P6a-dash: dashed and dotted borders as Blink 145 paints them (device-pixels iOS 135→61, Android 182→90)

[thejackshelton]

P6a-dash (T075; notes/T008-p5-review.md; the T046 Amendment T075J split): dashed and dotted borders painted the way Blink 145 paints them, in device px.

Device-pixels delta (pnpm run parity:devices on this tree, against master 0ee050a)

Case	iOS	Android
color-border-sides	30 → 0	34 → 0
css-wide-keywords	6 → 0	10 → 0
logical-border	19 → 0	24 → 0
logical-border-rtl	19 → 0	24 → 0
Total device-pixels failures	135 → 61	182 → 90

• The new border-dash-fit and border-dot-fit cases pass on both targets.
• The remaining failures are master's position-* and selectors-universal-root cases, unchanged.
• Every other lane is in master's state, and lane parity passes.

What changed

• The dash geometry. packages/layout/src/paint-dash.ts ports:

  • BoxBorderPainter's complex side path, for boxes without radii;
  • StyledStrokeData's dash selection;
  • BorderEdge;
  • Skia's dashed-line geometry.

  It is translated to Swift and Kotlin. The border module draws a box with a visible dashed or dotted side from these operations; every other box keeps the band painter.

• Plants. dash-phase-1 and dash-gap-unfitted, each judged on its own cases and the border/edge sample rules (plantVerdict).

• The software-raster precondition. parity:pixel-capture refuses any raster path other than disabled_software, and records the path in the pixel manifest. Lane parity refuses a manifest set without it.

• Fixtures. border-dash-fit and border-dot-fit, plus dash paint vectors.

• docs/ports.json.

  • It registers box_border_painter.cc, styled_stroke_data.cc and border_edge.cc (145.0.7632.6), and SkDashPath.cpp (Skia 2ab8add5). Each entry has its sha256s, licence and cited ranges.
  • It adds computed_style_constants.h as a reference. That file is LGPL class A, and only the EBorderStyle order is used.
  • THIRD_PARTY_NOTICES.md is regenerated.

• regen.ts MANUAL. It names the producer of paint-vectors/*/inputs.jsonl: paint-dash.test.ts with DRAGON_WRITE_DASH_INPUTS=1. A regen step would never rerun, because regen ignores test-file changes. The test fails if the committed file is stale.

• Profiles. No profile row is added or removed, and no status changes.

What passed

• pnpm typecheck.
• pnpm test: 156 files; 3180 tests pass and 1 is skipped. The skipped test is the full pnpm regen --check, which runs only when asked.
• pnpm regen is at a fixed point.
• The device run above.

Changed tests

• chrome-ports.test.ts: .jsonl is added to its DATA list, so the dash vector inputs count as data. That file was the only unclassified one, and no check is relaxed.
• dragon paint-seams.test: it pins the two dash plants after the glyph plants.

No tolerance, check or test is loosened or removed. The reviewed diff is 116 KB in 25 files.

🤖 Generated with Claude Code

Note

Implement Blink 145 device-pixel dash and dot border painting for iOS and Android

• Adds paint-dash.ts, a shared device-pixel border painter ported from Blink 145, Skia, and StyledStrokeData. It produces structured border operations (layers, save/restore, clipping, polygon fills, dots) with dash lengths, fitted gaps, corner miters, and square-vs-round dots by thickness. New public exports: borderPaintOps, borderNeedsSidePainter, selectBestDashGap, BorderOp, NO_DASH_FAULTS
• Rewrites the UIKit and Android border emitters in border.ts to route dashed/dotted sides through the new side painter instead of the band painter, and removes the old Core Graphics DashPathEffect stroke paths. Double borders narrower than 3 device pixels paint as solid
• Adds two intentional dash-fault raster plants (dash-phase-1, dash-gap-unfitted) used as negative cases by the new pixel-oracle test in p6a-dash-oracle.test.ts
• Adds border-dash-fit and border-dot-fit parity fixtures, snapshots, and expected pixels at DPR 1, 2, 2.625, and 3 for darwin-arm64; recorded device-pixel failures drop from 135 to 61 on iOS and 182 to 90 on Android
• Risk: dashed or dotted sides that reach the fallback band painter now raise an identifier-bearing error instead of drawing a stroke; groove, ridge, inset, outset beside a dashed border are rejected from native programs

^{Macroscope summarized c4274db.}

[macroscopeapp]

Approvability

Verdict: Not approved

Macroscope's review found this PR not approvable — This PR adds a substantial Blink/Skia-derived border renderer and changes existing dashed/dotted rendering across both iOS and Android, creating a broad customer-visible runtime impact. An unresolved medium-severity oracle finding also concerns overlap coverage, so the production behavior and validation warrant human review.

^{Adjust the Minimum Blocking Severity for this repo — including turning it Off — in Settings. You can add or adjust custom eligibility rules. Learn more.}