path/to/venv/lib/python3.10/site-packages/fontTools/voltLib/voltToFea.py

"""\
MS VOLT ``.vtp`` to AFDKO ``.fea`` OpenType Layout converter.

Usage
-----

To convert a VTP project file:


    $ fonttools voltLib.voltToFea input.vtp output.fea

It is also possible convert font files with `TSIV` table (as saved from Volt),
in this case the glyph names used in the Volt project will be mapped to the
actual glyph names in the font files when written to the feature file:

    $ fonttools voltLib.voltToFea input.ttf output.fea

The ``--quiet`` option can be used to suppress warnings.

The ``--traceback`` can be used to get Python traceback in case of exceptions,
instead of suppressing the traceback.


Limitations
-----------

* Not all VOLT features are supported, the script will error if it it
  encounters something it does not understand. Please report an issue if this
  happens.
* AFDKO feature file syntax for mark positioning is awkward and does not allow
  setting the mark coverage. It also defines mark anchors globally, as a result
  some mark positioning lookups might cover many marks than what was in the VOLT
  file. This should not be an issue in practice, but if it is then the only way
  is to modify the VOLT file or the generated feature file manually to use unique
  mark anchors for each lookup.
* VOLT allows subtable breaks in any lookup type, but AFDKO feature file
  implementations vary in their support; currently AFDKO’s makeOTF supports
  subtable breaks in pair positioning lookups only, while FontTools’ feaLib
  support it for most substitution lookups and only some positioning lookups.
"""

import logging
import re
from io import StringIO

from fontTools.feaLib import ast
from fontTools.ttLib import TTFont, TTLibError
from fontTools.voltLib import ast as VAst
from fontTools.voltLib.parser import Parser as VoltParser

log = logging.getLogger("fontTools.voltLib.voltToFea")

TABLES = ["GDEF", "GSUB", "GPOS"]


class MarkClassDefinition(ast.MarkClassDefinition):
    def asFea(self, indent=""):
        res = ""
        if not getattr(self, "used", False):
            res += "#"
        res += ast.MarkClassDefinition.asFea(self, indent)
        return res


# For sorting voltLib.ast.GlyphDefinition, see its use below.
class Group:
    def __init__(self, group):
        self.name = group.name.lower()
        self.groups = [
            x.group.lower() for x in group.enum.enum if isinstance(x, VAst.GroupName)
        ]

    def __lt__(self, other):
        if self.name in other.groups:
            return True
        if other.name in self.groups:
            return False
        if self.groups and not other.groups:
            return False
        if not self.groups and other.groups:
            return True


class VoltToFea:
    _NOT_LOOKUP_NAME_RE = re.compile(r"[^A-Za-z_0-9.]")
    _NOT_CLASS_NAME_RE = re.compile(r"[^A-Za-z_0-9.\-]")

    def __init__(self, file_or_path, font=None):
        self._file_or_path = file_or_path
        self._font = font

        self._glyph_map = {}
        self._glyph_order = None

        self._gdef = {}
        self._glyphclasses = {}
        self._features = {}
        self._lookups = {}

        self._marks = set()
        self._ligatures = {}

        self._markclasses = {}
        self._anchors = {}

        self._settings = {}

        self._lookup_names = {}
        self._class_names = {}

    def _lookupName(self, name):
        if name not in self._lookup_names:
            res = self._NOT_LOOKUP_NAME_RE.sub("_", name)
            while res in self._lookup_names.values():
                res += "_"
            self._lookup_names[name] = res
        return self._lookup_names[name]

    def _className(self, name):
        if name not in self._class_names:
            res = self._NOT_CLASS_NAME_RE.sub("_", name)
            while res in self._class_names.values():
                res += "_"
            self._class_names[name] = res
        return self._class_names[name]

    def _collectStatements(self, doc, tables):
        # Collect and sort group definitions first, to make sure a group
        # definition that references other groups comes after them since VOLT
        # does not enforce such ordering, and feature file require it.
        groups = [s for s in doc.statements if isinstance(s, VAst.GroupDefinition)]
        for statement in sorted(groups, key=lambda x: Group(x)):
            self._groupDefinition(statement)

        for statement in doc.statements:
            if isinstance(statement, VAst.GlyphDefinition):
                self._glyphDefinition(statement)
            elif isinstance(statement, VAst.AnchorDefinition):
                if "GPOS" in tables:
                    self._anchorDefinition(statement)
            elif isinstance(statement, VAst.SettingDefinition):
                self._settingDefinition(statement)
            elif isinstance(statement, VAst.GroupDefinition):
                pass  # Handled above
            elif isinstance(statement, VAst.ScriptDefinition):
                self._scriptDefinition(statement)
            elif not isinstance(statement, VAst.LookupDefinition):
                raise NotImplementedError(statement)

