KIKIMR-19287: add task_stats_drawing script

1 files changed, 1711 insertions, 0 deletions

diff --git a/contrib/python/fonttools/fontTools/feaLib/builder.py b/contrib/python/fonttools/fontTools/feaLib/builder.py
new file mode 100644
index 00000000000..cfaf54d4d1f
--- /dev/null
+++ b/contrib/python/fonttools/fontTools/feaLib/builder.py
@@ -0,0 +1,1711 @@
+from fontTools.misc import sstruct
+from fontTools.misc.textTools import Tag, tostr, binary2num, safeEval
+from fontTools.feaLib.error import FeatureLibError
+from fontTools.feaLib.lookupDebugInfo import (
+    LookupDebugInfo,
+    LOOKUP_DEBUG_INFO_KEY,
+    LOOKUP_DEBUG_ENV_VAR,
+)
+from fontTools.feaLib.parser import Parser
+from fontTools.feaLib.ast import FeatureFile
+from fontTools.feaLib.variableScalar import VariableScalar
+from fontTools.otlLib import builder as otl
+from fontTools.otlLib.maxContextCalc import maxCtxFont
+from fontTools.ttLib import newTable, getTableModule
+from fontTools.ttLib.tables import otBase, otTables
+from fontTools.otlLib.builder import (
+    AlternateSubstBuilder,
+    ChainContextPosBuilder,
+    ChainContextSubstBuilder,
+    LigatureSubstBuilder,
+    MultipleSubstBuilder,
+    CursivePosBuilder,
+    MarkBasePosBuilder,
+    MarkLigPosBuilder,
+    MarkMarkPosBuilder,
+    ReverseChainSingleSubstBuilder,
+    SingleSubstBuilder,
+    ClassPairPosSubtableBuilder,
+    PairPosBuilder,
+    SinglePosBuilder,
+    ChainContextualRule,
+)
+from fontTools.otlLib.error import OpenTypeLibError
+from fontTools.varLib.varStore import OnlineVarStoreBuilder
+from fontTools.varLib.builder import buildVarDevTable
+from fontTools.varLib.featureVars import addFeatureVariationsRaw
+from fontTools.varLib.models import normalizeValue, piecewiseLinearMap
+from collections import defaultdict
+import itertools
+from io import StringIO
+import logging
+import warnings
+import os
+
+
+log = logging.getLogger(__name__)
+
+
+def addOpenTypeFeatures(font, featurefile, tables=None, debug=False):
+    """Add features from a file to a font. Note that this replaces any features
+    currently present.
+
+    Args:
+        font (feaLib.ttLib.TTFont): The font object.
+        featurefile: Either a path or file object (in which case we
+            parse it into an AST), or a pre-parsed AST instance.
+        tables: If passed, restrict the set of affected tables to those in the
+            list.
+        debug: Whether to add source debugging information to the font in the
+            ``Debg`` table
+
+    """
+    builder = Builder(font, featurefile)
+    builder.build(tables=tables, debug=debug)
+
+
+def addOpenTypeFeaturesFromString(
+    font, features, filename=None, tables=None, debug=False
+):
+    """Add features from a string to a font. Note that this replaces any
+    features currently present.
+
+    Args:
+        font (feaLib.ttLib.TTFont): The font object.
+        features: A string containing feature code.
+        filename: The directory containing ``filename`` is used as the root of
+            relative ``include()`` paths; if ``None`` is provided, the current
+            directory is assumed.
+        tables: If passed, restrict the set of affected tables to those in the
+            list.
+        debug: Whether to add source debugging information to the font in the
+            ``Debg`` table
+
+    """
+
+    featurefile = StringIO(tostr(features))
+    if filename:
+        featurefile.name = filename
+    addOpenTypeFeatures(font, featurefile, tables=tables, debug=debug)
+
+
+class Builder(object):
+    supportedTables = frozenset(
+        Tag(tag)
+        for tag in [
+            "BASE",
+            "GDEF",
+            "GPOS",
+            "GSUB",
+            "OS/2",
+            "head",
+            "hhea",
+            "name",
+            "vhea",
+            "STAT",
+        ]
+    )
+
+    def __init__(self, font, featurefile):
+        self.font = font
+        # 'featurefile' can be either a path or file object (in which case we
+        # parse it into an AST), or a pre-parsed AST instance
+        if isinstance(featurefile, FeatureFile):
+            self.parseTree, self.file = featurefile, None
+        else:
+            self.parseTree, self.file = None, featurefile
+        self.glyphMap = font.getReverseGlyphMap()
+        self.varstorebuilder = None
+        if "fvar" in font:
+            self.axes = font["fvar"].axes
+            self.varstorebuilder = OnlineVarStoreBuilder(
+                [ax.axisTag for ax in self.axes]
+            )
+        self.default_language_systems_ = set()
+        self.script_ = None
+        self.lookupflag_ = 0
+        self.lookupflag_markFilterSet_ = None
+        self.language_systems = set()
+        self.seen_non_DFLT_script_ = False
+        self.named_lookups_ = {}
+        self.cur_lookup_ = None
+        self.cur_lookup_name_ = None
+        self.cur_feature_name_ = None
+        self.lookups_ = []
+        self.lookup_locations = {"GSUB": {}, "GPOS": {}}
+        self.features_ = {}  # ('latn', 'DEU ', 'smcp') --> [LookupBuilder*]
+        self.required_features_ = {}  # ('latn', 'DEU ') --> 'scmp'
+        self.feature_variations_ = {}
+        # for feature 'aalt'
+        self.aalt_features_ = []  # [(location, featureName)*], for 'aalt'
+        self.aalt_location_ = None
+        self.aalt_alternates_ = {}
+        # for 'featureNames'
+        self.featureNames_ = set()
+        self.featureNames_ids_ = {}
+        # for 'cvParameters'
+        self.cv_parameters_ = set()
+        self.cv_parameters_ids_ = {}
+        self.cv_num_named_params_ = {}
+        self.cv_characters_ = defaultdict(list)
+        # for feature 'size'
+        self.size_parameters_ = None
+        # for table 'head'
+        self.fontRevision_ = None  # 2.71
+        # for table 'name'
+        self.names_ = []
+        # for table 'BASE'
+        self.base_horiz_axis_ = None
+        self.base_vert_axis_ = None
+        # for table 'GDEF'
+        self.attachPoints_ = {}  # "a" --> {3, 7}
+        self.ligCaretCoords_ = {}  # "f_f_i" --> {300, 600}
+        self.ligCaretPoints_ = {}  # "f_f_i" --> {3, 7}
+        self.glyphClassDefs_ = {}  # "fi" --> (2, (file, line, column))
+        self.markAttach_ = {}  # "acute" --> (4, (file, line, column))
+        self.markAttachClassID_ = {}  # frozenset({"acute", "grave"}) --> 4
+        self.markFilterSets_ = {}  # frozenset({"acute", "grave"}) --> 4
+        # for table 'OS/2'
+        self.os2_ = {}
+        # for table 'hhea'
+        self.hhea_ = {}
+        # for table 'vhea'
+        self.vhea_ = {}
+        # for table 'STAT'
+        self.stat_ = {}
+        # for conditionsets
+        self.conditionsets_ = {}
+        # We will often use exactly the same locations (i.e. the font's masters)
+        # for a large number of variable scalars. Instead of creating a model
+        # for each, let's share the models.
+        self.model_cache = {}
+
+    def build(self, tables=None, debug=False):
+        if self.parseTree is None:
+            self.parseTree = Parser(self.file, self.glyphMap).parse()
+        self.parseTree.build(self)
+        # by default, build all the supported tables
+        if tables is None:
+            tables = self.supportedTables
+        else:
+            tables = frozenset(tables)
+            unsupported = tables - self.supportedTables
+            if unsupported:
+                unsupported_string = ", ".join(sorted(unsupported))
+                raise NotImplementedError(
+                    "The following tables were requested but are unsupported: "
+                    f"{unsupported_string}."
