Lib/fontTools/varLib/instancer/featureVars.py

from fontTools.ttLib.tables import otTables as ot
from copy import deepcopy
import logging


log = logging.getLogger("fontTools.varLib.instancer")


def _featureVariationRecordIsUnique(rec, seen):
    conditionSet = []
    conditionSets = (
        rec.ConditionSet.ConditionTable if rec.ConditionSet is not None else []
    )
    for cond in conditionSets:
        if cond.Format != 1:
            # can't tell whether this is duplicate, assume is unique
            return True
        conditionSet.append(
            (cond.AxisIndex, cond.FilterRangeMinValue, cond.FilterRangeMaxValue)
        )
    # besides the set of conditions, we also include the FeatureTableSubstitution
    # version to identify unique FeatureVariationRecords, even though only one
    # version is currently defined. It's theoretically possible that multiple
    # records with same conditions but different substitution table version be
    # present in the same font for backward compatibility.
    recordKey = frozenset([rec.FeatureTableSubstitution.Version] + conditionSet)
    if recordKey in seen:
        return False
    else:
        seen.add(recordKey)  # side effect
        return True


def _limitFeatureVariationConditionRange(condition, axisLimit):
    minValue = condition.FilterRangeMinValue
    maxValue = condition.FilterRangeMaxValue

    if (
        minValue > maxValue
        or minValue > axisLimit.maximum
        or maxValue < axisLimit.minimum
    ):
        # condition invalid or out of range
        return

    return tuple(
        axisLimit.renormalizeValue(v, extrapolate=False) for v in (minValue, maxValue)
    )


def _instantiateFeatureVariationRecord(
    record, recIdx, axisLimits, fvarAxes, axisIndexMap
):
    applies = True
    shouldKeep = False
    newConditions = []
    from fontTools.varLib.instancer import NormalizedAxisTripleAndDistances

    default_triple = NormalizedAxisTripleAndDistances(-1, 0, +1)
    if record.ConditionSet is None:
        record.ConditionSet = ot.ConditionSet()
        record.ConditionSet.ConditionTable = []
        record.ConditionSet.ConditionCount = 0
    for i, condition in enumerate(record.ConditionSet.ConditionTable):
        if condition.Format == 1:
            axisIdx = condition.AxisIndex
            axisTag = fvarAxes[axisIdx].axisTag

            minValue = condition.FilterRangeMinValue
            maxValue = condition.FilterRangeMaxValue
            triple = axisLimits.get(axisTag, default_triple)

            if not (minValue <= triple.default <= maxValue):
                applies = False

            # if condition not met, remove entire record
            if triple.minimum > maxValue or triple.maximum < minValue:
                newConditions = None
                break

            if axisTag in axisIndexMap:
                # remap axis index
                condition.AxisIndex = axisIndexMap[axisTag]

                # remap condition limits
                newRange = _limitFeatureVariationConditionRange(condition, triple)
                if newRange:
                    # keep condition with updated limits
                    minimum, maximum = newRange
                    condition.FilterRangeMinValue = minimum
                    condition.FilterRangeMaxValue = maximum
                    shouldKeep = True
                    if minimum != -1 or maximum != +1:
                        newConditions.append(condition)
                else:
                    # condition out of range, remove entire record
                    newConditions = None
                    break

        else:
            log.warning(
                "Condition table {0} of FeatureVariationRecord {1} has "
                "unsupported format ({2}); ignored".format(i, recIdx, condition.Format)
            )
            applies = False
            newConditions.append(condition)

    if newConditions is not None and shouldKeep:
        record.ConditionSet.ConditionTable = newConditions
        if not newConditions:
            record.ConditionSet = None
        shouldKeep = True
    else:
        shouldKeep = False

    # Does this *always* apply?
    universal = shouldKeep and not newConditions

    return applies, shouldKeep, universal


def _instantiateFeatureVariations(table, fvarAxes, axisLimits):
    pinnedAxes = set(axisLimits.pinnedLocation())
    axisOrder = [axis.axisTag for axis in fvarAxes if axis.axisTag not in pinnedAxes]
    axisIndexMap = {axisTag: axisOrder.index(axisTag) for axisTag in axisOrder}

    featureVariationApplied = False
    uniqueRecords = set()
    newRecords = []
    defaultsSubsts = None

    for i, record in enumerate(table.FeatureVariations.FeatureVariationRecord):
        applies, shouldKeep, universal = _instantiateFeatureVariationRecord(
            record, i, axisLimits, fvarAxes, axisIndexMap
        )

        if shouldKeep and _featureVariationRecordIsUnique(record, uniqueRecords):
            newRecords.append(record)

        if applies and not featureVariationApplied:
            assert record.FeatureTableSubstitution.Version == 0x00010000
            defaultsSubsts = deepcopy(record.FeatureTableSubstitution)
            for default, rec in zip(
                defaultsSubsts.SubstitutionRecord,
                record.FeatureTableSubstitution.SubstitutionRecord,
            ):
                default.Feature = deepcopy(
                    table.FeatureList.FeatureRecord[rec.FeatureIndex].Feature
                )
                table.FeatureList.FeatureRecord[rec.FeatureIndex].Feature = deepcopy(
                    rec.Feature
                )
            # Set variations only once
            featureVariationApplied = True

        # Further records don't have a chance to apply after a universal record
        if universal:
            break

    # Insert a catch-all record to reinstate the old features if necessary
    if featureVariationApplied and newRecords and not universal:
        defaultRecord = ot.FeatureVariationRecord()
        defaultRecord.ConditionSet = ot.ConditionSet()
        defaultRecord.ConditionSet.ConditionTable = []
        defaultRecord.ConditionSet.ConditionCount = 0
        defaultRecord.FeatureTableSubstitution = defaultsSubsts

        newRecords.append(defaultRecord)

    if newRecords:
        table.FeatureVariations.FeatureVariationRecord = newRecords
        table.FeatureVariations.FeatureVariationCount = len(newRecords)
    else:
        del table.FeatureVariations
        # downgrade table version if there are no FeatureVariations left
        table.Version = 0x00010000


def instantiateFeatureVariations(varfont, axisLimits):
    for tableTag in ("GPOS", "GSUB"):
        if tableTag not in varfont or not getattr(
            varfont[tableTag].table, "FeatureVariations", None
        ):
            continue
        log.info("Instantiating FeatureVariations of %s table", tableTag)
        _instantiateFeatureVariations(
            varfont[tableTag].table, varfont["fvar"].axes, axisLimits
        )
        # remove unreferenced lookups
        varfont[tableTag].prune_lookups()