        # Lookup definitions need to be handled last as they reference glyph
        # and mark classes that might be defined after them.
        for statement in doc.statements:
            if isinstance(statement, VAst.LookupDefinition):
                if statement.pos and "GPOS" not in tables:
                    continue
                if statement.sub and "GSUB" not in tables:
                    continue
                self._lookupDefinition(statement)

    def _buildFeatureFile(self, tables):
        doc = ast.FeatureFile()
        statements = doc.statements

        if self._glyphclasses:
            statements.append(ast.Comment("# Glyph classes"))
            statements.extend(self._glyphclasses.values())

        if self._markclasses:
            statements.append(ast.Comment("\n# Mark classes"))
            statements.extend(c[1] for c in sorted(self._markclasses.items()))

        if self._lookups:
            statements.append(ast.Comment("\n# Lookups"))
            for lookup in self._lookups.values():
                statements.extend(getattr(lookup, "targets", []))
                statements.append(lookup)

        # Prune features
        features = self._features.copy()
        for ftag in features:
            scripts = features[ftag]
            for stag in scripts:
                langs = scripts[stag]
                for ltag in langs:
                    langs[ltag] = [l for l in langs[ltag] if l.lower() in self._lookups]
                scripts[stag] = {t: l for t, l in langs.items() if l}
            features[ftag] = {t: s for t, s in scripts.items() if s}
        features = {t: f for t, f in features.items() if f}

        if features:
            statements.append(ast.Comment("# Features"))
            for ftag, scripts in features.items():
                feature = ast.FeatureBlock(ftag)
                stags = sorted(scripts, key=lambda k: 0 if k == "DFLT" else 1)
                for stag in stags:
                    feature.statements.append(ast.ScriptStatement(stag))
                    ltags = sorted(scripts[stag], key=lambda k: 0 if k == "dflt" else 1)
                    for ltag in ltags:
                        include_default = True if ltag == "dflt" else False
                        feature.statements.append(
                            ast.LanguageStatement(ltag, include_default=include_default)
                        )
                        for name in scripts[stag][ltag]:
                            lookup = self._lookups[name.lower()]
                            lookupref = ast.LookupReferenceStatement(lookup)
                            feature.statements.append(lookupref)
                statements.append(feature)

        if self._gdef and "GDEF" in tables:
            classes = []
            for name in ("BASE", "MARK", "LIGATURE", "COMPONENT"):
                if name in self._gdef:
                    classname = "GDEF_" + name.lower()
                    glyphclass = ast.GlyphClassDefinition(classname, self._gdef[name])
                    statements.append(glyphclass)
                    classes.append(ast.GlyphClassName(glyphclass))
                else:
                    classes.append(None)

            gdef = ast.TableBlock("GDEF")
            gdef.statements.append(ast.GlyphClassDefStatement(*classes))
            statements.append(gdef)

        return doc

    def convert(self, tables=None):
        doc = VoltParser(self._file_or_path).parse()

        if tables is None:
            tables = TABLES
        if self._font is not None:
            self._glyph_order = self._font.getGlyphOrder()

        self._collectStatements(doc, tables)
        fea = self._buildFeatureFile(tables)
        return fea.asFea()

    def _glyphName(self, glyph):
        try:
            name = glyph.glyph
        except AttributeError:
            name = glyph
        return ast.GlyphName(self._glyph_map.get(name, name))

    def _groupName(self, group):
        try:
            name = group.group
        except AttributeError:
            name = group
        return ast.GlyphClassName(self._glyphclasses[name.lower()])

