Fix arabic_high_hamza check

CHANGELOG.md

@@ -9,6 +9,7 @@ A more detailed list of changes is available in the corresponding milestones for
 ### Changes to existing checks
 ### On the Universal profile.
   - **[no_debugging_tables]** and **[vttclean]** are now merged into unwanted_tables. (issues #4972 and #4975)
+  - **[arabic_high_hamza]** now checks U+0674 ARABIC LETTER HIGH HAMZA and not U+0675 ARABIC LETTER HIGH HAMZA ALEF, and the size check of _high hamza_ is now a warning instead of a fauilre. (issue #4290)
 
 ### On the OpenType Profile
   - **[opentype/slant_direction]:** SKIP instead of ERROR if a font does not contain 'H' (PR #4969)

Lib/fontbakery/checks/arabic_high_hamza.py

@@ -1,4 +1,4 @@
-from fontbakery.prelude import FAIL, SKIP, Message, check
+from fontbakery.prelude import FAIL, SKIP, WARN, Message, check
 from fontbakery.utils import get_glyph_name
 
 
@@ -8,10 +8,10 @@
         "https://github.com/googlefonts/fontbakery/issues/4290",
     ],
     rationale="""
-        Many fonts incorrectly treat ARABIC LETTER HIGH HAMZA (U+0675) as a variant of
+        Many fonts incorrectly treat ARABIC LETTER HIGH HAMZA (U+0674) as a variant of
         ARABIC HAMZA ABOVE (U+0654) and make it a combining mark of the same size.
 
-        But U+0675 is a base letter and should be a variant of ARABIC LETTER HAMZA
+        But U+0674 is a base letter and should be a variant of ARABIC LETTER HAMZA
         (U+0621) but raised slightly above baseline.
 
         Not doing so effectively makes the font useless for Jawi and
@@ -20,37 +20,41 @@
     severity=4,
 )
 def check_arabic_high_hamza(ttFont):
-    """Check that glyph for U+0675 ARABIC LETTER HIGH HAMZA is not a mark."""
+    """Check that glyph for U+0674 ARABIC LETTER HIGH HAMZA is not a mark."""
     from fontTools.pens.areaPen import AreaPen
     from copy import deepcopy
 
-    # This check modifies the font file with `.draw(pen)`
-    # so here we'll work with a copy of the object so that we
-    # do not affect other checks:
-    ttFont_copy = deepcopy(ttFont)
-
     ARABIC_LETTER_HAMZA = 0x0621
-    ARABIC_LETTER_HIGH_HAMZA = 0x0675
+    ARABIC_LETTER_HIGH_HAMZA = 0x0674
 
-    cmap = ttFont_copy.getBestCmap()
-    if ARABIC_LETTER_HAMZA not in cmap or ARABIC_LETTER_HIGH_HAMZA not in cmap:
+    cmap = ttFont.getBestCmap()
+    if ARABIC_LETTER_HIGH_HAMZA not in cmap:
         yield SKIP, Message(
             "glyphs-missing",
-            "This check will only run on fonts that have both glyphs U+0621 and U+0675",
+            "This check will only run on fonts that have U+0674 glyph",
         )
         return
 
-    if "GDEF" in ttFont_copy and ttFont_copy["GDEF"].table.GlyphClassDef:
-        class_def = ttFont_copy["GDEF"].table.GlyphClassDef.classDefs
-        reverseCmap = ttFont_copy["cmap"].buildReversed()
-        glyphOrder = ttFont_copy.getGlyphOrder()
-        for name in glyphOrder:
-            if ARABIC_LETTER_HIGH_HAMZA in reverseCmap.get(name, set()):
-                if name in class_def and class_def[name] == 3:
-                    yield FAIL, Message(
-                        "mark-in-gdef",
-                        f'"{name}" is defined in GDEF as a mark (class 3).',
-                    )
+    if "GDEF" in ttFont and ttFont["GDEF"].table.GlyphClassDef:
+        class_def = ttFont["GDEF"].table.GlyphClassDef.classDefs
+        name = get_glyph_name(ttFont, ARABIC_LETTER_HIGH_HAMZA)
+        if name in class_def and class_def[name] == 3:
+            yield FAIL, Message(
+                "mark-in-gdef",
+                f'"{name}" is defined in GDEF as a mark (class 3).',
+            )
+
+    if ARABIC_LETTER_HAMZA not in cmap:
+        yield SKIP, Message(
+            "glyphs-missing",
+            "This check will only run on fonts that have both glyphs U+0621 and U+0674",
+        )
+        return
+
+    # This check modifies the font file with `.draw(pen)`
+    # so here we'll work with a copy of the object so that we
+    # do not affect other checks:
+    ttFont_copy = deepcopy(ttFont)
 
     # Also validate the bounding box of the glyph and compare
     # it to U+0621 expecting them to have roughly the same size
@@ -66,9 +70,9 @@ def check_arabic_high_hamza(ttFont):
     high_hamza_area = area_pen.value
 
     if abs((high_hamza_area - hamza_area) / hamza_area) > 0.1:
-        yield FAIL, Message(
+        yield WARN, Message(
             "glyph-area",
-            "The arabic letter high hamza (U+0675) should have roughly"
-            " the same size the arabic letter hamza (U+0621),"
-            " but a different glyph outline area was detected.",
+            "The arabic letter high hamza (U+0674) should have roughly"
+            " the same size the arabic letter hamza (U+0621) while raised"
+            " above baseline, but a different glyph outline area was detected.",
         )