Abdelrehman Fouad
62faa8eee2
Optical kerning was treated exactly like Metrics: the font's kern pairs and nothing else, so text set with Optical in InDesign came out wider, rewrapped and went overset in tightly fitted frames. Now the font's pairs are turned off for Optical text and each pair is spaced from its outlines (crates/compose/src/optical.rs): every glyph's ink is sampled into 28 bands across the em, the pair's mean and smallest ink gap over the bands both glyphs ink are compared with the font's stem-to-stem gap (the pair nn, or HH then oo), and the pair moves 60% of the way towards it, keeping 30% of that gap and moving at most -0.12 or +0.06 em. Latin, Greek and Cyrillic letters, digits and Western punctuation take part; spaces, marks, missing glyphs, right-to-left runs, upright and tate-chu-yoko glyphs and pairs across a fallback font keep their font spacing. Profiles and references are cached, bounded. Tests: AV, To and r. close up and nn stays; HH closes up under Optical but not Metrics (fails on main); every change on a pangram stays within the bounds and spaces keep their width; profile, gap, adjustment and character-class unit tests. Docs: typography parity Kerning row and remaining effort, gap 4, ROADMAP milestone 6 and progress log. Fixes #181.
7.2 KiB
Typography and composition parity
Last reviewed: 2026-10-11 · Last updated: 2026-10-11 · Change: minor (Optical kerning from outlines (#181); 2026-10-10: major, first version, from the full re-measure) · Target: Adobe InDesign 2026 (21.6)
Typesetting is what InDesign is bought for. A feature can exist and still set text differently from InDesign: different line breaks, different page count, overset where InDesign fits. This document tracks both: does the attribute exist, and does it compose like InDesign? Script-specific detail lives in cjk-typography.md, cjk.md and arabic-typography.md. Overall numbers: target-app-parity.md.
Dimension score: ~45% ready (estimated), 120–200 h to parity. Presence is high (76% scored below, nothing absent); fidelity against InDesign is unmeasured, which is the main gap.
Fidelity: how we'd know
There is no oracle yet. What exists: unit tests of break points and invariants in
crates/compose/src/tests.rs (170 tests in the crate), IDML files built by DesignCraft and opened
in InDesign 2026 by hand, and user reports comparing the two (#179, #180, #181, #282–#295).
Needed (gap 4 in gaps.md): a set of synthetic stories (our own text and fonts:
Source Serif 4, Inter, Shippori Mincho from craft-fonts) covering each row below, set in InDesign
2026 by observation on the owner's Mac (results under plan/, never committed), exported as IDML;
DesignCraft opens the IDML and a test compares per paragraph: line count, break positions (by
character offset), last-line width, overset and frame fit. Report the share of paragraphs whose
breaks match exactly. Target for beta: ≥ 90% of Latin body paragraphs identical, 100% fit in the
same frames.
Checklist
Status: ✓ present and believed close · ~ present, known differences or partial · ✗ missing. Fidelity: unmeasured unless stated.
| Area | InDesign 2026 | DesignCraft | Status | Notes / evidence |
|---|---|---|---|---|
| Paragraph Composer | Adobe's multi-line composer | Knuth–Plass total fit, fitness classes, hyphen penalties | ~ | same family of algorithm, Adobe's weights unknown; breaks will differ on some paragraphs |
| Single-line Composer | greedy | greedy with the same ranges | ✓ | |
| World-Ready composers | Paragraph / Single-line World-Ready | RTL, Arabic and bidi in the main composer | ~ | Indic scripts (Devanagari etc.) shape through harfrust but are untested |
| Justification | word/letter spacing, glyph scaling min/desired/max, single-word, last line | all of these | ✓ | a justified line with a tab now justifies after the tab (#284) |
| Hyphenation | per-language dictionaries (~40), zone, limits, capitalized, last word, across columns | Liang patterns: English (trained from the public-domain Moby list) and Spanish (Bezos); zone, limits, exceptions in the user dictionary | ~ | other languages don't hyphenate (#87 reported "doesn't work") |
