path/to/venv/lib/python3.10/site-packages/fontTools/ufoLib/glifLib.py

"""
glifLib.py -- Generic module for reading and writing the .glif format.

More info about the .glif format (GLyphInterchangeFormat) can be found here:

	http://unifiedfontobject.org

The main class in this module is GlyphSet. It manages a set of .glif files
in a folder. It offers two ways to read glyph data, and one way to write
glyph data. See the class doc string for details.
"""

from __future__ import annotations

import logging
import enum
from warnings import warn
from collections import OrderedDict
import fs
import fs.base
import fs.errors
import fs.osfs
import fs.path
from fontTools.misc.textTools import tobytes
from fontTools.misc import plistlib
from fontTools.pens.pointPen import AbstractPointPen, PointToSegmentPen
from fontTools.ufoLib.errors import GlifLibError
from fontTools.ufoLib.filenames import userNameToFileName
from fontTools.ufoLib.validators import (
    genericTypeValidator,
    colorValidator,
    guidelinesValidator,
    anchorsValidator,
    identifierValidator,
    imageValidator,
    glyphLibValidator,
)
from fontTools.misc import etree
from fontTools.ufoLib import _UFOBaseIO, UFOFormatVersion
from fontTools.ufoLib.utils import numberTypes, _VersionTupleEnumMixin


__all__ = [
    "GlyphSet",
    "GlifLibError",
    "readGlyphFromString",
    "writeGlyphToString",
    "glyphNameToFileName",
]

logger = logging.getLogger(__name__)


# ---------
# Constants
# ---------

CONTENTS_FILENAME = "contents.plist"
LAYERINFO_FILENAME = "layerinfo.plist"


class GLIFFormatVersion(tuple, _VersionTupleEnumMixin, enum.Enum):
    FORMAT_1_0 = (1, 0)
    FORMAT_2_0 = (2, 0)

    @classmethod
    def default(cls, ufoFormatVersion=None):
        if ufoFormatVersion is not None:
            return max(cls.supported_versions(ufoFormatVersion))
        return super().default()

    @classmethod
    def supported_versions(cls, ufoFormatVersion=None):
        if ufoFormatVersion is None:
            # if ufo format unspecified, return all the supported GLIF formats
            return super().supported_versions()
        # else only return the GLIF formats supported by the given UFO format
        versions = {cls.FORMAT_1_0}
        if ufoFormatVersion >= UFOFormatVersion.FORMAT_3_0:
            versions.add(cls.FORMAT_2_0)
        return frozenset(versions)


# workaround for py3.11, see https://github.com/fonttools/fonttools/pull/2655
GLIFFormatVersion.__str__ = _VersionTupleEnumMixin.__str__


# ------------
# Simple Glyph
# ------------


class Glyph:
    """
    Minimal glyph object. It has no glyph attributes until either
    the draw() or the drawPoints() method has been called.
    """

    def __init__(self, glyphName, glyphSet):
        self.glyphName = glyphName
        self.glyphSet = glyphSet

    def draw(self, pen, outputImpliedClosingLine=False):
        """
        Draw this glyph onto a *FontTools* Pen.
        """
        pointPen = PointToSegmentPen(
            pen, outputImpliedClosingLine=outputImpliedClosingLine
        )
        self.drawPoints(pointPen)

    def drawPoints(self, pointPen):
        """
        Draw this glyph onto a PointPen.
        """
        self.glyphSet.readGlyph(self.glyphName, self, pointPen)


# ---------
# Glyph Set
# ---------


class GlyphSet(_UFOBaseIO):
    """
    GlyphSet manages a set of .glif files inside one directory.

    GlyphSet's constructor takes a path to an existing directory as it's
    first argument. Reading glyph data can either be done through the
    readGlyph() method, or by using GlyphSet's dictionary interface, where
    the keys are glyph names and the values are (very) simple glyph objects.

    To write a glyph to the glyph set, you use the writeGlyph() method.
    The simple glyph objects returned through the dict interface do not
    support writing, they are just a convenient way to get at the glyph data.
    """

    glyphClass = Glyph

    def __init__(
        self,
        path,
        glyphNameToFileNameFunc=None,
        ufoFormatVersion=None,
        validateRead=True,
        validateWrite=True,
        expectContentsFile=False,
    ):
        """
        'path' should be a path (string) to an existing local directory, or
        an instance of fs.base.FS class.

        The optional 'glyphNameToFileNameFunc' argument must be a callback
        function that takes two arguments: a glyph name and a list of all
        existing filenames (if any exist). It should return a file name
        (including the .glif extension). The glyphNameToFileName function
        is called whenever a file name is created for a given glyph name.

        ``validateRead`` will validate read operations. Its default is ``True``.
        ``validateWrite`` will validate write operations. Its default is ``True``.
        ``expectContentsFile`` will raise a GlifLibError if a contents.plist file is
        not found on the glyph set file system. This should be set to ``True`` if you
        are reading an existing UFO and ``False`` if you create a fresh	glyph set.
        """
        try:
            ufoFormatVersion = UFOFormatVersion(ufoFormatVersion)
        except ValueError as e:
            from fontTools.ufoLib.errors import UnsupportedUFOFormat

            raise UnsupportedUFOFormat(
                f"Unsupported UFO format: {ufoFormatVersion!r}"
            ) from e

        if hasattr(path, "__fspath__"):  # support os.PathLike objects
            path = path.__fspath__()

        if isinstance(path, str):
            try:
                filesystem = fs.osfs.OSFS(path)
            except fs.errors.CreateFailed:
                raise GlifLibError("No glyphs directory '%s'" % path)
            self._shouldClose = True
        elif isinstance(path, fs.base.FS):
            filesystem = path
            try:
                filesystem.check()
            except fs.errors.FilesystemClosed:
                raise GlifLibError("the filesystem '%s' is closed" % filesystem)
            self._shouldClose = False
        else:
            raise TypeError(
                "Expected a path string or fs object, found %s" % type(path).__name__
            )
        try:
            path = filesystem.getsyspath("/")
        except fs.errors.NoSysPath:
            # network or in-memory FS may not map to the local one
            path = str(filesystem)
        # 'dirName' is kept for backward compatibility only, but it's DEPRECATED
        # as it's not guaranteed that it maps to an existing OSFS directory.
        # Client could use the FS api via the `self.fs` attribute instead.
        self.dirName = fs.path.parts(path)[-1]
        self.fs = filesystem
        # if glyphSet contains no 'contents.plist', we consider it empty
        self._havePreviousFile = filesystem.exists(CONTENTS_FILENAME)
        if expectContentsFile and not self._havePreviousFile:
            raise GlifLibError(f"{CONTENTS_FILENAME} is missing.")
        # attribute kept for backward compatibility
        self.ufoFormatVersion = ufoFormatVersion.major
        self.ufoFormatVersionTuple = ufoFormatVersion
        if glyphNameToFileNameFunc is None:
            glyphNameToFileNameFunc = glyphNameToFileName
        self.glyphNameToFileName = glyphNameToFileNameFunc
        self._validateRead = validateRead
        self._validateWrite = validateWrite
        self._existingFileNames: set[str] | None = None
        self._reverseContents = None

        self.rebuildContents()

    def rebuildContents(self, validateRead=None):
        """
        Rebuild the contents dict by loading contents.plist.

