New check: base_has_width

Check base characters have non-zero advance width.

Added to the Universal profile

Back-ported from FontSpector:
simoncozens/fontspector@564e18c

(issue #4906)

CHANGELOG.md

@@ -11,6 +11,9 @@ A more detailed list of changes is available in the corresponding milestones for
   - to implement a backwards compatibility mechanism
 
 ### New checks
+#### Added to the Universal profile
+  - **EXPERIMENTAL - [base_has_width]:** Check base characters have non-zero advance width. (issue #4906)
+
 #### Added to the OpenType profile
   - **[STAT/ital_axis]**: Replaces the old checks (**opentype/italic_axis_in_stat**, **opentype/italic_axis_in_stat_is_boolean** and **opentype/italic_axis_last**) from the same profile (issue #4865)
 

Lib/fontbakery/checks/base_has_width.py

@@ -0,0 +1,50 @@
+import unicodedata
+
+from fontbakery.prelude import check, Message, FAIL
+from fontbakery.utils import bullet_list, mark_glyphs
+
+
+def is_space(codepoint):
+    return unicodedata.category(chr(codepoint)) in [
+        "Zs",  # Space Separator
+        "Zl",  # Line Separator
+        "Zp",  # Paragraph Separator
+        "Cf",  # Format
+        "Mn",  # Nonspacing Mark
+        "Cc",  # Control
+    ]
+
+
+@check(
+    id="base_has_width",
+    rationale="""
+        Base characters should have non-zero advance width.
+    """,
+    proposal="https://github.com/fonttools/fontbakery/issues/4906",
+    experimental="Since 2024/12/28",
+)
+def check_base_has_width(font, context):
+    """Check base characters have non-zero advance width."""
+
+    reversed_cmap = {v: k for k, v in font.ttFont.getBestCmap().items()}
+
+    problems = []
+    for gid, metric in font.ttFont["hmtx"].metrics.items():
+        advance = metric[0]
+
+        codepoint = reversed_cmap.get(gid)
+        if codepoint == 0 or codepoint is None:
+            continue
+
+        if advance == 0 and not gid not in mark_glyphs(font.ttFont):
+            if is_space(codepoint):
+                continue
+
+            problems.append(f"{gid} (U+{codepoint:04X})")
+
+    if problems:
+        problems = bullet_list(context, problems)
+        yield FAIL, Message(
+            "zero-width-bases",
+            f"The following glyphs had zero advance width:\n{problems}",
+        )

Lib/fontbakery/checks/tabular_kerning.py

@@ -1,4 +1,5 @@
 from fontbakery.prelude import check, Message, FAIL, SKIP
+from fontbakery.utils import mark_glyphs
 
 
 @check(
@@ -159,16 +160,6 @@ def digraph_kerning(ttFont, glyph_list, expected_kerning):
             and get_kerning(glyph_list) == expected_kerning
         )
 
-    def mark_glyphs(ttFont):
-        marks = []
-        if "GDEF" in ttFont and ttFont["GDEF"].table.GlyphClassDef:
-            class_def = ttFont["GDEF"].table.GlyphClassDef.classDefs
-            glyphOrder = ttFont.getGlyphOrder()
-            for name in glyphOrder:
-                if name in class_def and class_def[name] == 3:
-                    marks.append(name)
-        return marks
-
     # Font has no numerals at all
     if not all([glyph_name_for_character(ttFont, c) for c in "0123456789"]):
         yield SKIP, "Font has no numerals at all"

Lib/fontbakery/profiles/adobefonts.py

@@ -43,6 +43,7 @@
         "alt_caron",
         "arabic_high_hamza",
         "arabic_spacing_symbols",
+        "base_has_width",
         "case_mapping",
         "cjk_chws_feature",  # was temporarily removed
         "cjk_not_enough_glyphs",

Lib/fontbakery/profiles/fontbureau.py

@@ -4,6 +4,7 @@
     "pending_review": [
         "opentype/weight_class_fvar",
         "opentype/slant_direction",
+        "base_has_width",
         "cjk_not_enough_glyphs",
         "cmap/format_12",
         "color_cpal_brightness",

Lib/fontbakery/profiles/fontwerk.py

@@ -18,6 +18,7 @@
     ],
     "pending_review": [
         "epar",
+        "base_has_width",
         "googlefonts/axes_match",
         "overlapping_path_segments",
         "typographic_family_name",

Lib/fontbakery/profiles/microsoft.py

@@ -11,6 +11,7 @@
         "opentype/slant_direction",
         "opentype/weight_class_fvar",
         #
+        "base_has_width",
         "cjk_not_enough_glyphs",
         "cmap/format_12",
         "color_cpal_brightness",

Lib/fontbakery/profiles/typenetwork.py

@@ -41,6 +41,7 @@
     ],
     "pending_review": [
         "epar",
+        "base_has_width",
     ],
     "sections": {
         "Type Network": [

Lib/fontbakery/profiles/universal.py

@@ -24,6 +24,7 @@
             "alt_caron",
             "arabic_high_hamza",
             "arabic_spacing_symbols",
+            "base_has_width",
             "caps_vertically_centered",
             "case_mapping",
             "cjk_chws_feature",

Lib/fontbakery/utils.py

@@ -849,3 +849,14 @@ def close_but_not_on(value_expected, value_true, tolerance):
     if abs(value_expected - value_true) <= tolerance:
         return True
     return False
+
+
+def mark_glyphs(ttFont):
+    marks = []
+    if "GDEF" in ttFont and ttFont["GDEF"].table.GlyphClassDef:
+        class_def = ttFont["GDEF"].table.GlyphClassDef.classDefs
+        glyphOrder = ttFont.getGlyphOrder()
+        for name in glyphOrder:
+            if name in class_def and class_def[name] == 3:
+                marks.append(name)
+    return marks