# Source code for fontTools.designspaceLib

    """
        designSpaceDocument

        - Read and write designspace files
    """

    from __future__ import annotations

    import collections
    import copy
    import itertools
    import math
    import os
    import posixpath
    from io import BytesIO, StringIO
    from textwrap import indent
    from typing import Any, Dict, List, MutableMapping, Optional, Tuple, Union, cast

    from fontTools.misc import etree as ET
    from fontTools.misc import plistlib
    from fontTools.misc.loggingTools import LogMixin
    from fontTools.misc.textTools import tobytes, tostr

    __all__ = [
        "AxisDescriptor",
        "AxisLabelDescriptor",
        "AxisMappingDescriptor",
        "BaseDocReader",
        "BaseDocWriter",
        "DesignSpaceDocument",
        "DesignSpaceDocumentError",
        "DiscreteAxisDescriptor",
        "InstanceDescriptor",
        "LocationLabelDescriptor",
        "RangeAxisSubsetDescriptor",
        "RuleDescriptor",
        "SourceDescriptor",
        "ValueAxisSubsetDescriptor",
        "VariableFontDescriptor",
    ]

    # ElementTree allows to find namespace-prefixed elements, but not attributes
    # so we have to do it ourselves for 'xml:lang'
    XML_NS = "{http://www.w3.org/XML/1998/namespace}"
    XML_LANG = XML_NS + "lang"

    def posix(path):
        """Normalize paths using forward slash to work also on Windows."""
        new_path = posixpath.join(*path.split(os.path.sep))
        if path.startswith("/"):
            # The above transformation loses absolute paths
            new_path = "/" + new_path
        elif path.startswith(r"\\"):
            # The above transformation loses leading slashes of UNC path mounts
            new_path = "//" + new_path
        return new_path

    def posixpath_property(private_name):
        """Generate a propery that holds a path always using forward slashes."""

        def getter(self):
            # Normal getter
            return getattr(self, private_name)

        def setter(self, value):
            # The setter rewrites paths using forward slashes
            if value is not None:
                value = posix(value)
            setattr(self, private_name, value)

        return property(getter, setter)

    class DesignSpaceDocumentError(Exception):
        def __init__(self, msg, obj=None):
            self.msg = msg
            self.obj = obj

        def __str__(self):
            return str(self.msg) + (": %r" % self.obj if self.obj is not None else "")

    class AsDictMixin(object):
        def asdict(self):
            d = {}
            for attr, value in self.__dict__.items():
                if attr.startswith("_"):
                    continue
                if hasattr(value, "asdict"):
                    value = value.asdict()
                elif isinstance(value, list):
                    value = [v.asdict() if hasattr(v, "asdict") else v for v in value]
                d[attr] = value
            return d

    class SimpleDescriptor(AsDictMixin):
        """Containers for a bunch of attributes"""

        # XXX this is ugly. The 'print' is inappropriate here, and instead of
        # assert, it should simply return True/False
        def compare(self, other):
            # test if this object contains the same data as the other
            for attr in self._attrs:
                try:
                    assert getattr(self, attr) == getattr(other, attr)
                except AssertionError:
                    print(
                        "failed attribute",
                        attr,
                        getattr(self, attr),
                        "!=",
                        getattr(other, attr),
                    )

        def __repr__(self):
            attrs = [f"{a}={repr(getattr(self, a))}," for a in self._attrs]
            attrs = indent("\n".join(attrs), "    ")
            return f"{self.__class__.__name__}(\n{attrs}\n)"

    class SourceDescriptor(SimpleDescriptor):
        """Simple container for data related to the source

        .. code:: python

            doc = DesignSpaceDocument()
            s1 = SourceDescriptor()
            s1.path = masterPath1
            s1.name = "master.ufo1"
            s1.font = defcon.Font("master.ufo1")
            s1.location = dict(weight=0)
            s1.familyName = "MasterFamilyName"
            s1.styleName = "MasterStyleNameOne"
            s1.localisedFamilyName = dict(fr="Caractère")
            s1.mutedGlyphNames.append("A")
            s1.mutedGlyphNames.append("Z")
            doc.addSource(s1)

        """

        flavor = "source"
        _attrs = [
            "filename",
            "path",
            "name",
            "layerName",
            "location",
            "copyLib",
            "copyGroups",
            "copyFeatures",
            "muteKerning",
            "muteInfo",
            "mutedGlyphNames",
            "familyName",
            "styleName",
            "localisedFamilyName",
        ]

        filename = posixpath_property("_filename")
        path = posixpath_property("_path")

        def __init__(
            self,
            *,
            filename=None,
            path=None,
            font=None,
            name=None,
            location=None,
            designLocation=None,
            layerName=None,
            familyName=None,
            styleName=None,
            localisedFamilyName=None,
            copyLib=False,
            copyInfo=False,
            copyGroups=False,
            copyFeatures=False,
            muteKerning=False,
            muteInfo=False,
            mutedGlyphNames=None,
        ):
            self.filename = filename
            """string. A relative path to the source file, **as it is in the document**.

            MutatorMath + VarLib.
            """
            self.path = path
            """The absolute path, calculated from filename."""

            self.font = font
            """Any Python object. Optional. Points to a representation of this
            source font that is loaded in memory, as a Python object (e.g. a
            ``defcon.Font`` or a ``fontTools.ttFont.TTFont``).

            The default document reader will not fill-in this attribute, and the
            default writer will not use this attribute. It is up to the user of
            ``designspaceLib`` to either load the resource identified by
            ``filename`` and store it in this field, or write the contents of
            this field to the disk and make ```filename`` point to that.
            """

            self.name = name
            """string. Optional. Unique identifier name for this source.

            MutatorMath + varLib.
            """

            self.designLocation = (
                designLocation if designLocation is not None else location or {}
            )
            """dict. Axis values for this source, in design space coordinates.

            MutatorMath + varLib.

            This may be only part of the full design location.
            See :meth:`getFullDesignLocation()`

            .. versionadded:: 5.0
            """

            self.layerName = layerName
            """string. The name of the layer in the source to look for
            outline data. Default ``None`` which means ``foreground``.
            """
            self.familyName = familyName
            """string. Family name of this source. Though this data
            can be extracted from the font, it can be efficient to have it right
            here.

            varLib.
            """
            self.styleName = styleName
            """string. Style name of this source. Though this data
            can be extracted from the font, it can be efficient to have it right
            here.

            varLib.
            """
            self.localisedFamilyName = localisedFamilyName or {}
            """dict. A dictionary of localised family name strings, keyed by
            language code.

            If present, will be used to build localized names for all instances.

            .. versionadded:: 5.0
            """

            self.copyLib = copyLib
            """bool. Indicates if the contents of the font.lib need to
            be copied to the instances.

            MutatorMath.

            .. deprecated:: 5.0
            """
            self.copyInfo = copyInfo
            """bool. Indicates if the non-interpolating font.info needs
            to be copied to the instances.

            MutatorMath.

            .. deprecated:: 5.0
            """
            self.copyGroups = copyGroups
            """bool. Indicates if the groups need to be copied to the
            instances.

            MutatorMath.

            .. deprecated:: 5.0
            """
            self.copyFeatures = copyFeatures
            """bool. Indicates if the feature text needs to be
            copied to the instances.

            MutatorMath.

            .. deprecated:: 5.0
            """
            self.muteKerning = muteKerning
            """bool. Indicates if the kerning data from this source
            needs to be muted (i.e. not be part of the calculations).

            MutatorMath only.
            """
            self.muteInfo = muteInfo
            """bool. Indicated if the interpolating font.info data for
            this source needs to be muted.

            MutatorMath only.
            """
            self.mutedGlyphNames = mutedGlyphNames or []
            """list. Glyphnames that need to be muted in the
            instances.

            MutatorMath only.
            """

        @property
        def location(self):
            """dict. Axis values for this source, in design space coordinates.

            MutatorMath + varLib.

            .. deprecated:: 5.0
               Use the more explicit alias for this property :attr:`designLocation`.
            """
            return self.designLocation

        @location.setter
        def location(self, location: Optional[SimpleLocationDict]):
            self.designLocation = location or {}

        def setFamilyName(self, familyName, languageCode="en"):
            """Setter for :attr:`localisedFamilyName`

            .. versionadded:: 5.0
            """
            self.localisedFamilyName[languageCode] = tostr(familyName)

        def getFamilyName(self, languageCode="en"):
            """Getter for :attr:`localisedFamilyName`

            .. versionadded:: 5.0
            """
            return self.localisedFamilyName.get(languageCode)

        def getFullDesignLocation(self, doc: "DesignSpaceDocument") -> SimpleLocationDict:
            """Get the complete design location of this source, from its
            :attr:`designLocation` and the document's axis defaults.

            .. versionadded:: 5.0
            """
            result: SimpleLocationDict = {}
            for axis in doc.axes:
                if axis.name in self.designLocation:
                    result[axis.name] = self.designLocation[axis.name]
                else:
                    result[axis.name] = axis.map_forward(axis.default)
            return result

    class RuleDescriptor(SimpleDescriptor):
        """Represents the rule descriptor element: a set of glyph substitutions to
        trigger conditionally in some parts of the designspace.

        .. code:: python

            r1 = RuleDescriptor()
            r1.name = "unique.rule.name"
            r1.conditionSets.append([dict(name="weight", minimum=-10, maximum=10), dict(...)])
            r1.conditionSets.append([dict(...), dict(...)])
            r1.subs.append(("a", "a.alt"))

        .. code:: xml

            <!-- optional: list of substitution rules -->
            <rules>
                <rule name="vertical.bars">
                    <conditionset>
                        <condition minimum="250.000000" maximum="750.000000" name="weight"/>
                        <condition minimum="100" name="width"/>
                        <condition minimum="10" maximum="40" name="optical"/>
                    </conditionset>
                    <sub name="cent" with="cent.alt"/>
                    <sub name="dollar" with="dollar.alt"/>
                </rule>
            </rules>
        """

        _attrs = ["name", "conditionSets", "subs"]  # what do we need here

        def __init__(self, *, name=None, conditionSets=None, subs=None):
            self.name = name
            """string. Unique name for this rule. Can be used to reference this rule data."""
            # list of lists of dict(name='aaaa', minimum=0, maximum=1000)
            self.conditionSets = conditionSets or []
            """a list of conditionsets.

            -  Each conditionset is a list of conditions.
            -  Each condition is a dict with ``name``, ``minimum`` and ``maximum`` keys.
            """
            # list of substitutions stored as tuples of glyphnames ("a", "a.alt")
            self.subs = subs or []
            """list of substitutions.

            -  Each substitution is stored as tuples of glyphnames, e.g. ("a", "a.alt").
            -  Note: By default, rules are applied first, before other text
               shaping/OpenType layout, as they are part of the
               `Required Variation Alternates OpenType feature <https://docs.microsoft.com/en-us/typography/opentype/spec/features_pt#-tag-rvrn>`_.
               See ref:`rules-element` § Attributes.
            """

    def evaluateRule(rule, location):
        """Return True if any of the rule's conditionsets matches the given location."""
        return any(evaluateConditions(c, location) for c in rule.conditionSets)

    def evaluateConditions(conditions, location):
        """Return True if all the conditions matches the given location.

        - If a condition has no minimum, check for < maximum.
        - If a condition has no maximum, check for > minimum.
        """
        for cd in conditions:
            value = location[cd["name"]]
            if cd.get("minimum") is None:
                if value > cd["maximum"]:
                    return False
            elif cd.get("maximum") is None:
                if cd["minimum"] > value:
                    return False
            elif not cd["minimum"] <= value <= cd["maximum"]:
                return False
        return True

    def processRules(rules, location, glyphNames):
        """Apply these rules at this location to these glyphnames.

        Return a new list of glyphNames with substitutions applied.

        - rule order matters
        """
        newNames = []
        for rule in rules:
            if evaluateRule(rule, location):
                for name in glyphNames:
                    swap = False
                    for a, b in rule.subs:
                        if name == a:
                            swap = True
                            break
                    if swap:
                        newNames.append(b)
                    else:
                        newNames.append(name)
                glyphNames = newNames
                newNames = []
        return glyphNames

    AnisotropicLocationDict = Dict[str, Union[float, Tuple[float, float]]]
    SimpleLocationDict = Dict[str, float]

    class AxisMappingDescriptor(SimpleDescriptor):
        """Represents the axis mapping element: mapping an input location
        to an output location in the designspace.

        .. code:: python

            m1 = AxisMappingDescriptor()
            m1.inputLocation = {"weight": 900, "width": 150}
            m1.outputLocation = {"weight": 870}

        .. code:: xml

            <mappings>
                <mapping>
                    <input>
                        <dimension name="weight" xvalue="900"/>
                        <dimension name="width" xvalue="150"/>
                    </input>
                    <output>
                        <dimension name="weight" xvalue="870"/>
                    </output>
                </mapping>
            </mappings>
        """

        _attrs = ["inputLocation", "outputLocation"]

        def __init__(
            self,
            *,
            inputLocation=None,
            outputLocation=None,
            description=None,
            groupDescription=None,
        ):
            self.inputLocation: SimpleLocationDict = inputLocation or {}
            """dict. Axis values for the input of the mapping, in design space coordinates.

            varLib.

            .. versionadded:: 5.1
            """
            self.outputLocation: SimpleLocationDict = outputLocation or {}
            """dict. Axis values for the output of the mapping, in design space coordinates.

            varLib.

            .. versionadded:: 5.1
            """
            self.description = description
            """string. A description of the mapping.

            varLib.

            .. versionadded:: 5.2
            """
            self.groupDescription = groupDescription
            """string. A description of the group of mappings.

            varLib.