    def _coverage(self, coverage):
        items = []
        for item in coverage:
            if isinstance(item, VAst.GlyphName):
                items.append(self._glyphName(item))
            elif isinstance(item, VAst.GroupName):
                items.append(self._groupName(item))
            elif isinstance(item, VAst.Enum):
                items.append(self._enum(item))
            elif isinstance(item, VAst.Range):
                items.append((item.start, item.end))
            else:
                raise NotImplementedError(item)
        return items

    def _enum(self, enum):
        return ast.GlyphClass(self._coverage(enum.enum))

    def _context(self, context):
        out = []
        for item in context:
            coverage = self._coverage(item)
            if not isinstance(coverage, (tuple, list)):
                coverage = [coverage]
            out.extend(coverage)
        return out

    def _groupDefinition(self, group):
        name = self._className(group.name)
        glyphs = self._enum(group.enum)
        glyphclass = ast.GlyphClassDefinition(name, glyphs)

        self._glyphclasses[group.name.lower()] = glyphclass

    def _glyphDefinition(self, glyph):
        try:
            self._glyph_map[glyph.name] = self._glyph_order[glyph.id]
        except TypeError:
            pass

        if glyph.type in ("BASE", "MARK", "LIGATURE", "COMPONENT"):
            if glyph.type not in self._gdef:
                self._gdef[glyph.type] = ast.GlyphClass()
            self._gdef[glyph.type].glyphs.append(self._glyphName(glyph.name))

        if glyph.type == "MARK":
            self._marks.add(glyph.name)
        elif glyph.type == "LIGATURE":
            self._ligatures[glyph.name] = glyph.components

    def _scriptDefinition(self, script):
        stag = script.tag
        for lang in script.langs:
            ltag = lang.tag
            for feature in lang.features:
                lookups = {l.split("\\")[0]: True for l in feature.lookups}
                ftag = feature.tag
                if ftag not in self._features:
                    self._features[ftag] = {}
                if stag not in self._features[ftag]:
                    self._features[ftag][stag] = {}
                assert ltag not in self._features[ftag][stag]
                self._features[ftag][stag][ltag] = lookups.keys()

    def _settingDefinition(self, setting):
        if setting.name.startswith("COMPILER_"):
            self._settings[setting.name] = setting.value
        else:
            log.warning(f"Unsupported setting ignored: {setting.name}")

    def _adjustment(self, adjustment):
        adv, dx, dy, adv_adjust_by, dx_adjust_by, dy_adjust_by = adjustment

        adv_device = adv_adjust_by and adv_adjust_by.items() or None
        dx_device = dx_adjust_by and dx_adjust_by.items() or None
        dy_device = dy_adjust_by and dy_adjust_by.items() or None

        return ast.ValueRecord(
            xPlacement=dx,
            yPlacement=dy,
            xAdvance=adv,
            xPlaDevice=dx_device,
            yPlaDevice=dy_device,
            xAdvDevice=adv_device,
        )

    def _anchor(self, adjustment):
        adv, dx, dy, adv_adjust_by, dx_adjust_by, dy_adjust_by = adjustment

        assert not adv_adjust_by
        dx_device = dx_adjust_by and dx_adjust_by.items() or None
        dy_device = dy_adjust_by and dy_adjust_by.items() or None

        return ast.Anchor(
            dx or 0,
            dy or 0,
            xDeviceTable=dx_device or None,
            yDeviceTable=dy_device or None,
        )

    def _anchorDefinition(self, anchordef):
        anchorname = anchordef.name
        glyphname = anchordef.glyph_name
        anchor = self._anchor(anchordef.pos)

        if anchorname.startswith("MARK_"):
            name = "_".join(anchorname.split("_")[1:])
            markclass = ast.MarkClass(self._className(name))
            glyph = self._glyphName(glyphname)
            markdef = MarkClassDefinition(markclass, anchor, glyph)
            self._markclasses[(glyphname, anchorname)] = markdef
        else:
            if glyphname not in self._anchors:
                self._anchors[glyphname] = {}
            if anchorname not in self._anchors[glyphname]:
                self._anchors[glyphname][anchorname] = {}
            self._anchors[glyphname][anchorname][anchordef.component] = anchor

    def _gposLookup(self, lookup, fealookup):
        statements = fealookup.statements

        pos = lookup.pos
        if isinstance(pos, VAst.PositionAdjustPairDefinition):
            for (idx1, idx2), (pos1, pos2) in pos.adjust_pair.items():
                coverage_1 = pos.coverages_1[idx1 - 1]
                coverage_2 = pos.coverages_2[idx2 - 1]

