Merge pull request #819 from googlefonts/math-table

outlineCompiler: Support generating MATH table

Lib/ufo2ft/constants.py

@@ -43,6 +43,11 @@ class CFFOptimization(IntEnum):
 # ]
 COLR_CLIP_BOXES_KEY = UFO2FT_PREFIX + "colrClipBoxes"
 
+GLYPHS_MATH_PREFIX = "com.nagwa.MATHPlugin."
+GLYPHS_MATH_CONSTANTS_KEY = GLYPHS_MATH_PREFIX + "constants"
+GLYPHS_MATH_VARIANTS_KEY = GLYPHS_MATH_PREFIX + "variants"
+GLYPHS_MATH_EXTENDED_SHAPE_KEY = GLYPHS_MATH_PREFIX + "extendedShape"
+
 OBJECT_LIBS_KEY = "public.objectLibs"
 OPENTYPE_CATEGORIES_KEY = "public.openTypeCategories"
 OPENTYPE_META_KEY = "public.openTypeMeta"

Lib/ufo2ft/outlineCompiler.py

@@ -30,6 +30,10 @@
     COLOR_LAYERS_KEY,
     COLOR_PALETTES_KEY,
     COLR_CLIP_BOXES_KEY,
+    GLYPHS_MATH_CONSTANTS_KEY,
+    GLYPHS_MATH_EXTENDED_SHAPE_KEY,
+    GLYPHS_MATH_PREFIX,
+    GLYPHS_MATH_VARIANTS_KEY,
     OPENTYPE_META_KEY,
     OPENTYPE_POST_UNDERLINE_POSITION_KEY,
     UNICODE_VARIATION_SEQUENCES_KEY,
@@ -94,6 +98,7 @@ class BaseOutlineCompiler:
             "vhea",
             "COLR",
             "CPAL",
+            "MATH",
             "meta",
         ]
     )
@@ -175,6 +180,8 @@ def compile(self):
             self.setupTable_CPAL()
         if self.meta:
             self.setupTable_meta()
+        if any(key.startswith(GLYPHS_MATH_PREFIX) for key in self.ufo.lib):
+            self.setupTable_MATH()
         self.setupOtherTables()
         if self.colorLayers and self.colrAutoClipBoxes:
             self._computeCOLRClipBoxes()
@@ -1050,6 +1057,181 @@ def setupTable_meta(self):
                     f"public.openTypeMeta '{key}' value should be bytes or a string."
                 )
 