        ``validateRead`` will validate the data, by default it is set to the
        class's ``validateRead`` value, can be overridden.
        """
        if validateRead is None:
            validateRead = self._validateRead
        contents = self._getPlist(CONTENTS_FILENAME, {})
        # validate the contents
        if validateRead:
            invalidFormat = False
            if not isinstance(contents, dict):
                invalidFormat = True
            else:
                for name, fileName in contents.items():
                    if not isinstance(name, str):
                        invalidFormat = True
                    if not isinstance(fileName, str):
                        invalidFormat = True
                    elif not self.fs.exists(fileName):
                        raise GlifLibError(
                            "%s references a file that does not exist: %s"
                            % (CONTENTS_FILENAME, fileName)
                        )
            if invalidFormat:
                raise GlifLibError("%s is not properly formatted" % CONTENTS_FILENAME)
        self.contents = contents
        self._existingFileNames = None
        self._reverseContents = None

    def getReverseContents(self):
        """
        Return a reversed dict of self.contents, mapping file names to
        glyph names. This is primarily an aid for custom glyph name to file
        name schemes that want to make sure they don't generate duplicate
        file names. The file names are converted to lowercase so we can
        reliably check for duplicates that only differ in case, which is
        important for case-insensitive file systems.
        """
        if self._reverseContents is None:
            d = {}
            for k, v in self.contents.items():
                d[v.lower()] = k
            self._reverseContents = d
        return self._reverseContents

    def writeContents(self):
        """
        Write the contents.plist file out to disk. Call this method when
        you're done writing glyphs.
        """
        self._writePlist(CONTENTS_FILENAME, self.contents)

    # layer info

    def readLayerInfo(self, info, validateRead=None):
        """
        ``validateRead`` will validate the data, by default it is set to the
        class's ``validateRead`` value, can be overridden.
        """
        if validateRead is None:
            validateRead = self._validateRead
        infoDict = self._getPlist(LAYERINFO_FILENAME, {})
        if validateRead:
            if not isinstance(infoDict, dict):
                raise GlifLibError("layerinfo.plist is not properly formatted.")
            infoDict = validateLayerInfoVersion3Data(infoDict)
        # populate the object
        for attr, value in infoDict.items():
            try:
                setattr(info, attr, value)
            except AttributeError:
                raise GlifLibError(
                    "The supplied layer info object does not support setting a necessary attribute (%s)."
                    % attr
                )

    def writeLayerInfo(self, info, validateWrite=None):
        """
        ``validateWrite`` will validate the data, by default it is set to the
        class's ``validateWrite`` value, can be overridden.
        """
        if validateWrite is None:
            validateWrite = self._validateWrite
        if self.ufoFormatVersionTuple.major < 3:
            raise GlifLibError(
                "layerinfo.plist is not allowed in UFO %d."
                % self.ufoFormatVersionTuple.major
            )
        # gather data
        infoData = {}
        for attr in layerInfoVersion3ValueData.keys():
            if hasattr(info, attr):
                try:
                    value = getattr(info, attr)
                except AttributeError:
                    raise GlifLibError(
                        "The supplied info object does not support getting a necessary attribute (%s)."
                        % attr
                    )
                if value is None or (attr == "lib" and not value):
                    continue
                infoData[attr] = value
        if infoData:
            # validate
            if validateWrite:
                infoData = validateLayerInfoVersion3Data(infoData)
            # write file
            self._writePlist(LAYERINFO_FILENAME, infoData)
        elif self._havePreviousFile and self.fs.exists(LAYERINFO_FILENAME):
            # data empty, remove existing file
            self.fs.remove(LAYERINFO_FILENAME)

    def getGLIF(self, glyphName):
        """
        Get the raw GLIF text for a given glyph name. This only works
        for GLIF files that are already on disk.

        This method is useful in situations when the raw XML needs to be
        read from a glyph set for a particular glyph before fully parsing
        it into an object structure via the readGlyph method.

        Raises KeyError if 'glyphName' is not in contents.plist, or
        GlifLibError if the file associated with can't be found.
        """
        fileName = self.contents[glyphName]
        try:
            return self.fs.readbytes(fileName)
        except fs.errors.ResourceNotFound:
            raise GlifLibError(
                "The file '%s' associated with glyph '%s' in contents.plist "
                "does not exist on %s" % (fileName, glyphName, self.fs)
            )

    def getGLIFModificationTime(self, glyphName):
        """
        Returns the modification time for the GLIF file with 'glyphName', as
        a floating point number giving the number of seconds since the epoch.
        Return None if the associated file does not exist or the underlying
        filesystem does not support getting modified times.
        Raises KeyError if the glyphName is not in contents.plist.
        """
        fileName = self.contents[glyphName]
        return self.getFileModificationTime(fileName)

    # reading/writing API

    def readGlyph(self, glyphName, glyphObject=None, pointPen=None, validate=None):
        """
        Read a .glif file for 'glyphName' from the glyph set. The
        'glyphObject' argument can be any kind of object (even None);
        the readGlyph() method will attempt to set the following
        attributes on it:

        width
                the advance width of the glyph
        height
                the advance height of the glyph
        unicodes
                a list of unicode values for this glyph
        note
                a string
        lib
                a dictionary containing custom data
        image
                a dictionary containing image data
        guidelines
                a list of guideline data dictionaries
        anchors
                a list of anchor data dictionaries

        All attributes are optional, in two ways:

        1) An attribute *won't* be set if the .glif file doesn't
           contain data for it. 'glyphObject' will have to deal
           with default values itself.
        2) If setting the attribute fails with an AttributeError
           (for example if the 'glyphObject' attribute is read-
           only), readGlyph() will not propagate that exception,
           but ignore that attribute.

        To retrieve outline information, you need to pass an object
        conforming to the PointPen protocol as the 'pointPen' argument.
        This argument may be None if you don't need the outline data.

        readGlyph() will raise KeyError if the glyph is not present in
        the glyph set.

        ``validate`` will validate the data, by default it is set to the
        class's ``validateRead`` value, can be overridden.
        """
        if validate is None:
            validate = self._validateRead
        text = self.getGLIF(glyphName)
        try:
            tree = _glifTreeFromString(text)
            formatVersions = GLIFFormatVersion.supported_versions(
                self.ufoFormatVersionTuple
            )
            _readGlyphFromTree(
                tree,
                glyphObject,
                pointPen,
                formatVersions=formatVersions,
                validate=validate,
            )
        except GlifLibError as glifLibError:
            # Re-raise with a note that gives extra context, describing where
            # the error occurred.
            fileName = self.contents[glyphName]
            try:
                glifLocation = f"'{self.fs.getsyspath(fileName)}'"
            except fs.errors.NoSysPath:
                # Network or in-memory FS may not map to a local path, so use
                # the best string representation we have.
                glifLocation = f"'{fileName}' from '{str(self.fs)}'"

            glifLibError._add_note(
                f"The issue is in glyph '{glyphName}', located in {glifLocation}."
            )
            raise

    def writeGlyph(
        self,
        glyphName,
        glyphObject=None,
        drawPointsFunc=None,
        formatVersion=None,
        validate=None,
    ):
        """
        Write a .glif file for 'glyphName' to the glyph set. The
        'glyphObject' argument can be any kind of object (even None);
        the writeGlyph() method will attempt to get the following
        attributes from it:

        width
                the advance width of the glyph
        height
                the advance height of the glyph
        unicodes
                a list of unicode values for this glyph
        note
                a string
        lib
                a dictionary containing custom data
        image
                a dictionary containing image data
        guidelines
                a list of guideline data dictionaries
        anchors
                a list of anchor data dictionaries

        All attributes are optional: if 'glyphObject' doesn't
        have the attribute, it will simply be skipped.

        To write outline data to the .glif file, writeGlyph() needs
        a function (any callable object actually) that will take one
        argument: an object that conforms to the PointPen protocol.
        The function will be called by writeGlyph(); it has to call the
        proper PointPen methods to transfer the outline to the .glif file.

        The GLIF format version will be chosen based on the ufoFormatVersion
        passed during the creation of this object. If a particular format
        version is desired, it can be passed with the formatVersion argument.
        The formatVersion argument accepts either a tuple of integers for
        (major, minor), or a single integer for the major digit only (with
        minor digit implied as 0).