+                )
+        if "GSUB" in tables:
+            self.build_feature_aalt_()
+        if "head" in tables:
+            self.build_head()
+        if "hhea" in tables:
+            self.build_hhea()
+        if "vhea" in tables:
+            self.build_vhea()
+        if "name" in tables:
+            self.build_name()
+        if "OS/2" in tables:
+            self.build_OS_2()
+        if "STAT" in tables:
+            self.build_STAT()
+        for tag in ("GPOS", "GSUB"):
+            if tag not in tables:
+                continue
+            table = self.makeTable(tag)
+            if self.feature_variations_:
+                self.makeFeatureVariations(table, tag)
+            if (
+                table.ScriptList.ScriptCount > 0
+                or table.FeatureList.FeatureCount > 0
+                or table.LookupList.LookupCount > 0
+            ):
+                fontTable = self.font[tag] = newTable(tag)
+                fontTable.table = table
+            elif tag in self.font:
+                del self.font[tag]
+        if any(tag in self.font for tag in ("GPOS", "GSUB")) and "OS/2" in self.font:
+            self.font["OS/2"].usMaxContext = maxCtxFont(self.font)
+        if "GDEF" in tables:
+            gdef = self.buildGDEF()
+            if gdef:
+                self.font["GDEF"] = gdef
+            elif "GDEF" in self.font:
+                del self.font["GDEF"]
+        if "BASE" in tables:
+            base = self.buildBASE()
+            if base:
+                self.font["BASE"] = base
+            elif "BASE" in self.font:
+                del self.font["BASE"]
+        if debug or os.environ.get(LOOKUP_DEBUG_ENV_VAR):
+            self.buildDebg()
+
+    def get_chained_lookup_(self, location, builder_class):
+        result = builder_class(self.font, location)
+        result.lookupflag = self.lookupflag_
+        result.markFilterSet = self.lookupflag_markFilterSet_
+        self.lookups_.append(result)
+        return result
+
+    def add_lookup_to_feature_(self, lookup, feature_name):
+        for script, lang in self.language_systems:
+            key = (script, lang, feature_name)
+            self.features_.setdefault(key, []).append(lookup)
+
+    def get_lookup_(self, location, builder_class):
+        if (
+            self.cur_lookup_
+            and type(self.cur_lookup_) == builder_class
+            and self.cur_lookup_.lookupflag == self.lookupflag_
+            and self.cur_lookup_.markFilterSet == self.lookupflag_markFilterSet_
+        ):
+            return self.cur_lookup_
+        if self.cur_lookup_name_ and self.cur_lookup_:
+            raise FeatureLibError(
+                "Within a named lookup block, all rules must be of "
+                "the same lookup type and flag",
+                location,
+            )
+        self.cur_lookup_ = builder_class(self.font, location)
+        self.cur_lookup_.lookupflag = self.lookupflag_
+        self.cur_lookup_.markFilterSet = self.lookupflag_markFilterSet_
+        self.lookups_.append(self.cur_lookup_)
+        if self.cur_lookup_name_:
+            # We are starting a lookup rule inside a named lookup block.
+            self.named_lookups_[self.cur_lookup_name_] = self.cur_lookup_
+        if self.cur_feature_name_:
+            # We are starting a lookup rule inside a feature. This includes
+            # lookup rules inside named lookups inside features.
+            self.add_lookup_to_feature_(self.cur_lookup_, self.cur_feature_name_)
+        return self.cur_lookup_
+
+    def build_feature_aalt_(self):
+        if not self.aalt_features_ and not self.aalt_alternates_:
+            return
+        alternates = {g: set(a) for g, a in self.aalt_alternates_.items()}
+        for location, name in self.aalt_features_ + [(None, "aalt")]:
+            feature = [
+                (script, lang, feature, lookups)
+                for (script, lang, feature), lookups in self.features_.items()
+                if feature == name
+            ]
+            # "aalt" does not have to specify its own lookups, but it might.
+            if not feature and name != "aalt":
+                warnings.warn("%s: Feature %s has not been defined" % (location, name))
+                continue
+            for script, lang, feature, lookups in feature:
+                for lookuplist in lookups:
+                    if not isinstance(lookuplist, list):
+                        lookuplist = [lookuplist]
+                    for lookup in lookuplist:
+                        for glyph, alts in lookup.getAlternateGlyphs().items():
+                            alternates.setdefault(glyph, set()).update(alts)
+        single = {
+            glyph: list(repl)[0] for glyph, repl in alternates.items() if len(repl) == 1
+        }
+        # TODO: Figure out the glyph alternate ordering used by makeotf.
+        # https://github.com/fonttools/fonttools/issues/836
+        multi = {
+            glyph: sorted(repl, key=self.font.getGlyphID)
+            for glyph, repl in alternates.items()
+            if len(repl) > 1
+        }
+        if not single and not multi:
+            return
+        self.features_ = {
+            (script, lang, feature): lookups
+            for (script, lang, feature), lookups in self.features_.items()
+            if feature != "aalt"
+        }
+        old_lookups = self.lookups_
+        self.lookups_ = []
+        self.start_feature(self.aalt_location_, "aalt")
+        if single:
+            single_lookup = self.get_lookup_(location, SingleSubstBuilder)
+            single_lookup.mapping = single
+        if multi:
+            multi_lookup = self.get_lookup_(location, AlternateSubstBuilder)
+            multi_lookup.alternates = multi
+        self.end_feature()
+        self.lookups_.extend(old_lookups)
+
+    def build_head(self):
+        if not self.fontRevision_:
+            return
+        table = self.font.get("head")
+        if not table:  # this only happens for unit tests
+            table = self.font["head"] = newTable("head")
+            table.decompile(b"\0" * 54, self.font)
+            table.tableVersion = 1.0
+            table.created = table.modified = 3406620153  # 2011-12-13 11:22:33
+        table.fontRevision = self.fontRevision_
+
+    def build_hhea(self):
+        if not self.hhea_:
+            return
+        table = self.font.get("hhea")
+        if not table:  # this only happens for unit tests
+            table = self.font["hhea"] = newTable("hhea")
+            table.decompile(b"\0" * 36, self.font)
+            table.tableVersion = 0x00010000
+        if "caretoffset" in self.hhea_:
+            table.caretOffset = self.hhea_["caretoffset"]
+        if "ascender" in self.hhea_:
+            table.ascent = self.hhea_["ascender"]
+        if "descender" in self.hhea_:
+            table.descent = self.hhea_["descender"]
+        if "linegap" in self.hhea_:
+            table.lineGap = self.hhea_["linegap"]
+
+    def build_vhea(self):
+        if not self.vhea_:
+            return
+        table = self.font.get("vhea")
+        if not table:  # this only happens for unit tests
+            table = self.font["vhea"] = newTable("vhea")
+            table.decompile(b"\0" * 36, self.font)
+            table.tableVersion = 0x00011000
+        if "verttypoascender" in self.vhea_:
+            table.ascent = self.vhea_["verttypoascender"]
+        if "verttypodescender" in self.vhea_:
+            table.descent = self.vhea_["verttypodescender"]
+        if "verttypolinegap" in self.vhea_:
+            table.lineGap = self.vhea_["verttypolinegap"]
+
+    def get_user_name_id(self, table):
+        # Try to find first unused font-specific name id
+        nameIDs = [name.nameID for name in table.names]
+        for user_name_id in range(256, 32767):
+            if user_name_id not in nameIDs:
+                return user_name_id
+
+    def buildFeatureParams(self, tag):
+        params = None
+        if tag == "size":
+            params = otTables.FeatureParamsSize()
+            (
+                params.DesignSize,
+                params.SubfamilyID,
+                params.RangeStart,
+                params.RangeEnd,
+            ) = self.size_parameters_
+            if tag in self.featureNames_ids_:
+                params.SubfamilyNameID = self.featureNames_ids_[tag]
+            else:
+                params.SubfamilyNameID = 0
+        elif tag in self.featureNames_:
+            if not self.featureNames_ids_:
+                # name table wasn't selected among the tables to build; skip
+                pass
+            else:
+                assert tag in self.featureNames_ids_
+                params = otTables.FeatureParamsStylisticSet()
+                params.Version = 0
+                params.UINameID = self.featureNames_ids_[tag]
+        elif tag in self.cv_parameters_:
+            params = otTables.FeatureParamsCharacterVariants()
+            params.Format = 0
+            params.FeatUILabelNameID = self.cv_parameters_ids_.get(
