marseymoji/colrv1_postproc.py

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"""
Post-nanoemoji processing of the Noto COLRv1 Emoji file.
For now substantially based on copying from a correct bitmap build.
"""
from absl import app
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import functools
from fontTools import ttLib
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from fontTools.ttLib.tables import _g_l_y_f as glyf
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from fontTools.ttLib.tables import otTables as ot
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import map_pua_emoji
from nototools import add_vs_cmap
from nototools import unicode_data
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from pathlib import Path
from colrv1_add_soft_light_to_flags import add_soft_light_to_flags
def _is_colrv1(font):
return (
"COLR" in font
and font["COLR"].version == 1
)
def _is_cbdt(font):
return "CBDT" in font
def _is_compat_font(font):
return (
"meta" in font
and "Emji" in font["meta"].data
)
def _copy_emojicompat_data(colr_font, cbdt_font):
colr_font["meta"] = cbdt_font["meta"]
def _set_name(name_table, nameID):
name_table.getName(value, nameID, 3, 1, 0x409)
def _set_name(name_table, nameID, value):
name_table.setName(value, nameID, 3, 1, 0x409)
def _copy_names(colr_font, cbdt_font):
colr_font["name"] = cbdt_font["name"]
name_table = colr_font["name"]
assert all((n.platformID, n.platEncID, n.langID) == (3, 1, 0x409)
for n in name_table.names), "Should only have names Android uses"
# Amendments
_set_name(name_table, 10, "Color emoji font using COLRv1.")
_set_name(name_table, 11, "https://github.com/googlefonts/noto-emoji")
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_set_name(name_table, 12, "https://github.com/googlefonts/noto-emoji")
# CBDT build step: @$(VS_ADDER) -vs 2640 2642 2695 --dstdir '.' -o "$@-with-pua-varsel" "$@-with-pua"
def _add_vs_cmap(colr_font):
emoji_variants = unicode_data.get_unicode_emoji_variants() | {0x2640, 0x2642, 0x2695}
add_vs_cmap.modify_font("COLRv1 Emoji", colr_font, "emoji", emoji_variants)
def _is_variation_selector_cmap_table(table):
assert table.format in {4, 12, 14}
return table.format == 14
def _lookup_in_cmap(colr_font, codepoint):
result = set()
for table in colr_font["cmap"].tables:
if _is_variation_selector_cmap_table(table):
continue
assert codepoint in table.cmap
result.add(table.cmap[codepoint])
assert len(result) == 1, f"Ambiguous mapping for {codepoint}: {result}"
return next(iter(result))
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def _add_cmap_entries(colr_font, codepoint, glyph_name):
for table in colr_font["cmap"].tables:
if _is_variation_selector_cmap_table(table):
continue
if not _is_bmp(codepoint) and table.format == 4:
continue
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table.cmap[codepoint] = glyph_name
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print(f"Map 0x{codepoint:04x} to {glyph_name}, format {table.format}")
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def _map_missing_flag_tag_chars_to_empty_glyphs(colr_font):
# Add all tag characters used in flags
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tag_cps = (
set(range(0xE0030, 0xE0039 + 1))
| set(range(0xE0061, 0xE007A + 1))
)
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# Cancel tag
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tag_cps |= {0xE007F}
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# Anything already cmap'd is fine
tag_cps -= set(_Cmap(colr_font).keys())
# CBDT maps these to blank glyphs
glyf_table = colr_font["glyf"]
hmtx_table = colr_font["hmtx"]
glyph_order_size = len(glyf_table.glyphOrder)
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for cp in tag_cps:
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print(f"Map 0x{cp:04x} to a blank glyf")
glyph_name = f"u{cp:04X}"
assert glyph_name not in glyf_table, f"{glyph_name} already in glyf"
assert glyph_name not in hmtx_table.metrics, f"{glyph_name} already in hmtx"
glyf_table[glyph_name] = glyf.Glyph()
hmtx_table[glyph_name] = (0, 0)
_add_cmap_entries(colr_font, cp, glyph_name)
def _is_bmp(cp):
return cp in range(0x0000, 0xFFFF + 1)
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def _ligaset_for_glyph(lookup_list, glyph_name):
for lookup in lookup_list.Lookup:
if lookup.LookupType != 4:
continue
for liga_set in lookup.SubTable:
if glyph_name in liga_set.ligatures:
return liga_set.ligatures[glyph_name]
return None
def _Cmap(ttfont):
def _Reducer(acc, u):
acc.update(u)
return acc
unicode_cmaps = (t.cmap for t in ttfont['cmap'].tables if t.isUnicode())
return functools.reduce(_Reducer, unicode_cmaps, {})
def _map_empty_flag_tag_to_black_flag(colr_font):
# fontchain_lint wants direct support for empty flag tags
# so map them to the default flag to match cbdt behavior
# if the emoji font starts using extensions this code will require revision
cmap = _Cmap(colr_font)
black_flag_glyph = cmap[0x1f3f4]
cancel_tag_glyph = cmap[0xe007f]
lookup_list = colr_font["GSUB"].table.LookupList
liga_set = _ligaset_for_glyph(lookup_list, black_flag_glyph)
assert liga_set is not None, "There should be existing ligatures using black flag"
# Map black flag + cancel tag to just black flag
# Since this is the ligature set for black flag, component is just cancel tag
# Since we only have one component its safe to put our rule at the front
liga = ot.Ligature()
liga.Component = [cancel_tag_glyph]
liga.LigGlyph = black_flag_glyph
liga_set.insert(0, liga)
def main(argv):
if len(argv) != 3:
raise ValueError("Must have two args, a COLRv1 font and a CBDT emojicompat font")
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colr_file = Path(argv[1])
assert colr_file.is_file()
colr_font = ttLib.TTFont(colr_file)
if not _is_colrv1(colr_font):
raise ValueError("First arg must be a COLRv1 font")
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cbdt_file = Path(argv[2])
assert cbdt_file.is_file()
cbdt_font = ttLib.TTFont(cbdt_file)
if not _is_cbdt(cbdt_font) or not _is_compat_font(cbdt_font):
raise ValueError("Second arg must be a CBDT emojicompat font")
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print(f"COLR {colr_file.absolute()}")
print(f"CBDT {cbdt_file.absolute()}")
_copy_emojicompat_data(colr_font, cbdt_font)
_copy_names(colr_font, cbdt_font)
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# CBDT build step: @$(PYTHON) $(PUA_ADDER) "$@" "$@-with-pua"
map_pua_emoji.add_pua_cmap_to_font(colr_font)
_add_vs_cmap(colr_font)
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_map_missing_flag_tag_chars_to_empty_glyphs(colr_font)
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_map_empty_flag_tag_to_black_flag(colr_font)
add_soft_light_to_flags(colr_font)
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out_file = Path('fonts/Noto-COLRv1-noflags.ttf').absolute()
print("Writing", out_file)
colr_font.save(out_file)
if __name__ == "__main__":
app.run(main)