        An UnsupportedGLIFFormat exception is raised if the requested GLIF
        formatVersion is not supported.

        ``validate`` will validate the data, by default it is set to the
        class's ``validateWrite`` value, can be overridden.
        """
        if formatVersion is None:
            formatVersion = GLIFFormatVersion.default(self.ufoFormatVersionTuple)
        else:
            try:
                formatVersion = GLIFFormatVersion(formatVersion)
            except ValueError as e:
                from fontTools.ufoLib.errors import UnsupportedGLIFFormat

                raise UnsupportedGLIFFormat(
                    f"Unsupported GLIF format version: {formatVersion!r}"
                ) from e
        if formatVersion not in GLIFFormatVersion.supported_versions(
            self.ufoFormatVersionTuple
        ):
            from fontTools.ufoLib.errors import UnsupportedGLIFFormat

            raise UnsupportedGLIFFormat(
                f"Unsupported GLIF format version ({formatVersion!s}) "
                f"for UFO format version {self.ufoFormatVersionTuple!s}."
            )
        if validate is None:
            validate = self._validateWrite
        fileName = self.contents.get(glyphName)
        if fileName is None:
            if self._existingFileNames is None:
                self._existingFileNames = {
                    fileName.lower() for fileName in self.contents.values()
                }
            fileName = self.glyphNameToFileName(glyphName, self._existingFileNames)
            self.contents[glyphName] = fileName
            self._existingFileNames.add(fileName.lower())
            if self._reverseContents is not None:
                self._reverseContents[fileName.lower()] = glyphName
        data = _writeGlyphToBytes(
            glyphName,
            glyphObject,
            drawPointsFunc,
            formatVersion=formatVersion,
            validate=validate,
        )
        if (
            self._havePreviousFile
            and self.fs.exists(fileName)
            and data == self.fs.readbytes(fileName)
        ):
            return
        self.fs.writebytes(fileName, data)

    def deleteGlyph(self, glyphName):
        """Permanently delete the glyph from the glyph set on disk. Will
        raise KeyError if the glyph is not present in the glyph set.
        """
        fileName = self.contents[glyphName]
        self.fs.remove(fileName)
        if self._existingFileNames is not None:
            self._existingFileNames.remove(fileName.lower())
        if self._reverseContents is not None:
            del self._reverseContents[fileName.lower()]
        del self.contents[glyphName]

    # dict-like support

    def keys(self):
        return list(self.contents.keys())

    def has_key(self, glyphName):
        return glyphName in self.contents

    __contains__ = has_key

    def __len__(self):
        return len(self.contents)

    def __getitem__(self, glyphName):
        if glyphName not in self.contents:
            raise KeyError(glyphName)
        return self.glyphClass(glyphName, self)

    # quickly fetch unicode values

    def getUnicodes(self, glyphNames=None):
        """
        Return a dictionary that maps glyph names to lists containing
        the unicode value[s] for that glyph, if any. This parses the .glif
        files partially, so it is a lot faster than parsing all files completely.
        By default this checks all glyphs, but a subset can be passed with glyphNames.
        """
        unicodes = {}
        if glyphNames is None:
            glyphNames = self.contents.keys()
        for glyphName in glyphNames:
            text = self.getGLIF(glyphName)
            unicodes[glyphName] = _fetchUnicodes(text)
        return unicodes

    def getComponentReferences(self, glyphNames=None):
        """
        Return a dictionary that maps glyph names to lists containing the
        base glyph name of components in the glyph. This parses the .glif
        files partially, so it is a lot faster than parsing all files completely.
        By default this checks all glyphs, but a subset can be passed with glyphNames.
        """
        components = {}
        if glyphNames is None:
            glyphNames = self.contents.keys()
        for glyphName in glyphNames:
            text = self.getGLIF(glyphName)
            components[glyphName] = _fetchComponentBases(text)
        return components

    def getImageReferences(self, glyphNames=None):
        """
        Return a dictionary that maps glyph names to the file name of the image
        referenced by the glyph. This parses the .glif files partially, so it is a
        lot faster than parsing all files completely.
        By default this checks all glyphs, but a subset can be passed with glyphNames.
        """
        images = {}
        if glyphNames is None:
            glyphNames = self.contents.keys()
        for glyphName in glyphNames:
            text = self.getGLIF(glyphName)
            images[glyphName] = _fetchImageFileName(text)
        return images

    def close(self):
        if self._shouldClose:
            self.fs.close()

    def __enter__(self):
        return self

    def __exit__(self, exc_type, exc_value, exc_tb):
        self.close()


# -----------------------
# Glyph Name to File Name
# -----------------------


def glyphNameToFileName(glyphName, existingFileNames):
    """
    Wrapper around the userNameToFileName function in filenames.py

    Note that existingFileNames should be a set for large glyphsets
    or performance will suffer.
    """
    if existingFileNames is None:
        existingFileNames = set()
    return userNameToFileName(glyphName, existing=existingFileNames, suffix=".glif")


# -----------------------
# GLIF To and From String
# -----------------------


def readGlyphFromString(
    aString,
    glyphObject=None,
    pointPen=None,
    formatVersions=None,
    validate=True,
):
    """
    Read .glif data from a string into a glyph object.

    The 'glyphObject' argument can be any kind of object (even None);
    the readGlyphFromString() method will attempt to set the following
    attributes on it:

    width
            the advance width of the glyph
    height
            the advance height of the glyph
    unicodes
            a list of unicode values for this glyph
    note
            a string
    lib
            a dictionary containing custom data
    image
            a dictionary containing image data
    guidelines
            a list of guideline data dictionaries
    anchors
            a list of anchor data dictionaries

    All attributes are optional, in two ways:

    1) An attribute *won't* be set if the .glif file doesn't
       contain data for it. 'glyphObject' will have to deal
       with default values itself.
    2) If setting the attribute fails with an AttributeError
       (for example if the 'glyphObject' attribute is read-
       only), readGlyphFromString() will not propagate that
       exception, but ignore that attribute.

    To retrieve outline information, you need to pass an object
    conforming to the PointPen protocol as the 'pointPen' argument.
    This argument may be None if you don't need the outline data.

    The formatVersions optional argument define the GLIF format versions
    that are allowed to be read.
    The type is Optional[Iterable[Tuple[int, int], int]]. It can contain
    either integers (for the major versions to be allowed, with minor
    digits defaulting to 0), or tuples of integers to specify both
    (major, minor) versions.
    By default when formatVersions is None all the GLIF format versions
    currently defined are allowed to be read.

    ``validate`` will validate the read data. It is set to ``True`` by default.
    """
    tree = _glifTreeFromString(aString)

    if formatVersions is None:
        validFormatVersions = GLIFFormatVersion.supported_versions()
    else:
        validFormatVersions, invalidFormatVersions = set(), set()
        for v in formatVersions:
            try:
                formatVersion = GLIFFormatVersion(v)
            except ValueError:
                invalidFormatVersions.add(v)
            else:
                validFormatVersions.add(formatVersion)
        if not validFormatVersions:
            raise ValueError(
                "None of the requested GLIF formatVersions are supported: "
                f"{formatVersions!r}"
            )

