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