+    def _bboxWidth(self, glyph):
+        bbox = self.glyphBoundingBoxes[glyph]
+        if bbox is None:
+            return 0
+        return bbox.xMax - bbox.xMin
+
+    def _bboxHeight(self, glyph):
+        bbox = self.glyphBoundingBoxes[glyph]
+        if bbox is None:
+            return 0
+        return bbox.yMax - bbox.yMin
+
+    def setupTable_MATH(self):
+        """
+        This builds MATH table based on data in the UFO font. The data is stored
+        either in private font/glyph lib keys or as glyph anchors with specific
+        names.
+
+        The data is based on GlyphsApp MATH plugin data as written out by
+        glyphsLib to the UFO font.
+
+        The font lib keys are:
+            - com.nagwa.MATHPlugin.constants: a dictionary of MATH constants as
+              expected by fontTools.otlLib.builder.buildMathTable(). Example:
+
+                ufo.lib["com.nagwa.MATHPlugin.constants"] = {
+                    "ScriptPercentScaleDown": 70,
+                    "ScriptScriptPercentScaleDown": 60,
+                    ...
+                }
+
+            - com.nagwa.MATHPlugin.extendedShape: a list of glyph names that
+              are extended shapes. Example:
+
+                ufo.lib["com.nagwa.MATHPlugin.extendedShapes"] = ["integral", "radical"]
+
+        The glyph lib keys are:
+            - com.nagwa.MATHPlugin.variants: a dictionary of MATH glyph variants
+              keyed by glyph names, and each value is a dictionary with keys
+              "hVariants", "vVariants", "hAssembly", and "vAssembly". Example:
+
+                ufo["braceleft"].lib["com.nagwa.MATHPlugin.variants"] = {
+                    "vVariants": ["braceleft", "braceleft.s1", "braceleft.s2"],
+                    "vAssembly": [
+                        # glyph name, flags, start connector length, end connector length
+                        ["braceleft.bottom", 0, 0, 200],
+                        ["braceleft.extender", 1, 200, 200],
+                        ["braceleft.middle", 0, 100, 100],
+                        ["braceleft.extender", 1, 200, 200],
+                        ["braceleft.top", 0, 200, 0],
+                    ],
+                }
+
+        The anchors are:
+            - math.ic: italic correction anchor
+            - math.ta: top accent attachment anchor
+            - math.tr*: top right kerning anchors
+            - math.tl*: top left kerning anchors
+            - math.br*: bottom right kerning anchors
+            - math.bl*: bottom left kerning anchors
+        """
+        if "MATH" not in self.tables:
+            return
+
+        from fontTools.otlLib.builder import buildMathTable
+
+        ufo = self.ufo
+        constants = ufo.lib.get(GLYPHS_MATH_CONSTANTS_KEY)
+        min_connector_overlap = constants.pop("MinConnectorOverlap", 0)
+
+        italics_correction = {}
+        top_accent_attachment = {}
+        math_kerns = {}
+        kerning_sides = {
+            "tr": "TopRight",
+            "tl": "TopLeft",
+            "br": "BottomRight",
+            "bl": "BottomLeft",
+        }
+        for name, glyph in self.allGlyphs.items():
+            kerns = {}
+            for anchor in glyph.anchors:
+                if anchor.name == "math.ic":
+                    # The anchor x position is absolute, but we want
+                    # a value relative to the glyph's width.
+                    italics_correction[name] = anchor.x - glyph.width
+                if anchor.name == "math.ta":
+                    top_accent_attachment[name] = anchor.x
+                for aName in kerning_sides.keys():
+                    if anchor.name.startswith(f"math.{aName}"):
+                        side = kerning_sides[aName]
+                        # The anchor x positions are absolute, but we want
+                        # values relative to the glyph's width/origin.
+                        x, y = anchor.x, anchor.y
+                        if side.endswith("Right"):
+                            x -= glyph.width
+                        elif side.endswith("Left"):
+                            x = -x
+                        kerns.setdefault(side, []).append([x, y])
