279 lines
9.8 KiB
Python
279 lines
9.8 KiB
Python
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"""Reorder glyphs in a font."""
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__author__ = "Rod Sheeter"
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# See https://docs.google.com/document/d/1h9O-C_ndods87uY0QeIIcgAMiX2gDTpvO_IhMJsKAqs/
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# for details.
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from fontTools import ttLib
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from fontTools.ttLib.tables import otBase
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from fontTools.ttLib.tables import otTables as ot
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from abc import ABC, abstractmethod
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from dataclasses import dataclass
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from collections import deque
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from typing import (
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Optional,
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Any,
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Callable,
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Deque,
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Iterable,
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List,
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NamedTuple,
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Tuple,
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Union,
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)
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_COVERAGE_ATTR = "Coverage" # tables that have one coverage use this name
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def _sort_by_gid(
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get_glyph_id: Callable[[str], int],
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glyphs: List[str],
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parallel_list: Optional[List[Any]],
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):
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if parallel_list:
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reordered = sorted(
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((g, e) for g, e in zip(glyphs, parallel_list)),
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key=lambda t: get_glyph_id(t[0]),
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)
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sorted_glyphs, sorted_parallel_list = map(list, zip(*reordered))
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parallel_list[:] = sorted_parallel_list
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else:
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sorted_glyphs = sorted(glyphs, key=get_glyph_id)
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glyphs[:] = sorted_glyphs
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def _get_dotted_attr(value: Any, dotted_attr: str) -> Any:
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attr_names = dotted_attr.split(".")
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assert attr_names
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while attr_names:
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attr_name = attr_names.pop(0)
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value = getattr(value, attr_name)
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return value
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class ReorderRule(ABC):
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"""A rule to reorder something in a font to match the fonts glyph order."""
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@abstractmethod
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def apply(self, font: ttLib.TTFont, value: otBase.BaseTable) -> None: ...
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@dataclass(frozen=True)
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class ReorderCoverage(ReorderRule):
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"""Reorder a Coverage table, and optionally a list that is sorted parallel to it."""
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# A list that is parallel to Coverage
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parallel_list_attr: Optional[str] = None
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coverage_attr: str = _COVERAGE_ATTR
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def apply(self, font: ttLib.TTFont, value: otBase.BaseTable) -> None:
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coverage = _get_dotted_attr(value, self.coverage_attr)
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if type(coverage) is not list:
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# Normal path, process one coverage that might have a parallel list
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parallel_list = None
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if self.parallel_list_attr:
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parallel_list = _get_dotted_attr(value, self.parallel_list_attr)
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assert (
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type(parallel_list) is list
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), f"{self.parallel_list_attr} should be a list"
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assert len(parallel_list) == len(coverage.glyphs), "Nothing makes sense"
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_sort_by_gid(font.getGlyphID, coverage.glyphs, parallel_list)
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else:
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# A few tables have a list of coverage. No parallel list can exist.
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assert (
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not self.parallel_list_attr
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), f"Can't have multiple coverage AND a parallel list; {self}"
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for coverage_entry in coverage:
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_sort_by_gid(font.getGlyphID, coverage_entry.glyphs, None)
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@dataclass(frozen=True)
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class ReorderList(ReorderRule):
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"""Reorder the items within a list to match the updated glyph order.
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Useful when a list ordered by coverage itself contains something ordered by a gid.
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For example, the PairSet table of https://docs.microsoft.com/en-us/typography/opentype/spec/gpos#lookup-type-2-pair-adjustment-positioning-subtable.
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"""
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list_attr: str
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key: str
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def apply(self, font: ttLib.TTFont, value: otBase.BaseTable) -> None:
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lst = _get_dotted_attr(value, self.list_attr)
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assert isinstance(lst, list), f"{self.list_attr} should be a list"
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lst.sort(key=lambda v: font.getGlyphID(getattr(v, self.key)))
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# (Type, Optional Format) => List[ReorderRule]
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# Encodes the relationships Cosimo identified
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_REORDER_RULES = {
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# GPOS
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(ot.SinglePos, 1): [ReorderCoverage()],
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(ot.SinglePos, 2): [ReorderCoverage(parallel_list_attr="Value")],
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(ot.PairPos, 1): [ReorderCoverage(parallel_list_attr="PairSet")],
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(ot.PairSet, None): [ReorderList("PairValueRecord", key="SecondGlyph")],
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(ot.PairPos, 2): [ReorderCoverage()],
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(ot.CursivePos, 1): [ReorderCoverage(parallel_list_attr="EntryExitRecord")],
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(ot.MarkBasePos, 1): [
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ReorderCoverage(
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coverage_attr="MarkCoverage", parallel_list_attr="MarkArray.MarkRecord"
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),
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ReorderCoverage(
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coverage_attr="BaseCoverage", parallel_list_attr="BaseArray.BaseRecord"
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),
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],
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(ot.MarkLigPos, 1): [
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ReorderCoverage(
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coverage_attr="MarkCoverage", parallel_list_attr="MarkArray.MarkRecord"
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),
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ReorderCoverage(
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coverage_attr="LigatureCoverage",
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parallel_list_attr="LigatureArray.LigatureAttach",
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),
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],
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(ot.MarkMarkPos, 1): [
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ReorderCoverage(
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coverage_attr="Mark1Coverage", parallel_list_attr="Mark1Array.MarkRecord"
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),
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ReorderCoverage(