            .. versionadded:: 5.2
            """

    class InstanceDescriptor(SimpleDescriptor):
        """Simple container for data related to the instance

        .. code:: python

            i2 = InstanceDescriptor()
            i2.path = instancePath2
            i2.familyName = "InstanceFamilyName"
            i2.styleName = "InstanceStyleName"
            i2.name = "instance.ufo2"
            # anisotropic location
            i2.designLocation = dict(weight=500, width=(400,300))
            i2.postScriptFontName = "InstancePostscriptName"
            i2.styleMapFamilyName = "InstanceStyleMapFamilyName"
            i2.styleMapStyleName = "InstanceStyleMapStyleName"
            i2.lib['com.coolDesignspaceApp.specimenText'] = 'Hamburgerwhatever'
            doc.addInstance(i2)
        """

        flavor = "instance"
        _defaultLanguageCode = "en"
        _attrs = [
            "filename",
            "path",
            "name",
            "locationLabel",
            "designLocation",
            "userLocation",
            "familyName",
            "styleName",
            "postScriptFontName",
            "styleMapFamilyName",
            "styleMapStyleName",
            "localisedFamilyName",
            "localisedStyleName",
            "localisedStyleMapFamilyName",
            "localisedStyleMapStyleName",
            "glyphs",
            "kerning",
            "info",
            "lib",
        ]

        filename = posixpath_property("_filename")
        path = posixpath_property("_path")

        def __init__(
            self,
            *,
            filename=None,
            path=None,
            font=None,
            name=None,
            location=None,
            locationLabel=None,
            designLocation=None,
            userLocation=None,
            familyName=None,
            styleName=None,
            postScriptFontName=None,
            styleMapFamilyName=None,
            styleMapStyleName=None,
            localisedFamilyName=None,
            localisedStyleName=None,
            localisedStyleMapFamilyName=None,
            localisedStyleMapStyleName=None,
            glyphs=None,
            kerning=True,
            info=True,
            lib=None,
        ):
            self.filename = filename
            """string. Relative path to the instance file, **as it is
            in the document**. The file may or may not exist.

            MutatorMath + VarLib.
            """
            self.path = path
            """string. Absolute path to the instance file, calculated from
            the document path and the string in the filename attr. The file may
            or may not exist.

            MutatorMath.
            """
            self.font = font
            """Same as :attr:`SourceDescriptor.font`

            .. seealso:: :attr:`SourceDescriptor.font`
            """
            self.name = name
            """string. Unique identifier name of the instance, used to
            identify it if it needs to be referenced from elsewhere in the
            document.
            """
            self.locationLabel = locationLabel
            """Name of a :class:`LocationLabelDescriptor`. If
            provided, the instance should have the same location as the
            LocationLabel.

            .. seealso::
               :meth:`getFullDesignLocation`
               :meth:`getFullUserLocation`

            .. versionadded:: 5.0
            """
            self.designLocation: AnisotropicLocationDict = (
                designLocation if designLocation is not None else (location or {})
            )
            """dict. Axis values for this instance, in design space coordinates.

            MutatorMath + varLib.

            .. seealso:: This may be only part of the full location. See:
               :meth:`getFullDesignLocation`
               :meth:`getFullUserLocation`

            .. versionadded:: 5.0
            """
            self.userLocation: SimpleLocationDict = userLocation or {}
            """dict. Axis values for this instance, in user space coordinates.

            MutatorMath + varLib.

            .. seealso:: This may be only part of the full location. See:
               :meth:`getFullDesignLocation`
               :meth:`getFullUserLocation`

            .. versionadded:: 5.0
            """
            self.familyName = familyName
            """string. Family name of this instance.

            MutatorMath + varLib.
            """
            self.styleName = styleName
            """string. Style name of this instance.

            MutatorMath + varLib.
            """
            self.postScriptFontName = postScriptFontName
            """string. Postscript fontname for this instance.

            MutatorMath + varLib.
            """
            self.styleMapFamilyName = styleMapFamilyName
            """string. StyleMap familyname for this instance.

            MutatorMath + varLib.
            """
            self.styleMapStyleName = styleMapStyleName
            """string. StyleMap stylename for this instance.

            MutatorMath + varLib.
            """
            self.localisedFamilyName = localisedFamilyName or {}
            """dict. A dictionary of localised family name
            strings, keyed by language code.
            """
            self.localisedStyleName = localisedStyleName or {}
            """dict. A dictionary of localised stylename
            strings, keyed by language code.
            """
            self.localisedStyleMapFamilyName = localisedStyleMapFamilyName or {}
            """A dictionary of localised style map
            familyname strings, keyed by language code.
            """
            self.localisedStyleMapStyleName = localisedStyleMapStyleName or {}
            """A dictionary of localised style map
            stylename strings, keyed by language code.
            """
            self.glyphs = glyphs or {}
            """dict for special master definitions for glyphs. If glyphs
            need special masters (to record the results of executed rules for
            example).

            MutatorMath.

            .. deprecated:: 5.0
                Use rules or sparse sources instead.
            """
            self.kerning = kerning
            """ bool. Indicates if this instance needs its kerning
            calculated.

            MutatorMath.

            .. deprecated:: 5.0
            """
            self.info = info
            """bool. Indicated if this instance needs the interpolating
            font.info calculated.

            .. deprecated:: 5.0
            """

            self.lib = lib or {}
            """Custom data associated with this instance."""

        @property
        def location(self):
            """dict. Axis values for this instance.

            MutatorMath + varLib.

            .. deprecated:: 5.0
               Use the more explicit alias for this property :attr:`designLocation`.
            """
            return self.designLocation

        @location.setter
        def location(self, location: Optional[AnisotropicLocationDict]):
            self.designLocation = location or {}

        def setStyleName(self, styleName, languageCode="en"):
            """These methods give easier access to the localised names."""
            self.localisedStyleName[languageCode] = tostr(styleName)

        def getStyleName(self, languageCode="en"):
            return self.localisedStyleName.get(languageCode)

        def setFamilyName(self, familyName, languageCode="en"):
            self.localisedFamilyName[languageCode] = tostr(familyName)

        def getFamilyName(self, languageCode="en"):
            return self.localisedFamilyName.get(languageCode)

        def setStyleMapStyleName(self, styleMapStyleName, languageCode="en"):
            self.localisedStyleMapStyleName[languageCode] = tostr(styleMapStyleName)

        def getStyleMapStyleName(self, languageCode="en"):
            return self.localisedStyleMapStyleName.get(languageCode)

        def setStyleMapFamilyName(self, styleMapFamilyName, languageCode="en"):
            self.localisedStyleMapFamilyName[languageCode] = tostr(styleMapFamilyName)

        def getStyleMapFamilyName(self, languageCode="en"):
            return self.localisedStyleMapFamilyName.get(languageCode)

        def clearLocation(self, axisName: Optional[str] = None):
            """Clear all location-related fields. Ensures that
            :attr:``designLocation`` and :attr:``userLocation`` are dictionaries
            (possibly empty if clearing everything).

            In order to update the location of this instance wholesale, a user
            should first clear all the fields, then change the field(s) for which
            they have data.

            .. code:: python

                instance.clearLocation()
                instance.designLocation = {'Weight': (34, 36.5), 'Width': 100}
                instance.userLocation = {'Opsz': 16}

            In order to update a single axis location, the user should only clear
            that axis, then edit the values:

            .. code:: python

                instance.clearLocation('Weight')
                instance.designLocation['Weight'] = (34, 36.5)

            Args:
              axisName: if provided, only clear the location for that axis.

            .. versionadded:: 5.0
            """
            self.locationLabel = None
            if axisName is None:
                self.designLocation = {}
                self.userLocation = {}
            else:
                if self.designLocation is None:
                    self.designLocation = {}
                if axisName in self.designLocation:
                    del self.designLocation[axisName]
                if self.userLocation is None:
                    self.userLocation = {}
                if axisName in self.userLocation:
                    del self.userLocation[axisName]

        def getLocationLabelDescriptor(
            self, doc: "DesignSpaceDocument"
        ) -> Optional[LocationLabelDescriptor]:
            """Get the :class:`LocationLabelDescriptor` instance that matches
            this instances's :attr:`locationLabel`.

            Raises if the named label can't be found.

            .. versionadded:: 5.0
            """
            if self.locationLabel is None:
                return None
            label = doc.getLocationLabel(self.locationLabel)
            if label is None:
                raise DesignSpaceDocumentError(
                    "InstanceDescriptor.getLocationLabelDescriptor(): "
                    f"unknown location label `{self.locationLabel}` in instance `{self.name}`."
                )
            return label

        def getFullDesignLocation(
            self, doc: "DesignSpaceDocument"
        ) -> AnisotropicLocationDict:
            """Get the complete design location of this instance, by combining data
            from the various location fields, default axis values and mappings, and
            top-level location labels.

            The source of truth for this instance's location is determined for each
            axis independently by taking the first not-None field in this list:

            - ``locationLabel``: the location along this axis is the same as the
              matching STAT format 4 label. No anisotropy.
            - ``designLocation[axisName]``: the explicit design location along this
              axis, possibly anisotropic.
            - ``userLocation[axisName]``: the explicit user location along this
              axis. No anisotropy.
            - ``axis.default``: default axis value. No anisotropy.

            .. versionadded:: 5.0
            """
            label = self.getLocationLabelDescriptor(doc)
            if label is not None:
                return doc.map_forward(label.userLocation)  # type: ignore
            result: AnisotropicLocationDict = {}
            for axis in doc.axes:
                if axis.name in self.designLocation:
                    result[axis.name] = self.designLocation[axis.name]
                elif axis.name in self.userLocation:
                    result[axis.name] = axis.map_forward(self.userLocation[axis.name])
                else:
                    result[axis.name] = axis.map_forward(axis.default)
            return result

        def getFullUserLocation(self, doc: "DesignSpaceDocument") -> SimpleLocationDict:
            """Get the complete user location for this instance.

            .. seealso:: :meth:`getFullDesignLocation`

            .. versionadded:: 5.0
            """
            return doc.map_backward(self.getFullDesignLocation(doc))

    def tagForAxisName(name):
        # try to find or make a tag name for this axis name
        names = {
            "weight": ("wght", dict(en="Weight")),
            "width": ("wdth", dict(en="Width")),
            "optical": ("opsz", dict(en="Optical Size")),
            "slant": ("slnt", dict(en="Slant")),
            "italic": ("ital", dict(en="Italic")),
        }
        if name.lower() in names:
            return names[name.lower()]
        if len(name) < 4:
            tag = name + "*" * (4 - len(name))
        else:
            tag = name[:4]
        return tag, dict(en=name)

    class AbstractAxisDescriptor(SimpleDescriptor):
        flavor = "axis"

        def __init__(
            self,
            *,
            tag=None,
            name=None,
            labelNames=None,
            hidden=False,
            map=None,
            axisOrdering=None,
            axisLabels=None,
        ):
            # opentype tag for this axis
            self.tag = tag
            """string. Four letter tag for this axis. Some might be
            registered at the `OpenType
            specification <https://www.microsoft.com/typography/otspec/fvar.htm#VAT>`__.
            Privately-defined axis tags must begin with an uppercase letter and
            use only uppercase letters or digits.
            """
            # name of the axis used in locations
            self.name = name
            """string. Name of the axis as it is used in the location dicts.

            MutatorMath + varLib.
            """
            # names for UI purposes, if this is not a standard axis,
            self.labelNames = labelNames or {}
            """dict. When defining a non-registered axis, it will be
            necessary to define user-facing readable names for the axis. Keyed by
            xml:lang code. Values are required to be ``unicode`` strings, even if
            they only contain ASCII characters.
            """
            self.hidden = hidden
            """bool. Whether this axis should be hidden in user interfaces.
            """
            self.map = map or []
            """list of input / output values that can describe a warp of user space
            to design space coordinates. If no map values are present, it is assumed
            user space is the same as design space, as in [(minimum, minimum),
            (maximum, maximum)].

            varLib.
            """
            self.axisOrdering = axisOrdering
            """STAT table field ``axisOrdering``.

            See: `OTSpec STAT Axis Record <https://docs.microsoft.com/en-us/typography/opentype/spec/stat#axis-records>`_

            .. versionadded:: 5.0
            """
            self.axisLabels: List[AxisLabelDescriptor] = axisLabels or []
            """STAT table entries for Axis Value Tables format 1, 2, 3.

            See: `OTSpec STAT Axis Value Tables <https://docs.microsoft.com/en-us/typography/opentype/spec/stat#axis-value-tables>`_

            .. versionadded:: 5.0
            """

    class AxisDescriptor(AbstractAxisDescriptor):
        """Simple container for the axis data.

        Add more localisations?

        .. code:: python

            a1 = AxisDescriptor()
            a1.minimum = 1
            a1.maximum = 1000
            a1.default = 400
            a1.name = "weight"
            a1.tag = "wght"
            a1.labelNames['fa-IR'] = "قطر"
            a1.labelNames['en'] = "Wéíght"
            a1.map = [(1.0, 10.0), (400.0, 66.0), (1000.0, 990.0)]
            a1.axisOrdering = 1
            a1.axisLabels = [
                AxisLabelDescriptor(name="Regular", userValue=400, elidable=True)
            ]
            doc.addAxis(a1)
        """

        _attrs = [
            "tag",
            "name",
            "maximum",
            "minimum",
            "default",
            "map",
            "axisOrdering",
            "axisLabels",
        ]

        def __init__(
            self,
            *,
            tag=None,
            name=None,
            labelNames=None,
            minimum=None,
            default=None,
            maximum=None,
            hidden=False,
            map=None,
            axisOrdering=None,
            axisLabels=None,
        ):
            super().__init__(
                tag=tag,
                name=name,
                labelNames=labelNames,
                hidden=hidden,
                map=map,
                axisOrdering=axisOrdering,
                axisLabels=axisLabels,
            )
            self.minimum = minimum
            """number. The minimum value for this axis in user space.

            MutatorMath + varLib.
            """
            self.maximum = maximum
            """number. The maximum value for this axis in user space.

            MutatorMath + varLib.
            """
            self.default = default
            """number. The default value for this axis, i.e. when a new location is
            created, this is the value this axis will get in user space.