+            if kerns:
+                math_kerns[name] = {}
+                # Convert anchor positions to correction heights and kern
+                # values.
+                for side, pts in kerns.items():
+                    pts = sorted(pts, key=lambda pt: pt[1])
+                    # Y positions, the last one is ignored as the last kern
+                    # value is applied to all heights greater than the last one.
+                    correctionHeights = [pt[1] for pt in pts[:-1]]
+                    # X positions
+                    kernValues = [pt[0] for pt in pts]
+                    math_kerns[name][side] = (correctionHeights, kernValues)
+
+        # buildMathTable takes two dictionaries of glyph variants, one for
+        # horizontal variants and one for vertical variants, and items are
+        # tuples of glyph name and the advance width/height of the variant.
+        # Here we convert the UFO data to the expected format and measure the
+        # advances.
+        h_variants = {}
+        v_variants = {}
+        # It also takes two dictionaries of glyph assemblies, one for
+        # horizontal assemblies and one for vertical assemblies, and items are
+        # lists of tuples of assembly parts and italics correction, and the
+        # assembly part includes the advance width/height of the part. Here we
+        # convert the UFO data to the expected format and measure the advances.
+        h_assemblies = {}
+        v_assemblies = {}
+        for name, glyph in self.allGlyphs.items():
+            if GLYPHS_MATH_VARIANTS_KEY in glyph.lib:
+                variants = glyph.lib[GLYPHS_MATH_VARIANTS_KEY]
+                if "hVariants" in variants:
+                    h_variants[name] = [
+                        (n, self._bboxWidth(n)) for n in variants["hVariants"]
+                    ]
+                if "vVariants" in variants:
+                    v_variants[name] = [
+                        (n, self._bboxHeight(n)) for n in variants["vVariants"]
+                    ]
+                if "hAssembly" in variants:
+                    parts = variants["hAssembly"]
+                    h_assemblies[name] = (
+                        [(*part, self._bboxWidth(part[0])) for part in parts],
+                        # If the last part has italic correction, we use it as
+                        # the assembly's.
+                        italics_correction.pop(parts[-1][0], 0),
+                    )
+                if "vAssembly" in variants:
+                    parts = variants["vAssembly"]
+                    v_assemblies[name] = (
+                        [(*part, self._bboxHeight(part[0])) for part in parts],
+                        # If the last part has italic correction, we use it as
+                        # the assembly's.
+                        italics_correction.pop(parts[-1][0], 0),
+                    )
+
+        # Collect the set of extended shapes, and if a shape has vertical
+        # variants, add the variants to the set.
+        extended_shapes = set(ufo.lib.get(GLYPHS_MATH_EXTENDED_SHAPE_KEY, []))
+        for name, variants in v_variants.items():
+            if name in extended_shapes:
+                extended_shapes.update(v[0] for v in variants)
+
+        buildMathTable(
+            self.otf,
+            constants=constants,
+            italicsCorrections=italics_correction,
+            topAccentAttachments=top_accent_attachment,
+            extendedShapes=extended_shapes,
+            mathKerns=math_kerns,
+            minConnectorOverlap=min_connector_overlap,
+            vertGlyphVariants=v_variants,
+            horizGlyphVariants=h_variants,
+            vertGlyphAssembly=v_assemblies,
+            horizGlyphAssembly=h_assemblies,
+        )
+
     def setupOtherTables(self):
         """
         Make the other tables. The default implementation does nothing.
@@ -1652,6 +1834,7 @@ def __init__(
             self.draw = self._drawDefaultNotdef
             self.drawPoints = self._drawDefaultNotdefPoints
         self.reverseContour = reverseContour
+        self.lib = {}
 