    _readGlyphFromTree(
        tree,
        glyphObject,
        pointPen,
        formatVersions=validFormatVersions,
        validate=validate,
    )


def _writeGlyphToBytes(
    glyphName,
    glyphObject=None,
    drawPointsFunc=None,
    writer=None,
    formatVersion=None,
    validate=True,
):
    """Return .glif data for a glyph as a UTF-8 encoded bytes string."""
    try:
        formatVersion = GLIFFormatVersion(formatVersion)
    except ValueError:
        from fontTools.ufoLib.errors import UnsupportedGLIFFormat

        raise UnsupportedGLIFFormat(
            "Unsupported GLIF format version: {formatVersion!r}"
        )
    # start
    if validate and not isinstance(glyphName, str):
        raise GlifLibError("The glyph name is not properly formatted.")
    if validate and len(glyphName) == 0:
        raise GlifLibError("The glyph name is empty.")
    glyphAttrs = OrderedDict(
        [("name", glyphName), ("format", repr(formatVersion.major))]
    )
    if formatVersion.minor != 0:
        glyphAttrs["formatMinor"] = repr(formatVersion.minor)
    root = etree.Element("glyph", glyphAttrs)
    identifiers = set()
    # advance
    _writeAdvance(glyphObject, root, validate)
    # unicodes
    if getattr(glyphObject, "unicodes", None):
        _writeUnicodes(glyphObject, root, validate)
    # note
    if getattr(glyphObject, "note", None):
        _writeNote(glyphObject, root, validate)
    # image
    if formatVersion.major >= 2 and getattr(glyphObject, "image", None):
        _writeImage(glyphObject, root, validate)
    # guidelines
    if formatVersion.major >= 2 and getattr(glyphObject, "guidelines", None):
        _writeGuidelines(glyphObject, root, identifiers, validate)
    # anchors
    anchors = getattr(glyphObject, "anchors", None)
    if formatVersion.major >= 2 and anchors:
        _writeAnchors(glyphObject, root, identifiers, validate)
    # outline
    if drawPointsFunc is not None:
        outline = etree.SubElement(root, "outline")
        pen = GLIFPointPen(outline, identifiers=identifiers, validate=validate)
        drawPointsFunc(pen)
        if formatVersion.major == 1 and anchors:
            _writeAnchorsFormat1(pen, anchors, validate)
        # prevent lxml from writing self-closing tags
        if not len(outline):
            outline.text = "\n  "
    # lib
    if getattr(glyphObject, "lib", None):
        _writeLib(glyphObject, root, validate)
    # return the text
    data = etree.tostring(
        root, encoding="UTF-8", xml_declaration=True, pretty_print=True
    )
    return data


def writeGlyphToString(
    glyphName,
    glyphObject=None,
    drawPointsFunc=None,
    formatVersion=None,
    validate=True,
):
    """
    Return .glif data for a glyph as a string. The XML declaration's
    encoding is always set to "UTF-8".
    The 'glyphObject' argument can be any kind of object (even None);
    the writeGlyphToString() method will attempt to get the following
    attributes from it:

    width
            the advance width of the glyph
    height
            the advance height of the glyph
    unicodes
            a list of unicode values for this glyph
    note
            a string
    lib
            a dictionary containing custom data
    image
            a dictionary containing image data
    guidelines
            a list of guideline data dictionaries
    anchors
            a list of anchor data dictionaries

    All attributes are optional: if 'glyphObject' doesn't
    have the attribute, it will simply be skipped.

    To write outline data to the .glif file, writeGlyphToString() needs
    a function (any callable object actually) that will take one
    argument: an object that conforms to the PointPen protocol.
    The function will be called by writeGlyphToString(); it has to call the
    proper PointPen methods to transfer the outline to the .glif file.

    The GLIF format version can be specified with the formatVersion argument.
    This accepts either a tuple of integers for (major, minor), or a single
    integer for the major digit only (with minor digit implied as 0).
    By default when formatVesion is None the latest GLIF format version will
    be used; currently it's 2.0, which is equivalent to formatVersion=(2, 0).

    An UnsupportedGLIFFormat exception is raised if the requested UFO
    formatVersion is not supported.

    ``validate`` will validate the written data. It is set to ``True`` by default.
    """
    data = _writeGlyphToBytes(
        glyphName,
        glyphObject=glyphObject,
        drawPointsFunc=drawPointsFunc,
        formatVersion=formatVersion,
        validate=validate,
    )
    return data.decode("utf-8")


def _writeAdvance(glyphObject, element, validate):
    width = getattr(glyphObject, "width", None)
    if width is not None:
        if validate and not isinstance(width, numberTypes):
            raise GlifLibError("width attribute must be int or float")
        if width == 0:
            width = None
    height = getattr(glyphObject, "height", None)
    if height is not None:
        if validate and not isinstance(height, numberTypes):
            raise GlifLibError("height attribute must be int or float")
        if height == 0:
            height = None
    if width is not None and height is not None:
        etree.SubElement(
            element,
            "advance",
            OrderedDict([("height", repr(height)), ("width", repr(width))]),
        )
    elif width is not None:
        etree.SubElement(element, "advance", dict(width=repr(width)))
    elif height is not None:
        etree.SubElement(element, "advance", dict(height=repr(height)))


def _writeUnicodes(glyphObject, element, validate):
    unicodes = getattr(glyphObject, "unicodes", None)
    if validate and isinstance(unicodes, int):
        unicodes = [unicodes]
    seen = set()
    for code in unicodes:
        if validate and not isinstance(code, int):
            raise GlifLibError("unicode values must be int")
        if code in seen:
            continue
        seen.add(code)
        hexCode = "%04X" % code
        etree.SubElement(element, "unicode", dict(hex=hexCode))


def _writeNote(glyphObject, element, validate):
    note = getattr(glyphObject, "note", None)
    if validate and not isinstance(note, str):
        raise GlifLibError("note attribute must be str")
    note = note.strip()
    note = "\n" + note + "\n"
    etree.SubElement(element, "note").text = note


def _writeImage(glyphObject, element, validate):
    image = getattr(glyphObject, "image", None)
    if validate and not imageValidator(image):
        raise GlifLibError(
            "image attribute must be a dict or dict-like object with the proper structure."
        )
    attrs = OrderedDict([("fileName", image["fileName"])])
    for attr, default in _transformationInfo:
        value = image.get(attr, default)
        if value != default:
            attrs[attr] = repr(value)
    color = image.get("color")
    if color is not None:
        attrs["color"] = color
    etree.SubElement(element, "image", attrs)


def _writeGuidelines(glyphObject, element, identifiers, validate):
    guidelines = getattr(glyphObject, "guidelines", [])
    if validate and not guidelinesValidator(guidelines):
        raise GlifLibError("guidelines attribute does not have the proper structure.")
    for guideline in guidelines:
        attrs = OrderedDict()
        x = guideline.get("x")
        if x is not None:
            attrs["x"] = repr(x)
        y = guideline.get("y")
        if y is not None:
            attrs["y"] = repr(y)
        angle = guideline.get("angle")
        if angle is not None:
            attrs["angle"] = repr(angle)
        name = guideline.get("name")
        if name is not None:
            attrs["name"] = name
        color = guideline.get("color")
        if color is not None:
            attrs["color"] = color
        identifier = guideline.get("identifier")
        if identifier is not None:
            if validate and identifier in identifiers:
                raise GlifLibError("identifier used more than once: %s" % identifier)
            attrs["identifier"] = identifier
            identifiers.add(identifier)
        etree.SubElement(element, "guideline", attrs)


def _writeAnchorsFormat1(pen, anchors, validate):
    if validate and not anchorsValidator(anchors):
        raise GlifLibError("anchors attribute does not have the proper structure.")
    for anchor in anchors:
        attrs = {}
        x = anchor["x"]
        attrs["x"] = repr(x)
        y = anchor["y"]
        attrs["y"] = repr(y)
        name = anchor.get("name")
        if name is not None:
            attrs["name"] = name
        pen.beginPath()
        pen.addPoint((x, y), segmentType="move", name=name)
        pen.endPath()


def _writeAnchors(glyphObject, element, identifiers, validate):
    anchors = getattr(glyphObject, "anchors", [])
    if validate and not anchorsValidator(anchors):
        raise GlifLibError("anchors attribute does not have the proper structure.")
    for anchor in anchors:
        attrs = OrderedDict()
        x = anchor["x"]
        attrs["x"] = repr(x)
        y = anchor["y"]
        attrs["y"] = repr(y)
        name = anchor.get("name")
        if name is not None:
            attrs["name"] = name
        color = anchor.get("color")
        if color is not None:
            attrs["color"] = color
        identifier = anchor.get("identifier")
        if identifier is not None:
            if validate and identifier in identifiers:
                raise GlifLibError("identifier used more than once: %s" % identifier)
            attrs["identifier"] = identifier
            identifiers.add(identifier)
        etree.SubElement(element, "anchor", attrs)


def _writeLib(glyphObject, element, validate):
    lib = getattr(glyphObject, "lib", None)
    if not lib:
        # don't write empty lib
        return
    if validate:
        valid, message = glyphLibValidator(lib)
        if not valid:
            raise GlifLibError(message)
    if not isinstance(lib, dict):
        lib = dict(lib)
    # plist inside GLIF begins with 2 levels of indentation
    e = plistlib.totree(lib, indent_level=2)
    etree.SubElement(element, "lib").append(e)