+                (tag, "FeatUILabelNameID"), 0
+            )
+            params.FeatUITooltipTextNameID = self.cv_parameters_ids_.get(
+                (tag, "FeatUITooltipTextNameID"), 0
+            )
+            params.SampleTextNameID = self.cv_parameters_ids_.get(
+                (tag, "SampleTextNameID"), 0
+            )
+            params.NumNamedParameters = self.cv_num_named_params_.get(tag, 0)
+            params.FirstParamUILabelNameID = self.cv_parameters_ids_.get(
+                (tag, "ParamUILabelNameID_0"), 0
+            )
+            params.CharCount = len(self.cv_characters_[tag])
+            params.Character = self.cv_characters_[tag]
+        return params
+
+    def build_name(self):
+        if not self.names_:
+            return
+        table = self.font.get("name")
+        if not table:  # this only happens for unit tests
+            table = self.font["name"] = newTable("name")
+            table.names = []
+        for name in self.names_:
+            nameID, platformID, platEncID, langID, string = name
+            # For featureNames block, nameID is 'feature tag'
+            # For cvParameters blocks, nameID is ('feature tag', 'block name')
+            if not isinstance(nameID, int):
+                tag = nameID
+                if tag in self.featureNames_:
+                    if tag not in self.featureNames_ids_:
+                        self.featureNames_ids_[tag] = self.get_user_name_id(table)
+                        assert self.featureNames_ids_[tag] is not None
+                    nameID = self.featureNames_ids_[tag]
+                elif tag[0] in self.cv_parameters_:
+                    if tag not in self.cv_parameters_ids_:
+                        self.cv_parameters_ids_[tag] = self.get_user_name_id(table)
+                        assert self.cv_parameters_ids_[tag] is not None
+                    nameID = self.cv_parameters_ids_[tag]
+            table.setName(string, nameID, platformID, platEncID, langID)
+        table.names.sort()
+
+    def build_OS_2(self):
+        if not self.os2_:
+            return
+        table = self.font.get("OS/2")
+        if not table:  # this only happens for unit tests
+            table = self.font["OS/2"] = newTable("OS/2")
+            data = b"\0" * sstruct.calcsize(getTableModule("OS/2").OS2_format_0)
+            table.decompile(data, self.font)
+        version = 0
+        if "fstype" in self.os2_:
+            table.fsType = self.os2_["fstype"]
+        if "panose" in self.os2_:
+            panose = getTableModule("OS/2").Panose()
+            (
+                panose.bFamilyType,
+                panose.bSerifStyle,
+                panose.bWeight,
+                panose.bProportion,
+                panose.bContrast,
+                panose.bStrokeVariation,
+                panose.bArmStyle,
+                panose.bLetterForm,
+                panose.bMidline,
+                panose.bXHeight,
+            ) = self.os2_["panose"]
+            table.panose = panose
+        if "typoascender" in self.os2_:
+            table.sTypoAscender = self.os2_["typoascender"]
+        if "typodescender" in self.os2_:
+            table.sTypoDescender = self.os2_["typodescender"]
+        if "typolinegap" in self.os2_:
+            table.sTypoLineGap = self.os2_["typolinegap"]
+        if "winascent" in self.os2_:
+            table.usWinAscent = self.os2_["winascent"]
+        if "windescent" in self.os2_:
+            table.usWinDescent = self.os2_["windescent"]
+        if "vendor" in self.os2_:
+            table.achVendID = safeEval("'''" + self.os2_["vendor"] + "'''")
+        if "weightclass" in self.os2_:
+            table.usWeightClass = self.os2_["weightclass"]
+        if "widthclass" in self.os2_:
+            table.usWidthClass = self.os2_["widthclass"]
+        if "unicoderange" in self.os2_:
+            table.setUnicodeRanges(self.os2_["unicoderange"])
+        if "codepagerange" in self.os2_:
+            pages = self.build_codepages_(self.os2_["codepagerange"])
+            table.ulCodePageRange1, table.ulCodePageRange2 = pages
+            version = 1
+        if "xheight" in self.os2_:
+            table.sxHeight = self.os2_["xheight"]
+            version = 2
+        if "capheight" in self.os2_:
+            table.sCapHeight = self.os2_["capheight"]
+            version = 2
+        if "loweropsize" in self.os2_:
+            table.usLowerOpticalPointSize = self.os2_["loweropsize"]
+            version = 5
+        if "upperopsize" in self.os2_:
+            table.usUpperOpticalPointSize = self.os2_["upperopsize"]
+            version = 5
+
+        def checkattr(table, attrs):
+            for attr in attrs:
+                if not hasattr(table, attr):
+                    setattr(table, attr, 0)
+
+        table.version = max(version, table.version)
+        # this only happens for unit tests
+        if version >= 1:
+            checkattr(table, ("ulCodePageRange1", "ulCodePageRange2"))
+        if version >= 2:
+            checkattr(
+                table,
+                (
+                    "sxHeight",
+                    "sCapHeight",
+                    "usDefaultChar",
+                    "usBreakChar",
+                    "usMaxContext",
+                ),
+            )
+        if version >= 5:
+            checkattr(table, ("usLowerOpticalPointSize", "usUpperOpticalPointSize"))
+
+    def setElidedFallbackName(self, value, location):
+        # ElidedFallbackName is a convenience method for setting
+        # ElidedFallbackNameID so only one can be allowed
+        for token in ("ElidedFallbackName", "ElidedFallbackNameID"):
+            if token in self.stat_:
+                raise FeatureLibError(
+                    f"{token} is already set.",
+                    location,
+                )
+        if isinstance(value, int):
+            self.stat_["ElidedFallbackNameID"] = value
+        elif isinstance(value, list):
+            self.stat_["ElidedFallbackName"] = value
+        else:
+            raise AssertionError(value)
+
+    def addDesignAxis(self, designAxis, location):
+        if "DesignAxes" not in self.stat_:
+            self.stat_["DesignAxes"] = []
+        if designAxis.tag in (r.tag for r in self.stat_["DesignAxes"]):
+            raise FeatureLibError(
+                f'DesignAxis already defined for tag "{designAxis.tag}".',
+                location,
+            )
+        if designAxis.axisOrder in (r.axisOrder for r in self.stat_["DesignAxes"]):
+            raise FeatureLibError(
+                f"DesignAxis already defined for axis number {designAxis.axisOrder}.",
+                location,
+            )
+        self.stat_["DesignAxes"].append(designAxis)
+
+    def addAxisValueRecord(self, axisValueRecord, location):
+        if "AxisValueRecords" not in self.stat_:
+            self.stat_["AxisValueRecords"] = []
+        # Check for duplicate AxisValueRecords
+        for record_ in self.stat_["AxisValueRecords"]:
+            if (
+                {n.asFea() for n in record_.names}
+                == {n.asFea() for n in axisValueRecord.names}
+                and {n.asFea() for n in record_.locations}
+                == {n.asFea() for n in axisValueRecord.locations}
+                and record_.flags == axisValueRecord.flags
+            ):
+                raise FeatureLibError(
+                    "An AxisValueRecord with these values is already defined.",
+                    location,
+                )
+        self.stat_["AxisValueRecords"].append(axisValueRecord)
+
+    def build_STAT(self):
+        if not self.stat_:
+            return
+
+        axes = self.stat_.get("DesignAxes")
+        if not axes:
+            raise FeatureLibError("DesignAxes not defined", None)
+        axisValueRecords = self.stat_.get("AxisValueRecords")
+        axisValues = {}
+        format4_locations = []
+        for tag in axes:
+            axisValues[tag.tag] = []
+        if axisValueRecords is not None:
+            for avr in axisValueRecords:
+                valuesDict = {}
+                if avr.flags > 0:
+                    valuesDict["flags"] = avr.flags
+                if len(avr.locations) == 1:
+                    location = avr.locations[0]
+                    values = location.values
+                    if len(values) == 1:  # format1
+                        valuesDict.update({"value": values[0], "name": avr.names})
+                    if len(values) == 2:  # format3
+                        valuesDict.update(
+                            {
+                                "value": values[0],
+                                "linkedValue": values[1],
+                                "name": avr.names,
+                            }
+                        )
+                    if len(values) == 3:  # format2
+                        nominal, minVal, maxVal = values
+                        valuesDict.update(
+                            {
+                                "nominalValue": nominal,
