86 lines
2.4 KiB
Python
86 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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# ignores:
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# ignore sub {0} {0}' {1};
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# ignore sub {0}' {1} {1};
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rules = [
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ignore(prefix=liga[:1], head=liga[0], suffix=liga[1:]),
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ignore(head=liga[0], suffix=(liga[1:] + [liga[-1]])),
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]
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name = "_".join(liga)
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# substitution logic
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# sub {0}' {1} by LIG;
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# sub LIG {1}' by {0}_{1}.liga;
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for i in range(len(liga)):
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init = _join(["LIG" for lig in liga[:i]])
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tail = _join(liga[i + 1 :])
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replace = "LIG" if (i + 1 < len(liga)) else (name + ".liga")
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rules.append("sub{0} {1}'{2} by {3};".format(init, liga[i], tail, replace))
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# put it all together
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lines = (
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["lookup " + name + " {"] + [" " + r for r in rules] + ["}} {0};".format(name)]
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)
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return "\n".join(lines)
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def _join(items):
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return (" " + " ".join(items)) if items else ""
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def ignore(prefix=None, head=None, suffix=None):
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""" don't substitute `head` if it's surrounded by `prefix` and `suffix` """
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assert head
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pref = _join(prefix)
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rest = _join(suffix)
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return "ignore sub{0} {1}'{2};".format(pref, head, rest)
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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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