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https://github.com/storytold/designcraft.git
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Shao Wenbin
c861a9f75e
Port the CJK1 and AR1 changes from 3ecdb78 and de83cdc onto current main. Resolve translation and font-stack conflicts by retaining main localization and craft-fonts integration while preserving all typesetting code, tests, and documentation. Validation: all six CI gates passed, including 616 tests and WASM checks.
77 lines
5.3 KiB
Markdown
77 lines
5.3 KiB
Markdown
# Arabic import and composition
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Task: AR1. These changes repair verified gaps in the existing typesetting pipeline.
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They do not claim full InDesign or vendor-specific Naskh composition parity.
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## Architecture
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Portable character controls live in `doc::arabic` and the inherited attribute
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model. Story column direction and table column direction are independent of
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paragraph direction. The IDML adapter translates serialized values at the boundary.
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The font layer resolves script/direction runs and passes language and surrounding
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text to the OpenType shaper. The composer retains complete cluster text for
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paragraph-level bidi resolution, then applies line-level ordering and placement.
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The renderer continues to consume placed glyphs without Arabic-specific policy.
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Existing `type.char`, `type.para` and `table.options` commands edit the controls.
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`story.setDirection` edits column flow with history and cache invalidation;
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`story.get` reports it. Table cell indices remain logical even when their visual
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positions are reversed. Physical left/right insertion commands account for direction.
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## Implemented rules
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| Area | Behavior |
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| --- | --- |
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| Mixed scripts | Separate Hebrew/Arabic script runs, resolved shaping direction, language tags and OpenType joining features |
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| Style boundaries | Pre/post shaping context preserves joining when a character style changes within an Arabic word |
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| Font fallback | Combining marks and join controls stay with the preceding base face |
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| Bidirectional layout | Full paragraph context, cluster contents and Unicode controls survive line breaking; per-line UAX #9 ordering keeps marks attached, including lines with tab leaders |
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| Character direction | Imported default/LTR/RTL overrides participate in bidi resolution; single-character punctuation mirroring is corrected against final paragraph levels |
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| Digits | European, Arabic-Indic and Persian conversion in both directions, contextual defaults, language-sensitive native digits, original UTF-8 source ranges retained |
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| Diacritics | Font GDEF classification and OpenType mark anchors; explicit X/Y offsets affect marks only, in thousandths of an em |
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| Positional forms | Explicit isolated/initial/medial/final OpenType feature selection; automatic forms remain the default |
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| Kashidas | Paragraph and character switches, actual font coverage, shaper-approved insertion boundaries, nonjoiner protection, whole-cluster movement to keep marks attached |
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| Story direction | Independent right-to-left column flow, including span-column bounds |
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| Table direction | Right-to-left cell placement, merged spans, physical edge styles/borders, hit testing and left/right column insertion |
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| Serialization | Character controls, paragraph policy/width values, story/table directions survive native data and IDML round trips |
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## Remaining limitations
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- Vendor-specific Arabic/Naskh justification policies and Paragraph Kashida Width
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presets are preserved but not reproduced. Preflight reports their use.
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Automatic elongation still uses bounded, scaled tatweel insertion rather than
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full line reshaping or a vendor allocation algorithm.
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- Loose/Medium/Tight/OpenType-from-baseline diacritic presets are preserved and
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reported. Composition uses font anchors and explicit offsets instead.
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- Script-specific stretched alternates, contextual swash policies, complete RTL
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tab-stop semantics and re-shaping at emergency intra-word line breaks require
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further compatibility work. Tracking and arbitrary metric changes within a
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cursive word can still open joining gaps.
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- A font must contain the required glyphs and appropriate OpenType tables. This
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change neither embeds proprietary fonts nor makes missing-font errors disappear.
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- CJK compatibility boundaries remain documented in `cjk-typography.md`.
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## Verification and sources
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Regression tests cover independent IDML XML, round trips, forced line breaks,
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character overrides, original byte ranges, mark placement, style-boundary joining,
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kashida controls, story/table flow, merged cells, command validation and undo.
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Font-dependent tests use available fonts; no proprietary font or user document
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is committed. Synthetic Arabic documents provide visual smoke checks.
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The AR1 validation run passed all six `cargo xtask ci` gates and 616 tests
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(with two existing ignored tests). WASM checks used the installed Rust standard
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library sources via `-Z build-std=std,panic_abort`, because a prebuilt WASM standard
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library was unavailable. The synthetic Arabic proof was exported to IDML and
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reopened in the desktop app: preflight reported zero errors and zero warnings.
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The original Chinese IDML was also reopened; its four Mojikumi/kinsoku-priority
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compatibility warnings remain, along with separate font/link/overset findings.
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- [Unicode UAX #9](https://www.unicode.org/reports/tr9/) defines paragraph resolution
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and line-level bidirectional ordering.
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- [Adobe Middle Eastern scripting guide](https://developer.adobe.com/indesign/uxp/resources/recipes/rtl/)
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documents the distinct direction, digit, kashida and diacritic controls.
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- [Diacritic position enumeration](https://developer.adobe.com/indesign/uxp/dom/api/d/diacritic-position-options/)
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and [positional forms](https://developer.adobe.com/indesign/uxp/dom/api/p/positional-forms/)
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identify serialized options; their presence alone does not establish visual parity.
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