                # If not both are groups, use “enum pos” otherwise makeotf will
                # fail.
                enumerated = False
                for item in coverage_1 + coverage_2:
                    if not isinstance(item, VAst.GroupName):
                        enumerated = True

                glyphs1 = self._coverage(coverage_1)
                glyphs2 = self._coverage(coverage_2)
                record1 = self._adjustment(pos1)
                record2 = self._adjustment(pos2)
                assert len(glyphs1) == 1
                assert len(glyphs2) == 1
                statements.append(
                    ast.PairPosStatement(
                        glyphs1[0], record1, glyphs2[0], record2, enumerated=enumerated
                    )
                )
        elif isinstance(pos, VAst.PositionAdjustSingleDefinition):
            for a, b in pos.adjust_single:
                glyphs = self._coverage(a)
                record = self._adjustment(b)
                assert len(glyphs) == 1
                statements.append(
                    ast.SinglePosStatement([(glyphs[0], record)], [], [], False)
                )
        elif isinstance(pos, VAst.PositionAttachDefinition):
            anchors = {}
            for marks, classname in pos.coverage_to:
                for mark in marks:
                    # Set actually used mark classes. Basically a hack to get
                    # around the feature file syntax limitation of making mark
                    # classes global and not allowing mark positioning to
                    # specify mark coverage.
                    for name in mark.glyphSet():
                        key = (name, "MARK_" + classname)
                        self._markclasses[key].used = True
                markclass = ast.MarkClass(self._className(classname))
                for base in pos.coverage:
                    for name in base.glyphSet():
                        if name not in anchors:
                            anchors[name] = []
                        if classname not in anchors[name]:
                            anchors[name].append(classname)

            for name in anchors:
                components = 1
                if name in self._ligatures:
                    components = self._ligatures[name]

                marks = []
                for mark in anchors[name]:
                    markclass = ast.MarkClass(self._className(mark))
                    for component in range(1, components + 1):
                        if len(marks) < component:
                            marks.append([])
                        anchor = None
                        if component in self._anchors[name][mark]:
                            anchor = self._anchors[name][mark][component]
                        marks[component - 1].append((anchor, markclass))

                base = self._glyphName(name)
                if name in self._marks:
                    mark = ast.MarkMarkPosStatement(base, marks[0])
                elif name in self._ligatures:
                    mark = ast.MarkLigPosStatement(base, marks)
                else:
                    mark = ast.MarkBasePosStatement(base, marks[0])
                statements.append(mark)
        elif isinstance(pos, VAst.PositionAttachCursiveDefinition):
            # Collect enter and exit glyphs
            enter_coverage = []
            for coverage in pos.coverages_enter:
                for base in coverage:
                    for name in base.glyphSet():
                        enter_coverage.append(name)
            exit_coverage = []
            for coverage in pos.coverages_exit:
                for base in coverage:
                    for name in base.glyphSet():
                        exit_coverage.append(name)

            # Write enter anchors, also check if the glyph has exit anchor and
            # write it, too.
            for name in enter_coverage:
                glyph = self._glyphName(name)
                entry = self._anchors[name]["entry"][1]
                exit = None
                if name in exit_coverage:
                    exit = self._anchors[name]["exit"][1]
                    exit_coverage.pop(exit_coverage.index(name))
                statements.append(ast.CursivePosStatement(glyph, entry, exit))

