New check: CFF top dict in ASCII range.

Checks if all strings in a font's CFF table top dict fit in the range of ASCII values.

EXPERIMENTAL - com.adobe.fonts/check/cff_ascii_strings
Added to the Universal profile.

(issue #4619)

CHANGELOG.md

@@ -3,6 +3,9 @@ A more detailed list of changes is available in the corresponding milestones for
 
 ## Upcoming release: 0.12.8 (2024-Jun-??)
 ### New checks
+#### Added to the OpenType profile
+ - **EXPERIMENTAL - [com.adobe.fonts/check/cff_ascii_strings]:** Checks if all strings in a font's CFF table top dict fit in the range of ASCII values (issue #4619)
+
 #### Added to the Universal profile
  - **EXPERIMENTAL - [com.google.fonts/check/gsub/smallcaps_before_ligatures]:** Ensure 'smcp' (small caps) lookups are defined before ligature lookups in the 'GSUB' table (issue #3020)
 

Lib/fontbakery/checks/opentype/cff.py

@@ -10,6 +10,7 @@ def __init__(self):
  self.glyphs_endchar_seac = []
  self.glyphs_exceed_max = []
  self.glyphs_recursion_errors = []
+ self.string_not_ascii = []
 
 
 def _get_subr_bias(count):
@@ -61,6 +62,14 @@ def _analyze_cff(analysis, top_dict, private_dict, fd_index=0):
  global_subrs = top_dict.GlobalSubrs
  gsubr_bias = _get_subr_bias(len(global_subrs))
 
+ if hasattr(top_dict, "rawDict"):
+ raw_dict = top_dict.rawDict
+ for key in ["Notice", "Copyright", "FontName", "FullName", "FamilyName"]:
+ for char in raw_dict.get(key, ""):
+ if ord(char) > 0x7F:
+ analysis.string_not_ascii.append((key, raw_dict[key]))
+ break
+
  if private_dict is not None and hasattr(private_dict, "Subrs"):
  subrs = private_dict.Subrs
  subr_bias = _get_subr_bias(len(subrs))
@@ -109,7 +118,11 @@ def cff_analysis(font):
  ttFont = TTFont(font.file) # Use our own copy here since we are decompiling
 
  if "CFF " in ttFont:
- cff = ttFont["CFF "].cff
+ try:
+ cff = ttFont["CFF "].cff
+ except UnicodeDecodeError:
+ analysis.string_not_ascii = None
+ return analysis
 
  for top_dict in cff.topDictIndex:
  if hasattr(top_dict, "FDArray"):
@@ -218,3 +231,35 @@ def com_adobe_fonts_check_cff_deprecated_operators(cff_analysis):
  f'Glyph "{gn}" has deprecated use of "endchar"'
  f" operator to build accented characters (seac).",
  )
+
+
+@check(
+ id="com.adobe.fonts/check/cff_ascii_strings",
+ conditions=["ttFont", "is_cff", "cff_analysis"],
+ rationale="""
+ All CFF Table top dict string chars should fit into the ASCII range.
+ """,
+ proposal="https://github.com/fonttools/fontbakery/issues/4619",
+ experimental="Since 2024/Jun/20",
+)
+def com_adobe_fonts_check_cff_ascii_strings(cff_analysis):
+ """Does the font's CFF table top dict strings fit into the ASCII range?"""
+
+ if cff_analysis.string_not_ascii is None:
+ yield FAIL, Message(
+ "cff-unable-to-decode",
+ "Unable to decode CFF table, possibly due to out"
+ " of ASCII range strings. Please check table strings.",
+ )
+ elif cff_analysis.string_not_ascii:
+ detailed_info = ""
+ for key, string in cff_analysis.string_not_ascii:
+ detailed_info += (
+ f"\n\n\t - {key}: {string.encode('latin-1').decode('utf-8')}"
+ )
+
+ yield FAIL, Message(
+ "cff-string-not-in-ascii-range",
+ f"The following CFF TopDict strings"
+ f" are not in the ASCII range: {detailed_info}",
+ )

Lib/fontbakery/profiles/adobefonts.py

@@ -15,6 +15,7 @@
  "com.adobe.fonts/check/cff2_call_depth",
  "com.adobe.fonts/check/cff_call_depth",
  "com.adobe.fonts/check/cff_deprecated_operators",
+ "com.adobe.fonts/check/cff_ascii_strings",
  ],
  "fontwerk": [
  "com.fontwerk/check/inconsistencies_between_fvar_stat", # IS_OVERRIDDEN

Lib/fontbakery/profiles/opentype.py

@@ -23,9 +23,10 @@
  "com.google.fonts/check/varfont/wdth_valid_range",
  "com.google.fonts/check/varfont/stat_axis_record_for_each_axis",
  "com.google.fonts/check/loca/maxp_num_glyphs",
- "com.adobe.fonts/check/cff2_call_depth",
+ "com.adobe.fonts/check/cff_ascii_strings",
  "com.adobe.fonts/check/cff_call_depth",
  "com.adobe.fonts/check/cff_deprecated_operators",
+ "com.adobe.fonts/check/cff2_call_depth",
  "com.google.fonts/check/font_version",
  "com.google.fonts/check/post_table_version",
  "com.google.fonts/check/monospace",

tests/checks/opentype/cff_test.py

@@ -1,3 +1,5 @@
+from fontTools.ttLib import TTFont
+
 from fontbakery.codetesting import (
  assert_PASS,
  assert_results_contain,
@@ -98,3 +100,41 @@ def test_check_cff_deprecated_operators():
  " to build accented characters (seac)."
  ),
  )
+
+
+def test_check_cff_strings():
+ check = CheckTester("com.adobe.fonts/check/cff_ascii_strings")
+
+ ttFont = TTFont(TEST_FILE("source-sans-pro/OTF/SourceSansPro-Regular.otf"))
+
+ # check that a healthy CFF font passes:
+ assert_PASS(check(ttFont))
+
+ # FIXME: The condition cff_analysis creates a new ttFont object
+ # and, consequently, discards the modifications we made
+ # here prior to invoking the check.
+ #
+ # # put an out of range char into FullName field:
+ # rawDict = ttFont["CFF "].cff.topDictIndex[0].rawDict
+ # rawDict["FullName"] = "S\u00F2urceSansPro-Regular"
+ # assert_results_contain(
+ # check(ttFont),
+ # FAIL,
+ # "cff-string-not-in-ascii-range",
+ # (
+ # "The following CFF TopDict strings are not in the ASCII range:"
+ # f"- FullName: {rawDict['FullName']}"
+ # ),
+ # )
+
+ # Out-of-ascii-range char in the FontName field will cause decode issues:
+ ttFont = TTFont(TEST_FILE("unicode-decode-err/unicode-decode-err-cff.otf"))
+ assert_results_contain(
+ check(ttFont),
+ FAIL,
+ "cff-unable-to-decode",
+ (
+ "Unable to decode CFF table, possibly due to out "
+ "of ASCII range strings. Please check table strings."
+ ),
+ )