            MutatorMath + varLib.
            """

        def serialize(self):
            # output to a dict, used in testing
            return dict(
                tag=self.tag,
                name=self.name,
                labelNames=self.labelNames,
                maximum=self.maximum,
                minimum=self.minimum,
                default=self.default,
                hidden=self.hidden,
                map=self.map,
                axisOrdering=self.axisOrdering,
                axisLabels=self.axisLabels,
            )

        def map_forward(self, v):
            """Maps value from axis mapping's input (user) to output (design)."""
            from fontTools.varLib.models import piecewiseLinearMap

            if not self.map:
                return v
            return piecewiseLinearMap(v, {k: v for k, v in self.map})

        def map_backward(self, v):
            """Maps value from axis mapping's output (design) to input (user)."""
            from fontTools.varLib.models import piecewiseLinearMap

            if isinstance(v, tuple):
                v = v[0]
            if not self.map:
                return v
            return piecewiseLinearMap(v, {v: k for k, v in self.map})

    class DiscreteAxisDescriptor(AbstractAxisDescriptor):
        """Container for discrete axis data.

        Use this for axes that do not interpolate. The main difference from a
        continuous axis is that a continuous axis has a ``minimum`` and ``maximum``,
        while a discrete axis has a list of ``values``.

        Example: an Italic axis with 2 stops, Roman and Italic, that are not
        compatible. The axis still allows to bind together the full font family,
        which is useful for the STAT table, however it can't become a variation
        axis in a VF.

        .. code:: python

            a2 = DiscreteAxisDescriptor()
            a2.values = [0, 1]
            a2.default = 0
            a2.name = "Italic"
            a2.tag = "ITAL"
            a2.labelNames['fr'] = "Italique"
            a2.map = [(0, 0), (1, -11)]
            a2.axisOrdering = 2
            a2.axisLabels = [
                AxisLabelDescriptor(name="Roman", userValue=0, elidable=True)
            ]
            doc.addAxis(a2)

        .. versionadded:: 5.0
        """

        flavor = "axis"
        _attrs = ("tag", "name", "values", "default", "map", "axisOrdering", "axisLabels")

        def __init__(
            self,
            *,
            tag=None,
            name=None,
            labelNames=None,
            values=None,
            default=None,
            hidden=False,
            map=None,
            axisOrdering=None,
            axisLabels=None,
        ):
            super().__init__(
                tag=tag,
                name=name,
                labelNames=labelNames,
                hidden=hidden,
                map=map,
                axisOrdering=axisOrdering,
                axisLabels=axisLabels,
            )
            self.default: float = default
            """The default value for this axis, i.e. when a new location is
            created, this is the value this axis will get in user space.

            However, this default value is less important than in continuous axes:

            -  it doesn't define the "neutral" version of outlines from which
               deltas would apply, as this axis does not interpolate.
            -  it doesn't provide the reference glyph set for the designspace, as
               fonts at each value can have different glyph sets.
            """
            self.values: List[float] = values or []
            """List of possible values for this axis. Contrary to continuous axes,
            only the values in this list can be taken by the axis, nothing in-between.
            """

        def map_forward(self, value):
            """Maps value from axis mapping's input to output.

            Returns value unchanged if no mapping entry is found.

            Note: for discrete axes, each value must have its mapping entry, if
            you intend that value to be mapped.
            """
            return next((v for k, v in self.map if k == value), value)

        def map_backward(self, value):
            """Maps value from axis mapping's output to input.

            Returns value unchanged if no mapping entry is found.

            Note: for discrete axes, each value must have its mapping entry, if
            you intend that value to be mapped.
            """
            if isinstance(value, tuple):
                value = value[0]
            return next((k for k, v in self.map if v == value), value)

    class AxisLabelDescriptor(SimpleDescriptor):
        """Container for axis label data.

        Analogue of OpenType's STAT data for a single axis (formats 1, 2 and 3).
        All values are user values.
        See: `OTSpec STAT Axis value table, format 1, 2, 3 <https://docs.microsoft.com/en-us/typography/opentype/spec/stat#axis-value-table-format-1>`_

        The STAT format of the Axis value depends on which field are filled-in,
        see :meth:`getFormat`

        .. versionadded:: 5.0
        """

        flavor = "label"
        _attrs = (
            "userMinimum",
            "userValue",
            "userMaximum",
            "name",
            "elidable",
            "olderSibling",
            "linkedUserValue",
            "labelNames",
        )

        def __init__(
            self,
            *,
            name,
            userValue,
            userMinimum=None,
            userMaximum=None,
            elidable=False,
            olderSibling=False,
            linkedUserValue=None,
            labelNames=None,
        ):
            self.userMinimum: Optional[float] = userMinimum
            """STAT field ``rangeMinValue`` (format 2)."""
            self.userValue: float = userValue
            """STAT field ``value`` (format 1, 3) or ``nominalValue`` (format 2)."""
            self.userMaximum: Optional[float] = userMaximum
            """STAT field ``rangeMaxValue`` (format 2)."""
            self.name: str = name
            """Label for this axis location, STAT field ``valueNameID``."""
            self.elidable: bool = elidable
            """STAT flag ``ELIDABLE_AXIS_VALUE_NAME``.

            See: `OTSpec STAT Flags <https://docs.microsoft.com/en-us/typography/opentype/spec/stat#flags>`_
            """
            self.olderSibling: bool = olderSibling
            """STAT flag ``OLDER_SIBLING_FONT_ATTRIBUTE``.

            See: `OTSpec STAT Flags <https://docs.microsoft.com/en-us/typography/opentype/spec/stat#flags>`_
            """
            self.linkedUserValue: Optional[float] = linkedUserValue
            """STAT field ``linkedValue`` (format 3)."""
            self.labelNames: MutableMapping[str, str] = labelNames or {}
            """User-facing translations of this location's label. Keyed by
            ``xml:lang`` code.
            """

        def getFormat(self) -> int:
            """Determine which format of STAT Axis value to use to encode this label.

            ===========  =========  ===========  ===========  ===============
            STAT Format  userValue  userMinimum  userMaximum  linkedUserValue
            ===========  =========  ===========  ===========  ===============
            1            ✅          ❌            ❌            ❌
            2            ✅          ✅            ✅            ❌
            3            ✅          ❌            ❌            ✅
            ===========  =========  ===========  ===========  ===============
            """
            if self.linkedUserValue is not None:
                return 3
            if self.userMinimum is not None or self.userMaximum is not None:
                return 2
            return 1

        @property
        def defaultName(self) -> str:
            """Return the English name from :attr:`labelNames` or the :attr:`name`."""
            return self.labelNames.get("en") or self.name

    class LocationLabelDescriptor(SimpleDescriptor):
        """Container for location label data.

        Analogue of OpenType's STAT data for a free-floating location (format 4).
        All values are user values.

        See: `OTSpec STAT Axis value table, format 4 <https://docs.microsoft.com/en-us/typography/opentype/spec/stat#axis-value-table-format-4>`_

        .. versionadded:: 5.0
        """

        flavor = "label"
        _attrs = ("name", "elidable", "olderSibling", "userLocation", "labelNames")

        def __init__(
            self,
            *,
            name,
            userLocation,
            elidable=False,
            olderSibling=False,
            labelNames=None,
        ):
            self.name: str = name
            """Label for this named location, STAT field ``valueNameID``."""
            self.userLocation: SimpleLocationDict = userLocation or {}
            """Location in user coordinates along each axis.

            If an axis is not mentioned, it is assumed to be at its default location.

            .. seealso:: This may be only part of the full location. See:
               :meth:`getFullUserLocation`
            """
            self.elidable: bool = elidable
            """STAT flag ``ELIDABLE_AXIS_VALUE_NAME``.

            See: `OTSpec STAT Flags <https://docs.microsoft.com/en-us/typography/opentype/spec/stat#flags>`_
            """
            self.olderSibling: bool = olderSibling
            """STAT flag ``OLDER_SIBLING_FONT_ATTRIBUTE``.

            See: `OTSpec STAT Flags <https://docs.microsoft.com/en-us/typography/opentype/spec/stat#flags>`_
            """
            self.labelNames: Dict[str, str] = labelNames or {}
            """User-facing translations of this location's label. Keyed by
            xml:lang code.
            """

        @property
        def defaultName(self) -> str:
            """Return the English name from :attr:`labelNames` or the :attr:`name`."""
            return self.labelNames.get("en") or self.name

        def getFullUserLocation(self, doc: "DesignSpaceDocument") -> SimpleLocationDict:
            """Get the complete user location of this label, by combining data
            from the explicit user location and default axis values.

            .. versionadded:: 5.0
            """
            return {
                axis.name: self.userLocation.get(axis.name, axis.default)
                for axis in doc.axes
            }

    class VariableFontDescriptor(SimpleDescriptor):
        """Container for variable fonts, sub-spaces of the Designspace.

        Use-cases:

        - From a single DesignSpace with discrete axes, define 1 variable font
          per value on the discrete axes. Before version 5, you would have needed
          1 DesignSpace per such variable font, and a lot of data duplication.
        - From a big variable font with many axes, define subsets of that variable
          font that only include some axes and freeze other axes at a given location.

        .. versionadded:: 5.0
        """

        flavor = "variable-font"
        _attrs = ("filename", "axisSubsets", "lib")

        filename = posixpath_property("_filename")

        def __init__(self, *, name, filename=None, axisSubsets=None, lib=None):
            self.name: str = name
            """string, required. Name of this variable to identify it during the
            build process and from other parts of the document, and also as a
            filename in case the filename property is empty.

            VarLib.
            """
            self.filename: str = filename
            """string, optional. Relative path to the variable font file, **as it is
            in the document**. The file may or may not exist.

            If not specified, the :attr:`name` will be used as a basename for the file.

            .. note::
                This is intended to be a simple filename (basename or stem) only.
                Build tools will only use the basename component and ignore any
                directory separators for security reasons.
            """
            self.axisSubsets: List[
                Union[RangeAxisSubsetDescriptor, ValueAxisSubsetDescriptor]
            ] = (axisSubsets or [])
            """Axis subsets to include in this variable font.

            If an axis is not mentioned, assume that we only want the default
            location of that axis (same as a :class:`ValueAxisSubsetDescriptor`).
            """
            self.lib: MutableMapping[str, Any] = lib or {}
            """Custom data associated with this variable font."""

    class RangeAxisSubsetDescriptor(SimpleDescriptor):
        """Subset of a continuous axis to include in a variable font.

        .. versionadded:: 5.0
        """

        flavor = "axis-subset"
        _attrs = ("name", "userMinimum", "userDefault", "userMaximum")

        def __init__(
            self, *, name, userMinimum=-math.inf, userDefault=None, userMaximum=math.inf
        ):
            self.name: str = name
            """Name of the :class:`AxisDescriptor` to subset."""
            self.userMinimum: float = userMinimum
            """New minimum value of the axis in the target variable font.
            If not specified, assume the same minimum value as the full axis.
            (default = ``-math.inf``)
            """
            self.userDefault: Optional[float] = userDefault
            """New default value of the axis in the target variable font.
            If not specified, assume the same default value as the full axis.
            (default = ``None``)
            """
            self.userMaximum: float = userMaximum
            """New maximum value of the axis in the target variable font.
            If not specified, assume the same maximum value as the full axis.
            (default = ``math.inf``)
            """

    class ValueAxisSubsetDescriptor(SimpleDescriptor):
        """Single value of a discrete or continuous axis to use in a variable font.

        .. versionadded:: 5.0
        """

        flavor = "axis-subset"
        _attrs = ("name", "userValue")

        def __init__(self, *, name, userValue):
            self.name: str = name
            """Name of the :class:`AxisDescriptor` or :class:`DiscreteAxisDescriptor`
            to "snapshot" or "freeze".
            """
            self.userValue: float = userValue
            """Value in user coordinates at which to freeze the given axis."""

    class BaseDocWriter(object):
        _whiteSpace = "    "
        axisDescriptorClass = AxisDescriptor
        discreteAxisDescriptorClass = DiscreteAxisDescriptor
        axisLabelDescriptorClass = AxisLabelDescriptor
        axisMappingDescriptorClass = AxisMappingDescriptor
        locationLabelDescriptorClass = LocationLabelDescriptor
        ruleDescriptorClass = RuleDescriptor
        sourceDescriptorClass = SourceDescriptor
        variableFontDescriptorClass = VariableFontDescriptor
        valueAxisSubsetDescriptorClass = ValueAxisSubsetDescriptor
        rangeAxisSubsetDescriptorClass = RangeAxisSubsetDescriptor
        instanceDescriptorClass = InstanceDescriptor

        @classmethod
        def getAxisDecriptor(cls):
            return cls.axisDescriptorClass()

        @classmethod
        def getAxisMappingDescriptor(cls):
            return cls.axisMappingDescriptorClass()

        @classmethod
        def getSourceDescriptor(cls):
            return cls.sourceDescriptorClass()

        @classmethod
        def getInstanceDescriptor(cls):
            return cls.instanceDescriptorClass()

