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Levi Neuwirth bc9fb27d36 Clear P12-I11: casting-off widow-rebalance evens the stub last system 
RS-1 honestly failed the Minimal casting_off_quality threshold under the
reference engraver: greedy first-fit left a two-measure stub last system
(width CV 0.6145 -> clamped 1.0 > 0.90). Cleared the honest way — an
engrave-side balance pass, no Quality Metric Catalog or core-spec change.

Casting-off gains a second phase, a widow rebalance
(casting::rebalance_widows, run between the greedy walk and vertical
stacking): it moves whole trailing measures from a region's penultimate
system into its final one, choosing the shift that minimizes the larger of
the two distribution penalties the catalog defines for the break family —
the width imbalance (casting_off_quality, the CV of the region's system
widths) and the non-final break penalty (system_break_penalty, the mean of
|W-w|/W over non-final systems). distribution_cost computes each raw by the
same formula as quality.rs's casting_off_raw / system_break_raw (mean not
worst, abs not clamp), so the rebalance optimizes the values the metric
census will report. The two axes pull against each other, so their min-max
lands on a 6/4 split for RS-1 (casting_off 1.0 -> 0.4463, system_break
0.254 -> 0.677, every axis <= 0.90) — with comfortable margin, over the
fragile full-balance 5/5 (system_break 0.889, a hair under 0.90).

Scope is tight: only a region's last boundary moves, and only when greedy
placed it (an Automatic boundary with no break requirement or page force
pinned to its slot); a user/IR-anchored or page-forced boundary is never
disturbed, the penultimate system keeps >= 1 measure, the final never grows
past its predecessor, and the system count is unchanged — so every
break-count and page-assignment invariant (and all break-constraint tests)
hold untouched.

The casting_off 0.5 anchor and the 0.90 Minimal column were vindicated, not
relaxed: the engraver improved, no anchor rescale / threshold loosening /
RS-1 override. Core spec Chapter 9's "Minimal makes no optimality claim"
already permits the heuristic, so nothing normative changed (no .tex/PDF
rebuild). P12-I12 (the Standard-tier spacing floor on short scores) stays
open.

- engrave: rebalance_widows + distribution_cost + two-phase module docs;
  ENGRAVER_VERSION 2 -> 3 (a wrapping score's baked geometry differs from
  pure greedy); three new casting tests (even-split preference, the
  mean-not-worst break penalty for 3+ systems, and the resolved final
  system); the_wrapping_fixture_is_measured_honestly re-pinned to the 6/4
  values (both axes floor-warn under Standard, status untouched).
- testkit: RS-1 minimal_xfail row removed (promoted to a plain Pass); the
  suite ships no xfail rows.
- render-svg: ten_measure.engrave.{svg,snapshot} goldens regenerated
  (view_box width 83.99 -> 64.95; still two systems).
- process trail: PASS12_BATCH I11 struck; PASS12_RATIFICATION_LOG
  "no spec change" section; engrave DECISIONS casting-off decision 9 +
  quality item 7 + candidate promoted.

860 workspace tests pass; clippy -D warnings, fmt --check, rustdoc
-D warnings all clean.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NEs4aYiu8MXjdYdMxw8PTd
 		2026-07-03 19:09:51 -04:00
..
src Clear P12-I11: casting-off widow-rebalance evens the stub last system 2026-07-03 19:09:51 -04:00
Cargo.toml Phase 3 tranche 1: casting-off, K1 schema-fill, value-restoring undo 2026-07-02 21:55:26 -04:00
DECISIONS.md Clear P12-I11: casting-off widow-rebalance evens the stub last system 2026-07-03 19:09:51 -04:00
README.md Phase 3 tranche 1: casting-off, K1 schema-fill, value-restoring undo 2026-07-02 21:55:26 -04:00

README.md

epiphany-engrave

Agent I's engraving constraint solver (spec Chapter 9): turns a ConstrainedLayoutIR into a ResolvedLayoutIR with real geometry. It is the production-side replacement for epiphany-layout-ir's interface-only StubSolver; the two live in separate crates so the spec's core/product boundary stays sharp.

Status: Minimal tier, with casting-off

  • Engraver runs a deterministic horizontal spacing pass (the first axis of the two-pass spring layout): each spring slot is placed left-to-right by a collision-aware advance derived from real glyph bearings.
  • A casting-off pass (Phase 3's layout track) then breaks the spaced line into systems at measure boundaries (greedy first-fit against a PageGeometry — default A4 portrait at an 8 mm staff), stacks systems vertically at the vertical-band model's inter-system gap, assigns pages by content height, and populates the real ResolvedPage/ResolvedSystem tree. Every position is baked into a single y-up world frame (pages stacked vertically), so the SVG renderer and hit-testing consume the flat glyph/stroke lists unchanged.
  • The IR's declared constraints are evaluated — geometric families against the pre-casting spaced frame, break constraints against the final break structure (hard breaks are always honoured; a pathological soft break is skipped and recorded as an IrOverride decision). Chosen breaks are recorded as EngravingDecisions with SynthesisKind::EngravedBreak targets, attributed to the user override that requested them when one did.
  • It reports SolverTier::Minimal: hard constraints (break family included) satisfied, no optimality claim — the quality-metric vector stays the honest all-worst placeholder until the Quality Metric Catalog lands.

Deferred: the vertical soft-spring solve, per-system justification/stretch, optimal break search, widow/orphan control, and casting-off caching. See DECISIONS.md.

use epiphany_engrave::Engraver;
use epiphany_layout_ir::{ConstraintSolver, SolverConfig};

let report = Engraver::default().solve(&constrained_ir, &SolverConfig::default());
assert!(report.satisfied_hard_constraints);
let resolved = report.layout; // real pages/systems; hand to epiphany-render-svg