# -----------------------
# layerinfo.plist Support
# -----------------------

layerInfoVersion3ValueData = {
    "color": dict(type=str, valueValidator=colorValidator),
    "lib": dict(type=dict, valueValidator=genericTypeValidator),
}


def validateLayerInfoVersion3ValueForAttribute(attr, value):
    """
    This performs very basic validation of the value for attribute
    following the UFO 3 fontinfo.plist specification. The results
    of this should not be interpretted as *correct* for the font
    that they are part of. This merely indicates that the value
    is of the proper type and, where the specification defines
    a set range of possible values for an attribute, that the
    value is in the accepted range.
    """
    if attr not in layerInfoVersion3ValueData:
        return False
    dataValidationDict = layerInfoVersion3ValueData[attr]
    valueType = dataValidationDict.get("type")
    validator = dataValidationDict.get("valueValidator")
    valueOptions = dataValidationDict.get("valueOptions")
    # have specific options for the validator
    if valueOptions is not None:
        isValidValue = validator(value, valueOptions)
    # no specific options
    else:
        if validator == genericTypeValidator:
            isValidValue = validator(value, valueType)
        else:
            isValidValue = validator(value)
    return isValidValue


def validateLayerInfoVersion3Data(infoData):
    """
    This performs very basic validation of the value for infoData
    following the UFO 3 layerinfo.plist specification. The results
    of this should not be interpretted as *correct* for the font
    that they are part of. This merely indicates that the values
    are of the proper type and, where the specification defines
    a set range of possible values for an attribute, that the
    value is in the accepted range.
    """
    for attr, value in infoData.items():
        if attr not in layerInfoVersion3ValueData:
            raise GlifLibError("Unknown attribute %s." % attr)
        isValidValue = validateLayerInfoVersion3ValueForAttribute(attr, value)
        if not isValidValue:
            raise GlifLibError(f"Invalid value for attribute {attr} ({value!r}).")
    return infoData


# -----------------
# GLIF Tree Support
# -----------------


def _glifTreeFromFile(aFile):
    if etree._have_lxml:
        tree = etree.parse(aFile, parser=etree.XMLParser(remove_comments=True))
    else:
        tree = etree.parse(aFile)
    root = tree.getroot()
    if root.tag != "glyph":
        raise GlifLibError("The GLIF is not properly formatted.")
    if root.text and root.text.strip() != "":
        raise GlifLibError("Invalid GLIF structure.")
    return root


def _glifTreeFromString(aString):
    data = tobytes(aString, encoding="utf-8")
    try:
        if etree._have_lxml:
            root = etree.fromstring(data, parser=etree.XMLParser(remove_comments=True))
        else:
            root = etree.fromstring(data)
    except Exception as etree_exception:
        raise GlifLibError("GLIF contains invalid XML.") from etree_exception

    if root.tag != "glyph":
        raise GlifLibError("The GLIF is not properly formatted.")
    if root.text and root.text.strip() != "":
        raise GlifLibError("Invalid GLIF structure.")
    return root


def _readGlyphFromTree(
    tree,
    glyphObject=None,
    pointPen=None,
    formatVersions=GLIFFormatVersion.supported_versions(),
    validate=True,
):
    # check the format version
    formatVersionMajor = tree.get("format")
    if validate and formatVersionMajor is None:
        raise GlifLibError("Unspecified format version in GLIF.")
    formatVersionMinor = tree.get("formatMinor", 0)
    try:
        formatVersion = GLIFFormatVersion(
            (int(formatVersionMajor), int(formatVersionMinor))
        )
    except ValueError as e:
        msg = "Unsupported GLIF format: %s.%s" % (
            formatVersionMajor,
            formatVersionMinor,
        )
        if validate:
            from fontTools.ufoLib.errors import UnsupportedGLIFFormat

            raise UnsupportedGLIFFormat(msg) from e
        # warn but continue using the latest supported format
        formatVersion = GLIFFormatVersion.default()
        logger.warning(
            "%s. Assuming the latest supported version (%s). "
            "Some data may be skipped or parsed incorrectly.",
            msg,
            formatVersion,
        )

    if validate and formatVersion not in formatVersions:
        raise GlifLibError(f"Forbidden GLIF format version: {formatVersion!s}")

    try:
        readGlyphFromTree = _READ_GLYPH_FROM_TREE_FUNCS[formatVersion]
    except KeyError:
        raise NotImplementedError(formatVersion)

    readGlyphFromTree(
        tree=tree,
        glyphObject=glyphObject,
        pointPen=pointPen,
        validate=validate,
        formatMinor=formatVersion.minor,
    )


def _readGlyphFromTreeFormat1(
    tree, glyphObject=None, pointPen=None, validate=None, **kwargs
):
    # get the name
    _readName(glyphObject, tree, validate)
    # populate the sub elements
    unicodes = []
    haveSeenAdvance = haveSeenOutline = haveSeenLib = haveSeenNote = False
    for element in tree:
        if element.tag == "outline":
            if validate:
                if haveSeenOutline:
                    raise GlifLibError("The outline element occurs more than once.")
                if element.attrib:
                    raise GlifLibError(
                        "The outline element contains unknown attributes."
                    )
                if element.text and element.text.strip() != "":
                    raise GlifLibError("Invalid outline structure.")
            haveSeenOutline = True
            buildOutlineFormat1(glyphObject, pointPen, element, validate)
        elif glyphObject is None:
            continue
        elif element.tag == "advance":
            if validate and haveSeenAdvance:
                raise GlifLibError("The advance element occurs more than once.")
            haveSeenAdvance = True
            _readAdvance(glyphObject, element)
        elif element.tag == "unicode":
            try:
                v = element.get("hex")
                v = int(v, 16)
                if v not in unicodes:
                    unicodes.append(v)
            except ValueError:
                raise GlifLibError(
                    "Illegal value for hex attribute of unicode element."
                )
        elif element.tag == "note":
            if validate and haveSeenNote:
                raise GlifLibError("The note element occurs more than once.")
            haveSeenNote = True
            _readNote(glyphObject, element)
        elif element.tag == "lib":
            if validate and haveSeenLib:
                raise GlifLibError("The lib element occurs more than once.")
            haveSeenLib = True
            _readLib(glyphObject, element, validate)
        else:
            raise GlifLibError("Unknown element in GLIF: %s" % element)
    # set the collected unicodes
    if unicodes:
        _relaxedSetattr(glyphObject, "unicodes", unicodes)