        @classmethod
        def getRuleDescriptor(cls):
            return cls.ruleDescriptorClass()

        def __init__(self, documentPath, documentObject: DesignSpaceDocument):
            self.path = documentPath
            self.documentObject = documentObject
            self.effectiveFormatTuple = self._getEffectiveFormatTuple()
            self.root = ET.Element("designspace")

        def write(self, pretty=True, encoding="UTF-8", xml_declaration=True):
            self.root.attrib["format"] = ".".join(str(i) for i in self.effectiveFormatTuple)

            if (
                self.documentObject.axes
                or self.documentObject.axisMappings
                or self.documentObject.elidedFallbackName is not None
            ):
                axesElement = ET.Element("axes")
                if self.documentObject.elidedFallbackName is not None:
                    axesElement.attrib["elidedfallbackname"] = (
                        self.documentObject.elidedFallbackName
                    )
                self.root.append(axesElement)
            for axisObject in self.documentObject.axes:
                self._addAxis(axisObject)

            if self.documentObject.axisMappings:
                mappingsElement = None
                lastGroup = object()
                for mappingObject in self.documentObject.axisMappings:
                    if getattr(mappingObject, "groupDescription", None) != lastGroup:
                        if mappingsElement is not None:
                            self.root.findall(".axes")[0].append(mappingsElement)
                        lastGroup = getattr(mappingObject, "groupDescription", None)
                        mappingsElement = ET.Element("mappings")
                        if lastGroup is not None:
                            mappingsElement.attrib["description"] = lastGroup
                    self._addAxisMapping(mappingsElement, mappingObject)
                if mappingsElement is not None:
                    self.root.findall(".axes")[0].append(mappingsElement)

            if self.documentObject.locationLabels:
                labelsElement = ET.Element("labels")
                for labelObject in self.documentObject.locationLabels:
                    self._addLocationLabel(labelsElement, labelObject)
                self.root.append(labelsElement)

            if self.documentObject.rules:
                if getattr(self.documentObject, "rulesProcessingLast", False):
                    attributes = {"processing": "last"}
                else:
                    attributes = {}
                self.root.append(ET.Element("rules", attributes))
            for ruleObject in self.documentObject.rules:
                self._addRule(ruleObject)

            if self.documentObject.sources:
                self.root.append(ET.Element("sources"))
            for sourceObject in self.documentObject.sources:
                self._addSource(sourceObject)

            if self.documentObject.variableFonts:
                variableFontsElement = ET.Element("variable-fonts")
                for variableFont in self.documentObject.variableFonts:
                    self._addVariableFont(variableFontsElement, variableFont)
                self.root.append(variableFontsElement)

            if self.documentObject.instances:
                self.root.append(ET.Element("instances"))
            for instanceObject in self.documentObject.instances:
                self._addInstance(instanceObject)

            if self.documentObject.lib:
                self._addLib(self.root, self.documentObject.lib, 2)

            tree = ET.ElementTree(self.root)
            tree.write(
                self.path,
                encoding=encoding,
                method="xml",
                xml_declaration=xml_declaration,
                pretty_print=pretty,
            )

        def _getEffectiveFormatTuple(self):
            """Try to use the version specified in the document, or a sufficiently
            recent version to be able to encode what the document contains.
            """
            minVersion = self.documentObject.formatTuple
            if (
                any(
                    hasattr(axis, "values")
                    or axis.axisOrdering is not None
                    or axis.axisLabels
                    for axis in self.documentObject.axes
                )
                or self.documentObject.locationLabels
                or any(source.localisedFamilyName for source in self.documentObject.sources)
                or self.documentObject.variableFonts
                or any(
                    instance.locationLabel or instance.userLocation
                    for instance in self.documentObject.instances
                )
            ):
                if minVersion < (5, 0):
                    minVersion = (5, 0)
            if self.documentObject.axisMappings:
                if minVersion < (5, 1):
                    minVersion = (5, 1)
            return minVersion

        def _makeLocationElement(self, locationObject, name=None):
            """Convert Location dict to a locationElement."""
            locElement = ET.Element("location")
            if name is not None:
                locElement.attrib["name"] = name
            validatedLocation = self.documentObject.newDefaultLocation()
            for axisName, axisValue in locationObject.items():
                if axisName in validatedLocation:
                    # only accept values we know
                    validatedLocation[axisName] = axisValue
            for dimensionName, dimensionValue in validatedLocation.items():
                dimElement = ET.Element("dimension")
                dimElement.attrib["name"] = dimensionName
                if type(dimensionValue) == tuple:
                    dimElement.attrib["xvalue"] = self.intOrFloat(dimensionValue[0])
                    dimElement.attrib["yvalue"] = self.intOrFloat(dimensionValue[1])
                else:
                    dimElement.attrib["xvalue"] = self.intOrFloat(dimensionValue)
                locElement.append(dimElement)
            return locElement, validatedLocation

        def intOrFloat(self, num):
            if int(num) == num:
                return "%d" % num
            return ("%f" % num).rstrip("0").rstrip(".")

        def _addRule(self, ruleObject):
            ruleElement = ET.Element("rule")
            if ruleObject.name is not None:
                ruleElement.attrib["name"] = ruleObject.name
            for conditions in ruleObject.conditionSets:
                conditionsetElement = ET.Element("conditionset")
                for cond in conditions:
                    if cond.get("minimum") is None and cond.get("maximum") is None:
                        # neither is defined, don't add this condition
                        continue
                    conditionElement = ET.Element("condition")
                    conditionElement.attrib["name"] = cond.get("name")
                    if cond.get("minimum") is not None:
                        conditionElement.attrib["minimum"] = self.intOrFloat(
                            cond.get("minimum")
                        )
                    if cond.get("maximum") is not None:
                        conditionElement.attrib["maximum"] = self.intOrFloat(
                            cond.get("maximum")
                        )
                    conditionsetElement.append(conditionElement)
                # Serialize the conditionset even if it is empty, as this is the
                # canonical way of defining a rule that is always true.
                ruleElement.append(conditionsetElement)
            for sub in ruleObject.subs:
                subElement = ET.Element("sub")
                subElement.attrib["name"] = sub[0]
                subElement.attrib["with"] = sub[1]
                ruleElement.append(subElement)
            if len(ruleElement):
                self.root.findall(".rules")[0].append(ruleElement)

        def _addAxis(self, axisObject):
            axisElement = ET.Element("axis")
            axisElement.attrib["tag"] = axisObject.tag
            axisElement.attrib["name"] = axisObject.name
            self._addLabelNames(axisElement, axisObject.labelNames)
            if axisObject.map:
                for inputValue, outputValue in axisObject.map:
                    mapElement = ET.Element("map")
                    mapElement.attrib["input"] = self.intOrFloat(inputValue)
                    mapElement.attrib["output"] = self.intOrFloat(outputValue)
                    axisElement.append(mapElement)
            if axisObject.axisOrdering is not None or axisObject.axisLabels:
                labelsElement = ET.Element("labels")
                if axisObject.axisOrdering is not None:
                    labelsElement.attrib["ordering"] = str(axisObject.axisOrdering)
                for label in axisObject.axisLabels:
                    self._addAxisLabel(labelsElement, label)
                axisElement.append(labelsElement)
            if hasattr(axisObject, "minimum"):
                axisElement.attrib["minimum"] = self.intOrFloat(axisObject.minimum)
                axisElement.attrib["maximum"] = self.intOrFloat(axisObject.maximum)
            elif hasattr(axisObject, "values"):
                axisElement.attrib["values"] = " ".join(
                    self.intOrFloat(v) for v in axisObject.values
                )
            axisElement.attrib["default"] = self.intOrFloat(axisObject.default)
            if axisObject.hidden:
                axisElement.attrib["hidden"] = "1"
            self.root.findall(".axes")[0].append(axisElement)

        def _addAxisMapping(self, mappingsElement, mappingObject):
            mappingElement = ET.Element("mapping")
            if getattr(mappingObject, "description", None) is not None:
                mappingElement.attrib["description"] = mappingObject.description
            for what in ("inputLocation", "outputLocation"):
                whatObject = getattr(mappingObject, what, None)
                if whatObject is None:
                    continue
                whatElement = ET.Element(what[:-8])
                mappingElement.append(whatElement)

                for name, value in whatObject.items():
                    dimensionElement = ET.Element("dimension")
                    dimensionElement.attrib["name"] = name
                    dimensionElement.attrib["xvalue"] = self.intOrFloat(value)
                    whatElement.append(dimensionElement)

            mappingsElement.append(mappingElement)

        def _addAxisLabel(
            self, axisElement: ET.Element, label: AxisLabelDescriptor
        ) -> None:
            labelElement = ET.Element("label")
            labelElement.attrib["uservalue"] = self.intOrFloat(label.userValue)
            if label.userMinimum is not None:
                labelElement.attrib["userminimum"] = self.intOrFloat(label.userMinimum)
            if label.userMaximum is not None:
                labelElement.attrib["usermaximum"] = self.intOrFloat(label.userMaximum)
            labelElement.attrib["name"] = label.name
            if label.elidable:
                labelElement.attrib["elidable"] = "true"
            if label.olderSibling:
                labelElement.attrib["oldersibling"] = "true"
            if label.linkedUserValue is not None:
                labelElement.attrib["linkeduservalue"] = self.intOrFloat(
                    label.linkedUserValue
                )
            self._addLabelNames(labelElement, label.labelNames)
            axisElement.append(labelElement)

        def _addLabelNames(self, parentElement, labelNames):
            for languageCode, labelName in sorted(labelNames.items()):
                languageElement = ET.Element("labelname")
                languageElement.attrib[XML_LANG] = languageCode
                languageElement.text = labelName
                parentElement.append(languageElement)

        def _addLocationLabel(
            self, parentElement: ET.Element, label: LocationLabelDescriptor
        ) -> None:
            labelElement = ET.Element("label")
            labelElement.attrib["name"] = label.name
            if label.elidable:
                labelElement.attrib["elidable"] = "true"
            if label.olderSibling:
                labelElement.attrib["oldersibling"] = "true"
            self._addLabelNames(labelElement, label.labelNames)
            self._addLocationElement(labelElement, userLocation=label.userLocation)
            parentElement.append(labelElement)

        def _addLocationElement(
            self,
            parentElement,
            *,
            designLocation: AnisotropicLocationDict = None,
            userLocation: SimpleLocationDict = None,
        ):
            locElement = ET.Element("location")
            for axis in self.documentObject.axes:
                if designLocation is not None and axis.name in designLocation:
                    dimElement = ET.Element("dimension")
                    dimElement.attrib["name"] = axis.name
                    value = designLocation[axis.name]
                    if isinstance(value, tuple):
                        dimElement.attrib["xvalue"] = self.intOrFloat(value[0])
                        dimElement.attrib["yvalue"] = self.intOrFloat(value[1])
                    else:
                        dimElement.attrib["xvalue"] = self.intOrFloat(value)
                    locElement.append(dimElement)
                elif userLocation is not None and axis.name in userLocation:
                    dimElement = ET.Element("dimension")
                    dimElement.attrib["name"] = axis.name
                    value = userLocation[axis.name]
                    dimElement.attrib["uservalue"] = self.intOrFloat(value)
                    locElement.append(dimElement)
            if len(locElement) > 0:
                parentElement.append(locElement)

        def _addInstance(self, instanceObject):
            instanceElement = ET.Element("instance")
            if instanceObject.name is not None:
                instanceElement.attrib["name"] = instanceObject.name
            if instanceObject.locationLabel is not None:
                instanceElement.attrib["location"] = instanceObject.locationLabel
            if instanceObject.familyName is not None:
                instanceElement.attrib["familyname"] = instanceObject.familyName
            if instanceObject.styleName is not None:
                instanceElement.attrib["stylename"] = instanceObject.styleName
            # add localisations
            if instanceObject.localisedStyleName:
                languageCodes = list(instanceObject.localisedStyleName.keys())
                languageCodes.sort()
                for code in languageCodes:
                    if code == "en":
                        continue  # already stored in the element attribute
                    localisedStyleNameElement = ET.Element("stylename")
                    localisedStyleNameElement.attrib[XML_LANG] = code
                    localisedStyleNameElement.text = instanceObject.getStyleName(code)
                    instanceElement.append(localisedStyleNameElement)
            if instanceObject.localisedFamilyName:
                languageCodes = list(instanceObject.localisedFamilyName.keys())
                languageCodes.sort()
                for code in languageCodes:
                    if code == "en":
                        continue  # already stored in the element attribute
                    localisedFamilyNameElement = ET.Element("familyname")
                    localisedFamilyNameElement.attrib[XML_LANG] = code
                    localisedFamilyNameElement.text = instanceObject.getFamilyName(code)
                    instanceElement.append(localisedFamilyNameElement)
            if instanceObject.localisedStyleMapStyleName:
                languageCodes = list(instanceObject.localisedStyleMapStyleName.keys())
                languageCodes.sort()
                for code in languageCodes:
                    if code == "en":
                        continue
                    localisedStyleMapStyleNameElement = ET.Element("stylemapstylename")
                    localisedStyleMapStyleNameElement.attrib[XML_LANG] = code
                    localisedStyleMapStyleNameElement.text = (
                        instanceObject.getStyleMapStyleName(code)
                    )
                    instanceElement.append(localisedStyleMapStyleNameElement)
            if instanceObject.localisedStyleMapFamilyName:
                languageCodes = list(instanceObject.localisedStyleMapFamilyName.keys())
                languageCodes.sort()
                for code in languageCodes:
                    if code == "en":
                        continue
                    localisedStyleMapFamilyNameElement = ET.Element("stylemapfamilyname")
                    localisedStyleMapFamilyNameElement.attrib[XML_LANG] = code
                    localisedStyleMapFamilyNameElement.text = (
                        instanceObject.getStyleMapFamilyName(code)
                    )
                    instanceElement.append(localisedStyleMapFamilyNameElement)