     def __len__(self):
         if self.name == ".notdef":

requirements.txt

@@ -1,4 +1,4 @@
-fonttools[ufo,lxml]==4.48.1
+fonttools[ufo,lxml]==4.49.0
 defcon==0.10.3
 compreffor==0.5.5
 booleanOperations==0.9.0

setup.py

@@ -29,7 +29,7 @@
     setup_requires=pytest_runner + wheel + ["setuptools_scm"],
     tests_require=["pytest>=2.8"],
     install_requires=[
-        "fonttools[ufo]>=4.47.2",
+        "fonttools[ufo]>=4.49.0",
         "cffsubr>=0.3.0",
         "booleanOperations>=0.9.0",
     ],

tests/data/TestMathFont-Regular.ufo/features.fea

@@ -0,0 +1,4 @@
+# Prefix: Languagesystems
+languagesystem DFLT dflt;
+languagesystem math dflt;
+

tests/data/TestMathFont-Regular.ufo/fontinfo.plist

@@ -0,0 +1,46 @@
+<?xml version='1.0' encoding='UTF-8'?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+  <dict>
+    <key>ascender</key>
+    <integer>800</integer>
+    <key>capHeight</key>
+    <integer>656</integer>
+    <key>descender</key>
+    <integer>-200</integer>
+    <key>familyName</key>
+    <string>Test Math Font</string>
+    <key>italicAngle</key>
+    <integer>0</integer>
+    <key>openTypeHeadCreated</key>
+    <string>2024/02/12 18:20:25</string>
+    <key>openTypeOS2Type</key>
+    <array>
+      <integer>3</integer>
+    </array>
+    <key>postscriptBlueValues</key>
+    <array>
+      <integer>-18</integer>
+      <integer>0</integer>
+    </array>
+    <key>postscriptOtherBlues</key>
+    <array>
+      <integer>-201</integer>
+      <integer>-200</integer>
+    </array>
+    <key>postscriptUnderlinePosition</key>
+    <integer>-150</integer>
+    <key>postscriptUnderlineThickness</key>
+    <integer>50</integer>
+    <key>styleName</key>
+    <string>Regular</string>
+    <key>unitsPerEm</key>
+    <integer>1000</integer>
+    <key>versionMajor</key>
+    <integer>1</integer>
+    <key>versionMinor</key>
+    <integer>0</integer>
+    <key>xHeight</key>
+    <integer>449</integer>
+  </dict>
+</plist>

tests/data/TestMathFont-Regular.ufo/glyphs/contents.plist

@@ -0,0 +1,38 @@
+<?xml version='1.0' encoding='UTF-8'?>
+<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+<plist version="1.0">
+  <dict>
+    <key>parenleft</key>
+    <string>parenleft.glif</string>
+    <key>parenleft.bot</key>
+    <string>parenleft.bot.glif</string>
+    <key>parenleft.ext</key>
+    <string>parenleft.ext.glif</string>
+    <key>parenleft.size1</key>
+    <string>parenleft.size1.glif</string>
+    <key>parenleft.size2</key>
+    <string>parenleft.size2.glif</string>
+    <key>parenleft.size3</key>
+    <string>parenleft.size3.glif</string>
+    <key>parenleft.size4</key>
+    <string>parenleft.size4.glif</string>
+    <key>parenleft.top</key>
+    <string>parenleft.top.glif</string>
+    <key>parenright</key>
+    <string>parenright.glif</string>
+    <key>parenright.bot</key>
+    <string>parenright.bot.glif</string>
+    <key>parenright.ext</key>
+    <string>parenright.ext.glif</string>
+    <key>parenright.size1</key>
+    <string>parenright.size1.glif</string>
+    <key>parenright.size2</key>
+    <string>parenright.size2.glif</string>
+    <key>parenright.size3</key>
+    <string>parenright.size3.glif</string>
+    <key>parenright.size4</key>
+    <string>parenright.size4.glif</string>
+    <key>parenright.top</key>
+    <string>parenright.top.glif</string>
+  </dict>
+</plist>

tests/data/TestMathFont-Regular.ufo/glyphs/parenleft.bot.glif

@@ -0,0 +1,18 @@
+<?xml version='1.0' encoding='UTF-8'?>
+<glyph name="parenleft.bot" format="2">
+  <advance width="645"/>
+  <outline>
+    <contour>
+      <point x="595" y="-1129" type="line"/>
+      <point x="291" y="-729"/>
+      <point x="136" y="-184"/>
+      <point x="136" y="373" type="curve" smooth="yes"/>
+      <point x="136" y="687" type="line"/>
+      <point x="90" y="687" type="line"/>
+      <point x="90" y="373" type="line" smooth="yes"/>
+      <point x="90" y="-192"/>
+      <point x="247" y="-749"/>
+      <point x="559" y="-1157" type="curve"/>
+    </contour>
+  </outline>
+</glyph>

tests/data/TestMathFont-Regular.ufo/glyphs/parenleft.ext.glif

@@ -0,0 +1,12 @@
+<?xml version='1.0' encoding='UTF-8'?>
+<glyph name="parenleft.ext" format="2">
+  <advance width="645"/>
+  <outline>
+    <contour>
+      <point x="136" y="0" type="line"/>
+      <point x="136" y="800" type="line"/>
+      <point x="90" y="800" type="line"/>
+      <point x="90" y="0" type="line"/>
+    </contour>
+  </outline>
+</glyph>