# Source code for fontTools.ttLib.tables._c_v_a_r

    from . import DefaultTable
    from fontTools.misc import sstruct
    from fontTools.misc.textTools import bytesjoin
    from fontTools.ttLib.tables.TupleVariation import \
        compileTupleVariationStore, decompileTupleVariationStore, TupleVariation

    # https://www.microsoft.com/typography/otspec/cvar.htm
    # https://www.microsoft.com/typography/otspec/otvarcommonformats.htm
    # https://developer.apple.com/fonts/TrueType-Reference-Manual/RM06/Chap6cvar.html

    CVAR_HEADER_FORMAT = """
        > # big endian
        majorVersion:        H
        minorVersion:        H
        tupleVariationCount: H
        offsetToData:        H
    """

    CVAR_HEADER_SIZE = sstruct.calcsize(CVAR_HEADER_FORMAT)

    class table__c_v_a_r(DefaultTable.DefaultTable):
        dependencies = ["cvt ", "fvar"]

        def __init__(self, tag=None):
            DefaultTable.DefaultTable.__init__(self, tag)
            self.majorVersion, self.minorVersion = 1, 0
            self.variations = []

        def compile(self, ttFont, useSharedPoints=False):
            tupleVariationCount, tuples, data = compileTupleVariationStore(
                variations=[v for v in self.variations if v.hasImpact()],
                pointCount=len(ttFont["cvt "].values),
                axisTags=[axis.axisTag for axis in ttFont["fvar"].axes],
                sharedTupleIndices={},
                useSharedPoints=useSharedPoints)
            header = {
                "majorVersion": self.majorVersion,
                "minorVersion": self.minorVersion,
                "tupleVariationCount": tupleVariationCount,
                "offsetToData": CVAR_HEADER_SIZE + len(tuples),
            }
            return b''.join([
                sstruct.pack(CVAR_HEADER_FORMAT, header),
                tuples,
                data
            ])

        def decompile(self, data, ttFont):
            axisTags = [axis.axisTag for axis in ttFont["fvar"].axes]
            header = {}
            sstruct.unpack(CVAR_HEADER_FORMAT, data[0:CVAR_HEADER_SIZE], header)
            self.majorVersion = header["majorVersion"]
            self.minorVersion = header["minorVersion"]
            assert self.majorVersion == 1, self.majorVersion
            self.variations = decompileTupleVariationStore(
                tableTag=self.tableTag, axisTags=axisTags,
                tupleVariationCount=header["tupleVariationCount"],
                pointCount=len(ttFont["cvt "].values), sharedTuples=None,
                data=data, pos=CVAR_HEADER_SIZE, dataPos=header["offsetToData"])

        def fromXML(self, name, attrs, content, ttFont):
            if name == "version":
                self.majorVersion = int(attrs.get("major", "1"))
                self.minorVersion = int(attrs.get("minor", "0"))
            elif name == "tuple":
                valueCount = len(ttFont["cvt "].values)
                var = TupleVariation({}, [None] * valueCount)
                self.variations.append(var)
                for tupleElement in content:
                    if isinstance(tupleElement, tuple):
                        tupleName, tupleAttrs, tupleContent = tupleElement
                        var.fromXML(tupleName, tupleAttrs, tupleContent)

        def toXML(self, writer, ttFont):
            axisTags = [axis.axisTag for axis in ttFont["fvar"].axes]
            writer.simpletag("version",
                             major=self.majorVersion, minor=self.minorVersion)
            writer.newline()
            for var in self.variations:
                var.toXML(writer, axisTags)