split out glyphset checks

Lib/fontbakery/checks/case_mapping.py

@@ -0,0 +1,80 @@
+from fontbakery.prelude import check, Message, FAIL
+
+
+@check(
+    id="case_mapping",
+    rationale="""
+        Ensure that no glyph lacks its corresponding upper or lower counterpart
+        (but only when unicode supports case-mapping).
+    """,
+    proposal="https://github.com/googlefonts/fontbakery/issues/3230",
+    severity=10,  # if a font shows tofu in caps but not in lowercase
+    #               then it can be considered broken.
+)
+def check_case_mapping(ttFont):
+    """Ensure the font supports case swapping for all its glyphs."""
+    import unicodedata
+    from fontbakery.utils import markdown_table
+
+    # These are a selection of codepoints for which the corresponding case-swap
+    # glyphs are missing way too often on the Google Fonts library,
+    # so we'll ignore for now:
+    EXCEPTIONS = [
+        0x0192,  # ƒ - Latin Small Letter F with Hook
+        0x00B5,  # µ - Micro Sign
+        0x03C0,  # π - Greek Small Letter Pi
+        0x2126,  # Ω - Ohm Sign
+        0x03BC,  # μ - Greek Small Letter Mu
+        0x03A9,  # Ω - Greek Capital Letter Omega
+        0x0394,  # Δ - Greek Capital Letter Delta
+        0x0251,  # ɑ - Latin Small Letter Alpha
+        0x0261,  # ɡ - Latin Small Letter Script G
+        0x00FF,  # ÿ - Latin Small Letter Y with Diaeresis
+        0x0250,  # ɐ - Latin Small Letter Turned A
+        0x025C,  # ɜ - Latin Small Letter Reversed Open E
+        0x0252,  # ɒ - Latin Small Letter Turned Alpha
+        0x0271,  # ɱ - Latin Small Letter M with Hook
+        0x0282,  # ʂ - Latin Small Letter S with Hook
+        0x029E,  # ʞ - Latin Small Letter Turned K
+        0x0287,  # ʇ - Latin Small Letter Turned T
+        0x0127,  # ħ - Latin Small Letter H with Stroke
+        0x0140,  # ŀ - Latin Small Letter L with Middle Dot
+        0x023F,  # ȿ - Latin Small Letter S with Swash Tail
+        0x0240,  # ɀ - Latin Small Letter Z with Swash Tail
+        0x026B,  # ɫ - Latin Small Letter L with Middle Tilde
+    ]
+
+    missing_counterparts_table = []
+    cmap = ttFont["cmap"].getBestCmap()
+    for codepoint in cmap:
+        if codepoint in EXCEPTIONS:
+            continue
+
+        # Only check letters
+        if unicodedata.category(chr(codepoint))[0] != "L":
+            continue
+
+        the_char = chr(codepoint)
+        swapped = the_char.swapcase()
+
+        # skip cases like 'ß' => 'SS'
+        if len(swapped) > 1:
+            continue
+
+        if the_char != swapped and ord(swapped) not in cmap:
+            name = unicodedata.name(the_char)
+            swapped_name = unicodedata.name(swapped)
+            row = {
+                "Glyph present in the font": f"U+{codepoint:04X}: {name}",
+                "Missing case-swapping counterpart": (
+                    f"U+{ord(swapped):04X}: {swapped_name}"
+                ),
+            }
+            missing_counterparts_table.append(row)
+
+    if missing_counterparts_table:
+        yield FAIL, Message(
+            "missing-case-counterparts",
+            f"The following glyphs lack their case-swapping counterparts:\n\n"
+            f"{markdown_table(missing_counterparts_table)}\n\n",
+        )

Lib/fontbakery/checks/control_chars.py

@@ -0,0 +1,32 @@
+from fontbakery.prelude import check, Message, FAIL
+
+
+@check(
+    id="control_chars",
+    conditions=["are_ttf"],
+    rationale="""
+        Use of some unacceptable control characters in the U+0000 - U+001F range can
+        lead to rendering issues on some platforms.
+
+        Acceptable control characters are defined as .null (U+0000) and
+        CR (U+000D) for this check.
+    """,
+    proposal="https://github.com/fonttools/fontbakery/pull/2430",
+)
+def check_family_control_chars(ttFont):
+    """Does font file include unacceptable control character glyphs?"""
+    # list of unacceptable control character glyph names
+    # definition includes the entire control character Unicode block except:
+    #    - .null (U+0000)
+    #    - CR (U+000D)
+    UNACCEPTABLE_CC = {f"uni{n:04X}" for n in range(32) if n not in [0x00, 0x0D]}
+
+    glyphset = set(ttFont["glyf"].glyphs.keys())
+    bad_glyphs = glyphset.intersection(UNACCEPTABLE_CC)
+
+    if bad_glyphs:
+        bad = ", ".join(bad_glyphs)
+        yield FAIL, Message(
+            "unacceptable",
+            f"The following unacceptable control characters were identified:\n{bad}",
+        )