def _readGlyphFromTreeFormat2(
    tree, glyphObject=None, pointPen=None, validate=None, formatMinor=0
):
    # get the name
    _readName(glyphObject, tree, validate)
    # populate the sub elements
    unicodes = []
    guidelines = []
    anchors = []
    haveSeenAdvance = haveSeenImage = haveSeenOutline = haveSeenLib = haveSeenNote = (
        False
    )
    identifiers = set()
    for element in tree:
        if element.tag == "outline":
            if validate:
                if haveSeenOutline:
                    raise GlifLibError("The outline element occurs more than once.")
                if element.attrib:
                    raise GlifLibError(
                        "The outline element contains unknown attributes."
                    )
                if element.text and element.text.strip() != "":
                    raise GlifLibError("Invalid outline structure.")
            haveSeenOutline = True
            if pointPen is not None:
                buildOutlineFormat2(
                    glyphObject, pointPen, element, identifiers, validate
                )
        elif glyphObject is None:
            continue
        elif element.tag == "advance":
            if validate and haveSeenAdvance:
                raise GlifLibError("The advance element occurs more than once.")
            haveSeenAdvance = True
            _readAdvance(glyphObject, element)
        elif element.tag == "unicode":
            try:
                v = element.get("hex")
                v = int(v, 16)
                if v not in unicodes:
                    unicodes.append(v)
            except ValueError:
                raise GlifLibError(
                    "Illegal value for hex attribute of unicode element."
                )
        elif element.tag == "guideline":
            if validate and len(element):
                raise GlifLibError("Unknown children in guideline element.")
            attrib = dict(element.attrib)
            for attr in ("x", "y", "angle"):
                if attr in attrib:
                    attrib[attr] = _number(attrib[attr])
            guidelines.append(attrib)
        elif element.tag == "anchor":
            if validate and len(element):
                raise GlifLibError("Unknown children in anchor element.")
            attrib = dict(element.attrib)
            for attr in ("x", "y"):
                if attr in element.attrib:
                    attrib[attr] = _number(attrib[attr])
            anchors.append(attrib)
        elif element.tag == "image":
            if validate:
                if haveSeenImage:
                    raise GlifLibError("The image element occurs more than once.")
                if len(element):
                    raise GlifLibError("Unknown children in image element.")
            haveSeenImage = True
            _readImage(glyphObject, element, validate)
        elif element.tag == "note":
            if validate and haveSeenNote:
                raise GlifLibError("The note element occurs more than once.")
            haveSeenNote = True
            _readNote(glyphObject, element)
        elif element.tag == "lib":
            if validate and haveSeenLib:
                raise GlifLibError("The lib element occurs more than once.")
            haveSeenLib = True
            _readLib(glyphObject, element, validate)
        else:
            raise GlifLibError("Unknown element in GLIF: %s" % element)
    # set the collected unicodes
    if unicodes:
        _relaxedSetattr(glyphObject, "unicodes", unicodes)
    # set the collected guidelines
    if guidelines:
        if validate and not guidelinesValidator(guidelines, identifiers):
            raise GlifLibError("The guidelines are improperly formatted.")
        _relaxedSetattr(glyphObject, "guidelines", guidelines)
    # set the collected anchors
    if anchors:
        if validate and not anchorsValidator(anchors, identifiers):
            raise GlifLibError("The anchors are improperly formatted.")
        _relaxedSetattr(glyphObject, "anchors", anchors)


_READ_GLYPH_FROM_TREE_FUNCS = {
    GLIFFormatVersion.FORMAT_1_0: _readGlyphFromTreeFormat1,
    GLIFFormatVersion.FORMAT_2_0: _readGlyphFromTreeFormat2,
}


def _readName(glyphObject, root, validate):
    glyphName = root.get("name")
    if validate and not glyphName:
        raise GlifLibError("Empty glyph name in GLIF.")
    if glyphName and glyphObject is not None:
        _relaxedSetattr(glyphObject, "name", glyphName)


def _readAdvance(glyphObject, advance):
    width = _number(advance.get("width", 0))
    _relaxedSetattr(glyphObject, "width", width)
    height = _number(advance.get("height", 0))
    _relaxedSetattr(glyphObject, "height", height)


def _readNote(glyphObject, note):
    lines = note.text.split("\n")
    note = "\n".join(line.strip() for line in lines if line.strip())
    _relaxedSetattr(glyphObject, "note", note)


def _readLib(glyphObject, lib, validate):
    assert len(lib) == 1
    child = lib[0]
    plist = plistlib.fromtree(child)
    if validate:
        valid, message = glyphLibValidator(plist)
        if not valid:
            raise GlifLibError(message)
    _relaxedSetattr(glyphObject, "lib", plist)


def _readImage(glyphObject, image, validate):
    imageData = dict(image.attrib)
    for attr, default in _transformationInfo:
        value = imageData.get(attr, default)
        imageData[attr] = _number(value)
    if validate and not imageValidator(imageData):
        raise GlifLibError("The image element is not properly formatted.")
    _relaxedSetattr(glyphObject, "image", imageData)


# ----------------
# GLIF to PointPen
# ----------------

contourAttributesFormat2 = {"identifier"}
componentAttributesFormat1 = {
    "base",
    "xScale",
    "xyScale",
    "yxScale",
    "yScale",
    "xOffset",
    "yOffset",
}
componentAttributesFormat2 = componentAttributesFormat1 | {"identifier"}
pointAttributesFormat1 = {"x", "y", "type", "smooth", "name"}
pointAttributesFormat2 = pointAttributesFormat1 | {"identifier"}
pointSmoothOptions = {"no", "yes"}
pointTypeOptions = {"move", "line", "offcurve", "curve", "qcurve"}

# format 1


def buildOutlineFormat1(glyphObject, pen, outline, validate):
    anchors = []
    for element in outline:
        if element.tag == "contour":
            if len(element) == 1:
                point = element[0]
                if point.tag == "point":
                    anchor = _buildAnchorFormat1(point, validate)
                    if anchor is not None:
                        anchors.append(anchor)
                        continue
            if pen is not None:
                _buildOutlineContourFormat1(pen, element, validate)
        elif element.tag == "component":
            if pen is not None:
                _buildOutlineComponentFormat1(pen, element, validate)
        else:
            raise GlifLibError("Unknown element in outline element: %s" % element)
    if glyphObject is not None and anchors:
        if validate and not anchorsValidator(anchors):
            raise GlifLibError("GLIF 1 anchors are not properly formatted.")
        _relaxedSetattr(glyphObject, "anchors", anchors)


def _buildAnchorFormat1(point, validate):
    if point.get("type") != "move":
        return None
    name = point.get("name")
    if name is None:
        return None
    x = point.get("x")
    y = point.get("y")
    if validate and x is None:
        raise GlifLibError("Required x attribute is missing in point element.")
    if validate and y is None:
        raise GlifLibError("Required y attribute is missing in point element.")
    x = _number(x)
    y = _number(y)
    anchor = dict(x=x, y=y, name=name)
    return anchor


def _buildOutlineContourFormat1(pen, contour, validate):
    if validate and contour.attrib:
        raise GlifLibError("Unknown attributes in contour element.")
    pen.beginPath()
    if len(contour):
        massaged = _validateAndMassagePointStructures(
            contour,
            pointAttributesFormat1,
            openContourOffCurveLeniency=True,
            validate=validate,
        )
        _buildOutlinePointsFormat1(pen, massaged)
    pen.endPath()


def _buildOutlinePointsFormat1(pen, contour):
    for point in contour:
        x = point["x"]
        y = point["y"]
        segmentType = point["segmentType"]
        smooth = point["smooth"]
        name = point["name"]
        pen.addPoint((x, y), segmentType=segmentType, smooth=smooth, name=name)


def _buildOutlineComponentFormat1(pen, component, validate):
    if validate:
        if len(component):
            raise GlifLibError("Unknown child elements of component element.")
        for attr in component.attrib.keys():
            if attr not in componentAttributesFormat1:
                raise GlifLibError("Unknown attribute in component element: %s" % attr)
    baseGlyphName = component.get("base")
    if validate and baseGlyphName is None:
        raise GlifLibError("The base attribute is not defined in the component.")
    transformation = []
    for attr, default in _transformationInfo:
        value = component.get(attr)
        if value is None:
            value = default
        else:
            value = _number(value)
        transformation.append(value)
    pen.addComponent(baseGlyphName, tuple(transformation))


