Fix halfwidth katakana voiced and semi-voiced sound marks in width calculations#89
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tats-u wants to merge 1 commit into
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Fix halfwidth katakana voiced and semi-voiced sound marks in width calculations#89tats-u wants to merge 1 commit into
tats-u wants to merge 1 commit into
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Manishearth
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May 26, 2026
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| //! with the [`Grapheme_Extend`] property, except [`'\u{FF9E}'` HALFWIDTH KATAKANA VOICED SOUND MARK](https://util.unicode.org/UnicodeJsps/character.jsp?a=FF9E) | ||
| //! and [`'\u{FF9F}'` HALFWIDTH KATAKANA SEMI-VOICED SOUND MARK](https://util.unicode.org/UnicodeJsps/character.jsp?a=FF9F). |
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Instead of making this a carve-out in rule 4, I think these should be added to rule 1 above. In other word, replace "U+2D7F has width 1" above with "U+2D7F, U+FF9E, and U+FF9F have width 1".
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Related: microsoft/terminal#18087
Halfwidth katakana (semi-)voiced sound marks U+FF9E & U+FF9F are the only Grapheme Extenders that belong to Letter (Lm). They are typical edge cases when you cosider grapheme clusters.
They should be counted as 1 (their EAW is H), not 0.
English transtion of initial Prompt (Copilot + GPT-5.4 high):
Add
test_halfwidth_katakana:ﾊﾟｸﾞ→4 characters
English translation of additional handling prompt after discovering that the added test fails (because GPT started flailing around trying to fix it):
The half-width Kana voiced mark test failed because they're Grapheme Extenders despite being Letters. The current spec sucks, so please fix it together
"pug dog" was hand-written. The rest part of that comment was completed by Copilot line completion.