+                                "rangeMinValue": minVal,
+                                "rangeMaxValue": maxVal,
+                                "name": avr.names,
+                            }
+                        )
+                    axisValues[location.tag].append(valuesDict)
+                else:
+                    valuesDict.update(
+                        {
+                            "location": {i.tag: i.values[0] for i in avr.locations},
+                            "name": avr.names,
+                        }
+                    )
+                    format4_locations.append(valuesDict)
+
+        designAxes = [
+            {
+                "ordering": a.axisOrder,
+                "tag": a.tag,
+                "name": a.names,
+                "values": axisValues[a.tag],
+            }
+            for a in axes
+        ]
+
+        nameTable = self.font.get("name")
+        if not nameTable:  # this only happens for unit tests
+            nameTable = self.font["name"] = newTable("name")
+            nameTable.names = []
+
+        if "ElidedFallbackNameID" in self.stat_:
+            nameID = self.stat_["ElidedFallbackNameID"]
+            name = nameTable.getDebugName(nameID)
+            if not name:
+                raise FeatureLibError(
+                    f"ElidedFallbackNameID {nameID} points "
+                    "to a nameID that does not exist in the "
+                    '"name" table',
+                    None,
+                )
+        elif "ElidedFallbackName" in self.stat_:
+            nameID = self.stat_["ElidedFallbackName"]
+
+        otl.buildStatTable(
+            self.font,
+            designAxes,
+            locations=format4_locations,
+            elidedFallbackName=nameID,
+        )
+
+    def build_codepages_(self, pages):
+        pages2bits = {
+            1252: 0,
+            1250: 1,
+            1251: 2,
+            1253: 3,
+            1254: 4,
+            1255: 5,
+            1256: 6,
+            1257: 7,
+            1258: 8,
+            874: 16,
+            932: 17,
+            936: 18,
+            949: 19,
+            950: 20,
+            1361: 21,
+            869: 48,
+            866: 49,
+            865: 50,
+            864: 51,
+            863: 52,
+            862: 53,
+            861: 54,
+            860: 55,
+            857: 56,
+            855: 57,
+            852: 58,
+            775: 59,
+            737: 60,
+            708: 61,
+            850: 62,
+            437: 63,
+        }
+        bits = [pages2bits[p] for p in pages if p in pages2bits]
+        pages = []
+        for i in range(2):
+            pages.append("")
+            for j in range(i * 32, (i + 1) * 32):
+                if j in bits:
+                    pages[i] += "1"
+                else:
+                    pages[i] += "0"
+        return [binary2num(p[::-1]) for p in pages]
+
+    def buildBASE(self):
+        if not self.base_horiz_axis_ and not self.base_vert_axis_:
+            return None
+        base = otTables.BASE()
+        base.Version = 0x00010000
+        base.HorizAxis = self.buildBASEAxis(self.base_horiz_axis_)
+        base.VertAxis = self.buildBASEAxis(self.base_vert_axis_)
+
+        result = newTable("BASE")
+        result.table = base
+        return result
+
+    def buildBASEAxis(self, axis):
+        if not axis:
+            return
+        bases, scripts = axis
+        axis = otTables.Axis()
+        axis.BaseTagList = otTables.BaseTagList()
+        axis.BaseTagList.BaselineTag = bases
+        axis.BaseTagList.BaseTagCount = len(bases)
+        axis.BaseScriptList = otTables.BaseScriptList()
+        axis.BaseScriptList.BaseScriptRecord = []
+        axis.BaseScriptList.BaseScriptCount = len(scripts)
+        for script in sorted(scripts):
+            record = otTables.BaseScriptRecord()
+            record.BaseScriptTag = script[0]
+            record.BaseScript = otTables.BaseScript()
+            record.BaseScript.BaseLangSysCount = 0
+            record.BaseScript.BaseValues = otTables.BaseValues()
+            record.BaseScript.BaseValues.DefaultIndex = bases.index(script[1])
+            record.BaseScript.BaseValues.BaseCoord = []
+            record.BaseScript.BaseValues.BaseCoordCount = len(script[2])
+            for c in script[2]:
+                coord = otTables.BaseCoord()
+                coord.Format = 1
+                coord.Coordinate = c
+                record.BaseScript.BaseValues.BaseCoord.append(coord)
+            axis.BaseScriptList.BaseScriptRecord.append(record)
+        return axis
+
+    def buildGDEF(self):
+        gdef = otTables.GDEF()
+        gdef.GlyphClassDef = self.buildGDEFGlyphClassDef_()
+        gdef.AttachList = otl.buildAttachList(self.attachPoints_, self.glyphMap)
+        gdef.LigCaretList = otl.buildLigCaretList(
+            self.ligCaretCoords_, self.ligCaretPoints_, self.glyphMap
+        )
+        gdef.MarkAttachClassDef = self.buildGDEFMarkAttachClassDef_()
+        gdef.MarkGlyphSetsDef = self.buildGDEFMarkGlyphSetsDef_()
+        gdef.Version = 0x00010002 if gdef.MarkGlyphSetsDef else 0x00010000
+        if self.varstorebuilder:
+            store = self.varstorebuilder.finish()
+            if store:
+                gdef.Version = 0x00010003
+                gdef.VarStore = store
+                varidx_map = store.optimize()
+
+                gdef.remap_device_varidxes(varidx_map)
+                if "GPOS" in self.font:
+                    self.font["GPOS"].table.remap_device_varidxes(varidx_map)
+            self.model_cache.clear()
+        if any(
+            (
+                gdef.GlyphClassDef,
+                gdef.AttachList,
+                gdef.LigCaretList,
+                gdef.MarkAttachClassDef,
+                gdef.MarkGlyphSetsDef,
+            )
+        ) or hasattr(gdef, "VarStore"):
+            result = newTable("GDEF")
+            result.table = gdef
+            return result
+        else:
+            return None
+
+    def buildGDEFGlyphClassDef_(self):
+        if self.glyphClassDefs_:
+            classes = {g: c for (g, (c, _)) in self.glyphClassDefs_.items()}
+        else:
+            classes = {}
+            for lookup in self.lookups_:
+                classes.update(lookup.inferGlyphClasses())
+            for markClass in self.parseTree.markClasses.values():
+                for markClassDef in markClass.definitions:
+                    for glyph in markClassDef.glyphSet():
+                        classes[glyph] = 3
+        if classes:
+            result = otTables.GlyphClassDef()
+            result.classDefs = classes
+            return result
+        else:
+            return None
+
+    def buildGDEFMarkAttachClassDef_(self):
+        classDefs = {g: c for g, (c, _) in self.markAttach_.items()}
+        if not classDefs:
+            return None
+        result = otTables.MarkAttachClassDef()
+        result.classDefs = classDefs
+        return result
+
+    def buildGDEFMarkGlyphSetsDef_(self):
+        sets = []
+        for glyphs, id_ in sorted(
+            self.markFilterSets_.items(), key=lambda item: item[1]
+        ):
+            sets.append(glyphs)
+        return otl.buildMarkGlyphSetsDef(sets, self.glyphMap)
+
+    def buildDebg(self):
+        if "Debg" not in self.font:
+            self.font["Debg"] = newTable("Debg")
+            self.font["Debg"].data = {}
+        self.font["Debg"].data[LOOKUP_DEBUG_INFO_KEY] = self.lookup_locations
+
+    def buildLookups_(self, tag):
+        assert tag in ("GPOS", "GSUB"), tag
+        for lookup in self.lookups_:
+            lookup.lookup_index = None
+        lookups = []
+        for lookup in self.lookups_:
+            if lookup.table != tag:
+                continue
+            lookup.lookup_index = len(lookups)
+            self.lookup_locations[tag][str(lookup.lookup_index)] = LookupDebugInfo(
+                location=str(lookup.location),
+                name=self.get_lookup_name_(lookup),
+                feature=None,
+            )
+            lookups.append(lookup)
+        otLookups = []
+        for l in lookups:
+            try:
+                otLookups.append(l.build())
+            except OpenTypeLibError as e:
+                raise FeatureLibError(str(e), e.location) from e
+            except Exception as e:
+                location = self.lookup_locations[tag][str(l.lookup_index)].location
+                raise FeatureLibError(str(e), location) from e
+        return otLookups
+
+    def makeTable(self, tag):
+        table = getattr(otTables, tag, None)()
+        table.Version = 0x00010000
+        table.ScriptList = otTables.ScriptList()
+        table.ScriptList.ScriptRecord = []
+        table.FeatureList = otTables.FeatureList()
+        table.FeatureList.FeatureRecord = []
+        table.LookupList = otTables.LookupList()
+        table.LookupList.Lookup = self.buildLookups_(tag)
+
+        # Build a table for mapping (tag, lookup_indices) to feature_index.