# format 2


def buildOutlineFormat2(glyphObject, pen, outline, identifiers, validate):
    for element in outline:
        if element.tag == "contour":
            _buildOutlineContourFormat2(pen, element, identifiers, validate)
        elif element.tag == "component":
            _buildOutlineComponentFormat2(pen, element, identifiers, validate)
        else:
            raise GlifLibError("Unknown element in outline element: %s" % element.tag)


def _buildOutlineContourFormat2(pen, contour, identifiers, validate):
    if validate:
        for attr in contour.attrib.keys():
            if attr not in contourAttributesFormat2:
                raise GlifLibError("Unknown attribute in contour element: %s" % attr)
    identifier = contour.get("identifier")
    if identifier is not None:
        if validate:
            if identifier in identifiers:
                raise GlifLibError(
                    "The identifier %s is used more than once." % identifier
                )
            if not identifierValidator(identifier):
                raise GlifLibError(
                    "The contour identifier %s is not valid." % identifier
                )
        identifiers.add(identifier)
    try:
        pen.beginPath(identifier=identifier)
    except TypeError:
        pen.beginPath()
        warn(
            "The beginPath method needs an identifier kwarg. The contour's identifier value has been discarded.",
            DeprecationWarning,
        )
    if len(contour):
        massaged = _validateAndMassagePointStructures(
            contour, pointAttributesFormat2, validate=validate
        )
        _buildOutlinePointsFormat2(pen, massaged, identifiers, validate)
    pen.endPath()


def _buildOutlinePointsFormat2(pen, contour, identifiers, validate):
    for point in contour:
        x = point["x"]
        y = point["y"]
        segmentType = point["segmentType"]
        smooth = point["smooth"]
        name = point["name"]
        identifier = point.get("identifier")
        if identifier is not None:
            if validate:
                if identifier in identifiers:
                    raise GlifLibError(
                        "The identifier %s is used more than once." % identifier
                    )
                if not identifierValidator(identifier):
                    raise GlifLibError("The identifier %s is not valid." % identifier)
            identifiers.add(identifier)
        try:
            pen.addPoint(
                (x, y),
                segmentType=segmentType,
                smooth=smooth,
                name=name,
                identifier=identifier,
            )
        except TypeError:
            pen.addPoint((x, y), segmentType=segmentType, smooth=smooth, name=name)
            warn(
                "The addPoint method needs an identifier kwarg. The point's identifier value has been discarded.",
                DeprecationWarning,
            )


def _buildOutlineComponentFormat2(pen, component, identifiers, validate):
    if validate:
        if len(component):
            raise GlifLibError("Unknown child elements of component element.")
        for attr in component.attrib.keys():
            if attr not in componentAttributesFormat2:
                raise GlifLibError("Unknown attribute in component element: %s" % attr)
    baseGlyphName = component.get("base")
    if validate and baseGlyphName is None:
        raise GlifLibError("The base attribute is not defined in the component.")
    transformation = []
    for attr, default in _transformationInfo:
        value = component.get(attr)
        if value is None:
            value = default
        else:
            value = _number(value)
        transformation.append(value)
    identifier = component.get("identifier")
    if identifier is not None:
        if validate:
            if identifier in identifiers:
                raise GlifLibError(
                    "The identifier %s is used more than once." % identifier
                )
            if validate and not identifierValidator(identifier):
                raise GlifLibError("The identifier %s is not valid." % identifier)
        identifiers.add(identifier)
    try:
        pen.addComponent(baseGlyphName, tuple(transformation), identifier=identifier)
    except TypeError:
        pen.addComponent(baseGlyphName, tuple(transformation))
        warn(
            "The addComponent method needs an identifier kwarg. The component's identifier value has been discarded.",
            DeprecationWarning,
        )


# all formats


def _validateAndMassagePointStructures(
    contour, pointAttributes, openContourOffCurveLeniency=False, validate=True
):
    if not len(contour):
        return
    # store some data for later validation
    lastOnCurvePoint = None
    haveOffCurvePoint = False
    # validate and massage the individual point elements
    massaged = []
    for index, element in enumerate(contour):
        # not <point>
        if element.tag != "point":
            raise GlifLibError(
                "Unknown child element (%s) of contour element." % element.tag
            )
        point = dict(element.attrib)
        massaged.append(point)
        if validate:
            # unknown attributes
            for attr in point.keys():
                if attr not in pointAttributes:
                    raise GlifLibError("Unknown attribute in point element: %s" % attr)
            # search for unknown children
            if len(element):
                raise GlifLibError("Unknown child elements in point element.")
        # x and y are required
        for attr in ("x", "y"):
            try:
                point[attr] = _number(point[attr])
            except KeyError as e:
                raise GlifLibError(
                    f"Required {attr} attribute is missing in point element."
                ) from e
        # segment type
        pointType = point.pop("type", "offcurve")
        if validate and pointType not in pointTypeOptions:
            raise GlifLibError("Unknown point type: %s" % pointType)
        if pointType == "offcurve":
            pointType = None
        point["segmentType"] = pointType
        if pointType is None:
            haveOffCurvePoint = True
        else:
            lastOnCurvePoint = index
        # move can only occur as the first point
        if validate and pointType == "move" and index != 0:
            raise GlifLibError(
                "A move point occurs after the first point in the contour."
            )
        # smooth is optional
        smooth = point.get("smooth", "no")
        if validate and smooth is not None:
            if smooth not in pointSmoothOptions:
                raise GlifLibError("Unknown point smooth value: %s" % smooth)
        smooth = smooth == "yes"
        point["smooth"] = smooth
        # smooth can only be applied to curve and qcurve
        if validate and smooth and pointType is None:
            raise GlifLibError("smooth attribute set in an offcurve point.")
        # name is optional
        if "name" not in element.attrib:
            point["name"] = None
    if openContourOffCurveLeniency:
        # remove offcurves that precede a move. this is technically illegal,
        # but we let it slide because there are fonts out there in the wild like this.
        if massaged[0]["segmentType"] == "move":
            count = 0
            for point in reversed(massaged):
                if point["segmentType"] is None:
                    count += 1
                else:
                    break
            if count:
                massaged = massaged[:-count]
    # validate the off-curves in the segments
    if validate and haveOffCurvePoint and lastOnCurvePoint is not None:
        # we only care about how many offCurves there are before an onCurve
        # filter out the trailing offCurves
        offCurvesCount = len(massaged) - 1 - lastOnCurvePoint
        for point in massaged:
            segmentType = point["segmentType"]
            if segmentType is None:
                offCurvesCount += 1
            else:
                if offCurvesCount:
                    # move and line can't be preceded by off-curves
                    if segmentType == "move":
                        # this will have been filtered out already
                        raise GlifLibError("move can not have an offcurve.")
                    elif segmentType == "line":
                        raise GlifLibError("line can not have an offcurve.")
                    elif segmentType == "curve":
                        if offCurvesCount > 2:
                            raise GlifLibError("Too many offcurves defined for curve.")
                    elif segmentType == "qcurve":
                        pass
                    else:
                        # unknown segment type. it'll be caught later.
                        pass
                offCurvesCount = 0
    return massaged


# ---------------------
# Misc Helper Functions
# ---------------------


def _relaxedSetattr(object, attr, value):
    try:
        setattr(object, attr, value)
    except AttributeError:
        pass


def _number(s):
    """
    Given a numeric string, return an integer or a float, whichever
    the string indicates. _number("1") will return the integer 1,
    _number("1.0") will return the float 1.0.

