Merge branch 'main' into new-check-CPAL-brightness

Author: felipesanches

CHANGELOG.md

@@ -2,16 +2,17 @@ Below are the most important changes from each release.
 A more detailed list of changes is available in the corresponding milestones for each release in the Github issue tracker (https://github.com/googlefonts/fontbakery/milestones?state=closed).
 
 
-## Upcoming release: 0.8.11 (2022-Sep-??)
+## 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/description/noto_has_article]:** Noto fonts must have an ARTICLE.en_us.html file. (issue #3841)
-  - **[com.google.fonts/check/color_cpal_brightness]:** Warn if COLRv0 layers are colored too dark or too bright instead of foreground color
+  - **[com.google.fonts/check/color_cpal_brightness]:** Warn if COLRv0 layers are colored too dark or too bright instead of foreground color (PR #3908)
+  - **[com.google.fonts/check/slant_direction]:** Check slant direction of outline to match values of slnt axis extrema. (PR #3910)
 
 ### BugFixes
   - **[com.adobe.fonts/check/varfont/valid_default_instance_nameids]:** The check did not account for nameID 17. (issue #3895)
-  - **[com.google.fonts/check/colorfont_tables]:** Check for four-digit 'SVG ' table instead of 'SVG'
+  - **[com.google.fonts/check/colorfont_tables]:** Check for four-digit 'SVG ' table instead of 'SVG' (PR #3903)
   - Added a `--timeout` parameter and set timeouts on all network requests. (PR #3892)
 
 ### Changes to existing checks

Lib/fontbakery/profiles/googlefonts.py

@@ -158,6 +158,7 @@
     'com.google.fonts/check/epar',
     'com.google.fonts/check/font_copyright',
     'com.google.fonts/check/italic_angle',
+    'com.google.fonts/check/slant_direction',
     'com.google.fonts/check/has_ttfautohint_params',
     'com.google.fonts/check/name/version_format',
     'com.google.fonts/check/name/familyname_first_char',
@@ -3164,6 +3165,65 @@ def com_google_fonts_check_italic_angle(ttFont, style):
                      f' with style="{style}".')
 
 
+@condition
+def uharfbuzz_blob(font):
+    import uharfbuzz as hb
+    return hb.Blob.from_file_path(font)
+
+
+@check(
+    id = 'com.google.fonts/check/slant_direction',
+    conditions = ['is_variable_font'],
+    rationale = """
+        The 'slnt' axis values are defined as negative values for a clockwise (right)
+        lean, and positive values for counter-clockwise lean. This is counter-intuitive
+        for many designers who are used to think of a positive slant as a lean to
+        the right.
+
+        This check ensures that the slant axis direction is consistent with the specs.
+
+        https://docs.microsoft.com/en-us/typography/opentype/spec/dvaraxistag_slnt
+    """,
+    proposal = 'https://github.com/googlefonts/fontbakery/pull/3910'
+)
+def com_google_fonts_check_slant_direction(ttFont, uharfbuzz_blob):
+    """Checking direction of slnt axis angles"""
+    from fontbakery.utils import (axis,
+                                  PointsPen)
+    import uharfbuzz as hb
+
+    if not axis(ttFont, 'slnt'):
+        return PASS, "Font has no slnt axis"
+
+    hb_face = hb.Face(uharfbuzz_blob)
+    hb_font = hb.Font(hb_face)
+    buf = hb.Buffer()
+    buf.add_str("H")
+    features = {"kern": True,
+                "liga": True}
+    hb.shape(hb_font, buf, features)
+
+    def x_delta(slant):
+        """
+        Return the x delta (difference of x position between highest and lowest point)
+        for the given slant value.
+        """
+        hb_font.set_variations({"slnt": slant})
+        pen = PointsPen()
+        hb_font.draw_glyph_with_pen(buf.glyph_infos[0].codepoint, pen)
+        x_delta = pen.highestPoint()[0] - pen.lowestPoint()[0]
+        return x_delta
+
+    if x_delta(axis(ttFont, 'slnt').minValue) < x_delta(axis(ttFont, 'slnt').maxValue):
+        yield FAIL,\
+              Message("positive-value-for-clockwise-lean",
+                      "The right-leaning glyphs have a positive 'slnt' axis value,"
+                      " which is likely a mistake. It needs to be negative"
+                      " to lean rightwards.")
+    else:
+        yield PASS, "Angle of 'slnt' axis looks good."
+
+
 @check(
     id = 'com.google.fonts/check/mac_style',
     conditions = ['style'],

Lib/fontbakery/utils.py

@@ -653,4 +653,59 @@ def iterate_lookup_list_with_extensions(ttFont, table, callback, *args):
             callback(lookup, *args)
 
 
-
+def axis(ttFont, tag):
+    """Return the axis with the given tag."""
+    for axis in ttFont["fvar"].axes:
+        if axis.axisTag == tag:
+            return axis
+
+
+from fontTools.pens.basePen import BasePen
+class PointsPen(BasePen):
+    def __init__(self):
+        super().__init__()
+        self.points = []
+
+    def _moveTo(self, pt):
+        self.points.append(pt)
+
+    def _lineTo(self, pt):
+        self.points.append(pt)
+
+    def _curveToOne(self, pt1, pt2, pt3):
+        self.points.append(pt1)
+        self.points.append(pt2)
+        self.points.append(pt3)
+
+    def _qCurveToOne(self, pt1, pt2):
+        self.points.append(pt1)
+        self.points.append(pt2)
+
+    def _closePath(self):
+        pass
+
+    def _endPath(self):
+        self.points = []
+        self.beginPath()
+
+    def getPoints(self):
+        return self.points
+
+    def highestPoint(self):
+        highest = None
+        for p in self.points:
+            if (highest is None
+                or p[1] > highest[1]): # pylint: disable=unsubscriptable-object
+                highest = p
+        return highest
+
+    def lowestPoint(self):
+        lowest = None
+        for p in self.points:
+            if (lowest is None
+                or p[1] < lowest[1]): # pylint: disable=unsubscriptable-object
+                lowest = p
+        return lowest
+
+    def _addComponent(self, glyphName, transformation):
+        self.glyphSet[glyphName].draw(self)

data/test/slant_direction/Cairo_correct_slnt_axis.ttf

@@ -2298,6 +2298,19 @@ def test_check_italic_angle():
                         f'with italic-angle:{value} style:{style}...')
 
 
+def test_check_slant_direction():
+    """Checking direction of slnt axis angles"""
+    check = CheckTester(googlefonts_profile,
+                        "com.google.fonts/check/slant_direction")
+
+    font = TEST_FILE("slant_direction/Cairo_correct_slnt_axis.ttf")
+    assert_PASS(check(font))
+
+    font = TEST_FILE("slant_direction/Cairo_wrong_slnt_axis.ttf")
+    assert_results_contain(check(font),
+                           FAIL, 'positive-value-for-clockwise-lean')
+
+
 def test_check_mac_style():
     """ Checking head.macStyle value. """
     check = CheckTester(googlefonts_profile,