cesnimda
36 lines
2.0 KiB
Python
36 lines
2.0 KiB
Python
"""Read shipped font tables and explain platform descriptor differences; no font edits."""
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import argparse
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import hashlib
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import json
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import struct
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from pathlib import Path
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parser=argparse.ArgumentParser(description=__doc__)
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parser.add_argument('output',type=Path)
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args=parser.parse_args()
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if args.output.exists():raise ValueError('Keep earlier font inventories immutable')
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rows=[]
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for name in ['selawkb.ttf','Roboto-Bold.ttf','Arimo-Bold.ttf','Gelasio-Bold.ttf','Gelasio-SemiBold.ttf','Poppins-Bold.ttf']:
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file=Path(__file__).resolve().parents[2]/'JobTrackerApi/DocumentFonts'/name
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data=file.read_bytes()
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assert data[:4]==b'\x00\x01\x00\x00' and len(data)<5*1024*1024
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count=struct.unpack_from('>H',data,4)[0];assert 1<=count<=64
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tables={}
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for index in range(count):
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tag,checksum,offset,length=struct.unpack_from('>4sIII',data,12+index*16)
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assert offset+length<=len(data)
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tables[tag]=data[offset:offset+length]
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assert len(tables[b'head'])>=20 and len(tables[b'hhea'])>=8 and len(tables[b'OS/2'])>=78
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units=struct.unpack_from('>H',tables[b'head'],18)[0];assert units>0
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ascent,descent=struct.unpack_from('>hh',tables[b'hhea'],4)
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typo_ascent,typo_descent=struct.unpack_from('>hh',tables[b'OS/2'],68)
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win_ascent,win_descent=struct.unpack_from('>HH',tables[b'OS/2'],74)
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selection=struct.unpack_from('>H',tables[b'OS/2'],62)[0]
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rows.append(dict(file=file.name,sha256=hashlib.sha256(data).hexdigest(),unitsPerEm=units,
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hheaAscent1000=ascent/units*1000,hheaDescent1000=descent/units*1000,
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typoAscent1000=typo_ascent/units*1000,typoDescent1000=typo_descent/units*1000,
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windowsAscent1000=win_ascent/units*1000,windowsDescent1000=win_descent/units*1000,
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useTypoMetrics=bool(selection & (1<<7))))
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args.output.write_bytes((json.dumps(dict(evidenceOnly=True,fonts=rows),indent=2)+'\n').encode())
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print('Inspected6 bundled font metric tables without modifying fonts')
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