+        # For example, ('liga', (2,3,7)) --> 23.
+        feature_indices = {}
+        required_feature_indices = {}  # ('latn', 'DEU') --> 23
+        scripts = {}  # 'latn' --> {'DEU': [23, 24]} for feature #23,24
+        # Sort the feature table by feature tag:
+        # https://github.com/fonttools/fonttools/issues/568
+        sortFeatureTag = lambda f: (f[0][2], f[0][1], f[0][0], f[1])
+        for key, lookups in sorted(self.features_.items(), key=sortFeatureTag):
+            script, lang, feature_tag = key
+            # l.lookup_index will be None when a lookup is not needed
+            # for the table under construction. For example, substitution
+            # rules will have no lookup_index while building GPOS tables.
+            lookup_indices = tuple(
+                [l.lookup_index for l in lookups if l.lookup_index is not None]
+            )
+
+            size_feature = tag == "GPOS" and feature_tag == "size"
+            force_feature = self.any_feature_variations(feature_tag, tag)
+            if len(lookup_indices) == 0 and not size_feature and not force_feature:
+                continue
+
+            for ix in lookup_indices:
+                try:
+                    self.lookup_locations[tag][str(ix)] = self.lookup_locations[tag][
+                        str(ix)
+                    ]._replace(feature=key)
+                except KeyError:
+                    warnings.warn(
+                        "feaLib.Builder subclass needs upgrading to "
+                        "stash debug information. See fonttools#2065."
+                    )
+
+            feature_key = (feature_tag, lookup_indices)
+            feature_index = feature_indices.get(feature_key)
+            if feature_index is None:
+                feature_index = len(table.FeatureList.FeatureRecord)
+                frec = otTables.FeatureRecord()
+                frec.FeatureTag = feature_tag
+                frec.Feature = otTables.Feature()
+                frec.Feature.FeatureParams = self.buildFeatureParams(feature_tag)
+                frec.Feature.LookupListIndex = list(lookup_indices)
+                frec.Feature.LookupCount = len(lookup_indices)
+                table.FeatureList.FeatureRecord.append(frec)
+                feature_indices[feature_key] = feature_index
+            scripts.setdefault(script, {}).setdefault(lang, []).append(feature_index)
+            if self.required_features_.get((script, lang)) == feature_tag:
+                required_feature_indices[(script, lang)] = feature_index
+
+        # Build ScriptList.
+        for script, lang_features in sorted(scripts.items()):
+            srec = otTables.ScriptRecord()
+            srec.ScriptTag = script
+            srec.Script = otTables.Script()
+            srec.Script.DefaultLangSys = None
+            srec.Script.LangSysRecord = []
+            for lang, feature_indices in sorted(lang_features.items()):
+                langrec = otTables.LangSysRecord()
+                langrec.LangSys = otTables.LangSys()
+                langrec.LangSys.LookupOrder = None
+
+                req_feature_index = required_feature_indices.get((script, lang))
+                if req_feature_index is None:
+                    langrec.LangSys.ReqFeatureIndex = 0xFFFF
+                else:
+                    langrec.LangSys.ReqFeatureIndex = req_feature_index
+
+                langrec.LangSys.FeatureIndex = [
+                    i for i in feature_indices if i != req_feature_index
+                ]
+                langrec.LangSys.FeatureCount = len(langrec.LangSys.FeatureIndex)
+
+                if lang == "dflt":
+                    srec.Script.DefaultLangSys = langrec.LangSys
+                else:
+                    langrec.LangSysTag = lang
+                    srec.Script.LangSysRecord.append(langrec)
+            srec.Script.LangSysCount = len(srec.Script.LangSysRecord)
+            table.ScriptList.ScriptRecord.append(srec)
+
+        table.ScriptList.ScriptCount = len(table.ScriptList.ScriptRecord)
+        table.FeatureList.FeatureCount = len(table.FeatureList.FeatureRecord)
+        table.LookupList.LookupCount = len(table.LookupList.Lookup)
+        return table
+
+    def makeFeatureVariations(self, table, table_tag):
+        feature_vars = {}
+        has_any_variations = False
+        # Sort out which lookups to build, gather their indices
+        for (_, _, feature_tag), variations in self.feature_variations_.items():
+            feature_vars[feature_tag] = []
+            for conditionset, builders in variations.items():
+                raw_conditionset = self.conditionsets_[conditionset]
+                indices = []
+                for b in builders:
+                    if b.table != table_tag:
+                        continue
+                    assert b.lookup_index is not None
+                    indices.append(b.lookup_index)
+                    has_any_variations = True
+                feature_vars[feature_tag].append((raw_conditionset, indices))
+
+        if has_any_variations:
+            for feature_tag, conditions_and_lookups in feature_vars.items():
+                addFeatureVariationsRaw(
+                    self.font, table, conditions_and_lookups, feature_tag
+                )
+
+    def any_feature_variations(self, feature_tag, table_tag):
+        for (_, _, feature), variations in self.feature_variations_.items():
+            if feature != feature_tag:
+                continue
+            for conditionset, builders in variations.items():
+                if any(b.table == table_tag for b in builders):
+                    return True
+        return False
+
+    def get_lookup_name_(self, lookup):
+        rev = {v: k for k, v in self.named_lookups_.items()}
+        if lookup in rev:
+            return rev[lookup]
+        return None
+
+    def add_language_system(self, location, script, language):
+        # OpenType Feature File Specification, section 4.b.i
+        if script == "DFLT" and language == "dflt" and self.default_language_systems_:
+            raise FeatureLibError(
+                'If "languagesystem DFLT dflt" is present, it must be '
+                "the first of the languagesystem statements",
+                location,
+            )
+        if script == "DFLT":
+            if self.seen_non_DFLT_script_:
+                raise FeatureLibError(
+                    'languagesystems using the "DFLT" script tag must '
+                    "precede all other languagesystems",
+                    location,
+                )
+        else:
+            self.seen_non_DFLT_script_ = True
+        if (script, language) in self.default_language_systems_:
+            raise FeatureLibError(
+                '"languagesystem %s %s" has already been specified'
+                % (script.strip(), language.strip()),
+                location,
+            )
+        self.default_language_systems_.add((script, language))
+
+    def get_default_language_systems_(self):
+        # OpenType Feature File specification, 4.b.i. languagesystem:
+        # If no "languagesystem" statement is present, then the
+        # implementation must behave exactly as though the following
+        # statement were present at the beginning of the feature file:
+        # languagesystem DFLT dflt;
+        if self.default_language_systems_:
+            return frozenset(self.default_language_systems_)
+        else:
+            return frozenset({("DFLT", "dflt")})
+
+    def start_feature(self, location, name):
+        self.language_systems = self.get_default_language_systems_()
+        self.script_ = "DFLT"
+        self.cur_lookup_ = None
+        self.cur_feature_name_ = name
+        self.lookupflag_ = 0
+        self.lookupflag_markFilterSet_ = None
+        if name == "aalt":
+            self.aalt_location_ = location
+
+    def end_feature(self):
+        assert self.cur_feature_name_ is not None
+        self.cur_feature_name_ = None
+        self.language_systems = None
+        self.cur_lookup_ = None
+        self.lookupflag_ = 0
+        self.lookupflag_markFilterSet_ = None
+
+    def start_lookup_block(self, location, name):
+        if name in self.named_lookups_:
+            raise FeatureLibError(
+                'Lookup "%s" has already been defined' % name, location
+            )
+        if self.cur_feature_name_ == "aalt":
+            raise FeatureLibError(
+                "Lookup blocks cannot be placed inside 'aalt' features; "
+                "move it out, and then refer to it with a lookup statement",
+                location,
+            )
+        self.cur_lookup_name_ = name
+        self.named_lookups_[name] = None
+        self.cur_lookup_ = None
+        if self.cur_feature_name_ is None:
+            self.lookupflag_ = 0
+            self.lookupflag_markFilterSet_ = None
+
+    def end_lookup_block(self):
+        assert self.cur_lookup_name_ is not None
+        self.cur_lookup_name_ = None
+        self.cur_lookup_ = None
+        if self.cur_feature_name_ is None:
+            self.lookupflag_ = 0
+            self.lookupflag_markFilterSet_ = None
+
+    def add_lookup_call(self, lookup_name):
+        assert lookup_name in self.named_lookups_, lookup_name
+        self.cur_lookup_ = None
+        lookup = self.named_lookups_[lookup_name]
+        if lookup is not None:  # skip empty named lookup
+            self.add_lookup_to_feature_(lookup, self.cur_feature_name_)
+
+    def set_font_revision(self, location, revision):
+        self.fontRevision_ = revision
+
+    def set_language(self, location, language, include_default, required):