            # Write any remaining exit anchors.
            for name in exit_coverage:
                glyph = self._glyphName(name)
                exit = self._anchors[name]["exit"][1]
                statements.append(ast.CursivePosStatement(glyph, None, exit))
        else:
            raise NotImplementedError(pos)

    def _gposContextLookup(
        self, lookup, prefix, suffix, ignore, fealookup, targetlookup
    ):
        statements = fealookup.statements

        assert not lookup.reversal

        pos = lookup.pos
        if isinstance(pos, VAst.PositionAdjustPairDefinition):
            for (idx1, idx2), (pos1, pos2) in pos.adjust_pair.items():
                glyphs1 = self._coverage(pos.coverages_1[idx1 - 1])
                glyphs2 = self._coverage(pos.coverages_2[idx2 - 1])
                assert len(glyphs1) == 1
                assert len(glyphs2) == 1
                glyphs = (glyphs1[0], glyphs2[0])

                if ignore:
                    statement = ast.IgnorePosStatement([(prefix, glyphs, suffix)])
                else:
                    lookups = (targetlookup, targetlookup)
                    statement = ast.ChainContextPosStatement(
                        prefix, glyphs, suffix, lookups
                    )
                statements.append(statement)
        elif isinstance(pos, VAst.PositionAdjustSingleDefinition):
            glyphs = [ast.GlyphClass()]
            for a, b in pos.adjust_single:
                glyph = self._coverage(a)
                glyphs[0].extend(glyph)

            if ignore:
                statement = ast.IgnorePosStatement([(prefix, glyphs, suffix)])
            else:
                statement = ast.ChainContextPosStatement(
                    prefix, glyphs, suffix, [targetlookup]
                )
            statements.append(statement)
        elif isinstance(pos, VAst.PositionAttachDefinition):
            glyphs = [ast.GlyphClass()]
            for coverage, _ in pos.coverage_to:
                glyphs[0].extend(self._coverage(coverage))

            if ignore:
                statement = ast.IgnorePosStatement([(prefix, glyphs, suffix)])
            else:
                statement = ast.ChainContextPosStatement(
                    prefix, glyphs, suffix, [targetlookup]
                )
            statements.append(statement)
        else:
            raise NotImplementedError(pos)

    def _gsubLookup(self, lookup, prefix, suffix, ignore, chain, fealookup):
        statements = fealookup.statements

        sub = lookup.sub
        for key, val in sub.mapping.items():
            if not key or not val:
                path, line, column = sub.location
                log.warning(f"{path}:{line}:{column}: Ignoring empty substitution")
                continue
            statement = None
            glyphs = self._coverage(key)
            replacements = self._coverage(val)
            if ignore:
                chain_context = (prefix, glyphs, suffix)
                statement = ast.IgnoreSubstStatement([chain_context])
            elif isinstance(sub, VAst.SubstitutionSingleDefinition):
                assert len(glyphs) == 1
                assert len(replacements) == 1
                statement = ast.SingleSubstStatement(
                    glyphs, replacements, prefix, suffix, chain
                )
            elif isinstance(sub, VAst.SubstitutionReverseChainingSingleDefinition):
                assert len(glyphs) == 1
                assert len(replacements) == 1
                statement = ast.ReverseChainSingleSubstStatement(
                    prefix, suffix, glyphs, replacements
                )
            elif isinstance(sub, VAst.SubstitutionMultipleDefinition):
                assert len(glyphs) == 1
                statement = ast.MultipleSubstStatement(
                    prefix, glyphs[0], suffix, replacements, chain
                )
            elif isinstance(sub, VAst.SubstitutionLigatureDefinition):
                assert len(replacements) == 1
                statement = ast.LigatureSubstStatement(
                    prefix, glyphs, suffix, replacements[0], chain
                )
            else:
                raise NotImplementedError(sub)
            statements.append(statement)

    def _lookupDefinition(self, lookup):
        mark_attachement = None
        mark_filtering = None

        flags = 0
        if lookup.direction == "RTL":
            flags |= 1
        if not lookup.process_base:
            flags |= 2
        # FIXME: Does VOLT support this?
        # if not lookup.process_ligatures:
        #     flags |= 4
        if not lookup.process_marks:
            flags |= 8
        elif isinstance(lookup.process_marks, str):
            mark_attachement = self._groupName(lookup.process_marks)
        elif lookup.mark_glyph_set is not None:
            mark_filtering = self._groupName(lookup.mark_glyph_set)

