import contextlib
 import difflib
 import logging
@@ -204,6 +204,29 @@ class SubsetTest(unittest.TestCase):
         self.assertTrue(filter(lambda l: l.args['msg'] == "subset 'cmap'", logs))
         self.assertTrue(filter(lambda l: l.args['msg'] == "subset 'glyf'", logs))
 
+    def test_passthrough_tables(self):
+        _, fontpath = self.compile_font(self.getpath("TestTTF-Regular.ttx"), ".ttf")
+        font = TTFont(fontpath)
+        unknown_tag = 'ZZZZ'
+        unknown_table = newTable(unknown_tag)
+        unknown_table.data = b'\0'*10
+        font[unknown_tag] = unknown_table
+        font.save(fontpath)
+
+        subsetpath = self.temp_path(".ttf")
+        subset.main([fontpath, "--output-file=%s" % subsetpath])
+        subsetfont = TTFont(subsetpath)
+
+        # tables we can't subset are dropped by default
+        self.assertFalse(unknown_tag in subsetfont)
+
+        subsetpath = self.temp_path(".ttf")
+        subset.main([fontpath, "--passthrough-tables", "--output-file=%s" % subsetpath])
+        subsetfont = TTFont(subsetpath)
+
+        # unknown tables are kept if --passthrough-tables option is passed
+        self.assertTrue(unknown_tag in subsetfont)
+
 
 if __name__ == "__main__":
     unittest.main()