+        assert len(language) == 4
+        if self.cur_feature_name_ in ("aalt", "size"):
+            raise FeatureLibError(
+                "Language statements are not allowed "
+                'within "feature %s"' % self.cur_feature_name_,
+                location,
+            )
+        if self.cur_feature_name_ is None:
+            raise FeatureLibError(
+                "Language statements are not allowed "
+                "within standalone lookup blocks",
+                location,
+            )
+        self.cur_lookup_ = None
+
+        key = (self.script_, language, self.cur_feature_name_)
+        lookups = self.features_.get((key[0], "dflt", key[2]))
+        if (language == "dflt" or include_default) and lookups:
+            self.features_[key] = lookups[:]
+        else:
+            self.features_[key] = []
+        self.language_systems = frozenset([(self.script_, language)])
+
+        if required:
+            key = (self.script_, language)
+            if key in self.required_features_:
+                raise FeatureLibError(
+                    "Language %s (script %s) has already "
+                    "specified feature %s as its required feature"
+                    % (
+                        language.strip(),
+                        self.script_.strip(),
+                        self.required_features_[key].strip(),
+                    ),
+                    location,
+                )
+            self.required_features_[key] = self.cur_feature_name_
+
+    def getMarkAttachClass_(self, location, glyphs):
+        glyphs = frozenset(glyphs)
+        id_ = self.markAttachClassID_.get(glyphs)
+        if id_ is not None:
+            return id_
+        id_ = len(self.markAttachClassID_) + 1
+        self.markAttachClassID_[glyphs] = id_
+        for glyph in glyphs:
+            if glyph in self.markAttach_:
+                _, loc = self.markAttach_[glyph]
+                raise FeatureLibError(
+                    "Glyph %s already has been assigned "
+                    "a MarkAttachmentType at %s" % (glyph, loc),
+                    location,
+                )
+            self.markAttach_[glyph] = (id_, location)
+        return id_
+
+    def getMarkFilterSet_(self, location, glyphs):
+        glyphs = frozenset(glyphs)
+        id_ = self.markFilterSets_.get(glyphs)
+        if id_ is not None:
+            return id_
+        id_ = len(self.markFilterSets_)
+        self.markFilterSets_[glyphs] = id_
+        return id_
+
+    def set_lookup_flag(self, location, value, markAttach, markFilter):
+        value = value & 0xFF
+        if markAttach:
+            markAttachClass = self.getMarkAttachClass_(location, markAttach)
+            value = value | (markAttachClass << 8)
+        if markFilter:
+            markFilterSet = self.getMarkFilterSet_(location, markFilter)
+            value = value | 0x10
+            self.lookupflag_markFilterSet_ = markFilterSet
+        else:
+            self.lookupflag_markFilterSet_ = None
+        self.lookupflag_ = value
+
+    def set_script(self, location, script):
+        if self.cur_feature_name_ in ("aalt", "size"):
+            raise FeatureLibError(
+                "Script statements are not allowed "
+                'within "feature %s"' % self.cur_feature_name_,
+                location,
+            )
+        if self.cur_feature_name_ is None:
+            raise FeatureLibError(
+                "Script statements are not allowed " "within standalone lookup blocks",
+                location,
+            )
+        if self.language_systems == {(script, "dflt")}:
+            # Nothing to do.
+            return
+        self.cur_lookup_ = None
+        self.script_ = script
+        self.lookupflag_ = 0
+        self.lookupflag_markFilterSet_ = None
+        self.set_language(location, "dflt", include_default=True, required=False)
+
+    def find_lookup_builders_(self, lookups):
+        """Helper for building chain contextual substitutions
+
+        Given a list of lookup names, finds the LookupBuilder for each name.
+        If an input name is None, it gets mapped to a None LookupBuilder.
+        """
+        lookup_builders = []
+        for lookuplist in lookups:
+            if lookuplist is not None:
+                lookup_builders.append(
+                    [self.named_lookups_.get(l.name) for l in lookuplist]
+                )
+            else:
+                lookup_builders.append(None)
+        return lookup_builders
+
+    def add_attach_points(self, location, glyphs, contourPoints):
+        for glyph in glyphs:
+            self.attachPoints_.setdefault(glyph, set()).update(contourPoints)
+
+    def add_feature_reference(self, location, featureName):
+        if self.cur_feature_name_ != "aalt":
+            raise FeatureLibError(
+                'Feature references are only allowed inside "feature aalt"', location
+            )
+        self.aalt_features_.append((location, featureName))
+
+    def add_featureName(self, tag):
+        self.featureNames_.add(tag)
+
+    def add_cv_parameter(self, tag):
+        self.cv_parameters_.add(tag)
+
+    def add_to_cv_num_named_params(self, tag):
+        """Adds new items to ``self.cv_num_named_params_``
+        or increments the count of existing items."""
+        if tag in self.cv_num_named_params_:
+            self.cv_num_named_params_[tag] += 1
+        else:
+            self.cv_num_named_params_[tag] = 1
+
+    def add_cv_character(self, character, tag):
+        self.cv_characters_[tag].append(character)
+
+    def set_base_axis(self, bases, scripts, vertical):
+        if vertical:
+            self.base_vert_axis_ = (bases, scripts)
+        else:
+            self.base_horiz_axis_ = (bases, scripts)
+
+    def set_size_parameters(
+        self, location, DesignSize, SubfamilyID, RangeStart, RangeEnd
+    ):
+        if self.cur_feature_name_ != "size":
+            raise FeatureLibError(
+                "Parameters statements are not allowed "
+                'within "feature %s"' % self.cur_feature_name_,
+                location,
+            )
+        self.size_parameters_ = [DesignSize, SubfamilyID, RangeStart, RangeEnd]
+        for script, lang in self.language_systems:
+            key = (script, lang, self.cur_feature_name_)
+            self.features_.setdefault(key, [])
+
+    # GSUB rules
+
+    # GSUB 1
+    def add_single_subst(self, location, prefix, suffix, mapping, forceChain):
+        if self.cur_feature_name_ == "aalt":
+            for from_glyph, to_glyph in mapping.items():
+                alts = self.aalt_alternates_.setdefault(from_glyph, set())
+                alts.add(to_glyph)
+            return
+        if prefix or suffix or forceChain:
+            self.add_single_subst_chained_(location, prefix, suffix, mapping)
+            return
+        lookup = self.get_lookup_(location, SingleSubstBuilder)
+        for from_glyph, to_glyph in mapping.items():
+            if from_glyph in lookup.mapping:
+                if to_glyph == lookup.mapping[from_glyph]:
+                    log.info(
+                        "Removing duplicate single substitution from glyph"
+                        ' "%s" to "%s" at %s',
+                        from_glyph,
+                        to_glyph,
+                        location,
+                    )
+                else:
+                    raise FeatureLibError(
+                        'Already defined rule for replacing glyph "%s" by "%s"'
+                        % (from_glyph, lookup.mapping[from_glyph]),
+                        location,
+                    )
+            lookup.mapping[from_glyph] = to_glyph
+
+    # GSUB 2
+    def add_multiple_subst(
+        self, location, prefix, glyph, suffix, replacements, forceChain=False
+    ):
+        if prefix or suffix or forceChain:
+            chain = self.get_lookup_(location, ChainContextSubstBuilder)
+            sub = self.get_chained_lookup_(location, MultipleSubstBuilder)
+            sub.mapping[glyph] = replacements
+            chain.rules.append(ChainContextualRule(prefix, [{glyph}], suffix, [sub]))
+            return
+        lookup = self.get_lookup_(location, MultipleSubstBuilder)
+        if glyph in lookup.mapping:
+            if replacements == lookup.mapping[glyph]:
+                log.info(
+                    "Removing duplicate multiple substitution from glyph"
+                    ' "%s" to %s%s',
+                    glyph,
+                    replacements,
+                    f" at {location}" if location else "",
+                )
+            else:
+                raise FeatureLibError(
+                    'Already defined substitution for glyph "%s"' % glyph, location
+                )
+        lookup.mapping[glyph] = replacements
+
+    # GSUB 3
+    def add_alternate_subst(self, location, prefix, glyph, suffix, replacement):
+        if self.cur_feature_name_ == "aalt":
+            alts = self.aalt_alternates_.setdefault(glyph, set())
+            alts.update(replacement)
+            return
+        if prefix or suffix:
+            chain = self.get_lookup_(location, ChainContextSubstBuilder)
+            lookup = self.get_chained_lookup_(location, AlternateSubstBuilder)
+            chain.rules.append(ChainContextualRule(prefix, [{glyph}], suffix, [lookup]))
+        else:
+            lookup = self.get_lookup_(location, AlternateSubstBuilder)
+        if glyph in lookup.alternates:
+            raise FeatureLibError(
+                'Already defined alternates for glyph "%s"' % glyph, location
+            )
+        # We allow empty replacement glyphs here.