        lookupflags = None
        if flags or mark_attachement is not None or mark_filtering is not None:
            lookupflags = ast.LookupFlagStatement(
                flags, mark_attachement, mark_filtering
            )
        if "\\" in lookup.name:
            # Merge sub lookups as subtables (lookups named “base\sub”),
            # makeotf/feaLib will issue a warning and ignore the subtable
            # statement if it is not a pairpos lookup, though.
            name = lookup.name.split("\\")[0]
            if name.lower() not in self._lookups:
                fealookup = ast.LookupBlock(self._lookupName(name))
                if lookupflags is not None:
                    fealookup.statements.append(lookupflags)
                fealookup.statements.append(ast.Comment("# " + lookup.name))
            else:
                fealookup = self._lookups[name.lower()]
                fealookup.statements.append(ast.SubtableStatement())
                fealookup.statements.append(ast.Comment("# " + lookup.name))
            self._lookups[name.lower()] = fealookup
        else:
            fealookup = ast.LookupBlock(self._lookupName(lookup.name))
            if lookupflags is not None:
                fealookup.statements.append(lookupflags)
            self._lookups[lookup.name.lower()] = fealookup

        if lookup.comments is not None:
            fealookup.statements.append(ast.Comment("# " + lookup.comments))

        contexts = []
        if lookup.context:
            for context in lookup.context:
                prefix = self._context(context.left)
                suffix = self._context(context.right)
                ignore = context.ex_or_in == "EXCEPT_CONTEXT"
                contexts.append([prefix, suffix, ignore, False])
                # It seems that VOLT will create contextual substitution using
                # only the input if there is no other contexts in this lookup.
                if ignore and len(lookup.context) == 1:
                    contexts.append([[], [], False, True])
        else:
            contexts.append([[], [], False, False])

        targetlookup = None
        for prefix, suffix, ignore, chain in contexts:
            if lookup.sub is not None:
                self._gsubLookup(lookup, prefix, suffix, ignore, chain, fealookup)

            if lookup.pos is not None:
                if self._settings.get("COMPILER_USEEXTENSIONLOOKUPS"):
                    fealookup.use_extension = True
                if prefix or suffix or chain or ignore:
                    if not ignore and targetlookup is None:
                        targetname = self._lookupName(lookup.name + " target")
                        targetlookup = ast.LookupBlock(targetname)
                        fealookup.targets = getattr(fealookup, "targets", [])
                        fealookup.targets.append(targetlookup)
                        self._gposLookup(lookup, targetlookup)
                    self._gposContextLookup(
                        lookup, prefix, suffix, ignore, fealookup, targetlookup
                    )
                else:
                    self._gposLookup(lookup, fealookup)


def main(args=None):
    """Convert MS VOLT to AFDKO feature files."""

    import argparse
    from pathlib import Path

    from fontTools import configLogger

    parser = argparse.ArgumentParser(
        "fonttools voltLib.voltToFea", description=main.__doc__
    )
    parser.add_argument(
        "input", metavar="INPUT", type=Path, help="input font/VTP file to process"
    )
    parser.add_argument(
        "featurefile", metavar="OUTPUT", type=Path, help="output feature file"
    )
    parser.add_argument(
        "-t",
        "--table",
        action="append",
        choices=TABLES,
        dest="tables",
        help="List of tables to write, by default all tables are written",
    )
    parser.add_argument(
        "-q", "--quiet", action="store_true", help="Suppress non-error messages"
    )
    parser.add_argument(
        "--traceback", action="store_true", help="Don’t catch exceptions"
    )

    options = parser.parse_args(args)

    configLogger(level=("ERROR" if options.quiet else "INFO"))

    file_or_path = options.input
    font = None
    try:
        font = TTFont(file_or_path)
        if "TSIV" in font:
            file_or_path = StringIO(font["TSIV"].data.decode("utf-8"))
        else:
            log.error('"TSIV" table is missing, font was not saved from VOLT?')
            return 1
    except TTLibError:
        pass

    converter = VoltToFea(file_or_path, font)
    try:
        fea = converter.convert(options.tables)
    except NotImplementedError as e:
        if options.traceback:
            raise
        location = getattr(e.args[0], "location", None)
        message = f'"{e}" is not supported'
        if location:
            path, line, column = location
            log.error(f"{path}:{line}:{column}: {message}")
        else:
            log.error(message)
        return 1
    with open(options.featurefile, "w") as feafile:
        feafile.write(fea)


if __name__ == "__main__":
    import sys

    sys.exit(main())