| Spelling | per-language dictionaries | English (Moby) + document/user dictionary | ~ | |
| Kerning | Metrics, Optical, manual, none | Metrics, Optical (outline-based: pairs pulled towards the font's stem gap, crates/compose/src/optical.rs), manual, none |
~ | Optical is an approximation of Adobe's algorithm (#181), not a match: imported display text can still break differently |
| Tracking, scale, skew, baseline shift | ✓ | ✓ | ✓ | |
| OpenType features | ligatures, discretionary, swash, fractions, ordinals, figures, small caps, stylistic sets, positional forms | through harfrust | ✓ | |
| Variable fonts | axes in Character panel | named instances and free axis values; PDF embeds the instance | ✓ | |
| Leading | auto (120%), absolute, leading model | ✓ | ✓ | CJK leading models in cjk-typography.md |
| First baseline | ascent, cap height, x-height, leading, fixed, min | ✓ | ✓ | |
| Frame fit / overset | baseline of the last line must fit | descenders must fit | ~ | differs (#180): frames go overset where InDesign fits |
| Baseline grid | document and frame grids | ✓ | ✓ | |
| Vertical justification | top, centre, bottom, justify, paragraph spacing limit | ✓ | ✓ | |
| Columns, span / split columns | ✓ | ✓ | ✓ | split columns within a column (#295); text after a span flows below it (#276) |
| Column rules | ✓ | ✓ (screen, PDF, IDML) | ~ | no stroke types or overprint (#274) |
| Keep options and breaks | keep with next, lines together, start in next column/frame/page/odd/even | ✓ | ✓ | break characters end paragraphs (#285); the line before a break is a last line (#283) |
| Drop caps, nested, line and GREP styles | ✓ | ✓ | ✓ | |
| Bullets and numbering | lists, levels, formats, restart, across stories | ✓ | ~ | numbering expressions from IDML (#298); Convert Bullets/Numbering to Text missing |
| Tabs | left/center/right/decimal/align-on, leaders, right-indent tab | ✓ | ~ | Tabs panel missing (#326); wrapping of lines with tabs fixed (#282) |
| Paragraph rules, borders, shading | ✓ | ✓ | ✓ | |
| Balance ragged lines | ✓ | ✓ | ✓ | |
| Optical margin alignment | ✓ | ✓ (hang table of our own) | ~ | hang amounts are ours, InDesign's unknown |
| Text wrap | bounding box, shape, jump object/column, contour options | ✓ | ✓ | |
| Anchored objects | inline, above line, custom | ✓ | ~ | anchored objects in table cells not drawn (#163) |
| Footnotes, endnotes | ✓ | ✓ | ~ | footnotes don't split across columns yet |
| Type on a path | ✓ | ✓ | ✓ | |
| Vertical text (CJK) | ✓ | ✓ | ~ | see cjk.md |
| CJK composition | mojikumi, kinsoku, aki, tsume, ruby, kenten, warichu, frame grid | most; mojikumi tables kept but not applied; ruby group-only; no frame grid | ~ | cjk.md, cjk-typography.md |
| Arabic / Hebrew | kashida, digits, diacritic positioning, RTL stories and tables | ✓ | ~ | vendor justification presets unsupported; list bullets and multi-column RTL (#100) |
| Missing glyphs and fonts | pink highlight, substitution | ✓ | ✓ | |
| Installed fonts | every activated font | system font folders; user folders, font managers and Adobe Fonts not always found | ~ | #161, #110, #107, #327, #261 |
| Composition highlights | H&J, keeps, custom tracking/kerning, substituted fonts | ✓ | ✓ |
Measured from the table above (2026-10-10): 34 rows, 18 ✓, 16 ~, 0 ✗, scoring ✓ = 1 and ~ = 0.5: 76%. Every row exists in some form; the ~ rows are where InDesign users will see a difference.
Remaining effort
| Work | Opus 5.5 h |
|---|---|
| Oracle harness (synthetic stories, IDML exchange, comparison metric) | 20–30 |
| Optical kerning tuning against InDesign (measured pairs per class, once the oracle harness exists) | 5–10 |
| Overset rule (baseline fits) and frame-fit parity | 5–10 |
| Fixing composer differences the harness finds (weights, penalties, glyph-scaling order) | 40–70 |
| Hyphenation patterns for the top 15 InDesign languages (permissive sources) | 20–35 |
| Spelling dictionaries beyond English (licence review per language) | 10–20 (+ owner review) |
| Tabs panel, list conversion commands | 8–15 |
| Total | 120–200 |
Revision history
| Date | Change | Summary |
|---|---|---|
| 2026-10-10 | major | Created: typography checklist (34 rows), fidelity gap and oracle plan |