+        lookup.alternates[glyph] = replacement
+
+    # GSUB 4
+    def add_ligature_subst(
+        self, location, prefix, glyphs, suffix, replacement, forceChain
+    ):
+        if prefix or suffix or forceChain:
+            chain = self.get_lookup_(location, ChainContextSubstBuilder)
+            lookup = self.get_chained_lookup_(location, LigatureSubstBuilder)
+            chain.rules.append(ChainContextualRule(prefix, glyphs, suffix, [lookup]))
+        else:
+            lookup = self.get_lookup_(location, LigatureSubstBuilder)
+
+        if not all(glyphs):
+            raise FeatureLibError("Empty glyph class in substitution", location)
+
+        # OpenType feature file syntax, section 5.d, "Ligature substitution":
+        # "Since the OpenType specification does not allow ligature
+        # substitutions to be specified on target sequences that contain
+        # glyph classes, the implementation software will enumerate
+        # all specific glyph sequences if glyph classes are detected"
+        for g in sorted(itertools.product(*glyphs)):
+            lookup.ligatures[g] = replacement
+
+    # GSUB 5/6
+    def add_chain_context_subst(self, location, prefix, glyphs, suffix, lookups):
+        if not all(glyphs) or not all(prefix) or not all(suffix):
+            raise FeatureLibError(
+                "Empty glyph class in contextual substitution", location
+            )
+        lookup = self.get_lookup_(location, ChainContextSubstBuilder)
+        lookup.rules.append(
+            ChainContextualRule(
+                prefix, glyphs, suffix, self.find_lookup_builders_(lookups)
+            )
+        )
+
+    def add_single_subst_chained_(self, location, prefix, suffix, mapping):
+        if not mapping or not all(prefix) or not all(suffix):
+            raise FeatureLibError(
+                "Empty glyph class in contextual substitution", location
+            )
+        # https://github.com/fonttools/fonttools/issues/512
+        # https://github.com/fonttools/fonttools/issues/2150
+        chain = self.get_lookup_(location, ChainContextSubstBuilder)
+        sub = chain.find_chainable_single_subst(mapping)
+        if sub is None:
+            sub = self.get_chained_lookup_(location, SingleSubstBuilder)
+        sub.mapping.update(mapping)
+        chain.rules.append(
+            ChainContextualRule(prefix, [list(mapping.keys())], suffix, [sub])
+        )
+
+    # GSUB 8
+    def add_reverse_chain_single_subst(self, location, old_prefix, old_suffix, mapping):
+        if not mapping:
+            raise FeatureLibError("Empty glyph class in substitution", location)
+        lookup = self.get_lookup_(location, ReverseChainSingleSubstBuilder)
+        lookup.rules.append((old_prefix, old_suffix, mapping))
+
+    # GPOS rules
+
+    # GPOS 1
+    def add_single_pos(self, location, prefix, suffix, pos, forceChain):
+        if prefix or suffix or forceChain:
+            self.add_single_pos_chained_(location, prefix, suffix, pos)
+        else:
+            lookup = self.get_lookup_(location, SinglePosBuilder)
+            for glyphs, value in pos:
+                if not glyphs:
+                    raise FeatureLibError(
+                        "Empty glyph class in positioning rule", location
+                    )
+                otValueRecord = self.makeOpenTypeValueRecord(
+                    location, value, pairPosContext=False
+                )
+                for glyph in glyphs:
+                    try:
+                        lookup.add_pos(location, glyph, otValueRecord)
+                    except OpenTypeLibError as e:
+                        raise FeatureLibError(str(e), e.location) from e
+
+    # GPOS 2
+    def add_class_pair_pos(self, location, glyphclass1, value1, glyphclass2, value2):
+        if not glyphclass1 or not glyphclass2:
+            raise FeatureLibError("Empty glyph class in positioning rule", location)
+        lookup = self.get_lookup_(location, PairPosBuilder)
+        v1 = self.makeOpenTypeValueRecord(location, value1, pairPosContext=True)
+        v2 = self.makeOpenTypeValueRecord(location, value2, pairPosContext=True)
+        lookup.addClassPair(location, glyphclass1, v1, glyphclass2, v2)
+
+    def add_specific_pair_pos(self, location, glyph1, value1, glyph2, value2):
+        if not glyph1 or not glyph2:
+            raise FeatureLibError("Empty glyph class in positioning rule", location)
+        lookup = self.get_lookup_(location, PairPosBuilder)
+        v1 = self.makeOpenTypeValueRecord(location, value1, pairPosContext=True)
+        v2 = self.makeOpenTypeValueRecord(location, value2, pairPosContext=True)
+        lookup.addGlyphPair(location, glyph1, v1, glyph2, v2)
+
+    # GPOS 3
+    def add_cursive_pos(self, location, glyphclass, entryAnchor, exitAnchor):
+        if not glyphclass:
+            raise FeatureLibError("Empty glyph class in positioning rule", location)
+        lookup = self.get_lookup_(location, CursivePosBuilder)
+        lookup.add_attachment(
+            location,
+            glyphclass,
+            self.makeOpenTypeAnchor(location, entryAnchor),
+            self.makeOpenTypeAnchor(location, exitAnchor),
+        )
+
+    # GPOS 4
+    def add_mark_base_pos(self, location, bases, marks):
+        builder = self.get_lookup_(location, MarkBasePosBuilder)
+        self.add_marks_(location, builder, marks)
+        if not bases:
+            raise FeatureLibError("Empty glyph class in positioning rule", location)
+        for baseAnchor, markClass in marks:
+            otBaseAnchor = self.makeOpenTypeAnchor(location, baseAnchor)
+            for base in bases:
+                builder.bases.setdefault(base, {})[markClass.name] = otBaseAnchor
+
+    # GPOS 5
+    def add_mark_lig_pos(self, location, ligatures, components):
+        builder = self.get_lookup_(location, MarkLigPosBuilder)
+        componentAnchors = []
+        if not ligatures:
+            raise FeatureLibError("Empty glyph class in positioning rule", location)
+        for marks in components:
+            anchors = {}
+            self.add_marks_(location, builder, marks)
+            for ligAnchor, markClass in marks:
+                anchors[markClass.name] = self.makeOpenTypeAnchor(location, ligAnchor)
+            componentAnchors.append(anchors)
+        for glyph in ligatures:
+            builder.ligatures[glyph] = componentAnchors
+
+    # GPOS 6
+    def add_mark_mark_pos(self, location, baseMarks, marks):
+        builder = self.get_lookup_(location, MarkMarkPosBuilder)
+        self.add_marks_(location, builder, marks)
+        if not baseMarks:
+            raise FeatureLibError("Empty glyph class in positioning rule", location)
+        for baseAnchor, markClass in marks:
+            otBaseAnchor = self.makeOpenTypeAnchor(location, baseAnchor)
+            for baseMark in baseMarks:
+                builder.baseMarks.setdefault(baseMark, {})[
+                    markClass.name
+                ] = otBaseAnchor
+
+    # GPOS 7/8
+    def add_chain_context_pos(self, location, prefix, glyphs, suffix, lookups):
+        if not all(glyphs) or not all(prefix) or not all(suffix):
+            raise FeatureLibError(
+                "Empty glyph class in contextual positioning rule", location
+            )
+        lookup = self.get_lookup_(location, ChainContextPosBuilder)
+        lookup.rules.append(
+            ChainContextualRule(
+                prefix, glyphs, suffix, self.find_lookup_builders_(lookups)
+            )
+        )
+
+    def add_single_pos_chained_(self, location, prefix, suffix, pos):
+        if not pos or not all(prefix) or not all(suffix):
+            raise FeatureLibError(
+                "Empty glyph class in contextual positioning rule", location
+            )
+        # https://github.com/fonttools/fonttools/issues/514
+        chain = self.get_lookup_(location, ChainContextPosBuilder)
+        targets = []
+        for _, _, _, lookups in chain.rules:
+            targets.extend(lookups)
+        subs = []
+        for glyphs, value in pos:
+            if value is None:
+                subs.append(None)
+                continue
+            otValue = self.makeOpenTypeValueRecord(
+                location, value, pairPosContext=False
+            )
+            sub = chain.find_chainable_single_pos(targets, glyphs, otValue)
+            if sub is None:
+                sub = self.get_chained_lookup_(location, SinglePosBuilder)
+                targets.append(sub)
+            for glyph in glyphs:
+                sub.add_pos(location, glyph, otValue)
+            subs.append(sub)
+        assert len(pos) == len(subs), (pos, subs)
+        chain.rules.append(
+            ChainContextualRule(prefix, [g for g, v in pos], suffix, subs)
+        )
+
+    def add_marks_(self, location, lookupBuilder, marks):
+        """Helper for add_mark_{base,liga,mark}_pos."""
