check/colorfont_tables: update conditions

CHANGELOG.md

@@ -5,7 +5,7 @@ A more detailed list of changes is available in the corresponding milestones for
 ## Upcoming release: 0.8.11 (2022-Oct-??)
 ### New Checks
 #### Added to the Google Fonts Profile
-  - **[com.google.fonts/check/colorfont_tables]:** Fonts must have neither or both the tables `COLR` and `SVG`. (issue #3886)
+  - **[com.google.fonts/check/colorfont_tables]:** Check if fonts contain the correct color tables. (issue #3886)
   - **[com.google.fonts/check/description/noto_has_article]:** Noto fonts must have an ARTICLE.en_us.html file. (issue #3841)
   - **[com.google.fonts/check/slant_direction]:** Check slant direction of outline to match values of slnt axis extrema. (PR #3910)
   - **[com.google.fonts/check/color_cpal_brightness]:** Warn if COLRv0 layers are colored too dark or too bright instead of foreground color. (PR #3908)

Lib/fontbakery/profiles/googlefonts.py

@@ -6220,34 +6220,43 @@ def com_google_fonts_check_metadata_category_hint(family_metadata):
 @check(
     id = "com.google.fonts/check/colorfont_tables",
     rationale = """
-        No one color font format supports all major user agents, but the combination
-        of COLR & SVG tables is pretty good.
+        Colr v0 fonts are widely supported in most browsers so they do not require
+        an SVG color table. However, Colr v1 is only well supported in Chrome so
+        we need to add an SVG table to these fonts.
 
-        A smart server could prune away one or the other based on user agent,
-        and a dumb server will at least have something that works.
-
-        Fonts that do not pass this check can be fixed with the maximum_color tool
-        available at https://github.com/googlefonts/nanoemoji
+        To add an SVG table, run the maximum_color tool in Nano Emoji,
+        https://github.com/googlefonts/nanoemoji
     """,
     proposal = 'https://github.com/googlefonts/fontbakery/issues/3886'
 )
 def com_google_fonts_check_colorfont_tables(ttFont):
-    """Fonts must have neither or both the tables 'COLR' and 'SVG '."""
-    SUGGESTED_FIX = ("To fix this, please run the font through the maximum_color tool"
-                     " that installs as part of the nanoemoji package"
-                     " (https://github.com/googlefonts/nanoemoji)")
-    if 'COLR' in ttFont.keys() and 'SVG ' not in ttFont.keys():
-        yield FAIL,\
-              Message('missing-table',
-                      "This is a color font (it has a 'COLR' table)"
-                      " but it lacks an 'SVG ' table. " + SUGGESTED_FIX)
-    elif 'COLR' not in ttFont.keys() and 'SVG ' in ttFont.keys():
-        yield FAIL,\
-              Message('missing-table',
-                      "This is a color font (it has a 'SVG ' table)"
-                      " but it lacks an 'COLR' table. " + SUGGESTED_FIX)
-    else:
-        yield PASS, "Looks good!"
+    """Check font has the expected color font tables"""
+    if "COLR" in ttFont:
+        colr_table = ttFont["COLR"]
+        if colr_table.version == 0 and "SVG " in ttFont:
+            yield FAIL, Message(
+                "drop-svg",
+                "Font has a COLR v0 table, which is already widely supported, "
+                "so the SVG table isn't needed."
+            )
+            return
+        elif colr_table.version == 1 and "SVG " not in ttFont:
+            yield FAIL, Message(
+                "add-svg",
+                "Font has COLRv1 but no SVG table; for CORLv1, we require "
+                "that an SVG table is present to support environments where "
+                "the former is not supported yet."
+            )
+            return
+    elif "SVG " in ttFont:
+        if "COLR" not in ttFont:
+            yield FAIL, Message(
+                "add-colr",
+                "Font only has an SVG table. Please add a COLR table as well. "
+            )
+            return
+    yield PASS, "Looks Good!"
+
 
 
 @check(

tests/profiles/googlefonts_test.py

@@ -4227,33 +4227,43 @@ def test_check_override_freetype_rasterizer(mock_import_error):
 
 
 def test_check_colorfont_tables():
-    """Fonts must have neither or both the tables 'COLR' and 'SVG '."""
+    """Fonts must have neither or both the tables 'COLR' and 'SVG'."""
+    from fontTools.ttLib import newTable
     check = CheckTester(googlefonts_profile,
                         "com.google.fonts/check/colorfont_tables")
 
     ttFont = TTFont(TEST_FILE("color_fonts/noto-glyf_colr_1.ttf"))
-    assert 'COLR' in ttFont.keys()
     assert 'SVG ' not in ttFont.keys()
+    assert 'COLR' in ttFont.keys()
+    # Check colr v1 font has an svg table. Will fail since font
+    # doesn't have one.
     assert_results_contain(check(ttFont),
-                           FAIL, 'missing-table',
+                           FAIL, 'add-svg',
                            'with a color font lacking SVG table')
 
     # Fake an SVG table:
-    ttFont["SVG "] = "fake!"
+    ttFont["SVG "] = newTable('SVG ')
     assert 'SVG ' in ttFont.keys()
     assert 'COLR' in ttFont.keys()
     assert_PASS(check(ttFont),
                 f'with a font containing both tables.')
 
-    # Now remove the COLR one:
+    # Now downgrade to colr table to v0:
+    ttFont["COLR"].version = 0
+    assert 'SVG ' in ttFont.keys()
+    assert_results_contain(check(ttFont),
+                           FAIL, 'drop-svg',
+                           'with a font which should not have an SVG table')
+
+    # Delete colr table and keep SVG:
     del ttFont["COLR"]
-    assert 'COLR' not in ttFont.keys()
     assert 'SVG ' in ttFont.keys()
+    assert 'COLR' not in ttFont.keys()
     assert_results_contain(check(ttFont),
-                           FAIL, 'missing-table',
-                           'with a font with SVG table but no COLR table.')
+                           FAIL, 'add-colr',
+                           'with a font which should have a COLR table')
 
-    # Finally, get rid of both:
+    #finally delete both color font tables
     del ttFont["SVG "]
     assert 'SVG ' not in ttFont.keys()
     assert 'COLR' not in ttFont.keys()