Check for dotted circle

CHANGELOG.md

@@ -8,6 +8,8 @@ A more detailed list of changes is available in the corresponding milestones for
   - Include most of the `googlefonts` profile checks. (PR #3579)
   - **[com.fontwerk/check/vendor_id]:** Vendor ID must for 'WERK' on FontWerk fonts. (PR #3579)
   - **[com.fontwerk/check/weight_class_fvar]:** usWeightclass must match fvar default value. (PR #3579)
+#### Added to the Universal Profile
+  - **[com.google.fonts/check/dotted_circle]:** Check dotted circle is present and correct (issue #3600)
 
 ### Changes to existing checks
 #### On the Google Fonts Profile

Lib/fontbakery/profiles/universal.py

@@ -62,7 +62,8 @@
         'com.google.fonts/check/unreachable_glyphs',
         'com.google.fonts/check/contour_count',
         'com.google.fonts/check/cjk_chws_feature',
-        'com.google.fonts/check/transformed_components'
+        'com.google.fonts/check/transformed_components',
+        'com.google.fonts/check/dotted_circle'
     ]
 
 
@@ -1413,5 +1414,77 @@ def com_google_fonts_check_transformed_components(ttFont):
         yield PASS, "No glyphs had components with scaling or rotation"
 
 
+@check(
+    id = 'com.google.fonts/check/dotted_circle',
+    conditions = ['is_ttf'],
+    severity = 3,
+    rationale = """
+        The dotted circle character (U+25CC) is inserted by shaping engines before mark glyphs which do not have an associated base, especially in the context of broken syllabic clusters.
+
+        For fonts containing combining marks, it is recommended that the dotted circle character be included so that these isolated marks can be displayed properly; for fonts supporting complex scripts, this should be considered mandatory.
+
+        Additionally, when a dotted circle glyph is present, it should be able to display all marks correctly, meaning that it should contain anchors for all attaching marks.
+    """,
+    proposal = 'https://github.com/googlefonts/fontbakery/issues/3600',
+)
+def com_google_fonts_check_dotted_circle(ttFont, config):
+    """Ensure dotted circle glyph is present and can attach marks."""
+    from fontbakery.utils import bullet_list, is_complex_shaper_font
+
+    mark_glyphs = []
+    if "GDEF" in ttFont and hasattr(ttFont["GDEF"].table, "GlyphClassDef"):
+      mark_glyphs = [k for k, v in ttFont["GDEF"].table.GlyphClassDef.classDefs.items() if v == 3]
+    # Only check for encoded
+    mark_glyphs = set(mark_glyphs) & set(ttFont.getBestCmap().values())
+    nonspacing_mark_glyphs = [g for g in mark_glyphs if ttFont["hmtx"][g][0] == 0]
+
+    if not nonspacing_mark_glyphs:
+        yield SKIP, "Font has no nonspacing mark glyphs."
+        return
+
+    if 0x25CC not in ttFont.getBestCmap():
+        # How bad is this?
+        if is_complex_shaper_font(ttFont):
+            yield FAIL, Message('missing-dotted-circle-complex',
+                          "No dotted circle glyph present and font uses a complex shaper")
+        else:
+            yield WARN, Message('missing-dotted-circle',
+                          "No dotted circle glyph present")
+        return
+
+    # Check they all attach to dotted circle if they attach to
+    # something else
+    dotted_circle = ttFont.getBestCmap()[0x25CC]
+    attachments = {dotted_circle: []}
+    does_attach = {}
+    if "GPOS" in ttFont and ttFont["GPOS"].table.LookupList:
+        def find_mark_base(lookup, attachments):
+            if lookup.LookupType == 9:
+                for xt in lookup.SubTable:
+                    xt.SubTable = [xt.ExtSubTable]
+                    xt.LookupType = xt.ExtSubTable.LookupType
+                    find_mark_base(xt, attachments)
+            if lookup.LookupType == 4:
+                # Assume all-to-all
+                for st in lookup.SubTable:
+                    for base in st.BaseCoverage.glyphs:
+                        for mark in st.MarkCoverage.glyphs:
+                            attachments.setdefault(base,[]).append(mark)
+                            does_attach[mark] = True
+
+        for lookup in ttFont["GPOS"].table.LookupList.Lookup:
+            find_mark_base(lookup, attachments)
+
+    unattached = []
+    for g in nonspacing_mark_glyphs:
+        if g in does_attach and g not in attachments[dotted_circle]:
+            unattached.append(g)
+    if unattached:
+        yield FAIL, Message("unattached-dotted-circle-marks",
+            "The following glyphs could not be attached to the dotted circle glyph:\n"+ bullet_list(config, unattached))
+    else:
+        yield PASS, "All marks were anchored to dotted circle"
+
+
 profile.auto_register(globals())
 profile.test_expected_checks(UNIVERSAL_PROFILE_CHECKS, exclusive=True)

Lib/fontbakery/utils.py

@@ -17,8 +17,10 @@
 import sys
 
 from fontTools.ttLib import TTFont
+from fontTools.unicodedata import ot_tag_to_script
 from typing import Text, Optional
 from fontbakery.constants import NO_COLORS_THEME, DARK_THEME, LIGHT_THEME
+from ufo2ft.constants import INDIC_SCRIPTS, USE_SCRIPTS
 from vharfbuzz import Vharfbuzz
 
 
@@ -544,3 +546,16 @@ def _invertClassDef(a, font):
                         for right in class2[ix2]:
                             rules.append((left, right, c2.Value1, c2.Value2))
     return rules
+
+
+def is_complex_shaper_font(ttFont):
+    for table in ["GSUB", "GPOS"]:
+        if table not in ttFont:
+            continue
+        for rec in ttFont[table].table.ScriptList.ScriptRecord:
+            script = ot_tag_to_script(rec.ScriptTag)
+            if script in USE_SCRIPTS or script in INDIC_SCRIPTS:
+                return True
+            if script in ["Khmr", "Mymr", "Hang"]:
+                return True
+    return False

requirements.txt

@@ -21,4 +21,5 @@ toml==0.10.2
 ufolint==1.2.0
 unicodedata2==14.0.0
 vharfbuzz==0.1.1
+ufo2ft==2.25.2
 -e .

setup.py

@@ -83,6 +83,7 @@
         'stringbrewer',
         'toml',
         'ufolint',
+        'ufo2ft>=2.25.2',  # 2.25.2 updated the script lists for Unicode 14.0
         'unicodedata2',
         'vharfbuzz',
     ],

tests/profiles/universal_test.py

@@ -905,3 +905,21 @@ def test_check_transformed_components():
     font = TEST_FILE("dm-sans-v1.100/DMSans-Regular.ttf")
     assert_results_contain(check(font),
                            FAIL, 'transformed-components')
+
+
+def test_check_dotted_circle():
+    """Ensure dotted circle glyph is present and can attach marks."""
+    check = CheckTester(universal_profile,
+                        "com.google.fonts/check/dotted_circle")
+
+    font = TEST_FILE("mada/Mada-Regular.ttf")
+    assert_PASS(check(font),
+                "with a good font...")
+
+    font = TEST_FILE("cabin/Cabin-Regular.ttf")
+    assert_results_contain(check(font),
+                "WARN", "missing-dotted-circle")
+
+    font = TEST_FILE("broken_markazitext/MarkaziText-VF.ttf")
+    assert_results_contain(check(font),
+                "FAIL", "unattached-dotted-circle-marks")