            if self.effectiveFormatTuple >= (5, 0):
                if instanceObject.locationLabel is None:
                    self._addLocationElement(
                        instanceElement,
                        designLocation=instanceObject.designLocation,
                        userLocation=instanceObject.userLocation,
                    )
            else:
                # Pre-version 5.0 code was validating and filling in the location
                # dict while writing it out, as preserved below.
                if instanceObject.location is not None:
                    locationElement, instanceObject.location = self._makeLocationElement(
                        instanceObject.location
                    )
                    instanceElement.append(locationElement)
            if instanceObject.filename is not None:
                instanceElement.attrib["filename"] = instanceObject.filename
            if instanceObject.postScriptFontName is not None:
                instanceElement.attrib["postscriptfontname"] = (
                    instanceObject.postScriptFontName
                )
            if instanceObject.styleMapFamilyName is not None:
                instanceElement.attrib["stylemapfamilyname"] = (
                    instanceObject.styleMapFamilyName
                )
            if instanceObject.styleMapStyleName is not None:
                instanceElement.attrib["stylemapstylename"] = (
                    instanceObject.styleMapStyleName
                )
            if self.effectiveFormatTuple < (5, 0):
                # Deprecated members as of version 5.0
                if instanceObject.glyphs:
                    if instanceElement.findall(".glyphs") == []:
                        glyphsElement = ET.Element("glyphs")
                        instanceElement.append(glyphsElement)
                    glyphsElement = instanceElement.findall(".glyphs")[0]
                    for glyphName, data in sorted(instanceObject.glyphs.items()):
                        glyphElement = self._writeGlyphElement(
                            instanceElement, instanceObject, glyphName, data
                        )
                        glyphsElement.append(glyphElement)
                if instanceObject.kerning:
                    kerningElement = ET.Element("kerning")
                    instanceElement.append(kerningElement)
                if instanceObject.info:
                    infoElement = ET.Element("info")
                    instanceElement.append(infoElement)
            self._addLib(instanceElement, instanceObject.lib, 4)
            self.root.findall(".instances")[0].append(instanceElement)

        def _addSource(self, sourceObject):
            sourceElement = ET.Element("source")
            if sourceObject.filename is not None:
                sourceElement.attrib["filename"] = sourceObject.filename
            if sourceObject.name is not None:
                if sourceObject.name.find("temp_master") != 0:
                    # do not save temporary source names
                    sourceElement.attrib["name"] = sourceObject.name
            if sourceObject.familyName is not None:
                sourceElement.attrib["familyname"] = sourceObject.familyName
            if sourceObject.styleName is not None:
                sourceElement.attrib["stylename"] = sourceObject.styleName
            if sourceObject.layerName is not None:
                sourceElement.attrib["layer"] = sourceObject.layerName
            if sourceObject.localisedFamilyName:
                languageCodes = list(sourceObject.localisedFamilyName.keys())
                languageCodes.sort()
                for code in languageCodes:
                    if code == "en":
                        continue  # already stored in the element attribute
                    localisedFamilyNameElement = ET.Element("familyname")
                    localisedFamilyNameElement.attrib[XML_LANG] = code
                    localisedFamilyNameElement.text = sourceObject.getFamilyName(code)
                    sourceElement.append(localisedFamilyNameElement)
            if sourceObject.copyLib:
                libElement = ET.Element("lib")
                libElement.attrib["copy"] = "1"
                sourceElement.append(libElement)
            if sourceObject.copyGroups:
                groupsElement = ET.Element("groups")
                groupsElement.attrib["copy"] = "1"
                sourceElement.append(groupsElement)
            if sourceObject.copyFeatures:
                featuresElement = ET.Element("features")
                featuresElement.attrib["copy"] = "1"
                sourceElement.append(featuresElement)
            if sourceObject.copyInfo or sourceObject.muteInfo:
                infoElement = ET.Element("info")
                if sourceObject.copyInfo:
                    infoElement.attrib["copy"] = "1"
                if sourceObject.muteInfo:
                    infoElement.attrib["mute"] = "1"
                sourceElement.append(infoElement)
            if sourceObject.muteKerning:
                kerningElement = ET.Element("kerning")
                kerningElement.attrib["mute"] = "1"
                sourceElement.append(kerningElement)
            if sourceObject.mutedGlyphNames:
                for name in sourceObject.mutedGlyphNames:
                    glyphElement = ET.Element("glyph")
                    glyphElement.attrib["name"] = name
                    glyphElement.attrib["mute"] = "1"
                    sourceElement.append(glyphElement)
            if self.effectiveFormatTuple >= (5, 0):
                self._addLocationElement(
                    sourceElement, designLocation=sourceObject.location
                )
            else:
                # Pre-version 5.0 code was validating and filling in the location
                # dict while writing it out, as preserved below.
                locationElement, sourceObject.location = self._makeLocationElement(
                    sourceObject.location
                )
                sourceElement.append(locationElement)
            self.root.findall(".sources")[0].append(sourceElement)

        def _addVariableFont(
            self, parentElement: ET.Element, vf: VariableFontDescriptor
        ) -> None:
            vfElement = ET.Element("variable-font")
            vfElement.attrib["name"] = vf.name
            if vf.filename is not None:
                vfElement.attrib["filename"] = vf.filename
            if vf.axisSubsets:
                subsetsElement = ET.Element("axis-subsets")
                for subset in vf.axisSubsets:
                    subsetElement = ET.Element("axis-subset")
                    subsetElement.attrib["name"] = subset.name
                    # Mypy doesn't support narrowing union types via hasattr()
                    # https://mypy.readthedocs.io/en/stable/type_narrowing.html
                    # TODO(Python 3.10): use TypeGuard
                    if hasattr(subset, "userMinimum"):
                        subset = cast(RangeAxisSubsetDescriptor, subset)
                        if subset.userMinimum != -math.inf:
                            subsetElement.attrib["userminimum"] = self.intOrFloat(
                                subset.userMinimum
                            )
                        if subset.userMaximum != math.inf:
                            subsetElement.attrib["usermaximum"] = self.intOrFloat(
                                subset.userMaximum
                            )
                        if subset.userDefault is not None:
                            subsetElement.attrib["userdefault"] = self.intOrFloat(
                                subset.userDefault
                            )
                    elif hasattr(subset, "userValue"):
                        subset = cast(ValueAxisSubsetDescriptor, subset)
                        subsetElement.attrib["uservalue"] = self.intOrFloat(
                            subset.userValue
                        )
                    subsetsElement.append(subsetElement)
                vfElement.append(subsetsElement)
            self._addLib(vfElement, vf.lib, 4)
            parentElement.append(vfElement)

        def _addLib(self, parentElement: ET.Element, data: Any, indent_level: int) -> None:
            if not data:
                return
            libElement = ET.Element("lib")
            libElement.append(plistlib.totree(data, indent_level=indent_level))
            parentElement.append(libElement)

        def _writeGlyphElement(self, instanceElement, instanceObject, glyphName, data):
            glyphElement = ET.Element("glyph")
            if data.get("mute"):
                glyphElement.attrib["mute"] = "1"
            if data.get("unicodes") is not None:
                glyphElement.attrib["unicode"] = " ".join(
                    [hex(u) for u in data.get("unicodes")]
                )
            if data.get("instanceLocation") is not None:
                locationElement, data["instanceLocation"] = self._makeLocationElement(
                    data.get("instanceLocation")
                )
                glyphElement.append(locationElement)
            if glyphName is not None:
                glyphElement.attrib["name"] = glyphName
            if data.get("note") is not None:
                noteElement = ET.Element("note")
                noteElement.text = data.get("note")
                glyphElement.append(noteElement)
            if data.get("masters") is not None:
                mastersElement = ET.Element("masters")
                for m in data.get("masters"):
                    masterElement = ET.Element("master")
                    if m.get("glyphName") is not None:
                        masterElement.attrib["glyphname"] = m.get("glyphName")
                    if m.get("font") is not None:
                        masterElement.attrib["source"] = m.get("font")
                    if m.get("location") is not None:
                        locationElement, m["location"] = self._makeLocationElement(
                            m.get("location")
                        )
                        masterElement.append(locationElement)
                    mastersElement.append(masterElement)
                glyphElement.append(mastersElement)
            return glyphElement

    class BaseDocReader(LogMixin):
        axisDescriptorClass = AxisDescriptor
        discreteAxisDescriptorClass = DiscreteAxisDescriptor
        axisLabelDescriptorClass = AxisLabelDescriptor
        axisMappingDescriptorClass = AxisMappingDescriptor
        locationLabelDescriptorClass = LocationLabelDescriptor
        ruleDescriptorClass = RuleDescriptor
        sourceDescriptorClass = SourceDescriptor
        variableFontsDescriptorClass = VariableFontDescriptor
        valueAxisSubsetDescriptorClass = ValueAxisSubsetDescriptor
        rangeAxisSubsetDescriptorClass = RangeAxisSubsetDescriptor
        instanceDescriptorClass = InstanceDescriptor

        def __init__(self, documentPath, documentObject):
            self.path = documentPath
            self.documentObject = documentObject
            tree = ET.parse(self.path)
            self.root = tree.getroot()
            self.documentObject.formatVersion = self.root.attrib.get("format", "3.0")
            self._axes = []
            self.rules = []
            self.sources = []
            self.instances = []
            self.axisDefaults = {}
            self._strictAxisNames = True

        @classmethod
        def fromstring(cls, string, documentObject):
            f = BytesIO(tobytes(string, encoding="utf-8"))
            self = cls(f, documentObject)
            self.path = None
            return self

        def read(self):
            self.readAxes()
            self.readLabels()
            self.readRules()
            self.readVariableFonts()
            self.readSources()
            self.readInstances()
            self.readLib()

        def readRules(self):
            # we also need to read any conditions that are outside of a condition set.
            rules = []
            rulesElement = self.root.find(".rules")
            if rulesElement is not None:
                processingValue = rulesElement.attrib.get("processing", "first")
                if processingValue not in {"first", "last"}:
                    raise DesignSpaceDocumentError(
                        "<rules> processing attribute value is not valid: %r, "
                        "expected 'first' or 'last'" % processingValue
                    )
                self.documentObject.rulesProcessingLast = processingValue == "last"
            for ruleElement in self.root.findall(".rules/rule"):
                ruleObject = self.ruleDescriptorClass()
                ruleName = ruleObject.name = ruleElement.attrib.get("name")
                # read any stray conditions outside a condition set
                externalConditions = self._readConditionElements(
                    ruleElement,
                    ruleName,
                )
                if externalConditions:
                    ruleObject.conditionSets.append(externalConditions)
                    self.log.info(
                        "Found stray rule conditions outside a conditionset. "
                        "Wrapped them in a new conditionset."
                    )
                # read the conditionsets
                for conditionSetElement in ruleElement.findall(".conditionset"):
                    conditionSet = self._readConditionElements(
                        conditionSetElement,
                        ruleName,
                    )
                    if conditionSet is not None:
                        ruleObject.conditionSets.append(conditionSet)
                for subElement in ruleElement.findall(".sub"):
                    a = subElement.attrib["name"]
                    b = subElement.attrib["with"]
                    ruleObject.subs.append((a, b))
                rules.append(ruleObject)
            self.documentObject.rules = rules

        def _readConditionElements(self, parentElement, ruleName=None):
            cds = []
            for conditionElement in parentElement.findall(".condition"):
                cd = {}
                cdMin = conditionElement.attrib.get("minimum")
                if cdMin is not None:
                    cd["minimum"] = float(cdMin)
                else:
                    # will allow these to be None, assume axis.minimum
                    cd["minimum"] = None
                cdMax = conditionElement.attrib.get("maximum")
                if cdMax is not None:
                    cd["maximum"] = float(cdMax)
                else:
                    # will allow these to be None, assume axis.maximum
                    cd["maximum"] = None
                cd["name"] = conditionElement.attrib.get("name")
                # # test for things
                if cd.get("minimum") is None and cd.get("maximum") is None:
                    raise DesignSpaceDocumentError(
                        "condition missing required minimum or maximum in rule"
                        + (" '%s'" % ruleName if ruleName is not None else "")
                    )
                cds.append(cd)
            return cds

        def readAxes(self):
            # read the axes elements, including the warp map.
            axesElement = self.root.find(".axes")
            if axesElement is not None and "elidedfallbackname" in axesElement.attrib:
                self.documentObject.elidedFallbackName = axesElement.attrib[
                    "elidedfallbackname"
                ]
            axisElements = self.root.findall(".axes/axis")
            if not axisElements:
                return
            for axisElement in axisElements:
                if (
                    self.documentObject.formatTuple >= (5, 0)
                    and "values" in axisElement.attrib
                ):
                    axisObject = self.discreteAxisDescriptorClass()
                    axisObject.values = [
                        float(s) for s in axisElement.attrib["values"].split(" ")
                    ]
                else:
                    axisObject = self.axisDescriptorClass()
                    axisObject.minimum = float(axisElement.attrib.get("minimum"))
                    axisObject.maximum = float(axisElement.attrib.get("maximum"))
                axisObject.default = float(axisElement.attrib.get("default"))
                axisObject.name = axisElement.attrib.get("name")
                if axisElement.attrib.get("hidden", False):
                    axisObject.hidden = True
                axisObject.tag = axisElement.attrib.get("tag")
                for mapElement in axisElement.findall("map"):
                    a = float(mapElement.attrib["input"])
                    b = float(mapElement.attrib["output"])
                    axisObject.map.append((a, b))
                for labelNameElement in axisElement.findall("labelname"):
                    # Note: elementtree reads the "xml:lang" attribute name as
                    # '{http://www.w3.org/XML/1998/namespace}lang'
                    for key, lang in labelNameElement.items():
                        if key == XML_LANG:
                            axisObject.labelNames[lang] = tostr(labelNameElement.text)
                labelElement = axisElement.find(".labels")
                if labelElement is not None:
                    if "ordering" in labelElement.attrib:
                        axisObject.axisOrdering = int(labelElement.attrib["ordering"])
                    for label in labelElement.findall(".label"):
                        axisObject.axisLabels.append(self.readAxisLabel(label))
                self.documentObject.axes.append(axisObject)
                self.axisDefaults[axisObject.name] = axisObject.default

            self.documentObject.axisMappings = []
            for mappingsElement in self.root.findall(".axes/mappings"):
                groupDescription = mappingsElement.attrib.get("description")
                for mappingElement in mappingsElement.findall("mapping"):
                    description = mappingElement.attrib.get("description")
                    inputElement = mappingElement.find("input")
                    outputElement = mappingElement.find("output")
                    inputLoc = {}
                    outputLoc = {}
                    for dimElement in inputElement.findall(".dimension"):
                        name = dimElement.attrib["name"]
                        value = float(dimElement.attrib["xvalue"])
                        inputLoc[name] = value
                    for dimElement in outputElement.findall(".dimension"):
                        name = dimElement.attrib["name"]
                        value = float(dimElement.attrib["xvalue"])
                        outputLoc[name] = value
                    axisMappingObject = self.axisMappingDescriptorClass(
                        inputLocation=inputLoc,
                        outputLocation=outputLoc,
                        description=description,
                        groupDescription=groupDescription,
                    )
                    self.documentObject.axisMappings.append(axisMappingObject)

