Retain Unicode joining facts through shaping - #712
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Layout policy needs to distinguish scripts whose letters participate in cursive joining without treating every `Join_Causing` character as evidence of a cursive script. In particular, U+200D ZERO WIDTH JOINER has `Joining_Type=Join_Causing` and can occur in Latin or emoji text. Pack `Joining_Type` into `parley_data::Properties`, and generate a sorted lookup of ISO 15924 tags for scripts containing `Left_Joining`, `Right_Joining`, or `Dual_Joining` characters. Excluding `Join_Causing` and `Transparent` keeps `Zyyy` from being classified solely because it owns ZWJ and inherited marks. Expose `script_has_joining_characters` in `parley_engine` for its `parlance::Script` vocabulary, and retain the resolved `script` in each `ShapedRun`. `Item` and `ShapedRun` derive their convenience accessor from that script instead of caching duplicate state, so public record construction remains straightforward and there is no script/classification invariant to maintain. The lookup deliberately reports a Unicode fact. It does not inspect a particular string or decide letter-spacing policy.
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This was done with assistance by GPT 5.6, Sol, xhigh. I've been through it though and made alterations. |
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This is needed for Underwood. I also have a patch that uses this within |
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Layout policy needs to distinguish scripts whose letters participate in cursive joining without treating every
Join_Causingcharacter as evidence of a cursive script. In particular, U+200D ZERO WIDTH JOINER hasJoining_Type=Join_Causingand can occur in Latin or emoji text.Pack
Joining_Typeintoparley_data::Properties, and generate a sorted lookup of ISO 15924 tags for scripts containingLeft_Joining,Right_Joining, orDual_Joiningcharacters. ExcludingJoin_CausingandTransparentkeepsZyyyfrom being classified solely because it owns ZWJ and inherited marks.Expose
script_has_joining_charactersinparley_enginefor itsparlance::Scriptvocabulary, and retain the resolvedscriptin eachShapedRun.ItemandShapedRunderive their convenience accessor from that script instead of caching duplicate state, so public record construction remains straightforward and there is no script/classification invariant to maintain.The lookup deliberately reports a Unicode fact. It does not inspect a particular string or decide letter-spacing policy.