    >>> _number("1")
    1
    >>> _number("1.0")
    1.0
    >>> _number("a")  # doctest: +IGNORE_EXCEPTION_DETAIL
    Traceback (most recent call last):
        ...
    GlifLibError: Could not convert a to an int or float.
    """
    try:
        n = int(s)
        return n
    except ValueError:
        pass
    try:
        n = float(s)
        return n
    except ValueError:
        raise GlifLibError("Could not convert %s to an int or float." % s)


# --------------------
# Rapid Value Fetching
# --------------------

# base


class _DoneParsing(Exception):
    pass


class _BaseParser:
    def __init__(self):
        self._elementStack = []

    def parse(self, text):
        from xml.parsers.expat import ParserCreate

        parser = ParserCreate()
        parser.StartElementHandler = self.startElementHandler
        parser.EndElementHandler = self.endElementHandler
        parser.Parse(text)

    def startElementHandler(self, name, attrs):
        self._elementStack.append(name)

    def endElementHandler(self, name):
        other = self._elementStack.pop(-1)
        assert other == name


# unicodes


def _fetchUnicodes(glif):
    """
    Get a list of unicodes listed in glif.
    """
    parser = _FetchUnicodesParser()
    parser.parse(glif)
    return parser.unicodes


class _FetchUnicodesParser(_BaseParser):
    def __init__(self):
        self.unicodes = []
        super().__init__()

    def startElementHandler(self, name, attrs):
        if (
            name == "unicode"
            and self._elementStack
            and self._elementStack[-1] == "glyph"
        ):
            value = attrs.get("hex")
            if value is not None:
                try:
                    value = int(value, 16)
                    if value not in self.unicodes:
                        self.unicodes.append(value)
                except ValueError:
                    pass
        super().startElementHandler(name, attrs)


# image


def _fetchImageFileName(glif):
    """
    The image file name (if any) from glif.
    """
    parser = _FetchImageFileNameParser()
    try:
        parser.parse(glif)
    except _DoneParsing:
        pass
    return parser.fileName


class _FetchImageFileNameParser(_BaseParser):
    def __init__(self):
        self.fileName = None
        super().__init__()

    def startElementHandler(self, name, attrs):
        if name == "image" and self._elementStack and self._elementStack[-1] == "glyph":
            self.fileName = attrs.get("fileName")
            raise _DoneParsing
        super().startElementHandler(name, attrs)


# component references


def _fetchComponentBases(glif):
    """
    Get a list of component base glyphs listed in glif.
    """
    parser = _FetchComponentBasesParser()
    try:
        parser.parse(glif)
    except _DoneParsing:
        pass
    return list(parser.bases)


class _FetchComponentBasesParser(_BaseParser):
    def __init__(self):
        self.bases = []
        super().__init__()

    def startElementHandler(self, name, attrs):
        if (
            name == "component"
            and self._elementStack
            and self._elementStack[-1] == "outline"
        ):
            base = attrs.get("base")
            if base is not None:
                self.bases.append(base)
        super().startElementHandler(name, attrs)

    def endElementHandler(self, name):
        if name == "outline":
            raise _DoneParsing
        super().endElementHandler(name)


# --------------
# GLIF Point Pen
# --------------

_transformationInfo = [
    # field name, default value
    ("xScale", 1),
    ("xyScale", 0),
    ("yxScale", 0),
    ("yScale", 1),
    ("xOffset", 0),
    ("yOffset", 0),
]


class GLIFPointPen(AbstractPointPen):
    """
    Helper class using the PointPen protocol to write the <outline>
    part of .glif files.
    """

    def __init__(self, element, formatVersion=None, identifiers=None, validate=True):
        if identifiers is None:
            identifiers = set()
        self.formatVersion = GLIFFormatVersion(formatVersion)
        self.identifiers = identifiers
        self.outline = element
        self.contour = None
        self.prevOffCurveCount = 0
        self.prevPointTypes = []
        self.validate = validate

    def beginPath(self, identifier=None, **kwargs):
        attrs = OrderedDict()
        if identifier is not None and self.formatVersion.major >= 2:
            if self.validate:
                if identifier in self.identifiers:
                    raise GlifLibError(
                        "identifier used more than once: %s" % identifier
                    )
                if not identifierValidator(identifier):
                    raise GlifLibError(
                        "identifier not formatted properly: %s" % identifier
                    )
            attrs["identifier"] = identifier
            self.identifiers.add(identifier)
        self.contour = etree.SubElement(self.outline, "contour", attrs)
        self.prevOffCurveCount = 0

    def endPath(self):
        if self.prevPointTypes and self.prevPointTypes[0] == "move":
            if self.validate and self.prevPointTypes[-1] == "offcurve":
                raise GlifLibError("open contour has loose offcurve point")
        # prevent lxml from writing self-closing tags
        if not len(self.contour):
            self.contour.text = "\n  "
        self.contour = None
        self.prevPointType = None
        self.prevOffCurveCount = 0
        self.prevPointTypes = []

    def addPoint(
        self, pt, segmentType=None, smooth=None, name=None, identifier=None, **kwargs
    ):
        attrs = OrderedDict()
        # coordinates
        if pt is not None:
            if self.validate:
                for coord in pt:
                    if not isinstance(coord, numberTypes):
                        raise GlifLibError("coordinates must be int or float")
            attrs["x"] = repr(pt[0])
            attrs["y"] = repr(pt[1])
        # segment type
        if segmentType == "offcurve":
            segmentType = None
        if self.validate:
            if segmentType == "move" and self.prevPointTypes:
                raise GlifLibError(
                    "move occurs after a point has already been added to the contour."
                )
            if (
                segmentType in ("move", "line")
                and self.prevPointTypes
                and self.prevPointTypes[-1] == "offcurve"
            ):
                raise GlifLibError("offcurve occurs before %s point." % segmentType)
            if segmentType == "curve" and self.prevOffCurveCount > 2:
                raise GlifLibError("too many offcurve points before curve point.")
        if segmentType is not None:
            attrs["type"] = segmentType
        else:
            segmentType = "offcurve"
        if segmentType == "offcurve":
            self.prevOffCurveCount += 1
        else:
            self.prevOffCurveCount = 0
        self.prevPointTypes.append(segmentType)
        # smooth
        if smooth:
            if self.validate and segmentType == "offcurve":
                raise GlifLibError("can't set smooth in an offcurve point.")
            attrs["smooth"] = "yes"
        # name
        if name is not None:
            attrs["name"] = name
        # identifier
        if identifier is not None and self.formatVersion.major >= 2:
            if self.validate:
                if identifier in self.identifiers:
                    raise GlifLibError(
                        "identifier used more than once: %s" % identifier
                    )
                if not identifierValidator(identifier):
                    raise GlifLibError(
                        "identifier not formatted properly: %s" % identifier
                    )
            attrs["identifier"] = identifier
            self.identifiers.add(identifier)
        etree.SubElement(self.contour, "point", attrs)

    def addComponent(self, glyphName, transformation, identifier=None, **kwargs):
        attrs = OrderedDict([("base", glyphName)])
        for (attr, default), value in zip(_transformationInfo, transformation):
            if self.validate and not isinstance(value, numberTypes):
                raise GlifLibError("transformation values must be int or float")
            if value != default:
                attrs[attr] = repr(value)
        if identifier is not None and self.formatVersion.major >= 2:
            if self.validate:
                if identifier in self.identifiers:
                    raise GlifLibError(
                        "identifier used more than once: %s" % identifier
                    )
                if self.validate and not identifierValidator(identifier):
                    raise GlifLibError(
                        "identifier not formatted properly: %s" % identifier
                    )
            attrs["identifier"] = identifier
            self.identifiers.add(identifier)
        etree.SubElement(self.outline, "component", attrs)


if __name__ == "__main__":
    import doctest

    doctest.testmod()