        def readAxisLabel(self, element: ET.Element):
            xml_attrs = {
                "userminimum",
                "uservalue",
                "usermaximum",
                "name",
                "elidable",
                "oldersibling",
                "linkeduservalue",
            }
            unknown_attrs = set(element.attrib) - xml_attrs
            if unknown_attrs:
                raise DesignSpaceDocumentError(
                    f"label element contains unknown attributes: {', '.join(unknown_attrs)}"
                )

            name = element.get("name")
            if name is None:
                raise DesignSpaceDocumentError("label element must have a name attribute.")
            valueStr = element.get("uservalue")
            if valueStr is None:
                raise DesignSpaceDocumentError(
                    "label element must have a uservalue attribute."
                )
            value = float(valueStr)
            minimumStr = element.get("userminimum")
            minimum = float(minimumStr) if minimumStr is not None else None
            maximumStr = element.get("usermaximum")
            maximum = float(maximumStr) if maximumStr is not None else None
            linkedValueStr = element.get("linkeduservalue")
            linkedValue = float(linkedValueStr) if linkedValueStr is not None else None
            elidable = True if element.get("elidable") == "true" else False
            olderSibling = True if element.get("oldersibling") == "true" else False
            labelNames = {
                lang: label_name.text or ""
                for label_name in element.findall("labelname")
                for attr, lang in label_name.items()
                if attr == XML_LANG
                # Note: elementtree reads the "xml:lang" attribute name as
                # '{http://www.w3.org/XML/1998/namespace}lang'
            }
            return self.axisLabelDescriptorClass(
                name=name,
                userValue=value,
                userMinimum=minimum,
                userMaximum=maximum,
                elidable=elidable,
                olderSibling=olderSibling,
                linkedUserValue=linkedValue,
                labelNames=labelNames,
            )

        def readLabels(self):
            if self.documentObject.formatTuple < (5, 0):
                return

            xml_attrs = {"name", "elidable", "oldersibling"}
            for labelElement in self.root.findall(".labels/label"):
                unknown_attrs = set(labelElement.attrib) - xml_attrs
                if unknown_attrs:
                    raise DesignSpaceDocumentError(
                        f"Label element contains unknown attributes: {', '.join(unknown_attrs)}"
                    )

                name = labelElement.get("name")
                if name is None:
                    raise DesignSpaceDocumentError(
                        "label element must have a name attribute."
                    )
                designLocation, userLocation = self.locationFromElement(labelElement)
                if designLocation:
                    raise DesignSpaceDocumentError(
                        f'<label> element "{name}" must only have user locations (using uservalue="").'
                    )
                elidable = True if labelElement.get("elidable") == "true" else False
                olderSibling = True if labelElement.get("oldersibling") == "true" else False
                labelNames = {
                    lang: label_name.text or ""
                    for label_name in labelElement.findall("labelname")
                    for attr, lang in label_name.items()
                    if attr == XML_LANG
                    # Note: elementtree reads the "xml:lang" attribute name as
                    # '{http://www.w3.org/XML/1998/namespace}lang'
                }
                locationLabel = self.locationLabelDescriptorClass(
                    name=name,
                    userLocation=userLocation,
                    elidable=elidable,
                    olderSibling=olderSibling,
                    labelNames=labelNames,
                )
                self.documentObject.locationLabels.append(locationLabel)

        def readVariableFonts(self):
            if self.documentObject.formatTuple < (5, 0):
                return

            xml_attrs = {"name", "filename"}
            for variableFontElement in self.root.findall(".variable-fonts/variable-font"):
                unknown_attrs = set(variableFontElement.attrib) - xml_attrs
                if unknown_attrs:
                    raise DesignSpaceDocumentError(
                        f"variable-font element contains unknown attributes: {', '.join(unknown_attrs)}"
                    )

                name = variableFontElement.get("name")
                if name is None:
                    raise DesignSpaceDocumentError(
                        "variable-font element must have a name attribute."
                    )

                filename = variableFontElement.get("filename")

                axisSubsetsElement = variableFontElement.find(".axis-subsets")
                if axisSubsetsElement is None:
                    raise DesignSpaceDocumentError(
                        "variable-font element must contain an axis-subsets element."
                    )
                axisSubsets = []
                for axisSubset in axisSubsetsElement.iterfind(".axis-subset"):
                    axisSubsets.append(self.readAxisSubset(axisSubset))

                lib = None
                libElement = variableFontElement.find(".lib")
                if libElement is not None:
                    lib = plistlib.fromtree(libElement[0])

                variableFont = self.variableFontsDescriptorClass(
                    name=name,
                    filename=filename,
                    axisSubsets=axisSubsets,
                    lib=lib,
                )
                self.documentObject.variableFonts.append(variableFont)

        def readAxisSubset(self, element: ET.Element):
            if "uservalue" in element.attrib:
                xml_attrs = {"name", "uservalue"}
                unknown_attrs = set(element.attrib) - xml_attrs
                if unknown_attrs:
                    raise DesignSpaceDocumentError(
                        f"axis-subset element contains unknown attributes: {', '.join(unknown_attrs)}"
                    )

                name = element.get("name")
                if name is None:
                    raise DesignSpaceDocumentError(
                        "axis-subset element must have a name attribute."
                    )
                userValueStr = element.get("uservalue")
                if userValueStr is None:
                    raise DesignSpaceDocumentError(
                        "The axis-subset element for a discrete subset must have a uservalue attribute."
                    )
                userValue = float(userValueStr)

                return self.valueAxisSubsetDescriptorClass(name=name, userValue=userValue)
            else:
                xml_attrs = {"name", "userminimum", "userdefault", "usermaximum"}
                unknown_attrs = set(element.attrib) - xml_attrs
                if unknown_attrs:
                    raise DesignSpaceDocumentError(
                        f"axis-subset element contains unknown attributes: {', '.join(unknown_attrs)}"
                    )

                name = element.get("name")
                if name is None:
                    raise DesignSpaceDocumentError(
                        "axis-subset element must have a name attribute."
                    )

                userMinimum = element.get("userminimum")
                userDefault = element.get("userdefault")
                userMaximum = element.get("usermaximum")
                if (
                    userMinimum is not None
                    and userDefault is not None
                    and userMaximum is not None
                ):
                    return self.rangeAxisSubsetDescriptorClass(
                        name=name,
                        userMinimum=float(userMinimum),
                        userDefault=float(userDefault),
                        userMaximum=float(userMaximum),
                    )
                if all(v is None for v in (userMinimum, userDefault, userMaximum)):
                    return self.rangeAxisSubsetDescriptorClass(name=name)

                raise DesignSpaceDocumentError(
                    "axis-subset element must have min/max/default values or none at all."
                )

        def readSources(self):
            for sourceCount, sourceElement in enumerate(
                self.root.findall(".sources/source")
            ):
                filename = sourceElement.attrib.get("filename")
                if filename is not None and self.path is not None:
                    sourcePath = os.path.abspath(
                        os.path.join(os.path.dirname(self.path), filename)
                    )
                else:
                    sourcePath = None
                sourceName = sourceElement.attrib.get("name")
                if sourceName is None:
                    # add a temporary source name
                    sourceName = "temp_master.%d" % (sourceCount)
                sourceObject = self.sourceDescriptorClass()
                sourceObject.path = sourcePath  # absolute path to the ufo source
                sourceObject.filename = filename  # path as it is stored in the document
                sourceObject.name = sourceName
                familyName = sourceElement.attrib.get("familyname")
                if familyName is not None:
                    sourceObject.familyName = familyName
                styleName = sourceElement.attrib.get("stylename")
                if styleName is not None:
                    sourceObject.styleName = styleName
                for familyNameElement in sourceElement.findall("familyname"):
                    for key, lang in familyNameElement.items():
                        if key == XML_LANG:
                            familyName = familyNameElement.text
                            sourceObject.setFamilyName(familyName, lang)
                designLocation, userLocation = self.locationFromElement(sourceElement)
                if userLocation:
                    raise DesignSpaceDocumentError(
                        f'<source> element "{sourceName}" must only have design locations (using xvalue="").'
                    )
                sourceObject.location = designLocation
                layerName = sourceElement.attrib.get("layer")
                if layerName is not None:
                    sourceObject.layerName = layerName
                for libElement in sourceElement.findall(".lib"):
                    if libElement.attrib.get("copy") == "1":
                        sourceObject.copyLib = True
                for groupsElement in sourceElement.findall(".groups"):
                    if groupsElement.attrib.get("copy") == "1":
                        sourceObject.copyGroups = True
                for infoElement in sourceElement.findall(".info"):
                    if infoElement.attrib.get("copy") == "1":
                        sourceObject.copyInfo = True
                    if infoElement.attrib.get("mute") == "1":
                        sourceObject.muteInfo = True
                for featuresElement in sourceElement.findall(".features"):
                    if featuresElement.attrib.get("copy") == "1":
                        sourceObject.copyFeatures = True
                for glyphElement in sourceElement.findall(".glyph"):
                    glyphName = glyphElement.attrib.get("name")
                    if glyphName is None:
                        continue
                    if glyphElement.attrib.get("mute") == "1":
                        sourceObject.mutedGlyphNames.append(glyphName)
                for kerningElement in sourceElement.findall(".kerning"):
                    if kerningElement.attrib.get("mute") == "1":
                        sourceObject.muteKerning = True
                self.documentObject.sources.append(sourceObject)

        def locationFromElement(self, element):
            """Read a nested ``<location>`` element inside the given ``element``.

            .. versionchanged:: 5.0
               Return a tuple of (designLocation, userLocation)
            """
            elementLocation = (None, None)
            for locationElement in element.findall(".location"):
                elementLocation = self.readLocationElement(locationElement)
                break
            return elementLocation

        def readLocationElement(self, locationElement):
            """Read a ``<location>`` element.

            .. versionchanged:: 5.0
               Return a tuple of (designLocation, userLocation)
            """
            if self._strictAxisNames and not self.documentObject.axes:
                raise DesignSpaceDocumentError("No axes defined")
            userLoc = {}
            designLoc = {}
            for dimensionElement in locationElement.findall(".dimension"):
                dimName = dimensionElement.attrib.get("name")
                if self._strictAxisNames and dimName not in self.axisDefaults:
                    # In case the document contains no axis definitions,
                    self.log.warning('Location with undefined axis: "%s".', dimName)
                    continue
                userValue = xValue = yValue = None
                try:
                    userValue = dimensionElement.attrib.get("uservalue")
                    if userValue is not None:
                        userValue = float(userValue)
                except ValueError:
                    self.log.warning(
                        "ValueError in readLocation userValue %3.3f", userValue
                    )
                try:
                    xValue = dimensionElement.attrib.get("xvalue")
                    if xValue is not None:
                        xValue = float(xValue)
                except ValueError:
                    self.log.warning("ValueError in readLocation xValue %3.3f", xValue)
                try:
                    yValue = dimensionElement.attrib.get("yvalue")
                    if yValue is not None:
                        yValue = float(yValue)
                except ValueError:
                    self.log.warning("ValueError in readLocation yValue %3.3f", yValue)
                if userValue is None == xValue is None:
                    raise DesignSpaceDocumentError(
                        f'Exactly one of uservalue="" or xvalue="" must be provided for location dimension "{dimName}"'
                    )
                if yValue is not None:
                    if xValue is None:
                        raise DesignSpaceDocumentError(
                            f'Missing xvalue="" for the location dimension "{dimName}"" with yvalue="{yValue}"'
                        )
                    designLoc[dimName] = (xValue, yValue)
                elif xValue is not None:
                    designLoc[dimName] = xValue
                else:
                    userLoc[dimName] = userValue
            return designLoc, userLoc

        def readInstances(self, makeGlyphs=True, makeKerning=True, makeInfo=True):
            instanceElements = self.root.findall(".instances/instance")
            for instanceElement in instanceElements:
                self._readSingleInstanceElement(
                    instanceElement,
                    makeGlyphs=makeGlyphs,
                    makeKerning=makeKerning,
                    makeInfo=makeInfo,
                )

