81 lines
2.4 KiB
Python
81 lines
2.4 KiB
Python
# Generate features for ligatures
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#
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# Adapted from https://github.com/tonsky/FiraCode/blob/master/gen_calt.clj
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from textwrap import dedent
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import tempfile
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def update_features(font):
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"""Find ligatures in the font and generate features for them."""
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# [ ["dash" "greater" "greater"] ... ]
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ligas = [name[:-len('.liga')].split('_')
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for name in font if name.endswith('.liga') and
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font[name].isWorthOutputting()]
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rules = '\n\n'.join(rule(liga)
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for liga in sorted(ligas, key=lambda l: -len(l)))
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fea_code = dedent('''\
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languagesystem DFLT dflt;
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languagesystem latn dflt;
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languagesystem grek dflt;
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languagesystem cyrl dflt;
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feature calt {{
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{}
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}} calt;
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''').format(indent(rules, ' '))
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# print(fea_code) # DEBUG
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# Add the dummy "LIG" glyph
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lig = font.createChar(-1, 'LIG')
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lig.width = font['space'].width
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with tempfile.NamedTemporaryFile(suffix='.fea') as f:
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f.write(fea_code)
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f.seek(0)
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font.mergeFeature(f.name)
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def rule(liga):
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"""
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[f f i] => { [LIG LIG i] f_f_i.liga
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[LIG f i] LIG
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[ f f i] LIG }
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"""
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if len(liga) == 2:
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return dedent('''\
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lookup {0}_{1} {{
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ignore sub {0} {0}' {1};
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ignore sub {0}' {1} {1};
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sub {0}' {1} by LIG;
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sub LIG {1}' by {0}_{1}.liga;
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}} {0}_{1};
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''').format(*liga)
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elif len(liga) == 3:
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return dedent('''\
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lookup {0}_{1}_{2} {{
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ignore sub {0} {0}' {1} {2};
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ignore sub {0}' {1} {2} {2};
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sub {0}' {1} {2} by LIG;
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sub LIG {1}' {2} by LIG;
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sub LIG LIG {2}' by {0}_{1}_{2}.liga;
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}} {0}_{1}_{2};
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''').format(*liga)
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elif len(liga) == 4:
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return dedent('''\
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lookup {0}_{1}_{2}_{3} {{
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ignore sub {0} {0}' {1} {2} {3};
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ignore sub {0}' {1} {2} {3} {3};
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sub {0}' {1} {2} {3} by LIG;
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sub LIG {1}' {2} {3} by LIG;
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sub LIG LIG {2}' {3} by LIG;
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sub LIG LIG LIG {3}' by {0}_{1}_{2}_{3}.liga;
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}} {0}_{1}_{2}_{3};
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''').format(*liga)
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def indent(text, prefix):
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return '\n'.join(prefix + line for line in text.split('\n'))
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