[buildcff2vf] Add logic to subset source fonts, using a subset which …

…is specific to each font.

This is useful for workflows where the workflow builds a complete glyph set for each source font, even though not all glyphs use the same set of design axes or source fonts. An example case is SourceHanSans, where only 55 glyphs use more than two axes, and many of the 55 use different axes than the other special glyphs.

python/afdko/buildcff2vf.py

@@ -7,13 +7,15 @@
 import logging
 import os
 from pkg_resources import parse_version
+import re
 import sys
 
 from fontTools import varLib, version as fontToolsVersion
 from fontTools.cffLib.specializer import commandsToProgram
 from fontTools.designspaceLib import DesignSpaceDocument
 from fontTools.misc.fixedTools import otRound
 from fontTools.misc.psCharStrings import T2OutlineExtractor, T2CharString
+from fontTools.ttLib import TTFont
 from fontTools.varLib.cff import CFF2CharStringMergePen
 
 __version__ = '1.15.0'
@@ -96,6 +98,15 @@ def get_options(args):
         'curves.\n',
         default=False,
     )
+    parser.add_argument(
+        '-i',
+        '--include_glyphs_path',
+        metavar='PATH',
+        dest='include_glyphs_path',
+        type=_validate_path,
+        help='Path to file containing a python dict specifying which\n'
+        'glyph names should be included from which source fonts.\n'
+    )
     options = parser.parse_args(args)
     if not options.var_font_path:
         var_font_path = os.path.splitext(options.design_space_path)[0] + '.otf'
@@ -113,6 +124,58 @@ def get_options(args):
     return options
 
 
+def getSubset(subset_Path):
+    if not os.path.exists(subset_Path):
+        raise ValueError("could not find subset file path", subset_Path)
+    fp = open(subset_Path, "rt")
+    text_lines = fp.readlines()
+    locationDict = {}
+    cur_key_list = None
+    for li, line in enumerate(text_lines):
+        idx = line.find('#')
+        if idx >= 0:
+            line = line[:idx]
+        line = line.strip()
+        if not line:
+            continue
+        if line[0] == "(":
+            cur_key_list = []
+            location_list = eval(line)
+            for location_entry in location_list:
+                cur_key_list.append(location_entry)
+                if location_entry not in locationDict:
+                    locationDict[location_entry] = []
+        else:
+            m = re.match(r"(\S+)", line)
+            if m:
+                if cur_key_list is None:
+                    logger.error(
+                        "Error parsing subset file. "
+                        "Seeing a glyph name record before "
+                        "seeing a location record.")
+                    logger.error("Line number: {}.".format(li))
+                    logger.error("Line text: {}.".format(line))
+                for key in cur_key_list:
+                    locationDict[key].append(m.group(1))
+    return locationDict
+
+
+def subset_masters(designspace, subsetDict):
+    from fontTools import subset
+    subset_options = subset.Options(notdef_outline=True)
+    for ds_source in designspace.sources:
+        key = tuple(ds_source.location.items())
+        included = set(subsetDict[key])
+        ttf_font = ds_source.font
+        subsetter = subset.Subsetter(options=subset_options)
+        subsetter.populate(glyphs=included)
+        subsetter.subset(ttf_font)
+        subset_path = os.path.splitext(ds_source.path)[0] + ".subset.otf"
+        logger.progress("Saving subset font %s", subset_path)
+        ttf_font.save(subset_path)
+        ds_source.font = TTFont(subset_path)
+
+
 class MergeTypeError(Exception):
     pass
 
@@ -399,6 +462,12 @@ def run(args=None):
     for i, master_font in enumerate(master_fonts):
         designspace.sources[i].font = master_font
 
+    # Subset source fonts
+    if options.include_glyphs_path:
+        logger.progress("Subsetting source fonts...")
+        subsetDict = getSubset(options.include_glyphs_path)
+        subset_masters(designspace, subsetDict)
+
     if options.check_compatibility:
         logger.progress("Checking outline compatibility in source fonts...")
         font_list = [src.font for src in designspace.sources]
@@ -410,8 +479,7 @@ def run(args=None):
         do_compatibility(vf, font_list)
 
     logger.progress("Building VF font...")
-    varFont, _, masterPaths = varLib.build(
-        options.design_space_path, otfFinder)
+    varFont, _, _ = varLib.build(options.design_space_path, otfFinder)
 
     if options.keep_glyph_names:
         default_font = designspace.sources[ds_data.base_idx].font