        def _readSingleInstanceElement(
            self, instanceElement, makeGlyphs=True, makeKerning=True, makeInfo=True
        ):
            filename = instanceElement.attrib.get("filename")
            if filename is not None and self.documentObject.path is not None:
                instancePath = os.path.join(
                    os.path.dirname(self.documentObject.path), filename
                )
            else:
                instancePath = None
            instanceObject = self.instanceDescriptorClass()
            instanceObject.path = instancePath  # absolute path to the instance
            instanceObject.filename = filename  # path as it is stored in the document
            name = instanceElement.attrib.get("name")
            if name is not None:
                instanceObject.name = name
            familyname = instanceElement.attrib.get("familyname")
            if familyname is not None:
                instanceObject.familyName = familyname
            stylename = instanceElement.attrib.get("stylename")
            if stylename is not None:
                instanceObject.styleName = stylename
            postScriptFontName = instanceElement.attrib.get("postscriptfontname")
            if postScriptFontName is not None:
                instanceObject.postScriptFontName = postScriptFontName
            styleMapFamilyName = instanceElement.attrib.get("stylemapfamilyname")
            if styleMapFamilyName is not None:
                instanceObject.styleMapFamilyName = styleMapFamilyName
            styleMapStyleName = instanceElement.attrib.get("stylemapstylename")
            if styleMapStyleName is not None:
                instanceObject.styleMapStyleName = styleMapStyleName
            # read localised names
            for styleNameElement in instanceElement.findall("stylename"):
                for key, lang in styleNameElement.items():
                    if key == XML_LANG:
                        styleName = styleNameElement.text
                        instanceObject.setStyleName(styleName, lang)
            for familyNameElement in instanceElement.findall("familyname"):
                for key, lang in familyNameElement.items():
                    if key == XML_LANG:
                        familyName = familyNameElement.text
                        instanceObject.setFamilyName(familyName, lang)
            for styleMapStyleNameElement in instanceElement.findall("stylemapstylename"):
                for key, lang in styleMapStyleNameElement.items():
                    if key == XML_LANG:
                        styleMapStyleName = styleMapStyleNameElement.text
                        instanceObject.setStyleMapStyleName(styleMapStyleName, lang)
            for styleMapFamilyNameElement in instanceElement.findall("stylemapfamilyname"):
                for key, lang in styleMapFamilyNameElement.items():
                    if key == XML_LANG:
                        styleMapFamilyName = styleMapFamilyNameElement.text
                        instanceObject.setStyleMapFamilyName(styleMapFamilyName, lang)
            designLocation, userLocation = self.locationFromElement(instanceElement)
            locationLabel = instanceElement.attrib.get("location")
            if (designLocation or userLocation) and locationLabel is not None:
                raise DesignSpaceDocumentError(
                    'instance element must have at most one of the location="..." attribute or the nested location element'
                )
            instanceObject.locationLabel = locationLabel
            instanceObject.userLocation = userLocation or {}
            instanceObject.designLocation = designLocation or {}
            for glyphElement in instanceElement.findall(".glyphs/glyph"):
                self.readGlyphElement(glyphElement, instanceObject)
            for infoElement in instanceElement.findall("info"):
                self.readInfoElement(infoElement, instanceObject)
            for libElement in instanceElement.findall("lib"):
                self.readLibElement(libElement, instanceObject)
            self.documentObject.instances.append(instanceObject)

        def readLibElement(self, libElement, instanceObject):
            """Read the lib element for the given instance."""
            instanceObject.lib = plistlib.fromtree(libElement[0])

        def readInfoElement(self, infoElement, instanceObject):
            """Read the info element."""
            instanceObject.info = True

        def readGlyphElement(self, glyphElement, instanceObject):
            """
            Read the glyph element, which could look like either one of these:

            .. code-block:: xml

                <glyph name="b" unicode="0x62"/>

                <glyph name="b"/>

                <glyph name="b">
                    <master location="location-token-bbb" source="master-token-aaa2"/>
                    <master glyphname="b.alt1" location="location-token-ccc" source="master-token-aaa3"/>
                    <note>
                        This is an instance from an anisotropic interpolation.
                    </note>
                </glyph>
            """
            glyphData = {}
            glyphName = glyphElement.attrib.get("name")
            if glyphName is None:
                raise DesignSpaceDocumentError("Glyph object without name attribute")
            mute = glyphElement.attrib.get("mute")
            if mute == "1":
                glyphData["mute"] = True
            # unicode
            unicodes = glyphElement.attrib.get("unicode")
            if unicodes is not None:
                try:
                    unicodes = [int(u, 16) for u in unicodes.split(" ")]
                    glyphData["unicodes"] = unicodes
                except ValueError:
                    raise DesignSpaceDocumentError(
                        "unicode values %s are not integers" % unicodes
                    )

            for noteElement in glyphElement.findall(".note"):
                glyphData["note"] = noteElement.text
                break
            designLocation, userLocation = self.locationFromElement(glyphElement)
            if userLocation:
                raise DesignSpaceDocumentError(
                    f'<glyph> element "{glyphName}" must only have design locations (using xvalue="").'
                )
            if designLocation is not None:
                glyphData["instanceLocation"] = designLocation
            glyphSources = None
            for masterElement in glyphElement.findall(".masters/master"):
                fontSourceName = masterElement.attrib.get("source")
                designLocation, userLocation = self.locationFromElement(masterElement)
                if userLocation:
                    raise DesignSpaceDocumentError(
                        f'<master> element "{fontSourceName}" must only have design locations (using xvalue="").'
                    )
                masterGlyphName = masterElement.attrib.get("glyphname")
                if masterGlyphName is None:
                    # if we don't read a glyphname, use the one we have
                    masterGlyphName = glyphName
                d = dict(
                    font=fontSourceName, location=designLocation, glyphName=masterGlyphName
                )
                if glyphSources is None:
                    glyphSources = []
                glyphSources.append(d)
            if glyphSources is not None:
                glyphData["masters"] = glyphSources
            instanceObject.glyphs[glyphName] = glyphData

        def readLib(self):
            """Read the lib element for the whole document."""
            for libElement in self.root.findall(".lib"):
                self.documentObject.lib = plistlib.fromtree(libElement[0])

    class DesignSpaceDocument(LogMixin, AsDictMixin):
        """The DesignSpaceDocument object can read and write ``.designspace`` data.
        It imports the axes, sources, variable fonts and instances to very basic
        **descriptor** objects that store the data in attributes. Data is added to
        the document by creating such descriptor objects, filling them with data
        and then adding them to the document. This makes it easy to integrate this
        object in different contexts.

        The **DesignSpaceDocument** object can be subclassed to work with
        different objects, as long as they have the same attributes. Reader and
        Writer objects can be subclassed as well.

        **Note:** Python attribute names are usually camelCased, the
        corresponding `XML <document-xml-structure>`_ attributes are usually
        all lowercase.

        .. code:: python

            from fontTools.designspaceLib import DesignSpaceDocument
            doc = DesignSpaceDocument.fromfile("some/path/to/my.designspace")
            doc.formatVersion
            doc.elidedFallbackName
            doc.axes
            doc.axisMappings
            doc.locationLabels
            doc.rules
            doc.rulesProcessingLast
            doc.sources
            doc.variableFonts
            doc.instances
            doc.lib

        """

        def __init__(self, readerClass=None, writerClass=None):
            self.path = None
            """String, optional. When the document is read from the disk, this is
            the full path that was given to :meth:`read` or :meth:`fromfile`.
            """
            self.filename = None
            """String, optional. When the document is read from the disk, this is
            its original file name, i.e. the last part of its path.

            When the document is produced by a Python script and still only exists
            in memory, the producing script can write here an indication of a
            possible "good" filename, in case one wants to save the file somewhere.
            """

            self.formatVersion: Optional[str] = None
            """Format version for this document, as a string. E.g. "4.0" """

            self.elidedFallbackName: Optional[str] = None
            """STAT Style Attributes Header field ``elidedFallbackNameID``.

            See: `OTSpec STAT Style Attributes Header <https://docs.microsoft.com/en-us/typography/opentype/spec/stat#style-attributes-header>`_

            .. versionadded:: 5.0
            """

            self.axes: List[Union[AxisDescriptor, DiscreteAxisDescriptor]] = []
            """List of this document's axes."""

            self.axisMappings: List[AxisMappingDescriptor] = []
            """List of this document's axis mappings."""

            self.locationLabels: List[LocationLabelDescriptor] = []
            """List of this document's STAT format 4 labels.

            .. versionadded:: 5.0"""
            self.rules: List[RuleDescriptor] = []
            """List of this document's rules."""
            self.rulesProcessingLast: bool = False
            """This flag indicates whether the substitution rules should be applied
            before or after other glyph substitution features.

            - False: before
            - True: after.

            Default is False. For new projects, you probably want True. See
            the following issues for more information:
            `fontTools#1371 <https://github.com/fonttools/fonttools/issues/1371#issuecomment-590214572>`__
            `fontTools#2050 <https://github.com/fonttools/fonttools/issues/2050#issuecomment-678691020>`__

            If you want to use a different feature altogether, e.g. ``calt``,
            use the lib key ``com.github.fonttools.varLib.featureVarsFeatureTag``

            .. code:: xml

                <lib>
                    <dict>
                        <key>com.github.fonttools.varLib.featureVarsFeatureTag</key>
                        <string>calt</string>
                    </dict>
                </lib>
            """
            self.sources: List[SourceDescriptor] = []
            """List of this document's sources."""
            self.variableFonts: List[VariableFontDescriptor] = []
            """List of this document's variable fonts.

            .. versionadded:: 5.0"""
            self.instances: List[InstanceDescriptor] = []
            """List of this document's instances."""
            self.lib: Dict = {}
            """User defined, custom data associated with the whole document.

            Use reverse-DNS notation to identify your own data.
            Respect the data stored by others.
            """

            self.default: Optional[str] = None
            """Name of the default master.

            This attribute is updated by the :meth:`findDefault`
            """

            if readerClass is not None:
                self.readerClass = readerClass
            else:
                self.readerClass = BaseDocReader
            if writerClass is not None:
                self.writerClass = writerClass
            else:
                self.writerClass = BaseDocWriter

        @classmethod
        def fromfile(cls, path, readerClass=None, writerClass=None):
            """Read a designspace file from ``path`` and return a new instance of
            :class:.
            """
            self = cls(readerClass=readerClass, writerClass=writerClass)
            self.read(path)
            return self

        @classmethod
        def fromstring(cls, string, readerClass=None, writerClass=None):
            self = cls(readerClass=readerClass, writerClass=writerClass)
            reader = self.readerClass.fromstring(string, self)
            reader.read()
            if self.sources:
                self.findDefault()
            return self

        def tostring(self, encoding=None):
            """Returns the designspace as a string. Default encoding ``utf-8``."""
            if encoding is str or (encoding is not None and encoding.lower() == "unicode"):
                f = StringIO()
                xml_declaration = False
            elif encoding is None or encoding == "utf-8":
                f = BytesIO()
                encoding = "UTF-8"
                xml_declaration = True
            else:
                raise ValueError("unsupported encoding: '%s'" % encoding)
            writer = self.writerClass(f, self)
            writer.write(encoding=encoding, xml_declaration=xml_declaration)
            return f.getvalue()

        def read(self, path):
            """Read a designspace file from ``path`` and populates the fields of
            ``self`` with the data.
            """
            if hasattr(path, "__fspath__"):  # support os.PathLike objects
                path = path.__fspath__()
            self.path = path
            self.filename = os.path.basename(path)
            reader = self.readerClass(path, self)
            reader.read()
            if self.sources:
                self.findDefault()

        def write(self, path):
            """Write this designspace to ``path``."""
            if hasattr(path, "__fspath__"):  # support os.PathLike objects
                path = path.__fspath__()
            self.path = path
            self.filename = os.path.basename(path)
            self.updatePaths()
            writer = self.writerClass(path, self)
            writer.write()

        def _posixRelativePath(self, otherPath):
            relative = os.path.relpath(otherPath, os.path.dirname(self.path))
            return posix(relative)

        def updatePaths(self):
            """
            Right before we save we need to identify and respond to the following situations:
            In each descriptor, we have to do the right thing for the filename attribute.

            ::

                case 1.
                descriptor.filename == None
                descriptor.path == None

                -- action:
                write as is, descriptors will not have a filename attr.
                useless, but no reason to interfere.

                case 2.
                descriptor.filename == "../something"
                descriptor.path == None

                -- action:
                write as is. The filename attr should not be touched.

                case 3.
                descriptor.filename == None
                descriptor.path == "~/absolute/path/there"

                -- action:
                calculate the relative path for filename.
                We're not overwriting some other value for filename, it should be fine

                case 4.
                descriptor.filename == '../somewhere'
                descriptor.path == "~/absolute/path/there"

                -- action:
                there is a conflict between the given filename, and the path.
                So we know where the file is relative to the document.
                Can't guess why they're different, we just choose for path to be correct and update filename.
            """
            assert self.path is not None
            for descriptor in self.sources + self.instances:
                if descriptor.path is not None:
                    # case 3 and 4: filename gets updated and relativized
                    descriptor.filename = self._posixRelativePath(descriptor.path)

        def addSource(self, sourceDescriptor: SourceDescriptor):
            """Add the given ``sourceDescriptor`` to ``doc.sources``."""
            self.sources.append(sourceDescriptor)

        def addSourceDescriptor(self, **kwargs):
            """Instantiate a new :class:`SourceDescriptor` using the given
            ``kwargs`` and add it to ``doc.sources``.
            """
            source = self.writerClass.sourceDescriptorClass(**kwargs)
            self.addSource(source)
            return source

        def addInstance(self, instanceDescriptor: InstanceDescriptor):
            """Add the given ``instanceDescriptor`` to :attr:`instances`."""
            self.instances.append(instanceDescriptor)

        def addInstanceDescriptor(self, **kwargs):
            """Instantiate a new :class:`InstanceDescriptor` using the given
            ``kwargs`` and add it to :attr:`instances`.
            """
            instance = self.writerClass.instanceDescriptorClass(**kwargs)
            self.addInstance(instance)
            return instance

        def addAxis(self, axisDescriptor: Union[AxisDescriptor, DiscreteAxisDescriptor]):
            """Add the given ``axisDescriptor`` to :attr:`axes`."""
            self.axes.append(axisDescriptor)

        def addAxisDescriptor(self, **kwargs):
            """Instantiate a new :class:`AxisDescriptor` using the given
            ``kwargs`` and add it to :attr:`axes`.

            The axis will be and instance of :class:`DiscreteAxisDescriptor` if
            the ``kwargs`` provide a ``value``, or a :class:`AxisDescriptor` otherwise.
            """
            if "values" in kwargs:
                axis = self.writerClass.discreteAxisDescriptorClass(**kwargs)
            else:
                axis = self.writerClass.axisDescriptorClass(**kwargs)
            self.addAxis(axis)
            return axis

        def addAxisMapping(self, axisMappingDescriptor: AxisMappingDescriptor):
            """Add the given ``axisMappingDescriptor`` to :attr:`axisMappings`."""
            self.axisMappings.append(axisMappingDescriptor)

        def addAxisMappingDescriptor(self, **kwargs):
            """Instantiate a new :class:`AxisMappingDescriptor` using the given
            ``kwargs`` and add it to :attr:`rules`.
            """
            axisMapping = self.writerClass.axisMappingDescriptorClass(**kwargs)
            self.addAxisMapping(axisMapping)
            return axisMapping

        def addRule(self, ruleDescriptor: RuleDescriptor):
            """Add the given ``ruleDescriptor`` to :attr:`rules`."""
            self.rules.append(ruleDescriptor)

        def addRuleDescriptor(self, **kwargs):
            """Instantiate a new :class:`RuleDescriptor` using the given
            ``kwargs`` and add it to :attr:`rules`.
            """
            rule = self.writerClass.ruleDescriptorClass(**kwargs)
            self.addRule(rule)
            return rule

        def addVariableFont(self, variableFontDescriptor: VariableFontDescriptor):
            """Add the given ``variableFontDescriptor`` to :attr:`variableFonts`.