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coverage_attr="Mark2Coverage", parallel_list_attr="Mark2Array.Mark2Record"
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),
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],
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(ot.ContextPos, 1): [ReorderCoverage(parallel_list_attr="PosRuleSet")],
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(ot.ContextPos, 2): [ReorderCoverage()],
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(ot.ContextPos, 3): [ReorderCoverage()],
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(ot.ChainContextPos, 1): [ReorderCoverage(parallel_list_attr="ChainPosRuleSet")],
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(ot.ChainContextPos, 2): [ReorderCoverage()],
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(ot.ChainContextPos, 3): [
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ReorderCoverage(coverage_attr="BacktrackCoverage"),
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ReorderCoverage(coverage_attr="InputCoverage"),
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ReorderCoverage(coverage_attr="LookAheadCoverage"),
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],
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# GSUB
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(ot.ContextSubst, 1): [ReorderCoverage(parallel_list_attr="SubRuleSet")],
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(ot.ContextSubst, 2): [ReorderCoverage()],
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(ot.ContextSubst, 3): [ReorderCoverage()],
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(ot.ChainContextSubst, 1): [ReorderCoverage(parallel_list_attr="ChainSubRuleSet")],
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(ot.ChainContextSubst, 2): [ReorderCoverage()],
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(ot.ChainContextSubst, 3): [
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ReorderCoverage(coverage_attr="BacktrackCoverage"),
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ReorderCoverage(coverage_attr="InputCoverage"),
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ReorderCoverage(coverage_attr="LookAheadCoverage"),
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],
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(ot.ReverseChainSingleSubst, 1): [
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ReorderCoverage(parallel_list_attr="Substitute"),
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ReorderCoverage(coverage_attr="BacktrackCoverage"),
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ReorderCoverage(coverage_attr="LookAheadCoverage"),
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],
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# GDEF
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(ot.AttachList, None): [ReorderCoverage(parallel_list_attr="AttachPoint")],
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(ot.LigCaretList, None): [ReorderCoverage(parallel_list_attr="LigGlyph")],
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(ot.MarkGlyphSetsDef, None): [ReorderCoverage()],
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# MATH
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(ot.MathGlyphInfo, None): [ReorderCoverage(coverage_attr="ExtendedShapeCoverage")],
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(ot.MathItalicsCorrectionInfo, None): [
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ReorderCoverage(parallel_list_attr="ItalicsCorrection")
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],
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(ot.MathTopAccentAttachment, None): [
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ReorderCoverage(
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coverage_attr="TopAccentCoverage", parallel_list_attr="TopAccentAttachment"
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)
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],
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(ot.MathKernInfo, None): [
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ReorderCoverage(
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coverage_attr="MathKernCoverage", parallel_list_attr="MathKernInfoRecords"
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)
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],
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(ot.MathVariants, None): [
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ReorderCoverage(
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coverage_attr="VertGlyphCoverage",
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parallel_list_attr="VertGlyphConstruction",
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),
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ReorderCoverage(
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coverage_attr="HorizGlyphCoverage",
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parallel_list_attr="HorizGlyphConstruction",
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),
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],
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}
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# TODO Port to otTraverse
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SubTablePath = Tuple[otBase.BaseTable.SubTableEntry, ...]
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def _bfs_base_table(
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root: otBase.BaseTable, root_accessor: str
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) -> Iterable[SubTablePath]:
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yield from _traverse_ot_data(
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root, root_accessor, lambda frontier, new: frontier.extend(new)
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)
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# Given f(current frontier, new entries) add new entries to frontier
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AddToFrontierFn = Callable[[Deque[SubTablePath], List[SubTablePath]], None]
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def _traverse_ot_data(
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root: otBase.BaseTable, root_accessor: str, add_to_frontier_fn: AddToFrontierFn
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) -> Iterable[SubTablePath]:
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# no visited because general otData is forward-offset only and thus cannot cycle
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frontier: Deque[SubTablePath] = deque()
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frontier.append((otBase.BaseTable.SubTableEntry(root_accessor, root),))
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while frontier:
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# path is (value, attr_name) tuples. attr_name is attr of parent to get value
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path = frontier.popleft()
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current = path[-1].value
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yield path
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new_entries = []
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for subtable_entry in current.iterSubTables():
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new_entries.append(path + (subtable_entry,))
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add_to_frontier_fn(frontier, new_entries)
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def reorderGlyphs(font: ttLib.TTFont, new_glyph_order: List[str]):
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old_glyph_order = font.getGlyphOrder()
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if len(new_glyph_order) != len(old_glyph_order):
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raise ValueError(
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f"New glyph order contains {len(new_glyph_order)} glyphs, "
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f"but font has {len(old_glyph_order)} glyphs"
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)
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if set(old_glyph_order) != set(new_glyph_order):
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raise ValueError(
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"New glyph order does not contain the same set of glyphs as the font:\n"
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f"* only in new: {set(new_glyph_order) - set(old_glyph_order)}\n"
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f"* only in old: {set(old_glyph_order) - set(new_glyph_order)}"
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)
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# Changing the order of glyphs in a TTFont requires that all tables that use
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# glyph indexes have been fully.
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# Cf. https://github.com/fonttools/fonttools/issues/2060
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font.ensureDecompiled()
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not_loaded = sorted(t for t in font.keys() if not font.isLoaded(t))
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if not_loaded:
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raise ValueError(f"Everything should be loaded, following aren't: {not_loaded}")
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font.setGlyphOrder(new_glyph_order)
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coverage_containers = {"GDEF", "GPOS", "GSUB", "MATH"}
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for tag in coverage_containers:
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if tag in font.keys():
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for path in _bfs_base_table(font[tag].table, f'font["{tag}"]'):
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value = path[-1].value
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reorder_key = (type(value), getattr(value, "Format", None))
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for reorder in _REORDER_RULES.get(reorder_key, []):
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reorder.apply(font, value)
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