+        for _, markClass in marks:
+            for markClassDef in markClass.definitions:
+                for mark in markClassDef.glyphs.glyphSet():
+                    if mark not in lookupBuilder.marks:
+                        otMarkAnchor = self.makeOpenTypeAnchor(
+                            location, markClassDef.anchor
+                        )
+                        lookupBuilder.marks[mark] = (markClass.name, otMarkAnchor)
+                    else:
+                        existingMarkClass = lookupBuilder.marks[mark][0]
+                        if markClass.name != existingMarkClass:
+                            raise FeatureLibError(
+                                "Glyph %s cannot be in both @%s and @%s"
+                                % (mark, existingMarkClass, markClass.name),
+                                location,
+                            )
+
+    def add_subtable_break(self, location):
+        self.cur_lookup_.add_subtable_break(location)
+
+    def setGlyphClass_(self, location, glyph, glyphClass):
+        oldClass, oldLocation = self.glyphClassDefs_.get(glyph, (None, None))
+        if oldClass and oldClass != glyphClass:
+            raise FeatureLibError(
+                "Glyph %s was assigned to a different class at %s"
+                % (glyph, oldLocation),
+                location,
+            )
+        self.glyphClassDefs_[glyph] = (glyphClass, location)
+
+    def add_glyphClassDef(
+        self, location, baseGlyphs, ligatureGlyphs, markGlyphs, componentGlyphs
+    ):
+        for glyph in baseGlyphs:
+            self.setGlyphClass_(location, glyph, 1)
+        for glyph in ligatureGlyphs:
+            self.setGlyphClass_(location, glyph, 2)
+        for glyph in markGlyphs:
+            self.setGlyphClass_(location, glyph, 3)
+        for glyph in componentGlyphs:
+            self.setGlyphClass_(location, glyph, 4)
+
+    def add_ligatureCaretByIndex_(self, location, glyphs, carets):
+        for glyph in glyphs:
+            if glyph not in self.ligCaretPoints_:
+                self.ligCaretPoints_[glyph] = carets
+
+    def makeLigCaret(self, location, caret):
+        if not isinstance(caret, VariableScalar):
+            return caret
+        default, device = self.makeVariablePos(location, caret)
+        if device is not None:
+            return (default, device)
+        return default
+
+    def add_ligatureCaretByPos_(self, location, glyphs, carets):
+        carets = [self.makeLigCaret(location, caret) for caret in carets]
+        for glyph in glyphs:
+            if glyph not in self.ligCaretCoords_:
+                self.ligCaretCoords_[glyph] = carets
+
+    def add_name_record(self, location, nameID, platformID, platEncID, langID, string):
+        self.names_.append([nameID, platformID, platEncID, langID, string])
+
+    def add_os2_field(self, key, value):
+        self.os2_[key] = value
+
+    def add_hhea_field(self, key, value):
+        self.hhea_[key] = value
+
+    def add_vhea_field(self, key, value):
+        self.vhea_[key] = value
+
+    def add_conditionset(self, location, key, value):
+        if "fvar" not in self.font:
+            raise FeatureLibError(
+                "Cannot add feature variations to a font without an 'fvar' table",
+                location,
+            )
+
+        # Normalize
+        axisMap = {
+            axis.axisTag: (axis.minValue, axis.defaultValue, axis.maxValue)
+            for axis in self.axes
+        }
+
+        value = {
+            tag: (
+                normalizeValue(bottom, axisMap[tag]),
+                normalizeValue(top, axisMap[tag]),
+            )
+            for tag, (bottom, top) in value.items()
+        }
+
+        # NOTE: This might result in rounding errors (off-by-ones) compared to
+        # rules in Designspace files, since we're working with what's in the
+        # `avar` table rather than the original values.
+        if "avar" in self.font:
+            mapping = self.font["avar"].segments
+            value = {
+                axis: tuple(
+                    piecewiseLinearMap(v, mapping[axis]) if axis in mapping else v
+                    for v in condition_range
+                )
+                for axis, condition_range in value.items()
+            }
+
+        self.conditionsets_[key] = value
+
+    def makeVariablePos(self, location, varscalar):
+        if not self.varstorebuilder:
+            raise FeatureLibError(
+                "Can't define a variable scalar in a non-variable font", location
+            )
+
+        varscalar.axes = self.axes
+        if not varscalar.does_vary:
+            return varscalar.default, None
+
+        default, index = varscalar.add_to_variation_store(
+            self.varstorebuilder, self.model_cache, self.font.get("avar")
+        )
+
+        device = None
+        if index is not None and index != 0xFFFFFFFF:
+            device = buildVarDevTable(index)
+
+        return default, device
+
+    def makeOpenTypeAnchor(self, location, anchor):
+        """ast.Anchor --> otTables.Anchor"""
+        if anchor is None:
+            return None
+        variable = False
+        deviceX, deviceY = None, None
+        if anchor.xDeviceTable is not None:
+            deviceX = otl.buildDevice(dict(anchor.xDeviceTable))
+        if anchor.yDeviceTable is not None:
+            deviceY = otl.buildDevice(dict(anchor.yDeviceTable))
+        for dim in ("x", "y"):
+            varscalar = getattr(anchor, dim)
+            if not isinstance(varscalar, VariableScalar):
+                continue
+            if getattr(anchor, dim + "DeviceTable") is not None:
+                raise FeatureLibError(
+                    "Can't define a device coordinate and variable scalar", location
+                )
+            default, device = self.makeVariablePos(location, varscalar)
+            setattr(anchor, dim, default)
+            if device is not None:
+                if dim == "x":
+                    deviceX = device
+                else:
+                    deviceY = device
+                variable = True
+
+        otlanchor = otl.buildAnchor(
+            anchor.x, anchor.y, anchor.contourpoint, deviceX, deviceY
+        )
+        if variable:
+            otlanchor.Format = 3
+        return otlanchor
+
+    _VALUEREC_ATTRS = {
+        name[0].lower() + name[1:]: (name, isDevice)
+        for _, name, isDevice, _ in otBase.valueRecordFormat
+        if not name.startswith("Reserved")
+    }
+
+    def makeOpenTypeValueRecord(self, location, v, pairPosContext):
+        """ast.ValueRecord --> otBase.ValueRecord"""
+        if not v:
+            return None
+
+        vr = {}
+        for astName, (otName, isDevice) in self._VALUEREC_ATTRS.items():
+            val = getattr(v, astName, None)
+            if not val:
+                continue
+            if isDevice:
+                vr[otName] = otl.buildDevice(dict(val))
+            elif isinstance(val, VariableScalar):
+                otDeviceName = otName[0:4] + "Device"
+                feaDeviceName = otDeviceName[0].lower() + otDeviceName[1:]
+                if getattr(v, feaDeviceName):
+                    raise FeatureLibError(
+                        "Can't define a device coordinate and variable scalar", location
+                    )
+                vr[otName], device = self.makeVariablePos(location, val)
+                if device is not None:
+                    vr[otDeviceName] = device
+            else:
+                vr[otName] = val
+
+        if pairPosContext and not vr:
+            vr = {"YAdvance": 0} if v.vertical else {"XAdvance": 0}
+        valRec = otl.buildValue(vr)
+        return valRec