            .. versionadded:: 5.0
            """
            self.variableFonts.append(variableFontDescriptor)

        def addVariableFontDescriptor(self, **kwargs):
            """Instantiate a new :class:`VariableFontDescriptor` using the given
            ``kwargs`` and add it to :attr:`variableFonts`.

            .. versionadded:: 5.0
            """
            variableFont = self.writerClass.variableFontDescriptorClass(**kwargs)
            self.addVariableFont(variableFont)
            return variableFont

        def addLocationLabel(self, locationLabelDescriptor: LocationLabelDescriptor):
            """Add the given ``locationLabelDescriptor`` to :attr:`locationLabels`.

            .. versionadded:: 5.0
            """
            self.locationLabels.append(locationLabelDescriptor)

        def addLocationLabelDescriptor(self, **kwargs):
            """Instantiate a new :class:`LocationLabelDescriptor` using the given
            ``kwargs`` and add it to :attr:`locationLabels`.

            .. versionadded:: 5.0
            """
            locationLabel = self.writerClass.locationLabelDescriptorClass(**kwargs)
            self.addLocationLabel(locationLabel)
            return locationLabel

        def newDefaultLocation(self):
            """Return a dict with the default location in design space coordinates."""
            # Without OrderedDict, output XML would be non-deterministic.
            # https://github.com/LettError/designSpaceDocument/issues/10
            loc = collections.OrderedDict()
            for axisDescriptor in self.axes:
                loc[axisDescriptor.name] = axisDescriptor.map_forward(
                    axisDescriptor.default
                )
            return loc

        def labelForUserLocation(
            self, userLocation: SimpleLocationDict
        ) -> Optional[LocationLabelDescriptor]:
            """Return the :class:`LocationLabel` that matches the given
            ``userLocation``, or ``None`` if no such label exists.

            .. versionadded:: 5.0
            """
            return next(
                (
                    label
                    for label in self.locationLabels
                    if label.userLocation == userLocation
                ),
                None,
            )

        def updateFilenameFromPath(self, masters=True, instances=True, force=False):
            """Set a descriptor filename attr from the path and this document path.

            If the filename attribute is not None: skip it.
            """
            if masters:
                for descriptor in self.sources:
                    if descriptor.filename is not None and not force:
                        continue
                    if self.path is not None:
                        descriptor.filename = self._posixRelativePath(descriptor.path)
            if instances:
                for descriptor in self.instances:
                    if descriptor.filename is not None and not force:
                        continue
                    if self.path is not None:
                        descriptor.filename = self._posixRelativePath(descriptor.path)

        def newAxisDescriptor(self):
            """Ask the writer class to make us a new axisDescriptor."""
            return self.writerClass.getAxisDecriptor()

        def newSourceDescriptor(self):
            """Ask the writer class to make us a new sourceDescriptor."""
            return self.writerClass.getSourceDescriptor()

        def newInstanceDescriptor(self):
            """Ask the writer class to make us a new instanceDescriptor."""
            return self.writerClass.getInstanceDescriptor()

        def getAxisOrder(self):
            """Return a list of axis names, in the same order as defined in the document."""
            names = []
            for axisDescriptor in self.axes:
                names.append(axisDescriptor.name)
            return names

        def getAxis(self, name: str) -> AxisDescriptor | DiscreteAxisDescriptor | None:
            """Return the axis with the given ``name``, or ``None`` if no such axis exists."""
            return next((axis for axis in self.axes if axis.name == name), None)

        def getAxisByTag(self, tag: str) -> AxisDescriptor | DiscreteAxisDescriptor | None:
            """Return the axis with the given ``tag``, or ``None`` if no such axis exists."""
            return next((axis for axis in self.axes if axis.tag == tag), None)

        def getLocationLabel(self, name: str) -> Optional[LocationLabelDescriptor]:
            """Return the top-level location label with the given ``name``, or
            ``None`` if no such label exists.

            .. versionadded:: 5.0
            """
            for label in self.locationLabels:
                if label.name == name:
                    return label
            return None

        def map_forward(self, userLocation: SimpleLocationDict) -> SimpleLocationDict:
            """Map a user location to a design location.

            Assume that missing coordinates are at the default location for that axis.

            Note: the output won't be anisotropic, only the xvalue is set.

            .. versionadded:: 5.0
            """
            return {
                axis.name: axis.map_forward(userLocation.get(axis.name, axis.default))
                for axis in self.axes
            }

        def map_backward(
            self, designLocation: AnisotropicLocationDict
        ) -> SimpleLocationDict:
            """Map a design location to a user location.

            Assume that missing coordinates are at the default location for that axis.

            When the input has anisotropic locations, only the xvalue is used.

            .. versionadded:: 5.0
            """
            return {
                axis.name: (
                    axis.map_backward(designLocation[axis.name])
                    if axis.name in designLocation
                    else axis.default
                )
                for axis in self.axes
            }

        def findDefault(self):
            """Set and return SourceDescriptor at the default location or None.

            The default location is the set of all `default` values in user space
            of all axes.

            This function updates the document's :attr:`default` value.

            .. versionchanged:: 5.0
               Allow the default source to not specify some of the axis values, and
               they are assumed to be the default.
               See :meth:`SourceDescriptor.getFullDesignLocation()`
            """
            self.default = None

            # Convert the default location from user space to design space before comparing
            # it against the SourceDescriptor locations (always in design space).
            defaultDesignLocation = self.newDefaultLocation()

            for sourceDescriptor in self.sources:
                if sourceDescriptor.getFullDesignLocation(self) == defaultDesignLocation:
                    self.default = sourceDescriptor
                    return sourceDescriptor

            return None

        def normalizeLocation(self, location):
            """Return a dict with normalized axis values."""
            from fontTools.varLib.models import normalizeValue

            new = {}
            for axis in self.axes:
                if axis.name not in location:
                    # skipping this dimension it seems
                    continue
                value = location[axis.name]
                # 'anisotropic' location, take first coord only
                if isinstance(value, tuple):
                    value = value[0]
                triple = [
                    axis.map_forward(v) for v in (axis.minimum, axis.default, axis.maximum)
                ]
                new[axis.name] = normalizeValue(value, triple)
            return new

        def normalize(self):
            """
            Normalise the geometry of this designspace:

            - scale all the locations of all masters and instances to the -1 - 0 - 1 value.
            - we need the axis data to do the scaling, so we do those last.
            """
            # masters
            for item in self.sources:
                item.location = self.normalizeLocation(item.location)
            # instances
            for item in self.instances:
                # glyph masters for this instance
                for _, glyphData in item.glyphs.items():
                    glyphData["instanceLocation"] = self.normalizeLocation(
                        glyphData["instanceLocation"]
                    )
                    for glyphMaster in glyphData["masters"]:
                        glyphMaster["location"] = self.normalizeLocation(
                            glyphMaster["location"]
                        )
                item.location = self.normalizeLocation(item.location)
            # the axes
            for axis in self.axes:
                # scale the map first
                newMap = []
                for inputValue, outputValue in axis.map:
                    newOutputValue = self.normalizeLocation({axis.name: outputValue}).get(
                        axis.name
                    )
                    newMap.append((inputValue, newOutputValue))
                if newMap:
                    axis.map = newMap
                # finally the axis values
                minimum = self.normalizeLocation({axis.name: axis.minimum}).get(axis.name)
                maximum = self.normalizeLocation({axis.name: axis.maximum}).get(axis.name)
                default = self.normalizeLocation({axis.name: axis.default}).get(axis.name)
                # and set them in the axis.minimum
                axis.minimum = minimum
                axis.maximum = maximum
                axis.default = default
            # now the rules
            for rule in self.rules:
                newConditionSets = []
                for conditions in rule.conditionSets:
                    newConditions = []
                    for cond in conditions:
                        if cond.get("minimum") is not None:
                            minimum = self.normalizeLocation(
                                {cond["name"]: cond["minimum"]}
                            ).get(cond["name"])
                        else:
                            minimum = None
                        if cond.get("maximum") is not None:
                            maximum = self.normalizeLocation(
                                {cond["name"]: cond["maximum"]}
                            ).get(cond["name"])
                        else:
                            maximum = None
                        newConditions.append(
                            dict(name=cond["name"], minimum=minimum, maximum=maximum)
                        )
                    newConditionSets.append(newConditions)
                rule.conditionSets = newConditionSets

        def loadSourceFonts(self, opener, **kwargs):
            """Ensure SourceDescriptor.font attributes are loaded, and return list of fonts.

            Takes a callable which initializes a new font object (e.g. TTFont, or
            defcon.Font, etc.) from the SourceDescriptor.path, and sets the
            SourceDescriptor.font attribute.
            If the font attribute is already not None, it is not loaded again.
            Fonts with the same path are only loaded once and shared among SourceDescriptors.

            For example, to load UFO sources using defcon:

                designspace = DesignSpaceDocument.fromfile("path/to/my.designspace")
                designspace.loadSourceFonts(defcon.Font)

            Or to load masters as FontTools binary fonts, including extra options:

                designspace.loadSourceFonts(ttLib.TTFont, recalcBBoxes=False)

            Args:
                opener (Callable): takes one required positional argument, the source.path,
                    and an optional list of keyword arguments, and returns a new font object
                    loaded from the path.
                **kwargs: extra options passed on to the opener function.

            Returns:
                List of font objects in the order they appear in the sources list.
            """
            # we load fonts with the same source.path only once
            loaded = {}
            fonts = []
            for source in self.sources:
                if source.font is not None:  # font already loaded
                    fonts.append(source.font)
                    continue
                if source.path in loaded:
                    source.font = loaded[source.path]
                else:
                    if source.path is None:
                        raise DesignSpaceDocumentError(
                            "Designspace source '%s' has no 'path' attribute"
                            % (source.name or "<Unknown>")
                        )
                    source.font = opener(source.path, **kwargs)
                    loaded[source.path] = source.font
                fonts.append(source.font)
            return fonts

        @property
        def formatTuple(self):
            """Return the formatVersion as a tuple of (major, minor).

            .. versionadded:: 5.0
            """
            if self.formatVersion is None:
                return (5, 0)
            numbers = (int(i) for i in self.formatVersion.split("."))
            major = next(numbers)
            minor = next(numbers, 0)
            return (major, minor)

        def getVariableFonts(self) -> List[VariableFontDescriptor]:
            """Return all variable fonts defined in this document, or implicit
            variable fonts that can be built from the document's continuous axes.

            In the case of Designspace documents before version 5, the whole
            document was implicitly describing a variable font that covers the
            whole space.

            In version 5 and above documents, there can be as many variable fonts
            as there are locations on discrete axes.

            .. seealso:: :func:`splitInterpolable`

            .. versionadded:: 5.0
            """
            if self.variableFonts:
                return self.variableFonts

            variableFonts = []
            discreteAxes = []
            rangeAxisSubsets: List[
                Union[RangeAxisSubsetDescriptor, ValueAxisSubsetDescriptor]
            ] = []
            for axis in self.axes:
                if hasattr(axis, "values"):
                    # Mypy doesn't support narrowing union types via hasattr()
                    # TODO(Python 3.10): use TypeGuard
                    # https://mypy.readthedocs.io/en/stable/type_narrowing.html
                    axis = cast(DiscreteAxisDescriptor, axis)
                    discreteAxes.append(axis)  # type: ignore
                else:
                    rangeAxisSubsets.append(RangeAxisSubsetDescriptor(name=axis.name))
            valueCombinations = itertools.product(*[axis.values for axis in discreteAxes])
            for values in valueCombinations:
                basename = None
                if self.filename is not None:
                    basename = os.path.splitext(self.filename)[0] + "-VF"
                if self.path is not None:
                    basename = os.path.splitext(os.path.basename(self.path))[0] + "-VF"
                if basename is None:
                    basename = "VF"
                axisNames = "".join(
                    [f"-{axis.tag}{value}" for axis, value in zip(discreteAxes, values)]
                )
                variableFonts.append(
                    VariableFontDescriptor(
                        name=f"{basename}{axisNames}",
                        axisSubsets=rangeAxisSubsets
                        + [
                            ValueAxisSubsetDescriptor(name=axis.name, userValue=value)
                            for axis, value in zip(discreteAxes, values)
                        ],
                    )
                )
            return variableFonts

        def deepcopyExceptFonts(self):
            """Allow deep-copying a DesignSpace document without deep-copying
            attached UFO fonts or TTFont objects. The :attr:`font` attribute
            is shared by reference between the original and the copy.

            .. versionadded:: 5.0
            """
            fonts = [source.font for source in self.sources]
            try:
                for source in self.sources:
                    source.font = None
                res = copy.deepcopy(self)
                for source, font in zip(res.sources, fonts):
                    source.font = font
                return res
            finally:
                for source, font in zip(self.sources, fonts):
                    source.font = font

    def main(args=None):
        """Roundtrip .designspace file through the DesignSpaceDocument class"""

        if args is None:
            import sys

            args = sys.argv[1:]

        from argparse import ArgumentParser

        parser = ArgumentParser(prog="designspaceLib", description=main.__doc__)
        parser.add_argument("input")
        parser.add_argument("output")

        options = parser.parse_args(args)

        ds = DesignSpaceDocument.fromfile(options.input)
        ds.write(options.output)